# Another Radial - this time 18 Cylinders



## mayhugh1

I was so happy with how my 9 cylinder radial turned out that I've decided to try my hand at an 18 cylinder twin. I came across a beautiful set of photos from another pair of builders that has inspired me to build something similar:
https://plus.google.com/photos/1114...ms/5278304464310065009?banner=pwa&gpsrc=pwrd1
Their project seems to be a heavily modifed Hodgson built several years ago. I'm going to attempt something similar. I've studied their very thorough set of construction photos; and I believe that using them and the H-9 info that I already own I can come up with a good-looking, and hopefully, working 18 cylinder model. Basically, it will be two 9 cylinder crankcases mounted back-to-back. I very much like their head and cylinder design because I think their combo looks realistic, and the heads will not require so many different machining setups as the original Hodgson design. Even though I already have all the fixtures I used in my 9 cylinder model, I'm not sure I have the needed enthusiasm to build another 20 of them without some significant simplifications. I like the looks of the open pushrods so I don't plan to use their pushrod tubes, but I will do something similar for the rocker arm boxes/supports. I don't have the crankshaft figured out yet, and so I will wait until I get the crankcase and bearings completed so I have some parts in my hands to help visualize the assembly process. 
The crankcase will consist of 4 sections connected with tie bolts:
1) rear cover containing the carb and a pair of distributors
2) rear cylinder section containing the rear 9 cylinders and the fuel distribution plenum
3) front cylinder section containing the front 9 cylinders, and
4) front cover.
It is critical that these sections be carefully machined since when stacked they will register the 4 bearings that support the built-up crankshaft and my goal is only a .00075" (diameter) oil film clearance between the bearings and the crank journals.
Construction started in early July. My plan was to attempt to reach, with lots of photos along the way, what I felt was the most difficult milestone in this project - laying a freely turning crankshaft inside the crankcase. If I was successful in doing this, my plan was to then start a build thread which included all the work that went into getting the project to this point, and then continue the build thread in real time after that point.  
Here we go. 
I'm starting construction with the front crankcase section which is very similar to the crankcase in my 9 cylinder. I still have a 5 inch diameter length of "6061" that I purchased for 30 cents per pound some 15 years ago from a local scrap yard. It is stamped with markings from a Chinese foundry but it turns very nicely. This is the same material I used for my 9 cylinder. The recesses which will eventually register the bronze crankshaft bushings are the most critical turning operations and they are all be turned in the same setup on my Enco lathe. I&#8217;m using Korloy inserts for the turning operations. These inserts are designed for aluminum, are razor sharp with lots of rake, and give a polished finish right off the machine. The sequence of photos should be self-explanatory. The finished turned part is then moved to the mill and the end holes are then drilled. A vertical rotary table is used to cut the flats and bores for the cylinders as well as the tappet bushing bores on my Tormach. I was able to use the CAD/CAM that I had developed for my 9 cylinder for this part since it is identical to the one in my 9 cylinder model. The 4-40 cylinder mounting holes (72 of them) are then drilled and hand tapped. I'm happy to report that I got through the whole process without breaking a single tap. - Terry


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## Davewild

This is amazing stuff, one day maybe but I really don't think I would have the staying power for so many repetitions, I will be following along.

Dave


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## mayhugh1

The next part is the rear crankcase section. Portions of it are similar to the front section, but much busier. It will contain two of the three bronze bushings that support the crank and will support the rear nine cylinders. It will house the cam ring assembly for the rear 9 cylinders, the oil pump, the impeller, and the air-fuel plenum for all 18 cylinders. It is critical that concentricity be maintained between this section and the front section so there will be no bind in the crankshaft. Nine 6-32 3 inch long SHCS pass through the front section to secure it to this section and concentricity between the two is maintained to a few tenths with a registration boss and recess scheme that also minimizes the chances for oil leaks. There are no gaskets between any of the 4 crankcase sections. Sealing is done with well finished machined surfaces and lots of screws. After completion, I was able to verify the concentricity between the two sctions to a few tenths.
On the nine cylinder engine the air intake tubes were rather simple single pipes running from the crankcase plenum to each cylibder head. On this engine the intake pipes are one-into-two's in order to feed both rows of cylinders from a common plenum pipe. This complication requires a different method for sealing the pipes to the crankcase in order to avoid interference with the very busy rear end of the crankcase. Brass bushings will be machined to compress o-rings around the intake pipes in order to seal them into the rear portion of this section. I expect the fabrication of the y-pipe assemblies will be extremely difficult later on especially since I will want to make them from stainless tubing as I did for my 9 cylinder. All the machining is completed on this section after moving from the lathe to the mill except for a few features primarily related to the oil pump and sump. The machining of these features will define the bottom of this crankcase section and so they will be done later after checking the fit of the crankshaft in the completed crankcase just in case there is a "preferred" orientation for smoothest crankshaft rotation. The lathe machining of this section filled my 30 gallon garbage can two times with swarf
Another 72 4-40 holes were hand-tapped not including some three dozen miscellaneous holes of various other sizes without incident. At this point I'm just about tapped out. - Terry


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## mayhugh1

The next part doesn't require a lot a hole tapping and should be a nice break from the previous two crankcase sections. The rear cover on my 9 cylinder radial was a casting that I purchased with the original planset. I spent a good bit of time cleaning up unused features on this casting and polishing the outer surfaces. Since the air/fuel mixture flows through this section from the carb on its way to the diffuser, a machined air guide was also inserted internally to smoothly direct this flow. This rear section also houses the distributor. In this 18 cylinder twin, I have no casting and so I'm on my own. My plan is to machine the air guide integral to the rear section out of a single chunk of metal. I have a forged aluminum piston blank that I acquired many years ago from my favorite recycling yard that I will use as the starting workpiece. Another wrinkle in this particular engine is that two distributors are required. I plan to use the distributor design that I developed for my 9 cylinder and so I have proven dimensions from that part to work from. I was able to identify the helical gear set used to drive the distributor from the Chaos Industries Photobucket photos. I will purchase these rather than attempt to machine them myself as they would be pretty significant projects in themselves, and right now I'm focused on getting the crank into the crankcase. In my 9 cylinder I was able to time the distributor by pulling the rear cover back to un-mesh the gears in order to rotate the distributor shaft. This technique isn't applicable here as I would likely lose the timing on one distributor while setting it on the other. So I will mill a clearance pocket in the air guide around each distributor gear so that each distributor can be independently lifted with the rear cover installed in order to un-mesh the gears. The machining begins on the lathe by turning the internal air guide contour and the registration boss to the rear crankcase section . This same contour will be used later to machine the close fitting impeller. The rear cover is then moved to the mill where the pockets for the distributor gears are the milled. The rear cover is then flipped over where the real fun begins. I decided to do two rough waterline passes in order to remove as much material as possible from the part before doing the finishing pass. The reason for this is that I plan to use a new ball cutter that I have no experience with on my Tormach. For the finishing pass I need a 2 inch long spherical cutter with a diameter less than 5/16". For me this is typically a recipe for chatter and poor surface finish. The body of this cutter is tapered for maximum strength and worked well even though I still had to modify it prevent rubbing on the finished part. The part came out beautiful and I was able to polish the outer surface to a brilliant sheen with only a fine Scotchbrite pad. This is probably the most complicated part I've ever made on my Tormach since it contained a number of very complex fillets. It taxed my CAD/CAM software, my computer, and my own abilities. The runtime on the exterior surface was about three hours. I checked the resulting gear mesh with a dummy distributor shaft. It turned smoothly with no noticeable backlash. I was also able to verify the length of the rear crankshaft section in my CAD model. - Terry


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## stevehuckss396

That's some mighty fine work you did there.


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## mayhugh1

The final crankcase section is the front cover. It covers the cam ring for the front row of cylinders. It also contains a ball bearing that supports the front of the crankshaft, and so it is again important to maintain concentricity with the other three sections. It is fastened to the front crankcase section with eighteen 6-32 SHCS. Nine of these are the 3 inch tie bolts that hold the front three crankcase sections together. The starting workpiece is a sawed disk from the same 5 inch diameter chunk of scrap that I used for the other sections. All the machining was done on my 9x20 Wabeco lathe using matching spline contours on both the interior and exterior surfaces. The finished part was moved to the mill in order to drill the 18 mounting holes. An end mill was plunged into the part to create interpolated counterbores for the heads of the SHCS. The thru holes for the bolts were then spotted and drilled. I got so busy controlling the swarf coming off the part while in the lathe that I forgot to take more photos and the ones I did take were a bit blurry. - Terry


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## Art K

Terry,
I just found that you're doubling the ante on that 9 cylinder radial you just finished. That sounds quite ambitious to me. I will be following along.
Art


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## mayhugh1

stevehuckss396 said:


> That's some mighty fine work you did there.



Thanks, Steve. Coming from you I take that as a great complement. - Terry


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## mayhugh1

The crankcase houses three bronze bearings in which the crankshaft will run. These are a light press fits into recesses turned earlier in the front and rear crankcase sections in order to their concentricity. All three bearings were turned from 3-1/2" diameter SAE660 drops which were about one inch thick. Most of this expensive material went into the swarf bucket. Since I have a length of precision ground rod that is .5952" in diameter that I can use later to check the alignment of my bearings and crankcase sections, I decided to make all the crankshaft journals this same diameter and to bore the i.d.'s of all three bronze bearings to .5960". This will leave a running diametrical clearance of .0008" between the bronze bearings and the crank journals for an oil film. This is the same thing I did in my 9 cylinder engine and seemed to work out well. The front and rear crankcase bearings are identical, and they also contain the bearing surfaces for the cam rings as well as the jack shafts needed to drive them. The center bearing will eventually hold the oil pump and and so an o-ring groove is cut into the o.d. of the crankshaft bore to control leakage. As with the crankcase sections no machining is yet done on the bearings which will define their rotational position in their respective crankcase position. This will be done later when the fit of the crankshaft is verified just in case there is a preferred orientation of one of the bearings for the "free-est" rotation. Some other openings may be needed to help with final assembly but I haven't thought things through that far ahead. The Chaos Industries guys did a lot of machining on their bearings and in the end they looked like 9-legged spiders. This was required for assembly of their engine because of their pushrod tubes. It looks cool and I just might do it also. It would allow me to extend the lifter bushings a bit into the interior of the crankcase and partially eliminate the pesky oil leakage around the lower pushrods where they exit the crankcase. - Terry


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## John Rus

Looks great! Whats next a 36 cylinder radial? 

That thing is going to sound great when finished, I can't wait!

Regards,
John.


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## mayhugh1

At this point in the build I have just under 300 hours invested in the crankcase. The four crankcase sections and their bearings are essentially finished and, when assembled, my test rod turns freely with no sign of binding as I hoped. I've also been able to check the mesh of my distributor drive gear with dummy distributor shafts in the rear crankcase cover and can feel no sign of binding or backlash. Considering the alignment requirements for these seven parts to achieve this with less than .0008" diametrical bearing clearance, it's pretty obvious that luck has been on my side so far. When I started the crankcase I promised myself that I'd walk away from this project with no regrets if I'm not happy with the crankshaft fit. It's just a personal issue with me but without a near perfect foundation to build upon, I feel it would be impossible for me to keep enough interest in the project over the next year or so to slog through the huge number of parts that are going to be required to finish the engine. So, my next goal is to come up with a crankshaft which turns just as freely as my test bar, is easy to assemble/disassemble, and is robust enough to handle the torque of the twin. I don't consider this project to even be real until the crank is spinning freely in place. The remainder of the work, although tedious, will consist of smaller, less complicated parts and assemblies that should be within my capabilities since I've already built similar parts for my 9 cylinder. If I'm not successful with the crankshaft then the crankcase will just become a neat conversation piece on my desk. - Terry


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## Tony B

That is some beautiful work you are doing, look forward to hearing it run


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## mayhugh1

The construction of the crankshaft in the Chaos Industries engine seems to follow what I expect is the recommendation of the Hodgson twin planset since it is very similar to the one in the 9 cylinder planset. It is a built-up of nine individual pieces held together with taper pins. It requires a separate precision jig to be constructed for drilling the holes for the taper pins while the crankshaft parts are held in proper alignment. In my 9 cylinder engine Iwas able to significantly reduce the number of parts by constructing the crankshaft from a solid piece of steel and then cutting it in half after the crankpin and alignment pin holes were drilled. I then used pinch bolts to secure the two crank cheeks to the crank pin. This 3 piece approach eliminated the need for the alignment fixture, the need to broach two precisely placed square holes, and pretty much guaranteed a precise alignment in the crankcase. Taper pins work best when the parts aren't likely to have to be disassembled multiple times. In the Hodgson approach the pins are bradded over at final assembly with their limited access inside the crankcase making it difficult to later remove the crank without chance of damage. I followed the saga of Ken-ichi Tsuzuki http://homepage2.nifty.com/modelicengine/h9index.htm as he completed 4 crankshafts before getting an acceptable result for his 9 cylinders gone. Many but not all of his issues were related to the taper pin construction. I'm sure many others have successfully built this engine according to the original planset; and I'm not criticizing the original design, but it just isn't for me. My background includes many years of designing easily maintained oilfield equipment, and so I looked for another approach. I like to verify the fit and operation of each sub-assembly as I go along on a large project and leave final assembly to just finally assembling proper fitting parts and tested assemblies. This means that I'm likely to take the crank in and out of the engine many times before final assembly, and so my crank needs to be easily taken apart and put back together in precise alignment every time. The crank cheek pinch bolts worked well on my 9 cylinder. I estimated the torque produced by that engine to be less than 5 ft-lbs. Experiments showed that a steel 6-32 SHCS torqued to 20 in-lbs in the 1/4" steel crank cheek would grip a .375" shoulder on the crank pin and maintain a holding torque of 15 to 20 ft-lbs. This gave me a factor of 3-4 margin and it still seems to be working well. This was repeatable so long as the bore in the crank cheek is no more than a few tenths over the diameter of the crank pin shoulder. If the bore is a full thousandth over the diameter of the shoulder then the measured holding torque drop to almost half. In addition the actual location of the pin in the cheek can shift a bit from its desired location. I expect the twin will generate twice this torque and even though on paper I still have margin, it is uncomfortably small for me. The solution I eventually came up with was to add a dowel pin key to positively lock each cheek to its corresponding crank pin shoulder. I decided to make the crank shaft in two separate assemblies -a front section with and a rear section. Each section will be turned from a solid steel round. The crank pin hole and a separate alignment pin hole will then be drilled. The two halves are then separated by sawing them in half and then the cheek contours are milled. When the crank pins are keyed to the cheeks using an alignment pin in the alignment holes, I will have two easily separated crankshaft assemblies that should fit perfectly between their bronze bearings.However there still remains the issue of tying these two assemblies together while maintaining precise alignment between them. I decided on the square drive approach. I own the square broach recommended in the 9 cylinder planset but found that it was very difficult to press the broach through a quarter inch of steel while keeping the hole perpendicular to the workpiece. This is because the broach is very long and thin and it tends to bend to one side or another during the pressing operation. The adapter recommended to keep the broach perpendicular costs some $500 and so is not an option for me. So I decided to mill a square recess in the front of the rear crank section and to mill the square boss on the rear of the front crank section. I also decided to go for a light press fit between these two sub assemblies and to not tie them together with any type of fastener. The two crank sections are captured between their bronze bearings and will not move axially. When the engine is disassembled these two sections can then be easily separated. If I fail to get the square recess in the exact center of the rear crank section I'll have the option of opening it up a few tenths before scrapping the rear section. The pressurized oiling system will keep some oil in the interface to minimize metal-to-metal contact should there be any relative motion between the two section because of misalignment. The photos below show some of my test pieces. The next post will detail my process for machining the entire crankshaft. - Terry


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## petertha

Wow, impressive. I was happy to see these new posts & will certainly enjoy another of your projects!

Can you elaborate on how you are centering & clamping the crankcase to (I assume its) an upright rotary table for milling operations? 

One pic looks like a wooden plug/plate inside the CC. Is this connected to a threaded stud through the RT hole & thats how its clamped down? How about centering - somehow clock runout with a dial by gently bumping it into position or something?

The other pic shows some hexagon thingy's in the T-slot grooves. Are those eccentric clamps or something?

Re the radial holes for cylinder mounting, whats the plan there? Threaded studs that screw in & the cylinders jugs are then clamped down with nuts? Are they blind tapped or all the way through?


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## mayhugh1

Petertha,
It's nice to hear from you again. The crankcase section is actually centered on the rotary with a tooling button that I turned. One side of the button is fit to the center hole of the rotary and the other is a snug fit to a recess in the crank section. The piece of wood is just a large washer to prevent marring the crank section when the nut on the threaded rod is drawn down to hold the workpiece tight against the rotary.
In the second photo I am using eccentric clamps to do the centering as I had a job on my lathe that I didn't want to disturb and so I couldn't turn another tooling button. A threaded rod is used to draw the workpiece tight against the rotary.
The 4-40 threaded holes that will hold the cylinders to the base are blind holes. During final assembly I will Loctite socket head grub screws for use as studs in these holes. The cylinders will be then secured with small pattern washers, lock washers, and nuts. - Terry


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## mayhugh1

My crankshaft starts out as two sawed lengths of 2 inch diameter cold rolled 12L14. One of these lengths will become the front section and one will become the rear section. I rough turned both blanks to about .050" over their eventual final dimensions on my Enco lathe since the metal removal rate of this lathe is much better than my 9x20 . The disadvantage of my design is that a lot of material is wasted to create the two blanks. I then attempted to stress relieve the blanks some at 600F for 6 hours and allowed them to cool in the oven overnight. Although some will argue I didn't use a high enough temperature, I felt that anything was better than nothing. I then used my 9x20 lathe to turn the shaft features to final size including the bearings and gear blanks and then drilled the axial oil passages and PCV vent. The diameter of the bearings was turned to match that of my test rod. The cheek disk was left .050" over. The parts were then moved to a 4-jaw chuck on the horizontal 4th axis of my mill. Here I cut the square boss on the rear of the front section. I was able to reduce the TIR of the shaft to a tenth or so in the 4 jaw to insure the square boss ends up in the center of the shaft. I cut the integral CAM drive gears on the front and rear sections using a custom 3/8" diameter gear cutter that I made for the crankshaft in my 9 cylinder. A keyway was cut on the front of the front section for the prop hub and the cross drills for the oil passages were completed. The front section was threaded with a left hand 3/8-24 thread for the prop spinner. At this point the sections are ready to have their crank and alignment pin holes drilled just before being sawed apart. -Terry


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## Canman

Hey terry I read your thread on your last one  and that sir was amazing. I can't wait to see this one running.your skills as a machinist are amazing and the work is fantastic. Can't wait to see the finished product.
All the best James.


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## Skywalker

Unreal....great quality, amazing planning. A lot of repetition in the little monster. 
___>Be watching.


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## idahoan

Hi Terry 

Wow amazing progress so far! I'm really enjoying the CNC aspect of your work; The crank case assembly is a work of art!

Thanks for posting.

Dave


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## mayhugh1

The two crankshaft sections are next inserted into a sacrificial block that has been skimmed flat on the mill table. The sacrificial block has been bored with two holes the same diameter as the bronze crank bearings so each crank section can be clamped flat on the sacrificial block with the shafts extending safely through the block. I machined each crank section in its own position in the jig. A 3/8" hole for the crank pin shoulder is then drilled and reamed through each disk. A 3/16" hole is also drilled and reamed through the disk and this will be used later to align the cheek halves when they are keyed to the crank pin. The drilled/reamed holes are continued into the fixture block for dowel pins which will later locate the cheeks in proper position while their profiles are being milled. Holes for a pair of .063" drive pins are drilled into the rear of the front crankshaft section. These pins lock a gear to the crankshaft that will drive the oil pumps. The square recess is milled into the front end of the rear crank section. Holes are plunged into the four corners of the recess with an .093" end mill to eliminate corner chatter later when the recess is finished. A 1/4" diameter end mill is used to rough out the recess followed by an .093" cutter used to mill the linear edges of the recess. Light cuts are taken and the dimensions of the recess are continuously checked until a very light press fit with the front crank section is achieved. After the crank and alignment pin holes are reamed, the section halves are separated by sawing them apart on a bandsaw. The cheeks are also manually roughed out on a vertical bandsaw before moving them back to the mill for machining their finished profiles. The parts are placed back onto the fixture and registered into position using dowels in the crank and/or alignment pin holes. These dowels have been thru-drilled so the parts can be held down to the fixture with threaded fasteners. When the cheek profiles are completed the crank sections are ready to be keyed to their crank pins. The crank pins are turned from drill rod but will not be hardened. Their lengths are adjusted for .0015" thrust clearance between the bronze bearings of each crank section. The shoulder diameters are turned for 2-3 tenths clearance fit in the cheek bores. The pins are then marked to associate them to a particular cheek for consistent assembly/disassembly later on. The parts are then moved to a final setup in the mill where they will be keyed and the radial oil passages drilled. - Terry


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## mayhugh1

A .218" end mill is plunged into the center of the edge of the cheek to create the counterbore for 6-32 SHCS pinch screw. There isn't much meat left in the .250" thick cheek, and the diameter of the screw head will have to be reduced slightly. The counterbore is then spotted, drilled through and threaded for the 3/4" pinch screw. It is important to slightly chamfer the bottom edge of the counterbore in order to clear the radius under the head of the steel (not SS) SHCS. A .020" slitting saw is then used to cut the the slot in the center of the crank pin bore in the cheek. After all the holes for the pinch screws are finished and the slots are all cut the crank cheek pairs are assembled onto their crank pins with the alignment pins inserted, and the screws are snugged down to about 10 in-lbs to secure the crankpins. The entire crank section is then clamped down to the milling plate used earlier to mill the cheeks. The alignment pin fits into the hole in the fixture plate that reamed for it earlier. A 7/64" 4 flute end mill is plunged squarely into the intersection of the slot and the crank pin shoulder. Half of the 1/8" diameter dowel will be in the cheek and the other half will be in the crank pin shoulder. A 1/4" long dowel pin is used for the key and so the plunge should be a bit deeper than 1/4" to compensate for the tip of the reamer that will be used to finish the diameter of the hole. I used a .124" reamer, followed by a .125", followed by a .126" reamer until the dowel could be pushed in with my finger. Later when the pinch screw is torqued to its final value the dowel will be tightly retained. The dowel also prevents the cheek metal from yielding around the crank pin which would make later assembly/disassembly more difficult. The part is flipped over on the plate and the key for the other side is cut. In my case it is necessary to use a small diameter endmill extender when machining the dowell pin holes on the sides of the sections that have the crankshaft protruding upward. After all four keys were cut I checked the two mated crank sections in the crankcase and they turned as a single mated assembly just as freely as my test bar. I disassembled and reassembled both sections four times, retested the fit; and it was perfect every time. The last operations involve drilling the radial oil passages, plugging the oil passage ends with shortened (.080" long) Loctited grub screws and then testing the complete oil path for leakage. I now have some 600 hours invested in this project and have detailed in a number of rapid fire posts what it has taken to get this far. From this point on I'll be posting in real time and so everyone will get to see just how slowly I really work.  - Terry


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## jwcnc1911

Wow!  You work fast!  Looking great!


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## mayhugh1

My completed crankshaft consists of two sub-assemblies - a front section and a rear section. The rear section drives the master/slave rod assembly for the rear 9 cylinders and is constrained between the center and rear bronze bearings for a thrust clearance of approximately .0015". The front section drives the master/slave rod assembly for the front 9 cylinders. It is constrained between the center and front bronze bearings and the thrust clearance currently measures .003". Since this section of the crankshaft drives the prop, it will be pulled forward when the engine is running. (Remember, the two crank sections are slip-fitted together with a square drive mechanism, and they can move axially with respect one another within the limits of their bearing constraints.) It probably isn't a good idea to allow the front bronze bearing to carry the full thrust load of the running engine as it would wear prematurely. Therefore a step was designed on the front section of the steel crankshaft in order to transfer the thrust load to the inner race of the ball bearing that was pressed into the front cover. I designed the front cover so the outer race of the ball bearing lies below the front surface of the front cover when the inner race contacts the crankshaft step. So, I will now machine a bearing retainer that will be bolted to the front cover to keep the bearing in its proper position. A brass shim of the necessary thickness to hold the bearing against the step on the crankshaft for a final front section thrust clearance of .001" is then sandwiched between the bearing retainer and the outer race. The .005" thick brass shim was cut on my Tormach using their carbide vinyl cutter. I have cut many non- metal gaskets with this cutter but this metal shim stock pushed the cutter to its limits and doesn't seem like a good use for it. The bearing retainer was turned /milled from 303 stainless and secured to the front cover with flat head button screws. Tightening the screws pressed the bearing into it final position in the front cover for a final measured thrust clearance of .001". - Terry


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## Scott_M

Hi Terry

Once again beautiful work !!

I have done a lot of work with the Tormach Drag knife.  I too have used it for .005" brass shim stock. I found that if I use the heavy spring, tightened up pretty tight but still giving me full compression and making several passes (the more the better) with a couple of progressive Z depths. That I could cut the .005" shim pretty well. It would leave a slight rolled edge but that was easily burnished out with a smooth steel rod.

I am following along with great interest. Thank you so much for taking the time to share such a detailed account of your amazing build.

Regards

Scott


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## oneKone

this is such beautiful machine work. im looking forward to your future posts, 
in short.... great bloody work mate!


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## mayhugh1

Thanks all for the complements. I'm still just learning as I go.

Scott,
       Thanks for the advice. I ended up doing pretty much what you said but I think I may have dulled my cutter as I spent a great deal of tinker trying to make the shim out of stainless but gave up an went to brass. - Terry


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## petertha

That square socket mate joint is just so neat. I have seen a somewhat similar lap joint made from cutting off opposing halves of the crankshaft journal, but the square hole in a 'notch' above 

One thing I still dont understand, is there the equivalent of a center bearing/bushing over this area? (green arrow). The pics from the link show a kind of mid section bearing/bulkhead bolted to ears radially, but I'm not sure if that is for supporting the crank or another purpose...it seems close to the gear. 

Man, lots of parts in there! I'm having a tough time even visualizing assembly sequence & alignment, but I'm sure all that & more will be revealed!


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## mayhugh1

Petertha,
You've got a good eye. The oil pump(s) housing will eventually be built and bolted to the center bronze bearing. In the photo your green arrow points to the section of the crankshaft that will be turning inside the body of the oil pump. That groove you see just below your arrow is where the pressure pump will pump oil into the crankshaft. There is a radial hole in the middle of this groove that is not visible in the photo. Oil enters here and is sent to both ends of the crankshaft to oil the front/rear main bearings and the front/rear master rod bearings. That gear you see will drive the oil pump(s), i.e. the pressure and scavenger pumps. The Chaos Industries photo may be confusing you. I don't think that photo is at the same portion of the crankcase They built their cam according to the original planset. It has four square mated sections but they are pinned together with taper pins to make a singe solid built-up crank. I eliminated three of these sections in my design by turning the sections from solid rounds, but I had to leave one in order to be able to final assemble the engine. I saw no reason to pin this last section in my particular design and  so I left it as a slip fit. - Terry


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## ShedBoy

WOW!

That is all I can say.:bow:

Brock


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## mayhugh1

Next, I'm going to finish up some miscellaneous crankshaft related parts. None of these have anything to do with its alignment and so the stress level should be a lot lower. The first part will be the prop hub. It consists of two parts which will sandwich the prop using six 8-32 button head screws. The two parts are designed to butt against each other inside the prop so the prop is not crushed when the screws are tightened. The assembly is then slipped onto the end of the crankshaft where it bottoms on a step turned on the crankshaft. It will eventually be secured to the crankshaft with a large nut/spinner combination. In addition it is keyed and so the internal slot for the key will have to be broached. When I made the front section of the crankshaft one of the last machining operations was to mill the key slot. The part slipped in my setup and the eventual result was that the slot was cut too wide. Due to the small diameter of the crankshaft I didn't want go up to the next standard key size and so I had to spend a few hours making a tiny and odd shaped key with one width inside the od of the crankshaft and another width inside the id of the hub. I feel like it belongs in a safe until final assembly as it it one of those parts that just goes missing, and I really don't want to make another one. The construction photos should be self explanatory. The only other wrinkle is that I happened to have a piece of 304 stainless scrap that was already turned to suitable roughing dimensions and so I decided to use it. This was my first (and last) time trying to machine that stuff. I ruined two carbide inserts before I was done and my broach isn't speaking to me anymore. Well, at least I now won't have any corrosion worries with the prop hub. - Terry


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## myrickman

Wow ! Truly an inspirational project. What is so neat is the sheer number of operations which have to be spot on or else...! I tip my hat to you sir, well done.


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## mayhugh1

The prop nut/spinner completes the front crankshaft components. The original 9 cylinder planset calls out a simple hex nut to secure the prop assembly onto the crankshaft. I designed a more complicated part for my 9 cylinder that consisted of a stainless steel hex pressed into an aluminum spinner. The completed assembly is tapped for a 3/8"-24 left hand thread and is threaded onto the end of the crankshaft to secure the prop and its two-piece hub onto the crankshaft. I also machined a Delrin drill starter with a one-way clutch that slides over this hex for starting the engine. I found that the starter is usually only needed for starting the engine after its has been sitting for a few weeks, but I decided to duplicate the same prop nut/spinner for this engine.
The 9 cylinder engine uses an axial hole through a portion of the front crankshaft section as a crankcase vent. My experience with my 9 cylinder showed this vent probably isn't doing much as most of the venting is done through the scavenging pump as it recirculates oil back to the vented oil tank. I decided to retain this crankshaft vent for the 18 cylinder engine, though, as there will be twice the blow-by and the vent may be functional in this case. The axial and radial holes in my hex nut provide a path for the escaping gasses from the end of the crankshaft. I also engraved warnings about the left hand thread, and this has always been a practice of mine. I had to re-make the front prop hub that I made in my last posting as I had the diameter wrong. This time I used 316 stainless and the machining was a lot easier.
The aluminum spinner was turned on my 9x20 cnc converted lathe. It was reversed in a Set-True chuck and the registering recess was bored. After pressing the spinner onto the hex and threading the complete assembly onto the crankshaft up against the prop hub assembly I measured .002" TIR on the spinner. I don't like wobbly stuff and this was right at my limit otherwise I would have 
re-finished the spinner on a LH threaded mandrel. 
My next step will be to make the assembly/display stand. I am just about at the point where I will start making the internal parts, and the assembly stand will come in handy for holding the crankcase while I check their fit and operation. - Terry


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## John Rus

Now you just need some micro mesh to really pollish that spinner and show us how you build that slick radial from the reflection!

Simply floored!

John.


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## petertha

mayhugh1 said:


> ...completed assembly is tapped for a 3/8"-24 left hand thread and is threaded onto the end of the crankshaft....
> 
> ... Delrin drill starter with a one-way clutch that slides over this hex for starting the engine....


 
So the left hand CS thread is because your starter direction is driving it counter-clockwise prop direction (viewed from front) & this mitigates the nut from loosening if it was RH thread? (my only experience is with RC engines, much smaller than this, but amazingly always RH thread. Never thought about that till now, but I have seen nuts come loose even with a backfire kick or fuel loaded).

And the delrin piece, it locks onto the hex part but has a relief to accomodate the rounded spinner part? I dont understand the clutch, can you elaborate. It somehow allows freee rotation once the engine starts running & overspeeding the drive rpm? Is it part of a cordless drill setup or some aftermarket part?


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## mayhugh1

petertha said:


> So the left hand CS thread is because your starter direction is driving it counter-clockwise prop direction (viewed from front) & this mitigates the nut from loosening if it was RH thread? (my only experience is with RC engines, much smaller than this, but amazingly always RH thread. Never thought about that till now, but I have seen nuts come loose even with a backfire kick or fuel loaded).
> 
> And the delrin piece, it locks onto the hex part but has a relief to accomodate the rounded spinner part? I dont understand the clutch, can you elaborate. It somehow allows freee rotation once the engine starts running & overspeeding the drive rpm? Is it part of a cordless drill setup or some aftermarket part?



Petertha,
Yes, the LH thread is so that the spinner will tighten rather tend to loosen when the engine is rotated by the starter. The Delrin piece is machined to slide down over the flats of the hex and engage them so the engine can be rotated. I normally use it with my battery powered drill. I learned with my 9 cylinder to set the break-away torque of the drill to a point just above where it will turn the engine over just in case the carb fails and allows fuel to flood a cylinder and create a hydrolock. The Delrin hub is designed to clear the spinner so it isn't marred. I included a one-way (sprag) clutch so when the engine starts the starter can be smoothly withdrawn without loosening the nut even if the engine rpm is greater than the drill rpm. -Terry


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## mayhugh1

Construction of the stand begins with a mounting ring that will be bolted to the rear cover with six of the eight 8-32 SHCS holding the rear cover to the rear crankcase section. Legs will be welded onto this ring and then to a baseplate to form a rigid three point engine stand that will be used to assemble and eventually display the engine. There will be quite a bit of weight cantilevered out from this stand and so the ring is being machined from 3/8" steel while the legs and baseplate will be made from 1/4" steel. I had to include the stand in my engine modelling as the rear of the engine will eventually become busy with oil lines, carburetion, and various linkages. I'll also need access to the lower rear cylinders in order to change their plugs while the engine is on the stand. The sump is beginning to be a concern because it looks like the drain plug will need to be at the rear of the engine instead of at the front as on the 9 cylinder. It's going to become very busy in that area, and I don't yet have my cylinders and heads designed; and so I'm trying to keep the stand back and out of the way of the sump. 
After several 'interesting' minutes at my bandsaw with an over-size chunk of 3/8" steel plate I ended up with a 7" square workpiece. This was bolted to a sacrificial fixture plate which was clamped in my vise. This plate will be also be used for fixturing during welding. I first drilled the ring mounting holes and then extended and tapped them into the fixture plate. This was done to hold the completed part in place during the second machining operation when it was being cut loose from the workpiece. I designed the ring with circular bosses around the mounting holes that fit into machined recesses in the rear cover to prevent marring the rear cover. The final machining operation was cutting a relief fillet around the perimeter of the part in order to clear the spherical body of the rear cover. I don't want any sharp edges on the mounting ring that will scratch up the machined surfaces of rear cover when the awkward and very heavy engine is being muscled on and off the stand. The final photo shows the bead-blasted mounting ring in place on the rear cover to check the fit. - Terry


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## mayhugh1

Construction of the legs for the engine stand starts with two pieces of 1/4" hot rolled steel plate that are glued down to 3/4" MDF backing plates. I use a Devcon fast drying gel adhesive sold at Lowes and allow it to cure for a few hours. The parts are contour-milled in two steps. The first step leaves .005" radial stock around the part and is milled to a depth of .235". The second contouring operation removes this excess stock and the parts are milled to the full depth of the workpiece. Doing the machining in two operations in this way results in maximum adhesive area during the roughing cuts which generate the highest forces trying to move the parts. The light finishing operation gives a nice surface finish and reduces the chances of the parts coming loose when they are cut free from the surrounding workpieces. A heat gun carefully directed at the completed parts releases them from the MDF, and the left-over workpiece material can be used for future projects. Any remaining adhesive is easily removed with ordinary paint/epoxy remover. The legs are then moved back to the mill vise and cosmetic accents are cut into both sides of each leg. A trip to the bead blaster prepares the finished parts for fit-up and welding to the mounting ring and base plate. - Terry


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## petertha

mayhugh1 said:


> ..glued down to 3/4" MDF backing plates. I use a Devcon fast drying gel adhesive sold at Lowes Terry


 
Interesting. Is that an epoxy like below or CA-glue (gel)? Is that a standard trick of yours to position metal onto sacrificial backing plate for machining?
http://www.devcon.com/products/products.cfm?market=OEM Adhesives&family=5 Minute® Epoxy Gel

I've got all sorts of epoxy in teh shop. I tried CA glue once (thick/gel) between 2 aluminum pieces once for matched machining. Not sure what happened but it ended up de-laminating. Maybe cutting fluid in the joint or vibration or clamping pressure... 

I'd also like to learn more about your bead blasting apparatus & method one day if you have the time. The parts look great,


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## mayhugh1

petertha said:


> Interesting. Is that an epoxy like below or CA-glue (gel)? Is that a standard trick of yours to position metal onto sacrificial backing plate for machining?
> http://www.devcon.com/products/products.cfm?market=OEM Adhesives&family=5 Minute® Epoxy Gel
> 
> I've got all sorts of epoxy in teh shop. I tried CA glue once (thick/gel) between 2 aluminum pieces once for matched machining. Not sure what happened but it ended up de-laminating. Maybe cutting fluid in the joint or vibration or clamping pressure...
> 
> I'd also like to learn more about your bead blasting apparatus & method one day if you have the time. The parts look great,


Petertha,
        I glue I use is a 2 part epoxy. It is Devcon 5 minute epoxy gel available from Lowe's. I usually let it cure for a few hours before using putting it under stress.  It is a gel and does now flow out very well which is what I usually want for my applications. I often use this technique as it lets me machine an entire part without moving clamps around. 
       My bead blaster is an enclosed cabinent that I aquired many years ago when I was doing car restoration projects. I use glass beads equivalent to about 150 grit. This is a little finer than I'd like since I usually use it for surface prep for painting and 80 grit would give a nice surface with a better 'byte' for the paint. But, I have about 25 lbs of this stuff and am just using it up. Actually it doesn't use up very quickly. Its the same 25 lbs I bought some 15 years ago. - Terry


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## mayhugh1

The baseplate is the final piece needed for the engine stand. Again, I started with a 1/4" sawed steel plate glued to a piece of 3/4" MDF. After drilling the four corner mounting holes (the engine stand will eventually be bolted down to a faux firewall), I used them help secure the plate to the MDF. After milling the perimeter of the baseplate, I machined a trough to collect leaked oil from the engine. After sitting for several days my 9 cylinder starts seeping oil from the lower lifters and also from any open exhaust valve from either of the bottom cylinders. There just seems to be no way to solve the cylinder oil leak problem since the oil slowly but surely (and incredibly!) passes through three ring gaps to find its way into the combustion chamber. Sealed pushrods tubes would solve the leaking lifter problem, but I like watching the pushrods in action in the running engine. I also milled pockets for the three legs to help keep them in alignment during welding. The parts were fitted together and tig-tac'd while continually checking the alignment. During final welding, a heavy plate was temporarily bolted to the mounting ring to control warpage. Once the welding was completed, the completed stand was once more bead blasted and then painted. I used a relatively new Rustoleum texture paint with which I've been experimenting. It dries to a hard and coarse texture (it's not a wrinkle finish paint) that hides machining marks and minor surface imperfections one would expect from hot-rolled plate. An additional plus is that it is oil and fuel resistant after a several day curing period. The final photo shows all the parts I've made to date for this engine assembled and mounted to the stand. Since I hadn't yet drilled the mounting ring mounting holes into the rear crankcase section, I had to do that. Six 8-32 SHCS sunk 3/4" deep into the crankcase will be supporting the full cantilevered weight of the running engine. I think my next step will be to make, assemble, and test all the components of the oiling system. - Terry


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## stevehuckss396

Man oh man does that look sweet


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## mayhugh1

I've been working on the design of the oil system components including the oil pump, transfer tubes, and sump. I was hoping to use the exact same components that I used in the 9 cylinder engine, but the CAD modeling I've been doing the past several days tells me that sump will have to be significantly modified due to avoid interference with the rear row of cylinders. In this engine the oil pump is in the middle of the engine and it pumps oil to the front and rear crankshaft sections. The sump is located toward the rear of the engine and this means that return oil from the front bank of cylinders will have to travel over the lower cylinders of the rear bank in order to get to the sump. This compounds the oil control issues for the lower cylinders in the rear bank. Therefore, I'm trying to make the return path as free-flowing as possible by opening up multiple passages through the crankcase and enlarging the sump inlet tube. I don't yet have the sump fully figured out.
I've got enough of the oil pump designed, though, to start making parts for it and so I'm taking a break from the CAD to get back into the shop to make parts. I'm starting with the pump shafts and gears so I can use them to test their fits in the pump body while I'm machining it. These gears will be identical to those in the 9 cylinder. When I originally cut those gears I actually created lengths of gear stock from which I sliced off the gears. I have enough of those stocks left over to create the gears for this engine. The first and trivial photo shows the turning of jone of the gear shafts. What I will be doing later is using the tooling marks left on the ends of the shafts in these operations to find their true centers after they are located in the pump body in order to accurately machine the cavities for them. 
When I sliced off the larger drive gears, I forgot to ream their center holes and so I had to re-chuck them in the lathe. The third photo shows a shop-made tool I use to align thin parts in my lathe chucks. In use, the carriage is slowly moved toward the headstock while turning the spindle over by hand and iteratively tightening the chuck until the bearing consistently rotates against the part. It is not difficult to get the part perpendicular to the lathe axis to within a tenth or so.
In the oil pump I want to keep the clearance between the gears and their pocket walls to less than .0015", but I also want to interpolate the pockets in the pump body using my Tormach. After Loctiting the gears to their shafts I trued them in the lathe for 0 run-out. My Tormach has .0005"-.00075" backlash and so I practiced on a piece of scrap to figure out how I could compensate for most of it and end up with a truly circular pocket of the precisely correct diameter and location. The process I ended up with will be duplicated later when I machine the actual pump body. For now, I'm creating a fixture that I will use to cross-drill a hole through the gears and their shafts for locking pins.
The last two photos are pictures of my shop. When I built my shop many years ago I injured my back and spent several months recuperating from back surgery. My shop ended up pretty close to our rear patio door and according to my wife it was an eyesore. So, I created what I called my dry aquarium. While I was unable to do any heavy lifting, I drew and cut all those sea creatures from 16 gage steel on my plasma cutting table. Each is attached to the Harding-board siding with it own screw anchor(s). Later, when I was fully recovered, I bought a shovel and dug a 1200 gallon pond on the backside of my shop. The fish, turtles, and frogs in this one, though, require feeding and a lot more maintenance. My wife and I spent the next seven summers landscaping what was left of our backyard. I'll post more pictures of our landscaping project as this project 
progresses. - Terry


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## petertha

mayhugh1 said:


> ...After Loctiting the gears to their shafts I trued them in the lathe for 0 run-out. ... I'm creating a fixture that I will use to cross-drill a hole through the gears and their shafts for locking pins.
> - Terry


 
So the first loctite application is intended to stick the gear to the shaft with enough retention that you can touch them up on the lathe? What loktite do you use for this?

Re the cross drill & pin business, assume the pin is centered through a tooth 'valley', into the shaft. Do you continue part way into the other side of the gear but dead-ended in the hub part? Will you use tapered pins or straight segment? 

Nice pond!
 -Peter


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## mayhugh1

petertha said:


> So the first loctite application is intended to stick the gear to the shaft with enough retention that you can touch them up on the lathe? What loktite do you use for this?
> 
> Re the cross drill & pin business, assume the pin is centered through a tooth 'valley', into the shaft. Do you continue part way into the other side of the gear but dead-ended in the hub part? Will you use tapered pins or straight segment?
> 
> Nice pond!
> -Peter


Petertha,
I use 620 bearing retainer. And yes, the pin hole is centered between two teeth and the hole is drilled completely through to the other side of the gear. This gives me twice the shear strength and also allows me to easily remove the pin during the fitting process before it is loctited in place. Only the pins in the four small pump gears are loctited. The two large drive gears which will mesh with the gear on the crankshaft and drive the pump gears are pinned but not loctited since they will have to be removed should the pump ever need to come apart. The pins in these gears will be kept in place by the meshing action of the crankshaft gear. If the pins tend to move outward they will be driven back each revolution by a tooth on the crankshaft gear. I'm using straight 1/16" dowells for all the pins. The purpose of the drilling jig is to make sure the hole that starts betwen two teeth  also comes out between two teeth on the other side. - Terry


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## mayhugh1

The oil pump body is sealed to the center bearing with eleven 4-40 SHCS, and so the first step is to drill and tap these holes in the bearing using the fixture plate I originally created to machine the bearings. Three jackscrew holes were also drilled and tapped to later help separate the pump body from the bearing. Most of the mounting holes are symmetrical around the y-axis so the part can be flipped over and still be secured to the fixture plate. The pump body, itself, starts out life as a 1/2" aluminum plate glued to a piece of 3/4" MDF. I spot drilled the center of the plate and used it as a reference point to press in phosphor bronze inserts that will be used for the gear shaft bushings. The bottom surface of the pump body is first milled flat; and then the mounting holes, center hole, and outer perimeter are machined. The Chaos Industries guys included a port in their body to measure the pump pressure. I don't think it's a worthwhile feature with the drip-feed from the oil tank needed to control oil flow into the engine, and so I didn't include it on my version. 
The pump body with its milled bottom side down is then bolted to the bearing and fixture plate, and in two separate steps the mounting holes are counter-bored for the SHCS. The top surface is then milled to its finished height. It is very important that the top and bottom surfaces of the pump body be parallel to one another since the gear shaft holes will be drilled/reamed from one side and the close fitting gear pockets will be machined from the other side. Even though there are eleven mounting screws securing the pump body to the bearing, these threaded fasteners can't be relied upon to accurately align the holes for the gear shafts to allow minimum clearance between the gears and their pockets. Therefore, holes for three close-fitting dowels were match drilled and reamed through the pump and center bearing before the four shaft holes were machined. After doing this, the jack screws mentioned previously are absolutely required to separate the two parts.
Eighth-inch oil passages are drilled into the the ends of the three arms of the pump. The transfer slots were used to indicate the part vertical in order to center these holes over the transfer slots. I wedged a 1/8" gage lock into the transfer slot and used it and a dial indicator to get each of the slots truly vertical. The scavenger intake port at the bottom of the pump is also counter bored for an o-ring sealed connection to the sump drain through the crankcase wall. 
The pump was then removed from the bearing, flipped over, and secured back onto the fixture plate where the gear pockets were milled using the machining parameters derived earlier when making the gear shaft cross-drilling fixture. The spindle microscope was again used to center the spindle over gear shafts. The final step will be to match drill the two pump ports through the crankcase side wall. The pressure input and scavenger output ports are bored and threaded for transfer tubes with banjo fittings that connect to the oil tank through flexible lines. These operations and the oil return passages still need to be done on my nearly irreplaceable rear crankcase section. I'll likely procrastinate, though, and start on the sump. -Terry


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## Davewild

Amazing work, I love it!!!

Dave


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## mayhugh1

The transfer tubes are the interfaces between the external flexible oil tank lines and the internal oil pumps. They provide a (hopefully) leak proof connection that can be adjusted at final assembly to route the oil lines free of interference to the rear of the engine. It might be tempting to rig up something quick and dirty here since they 
will eventually be covered up with a maze of tubing and wiring, but I like to pay attention to detail in hidden areas like this. My 9 cylinder used tubes similar the ones that I'm making for this engine, but changes are needed to accommodate a new cylinder design (similar to the one used by the Chaos guys) that I plan to use. I started with some 1/4" flare unions that I bought from a local Lowes. I cut off a pair of flares and turned spigots on one of their ends for soldering into the banjo fittings that I machined. The banjos and their locking nuts were all machined from a 1/2" thick brass block glued down to a piece of MDF. I added grooves on either side of the shaft holes in the banjos for a pair of o-rings to seal the oil path at the rotating joint. This is necessary because my modeling shows I have limited access for a wrench after final assembly to tightly torque the fittings to eliminate leaks. The tubes, themselves, were turned from some 303 stainless drops I had in my scrap box. The ends of these tubes are threaded and screwed into the pump body through the wall of the rear crankcase section. To insure perfect alignment, the oil pump and center bearing were temporarily assembled into the crankcase and the pump and crankcase were match-drilled and threaded. The crankcase wall was then bored to match the larger o.d. of the transfer tube body for added support for the transfer tubes which protrude outward from the crankcase. Since I was already machining on the rear crankcase, I decided to finish up the oil flow path through it. I machined two slots as low in the center crankcase section as I dared in order to move the oil from the front crankcase section as quickly as possible into the sump. I also drilled the holes for the oil sump. I was able to double the flow area into the sump compared with my 9 cylinder as this will be needed for an additional 9 cylinders. I'm relieved that this completely finishes the machining on the rear crankcase section. It is a very complicated part and screwing it up at this late date would probably be a show-stopper. 
I was able to do some preliminary testing testing of the oiling system by squirting oil into the intake transfer tube and manually spinning the crankshaft with the front crankcase and crankshaft sections added. Oil freely flowed out the oil ports in the front and rear master rod bearings. When I finish the sump I will block the rod bearing holes to make sure oil is finding its way to the front and rear bearings. - Terry


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## petertha

Can you elaborate on your technique of (I think) inserting solid bushing material into the aluminum blank, then some in-between part machining steps, then eventualy finish drilling final holes in the bushings. 

I have a hunch its so you dont have to insert a finicky finished bushing 'ring' into a hole & thus maybe better dimensional control between shaft centers, is that it? Is the bushing material locktited in the aluminum?


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## mayhugh1

Petertha,
 Yes, you're correct. Pressing in the slug first eliminates any chance of distorting the finished bushing (if pressed in) or getting it off center (if slip-fitted and Loctited). My technique is to square up one corner of the rough workpiece so I can accurately touch off x=0,y=0 and then locate and drill/ream the holes for a light press-fit of the bearing slugs. I do Loctite them in place. After an overnight cure I re-find my zero reference and then machine the bushings in place. It isn't a big problem if the part has to be re-referenced for the machining since if the bearing ends up a few thou off center from the slug, it won't be noticeable either cosmetically or functionally. The part always looks better than if the finished bushing is fitted since the Loctite fills in any imperfections between the slug od and the workpiece id and after being fly-cut the workpiece looks like a single piece of metal. - Terry


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## mayhugh1

The oil sump on my 9 cylinder was a major pita because its construction included being permanently soldered to the crankcase before verifying the completed assembly was leak-free. Some who have built this engine have come up with ways of making it detachable, but at the end of the day more points of failure were added and the result didn't look clean.
My original vision for the sump on this engine was a nice cylindrical body with hemispherical ends - one of which would be unscrewed to drain the sump. My CAD modeling, however, showed this was not going to happen. The front of the sump is up against the lower front-row cylinder while the rear of the sump is very close to the intake pipes. The minimum body length is set by the locations of the pick-up and drain tubes in the rear crankcase section and these are fixed by the geometry of the crankcase. So, there isn't room for my spherical ends. After assembly there will be no access to either end of the sump which means the drain will have to be located at the bottom of the sump. The Chaos Industries realistic-looking cylinder/head design that I want to use further complicates the sump design and even affects the final assembly of the engine in this area. I've carefully studied the 500 online photos of the Chaos engine construction, and there is not a single photo showing a sump. They may not have used one, and this may be one of the reasons they opened up their main bearings to create a single common volume for the oiled components within the engine. 
The sump design I came up with is shown in the photos. It consists of six individual pieces. The drain plug screws into a bung which was soldered to the bottom of the main body. I cut an o-ring groove under its head to seal against leaks. A socket head set screw was embedded into the head of the drain plug so a small hex wrench can be used to access it. There won't be any room for my fingers in this area after the engine is assembled because the drain plug sits in between the intake and exhaust pipes of the front row bottom cylinder and, in fact, nearly touches them. My modeling shows that removing the plug will probably be awkward even with the hex wrench. I added a magnet to the inside end of the drain plug to collect ring debris during break-in as I did with my 9 cylinder. The front of the sump body is angle-cut to clear the compromise envelope of the cylinder/head combination that I plan to use. The narrowed area in the center of the body is needed to clear the flanges of the adjacent rear row cylinders when they are inserted into the crankcase over their studs during assembly. I didn't have room at the rear of the sump for my hemispherical end, but I was able to make it elliptical. It is an o-ringed screwed-on part rather than soldered just in case I ever need to get into the sump to clear a blockage. The bung for the drain plug was soldered onto the bottom of the body with high temp (Sn5-Pb93-Ag2) solder. For good measure, it was also pinned with two 1/16" dowel pins. The pick-up and drain tubes are threaded into the crankcase and then the sump body is soldered to them with low-temp solder. This step permanently connects the sump to the crankcase. The threads were sealed with thread locker before soldering.
In my limited experience with soldering I have learned to use activated rosin flux with my soft solders and to design my parts so the solder can inserted between the pieces before heat is applied. I try to never hand feed the solder as this usually ends up needing lots of post clean-up. Even so, because I didn't have any small gage high temp solder I got some unwanted wicking when I soldered the bung onto the sump body. I ended up spending an hour under a microscope with a tiny needle file cleaning this up and blending the fillet around the saddle area. The drain and scavenger tubes didn't need any clean up after being soldered to the sump body with low-temp solder. The last photo shows all the components of the completed oil system installed into the rear crankcase section. I plan to start working next on the cam ring assembly for the front cylinder bank. This shouldn't require much new design work as it will be nearly identical to the one used in my 9 cylinder. - Terry


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## mayhugh1

For the remaining internal parts I plan to start under the front cover and work my way toward the distributors at the rear of the engine. I'll leave the master/slave rods to the end as they'll just be in the way as I test each completed subassembly driven by the crankshaft. 
My first step is to machine the cam disk(s). The front one should be straightforward as it's identical to the one in my 9 cylinder. I'll machine the front and rear cam disks at the same time since the setups will be identical. I had to re-make the fixture I used to mill the cam profiles for my 9 cylinder since it seems to have already been re-appropriated for another project. The intake and exhaust lobes are machined on their own separate rings on the cam disk. I'm using the "Patterson" cam profile that was recommended for my 9 cylinder. Basically, it is an equal acceleration/deceleration ramp profile with symmetrical lobes equally spaced around the perimeter. The separation between exhaust and intake lobes is 216 (crank) degrees while the intake/exhaust durations measured at .006" valve lift are 208/248 degrees, respectively. The only difference between the front and rear cam disks is that the exhaust lobes are on the top ring of the front cam, while they are on the bottom ring of the rear cam. The cam for the front row of cylinders rotates in a direction opposite to the cam for the rear row of cylinders, and both are geared to rotate at 1/8 the speed of the crankshaft. 
The cam disks begin life as slices of 4140 thick-wall tubing that I salvaged from a scrapped oilfield pressure vessel. I annealed the drop and then sliced off two 1/2" thick disks. The disks were chucked into a lathe and the bearing faces were machined. These faces were polished as they will ride against surfaces that were machined into the front and rear bronze bearings. The centers are then bored out to later accept a ring gear. The parts were flipped around in the lathe chuck and a second bearing surface was machined on each disk. Delrin retainers will bear against these surfaces to hold the cam disks in place as they are driven by jackshafts which, in turn, are driven by integral gears machined into the crankshaft.
A fixture holds the disks in place in the mill vise while the cam profiles are milled into the rings. The rings, themselves, are only .093" wide and .060" apart. I created full models of both the front and rear cam disks in SolidWorks in order to keep my own confusion to a minimum. I generated the lobe profiles by manually entering the lobe heights for each degree of rotation. Four g-code programs were generated so the profiles could be milled on both sides of each disk. In order to maintain the workpiece reference when the disks were flipped over, a tiny hole was drilled through each disk and into the fixture at the 0 degree position before the first profile was run. When the disk was flipped over for the second profile, a pin was inserted into the cam disk and into the fixture to maintain the 0 degree location. A shallow oil groove was machined across the bearing surfaces that mate with the bronze bearings.
While machining the front cam profile I stumbled across the same bug in my CAM software that I ran into more than a year ago when I machined the cam profile for my 9 cylinder. I eventually found a work-around, but the 9 cylinder cam was gouged slightly and had to be re-made from scratch. When I saw the exact same gouge on my new front cam I couldn't believe that I had forgotten about my work-around. Now I have two identically spoiled parts in my scrap box. 
After machining, the disks were heat treated to restore the hardness of the 4140. I sealed the disks in stainless foil wraps filled with argon to eliminate scaling. They were then heated to 1550F for one hour, quenched in oil, and then tempered at 500F. The Rockwell hardness should be somewhere around 50. After heat treating, the bearing surfaces were cleaned up a thousandth or so on a surface grinder and the bearing surfaces were re-polished. The open ring design evidently helps to reduce warpage during the quench as I was expecting the part to twist several thousandths.
The cam disks were finished by pressing in the ring gears which drive them. A commercial internal gear was purchased, modified, and lightly pressed into the center of the cam disk. Loctite bearing retainer was used to maintain the assembly. -Terry


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## rcfreak177

I'm loving this build as I did with the 9 cyl radial.

The stainless steel bag and argon method is a great idea to avoid carbon scaling, might have to try it some time. Thanks for the tip.

keep up the great work, I have found this build very detailed and have learnt lots of little tips and tricks. Much appreciated.

Baz.


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## mayhugh1

The cam retainer and some hole additions to the front main bearing will finish off the internals of the engine under the front cover. The cam retainer supports a jackshaft which connects the cam to the crankshaft. The integral gear that was cut into the front crankshaft meshes with the top gear on the jackshaft. The bottom gear on that shaft engages the ring gear now integral to the cam. The result is that when the crankshaft spins, the cam is driven at 1/8 speed in the opposite direction. The retainer also keeps the bearing surface of the cam disk against it's mating surface on the front main bearing. 
An important requirement of the retainer comes into play during final assembly when the relative positions of the crankshaft and cam are being adjusted to synchronize the valve timing to the position of the piston in the cylinder. In order to do this the jackshaft has to be pulled forward to disengage the ring gear without disturbing the position of the crankshaft in order for the cam to be rotated. Done by trial and error, this is repeated as necessary until measurements show an optimum compromise position is found. This means the retainer plate will need to come off the main front bearing several times. On the front crankshaft there is an integral shoulder which bears against the inner race of the ball bearing in the front cover to set the thrust clearance for the front crankshaft section. The position of this collar on the crankshaft is, by design, sufficiently forward to clear the top gear on the jackshaft when the jackshaft bottom gear is disengaged from the cam ring gear. The inside contour of the front cover was designed to accommodate the position of this shoulder as well as the retainer plate, itself. In my 9 cylinder there was a similar retainer. Three spacers secured it to the front main bearing. Because of the close meshing of the two sets of gears and the precision fit of the jackshaft to its bearings, these spacers could not be interchanged without creating a bind. Rather than open up the bearing or gear clearances, I uniquely marked each spacer so they could be returned to their proper locations during assembly/disassembly. In this engine I'm machining these spacers integral to the retainer plate to eliminate this problem and to simplify the timing adjustment a bit. I've been thinking ahead about the rear cam and, as will be seen later, integral spacers will definitely be helpful back there.
The retainer starts out as a 1" thick block of aluminum with a bearing bronze slug Loctited and pressed into it. This slug will become the bearing for the top end of the jackshaft. Three arms are machined at the outer periphery of the retainer. These arms will hold Delrin bumpers to keep the cam disk from moving more than a 3-4 thousandths away from the main bearing. The integral spacers set the height of the retainer plate from the main bearing. This height, in turn, sets the jackshaft thrust clearance to about .010". Nearly all the machining for the retainer was done from the same side of the workpiece so it was simply held in the mill vise. All features were roughed and finished in two separate operations before drilling the holes. The retainer was then flipped over and the counterbores for the SHCS mounting bolts were bored. This allowed me to mount the semi-finished retainer to the front main bearing for final machining. 
The front main bearing was mounted to its original machining fixture on the mill, and then the retainer mounting holes were drilled and tapped. The retainer was then attached to the bearing with its mounting screws, and the retainer plate was faced to its final thicknesses. The hole for the jackshaft was then drilled and reamed through both the retainer and main bearing. Delrin bumpers were turned and pressed into the three flat bottom holes at the outer arms of the retainer. Their lengths were adjusted for a .004" clearance to the top surface of the cam disk. 
The jackshaft, itself, was turned from 303 stainless. I noticed from the Chaos Industries photos that they milled small oil grooves into the jackshaft to promote oiling in the close-fitting bearing at either end of the shaft. This was not a feature in my 9 cylinder plan set but sounds like a really good idea, and so I included it here. The gears were sliced from left-over stock that I had machined for my 9 cylinder. They were pressed/Loctited into position on the shaft and then pinned with 1/16" dowel pins. The final result was that the cam turns freely with no hint of drag or bind when the crankshaft is manually spun in the front crankcase assembly. The next step is to tackle the much more challenging retainer for the rear row of cylinders. - Terry


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## ozzie46

Your doing amazing stuff here. Thanks for sharing.

Ron


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## John Rus

Fabulous work there mate. :bow::bow::bow:

Everytime I look at this thread it keeps raising the bar higher and higher on my V16! If it wasn't for people like you I would probably never design or build a engine half so nice!

Regards,
John.


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## don-tucker

This is indeed wonderful work,makes my steam engines seem like toy town,I usually turn my nose up at ic engines and Cnc but you have made me sit up and take notice,an inspiration
Thank you
Don


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## petertha

2 questions Terry

Re the 4140 cam disc, you mentioned sourcing from oilfield pressure vessel, annealed, sliced, machined, then heat treated @1550F, oil quenched, temper @ 500F 'to restore the hardness of 4140'. 
- was the first stage (annealing) because it was originally in some other hardness state from its oilfield purpose?
- ie if you happen to have stock 4140, would it be just slice/machine, then harden?
- out of interest, does this exceed what Hodgson plans call for? Ive seen so many ways of going about this on model engines ranging from nothing to case harden to what looks like cadillac here

Re the bronze bushing slug technique again, what is your recipie in terms of OD/ID fit & locktite PN? Any recipie difference between aluminum vs steel as the parent metal? Ive always been scratching my head how thin wall bushings could be pressed into connecting rods & such without distorting, but I now I know better - a better technique with a slug.


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## mayhugh1

petertha said:


> 2 questions Terry
> 
> Re the 4140 cam disc, you mentioned sourcing from oilfield pressure vessel, annealed, sliced, machined, then heat treated @1550F, oil quenched, temper @ 500F 'to restore the hardness of 4140'.
> - was the first stage (annealing) because it was originally in some other hardness state from its oilfield purpose?
> - ie if you happen to have stock 4140, would it be just slice/machine, then harden?
> - out of interest, does this exceed what Hodgson plans call for? Ive seen so many ways of going about this on model engines ranging from nothing to case harden to what looks like cadillac here
> 
> Re the bronze bushing slug technique again, what is your recipie in terms of OD/ID fit & locktite PN? Any recipie difference between aluminum vs steel as the parent metal? Ive always been scratching my head how thin wall bushings could be pressed into connecting rods & such without distorting, but I now I know better - a better technique with a slug.



Hi Peter,
        The 4140 that I had was originally hardened for use as a high pressure cryostat. I was given a piece of that had been sawed off with an abrasive chop saw when the vessel was scrapped. I had to anneal it in my shop so I could work with it. When you purchase a length of 4140 from a metal supplier, it is most likely already in an annealed state. 
My 9 cylinder plan set called for hardening the cam rings to about R45 but did not specify anything about hardening the lifters. This would put all the wear on the lifters. Since there is only a small point of contact between the two in my version of the engine, especially since I was machining true hemispherical ends on the lifters, I decided to harden the cam on my 9 cylinder to about R45 and then hardened the lifters to about R50.  I decided to reverse it on this engine to put the wear back on the lifters instead of the cam. So I went to R50 on the cam and plan R45 for the lifters.
With respect to my "press fits" and "slip fits", I have to admit I throw the terms around carelessly. In my shop there is no more difficult measurement to make than one involving the i.d. of one part and the o.d. of another when dealing with diameters are greater than the limited pin gage set that I own and when a few tenths makes a difference. I like my slug bushing technique because I can be off several tenths to the tight side and then just use more pressing force without worrying about distorting something. I always use Loctite high temp bearing retainer for good measure just I case during the pressing operation I find out the hole was bigger that I thought. But it doesn't come without its own problems. If the hole is equal to or less than the diameter of the part you are pressing in and if the surfaces are finished properly and clean, the Loctite will start to set immediately from the heat generated by the pressing operation and so you have to be prepared to finish the pressing operation right now or the part will be stuck half way with no hope of recovery.
With something as precious as my cam disk assembly with a large number of hours invested in the cam and a $95 commercial ring gear I made sure I had what I called a slip fit. Qualitatively, what this meant was that I could snap the two parts together with my fingers. In fact, I practiced a few times before adding the Loctite. I was also standing beside my press with and ready to use it if things started going wrong. In this particular case there is so much surface area between the two parts that the Loctite will provide the same holding that a very tight press fit would provide without any of the distortion. I did some experiments several years ago with with this bearing retainer using different classes of fits and seeing just what it takes to bond and unbound two parts together and became a big believer in it. Another thing I've learned is how to tell if you achieved the perfect slip fit with respect to surface finish and cleanliness. The parts will set up up within a few few seconds - not to full strength, but enough that you can tell - within 5 to 10 seconds. If they don't, I put them in my welding rod oven (about 100F) for a few hours to kick off the cure. - Terry


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## petertha

Real good info, thanks. Your material usage caught my eye because I have a feeling there may be similar resources of suitable metal cut-offs via scrap/salvage shops in my (oily) neck of the woods. I'm not in that line of work per se but I have seen 4140 for example as being pretty common. But real important point noted - all depends on where it originated from &any  previous heat treatment. 

So what Locktite flavour would you typically use for bronze slug inside aluminum parent material & same question if steel parent? How about primers or whatever they call prep agents for certain Locktite PN's?


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## mayhugh1

petertha said:


> Real good info, thanks. Your material usage caught my eye because I have a feeling there may be similar resources of suitable metal cut-offs via scrap/salvage shops in my (oily) neck of the woods. I'm not in that line of work per se but I have seen 4140 for example as being pretty common. But real important point noted - all depends on where it originated from &any  previous heat treatment.
> 
> So what Locktite flavour would you typically use for bronze slug inside aluminum parent material & same question if steel parent? How about primers or whatever they call prep agents for certain Locktite PN's?



Peter,
      I use Loctite 609 if I have less than .0005" (radius, not diameter) gap and I use 620 if the gap is between .0005" and .0015". If it is more than .00015" I consider re-doing the part depending on the application and my cost in time or dollars. I use the same retainers regardless of the metals I'm joining. I don't use any primers but I finish the part's surfaces as though I were putting a shaft through a bearing. I clean and dry the parts with acetone before applying the adhesive. I'm also careful to clean the adhesive off any outside surfaces especially if the parts are going inside my rod oven for curing. Any adhesive left on an open air surface will cure to a very hard and difficult to remove crust when heated. Without heat, you can usually clean off the surfaces even after a 24 hour cure. - Terry


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## DICKEYBIRD

Dunno how I missed this masterpiece 'til now, kudos to you sir!  I want to express my sincere appreciation for the patience & time you've invested in sharing your build process and the many clear and practical tips you have presented here.

You have a gift for making extremely complicated operations look easy & within reach of the rest us hacks.


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## kvom

I used Loctite 620 on my locomotive axle shafts/drivers, and it's a  very strong hold.  I didn't measure the degree of fit, but it's a close sliding fit, probably about .001.  When I had to remake one of the axles, I heated the joint with an oxy torch, then pressed the axle out.  It still took a pretty strong press, and came out with a loud bang.  I don't worry about them coming loose.

With that degree of fit I found that it would being to set within 10 seconds; after that I couldn't move the joint by hand.


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## mayhugh1

Because there seems to be some interest in the technique I've been using to create bearings in a workpiece, I thought I would also show you what can go wrong. In preparing the workpiece for my rear cam retainer I pressed a bearing bronze slug into an aluminum disk. The slug was about .0004" over the hole size, and against my better judgement I decided to press it in anyway just to see what would happen. Both surfaces were mirror-finished and coated with Loctite 609. When I started the pressing operation I could tell it wasn't going well since the force needed was quite a bit more than I'm used to. Looking at the bottom of the workpiece when it was over, I could see that the bronze had galled the soft aluminum and had peeled and pushed it forward of the slug as it was pressed in. I normally would have immediately scrapped the workpiece at this point but I faced it to its final thickness on the lathe, anyway, hoping I might get lucky. The photo shows the poor result. You can see a slight gap between the bronze and the aluminum where the aluminum was peeled away from the boundary as the slug was pushed through. The Loctite was scrapped away at the same time leaving no hope of filling in the gap. The truth is, if the final thickness of the bearing within the aluminum were too be, say, 3/16" or so, it probably would have been OK, since the two materials are likely intimately bonded over such a thickness. However, in my case the bearing will end up in only about 1/16" thick aluminum, and so I scrapped the workpiece at this point. When done correctly, there will be no gap whatsoever between the two metals. Only a color difference will distinguish the boundary between the two. - Terry


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## Swifty

Could you not have bored it out slightly oversize and inserted a new piece?

Paul.


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## mayhugh1

Paul,
    You're right. I just didn't think of it. - Terry


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## mayhugh1

When I modeled the rear crankcase section of my engine from the Chaos Industries photos, I noticed the rear cam retainer was integrated with the engine's rear seal. In these Hodgson-style engines the rear seal is an o-ringed radial plate, just forward of the impeller, that isolates the engine's oiled parts from the fuel plenum. Everything forward of this seal is wet with oil and everything aft is wet with gasoline. I was concerned this combination would further complicate the cam timing adjustments for the rear row of cylinders, and so I included sufficient space in my rear crankcase section to keep these two functions separate. When I realized that machining the mounting spacers integral to the front retainer would simplify the front cam timing adjustments, I felt like this would also work well at the rear. So, I decided to also integrate these two functions since I'll end up with a much more interesting part to make compared with just duplicating the front retainer.
My (2nd) rear retainer starts out as a 1-1/4" slice of 3-3/4" diameter aluminum with a bearing bronze slug pressed and Loctited into position at the required distance from the center to eventually become the jackshaft top bearing. All features that need to be concentric can be machined from the same side of the workpiece, and so the first step is to turn a spigot to hold the workpiece while machining them. This spigot will eventually be shortened and become a hub with a lip seal for the crankshaft. After creating the spigot, the workpiece was turned around and chucked in a 5C collet chuck. Here, the final o.d. was turned and the o-ring groove was cut. I was then able to verify the fit of the retainer to the crankcase with the o-ring installed and the workpiece still on the lathe without disturbing the set-up. The workpiece was then faced to its final maximum thickness which includes the height of the integral mounting spacers. The through-hole for the crankshaft was bored as well as the pocket for the lip seal. While on the lathe, additional excess stock was removed from the workpiece in order to minimize cutting time later on the mill. 
The chucked part was then moved to a horizontal rotary on my mill and the center of the the part was located. The part was rotated about this center to bring the bearing slug to its 6 o'clock position. The three mounting holes were then spotted and drilled. The remainder of the retainer could also have been machined at this time; but with so much of the soon-to-become thin part overhanging the chuck, chatter would have been a problem. 
So, the semi-finished part was moved to a rectangular fixture plate with a matching set of tapped mounting holes. All the remaining features were machined except for the jackshaft bore. The part was then flipped over on the fixture, and the counterbores for the SHCS mounting screws were plunge-cut. Two additional non-penetrating holes were drilled and tapped for a puller that will be used to install/rotate/remove the o-ringed retainer from the engine. 
All that remained was to match drill and ream the jackshaft bore through the retainer and rear main bearing. This was done with the retainer and main bearing mounted together within the rear crankcase section and with the o-ring in place. The three mounting fasteners, themselves, can't be relied upon to accurately and repeatably locate the retainer on the rear main bearing. In addition, it isn't reasonable to expect the jackshaft to act as a locating dowel to help them find their proper positions as was done for the front retainer. This is because the radial forces of the compressed o-ring will cause the retainer to locate itself in the center of the crankcase bore. If the jackshaft bore in the retainer doesn't perfectly align with the bore in the rear main bearing, this force will have to be overcome when jockeying the retainer over the bearing and onto the jackshaft. This will make assembly much more difficult and perhaps even cause a bind. If the boring operation for the jackshaft is done with the parts inside the crankcase while the o-ring is compressed, this radial force can be used to help align the jackshaft with its bore in the retainer during assembly.
The jackshaft was turned from 303 stainless and is similar to the one in the front cam assembly. Because the top jackshaft bearing is somewhat shrouded from the oil windage, I'll later open up a port through the rear main bearing to encourage oil mist generated by the rear row of cylinders to enter this area and help lubricate the bearing through an oil groove cut into the top of the shaft. 
The jackshaft bore is the only unsealed penetration through the retainer and into the fuel area. The positive crankcase pressure vs. the expected slightly negative pressure in the fuel plenum means that a bit of oil may be pushed into the air/fuel stream rather than the other way around.
Delrin bumpers were pressed into holes in the retainer plate in a manner similar to the front. The lip seal will not be installed until final assembly to avoid damaging it during the remaining construction and fitting. After the rear cam subassembly parts were completed the rear main bearing was installed in the rear crankcase section along with the crankshaft. The jackshaft was installed on the rear main bearing and the o-ring was installed on the retainer plate. A pair of long SHCS were threaded into the puller holes and used to help install the snug fitting o-ringed retainer. It easily went down over the jackshaft whose running clearances are .001". The crankshaft still turned freely with with no drag or bind, and the cam disk turned smoothly as hoped. After verifying the fit and operation of the cam with the o-ring in place, it was removed it until final assembly. 
The next step will be to tackle the impeller. I really want to make a complex one with compound curved fins like the Chaos Industries version, but I'm not sure I can design one that can be cut in any reasonable amount of time on my Tormach. My 4th axis CAM capabilities are somewhat limited, and so I'll probably be in some deep water trying to make my CAD/CAM work. I plan to break up this 'skull' time with the machining of some of the more mundane parts like the tappets and tappet bushings. I need to make 40 each of these, and if the truth be known, I really don't like making more than one of anything. For some wondering why, then, I would ever get involved with this particular engine I have to confess that I never really expected to get past the crankcase and crankshaft. - Terry


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## kvom

Nice solution to clamping the crankcase to the table in one of the above photos.  I need to remember that one.


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## Tinkerer58

WOW what an amazing build and the skill and workmanship is mind blowing. I don't think I will live long enough to be able to obtain the same skills presented here. I don't know what else to say, I'm speechless for once in my life.th_wav


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## mayhugh1

An impeller is located on the rear of the crankshaft in the fuel plenum of this model engine. In some full-scale radials there is actually a supercharger in this area delivering a pressurized air/fuel mixture to the cylinders for increased power. In these model engines the impeller is usually not sealed to the walls of the plenum and is not spinning fast enough to generate any significant boost. It does, however, perform an important function by helping to keep the fuel mixture diffused in the plenum and limiting the amount of fuel that falls out of suspension. 
Making an impeller is an neat CNC project and is often used as a demo part to show off multi-axis mills. I made a rather simple straight blade impeller for my 9 cylinder model that was similar to the one in the original plan set. I designed mine with a fully filleted 3D profile to give it a nice finished look, but for this engine I wanted to do something special with more complexity. The complexity I added is primarily cosmetic and probably won't add any performance. In fact, all the extra effort will end up buried inside the engine, hopefully never to be seen again after final assembly. 
The impeller I visualized was one with compound curved blades. With blades curved both radially and axially, and the impeller would be reminiscent of some of the demo parts I've seen. As a test I managed to design a single compound blade in SolidWorks; but after spending many hours trying to generate the tool cutting paths with my CAM software, it eventually became obvious that a 5-axis mill was required. Since I'm only interested in parts I can make on my own equipment, I finally gave up on the compound blades. This decision reduced the mill requirement to only 3 axes and greatly simplified the machining. I settled on simpler curved blades that mimic those of a centrifugal pump. My design is similar to the Chaos impeller, but I axially profiled the blades to closely follow the profile of my plenum air guide just to add some challenge back into the project. There is only some .015" clearance between the air guide wall and the blades over their entire length. It's just possible with both of these features working together I might achieve a slight increase in air/fuel velocity through the plenum. With this impeller design, the total volume of the plenum greatly reduced, and the fuel path is primarily through the spaces between adjacent impeller blade pairs and the air guide wall. I also decided to reduce the number of blades from nine to seven. The real reason for this is that seven blades results in a spacing that allows me to use my Tormach .312" spherical profiling cutter to finish profile the entire impeller. I used this cutter (modified) earlier to finish profile the rear cover of this engine and it performed beautifully. I don't believe there is any real functional reason to match the number of blades to the number of cylinders. The intake duration is 208 degrees. With a nine blade impeller five blades will rotate across and partially block the intake port while the cylinder is filling with fuel. With a seven blade design only four blades pass by the intake port in the same amount 
of time. There's no issue with sharing of the air/fuel charge between two cylinders whose intake durations overlap since they are too far apart to be affected by either number of blades. My humble conclusion is that, if anything, the seven blade design may be marginally better than the nine blade design.
The impeller started out as a slice of 3-1/2" aluminum round. I began the machining on the lathe where I removed a good bit of excess stock which conveniently left me with a spigot. I turned the workpiece around and used the spigot to hold the part while turning all the concentric features to their final finished values. This included the final o.d. of the impeller as well as the bores for the crankshaft, a height locating step, and a clearance pocket for the cam retainer hub. The milling cutter needs access to the entire top portion of the impeller as it mills the finished profiles in the upper blade areas. Therefore, I milled a rectangular boss on the bottom of the workpiece, where I had left 1/4" excess stock, so the workpiece could be held in my vise during the milling operations. This boss will be removed later from the finished impeller 
using a mandrel to hold it in the lathe. In use, the impeller will be secured to the crankshaft with two grub screws 104 degrees apart, and so their holes were drilled and tapped on the still-simple workpiece before any milling was done. This required me to generate the blade profiling tool paths with my CAM with the workpiece is properly rotated to insure the holes actually end up between two blades. Before moving the workpiece to the mill, I began having second thoughts about the small clearances I was planning between the blades and the air guide. The interior profile of the air guide which is integral to the rear cover, was machined on my 9x20 CNC lathe using the same CAM software that I use on my Tormach. In the past when I have tried to match complex lathe and mill cut profiles on pairs of parts I was sometimes disappointed with results. I suspect that either I or my software is not always handling the lathe tool geometry properly, but I haven't done enough testing to fully understand the problem. Therefore, I decided to measure the existing internal profile of the air guide at some dozen points to verify its dimensions with those in my current CAD model from which the impeller was designed. The results were pretty close, and so I felt safe in starting the milling of the impeller. 
The first milling operation was a coarse waterline roughing operation which quickly removed the bulk of the excess stock. The second operation was a finer roughing operation with a smaller diameter cutter and smaller steps that left some .015" stock for a final finishing operation. This finishing operation was done with the .312" spherical profiling tool using cutting parameters I had already derived while machining the exterior of the rear cover. The profiling tool paths were generated for a .0003" maximum scallop, and this left a bright and smooth surface finish that needed no manual cleanup. The total run time was about 2-1/2 hours. The gripping boss was then removed by turning a mandrel and facing it off in the lathe. I verified the actual blade to air guide wall clearance with modeling clay since there was no other direct way of measuring it.
I haven't yet gotten to the tappets or their bushings since the impeller ended up absorbing all my interest during the past week. I hope to make progress on them while working up the design of the distributors which is my next step. - Terry


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## petertha

Fascinating stuff! 
Can you elaborate on your clearance. Is it the same (0.015") amount at the outer diameter ring edge (blue line) as along the curve edge blade profile (red line)? 

I just naively assumed gap clearance would have to be very small on something like this, so there is no pressure leak-off betwen individual impeller chambers. Kind of analagous to valve sealing. But I dont have a good grasp of impeller dynamics. Maybe pressure differences are very low to begin with & nothing really happens flow wise until any given inlet valve becomes open, then any adjacent chamber is going to 'feed' it? Is that the general principle?


>There is only some .015" clearance between the air guide wall and the blades over their entire length. It's just possible with both of these features working together I might achieve a slight increase in air/fuel velocity through the plenum.


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## mayhugh1

petertha said:


> Fascinating stuff!
> Can you elaborate on your clearance. Is it the same (0.015") amount at the outer diameter ring edge (blue line) as along the curve edge blade profile (red line)?
> 
> I just naively assumed gap clearance would have to be very small on something like this, so there is no pressure leak-off betwen individual impeller chambers. Kind of analagous to valve sealing. But I dont have a good grasp of impeller dynamics. Maybe pressure differences are very low to begin with & nothing really happens flow wise until any given inlet valve becomes open, then any adjacent chamber is going to 'feed' it? Is that the general principle?
> 
> Peter,
> The clearance I'm talking about is between the edge of the impeller blade (the red line in your drawing) and the air guide integral to the rear cover that fits down over this section of the crankcase. If you look back in my earlier post where I was machining the rear cover you'll see a photo showing the interior profile of the rear cover. This profile forms a smooth funnel-shaped volume which guides the air/fuel to the intake ports. I designed the profile of the impeller blades (your red lined ends) to fit up into this funnel profile and to clear it by .015" along the length of most of your red line.
> When a valve opens, then the pressure will drop and the 'chamber' over the intake port will feed the valve instead of the entire plenum. This may (hopefully) result in a bit higher velocity in the plenum or it may not. The numbers show that, even with only seven blades, 3-4 chambers will pass by the intake port during a 208 degree intake duration. - Terry


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## mu38&Bg#

Radial flow impellers require a high tip velocity in order to generate significant pressure. In this case running at crank speed (max 5000 RPM?) the pressure will be negligible. I was under the impression that most model engines benefit from the impeller by improving fuel distribution. If the carb flowed into a large plenum, fuel flowing on the walls would tend to fall to the bottom and make the lower cylinders run rich and the upper cylinders lean. I don't really follow model radial designs, is it typical to omit the diffuser for the impeller? I see a big chance for separation of flow on the leading edge of the intake port.

The machining is great on the impeller. I'm surprised to see a radius on the top of the fins, usually this is kept sharp. The photo doesn't really do it justice. If you 3D mill parts you'll know that the camera exaggerates the tool marks. The finish is much smoother than it looks. A swipe with 1000 grit paper should give a mirror finish.

I'd love to see a screenshot of the engine in SW. I just started using 2013.

Greg


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## mayhugh1

Greg,
Thanks for the comments. I know pretty much nothing about impeller air flow and so I hope I haven't messed up. I believe, though, from my research that the earliest versions of the Hodgson 9 cylinder had no impeller or diffuser and some of the early builders complained about hard starting and poor fuel distribution. The design was later revised with a half-size diffuser and then shortly after that it was changed again to a full-size (essentially an impeller) diffuser. This is the one I built for my 9 cylinder, and I had no starting problems and only a minor mis-match in upper/lower cylinder fuel distribution. The consensus among builders seems to be that the impeller performs better. I don't know what is being used in the 18 cylinder twin plan set. The Chaos Industries approach, though, seems to be a full-blown impeller/air guide approach which is what I'm trying to mimic. I don't know what their blade-to-air guide clearance is but I'd bet it's pretty close from studying their photos. I don't know how easily their engine starts; but they built two identical models and, according to the YouTube video, they run really well. - Terry


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## mayhugh1

Greg,
Here are some shots of my (ancient) 2007 SolidWorks model. The first is a complete model of where I'm at so far. The second is a sectioned model in the area of the rear crankcase where I've been working recently. I tried to rotate the impeller for this shot to show the blade profiles with respect to the air guide wall, but since they are curved there is no single section that displays it in any really meaningful way. - Terry


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## mu38&Bg#

That looks great. The diffuser in terms of radial flow compressors is a set of vanes around the impeller, or on a turbo a scroll. I didn't mean to imply the arrangement wouldn't run well. I was going to write something about that, but must have posted it before doing so. In terms of high speed power, the sharp inlet might not be the best, but these models rarely bench race.


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## ozzie46

Masterful work that is!!!   th_confused0052th_confused0052th_confused0052

Ron


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## mayhugh1

Before starting on the distributors, I thought I'd better tie up some loose ends and also tackle the tappets and tappet bushings. The first photo shows the completed rear crankshaft section which now includes the distributor drive gear. The gear was a purchased part, and it has a cross slot for a drive pin. Even though the distributors won't present any appreciable load to the crankshaft, I decided mate the slot with a dowel pin inserted into a cross-drilled hole in the crankshaft. I turned a pair of stainless steel spacers which slide onto the crankshaft on either side of the drive gear. I contoured the one between the gear and the impeller, and it is purely cosmetic. The one at the rear is pinched between the gear and a button head screw threaded into the end of the crankshaft and holds the gear tight on the crankshaft. Using a dummy distributor body I was able to determine the length of the distributor shaft that will later be required to properly mesh the drive gear with the pair of driven gears. 
The tappets, as expected, turned out to be miserable parts to make, and I had to make 40 of them. They're 3/4" long and 3/16" in diameter. One end is spherical and the other end has a beveled spherical recess. I carefully modeled the valve train components during my 9 cylinder construction, and I'm duplicating that geometry in this 18 cylinder model. I wrote a program for my 9x20 lathe which turned the spherical end and then allowed me a brief manual polishing interval with a Scotchbrite pad before it parted off the tappet to its final length. When I got underway, I was hand feeding 3/16" O1 drill rod through my 5C collet chuck 0.8" at a time and making a new part every 4 minutes. Due to the long stick-out, I used a very sharp cutting insert and took only .003" doc. However, this still left a tedious secondary operation on the other end. This end requires a spherical recess with a beveled edge. I'm sinking the pushrods a little deeper into the tappet than was specified by the H9 plan set. Another H9 builder wrote that he had experienced issues with his rods popping out of place, and so I sank mine a little deeper into the tappet and, to date, have had no issues. This deeper cavity, however, creates the need for the addition of a beveled top inner edge.The machining of this end of the tappet was done manually using the lathe tailstock. The process was 1) remove the nub left over from the previous parting operation, 2) spot drill the end, 3) rough drill the cavity to partial depth with a undersize drill bit, 4) finish recess by plunging a ball mill to final depth, 4) cut the inner edge bevel with v-cutter, 5) deburr the outer edge, 6) polish the recess with a Craytex bullet, 7) check o.d. fit with go-no-go gage, and finally 7) repeat 39 more times. Since the tappets are unsealed oil leaks, I want as close of a sliding fit to the tappet bushing as I can get. The valve springs are fairly weak, and so any bind or drag is a problem. To maximize consistency I made all my tappets from the same piece of Enco drill rod. The drill rod o.d. measured on the high side of 0.1875" but after the brief polishing, the tappets were consistent sliding fits to the gage I made with my +.001 reamer. This is the same reamer that will be used later to finish the i.d.'s of the bushings. Several test parts had to be made to get the spindle speed optimized for the best possible finish from the ball mill at the bottom of the recess. I took some microscope photos because I was curious about the surface finish at the bottom of the recess. Even though, to the naked eye, the finishes on both ends of the tappet are brilliantly mirror-like, the high power photos show a somewhat different story when viewed close-up. I hardened the tappets to about Rockwell 55. My original plan was to make them a bit softer than the hardened cam; but an article I recently read recommended that the lifters be 5 to 10 points harder than the cam because, being smaller, they absorb more heat abuse and wear. (The author was referring to automotive applications which may or may not apply to model engines.) After heat treating, to my dismay, the o.d. of every tappet at the recess end had swelled slightly and would no longer slide easily through my gage. I had to spend a few more hours carefully polishing the (now hardened) o.d.'s of each one back down a few tenths to its original dimension. While I was at it, I made a tiny spherical wooden lap and polished the recess of each tappet with 600 grit valve grinding compound. In total, I spent some 15 hours of mind-numbing work on that little pile of parts. Even though the mirror finish in the recess was now even more brilliant than before, there was little change in the view through the microscope.
The phosphor bronze tappet bushings were not so bad. I broke the machining of these parts up into two steps. I turned the o.d., added a cosmetic bevel on the outer edge, and then parted off the bushing with one scratch written lathe program. The o.d.'s were carefully controlled as I wanted to insure a Loctited slip fit into the crankcase to avoid any chance of distorting the i.d.'s. After creating all the semifinished parts, I then re-chucked each part and used the tailstock to manually spot/drill/ream the i.d. of each part. The i.d. of each bushing was verified using a worst-case completed tappet as a gage. I didn't combine these two operations because I was afraid the hole center would wonder around since the previous drilling operation would end up creating the drill spot for the next operation. With my equipment, history has shown that the reamed hole would then likely end up inconsistently oversized after running the first few parts. The bushings were finally Loctited into the two crankcase sections. I'm going to have to start interspersing these tedious high volume parts among the more interesting one-off parts to keep from getting burned out during this project. Unfortunately, most of them won't be defined until I get to the heads and then suddenly it's 40 of nearly everything. - Terry


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## mayhugh1

Another smaller batch (10 pieces) of parts that I can make at this point in the construction are the compression nuts that are used to support the intake pipes in the fuel plenum in the rear crankcase. Initially, it wasn't clear to me from the Chaos photos how these were used. They didn't seem to be pipe threads nor did they use ferrules or flares. I eventually decided they must compress a rubber o-ring through which the intake pipes pass. So, I threaded the nine bosses in my rear crankcase section with simple 1/2" fine threads. The nuts in the Chaos photos look to be brass to match the tubing they used for their intake pipes. I'm still planning to use stainless steel tubing, and so I made mine from some (questionable) 303 stainless I had laying around. I'm using drops that I think were left over from the material I used to machine the valves for my 9 cylinder, but this particular material doesn't seem to turn like the free machining stainless I've used in the past.
This part was particularly interesting because my plan was to write a single lathe program that would turn, groove, thread, and then part off the nut after I had manually reamed the through-hole for the tube. A simple milling program would then cut the hex head, and the part would be completed.
The program was easy to construct and called three tools: a turning tool, a parting tool, and a threading tool. This was actually to be the first time I've used multiple tools in a single lathe program because it seems I'm always trying to keep a thousandth accuracy in my lathe parts, and my inexpensive tool post is just not that consistent. Even though the tool compensation software within MachTurn - my lathe control program - should easily be capable of handling the task, I had no end of problems with re-referencing each new workpiece. The software seemed to be 'remembering' the tool's work-offsets from the previous run. As a result, the whole batch of parts took longer to make that if I had just machined them manually. And, I never did figure out what I or the software was doing wrong. Also, midway through the batch of parts, I broke my next-to-the-last parting insert and had to start sawing off the semi-finished parts in the lathe chuck. This run of bad luck really broke up the nice workflow I was hoping to achieve. I eventually ended up with a dozen parts which includes three spares. I used my toy USB microscope to get a close-up view of my suspicious material in the root of the threads and was happy to see no tearing. If you look closely at the crankcase photos with the nuts installed you'll notice the axes of the fuel pipes will not intersect the diametrical center of the crankcase as they did with the 9 cylinder engine. From the Chaos photos It can be seen that this is necessary to avoid interference between the rear cylinder row pushrods and the two-into-one 
intake pipes. Incidentally, it might also provide an improved transition for the air/fuel entry from the plenum to the intake pipes.
While I was in a batch building mode I decided to do what work I could on the pushrods. Of course, forty of these are needed. Although I'm expecting them to be the same length as those in my 9 cylinder, I can't be 100% sure since I haven't yet designed the heads. For safety, I machined the spherical head on only one end and left them all about .200" longer than my 9 cylinder rods.
This wraps up the all the high volume parts that are sufficiently defined at this point in the project, and so now it's back to the more fun and interesting one (or two) offs. 
The last photo is an entrance I made to our backyard during my wife's and my seven summers landscaping project behind my shop. (I sometimes like to work on big 
metal projects also.) I welded it up totally from scrapyard steel, and I cut the art panels on my plasma cutter. - Terry


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## John Rus

I'll probably be in a coma by the time this is finnished. :big:

So excited to see this run!
John


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## mayhugh1

I just realized that I forgot to mention something in my earlier post about the tappets that I had made. Although the end that mates with the pushrod does have a truly spherical recess to match the spherical end of the pushrod, the other end that rides on the cam ring is not truly spherical. A comment by Petertha on another thread about the potential issues at the contact point of such an interface got me to thinking about the problem. I actually turned a slight partial elliptical surface on the very end of the tappet to add a bit more contact area to the interface with the cam. The purpose of the microscope photo of the convex end was to show this. It, in fact, comes across looking like a "hole" in the very end of the tappet in that photo. - Terry


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## mayhugh1

I've been out of town and at my son's wedding for the past five days. When I returned, I decided to resume construction with the connecting rods instead of the distributors because I may have some unfinished machining to do on the main bearings. I may have to cut some additional openings in some of the main bearings to help with assembly of the crankshaft sections when the rods are installed, and I'd like to tie up those loose ends. I'm having trouble visualizing an order of assembly without the actual pieces in my hands. A lot will depend on whether the rod assemblies can be assembled onto the crankshaft sections outside the engine and then inserted in the crankcase sections or whether everything has to be assembled within the crankcase as was necessary with my 9 cylinder.
I started with the slave rods and a goal of 20 completed parts. I designed my own rods for my 9 cylinder engine, and I'm using the same design here. These rods have the maximum possible amount of material in their stressed areas and a worst-case .020" minimum clearance to other components of the engine when running. I gathered up all the half-inch known 7075 (approx. 75% higher strength than 6061) aluminum plate I had on hand; and, with no screw-ups, I should have just enough for the job. I very much wanted bronze bearings at each end of the slave rods, but doing so would have compromised their strength especially at the master rod end because they would have replaced significant amounts of high strength aluminum in critical areas.
I used the CNC program that I had previously developed but with a few minor tweaks to nest the parts among my scrap plates. Four arrays of either four or eight rods were machined at a time. The holes at either end were first drilled and reamed, and then the top halves of the rods were completely machined with roughing and finishing passes using 1/8" cylindrical and spherical cutters. I then glued the perimeters of the rods to their workpieces before flipping them horizontally in the machining vise and running similar machining operations on the opposite sides. These bottom-side operations cut the rods free from their workpieces leaving only the cured epoxy gel to hold them in place. The parts were finally released free of their workpieces by heating them to about 175F with a heat gun.
Due to the fairly complex cross-section and filleting, the total machining time for all the rods was about 20 hours. The spindle speed using my Tormach Speeder was 13k rpm, and this allowed me to use feed-rates up to 25 ipm. Without the Speeder the machining time would have been close to 60 hours, and I likely would have opted to greatly simplify and (maybe) compromise) the rod design.
It's with this part that the enormity of this project has struck me. It's one thing to need 20-40 pieces of something requiring 10 or 15 minutes of machining time each but quite another when the required machining time for each part is an hour or more.
After the parts were free of their workpieces I made a simple fixture to support them while oil holes were drilled at each end. These holes actually have tapered lead-ins to encourage oil entry and so their sectioned profiles look like tiny funnels.
The resulting offset between the top and bottom finished sides ended up being nearly zero along the y axis but was about .002" along the y axis. I planned on leaving the rods 'as machined' since they are internal to the engine, and the offsets gave them a realistic 'cast' appearance. But, I couldn't leave well enough alone and eventually polished out the offsets as well as the machining marks.
The next step will to be machine the master rods. Fortunately, I need only two of these. - Terry


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## petertha

Your epoxy backfilling technique is neat! 
PS, I noticed you used a disposable syringe for spooge injection. I've probably done about 40 lineal miles of fillets & joints for RC composite layup work. A good (cheap) alternative is a Ziplock baggy. Put the epoxy premix into a corner, snip the end to desired 'nozzle' size, purge any air, then squeeze a controlled amount, similar principle to those cake decorator thingy's.

I've been paying attention to how various radial engine link rods are configured on their ends. I noticed many don't use bushings, they seem to rely on the aluminum (lubricity?) itself & sometimes in conjunction with oil holes. Yet in a typical commercial RC engine, its rare to see anything but bushing inserts. Maybe its an RPM thing? 

 I'd like to hear your design comments on the oil passage hole because I've noticed engines seem to vary a lot between no holes, to a single axial hole, to 2 holes at 45 deg either side of centerline, sometimes staggered... and even the occasional slit vs. hole. Mind you, I've confined my mental data-basing to methanol fuel with pre-mix oil.


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## mayhugh1

Peter,
     Thanks for the tip on the epoxy applicator. 
 Your question on the oil holes is a good one, and I have pretty much the same question myself. I think splash lubrication of the wrist pin end of the rod (the so-called small end inside the piston) is probably sufficient without adding any type of hole. I say this because in my past I restored several Mustangs for myself, and this included two engine re-builds. One was a 289c.i. 1966 fastback. The rods on that engine did not have bearings on the small end but did have an oil passage for oil. When I purchased replacement rods for the rebuild (bearings had spun on big end) I noticed that there were no oil holes on the replacement rods from Ford. When I asked about this I was told that Ford engineers had determined that the holes did nothing and so they dropped them from later production. I also cannibalized a lawn mower engine recently and there was no oil passage or hole there either.
I've seen examples of model engines that relied on splash lubrication for both ends of the rods -Steve Hucks' recent Demon V8 for example. I don't see any reason why a radial would be any different at the small end. On my two engines there is about .025" clearance between the small-end rod sides and the internal piston boss which means there is .050" of exposed wrist pin within the piston and this seems like plenty enough area to collect oil for capillary action to draw oil between the wrist pin and the rod.
On the other end of the rod, though, there is only a thousandth or so clearance between the sides of the slave rods and the carrier portion of the master rod in my two engines. I think an oil hole on this end would probably enhance its lubrication since it would probably take considerably longer for oil to wick into the interface between the rod and the shaft on this end compared with the wrist pin end. -Terry


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## rcfreak177

Terry,

Great tip with the glue on the connecting rods, I must have broken over a dozen end mills using this method without the glue to support the part, not to mention scrapped many parts as well.

Thanks heaps, I will try the method you use.

Baz.


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## kvom

Rather than a 20 hour 3D 2-sided mill job, it seems that a 2.5D job followed by turning the shafts on the lathe would have worked.  But then we wouldn't see this technique, which is "cool".


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## mu38&Bg#

It's very common to find unbushed little ends in RC engines. The motion is an oscillation, so the requirements are different than the big end. Many engines also have unbushed big ends if they can get away with it. The bushing weakens the rod end and increases cost. Oil holes in engines is almost like religion, but several methods work. Seeing as both ends oscillate in a radial and the speed is low, as long as there is some oil present it will be fine. In a high speed big end fresh oil is important in cooling and lubrication because the the oil shear is very high. Even the clearance between journal and placement of oil holes can be critical in extrmely high performance engines.

I think I would have redesigned for an I beam rod if I was going to build this. I try to cut machining time down to a minimum, even if it's just the CNC turning the wheels. Because I don't have quick change tooling, I use corner radius endmills to do milling and contouring without tool changes. It's always interesting to see different methods. I might have to try the epoxy on an upcoming project.

Greg


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## mayhugh1

The machining of the master rods began with two 1" thick drops of 7075. I bored a hole in each one where the crank pin center will end up, and there I Loctited a slug of SAE 660 bearing bronze. The diameter of the slug was chosen to leave a minimum .065" of aluminum around its outer perimeter (for strength) after the clearances for the slave rod ends were milled.<BR>The scrap extrusions I used for the slave rods were remarkably flat (few tenths), and so I didn't need to face them in preparation for mounting in the mill vise. The faces of these drops, however, were out of parallel by several thousandths, and so I began by machining their sides parallel. While I was at it, I finished their thicknesses to those of the finished rod widths.
The next step was to spot, drill, and ream all the holes. The center of the crank pin bore was then used to reference the part for all subsequent operations. The top sides of both rods were roughed and finished to one-half the rod's thickness and then back-filled with the epoxy gel. I tried Peter's 'cake decorator' suggestion for dispensing the epoxy into the narrow slot around the semifinished part, but this particular gel was just too thick to flow under the hand pressure I was able to exert on the polyethylene bag.
After letting the epoxy cure overnight, I flipped the parts over and machined the opposite sides using programs that were similar to those I created for the tops. Due to the large size of these parts, though, the outer perimeters were initially cut to a depth that left a .015" thick aluminum web connecting the part to its workpiece. This web helped support the part under the subsequent heavy roughing cuts. The roughing and finish machining was completed before a final perimeter pass was made to cut the rods free of the workpieces. As before, a heat gun was used to cleanly release the parts from the epoxy.
The semi-finished rods were mounted to a horizontal rotary under the mill spindle, where the clearances for the slave rods were milled. Watching the rotary turn back and forth as corner material was removed at various acute angles inside the perimeter of the rod was a lot of fun but also nerve-wrecking, especially on the first part.
My method for retaining the slave rod pins within the master rod assembly is a pair of 2-56 set screws bearing against flats milled into either end of the pins. The holes for these screws were 
drilled while the parts were on the rotary and later tapped by hand. Two screws each may be over-kill but that's just me.
For some inexplicable reason I used a known oversized reamer in my shop to ream the pin holes in both the master and slave rods. With the on-hand 3/16" drill rod I was planning to use for pins, my reamed holes are now .0025" oversize. The maximum I'll accept for this clearance is .001" with .0005" being ideal, and so the next step is to work on the pins. - Terry


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## DICKEYBIRD

mayhugh1 said:


> For some inexplicable reason I used a known oversized reamer in my shop to ream the pin holes in both the master and slave rods.


Wow, I'll bet some salty new phrases were coined after that one!  Whatever affliction causes that kinda problem is alive & well in my shop too and when it happens I literally have to force myself away from anything throwable.

I'm sure you'll come up with a fix that'll be good as gold!


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## gadabout

Terry, maybe you could go to 5mm pins, thats only 6.9 thou up from where you are at present

Mark


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## petertha

mayhugh1 said:


> My method for retaining the slave rod pins within the master rod assembly is a pair of 2-56 set screws bearing against flats milled into either end of the pins. Terry


 
Will you access the set screws with a typical 90-deg allen key from the front & rear at the assembly stage once the link rods are on the pins, or through a cylnder hole in the crankcase, or?

What are your thoughts about locktite on the setscrews?


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## mayhugh1

Peter,
The set screws will be accessed radially through the cylinder holes in the crankcase. I probably won't use Loctite here as I don't think it's needed and will just make disassembly more difficult if it is ever required. The set screws are 1/8" long, resting on flats, and aren't under any significant moments trying to loosen them. 

Mark,
Great suggestion.

Terry


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## mayhugh1

A seemingly simple solution to the pins for my over-sized holes is to just turn them to the correct diameter from over-size drill rod. My personal experience, though, is that to get the accuracy I'm looking for I would have to uniformly polish off the last thousandth over the entire length of each pin. I'm OK with doing that for a few parts but not for some nearly 40 pieces.
Mark's suggestion of switching to 5 mm drill rod and re-reaming the rods is an excellent solution that just didn't occur to me. I would have taken his advice if, by the time I had read his comment, I hadn't already started down a 'different' path. 
While searching through the MSC website I discovered it is possible to buy individual gage pins in practically any diameter. Even more remarkable, at least to me, is the fact that they actually stock them and in large quantities. For a little over $25 including my expires-tomorrow free shipping coupon, I was able to buy enough gages of the exact diameter (.190") I needed to make the 34 pins I need plus spares.
I received the gages and found they were, indeed, a highly polished and perfect fit. The only problem, of course, was that they were harder than the back of Superman's head. After some experimenting, I found I could anneal them to a reasonable state for machining using a soak at 1475F for 1-1/2 hours followed by a slow furnace cool-down. After annealing, they machined somewhat like air hardening drill rod - maybe a bit harder - but they did tend to work-harden with timid feed rates.
I needed two types of rod pins: one for the master rod assembly end and one for the piston wrist pin. The pins at the master rod end have a pair of milled flats for the set screws and a shallow 2-56 tapped hole at one end for temporarily attaching a simple installation tool. The piston wrist pins are full floaters with soft aluminum buttons (rivets) pressed into either end. This wrist pin design is from the H9 plan set and is what I also used on my 9 cylinder model. After pressing in the rivets, the soft ends were machined with a radius matching that of the cylinder. 
All lathe operations but one were done manually rather than with CNC due to the large number of set-ups involved in dealing with each pin. Machining the pins from 2" long gages instead of a single length of drill rod significantly increased the total lathe time. Since the ends of the gages were ground at an angle (probably to aid their entry into the hole under measurement) they had to be faced. The flats on the master rod assembly pins were manually milled together using a simple holding fixture. The radii on the soft ends of the wrist pins were turned using a simple program on my 9x20 lathe.
The wrist pins were the most tedious parts to make and were worse to deal with than the tappets. My 1/8" drill bits all drilled oversize and would not give me an acceptable press fit of the rivet, and so I had to wait several hours for a Loctite slip-fit adhesive to cure on each end before machining its radius. And, because the un-machined rivet heads started out with a diameter larger than that of the pins, the un-machined ends would not fit into the lathe chuck. So, only one end could be Loctited, cured, and then machined per session. The total machining time for each wrist pin averaged about 45 minutes and had to be spread over a couple days to allow for two curing cycles per pin.
Using the gage pins was an interesting exercise; but, in retrospect, Mark's suggestion was a more practical and much more economical solution. The annealed gages remained hard enough to dull two HSS drill bits, two HSS center drills, and a carbide parting insert over the course of making some 45 parts which included several rejects and a few spares. Looking for a positive, though, the finished parts didn't need to be heat-treated. Using the parts I've made so far I was able to sketch out an assembly process that I think will work with the way I've divided up the crankcase and crankshaft. I've had my fill, though, of these high quantity tiny tedious parts for a while and am looking forward to finally getting on with the distributors. - Terry


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## Rivergypsy

Very nice work ;D


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## necchiom

Amazing!  With compliment!


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## mayhugh1

This distributor design is one that has evolved over my last three engines. My requirements for a distributor have always included not only a realistic appearance but a high level of reliability especially with respect to the Hall-effect trigger. In this design the Hall device is safely tucked away inside the bottom of the main housing and is shielded by a 'cage' created by the aluminum main housing and the brass trigger disk. For additional protection a dielectric spark shield is located between the Hall trigger and the lightning storm going on above it. 
The Hall device can be rotated around the center axis of the distributor up to 30 degrees and then locked down even after the distributor is assembled and in place on the engine. This feature allows fine tuning of the ignition timing while maintaining a particular orientation of the distributor. Such capability is important on this engine since the distributor mounting flanges must be nearly perpendicular to the crankshaft axis in order to avoid interference with the intake pipes on the rear cylinder row. The limited number of teeth on the distributor gear allows a minimum increment of only 20 degrees for a rough adjustment of the timing. The distance between the Hall device and the center axis of the distributor will be determined later by the dwell requirements after some experimental measurements are performed using an actual trigger disk magnet.
This distributor design also allows a minimum gap between the rotor and tower electrodes without requiring tight control over the rotor's vertical clearance position. This gap should be as small as possible with respect to the .018" plug gap so that as much of the ignition energy as possible is available to ignite the air/fuel mixture instead of being wasted while burning up the rotor and tower electrodes. The fractional portion of the wasted ignition power is approximately given by the ratio: (rotor gap)/(rotor gap +plug gap).
Actual construction began with the distributor shaft. It was turned from drill rod and polished but was not hardened due to concerns about warping. The bottom of the distributor housing was turned from a 2-1/2" round aluminum drop, and the bore for the distributor neck was done in the same lathe set-up. The neck was turned and bored in a 4-jaw chuck separately from the main housing and then pressed into it. Stainless steel rather than aluminum was used for the neck for its durability against the set screw that will be used to lock the distributor position to the rear cover. A peripheral groove was cut around the neck to accommodate this 6-32 set screw. The neck was turned from 303 stainless after a phosphor bronze slug was pressed into its bottom end.
The distributor shaft is supported at its lower end by the bearing machined into the phosphor bronze slug and at its upper end by a 1/2" ball bearing. A stainless bushing, drilled and tapped for dual set screws, was turned and pressed into the the distributor gear. The machined face of the bronze slug acts as a thrust bearing in conjunction with the polished face of the gear bushing and limits the upward vertical travel of the distributor shaft. The downward travel is limited by the magnetic disk which is screwed onto the top of the shaft while bearing against the inner race of the ball bearing through a spacer. The final thrust clearance is set when the distributor gear is assembled onto the lower end of the distributor shaft.
In this engine the lower bearing of the distributor shaft is lubricated only by the air/fuel mixture which will be pump gasoline. I have never been entirely comfortable with this aspect of the radial design, but I am not aware of any spectacular failures. An alternative that some Hodgson builders have used for the lower bearing is oil-impregnated bronze, but I'm not sure that fuel would eventually wash away the oil allowing the softer bearing material to quickly erode. Phosphor bronze has significantly better wear characteristics, and I made the bearing length some 3/4" long to hopefully help 
add to its longevity. - Terry


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## ShedBoy

Been a while since I checked in and WOW. Truly amazing work.

Brock


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## mayhugh1

Construction of the distributor continued with the removal of the chucking spigot from the top of the distributor housing. The interior of the housing was then lathe-bored using a four jaw chuck with the X-axis indicated off a long and snug-fitting pin gage inserted into the lower bronze bearing from the top of the distributor. This wasn't the easiest surface to indicate, but the distributor internals to be concentric with the distributor shaft even if the bore through the lower bearing is not perfectly concentric with the rest of the distributor. I've had trouble in the past with drills wondering off-center in the (CDA 544) phosphor bronze material I used for the lower bearing. A carbide drill usually solves the problem, but I didn't have one of the proper size. 
The interior of the housing was bored followed by a pocket for the ball bearing, and then a shallow recess was cut in the floor of the housing to clear the ball bearing's inner race. The final lathe operation was a locating ring for the distributor cap. When completed, the rotor will end up concentric with the distributor cap so I can maintain a minimum rotor gap.
The shafts were trial-fitted in the distributor housings with the ball bearings in place. I discovered that one of my shafts was slightly bent with some .004" run-out, and so I made a replacement. Much of my drill rod has come from machine shop drops salvaged many years ago from a local scrap yard where it was badly mis-treated before receiving the TLC it rightfully deserves in my shop. 
The brass trigger disks and their stainless spacers were then turned and assembled onto the tops of the distributor shafts using 2-56 SHCS's. The distributor sub-assemblies were inserted into their bores in the rear cover, and the mesh with the crankshaft drive gear in the rear crankcase section was verified. Both shafts turned smoothly with no sign of binding when the crankshaft was turned manually. The real test, though, was a backlash check, and it was much less than a degree. 
The Hall retaining disk, the spark shield, and the rotor were turned from white Delrin because of its excellent dielectric properties. The diameter of the Hall disk is a few thousandths less than the i.d. of the housing so it can be easily rotated later when fine tuning the position of the Hall sensor. The spark shield is a snug fit to the distributor housing. When finally assembled, the spark shield is tightly sandwiched between distributor cap and the distributor housing. 
I have not yet decided on the ignition I will use. I have the parts for a pair of TM-6 modules identical to those used on my H-9, but The only coils I have are the new and smaller style versions that are 
currently sold through Jerry Howell's website. These coils come with an ominous warning about multi-cylinder engine use that leads me to believe they may not have the same dwell/current capacity of the larger and older style coil I used with my H-9. The trigger disk for that engine was sized for a 10 deg dwell which is only half of what it should have been, but the ignition did perform well with just under 2 mJ output at 5000 rpm. If I leave the dwell at 10 deg the inductance of the new coil may be too low to reliably fire the the plug at higher rpms. If I increase the dwell, the power dissipation in the smaller coil may cause it to overheat at low rpms.
Another issue is the fact that the TIM-6 is dc coupled, and so the ignition components are prone to overheating if the engine is stopped with the coil current ON. With my nine cylinder engine I had 40 degree (prop) wide safe zones, and rotating the prop while watching the trigger led to find a safe rest position was not at all difficult. With 18 cylinders the safe positions are only half as wide, and the rotary forces from cylinder compression may tend to nudge the engine into unsafe rest positions.
I spoke to Roy Sholl at S/S Engineering who supplies turnkey ignition modules to the model engine community. He supplies a CDI ignition module (essentially, no dwell requirement), but the spec for his standard module is only 12,000 sparks/min. If this is a literal spec, the ignition would limit the rpm of a nine cylinder engine to just over 2600 rpm. Roy mentioned he can also supply an 'off-menu' 30,000 sparks/min module which would boost the rpm capability to 6500 rpm. It uses a smaller discharge capacitor to gain rpms, and so I need to investigate its mJ output capacity.
For now I want to finish up the distributors, and so I've decided to set the magnets into the trigger disk for a compromise 15 deg dwell. I made some measurements on a rotary table using the .078" diameter x .042" thick magnets I have on hand, along with the pig-tailed Hall sensors I've been using from Roy. I came up with .9" for the diameter of the magnet array for 15 deg dwell. I'll come back to the ignition after the distributors are completed, but Roy's 30k spark/sec modules may be my best solution.
The trigger disks were drilled and reamed for the magnets which were Loctited into place. The pocket for the Hall sensor could then be milled into the Hall retaining disks, as well as the slots for the Hall sensor and locking screw in the floor of the main housing. Milling of the distributor cap mounting flanges and peripheral timing indicator marks finished the machining on the distributor housing. The green stuff in one of the distributor machining photos is modeling clay that I used to damp the vibration in the housing while its peripheral was being milled. A reference mark was drilled into the top of each housing to mark the tower to which the rotor will be pointing during the 'number 1' cylinder TDC for the distributor's associated cylinder row.
The rotor electrode is a strip of .003" phosphor bronze with an .030" thick brass tip soldered to it. The electrode is pressed into a slot in the Delrin rotor disk with some super glue for extra measure. Next on the list is the distributor - Terry


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## Lesgsy

I've never seen work this good before wow!

                   Les


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## mayhugh1

The final parts needed for the distributors are their caps. In the past, I've machined my distributor caps from clear polycarbonate due to its good machinability and resistance to cracking. A transparent distributor allows me to easily spot plug firing problems as crossfires are visible through the cap. For this engine, I decided to make a pair of transparent caps for troubleshooting purposes, but I also wanted something long term without the 'Visible V8' look. I had three short drops of 2-1/2" diameter blue Delrin rod in my scrap box left over from a project I was involved with several years ago. Each had enough volume to be machined into the cap I've designed for this engine. My plan was to also make three Delrin distributors and end up with a spare for that blown V8 I hope to make someday. 
Construction started with mounting the rod drop in a flat-back 4-jaw chuck on my lathe. The workpiece was turned to the distributor's final o.d. and a cosmetic fillet was added just above a larger diameter pedestal what will eventually become the mounting flange. The chuck with the blank still in it was then moved to the mill where the more interesting machining took place. I filleted all the edges of the design in order to make the distributor look like a full-size extruded part. For once this didn't result in my typical outlandish machining times because Delrin is easy to machine, and beautiful surface finishes can be obtained even with aggressive feeds and d.o.c.'s. Flat-bottomed holes were plunged into each tower, using a cylindrical end mill, for bronze inserts that will be later pressed in and used as sockets for the plug wires. The total machining time for the top of each cap was about an hour. 
The bulk of the excess spigot material was then parted off in the lathe, and the semi-finished cap was re-chucked with its bottom side up in a vertically mounted chuck on the mill table. Here, the remainder of the excess stock on the bottom of the cap, except for the last .005", was removed. An interpolated pocket which will become a clearance recess for the rotor's center tower spring contact was then milled. The dimensions of this recess aren't critical and don't even need to be perfectly circular, but cutting it at this time will provide a nice roughed-in i.d. for the critical boring that will be done later on the lathe. The real reason for semi-finishing the base before boring the interior of the distributor on the lathe is that the tower bronze inserts must be pressed in before the interior is bored, and a good flat base will help to get them in straight.
The inserts that I've made in the past were overly complex and machined with a shoulder but I decided to simplify these since the shoulder isn't really needed. The new insert is just a .620" length of 3/16" phosphor bronze. The under-size 3/16" end mill used to plunge the holes in the high voltage towers results in an interference fit with the bronze insert of just over .001". This is sufficient to prevent the insert from spinning while it is being cut during the internal boring operation. A hole was drilled in the top end of each contact before it was inserted into the distributor. This hole was sized to receive an electrical contact that will be soldered onto the plug wires during final assembly. For my last engines I came up with a process using several pieces of shrink tubing that will be built up to cover and strain relieve the contact on the wire and, in fact, end up looking like a pretty decent plug boot. I'll detail those construction steps later when I build up the plug wires.
The cap was then moved to a set-true chuck in the lathe and the i.d. was indicated. The .005" excess was skimmed from the bottom to re-true the part. The first boring operation opened up the i.d. for a snug fit to the distributor cap locating ring on the distributor housing. The final operation was boring the main i.d. for the rotor disk. The distributor housing with its rotor was trial fitted to the cap during both boring operations, and the last several thousandths were bored .001" at a time until the rotor spun freely with no rubbing. (It was during this last boring operation on my third Delrin part that I screwed up and trashed my spare cap.) At this point the housings became married to their particular fitted caps and the caps were temporarily marked accordingly.
The plug wires to the front row of cylinders will come from the engine's left-side distributor, and the wires to the rear row of cylinders will come from the engine's right-side distributor. The last machining operation on the caps was engraving the plug wire numbers onto the tops of the caps near their associated high voltage towers. When the crankshaft turns, the rotors spin in opposite directions and their directions were also engraved on the caps around the center towers.
The center tower inserts which rub against the rotor's spring contact were finally pressed in. The bottoms of these inserts have hemispherical ends for a better interface to the rotor's spring contact. - Terry


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## cfellows

You have to be proud of those, Terry.  They really turned out nice!

 Chuck


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## Swifty

They look fantastic Terry, got to get me a CNC mill.

Paul.


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## mayhugh1

I received a pair of Roy Sholl's CDI ignition modules with his 30k spark/sec modification. The pcb is different from the one used in his standard module that I purchased a year ago, and in this model Roy doesn't offer his LED trigger indicator option. Roy told me that the major change in the design of this higher speed module is a reduction in the size of the discharge capacitor from .47uF to .22uF. The output voltage of the dc/dc converter is the same as the standard module and is nominally 300V with a worst-case minimum of 125V. This combination should result in a nominal output of 10 mJ and a minimum of just under 2 mJ. Based on my research and the experience I gained during my 9 cylinder radial build http://www.homemodelenginemachinist.com/f31/my-hodgson-9-radial-final-assembly-20397/index10.html
2 mJ should be fine.
Basically, the CDI ignition is a dc-to-dc converter which steps the 6V battery voltage up to 300Vdc. This voltage is then used to charge a capacitor. The trigger signal from the Hall device is ac coupled to the gate of an SCR that is used to discharge this capacitor through the primary of a step-up transformer. This discharge spike multiplied by the turns ratio of the output transformer generates the voltage used to fire the plug. With a CDI the spark rise time is generally faster and of shorter duration than the spark from a coil type ignition. Very high output voltages and impressively long sparks are often available from CDI ignitions. Even though these fast rise times and high voltages can sometimes be beneficial with oil fouled plugs they can also be a nuisance since they can become a major source of cross fires in whole ignition system. It is the energy in the spark and NOT just the firing voltage that is important when igniting the air/fuel mixture in an engine. 
Most of the pcb real estate is taken up by the dc-dc converter components. This includes an additional fairly large transformer and switching transistor that make up the oscillator section of the converter. I noticed the switching transistor used in the standard module has been morphed into a pair of paralleled non-heatsink'd transistors in the 30k sparks/sec module. (I don't think this is good practice for discrete bipolar devices without emitter degeneration.) The critical output transformer which handles the high voltage is a nicely potted component. It's the art involved with making these transformers that keeps me from making my own ignition modules.
The relatively small gate trigger signal combined with the inevitable EMI of the dc-dc converter means that noise is a potential problem especially in my application where I will be using two of these modules. Therefore I decided to individually package the ignitions and to keep them separated from one another with short connections to the engine and extra 6V supply filtering. I also added toggle switches and led trigger indicators so I can separately power only the Hall device and LEDs during timing set-up and verification without dealing with the high voltage. It is important to not allow the ignition to fire without a plug connected to the high voltage output or cumulative damage to the secondary winding of the output transformer can occur. My testing shows that connecting/disconnecting the 6V supply to the module even with the Hall device disconnected can create an output spark. 
A trigger led is a really nice indicator that lets the user know the Hall device is alive and well. The hand sketch in one of the photos shows the circuitry I added to the front of each CDI module. I breadboarded these additional components around one of the CDI modules to make a test bed for my completed distributors and to help me visualize the final packaging for the ignition modules. I tested the distributors in a dark room with the transparent caps so I could see the light flashes from the arcs in the rotor-to-HV tower contact gaps and judge their sizes relative to the spark plug gaps. They were reasonably consistent but not perfect indicating I had still managed to accumulate a bit of runout between the rotor and tower inserts inside the caps. 
The Hall device in one of my finished distributors didn't trigger the LED indicator at all. I discovered that I hadn't removed enough of the protective shrink tubing around the pig-tailed sensor, and so it wasn't properly seated in its cavity in the Delrin cover plate and ended up too far away from the magnets on the trigger disk. After some re-work it functioned properly. 
I used SolidWorks to design a pcb for my front-end circuitry and my CAM program to generate the cut paths for a pair of circuit boards. This was my first attempt at pcb design with non-dedicated pcb software and I soon decided it isn't the best way to create circuit board traces. But, it isn't too unreasonable for a simple board. The additional circuitry I added in combination with my own requirement to be able to easily access the electronics in place on the engine's eventual firewall (I plan to make one similar to the one I did for my H-9) resulted in completed ignition modules larger than I really wanted. I spent a frustrating week massaging the module packaging to minimize its size and to come up with a form factor that wouldn't look like a pair of warts stuck on the engine. I ended up scrapping a set of completed (and populated) pcb's in order to shrink them another factor of two. I went through three complete enclosure designs before I called it quits. I can't tell anymore if I finally ended up with something I'm happy with or if I just decided it was time to move on.
Each machined ABS plastic enclosure contains two trigger LEDs with one each to be visible from either side of the firewall. It also contains the HV enable toggle switch and a bulkhead-mounted mating connector for the distributor Hall device. To reduce the module size I decided to move the 6v toggle switch to a later-to-be determined position on the firewall. An LED indicator was added to each module so I can easily tell when the CDI is energized. I used a tiny breadboard area available on the CDI pcb to mount the LED and its resistor. 
The enclosure is designed so a portion of it containing a bulkhead Hall connector will protrude through the firewall. I'm using Robert Sholl's pigtailed sensors which come terminated with a Futaba J series RC type female connector. I replaced the stock connector with the male equivalent since the female is much easier to mount as a bulkhead connector. In addition, I formed a shrink tubing boot around the male pigtailed connector to keep oil, etc. out of the contacts.
All the circuitry will be easily accessible under the enclosure's lid without removing the module from the firewall. In order to improve the appearance a bit, I machined the covers for a look reminiscent of the old style MSD ignition modules. The packaging is very tight, but the electronics is modular and readily maintainable. Final soldering of several components is a process as they protrude off the circuit boards and into recesses in the bulkhead and removable cover. Both distributors were thoroughly tested with both modules and 'burned-in' for some 20 minutes. I'm really glad this portion of the build is finally completed; and, hopefully, it won't have to be re-visited later. 
The next step in this build is to start on the cylinders and heads. The CAD time will likely take several weeks as I don't yet know how they'll look, but I'm hoping I'll know them when I see them. Since long stretches of design time without making chips tends to bore me, I plan to break up this CAD phase with the monotonous task of machining some twenty pistons. I plan to use my H9 pistons in this engine and so I already have their design. If the cylinder and head designs aren't completed by the time the pistons are finished, I'll also start on some of the final display components. -Terry


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## Walltoddj

Nice job looks great!


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## petertha

mayhugh1 said:


> Even though these fast rise times and high voltages can sometimes be beneficial with oil fouled plugs they can also be a nuisance since they can become a major source of cross fires in whole ignition system....



 Wow, you are a man of many talents! 

 One thing I've wondered about on the big multi-cylinder model engines are the ignition wires themselves. What did you end up using on your 9-cyl? I see that braided metal sheathed wire used on RC gassers, maybe has more to do with shielding RF interference to radio gear. Do all those wires congregating together at your distributer present any special issues? Interested to hear what you came up with & why, obviously its working well. Is there such a thing as small gauge solid/graphite core wire like cars use these days?


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## mayhugh1

Peter,
       The wire I used on my 9 cylinder is 20KV wire purchased from S/S Engineering (Robert Sholl). I plan to use it in this engine also. It is just a tinned braided core with a thick silicone insulator. It is black and about 1/8" in diameter. The white stuff in the above test bed photo is quite a bit thicker and it rated at 25KV and is just some stuff I had purchased in a surplus sale many years ago. I was planning to use it on this engine but I'm going to have so many wires and that wire is so thick that I don't think it will look right. And, I didn't have enough of it anyway.
        The self inductance of the plug wires and their stray capacitances form a resonant circuit which can be excited by the fast edges of the voltages in the secondary of the output transformer in both a CDI or a coil-type ignition. This can be a source of EMI especially in the servo electronics in RC applications. Besides shielding, it can be advantageous to use wires with a resistive core as the added resistance will spoil the quality of the resonant circuit and reduce the magnitude of this EMI. I notice that these CDI modules have a small resistor in series with the output wire and this is doing approximately the same thing. I'm pretty sure that resistor was placed there because of the RC market. The faster rise times of the CDI ignitions make the EMI situation worse. Their advantage over a coil-type ignition is smaller size and less weight. 
          The resistance doesn't significantly affect plug firing voltage because even at a few K ohm it is much smaller that the plug gap resistance. - Terry


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## mayhugh1

The design of the heads for my twin-18 has turned out to be every bit as difficult as I figured it would be. The cylinder design wasn't a problem because I started out with a vision of how I want them to look. Instead of the vanilla straight-walls of the H-9 cylinders I wanted a tapered walled design for a more integrated fit with the head. This will complicate the machining, but I think the improved appearance will make the extra work worthwhile. In addition, I decided to double the widths of the fins and grooves and to deepen them by 50%. I think this improves the look and maybe also the cooling since air might flow more easily through the wider grooves.
The head and rocker support design, though, has been an entirely different story. Part of the reason for this is that I'm still not sure how I want these to look. My goal was to come up with something that would look in place on a full size engine and, hopefully, require fewer machining set-ups than the H-9 heads. I was also hoping to duplicate the proven valve train geometry of my H-9 and re-use as many of its already-constructed tooling fixtures as possible. 
I very much like the appearance of the Chaos heads, and they ended up greatly influencing my design. I designed and inserted four different heads into my over-all CAD model before ending up with my current result. My favorite head design had a really pleasing elliptical shape that looked great in my model. But, I eventually realized the entire exterior would have to be inefficiently machined on my mill with a lot of complex under-cutting that I'm not sure that I or my CAM is capable of handling. Morphing the elliptical geometry into circular so I can do most of the machining on a lathe required me to modify the stock valve train geometry in order to get the proper pushrod clearance. Another clearance issue that arose with all my large bulbous designs involved the front row intake pipes and the rear cylinder row. The heads in the rear row will have to be notched to clear the intake pipes that feed the front row of cylinders. A close inspection of the Chaos photos shows they ran into the same issue. 
The sparkplugs in both rows of cylinders are located in the front halves of the heads. However, the pushrods for the front row are located toward the front of the engine while the pushrods for the rear row are at the rear of the engine. This also complicates any head design for this engine since the rocker arm supports have to be capable of being mounted on the heads while facing in either direction. This, along with the intake pipe clearance, will require two flavors of heads. This really isn't a big deal except for the fact it will double the number of spares that I'll have to make.
The first two illustrations show the original SolidWorks model for my original H-9 cylinder/head assembly. That engine uses the stock Hodgson cylinders and heads but my own rocker arm supports and intake/exhaust flanges. It also uses valve cages instead of the stock pressed-in valve seats. 
The rest of drawings show the current models for my twin-18 components. The new valve train geometry is such that the pushrods will be perpendicular to the crankshaft axis instead of being canted 4 deg toward the head. The 16 deg port/aft cant of the stock H-9 head assembly, though, is maintained. My H-9 valve cages will also be carried over to the new head design. I'm slowly becoming fond of the new heads and cylinders, but I've not yet made peace with the rocker arm supports. I had the same misgivings with those I designed for the H-9. I started out leaning toward rocker boxes, but soon felt they would overly complicate the valve lash adjustments on the lower cylinders. 
I plan to fine tune the models over the next week and make sure, as best I can, that I can actually fabricate them on the equipment I have and insure they will actually fit into the available space. I will also build and verify separate front and rear models. I've ordered the 12L14 rod for the cylinders as I don't have much left in my scrap collection, although I have plenty of 6061 for the heads. - Terry


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## dave-in-england

Nice Solidworks modelling   !!!!


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## petertha

Verrry nice Terry. I think I understand the machining / setup logic behind the original head that incorporates those kind of cylindrical, finned valve towers. But your rendition looks much nicer IMO. Its amazing how complex 1:1 scale head castings on radials really are when up close. And how thin the fins are. Tough to miniaturize this, but yours look great.

 - do the inlet & exhaust ports go perpendicular from that flat segment & axially intersect the centerline of valve/cage? Or at an angle or penetrate the cage on either side for example?

 - I see just one screw hole for securing the flange piece to the head? Probably tough to get more & work around the I/O pipes? Are you relying on a gasket or is there any issue with the hot exhaust & cool inlet pipes on the same flange plate? Do the pipes themselves get soldered/welded on those little stubs?

 - I guess these heads screw onto the cylinders?


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## mayhugh1

Peter,
The pipes will perpendicularly intersect the axis of the axis of the valve cage. There will be a gasket between the flange and the head, and the flange will be machined from stainless steel. The pipes will be silver soldered into the flange and they will extend about .030" past the gasket and into the head. This will be identical to what I did on my nine cylinder. After silver soldering I had a jig that held the assembly in the mill and then milled the flange surface flat and put a slight taper on the portions of the tubes that protruded past the gasket. This gave a nice snug fit of the assembly into the head that was then held with the single screw. The intake/exhaust assembly is held in place at three points in the final engine and so it really isn't going to loosen up with vibration. The real issues will be getting them seated in place. This is one of the possible problems I've been concerned about since day one of this build. I will need a near perfect jig to hold the assembly in place while the stainless two-into-one pipe stainless pipe assembly is being welded together and then the pipe assembly silver soldered to a pair of flanges. Then it will need to be snaked into position in a very crowded portion of the engine with three ends ending up in precise positions. And then I'll need to do it 9 times. This will likely be the very last fabrication step and so I still have a long time to think on it. And yes, the heads will screw onto the cylinders. I just don't do threads well in SolidWorks. -Terry


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## dave-in-england

.

Odd question ....but why don't you make the crank-case longer to give more space between the cylinders so that 

the exhaust pipes will be easier to fit in ?

.


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## mayhugh1

Dave,
I think it's mainly a problem of radial spacing. There just isn't much space between the cylinders in a two row 9 cylinder radial. Essentially there is a cylinder every 20 deg and each cylinder has two pushrods and a pair of intake and exhaust pipes going to it. Lengthening the crankcase would lengthen the pipes but I'd still be left with the same space between the cylinders to route them. Or maybe you're thinking the extra length would help with angling them into place? Anyway, the Chaos guys did it and so I should be able also. The thing that worries me though is that I noticed they removed the skirts from their cylinders and that was a BIG deal thing to have done. They may have found during assembly they needed to do it in order to get the pipes assembled to the cylinders. The stroke of this engine is such that the pistons go down deep into the cylinder skirt and so there had to have been a really good reason for them to have removed theirs. -Terry


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## mayhugh1

I've been anxious to get back into the shop, and so I decided to take a break from the head design and make a 'small' trial run of cylinders. I'm pretty satisfied with the current cylinder design, and after all the time I've spent thinking about them, it's probably safe to find out if I can build them. I decided to make an initial lot of six parts since I was able to round up enough scrap in my shop for that many, and I need at least four cylinders to verify the critical clearances around the oil sump on the bottom of my crankcase. My approach to making a large batch of identical parts is to make a 'prototype' run and to develop a step-by-step process for making them as efficiently as I possibly and then carefully document it. Due to the large number of parts I'll eventually be making I want to have the machines do as much of the finishing as possible in order to minimize manual clean-up. I'll use this process later to make the remainder of the parts and also any replacements I may need in the future.
I started by sawing six identical lengths of 1-3/4" diameter 12L14 rod. These were chucked in my Enco 12x36 lathe where all the heavy cutting was done to prepare them as blanks for my cylinders. The parts were faced to .050" over the cylinder's finished length, and then the centers were drilled out in two steps to 15/16". The OD's were finally turned to .025" over the cylinder's maximum finished OD. The manual preparation time for each of these blanks turned out to be about 45 minutes.
The blanks were then chucked into my 9x20 CNC converted lathe where the bores were completed. I wrote two simple programs to bore the IDs. The first one roughed the ID to 0.986", and the second one finished the bore out at 0.998". The tool offset was corrected to match the actual measured ID of each roughed part before the final finishing program was run. This resulted in all the finished bores being within 0.0002" of each other. I used high rake Korloy inserts designed for aluminum to get a mirror finish even though the cylinders will be honed later. My own personal experience with honing is that trying to remove more than a half thousandth is a long, messy, and, in general, miserable experience with sometimes inconsistent results. Therefore, I try to get the cylinders as close as possible to their finished state before honing. If I can hold the .0002" over my complete run of cylinders, I may lap them instead of honing. My lathe left a 0.0005" taper over the length of the blank, and so I was careful to make sure the small end wound up at the top of the combustion chamber. The important part of the taper which is that seen by the combustion rings is less than half of the total; and nearly all of that will, hopefully, be honed or lapped away later.
I was only able to get four finished bores per insert edge which is pretty extravagant, but the worn inserts still have lots of aluminum roughing time left on them for later projects.
For the remainder of the lathe work the blanks must be supported by their IDs using an expandable mandrel that I turned for this purpose during my H-9 build. 
The aluminum heads will eventually be screwed onto the cylinders. The first operation on the mandrel was to prepare the top of the cylinder and to turn the threads, thread relief, and a mating surface for a soft aluminum head gasket. 
The tapered body with its fully radiused fins and filleted cooling grooves is a complex feature of my cylinder design, and it has to be carefully machined to avoid a lot of tedious and inconsistent manual clean-up. My plan involved using a full radius grooving tool and a CAM program to fully machine the complex surfaces with negligible scallops. Unfortunately, the grooving operation available in my CAM software didn't seem to like the tapered body of my cylinders. Grooving and parting on my lathe, especially in steel, is always a sobering experience because of the machine's lack of rigidity. Every new project is a new experience requiring lots of experiments and sacrificial inserts to find just the right combination of feeds and speeds that not only just machine the groove but also give a nice surface finish. I generally have to take small bites with aggressive feeds and plenty of chip breaks. Because of the shape of my cylinder, the CAM software wanted to generate tool paths that spent most of the machining time cutting air and using up the chip breaks before plunging the tool into the workpiece the full depth of the groove. Adding insult to injury, the simulator estimated the machining time to well over an hour. I spent some 10 hours convincing it to behave rationally and eventually ended up with a 10 minute operation that did a beautiful job. As is sometimes the case, I had to lie to the software about the shapes of the workpiece and the part and then fiddle, in trial and error fashion, with several of the operation's parameters. If the real truth were known, though, I wouldn't be surprised if most of my problems were caused by my incomplete understanding of the software.
Another grooving program was written to clear out the material above the mounting flange where no other turning tool would fit. This grooving operation was relatively straightforward after my experience with the first one. Two final programs had to be created. One removed OD material from below the mounting flange and the other cut a short ID taper in the bottom of the bore to provide clearance for the connecting rod. This taper will also help ease the insertion of the ringed pistons during assembly.
The final results are shown in the photos. The surface finish is as the parts came off the lathe and will require no polishing before being blued. The only manual clean-up required is the removal of a 'whisker' where the last thread at the top of the cylinder terminates in the thread relief groove. The cylinder clearances around the oil sump were checked, and I also verified that I could actually insert the cylinders into the crankcase bores around the sump with the studs temporarily installed. One of the photos also shows a side-by-side comparison of my twin-18 cylinder with a stock Hodgson cylinder from my H-9 build. All six blanks made it through to good finished parts even though I had expected to ruin a couple along the way.
The machining of these cylinders is an example of a fairly complex project done on hobby-level CNC equipment but which could also have been done manually. I think it's interesting to recall what was required to create the first articles.
Approximately 45 minutes of manual prep was required to create each blank that my CNC lathe could handle. Ten individual g-code programs were created to complete the machining of the cylinder. Seven of these were rather trivial, and were quickly done using the conversational wizards within the Mach-3 control program. The other three required CAM software for their creation. I spent a total of 12 hours creating these programs, but the learning experience with the particularly troublesome grooving program consumed 10 of those hours. The total CNC machining time for all ten programs turned out to be about one hour per cylinder. This included the part set-ups, machine referencing, and verification of the parts. Therefore, amortized over an eventual 24 cylinders, my CAM time per part will be about 1/2 hour. The total fabrication time per cylinder added up to be 1-3/4 hours for a grand total 2-1/4 hours of my actual time per cylinder.
Hodgson estimates 8 hours of machining time by a typical builder for one of his H-9 cylinders, and they are comparable in complexity to my design. That's probably close to the time it would take me to make one assuming I could create a form tool for the fins that my lathe can handle. Unfortunately, though, after the third or fourth cylinder I'd probably set the project up on a high shelf. - Terry


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## petertha

Terry, I think you mentioned you jobbed out the blueing/blackening operation to gunsmith or similar service on your last engine. Is that step done before final bore finishing or is it ok to run the rings against that surface? Are the threads or any other areas somehow 'masked off' or the whole jug gets the dipper-oo? I've heard different variations of surface prep treatments from mild acid to even light blasting. But looks like your fins & profiles are 'final shape' so assume they cant be doing anything too harsh? Do you have to oil or treat the blackening some how initially to seal it in?


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## Scott_M

Terry
 It is coming along nicely ! Very nice work.  What cam package are you using ? I have to lie to mine all the time. ( SprutCam )

 Peter
 Bluing is just a fancy form of rust. Commonly know as black oxide. Gunsmiths use a refined form of salts for a deeper more lustrous color. But it is still just a "Stain" on the metal. For surface prep all it really needs is to be clean and oil free. Acid etching and blasting or polishing are all for the final appearance. If you want a bright finish you polish it if you want a matte finish you either etch it or blast it.
 There would really be no need to mask the bore or hone it later. The rings will clean it up with a few strokes of the piston.
 I don't mask the inside of barrels when bluing.

 Scott


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## Walltoddj

I like what you did with the cyl it looks more realistic if you look at the original engines, we had one at GM Powertrain in Buffalo, NY they built them there. The test rooms were cool two foot thick concrete walls and they had holes in them. Are you going to have some prints of your changes? How can I get some or the changes dimensions? I feel it would be worth changing it looks much better. Did you see chaos changes he did the heads and rocker boxes too.

Todd


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## mayhugh1

Peter,
     The bluing will be done after the honing plus everything Scott said.

Scott,
      I'm using Sprutcam also. I think I will try to make a movie of the fin grooving on my next run of cylinders. It's a lot of fun to watch especially if you've ever cut similar fins manually.


Todd,
      I haven't created any dimensioned drawings of anything I've done as I go directly from my SolidWorks model into my CAM software and no drawings are involved. If there is enough interest, though, I might create a drawing package of the cylinders and heads when I'm done. Anyone building a Hodgson nine cylinder could drop these in place of the stock parts.

Terry


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## Walltoddj

That was my idea to use those instead!

Todd


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## mayhugh1

SolidWorks uses something called a hierarchical structure to keep track of a part design. This means that a user designs his part by sequentially adding features such as cuts, extrusions, holes, fillets, etc.; and SolidWorks stores the design in a sequential hierarchy where each added feature depends upon the current state of the part created by all the previously added features. To the user this also means that even small changes to a design may not be possible without major re-work (read sometimes as must start over) to the part. So, a user is warned to design his part with potential design changes in mind so they can be easily made even after the design is finished. This is probably one of the hardest aspects of a CAM tool to master, and I'm still learning even after several years of hobbyist experience.
I designed my heads with this in mind since I was constantly making changes to the design while searching for something I liked. When it came time to start thinking about how I was going to build the part, though, I found that I had ended up with a poor hierarchy. For example, I left the fin profiling until the end of the design after the valve towers, sparkplug port, and exhaust manifold were completed. I did this to avoid continually un-doing and re-doing the fillets every time a fin was affected by one of my changes. However, when I actually machine the head, I plan to turn the finished profile including the fins during one of the very early operations. 
As soon as I tried to drag the filleting features from the bottom of the design hierarchy to the top my entire CAD model fell apart since several of the features that I was trying to fillet didn't yet exist at that point in the model. It's important that I have access to legitimate intermediate states in the hierarchy, because they represent the current workpiece that my CAM will need to generate the tool paths for the various machining operations. Also, I want an accurate step-by-step rendering of my part so I can decide whether the effort to machine certain minor features such as the fin radii in and around the spark plug recess is really justified. Therefore I'm starting over and re-creating a SolidWorks model driven by my machining sequence. This time, though, I have a visual model to work toward. A pro would probably have been able to do both the first time around. I also need to come up with lathe and mill work-holding fixtures with proper geometry to not only hold the workpieces while they are being machined but to also provide machine reference points that can be easily indicated.
That aside, the 12L14 material that I ordered online arrived, and so I actually spent most of the week making the rest of my cylinders. I don't buy much metal since I prefer to use, whenever possible, the pennies/pound scrap that I've accumulated over the years. The shipping costs for this piece of steel turned out to be comparable to the cost of the material. Most of my scrap originated as drops from machine shops and is usually quality stuff although the exact alloy can sometimes be tricky to identify. 
Anyway, while drilling the 15/16" hole through this new rod to prepare more cylinder blanks I noticed things felt very 'different" from when I made the first six. It wasn't more or less difficult, but it was just somehow different. All went well until some 30 hours into the run when I got to the cylinder grooving operation. The grooving code that had run so beautifully on the first six pieces would not run on this new material without really serious chatter. I spent several hours with test pieces of this new rod trying to the find a new feed/speed sweet spot, but there just wasn't any. I eventually had to abandon the 5C expandable mandrel I had been using and turned a new one for my 3-jaw chuck. This only slightly increased the rigidity of my set-up, but it was enough along with an additional reduction in peck depth to get me going again. Something was very different about the stiffness of this lot of 12L14. My grooving tool seemed to be exciting a new resonance with this new material in my original work holding fixture and causing a violent chatter. Changing the fixture a bit evidently damped or moved the resonance and reducing the peck depth reduced the amount of time the cutter had to excite it. I think the 12L14 that I used for the first six parts came from at least four different lots, and so I think the real culprit was the expensive stuff I had just purchased. I tried to make a video of the fin profiling process because once it was running again it was neat to watch, but getting a viewable close-up image from my flip video camera was not possible.
I made 18 more cylinders for a total of 24. I'm not sure why I made so many. Every blank made it through to a useable finished part. The cylinder bores ranged from 0.9972" to 0.9979" on 23 of the finished parts with the 24th coming in at 0.9997" due to a start-up tool calibration error. I'll finish them later with a combination of honing and lapping as I did on my H-9 before having them hot-blued. At this point it looks like the finish of the parts as they came off the lathe will be adequate preparation for the bluing process. -Terry


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## Walltoddj

Nice job how about doing another 27 so I can do my engines, no I'll be doing mine by hand don't have CNC. They look great as I said I like what you've done to improve the design it looks a whole lot better to me!!

Todd


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## barnesrickw

Nice job on the cylinders, and great photo log of the build. 


Sent from my iPad using Model Engines


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## DICKEYBIRD

What a monumental & amazing project you're sharing with us Terry; thanks!;D

I'm very curious about your CNC lathe work as I have a similar sized machine that is now Mach3 controlled (Denford ORAC)  I've been pidding with threading lately and was curious if you're using the Simple Threading Wizard that comes with the program or something else.  Your threads look great!

Also, what's your spindle motor & speed control setup?  Is there a thread somewhere showing your conversion?


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## mayhugh1

Hi,
    My 9x20 lathe is a Wabeco lathe that was converted and sold by MDA Precision located in Ca. I purchased it some 6 or 7 years ago. The conversion was nicely thought out and well done but the lathe is really pricey. It uses a control board from Texas MicroCircuits located in Dallas. The motor is a Varicon 1.5 kW unit with VFD drive. I replaced the cross-slide on the carriage with a large chunk of aluminum to improve the rigidity, and this made a world of difference. This lathe shares the same weak cross-slide/carriage set-up that the rest of the 9x20 imports have. I also replaced the round style stepper motors that came with the lathe from MDA with standard NEMA motors. Their round style steppers generated way too little torque and the NEMA's greatly improved the lathe's repeatibility. I also replaced the control board with a newer version from TMC that had a built-in spindle control.
I always use the simple threading wizard in Mach even though my CAM supports threading. It's quick and easy to work with. Threading in Mach has always been a problem that wasn't fixed until Art from ArtSoft sold Mach to another party for support a few years ago. I guess he got bored and came back to Mach temporarily to figure it out. He worked with a user named Rich who ran some careful tests while Art made software changes. Remarkably, Art didn't have the hardware to test his own code. They finally figured it out on one of the open forums, and it works pretty flawlessly now and the threads look great. You have to get the latest version of Mach to be certain you have the improved threading code. I was followed their work while they were doing it and picked up an interim patch that Art made that included all his threading fixes. I applied the patch to my then current version but I've never updated to the most recent version of a Mach myself. For threading I use a partial profile insert but it still takes a few trial and error passes to come up with the right threading depth for a nice fitting thread. I've learned to let the threading tool itself turn the last .005" of the starting OD on an external thread or the starting ID of an internal thread before starting the actual threading. -Terry


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## DICKEYBIRD

Thanks for the info Terry!  All CNC lathe stuff excites me and I'm  trying to learn as much as I can.  I built a CNC router 16 yrs ago to  cut out r/c model airplane parts (before I got this metal disease.)  I got pretty productive with it but this CNC lathe stuff is much harder  even though it has fewer axes.  I have Dolphin Partmaster CAM for the  lathe but it's been a struggle so far.




mayhugh1 said:


> For threading I use a partial profile insert but it still takes a few trial and error passes to come up with the right threading depth for a nice fitting thread. I've learned to let the threading tool itself turn the last .005" of the starting OD on an external thread or the starting ID of an internal thread before starting the actual threading. -Terry


So you're making the finish cut of the blank with the threading tool instead of a regular turning insert so that you're more likely to hit the intended thread depth?  Good idea, thanks!

I just finished an ER40 collet chuck which had M50x1.5 threads....a tall order for my 3/4 hp DC spindle motor.  I had recently added a 4:1 reduction pulley system so it has enough torque & speed stability but the thread came out a few thou too large.  I attempted to rerun it with a little deeper cut but somehow fumble fingered & crashed the tool.  I tried to pick up the thread but that proved impossible at my level of experience.  Fortunately I was able to throw it on a manual lathe & finish it off successfully at 17 TPI; close enough!

ps: I'm using Mach v.057 which seems to be OK.  If you decide to update yours, stay away from the latest one (.066) as it has known problems in Turn which probably won't ever be fixed since they're working on Mach4 now.


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## mayhugh1

I started over with my SolidWorks modeling of the heads but this time with the machining sequence in mind. I started with a 'generic' head that contains features common to both the front and rear row heads, and from this I created the actual two head models. I think the design is pretty much finished except for some decisions about filleting the edges of the fins between the valve towers and in the spark plug area. I'll probably need to see some actual parts before I finally decide. The model tells me filleting looks better, but I know there'll be issues with me convincing my CAM to properly blend the skewed intersections. I left the models in the photos un-filleted for now. I ground and hardened two filleting cutters, a 1/32" corner rounding cutter and a concave radius cutter with a 1/32" full radius profile, for some some experiments though. 
The majority of the fin profiling will be done on the lathe using grooving code and a full radius grooving tool similar to what I did on the cylinders. The fin area between the valve towers that's un-reachable by lathe tooling will be done on the mill, and a Woodruff cutter will be used for the undercutting. Undercutting will be another new CNC experience for me, and it's only 'somewhat' supported by my CAM.
I decided to start a pair of heads to begin documenting a build process and to create test beds for some of the tricky CAM coming up. I don't expect either of these to end up as final parts. I started by sawing two pieces of 2-1/2" dia 6061 just under 2" long. To prepare them as head blanks, I reduced their diameters (turns out, by too much) and faced the ends on my manual lathe. I also roughed the combustion chambers by pre-drilling one end with a shallow recess using a 15/16" drill.
The blanks were chucked in my CNC lathe, and the finished conical combustion chambers were turned. The ID's were then threaded to match my cylinders. I went through each of my completed cylinders and searched for the one with the closest fit to use as a gage.
At this point I turned a threaded mandrel so the heads can be supported by their combustion chambers for the remainder of their lathe work. The next step was to determine the machining parameters for the grooving operation. I decided to run some single groove test programs on scrap rather than my head blanks to avoid ruining them early on. I was hoping these experiments would go a lot smoother than the ones on the steel cylinders.
Because of the OD profile of my head design, a left-hand grooving tool holder and left hand inserts are required. I had to order these, and after a few hours of frustrating results I discovered my new Nicole tool holder had been mis-machined and was not supporting the insert truly vertical. After re-machining the holder, I was able to find a sweet spot of 2 ipm and 1400 rpm that seemed to work on my little lathe. With the 12L14 I used for my cylinders, I ended up with 1 ipm and 1000 rpm; and so the aluminum chip load was, disappointingly, only about 50% better. However, the deep full-width grooving passes still sounded very rough, and the stringers coming off the workpiece were ragged even though the part's surface finish was great. Interestingly, increasing the federate made things even worse. I switched to 7075 aluminum; and the grooving not only sounded better, but the stringers coming off the workpiece were nicely uniform and peeled away from the workpiece a lot more smoothly. The full radius C6 inserts I'm using have a rather low rake since they are designed for steel, and they don't seem entirely happy with the soft 6061. The 7075 is somewhat harder and maybe a little better match for them. So, I decided to switch the head material to 7075. I also ordered a few C2 inserts. Their rake is probably the same, but I'm hoping their built-up edge resistance will be better than I'm experiencing with the mist lubricated C6 inserts. The grooving time looks like it will be just over 20 minutes per head. 
I was able to use one of the partially finished heads to verify the narrow clearance between the bottom-most front row cylinder and the front-end of the oil sump which is already irreversibly mounted on the crankcase. 
The next step will be to be to create the milling fixture(s) and figure out a strategy for removing workpiece material from the valley between the valve towers as well as the area above the intake/exhaust flange recess. -Terry


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## mayhugh1

The simple threaded mandrel that I made to hold the heads for their turning operations worked OK on the lathe since the cutters created only tightening forces. The heads do end up pretty snug on the mandrel, though, and have to be carefully 'wrenched' off. The milling operations, though, create both tightening and loosening forces; and so I made a second, threaded and expandable, mandrel for use on the mill.
I created a few single and double groove test disks in order to try my hand at generating code to eventually undercut and fully radius the fins between the valve towers. I was pleasantly surprised to find that my CAM performed well on these new (to me) operations. After coming up with the machining parameters for my fin cutting tools, it was time to generate the tool paths to continue the machining on my two test heads.
I then started a week long trip to Hell. It all began during my CAM simulations when I began getting tool collision warnings created by my fin radiusing tool. These warnings surprised me because in my CAM these particular operations work only with curves and aren't supposed to consider the part or workpiece at all. But, they were legitimate, and I eventually realized they were happening because I hadn't fully taken my tooling into account in my head design. The troublesome areas were where the profiled fins in the tower valley and intake/exhaust flange areas blended into the existing fins in the lathe-turned blank. 
About this time I suddenly came down with some really bad flu-like symptoms. Instead of resting, I decided to make a new cutter to see if I could avoid redesigning the head, So, I started with a carbide reamer, a diamond hone, and a handful of Harbor Freight diamond Dremel points. The carbide decision was irrational and totally flu-related. Anyway, two full days of work later I had a working tool with perfect contours and proper cutting edge clearances, but it still wouldn't pass my simulations. I had also made a .031" corner rounding cutter out of carbide reamer.
At this point, and in no physical or mental shape to make such a decision, I suddenly didn't like my head design anymore. So, instead of fixing the tool interference problems with the current design, I started over - again. This time, knowing my CAM was capable of what I needed, I became obsessed with the minutia of perfectly blending the fillets, radii, and undercuts together at all the complicated intersections I was creating in the new design. Getting the necessary tooling clearances simultaneously with the esthetics I was looking for turned out to be much more complicated that I had ever imagined. I spent dozens and dozens of hours on such incredibly small details that probably only I would notice.
All the CAD file saves I was doing caused me to bump into a SolidWorks bug. My file sizes had begun growing exponentially even though the many design changes I was continually making to the design were minor. This turned out to be known bug with the old (2007) version I'm using. My one meg design file had blown up to some 200 meg and 199 meg of it was SolidWorks bloat that slowed my computer to a crawl. Just when I was almost finished with the design, I had no choice but to delete all my cumulative design work and start over. I had never run into this problem before, but then I had never made so many changes to the same file either. Several days later, I had a design ready to submit to my CAM. The CAM work went smoothly, but after my flu symptoms began subsiding, the jpgs of my original design started looking better to me than my latest design. Unfortunately while in a mental stupor earlier, I lost all my early design versions in a major delete accident. 
After getting a successful simulation, I set one of my two blanks up on the mill, started the program, and held my breath. To my amazement, the part came out exactly as I had visualized it. I found three minor tool gouges at the rear of the part that my CAM, as expected, had failed to flag. I was really lucky I didn't break either of my one-of-a-kind cutters. I tweaked the design slightly to improve the tool clearances before regenerating the tool paths to start the second blank. The second part ran cleanly and looked as good as I had hoped. After seeing the two parts in actual metal, I'm very happy with the result.
There are four more operations needed to complete the head, but these are simple compared with what I've already done. Figuring out the work holding for them will be the most difficult part as all four operations are at unique angles to the axis of the head and new coordinate systems and fixtures need to be created for each one of them.
I also plan to re-work the rocker arm support design as what I've shown earlier has only been a placeholder. That should be an opportunity for me to jump down another rabbit hole. -Terry


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## Scott_M

Hi Terry
 Absolutely beautiful !
 I came down with the flu last week too. I had trouble working the remote for the TV....I have no idea how you pulled that off.
 The cutters look great and the end result in metal is a sight to behold.
 Nicely done.

 Scott


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## gbritnell

CNC or not those are some gorgeous looking pieces. When I worked as a CAD modeler and cutter path generator I had a computer system that had almost unlimited storage so huge files weren't a problem. How did you reduce the size of you Solidworks files to an acceptable size? I have modeled a lot of my engine parts in ver. 2005 and some are quite complex but the files sizes don't seem to be that big. 
Oh and by the way I also have to compliment you on the tool making, once again first rate. 
gbritnell


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## mayhugh1

Thanks all for the compliments. 
George, I don't have a way to reduce the file size. The current file size is just over 60 meg and I'm probably two saves away from it becoming too unwieldy to work with anymore. So, I don't plan to make any more nice-to-have changes to it. I'm saving my last 'save' for my new rocker box design if one is needed. My understanding of the problem is, that for some reason, SolidWorks is storing multiple display modes of the same model in the file to cause all the bloat. This was discovered by users in ver 2007. SW never found the root cause of the problem until 2010, but they released a utility in an update to delete these excess display modes late in 2007. My version doesn't have the utility; and I don't have the $3k-$5k needed to get a new version, and so I'll just have to deal with it. This is the only project out of hundreds I've done where this has become a major limitation. There is something about this design or the way I keep creating it that has SolidWorks confused.  Terry


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## Rivergypsy

Beautiful work as usual Terry - well done!


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## robcas631

Amazing work!


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## happykingkong

HELLO Is the best job I've ever seen

Looking forward to can see him run

&#20320;&#22909; &#36825;&#26159;&#25105;&#35265;&#21040;&#26368;&#22909;&#30340;&#20316;&#19994;&#65281;  &#26399;&#24453;&#23427;&#21487;&#20197;&#36816;&#34892;&#36215;&#26469;&#65281;


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## mayhugh1

I appreciate the interest that my little project has generated. I've been getting a number of personal emails from readers asking to purchase or somehow obtain the drawings for the engine I'm building. As I mentioned at the beginning of this thread, I'm working from a set of online photos published by Chaos Industries which is a great looking engine they designed around, I think, Hodgson's twin 18 cylinder plan set. I have no dimensions to work from; and so I've been designing my own parts, as I go, in SolidWorks 2007. Not being an experienced engine builder or even machinist, for that matter, I've been using the Hodgson nine cylinder plan set that I own to fill in some of the missing DNA for this engine. I've incorporated the cam ring design as well as several basic and internal crankcase dimensions from the H-9 engine into my own twin-18 design. But, pretty much every part has started from a clean sheet of paper (or should I say new CAD sketch). That being said, I don't feel comfortable with distributing the entire set of CAD files or drawings because they will contain content owned by the Hodgson family. I have absolutely no interest in making any money associated with this engine, and if it weren't for the Hodgson IP content I would be thrilled to give it all away. However, I feel the cylinders and heads are a different story. I think my design, when finished, may make a significant cosmetic improvement over the H-9 counterparts. And, with all the work I'm putting into them it would be a shame to have only the only set in existence. I've been designing them to be drop-in replacements for the H-9 heads, but there is no way for me to tell if they will drop into the Hodgson twin-18 engine. I don't know yet how I would make them freely available since the file sizes would preclude emailing them, and so I'm open to suggestions. I would prefer to minimize any additional work on my part and just give away the SolidWorks files I created. I could probably call upon a friend with a recent version of SolidWorks to 'scrub' them to remove the accumulated bloat and save them out to a more recent version that I'll no longer be able to read, but I'm sure the file sizes would still be too large for email. -Terry


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## stevehuckss396

mayhugh1 said:


> I don't feel comfortable with distributing the entire set of CAD files or drawings because they will contain content owned by the Hodgson family. However, I feel the cylinders and heads are a different story. I think my design, when finished, may make a significant cosmetic improvement over the H-9 counterparts. And, with all the work I'm putting into them it would be a shame to have only the only set in existence. I've been designing them to be drop-in replacements for the H-9 heads




Maybe you could make your head design available to whoever wants them. If they purchase the plans from Lee and opt to use your head design there should be no problem with infringment of any kind. You would simply be making available an add on.


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## mayhugh1

Yeah,
      I guess that's what I was trying to say. Thanks. -Terry


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## mayhugh1

The first off-axis milling operation is the pocket for the intake/exhaust flange. This one is simple since the spindle axis is perpendicular to the axis of the head, and so the part is just supported by its mandrel in a horizontal rotary. I machined a tee-square tool for a close fit between the linear edges of the fins in the valve tower valley for use in vertically aligning the part. The machining of the pocket and the reamed holes for the intake/exhaust ports went smoothly in both test parts and produced a nice surface finish.
The machining of the spark plug port and the valve guide bores, however, is a totally different animal. The axes of these operations are at 25 degrees to the axis of the head, and they each intersect the axis of the head at different points.
An engineered fixture is needed to accurately and consistently perform these operations. The operations for the spark plug port are probably the most critical. If the spark plug port doesn't end up accurately between the already finished fins the appearance will be spoiled. 
After designing a complicated fixture that I wasn't even sure I could machine, I realized I already had two components of the fixture that I need: 1) the Hodgson fixture that I used to machine my H-9 heads and 2) a completed spare H-9 head. I designed my twin-18 heads with the same basic geometry of the H-9 heads so they can replace the heads in an H-9 engine. The valve towers and the spark plug ports of both engines are on identical axes. My twin-18 heads don't have the straight-wall o.d. of the H-9 heads, however, and so they can't be directly held in the H-9 fixture. So, I reduced the o.d. of my threaded expandable mandrel, which does have straight walls, to match the i.d. of the fixture. Then I bored out the fixture's center so it could accept the mandrel. The plan is to insert an H-9 head into the fixture and then align it to the fixture for either the plug or tower machining operation using the head's exhaust flat exactly as I did when I originally machined the H-9 head. The mill spindle is then positioned over the center of the already machined H-9 feature. The H-9 head is then removed and replaced with the twin-18 head on its mandrel. The twin-18 head is rotated and locked into place in the fixture after being properly aligned to it using the linear edges of the valley fins. Some simple trigonometry corrects the z and x axes for the displacements created by the mandrel. After going through this calibration procedure with the H -9 head one time, the twin-18 heads can then be fed one after another into the fixture and the spark plug operations finished. In order to get the best possible seal, all the spark plug operations are done in the same setup including manually threading the port with a spring-loaded tap starter under the spindle. Using this procedure the spark plug ports appear to have come out perfectly centered in both test heads.
One of the goals of my head design is to shroud a large portion of the upper body of the CM-6 spark plug so it does not appear so far out of scale in this engine as it does in the H-9. The photos show side-by-side comparisons with the H-9 heads. 
The last head operations are the machining of the valve tower tops for the rocker arm supports and the bores for the valve guides. I should be able to use a fixturing scheme similar to what I came up with for the spark plug operations. I don't have this portion of the design finalized yet, and so that will be my next CAD project. Our Texas winter is starting to subside, and I want to get the head production underway before the shop heat returns. I think I may start to bring a batch of 25 heads up to the current stage of completion while I finalize the design of the rockers. I've already sawed 25 pieces of 2-1/2" dia. 7075 to begin making the blanks. -Terry


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## Walltoddj

stevehuckss396 said:


> Maybe you could make your head design available to whoever wants them. If they purchase the plans from Lee and opt to use your head design there should be no problem with infringment of any kind. You would simply be making available an add on.




You could talk to Lee about it since I got my plans many years ago they have had a couple of revisions. Yours is a major revision that looks great one problem with Lee as with most engineer type they just see the plans, I tried to see if the plans had been revised again when Bill was doing his build and Lee had no idea which revision I was talking about due to lack of revision numbers just a date. This to me is not a good way to keep track of print changes.

Todd



Sent from my iPad using Model Engines


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## mayhugh1

The object of the head blanks is to have consistent workpieces that I can feed into the canned lathe and mill finishing operations that I generated while creating my first two test heads. This step could be bypassed with the production-level CNC equipment, but hobby-level machines are better suited at giving their user the ability to profile parts that would be impractical with manual machining than they are at efficiently producing large numbers of the same part. 
The o.d.'s and the lengths of the blanks were manually skimmed to consistent dimensions that are slightly over the maximum dimensions of the finished part. I roughed-in the combustion chambers using a 15/16" tailstock drill bit on my 12"x36" Enco lathe which was used for the blank preparation. A semi-finishing operation involving a portion of the eventual bottom-most fin was also completed at this time on the blank in order to save a tool change in the first lathe CNC operation. The machining time per blank averaged about 20 minutes, and the total blank preparation time including rounding up and pre-sawing the material was about a dozen hours spread over four days. - Terry


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## mayhugh1

The first CNC operation is lathe operation to finish the conical combustion chamber. The portion of the i.d. that will be threaded later is only semi-finished at this time. I can't seem to hold the tolerances I want when doing lathe tool changes, and so when I run batches of parts I typically do only what I can in any given operation with a single tool in a single set-up. In addition, I add code to each of my lathe programs that rapids the tool away from the part after the operation is completed and to an X-axis location that corresponds to a key measurable diameter on the part. I then correct the X-axis DRO to the actual measured diameter on the current part before running the next part. Although this extra step adds to the cycle time it typically allows me to hold 2-3 tenths over any size run. The Z-axis is re-referenced when each new piece is chucked, and so this axis is continually corrected. On this run of 25 parts I only had to correct the DRO once. When taking heavier cuts or working with steel, I sometimes have to make corrections every two or three parts.
For internal profiling operations such as the one within this combustion chamber I use a SVJCR tool holder that I've aggressively ground for increased axial clearances. Even the bottom of the insert is ground for a little additional clearance. All 25 parts were done on a single edge of a single Korloy insert that still showed showed no wear at the end of the run.
The average machining time per part was about 10 minutes and so I ran about 5 consecutive parts and then allowed the machine (and me) rest for an hour or so. The headstock on my lathe gets pretty warm after 30 minutes or so of continuous running, and so I try to avoid extended running times especially when the shop temperature gets above 80F. 
The second lathe operation uses an internal threading tool but it finishes the head gasket sealing surface as well as threads. The previously semi-finished gasket surface is skimmed with the not-intended-for-cutting end of the threading insert. The threading tool is also used at high rpm as a boring tool to finish the i.d. of the combustion chamber to the minor diameter of the 1-1/4 x 24 internal thread before the actual threading operation. The i.d. is then measured, and the X-axis DRO is corrected for the next part as described earlier. Keeping the starting minor diameter consistent is key to keeping the thread fit close and consistent over the entire batch of parts. This operation results in the gasket surface being machined square to the axis of the threads for the best seal against the cylinder. After threading, each part is checked with the thread gage that I made during my H-9 engine build. I also selected a few completed cylinders for their close fit to the two test heads I previously made and used them to spot check their fits with my new heads. The threading with all its secondary operations and manual checks required an average time of about 12 minutes per part. Since the actual lathe duty cycle was low I threaded all the parts in a single grueling six hour run. The total machining time invested in this run of 25 parts is now at 22 hours. -Terry


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## mayhugh1

The third lathe operation was fun because it's about as close to a real shop production run as I'll ever get. I set my threaded mandrel up in the 5C chuck, and touched off the tool's Z-axis to the mandrel's reference surface. Then I threaded the part onto the mandrel and started the cutting program. Ten minutes later the part was removed, and its maximum diameter and length were measured. The lathe DRO's were corrected if needed, and then the next part was then ready to go. The difference between my run and one in a commercial shop, though, is that I was scrambling during the entire operation to guide the hot, sharp stringers away from a tiny gap between the mandrel and the chuck collet and from behind the chuck where they seemed to be drawn by some mystical force to create a scary coiled up mess. This is a common problem when cutting aluminum with a CNC converted lathe that doesn't have a slant bed.
The purpose of this operation is prepare the part for the final lathe operation which is the fin profiling. It removes a lot of material, and the shape of the head finally begins to emerge. It's most important function, though, is to present an optimally shaped workpiece to the fin grooving operation. The flat workpiece surfaces above the eventual fin grooves help make my CAM's grooving operation happy so it will behave and generate the pecking cuts that my lathe likes to see.
I expected the fin profiling operation to be the most stressful step in the entire head machining process. During the first two test heads the deep grooving in the rightmost three or four grooves felt like they were on the verge of uncontrolled chatter. I had to continually vary the spindle speed vernier manually in order to quell an audible tone that was my indication that trouble was beginning. Modulating the spindle speed kept the surface finish pristine, but the whole process was scary and tedious at the same time. And, I was about to do it 25 more times. The C2 inserts that I had switched to for this run really didn't seem to help much. In addition, during the entire operation I have to continually clear stringers again; but this time it's more critical. In this operation the stringers have to be quickly fished from the bottom of each groove before the grooving tool continues with its finishing passes at the bottom of the narrow filleted groove. The full radius inserts that I'm using aren't designed for the lateral finishing that I'm doing, and so if the chips aren't kept cleared the insert can become jammed in an ensuing mess at the bottom of the groove. After some practice it really isn't all that bad, but I really have to stay focused throughout the whole 25 minute operation. 
Then serendipity stepped in. I was on the third head of my run of 25 when I noticed that I didn't seem to have a chatter problem anymore. Sure enough, it was also completely gone on the next two heads. While clearing stringers I was trying come up with a reason why my insert might somehow becoming 'conditioned' with use, but eventually decided that wasn't sensible. Then I realized I had forgotten to set up the tailstock on the last several parts. During the development of my cylinder grooving operation I discovered that tailstock support was required to stop the chatter while grooving those parts. I assumed it would help with the head grooving also. When I added the tailstock back into the setup for the next head the chatter returned. It seems that rigidly supporting the head between its two ends sets up a resonance that is excited by the cutting tool running in the rpm range I'm using. Removing the tailstock frees that end; and, if the resonance is longitudinal, drops its frequency a factor of two which evidently moves it out of the excitation range of my operation. This probably also explains why it was the grooves near the far end of the part that seemed to create most of the chatter. Another thing that I noticed was that if I didn't use the tailstock, the parts easily unscrewed from the mandrel when the operation was completed. If I did use the tailstock, the parts ended up so tight in the mandrel that I had to use a strap wrench to separate them. I think the vibration from the resonance was working with the tightening forces created by the tool to over-tighten the part on he mandrel. Needless to say, I quit using the tailstock.
The fin profiling operation completes the lathe work on the heads, and maybe my lathe but surely my back is grateful. My run of twenty-five parts accumulated another 23 hours of machining time during these last two operations, and so I'm now at a total of 45 hours.
Before beginning the milling operations I really have to get back to my CAD work on the rocker arm supports. I've been thinking about a new design for them, and it might affect the first milling operation somewhat. So, it's time to finalize this portion of the head design before doing any more cutting. - Terry


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## Walltoddj

They look better every time I see them great work. Now I'm going to have to buy a CNC lathe and it's all your fault( that's my story and I'm sticking to it).

Todd


Sent from my iPad using Model Engines


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## mayhugh1

Over the past few days I've revised the design of the rocker arm supports. I really wasn't fond of my original 'duck bill' design, but I kept it as a placeholder so I could get on with the remainder of the head design and test its machining feasibility on some trial parts. 
I finally decided to go with more conventional rocker boxes especially since I've already made the cutters and developed the CAM know-how to add head-matching filleted fins to their peripheries. I decided to keep the tops open even though I think they would look better fully enclosed. I need to be able to make valve lash adjustments on the assembled engine which means the locking nuts need to be above the top surface of the box so I can easily get a wrench on them while adjusting the valves in the cramped space under the engine. Dealing with the cover plates under the engine would also be a maintenance hassle. 
The valve guide design still needs to be finalized, but I was careful to design the heads to accept the maximum o.d. of the guides I developed for my H-9. The valve towers of these heads also have the same deck height as the stock H-9 heads. This lets me use the same valves, springs, keepers, and locks that I developed for my H-9. I had to lengthen the rocker arms, though, for additional pushrod clearance to my larger diameter head. I re-positioned the rocker arm shaft, though, to maintain the stock H-9 rocker arm ratio. The skinny H-9 pushrods may look out of place with these larger heads, and so with the extra clearance I added I also have the option to increase their diameter. Unfortunately, I partially completed a set of H-9 diameter pushrods several months ago. In SolidWorks I was able to overlay my new head/cylinder/rocker arm assembly with my stock H-9 model to prove one is a drop-in replacement for the other.
My next step is to machine the valve towers on my two test heads and to make two pairs of rocker boxes. I plan to make both a front and rear row head assembly in order to verify the designs and their machining feasibilities. The major concern I have about my current design are the potentially fragile ends that are left to wrap around the rear of the rocker arm boxes after the tower machining. These ends narrow down to thin, pointed cross-sections; and I'm concerned they may chatter and become damaged while the tower decks are being faced. I plan to reinforce their exteriors with my favorite Devcon gel before machining, though. If this turns out to be a non-issue I'll begin the milling operations on my 25 heads to bring them up to the current state of completion of my two test heads while the weather is still cool down here. -Terry


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## mayhugh1

I enjoy this machining hobby because I like coming up with solutions to the various mechanical issues I run into during the construction of the engines I've been building. When it comes to finalizing esthetics, though, I can't be trusted. I wonder off too easily into the high weeds of minutia and get lost. I've spent countless hours on the cosmetic details of my heads, because I can never seem to be completely satisfied with what I've done. Last week after I thought I had settled on a final design on the rocker boxes I looked back on some of my original designs and decided I didn't like my current design any more. So, I spent another week on the rocker box design massaging minor details and ended up with yet another final version. I decided the only way I was going to be able to get past my OCD and put a period at the end of their design was to machine my test heads to accept what I have now and never look back. 
And so the CAM fun began. Since the heads were designed symmetrically about a central axis, new local coordinate systems have to be generated for my CAM in order to handle the off-axis machining of the valve tower tops. This was not as big of a problem for my spark plug cavity machining which was similarly off-axis because the cavity shape was simple. I was able to create a dummy job assignment for a dummy part in a dummy workpiece for my CAM, and it never had to know anything about my actual head. 
The valve tower machining is not simple, though. The CAM needs to know about the actual head and, even worse, it needs to know about the exact workpiece that I will be using. Both the part and workpiece are complicated structures with some 10,000 features between them, and the combination of the two slowed my CAM computer down to a crawl. So, in my CAD I simplified the machining models by cutting away most of their lower portions that were not involved with the tower top machining. This solved my computer performance problem, and I was able to create new local coordinate systems for my tower machining operations to match the orientations of my workpieces while being held in my modified H-9 fixture. It really wasn't as complicated as it sounds.
This approach resulted in four separate cutting programs: one each for the exhaust and intake valve towers on both the front and rear row heads. I immediately realized this was going to be a possible source of confusion for me later and probably end up creating some scrapped parts. Each operation requires its own orientation in the milling fixture, and each head requires two different operations. I will eventually need to match the proper program to 100 different part orientations.
When I was ready to verify the programs on my test heads, it was as though I had launched a stand-up comedy routine for a room full of machinists. For my opening act I didn't have my touch-off gage block fully seated in the H-9 head I was using as a reference fixture to establish the machine's center of my local coordinate system. This created a significant error in the first result. During the second operation, I ran into a disastrous CAM bug that violated the part and machined away material that should not have been touched. This didn't show up in the simulation, but if I had carefully studied the CAM generated tool paths instead of relying on the simulation I would have spotted it. I then began the process of mindlessly changing random CAM parameters to nudge the CAM software away from generating the gouging code. Setting the bottom machining depth to .0001" instead of zero happen to solve it in this case, for some reason; but this was another bug in the CAM software that I had never seen before. 
While in the middle of my third program on my second head I noticed the result wasn't looking right, and so I stopped the machine. It turned out that I had already confused the four different operations. The confusion had begun early as I had mis-named the two rear row operations when I created them, and I was now machining an exhaust tower when I should have been working on an intake tower. Adding insult to injury, the fourth program that did run as I intended left the part with some unacceptable visible steps due to a poor choice, on my part, of cutting sequences. When the massacre was over, neither of my test heads were usable for verifying the rocker box fits. However, they had served their purpose in verifying the drilling and reaming operations for the valve cage. I had been concerned about the drill and reamer tip clearances to the top of my threaded mandrel as I only had .030" clearance to its top surface while in my fixture.
After a few more days of work I was ready to retest new versions of my programs, but I didn't want to risk spoiling any of my 25 threaded and grooved parts waiting to be finished. I turned a simple blank to match the OD of my head and to fit into my fixture, and then I ran each of the four programs on its own quadrant on this blank to, at least partially, verify them. I won't be able declare success until they've been run on an actual finished head, but I'd say this definitely locks in my rocker box design. 
At this point I'm anxious to continue the milling operations on my run of 25 parts while the weather is still cool. The design of the valve cages is finished, and I've made a few trial parts, checked them in my test heads and have iterated the design. I plan to start a production run of 52 cages and alternate machining runs between them and the heads during the next week or so. -Terry


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## mayhugh1

I'm using valve cages similar to the ones I designed for my H-9. With my new head design it's not practical to get lathe access to machine a step for the cage in the combustion chamber, and so these cages will be simple cylinders.
It seems that half of the model engine builders have their own best way of coming up with seats for their valves, and the other half dreads the long and chaotic process that always seems to be required. I'm somewhere in between, but I'm becoming fond of a manually cut seat in a stand-alone cage that is sized for a Loctited slip fit in the head. With this approach the seat can be pre-tested before it becomes an integral part of the head, and the slip fit will insure there's no distortion due to installation.
When I made the cages for my H-9, I started with 954 aluminum bronze but quickly decided it was just too much of a hassle to work with, and so I switched to 544 phosphor bronze. About that time I chatted with Dwight Giles at the Gears Show in Portland, and he told me he was moving away from aluminum bronze for his valve seats since he had been seeing excessive wear over time on the stainless valves in his Black Widows. His comments reinforced my decision to go with 544. Unfortunately, after finishing the cages and irreversibly installing them in my H-9 heads I discovered that I had mis-labeled my scrap bronze stock and had, in fact, used 660 bearing bronze. I researched model engine plans in my own library as well as online and found very few examples of 660 being specified for valve seats in a model engine. Most plan sets contained a non-specific 'bronze' specification. Bearing bronze has two possible issues that might limit its use in this application. First, it is very soft - softer than either aluminum or brass. Second, it isn't intended for high temperature operation; and I couldn't find a spec for its metallurgical properties at elevated temperatures. The seat is well heat-sunk to the relatively cool head, but I guessed the exhaust valve seat might still see 300F in a model engine combustion chamber. I did yield calculations on the faces of the seats using pressures I expected to see during combustion, and they showed I had good margins. But these calculations were at room temperature, and I have no idea how the 660 properties degrade with temperature. So far, I haven't seen any issues with my 9 cylinder radial. It could be, in fact, that the softer material might even be of some benefit in the valve seating-in process. For piece of mind, though, I decided to actually use 544 for the cages in this engine.
My T-18 valve cages, except for their seats, were completely machined in three manual lathe operations. After the valve tower machining is completed the cages will be Loctited using high temperature (450F) 620 retainer with the upper ends of the cages flush with the valve tower surfaces. There is a good bit of surface area for adhesion, and I added several glue grooves around the body of the cage. These shallow grooves, which were randomly filed during the first turning operation, will collect excess adhesive as the cage is being inserted into the head and help seal the cage to the head. The rocker box mounting holes are located so that after the holes are threaded, the mounting screw threads will press into the cage for additional security. And, the rocker boxes themselves will prevent the cages from moving upward. Most of the cage will be heat sunk to the relatively cool head, and so there should be plenty of margin against any heat deterioration of the adhesive.
I started a run of 70 valve cages while still working on my run of 25 heads in order to break up the monotony I'm experiencing and to even out the workload on my two machines. In any event, I'll need the completed cages in order to complete the final head machining operation. I've added 20 spares since I don't expect 100% yield, and I'd like a number of practice parts for experiments.
I started making the valve cages by turning the OD on the end of a 544 rod to .0005" under the ID of the bore in the head. I used 400 grit paper to de-burr the adhesive grooves and to verify the cages fit into a gage that I made using the same reamer that will bore the heads. All 70 blanks in my little production run are completed to this point before moving to the next step.
In the next step the blanks are re-chucked, and all the important seat-related operations are completed in the same setup. Only tailstock tooling is used. The end is spot-drilled and then drilled-through with a carbide drill for the straightest and most centered hole I can manage. I used a sharp 90 degree 2-flute v-cutter as a spotting tool to make sure the start of the hole ended up precisely on the spindle's axis even if the cutter, itself, wasn't exactly on center. The carbide drill was held in a MT-2 tapered collet tailstock holder. A floating reamer finished the ID for the valve stem, but it just follows the drilled hole whether or not it is on the spindle axis. Next, the end was pre-drilled and plunged with a stub ball mill that was rigidly supported in a second tailstock collet holder. This step formed a smooth fuel flow area behind the valve and created the edge that will eventually become the seat. This radial edge has a high probability of ending up exactly on the spindle axis due to the rigidity of the ball mill and side cutting action of its flutes. If the axes of the valve stem and the radial seat edge are coincident then a piloted seat cutter can create a very effective seal that is relatively immune to the machining of the backside of the valve. If the two axes are not coincident, the seat area will bear against this machined surface in a skewed manner, and the integrity of the seal can be affected.
My tailstock DRO was used to control all cutting depths. A gage block was used between the workpiece and tailstock tools to reference the Z-axis tools against the through-drilled parts. In order to save time, all operations in this second operation including the gage block referencing were performed without stopping the spindle. Again, all the parts in the run were completed to this point before going to the last step.
For the final step the part was reversed in the chuck, and the cavity for the valve spring was cut. After pre-drilling, the cavity was plunged with a cylindrical end mill for a nice flat bottom.
Due to the number of valves in this engine, it's important to cull out cages as early as possible with any potential for creating sealing issues. I especially don't want them finding their way into finished heads. As a first step even before cutting the seat, I visually inspected each cage under a microscope with a pristine H-9 valve inserted. If the 360 degree virgin edge contact didn't look perfect I discarded it. In order to properly do this inspection a slight burr raised by the ball mill had to be polished out. I used a simple fixture to support the cage while I twisted it back and forth a few times over a sheet of 600 grit paper on a surface plate. Even with all the machining care I took, I ended up scrapping five cages. One of the photos shows one of the rejects. I actually performed this inspection on groups of ten parts during step two so I could correct my process if it started to wonder. 
The intake and exhaust ports will be cut after the cages are installed in the head during the exhaust flange machining step. The total machining time per cage was 20 minutes. Inspection and preliminary leak-checking (to be described in my next post) will add another 10-15 minutes for a total cage fabrication time of about 35 hours. -Terry


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## Ethan D

Hey 'Mayhugh1'
This is a incredible build! I'm looking forward to seeing more updates.
Great work with it all.
Cheers


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## mayhugh1

For my last two engines I made manual seat cutters by drilling pilot holes through the ends of 90 degree HSS countersinks. I recently came across a better solution from Brownells. They sell a 45 degree muzzle reamer which is a turn-key solution to the part I've been making. It also has many more flutes than the counter sinks I've been using for smoother cutting. I've found there is some art involved in using these cutters with bronze. Very light pressure of the cutter against the seat seems to give the best result. Held vertically, the weight of the Brownells cutter is almost enough force on its own to cut a nice .005" seat. Pushing the cutter hard into the seat can cause it to grab the bronze and the seat will end up wider than desired. A seat width of about .010" seems to be optimum for model engines.
For my twin-18 I need more assurance, than just a visual inspection, that the seats are going to seal after they're installed in the heads. For my last two engines I used a vacuum leak-down (up?) test to verify my seals. I used a MityVac to pull a vacuum on the cage containing the installed valve after it was installed in the head. The vacuum was pulled through a rubber adapter inserted into the intake or exhaust port while the valve stem was sealed to the valve guide bores with a silicone plug. My subjective 'pass' criteria was a leak-down time from 25 inHg to 15 inHg of 15 seconds or greater. 
I want to do a similar test on my T-18 cages but before they are installed in the heads. To create a test fixture, I cut a v-groove along the stem of a pristine H-9 valve that was left over from that build. For my test I insert this valve into the cage-under-test and draw the vacuum at the rear of the cage. The groove allows any leaking air to escape. Without it, the close fit of the valve stem and guide significantly affects the leak-down time and can completely mask a badly leaking valve.
With unlapped manually cut seats my H-9 notes show I was typically achieving a 5 second leak-down. Under a microscope the seats showed perfect concentricity with the valves and layout fluid on the seat showed a uniform 360 degree contact line. Microscopically visible circular grooves left in the seat by the seat cutter, though, limited the integrity of the seal. My stainless valves, on the other hand, had mirror finishes on their seat contact areas due to a final polishing step I did before removing them from the lathe. 
While I was making my H-9 valves, I made a number of stainless steel laps, which were nothing more than polished rear valve shapes with handles. Using these with very fine TimeSaver lapping compound I achieved my desired leak down time after about a minute of lapping.
I prefer to do lapping with a separate lap instead of using the actual valve. Lapping damages the fine finish on the rear of the valve because the process starts by transferring the coarse circular grooves in the seat to the valves themselves. Getting a smooth surface finish on both parts by lapping takes a long time, isn't really necessary, and ends up leaving a trough around the valve that's equivalent to a lot of engine running time. There's a temptation to go to a coarser lapping compound to speed things up, but this really only speeds up the damage to the valve. The TimeSaver compound breaks down quickly, helps protect me from myself, and minimizes the damage to the lap. When I hear the squeaky sound of metal-against-metal as I wring the two parts together, it's time for a leak test or, if necessary, a new charge of lapping compound.
When lapping, it's difficult to tell when you're done from just a visual inspection of the smoothness of the seat. A seat can appear to have a mirror finish to the naked eye, but under a microscope it can contain circular grooves that are coarse enough to prevent the valve from sealing. Conversely, under a microscope the seat can appear to still have grooves; but seals just fine.
To illustrate this, I took four microscope photos while experimenting with one of my T-18 cages. The first photo shows a de-burred but uncut seat. The measured leak-down time with my grooved H-9 valve was 5 seconds. For the second photo the Brownells tool was used to cut a .005" wide seat. The circular grooves are very prominent, but the leak-down time measured a passable 20 seconds. By the way, these grooves are nearly identical to the grooves created in my H-9 seats by my shop-made cutters. For the next photo the seat was widened to about .008", and the leak down time worsened to about 9 seconds illustrating that thinner is better. The fourth photo shows the same seat after 2 one-minute lapping sessions with TimeSaver and a well-used H-9 lap. There's only a small visual improvement in the grooves, but the leak-down time improved by almost a factor of two to 35 seconds. 
Before I finally installed the H-9 valves in their heads, I lightly lapped the valves to their cages and achieved final leak down times approaching a minute. I've not yet decided if I'll do this same last step with this engine. If I achieve my pass criteria with a sacrificial lap, I'll likely stop and avoid any damage to the valves.
I duplicated the above steps on five more of my new cages, and the results were pretty much the same. My plan now is to wait until the head machining is completed to the point where the cages must be installed. At that time I'll cut the seats, lap them, perform the leak-down tests, and Loctite the cages in place. The heads will be numbered and the results recorded for later comparisons with the final leak down tests using the actual valves. The last step in the head machining is the milling of the surface for the intake/exhaust flange. In this step the intake and exhaust ports are also drilled into the cages. 
For perfectly concentric valves and seats it seems that the circular machining grooves ultimately limit the quality of the seal. Thinner seats with fewer grooves seem to produce better seals. One can imagine the additional complications that come into play if the valve and seat aren't concentric. For example, if the valve axis is skewed to the seat axis because the valve guide wasn't drilled straight, the circular grooves can straddle the the seat and act as tiny pipelines to allow air to escape past the seal. The grooves will have to be completely lapped away to solve this, and the final result may a deep, wide seat with other issues. Another problem that can arise with skewed axes involves the actual shape of the contact ring of the valve. If the rear of the valve was dressed with an abrasive in an attempt to polish it and the resulting surface became non-spherically curved, then the 360 degree contact ring can be lost. -Terry


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## camm-1

Love your build! Outstanding!
Do you have a link were to by this valveseat cutter?
Ove


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## mayhugh1

Here you go:

http://www.brownells.com/gunsmith-t...ing-cutters/45-chamfer-cutters-prod41716.aspx


Terry


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## mayhugh1

The milling operations on my run of 25 heads was continued while I worked on the valve cages. The cages need to be finished and installed before the final milling operation, and so I alternated between the machining of these two parts to help with the tedium. Except for tool changes, the mill can run unattended; but the valve cage work is manual. 
The first of the five head operations was the most grueling as it required five tool changes and some 50 minutes each of run time. This on-axis operation removed excess material from between the valve towers and created the finished fins in this area. The holding fixture for this step was a 5C collet chuck bolted vertically to my milling table. My threaded expandable mandrel which gripped the head was held in the collet. The stacked TIR's of the workpiece and mandrel combined to move the effective center of my fixture around by as much as .004", and so I re-referenced the machine for each part. An error this size would have caused visible flaws in the fin profiles.
Due to my own carelessness, I trashed a head early on in this operation when an un tightened roughing tool pulled down slightly in its collet leaving me with 24 parts. This first operation consumed about 25 hours spread over several days. The carbide tooling still looked like new when this step was completed, but I did consume two HSS roughers. 
The second operation created the spark plug cavity and drilled the hole for a CM6 spark plug. After the cavity was completed, I manually tapped the hole using a spindle tap starter while the spindle was still in position over the drilled hole. This operation was 25 degrees off the head's center axis, and the workpiece was gripped by my threaded mandrel which was, in turn, held in my modified H-9 head fixture. This fixture was calibrated only once at the start of the run with the help of a spare H-9 head and some some trigonometry. The part cycle time for this operation was about 30 minutes for a total of 12 hours.
The first parts machined by the next four operations were pretty stressful. These four operations created the 25 degree surfaces on the valve towers for the rocker boxes and blended the tower fins to the rear of the rocker boxes. I had to create different operations for the intake and exhaust towers on both the front and rear row heads. After this step was completed there were two flavors of heads - one for the front row and one for the rear row. In addition to my own confusion with four similar but different operations, I had a lot of trouble getting them to compile as I wanted. The issue was the tower fins that were being cut and terminated at an angle. The tool paths that my CAM wanted to generate very visible machining steps in the result and I had to over-complicate the tool paths to get a clean result.
I screwed up both of my test heads in the process of getting these operations to run properly and really never saw any of the four operations run successfully on an actual head blank. Each operation took 20 minutes to run and there were 48 of them for a total of 16 hours. I decided to plow through the whole lot in an exhausting day and a half.
At this point, only the operation to cut the opening for the intake/exhaust flange remains. (I also need to hand-tap 192 2-56 holes in the tower tops.) So far I've accumulated about four hours of machining time on each head, for a grand total of about 100 hours. The valve cages, with their cut and pre-tested seats, will be installed before this step is started. The intake and exhaust ports will also drilled through the head and into the installed cages at this time.
I'm anxious to get on with the rocker boxes since it looks like their machining will also be pretty involved. This run of 50 (or so) parts is going to be another big deal that I want to finish up while the weather is still cool, and so I'm turning my full attention to them. I've begun the programming, and it looks risky enough that I'll also need to do a small trial run. I've also ground another custom round-over tool for my CAM to work with since I made yet another change to my final, final rocker box design. I'm now planning to radius the topside of the rocker box bottom. There's also two significant work holding fixtures that need be designed and built before starting. - Terry


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## creast

OMG!!!
I think I am going to die looking at such work!!
AMAZING!!


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## mayhugh1

All the cosmetic detail that I added to the rocker boxes turned them into fairly complicated parts to make. They're irregularly shaped and need to be machined on three sides, but fortunately most of the complex milling can done from the top. My first attempt at the topside CAM went pretty smoothly as I was able to re-use some of the fin profiling tricks and custom cutters that I created for the heads. 
My plan was to make about 50 parts in cookie sheet fashion but to do them in small batches of six pieces or so. My simulator predicted about 3/4 hour of topside milling per part, but the actual cycle time with its ridiculous 12 tool changes was closer to an hour per part. I prefer working with small batches especially on complex parts because it can sometimes take several runs to get all the process kinks worked out on a part this complex.
It didn't occur to me during the design, but the finished thickness of these parts ended up at a miserable something over .500", and so I wasn't able to make use of the pile of 1/2" 6061 scrap that I've collected over the years. I was able, though, to scrounge up some pieces of 5/8" thick material that had lots of deep gouges and had evidently spent much of its life out in the weather. 
For my test batch of four parts I surfaced both sides of a 5" square piece of this material and then glued it down to a piece of MDF. The test run uncovered a number of minor issues with my code; but, more seriously, I ended up crashing my new shop-ground 1/2" corner round-over cutter. This caused the workpiece to shift in my set-up and the machine to probably lose steps. I wasn't able to re-reference the workpiece, and so the run was scrapped before the parts were completed. Sometimes you get into trouble when you try to outsmart the CAM by lying to it about the exact size of the workpiece. In this case, a retract trajectory that this huge tool tried to use was in the path of workpiece material that it didn't know anything about. I did get enough information from this run, though, to generate an improved version of the code. And, I managed to salvage a few partially finished parts to test out the two work holding fixtures that I made to machine the other two sides.
Some of my scrap was long enough to yield two batches of parts, and so I planned to run multiple batches on a single workpiece rather than cut up the workpieces. I faced both sides of all my plates to remove as many of the dings as I could, and I planned the layouts to avoid the ones I couldn't remove. Since I ended up getting very close to my finished thickness, I tried to keep the long surfaced workpieces flat to better than .001" mostly, though, as a practice exercise. The final skim pass left me with less than .010" excess stock, and it was done after the blank was glued down to the MDF. I also added 8-32 hold-down screws in the four corners for extra support during the heavy roughing that I was planning. Although the 16 inch long pieces of MDF measured flat to better than .001" over their entire lengths, I was getting some significant 'drumming' in the center due to the lifting forces of the surfacing cutter. I was able to hold the MDF down with my hand to maintain a smooth finish during surfacing, but I made some quick-and-dirty hold-down clamps from oak for the actual machining later.
I ran another three pairs of parts during my second run to verify my new code. An .087" drill that I was pecking to full depth in the half inch workpiece broke due to its built-up edge and spoiled one of the second run parts. I replaced it and began seeing the same issue in the next run. I ordered a Guhring deep drill from MSC and had no more trouble. 
The roughing step that removed most of the excess stock from the workpiece was done with a three flute 3/8" rougher running at 20 ipm and at a half-diameter depth. Just after the operation completed, I measured the temperature of the residual workpiece at 155F which is uncomfortably close to the maximum service temperature of the Devcon adhesive. So, I decided to add hold-down screws to the centers of the parts for extra support during the tool change pause of the final contouring operation when they are cut free. As it turned out, the adhesive in about one out of every five parts released from the heat of the roughing pass. 
I don't run flood coolant; but, instead, I use Trico's Micro-Drop system. This coolant system is very marginal for the deep aluminum roughing that I was doing. During my fourth run, I evidently didn't have the nozzles positioned optimally, and the flutes filled with hot sticky aluminum. The cutter broke, and the workpiece shifted slightly. I was able to re-position the workpiece, replace the cutter, and re-reference the machine so I could continue. The finished parts in this batch all turned out perfect.
The total topside machining time for all the parts was about 50 hours, and I was able to run about 10 hours per day. It wasn't until my fifth batch of parts, though, that I really had a stable and reliable process with which I was comfortable.
The next step is to complete the simpler machining on the other two sides. The bottom must be faced to final thickness before its inner and outer perimeters are rounded over. A tapped 2-56 hole is also added so the rocker shaft can be secured with a set-screw. And, of course, the rocker shaft hole must be drilled and reamed. I've made two fixtures to perform these operations. -Terry


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## mayhugh1

There was just some simple machining left to do on the rocker boxes, but the huge number of parts involved took some of the fun out of it. I didn't expect to end up with so many extras because I didn't expect my yield to be as high as it was. At this point, though, it seems a shame to not finish them all out.
The first step was to surface the bottoms, and bring each part to its finished height. It's important to get them all at the same height so a common z-axis reference can be used for the corner rounding operations in the next step. I made a very close fitting fixture to hold the parts one at a time in a vise with their bottoms up. This was set up under a small surfacing cutter in the spindle of my manual mill, and then I continually fed all the parts into the fixture in one large batch. Over half of the two minute cycle time was taken up cleaning the chips out of the fixture between parts.
For the second step I moved the fixture to the Tormach. It was referenced once at the beginning of the run with the bottom of a surfaced scrap part facing up. I used my shop-ground corner rounding cutter and some simple contouring code to round over the edges of the inner and outer perimeters of the bottom. I want the bottom surfaces of the rocker boxes finished because they will be visible in the engine's lower cylinders. A few scrap parts were used to fine tune the code for the best edge blending before I started the actual run. The line that a corner rounding end mill can leave on the top surface drives me crazy.
In the third step I drilled the hole for the rocker arm shaft. I created a second fixture to do this operation under the spindle of my manual mill. The hole has to be spotted, drilled, and reamed; and by design it's centered between two fins. I designed the fixture to be a close fit to the parts so I could swap them in quickly and easily hold them in place with a simple pinch clamp. My procedure was to do all the parts in three steps. The first step spotted all the parts, the second step did all the drilling; and in the third step all the parts were reamed. Performing each individual operation on all the parts in complete batches was a lot more efficient than dealing with 150 tool changes, but it required a repeatable fixture.
The final machining operation drilled the hole for a setscrew to secure the rocker arm shaft. This, again, was done on the manual mill using my first fixture. The 2-56 holes were hand-tapped, and then a few hours were spent de-burring the shaft holes and manually re-reaming them. A close-fitting dummy rocker arm was used to verify the shaft holes are perpendicular to the rocker arm clearance slots. I spot checked about a dozen parts and found no rejects. 
After all the work during the past several days, I couldn't wait to see how the rocker boxes looked atop the heads. The photos I took are are staged in that the mounting holes in the heads aren't yet tapped, and so the rocker boxes are just sitting on the valve towers. Keep in mind that the intake/exhaust flanges have not yet been cut out of the rear of the heads. I also set one of my new assemblies in one of the crankcase sections, along side one of my H-9 spares for a sanity check on the pushrod angles and clearances. I wasn't able to create a SolidWorks model that I trusted for a clearance study, but it appears I have plenty of clearance. The second piece of good news is that the half-completed batch of pushrods I made several months ago have enough excess length to be useable. I still may increase their diameters by gluing light-weight slip-fit aluminum tubes over them for improved appearance.
I have some de-burring to do on the rocker boxes and the heads. It will probably take several days because it is one of my least favorite things to do. I'll likely start on the rocker arms next so the rocker box assemblies can be completely finished. I still have to install the valve cages in the heads and run the last milling operation on them. - Terry


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## aonemarine

looking great! Does the rocker box get a cover on top of it?


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## mayhugh1

Hi,
     No, I'm leaving the tops open so the valve lash adjustments in the lower cylinders won't be so difficult. 

Terry


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## mayhugh1

I took some time off from my build to visit my ill mother-in-law and to attend the Cabin Fever Expo which happened to be within a few hours drive. I was able to purchase the last three 'old style' Exciter ignition coils from the Jerry Howell booth, and so I now have TIM-6 back-up options to my CDI ignitions. Lee Hodgson was showing his impressive slide valve radial. I was tempted by the massive two volume plan set he was selling at the show, but I think for now I'll let the design simmer for a while in the hands of some other ambitious souls.
I also made a pilgrimage to Edison's lab in West Orange, N.J.. It was another 2-1/2 hour drive from the York show, but it was well worth the effort. Edison was my childhood hero, and his biography had a major influence on my career. His R&D machine shop is huge and was one of the highlights of our trip. It was pretty much a self-guided visit, and we spent the better part of a day wondering around the site which is now a National Park.
Getting back to the build, my next task is to finish up the rocker boxes which are lacking only their rocker arms. Since I'm not planning to make covers for the boxes, I want the arms to completely 'fill' them, and that means their profiles will be a bit complicated. Like the rocker boxes, they will be machined on three sides, and a special fixture will support them during the final side machining. I designed ball socket ends to mate with the hemispherical pushrods. The sockets also have the clearances needed for the skewed pushrod angles. The two CAD drawings show sections taken across the sockets that I used to verify their clearances at the extreme positions of the arms. Because of the complex shape and the number of pieces involved, I decided to make the arms out of 7071 aluminum instead of steel. For durability, I inserted phosphor bronze slugs into the arms for both the pushrod sockets and rocker shaft bearings. I'm using oval-ended socket head set screws as bearing surfaces against the valve stem ends.
The first step in the arm construction was to saw some 3/8" thick stock into several lengths sufficiently long to make the arms in batches of ten. An array of holes was first drilled in each blank for the lash adjusters and the bronze inserts for the ball sockets. The lash adjuster holes were free-hand tapped for the 4-40 set screws. Even though I've tapped almost 400 holes on this engine without breaking a single tap, I managed to break two 4-40 taps on the lash adjuster holes. I was using the tap in an electric drill to speed things up, and so maybe I got what I deserved. The inserts were lathe-turned for a Loctited slip-fit, and the 680 adhesive was allowed to cure overnight in an oven.
The ball sockets were then milled from the bottom side of the blanks. I used my Tormach Speeder for most of the arm milling operations. It increased my spindle speed to 15k rpm and saved several hours of machining time with the small cutters I was using.
The blanks were then flipped over and the outer profiles of the arms were cut to their full depth. This avoided any 'parting' line in the side of the arm and left about .040" excess stock at the bottom of each arm which still connected them to the blank. The tops of the arms were then filleted with the same round-over cutter used during the head and rocker box machining. I then used my favorite Devcon epoxy gel to re-bridge the arms to the topside of the blanks for support while the bottom side machining was done. Unfortunately, I didn't get the blanks cleaned properly before I applied the epoxy. Normally, for smaller batches of parts I use acetone as a final surface cleaning step, but I skipped that step this time and just cleaned the vegetable-based cutting lubricant from the blanks in the kitchen sink using dish soap. Normally this would have been fine, but I evidently didn't do a good job of scrubbing the cutting oil out the troughs cut around the parts because I ran into an adhesion problem during machining. After looking closely I could see the still-oily surfaces under the epoxy that had broken free. I added a glued-in MDF bridge as well as a lot of additional adhesive to stabilize the arms during the bottom-side profiling, but I still ended up trashing some half dozen parts. The bottoms were machined in two steps using a cylindrical cutter for the flat areas and a ball cutter for the contour around the shaft bushing. Normally I use a heat gun to loosen the epoxy from the finished parts. Since I was dealing with nearly sixty parts I tried, instead, baking the blanks in an oven at 190F for half an hour. This worked beautifully, and all the parts broke free with very little effort with absolutely no clean-up required.
After the bottom-side machining was completed the rocker shaft bearings were installed. A fixture was machined to hold the arms one at a time under the spindle of my manual mill while the through-hole for a phosphor bronze slug was drilled. A carbide vee-drill was used to get a precise hole with a single drilling operation. The slug is .010" longer than the width of the arm, and so when it was Loctited in place I was left with a .005" spacer bearing on either side of the arm. After the adhesive cured, the parts were returned to the drilling fixture where the hole for the rocker shaft was drilled. Again, a carbide vee-drill was used to save spotting and reaming steps. Machining this hole after the bearing was inserted into the arm speeded up the bearing fabrication, and gave me the best possible perpendicularity to the arm axis and provided some serendipity. After fitting the first completed arm into position in a rocker box I realized I had mis-machined my rocker box shaft drilling fixture; and, as a result, the rocker arm was .015" too far forward in the box. With the minimal clearances I had designed between the arms and the rocker boxes I now had a bind that wouldn't allow the arms to reach the full limits of their swing. I solved the problem by moving the shaft holes in the rest of the arm bearings to compensate for my error. There's plenty of bearing material around the offset shaft holes so there should be no operational problem and, cosmetically, my mistake will be hidden inside the rocker box; but I hate it when these things happen. I'm really glad these jinxed parts are finally finished. -Terry


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## sbdtasos

just incredible.....


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## mayhugh1

I thought I would spend the next week or so making some of what I call the 'nuisance' parts of the engine. I'm going to start with the gaskets. There are three sets of gaskets in this engine. The first are the soft aluminum gaskets that go between the threaded cylinders and heads to seal the connection between the two. A common way of making these is to bolt a stack of dead soft aluminum sheets of the proper thickness together and then turn and bore the sandwich into a set of completed gaskets. When I built my H-9, I finish turned and bored a piece of 6061 tubing that I had on hand, and then I just parted off the gaskets. After annealing, they were quite a bit softer even though they were still 6061. Since this approach seemed to work OK for my H-9, and since I still have some of the same tubing, I'm doing the same for this engine.
The parting operation leaves a thin but easily removed lip on the headstock-side of the gasket. After pulling it off with a pair of side-cutters, I polished both sides of the gasket using a wet sheet of 600 grit paper on a lapping plate and a simple shop-made tool to hold the gasket down flat. I left the corners of the inside diameter sharp. After polishing, the gaskets were checked for uniform thickness at four points on their circumference. I then annealed them in my heat treat oven for three hours at 775F and then cooled them at a rate of 50F per hour to 500F after which they were allowed them to cool to room temperature inside the oven.
The next set of gaskets are the thin paper gaskets that seal the cylinder flanges to the crankcase. For these I used some sheets of linen or 'rag' paper that I removed from a 30 year old university dissertation. I cut these gaskets on my Tormach using a 60 degree vinyl cutting tool and the same program that I had previously generated for my H-9 gaskets.
The last set of gaskets are the ones between the heads and the intake/exhaust flanges. For these I used a 1/64" thick black rubberized FelPro automotive gasket material. This material is not designed for automotive exhaust applications but should be fine in this application. My testing showed that it begins deteriorating somewhere above 450F. I cut the gaskets for a .002" peripheral clearance around the opening in the head for the intake/exhaust flange. After a slight burnishing they become a snug fit. -Terry


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## mayhugh1

My final set of 'nuisance' parts involves the hardware used to retain the valve springs. I'm using the same two piece retaining scheme that I've used on my previous two IC engines. It consists simply of a stainless steel retaining cap held in place by a U-clip. These particular parts have all the features that I personally don't like dealing with including trivial design, tiny size, and large quantity. 
In use, the cap slips over the end of the valve stem and is held in place against the valve spring by the U-clip that rests in a recess and is retained in a groove on the valve stem. The spring caps are simple to make; but since many are required, the challenge is to figure a way to make them using as few Individual operations as possible. 
I started by drilling a one inch deep hole in the center of a length of a 5/16" diameter 303 S.S. round. I used a sharp carbide vee-drill of the finished valve stem diameter in a tailstock collet to avoid the center-drilling and reaming operations. I then bored the shallow U-clip recess using a 1/4" cylindrical end mill also held in a tailstock collet. I began the manual parting operation using a .035" thin bade insert, but before it was completed, I chamfered both sides of the groove using a small triangular file. This simultaneously chamfered the bottom corner of the current part and the top corner of the next part. I repeated the boring, chamfering, and parting operations for seven or eight caps until I ran out center-drilled rod. I then re-positioned the the stock in the chuck, drilled another one inch deep hole, and repeated the process for another seven or eight parts. I couldn't figure a way to speed things up with CNC, and so the parts were made manually. The final step was to polish off about .0005" from each side of the cap using wet 600 grit paper on a lapping plate.
The U-clips were started by again drilling a 1" deep hole in each end of a 1/4" diameter stainless rod, but this time slots were milled along the edges to form the U-grooves. Working with both ends of the workpiece doubled the number of clips I was able to produce per grooving set-up. The clips were then simply parted off in my CNC lathe in an interrupted cut operation using a .020" wide carbide insert. The U-clips themselves are only .017" thick and are difficult for arthritic fingers to handle, but they were also lapped on both sides.
My yield on both parts turned out to be rather poor due mostly to my clumsiness in handling the finished parts. My fingers just don't seem to handle tiny parts as well as they used to. It was important to make a number of spares of these particular parts since during final assembly there will be plenty of them flying across the shop under spring force.
Although I don't consider the valve springs to be nuisance parts, this seemed like a good time to make them as well. The stock H-9 springs are very pricey commercial items, but they are easily shop wound. The specs I used were 8.5 turns per inch of .020" diameter stainless steel music wire with a finished o.d. of .250" and an uncompressed height of .450". Before I got my CNC lathe I used the threading capability of my manual lathe to wind springs using a simple shop-made tool-post wire feeder. With my CNC lathe I have the ability on most days to include a pair of close wound coils on either end for a more 'commercial' look. I say 'on most days' because I need to run the lathe spindle considerably less than its minimum spec'd rpm in order to handle the feedrate required for the close-wound coils. Some days the VFD just doesn't want to cooperate. The required mandrel diameter in my set-up was determined by trial and error to be .140 inches. Some experimenting with the feed-rate is also required to arrive at the proper turns per inch.
After cutting the wound mandrel coil into individual springs, I ground the ends flat using a simple holding fixture over a sheet of 200 grit dry paper. I then stress relieved them at 500F in my heat treating oven for one hour before allowing them to slowly cool.
I've been rounding up the metal to machine the intake/exhaust flanges, and this looks to be the next step in this project. -Terry


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## mu38&Bg#

Very nice work!


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## mayhugh1

I've had major concerns about two aspects of this build from its beginning. The first was my ability to get a built-up crankshaft aligned and spinning freely to my satisfaction in a four piece crankcase. Somehow, that hurdle is long behind me. My second concern involves the intake system. This engine uses a two-into-one intake pipe with silver soldered flanges on the two legs of the 'Y' that mate the pipe assembly to the heads. Each fabricated 'Y' pipe is shared between a front row and a back row head. This means that a fairly complex and rigid pipe assembly will have to be accurately fabricated and sealed without leaks to three different surfaces in the engine. And, it will have to be repeated nine times. Three steps in order of increasing difficulty are required to build the assemblies: 1) accurately forming the stainless tubing bends and silver soldering the flanges, 2) neatly welding the 'Y's, and 3) actually installing the completed assemblies. I think the first step can be done with the proper care, and I hope the second one can be accomplished with enough practice. The third one, though, may not be possible with much of the design that I've already completed and grown fond of.
I had a chance to examine Hodgson's 18 cylinder twin at the Cabin Fever show. His engine uses similar 'Y' pipes, but with his head design the pipe assemblies slide easily into place from above the engine since the pipe flanges mount to easily accessible exterior vertical flats on the heads. Both he and the Chaos guys also used soft brass tubing that can be man-handled some to coax the flanges into position. 
In my engine the mounting flanges are sunk into pockets in the heads (mostly for cosmetic reasons), and I'm using stainless tubing which is more difficult to deal with. And, if all this wasn't enough additional challenge, I'm starting out with a known interference problem between the bulbous rear row heads and the front row intake pipes. My modeling shows that after notching one side of each of the rear row heads I'll have the space needed for the pipe assemblies. What I haven't been to tell from my modeling, though, is whether I have the needed 'wiggle room' to actually maneuver the completed pipe assemblies into final position. 
So far, I've only milled the recesses for the intake/exhaust flanges in my two test heads. My next step is to machine a few test flanges and do some experiments with actual parts in my hands to see if my current design can actually be assembled.
My only stainless scrap of the dimensions I need for the flanges is of an unknown alloy, and so I was prepared for a frustrating experience. While at Cabin Fever, though, I purchased two $10 unused 1/4" end mills from a vendor who told me they were specifically designed for cutting 304 stainless. They're center-cutting with a sharp corner, have five wavy flutes and a blue-violet coating, and they are razor sharp. Whatever my scrap alloy was, these cutters chewed through it with no effort or noise and produced a beautiful surface finish. I wish I knew more about them, but they have no markings of any sort.
My piece of scrap was long enough to make five flanges. I spotted, drilled, and reamed all the holes before contouring their peripheries. The workpiece was .080" thicker than my flange and so after contouring I simply cut the parts free using my bandsaw and milled them to finished thickness on my manual mill. My bandsaw whispered to me that the alloy was probably 304.
I partially assembled the crankcase and then set the two test heads in place atop cylinders - one in the front row and one in the adjacent position in the rear row. After several tries, I eventually had two pieces of tubing bent by eye that approximated a crude 'Y' to which I temporarily added the flanges. After playing with the pieces for a while it quickly became obvious that it was actually was impossible to install and remove the intake assemblies in my current design.
For one thing my flanges are thick and their fit in the deep recesses is fairly close with only .003" clearance. I designed them this way for a good looking and leak-free fit. There is also too little 'slop' in the fit of the intake tube in the crankcase plenum for 'wiggle room' before the o-ring compression nut is tightened. This was also intentionally done to reduce the chance of a leak at this connection. The intake tube assembly can slide vertically, but there is very little forward-aft clearance to rock the flanged ends into position in their recesses. The wide widths of the flanges combined with their close fits in the head recesses mean they can only be inserted when they are closely concentric to the recesses. The front/rear row cylinder-head pairs cannot be simply raised to accomplish this because there is a 20 degree angle between them. When they are lifted high enough to slide the flanges in place the lateral distance between them has increased to nearly 1/4" and prevents it. The close fit of the cylinder skirts in the crankcase as well as, eventually, the cylinder mounting studs prevent the heads from being tilted to gain the needed clearance. 
There seems to me to be three possible solutions. The most radical and the one I least like is to re-design the flange mounting surfaces on the heads so they are vertically accessible like those on the H-9 heads and the pipe assemblies can be dropped into place from above the engine.
The second solution is one that I've gleaned studying the Chaos Industries photos. They are using the same deep recesses for their mounting flanges that I am using. However, their flanges are considerably thinner than mine even though they are mounted at the bottom of the recesses in their heads. In my opinion, the deep mounted thin flanges have a poor appearance because they expose the machined flat ends of the radius'd fins. But they were probably have enough clearance around them to rock the intake assemblies into position with the head pair slightly raised. Burying the flanges deep inside the recesses will tend to hide the these clearances.
Before the third solution occurred to me, I thinned a pair of my flanges and then machined two spacers to partially fill the flange recesses. This created a finished appearance identical to my original design but moved the now-thin flanges out toward the front of the heads where some misalignment during insertion could be tolerated. As far as I could tell without building up an actual welded assembly, I may have been able to coax the assembly into place. I might be more difficult to remove it, though, if the need should arise. 
The third solution was one of those things that finally smacks you upside the head after you've spent too much time thinking inside the same box. This solution involves simply cutting the long intake pipe into two pieces in order to separate the troublesome connection between the front and rear row cylinders during assembly. This allows the two sub-assemblies to be easily and individually installed. A sleeve is then slid over the junction to seal the connection. In my design the sleeve will be mostly hidden from view within the notch of the adjacent rear row cylinder. 
I'd like to come up with low profile stainless sleeves since some of them will be visible in the lower cylinders, but so far I haven't been able to come up with a suitable seal. 
I've started a fuel compatibility test with a piece of clear Tygon tubing That I had on hand, but I plan to do more thinking about a suitable seal in the next few days. A sleeve of innocuous clear heat shrink tubing failed my fuel test during the first few minutes. -Terry


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## Sparky_SC

Amazing work !      I find this thread a "graduate course" in workholding techniques which is often a huge challenge.    

I am curious how the tubing bends were done?    Some of the  tubes are pretty short and most have multiple precise bends.     Once again,  amazing work !


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## mayhugh1

Sparky,
      Thank you for the complement. The bender that I'm using is a handheld unit from Rigid. My wife got it for me two years ago for Christmas when I was doing the piping for the H-9 I was building at the time. Its not stocked in the usual home supply stores. She had to look up a Rigid dealer on line. You have to buy the unit for a particular diameter tubing.
Here is Rigid Youtube demonstration videos of it in action:

[ame]https://www.youtube.com/watch?v=ATrDYYPsXaw[/ame]

Terry


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## cfellows

Really Pretty, Terry.  Not only your usual flawless work, but highly pleasing to the eye as well.

 Chuck


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## vederstein

That bender looks exactly like Swagelok benders I use at work.  The only difference is the color of the label - but the text and font is the same.  I wonder who the actual manufacturer is?

...Ved.


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## mayhugh1

I spent a few more days playing with my CAD models and mock-up parts looking for a way to avoid splicing the intake pipe assemblies. I made some small changes to the area around the flange recesses on the test heads and played with the flange thickness, but the fits of all the involved components are just too close.
A very thin flange with lots of clearance around it is the only way I can see to make it work, and I've convinced myself that's what the Chaos guys did. I modeled a thin flange mounted in a shallow recess to maintain the current appearance I want to keep, but I soon remembered the deep recesses weren't there just for cosmetic reasons. They have to be deeper than the fin grooves or their remnants will pass through the sealing surface and create leaks. I considered adding a second gasket and spacer to fill in a portion of the recess, but with the minimum gasket margin I have around the tube openings the risk of creating a leak is just too great. So, a splice is now part of my design.
A short Tygon sleeve looks like it will work, but a better looking solution that I'm thinking about is a stainless steel sleeve. If I build the pipe assembly as a single unit and then cut the long straight tube into two pieces with a thin slitting saw there will be room between the two butted ends for a small compressed o-ring. After installing the two sections and slipping in the o-ring, I should be able to slide a thin stainless sleeve over the joint to hold the ends in alignment and the o-ring in place. With the right amount of compression the friction of the o-ring may keep the sleeve in place. I mocked up a splice and vacuum tested it with some o-rings I had on hand. It looks like the o-ring selection will be a compromise between ease of assembly and amount of friction generated to hold it in place. 
Since the flange design was no longer a variable; and since I want to make some progress on the high volume work, I made a run of 28 flanges using my original design. One of my $10 end mills cut for nearly 8 hours while making those parts, and there is still life left on it. 
Since I only have about half of the scrap 5/16 stainless tubing on hand that I need for this project I had to order a length from an online vendor. I specified 316L (low carbon) annealed tubing because I may have to tig weld the 'Y' in the assemblies. It arrived just as I was deburring my run of finished flanges. I discovered the new tubing measured .316" in diameter while the scrap tubing I had been designing around measured .310". So, it looks like I'm going to have to re-ream the flanges. For deburring I ran the parts in my little vibratory tumbler with tiny (approx. 1/8") ceramic ball media for about 10 minutes. I can only run 3-4 parts at a time because the parts seem to find one another and sometimes scratch up already polished surfaces. When I manually de-burr the edge of a reamed hole I use the nose of larger reamer as a deburring tool. For instance, on the .312" flange bores a .355" reamer with a nicely beveled six-fluted nose works great and gives a nice smooth finish. I typically don't use my good reamers for this, but instead I use specialty-size carbide reamers that I occasionally run across in surplus sales.
Continuing with the high volume work, I milled the clearance slot in the rear row test head for the front row intake pipe using a 7/16" ball cutter to clear a worst-case 3/8" diameter splice sleeve. After verifying the fit with a Tygon sleeve, and while the setup was still in my manual mill, I went ahead and cut the clearance slots in all the rear row heads. The flange recess cutting program is the last head operation to be done on the heads, and it will be run after the valve cages are installed. Now, I also know I'll have to adjust the bore size for the larger intake pipes.
At this point, the most logical step would probably be to install the valve cages so I can completely finish up the heads. Since the intake assemblies have gotten hold of my interest, though, I think I'll continue with them for a while. -Terry


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## mayhugh1

I definitely ran into a difficult and frustrating phase of this project. I spent dozens of hours and used up all the tubing that I had to wind up with only two rear intake tubes having a reasonable fit between a rear head and the crankcase plenum. This tube has two bends that are orthogonal to each other. One end of the tube extends into the plenum through a close-fitting reamed hole in the center of a nut and is sealed with an o-ring to the crankcase by the compression of this nut. The other end passes through a .300" thick flange/gasket combination and protrudes into the head about 1/16". The flange at this end will eventually be hard soldered to the tube in a fixture, and then the flanged assembly will be bolted into the close-fitting recess in the head. I have net clearances of only about .003" at each end of the tube to work with, and so the final shape of this tube has to be very accurate. The lengths of the close-fitting bores into which each end is inserted are long enough that it is also important that the tube ends wind up precisely perpendicular to each other.
My CAD model has been useful only as a starting point because so many second order effects creep into the process of bending this tubing, and I empirically found the bends need to be accurate to less than a quarter degree. And, even accounting for spring-back, my bender doesn't seem to make perfect constant radius bends probably due to uneven work-hardening stresses induced in the tubing during bending. I eventually wound up with two reasonably fitting tubes, but the yield of my free-hand bend-and-tweak process was only a few percent. Even using the special tools I made, my hand tweaking usually distorted ends of the tubes beyond usability. 
The challenge then became making a set of fixtures and templates to make the process repeatable. Since I'll likely need several practice parts to use while coming up the learning curve for joining the two tubes, I probably need more than a dozen finished parts. The clearances I'm currently working with are probably unrealistic for the final assemblies, but I want to maintain them while making the individual parts.
I used red oak for several of the fixtures and templates. Their creation, for the most part, was by trial and error; and working with wood let me iterate more quickly and cheaply than with metal. I was also never able to characterize the actual shape of my bends to the precision that I needed, and so I took advantage of the compliance of the wood which didn't mar the tubing. 
I ended up with 10 fixtures and templates just to create the single rear row intake tube. This number could have been greatly reduced by combining the fixtures (used to verify bends and rough cut lengths) with the templates (used for checking finished lengths). But, once I had a working fixture it became 'gold', and I didn't want to make any changes to it. Two overly complex fixtures eventually emerged to hold the small irregularly shaped tube so it could be safely cut to length on my vertical bandsaw. My fingers ended up in the saw blade several times during my initial bend-and-tweak phase.
The most interesting fixture was CNC'd in aluminum, and it is the final rear tube fixture that is used to cut the notch for the 'Y' with the front tube. It was created in CAD from my engine model, and it precisely determines the position and shape of a milled tube notch. The intersection was designed for a wide flat interface between the two tubes which, hopefully after joining, will become invisible. The closeness of the fit-up of this joint will help determine the actual process I later use to join them. The clearances in this fixture are significantly less than those in the other fixtures, and so it also serves as a final go-no-go template for the rear intake tube.
The first photo shows the scrap I generated while characterizing my bender and coming up with only two usable hand-bent-and-tweaked tubes. Some of this scrap will hopefully be useful later for welding/solder practice. The next photo shows the series of tools and fixtures I created while coming up with a repeatable process for making the rear intake tube. The last photos show a test run of eight parts I made using this process. Only one of the eight parts was rejected due to a poor fit.
The next step is to create a similar process for the simpler front tube and to see how precisely I can fit-up the joint between the two tubes. -Terry


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## jaggus

Thats kol. lot of work there.


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## gbritnell

Although my perseverance is quite good when working on my engine projects I think that the tubing bending and fitting would come close to wearing me down. Wonderful job on the engine!
gbritnell


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## mayhugh1

After a lot of geometry and some machining I finally had a fixture to make the front intake tube. This tube is long and straight with a simple 90 degree bend. But, it's complicated by the fact that one end needs to be machined to fit into the notch of the angled rear intake tube. The goal is to match the rear tube notch as closely as possible while maintaining parallelism between the right-angled front tube and the three axes of the engine. As the photos show I was lucky and got pretty close. I did, though, have to make a small modification to the rear tube notching fixture and then re-work the run of rear tubes that I had already made to correct for an error I had made in that fixture. Fortunately, I was also able to verify similar fit-ups in the other head positions around the engine. With fit-ups this close, one of the options for joining the tubes becomes a thin (.005") disk of silver solder inserted in the interface between the two tubes. An ideal soldering fixture will exert a small force on the joint to push the tubes together and into final position just after the solder melts so my hands can stay completely out of the process. According to feeler gage measurements, the two faces at the interface seem to be parallel to better than .001". The surface area at the interface is .057 in^2, and the silver solder tensile strength is 16 kpsi. If the soldering goes well I could end up a strong (900 lbs), vibration resistant joint.
For testing, I've ordered minimum quantities of two hard solders that are compatible with 300 series stainless. The first is Silvaloy 355 which is a popular 56% silver (probably with nickel) alloy designed for stainless and sold by Brownell's and others in .005" sheet form. Since it doesn't contain cadmium it's marketed as a good color match to stainless. The second is a similar silver/nickel alloy that does contain cadmium, is also available in .005" sheet, and is sold by McMaster-Carr. This solder may flow more easily than the Silvaloy, but the cadmium will give the joint a yellow tinge if I don't manage to keep the solder wholly within the interface. For flux, I still have a double lifetime supply of Brownells 'Ultra Flux' left over from my H-9 project.
After verifying that random tube pairs fit up similarly in the other head-pair locations around the engine, I went into production mode and made the 40 tubes needed for 20 assemblies even though I really only need 9 completed assemblies. I'm anticipating a steep learning curve with the soldering, and I expect some finished assemblies may fit better than others. So, I want plenty of parts to work with. 
I also created a fixture for making, what seemed at the time, the much simpler exhaust pipes. Because I didn't have a plan when I started this one it took me five iterations before I had a final fixture. In order to avoid interference with the heads, the exhaust pipes have to turn upward at a sharper angle than my minimum bend radius will allow. I had to cheat some and move a portion of the curved section pipe into the straight bore of the flange. This required increasing the diameter of the flange bore; and, later, a fixture will be needed to hold the pipe in proper position during soldering. I then made enough exhaust pipes also for 20 assemblies.
The next step, while waiting for the solder to arrive, is to create the last fixture to hold everything in position while the tubes are being soldered into a final assembly. This fixture needs to faithfully replicate the positions and orientations of the tube flanges and plenum compression nut bore that exist in the actual engine. 
For now, I've all but given up on tig welding the assemblies even though, with the fit-up I have, I would get away without using filler rod and probably end up with a nice looking result. After my experiences with the fits of these parts during the past few weeks, though, I'm afraid the stainless will move around too much under the heat of welding. And, designing the holding fixture for access around the entire joint will greatly complicate its design. If the sheet solder approach doesn't work, my current plan B is to wrap a ring of solder around the exterior perimeter of the joint and flow the solder into it with an exterior fillet. For that reason, I've also ordered some 1/32" diameter color-matching Silvaloy. -Terry


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## barnesrickw

I'm blown away.  Your jig and fixture use is very inspiring.  


Sent from my iPad using Model Engines


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## petertha

Hi Terry. Awesome work as usual. I'm not sure if you are already familiar with Kent's offerings, but thought I'd point it out in case. Last fall I treated myself to his OA torch class. (A long haul from Canada, but beautiful part of California & big checkmark off my bucket list . Anyway, I'm pretty sure this is one of the goodies we got to try. I recall the solder color being very close to native stainless, but not 100% & obviously its wire not sheet if that was a requirement. I'm sure he'd be happy to provide details.

https://www.tinmantech.com/html/silver_solder.php


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## mayhugh1

Peter,
Thanks for the info. Yes, I'm familiar with that particular solder. I bought the identical product from McMaster Carr a few years ago and just checked, and I still have it. I didn't realize the tensile strength was that high, and so I wasn't considering soft solders for this application. It's now a definite possibility for me to try. I was thinking earlier that even if my hard solder sheet idea works the joint appearance might be improved with an exterior fillet. The lower temperature of this solder might be perfect for adding it. 

Thanks,
Terry


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## mayhugh1

All my tubing work literally comes together in this final soldering fixture, and so it deserves its share of thoughtful planning and careful construction. It has to present mounting surfaces for the two intake/exhaust flanges that accurately match those in the engine while supporting the bottom end of the rear intake tube in a precisely simulated plenum bore.
The flange mounting surfaces and their orientations were computed from my model, and their dimensions were checked against measurements on the engine mock-up that I've been using to test fit the tubes and validate the numerous fixtures and templates.
I used hot rolled steel for the entire fixture rather than more easily-machined aluminum in order to reduce heat conduction away from the joints during soldering. The wide range of heights among the three mounting points made it impractical to machine the fixture from a single piece of steel, and so I decided to make up a welded assembly. Even though the pieces were only tac-welded, the welding left stresses in the assembly that had to be relieved. I did this by heating the weldment to 1200F for 2-1/2 hours and then allowing it to slowly cool in the oven overnight. If the stresses had not been relieved prior to machining, the silver soldering temperatures would have eventually relieved them, and the dimensions of the fixture would also have creeped over my run of parts. 
Construction started by squaring up a half inch baseplate of steel. Three pieces of 3/4" thick steel plate were cut and squared up for the mounting surface columns. Some material was drilled out of the columns just below where the flange mounting surfaces will be later machined in order to increase their thermal resistances. Shallow pockets were milled into the baseplate to locate the positions of the three columns prior to welding. The columns were also rough machined to within .030" of their final heights before welding because of the difficulty in removing large amounts of material later. The components were tig welded, and the entire assembly was then stress relieved. For this step the weldment was sealed in a stainless steel foil package that was filled with argon welding gas to prevent scaling. After cooling, the bottom of the baseplate was re-ground flat. Keeping the baseplate flat and square will become important if the assembly has be returned to the mill vise for re-work after the machining has been completed.
On the mill, the top surfaces were drilled and tapped for the flange mounting screws. Shallow bores were drilled and reamed on either side of the mounting holes to match those on the flange mounting recesses in the heads. These bores allow the tubes to extend slightly through the flange and into the fixture just as they will when they are mounted to the head. Since the ends of the tubes are slightly beveled, though, they can't be used to accurately locate the flange on the fixture during soldering. Therefore, an alignment edge was incorporated into each flange mounting surfaces.
A square slot was milled into the fixture's highest surface to position and support the plenum end of the rear intake tube. The square slot offers a minimum contact patch with the tube and minimizes heat conduction away from the 'Y' joint. The wide range of fixture heights over the rather small base area complicated the machining and required the tools to be set up with very long stick-outs that limited their depths of cut to about .005". This was the reason the three columns were roughed so close to their final dimensions before welding.
I was very happy and, to be honest, a little surprised with the final result. As the photos show, the fit-up appears to be identical to what I have on the actual engine. I won't know for sure, though, until at least one tube assembly is actually soldered together and trial fitted into the engine.
My solders should arrive any day now; and after some practice, I should be ready to start assembling them. - Terry


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## mayhugh1

The Silvaloy 355 sheet solder arrived immediately after my last post, and I couldn't wait to see if my solder disk idea had a chance of working. I decided to make a quick and dirty test using my new soldering fixture and a pair of notched intake tubes that I had previously scrapped just to see what kind of learning curve was ahead. I used a pair of my flanges to hold two of the three ends of the assembly in the fixture, but I decided to not solder and waste them in this first attempt. At this point I was only interested in the critical 'Y' joint. I really don't expect problems with the flange soldering as the ones in this engine are very similar to the ones I designed and soldered for my H-9 build.
I cut a disk out of the .005" solder sheet to roughly match the outer profile of the joint, punched a 1/8" hole in its center, and then bent it 90 degrees. For flux I used UltraFlux which is a creamy white water-based fluoride+borax product popular for brazing and silver soldering. I painted both joint interfaces as well as the disk with a light coat of this flux before inserting the solder disk between the tubes. An serendipitous design feature of my soldering fixture is that when the flange mounting screws are tightened down, the fixture pinches the two tubes together at the 'Y' joint and captures the solder disk between them. However, I had some trouble adjusting the height of the front tube at the interface to the exact height of the rear tube because the solder disk between them made it difficult to tell when they were perfectly aligned. I continued, though, and heated the tubes on either side of the joint with a mapp gas torch. After several seconds, the flux began bubbling just before the solder melted and flowed nicely around the joint. The first photo shows my first 'Y' joint attempt while it was cooling in the fixture. After it had cooled to the touch, I dipped it in a pickling solution of sulphuric acid (purchased from Lowe's as drain cleaner) for about ten minutes to remove the flux residue. I used a small stainless steel brush to swab the interior, and then I neutralized the remaining acid by dipping the assembly in a solution of water and baking soda. When the fizzing stopped I lightly buffed the joint with a fine ScotchBrite pad. One of the photos shows the final result. The joint looks great except for the misalignment of the two tubes, and so my alignment technique needs some improvement.
I leak-checked the assembly by plugging two ends and pulling a vacuum on the third. I was then curious about the strength of the joint. The test I did was not at all quantitative, though. I just tightened the long front intake tube in a vise with its ID backed up with a piece of drill rod. I then grabbed the rear intake tube with a pair of locking pliers and pulled until the joint separated. It was difficult to tell for sure, but even though I put a good bit of my weight behind it I probably pulled with less than a hundred pounds. In any event, the tubing at the joint appears to have distorted before the joint separated. The joint strength was certainly less than my estimated 900 pounds, but it feels adequate for this application. The third photo shows a close-up of the distorted halves of the separated joint. 
The entire surfaces of both tubes at the interface are wetted with solder, and it appears that it was the solder itself that yielded rather than the solder separating from the metal. This would seem to imply that the metal was adequately cleaned. There are a significant number of gas bubbles, though, in the solder itself visible in the interface where the two halves of the joint separated. These voids total about 25% of the interface area are for sure partially responsible for the lower strength joint. I need to do some research, but these bubbles may be related to an over or under heating of the joint. The solder flowed so nicely in the outside fillet, though, that I wouldn't expect it to be an under-heating problem.
On a more positive note, the flux seems to have been completely removed from the interior by the acid bath. A clean interior is very important for the intake tubes so that foreign debris doesn't eventually end up becoming embedded in the seats of the intake valves. - Terry


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## Swifty

Very nice looking soldered joint, I'm following along with interest.

Paul.


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## mayhugh1

I did some research and found that Silvaloy 355 actually contains 56% Ag, 22%Cu, 17% Zn, and 5% Sn for a flow temperature just over 1300F. My first thought was maybe the gas bubbles were caused by me overheating the joint and perhaps causing the zinc to outgas. During my first attempt I left the torch on the joint for several seconds after I saw the solder flow on the outside. Zinc boils at 1664F, but I know in it its free state, at least, it can actually start fuming just above its melting point at around 800F. If this is also true with it in a solder alloy the bubbles may be a fact of life.
I soldered up two more sets of practice tubes and tried my best to limit the temperature so as not to go any higher than necessary to melt the solder. In both cases I immediately removed the torch just after getting a beautifully flowed external fillet. But, during my pull tests, both pairs of tubes separated with noticeably less effort than that of my very first attempt. The first photo shows one of my results. In both attempts the solder inside the joint had not gotten hot enough to fully melt and wet the entire area of the joint. This caused a large portion of the solder to separate cleanly and easily during the pull test. For what it was worth I didn't see any bubbles, though. This seems scary to me since it looks like it may be very difficult to judge the proper temperature for an ideal joint.
I also discovered there are basically two types of fluxes used for silver soldering. The first is a "white" flux, and is the one I've been using. The second is a "black" flux which is pretty much the same as the white variety except that it contains more borax for better joint protection. It's also useable up to a few hundred degrees higher than the white flux. So, I soldered a pair of tubes together using a sample of the black flux that I got from a friend. I used enough heat to get a nice exterior fillet and then "a little more." This pair of tubes required noticeably more force to separate them than my very first attempt. The second photo shows there are still gas bubbles in the interface, but maybe not quite as many as there were in my first attempt with the white flux. It's also possible the flux made no real difference, and the slight improvement I saw was due to something else.
At this point I began looking to see if there were other hard solders recommended for stainless steel that do not contain zinc. To my surprise, I found that zinc is a common component in all of them - even in those containing cadmium.
Before I do anymore hard soldering, I want to experiment with the soft solder that Peter mentioned in his post. It is 96.5% Sn and 3.5% Ag and contains no Zn. Surprisingly it has about the same tensile strength as the hard solders and melts at a much lower temperature. I have some of this solder on hand, but I don't have the flux for it; and so I'll have to wait for a delivery to arrive. -Terry


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## mayhugh1

I received the flux for my Sn(97%)-Ag(3%) soft solder, and it appears to be mixture of zinc chloride and hydrochloric acid. The solder I have is .093" diameter wire; and so, I used my hydraulic press squeeze a half inch long piece into to a .010" thick disk. I also used a jeweler's ring expander to draw a length out to about .063" diameter. After fluxing both surfaces of the notch as well as the center-drilled and 90 degree bent disk itself, I used a mapp torch to heat the joint in my fixture. The solder wetted the interface and flowed nicely throughout the joint with negligible heat discoloration of the tubing. I didn't trim the disk close to the size of the joint as I had been doing with the hard solders because I wanted gravity to over-fill the underside of the joint so I could metal-finish it as a test to see how it might look. The first photo shows the joint cooling in the fixture. The next two photos show the raw topside and the final metal-finished bottom side of the joint. Disappointingly, it took about the same effort to pull this soft-soldered joint apart as it did to pull apart my original hard soldered joint. The fourth photo shows the nice looking interior of the pulled joint. The solder thoroughly wetted both surfaces; and the joint cleanly separated along a line entirely within the solder. I don't know why I seem to consistently get joint strengths that are nearly an order of magnitude less than what I calculate from the solder's tensile strength. In this particular case, though, the solder line may have been too wide.
I decided to continue using soft solder for my 'production' assemblies since the lower temperature is less traumatic to the metal, and the achievable strength of my particular joint seems to be similar with either solder. I like the appearance of the heavier fillets that I'm able to sculpt with the soft solder even though the manual metal finishing adds another hour of work. If I have to re-solder a joint before things are just right the soft solder seems to be easily re-worked. One might raise a question about the lower service temperature of soft solder in this application, but previous measurements on my H-9 exhaust pipes (150F) tells me this shouldn't be a problem. The flux residue was simply removed from these parts by boiling them in water. 
I added a spring to my soldering fixture to help pull the two tubes closer together at the 'Y' just after the solder disk between them melts. I did this to help reduce the thickness of the solder line in the joint just in case it was a limiting factor in my joint strength. I didn't do anymore pull tests, though, to verify any change in the results. I cobbled up some simple fixtures to hold the two exhaust pipe turn-ups in proper position, and then I soldered my first complete assembly. The last series of photos show the final results. It took about three hours from the time I pulled the pre-formed tubes out of their storage bags to when I finally inserted the completed assembly in the engine. The good news was that it fit as expected in random head positions around the engine. As expected, but unfortunately, I also verified that a splice will definitely be required on the long front intake tube. The soldered assembly is too rigid and the clearances are too tight for it be wiggled into position inside flange recesses of both heads simultaneously. The color match of the tin-based solder is pretty close to that of the stainless tubing, but it's not perfect. It's noticeably better, though, than what I observed with the Silvaloy.
Pre-fitting, cleaning, and fixturing the parts and preparing the solder is necessary, but takes much longer than I expected. My current plan, though, is to continue with this process for the remainder of the parts. - Terry

p.s. Thanks Peter, for your suggestion.


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## petertha

mayhugh1 said:


> Thanks Peter, for your suggestion.



 My pleasure. (Lucky rookie suggestion!). Your joints are a work of art. I hope they provide many hours of trouble-free, rumbling, radial service!


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## kuhncw

Terry, thank you for all the work that goes into your posts as they are very educational.  I especially enjoy your fixturing.

Regards,

Chuck


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## Swifty

Well I have to agree, they are certainly a work of art, those fillets are amazing. It brought to mind a job that I did for one customer years ago, we had to machine a very high temperature resistant stainless steel material, flat plates with circular grooves in different positions, and tubes machined to length that fitted in the grooves. They were made up into top and bottom plates, with the tubes like pillars between the plates. The assemblies were air freighted to the US for specialised soldering and then returned. The assemblies were all part of a gas powered generator set.

Paul.


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## mayhugh1

I can't say that finishing up these tube assemblies has been one of my favorite parts of this build. It seemed that no matter what I did to try to make the process more efficient it still took me three hours to complete each one of them. More than half of that time was metal finishing with a file. To save some steps I tried cleaning (Scotch-Brite'ng) all the parts at one time, but I then found the solder didn't seem to wet as well as when the parts were cleaned immediately before the fluxing/soldering. Evidently, the surface oxide on stainless reforms pretty quickly after machining. It was really tempting to call it quits after completing only the nine assemblies I actually need, but since I had the extra parts I went ahead and finished out 15.
As solders go, this one is reasonably easy and safe to work with since it contains no lead or cadmium. The flux, though, is another matter. After soldering the first few assemblies my fixture had become badly corroded, and the registration surfaces had to be Scotch-Brite'd before building up each assembly. Even though I was running an exhaust fan, all the hand tools on my bench within a couple feet of the soldering fixture also ended up with surface corrosion. And, I came down with an unusual (for me this time of year) chest cold which makes me wonder if chlorine fumes from the flux changed the balance of bacteria in my lungs.
I took some photos of the metal finishing steps used to form the fillets at the 'Y' joint mainly to break up the tedium, but also because the process might be of some interest in other's projects. It seems like a useful tool to have in one's bag of tricks - not only for manually creating complex surfaces but also for repairing accidents to high value parts.
This type of metal finishing is very similar to blending auto body seams with body solder. The biggest difference is that body solder contains a large percentage of lead which separates its melting and flowing temperatures a bit to aid in 'buttering' a vertical surface. The solder I'm using, though, flows like water as soon as its melting temperature is reached. A practiced hand with the torch was even needed to keep excess solder from flowing off the top of the relatively level joint that I was working with. The trick became getting the surface to just the right temperature so the solder melted but then was immediately chilled by feeding in additional solder. It was also important in my particular case to not mechanically clean the interior of either tube in order to discourage solder from flowing beyond the joint and sticking to the tube's interior where it would reduce its i.d. Examination of the sections in my pull tests showed it was easy to keep the i.d.'s open. 
After buttering the solder around the joint and allowing it to cool, the assembly was dipped briefly in a pickling bath of diluted sulphuric acid, neutralized in a baking soda solution, and then boiled in water for ten minutes to remove any flux residue. A belt sander was used to knock down the tall blobs of solder that liked to form on the underside of the joint. 
A 3/16" circular rasp file was used for most of the metal finishing. It was used to create the fillets and feather their edges into the stainless. A rasp is an effective tool for this first step because it's capable of removing large amounts of solder with little effort and without loading up with solder. Because of the difference in hardness between the solder and the stainless it's very easy to stay within the solder and minimize gouging or severely scratching the tubes. A medium 3/16" circular file was then used to remove the filing marks left by the rasp and to fine tune the blending. This was followed by a fine 1/8" circular file which removed the medium file marks, and smoothed the smaller radius between the two tubes that wasn't reachable by the larger files. A piece of 200 grit paper was then wrapped around the 1/8" file to removed the remaining file marks. The whole assembly was then burnished with a medium (red) ScotchBrite pad followed by an extra fine (white) pad. 
Each assembly was completed and checked for proper fit in random positions around the engine before starting on the next one just in case something went wrong. The assembly with the tightest fit was marked for identification. This one will be used later to determine any needed changes in the final clearances of the CNC program used to complete the exhaust flange recesses as well as the bores in the plenum compression nuts. 
The next step is to finish the design of the front intake tube splice and to modify the tube assemblies accordingly. - Terry


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## Scott_M

Wow!
 That is truly beautiful. A sight to behold. Your attention to detail and perseverance is a testament to be jealous of.
 Thank you so much for taking the time to document all of this build. I am sure many of us would not have the patience to be so thorough.

 Scott


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## petertha

mayhugh1 said:


> To save some steps I tried cleaning (Scotch-Brite'ng) all the parts at one time, but I then found the solder didn't seem to wet as well as when the parts were cleaned immediately before the fluxing/soldering. Evidently, the surface oxide on stainless reforms pretty quickly after machining.- Terry



Well you are light years ahead of what probably amounted to my ~hour of 'learning' silver soldering on stainless coupons so passing on FWIW. But I recall Kent was adamant about using isopropyl alcohol + fresh stainless wire brushing + alcohol wipe again for nearly all pre-soldering joint prep (& incidentally same procedure for aluminum brazing). The Scotch-brite seemed to be reserved for post-cleanup, maybe this is why? I noticed my shiny fillets I was so proud of developed a slight, whitish chalky streak on them by the time I got them home so yes, must be something in the flux.

 Maybe if you got some ~1"dia mini stainless wire wheels on a variable Dremel tool, that could make the tubing pre-solder prep go quicker? I've found the jewelry supply places sell them very reasonably by the bags vs. typical hobby suppliers. Hope this helps & thanks again for sharing.
 -Peter


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## mayhugh1

Peter,
     You're probably right about the stainless wheels speeding up the cleaning. It didn't occur to me to try them. I forgot to mention it in my post, but I actually was doing a swab with a paper towel dipped in rubbing alcohol just after pre-cleaning with the  ScotchBrite pad. There was always a dark reddish smudge left on the  towel which was probably the alcohol cleaning off debris left behind by the pad. -Terry

Also, thanks Scott...


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## mayhugh1

After doing some more research I came up with a solution to my intake tube splice that I'm reasonably happy with. Earlier I found that clear heat shrink tubing gave what I thought was the least conspicuous solution of all the connections I was able to mock up. But, when I checked the fuel resistance of the tubing I had on hand I found that it was quickly attacked by unleaded gas. What I didn't know at the time was that specialty heat shrink tubing is available in a wide variety of materials. 
I located a variety made from a gasoline resistant material from Buyheatshrink.com. It's Kynar which is a chemical resistant material designed for hot and nasty areas. It's standardly available in clear and just happened to be the only product available from them in small quantities at about a dollar per foot. The tubing I bought is semi-rigid and comes in four foot lengths. After cutting the long intake tube in my assembly with a thin slitting saw and installing the two assembly halves into the heads, the ends should align perfectly when mounted in the engine. A short length of this tubing can be then be slid over the tiny gap and shrunk in place. If the engine has to be unassembled the splice is easily cut off and replaced with a new one during reassembly.
I cut a few test pieces and put them in a beaker of unleaded gas for several days to verify their fuel resistance. I also leak checked a few test splices with my MityVac to make sure there would be no issues with intake leaks. The worst-case measured leakage was less than a tenth of my best measured valve leakage and probably would have been just fine. But, I elected to compress a small Viton o-ring in the space between the tubing ends in order to positively seal the connection. The job of the shrink tubing then becomes one of holding the o-ring in place while the leakage is reduced to zero. As was the case here, I often find I need an odd size o-ring that isn't quite covered by a standard AS568 size. Metric o-rings come in nice in-between sizes and TheOringStore.com stocks a wide range of sizes and materials. The shrink temperature of this tubing is quite a bit higher than the common electrical variety, and is the reason I chose a high temperature o-ring. After cooling, even when pulled off the metal tubing, the shrunk tubing is quite rigid standalone.
I was able to determine that the clearances in my current flange machining program are adequate to complete the machining on the rest of the heads. I did decide, though, to open up the bore in the plenum compression nuts to clear a slight curvature in the rear intake tube. This curvature was a result of the minimum bend radius capability of my tubing bender. With this change, the rear intake tubes appear to be sealed perfectly by the o-rings that are compressed by these nuts.
I made a fixture to support the intake tube assembly while a slitting saw cut the long front tube into two pieces. The thickness of the saw was determined by my o-ring thickness. The backsides of the flanges were scribed with matching numbers in order to keep the flange pairs together during final assembly. These numbers will also be used to key each completed tube assembly to a consistent location in the engine after its spliced fit has been verified. I did trial cuts and fits on two different assemblies using my two test heads but decided to wait until the final machining on the heads is completed before cutting any more. The tube assemblies can then be fit and keyed to their actual head pairs. 
I was anxious to try out a completed tube assembly in the head positions around the oil sump. As the photos show this area is very busy, but the clearances ended up as designed; and that I have clear access to the oil drain plug at the bottom of the engine. In the last photo I also added a cosmetic stainless sleeve over the Kynar splice. I may or may not use these during final assembly depending upon whether I find the friction from the shrink tubing to be sufficiently consistent to keep them in place.
Since I'm now confident in the program used to machine the flange recesses in the two test heads, my next step is to install the valve guides and complete the final machining step on the rest of the heads. - Terry


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## mayhugh1

Finishing up the 24 heads was just a matter of installing 48 valve guides that I'd already machined, tapping 192 2-56 rocker box mounting screw holes that I'd already drilled, machining and tapping 24 intake flange recesses, drilling/reaming 48 intake/exhaust tube ports, and then finally de-burring, numbering, and scrubbing the finished parts clean. Being someone who doesn't like repetitive work, I couldn't wait to get started.
Earlier, when I machined the valve guides, I delayed cutting the seats until now just before their installation. My process was to use the Brownells seat cutter I described in an earlier post to cut a preliminary .005"- .007" wide seat and then verify it with a vacuum leak check before installing the guide in the head. It was installed only after passing my leak-down criteria, also described earlier. Later, when the valves are finally installed in the heads the seats may be widened a tad more during the final lapping process. As described earlier, this lapping will be done with a separate lapping tool and not with the actual valve. 
Some 'back of the envelope' calculations I did showed that a seat width of .005" will give me a factor ten margin against any further widening due to hammering by the pressures of combustion. Unnecessary widening causes unnecessary valve lash adjustments and is something I would especially like to avoid in this engine. The microscopic machining marks (<.0005" grooves and ridges) left behind by the seat cutter that initially limit valve sealing should still be hammered out in the first several minutes of actual running.
In the past I've cut the seats dry, but this time I discovered that I could significantly improve the leak-down times if I dipped the end of the guide in WD-40 before cutting the seat. Under a microscope it was obvious that the surfaces of the wet-cut seats had better surface finishes, and an improved smoothness in the cutting action of the seat cutter was also clearly felt. I'm using 544 phosphor bronze guides - other materials may give different results.
The guides are an approximate .002" slip fit in the heads in order to avoid seat distortion during installation. As an earlier photo showed, I previously cut shallow circumferential grooves in the o.d.'s of the guides to collect excess Loctite adhesive as the guides are pushed into place through the bottom of the head using a simple installation tool I made. After cleaning the head bores and guides with acetone, both surfaces were coated with a very thin layer of Loctite 620 by swabbing them with a cylindrical wooden toothpick. The installation of the guides had to be done in a single swift action because the adhesive set up almost immediately. I held a machined-flat plastic backing plate against the top of the head with one hand and pushed the guide upward with the other hand until it bottomed on this plate. This plate set the proper installation depth. A pair of plastic coated wires were temporarily inserted into the rocker box mounting holes to keep them from being filled with excess adhesive. Within seconds the adhesive between the two parts set up,mand then Q-tips were used to thoroughly clean away excess adhesive from both ends of the guide. The Loctite was allowed to cure at room temperature for a few days before the flange recess machining was started.
With the rocker box mounting holes now threaded it was finally possible to mount a few rocker boxes on a few heads and assemble them to the crankcase for a sanity check on the fit.
The most logical next step would be to machine the valves. I've gathered up the raw material, but I'm a little burned out on high volume parts right now; and so I might start working on the carburetor mount. I've already chosen the carburetor, and so I need to design and build an adapter between it and my rear housing and then add to it a fuel bowl. -Terry


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## mayhugh1

I decided to continue on with the high volume parts in his build after all, and so My next step was the valves. Since I had so many to do, I wanted an efficient process for making them in volume. What I ended up with was a five step lathe machining process that is very similar to the one I developed for my H-9 valves. This process is most suitable for making a large batch of valves. If I were making 6 instead of 60, I would combine some of the steps and also make use of the lathe tailstock.
I started by cutting up an odd diameter 303 stainless rod that I had on hand into 30 pieces each about 4-1/2" long. This rod was salvaged from a scrapped oilfield tool some 20 years ago and had been precision ground to .433" +/-.0001" over its entire eleven foot length. I had been saving it for something special, but life is short and 'special' never showed up to claim it. My process includes machining two valves, one on either end of each of these short workpieces. The work-holding spigots between the two valves will eventually be recovered for future use.
I compiled two CNC programs for my lathe - a roughing program and a finishing program. The roughing program machined the entire profile of each valve but left .020" excess stock for the finishing operation. The roughing program was run on both ends of the entire batch of 30 workpieces before reconfiguring the set-up for the finishing program. Since there were no final dimensions machined during roughing I was able to rough out the batch of blanks relatively quickly over a period of a couple days. The workpieces were fed into the lathe collet chuck one after another without much thinking or measurement checks to slow things down.
For expediency, and counter to common practice, the tailstock wasn't used in either operation to support the workpieces even with their long stick-outs. I did this to avoid a later secondary operation to finish the valve stem tip. In my process the tip was faced to its finished surface state at the start of the roughing operation, and then it was used as the z=0 datum for all succeeding operations. Lack of outboard support, though, caused a high pitch squeal whenever the cutter removed material from the far end of the stem. It didn't seem to affect the surface finish, but it was really annoying and potentially created unnecessary wear on the cutter. To squelch it, I pinched a narrow strip of leather between the valve stem tip and a small diameter metal rod chucked in the tailstock. This damped the oscillation that was causing the squeal without creating the need for a secondary tip operation. As a bonus, it burnished and probably slightly hardened the tip surface. I couldn't resist the cheesy photo of the completed roughed valve blanks posing in front of the swarf left after chewing up what was probably once an incredibly expensive piece of metal.
Concentricity of the valve's finished dimensions was achieved by machining them all in a single setup in the finishing program. The finished diameter of the valve stem is .184", but it is necked down to .140" for a short distance behind the head. After finishing the valves and taking a second look at the valve-in-valve cage drawing I included in this post, though, I wish that I had extended the necked-down area an additional hundred thousandths.
The method I'm using for machining these valves takes advantage of the fact that only a portion of the valve stem has a diameter that is actually critical. In my case, this is a half inch section behind the necked-down area that slides back and forth in the reamed bore of the guide. My goal here was a .0005" sliding fit. To achieve this, the stem was turned to a target of .185" during the finishing step. Later, in a third lathe operation, this area was manually polished to its final dimension with 400 grit paper. The remainder of the stem is not critical and needs only sufficient clearance to pass through the guide. Because the finishing step removed minimal material it ran quickly, and so I just held the leather damper against the outboard end of the stem with my fingers while the program was running. This allowed me to 'lean on' the stem a bit while the non-critical diameter of the outboard end was being cut in order to reduce the polishing time needed on this portion. The critical diameter section was tracked on each part during its finishing operation, and the work offset was adjusted as necessary to attempt to maintain a .001" excess stock in this area on the next part. In reality, the excess stock typically came out between .001" and .002" because of variations in workpiece deflection. The extra polishing time added by this uncontrolled deflection offset some of the secondary machining time I was trying to save by not using the tailstock for outboard support.
Some additional polishing was added to the third step. The valve's seat face was polished with a piece of tightly folded 600 grit paper, and then the entire valve was polished to a mirror finish with a shop towel dabbed in metal polish. Microscopic machining marks removed from the seat face by polishing will improve valve sealing. Spare valve guides were used as gages during this third step to verify the close fit of each valve blank. For efficiency, the finishing program was run on both ends of the entire batch of parts before the polishing was done. The polished valves on each end of every blank were leak-checked using a finished head before they were sawed away from the central spigot. This kept my valve making process from quietly drifting off into oblivion. Every valve passed with essentially the same vacuum leak down time: 10 secs for 25inHg to 15inHg pressure drop in a .25 cubic inch total volume. This un-lapped time matched the final average leak down time I was able to achieve with my lapped H-9 valves. I'm making several extra valves so I can experiment with improving the sealing even further.
After the polishing and leak checks were completed, the valve blanks were taken back to the bandsaw where the semi-finished valves were cut free from their work holding spigots. A simple shouldered Delrin split collet was turned and inserted into the lathe collet chuck. This allowed each semi-finished valve to be safely and consistently located on the z-axis while the valve heads were faced to their finished length. A second shouldered fixture was turned to grip each valve in the lathe collet chuck for the final operation. This time the stem tip was available so the narrow groove for the U-clip spring retainer could be cut. 
The actual machining time averaged out to about 30 minutes per valve, but the total time I actually spent working on the entire batch came out closer to 60 hours. For those interested, the lathe insert I used for roughing was a Seco DCMT21.51 MF2 TP250, and for finishing I used a Kenametal DCMT21.51UF. I was able to cut all 52 valves and 3 double laps with a single edge of each insert. 
Finally, I used the parts I now had available to verify with measurements what I expect for my worst-case valve-piston clearance. Fortunately, it matched the clearance in my model. My next step will be to install the valves in the heads and finally, after six months, declare the heads finished. - Terry


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## petertha

Wow! 

 Is this the correct way to interpret your seal test setup:
 1 = vacuum applied to port
 2 = the 'double ended' valve work piece, seat finished but prior to parting off/finishing into 2 valves
 3 = some kind of rubber/plastic 'blank off' piece?

 - if so, can you elaborate on 3, does it somehow snub into the valve guide hole indexed into those 4 holes on the flange?

 - can you elaborate on the dimensional (volume) part in "the pressure drop in a .25 cubic inch total volume"


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## mayhugh1

Peter,
You're right on 1 and 2. Number 3 is a silicone plug that goes down over the protruding valve stem and seals against the walls of the valve guide in the area where the spring will eventually go. This is needed to seal a potential leak between the valve guide and the valve stem because I'm pulling the test vacuum at the intake/exhaust port behind the valve. This leak is only present in my test and not present in actual use.
When you measure a leak by measuring a pressure drop over time, it isn't really meaningful unless the volume of the thing being measured is also known. For example a 5 psi drop over 5 seconds indicates a much larger "hole" if you're measuring that pressure drop in a 20,000 gallon tank compared with measuring the same drop in a .5 cubic inch combustion chamber. I've always used the same MityVac and same connecting hose for doing my leak down tests on all the engines I've built and so the comparative numbers mean something to me. If someone else tried to get the same numbers on one of their engines they would need to be measuring with the same volume as I am in order to try for the same leak down numbers. In my case the total .25 cubic inch volume is mostly measuring instrument volume, i.e. meter and connecting hose volume. The volume behind my actual valve is only .067 cubic inch. By the way, the 10 Hgin pressure drop measured on my MityVac works out to be a 5 psi pressure drop which, for most, is a more intuitive unit. -Terry


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## mayhugh1

In the process of gathering up all my bagged parts related to valve installation I ran across a note I had written to remind me about a cosmetic chamfer I had decided to add to the tops of the spring caps. So, I spent a couple hours finishing up some parts that I thought were already done. If you think this was an extravagant waste of time wait till you read below about what I did next.
Before starting the valve installation, though, it might be useful to review the parts involved since their fabrication has been spread over several weeks. First, the valves are completely finished. The heads and seats were turned concentrically with the stems, and the seat faces have been brilliantly polished. The valve cages, though, are only semi-finished. The seats have been cut to a width of just under .005" using a manual piloted seat cutter which insured they are concentric with the integral guides. However, the machining marks left in the seats by the seat cutter have not yet been addressed. I have two seat cutters - one shop made and one recently purchased - and they both leave machining marks that ultimately limit sealing. The one I've been using most recently is a ten flute 45 degree muzzle cutter from Brownells. To the naked eye it produces a nice surface finish, but under magnification tiny circumferential grooves can be seen in the seat's surface similar to the ones left by my shop-made cutter. The prominence of these grooves is important and at the end of the day their depths can't seem to be limited by manipulating the cutter. With either cutter used individually, I get about the same results. The leak-down times they produce are essentially identical and remarkably consistent across a large number of seats.
What I learned through some testing, however, is that if the seats are cut using both cutters - one alternated with the other - I can always get a significantly longer (up to 2X) leak-down time compared with what I can get with either cutter used individually. I eventually discovered that with the pair of cutters I could often reach 20 seconds, and with a time this long lapping really isn't necessary. It appears each cutter is knocking down the machining marks left by the other, and the net result is a better over-all surface finish. But, I've jumped ahead.
The cages have already been installed in the heads with high temperature Loctite and are free of any distortion due to installation. Just before installation each seat was cut with the Brownells cutter and then leak-checked using a single H-9 test valve. The average leak-down time was typically 10 seconds +/- 3 seconds for a vacuum leak of 25 Hgin to 15 Hgin. The total involved volume for this measurement including the vacuum gage and connecting hose was approximately .25 cubic inches.
This leak-down time is probably only meaningful to me because it became an empirically derived target while building my previous two multi-cylinder engines. It might be more interesting to others, though, if it is converted into something a little more familiar. With just a simple units conversion this 10 second leak-down can be shown to be equal to a 5 psi pressure drop over 10 secs or, equivalently, a 0.5 psi drop per second. Through sheer coincidence the volume of my combustion chamber at TDC is also approximately .25 cubic inch. So, without having to correct for a volume difference the effect of this leak on, say, a compression measurement can be roughly estimated for my shop-made peak-reading compression gauge. This gauge has negligible internal volume compared with that of my combustion chamber. Assuming a compression ratio of something over five, the expected pressure in the combustion chamber during a compression test will be about 5X atmospheric or about 75 psi. Scaling my measured pressure drop created by a single leaking valve to the increased internal pressure during a compression measurement gives, roughly, a 5X or 2.5 psi drop per second. With a cranking speed of 120 rpm or 1/2 second per 4-stroke cycle, a cylinder with this single leaking valve will have about 1/2 second (yes, I'm making some outrageous simplifications here) to lose roughly 2.5 psi or about 3% of its actual value.
The effect of this leak on combustion pressure during worst-case running can also be roughly estimated. Assuming the maximum combustion pressure is about 5 times the compression pressure (rough rule of thumb I found on the web) the pressure loss due to this single valve during running will scale up another factor of 5 to some 12.5 psi drop per second. With a worst-case minimum running speed of, say, 600 rpm or .2 sec per 4-stroke cycle, the cylinder will lose roughly 2.5 psi of its 375 peak pressure (simplification alert again) for a loss less than 1%.
So, it seems perfectly reasonable to leave things as they are. That is, I can with good conscience install the valves and let the pressure pulses from combustion beat the final machining marks on the valve seats into submission even though with this level of sealing the leaks really aren't significant. But, I like to experiment, and I'm interested in learning more about what's involved in getting to the next level in valve sealing. I have plenty of parts to play with, and I've never been one to stop at a point of diminishing returns. 
So, the goal in front of me was to remove the machining marks from the valve seats in order to obtain the best possible seal with the valves. In previous builds I've learned that lapping valves to their seats immediately after cutting them is not always a good idea because if the machining marks left on the seats are prominent, lapping will just transfer them over onto the valves and score their beautifully polished surfaces. I've also learned that the grit of the lapping compound needs to be scaled for the narrow seats typically found in a model engine. For my own lapping I now use nothing coarser than metal polish. In a model engine the effect of using typical automotive valve lapping compounds can be inconsistent, and even disastrous.
I made three double-ended metal laps for lapping my seats while I was making the valves for this engine. My intentions were to use them instead of my valves to do any needed lapping. But, I began having second thoughts about them wearing too quickly even with metal polish as a lapping compound. The hardness and narrow seat widths of my new phosphor bronze valve cages were my concern. When I made my H-9 valves I inadvertently used a softer bearing bronze for the cages and was forced to cut the seats to a width of .015" - .020" in order to clean up distortion created by pressing them into the heads. The two double-ended laps that I made for that project lasted long enough to lap all the seats in that engine plus a few spares. With the much narrower and harder seats in these cages, though, I'm afraid the laps will wear out before I finish the whole lot of 48 valves.
The first alternative I came up with was a new piloted lap turned from a wood dowel rod. Two photos show the lap and the seat in a spare valve cage after one minute of lapping with Honda (motorcycle) metal polish. The grooves in this particular seat were almost entirely polished out as evidenced by its initial 10 second leak-down time increasing to over a minute. One minute is actually close to the noise floor of my measurement set-up. Using the same lap on a second valve cage, though, improved the leak down time to only 20 seconds and then on a third there was no improvement and, in fact, minor damage to the seat. Examination of the lap under magnification showed that even with super fine metal polish the narrow seat had eroded away the surface of the lap and destroyed its profile. It would be possible to make a separate lap for each valve - something not unreasonable for a smaller engine - but I wanted to see if I could avoid making another 50 somethings for this engine. I have a note of caution to anyone who might want to try a wood lap. I found it only useful with metal polish as a lapping compound. Some testing I did showed that even fine TimeSaver lapping compound is much too aggressive for wood and can destroy the lap during its first time use.
As a second alternative, I made some protective covers for my metal laps. I tried several fabrics but eventually settled on strips of thin suede leather purchased from a craft store. I punched a hole in the center of the strip through which I inserted the stem of my lap. With the thin leather patch coated with metal polish and sandwiched between the lap and the seat I was again able to increase the leak-down time on a few test valves to 20-30 seconds after one minute of lapping. These leather patches need to be replaced after lapping four or five valves, but they are very simple to make. The thin suede stretches nicely over the end of the lapping tool so there is no puckering in the seat area to give an inconsistent contact patch. One of the photos shows some of the patches I used. The combination of the leather patch and metal lap is a bit awkward to deal with after the valves have been installed in the heads, but it works really well on cages that have not yet been installed. After only several seconds of lapping a bronze colored ring shows up on the patch to indicate where to add more polish.
And so, after several days of experimenting with all my spare parts and nearly a third of my finished heads, I finally settled on a process I was happy with: 1) re-cut the seats using my two manual piloted seat cutters and alternate between them for several light (to avoid unnecessary widening of the seat) cycles until reaching a 15-20 second leak-down time, and then 2) lap the seat for one minute using metal polish on a thin suede patch sandwiched between the seat and a metal lap to obtain 20-30 seconds, and then 3) lap the valve against the seat using metal polish to extend the leak-down up to 60 seconds. (Skipping step two would never be noticed in an engine's actual use.) One of the photos shows a silicone cap that I used to grip the stems of the valves in their installed cages during lapping. (Harbor Freight used to sell a nice assortment of these caps in various sizes, and I've used the one I bought to solve lots of different problems around the shop.) The ultimate goal of my process became a 60 second leak-down with mInimum damage to the valve. All but two of my seats ended up less than .007" wide, and the histogram shows the distribution of leak-down times I actually achieved. This histogram includes several valves I went back to and re-worked after learning about the dual cutter technique. I wasn't able to reach my ridiculous goal on most of my valves, frankly, because after some 60 hours I was getting weary of the project. But I kept working until every valve reached at least 20 seconds just to prove to myself I could. On about the last dozen valves the dual cutters produced 20-30 second leak-down times on their own before any lapping. I think this was because I was developing a feel for using the cutters. Even though I could have skipped their lapping steps, I chose not to because I wanted to add more valves on the right side of the histogram.
I'm still curious as to why it was so difficult to reach one minute leak-downs on some valves but not others. Any further improvements and learning will have to be left to a future project where not so many parts are involved. Again, what turned out out to be a 40 hour diversion created by a ridiculous target was totally unnecessary and done only for the sake of learning.
I ran into a few frustrating issues involving my own poor quality control that ended up taking a lot of time to sort out. For example, I had evidently damaged a couple seats while drilling and de-burring the intersection of the valve cages with the cross-drilled intake/exhaust ports. Some tiny nicks located on a difficult to see area of the installed seats were only visible only under 10X magnification. One of the seat photos is actually of one of these seats. They were probably caused by slips of the X-Acto knife I had used for de-burring. Until I deepened the seats beyond those nicks I was not able to get leak-down times better than 5 seconds no matter how much lapping I did. 
On several heads I found I had left burr remnants on the top of the valve guide bore while machining the spring cavity. My process for machining the heads included manually running a reamer in the guide bore to remove these, but I had evidently skipped this step for one of my batches. Even with only .0005" valve stem clearance this burr tilted the valve enough on its seat to limit the leak-down time to 15 seconds regardless of lapping. By the time I had discovered the source of the problem in the first head that had the problem I had leather-lapped the seat so many times that when the burr was finally removed I had absolutely no measurable leakage. After this experience every valve guide was re-reamed before starting the valve seating work.
After completing four heads and then reviewing the notes I made while sealing my H-9 valves I found a note I had made to remind me in the future to clean the seat surfaces with alcohol before making a leak test. I had found the metal polish could leave some residue on the seat that wasn't being buffed away by the Q-tips I was using, and this residue was sometimes preventing an ultimate seal. I verified the benefit of the alcohol on one head that was giving me inconsistent measurement results. When I found it stabilized my measurements on this particular head to 2X the best time previously measured on it, I added an alcohol swabbing step to my t-18 valve process. 
I did a lot of other experiments - several of them destructive, but too numerous to include here - on the many extra parts that I had made. The really important things I learned while seating these 48 valves and those things that I'll apply to my next engine are:
1) Cut the seats using two different piloted seat cutters so that one can mitigate the machining marks left behind by the other. Alternate using them for 3 or 4 cycles until, with very light pressure, no further cutting action is felt,
2) Keep the seat width to .005" - .007",
3) If the concentricity's were well maintained during the original machining a leak-down time of 20 seconds or more should result from using the dual cutters with no lapping needed, 
3) Blowing into a closed valve using one's lung power can only tell you that you have a leak so big that it should be visually very obvious,
4) Don't use lapping compound coarser than metal polish on a model engine,
4) If, during final assembly, the valve stems are lubed with a drop of light sewing machine oil don't get too excited when you come back later to re-check the leak-down times on the completed heads. You'll likely measure infinitely long leak-down times on all of them. What has really happened is that the oil has flowed down the stems and onto the seats where it has been wicked into what's left of the machining grooves leaving the valves with a false appearance that they are perfectly sealed. Don't ask me how I know this.
I don't plan to make much progress during the next week. Some of my grand kids are coming to spend a week with us and they aren't much interested in shop stuff. - Terry


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## danstir

Thanks for the excellent discussion on valves and valve lapping.


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## mayhugh1

Before I can start work on the pistons and rings I need to return briefly to the cylinders I made seven months ago. Although their machining was completed, their bores were not honed to an exact same diameter nor were they lapped to an acceptable surface finish for the rings. After finishing the machining, I sprayed each cylinder with light gun oil and individually bagged them in plastic sandwich bags because I was concerned about the 12L14 rusting from my own handling. To my surprise the exteriors of a few of the cylinders had grown some brown splotches on them from oxidized coolant that hadn't been completely removed before storing them. Fortunately, it cleaned off with WD-40 and some light scrubbing.
My preferred goal is to finish the cylinders for an eventual -0.0000"/+.0002" interference fit with the pre-gapped rings. After gapping and installing the rings, the tiny remaining high spots will quickly wear down after several minutes of 'motoring', and the rings should then fit the cylinders perfectly. If I try, instead, for a zero interference fit I'll likely miss it, and the rings will end up undersize. In that case if the clearance wasn't too great they can still wear-in to the bores, but the process will take much longer. I tried this oversize technique on my H-9 and was able to almost immediately measure a cranking cylinder pressure very close to what I was expecting from my compression ratio.
My first step was to engrave a tiny tracking number on the skirt of each cylinder and then create a set of worksheets on which I could track the measurements of each bore during the lapping process. I next made a cardboard crate to keep the cylinders organized during these final steps and also for use as a container to transport them later to a gunsmith for bluing. 
I filled in the first lines of the worksheets with starting measurements taken at the top, center, and bottom of each cylinder. Since I can make my rings any diameter I choose, my goal was to finish the upper 75% of each cylinder bore to an exact same diameter as best I can. It's only this portion of the cylinder that actually comes into contact with the compression rings. I'm not as concerned with the lower 25% since this area sees little compression, and so I'll accept up to a +.001" diameter down there. Since the lathe I used to bore the cylinders cuts a slight taper, the cylinders were oriented during machining so the largest diameter ended up at their bottoms. I could lap these tapers completely away, but I think a bit of taper is of some advantage in lubricating the cylinders.
With one of my dial bore gauges, a lot of care, and some luck, I can sometimes get a measurement repeatability of just over .0001" if all the measurements are taken during a single fitting session. Of my 24 cylinders all but three started out within +/-.00025" of an arbitrary reference point I set on my dial bore gauge. The diameters of the three 'rogue' cylinders were .002" under-size and were likely the first cylinders bored after each insert change during the finish-boring step last year. These were the only cylinders to now be honed. The rest were lapped. I managed to bring two of them into the same ballpark as the rest of the batch using 180 grit brush hones, but in the process I discovered the third was also out of round by a whopping .001" at the top of its bore. My notes showed that I didn't have my boring tool properly tightened down in the tool post when I finish-bored one of the cylinders, and I suspect this particular cylinder was that one. I wore out three brush hones on these three cylinders, and so their correction was an expensive exercise. The still non-circular third cylinder was then lapped with a 180 grit barrel lap which repaired the bore circularity issue but in the process opened up its diameter to .0010" beyond the starting diameters of all the rest of the cylinders. Rather than lap the entire batch of cylinders an extra .0005" to match this one, I decided it will just become the guinea pig for the final head installation step and cylinder flange drilling program. 
The 23 cylinder bores were next lapped using a 600 grit barrel lap. Rather than lap each cylinder until its particular diameter opened up to my target value, I moved from cylinder to cylinder always working with the smallest bore and lapping it a tenth or so at a time until the batch as a whole arrived at the same diameter. I like working with a batch of parts in this way since less re-work is generated by a subtle change in gauge calibration. Since lapping proceeds pretty slowly with only small amounts of material being removed at a time it isn't difficult, with care, to avoid overshooting a final dimension and adding a lot of extra work to the rest of the batch. After all 23 bores measured within .0001" of one another, I switched to a 1000 grit barrel lap and then removed a final tenth from each one. This last step left a nice finish on the bores for the rings.
Finally after some remorse I went back to my oversize cylinder and finish-lapped it. I'll likely make a special +.001" piston and ring set for it. The cylinders are now ready for hot bluing by a local gunsmith. I hate losing control of them to someone else, but I really need the corrosion protection of the bluing, and that's a process I'm not willing to get involved with for a number of reasons. - Terry


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## Scott_M

As usual...Beautiful work Terry!

 In your last picture of the lap, is that an expanding mandrel ? Or was it turned to size and hope it does not wear much with the 1000 grit?
 Thank you so much for taking the time to document this impressive build for us!

 Scott


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## mayhugh1

Scott,
    It's a commercial expandable brass lap available from MSC in sets or individually:


http://www.mscdirect.com/product/details/05060645

For this project I was able to set the lap and run through all 23 cylinders with the same setting. I haven't noticed any wear. I typically overload the lap with valve grinding grease and it quickly collects in the grooves of the lap while in the cylinder at low rpm. I can then adjust the rpm of the drill until the grease starts coming out of the grooves under centrifugal force and then I can feel the cutting action. The lapping compound I use is Clover valve grinding grease which I think is now owned by Loctite. The brass portion is available separately from the expanding mandrel and I use a different one for each grit.  - Terry

Terry


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## ICEpeter

Hi, 
If somebody is looking for this type of laps they are manufactured by Acro Laps and are also being sold at Penn Tool at a very competitive price. 

http://www.penntoolco.com/catalog/products/products.cfm?categoryID=5641 

Peter J.


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## mayhugh1

The carburetor that I ended up using on my H-9 was a Super Tigre model 12163145. This RC barrel carb had high and low speed mixture adjustments, a measured venturi diameter of about .35", and was marketed for .40"-.52" RC engines. Remarkably, this carb was probably too big for my H-9 since although the final tuning has been stable, both mixture adjustments ended up near fully closed. With an additional nine cylinders I figured it might be closer to optimum for this engine, and so when I started construction on my 18 cylinder radial I placed an order for a second one. A year later, delivery is still 'pending' since it appears last year's Fukushima tsunami has evidently disrupted it's supply to the U.S for the foreseeable future.
After some web searching, though, I came across Perry Carburetors:
http://www.perrypumps.com
which is now owned by Gary Conley, a well-known member of the model engine building community. Perry offers a large variety of model engine carbs, and the best thing about their website is the way their products are categorized. If you're trying to replace a particular manufacturer's part they have their list of direct replacements. Of more interest to me, though, was their listing of carbs by venturi size. With an intake runner i.d. of .257", I finally decided on a carb with a .312" throat. Venturi's with other i.d.'s but with the same o.d. are also available; and so, if necessary, I can later change the throat size without having to purchase a new carb or make a new engine adapter. Gary also changed the fuel mixture disk for me to improve the carb's compatibility with gasoline. 
Since I plan to use a fuel pump to maintain a constant fuel level to the carb, I need an adapter between this new carb and the rear end of my engine with a fuel bowl to support the recirculating fuel system I plan to use. I previously built two of these closed loop systems for my H-9 - one for the Super Tigre carb and one for a Walbro carb that I unsuccessfully tried to use with that engine. So, I decided to save some work and re-cycle the Walbro adapter by sleeving and re-boring it to accept the Perry carb. I designed the rear end of my T-18 crankcase to match that of my H-9, and so no changes were required on the engine-side of the adapter. The fuel bowl, however, was another matter. I originally designed the Walbro fuel bowl with an internal adjustable pressure regulator to drop the 10-15 psi of my fuel pump down to the 1.5 psi that the Walbro wanted to see. I had to do some re-machining of the internals to remove the regulator and to install new inlet/outlet tubes in order to adapt it for use with the Perry. The re-design work cut into my time savings a bit. In the end, though, the combination adapter and fuel bowl fits nicely on the rear of the engine and without interference from the engine stand. I was able to try out the re-circulator using my H-9 fuel pump. The level of fuel inside the bowl is nicely regulated to a half inch below the sealed top cover, and this level is about 1/4" below the carb's spray bar. Later, I plan to swap this new carb assembly with the Super Tigre on my H-9 in order to verify the carb works and to get some starting carb settings for my new engine.
I'm getting very close to being able to start final assembly. The cylinders came back safely from my local gunsmith, and the bluing job is gorgeous. The stacks of bagged and boxed parts on my workbench are now only missing the pistons and rings. I still have several pieces of external running gear such as the firewall and the oil and fuel tanks to make, but I plan to continue on with those during final assembly. I'm also planning to design an analog tach for this engine around an old-style panel meter if I can find just the right one. -Terry


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## kvom

Rather OT, but can you explain how the through hole lap works?


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## mayhugh1

Kvom,
      Well, I can tell you how I used them. Since I'm learning as I go this might not match up with how they are supposed to be used. Others are welcome to add their expertise and experience.
The barrel, itself, is threaded onto a mandrel which I held in my drill. The barrel has four longitudinal slots which allow it to expand when a threaded tapered bolt is turned into its end. When the lap is expanded one would think that a good portion of its length expands parallel to the longitudinal axis without introducing a slight taper in the barrel. But, the fact is, unless the barrel is re-cut for a particular setting there will always be a taper when you consider you're working with tenths. A slight taper isn't an issue, though, and ends up being useful. Anyway, the barrel is made from soft brass and so when the lapping compound is smeared over it and then the lap is inserted int the cylinder, the lapping compound embeds itself into the brass and the barrel becomes a precision grinding tool. The expanding screw is turned in small increments until there is a slight drag on the lap when the drill is spinning. It's best to not use a lapping compound such as TimeSaver that breaks down easily during the lapping process so that the compound has a chance to embed and do its job. Anyway, while spinning, the lap is continually oscillated back and forth within the cylinder. I hold the drill in one hand and the cylinder in the other and allow the lap to find its own center of the cylinder as I feed the cylinder back and forth over the lap. The larger o.d. portion of the lap can easily be felt cutting on the 'tight' portions of the cylinder as you pass over them. I kept the same screw setting as I went through each of my cylinders increasing their bores a tenth at a time. I was turning the screw about 1/8 turn at a time. During the final pass I used the same setting on all 23 cylinders to open them up the the last tenth, and I noticed no wear on the lap. At the same lap setting, all 23 cylinders came out to within .0001" of one another. 
I wasn't interested in taking all the taper out of my cylinders since the .0005" taper I had at the bottom wasn't important and maybe even desirable. I was interested in removing all the taper from the top 3/4 of the cylinders and so I lapped for 1 minute and then measured at three places in the cylinder to see if I was working in the right part of the cylinder. The slightly larger o.d. of the lap always turned out to be at its outer end, and so it was easy to oscillate the lap back and forth in the right portion of the cylinder. One issue I ran into was cleaning the lapping compound out of the cylinder for measurement. I used dry shop paper towels to clean out the bores and I kept cleaning until the towel came perfectly clean. What I didn't figure out until very late in the process was that some fibers from the towels were embedding into the cylinder bore even though the bore looked perfectly clean. Eventually on the third or fourth lapping session these fibers would start showing up in the lapping compound on the lap. They would slightly increase the diameter of the lap (always at the bottom of the lap for some reason) and keep the taper I had at the bottom of the bore from cleaning up. It wasn't until I started using lacquer thinner to clean the bores that this problem went away. 
So, the through-laps give you the ability to lap the whole bore or only a portion of the bore if you are trying to remove a taper. They are very effective in cleaning up non-circular bores. They don't round over the ends of the cylinders as do the brush hones, and they are much cheaper. Unlike the brush hones they don't remove a lot I material, though. They seem to be more suitable for removing up to a max .0005" over a reasonable time of ten minutes or so including measurements. -Terry


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## DICKEYBIRD

Fantastic info Terry, thanks.  It's like I've been there & done that when I really haven't.  This thread is a treasure trove of instructions for future use by many of us.;D


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## mayhugh1

My next step was the machining of the pistons. I used 6061 aluminum and happened to have a 23 inch long rod whose diameter was just .012" over the finished diameter of my pistons. So, there wasn't many chips associated with the lathe work. 
I'm using the exact same piston that I used in my H-9 except for a slight change in diameter to accommodate my T-18 cylinder bores. The pistons' finished diameters are .0025" smaller than the cylinder bores to insure adequate clearance between the aluminum pistons and the steel cylinders over the pistons' expected operating temperature. 
These pistons are essentially stock H-9 design but with modified ring groove clearances and a slight relocation of the oil ring. The compression ring grooves' axial width clearance is .001" and the radial thickness clearance is .005". The compression ring grooves' axial widths are .027" because that is a standard width grooving insert available for my particular grooving tool. This set my compression rings' axial width to .026". This width is on the low end of the usual recommendations for a one inch piston, but with 54 of them on a single crankshaft frictional losses aren't insignificant. Assuming the same 350 psi peak cylinder pressure used earlier, the top ring will end up with some 25 pounds of radial force pressing it against the cylinder wall during the power stroke. This is a nice number for ring seating, sealing, and heat transfer but not so nice for frictional losses. The downside of a narrow width compression ring is its higher thermal resistance to removing heat from the piston's crown. 
These pistons have two compression rings and one oil ring, although the second compression ring provides more oil and piston temperature control than it does compression sealing. The wrist pins are full floating and my saga dealing their machining was the topic of a much earlier post.
In order to conserve material I fed the workpiece through the lathe's headstock where each piston was faced and turned, and the ring grooves were cut. The depths of the grooves were machined so the radial clearance behind the compression rings will be .005" and behind the oil scraper rings the clearance will be .010".
I used a new side-relieved grooving insert to cut the ring grooves at high rpm with a low feed rate in order to get the best possible surface finish on the side walls of the grooves. A fine surface finish is especially important on the lower wall of the compression ring groove since it is an important ring sealing surface. Previous valve sealing experience showed that narrow seats are much easier to seal than wide seats, and the sealing surfaces formed by the rings against the lower wall of the grooves are an order of magnitude greater in width than the valve seats. Fortunately, under normal operation cylinder oil is scraped into the interface (assuming the ring has a proper clearance and isn't frozen in position with cylinder deposits) to fill in minor machining grooves and help with the seal. Sometimes, in fact, a bit of oil added to the cylinders of an engine left standing for a long period of time is helpful in replacing this film when trying to measure compression.
Parting off stock at this diameter in my 9X20 lathe is usually not pretty, and so after turning the semi-finished piston the workpiece was removed from the lathe and taken to the bandsaw where it was removed before returning the workpiece to the lathe for the next part. The pistons were brought to their finished length later in the mill during the pistons' bottom and interior machining. I made a fixture to hold my H-9 pistons while their interiors were being machined, and I was able to re-use it for these pistons. The fixture was rotated 90 degrees after machining the bottom of the piston in order to spot, drill, and ream the wrist pin hole. The last thousandth of the wrist pin hole was reamed in a secondary operation in order to insure a precise fit with the wrist pin. The accuracy of the piston machining fixture is very important because the wrist pin must wind up precisely square to the longitudinal axis of the piston in order to avoid a connecting rod bind and an eventual worn taper on the rings.
The last operation on the pistons was drilling eight .050" diameter radial oil return holes in the bottom of each oil ring groove, and this was done on a horizontal rotary under the mill's spindle. The ring grooves' locations were originally referenced to the crown of the piston, and so a collet stop was a sufficient workpiece locator for the hole drilling. In total, 176 holes were drilled using a single re-sharpened carbide circuit board drill purchased on E-Bay.
I made a total of 22 pistons including one that is .001" oversize to fit the PITA over-size cylinder that I ended up with during honing. The next step will be the piston rings. - Terry


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## petertha

Very nice. I'm keenly following your cylinder boring/lapping workflow & now the piston details. But now that I see it all come together, I'm re-thinking my forthcoming winter project plan of attack. Sorry for the sidestep, but would appreciate your input. 

 Basically I was thinking of slightly altering the original ?arbitrary?design internal dimensions by replicating a 'pretty close' bore ID & piston OD combo of existing commercial RC engine dimensions. My logic being, utilize & replicate those 'known' dimensions, utilize the commercially available rings & that's several variables less for me to mess up at my novice level. If the engine ran, great, maybe then proceed to replicate ring making in home shop & join the elite club. But maybe this solves one problem but creates others?

 What I think I see you doing is starting with finished, identical bores to some known consistent dimension, then pistons, then rings? When I re-read your post, its almost like you had a sample sizing ring pre-made & then nailed the bore diameter to that. But I think you're saying, the rings are coming next? If so, is this to facilitate any necessary adjustment tweak to ring dimensions if anything did go south on the bores (more work invested in the cylinders?). I've pulled your excerpt for reference below, maybe I misunderstood. What would you do if you were in my shoes? Is it reasonable to hit 5 target bores/tolerances by honing/lapping knowing pistons will be made, but not the rings?

_My preferred goal is to finish the cylinders for an eventual -0.0000"/+.0002" interference fit with the pre-gapped rings. After gapping and installing the rings, the tiny remaining high spots will quickly wear down after several minutes of 'motoring', and the rings should then fit the cylinders perfectly. If I try, instead, for a zero interference fit I'll likely miss it..._


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## mayhugh1

Peter,
       My goal was, as you said, to first get the all the cylinders to a consistent bore diameter. I had a lot of time invested in their external features that I didn't want to risk, but I knew I could eventually lap them all to a common diameter even though at the time I didn't know what that diameter would be. It would just be a matter of me putting the necessary time into a process that removes material very slowly.
       After finishing the cylinders I decided to make the pistons. The rings could just as easily done at this time instead since there really wasn't any close fits involving the pistons with either the cylinders or rings. By 'close fits' I mean fits that have to be verified by actually trying them because they may be too close to rely only on my measurement ability.
After finishing the pistons I'm now moving onto the rings. Even though I now know what their o.d.'s need to be after measuring the common i.d. of the cylinders, I won't be able to test such a close fit in the cylinders without risking damage to their finished walls until the rings are gapped. And, since the heat treatment may change their shape slightly I really won't be able to check their final fit until after heat treating. Then I'll use a light test to verify their contact patch to the cylinder wall. If the batch fails my light test it will be scrapped, and I'll mitigate my losses by limiting the batch size to ten or so rings which is the number my heat treat fixture can handle at one time. Scrapping a few batches of rings in my particular case at this particular time is much preferable to scrapping even one completed cylinder. The truth is, the scrapped rings will go into a labeled box and may end up perfectly fitting a cylinder in some future project. 
My comment that you asked about concerning an undersize or oversize ring was trying to say that I felt it was better to be slightly over-size on the ring o.d. than it is to be undersize. The light pattern will show 2-3 very narrow point contacts on a slightly oversize ring that will quickly wear down to give a perfectly fitted ring. A slightly undersize ring will have a wide non-contact and a wide contact area that will take much longer to wear down and seal to the cylinder bore. It is totally a judgement call on what to accept and what to scrap. I will likely start out rejecting any ring that shows any light at all until my scrap rate is so high that it starts wearing me down. I'll then start accepting some slightly oversize rings. 
Now I'll try to answer the main question of your post. If you're planning on using commercial rings I see nothing wrong with lapping your cylinders to the o.d.'s required by the rings. There is a slightly greater rusk to your cylinders in doing this compared with what I did, but what you are proposing is very reasonable and done by others all the time. If it were me, I would have the actual rings in hand before I started lapping and, in addition to actually measuring the lapped bores, I would perform a light test with the ring in its actual cylinder when I got close to the finished value. Once I was satisfied with the light test results I would make sure those rings stayed with those particular cylinders. - Terry


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## kuhncw

Terry, thank you very much for continuing to post such an educational build log.  I like the fixture you use for putting pin bores in pistons.

 Regards,

 Chuck


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## Tony B

There certainly are some clever people in this world, and you sure are one of them, love your tooling and the indent explanation,
Cant wait to hear this baby fire up


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## mayhugh1

For my piston rings I gathered up a couple one foot lengths of one inch diameter cast iron obtained from long-forgotten sources several years ago. Some of this 'aged' material has already been used for rings for a couple earlier engines including my H-9. Class 40 gray or just 'gray' cast iron is a theoretically good choice for piston rings because of its close grain structure, natural lubricity, and good machinability. Except for the messy, abrasive residue left behind, the excellent surface finishes that are readily obtainable with this material makes it a good candidate for sealing surfaces. One inch cast iron rounds are cast some 10% over-size; and so, by design, there is sufficient excess material from which to machine one inch diameter parts.
I've used George Trimble's method for making most of my rings, and my own experience has been that the most difficult step in his process is creating an ideal cylinder of the proper diameter from which to slice the rings. Once the finished blanks are completed, the rest of his process is pretty straight forward. I briefly experimented with an alternative method for making rings during my H-9 build that included a final o.d. turning operation on the completed ring. This method requires yet another precision fixture to be machined to the cylinder's exact i.d.. The reasons I went back to Trimble's method, after only a few parts, were the difficulties I had with polishing the o.d. as well as using the fixture for more than one part at a time.
I started the rings for my T-18 by saw-cutting my one inch stock into ten 2-1/2" long pieces in order to create starting blanks for ten batches of rings. I need a minimum of 36 compression rings and 18 oil rings; and, with luck, each blank could potentially yield more than half of what I need of either ring. From experience, though, I've learned there will likely be a high scrap rate while machining the blanks. 
The finished o.d. and i.d. targets for my rings are .9978" and .9120", respectively. The o.d. target was set .0004" greater than the i.d. of my cylinders to help me avoid ending up undersize. Using my 12X36 Enco lathe I rough turned the o.d.'s of the blanks to 1.015" and then drilled out their centers with a .812" drill. These two roughing operations removed a lot of material and likely changed the distribution of any stresses remaining in the cast material after it was cooled.
George Trimble's recipe requires a final stress relieving heat treatment to set the expanded shape of the ring. If Trimble's method is closely followed, the heat treated ring will, theoretically, fit the cylinder bore perfectly when it is compressed by being inserted into it. If there are stresses related to the casting process remaining in the metal after the ring's machining is completed, the shape of the ring could change from Trimble's theoretical shape during this final heat treatment when those stresses are relieved. Therefore, I performed an initial stress relieving operation on the rough blanks before the ring machining was actually started. The ten blanks were heated to 920F for one hour and then allowed to slowly cool overnight before doing any finish machining on them. For this heat cycle, the blanks were wrapped in a double-folded stainless steel envelope filled with argon to avoid scaling.
After the blanks cooled they were taken to my 9X20 lathe which has tight bearings and the capability of turning nearly perfectly round parts. Here, the centers of the blanks were bored out to the finished i.d. of my rings. This left a cylindrical workpiece with only a .051" wall. I did not, however, bore completely through to the portion of the blank inside the lathe's collet chuck. I used a high rake Korloy carbide insert designed for aluminum in order to give nice surface finish to the bore. The critical o.d.'s were then turned to .9983" which is .0005" over the ring's finished o.d.. I then used abrasive papers in 400g and 600g to polish the o.d.'s of the blanks to .9978" +0/-.0001" over their full lengths outside the chuck. I tracked my progress on worksheets by carefully measuring at three points with respect to a reference mark on the cylinder and working down the high areas. 
Finishing the o.d.'s is the most critical step in the blank creation process, and there are at least three potential issues with which to be aware.
The easiest issue to deal with is the surface finish. Just as with my valves, I removed the machining marks by polishing the o.d.'s to a final bright finish; but with the ring blanks I stopped with 600 grit paper. 
Matching the finished o.d. of the blank to the cylinder's i.d. is a moderately difficult step. In my shop it is primarily a measurement issue of trying to match the o.d. of one part to the i.d. of another part using two different measuring instruments at a precision to which neither is actually capable. I used the same micrometer for measuring the o.d. of the blank that was used to measure over the cylinder's bore indicator. I also allowed the blanks to cool before measuring them whenever the polishing managed to get them too hot to touch. 
The most difficult issue that I dealt with while creating the blanks, though, was turning them truly round. Lots of subtle sources affecting this error seem to creep into the process. My 9X20's spindle bearings, limit the minimum circularity error to .0001". While gripping these thin-walled cylindrical blanks my economy 5C collets can add up to another .0005" error over a significant portion of the blank even if the collet chuck is only moderately tightened. I bored only the portion of the blank outside the chuck to the final ring's o.d. in order to leave the portion of the blank inside the collet with a thicker wall in order to help reduce the collet error. 
It seems that in some batches of cast iron even my initial stress relief heat treatment can't seem to stop the thin-walled cylinder's shape from moving around uncontrollably as it is machined. My lathe's spindle vibration at the high speeds I use for polishing also contributes circularity errors. Fortunately, I can continuously vary the spindle speed and find 'quiet' windows by lightly laying my hand on the workpiece. 
In this project I came across a new source of circularity error. The photo of the o.d. finishing operation show the outer end of a metal slug dampener I inserted into the end of the blank during machining to prevent squeal-induced chatter. After boring the i.d. the blank becomes a chime just waiting to ring when it makes contact with the o.d. turning tool. This slug of metal, wrapped with plastic electrical tape was loosely inserted into the workpiece and completely eliminated the squeal. However, the undetectable wobble it evidently created resulted in a whopping .0007" circularity error on three of my blanks before I realized what was going on. I later found that a dampener made from a short piece of wood dowel, wrapped with tape, and inserted into the tube also deadened the cutter squeal just as effectively as the metal slug without affecting the circularity of the blank.
The final photo shows the completed blanks ready to be sliced into rings. The areas marked in red are the areas I've tentatively chosen to scrap due, primarily, to circularity errors. I ended up with only a 50% yield of 'good' material. My arbitrary cut-off point for this 'good' material was at a .0003" maximum circularity error. The top compression rings will likely be first selected from this material. At this point, though, I don't really know how big of an error is too big and whether I may be discarding useable material. I hope to run some 'eclipse' tests by shining light through a test cylinder containing a ringed dummy piston in order to compare ring/cylinder contact patches for various degrees of circularity and diametrical errors. - Terry


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## Buchanan

Terry. 
I have watched most of your previous thread and all of this one and would like to say how much I enjoy all you do.I especialy like your self imposed quality controls not to mention your beautiful wrkmanship. I also enloy your depatures from the set plans and really like the results on the cylinders and heads. Thank you. Buchanan


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## Tony B

This maybe a stupid question, but wouldn't the ring match the bore after it is run? so chasing 0.003 maybe in vain, I never built anything like this so I wouldn't know
Beautiful work,  with an incredible eye for detail,


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## mayhugh1

Tony,
      No doubt you're probably right. I've just never seen any real data showing what, in the real world, makes the difference between a good and a great piston ring. 
For me, pretty much all the satisfaction of working on one of these long term projects is trying to understand and trying to do the best possible job I can with all the minutia that contribute to an engine's operation. It isn't at all important to me to quickly get one running so I can move on to the next one. I try to be careful in my write-ups to be clear that what I document is only what I've done and in no way is it the 'best' - whatever that means - way to do it. I go down lots of questionable paths for nothing more than the opportunity of a different path. It's much more important at this point in my life that I experience a thoughtful journey than it is that I arrive on time. - Terry


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## Scott_M

Terry

I too am old enough to agree with you. That was a great explanation !
However...
Remember when somebody saw you limping and asked what happened and you got to tell a cool story about flipping a dirt bike on a hill climb ?
And now the explanation is more like " I sneezed in the shower and threw my back out"

Getting older is not all it's cracked up to be.

Scott


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## wrljet

I'm recovering from a hernia operation right now.

Years of moving car engines and Bridgeport mills around didn't cause it.
Had a violent coughing fit while brushing my teeth and "busted a gut".

-Bill



Scott_M said:


> And now the explanation is more like " I sneezed in the shower and threw my back out"
> 
> Getting older is not all it's cracked up to be.
> 
> Scott


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## gbritnell

Terry,
Let me start off by saying how much I enjoy following your build. Knowing the time and effort it takes to document a large project like your radial I can appreciate what you're doing. 
Your processes are much similar to mine with the exception of owning and using bore gauges. I have made up an attachment to hold a dial test indicator that is a poor man's I.D. measuring tool. 
I use brass laps like you have used and find them to work very well. 
As far as piston ring making I too use the Trimble method. I have read and tried several of the other processes and they do wok but the extra cutting and fixtures required just isn't worth the time. 
After installing my rings and running them in on the bench I find that after about 1/2 hour of running time the rings usually have the darkened color from the heat treat process polished off. Sometimes there's an area of say 10-15 degrees that is still dark so I'm guessing we're talking .00005 difference and will polish out once the engine is running. 
In the construction of an I.C. engine I have found that the ring/bore fit isn't quite as critical for good operation as getting the valves to seat properly. When you consider that most of these engines will idle somewhere around 1000 rpm the ring leakage should be minimal but with a leaky valve it never goes away. 
Keep up the great work. 
gbritnell


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## mayhugh1

I had to make/gather up some tools and gages before continuing with the rings. The first 'tool' is a simple piece of aluminum round stock with a turned end such that a ring can be slipped onto it and held consistently by its i.d. against a flat surface while the sides of the rings are being lapped. This lapping will bring the width of the ring to its finished value so there is a proper clearance between it and the walls of the piston grooves. Lapping will also create the ring sealing surfaces that bear against the piston groove walls.
The second fixture is short piece of scrap steel with a bored i.d. that matches the engine cylinders' i.d.. This gage will be used to set and measure the running gap of the finished ring after heat treatment. An actual cylinder could be used instead, but with so many rings to deal with, there is risk of unnecessarily scratching up the bore of a pristine cylinder. 
The third fixture is, in my case, an overly elaborate tool that I made several years ago to cleave rings just before they are heat treated. For my first two engines I simply broke the rings over a piece of 16 gauge wire on a surface plate by applying thumb pressure to the ring on either side of the wire. After moving up to more performant oil control rings, I needed a way to better control the actual location of the break. I allowed the construction of this tool get out of hand, and it turned into a full weekend project several years ago.
The heat treat fixture for 'setting' the uncompressed ring shape is a subtly important tool, and its Trimble specific design details can be found on the web. If the theory behind Trimble's method is carefully studied it may become apparent that there is more to the design of the fixture's gap spreading wedge than is noticed at first glance. This fixture is designed around a particular diameter ring, and a new one is required for a different size ring. I made a small modification to the original design by lengthening it so I could heat treat large batches of rings for my H-9. I also made a spacer so the same fixture could also handle small batches. 
The last tool is new for me and will be used to examine the precision of the final fit of a completed ring in an actual cylinder. Although a compression check is the final word on the fit, a light leak test may be useful for eliminating poorly fitting rings before an engine is actually assembled. (Remember buying new cars in the good old days when oil consumption was a crap shoot? I had more than one dealer in the eighties tell me that burning a quart of oil every thousand miles, even after 4000 miles on the odometer, was within factory spec and not covered by a new car warranty.) Basically, the ring under test is inserted onto the end of a short length of black Delrin rod that has been turned to the pistons' diameter. The top end of the rod was turned to match the i.d. of the ring. In use, the ring is slipped onto the end of the Delrin rod, and the pair are inserted into the cylinder through its bottom and pushed up until the ring is near its position in the cylinder during TDC. A white light is then shown into the bottom of the cylinder, and any light escaping from the top of the combination is an indication of an imperfectly fitting ring. The give-away Harbor Freight led flashlights are not bright enough for this application. I had to use a 250 lumen miniature flashlight spaced away from the bottom of the cylinder by a trial-and-error derived distance in order to get enough light into the gap between the dummy Delrin piston and the cylinder wall in order to produce consistent results. 
The difficulty with the process with which I'm planning to experiment will be judging the difference between a useable and an un-useable piston ring. I'm hoping that the rings from my measured good blanks will pass no light, and the rings cut from the imperfect blank areas will pass varying degrees of light for which I can, over time, develop some sort of pass-fail criteria for 'good enough' rings. I'm not expecting things to come out that 'black-or-white' though, and so this may turn into one of those interesting but not really useful exercises. 
I took two preliminary test photos while developing the fixture. The first photo shows the light escaping from the top of my .001" oversize cylinder. The ring in the cylinder was cut from one of my on-size scrap blanks that had a .0004" circularity error. The ring was lapped but un-gapped, and it had not yet been heat treated. This test was used to decide if our household flashlight was bright enough to get a meaningful result. The second photo is the light passing through one of my production cylinders using the same ring. There is a clear difference in the light pattern between the two cylinders. Because the end of the Delrin piston was machined to give the same ring back clearance as an actual piston, the rings are not necessarily centered in the cylinders' bores. If the rings had been gapped and heat treated the patterns would have been somewhat different since a portion of the ring would have been sprung into contact with the cylinder wall. The total emitted light in each case, though, would have remained about the same. I think these early tests show that more experiments are worth continuing on finished rings. - Terry


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## mayhugh1

I continued my ring construction with the goal of creating the best possible initial fitting rings by measuring and recording one of my good blank's dimensions one last time before slicing it up into 26 candidate compression rings. I decided to polish off the excess .0003" that I had previously left on this blank, though, so it would exactly match the i.d. of my cylinders. I did this so I could establish some kind of baseline for the light tests I had planned.
I used my 9X20 lathe, a .019" carbide grooving insert, and a few lines of scratch-written code to uniformly part off the individual rings. I ran the spindle at 1000rpm which was a little high for one inch cast iron, but I used an extremely low (.0001 inch/rev) feed-rate hoping to not raise any burrs on the rings' corners. My tape-wrapped wood dampener eliminated the flash on the parted off rings by holding them in place until they were completely cut free.
But, as the first ring photos shows, there were still slight burrs raised on the o.d. and i.d. corners of each ring. I removed the i.d. burrs by manually working a very hard 1/4" diameter cylindrical ceramic stone around both i.d. corners of each ring in order to break them. I removed the o.d. burrs by manually rotating the rings' o.d. corners against a sheet of 1000 grit paper for a couple revolutions using light pressure.
The rings came off the lathe having a width equal to that of the piston ring groove. The lapping tool was then used with 1200 grit lapping grease against a glass plate to remove .0005" from each side of the ring. Lapping reduced the total width by .001" which is my target piston groove clearance. (By the way, I think it is this clearance plus the ring gap through which crankcase oil flows in a stored radial engine to accumulate in the combustion chamber and possibly hydrolock the piston.) At this point, as a second ring photo shows, all the rings' surfaces were nicely polished.
The final step before heat treatment was breaking the rings using my shop-made cleaver. A folded-over two inch long strip of 1000 grit paper was pulled through the break just once to lightly clean up the faces. The actual running gap was set after heat treatment. The de-burring, lapping, cleaning, and measuring added some 10 minutes of tedious work to each ring; and so cleaving became a celebratory step in the process. The whole first batch of 26 rings was loaded into the heat treat fixture, and it was enclosed in a double-folded stainless steel foil bag filled with argon gas. The package was raised to a temperature of 970F (this is considerably lower than the Trimble's 1475F) for 1-3/4 hours and then allowed to cool overnight to room temperature. I've found that if the stainless foil bag isn't pre-conditioned with a heat cycle of its own, the rings will come out of the fixture stuck together, and they will have to be carefully separated with an X-Acto knife. In addition there will be a thin powdery coating on them that isn't difficult to remove. I believe this happens because the stainless foil probably comes with some sort of oil coating on it that is burned off in the heat cycle.
The running gap was then set for each ring using a diamond file and the cylindrical bore gage mentioned earlier. The purpose of the ring's running gap is to allow the ring to expand without breaking when it's exposed to the high temperatures of combustion. I use the same .004" gap that many others use. Although it might come as a surprise to a few, this ring gap creates an all but invisible leak in the combustion chamber, and this can be demonstrated with some simple math. The opening to the crankcase created by the ring gap is bordered by the o.d. of the piston, the i.d. of the cylinder, and the two ends of the gapped ring. For a .003" diametrical piston clearance and a .004" gap the area of this leak is only 6 millionths of a square inch. It's difficult to appreciate the significance of a leak this small in the combustion chamber; but if the volume of the combustion chamber at TDC is scaled up to the volume of a 50 gallon drum, this leak would be equivalent to a hole the size of a lead pencil punched in its bottom. Even under combustion pressure, it's only the amount of air that can escape from the drum during some worst-case tenth second idle power pulse that is lost.
After setting the running gap I lightly re-lapped the sides of the rings and de-burred the area around the gap. The third ring photo shows a typical finished ring. I checked several of the rings in my light fixture using various cylinders and could see absolutely no light escaping anywhere except for a brilliant pinhole of light coming from the ring gap. I was pleasantly surprised because I thought there might be some visible light on the ring's perimeter due to the theoretical impossibility of obtaining a perfect fit with the .0001" circularity errors in both my cylinders and rings. My biggest surprise came later when I got exactly the same light test results using the same ring with my .001" oversize cylinder. With the ring sprung outward against the wall of the cylinder, the light loss picture improved dramatically compared with the same un-gapped ring in the same oversize cylinder shown in the photo of my previous post. Where did all the leak indicating light go? It appears that even a .001" diametrical error doesn't create a sufficient curvature mismatch with the cylinder wall to create a measurable leak. Most of the area mismatch that allowed light to pass by the ring in the previous light photo is now hidden within the piston groove. As long as there is an adequate seal between the ring and the lower wall of the piston groove in actual use, this mismatch won't contribute to an actual combustion chamber leak. My conclusion is that a well-lapped ring sealed against the lower wall of the piston groove can cover up some otherwise loose machining on the ring's o.d. There isn't any way to verify the net leakage under these circumstances, though, without a compression test. Unfortunately, circularity errors won't behave in the same favorable way. They will just move slightly around the periphery while maintaining the same leak and light loss. Even worse, the theory behind Trimble's heat treatment falls apart when a significant circularity machining error is present, and the net result becomes fairly indeterminate.
After seeing these results and experiencing the friction of a single ring in a single cylinder of an 18 cylinder engine, I decided to polish off the excess .0003" from the remainder of my blanks before slicing them into rings. During engine assembly I plan to light test each cylinder with only the top compression ring installed on its piston. I'll log the location of each combination and see if there is any correlation between any differences in compression and the light test results for each cylinder at the end of assembly.
A second batch of 28 compression rings was cut from two more partial blanks. I completed these rings using the same process used for the first batch in order to end up with a total of 54 compression rings. This is enough for all pistons I've made including several spares. As it turns out, a spare ring set from my H-9 build will nearly perfectly fit my .001" oversize piston/cylinder combination, and so I won't have to make a special set of rings for it.
The oil rings are my final parts to make, They're more complicated but more interesting parts to make compared with the plain square compression rings. Thankfully, though, I only need to make half as many. - Terry


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## petertha

mayhugh1 said:


> IThe heat treat fixture for 'setting' the uncompressed ring shape is a subtly important tool, and its Trimble specific design details can be found on the web. - Terry



Hi Terry. Many moons ago I took a crack at writing a spreadsheet with the Trimble design parameters from SIC article, more-so out of interest at that time. I seem to recall other individuals subsequently made corrections (or maybe 'suggested contributions' is a better phrase) to some of the metrics employed. It kind of left me in a limbo state. Sometimes I could back out some resultant numbers on a particular design that referenced Trimble & sometimes not. Do you have a go-to link with what you considered the complete method, or did you base your dimensions entirely on the SIC equations?

 I found this link (which then refers 2 other sub-links named Feeney & Cirrus. 
http://modelenginenews.org/techniques/piston_rings.html

 Id be happy to write & share a spreadsheet, but would really prefer it had an approval stamp of experience from someone like yourself. Or maybe you did this already?


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## mayhugh1

Peter,
I was a subscriber to Strictly IC magazine and my source for Trimble's method is his original 1989 articles in vol. 2 nos. 7,8, and 9. His design equations are in the second article.
By the way, George Trimble, in his original SIC no.9 article admitted that practically any of the current ring construction techniques of his day was capable of producing acceptable compression rings if one was willing to let the pressures of combustion wear the ring into the cylinder bore by running the engine under its own power for six to twenty hours. His assumption, of course, was that the ring was machined to yield sufficient initial compression to actually get the engine started.
The oil control rings are an entirely different matter as they see no combustion pressure. These rings rely totally on spring force to hold them against the cylinder wall.  Trimble's theoretical work and the extensive testing he did was actually focused on developing a method for creating a perfectly contoured oil ring. Trimble's eventual claim was that his method for setting the open contour of such a ring was the only one at that time that could accomplish this goal. Of course, anyone who claims to have a recipe for perfection is opening himself up for a lot of debate, and that is just what happened. And, it is one of the reasons we have so many ring making religions today. After studying his articles, reading the various debates, and briefly trying at least one alternative, I adopted his method as my own. The only thing I changed was the temperature of the stress relieving step. I was swayed by the arguments of others having much more metallurgy knowledge than me that Trimble's 1475F was unnecessarily high and could create more problems that a more moderate 1000F would solve. 
Your spreadsheet is a good idea and maybe it would be a good candidate for one of those 'how-to' articles that this forum has been soliciting. - Terry


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## mayhugh1

I've been just a bit curious about the fact that of the 25 T-28 rings I've since tested using my light fixture, I've seen no light escaping past any of them except for in the area of the gap. I'd like to believe I've made a perfect batch of rings, but there was also the nagging possibility that the test is somehow flawed - maybe the light source isn't bright enough, for instance.
I went through my H-9 spares parts box and came up with three spare cylinders and fifteen spare rings. So, I tested all these rings in one of the spare cylinders for light leakage and got an array of results. Nine of the rings gave results similar to my T-18 cylinders. But six of the H-9 rings had obvious and significant amounts of light passing by them due to imperfect fits with the same cylinder. I've included four example photos of the results. (In these light photos as well as the others I've posted, it's necessary for me to angle and focus the camera to pick up the brightest leak, and in some of the photos there are actually other, smaller leaks that don't show up in the photo.) Both sets of rings came from similar material and received essentially the same final heat treatment using the same fixture. The H-9 blanks, however, did not receive the same pre-machining stress relief heat treatment that I performed on the T-18 blanks. The main differences between them are most likely their circular machining accuracies since my H-9 construction notes don't show me having made any circularity measurements on the blanks from which those rings were made. Since both sets of rings were made using the same equipment, I believe the improved T-18 results are just due to the better care and selection that was done. - Terry


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## mayhugh1

Machining of the actual engine parts concludes with the oil rings. The oil ring design I'm using is straight out of Trimble's SIC no. 9 article. This single-piece double scraper ring with a central oil collection groove is a fairly old school design as far as automotive piston rings go, but it's nicely adaptable to a model engine. Hodgson, in fact, added it to the H-9 design several years ago.
Since the oil rings don't see the pressures of combustion they rely totally on the ring's outward spring force to hold them against the cylinder wall. The edges of the scrapers are slightly beveled to increase their pressure against the cylinder for better oil control. The oil grooves contain ten radially-drilled holes to allow oil collected in the groove to flow into the clearance space behind the ring. An even number of holes insures that one doesn't end up directly across from the ring gap. Another series of radial holes drilled through the piston groove allows this oil to escape into the interior of the piston and drain back into the crankcase. Two pairs of these holes are located on just either side of the wrist pin to aid its lubrication. 
In order to do their best possible job the oil rings need to have the correct shape when they're installed. It isn't likely that the oil rings will ever be able to 'wear in' to their cylinders with the flood of oil they constantly experience combined with the lack of combustion pressure. 
Of course, it isn't clear that a model engine operating with oil control rings operating at 100% efficiency is a good idea, either. Some oil consumption is beneficial to top-end cylinder and ring wear. What's disappointing, though, is oil fouled plugs and smoky exhausts that tattle poor oil control. The lower cylinders on a radial are particularly vulnerable since the bottoms of the cylinders are continually filled with oil. It's not at all obvious how one designs for the 'goldielocks' operating area where the amount of oil control is just right. In this engine, the approach I've decided to take is to aim for a perfect fitting oil ring in the center of the cylinder when the piston is at the top of its stroke. I'll then let the .0005" diameter outward taper that I've left in the lower portion of my cylinders control the amount of oil that is allowed to reach the second compression ring. Most likely this ideally fit ring will prevent excessive oil from reaching the combustion chamber. 
Construction began by re-measuring the blanks I had left over after finishing the compression rings. I was pleasantly surprised to discover that the circularity errors on a couple of my reject blanks had improved to a state of usability during the past week while they were resting and recuperating from their finishing operations. I was disappointed, though, to learn that one of my perfect blanks had taken a turn for the worst and was now scrap. Fortunately, though, I now had more useable material than I had last week. This cast iron instability was reminiscent of my experience with the thin-wall cast iron slip-in, o-ringed liners I made for my Howell V-4. I spent nearly a month dealing with material and process problems that created significant circularity errors in those parts that prevented the rings from properly sealing. For this build I had hoped the stress relief heat treatment that I performed earlier on the ring blanks would eliminate this frustrating issue, but evidently it did not.
Construction resumed on the lathe by first turning all the oil grooves. The blanks were then transferred to the horizontal rotary on the mill where the .020" diameter radial oil holes were drilled. Each blank of 18 rings had 180 of these holes drilled using a carbide circuit board drill. Due to a senior moment that lasted an afternoon, I drilled holes in twice as many blanks as I actually needed. Before I was done I had drilled some 500 holes in three blanks using a single drill bit! After transferring the blanks back to the lathe, the scraper lands were chamfered with a 60 degree threading insert. The rings were then parted off with a carbide grooving insert. After the machining was completed, the rings received the same lapping and heat treatment that was previously performed on the compression rings. I ended up with a total of some 50 oil rings. All of them passed my light test even at the bottom of the cylinder where the i.d. was .0005" over the ring o.d..
Trimble's method for making rings is maligned by some who probably tried it and got poor results after following what they truly believed was his process. Unfortunately, his process has been paraphrased and passed along over the last 25 years with seemingly innocent modifications and 'improvements' that created these results. The gap setting dowel in his heat treat fixture is an example. The theory in his original article showed that its purpose is to resolve his calculated spreading forces into a single vector along the neutral axis of the ring. He is able to do this with a circular dowel of the proper diameter that is in a precise location and tangent to a truly radial ring break. The effect he is trying to produce can't be duplicated with a rectangular wedge and/or a non-radial snapped breaks that I and others have tried to use. In fact, in his article, he graphs possible resulting radial contour errors as large as .010" that can result. An alarming but counter-intuitive statement that he makes is that a ring completed using his method but ending up with a fit issue can't be corrected by re-machining the o.d.. Since he didn't provide any further explanation, I've never been able to understand the reasoning behind his claim.
Trimble's method is but one method for making rings; and if one wants to use it, the original three articles in the back issues of SIC are the best source material for his process. It's probably a mistake to mix portions of his process with portions of other processes without properly working out and testing the applicable theory. The theory he outlines in one of his original articles is not overly difficult to follow and can help the builder appreciate the subtleties involved in his process and its associated hardware. - www.strictlyic.com - Terry


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## petertha

mayhugh1 said:


> ..where the .020" diameter radial oil holes were drilled. Each blank of 18 rings had 180 of these holes drilled using a carbide circuit board drill. - Terry



That's a lot-o-holes. I recognized the drill in your pic as similar to what I bought on ebay. So no problem on the cast iron, just straight in? In general on the CI ring machining, is it usually dry cutting or fluid depending on the job? You likely mentioned this in a prior post, but on the heat setting operation, do you use the sealed stainless foil & sacrificial burn paper to mitigate scale?


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## mayhugh1

petertha said:


> That's a lot-o-holes. I recognized the drill in your pic as similar to what I bought on ebay. So no problem on the cast iron, just straight in? In general on the CI ring machining, is it usually dry cutting or fluid depending on the job? You likely mentioned this in a prior post, but on the heat setting operation, do you use the sealed stainless foil & sacrificial burn paper to mitigate scale?



Peter,
I peck drilled the holes going .025" deep at a time, and I did all the cast iron drilling and cutting dry. The drill bit showed only a slight amount of wear after all those holes. I used the sealed stainless foil wrap, but I filled it with argon gas from one of my welding cylinders instead of using the burn paper. I tried the burn paper technique several times but always ended up with a sticky brown goo on the parts I was heat treating. I tried a couple different lots of brown wrapping paper as well as some white typing paper, but the results were always the same. I was going to try a wooden match stick but then got the idea of using an inert gas and that's what I've been using since. I don't think scaling is a real big problem below 1000F, though. -Terry


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## mayhugh1

One of the most critical assembly steps in this engine is mating the finished heads to the finished cylinders. This is because the heads are permanently screwed onto the cylinders and are, hopefully, sealed by a .032" thick annealed aluminum head gasket. Once these pairs are assembled, the cylinder flanges can finally be drilled for the crankcase studs. In order to drill these flange holes the head/cylinder assembly must be supported so the head's intake flange is oriented precisely perpendicular to the crankshaft axis when the cylinder is installed on the crankcase. This is necessary so the intake tube assemblies will properly align with the intake ports on the crankcase. Once the flange holes are drilled, the head, cylinder, and head gasket are permanently married. If they are ever separated it will be extremely difficult to reassemble them and end up with the exact same head flange orientation. It's for this reason that it's a good idea to have some number of spare head assemblies tested and ready to go. 
Since two-thirds of my build time on this engine has, in one way or another, been related to the heads and cylinders, I want the assurance of a final head/cylinder integrity check before drilling these holes. The valve seals in the heads have been previously measured and accepted, and so the spark plug and head gasket seals should be the only new variables in the completed assemblies. In order to verify these, I created a fixture to pressurize each head/cylinder assembly so the total leak-down time of each combination can be measured. The cylinder flange is safely secured to the fixture by a pair of screw-down clamps and sealed to it by an o-ring temporarily placed on the cylinder skirt beneath the flange. A filler block inserted into the cylinder reduces the total pressurized volume to that of the combustion chamber at TDC. This reduction in volume allows the measured leak down times in this test to be directly compared with the leak-down times previously measured and recorded for the individual valves. Since this volume has a direct influence on the maximum combustion pressure in an IC engine, it's a reasonable volume to use for a final leak check. In an earlier post, I predicted a worst-case 2.5 psi drop per second per valve at a cylinder compression test pressure of 75 psi assuming my arbitrary minimum acceptable Mity-Vac valve leak-down time. Using a 75 psi test pressure, a worst-case 5 psi drop per second would be expected if the only leaks in the head/cylinder assembly come from two worst-case valves.
The fixture, itself, was measured and found to leak less than .01 psi/sec at a 75 psi test pressure using a simple block-off plate. The fixture was then tried out on three unused spare H-9 head/cylinder assemblies that I have left over from that build. The leak-downs on those three cylinder assemblies measured 1.2, 1.8, and 4 psi per second; and these measurements correlate reasonably, but not perfectly, well with the valve leak-down results recorded for those heads. Although those numbers are fine, I'm expecting significantly better results from my T-18 assemblies since I put so much more effort into sealing those valves. But, I realize an assembly's leak-down time can be dominated by the worst-case valve especially if the valves' leak rates are well separated.
In order to torque the heads onto the cylinders, the cylinder skirts can be gripped in a vertical 5C collet chuck. The complex shape of the head, though, makes it very difficult to obtain a substantial grip for tightening the assembly even with a strap wrench. I eventually came up with a simple tool made from a brass block silver-soldered to a half inch ratchet adapter that mates with my torque wrench. In use, the block is inserted into the snug fitting space between the bottom pair of valve tower fins and the head is tightened onto the cylinder with a torque wrench. Soft brass was used for the block so it would conform to the radius'd edges of the fins and reduce the applied pressure that might damage them. I also wrapped the block with a protective layer of .002" stainless shim stock, but later used a strip of paper. I experimented with my two test heads and a scrap H-9 cylinder and finally decided upon a torque spec of 35 ft-lbs. I cringed the first few times I applied this tightening stress to the valve towers of my test heads. I was concerned I might be straining the delicate valve seals inside the towers. In order to check on this, I pulled a vacuum on the rear of one of the installed valves with my Mity-Vac and monitored the valve leak down in real time while I repeatedly torqued one of the test heads. I could see no effect on the dynamics of the leak-down, and so I felt a little better about the abuse I had planned for my heads. For peace of mind, though, I decided to continue the Mity-Vac measurements before and after torquing each assembly.
The fixture for drilling the flange holes may be the last significant fixture I will need to machine for this build. Again, the shape of the head complicates any scheme to secure the intake/exhaust flange parallel to one of the axes of my mill so the flange hole pattern can be accurately oriented. The photos show the two-part swan song fixture I came up with. The head's intake/exhaust flange is the important reference surface, and it is directly mounted to the fixture while clamped in the mill vise. The machined parallel surfaces of the fixture insure the parallelism of the intake/exhaust flange to the x-axis of the mill. An adjustable top plate helps to support the assembly during drilling and also helps to keep chips away from the completed assembly underneath. As an extra precaution, the assembly will be wrapped in plastic during drilling to help protect it from cutting oil and chips.
The assembly process starts by selecting a cylinder, head, and piston, all of which are uniquely numbered. Three piston rings are then selected and individually light tested in the cylinder. The rings are then installed on the piston, and it is then inserted into the oiled cylinder and pumped back and forth for about a minute using a spare connecting rod. This is just my sanity check on the fit and allows me to get a hands-on feel for the level of friction. It also kicks off the rather dirty process of rubbing the bluing from the cylinder wall. The piston is then removed, cleaned, and bagged so it can be returned to the same cylinder later. 
The Mity-Vac will be used to measure the valve leak-down times before and after torquing the head onto the cylinder at 35 ft-lbs. The exact thickness of the head gasket used is also measured and recorded - just in case. An NGK CM-6 spark plug is installed in the head. I plan to use the same plug for as many assemblies as possible since I have only one of these on hand, and I've always wondered how many tightening cycles the compression washer can take. I've purchase a full box of Rxcel CM-6's that I'm saving to install during final assembly. 
The assembly is then placed into the test fixture with the filler block, pressurized to 75 psi, and then total leak-down rate is measured and recorded. The assembly is then moved to the flange drilling fixture where the stud holes are spotted and drilled. Finally, each completed assembly will be set into a cylinder test position on the crankcase where the fit of a test intake tube will be verified. - Terry


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## mayhugh1

After measuring three T-18 assemblies things took an unexpected bad turn. Although I measured acceptable 5 psi/sec leak-down numbers on the first two assemblies, both were curiously identical and more than twice what I was expecting from the Mity-Vac data. The third assembly came in at an even worse 20 psi/sec, and a distinct hiss was coming from the spark plug. Initially, I assumed the compression washer on my used NGK CM-6 plug might have come to its end of life, so I borrowed two more NGK's from another engine. I used one of them to make up a 'test plug' by removing the compression washer and pressing a metal ring around its body for a rubber o-ring to do the sealing for these tests. I retested my third assembly, and the result was a much better 10 psi/sec. When I repeated the tests on my previous two T-18 assemblies using using my test plug I got 0.1 psi/sec. I then re-tested my three H-9 assemblies, and their measurements had also improved a bit and were now in better agreement with their Mity-Vac data. These results told me that my spark plug had been leaking air and had been dominating my leakage measurements. 
To be honest, I wasn't entirely surprised to see better leak-down times for some of the assemblies in this test than was predicted by my Mity-Vac tests. When I ran those tests on the finally lapped valves I noticed that on some valves I could improve the results by pressing the valve hard into the seat with my thumb. The results I recorded were, for consistency, only with atmospheric pressure doing the pushing. In this test, the 75 psi pressurized head is adding another 10 pounds of force above atmospheric and probably over-whelming the slight surface irregularities that still remained after lapping. It could also be that the additional force is slightly bending the valve stem in some cases to allow a little better centering of the valve on its seat. In any event, these results showed that my Mity-Vac data should be treated as only a worst-case prediction in this final test. 
I never expected to see an air leak at the spark plug, though. The problem with using a special test plug is that I could miss a potentially significant leak.
I decided it was time to break open my new box of Rcxel plugs and test each assembly using a new plug. I tried six of these plugs and could not get even one of them to seal to any of my three T-18 assemblies. The seal was so bad, in fact, that I could hear the tell-tale hiss of a major leak; and, according to my wife, my hearing isn't all that great. I took two photos comparing the compression gaskets of the Rcxel and NGK plugs. The NGK plug creates, in my opinion, a superior seal to the head thanks to a narrow sealing ridge spaced well away from the threads. The rear of the gasket is contoured for what appears to be a nice fit to a tapered area on the plug body adjacent to the hex. The Rcxel gasket, on the other hand, has a much broader sealing surface that is located very close to the threads. The rear sealing surface is similar. My experience with valve sealing has convinced me that a narrow sealing surface is usually a better performer than a wide sealing surface. I think the compression washer on the Rcxel plugs make them much less forgiving against an imperfectly machined engine-side mounting surface.
But, I didn't understand why the mounting surfaces on my heads weren't perfect. I machined, drilled, and tapped them in the same mill set-up. I used a spindle tap starter directly over the drilled holes, and the surface finish couldn't be better. I used the recommended 10mm x 1 tap for the CM-6, and the fit of the thread feels like it should. Still, soapy water showed the leak was coming from a poor seal between the plug and the head. Assuming my machining was somehow flawed, I made up a piloted scraper and manually re-surfaced the top .010" of the head mounting surface. The scraper, however, left machining marks in the surface that made the leak even worse, and so I also had to make a piloted lap to smooth out the surface again. After a full day of entertainment going down this dead end, I ended up with exactly the same unbelievably bad leak.
Since I couldn't see what anything wrong, I tried change the leak in some way hoping I could get another symptom to expose it. I tried Teflon tape on the threads. I tried .005" soft aluminum shim washers under the plugs' compression washers. I even machined and annealed my own compression washers although, in hindsight, they were much too thick at .070" to conform to the head with the torque I was willing to apply to the plug. The results were always the same. The Rxcel plugs hissed and caused immediate leak-downs, and two of the three NGK's sometimes managed to eek out a barely acceptable 10 psi/sec. Clearly, something was hiding in plain sight.
I won't list all the things I tried in order to affect the problem, but my notes show a total of 47 leak-down tests on that third assembly. I suspected my NGK plugs were also complicating the problem because theIr compression washers were, by now, worn out and obviously giving inconsistent results. I had completely given up on the Rcxels, and so I had a local auto parts store special order some new NGK's for me.
A possible cause of the leak came to me while I was studying my notes for the spark plug cavity machining. During machining a burr had been raised around the periphery of the plug hole by the drilling and tapping operations. I manually de-burred the hole at the bottom of the cavity using an oversized reamer since the cavity was too deep for any of my countersinks. It isn't at all obvious to the naked eye while looking into the head's spark plug cavity, but the microphotograph shows the de-burring removed an excess bit of metal near the start of the thread. This effectively left a slight 'gouge' in the head's surface with a depth and width that were dependent upon some variables I wasn't controlling very well. On my third assembly this gouge happens to extends underneath the Rcxel compression washer. However, it barely touches the sealing ridge of the NGK plug. I checked all my T-18 heads, and all of them have this problem to some degree.
I repaired the head of my third assembly by turning a .030" thick stainless steel washer and JB Welding it in the spark plug cavity over the old sealing surface. The i.d. of the disk closely matches the plug's threaded o.d. and the o.d. of the disk is just .010" smaller than the cavity i.d. The JB Weld's service temperature is 600F and should be fine in this application as a leak eliminating filler below the disk. I made a simple threaded fixture out of an Rcxel plug to secure the disk against the old sealing surface and to keep it normal to the threaded hole while the epoxy cures. This new surface will sink the plug about .040", but it is still remains un-shrouded in the combustion chamber. As the final photo shows, I ended up with a more robust sealing surface. The dark rings around the i.d. and o.d. is the JB Weld that flowed into the gaps between the disk and the head. The gouge created by the de-burring is even more prominent now.
After the epoxy cured, I re-measured the leakage with all the various plugs I had been using. My o-ringed test plug gave the best result at 2.2 psi/sec which was almost twice my Mity-Vac predictions. I tried my other two used NGK plugs, and they produced 3.5 psi/sec and 5 psi/sec. Soapy water around the base of these plugs showed that even though the inconsistent leakage numbers were acceptable, the compression washers are shot. The Rcxel plugs were still very disappointing. Only one new one was able to match the leakage of my best used NGK. Several brand new ones still leaked badly with an audible hiss.
My new NGK's arrived, and the three I checked yielded identical 1.2 psi/sec results that matched my Mity-Vac prediction for that assembly almost exactly. My plan is to repeat this fix on two more of my worst-looking heads. If the results still look good, I'll modify all of them including the first two that have already been tested. -Terry


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## DICKEYBIRD

Wow, more amazing craftsmanship & attention to detail.  The finish line is in sight!

What effect do you think the big difference in thermal conductivity & expansion between the aluminum heads & stainless steel washers will have?  Bottom line the plug runs cooler?  Is that a good thing or a bad thing?  You think there's any danger of the epoxy cracking & leaking down the road due to the differing expansion rates?  

Definitely not trying to be critical; it just worries me.  I'm no engineer though so ignore this if I'm being overly paranoid.


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## Charles Lamont

Have you tried making your own annealed copper washers?


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## mayhugh1

Those are all really good questions, and I have some of the same concerns. JB Weld says their product can take 550F-600F intermittently (10 minutes), and 500F continuously; and I'm hoping they mean it can also handle the accompanying expansion. My application, though, will include a clamping force of around 1000 lbs putting the epoxy in 360 psi compression when the plug is tightened, and I can see both good and bad points associated with that. I'm curing the epoxy under about 100 psi compression. The epoxy isn't inside the combustion chamber, and so I don't believe it will ever see even 300F. The prop on these big radials does a great job in keeping the heads cool. When I measured the head temperatures on my nine cylinder I don't believe I saw anything over 200F. The exhaust gas temperature might hit 300F-350F, and I'm a bit more concerned about the 450F solder I used on the intake/exhaust flange. Of course, besides the temperature measurements I made, my reasoning there was that if that intake flange ever reaches 450F I'm not going to get any fuel into the engine anyway. As far as affecting the plug temperature goes, there might be an effect, but it's the temperature of the center electrode that's most important and there is a pretty high thermal resistance between it and the shell of the plug. Also, JB Weld gets its 4000 psi tensile strength from powdered metal filler, and so its thermal resistance is a bit lower than other epoxies.
Instead of the epoxy I could use an automotive paper gasket under the disk, but that sounded like a lot of hassle when taking the lower plugs in and out as is constantly done on a radial. I'm in the process of curing only two more heads, and so it isn't too late to back away from the epoxy if others have had a bad experience doing something similar.


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## mayhugh1

Charles Lamont said:


> Have you tried making your own annealed copper washers?



Charles,
As a matter of fact I did make up several and tried them. I was concerned about running copper against the aluminum head and the corrosion I might get as a result. Because of the oil and fuel that would inevitably end up between them I figured Murphy would find a way to use the mixture as an electrolyte; and with the heat involved, galvanic corrosion seemed like a real possibility. So I switched to aluminum. I made up a few dozen aluminum washers and annealed them similarly to my head gaskets. But these had to be .070" thick to properly set the plug depth which, as it turned out was too thick to conform and flow into the surface defect. I started thinking about using two separate washers - one thick and one thin - but since that doubled the number of seals I had to deal with, and so I started down this epoxied disk road. It's not too late to re-consider, though. -Terry


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## mayhugh1

Charles,
I wanted to add one other thing to my reply to your question. I initially tried a thin .005" soft aluminum washer under the compression gasket of the plug. This was before I discovered my gouge. My reasoning was that if there was some defect in the surface of my head causing the leak, the soft aluminum would flow into it and seal it. What I saw was that the contact patch of the plugs' compression gasket pressed down into the washer and caused its outer periphery to lift and there was no effect on the leak. In hindsight, the gouge probably extended out past where the aluminum washer lifted, and the gouge was too deep to be filled this way. This was when I went to the thicker washer, and ran into yet a different limitation. -Terry


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## mu38&Bg#

I think the lay of the cutting marks is the problem here. If it was circular leakage should not be a problem. The radial lay allows a direct path across the sealing surface, even a soft O-ring won't seal properly. I would guess a plug seat milled using circular interpolation would be  acceptable if a bullnose endmill was used along with proper feed rate. I  use bullnose (also called corner radius) end mills almost exclusively  and surface finish in aluminum is almost mirror smooth. You can be  certain that in production plug holes and seats are finished with step  drill/counterbore type tools.

I don't understand the comment about the gouge. I don't see it in the image.

Copper is used for RC glow plug washers. It's extremely rare to see corrosion that could be attributed to the copper washer. Besides, if galvanic corrosion was a concern do you worry about the copper bearing alloys in the rod bushes, valve cages, etc?

Thank you for providing the in depth details of this excellent build.

Greg


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## mayhugh1

Greg,
Thanks for the comments. Gouge isn't a good term for the chamfered edge that I think is the problem. It's not real obvious, but in the image without the disk it extends radially outward a bit further than it should and ends up kissing the compression washer contact point on both plug styles. 
You have a totally reasonable comment about the machining marks. I, too, wondered if they could have been the problem, but I could not feel anything with my finger or by dragging a toothpick across the surface. I have noticed, though, after after a plug has been tightened down against an aluminum head a few times that a mark is usually left behind by the compression washer that I can feel with my finger. If a plug's compression washer isn't capable of sealing against a mark at least that shallow, it would seem that once a head has seen one manufacturer's brand of plug it would forever be tied to that particular brand if not that exact same plug.
By the way, I'm currently setting up an experiment to test the heat cycling capability of JBWeld in this application. I've drilled and tapped an aluminum plate and JB Welded three disks to it that are held in place with some (now scrap) Rcxel plugs. I plan to heat cycle the plate a dozen times or so with a torch and see if the epoxy bond shows any sign of deteriorating. I'm also going to cut out some gaskets, just in case. - Terry


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## Charles Lamont

I don't understand why a soft washer would be "too thick to conform". Surely the thicker it is (within reason) the more easily it will deform to accommodate its mating surface, since the percentage deformation will be less?


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## DICKEYBIRD

It looks like you've found an inherent problem with tiny spark plugs and their threads being coarser in relation to their diameter.  Too bad they aren't made with taper seating or a bigger flange & gasket to get outside of that thread start.

It would seem to me that if a 1/4-32 glow plug seals OK with a soft copper washer, that method should work here too.  I forget, what size are your plugs?


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## mu38&Bg#

The NGK CM-6 plugs have M10x1 threads. They are the most common plug for RC gas engines. I'm surprised about sealing concerns with the RCEXL plugs as many people use them and I don't think there have been any issues. These plugs are unique in that they are very small, nothing else really comes close, and there are no taper seat plugs this small. You cam find 10mm taper seat plugs, but they have much deepr reacha nd overall length.


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## mayhugh1

Charles,
You're exactly right. It's been the width of my shop-made rings that prevents them from sealing. Their thickness is .070" but their radial width is .090". I chose this width when I made them to match the width of the compression washers on the commercial plugs I have. The difference is that mine are flat, and the commercial versions are not so they can apply more pressure. The NGK's have a narrow ridge, and the Rcxel plugs have a broad contoured face. If I machined the face of my washers to have a ridge that would probably solve the problem on that side. I would still have to do something about the seal on the plug side. I can't just make narrow washers with a smaller i.d. since the seal has to occur somewhat away from the threads, but yet the washer will need to be centered on them. Your question does give me an idea for another option, though.

Dickiebird,
The plugs I'm using are 10 mm CM6's. The major o.d. of the threaded body is about .390". 

Last night, I completed the assembly and testing of he two worst-case looking heads onto which I JB-Welded the two stainless repair disks. The results were perfect at 0.2 psi/sec leak down which closely agreed with the Mity-Vac data. I'm not doing anymore repairs that way, though, until I see the results of my heat cycling tests on the JB Weld as well as some more thinking. One Rcxel plug sealed, but not as well, and two would not seal. I just don't understand my experience with the Rcxel plugs. I've done a Google search and can find no one else with any complaints about them. Maybe it's a lot problem with the batch I have, since they have all come from the same box. Terry


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## DICKEYBIRD

mayhugh1 said:


> I just don't understand my experience with the Rcxel plugs. I've done a Google search and can find no one else with any complaints about them.


Most likely, nobody else tested them for leaking and just assumed they were sealing.


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## mayhugh1

DICKEYBIRD said:


> Most likely, nobody else tested them for leaking and just assumed they were sealing.



You could be right. After what I've seen the past several days I could envision a scenario where someone finishes up a new engine and has a really difficult time getting it to start while they listen to the hiss from a leaky plug they mistake for the sound of a healthy intake. Then, to add insult to injury they make a compression test using a gauge that actually does seal to the head, and they end up with a great compression test that sends them off looking for ignition and/or carburetor problems. A simple test putting a few drops of soapy water at the base of the plug of a new engine is going to become S.O.P. for me. - Terry


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## gbritnell

Hi Terry,
I know that you are using commercial plugs but I have found that we as engine builders try to replicate plug proportions when making them, for that matter even Rimfire plugs have a small seat area relative to the thread O.D. I have had similar problems to what you have described. I guess the cure would be to increase the body diameter to make sure that the seating are was well out of the way of the thread chamfer or thread start. I use copper washers that I punch out of a sheet of copper then anneal them. Even at that I get the occasional leak. The plugs are so small that torquing them down is not an option lest the body break away from the threads. I'm tempted to try a tapered seat on my next engine build. 
gbritnell


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## mayhugh1

George,
What thickness copper do use for your washers?
Thanks - Terry


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## gbritnell

Hi Terry,
I use .020
gbritnell


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## mayhugh1

So, after verifying my leak-fix on three assemblies, I was ready to apply it to the rest of my heads. JB Weld's temperature spec of 500F continuous and up to 600F intermittent sounded plenty adequate for my needs. Then, Dickiebird asked if I had considered a possible issue with temperature cycling the epoxy. After some more thought and web research, I could imagine JB Weld's loosely worded high temperature spec might not actually include an ability to be temperature cycled. And, I ran across lots of stories of users' repairs gone bad that were blamed on temperature cycling.
I decided to run my own test before repairing any more of my heads. I made a test bed by drilling and tapping a 3/8" aluminum plate for five spark plugs. Stainless washers were epoxied into three of the positions and temporarily secured with spark plugs tightened with a clamping force of about 100 psi while they cured just as was done on the first three head assemblies. For comparison, I also threaded in two additional plugs with stainless washers sealed against the plate using gaskets I made from commonly available 1/64th inch thick brown automotive gasket material. In fact, it's the same material I'm using for my exhaust flange gaskets. I decided, at the last minute to include these gaskets in my testing as another potential solution. After considering some of the other readers' comments; and, depending upon my test results, I might find myself machining a batch of ridged compression washers. Finally, I sprayed portions of the plate with a Rustoleum 500F high heat paint that I also want to test. The black painted surfaces will also provide nice targets for my non-contact thermometer.
As a control, I JB Welded a similarly cured sixth washer to a separate plate that will not be heated. This control might be used later to quantitatively compare the forces needed to push a cycled vs. non-cycled epoxied joint to failure.
After a 15 hour cure and with the plugs torqued to 75 in.-lbs., I used a torch to heat the back side the plate for 2-3 minutes until the target test temperature was reached and then held for about 30 seconds on the washer side of the plate. After 45 minutes or so when the plate had cooled back to room temperature, I repeated the cycle using the same test temperature. After the fifth cycle I un-torqued and re-torqued all the plugs a half dozen times each before removing them and attempting to dislodge the three epoxied washers from the plate by pressing hard against their edges with a wood block. After the tenth heat cycle, I repeated the torquing tests and then I also baked the entire plate of re-torqued plugs in an oven for three hours at the test temperature. The purpose of this constant temperature bake was to accelerate the aging of the resin. I performed the same ten cycle heat, torque/un-torque, and aging bake for test temperatures of 300F, 350F, and 400F.
I really don't expect the JB-Weld to even come close to 300F on my radial because of the huge finned heads and massive prop wash. The reason for the higher test temperatures is to accelerate the failure mechanisms created by temperature cycling the epoxy and to force the failures to occur as early as possible during testing. Also, it's an opportunity to learn more about JB Weld for a possible future application.
At the end of the 300F tests, I began having doubts about a gasket solution. Both gaskets had become stuck fast to their washers which was a good. But, the side of the gasket against the smooth aluminum plate did not stick; and the material had become very hard and its surface glazed from the heat. These gaskets would probably continue to seal until the plugs were removed the first time. But, it would be difficult to re-install them with the washers in their original orientations; and the gasket material no longer seemed to have the compliance needed to re-seal the surfaces against combustion pressures. I've dealt with this on old automobile engines. Some of their irregularly shaped gaskets, if not damaged during disassembly, can sometimes be returned to their original positions and re-used but only in low pressure sealing applications.
After successfully passing the 400F tests (total accumulated 30 temperature cycles, 36 torque/un-torque cycles, and 9 hours total bake time) I decided it was safe to continue on with the JB-Weld repair of my heads. 
As one of the photos shows, the gaskets had by this time completely deteriorated. Since none of the epoxy bonds had yet failed, I continued on with the 450F test. At a 450F head temperature the Loctite 620 sealing my valve cages would decompose and the soft solder used on the exhaust flange would melt, and so further testing was just more for my curiosity. 
I modified the 450F test slightly by leaving out one of the spark plugs to see if the clamping pressure had been playing a major role in maintaining the bonds on either side of the washer. I also stopped the gasket testing since there wasn't anything left to test. After five 450F heat cycles, all three washers were still holding tight; and so I baked the test plate containing two torqued spark plugs and one open washer at 500F for three hours. At the conclusion of that test the washers were still being held in place by the JB Weld, but using the same moderate force I was able to dislodge all three of them from the plate. Inspection of the washers showed it was the bond between the epoxy and stainless that released. 
In any event, I came away from this little diversion with a healthy respect for JB Weld. One important manufacturer's application tip I ran across in my research is that cleaning the surfaces to be bonded with acetone or lacquer thinner is recommended, but use the use of alcohol is specifically discouraged. I previously assumed that JB Weld became hard and brittle when cured. But after recently mixing several batches of the stuff and monitoring the leftover I discovered that there is always a small degree of compliance left in the material that probably accounts for its ability to be temperature cycled. - Terry


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## gbritnell

Hi Terry,
While thoroughly enjoying your build the thing I like most about it is your in-depth experimenting with different materials and processes. Although I have the machining part down I can't tell you how much I have learned from this thread. 
Thanks so much,
gbritnell


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## petertha

mayhugh1 said:


> ...In any event, I came away from this little diversion with a healthy respect for JB Weld. Terry



Well, those tests were very enlightening. Thanks for the effort & documenting real world results. I would have placed a small wager the washers would have dropped off in a sticky goo. But I'm glad you found a potential solution & now have the confidence & knowledge to proceed.

I made a few carbon fiber composite tuned pipes for RC engines back in the day, playing with different shapes & baffle configurations. The resins have changed over the years but it was basically this kind of 600F stuff until cost & hazmat shipping made it silly expensive for me.
http://www.cotronics.com/vo/cotr/ea_ultratemp.htm

I recall (and experienced) an important pre-requisite of these HT resins successfully achieving their spec T is following the temp ramp-up & soak schedule to the letter. Nominally it was about 40-60% of ultimate temp, but it varied by formulation. That's why I'm amazed that an ambient cure formulation like JB achieved those temps. However I also think JB-like filled adhesives are a different animal than laminating resins used in composite parts, specifically resin concentration. A typical layup, even vacuum bagged, is hard to achieve much better than 40/60 resin/matrix proportion. But possibly they can pack more metal/ceramic filler in a glue/putty form. The way I visualize it is, you can have 10,000 deg Kryptonite powder, but if its suspended in a matrix of 400 degF resin binder, basically things will start to flow at that minimum, critical temp. Typically I think resins expand a bit, so when joints are in compression & then cool, maybe its not as bad as tension or flexural? 

Anyway, blah-blah (composites gives me a nerd-on). I guess the only thing I could offer is: 
a) try a moderately elevated temp pre-cure soak of the cured resin & see if that improves JB results even more
b) If you are feeling the need for a bit more safety factor, I suspect there are other industrial strength versions out there, for ex
http://www.cotronics.com/vo/cotr/rm_adhesive.htm
c) give it the representative 'oily' test of engine conditions. Some epoxies can start to degrade in the presence of light ends like gasoline, oils etc.
d) I have not heard that particular no-alcohol rule before, but I'd agree. For epoxies I really prefer acetone anyway. It cleans oils & waxes aggressively & flashes almost instantly. Same for LT although I cant stand the smell anymore. Alcohols come in too many variants, % grades by water content, some I suspect with extra additives packaged as 'rubbing' alcohol. I could see that being undesirable.

But yeah, for an adhesive you can get at the hardware store, JB has moved up my personal glue ranking!


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## mayhugh1

Peter,
Thanks for the Cotronics website. I looked through it pretty closely, and they have a lot of really neat products. Their RK454, in fact, sounds a lot like JB Weld. Some of their repair products are the kind that can get you out of those corners that we sometimes paint ourselves into.
A lot of epoxies are exothermic, and so trying to add heat during their cure cycle can be counter-productive. The JB Weld people don't recommend adding heat until after the first six hours of room temperature curing time. I've dealt with some high temperature ceramic paints, though, that had to be cured with a high temp cycle before they could be taken to their full service temperature. -Terry


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## mu38&Bg#

Why not use or make a spark plug seat cutter? http://www.timesert.com/html/howtosp.html This method looks simple enough. You probably need to make on for M10 though.







Greg


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## mayhugh1

Greg,
Yeah, that was the first thing I tried with my shop made piloted cutter and lap. The one in your picture looks like it might be better suited, though. The chamfer's undercut was so deep that I don't think my .01" deep re-cut was probably deep enough. -Terry


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## mayhugh1

I returned to assembling and testing the head/cylinder pairs. My little spark plug diversion spooked me, and so I put off the flange drilling until all the pairs were completed and the dust was allowed to settle. Then I drilled them all in one final operation. For extra measure I increased the head tightening torque from 35 to 40 ft.-lbs, and I went back and re-torqued the already finished assemblies. I eventually modified all the heads with the JB Welded re-surfacing washers. The leak-downs of the first two assemblies that had passed with passable numbers before I discovered the spark plug air leak actually improved 2X after the washers were added. It's likely that all my heads would have leaked to some degree without the modification.
My leaky plug experience got me even more curious about the maximum number of torqued installs the plugs I'm using can receive and still retain their ability to seal. I measured the leak-downs of each of my assemblies using my o-ringed test plug and also a single standard NGK. I recorded the two leak-down times for comparison as well as the number of installs accumulated on the NGK. After 30 installs I could still see no statistical difference between the readings obtained using the two plugs.
Plug install life is worth a consideration with this engine since the usual recommendation on a model radial is to remove the plugs from the lower cylinders after running so oil seeping into the combustion chamber can drain out without causing hydrolock. As I found out, it takes about three weeks for the 40 wt. crankcase oil in my H-9 to find its way past the rings and into the combustion chambers of the lower two cylinders. Evidently the oil seeps through the ring gaps and piston groove side wall clearances.
Out of 80 piston rings that I light-tested during assembly, 11 failed. In all these cases there was only a minor sliver of leakage in random spots with respect to the gap. In one or two instances it might even have been my imagination. The rejects were likely due to circularity errors in the starting blanks. My notes show that the batch that contained nearly all the rejects came from two blanks I had used that contained .0003" circularity errors near their ends. 
I ended up with six assemblies that had no measurable leak-down, and I used one of them to check out my shop-made compression gauge. I found and fixed an o-ring leak that it has probably had ever since I made it. I made this particular gauge during my H-9 build with the goal of creating one that could be installed in a tight location where the face might not be visible while cranking over the engine. The central part of the gauge contains a check valve from a tire pressure gauge. I added a 10 mm threaded nose and a miniature pressure readout on either end while being especially careful to minimize the gauge's own internal volume between the input and the check valve. Since model engines have relatively tiny combustion chambers, it's important for a compression gauge to add as little additional volume to the cylinder under test as possible or the compression numbers will be low. I also made sure the gauge can be screwed into the head to about the same depth as the spark plug body.
The flange drilling went smoothly. The drilling fixture worked well, and the plastic cling wrap did its job of protecting the assemblies from the chips. Eight studs were temporarily installed in one the crankcase cylinder locations, and each assembly was trial fitted in place along with an intake tube after it was drilled. When completed, I finally had 24 completely finished and tested head/cylinder pairs with leak-down rates ranging from zero to a maximum of 1.3 psi per second when measured at 75 psi. I also had 23 pistons whose installed rings had all been individually light tested and showed no leakage.
Now it's time to blow a year's dust off my stacks of boxed and bagged finished parts and get on with the final assembly. I think the next step will be to install the crankshaft and oil pump in the crankcase and then verify proper oil flow through the engine and to all the bearings. -Terry


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## mayhugh1

Final assembly of the multi-piece crankshaft into the multi-section crankcase is a bit tricky but do-able using a procedure I developed last year while designing those parts. The rear crankshaft section with its crank pin and installed master rod was maneuvered through the front of the rear crankcase section while the rear main bearing was simultaneously inserted into the rear of the rear crankcase section. The two met up inside with the master rod sticking out through cylinder hole number one. The rear main bearing was then bolted in place. The eight slave rods were next installed on the master rod hub by feeding them through the other eight cylinder holes. A simple shop-made tool was used to guide and insert the slave rod pins through the front of the crankcase and into the master rod assembly. This tool was also used to orient the pins so the milled flats on their ends aligned with the pair of 2-56 socket head set screws in the master rod assembly that are used to secure them in place. These screws are accessible through the cylinder holes and were tightened using a standard hex key. The front cheek was then slipped onto the crank pin using a temporary alignment rod inserted through alignment holes in the cheek pair, and then its pinch screw was tightened to 20 in-lbs. I used high strength 6-32 alloy SHCS's for the clamp screws that I had previously tested to failure at 30 in-lbs. This front cheek of the rear crankshaft section contains the female side of the square slip drive.
The center main bearing containing the pre-assembled and tested oil pumps was next installed in the front of the rear crankcase section. An o-ring was added to seal the sump pick-up to the scavenger pump inlet. The oil feed tubes were temporarily installed into the sides of the rear crankcase section where they also screw into the oil pump housing. This step insured the oil pump/center main bearing assembly was properly oriented in the crankcase before finally bolting it in place.
The short crankshaft center section with its installed crank pin and the male side of the square slip drive was then inserted through the oil pump and center main bearing and into the mating socket in the rear crankshaft section. The front master rod was slipped onto the crank pin of the short center crankshaft section and maneuvered to stick through cylinder hole number ten of the front crankcase section. All this was done while the front crankcase section was being stacked onto the rear crankcase section. The front slave rods were installed on the front master rod assembly just as the rear rods were installed on the rear master rod. The cheek of the remaining front crankshaft section was then aligned with its mate, again using a temporary alignment rod, and then its clamp screw was tightened to 20 in-lbs. 
At this point the crankshaft assembly was complete, and it turned smoothly with no tight spots just as it did a year ago. As discussed in the early posts dealing with the crankshaft design, dowel pin keys were captured by the tightened pinch screws on all four cheeks. These keys prevent the cheeks from rotating on their crank pins and insure the crankshaft is held in perfect alignment under the torque expected from this engine.
Operation of the pressurized oiling system was verified by using a syringe to inject oil into the intake feed tube while manually rotating the crankshaft counterclockwise. After a few revolutions, oil could be seen seeping from all the bearings. In this engine, oil is pumped into the center section of the crankshaft and forced to flow toward the front and rear of the engine where it lubricates both master rod bearings as well as the center, front, and rear main bearings. Oil seeping from the front and rear rear main bearings splash lubricates the moving parts of the front and rear cam assemblies. An o-ringed seal plate that will be installed later prevents oil from the rear main bearing entering the fuel plenum under the rear cover.
Oil is pumped through the square drive slip connection in order to reach the front of the engine. This precision slip fit connection is, itself, lubricated by its own minor seepage. Windage provides cylinder wall and slave rod lubrication. In the dry sump system of this engine the return oil flows through deep return channels milled in the two crankcase sections and into the sump. The scavenger pump returns the oil from the sump to an exterior oil tank where it is recycled through the engine by the oil pump. A variable flow restrictor will eventually be added to regulate the flow of oil into the engine so the scavenger pump is not overwhelmed while trying to empty the sump. The scavenging system was tested by filling the sump with oil and again manually rotating the crankshaft counterclockwise. After a few revolutions, oil began flowing out of the scavenger return feed tube and continued until the sump was empty.
So far, all is working as expected. The next step is to install and time the front and rear cam assemblies and generate the valve timing events diagrams for the two cylinder banks. - Terry


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## gbritnell

WOW!
gbritnell


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## kvom

Double wow!


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## Scott_M

And another WOW !


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## ShopShoe

And another WOW  And another WOW And another WOW

I've been following this all along, but there hasn't been much I could say.  Congratulations and thank you for your very good explanations and photos and diagrams.

I'll never even aspire to your level, I work too slowly and life keeps getting in the way, but I really like to watch this and I have learned some things about engineering that may be useful. You are an excellent teacher as well as an excellent engineer and designer.


--ShopShoe


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## johnny1320

You sir are a master craft's man!


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## Swifty

It's really an amazing piece of work. Can we have some sort of size reference in one photo when you post again.

Paul.


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## mayhugh1

Thanks, everyone for your kind comments. 
Swifty: In the last photo of my last post with the engine mounted on the stand and resting horizontally, the engine measures 12 inches long between the end of the rear cover and the end of the front crankshaft. - Terry


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## mayhugh1

Unlike V-engines, radials seem to have adopted a consistent cylinder numbering system. Double-row radial engine cylinders are numbered clockwise when viewed from the rear of the engine. Cylinder number 1 is at the top of the rear row. Cylinder number 2 is the first one clockwise from number 1, but it is located in the front row. Cylinder number 3 is the next one clockwise from number 2, but it is located in the rear row. All odd-numbered cylinders are located in the rear row, and all even-numbered cylinders are located in the front row. Cylinder number 10 is at the bottom of the front row.
In a radial engine the firing order follows a pattern that allows the firing impulses to continually follow the motion of the crank during its rotation. In a double-row radial engine, the firing order is a bit complicated. The firing order is such that a firing impulse occurring in a cylinder in one row is never immediately followed by a firing impulse occurring in a cylinder of the same row.
An easy technique for figuring the firing order of an 18-cylinder, double-row radial engine is to start with any number from 1 to 18, and then either add 11 or subtract 7 (in radial parlance these are called the firing order numbers), depending upon which gives an answer between 1 and 18. For example, beginning with cylinder 1, add 11 to get a result of 12. Then, because 11 cannot be added to 12 since the total would be greater than 18, subtract 7 to get a result of 5. Add 11 to 5 to get 16. Subtract 7 from 16 to get 9. Subtract 7 from 9 and the result is 2. Add 11 to 2 and the result is 13, and then continue this process for 18 cylinders. The resulting firing order is [1]-12-5-16-9-2-13-6-17-[10]-3-14-7-18-11-4-15-8. One cylinder fires every 40 degrees of crankshaft rotation.
The cams are timed to the crankshaft by focusing on the TDC events of the two cylinders containing the master rods i.e. cylinder 1 for the rear cam and cylinder 10 for the front cam. Even though these two cylinders oppose one other, their also opposing crank pin throws mean their pistons will reach TDC at exactly the same time.
In a four stroke engine each piston hits TDC twice within its 4-stroke cycle: once during the transition from its exhaust stroke to its intake stroke, and once during firing - the transition from its compression stroke to its power stroke. After the cams have been properly timed, the TDC's of cylinders 1 and 10 will occur on opposite halves of the 4-stroke cycle. That is, while cylinder 1 is transitioning from exhaust to intake, cylinder 10 will be firing.
However, to simplify the timing process, each cam will actually be timed using the TDC in the first half of the 4-stroke cycle. In this first half cycle, where the exhaust stroke is transitioning to the intake stroke, the flanks of the cam's lobes are adjacent, and the center between them is easily determined. After the rear cam has been timed, though, the crankshaft must be rotated 360 degrees before applying the same timing process to the front cam. This is necessary so that, after timing, cylinders 1 and 10 wind up on opposite halves of the engine's 4-stroke cycle as required by the engine's firing order.
The rear cam was timed first. A rear row head/cylinder assembly was temporarily installed on the crankcase in position number 1. A spare H-9 piston without rings was temporarily installed on the master rod, and a pair of tappets were inserted into the tappet bushings for this cylinder. A shop-made adapter was threaded into the spark plug hole of the cylinder so a dial indicator resting against the piston crown could indicate TDC. Two additional dial indicators were set up on the tappets and zeroed out while the tappets were resting on the base of the cam ring.
With the piston at TDC and the jackshaft temporarily removed, the cam ring was manually rotated until it was centered between the exhaust closing event and the intake opening event as determined by the dial indicators on the tappets. The resolution of the gear train is actually fairly coarse, but the teeth of the two gears on the jackshaft are randomly aligned. And so, with patience, a position can usually be found that maintains the center between the lobes within a few degrees after the jackshaft is re-inserted. After being satisfied with the result, the o-ringed rear seal plate was then installed followed by the impeller. 
A degree wheel was installed on the crankshaft, and the timing of the valve events was measured at a .010" tappet lift. The intake and exhaust durations were measured at 208 and 235 degrees, respectively. The intake lobe center was located at 107 degrees ATDC and the exhaust lobe center at 114 degrees BTDC. The cams in this engine are very mild, with an almost negligible 5 degrees of overlap 'near' TDC.
After rotating the crankshaft 360 degrees, a similar process was followed for the front cam assembly using cylinder number 10. After completion, the front cover was installed.
The next step is to install the head/cylinder assemblies as well as the intake/exhaust tube pairs. Terry


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## Scott_M

Hi Terry
 Very impressive.
 I really like the 11-7 rule for determining firing order. But I have a question ? Will that work on your next build, the 3 bank 27 cylinder ?  

 Scott


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## mayhugh1

Construction continued with Loctiting 164 4-40 cylinder flange studs around the perimeter of the crankcase. I used 1/2" long stainless steel socket head set screws instead of making a huge batch of custom studs. Each stud eventually receives a washer, lock washer, and nut - all of them small pattern parts. I trial-fitted the head assemblies down over the studs in a few tight areas near the sump and oil feed tubes to make sure there were no surprises ahead. 
Since I hadn't yet finalized how I was going to splice the long intake tubes, it was now time to decide. After a lot of back-and-forth I settled on a short length of Kynar shrink tubing covered by a cosmetic stainless sleeve. I had been also toying with an option to insert a thin Viton o-ring between the ends of the tubes for extra sealing insurance before shrinking down the Kynar. But, being concerned the o-ring might become dislodged and find its way into the intake, I decided to leave it out. I used a thin (.015") slitting saw to cut the intake tubes on the twelve remaining tube assemblies in order to leave a minimum gap between the ends. Just to make things even more difficult for myself, I turned the batch of stainless steel sleeves with very thin (.010") walls. The i.d.'s of the sleeves were reamed for a very snug fit over the Kynar. In fact, I had to make up a tiny rubber strap wrench to roll it into final position.
After installing my first assembly, I learned that even though the clearance notch I had milled in the side of the rear row heads wrapped nicely around the spliced intake tube, I hadn't fully taken the studs into account. There was a slight interference with one the fins just below the notch while the cylinder was being inserted into position over its studs. This interference would have increased the difficulty involved with removing cylinders later, if necessary; and so I set up a fixture on my manual mill to remove an additional bit of material from each of the twelve rear row heads.
Then, after installing the third pair of heads I began having second thoughts about two things I was doing. The first was how I was supporting the engine while installing the cylinders. Tightening the flange nuts on the 'easy' top cylinders had been an exercise in patience on more than half of the studs and required several tiny wrenches, a couple shop-made tools, and lots of re-positioning of the engine. Looking ahead, the studs on the bottom six cylinders, especially around the sump area, look nearly impossible to access with the engine mounted on its display stand. The engine already weighs nearly 20 pounds, and it's getting heavier and more awkward to deal with. I made up two simple work stands to support the engine vertically on either end, but it appears the bottom flange studs will still be too difficult to access without an ability to continually reposition the engine as I had been doing on the top cylinders. What I really need is a rotisserie engine stand in order to safely finish the assembly.
My second concern was with the gasket material I was using for the exhaust flanges. I made these gaskets from some no-longer available automotive gasket material that I had purchased from a local auto parts store several years ago. This was the same material I heat tested during my JB Weld evaluation and it's also the same material I used for the exhaust flanges on my H-9. What concerned me was the very close fit of my gaskets in the deep exhaust flange pockets in my T-18 heads. I saw this material adhere to the stainless washers in my JB Weld heat test. If the same thing happens in the pockets of my heads, it will be very difficult to remove the flanges and cleanly replace the gaskets if the need ever arises. I disassembled one of the exhausts from my H-9 build; and, sure enough, one side of the gasket was stuck fast to the exhaust flange in that engine. This adhesion isn't a problem in the H-9, though, since the exhaust flanges simply slide into place from the top and do not rest in pocketed recesses as they do in my T-18 heads. An old H-9 gasket is easily scraped away and replaced, but this would not be the case in these heads. Furthermore, the discoloration I saw on the H-9 gaskets told me they had been running at close to the maximum 250F temperature rating of this material. 
So, I ordered a more exotic 700F Aramid sheet material in order to re-make my exhaust flange gaskets. Unfortunately, I'll have to disassemble nearly two days work when I replace the six already-installed gaskets. 
While I'm waiting on the new gasket material I'm going to make a rotisserie engine stand that will be better suited for supporting the engine for its final assembly. - Terry


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## Scott_M

Hi Terry
Again WOW !

Those flange nuts do look like they are lots of fun. Have you considered a flexible shaft nut driver to get them started? I have a 1/4" drive one that is joined to the handle by a piece of aircraft cable. I really works well for getting things started. Maybe a smaller one could be made up , with a thin wall socket and a piece of 1/8" cable. It might help.

Scott


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## kvom

I have been watching the PBS/Ken Burns series on the Roosevelts this week.  One thing mentioned was that during the war Ford had a production line that could turn out a B24 bomber every hour, each with 4 14-cylinder engines (2 rows of 7).  Each airplane had about 1.5 million parts.  Following this build shows how incredible that production was back in the 1940s.

Another interesting tidbit was the American auto manufactures produced a total of about 150 cars during all of the US involvement in WWII.


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## mayhugh1

Scott,
Here's the problem I'm dealing with. The closeness of nut to the cylinder wall will only allow my highly modified closed end wrench to get around it. Then there is the tapered profile of the cylinder that forces me to come in from the side. I've been threading the nut on the little tool that I made and then coming in from the side and then threading the nut off the tool and onto the stud with a tiny probe. This works pretty well, but tightening the nuts that last half turn requires several different shaped open end wrenches and lots of re-positioning of the engine. - Terry


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## wrljet

Yup, I saw/heard that also.  I wondered how many of those 1.5 million parts were rivets.

Some time ago I was thinking that Terry's work on his engine was something it normally took an entire company to do.  And which they could not do as well.

-Bill



kvom said:


> I have been watching the PBS/Ken Burns series on the Roosevelts this week.  One thing mentioned was that during the war Ford had a production line that could turn out a B24 bomber every hour, each with 4 14-cylinder engines (2 rows of 7).  Each airplane had about 1.5 million parts.  Following this build shows how incredible that production was back in the 1940s.
> 
> Another interesting tidbit was the American auto manufactures produced a total of about 150 cars during all of the US involvement in WWII.


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## mayhugh1

After deciding that I was going to make an engine stand, my first inclination was to torch-cut the parts and weld up something substantial and quick. It seems I don't know how to work that way anymore, and so I ended up back in SolidWorks designing something that would fit both my T-18 and H-9 and maybe even my next project. I added a requirement that the stand has to be capable of holding either fully assembled engine including the distributors and carburetors. That feature will allow it to be used for routine maintenance on the engines including valve lash adjustments and compression checks. These chores were going to be very difficult to perform on the bottom six cylinders of this engine while on its display/running stand.
I started by milling a mounting ring from 3/8" steel plate. I used the code I'd already developed for the exact same ring I made for the display stand. I cut out three new support arms from 5/16" steel and welded them to the three mounting tabs on the ring. The other ends were radially welded to the outer diameter of a short length of 1.25" o.d. d.o.m. tubing. The base of the stand was torch cut from a 1/4" steel plate. The end of a short piece of 1" by 2" rectangular tubing was then welded to the baseplate to create the stand's upright column. The stand was completed by welding a short length of 1.25" i.d. d.o.m. tubing horizontally to the top of the column. The tube on the mounting ring fits perfectly inside the tube on the column so the mounting ring can be easily rotated. A 1/4"-20 grub screw was added to the tube on the upright in order to secure the mounting ring so the engine's crankshaft can be safely spun while the engine is mounted on the stand.
The wooden vertical stand that I previously made is used to temporarily support the engine while the display/running stand and rotisserie's mounting ring are exchanged. This bit of extravagance will be welcomed later as the engine grows in weight and awkwardness. After mounting the engine it was immediately obvious that a rotisserie stand is an absolute must for assembling this engine. If it weren't for the ignition wiring and the oil and fuel lines I'd integrate this feature into the final display/running stand.
The new gasket material has arrived, and so my next steps are to cut out the new exhaust flange gaskets, replace the old ones already installed, and then continue on with the engine assembly on my new stand. -Terry


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## johnny1320

After this work of art I can't imagine how you could top this Terry


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## kvom

And to think this started with seeing if he could make the crankshaft.


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## John Rus

johnny1320 said:


> After this work of art I can't imagine how you could top this Terry



"Another Radial - this time 36 Cylinders" 

John.


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## apointofview

I'm thinking an R4360 !


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## Henry

He is an artist and will need something more complex 

I can not wait to hear this new *Beauty*.


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## james_III

I'm so speechless, every time reading this monster cylinder topic  :bow: Thm:


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## Slinger

Maybe a sleeve valve radial or a monosoupape Gnome radial or a............:bow:


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## mayhugh1

Slinger said:


> Maybe a sleeve valve radial or a monosoupape Gnome radial or a............:bow:



... or a quarter scale Merlin V-12.


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## Woodster

mayhugh1 said:


> ... Or a quarter scale merlin v-12.




*Do It*!!!!!!!!!


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## apointofview

One more request, how about an Allison V-3420.
Pete


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## Charles Lamont

?Next:

http://modelenginenews.org/gallery/croft/eagle/index.html

speechless


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## mayhugh1

The 1/64" thick Aramid sheet gasket material that I ordered from MSC arrived, and while cutting out a new batch of exhaust flange gaskets I temperature tested some samples of this new material. MSC advertises its maximum temperature at 700F although it's not at all clear what that means. This material has a kid leather-like feel, but it cuts and tears like the auto gasket material I've been using. I did a web search, and what I have looks very much like a product called Durlon 8500. 
For my test, I cut out some washers and sandwiched them between metal washers in a stack on a 10-32 bolt. I heated the compressed stack to 500F for an hour. Disappointingly, the result looked pretty much like my over-heated auto gasket material as it had become very brittle and dark in color. The test gaskets also stuck to the metal washers but not as badly as I had seen with the auto gasket material. I re-ran the test at 300F which is more realistic for my application, and in this test the material did not discolor, and it remained flexible. In fact, it looked so good that I repeated the test to make sure I had programmed the oven properly. The results were the same, and so I started the process of replacing the gaskets already in my engine. Evidently MSC's maximum temperature isn't a service temperature but, instead, a point just below where the material combusts. For future reference I repeated the test at 350F and 400F using two new batches of test washers. The 350F results still looked pretty good, but the material had turned too brittle for my use after an hour at 400F.
Assembling the cylinders onto the crankcase wasn't as bad as I was expecting. The engine stand was invaluable for accessing the studs, and it was satisfying to see all the complexity finally coming together. I was expecting poor access to the studs around the sump, but the biggest challenge turned out to be working around the oil feed tubes. There were about a dozen nuts out of the 164 that became mini-milestones during the assembly. I was eventually able to tighten the nuts on every stud of every cylinder, but to do it I had to make up a set of 3/16" crowfoot wrenches.
The strap wrench for working the stainless steel sleeves over top of the heat-shrunk Kynar worked well on all the intake tubes. It even worked well under the notch of the very last installed cylinder. While I was dealing with the sleeves I also made a couple extraction tools that fit under the clearance notch in the rear heads and allow me to push the relatively flimsy thin-wall sleeves off during disassembly. Hopefully, they won't have to be used very much, if ever. Cylinder clearances around the sump and oil feed tubes came out as expected, and I should be able to remove any single cylinder should it become necessary. Kynar has a fairly high shrink temperature, and so a reflective shroud was required around the nose of my small heat gun to focus enough heat on the splice.
I measured 17 in-lbs of torque needed to spin the crankshaft and overcome the friction created by the 54 piston rings. This is equivalent to a 1/3 horsepower loss at 1000 rpm. This frictional loss should decrease some over time, but additional losses will be added when the pushrods are installed.
A temporary oil tank was jury-rigged and, after inserting some rubber plugs in the lower tappet bores, I used a drill to spin the engine and exercise the oiling system while flushing two quarts of oil through the engine. A borescope inserted into the front and rear tappet bores showed all the cams were being well oiled even with the drill running at very low speed. With the drill running at 600 rpm and gravity feeding the full 1/4" oil line to the engine's pressure pump I was easily able to get ahead of the scavenger pump and flood the crankcase. The oil pumps in this engine are similar to the ones in my H-9, and so an oil feed regulator similar to the one I made for my H-9 will eventually be required when the engine is actually running under its own power. After flushing the oil through the engine, I cleaned some ring debris from the magnetic drain plug in the sump. The next step is to finish the pushrods and install the rockers for the cylinder compression tests. Terry


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## petertha

Woah-Wait-What? The Kynar is heat shrink tubing right? (clear stuff you show with heat gun & reflector). So is the external SS sleeve pre-positioned on the straight segment up near the cylinder & then you slide it back over heat shrink? Is the intention to do this hot so the shrink tubing OD kind of bonds to SS sleeve or maybe some in-between adhesive step? Now what about disassembly? sacrificially cut & peel off the tubing sandwich? Very spiffy end result look!


_The strap wrench for working the stainless steel sleeves over top of the heat-shrunk Kynar worked well on all the intake tubes. .. I also made a couple extraction tools that fit under the clearance notch in the rear heads and allow me to push the relatively flimsy thin-wall sleeves off during disassembly... Kynar has a fairly high shrink temperature, and so a reflective shroud was required around the nose of my small heat gun to focus enough heat on the splice._


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## mayhugh1

petertha said:


> Woah-Wait-What? The Kynar is heat shrink tubing right? (clear stuff you show with heat gun & reflector). So is the external SS sleeve pre-positioned on the straight segment up near the cylinder & then you slide it back over heat shrink? Is the intention to do this hot so the shrink tubing OD kind of bonds to SS sleeve or maybe some in-between adhesive step? Now what about disassembly? sacrificially cut & peel off the tubing sandwich? Very spiffy end result look!
> 
> Peter,
> Yes, the SS sleeve is pre-positioned, as you said, and then slid over the heat shrunk Kynar tubing after it cools. The i.d. of the sleeve was reamed for a snug fit over the Kynar so vibration wouldn't cause it to slide around, and is the reason for needing the strap wrench to pull it into position. The sleeve is purely cosmetic to cover up the tacky looking clear shrink tubing with the visible gap between the two intake tube ends. If I could have found some colored gray without a $300 minimum order, I wouldn't have bothered with the sleeve. For disassembly, the extractor tool I made will push the sleeve off the Kynar tubing which is then cut and replaced during assembly. The sleeve is then re-used.- Terry


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## mayhugh1

I started a set of pushrods last year in order to get some of the high volume work done before the Texas heat set in. At that time I was able to machine only one end of the rods since the head design wasn't yet complete, and I was unsure of the final length. There's a total of 14 stacked machined parts with tolerances that affect this length, and so there is also a lash adjustment on the end of each rocker arm. To determine the exact final length, I made up a variable length pushrod and trial-fitted it in six different positions around the engine. This empirically determined length came out to within .010" of my design value, and fortunately the length was correct for all six positions.
After determining the pushrod length, I made a fixture to cut my batch of semi-finished rods to their final length + .003" using a slitting saw and fixture on my mill. The second end was then turned to a hemisphere using my 9x20 lathe and the CAM program I developed last year for the other end.
Although the 3/32" diameter pushrods look at home on my H-9, they're a bit too skinny looking in front of the massive heads on this engine. In my scrap collection I found a bag of 3"-6" drops of hardened hypodermic stock with the proper i.d. to slip over my rods to increase their o.d.'s to nearly 1/8". Unfortunately, both ends of the tubes had been crushed flat and would not fit into my lathe's collet chuck so I first rough cut the ends using an abrasive disk in a fixture on my mill, and then I finished them in the lathe. I heat treated the sleeves, not for any metallurgical reason, but for the dark color that the heat imparted to them. One of the photos shows a side-by-side comparison of the sleeved and un-sleeved rods.
With the pushrods completed, I was anxious to install a pair of rocker arm assemblies and run a first compression test on one of the cylinders to sanity check my work up to this point. Unfortunately, my compression gage would not fit between the rocker assemblies on the front row of cylinders due to an interference with the gage's pressure release button. I was able, though, to make a test on one of the rear cylinders thanks to the head geometry differences between the front and rear row cylinders.
The next problem I ran into was created by my jury-rigged oil tank. Without proper flow control, the engine quickly flooded with oil when the crankshaft was spun fast enough to get a consistent compression test. I rigged up a temporary flow-controller using a cheap aquarium air flow regulator purchased from a local pet supply store. Then I reluctantly added an extension to my compression gage to get the release button above the rocker assemblies. This was a lot easier said than done, though, and I spent an entire day chasing leaks in my gage created by the modification. I also had to make a special box wrench to access the lock nuts on the lash adjusters. The few tiny commercial wrenches I had on hand were too awkward to use in the rocker arm slots in the rocker boxes.
During my H-9 build, I estimated the engine's expected compression test pressures based on the simple formula:
Ptest = (CR)(Pman),
where CR is the static compression ratio, and Pman is the engine's manifold pressure. Pman is 14.7psi for a normally aspirated engine.
For my H-9's compression ratio of 5, the expected pressure was (5)(14.7)=74 psi, and all its cylinders measured to within 10% of this value just after the engine was first assembled.
This simple formula, though, does not take into account the cylinder's volumetric efficiency or the adiabatic heating of the compressed air charge during the test. A more complete expression is:
Ptest = (Veff)(CR^1.33)(Pman),
where Veff is the volumetric efficiency and is typically 0.6 during a cranking test. The 1.33 is a specific heat term to account for the self-heating of the compressed air in the combustion chamber during the test.
When the H-9's compression ratio is plugged into this equation:
Ptest = (.6)(5^1.33)(14.7) = 75 psi.
The two correction terms in the more complete expression work to offset one another, and for low CR's they nearly cancel. This is not the case, though, for higher CR's found in full-size engines or in model competition engines where the full equation is more applicable. For example, with a compression ratio of 10 the simple equation gives 147 psi while the more complete expression gives 189 psi.
The H-9 compression ratio of 5 that I've been using is considerably lower than the advertised 6.7 for that engine. I believe the difference is due to the fact that the cylinder's thread relief clearance as well as the head gasket thickness were not accounted for in the original calculation. Due to the small combustion chamber volume, the compression ratio is very sensitive to these relatively small errors. I eventually verified my H-9 calculation with a burette test on one of my spare H-9 heads. Since I used the same combustion chamber geometry for my T-18 heads, I'm assuming the compression ratio of this engine is 5 as well. 
Because the compression gage adds a portion of its own volume to the combustion chamber during the test, the raw readings need to be corrected for the additional volume below the gage's check valve. I had to modify my gage's correction factor when I added the extension needed to clear my rocker assemblies. Another issue that one has to be aware of when making compression tests on small model engines is excessive oil in the combustion chamber. An innocent looking puddle of oil on the top of a piston can raise the compression ratio of that cylinder significantly. My new engine stand allowed me to rotate the engine while I was installing the rocker arm assemblies and pushrods. When I started making the compression tests I wasn't being careful to return the engine to its full upright position before making each test. Since the oil return channels in the bottom of the crankcase were no longer at the lowest point in the engine, the crankcase partially filled with oil causing certain pistons, depending upon their locations, to pump oil into their cylinders. When I ran compression tests on those cylinders I found the pressures to be higher than expected. In fact, on one cylinder the excess oil had raised the compression high enough to damage the meter on my gage and it had to be replaced. I learned it was necessary to soak up the oil in those cylinders with Q-tips before running compression checks. 
Obtaining absolute numbers in a compression test is a pretty dicey exercise. It might not even be all that meaningful, especially in a model engine where the combustion chamber is so tiny, and so many small effects can contribute errors. In any event, with a target value of 75psi, my compression test results were:
#1=65psi, #3=75psi , #5=67psi, #7=61psi, 
#9=80psi, #11=80psi, #13=80psi, #15=68psi, #17=77psi,
#2=72psi, #4=68psi , #6=70psi, #8=71psi, 
#10=81psi, #12=77psi, #14=64psi , #16=67psi, #18=65psi.
The high readings on the three very bottom cylinders (9, 10, 11) are likely a result of these cylinders, behind their pistons, being filled with crankcase oil during the test. These three or four tablespoons of oil in these inverted cylinders insured the rings were absolutely sealed. The fact that the readings were 80psi instead of 75psi probably indicates an error in my gage's calibration or correction factor. This oil drainage problem is one of the 'features' of a radial. Under power, the scavenger pump and windage keep these areas from filling with oil. But when the engine is shut down, crankcase oil drains back into these areas and contributes to the billowing smoke typically seen on start-up.
I don't plan to do any 'motoring' to 'break-in' the rings. The compression test results show the rings are sealing pretty well as installed. After doing a lot of thinking about this 'motoring-in stuff', I've come to my own conclusion that it's not a good idea. 
At best, I feel it does nothing useful because there's no combustion pressure to push the rings hard against the cylinder walls which is required to properly seat them. Even with the pistons working against their cylinders' own compression only a fraction of the required pressure is produced compared to what's generated when the engine is running under power. 
At worst, without this high pressure, motoring a new set of rings in a new cylinder might cause their surfaces to glaze over and then delay or even inhibit break-in. In my mind, it's a bit analogous to a cutting tool rubbing against a workpiece when the chip load is too low.
I reluctantly ran two quarts of oil through this engine only because I felt I had to thoroughly verify my new and unproven oiling system before the engine was allowed to run under its own power when an oil failure could be catastrophic. It took about 30 minutes of total run time spread over several days to flush the two quarts of oil through the engine. If I had thought out the assembly process a little more, the engine would have been flushed without the rings installed. The torque needed to spin the crankshaft changed from 17 in-lbs to 15 in-lbs as a result of the flush, and the decrease was likely due to ring wear. Hopefully, it will turn out to be beneficial to the break-in. With all the pushrods but none of the spark plugs installed, the torque required to spin the crankshaft remained at 15 in-lbs. This indicates the frictional losses related to the cams are insignificant when compared to those of the 54 piston rings.
The next and final steps in the engine assembly is to install and time the distributors and to come up with a spark plug harness. I'm still about a month away from attempting to start the engine, though. I still have to design and build the final mounting and control components including a firewall, fuel and oil tanks, fuel pump, tach, throttle control, and electrical wiring. - Terry


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## Swifty

It's getting to be a real work of art, you certainly are a very skilled worker. Even people with no idea of the machining skill involved should be impressed with the beauty of the engine.

Paul.


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## stevehuckss396

holy cow does that look nice.


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## Olcoot

This build should impress anyone! I am a Tool and Die-maker (Injection mold maker) with over 40 years experience and I am blown away with this build.


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## idahoan

Terry I have been following with your build from the beginning. My hat is off to you; what an amazing project! Your attention to detail and quality of work is just amazing.

Dave


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## mayhugh1

Thanks all for your comments. - Terry


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## mayhugh1

The engine was temporarily moved from the rotisserie to its vertical stand so the rear cover could be removed and the distributors installed. The distributor gears were installed after the distributors are inserted into the rear cover. Their mesh with the crankshaft driving gear was verified several months ago before any components were added to the crankshaft and when any binding could be detected. The backlash was re-checked, though, and measured just over one crankshaft degree. Distributor backlash typically isn't a problem since IC engines run in only one direction, and all timing measurements and adjustments can made after rotating the crankshaft in that same direction. Once back on the rotisserie and with the transparent distributor caps installed, the engine was ready to have its distributors timed. Since the two distributor gears are on opposite sides of the crankshaft drive gear, the distributors rotate in opposite directions just to make things even more interesting. As a reminder, the rotors' directions are engraved on the tops of the caps.
I found the only way to maintain sanity during the timing process was to treat the engine as I had originally envisioned it: that is, two separate engines on the same crankshaft and each with its own distributor with its own firing order. Standing at the rear of the engine and looking forward, the right-hand distributor controls the 'fire and skip' firing order 1-5-9-13-17-3-7-11-15 of the rear row of cylinders which are driven from the rod assembly on the rear crankshaft throw. Cylinder number one is physically located at the very top of the engine, and TDC of its firing stroke was located using a dial indicator in its spark plug port. 
The distributor was lifted up from the rear cover to disengage its driven gear so the center of the rotor could be aligned as closely as possible to the number one cylinder tower. The TDC mark on the distributor body was kept in alignment with the stationary timing pointer on the engine. After getting the best rotor possible alignment, the hold-down setscrew was then retightened.
Because there are only 20 teeth on the distributor driven gear, the resolution of this adjustment is only 18 distributor degrees. To get the rotor more accurately positioned, the distributor cap must be removed to get access to a tiny setscrew that holds the rotor in place on the trigger disk. This setscrew tightens into a slot on the trigger disk so the two components are keyed together. The rotor was then removed to get access to a SHCS that secures the trigger disk to the shaft. The SHCS was loosened, the trigger disk rotated in the proper direction, and then the SHCS was re-tightened. The rotor was slipped back onto the trigger disk, its setscrew tightened, and its position was rechecked. The process was repeated until the centerline of the rotor was accurately aligned to the #1 tower.
After this step is completed, the firing event timing can be set. The distributor's trigger cable was then connected to an ignition module. The module was powered up with the high voltage switched off so its trigger LED could be used as a firing indicator without actually generating a spark. Even though the ignition is a CDI, the LED operation is designed to mimic a points-type ignition. That is, LED ON indicates 'coil' charging, and the plug fires when the LED turns OFF. A degree wheel was attached to the crankshaft, and the TDC dial indicator in the #1 cylinder plug port was used to zero the wheel. The crankshaft was then slowly rotated CCW until the LED turned ON and then OFF, and the firing error with respect to TDC was recorded. 
The Hall sensor is mounted on its own disk inside the distributor body under the trigger disk and can be rotated with respect to it in order to zero out the timing error. This was done by loosening a setscrew on the underside of the distributor housing and rotating it and the internal sensor disk in the crescent slot until the LED turned OFF precisely at TDC.
The whole process was then repeated for the front row of cylinders using the left hand distributor. In this case, the timing was performed with respect to TDC of the firing stroke of the bottom-most cylinder #12, and the firing order for this distributor is 12-16-2-6-10-14-18-4-8.
In normal use, the timing of each distributor can be individually advanced by loosening the distributor hold-down screw and rotating its body. The scribed timing marks on the distributor housing are 10 crankshaft degrees apart.
After running through the combined firing order and being satisfied with the distributor timing the transparent distributor caps were replaced with the blue Delrin caps.
One of the photos shows the results of a solid tantalum capacitor that exploded inside one of my ignition modules while I was working with the distributor timing. The electronic components that I used are from 30 year old stock, but it's possible that I caused the explosion by inadvertently reversing the supply wiring. I was too fatigued at the time to know for sure. Anyway, the ignition module cleaned up OK, and the damage was limited to just the single capacitor.
The last photo shows three high voltage boot/clip possibilities for a CM-6 spark plug. The white boot is a commercially available Rcxel product that I've actually never used. The clip, but with more layers of shrink tubing than shown in the photo, is what I used on my H-9. Both commercial parts are available from S/S Machine and Engineering. The clip works well and looks OK on my H-9, but I wanted to use plug boots for this new engine. I don't like the looks of the large white Rcxel boot, so I came up with the third alternative shown in the photo. This boot is based on a commonly available automotive vacuum fitting. I'm currently tweaking a process to convert the vacuum fitting to a spark plug boot, and I'm torture testing some of the results. I plan to detail this later in a separate post. - Terry


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## Scott_M

Wow Terry. it is looking really good. I am getting antsy to hear it run.

I know if it were me I would start it , and worry about boots later  The patience you exhibit is as impressive as the build.
Not to mention the time you have taken to document it for all of us. It is truly appreciated !

Many thanks
Scott


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## mayhugh1

I drove around to the local auto parts stores and purchased all the Dorman #47408 1/8" x 7/32" right angle vacuum fittings I could find because, to me, they looked like T-18 spark plug boots. Then, I experimented with various modifications to adapt them to both the CM-6 and the 1/8" diameter 20kV plug wire that I'm using. This wire is distributed by S/S Machine & Engineering.
Straight out of its package, the small diameter end of this fitting is a perfect size for gripping and strain relieving the 1/8" diameter plug wire. However, a simple shop-made insertion tool is needed to actually get the wire into the boot. The i.d. of the body, though, is too small to fit over the CM-6, and so it must be opened up some. This is much easier said than done in rubber, and I was only able to come up with a passable solution using tools I had on hand.
There are several ways, involving various degrees of complexity, to make an electrical connection to the top of the spark plug. The simplest way is to pull about four inches of wire through the boot, strip off 2-1/2 inches of insulation, and then coil the bare wire up into a small pillow. The wire is then pulled back through the boot until the pillow is at the bottom of the boot where it can contact the electrode when the plug is pushed into the boot. The boot will grip both the wire and the plug tight enough to maintain a reliable connection on practically any model engine. I torture tested a few boots made up this way because I was really interested in using this simple connection for my application. What I found, though, was that after twenty or so installs the ultra-fine strands making up the 1/8" diameter plug wire began to break away. I was more worried about this debris finding its way into a combustion chamber than I was about the integrity of the electrical connection. For most users where the plugs won't be frequently removed from the engine, this simple contact using this particular wire is probably very adequate. In my case, though, several plugs will frequently come in and out of the engine; and so I wasn't entirely comfortable with it.
After trying unsuccessfully to make compression springs work, I finally arrived at a tubular contact design similar to that found in plug wire kits for early era custom cars. The sequence of photos shows the steps I followed to make up four plug wires using the last four fittings left over from my experiments. Additional fittings for the rest of the wires are on order from an online supplier.
I started by sliding the boot onto a 3/16" diameter mandrel in my lathe and cutting off a portion of the body to give the boot a final height of 3/4". As mentioned earlier, the i.d. of the body must be opened up to fit over the plug body. The next photo shows the three tools I used to do this: a 1/4" rougher, a 5/16" rougher, and a 9/32" annular cutter. I found that 3-flute cutters produced a nicer hole than the 2 and 4-flute cutters that tended to create polygons. I manually held them in end-mill holders to reduce hand fatigue and marked the depth of cut directly on the cutter to avoid going too deep. A bi-directional twisting motion was used to grind away the rubber and open up the hole. I found it useful to first chill the fittings in a freezer for an hour or so. I started with the annular cutter using the rear of a drill bit as a pilot to get things started straight. I then went deeper using the 1/4" rougher, and followed that with the 5/16" rougher. I tried to grind a special purpose cutter, but I wasn't able to improve upon the grinding action of these cutters. When the boot slid onto the plug with the 'right' snug feel, I stopped and went onto the next part.
The contact I designed starts as a length of 9/32" o.d. brass tubing purchased from a local hobby shop. After cutting a .360" long piece, both ends were slightly beveled by manually rotating a 45 degree countersink in them. The bevel on the top end will later help guide the contact onto the plug. On the mill, a 1/16" wide slot was cut along the entire length of the tube. As shown in the photos the corners were chamfered using a pair of sharp side cutters. The bottom-end chamfers are wide enough to provide a clearance slot for the plug wire. An .040" diameter hole was drilled for the plug wire by passing the drill through the slot and drilling close to the bottom end of the contact. A half-round file then cleaned up all the sharp edges. Finally, the contact was slid onto a #3 drill and pliers were used to carefully reduce the diameter and close up the 1/16" slot while maintaining the circularity of the contact. The chamfered wire clearance slot was re-checked.
To prepare for soldering, the wire insertion tool was pushed into the boot. This tool is just a short length of .160" o.d. x .130" (reamed) i.d. brass tubing pressed into a convenient holder. This tool is a very snug fit going into the boot, but it will allow the plug wire to easily slide into the boot where it can be grabbed with pliers, or preferably, a hemostat and pulled through the boot. The insulation was was then stripped back about 1/8" and the wire was soldered into the hole that was drilled earlier. Care has to be taken to not allow excess solder to flow down inside the contact where it can block the insertion of the spark plug. Any wire left protruding outside the contact after soldering was clipped off and the sharp stub was rounded with a file.
The plug wire passing through the wire insertion tool was then rotated to orient the attached contact so the slot runs parallel with the insertion tool. The contact insertion tool was then used to push the contact down into the boot. This critical dimensions of this tool include a .218" dia. x .250" long nose followed by a .250" dia. x .250 long shoulder. The tool was inserted into the contact and then, with a coordinated effort between both hands, the contact was pushed into the boot while the excess plug wire was continually pulled out through the wire insertion tool. When the contact was fully inserted, the wire insertion tool was removed. The boot was then slid over a test plug several times to check the mechanical fit, and an ohmmeter was used to verify continuous electrical continuity while the boot was twisted on the plug. If the hole in the boot was enlarged correctly there will be enough spring force created by the surrounding rubber to hold the contact snugly closed around the plug electrode. 
I found it interesting that all my NGK plugs showed zero resistance as expected while the Rcxel plugs I have typically showed tens to hundreds of ohms of resistance. I got the exact same non-zero results measuring directly across them. I have no idea where the resistance is coming from. The CM-6 is not a resistor plug and the RcXels I have are not labeled as being iridium plugs. 
If there is any problem with the contact, it can be removed without damaging the boot by snipping the plug wire outside the boot and grabbing the contact with a pair of long nose pliers. Using a twisting motion the contact can be collapsed and pulled out of the boot so a new one to be installed. - Terry


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## Charles Lamont

Terry, here are some of my first experiences of machining rubber, which I hope may be of some use:
http://www.charleslamont.me.uk/Seagull/drive_coupling.html
I found grinding to work particularly well.
The tubular tools come from the famed _The Amateur's Lathe_ by L.H.Sparey.


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## e.picler

Heloo Terry!
Congratulations for you building, its is a stat of the art craftsman, amasing what you have done. Really impressing. I wish to have that skills.

Please could you explain how you have cut the gaskets? I`m guessing it was cut on CNC mill. Right? 
How you did that and what kind of tool/cutter have you used?

Thank you.


Edi


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## petertha

Real nice Terry. Looks like you have the boots all done up & provisions for reproducible spares based on accessible commercial parts. Thought Id throw out some links just in case.

 Paz shows his trials & tribulations with silicon. I'm not exactly sure why the issues but Ive heard can be fussy with any combination of incorrect release agent, mix ratios, curing conditions, shelf life...
http://homepage2.nifty.com/modelicengine/k090102.htm

 Ive not messed with silicones as much as equivalent durometer urethanes for composites work & they seem quite easy & forgiving for custom parts like this. But maybe there are some electric/insulation or gasoline/breakdown reasons why they wouldn't be suitable as rubber. I use this supplier (Cdn) but all the goodies come from USA. There is a whack of instructional stuff on youtube particularly SmoothOn & Aluminite. Maybe not for this particular application but something to keep in mind for similar custom items down the road. 
http://www.sculpturesupply.com/index.php


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## mayhugh1

e.picler said:


> Heloo Terry!
> Congratulations for you building, its is a stat of the art craftsman, amasing what you have done. Really impressing. I wish to have that skills.
> 
> Please could you explain how you have cut the gaskets? I`m guessing it was cut on CNC mill. Right?
> How you did that and what kind of tool/cutter have you used?
> 
> Thank you.
> 
> 
> Edi



Edi,
     I cut the gaskets on my Tormach CNC mill. I used a 60degree carbide vinyl knife that Tormach sells as an accessory. - Terry


----------



## mayhugh1

petertha said:


> Real nice Terry. Looks like you have the boots all done up & provisions for reproducible spares based on accessible commercial parts. Thought Id throw out some links just in case.
> 
> Paz shows his trials & tribulations with silicon. I'm not exactly sure why the issues but Ive heard can be fussy with any combination of incorrect release agent, mix ratios, curing conditions, shelf life...
> http://homepage2.nifty.com/modelicengine/k090102.htm
> 
> Ive not messed with silicones as much as equivalent durometer urethanes for composites work & they seem quite easy & forgiving for custom parts like this. But maybe there are some electric/insulation or gasoline/breakdown reasons why they wouldn't be suitable as rubber. I use this supplier (Cdn) but all the goodies come from USA. There is a whack of instructional stuff on youtube particularly SmoothOn & Aluminite. Maybe not for this particular application but something to keep in mind for similar custom items down the road.
> http://www.sculpturesupply.com/index.php



Peter,
    Here is another link that I studied before deciding to modify the vacuum fittings:
http://www.homemodelenginemachinist.com/showthread.php?t=14539&highlight=Ignition+boot+molding
I was considering moulding my own, but I wasn't sure anyone had come up with a solution for getting good black dielectric parts. - Terry


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## petertha

mayhugh1 said:


> Peter,
> Here is another link.... considering moulding my own, but I wasn't sure anyone had come up with a solution for getting good black dielectric parts.



Ah, that was the other link I was looking for, sorry. I notice in the SmoothOn line they make a color tint specifically for urethanes, but specify not for use for silicone
http://www.smooth-on.com/Urethane-Plastic-a/c5_1119_1213/index.html?catdepth=1
but looks like they do offer an equivalent for silicone
http://www.smooth-on.com/Silicone-Rubber-an/c2_1128_1190/index.html
Presuming urethanes could meet the electric insulation + gasoline/oil criteria, they offer a wide range of durometers, cure times, kit sizes, established releasing properties & bit less expensive. I'm not sure if these referenced builders chose silicone from the outset, completed the parts, mission accomplished & didn't look back. Or maybe they had some negative results with urethanes?
Notwithstanding selection, I'd be inclined to try lower viscosity (pourable) varieties, although the putty demonstrates more than one way to skin the cat. I base this on the detail level the sculpture crowd is molding with reverse curves, sometimes thin delicate features etc.
If you go explore down this path, I'd highly recommend a vac pot. There are inexpensive turn-key solutions. Made a huge difference to my results. Explanation + vendor example below. Sorry for the 'squishy-stuff' side tour, back to metal talk!
http://www.bestvaluevacs.com/index.html
http://youtu.be/GKddrZI4qAo


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## mayhugh1

petertha said:


> Ah, that was the other link I was looking for, sorry. I notice in the SmoothOn line they make a color tint specifically for urethanes, but specify not for use for silicone
> http://www.smooth-on.com/Urethane-Plastic-a/c5_1119_1213/index.html?catdepth=1
> but looks like they do offer an equivalent for silicone
> http://www.smooth-on.com/Silicone-Rubber-an/c2_1128_1190/index.html
> Presuming urethanes could meet the electric insulation + gasoline/oil criteria, they offer a wide range of durometers, cure times, kit sizes, established releasing properties & bit less expensive. I'm not sure if these referenced builders chose silicone from the outset, completed the parts, mission accomplished & didn't look back. Or maybe they had some negative results with urethanes?
> Notwithstanding selection, I'd be inclined to try lower viscosity (pourable) varieties, although the putty demonstrates more than one way to skin the cat. I base this on the detail level the sculpture crowd is molding with reverse curves, sometimes thin delicate features etc.
> If you go explore down this path, I'd highly recommend a vac pot. There are inexpensive turn-key solutions. Made a huge difference to my results. Explanation + vendor example below. Sorry for the 'squishy-stuff' side tour, back to metal talk!
> http://www.bestvaluevacs.com/index.html
> http://youtu.be/GKddrZI4qAo



Peter,
       The urethanes might be an even better choice. I don't have any experience with them, but I have run tests on silicone rubber and it is not compatible with gasoline. Some silicone fuel line samples I tested dissolved in gasoline within a day. It seems to be OK with alcohol and oil though. Fortunately plug wires don't come into extended direct contact with fuel. - Terry


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## mayhugh1

I took a couple weeks off from my build in order to drive up and visit my newborn grandson some 1200 miles away in Ohio. Our visit happened to overlap the Zanesville show where I had the honor of meeting and chatting with several builders and seeing a lot of really nice models. The models of Steve H. and George B. look even better close up and in person. A third highlight of our trip was the Wright Patterson AFB Museum in Dayton which I highly recommend to anyone who finds themselves in the area. There were actual full-size versions, some of them cross-sectioned, of nearly all the popular aero engine models that I've come across.
Getting back to this build, though... 
While I was searching the auto parts stores before our trip, I also came across a Dorman 47403 straight 1/8" x 7/32" vacuum fitting that fits nicely on the 1/4" diameter high voltage towers on my distributors. For the HV connections to the towers, the previously pressed-in bronze electrodes in the cap towers had been center drilled with a 1/4" deep .078" diameter hole. These holes provide a snug fit to some gold plated beryllium copper connector contacts that I found in one of my junk boxes. I don't know the manufacturer or part number, but similar contacts are commonly available from electronic parts distributors. 
These contacts are soldered on the distributor ends of the plug wires after trimming and forming their strain relief crimp barbs to into a 'tunnel' for the tinned wire. The soldered joint was then covered with two short pieces of shrink tubing to strengthen this weak area of the contact and to build up its diameter for a tight fit in the 1/8" end of the boot. The boot was shortened as shown in one of the photos before pushing it over the contact. The contact is left protruding about 1/32" beyond the 7/32" end of the boot before a piece of shrink tubing is shrunk down over the rear of the boot to seal and secure it to the plug wire. I included heat shrunk numbered labels on both ends of each wire because of the large number of wires in the completed harness.
I made up a set of wire looms to help organize the wires and to keep them out of the paths of the hot exhaust gasses which is where they tended to settle on their own. The looms also keep the wires away from the engine and effectively raise, even higher, the 20 kV breakdown voltage of the plug wire with respect to ground. Old school wax'd lacing cord was used to tidy up and complete the plug wiring harness.
It turned out to be very difficult to grip the plug boots and pull them off the plugs while in their recessed cavities in the heads, and so I made a tool to pry them off the plugs. While I was at it, I also made a puller to help remove the boots from the distributor cap.
The spark plug harness concludes the assembly of the engine. I would have added the carburetor, but even though I thought I had designed the rotisserie to clear the whole carb assembly, I ended up with an interference between it and the fuel bowl. So, the carb assembly can't be installed until the engine is moved to the display/running stand. I added a temporary cooling club to help when positioning the crankshaft, but it will be replaced later for running by a three blade prop. With the compression that showed up when the spark plugs were installed, the engine now requires a minimum of 150 inch-lbs to be 'slowly' turned over by hand. My 1/2" diameter crankshaft is starting to feel small. The keyless chucks on both of my 18V battery drills can't grip my starter adapter tightly enough to spin the engine now. I Loctited a sleeve with milled flats on my starter adapter to help the drill chucks get a grip, but I haven't yet tried it out. I can feel thumb suction on the 1/2" carb adapter port when the prop is manually rotated, and that seems like a good sign since the carb I'm planning to use will have only a 3/8" throat.
To reduce boredom during my wife's driving portion of our trip, I tallied up a total of 1057 shop-made parts and 1069 commercial fastener components that make up the engine as it currently sits. The T-18 engine file folder on my computer currently contains just over 900 CAD/CAM files created during the past fifteen months. The 'scale' of what I've done, though, didn't really hit home until I weighed the engine while on the rotisserie and found out it weighs 42 pounds.
Before attempting to start it, the next several weeks will be used to design and build the various support components including a firewall, throttle/advance linkages, fuel /oil tanks, fuel pump, tach, and electrical control panel. - Terry


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## Scott_M

Once again...WOW.

 Now I wished I had made it down to Zanesville.

 Scott


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## mayhugh1

My battery-powered drills now seem to be able to grip the flatted sleeve I made for my starter adapter; but neither of them, not even the 18V Ryobi, has enough torque to spin the engine over. My big Bosch electric drill with its key chuck has no problem with it, but it requires both hands to hold it.
Hopefully, the engine will start easily by rotating the prop 45 degrees or so by hand because there won't be any manual prop 'slapping' on this engine. But if it's a hard starter, I'm afraid I'll be tempted to pull out the big Bosch drill and that now raises a big concern about my starter adapter design. 
My crankshaft is 1/2" in diameter including the front portion that's keyed to the prop sleeve. However, the end of the crankshaft that's LH threaded for the spinner is only 3/8" diameter. According to the handbooks the maximum recommended bolt torque for this thread is on the order of 17 ft-lbs. I measured a thread yield of 30 ft-lbs on my own test rod which did not include the crankshaft's 1/8" diameter through-hole for crankcase ventilation. Approximately 14 ft-lbs torque is currently required to slowly rotate the crankshaft, but at cranking speeds the torque is likely higher because the compression pressure has less time to leak away. Therefore, my starter adapter which grips the hex on the rear of the spinner is dangerously close to twisting off the threaded portion of the crankshaft. The adapter needs to be re-designed to act upon the prop and not the spinner. 
I should have anticipated this when I decided to add the additional nine cylinders. A single cylinder four stroke engine spends roughly 180 degrees of its 720 degree cycle in compression. With 18 cylinders, I have a cylinder firing every 40 degrees which means that at any given time I have 4-5 cylinders in some state of compression. All those individual cylinder compression pressures instantaneously add up to produce the resistance felt when rotating the prop. As the engine passes through its firing order this continual summation produces a seemingly continuous resistance instead of the familiar and distinct compression "bumps" felt on engines with fewer cylinders. So, it looks like a new starter adapter has to be added to the list of things left to do. The really frustrating part of all this is that there was absolutely no reason to have reduced the diameter of the threaded portion of the crankshaft. Fortunately though, the problem was caught before some really serious damage occurred. - Terry


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## petertha

Hope your drill solution works so it doesn't require 'the next $tep'. Maybe there's a surplus type 12v high ratio GD type solution? I'm not familiar with torque delivery vs rpm curve on typical drills, but suspect the max rating is at full rpm & it cant get there trying to overcome initial resistance. 

 Only speaking from maybe non-comparable RC experience, but I see these pulley adaptions in the field. The (+/- same wattage) direct drive motors just stall & that's with the dangerous pre-windup-and-spinner-bump Keystone Cops routine. But the reducers turn them over. Seems the crank doesn't have rotate particularly fast before ignition kicks in, getting 'over the hump' is the challenge.


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## gbritnell

Hi Terry,
Looking at the end of your crankshaft I see the .500 dia. area with a key slot cut into it. The front portion as you stated is reduced to .375 dia. (with threads).
When the prop is mounted to the shaft is there a shoulder in the prop hub which sits against the step on the crankshaft so that the hub can be tightened to the shaft without putting load against the front engine bearing? If this is the case here's and idea for you. On my little radial I made a hardened threaded sleeve which has a through hole (radial) for tightening. The O.D. of the sleeve is made so that my starter with a one-way bearing rides on the sleeve. In your case the sleeve could have a flange that would press against the prop hub thereby imparting some of the torque against the hub and not all taken up by the threaded area. I hope this makes sense. Here is a video I made of my engine which shows what I'm talking about better than explaining it. 
gbritnell
http://youtu.be/V8SDqPE4kZA?list=UUPvNzXJm9KOlaQwjAmYW9Xw


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## mayhugh1

George,
Thanks for your reply. You're right about your understanding of how my prop hub mounts, but I'm not 100% sure I understand your suggestion of how to take the torque starting load off the small diameter threaded portion of the crankshaft. But let me define a few parts first to make sure we're both talking about the same things. I have three parts that go on to the end of the crankshaft. They are an inner prop hub that is keyed to the crank and an outer prop hub that bears against the offset on the crankshaft. The prop is sandwiched between these hubs and secured with six 10-32 bolts. The shoulder on the crank against which the outer hub bears insures there is no actual load on the front bearing. The third part is a spinner that threads onto the threaded portion of the crankshaft and bears against the outer prop hub. There are some flats on the rear of this spinner that my starter engages when it applies the starting torque to the weakest part of the crank.
So to take the load off the threaded section of the crank during starting I would need to make a new outer hub that included its own larger diameter threaded section onto which the spinner (re-tapped for the new larger diameter thread) would thread. Is this your suggestion or am I misunderstanding? - Terry


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## mayhugh1

While thinking more about the best way to solve my starting problem, I decided to continue forward progress by working on the fuel pump since it's relatively straight forward and pretty much identical to the one I made for my H-9. I plan to use a recirculating fuel system that pumps fuel into the carburetor bowl from the fuel tank. A constant fuel level is maintained with a standpipe in the bowl by continually returning excess fuel back to the fuel tank through a return line.
Using this system has three important advantages on a large size model engine. First, it allows complete freedom in the placement of a large fuel tank. Second, it presents a constant fuel level to the carburetor for a consistent fuel draw. And third, it provides a safe and convenient way for removing left-over fuel from the tank when preparing the engine for storage. The disadvantage for a small model, though, is that it is a relatively large component that many will probably want to hide or disguise.
The key components come from a thirteen dollar RC fuel tank filler commonly available in hobby stores. I chose this particular unit after examining several others because it will run on less than 6Vdc, and my own personal experience shows the pump, itself, is compatible with gasoline. I removed the key internals, consisting of a dc motor and mechanically linked pump, in order to repackage them. I machined an aluminum housing with divider walls between the pump and motor while maintaining their mechanical alignment. The housing is well vented and contains a drain, but one should be aware there is still some hazard due to internal sparking at the motor's brushes. Even when powering the unit from a 6V battery, it's necessary to add a 50 ohm series rheostat (to be physically located elsewhere) and a .022" fuel line restrictor to maintain fine control over the flow to the carb bowl. - Terry


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## petertha

I thought they made a distinction between gasoline & methanol versions, but you mentioned it worked for you. Just mentioning FWIW in case it was packaging fine print.

http://www3.towerhobbies.com/cgi-bin/WTI0001P?I=LXVZ40&P=8
_Current draw: .8A loaded, .2A with no fuel passing through Pump can move 1oz of fuel every 4 seconds on 12V supply Pump is for GLOW FUEL ONLY (NO gasoline, diesel or smoke oil)_


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## mayhugh1

Peter,
      I'm familiar with their spec, but I suspect they don't want their pump used with gasoline with its high volatility near that dc motor for liability reasons. I tested the materials compatibility of their pump with gasoline pretty thoroughly and saw no issue. All the filler pumps I came across that were spec'd for gasoline were manual crank varieties. I'm definitely not recommending their product for use with gasoline to others as the manufacturer understands their own product much better than I. - Terry


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## mayhugh1

The fuel tank was the next item on my list. For my H-9, I used a 10 oz polyethylene tank purchased from a local hobby shop. I appreciated the ability to be able to easily monitor the fuel level through the translucent tank, but I was never entirely happy with its appearance. I purchased an identical tank for this engine several months ago when I happened to be in the same shop. A full tank of fuel lasts only 4 minutes or so in my nine cylinder engine, and with this engine's 2X displacement the same amount fuel will last only about half as long. So, I don't want a smaller tank.
I machined a pair of mounting brackets to grip and secure the tank to the back of the engine's firewall similar to what I did for my H-9. After staring at the completed assembly for awhile, I decided to add a pair of metal end caps to try to improve the tank's appearance. I turned the end caps in aluminum and then modified the mounting brackets with a shallow recess around the tank openings so that when the end caps are inserted they are held in place with the bracket pinch bolts. This mounting arrangement has the additional advantage of removing the bracket clamping forces from the fragile plastic tank which now floats safely within the end caps. The appearance was a bit improved, and I still get to have my view of the fuel level in the translucent portion of the tank between the brackets. - Terry


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## Scott_M

Hi Terry
 The Fuel tank looks just as classy as the rest ! Nice job.

 I saw in your band saw photo that you used a filler at the back of the vise jaw for the short piece you were cutting. Here is a quick and easy mod that will save you trying to find the same thickness filler. Just drill and tap a 3/8 hole in the back of the vise jaw and put a piece of all thread in it. It works great and saves a bunch of time.

 Scott


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## mayhugh1

Scott,
Thanks for the tip. It's on my to-do list for this weekend. - Terry


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## dr_kingston

Hi Terry,
I am very inpressed with your build. What did you use to bond aluminium stock to particle board etc.
Regards Dale


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## mayhugh1

Dale,
It's a quick set 2-part epoxy distributed through Lowe's home building centers called Devcon Super Gel. When the machining is finished it releases cleanly when heated to 190F. - Terry


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## mayhugh1

After enough procrastination, I decided to tackle the starter adapter problem. Basically, I could see two options. The first option is to leave the existing design unchanged and create a new starter adapter that acts upon the prop instead of the spinner hex. Currently the prop is sandwiched between the front and rear prop hubs using six bolts. The rear hub is keyed to the stronger 1/2" diameter portion of the crankshaft. The prop assembly is held against a machined offset on the crankshaft by the spinner which is threaded on the weaker 3/8" portion of the crankshaft. The rear of the spinner has a machined hex that engages the starter adapter, but when it does so it places excessive stress on the small diameter portion of the crankshaft due to the high torque required to turn the engine over. 
A second option, which is my interpretation of George's suggestion, is to re-design the front hub with an integral large diameter threaded boss for the spinner. Although a 3/8" nut must be threaded onto the end of the crankshaft to secure the prop assembly against the machined offset, the weaker portion of the crankshaft will no longer see the starting torque. In addition, since the prop assembly is keyed to the crank, there'll be no net force except for the inertia of the nut trying to unthread it, and so its torque requirements are minimal.
I decided to go with the second option since it's what I should have done in the first place, and I don't want another starter adapter. The only potential issue with this option is the difficulty in keeping the spinner running true with respect to the crankshaft after it is re-threaded. I originally finish-turned the spinner while it was threaded onto the front section of the crankshaft to true it, but now that the engine is assembled, that's no longer an option. Wobbly flywheels and spinners drive me nuts.
My first step was to re-thread the spinner. I used a left-hand 3/4"x20 thread, since I happened to have a tap for that particular thread. Its major diameter must also be large enough to clear the 3/8" nut that will be threaded on the end of the crankshaft. I indicated the rear surface of the spinner's hex in my lathe before boring out the existing 3/8x24 thread, and the tailstock was used to support a tap holder in an attempt to keep the axis of the new thread coincident with the axis of the original thread. In retrospect, I probably should have turned the threads instead of tapping them.
Next, I turned a new stainless steel front hub with a 5/8" long .75" diameter boss. This boss was threaded for a close fit to the spinner. I cut the left hand thread using an inverted single point tool and a reverse-running spindle while continually checking the fit with the spinner. I got an extremely close fit when I was done, but the spinner ended up with some annoying run-out after all. I wrote a program to re-skim the spinner while it was threaded on the front hub. The spindle motor (or its controller) in my CNC lathe began acting up during this last step and thankfully allowed me to finish before it finally gave up the ghost. - Terry


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## gbritnell

Hi Terry,
I'm sorry I didn't get back to you but it seems you have solved the problem most exquisitely. I like you hate having runout on rotational parts. No matter how accurate the remaining parts are it just takes away from the whole picture. 
gbritnell


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## petertha

Hi Terry. Sorry for 'old post' question, but Im working on a similar design issue & remembered your pictures. Maybe you have a section view handy or can confirm how intake tube is retained in the housing. My hunch: slide intake tube through metal ferrule & through an O-ring, insert tubing end into case, its loose enough to allow positioning of flange end, bolt to cylinder head, then screw down ferrule, squishes O-ring, contact area seats/seals against tube? 
Your Post 77
http://www.homemodelenginemachinist.com/showthread.php?t=21601&page=8
_.. compression nuts that are used to support the intake pipes in the fuel plenum in the rear crankcase. Initially, it wasn't clear to me from the Chaos photos how these were used. They didn't seem to be pipe threads nor did they use ferrules or flares. I eventually decided they must compress a rubber o-ring through which the intake pipes pass. So, I threaded the nine bosses in my rear crankcase section with simple 1/2" fine threads..._


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## mayhugh1

Peter,
It's pretty much what you said if you're referring to the threaded nuts with the hole through their center as ferrules. There is a rubber o-ring sitting in a recess at the bottom of the threaded bore. The fuel tube goes through this o-ring, and the nut is screwed down on top of it. The nut compresses the o-ring around the tube and against the recess to create the seal. As you said, the other end of the tube is mechanically stabilized by its bolted flange, and this end 'floats' in the compressed o-ring. - Terry


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## mayhugh1

For the past five months I've been working on a background tachometer project for this engine. It's been one of the most frustrating projects I've been involved with because it has required so much time dealing with questionable documentation and flaky vendors.
The project began when I purchased a really cool miniature (1-1/4" square) aircraft tach in 'unknown condition' through eBay from someone in Bulgaria. I was hoping to make it the center piece of the control console I'm now designing for this engine. 'Unknown condition' on eBay usually means 'run away fast', but the meter's face looked OK in the photo so I decided to go for it. It wasn't very expensive, and I actually ended up paying less for it than the shipping charges to get it here. 
I've modified d'Arsonval meters in the past to alter their functionality for special applications, and so I only needed a working movement. The attraction of this particular one was that it was the right size, and I wasn't going to have to make a new face for it. When I received it there was no electronics - just a meter with four terminals in a four inch long housing where the original electronics had probably been located. I shortened the housing to the actual depth of the meter, which was about one inch, since I planned to add my own circuitry off to the sides instead of to its rear.
Some ohmmeter checks showed the meter probably contained a pair of coils which was puzzling enough, but I also found the meter was relatively unresponsive to dc current. After some web research I learned the meter was an air core movement, something totally new to me, and required complex quadrature signals instead of dc current to drive it. My guess is that my 'unknown condition' meter had been cannibalized for its more valuable electronics. After some more investigation I discovered there have been special purpose ICs manufactured to generate the needed signals to drive such meters since they were commonly found on automotive dashboards for many years. The current move seems to be toward stepper motor based-movements. A review of several on-line data sheets and an exhaustive Web search revealed the DIP version of the one that I probably needed (CS8190EN16) had been long discontinued and no longer available from common US distributors. However, a guy in Hong Kong claimed to have ten of them for sale on eBay. I ordered five parts at a good price from him hoping to get at least one that worked.
With help from the data sheet/application note I soon developed a schematic. The IC requires its own 12 Vdc source, and since I plan to run my engine from a single 6V lead acid battery I had to include a small dc/dc converter module in my design. Actually getting one of these converters in my hands grew into its own months' long saga created by several vendors who continually lied about having access to them. After finally receiving one, though, I breadboard it separately from the meter circuitry so I would have more flexibility later on with the final packaging. 
I made up a Hall-triggered test board to drive the meter circuitry as well as a nine magnet trigger disk that I could spin with a drill or mill spindle to test and calibrate the tach. This test circuitry duplicated the trigger circuitry I would be interfacing to in my already completed ignition modules so I wouldn't have to involve and possibly damage them in my early breadboarding attempts.
It was a good thing I had included a socket on the breadboard for the driver IC because after receiving them from Hong Kong I found that not a single one worked. Each presented different symptoms telling me I had probably purchased poorly QC'd counterfeit parts or else floor sweepings from someone who had worked at the original fab plant.
The discontinued part was available from several other Chinese direct suppliers, including some others also advertising on eBay. I decided to try once more with a different vendor. A month later when five more parts from the second vendor showed up, I found these ones almost worked. When powered up, the meter zero'd as it was supposed to, but all five of the IC's were totally unresponsive to any trigger input. I had troubleshooting access to a portion of the internals of the ICs through two key pins, and it seemed that all five parts suffered from the same internal defect. An internal block of circuitry known as a current mirror that connects the input signal conditioner to the F/V converter did not seem to be functional. This was really suspicious, and the real frustrating part was that the section of the data sheet that explained the operation of this portion of the circuitry and its effect on the selection of several external components that I had to add contained so many errors and ambiguous statements that I didn't trust it. I just couldn't be certain whether the problem with these ICs lay with me, the data sheet, or all the parts I had purchased.
I considered trying to breadboard the surface mount part because it is still in current production and available from reputable distributors, but I felt that with all the uncertainty over the past several months I needed to stick with a socketed part. After many false leads and lots of phone calls I eventually located a small Canadian automotive parts supplier who had been stuck with a batch of the DIP parts after dashboard designers quit using them in new designs. After being assured they were truly in stock in North America, I ordered another five parts and paid a healthy small quantity premium to get them.
While waiting on the third batch of IC's, I machined a housing for the meter; and I made a new breadboard designed to fit around the meter inside the housing. I also developed a new schematic using the functional meter driver portion of the last batch of ICs along with my own front-end circuitry just in case the third batch of parts didn't work either.
Since they had no experience in dealing with small orders to individuals, this last vendor made a paperwork error that triggered a customs and security snafu that ended up delaying delivery of the parts for nearly a month. Despite what I had been promised, the parcel had actually been shipped from India instead of Canada.
When I finally received them, and with very low expectations, I tested each one in my original breadboard. To my amazement and after nearly five months of frustration, I was finally rewarded with a rational movement of the tach's needle in response to my test generator. While wiping tears away I packaged my new circuit board and meter movement inside the enclosure I had made. I hauled the tach, battery, and test driver circuitry over to my mill spindle where I was finally able to run and calibrate the tach. As a final step I re-tested the tach with it connected to one of my ignition modules while actually firing a spark gap. I'm pretty sure I've never experienced a better example of Murphy's Law than I have with this 'little' side project. - Terry


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## ShopShoe

mayhugh1,

I am simply amazed. After looking everyday for more of your excellent design and machining, I find you have furnished an elegant electronic engineering project with more incredible documentation. In a former life I paid bigtime vendors bigtime bucks and they could not draw a simple schematic like you have just done. Nor could they actually explain how their assembled equipment actually worked without repeating propaganda from their marketing department. As far as Murphy's Law and ebay and vendors: been there and done that.

Thank you for going to the extra effort of writing incredible descriptions and fully documenting everything you do. This is the reason I keep looking for your posts. I'll probably never build a big radial, but I can try to work toward a better, complete, and understandable job when documenting some of the things I do.

Thanks again,

--ShopShoe


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## kuhncw

ShopShoe said it very well.

I'll just say, thanks again for all the time and effort you put into your posts.

Regards,

Chuck


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## mayhugh1

Hi,
Is anyone else having difficulty seeing the photos in my last several posts? Everything was OK yesterday, but today I can't see my own photos although I can see the photos of others in their threads. I've tried three computers as well as logging out and then back in but still no joy. - Terry


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## ozzie46

I can't see them today either. I saw them yesterday. 


  Ron


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## Cogsy

I could see them yesterday but now they are just a list of attachments.


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## Swifty

Still just a list of attachments today.

Paul.


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## mayhugh1

I've sent a few queries to the web care taker about the strangeness that has started going on with this thread, and I'll likely hold up any further posts until they have a chance to figure out what's going on. I expect it's likely related to the size that it has grown into, and so I don't want to take a chance on making things even worse by adding to it and possibly losing work. - Terry


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## Scott_M

I have also noticed that I cannot scroll in this post anymore. My scroll wheel works fine in other posts.

 I think you broke it Terry  

 Scott


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## Cogsy

mayhugh1 said:


> I expect it's likely related to the size that it has grown into, and so I don't want to take a chance on making things even worse by adding to it and possibly losing work.


 
I just came across another thread that's having the same issue - http://www.homemodelenginemachinist.com/showthread.php?t=23737 -but it's a very short thread, so I don't think size is the issue here. Seems to be a forum issue. I know this other thread was displaying photos properly 1-3 days ago but isn't now.


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## Charles Lamont

All works for me now


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## mayhugh1

It looks like someone may have fixed whatever was going on with the photos in this thread, and so I'll make a short post to test out their fix.
Something that I forgot to mention in my post about the tachometer is that the little dc/dc converter I'm using to generate the 12V supply requires a minimum current draw to insure that the converter starts up and regulates properly. This is a common requirement of these converters, and unfortunately my tach circuitry doesn't quite meet the minimum requirement even though everything seems to be currently working OK. Rather than just waste some of the output current in a resistor, I decided to use it to backlight a fuel level window in my fuel tank. 
After adding the metal end caps to the polyethylene tank, I liked the improved look but felt it would look even better if the entire tank was enclosed. I turned another cylindrical aluminum cover for the center section and then slotted it to make a window so I can still see the fuel level. I then installed two series connected high brightness white LEDs in the cover to illuminate the interior of the tank above the window. 
Peter's sharp eye is probably going to notice that the center section was made much thicker than the end caps, and I expect he'll ask why. The reason is that the polyethylene tank has a 'key' molded into its outer perimeter, and I used the extra wall thickness to cover it up and keep the finished tank cylindrical. Terry


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## mayhugh1

While the soldering iron was still hot, I decided to finish up the electrical portion of this build by constructing the control panel. But first, my 9x20 CNC lathe whose spindle died while I was turning my new prop hub was begging for attention. I had been putting off working on the lathe because the packaging of the Mach 3 interface electronics in this machine was designed with so little regard for maintenance that any attempt to troubleshoot it quickly becomes an exercise in frustration. I ran head into its packaging limitations immediately after purchasing the lathe several years ago when it arrived with an intermittent spindle controller. The vendor insisted it was a Mach software issue and pointed me to ArtSoft. I spent over a week tracing out and troubleshooting the circuitry on the lathe's third party break-out board. The problem turned out to be a flaky relay driver, but what really caught my attention was a pair of miniature PCB relays that I mistakenly thought were operating beyond their limits while controlling the 2kW 220V spindle motor. Every time the power was cycled to that spindle I thought about those little relays. I purchased several spares years ago while they were still available and waited for the originals on the control board to fail. After accumulating probably thousands of spindle cycles during these last two radial engine builds, I guessed the inevitable had finally happened. It was a miserable day getting to and replacing both relays, and then further investigation showed the relays actually had been operating within their specs. The lathe is running again, and so my fingers are crossed hoping one of those relays actually was the culprit.
Getting back to the control panel, though, it's purpose is to give me individual power control over the fuel pump, ignition modules, and the 12V converter that supplies power to the tach and, now, the fuel tank. I like having separate power control of the various components because having it can be an aid to troubleshooting. It's also safer to have the ignition switched off when the fuel pump is on and the engine is being manually primed or when pumping left-over fuel out of the tank. I admit I also like having the switches to play with.
While I was searching eBay for candidate meters for my tachometer several months ago I ran across a miniature 6 volt panel meter for sale by yet another overseas vendor. Fortunately, that purchase went without any drama, and I included it in the panel design. I also packaged the dc/dc converter for the tach inside panel's enclosure.
Although the control panel is basically just a handful of toggle switches, I couldn't resist having some fun with it and over-doing the enclosure. When I was finished with the design it pretty much had to be CNC milled from a block of aluminum. All these components I'm making will hopefully come together in a coherent looking assembly on the back engine's firewall. Next up will be the oil tank. - Terry


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## gbritnell

Although the whole panel is superb I really like the little touch you did with the hoods over the  meters. Classy!
gbritnell


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## petertha

mayhugh1 said:


> ..project began when I purchased a really cool miniature (1-1/4" square) aircraft tach in 'unknown condition' through eBay from someone


 Your control panel is very cool. I never knew miniaturized instruments like this even existed. Just curious from your trials & tribulations, what industry or hobby pursuit do they serve? ie. gutted from another application or kind of ground level developed with modern electronics?


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## mayhugh1

Peter,
I assume the tach was an actual cockpit instrument from a plane. There was only one being offered for sale by the seller, but I seem to remember he was offering some other aircraft gauges as well. The 6 volt panel meter, on the other hand, was being offered by its seller in quantites up to ten pieces. These may have been manufacturer's surplus from some piece of cheap equipment - maybe a battery charger. The tach was well made, but the 6 volt meter was very cheaply made. In fact, the clear front cover was secured to the main body of the movement with a piece of tape. One of the reasons I machined such an elaborate pocket for it in the rear of the panel was to provide an alternate way of holding it together. - Terry


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## petertha

mayhugh1 said:


> I assume the tach was an actual cockpit instrument from a plane.



 Ah, sorry I misunderstood. I thought you meant miniaturized units, maybe like what car guys are adapting for trendy functionality or whatever. Classic instrumentation seems to be all the rage, even wristwatches.
http://www.egauges.com/Gauges-Senders-and-Accessories-s/13.htm


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## mayhugh1

I made a functional rectangular oil tank for my H-9, but I was never satisfied with its 'blocky' appearance. For this engine, I decided on a more conventional looking cylindrical tank. My initial plan was to construct it entirely from aluminum and thread/Loctite the various pieces together, but I changed to brass at the last minute after finding a short length of 2-1/2" brass tube among my scrap.
I squared up the ends of the tube and then turned a pair of brass end caps for it. A shoulder was turned on each end cap with a .002" interference fit to the main tube so they could pressed/Loctited into the ends into the main tube. 
A common way of mounting a cylindrical tank to a flat surface is with metal bands, but for a different appearance I decided to solder a pair of mounting feet to the rear of the tank. These feet will serve as brackets to secure the tank to the engine firewall. In order to limit heat-induced distortion of the thin wall tube created by the high heat of silver-soldering, a pair of stainless end caps were temporarily pressed into both ends of the tube. I didn't use my finished end caps for this since I needed center holes for a puller to remove them after soldering. The mounting feet were also bolted to a temporary steel plate to maintain the whole assembly in alignment during soldering. 
Midway through the bracket soldering I had second thoughts about using silver solder instead of soft solder. I was surprised at the difficulty I had in getting sufficient heat to all the mass involved in the joints, and I eventually had to switch from the map gas torch I started with to a small acetylene rosebud. I used thin solder ribbon between the brackets and tank in order to keep the solder lines neat, and this made it difficult to tell when the joint had been sufficiently heated. It seems that every solder job I attempt comes with a new learning experience.
Two threaded bungs were turned and attached to the outer perimeter of the main tube with high temperature soft solder. One was soldered to the top of the tank for a filler cap, and the other to the bottom of the tank for a drain plug. The filler cap was drilled with a .070" diameter hole since the oil tank also acts as an oil separator in the crankcase ventilation system, and the filler cap is the ventilator. The whole assembly was dipped in a pickling bath of 10% sulphuric acid for about 10 minutes to remove the flux residue before neutralizing the assembly in a baking soda solution.
The end caps were drilled and tapped for an oil control valve on the output side of the tank as well as a sight gauge and flare fitting for the engine oil return line on the tank's input side. Drilling these relatively large NPT holes in the thick brass end caps proved to be the biggest challenge of the tank's construction. The finish-machined circular pieces were difficult to hold down on the drill press table; and when the material grabbed the drill as it exited the backside, a twisting torque was generated that overcame my best attempts at keeping the caps clamped down. I finally had to limit the topside drilling depth until the tip of the drill barely pierced the backside, and then I used a manual tapered reamer to finish the hole from the rear.
The sight gauge was simply constructed from an 1/8" brass street elbow, a short length of acrylic tubing, and an 1/8" brass pipe cap. I used Goop plumbing adhesive to seal the tube to both the elbow and end cap. The adhesive and the acrylic are compatible with engine oil, but I'm pretty sure they would not be suitable for use with fuel.
It's no secret that oil flow to these dry sump radials needs to be carefully controlled. A drip feeder, similar to those used on medical IV lines is almost a requirement on the output of the oil tank. I began by looking through my collection of brass fittings, and without a plan I started modifying them and turning the additional parts I needed to create an oil control valve. I don't like working this way as it's not satisfying and seldom turns out well, but I just couldn't get myself moving in the direction to create a proper design. It might have been the holidays, but when I looked through my notes on my H-9 build, I remembered I had likely done the same thing since I hadn't made a single drawing related to the oil control on that engine. Maybe I just don't like thinking about oil control valves. I had incorporated a cool looking sight window into the H-9 drip feeder, but when using transparent oil lines it adds little value in exchange for a lot of complication. So, I left it out of this feeder. I filled the tank with oil and allowed it to sit for a few days to check for leaks.
Unfortunately, the lathe work on the tank also uncovered the depressing fact that my earlier replacement of the spindle control relays on the Mach breakout board hadn't solved my intermittent spindle problem after all. Since I can't easily monitor signals on the breakout board because of its convoluted packaging, I'm going to take out some time to create a bus monitor for insertion in the DB-9 cable between the spindle motor and the Mach interface to see what signals may be getting lost when the spindle fails to start up. 
The last component required for the firewall is the throttle control. But, I think it would be wise to first create the firewall and start laying out the components I've already made before starting this last one. - Terry


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## ShopShoe

Another simply beautiful and instructive piece of on-the-fly engineering.

Thanks for posting the entire process so we can all be inspired.

Sorry about your controller problem. I know you'll get it solved.

--ShopShoe


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## rlo1

Never considered using the lathe chuck to hold parts in the band saw.  Great posts!  Thank you for taking the time to make them.


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## mayhugh1

I took some time off from my radial engine project to build a breakout box for monitoring the control signals in the DB-9 cable between the spindle motor and the Mach breakout board in my CNC lathe. Since my spindle start-up problem is intermittent and recently infrequent, I thought it best to build something robust enough to be left in place indefinitely. My biggest concern with adding something like this is dealing with potential grounding issues. The motor controller circuit 'ground' is at a different potential than the grounds of either the breakout board or my computer's parallel port. A failure inside this new box that mixes these returns could create some spectacular and expensive damage. Another ground related issue is electrical noise. I spent a lot of time carefully routing and shielding the numerous cables in my shop to get my mill and lathe to run error-free from a single computer with much longer than recommended USB and DB-25 control cables all within a pretty nasty electrical noise environment. At that time, when I had access to the proper test equipment, I discovered the spindle VFD noise was one of the culprits affecting the reliability of my set-up. So, it's possible my break-out box could introduce a new problem with similar symptoms to the one I'm trying to solve. In addition, since the lathe work on this engine is pretty much completed, it could take a while to realize any change I may have made to the noise environment or to capture the spindle acting up.
But, getting back to my radial build, progress has slipped a bit due to holiday stuff. I started a SolidWorks layout of the engine's firewall since I already had or could easily complete models for the various components that will be mounted on it. With CAD I'm able to shuffle virtual blocks around for a workable layout before cutting or drilling any holes in some expensive pieces of metal.
My highest priority for the layout is the placement of the ignition modules. They need to be located so their susceptible trigger cables are routed directly to their distributors and away from the high voltage tower wiring. The tach needs to be located close to the particular ignition module that will drive it since the driving signal is also low-level and noise susceptible. 
A second priority involves the height of the oil tank. The tank's drip feed outlet wants to be at or about the same level as the engine's oil input tube for best operation. The tank's return fitting, on the other hand, must be higher than the engine's oil return line. 
Due to its design, the placement of the components in the recirculating fuel system is less critical. The only requirement is that the fuel tank must be below the carb bowl in order for the gravity return line to work as needed.
Almost immediately, though, I realized I should have been working on the layout simultaneously with the design of its components. Although I had designed each of them with a minimum volume for a reasonable degree of maintainability, it quickly became apparent that I should have been more concerned with packaging envelopes and less concerned with packaging volumes. For example, my arbitrarily selected locations for the oil tank drain plug and the fuel tank inlet/outlet tubes significantly affected my choices for placement of the electrical components that don't like getting wet. As a result, because issues like this weren't were considered early enough, I had to settle for a larger firewall than I really wanted with excessive space between its components.
In order to reduce the width of the firewall size somewhat I ended up designing a new fuel tube assembly for the fuel tank. The issue was not only an interference problem with the electrical control panel but also my initial selection of the fuel tank return tube diameter. With the small volume carb bowl I'm using, it's important that the return line be as free-flowing as possible in order for the stand pipe return inside the bowl to regulate the fuel level over a reasonably wide range of fuel pump pressures. I used a 3/16" (o.d.) return line in my H-9, but I had reduced it to 1/8" in the T-18 tank for compatibility with a nice looking anodized cap that came with the polyethylene tank that I purchased. When I tested the operation of the fuel loop mocked up with the firewall's trial placement of the fuel components, I found the back pressure in the 1/8" return tube was too high. The fuel pump voltage, even with a .022" restrictor in the high pressure side had to be carefully adjusted to prevent pressurizing the bowl and squirting fuel out its vent. The solution was to increase the return tube to 3/16", but the minimum 90 degree bend radius for this diameter tube exiting the fuel tank created placement issues with the control panel. So, I made a new fuel tank tube inlet with machined 90 degree exits. The six tubes making up the new assembly were soft soldered into a brass cap using high temperature solder for the inner three, and low temperature solder for the outer three. The long internal tube with the bend is the tank's air vent while the tube with the flexible 'clunk' is the fuel pickup. The large diameter tube is, of course, the new return. The cap is sealed to the tank by a sandwiched rubber stopper drawn up between the cap and a metal backing disk using a long SHCS. 
Eventually, after arriving at a compromise placement that was more functional than esthetic, I was able to finalize the dimensions of the two large aluminum plates that will make up the engine's display/running platform. My scrap pile had final approval over the design with the bottom plate ending up 1/2" thick. Both plates turned out to be larger than the working envelope of my mill, and so a lot of time was spent re-indexing both workpieces so I could machine the features I wanted. I was careful to not waste any of the 1/2" plate material by recycling the drops from the machined baseplate contour into support brackets for the firewall. 
With the engine weighing over 40 pounds, I'm estimating a total assembly weight at around 65 pounds. Therefore, in addition to making it a robust platform, I also added a provision for carrying it without damaging months of work.
I assembled the basic platform which pretty much locked in my current component placement before the throttle and advance linkages were designed. Now that I have a concrete platform to work with, I'll next focus on them. Hopefully I haven't painted myself into some corner, and I can have some fun with their design even though my CAD tool doesn't handle rod ends. - Terry


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## mayhugh1

I wasn't yet ready to transfer the heavy engine from its assembly stand to the running/display stand, and so I made a simple wood bracket for the display stand on which to temporarily mount the carb assembly. This bracket positions the carb assembly in the same position where it will sit when the engine is finally installed, and it will allow me to pre-test the operation of the finished carb linkage without having to deal with the engine. 
At least one rod-end will be required in the final carb linkage since the plane of rotation of the throttle arm in many RC carbs changes as the throttle is rotated. My CAD tool doesn't handle rod ends, and so I played around with approximate virtual linkages that operate in a single plane.
My original plan included a throttle control that fits in the space available under the oil tank on the rear of the firewall and connects to the carb through complicated vertical and horizontal linkages connected with bell-cranks. The complexity got the best of me, though, and so I settled for a single linkage running straight between the throttle control and carb. It isn't at all what I originally had in mind, but it's functional and reliable.
The base for the throttle control was milled from a block of Delrin, and the control lever was machined from aluminum plate stock. The lever's rotational resistance is adjusted by pinching it within the slotted Delrin base with a captured locknut on its shaft. Simple spherical rod ends purchased from a local hobby store were threaded onto each end of a brass rod to create an adjustable length link capable of handling the carb's non-planar throttle arm. Since I had to cut an opening through the firewall for the linkage, I made it wide enough to handle two other carbs I happen to have on hand just in case my Perry carb, which is Plan A, doesn't work out.
I also machined a pair of brass feed-thrus for routing the fuel loop through the firewall. The return feed-thru has an i.d. of .150" while the one between the pump and the carb contains a .025" diameter restrictor to reduce the flow rate to the tiny fuel bowl. While working on the fuel loop routing I realized I had mixed up the positions of the inlet and outlet tubes on my custom fuel tank cap. Rather than make a new one I added a flexible extension to the return tube inside the tank and secured it to the tank's vent tube so it stands high inside the tank. This may or may not help reduce the back pressure in the return line seen by the stand pipe, but it was easy to do. 
I also filed-to-fit a pita bracket to support a tank filler valve that needed be shoe-horned into a crowded area on the firewall. The filler valve is hobby shop RC component.
My final Ebay pig-in-the-poke purchase for this engine arrived just in time to claim a place on the firewall. It's a tiny elapsed time meter that I figured had been lost in the holiday mail. It's capable of running off any dc source between 4.5 and 35 volts, and so I plan to power it with the switched fuel pump voltage in order to keep track of the engine's runtime. It's not resettable, but it will record up to 10,000 hours, and so I probably won't have to worry about rollover.
I've put a few hours on my lathe since I added the the spindle monitor, but I haven't yet seen the spindle act up again. There's an outside chance the problem could be related to the Mach software. After thinking about it for a while, I'm pretty sure that every time I saw the intermittent spindle starting problem it was during the same Mach session where I had previously run the spindle in reverse. If I can accumulate a dozen more running hours with no problems, I'll try adding in some reverse spindle cycles. - Terry


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## mayhugh1

I machined a tiny enclosure for the elapsed time meter and then wired it to connect to the wiring harness through the same blade terminals I've been using on the other firewall components. I also finalized the placement of the ignition modules and machined the firewall plate to clear the low and high voltage towers protruding from their rears. After temporarily bolting all the finished components onto the plate, I sketched out a wiring harness so I can locate and drill holes for the harness cable clamps. 
A few weeks ago when I cut the handhold into the top of the firewall, I made a mistake in the CAM program that was intended to round over the edge of the opening. I inadvertently specified the depth of the finishing operation in the quarter inch thick plate to be 2.0 inches instead of 0.2 inch while my 1/4" diameter finishing tool was only 1-1/2 inches long. Oblivious to what I had done, I started up the machine, watched it run for a few minutes, and then left the shop to rake up leaves in our front yard. When I returned, the operation had completed, but the shop was filled with an odor of burned metal. What I saw were the results of my first really serious CNC crash. Fortunately, I had a two inch thick sacrificial plate under the workpiece that saved my table; but after burying and eventually snapping off the carbide cutter, the mill also tried to bury the tool holder into the workpiece. The friction created between the end of the tool holder and the aluminum workpiece literally melted a ring of metal around the inner perimeter of my intended handhold. 
After checking out the mill and finding, thankfully, there was no serious damage, I changed the design of the handhold in an attempt to salvage my workpiece. I increased the size of the opening and created a two level fillet around its inner periphery to save as much undamaged metal as possible. The new stepped contour around the opening turned out to be pretty dumb looking, and so I tried to give it some purpose by turning it into a builder's plaque. Without knowing anything about how it had evolved, my wife remarked that she liked it, and so I decided to keep it.
A problem with the new design, though, was that the material around the opening had been thinned so much that the handhold was very uncomfortable. And, combined with the larger opening, the plate might have been weakened too much to carry the weight it needs to support.
To make matters worse, I damaged my hands several years ago using a poorly designed staple gun while building my shop, and now I have a condition known as 'trigger finger.' With a narrow line of pressure across the right area on some of my fingers, they will lock tightly closed and must be painfully pried open. My new handhold was now the perfect tool to demonstrate this. So, in a continuing effort to save my nearly finished firewall, I machined an additional part that bolts onto the front of the plate and increases the thickness of the handhold around its opening. I contoured it for a comfortable grip, and now I can lift it without grossing out my wife when I pry my fingers open.
In addition to wiring up the firewall, the final task before trying to start the engine is to fabricate a manual spark advance control. I left room for it on the firewall between the ignition modules. Since my H-9 only marginally benefitted from timing control during running, this functionality is really just a 'nice to have'. It should be an interesting little project since, in this engine, both distributors need to be simultaneously rotated in opposite directions by the same amount in order to advance the timing. Even though I won't be spending much time in the shop during the holidays while the kids and grandkids are visiting, I'll likely be thinking about its design. - Terry


----------



## Scott_M

Ah that pesky little decimal point of destruction.  

 Nice save though, the extra piece on the front looks intentional and functional.

 Thanks again for all the extra work of sharing this with the rest of us. Very , very nice.

 Scott


----------



## kvom

CAM error? Been there, done that, broke the bit, de-trammed the head.  Good recovery there.


----------



## camm-1

Te&#341;ry I read all your posts and also your 9 cyl build and love it.
Thanks for so much good info and pleasure to see your amazing craftmanship.
I have start building the 9 cyl and is finished with the crancase exept the tapping.
Now I am working on the cylinders and just have a simple question. The threads are says 1.24 42 or something and I have tested out the dimensions for threading 1.5 mm pitch.
Is that to big ? I think that a bit bigger than that inch thread that Im not used to.
Cheers
Ove


----------



## Art K

Terry,
I hate to admit it but I've done that with a cnc cylindrical grinder, offset .2 instead of .0002 throws a 6-8 inch shaft rite quick.:fan:
Art


----------



## camm-1

Ha. I did not understand nothing about that&#128516;


----------



## mayhugh1

camm-1 said:


> Te&#341;ry I read all your posts and also your 9 cyl build and love it.
> Thanks for so much good info and pleasure to see your amazing craftmanship.
> I have start building the 9 cyl and is finished with the crancase exept the tapping.
> Now I am working on the cylinders and just have a simple question. The threads are says 1.24 42 or something and I have tested out the dimensions for threading 1.5 mm pitch.
> Is that to big ? I think that a bit bigger than that inch thread that Im not used to.
> Cheers
> Ove



Ove,
My H-9 planset calls out 1.25-24 for the cylinder threads which, as far as I can tell, is a non-standard thread even in the U.S. I used this spec for my threads and made a matching set of thread gauges using my own major and minor diameters before starting on the cylinders. 
The 24 threads per inch is equivalent to a pitch of .0417" or, in your case, 1.058 mm. So if you use a 1 mm pitch so you can cut the threads on your metric lathe, you should be OK. You'll just need to come up with your own major and minor diameters while you're making your thread gauges. - Terry


----------



## camm-1

Ok .sorry read on the preveus tread and thought it was your answer &#128552;
Ok I thought it would be about 1mm pitch.
But now I have a a good messure to thread 1.5 so I think I go for that .can that be ok?


----------



## mayhugh1

camm-1 said:


> Ok .sorry read on the preveus tread and thought it was your answer &#65533;&#65533;
> Ok I thought it would be about 1mm pitch.
> But now I have a a good messure to thread 1.5 so I think I go for that .can that be ok?


 
Ove,
If you stick with the stock dimensions for the cylinder and take into account all the subltle details such as thread relief, etc., you will have just over 3 engaged threads if you use 1.5 mm pitch, and you will have 5 engaged threads if you use 1 mm pitch. The decision is yours, but if it were me I would use 1mm. If I remember correctly, I torqued my heads onto the cylinder at 35-40 ft-lbs; and that seems like a lot to ask of 3 threads in the aluminum heads.
You're getting ready to put hundreds of hours into the machining of those cylinders, and you may not want to base an important foundation decision on just several minutes of already invested time.   - Terry


----------



## camm-1

Thanks Terry!
Thats what I need to hear.
Merry christmas
Ove


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## mayhugh1

After a much too-short holiday I slowly migrated back into the shop. In addition to helping clear away some of the brain cobwebs it also became a sanctuary from the dreary wet and cold weather that's settled into central Texas. My older son who visited during Christmas was looking forward to seeing the new radial run, but at the time I was still 2-3 weeks away from the finish line. Anyway, it's been my experience that starting up a new engine for the very first time in front with an uninitiated audience can be a frustrating experience.
While helping my grandsons with their new quad-copters I realized I had set up the throttle on my engine backwards, and so I made a few minor changes to correct it. It now works opposite to the one on my H-9, and so I will also correct that one the next time it comes down from it's shelf.
After finishing the sketch for the firewall wiring harness I removed all its components (again) and then drilled and tapped the mounting holes for the harness cable clamps. I then turned my attention to what should be the last component of this build - the manual spark advance control.
After some investigation I realized the two distributors have significantly different resistances to rotation in the crankcase, and they are dominated by differences in the flexibilities of the bundled wires going to their caps. This means that each distributor will need its own separate link back to the control lever instead instead of the 2-into-1 bell-crank that I had been considering. The distributors rotate in opposite directions in different planes, and the linkage attachment points on the perimeters of their housings can move with three degrees of freedom. All this means that spherical rod ends will be required. Unlike with my throttle linkage I was not able to come up with a useable single plane approximation within SolidWorks to work around its lack of rod end support. Therefore I gave up using a CAD simulation and actually constructed a pair of distributor facsimiles in wood which I glued into position atop the distributor support I created to develop the throttle linkage. This hands-on simulator allowed me to better visualize the linkage requirements and to test the design as it progressed.
I eventually decided on a control lever similar to the one I made for the throttle. The link rods intersect the firewall in the middle of the oil tank, and the lever allowed me to move the actual control point above the tank and away from the filler cap.
The completed linkage appears to work well, and it feels very smooth while controlling the wood models. The lever base has two adjustable stops that limit the range of the control to between 0 and 30 degrees BTDC.
What remains now is to wire up the firewall, retest the fuel loop, and then transfer the engine from the assembly stand to its final position on the running stand behind the firewall. - Terry


----------



## gbritnell

Terry,
I've been following along since day one and like your son am anticipating the start-up. I know full well what you mean about start-up gremlins. It's the same as going to a show. I check and test all of my engines prior to leaving home and wouldn't you know it when there's a crowd around something happens. The worst was always the fried Hall transistor. Thankfully that hasn't happened for a long time. 
I have to say again that the detail on your build is outstanding. 
gbritnell


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## mayhugh1

I wired up the firewall after installing all its components, hopefully, for the last time. I then moved the engine from its assembly stand to its running stand and bolted it in place in front of the firewall. Due to the engine's excessive weight and awkward envelope this was a tricky two-step transfer that required an intermediate stand that I made to support the engine vertically on its front cover while the running stand was bolted to the rear of the engine. I re-tested the fuel loop after installing the carb on the engine and connecting the fuel lines. I then connected the throttle and spark advance linkages between the firewall levers and, for the first time, the actual engine. Space is pretty limited between the rear of the engine and the firewall, and this makes dealing with the the tiny rod end fasteners and my fat fingers difficult at best. I was really glad I was able to get most of the linkage work completed before involving the engine.
I then completed the connections between the ignition modules and the engine. Each module has its own dedicated braided ground connection to the engine crankcase. My ignition design provides several inches of separation between the Hall trigger cables and the high voltage distributor wiring in order to minimize emf issues. The engine's oil intake line was connected to the oil tank, but the engine's output line was temporarily run to a plastic catch bottle. My plan is to flush one or two quarts of oil through the engine for disposal before finally closing the oil loop and recirculating it. I'm using a straight 40 weight Shell aviation mineral oil purchased from a small local airport. This additive-free oil is designed for aircraft engine break-in. 
After installing the three blade 28x12 prop the engine suddenly seemed too big for my shop, and so I took it outdoors for the final assembly photos. The whole thing weighs just over 70 pounds, and it is pretty difficult to move around even with my firewall handhold. 
Today, in central Texas, we're having an exceptional one day winter heat wave with the outside temperature in the low 60's F; but the rest of the week is expected to only reach the mid 40's F. Since this is a radial with extremely long fuel intake tubes I suspect it will be very difficult to run it outdoors anytime soon after today. Unfortunately, the engine is much too big to be safely run inside my little shop. And so I will have to wait until the weather warms up, hopefully next week, before getting serious about running and tuning.
However, with only an hour of daylight left on the only day I'll have this week to play with it, I just had to see if I could at least get a first pop. I was surprised when I got much more. After choking the carb with my thumb for a few manual revolutions and then switching the ignition ON, I spun the prop with my hand; and the engine started right up and ran for about ten seconds. I didn't attempt any carb tuning since I was unprepared and currently unfamiliar with the Perry carb. I didn't receive any tuning information when I bought it, and so I have some research to do. But, I was able to restart the engine several times and eventually ran a dozen ounces of gasoline through it in several short runs lasting as long as 20 seconds. Currently, the engine doesn't have much throttle response, and the tach shows it tends to run at 1000 rpm. 
I also re-tried my drill starter, and with a newly-charged battery I can get about 20-30 seconds of spin time if needed. As the engine finally consumed its second tank of fuel, the rpm surged to a very smooth 3000 rpm as the mixture leaned out out telling me the carb is probably currently too rich. I found on my H-9's Super Tiger carb that both the high and low speed fuel adjustments had to be adjusted nearly OFF for optimum performance, and so this shouldn't be too big of a surprise. The elapsed time counter showed an accumulated run time of only 4.2 minutes when the sun began to set and the temperature drop, when I muscled the engine back into the shop.
While running, the engine spit/slung a lot of oil initially, but the amount decreased significantly after the first run. I believe I got carried away with the oiling while I was testing the oil pumps and running the compression tests a few months ago. The engine seemed to continually drip oil after that even though I had drained the sump. Some of the oil was obviously from the lower lifter bushings, as expected, but some was also coming an indeterminate source that left me wishing I had used a gasket between the crankcase sections. Several days later I also noticed oil dripping from the exhaust pipes on some of the bottom cylinders. This was also typical of the H-9 and was due to oil seeping into the combustion through the ring gaps on the lower cylinders. On this engine I have several more of these PITA cylinders to deal with.
The only real issue I ran into during these brief initial tests was with the LH threaded nut that keeps the prop on the crankshaft. This nut continually loosened during running creating a bone-chilling prop rattling noise. I was probably fortunate that these first runs were short or the prop might have come completely off. This wasn't an issue on my H-9 since this nut was integral to the spinner and was continually re-tightened during starting. I changed the design of the spinner on this engine to remove the T-18's excessive starting torque from the weak portion of the crank nose and transfer it to the keyed prop on the beefier section of the crankshaft. At the time I didn't think there would be any significant torque requirements on this nut, especially since the prop is keyed to the shaft, but I was evidently wrong. I'll re-visit this later in the week after today's excitement dies down. For the present I solved the problem with a hefty lock washer.
The next task is to familiarize myself with the operation of the Perry carb and, when the weather permits, go through the tuning process and verify it will actually perform on this engine. I'll then video the final result. If the weather doesn't warm up I wouldn't be surprised if I fire it up inside the shop against my wife's warning and my own better judgement. - Terry


----------



## Swifty

What an exciting time it must have been when it came to life. Looking forward to the video.

Paul.


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## petertha

Awesome Terry, that must be a great feeling. Its a big, beautiful Beast! Take your time on the home stretch & look forward to the hearing the roar when its ready.


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## Ethan D

Beautiful work! Can't wait to listen to the roar!


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## gbritnell

Hi Terry,
Not much more to say. Superlative job! The details on the controls and the engraving on the firewall are just icing on the cake. 
I too can't wait to hear it sing. 
gbritnell


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## kvom

The most impressive build thread I've ever seen here.  Wow!


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## Scott_M

WOW
 Just beautiful, right down to the last screw. Very impressive Terry !

 Hoping for warm weather in Central Texas  http://www.kwtx.com/weather

 And again...thank you for taking the time to document your build for the rest of us to see. I would bet that you also have an impressive number of hours into the Build Thread.

 Scott


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## vascon2196

Very impressive...amazing job.


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## mayhugh1

Thanks, everyone, for your kind comments.

Terry


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## kvom

Time to change your avatar.


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## brendanf

Terry telling us you got it running and not posting a video, and worse yet, telling us we have to wait until Texas gets better weather...

Your killing me here! Practically drooling on my keyboard, desperate to see a video of this thing run so I can show my dad..


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## kuhncw

Beautiful piece of work Terry.  Thanks again for the very educational build thread.

Chuck


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## mikemott

Your engine is one of the most inspiring builds, the firewall presentation really is as has been noted the icing on the cake. Thank you for all the work it takes to share such a complex build.

Mike


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## johnny1320

That's just beautiful Terry! Work of art!


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## gus

Hi Terry,

You are my " Sifu" aka '' GrandMaster'' ..


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## mayhugh1

When I built my first two IC engines, Jerry Howell's V-2 and V-4, I also built the carburetors for them. Jerry's carb is fairly complex, having high and low speed needles as well as a functional Bernoulli butterfly valve. The three copies I made (the V-2 required two) worked fine, but it seemed like I was continually adjusting the needles to not only start the engines but also to keep them running. With my limited experience I wasn't sure if this was due to the carb design, the engine designs, my machining, or whether constant fiddling is just the nature of the beast.
When I built my third engine, the Hodgson nine cylinder, I noticed the Howell carb design with its .25" bore had been licensed and included in the plan set I had purchased. After talking with Lee about the performance of such a tiny carb with the H-9, it wasn't clear that he actually had much personal experience with it. His carb of choice is a larger and very difficult-to-find unit from a vintage Cushman scooter. In fact, he mentioned that he maintains membership in a Cushman club in order to get access to them.
My research into what other builders were using for their H-9s was also disappointing. Those who were satisfied with their carbs were using models no longer available. Being intimidated by the complexity of the H9's induction system as well as the large number of machined parts that need to play nicely together, I decided to go with a commercial carb in order to reduce the number of unknowns that would be dependent upon my machining abilities. 
After a few false starts I ended up with a Super Tigre #12163145 - a dual needle barrel carb with a .35" bore. Although my final gasoline settings seemed extremely lean, the adjustments were not overly sensitive; and the carb seemed to work well on my H-9. Once dialed in, the transition from idle to full speed was smooth, and I never had to mess with the needles again.
The induction system on my T-18 is even more intimidating. With no real expertise I designed my own diffuser and plenum based more upon good looks than any flow theory. The front row intake tubes are nearly twice as long as the rear row intakes which, themselves, are pretty long. In addition, the thermal characteristics of my T-18 heads and cylinders which affect the intake temperatures just have to be much different from those on the H-9. I felt Jerry's carb was too small for this engine; and so, again, I decided to go with a commercial unit. My tried and proven Super Tigre, though, hasn't been available in this country since the Japanese tsunami of 2011.
Choosing an RC carb for a multi-cylinder model engine from a distributor's website is a bewildering experience. The selection is typically large but the availability is in constant flux since the carbs are designed for particular RC engines that seem to come and go with the frequency of women's fashions. And, RC engine size isn't a sufficient spec to use when shopping for a carb for a multi-cylinder model engine. The requirements of the two engines can be very different. For example, I'm more interested in a carb that can provide my 18 c.i. display engine with a quality idle and smooth transition to mid-range rpm compared with an RC enthusiast who wants his .60 c.i. acrobatic single cylinder engine to make reliable high rpm power.
During my search, I came across Perry Carbs now owned by Gary Conley who is a member of the model engine building community. I was attracted to his website because it includes an inventory listing by Venturi size which, to me, is a more useful spec than a recommendation for a particular single cylinder engine. I spoke to Gary about my requirements which included a maximum 3500 rpm. He assured me one of his carbs was capable of performing even better than the Super Tigre.
I purchased his model 1401 which has a .312" Venturi. Perry carbs are also barrel carbs with high and low speed adjustments. A needle valve is used to control the fuel flow at high speed. But, an adjustable disk with a cat's eye opening uncovers a slot in the spray bar to regulate the amount of fuel at idle as well as in the mid-range region. Because I plan to use gasoline instead of typical RC methanol-based fuel, Gary supplied a special disk with an opening better calibrated for use with gasoline. For some reason, no documentation arrived with the carb, but two of the photos show the information I was able to locate online.
The design has evidently evolved a bit since the version shown in the exploded diagram. The throttle arm is now plastic, and the high speed needle no longer requires a tool to make adjustments. After installing the carb on my engine and hooking up the throttle linkage, the sloppy feel resulting from flex in the plastic throttle control arm was a bit of an annoyance. So, while looking for something to do while progress on the radial is currently weather stalled, I machined a brass replacement that feels much better. While the carb was still off the engine I decided to disassemble it to better understand its internals, and it was probably a good thing that I did. The area between the o-rings on the aluminum disk was covered with a sticky gunk - maybe dust encrusted o-ring grease - and there was a piece of aluminum swarf stuck in the narrow fuel slot. I don't believe any of this could have from my end earlier in the week since I'm running a fuel filter just in front of the carb. 
The instructions mention that a only few thousandths movement of the idle control disk can make significant changes in the idle performance. I noticed the two o-rings tended to stick and slip when I attempted to rotate the disk a small amount (the documentation warns about this). So, it feels like this method for making small low-speed adjustments may be more difficult compared with a more conventional low speed needle. I'll reserve final judgement, though, until I actually go through the process. My T-18 carb adapter is designed around the standard carb dimensions of the Perry as well as a couple carbs salvaged many years ago from my younger son's RC junk box. If the Perry doesn't work out, I may have some other plug-n-play possibilities.
Perry's recommended starting point for the high speed adjustment is one turn open from fully OFF. After checking, I found that mine had been set 2-1/4 turns from fully OFF while I was first-starting my engine a few days ago. As I suspected at the time, the carb was probably set ridiculously rich; and I probably should have waited until I was familiar with it before attempting to start the engine. Anyway, it seems no harm was done; and now, with a bad case of cabin fever, I'm ready for the weather to warm back up. -Terry


----------



## cfellows

Congratulations on a beautiful build and successful first run, Terry.  You're truly an inspiration.

Chuck


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## mu38&Bg#

The engine looks incredible. I'm looking forward to hearing 18 cylinders firing.

I didn't know Conley offers gasoline compatible metering for the Perry carbs. That's good to know.

Greg


----------



## petertha

I was trying to find that gasoline/methanol distinction myself off the Conley website, but couldn't. I see 'standard' and 'pumped' version for the same engine application, but not fuel type? Maybe Terry can elaborate - did you swap out any Supertigre squishy bits to prepare for gasoline? Maybe Perry uses body/seal/o-ring materials are compatible with both fuels?
http://www.perrypumps.com/prod01.htm#mvvs

I can understand the frustration trying to size carbs from (lack of) RC engine venturi / orfice specs. They just dont catalog that dimension unless a helpful reviewer bothered to make note. Plus, there are just so many variations that may affect size even assuming a target displacement; sport 2S vs piped/boosted 2S vs 4-S vs boosted 4S vs pressurized fuel inlet vs muffler/pipe assist...

The Conley/Perry venturi size gradations are certainly helpful, but I assume the lookup table must be primarily derived by 1) matching OEM carb hole size 2) maybe orfice:displacement correlation? I'd be interested to know myself. Anyway, you could use this info to your advantage if the Perry didn't pan out - just back-track the Perry model# to the matching engine OEM part. (Personally I found Perry's somewhat fussy, particularly in the mid-range, but that was a different era & completely different application). 
If I had to suggest an alternative, it would be OS-4-S. Just going down this path myself, but luckily an easier matchmaking exercise than this 18C.


----------



## mu38&Bg#

I think it's something you need to call about to get. I might give Gary a call myself.


----------



## mayhugh1

Peter,
      I didn't change the o-rings in the Super Tigre for compatibility with gasoline. I, maybe erroneously, assumed they were compatible with either. I haven't noticed any o-ring related issues with the carb on the H-9, but since I didn't need to change the settings once the carb was dialed in, I might not have noticed any minor swelling if there was any.
I've noticed in the local hobby store that fuel components like tank stoppers that look like white silicone are sold for use with alcohol only; and they also have black ones, presumably nitrile or Viton that are sold for either gas or alcohol. I don't know why they wouldn't supply just the black stuff, whatever it is.
The Perry website doesn't discuss fuel type as far as I know, and frankly the pump stuff was unfamiliar and confusing to me and was the real reason I called. When I spoke to Gary I told him I was planning to use gasoline, and I wanted to make sure there wasn't an issue with the carb's plastic body. That was when he told me that he would supply my carb with an alternate idle disk that was calibrated for gas. I believe their inventory is probably a bunch of modular parts that are assembled per order. I wasn't real sure of the Venturi size I wanted, and Gary told me if I ended up needing a larger carb I could just purchase another throttle barrel instead of buying a whole new carb. I forgot to ask him about gasoline compatibility of the o-rings in his carb, but I think it's reasonable to assume that if he sells idle disks designed for gas then he is using o-rings compatible with either fuel.
By the way, I might be interested in that 40NA carb that you're looking at. What is its Venturi size? I looked it up on the Tower Hobbies website, and I just had to smile when I read it was listed as end of life with them. - Terry


----------



## gbritnell

Rather than hijacking Terry's wonderful build thread I am starting another one to discuss the last entries in this one about carburetion.
gbritnell


----------



## petertha

mayhugh1 said:


> By the way, I might be interested in that 40NA carb that you're looking at. What is its Venturi size? I looked it up on the Tower Hobbies website, and I just had to smile when I read it was listed as end of life. - Terry


 
Hopefully I didnt confuse matters, Terry. My intention was to show the style of OSs 4-S downdraft methanol carbs because you were happy with the ST & possibly evaluating alternatives. Basically just pointing out OS makes progressively larger suite of 4S engines all of similar carb flavors (62, 72, 81, 95, 110, 120, 155..) I believe the 56-FS-a is still the current '56' version, at least it shows up in catalogs. I recently bought a 56-FS-A piston liner set for my radial project, unfortunately not the carb yet or Id measure for you.  
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXRUF7&P=ML
http://www.osengines.com/engines-airplane/osmg0956/index.html
http://www3.towerhobbies.com/cgi-bin/wti0095p?FVPROFIL=&FVSEARCH=OSMG2485

And just to drive you crazy, OS also makes a GF40 4-Stroke gasoline version & correspondingly different looking carb.
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXCZLF&P=7
http://www.osengines.com/engines-airplane/osmg0800/index.html
Its designed around bigger displacement though; 2.4 cid, 1.57B x 1.25S (vs. 56A @ 0.57 in3 0.945"B x 0.811"S).  How that sizing might relate to your displacement & double-row net effect is way above my pay grade. Sorry, wish I could offer useful insight but I'd be blowing smoke.  At least with the Conleys sounds like you can swap & tune among his orifice barrels. If everything works, you are home free. If the orifice is basically correct but other operational misgivings, at least you will be armed with target size.

I agree with George, sorry, did not want to divert your great post.


----------



## mu38&Bg#

Seems like I've studied too many RC carbs. The bore of the OS 40NA found on the FSa-56 is 6mm. It has a spraybar and needle that should be roughly equal to a 1mm rod through the middle. Carb sizing is directly related to how much air the engine uses. If the fuel draw is solely due to pressure drop, without muffler pressure is in most RC applications, the venturi must be smaller.

Two needle type carbs are problematic when the air fuel ratio needs of the fuel is not as designed. A glow fuel carb on gasoline will end up rich in the midrange.

The carb on the GF-40 is a Walbro. The smaller GF-30 has a design like their diaphragm regulated glow carbs with a separate diaphragm pump.

Greg


----------



## mayhugh1

For the past few days the outside temperature has been in the mid-40's F with a very high humidity due to our rainy weekend. I was tempted to haul the engine outside and play with it anyway because I'm really anxious to see how it now runs with a reasonable carb setting. The only reason I didn't was my concern about condensation in the crankcase and on my 12L14 crankshaft. The weather people expect the current conditions to continue for at least another week, but I decided I just couldn't wait that long. 
Without telling my wife, I rearranged the furthest corner of my shop away from the computers to create some space where I set the engine up for a brief run. I only wanted to run it for a minute to see if I might now have some semblance of throttle response. With 18 cylinders I expected to quickly fill the enclosed area with fumes, but my real concern was staying out of the prop while moving in the limited space around the engine to make adjustments. The last thing I want is an accident where I end up with a bent crankshaft - neither mine nor the engine's. The ideal place would have been in front of an open door, but without some serious rearranging I just didn't have enough space in front of a door for both me and the engine. 
After cleaning the soot off the plugs from last week's run, I opened the high speed needle 3/4 turn from fully closed; and then, after manually priming the engine, I spun it with my drill starter. It started right up and ran great. It appeared to be running on all cylinders as far as I could tell by putting my hand near each exhaust tip. I think I tested all of them, but I'm not entirely sure. There wasn't much light where I was working, and I had to carefully stretch to reach around the nearly invisible spinning prop. 
The throttle seemed to smoothly control the engine, and I was able to adjust the high speed needle another 1/8" turn for a peak rpm of about 2500 with the throttle about 3/4 open. The engine responded nicely to the needle change without being overly sensitive. I realize the high speed needle really should be set with the throttle wide open, but I'm not ready to go there yet. I want to break-in the engine with several short runs between idle and a few thousand rpm with complete cool-downs in between before revving the engine up fully.
I noticed the engine seemed to run best with zero indicated spark advance. I wasn't expecting this, and so I need to verify my timing calibration. I didn't attempt to adjust the idle disk just yet. So far, the engine is capable of idling as low as 800-900 rpm, and its low speed idle sounds really great. The idle stop needs to be raised some because right now the engine stalls when the throttle is pulled fully back.
Against the agreement I had with myself I ran two tanks of gas through the engine. A 10 ounce tank of fuel still lasts about only about two minutes even with the new carb setting. I filled the tank for the third time, but the engine didn't sound right while being cranked. Then I noticed the Hall indicator led on the rear bank distributor was constantly ON. Later testing verified the Hall device in this distributor was dead. This is the first Hall sensor that has ever failed in any of the four engines I've built. I don't believe it was damaged by a direct discharge inside the distributor since it's well protected in there. Instead, I think it may have been destroyed by a transient on the power supply line. I installed 10 Volt MOV solid state transient protectors on the supply lines of all my TIM-6 ignitions to protect the semiconductors from transients created on the supply line by the high voltage section. I didn't use them on the T-18's CDI modules because I was cramped for space inside the enclosures; and then, well, I forgot about them. It might just be a coincidence, but the tach drive signal also comes off this particular sensor; and so I'll need to take a look at a possible power supply sequencing issue or maybe some other interaction with the tach electronics.
Another minor issue (again) was oil flow rate. With the drip feeder valve opened only one turn while running, the crankcase filled with oil to the point where it began running out the front bearing. At this drip feed setting the engine pumped the entire contents of the oil tank into the catch bottle during the four minutes of running. I had the same issue with the H-9, and it seems a much lower drip rate will be required for this larger engine. The drain-back channel between the front of the engine and the sump inlet at the rear of the engine is as big as I could safely make it, but it's still enough of a restriction that the pressure pump can easily get ahead of the scavenger pump unless the oil flow from the tank is severely restricted. 
The oil in the catch tank was very dark due to blow-by contamination, but I was thrilled that even though the shop was filled with exhaust fumes, there wasn't the slightest hint of oil smoke. After draining the sump I found an obvious build-up of ring material on the magnetic drain plug. In fact, after the four minutes of runtime I had more material on the drain plug than I remember accumulating during an hour of 'motoring-in' the engine while testing the oil pumps a few months ago. This reinforces my suspicion that motoring an engine without the pressures of combustion does little to seat the rings.
So now I have some repair work to do. The good news is that I think the engine is basically running well, and only some minor tweaking remains. From all early indications the Perry carb will likely be acceptable. I need to look into the timing advance and make sure I haven't mis-calibrated the indicator. And, of course, the major issue is that I need to replace the Hall sensor on the rear row distributor and figure out why it failed. I'm reasonably sure I can replace the sensor without pulling the distributor, but the tedious process of re-synching the timing will have to be done. The most important task is to figure out why it failed and then correct the problem so it doesn't happen again. - Terry


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## ozzie46

Wonderful report Terry! I bet your feet can't touch the ground yet.

 I know I'd be walking on cloud 9 even with the minor issues you've mentioned. 

Congrats and great work. 

Anxiously waiting a video.

 Ron


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## vascon2196

That is a great feeling...getting an engine running.

You can only make it better from there!

Great job...looking forward to hearing her run!


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## Mattsta

Just stumbled upon this amazing thread. Funny to find it right at the moment of truth when all this incredible workmanship comes to fruition.

I found this thread by accident, not being a hobby machinist but being fascinated by radial engine design.

A little while ago, I found the plans online for Karl Erik Olsryd's 9 cylinder radial engine which I subsequently modelled in Pro/Engineer.

_[ame="http://www.youtube.com/watch?v=XkcKMMa_kO8"]www.youtube.com/watch?v=XkcKMMa_kO8[/ame]_

And you can download the entire CAD model of it for free at Grabcad.com

There are some nice rendered images of the engine for those of you who don't have access to CAD software.

http://grabcad.com/library/olsryd-9-cylinder-radial-engine--1

I have been wanting to model an 18 cylinder radial ever since completing the 9 cylinder radial but I came to realise that the Olsryd engine had too many design problems for it to be converted into an 18 cylinder design.

This engine however, is in a totally different league of sophistication, having a pressure fed lubrication system and the ingenious bronze main bearings and built up crankshaft. It is an absolute work of art both in design and of course, the execution of this design into a real physical working engine. Incredible skill and attention to detail.

I would really like to get a set of engineering drawing for modelling my own 18 cylinder radial in Pro/Engineer.


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## Art K

Terry,
I just got caught up on your thread, wow. Its amazing that you had so little trouble firing it up for the first time. The 10 oz. fuel tank is going to seem to small once you get all the sorting out done. I must admit not making any chips recently but drywall dust instead, no fun.
Art


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## mayhugh1

Replacing the failed Hall sensor took much longer than expected because testing its replacement uncovered one timing foul-up after another. The whole experience left me wondering if I had been asleep when I originally set it up, and just how the engine had been able to run at all.
I started disassembly of the rear row distributor by temporarily replacing its blue Delrin cap with a transparent test cap that I had made earlier. After rotating the crankshaft to bring the rotor into firing position under tower #1, I pulled the spark plug from cylinder #1 to verify its piston was at TDC of its power stroke. Unfortunately, the piston wasn't even close to where it was supposed to be. I then discovered that I hadn't fully tightened the SHCS that is suppose to secure the trigger disk and its keyed rotor to the distributor shaft when I timed the engine months ago. Because of this 'screw-up,' the timing for half of the engine's cylinders had been slowly shifting as it ran. I couldn't believe I had pulled this stunt again. I made the exact same mistake three years ago when I initially timed my H-9. In the process sheet I wrote up for myself to do the timing on this engine I even made a note to not forget to tighten that screw this time.
I rotated the loose trigger disk by hand to exercise the sensor, but it still indicated bad. After removing the dead sensor from the distributor I noticed the shrink tubing that I was depending upon to insulate its leads from the distributor housing had been badly abraded. This might have happened when I inserted the sensor through the bottom of the distributor during assembly. I remember that it really should have gone in from the top, but I had already soldered on its connector making that impossible. It looked probable that the sensor's Vcc lead might have, at least intermittently, shorted to the distributor housing. I re-tested the sensor while it was off the distributor hoping the problem had just been the shorted lead; but I finally had to accept it was really dead.
I think it's very unlikely that at least one of these two screw-ups on my part wasn't somehow responsible for the failed sensor. One possibility is that the shifted timing allowed the rotor to end up between two tower electrodes when the CDI capacitor fired. The very long discharge path that resulted would have allowed the coil's secondary voltage to soar uncontrollably until, possibly, a breakdown occurred somewhere in the CDI module sending a killer spike back to the sensor. If the path had included Vcc, the missing MOV might have saved the sensor. I think it's more likely, though, that the spike was coupled back to the sensor's signal lead through the SCR used to discharge the cap. This scenario is pretty ugly because a similar result can routinely occur in an engine with a fuel-fouled plug or an excessively wide gap. As one of the photos shows I had made the rotors extra wide in order to encourage such misfires, if they occur, to dump the coil energy to an adjacent tower electrode before the coil's secondary voltage can rise to its open circuit maximum.
Another possibility is that the rotor actually did arc to the distributor housing. It's possible, but not likely, that the impedance below the portion of the housing containing the sensor allowed the housing to briefly rise to a high potential that eventually reached the sensor through its insulation-abraded lead.
After replacing the sensor I re-phased the trigger disk to cylinder #1 and finished the reassembly of the distributor. Establishing the timing of one of my distributors is complicated by its timing advance scale. Two separate but interacting adjustments must be made so that, at precisely TDC, the sensor is triggered by a magnet when the rotor electrode is directly under the correct tower electrode. The extra complication is that both of these events must occur while the distributor is rotated so the timing indicator on the crankcase is pointing exactly to 0 degrees on the advance scale on the distributor housing. 
I took a series of photos of the reassembly to show how the sensor is shrouded from the electrical storm in the distributor cap and also to point out a few of the culprit components. After verifying the rear row sensor led was now blinking as it should when the crank was rotated, I noticed it's relationship with respect to the blinking front row sensor led looked suspicious.
So, I put a test cap on the front row distributor and rotated the crankshaft 180 degrees until cylinder #1 was at TDC of its intake stroke. This should have placed the front row rotor electrode directly under tower #10's electrode. But, strangely, it was advanced by 30 degrees even though the SHCS on this distributor had been properly tightened.
I believe what happened was that when I timed this distributor I was confused by its opposite direction of rotation, and I probably timed it with the distributor rotated so its timing pointer was at the wrong end of the distributor housing's advance scale. 
After re-timing this distributor I then noticed its sensor light seemed to occasionally miss a blink as the crankshaft was turned. I think I had actually noticed this earlier when starting the engine, but at that time I thought it must have been my imagination since it was very infrequent, and the engine seemed to run OK. 
It turned out that the trigger disk in that distributor was just a bit too far away from the Hall device, and occasionally it would not fire on a particular cylinder. This distance is set by a machined spacer. When I made the distributors I made a pair of spacers for each one that were different by .01" in thickness. Since the required spacing is determined by the strength of the magnets as well as the sensitivity of the Hall device, I selected the proper spacer during the distributor's assembly and test. This distributor somehow ended up with the thicker spacer. Since I still had all the spacers I solved the problem by replacing the spacer with the thin one.
Despite my ugly twin's efforts to scuttle the timing on this engine, it somehow started and ran as long as it possibly could. All these timing issue could explain why the engine started so easily the very first time the prop was bumped by hand, but then needed the drill starter for all subsequent starts. I now also understand why, during the last session, it didn't like any additional timing advance. Half of the cylinders were already advanced 30 degrees, and the other half were, well, who knows where. After straightening out the final issue I carefully, once more, verified the timing of both distributors.
Without knowing for sure the exact cause of the sensor failure, but being reasonably sure it was related to a voltage spike, I decided to shotgun its protection. I added 12V unipolar transient protectors (LittleFuse SLD10U-017-B) between the sensor's Vcc line and ground and also between the sensor's signal line and ground. These particular devices, which are new to me, are essentially very fast, heavy-duty Zener diodes. Their clamp voltage is much better defined than that of an MOV, and they are used to protect sensitive electronics in automotive applications. I ordered mine from Mouser.com without checking their physical dimensions. When they arrived I was taken back by their huge size. Because of the limited space inside my ignition module enclosures, it was difficult to find room for them, but there is now a pair protecting each sensor.
The next time I try to start up this beast I plan to have a video camera sitting in front of it. - Terry


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## Mattsta

I've been reading this thread now for a couple of days (in complete AWE) but the one aspect of the Hodgson design I cannot fathom is how the cam rings are kept running concentric with the crankshaft. On the Olsryd design that I am familiar with, the cam ring has a centre bearing that runs on the crankshaft. This keeps the crank and the inner ring gear on the camshaft concentric

On this Hodgson design, the camrings are "centreless." There is no centre bearing

So how is concentricity maintained????


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## mayhugh1

Mattsta,
The cam ring concentricity is maintained with a circular groove machined into the rear of the cam ring assembly. A matching circular tenon is machined into the bronze crankcase bearing. The cam ring rides on this tenon which is concentric with the crank bearing. A Delrin bumper-like retainer, bolted to the bronze bearing, keeps the cam ring in place against the bronze bearing. - Terry


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## mayhugh1

Today was a beautiful 70F degree day here in central Texas making it a perfect opportunity to test the new timing on my engine. I set up my ancient flip video camera outside my shop to record the very first start-up. I apologize for the poor quality of the video. It seems I only use this camera every couple years to record a new running engine, and I find myself having to relearn its operation. Evidently, I still don't know how to use it in bright outdoor lighting.
There really isn't much to add to the video. The noise you hear in the video before the engine is started is the fuel pump. I manually choked the engine, set the timing at 10 degrees BTDC, and rotated the prop a fraction of a revolution by hand. As the video shows, the engine took off running. The carb settings haven't been changed since the last start-up, and the video included the engine idling at 900 rpm and running as high as 2500 rpm at about half-throttle. Again, I didn't push the engine or attempt any re-tuning of the carb since I want to wait until I accumulate more short runs. I plan to do the remainder of the tuning while keeping an eye on the spark plugs. I expect the final carb settings will be a compromise with the top rear cylinders running a bit lean in order to keep the lower front cylinders from running overly rich. 
I ran 3/4 tank of gasoline through the engine during the video, and then I re-filled the tank and started the engine a second time off-camera. I had to use the drill starter, though, for the re-start. I suspect the hot soak creates an intake lock near the intake/exhaust flange which is heated by the exhaust. The high velocity starting flow created by the drill probably helps cool the area.
My preliminary temperature measurements, though, showed the flange temperatures were only on the order of 130F. These measurements were made just after shutting the engine down since the plug wire EMI makes my non-contact thermometer pretty much useless on a running engine. 
The engine appeared to be consistently firing on all cylinders, and there was no oil smoke indicating all 54 cast iron rings were working as they should. The only oil I'm currently catching on the firewall appears just after the first start-up when the prop wash blows oil that has seeped down along the pushrods from the lower lifter bushings. If the engine is allowed to sit a few days, there is also some oil from one or two lower exhaust pipes whose cylinders were left standing with open exhaust valves. If I were starting the engine build over, I would include pushrod tubes.
I included a photo of the oil in the catch bottle. It's color is black due to the bluing on the cylinder walls being polished away by the piston rings. It will likely take at least a quart of flushed oil for the color to clear up, and it will be at this time when I'll close the oil loop and begin recirculating the oil. The oil spray visible on the interior wall of the bottle is created by the crankcase pressure pulses which work to reinforce the scavenger pump operation. I believe this action also helps to prime the scavenger pump even when the sump is drained between runs. The small amount of oil in the catch bottle after about four minutes of runtime probably indicates my new 1/4 turn open oil feed setting Is now a bit too low.
I have to mention that I really like my little tach. It was a real PITA to get functional, but it turned out to be well worth all the effort.
Over the next week or so I'll put more short runs on the engine and slowly start raising its rpm. By monitoring the plugs I'll be able, over time, to optimize the carb settings and learn whether the current carb is properly sized for my maximum target 3500 rpm. I also need to go through the engine and re-tighten any loose fasteners. After these loose ends are tied up I'll make a better quality video to wind up my little T-18 build. - Terry

[ame]https://www.youtube.com/watch?v=x6xtmo8hFRk[/ame]


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## DICKEYBIRD

Truly fabulous engine Terry!  Thanks so much for posting the video.  Next best thing to being there!


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## petertha

mayhugh1 said:


> ..my little T-18 build...


 
Little huh?  
OMG, what a sound! This whole build post, your latest methodical diagnostics & final tuning... truly inspirational effort. Thanks for taking the time to post. I have learned so much.


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## gbritnell

Terry,
I have the worst case of goose bumps I've ever had. What a sound!!!
Fantastic journey, fantastic destination.
Thanks so much for sharing.
gbritnell


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## Art K

Terry,
I'm with them it sounds wonderful ! great job.
Art


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## Swifty

An absolute work of art, sounds great as well. You gave me a fright when you leant forward to check something, I thought you might get a haircut from the prop.

Paul.


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## camm-1

Terry! You owns!
Thanks for sharing! You are a great inpiration and helpfull to we who also building Hodgson.
And ...what a sound
Ove


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## Mattsta

Congratulations Terry

I can't stream video here at work so I'll have to wait until I get home before I can view it

Thanks for the explanation regarding the cam ring concentricity. That's one hell of a big bearing surface to keep them concentric with the crank!!!!

Just one more question

I see you used a free cutting mild steel to manufacture your crankshaft assembly, 12L14. This is low carbon steel with added lead for good machinability but it can't have its mechanical properties improved by hardening. I 'm surprised by this choice of material for a crankshaft, even though it machines very nicely. Does Hodgson specify this steel for the crank?


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## Scott_M

WOW Terry !
I'm speechless 
It sounds really healthy 

Scott


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## Henry

Thanks for sharing all the process and the final music I was checking the weather reports in central Texas waiting for this.


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## ShopShoe

Fantastic. I've been following and I liked all of the build and now such a wonderful run. Nothing like the sound of a big radial: As gbritnell says, Goosebumps.

--ShopShoe


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## mayhugh1

Mattsta said:


> Congratulations Terry
> 
> 
> Just one more question
> 
> I see you used a free cutting mild steel to manufacture your crankshaft assembly, 12L14. This is low carbon steel with added lead for good machinability but it can't have its mechanical properties improved by hardening. I 'm surprised by this choice of material for a crankshaft, even though it machines very nicely. Does Hodgson specify this steel for the crank?



Mattsta,
I don't know what material Hodgson specifies for his 18 cylinder engine, but the planset I have for the H-9 calls out stainless for the crankshaft. I didn't have a piece of stainless that was big enough to make my crank the way I wanted to make it, but I did have chunks of 12L14 as well as lots of common mild steel. I used the 12L14 because it's tensile strength was a bit higher than mild steel (surprised me too). Since I don't have a way of grinding a finished crankshaft I wouldn't have attempted hardening even if the metal was capable. Getting the crankshaft layed into the crankcase with absolutely no binding was the original feasibility requirement I set for myself to actually do the project. Frankly, I never expected to be able to do it and was sure that today I would be looking at a cool looking paperweight instead of a running engine. - Terry


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## wirralcnc

Exceptional engine. The attention to detail is beyond believe.
The BIG question is what is next???.


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## Mattsta

mayhugh1 said:


> Mattsta,
> I don't know what material Hodgson specifies for his 18 cylinder engine, but the planset I have for the H-9 calls out stainless for the crankshaft. I didn't have a piece of stainless that was big enough to make my crank the way I wanted to make it, but I did have chunks of 12L14 as well as lots of common mild steel. I used the 12L14 because it's tensile strength was a bit higher than mild steel (surprised me too). Since I don't have a way of grinding a finished crankshaft I wouldn't have attempted hardening even if the metal was capable. Getting the crankshaft layed into the crankcase with absolutely no binding was the original feasibility requirement I set for myself to actually do the project. Frankly, I never expected to be able to do it and was sure that today I would be looking at a cool looking paperweight instead of a running engine. - Terry



Totally understand your methodology bearing in mind the complexity of this project

I guess hardening would create potential distortion problems in addition to having to grind the journals and crankpins to the correct diameters

How about an R-4360 for your next project!!!!!!

I just watched the video. It's an awsome build Terry. Many congratulations


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## Mattsta

Another question Tony

Which cylinders numbers do the master rods fit inside. From memory, on the full size R-2800, they aren't positioned where you'd expect them to be!

Interesting article about R-2800 crankshaft development here.

"As it turned out, the main factor contributing to the 1X
torsional vibration was master rod spacing. In the
original experimental test engines as well as the &#8220;A&#8221;
and &#8220;B&#8221; series production engines, master rods were
positioned 100 degrees apart (in cylinders 8 and 13)
to reduce the effects of second-order inertia torque."

http://www.enginehistory.org/NoShortDays/Development%20of%20the%20R-2800%20Crankshaft.pdf

I don't suppose this is relevent in a 1/5 scale engine but it's interesting nonetheless


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## mayhugh1

Mattsta ,
Thanks a lot for the article. It was very interesting. I used #1 and #10 which seemed logical to me, but according to the article it was evidently the worst-case choice for minimizing vibration.

Terry


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## Mattsta

mayhugh1 said:


> Mattsta ,
> Thanks a lot for the article. It was very interesting. I used #1 and #10 which seemed logical to me, but according to the article it was evidently the worst-case choice for minimizing vibration.
> 
> Terry



I'm sure it's far less important on a scale motor with much smaller inertial forces but I'd like to purchase a set of Hodgson's drawings and to see what he specifies, (and much else besides!!).

The R-4360 is ever more bizarre, having master rods in A7, B4, C4 and D1 and to complicate things further, the master rod journals are staggered, not in a straight line like a conventional in line engine. The crankshaft was a single piece forging and the master rods were split like a modern car connecting rod. So are the main bearings.

How they designed these engine with the design aids and computational technology of the era beggers belief 

Someone had a go at building one though!!!!!

http://www.nyemachine.com/pratt_whitney_r4360.php


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## kvom

Take a rest and build a wobbler next.


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## keith5700

Terry, I've been following all the way, and would like to say, Absolutely Fantastic, amazing job!
Cheers, Keith.


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## gus

Hi Terry,

You are my hero. I admire the superb skill.patience and diligence building this fantastic engine.

Now taking my time studying the Howell V-2 Prints before jumping in.


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## brendanf

wirralcnc said:


> the big question is what is next???.



merlin v12!!


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## mayhugh1

A few days after my last post I pulled the spark plugs for a baseline reading and was a little surprised by what I saw. The carb had only been partially tuned, and so sooty plugs weren't totally unexpected. What was unexpected, though, were the locations of the richest running plugs.
Model radials, similar in design to the Hodgson with its centrally-fed rear carburetor, typically suffer from an uneven mixture distribution between the upper and lower cylinders. In order to improve the H-9's distribution, an impeller was added to the original design and then revised a few years later. The result was a performance improvement, but builders still experience rich-running lower cylinders when the carb is tuned for the upper cylinders. This mirrors my own experience with my H-9. The consensus is that fuel tends to puddle in the lower portion of the plenum and enriches the mixture drawn by the nearby cylinders. The H-9 design even includes drain holes in the lower plenum to reduce this problem.
The plugs on my T-18, however, showed a completely opposite result. Its rear row cylinders have intake tubes similar to those on the H-9. The rear row plugs, though, clearly showed the lower cylinders had been running leaner than the upper cylinders. The plugs in the lower cylinders had a slightly rich to almost ideal color while the plugs in the top cylinders showed those cylinders had been running rather rich with obvious soot on the plugs. The front row cylinders with their much longer intakes showed a similar distribution but, overall, they looked as though had been running very rich. The top plugs in the front row were all excessively sooty while the lower plugs were comparable to those in the top cylinders in the rear row. 
These first baseline results were obtained using the 1401 Perry carb (.312" Venturi) with its high speed needle set at 8 o'clock (just over a half turn open from fully closed) and the idle disk still set at stock neutral. For fuel I'm using a product called Four Cycle Tru Fuel which is available from our local Lowe's store. This is an ethanol-free 92 octane gasoline designed for lawn equipment, and it contains an added stabilizer for long shelf life. What caught my eye about this fuel for my application was a claim that it also contains friction modifiers which I thought might be beneficial to the distributors' lower bearings and gears. Of course, this fuel could also be mostly advertising hype in order to justify its premium price. 
A majority of the 5 or 6 minutes runtime that produced these plug results was between 2000 and 2500 rpm, but it also included periods of idling as well as a pretty ragged restart. The restart was attempted during a hot soak period with the throttle insufficiently open. The engine eventually started, but it required the drill starter to spin the engine for several seconds. The sooty plugs indicated that either the carb needed a lot more leaning, or the unfortunate re-start had badly fouled the plugs; and the engine hadn't been run long or hard enough afterward to burn off the excess accumulated carbon.
To prepare for the next set of runs the plugs were cleaned, and the high speed needle was leaned another 1/8 turn by turning it CW from 8 o'clock to 10 o'clock. (Since the needle on the Perry carb actually rotates with the throttle, my needle positions are referred at w.o.t.) This setting turned out to be too lean, and the engine consistently died several seconds after being choked and started. The engine needed at least another 1/8 CCW turn in order to sustain smooth running. As a result, I returned the high speed setting to its previous 8 o'clock position.
I then broke the set on the idle disk and turned it about 1/8 turn in each direction while the engine was running but could see little or no effect on the idle. It's possible that I was fooled by the grip of the o-rings as this adjustment, semi-unique to the Perry, isn't all that user-friendly. I then decided to rev the engine up to 3500 rpm and hold it there while burning the remainder of the fuel in the tank. The reason I did this was to color the plugs for the next reading with a substantial high speed run with no restart nor idling time. I was still curious about the previous upper/lower plug differences and now really bothered by the earlier overly rich plug readings. My plan was to revisit the idle adjustment after the second plug readings. I then would be in a position to connect any further changes in plug conditions to changes in the idle setting.
At this point the engine has plenty of throttle left to rev past my self-imposed maximum of 3500 rpm, and so I'm confident the carb size is adequate. When starting the engine with the drill starter there is a neat sounding intake hiss that's louder than the fuel pump. Also at this point the engine likes timing advance up to about 20 degrees.
After the engine cooled, I once again pulled each spark plug and recorded the results. Fortunately the heavy soot was gone indicating what I previously saw was more of an operator problem than an engine or carb problem. The upside-down mixture distribution differences remained though. The four photos show typical plugs from the tops and bottoms of the front and rear row cylinders. The important part of the plug is the white insulator. The photos continue to show the lower plugs in both rows are running leaner than the upper plugs. This may be a result of my impeller/plenum design, but it's not at all obvious to me how I was able to invert the result compared with the H-9.
A model builder used to running alcohol may find these 'filthy' plugs appalling; but, for a gasoline model, they really aren't that bad. A proper heat range plug in a modern full-size fuel-injected engine typically won't show any insulator coloring when running on unleaded gas. In a model engine, though, carburetor tuning is always a compromise; and plugs with heat range options aren't available. Carb tuning and, to some extent, the reach of the plug into the combustion chamber are the only tools available to control carbon deposits on the insulators. If the carb is leaned as much as practicable, but the insulators still accumulate deposits that eventually affect the spark then a shift to an alternate fuel may be the only option. Personally, I've come to prefer gas over alcohol because of gasoline's easier starting due to its higher volatility as well as its lower production of water in the crankcase due to combustion. 
The cold rainy weather has settled back into our area. When it clears out I plan to work on the idle mixture.
While tying up some loose ends I also added a crude oil filter to the engine's oil line just after the drip feeder. It was made by drilling an array of .020" diameter holes through an inline bronze plug. It's purpose is to prevent chips that might have been inadvertently left behind from being recirculated. The most difficult part of its construction was clearing the chips left behind during its own construction. - Terry


----------



## Sparky_SC

mayhugh1 said:


> At this point the engine has plenty of throttle left to rev past my self-imposed maximum of 3500 rpm, and so I'm confident the carb size is adequate.  - Terry



I've been following this thread since the beginning and its simply fantastic work.

Have you considered that perhaps the "load" (prop) on the engine is insufficient for the power the engine develops?   That would give max rpm with a lot of throttle opening left.

I am sure the engine is a beast in its power developed,  the prop load is just a thought.     It would affect tuning.

George


----------



## Art K

Terry,
Just out of curiosity could the Y in the intake tube be having an effect on the fuel mixture between the front and rear bank of cylinders? That wouldn't affect the top and bottom mixture but might affect front to rear. But then again with a little fine tuning you may have the balance as well or better than can be expected.
Art


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## mayhugh1

George,
Thanks for the comment. You're very correct about the engine not being significantly loaded during any of my testing. The actual output horsepower from a static test like the ones I'm doing is dependent upon the diameter and pitch of the propeller, the engine rpm, and some air density parameters. When I was in the process of obtaining my prop I used the static thrust calculator located here: http://personal.osi.hu/fuzesisz/strc_eng/  to input its parameters (3-blade, 28x12) and came up with an expected 29 pounds of thrust and 3 output hp while running at 3500 rpm. The prop I'm using wasn't selected for its performance but for its availability. I realized at the time it was much too small to pull a significant fraction of the expected power available from this engine at the maximum rpm I was willing to run. But, that was OK because I wasn't building a flyer but a running display model. With my own imposed maximum 3500 rpm and the current prop, 3 hp is all the engine will ever be asked to put out. My comment about the Perry carb being a good size for this engine was made entirely in this context. If I were building an actual flyer with a performance-selected prop I'm sure it is too small.
...
...
Art,
Indeed, I was concerned about the quality of the Y-connection between the front and rear row intake tubes. I knew that if I didn't have gradual and smooth splits in these tubes there would be fuel distribution differences between the cylinders in the front and rear rows. If you'll remember, I put a lot of effort into getting the interior and exterior seams matched as well as I possibly could. I even pulled a few test joints apart to make sure the solder wasn't leaving a ridge on the interiors of the joints that could disturb the flow.
I was really concerned when, after all that, I saw a significant difference in richness between the front and rear row plugs during my first good runs. It now seems the plug readings from those runs were flawed by the operator, and the last more methodically-done test showed no difference between the front and rear rows. This will still need to be verified, though, at lower speeds and during idling. The persistent differences between the upper and lower cylinders is still a mystery, however.
Terry


----------



## Mattsta

Terry

What is the spur gear spec used in this engine?

Are they metric spur gears or imperial. I guessing they are about metric module = 1 but the imperial sizes 24 and 32 DP both seem to give the wrong diameters


----------



## mayhugh1

Mattsta,
They are all imperial gears 14-1/2 deg pressure angle and assorted DP depending upon the particular gear. Did you have a question about a particular gear? - Terry


----------



## Mattsta

mayhugh1 said:


> Mattsta,
> They are all imperial gears 14-1/2 deg pressure angle and assorted DP depending upon the particular gear. Did you have a question about a particular gear? - Terry


 
Hi Terry.

Well.......all of them really!

I guessed they were 14 1/2 gears from the shape of the teeth

I was looking at the teeth you cut into your crankshaft and was wondering what size the gear is. I assumed 16 teeth on a 0.5" PCD since this a standard regularly available gear size (32 DP) and with the addendum added, the OD of the gear would be just slightly smaller than your main bearing journal. This is all assumption on my part however!

I've designed a set of gear templates in Pro/Engineer CAD software and I can create any spur or helical gear in any configuration I like in a matter of seconds. I have input paramaters for PCD, number of teeth, pressure angle and helix angle (which is set to zero for straight cut teeth).


----------



## mayhugh1

Mattsta,
The front and rear cam drive gears that I cut into the crankshaft were .5PD, 16t, and 32 pitch. I made the (tiny) cutter to cut these integral gears. And, your assumption about their diameter is correct.
The large jackshaft gears were 1.0PD, 32t, and 32 pitch. I used a commercial gear cutter to make these.
The small jackshaft gears were .5PD, 12t, and 24 pitch. I also used a commercial gear cutter to make these.
The oil pump drive gear was .938 PD, 30t, and 32 pitch. Again I used a commercial gear cutter to make this one.
The internal cam rings were 2PD, 48t, and 24 pitch. I purchased these from Amazon, of all places.
The distributor drive gear and the driven gears were commercial gears H-2410R and H-2420R, respectively, also purchased from Amazon. - Terry


----------



## Mattsta

mayhugh1 said:


> Mattsta,
> The front and rear cam drive gears that I cut into the crankshaft were .5PD, 16t, and 32 pitch. I made the (tiny) cutter to cut these integral gears. And, your assumption about their diameter is correct.
> The large jackshaft gears were 1.0PD, 32t, and 32 pitch. I used a commercial gear cutter to make these.
> The small jackshaft gears were .5PD, 12t, and 24 pitch. I also used a commercial gear cutter to make these.
> The oil pump drive gear was .938 PD, 30t, and 32 pitch. Again I used a commercial gear cutter to make this one.
> The internal cam rings were 2PD, 48t, and 24 pitch. I purchased these from Amazon, of all places.
> The distributor drive gear and the driven gears were commercial gears H-2410R and H-2420R, respectively, also purchased from Amazon. - Terry


 
Awesome!

That's saved me some serious head scratching!

Thanks Terry


----------



## mayhugh1

We've been out of town for several days attending my grandson's birthday, but while the nice weather continued I managed to add runtime to the radial. So far, I've accumulated about 45 minutes of two minute (full tank) runs at various rpms with complete cool-downs in between. I've checked the plugs several times, and the results are pretty much always the same. The front and rear row plugs are always similar and have acceptable colors. The bottom plugs in both rows still show slightly leaner running conditions compared with the plugs in the upper cylinders. The final plug photos show these results which are still a bit of a puzzle when compared with a typical nine cylinder Hodgson-type radial.
I've done some thinking about this unexpected difference using a SolidWorks assembly model of the rear section of the engine. The lean conditions in the lower cylinders are probably created by the distributors which protrude into the plenum just ahead of the carburetor. The T-18's dual distributors with their relatively large helical gears take up a considerable portion of the plenum volume between the carburetor and the impeller. Much of this 'blocked' volume is below the center axis of the impeller; and, as such, the fuel distribution may be biased toward the upper portion of the plenum. One of the photos shows the rear section of the engine including the distributors behind a transparent model of the impeller. It's an interesting but very minor result given the engine is a running display model.
One-eighth turns in either direction of the idle disk still have little effect on the idle which is more of a mystery. But, the engine is capable of reliably idling at 900 rpm when the disk is within an eighth turn of its stock position, and I'm totally satisfied with that. If I were using a larger prop, I'm pretty sure I could throttle the engine down a few more hundred rpm. 
I'm still not yet recirculating the oil since the bluing on the cylinder walls is still being polished off by the rings. There has only been about a pint of oil flushed through the running engine so far. Closing the oil loop is the last step that remains before the engine is retired to a shelf in my shop, and then I'll start thinking about the next project. I don't plan to make another video, after all, since my last attempt ended up with even poorer quality than the original video I made. - Terry


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## gus

Watching and soaking up all your experience building this fanstastic engine. 
V-2 material not in yet. Gus idling and surfing net.
Take Care.


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## Scott_M

Hi Terry
Come on, those plugs look great ! I do not see enough difference to be of any concern.
I have a 1969 AMX with a 390 and a cross ram dual quad manifold with a large plenum and 2 650 double pumper Holley's. My 8 plugs show more variance than yours. And my car runs like a rapped ape.
I think that you may be being just a tad too critical. What you have done is an absolutely amazing accomplishment. And you did it in a miniature scale, plus it sure sounds good.
I really hope you reconsider the "no new video" statement.
Another vid from the firewall side would be really great, tach, throttle and all the good stuff you have spent so much time on. please, please, please.......
I'll send you my camera if you want.

And once again, thank you very much for taking the extra time and effort to share it with all of us.

Scott


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## Mattsta

mayhugh1 said:


> Closing the oil loop is the last step that remains before the engine is retired to a shelf in my shop, and then I'll start thinking about the next project. I don't plan to make another video, after all, since my last attempt ended up with even poorer quality than the original video I made. - Terry


 
R-4360 Terry!

You know it makes sense!

;D


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## Chaos_Industries

Hi Terry!

First of all I want to congratulate you to your fantastic work!

I`m sorry that I didn`t answer your question on the youtube comments. I have overlooked it. If I had known of your project a little bit before maybe I could have answer you a lot of questions.

It looks like you have cut out two windows into the cover plate of the impeller to get space for the distributor drive. My engine has a solid cover plate without any holes. Maybe this is the reason for the leaner lower cylinders but i would not change anything on your engine. In my opinion your spark plugs look really good.

I havn`t found better pictures but you can see how it looks like.

And an additional picture where you can see the oil sump 

Regards,
Christian


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## Charles Lamont

Just an idea which I do not have time to think through just now: are the impeller blades in the same position relative to the induction ports as the inlet valve opens for each cylinder?


----------



## mayhugh1

Christian,
Thanks very much for your comments. For the rest who have been following my build, if you look back at my very first post you'll see that the Chaos_Industries' build was the original inspiration for my engine. I downloaded and carefully studied hundreds of their online build photos to come up with the design of my engine. My Hodgson 9 drawings were an additional resource for the cam rings and front crankcase section. I built only one engine, but they built two at the same time!
A difference between our engines is, as Christian points out, that my air guide is integral to the rear cover; and I machined clearance cavities for the lower ends of the distributors instead of completely 'shelling' out the rear cover. My rationale for going this way was to reduce the volume of what seemed like an overly large plenum, but my decision was based more upon groundless instinct than any science. In the end, my distributors are likely influencing the flow - for better or for worse - more than the distributors in Christian's engines. 
Another difference, and this addresses Charles' question, is the number of blades on my impeller. If you compare the photo of my impeller with Christian's photo, you'll notice his has nine blades which matches the number of input ports while mine has only seven. I used seven blades because that was the maximum number I could fit into the available machining space using the profile cutter I had. I could have changed the machining strategy and used a smaller cutter, but I was afraid the resulting chatter would have been unacceptable in my particular setup. So, instead, I tried to come up with a design reason to justify seven blades. The only thing I could come up with was that when it came time to install a nine blade impeller, I might end up with an unfortunate positioning that would consistently block an intake port during a critical portion of the intake cycle. At the end of the day this didn't pass the B.S. test, but along the way I realized the exact number of blades probably wasn't really critical. 
So, Christian, I can't help but be curious about your own results. I've watched both of your YouTube videos and your engine(s) run really well. Do they also start easily, and do you see any differences in your plugs between the upper and lower cylinders or between your front and rear cylinders?
By the way, another great feature of your engine that I really wish I had incorporated into my own are the pushrod tubes. Without them, there is just no way to eliminate the prop wash-induced oil spray created by the seepage around the lifter bushings, especially on cold start-ups. - Terry


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## hussien95

Engine in very magnificence
Good job my friend.
:bow::bow::bow::bow::bow::bow::bow:


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## mayhugh1

I thought it might be interesting, if not prudent, to do a few calculations on the engine's power handling limitations. These calculation might be useful to others when it comes time to select a prop for their own radial. The first calculation is the maximum torque, from a materials perspective, that the crankshaft is capable of handling. In this engine the full power is transmitted to the propeller through the front crankshaft section. The average diameter of this section is .500", but there is a short portion just forward of the cam drive gear that is only .420" in diameter, and this is likely the weak point of the shaft. These first order calculations ignore any effects from stress risers in the corners left behind by machining as well as the 1/8" diameter PCV vent that was drilled through the front section.
The T-18 crankshaft is constructed from 12L14 steel which has a yield strength (tensile) of about 60,000 psi. Since the crankshaft is torsionally loaded it's the torsional yield strength that's of interest. This is typically estimated at 60% of the tensile value which, for 12L14, is about 36,000 psi.
From high school physics, a torque T (in-lbs) applied to a shaft of diameter d (inches) creates a torsional stress s (psi) according to the expression:
s = 16 * T / (pi * d^3)
The torque corresponding to the torsional yield stress at the crankshaft's weak point is:
T = s * pi * d^3 / 16
T = 36,000 * pi * .420^3 / 16 
T = 523 in-lbs
T = 44 ft-lbs
This number is in line with the destructive test results I recorded earlier during the design of the crankshaft.
The T-18, being a display model, is run only under static conditions. That is, a prop is fitted to the crankshaft, and the engine is run while being fixed to a bench. As a result, a static thrust is generated by the prop which tries to pull the engine forward, and the crankshaft is loaded by the power creating this thrust. The amount of thrust is dependent upon the pitch and diameter of the prop, the engine rpm, and the air density. An online static thrust calculator such as the one located at: http://personal.osi.hu/fuzesisz/strc_eng/ can be used to compute this thrust as well as the power generated by the engine. For example, with the current three blade, 28 x 12 prop running at 3500 rpm, this calculator predicts the engine will generate about 30 lbs of thrust and 3 hp. The horsepower can be easily converted into crankshaft torque using a well known equation relating the two:
Torque (ft-lbs) = HP * 5252 / RPM
While the engine is generating 3 hp at 3500 rpm the crankshaft torque is:
Torque = 3 * 5252 / 3500
Torque = 4.5 ft-lbs
which is an order of magnitude lower than the crankshaft's yield point. (NEMA standards use much larger safety factors for electric motors since they must contend with loads having high torque starting and stall conditions.)
The forward thrust which is totally supported by the engine's front bearing should also be considered. The T-18 crankshaft is designed so its loaded front section can move forward a few thousandths until a shoulder located just forward of the weak point contacts the inner race of the front bearing. This bearing is a generic 1/2" i.d. deep groove ball bearing. The axial load rating for these bearings is a complex quantity and is generally unspecified. An axial load pushes the balls up and onto the flat side of the race where the increased contact pressure and surface finish increase the probability of brinnelling. Conservative designers wishing to not impact bearing life with excessive axial loads will limit them to a few percent of the bearing's specified radial load. In this application, however, where dozens of hours of bearing life may be sufficient; an arbitrary 10% load factor may be acceptable. The radial load rating of the T-18 front bearing is 500 lbs which gives an arbitrary axial load rating of 50 lbs.
Shaft hp is a sensitive function of rpm in a statically loaded run. Using the same propeller, but running at 5000 rpm, the calculator predicts an increase in thrust to 60 lbs, and a shaft power of almost 9 hp. This level of output power is at the edge of any reasonable estimate of this engine's capability and is likely beyond the volumetric capacity of the existing carburetor. At this rpm and power level, though, the crankshaft torque increases to nearly 9.5 ft-lbs.
There is still almost a 5X safety factor at this increased level of torque, but it is common practice to maintain at least this level of margin to guard against second order effects such as fatigue and repetitive stress loading.
It is certainly possible to select a prop that will load the crankshaft dangerously close to its yield point even at a modest 3500 rpm. A three blade 36 x 16 prop is also available, and this prop will load the crankshaft with nearly 17 ft-lbs of torque in a static run. - Terry


----------



## Cogsy

mayhugh1 said:


> Conservative designers wishing to not impact bearing life with excessive axial loads will limit them to a few percent of the bearing's specified radial load. In this application, however, where dozens of hours of bearing life may be sufficient; an arbitrary 10% load factor may be acceptable. The radial load rating of the T-18 front bearing is 500 lbs which gives an arbitrary axial load rating of 50 lbs.


 
Just for a bit of extra info, when I worked at SKF and we had to design bearing arrangments, the basic guide was deep groove ball bearings could accept axial load in the order of 10% of actual radial load, rather than rated radial load. As the actual radial load of the bearing increases, the chances of skidding, or sliding ball contact is reduced. So in very light radial load situations, the axial load capability can be very low indeed.

I think you'll be perfectly fine in this engine, but I thought I'd mention it in case it influenced you bearing choice in future projects.


----------



## mayhugh1

Cogsy said:


> ....As the actual radial load of the bearing increases, the chances of skidding, or sliding ball contact is reduced. So in very light radial load situations, the axial load capability can be very low indeed.....



Cogsy,
Thanks for your experienced comment. It makes a lot of sense and is filed away for future reference. It probably explains why motorcycle wheel bearings can survive the side loads they encounter in lean turns. - Terry


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## Charles Lamont

mayhugh1 said:


> It probably explains why motorcycle wheel bearings can survive the side loads they encounter in lean turns.


Side loads, eh? You had me for a couple of minutes.


----------



## mayhugh1

Thanks to everyone for following my build and also for your comments along the way. I'm working on a second video as requested by Scott who's been religiously following this project from its start.
I plan to start another long term build, but it's been difficult finding another engine into which I'm willing to invest years of effort. I've developed a fondness for the WWII aero engines, but I'm not aware of any bar stock plans with the right level of complexity to keep me interested, and I'm not sure I want to build another radial right now.
The Rolls Royce V-12 Merlin, probably the most influential WWII-era engine used in the British Spitfire and American P-51 warplanes, has all the complexity I could ask for. I was fortunate to have purchased what might be the last available complete set of castings from the owners of Dynamotive, a small (now defunct?) San Diego start-up that planned to build and sell quarter scale Merlins a decade ago. I don't believe they ever produced any engines but instead sold off the castings they had so laboriously created to individuals to build their own.
The castings I received were investment cast and can be best described as large pieces of jewelry. They include all the intricacy and realism that was a part of the full-size engine. 
I've no experience in working with castings, and was taken back by the note accompanying them that being long, complex, and thin-walled; they will likely require straightening and, in some cases, heat treating.
My set of castings includes those for a functional supercharger, but it's not clear whether its scaled development was ever fully completed or just how much of it became a part of the prototype that was produced. The original designers opted for a glow plug engine, and so the magneto development was never completed. Finally, the notes mentioned fuel distribution issues with the Merlin's scaled-down intake manifold. The developers eventually designed an alternate configuration with multiple carburetors in order to get their prototype to run, but there doesn't appear to be information on its design. Over-heating issues were also mentioned, and I noticed a prop was never fit to their running prototype. Working these issues will hopefully make the project interesting, but I wish it wasn't going to involve very expensive and irreplaceable castings.
I've been able to find online evidence of only three other builders who have tackled this project using these castings. One posted his crankshaft build on 'the other' forum but he never returned after producing his own piece of art.
My plan is to spend the next month or so evaluating the castings I have so I can better understand the issues involved with straightening them. My first goal will be to get the castings to a point where, through straightening and minimal machining, they fit perfectly together before I commit to the project and begin making parts for it. My plan B is the same plan B I had for my 18 cylinder radial project, and that is to build Ron Colona's 270 Offy. -Terry
- Terry


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## kvom

Lots of gears in that engine.  I'll be following along.


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## Scott_M

Thanks Terry !

The Merlin sounds like an awesome project. Back in the 70's I saw a car at the drag strip named "Allison Thunderland" A thunderbird with an Allison V12, it had quite a unique sound. I was looking on Google to try and find a picture and stumbled across this , Just in case you needed something to do with the "18"








Scott


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## petertha

mayhugh1 said:


> My first goal will be to get the castings to a point where, through straightening and minimal machining, they fit perfectly together before I commit to the project and begin making parts for it. My plan B is the same plan B I had for my 18 cylinder radial project, and that is to build Ron Colona's 270 Offy. -Terry
> - Terry


 
Cant wait to hear your evaluation details Terry. The ultimate decision will be a win-win for us regardless of what you decide. But I think you should build us a dynamometer in the meantime... just to keep the hands busy 

I was about to 'wonder out loud' if your SW + CNC proficiency could replicate castings from bar stock on a design of your own choice... kind of along the lines of what Mr. Britnell does on manual mill with post-blending & finishing. 
http://www.modelenginemaker.com/index.php?topic=3846.165
Guessing this method brings forth different challenges & trade-offs; work holding, post machining distortion, no reverse cavities etc. Maybe more applicable to simpler/earlier gen V12 like a Liberty? 
http://en.wikipedia.org/wiki/Liberty_L-12#Variants

But I get the sense you are targeting something even meatier  The detail & intricacy of those Merlin castings... gosh, jewellery for sure. So they are no longer available in case of machining mis-steps?
http://www.quarterscalemerlin.com/prices.htm

Another link FYI showing some analogous casting & engine components. Don't know anything about it though.
http://pace-engines.com/index.php?ID=1


----------



## mayhugh1

petertha said:


> Cant wait to hear your evaluation details Terry. The ultimate decision will be a win-win for us regardless of what you decide. But I think you should build us a dynamometer in the meantime... just to keep the hands busy
> 
> I was about to 'wonder out loud' if your SW + CNC proficiency could replicate castings from bar stock on a design of your own choice... kind of along the lines of what Mr. Britnell does on manual mill with post-blending & finishing.
> http://www.modelenginemaker.com/index.php?topic=3846.165
> Guessing this method brings forth different challenges & trade-offs; work holding, post machining distortion, no reverse cavities etc. Maybe more applicable to simpler/earlier gen V12 like a Liberty?
> http://en.wikipedia.org/wiki/Liberty_L-12#Variants
> 
> But I get the sense you are targeting something even meatier  The detail & intricacy of those Merlin castings... gosh, jewellery for sure. So they are no longer available in case of machining mis-steps?i
> http://www.quarterscalemerlin.com/prices.htm
> 
> Another link FYI showing some analogous casting & engine components. Don't know anything about it though.
> http://pace-engines.com/index.php?ID=1



Peter,
I studied these castings also wondering if I could duplicate any of them if I happened to ruin one or two. Except for only a few simple cases the answer is pretty much no. The reach with long skinny profiling tools into the interiors of a typical part is beyond my and my machine's capabilities. 
I don't know how George B. does what he does manually. When I was at the Ohio show last year I got to see inside a few of his masterpieces where he had left the finish as machined with no filing. The interiors looked like perfect roughing-pass CNC surfaces. I couldn't see any 'oops' areas as closely as I looked. I mean it looked like he had twisted the x,y, and z dials using 5 to 10 thousandths step overs over the entire surface using what in my world is called a complex plane machining process. He once complemented me on my patience with forming the T-18's intake/exhaust tubing. What I did was nothing compared with what he did on those roughed surfaces.
I ordered the Merlin castings last year from the website you mentioned. It took weeks to get any response which left me thinking the site had been orphaned. Then one day I got a reply telling me they thought they might have enough castings left to make up a complete set. I asked them to check for sure before I ordered because I sensed I better start out with everything already in hand. A week later I got a message saying they had been able to round up a complete set of parts, and so I sent them a check for the full amount. Three weeks later I had the castings. Hopefully, if I really get deep into this project but run into a catastrophic problem with one of the parts they might have a replacement sitting around that I could purchase.
I wish I had known about the PACE engine at the time. After studying their website I think I might have gone with them instead. It looks like they might have taken liberties with the design to simplify the engine and perhaps get a more reliable scaled-down running engine. As Kvom remaked this thing has an unbelievable number of gears in it. The castings I have look more faithful to the Merlin engines whose photos I've seen, and the designers' notes seemed to continually emphasize their goal of building an actual Merlin. Their adherence to even the hidden webbing details inside the crankcase, for example, is remarkable to me. So, It's possible I might find out some day how well their design scaled  down to an actual running engine. - Terry


----------



## wirralcnc

I also have a full set of dynamotive merlin castings. I purchased last summer so must of got one of the last sets.
I think you should make a start on this great engine and then I can use all your knowledge from the build when I finally get round to building mine.


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## mayhugh1

Or maybe we could do a 'group' build?


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## Paul Erland

How about considering one of the WW2 sleeve valve aircraft engines?


----------



## Charles Lamont

Just in case you are not aware of it, Here is Barry Hares' 1/5 scale Merlin running:

[ame]https://www.youtube.com/watch?v=0xe1LL1IC7Y[/ame]

His next project leaves me dumbstruck:

http://www.modelenginenews.org/~modeng74/gallery/croft/eagle/index.html


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## mayhugh1

His work truly is remarkable. I found his webpage sometime ago when I was researching the Merlin and drooled over his model. He must do his own castings not to mention all the research needed to come up with a set of plans from which to work. In the video what you seem to hear most is all those internal gears. He probably included every single one of them. He is definitely one of a kind. It would be an honor to spend a month with him in his shop watching him work. - Terry


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## wirralcnc

What about a pratt and whitney r1830 radial from castings 1/6 scale. Bruce satra made the castings and I believe paul knapp has taken over.


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## mayhugh1

wirralcnc said:


> What about a pratt and whitney r1830 radial from castings 1/6 scale. Bruce satra made the castings and I believe paul knapp has taken over.



I have trouble with those really tiny parts nowadays. I have trouble seeing them, my fingers can't hold them, and someone keeps coming into the shop to hide them from me. - Terry:wall:


----------



## digiex-chris

I'm so glad I got caught up with this thread. Thanks for all of your detailed diagnostics and math, it's really helping us that are getting started designing an engine from scratch! I really love the sound of the thing. Very nice!


----------



## Mattsta

Hi Terry

I'm attempting to model an 18 cylinder radial in Pro/Engineer, similiar to Solidworks. This is just a bit of fun. I don't have the skills to even begin being able to produce one.

As you can see from the attached images, my connecting rods are too short and approaching TDC, the piston is still only half way up the bore. I'm doing this purely from photographic reference as I don't own Hodgson's drawings. The PCD of the journals on the crank and master rod is all correct so I must have the length of the master rod and slave rods considerably shorter than they should be. What length are they?


----------



## mayhugh1

Mattsta,
I used 2.700". - Terry


----------



## Mattsta

mayhugh1 said:


> Mattsta,
> I used 2.700". - Terry


 
Splendid

That's better!


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## robcas631

Terry,

What you have accomplished is outstanding! 

Rob


----------



## petertha

mayhugh1 said:


> If the engine is allowed to sit a few days, there is also some oil from one or two lower exhaust pipes whose cylinders were left standing with open exhaust valves. If I were starting the engine build over, I would include pushrod tubes.


 
Hi Terry. Early on the build thread you mentioned not bothering with pushrod tubes (or maybe you just preferred the exposed pushrods to see motion etc). Later in post #374 you mentioned tubes might be a good idea in hindsight. Can you elaborate? I didn't quite get the connection between the oil/exhaust & the tubes. Just overall cleanliness of grit getting into the pushrod ball end interfaces? Or would tubes somehow be used to contain lubrication? How is any lubrication contained on the upper pushrod ends in any event? (what prevents them from running dry?)

I could have sworn there was a pic/vid showing tubes on your engine, but now I cant seem to find. Maybe I'm mixed up with this build. (I'm having an issue accommodating the 3d pushrod/tube geometry, I think that's what these ball-in-socket ends are all about).
https://plus.google.com/photos/111407870409657577971/albums/5278304464310065009?banner=pwa

Anyway, just wondering if you had thoughts or since modded your engine in that regard.

thx/Peter


----------



## mayhugh1

Peter,
I didn't use pushrod tubes on either of my radials. What you may be remembering was the small diameter hypodermic tubing I added to tbe pushrods on my 18 cylinder radial in order to build up their diameters for cosmetic reasons. If I were doing it over again I would include pushrod tubes because most of the oil leakage over time comes from the lower lifter bushing clearances. - Terry


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## dondoerner

Beautiful work. Would anyone share a copy of this design in pdf or Solid edge or ACAD.
Much appreciated 
Don Doerner
[email protected]


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## mayhugh1

Don,
I extended the design of the 9 cylinder radial plan set that I purchased from Agelessengines.com to come up with my 18 cylinder radial. Ageless also offers plans for an 18 cylinder engine. - Terry


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## ChooChooMike

WOW, JUST WOW !!! th_confused0052  I've seen smaller models (5/7/9 cylinders), but haven't seen a running 18-cylinder.

None of us are worthy !!! :bow: :bow:

Mike


----------



## Stieglitz

Hi Terry,
           Totally gob smacked,lost for words,just have to watch.
Thank you for for taking me on the journey.
Cheers
Allen.


----------



## Bentwings

Hi.
im just getting started on Solid works modeling of this cool engine. It’s a bit overwhelming at first but your nice description and pictures really are helping. I’m used to building 2-3000 hp Hemi Engine not something micro miniature. One of my sons just bought a new mill and lathe. Not full sized thing like you have however. We debated a long time about getting a cnc set up but we each have different products and goals.   I’m an engineer by trade with toolmaker experience so I’m comfortable around machines and chip making.
my goal to start is to complete the three d model with the fixtures  so I have a better feel for making this engine. There are a lot of parts and fixtures .

anyway it really nice to se the beautiful machined parts. I hope I can at least  show something similar. I’ve had some medical issues so my shop efforts will take much care on my part. I must not let my doctor know of this. He has restricted from even playing tiddlywinks winkys due to eye injury.LOL.  


SO KEEP UP THE GOOD WORK.

HERE IS MY EMAIL.

Byron Nelson

[email protected]


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## Bentwings

I’ve been away for a while with login issues then this double vision thing came up . I hope you can forgive some spelling and context mistakes it’s very difficult to type.I do proof read but it hard to se some mistakes with a patch eye and magnifying glass. As a result I’m really limited in the shop. I’m not eve supposed to be thereno Ridley winks either. Without safety glasses.LOL

Anyway I think I understand your crankshaft. I came the same conclusion that many trial assemblies would be necessary so pressing the crank together seemed out of the question. Many years ago when we first started using narrowed rear ends in our dragsters. Custom axels were not available yet. The solution was to use a large axel cutbit off the flange and machine it for a common bearing. Then bore the old hub or new one for a press fit and weld it on the seam. It worked for a while but post weld heat treat was hard to get so the solution was to drill for a dowel pin on the joint line and weld this apparently reduced the stress on the welded joint as there were few issues until the very high power motors were developed axel came about then too . It appears that you have come up with about the same solution without the weld do the cranks are more easily separated. Looking at the original full size Gleason gear works created a spline and socket with a massive bolt to hold the crank in alighment for assembly. The square key seems ok so that’s good if the tool blank is square an true. So nice job with a nasty problem.  I haven’t finished my cadd model yet due to this med issue. There is no glasses solution to fix a messed up brain in fortunately. I’m reduced to transferring my old machine shop and welding skills to my son and grand son. Twin nice people to have around. My cat helps with personal comfort. I’m training her to wak on a leash so I can get out and about.. I’ve looked into service dogs but the stimulus package is still unsolved. There may be help later. Service dogs are very expensive 10_20 grand or more. I did find two retired ones but they were on opposite coasts and transportation was just too much.  You can fly out and bring them back but sometime you have to buy a seat. Often you may need proof that you have had instructive trading with a specific dog especially a large breed. The really can only sk two question. Is this a service dog. If you respond yes they can ask what service do’s he provide. You explain briefly but no demo is necessary. The dog must be very stable and be quiet. No other documentation is necessary or legal there are no registry in the us recognized by threads. Regardless of what sales people tell you. Flashing a fancy document or business car can get you removed in many states. More and more are becoming wise to fake registries. Our state had laws pertaining to this but not police enforced.vests are not necessary you don’t have to be polite if someone tries to pet or distract your dog. My 6 yr old saw the star trek episode that a guy touched 7 of 9 inappropriately and she said remove your hand before I remove it from your arm. Never under estimate a 6 yr old. He was holding my K9 dog leash and a guy reached over to pet the dog. My son said touch me or this dog and you may have one less @&$? hand. 100 pounds of dog 60 pound boy. The guy backed away the dog had a smile that only German shepherds have.  He probably had been around dad on a bad day. LOL. Kids are more observant than you think.
Nice job on your parts. I’ll try and follow more closely from here.

byron


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## Bentwings

Wow that was a lot o reading.  I s a huge amount of research and trial error and redo happening in the quest of perfection. I can’t in any way take away from this. Great work , all of the contributors.  
ill
Add a couple of comments myself. Certainly not in any attempt o refute what as been said and done I’ll just add my experience as automotive engine builder ant ex top fuel racer.
Kinda backing up let’s look at leak testing. This has been a backbone of the auto world since he ‘60 maybe even before that. About that time Sunnen honining was popular. I even ran the shop hone machine as a machinist apprentice . This simple device allowed unbelievable tolerances to be achieved in a relatively crue machine shop virtually every type of metal and semi metal was honed to perfection as needed the Sunnen rep was in the shop about every week with the latest things. I think we has samples of about their full line. This is where I’ll get to the leak tester shortly . A lot of cylinders were done carbide rings for the beverage can industry were a big part of the company I worked for. They got into war materials as the viet bam was grew there were lots of close tolerance items honed. Temp control both in inspection and as the shop machines was carefully monitored all the one there were gages and surface finish devices that were brand new to the industry that ere brought in almost daily the US government paid dearly fir these and the training to use them . I was fortunate to be a part of his.  Just breathing on parts could cause measurable changes in size . You didn’t just walk into the inspection dept. there was an air lock. If you ere hot and sweaty, you had to cool off before the door opened . You often had to request permission to be admitted if you had a good reason you ere allowed in . If you just wanted a tool verified you often handed it through s portal after calibration it would be returned.  Anyway it gave us apprentices a good introduction to what tolerances were about.

leak tester. As soon as got into big time drag racing I found leak testers Sunnen was the big maker of these and it was one of your first race tools they were very expensive then but easy to use. I just looked on Amazon and you can get a nice set for under $100 now. I think they were around $400 back then in 1960 dollars . Weeks pay.  These all work about the same you simply have a spark plug to air hose adaptor on the line from the tester it I turn is hooked to shop air or air supply. You set the piston to top dead center You adjust to fluid flow to the shop air the hook the spark plug line up and read the leakage. Some times you can pull the engine into compression and read at a certain angle or position of the piston . Some of these read in reverse but the number comes out the same . We used top dead center as that was where cylinder damage occurred mostly it would indicate a lifted ring land about 2% was considered good 5% and you had burned piston . I haven’t used this on model engines . At the time I was into high performance glow plug engines
These had ABC cylinders aluminum cylinder bronze liner with chrome facing the pistons ere lapped to slightly stick when cold at top center. This went away as soon as they ere run. Most of these engines were from . 40 cu in to . 91 chin rpm was abou 20 k plus or minus.  Life was a few minutes. Very high nitro fuels  later came weed eater types . Ironically I don’t recall leak testing one rpm with a given prop was the gage.

moving on in life I was laid off of my engineering job an went to Huntsville to work at international diesel . Here was a brand new engine manufacturing plant my honing experience put in charge of the honing operation of a v8 Diesel engine this was a fully automated manufacturing operation with just in time delivery of raw castings to finished ready to install engines. Here the blocks came to the hone with about .005 stock to be honed out for finishing this was done in three steps rough hone took about .002 1/5 out while the second step brought in the size to about .0005 with the final plateaue brought to final size al honed were cubic boron if any honed were changed during a shif it was rare it required a special inspection of a given block. It was easy to just poke a button and the block was electronically marked and diverted to the inspection station. Where a full coordinate measurement was done and recorded. There was an in process inspection I had to do on ever 50 th block this involved temp verification gage qualification then plugging in the gages or direct input to the data base . 
a little bit about these gages. These were all air calibrated obviously pressure monitored ring gages slipped over plug gages and the leakage vs pressure exactly monitored and input to the data base. Tolerances were in the 6th decimal place adjusted automatically to temps.
It was unusual to reject a single block in a 10-12 hour shift . These blocks were processed one block per minute through each station so a lot of cast iron got move d each night .  Ironically this job paid better than double my engineering job plus I got room and board. Essentially all the food I could eat  I had lots of sirloin and hot beef lunches  I didn’t gain an ounce 12 hours a day 7 days a week for almost two years  bough me a new van new car and new diesel dusky truck . Plus one heck of an experience in automation. My main engineering line .  I even got to work in the tool setup and grinding room for an extended period. Again automated machinery incredible tools I had never seen before or since. Automated carbide drill making machine also made carbide end mills fro round stock  all this stuff went into the central computer . I had run a much smaller central computer including cad support before so I knew a little about it . Pretty primitive by today’s standard.
I really got off track here sorry 

the point I was after that I YHINK some are missing is that when machining a cylinder bore for example there is a layer or skin of torn metal that the boring tool or drill as the case may be that needs to be removed by honing or as some are doing by lapping . Lapping being the hard time consuming way. In the auto shop when boring a cylinder about .005 was left fir finishing again honing was the answere about.0025 was taken out rough honing the finishing brought the cyl to size leaving the final cross hatch finish. What this did was remove the torn metal leaving a near perfect round well  surfaced surface for the rings to seat on rings ere supposed to be ready to run so I won’t get into finishing racers use a chrome faced top ring either dyke ring or plain ring second rings are filled moly rings today. They used to be cast iron with taper some times reverse taper inner chamfer some times overlap or hapless some very fancy have insert rings  oiled rings have been multi piece with expander as long as I’ve been around. There has always been the dot have gaps alighted.  The diesel plant had a piston ring installation station that installed ring exactly oriented interesting machine . One Christmas vacation my room mate and I were asked to disassemble some 200 engines double time and a half. Hard to pass up so we did we had to record ring position . Not a single piston of all those engines had the rings in the original position there was no way this was a failure ofvthe assembly process there were just too many checks and balances for this to happen. We put wash rod and piston in special boxes for inspection the company engineering mgr came down to see us ripping these engines apart he looked at the piston rings and just shook his head. I can’t feel you how many race engines I’ve seen the same ring rarely are the rings alighted as installed unless the engine blows up before it gets very far down the track . I’ve raken lots of high mileage engines apart with rings in every location. We even did a leak test on a new engine with rings alighted as usual and others alighted @wrong” no difference .  A model maybe I don’t know models don’t scale very well so some full size things just don’t apply . I love to see test results . Fir now I just stagger as we have always done . I’m open to new testing anytime

byron


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## ozzie46

Hi Terry. I am making the Hodgson 9 cyl Radial and I know you used the Jerry Howel design for the distributor for your H 18 Radial. 
When you made the 9 cyl distributor did you use Lees design or Jerrys? I know you placed the Magnets and the Hall Effect at .900 radius on the H18 dizzys, did you do the same on the H9?

I guess what I'm asking is will the .900 radius work on the H9 like it does on the H18? I also used the Jerry Howell design dizzy.

Thanks in advance for your attention to this matter.

Ron Osborn   aka ozzie46


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