Another Radial - this time 18 Cylinders

[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

 

[jwcnc1911]

Wow! You work fast! Looking great!

 

[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

 

[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

 

[oneKone]

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

 

[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

 

[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!

 

[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

 

[ShedBoy]

WOW!

That is all I can say.:bow:

Brock

 

[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

 

[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.

 

[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

 

[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.

 

[petertha]

...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?

 

[mayhugh1]

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

 

[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

 

[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

 

[petertha]

..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,

 

[mayhugh1]

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

 

[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