# My Hodgson 9 Radial Final Assembly



## mayhugh1

I started my Hodgson 9 build in Oct 2011 and have begun final assembly in March 2013. I was originally going to do a build thread, but when I started the project I wasn't yet fully committed to it, and I didn't want to publicly start something that I might not finish. After I did commit, I never got around to starting the thread but I did take a few photos along the way. Even though this thread isn't going to contain a lot of construction photos, I thought some would be interested in seeing the finished pieces and sub assemblies including many modifications I made to the original design. I'll try to do the final assembly and initial running in realtime, though.
My promise to myself was that I would start with the crankcase because, at the time, it seemed like the most difficult part of the project. And if I didn't feel the result was a near-perfect foundation for the project, I would stop and tackle something smaller. I've built only two other IC engines - my first was a Jerry Howell V-twin:

[ame]http://www.youtube.com/watch?v=McRGRD4lQY4[/ame] 
and the second was Jerry's V-4. 
[ame]http://www.youtube.com/watch?v=tEWLgS1Q9eY[/ame]
and I felt both of these were sucessful and needed experience before beginning the H9.
The photo is a picture of my second completed crankcase with the oil sump and lifter bushings installed. I spent a month making my first one and then ruined it during the very last machining step. If I hadn't found a second chunk of aluminum of the right size in my scrap box, I would be working on a different project this month. I machined the crankcase very carefully to Hodgson's dimensions including the permanently attached sump that many other builders don't seem to like. I didn't like permanently attaching it either, but so far it has not been a problem. My only changes to Hodgson's design were to add a magnet and o-ring to the screw-on sump front cover. I also enlarged the id of the drain-back tube in the sump. - Terry


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## mayhugh1

This is a photo of my rear bearing with the pressure/scavenger oil pumps housing installed. The planset calls out aluminum for the front and rear bearings as well as the oil pump housing. I wanted my main bearings machined from SAE660 bearing bronze even though this adds quite a bit of weight to the engine. The oil pumps are positive displacement types and each consists of a pair of driven and idler gears located inside the pump housing. All the gears are on hardened shafts turning in bearing bronze bushings. I added a few more screws to hold the pump housing to the rear main bearing and I also o-ring'd the id of the pump housing to the bearing to reduce leakage. Hodgson supplies commercial part numbers for all the gears but I decided to cut my own. All gears were loctited and pinned to their shafts. - Terry


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## mayhugh1

This is a photo of my cam ring sitting on the main front bearing. I machined the cam ring from 4140 and heat treated it to around R-50. I was concerned about the cam ring warping during the quenching process as the retainer plate is designed to hole the cam ring flat with Delrin followers to within .005". Mine came out dead flat. I loctited the cam ring which was a light press fit to the internal gear but I did not pin it as recommended by Hodgson. I hope this doesn't come back to bit me later. The rest of the gears are loctited and pinned to their shafts. I scratched witness marks on all the gears so I could see if something inadvertently moves. I was also concerned about the machining accuracy of the lobes. Since the cam turns at 1/8 the speed of the crank, a one degree error on the cam ring comes over as 8 degrees of crank error. Hodgson supplies the cam ring profile as a table of lobe heights versus rotation angle in 1 (cam) degree increments. I entered these coordinates into Solidworks to create a CAD/CAM program for my Tormach. When I was finished timing my engine during assembly, my measured error was equal to the resolution of the cam data and so I couldn't ask for more. Hodgson gives commercial part numbers for the gears but I cut all my own except for the internal gear which I purchased. - Terry


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## mayhugh1

This is a photo of my crankshaft. 
I deviated a good bit from Hodgson's planset with the construction of this part. The plans called for making a 5 piece crank and then assembling the pieces together on a custom precision fixture to hold the alignment while the parts were locked together with taper pins. The crank cheeks were to be broached with a square broach and then pressed into the front and rear portions of the crank. The cam drive gear is integral to the the front portion of the crank and so when cut with a commercial gear it destroys the front journal which then must sleeved. The final taper pin is set with the crankshaft installed in the crankcase during final assembly. The taper pins end up in the path of the oil passges through the crank and so the oil paths must be drilled around them at acute angles using another fixture.
I bought the broach and did some experiments on scrap, but I doubted my ability to piece the crank together as intended in what seemed an over-complicated process with so much fixturing. Instead, I turned the whole crank from a single scrap round of mild steel and drilled the hole for the crank pin before sawing the result into two pieces with guaranteed alignment. The cheeks were slit so the master rod journal could be clamped into place with an 8-32 SHCS in each cheek. I had to slightly alter the dimensions of the cheeks a bit for the SHCS, but I was careful to maintain the original balance around the crank centerline. To avoid sleeving the front journal, I made my own tiny spur gear cutter. I ended up only slightly nicking the front portion of the bearing that harmlessly protrudes outside the front main bearing.
The net result was that with .001" clearance for an oil film between the crank journals and the front and rear bearings, the crank spins buttery smooth with no binding whatsoever. - Terry


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## mayhugh1

These photos show the master rod assembly with the slave rods - all 7075 aluminum. I modified the design of the slave rods to give as much cross sectional area to the slave rods for maximum strength without interfering with the cylinder skirts. I modeled the assembly in Solidworks and modified the rod design until I couldn't eek any more strength out of the design. I also experimented with compensating the rod positions to achieve firing at TDC for all cylinders but there just was not enough room to achieve this and so I abandoned the idea. I had difficulty visualizing how I would easily remove the slave rods if I had to disassemble the engine for some reason with the original design which used a pair of cir-clips to retain the slave rod pins. Instead, I used a pair of socket head set screws at each end of the shaft. I drilled and tapped a shallow 2-56 hole at the forward end of the pins so they could be pulled out from the front of the engine after loosening the set setscrews should that become necessary. I added a bronze bearing for the master rod journal. I wanted to do the same for both ends of the slave rods, but there just wasn't room. 
I'm also including a construction photo showing how the rods were machined. They were machined as a batch on my Tormach using their new 3X Speeder. First, I machined one side of them to half depth and then I filled the area around them with Devcon 5 minute Epoxy Gel (available from Lowe's). After letting it cure a few hours, I flip the plate over and machine the rear to slightly greater than half depth cutting them free from the aluminum plate. The cured gel holds the parts tightly in place for near perfect surface finishes. When machining is completed, a heat gun releases them cleanly from the gel. - Terry


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## mayhugh1

These photos show the business end components of the engine. I selected a 23" three-blade commercial prop and then made a spinner for it. The spinner is turned from aluminum and polished, but the rear hex portion is stainless steel and is pressed into the aluminum spinner. This reduces the total weight. I decided to thread the nose of the crankshaft for a left-hand thread since the engine will be rotated ccw to start it and I will be using the hex portion of the spinner to turn it. The front cover is essentially Hodgson's design, but I was able to contour machine the inside to a uniform thickness. A ball bearing is pressed into the front cover for additional crankshaft support. I have only a few tenths clearance between the registering surfaces of the front cover and the crankcase. When the cover is installed there is a barely felt snugness at one position in the rotation of the crank showing that the crank crankshaft alignment is not as perfect as I originally thought. I machined a (huge) delrin adapter for my electric drill to start the engine. It includes a sprag clutch to allow the starter to freewheel when the engine starts. The adapter fits the hex portion of the spinner so the polished portion won't be marred. - Terry


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## mayhugh1

These two photos show my distributor and rear cover. The rear cover is the only casting or, for that matter, the only part that is available for this engine. The cover contains several unused bosses left over from previous revisions of the engine. I removed these and then decided to polish the rear cover. There is an airguide that must be fabricated to fit into the rear cover. I found the drawings detailing the needed machining modifications to the rear cover and the design of the airguide to be totally confusing and so I went off on my own. I finally got an airguide that fit the rear cover exactly, and I loctited the two permanently together after setting the distributor alignment. Basically, the distributor is my own design and resulted from transorming Jerry Howell's V-4 distributor into a 9 cylinder version while keeping Hodgson's external dimensions. Actually, I reduced Hodgson's max OD a bit to give better clearance to the exhaust/intake pipe assemblies. The distributor is an electronic Hall effect distributor with 9 magnets all safely tucked away in the metal base of the distributor. In addition there is a spark shield between the electronics and the high voltage rotor. The ignition is basically a TIM-6 design available on the web and will be shown later in another photo. The distributor was thoroughly tested for fit and functionality once the ignition module was completed. The two were 'burned-in' together for an hour or so. I machined my distributor cap from clear polycarbonate as this will help me locate misfires to a particular cylinder. I did not make any provision to easily advance the timing as a function of rpm. I'll wait and see if this is needed. -Terry


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## mayhugh1

The first photo shows all the fixtures and blanks used to construct the heads and cylinders. I started out with 13 sets trying to get 9 sets, and I ended up with 12 sets. I estimate I have 40 hours of work in each head/cylinder pair not counting the valves, seats, etc. The head is extremely complex because it requires so many machining set-ups. Members of my local metalworking club are surprised that each head was machined from a single piece of stock. The cylinders are machined from 12L14. This was recommended by Hodgson due to the deep narrow grooves that had to be cut to form the cooling fins. I didn't have much trouble with machining the fins, but if I had it to do over again I think I might use cast iron. Many have questioned the longevity of 12L14 as cylinder material in an IC engine. The 12L14 hot blues very nicely, but I don't know if that would be the case with cast iron. I learned from experiences with my other two IC engine projects that the cylinder bore, ring fabrication, and fit between the two need to be taken seriously. I used the Trimble method -same as for myV4- for making my rings. According to my measurements (and they are very difficult to consistently make) I should be OK. My personal go/no-go test was to test for light escaping between the ring and the cylinder when illuminated by a flashlight. A few of my rings failed this test and were discarded. I needed 18 rings and so I made 30 in two batches of 15. 
Hodgson's drawing for the head is a single sheet and so one must visualize the machining from his 'process' sheets. I struggled for days with this until I stumbled across Tom Blough's website detailing his head machining steps with lots of helpful photos:
http://thebloughs.net/hobbies/metalworking/hodgson9/cylinders/055/
This was a Godsend for me and I followed his process closely. That is, I followed it until it came to the valve seats. I have had so much trouble with getting valves to seal that I didn't want to follow (a new to me) Hodgson's design which included pressing in individual seats, leaving a sloppy fit between the valve stem and the integral guide in the aluminum head, cutting the seat 1 degree off from the angle of the valve, and then lapping the two together with valve grinding compound until they seal. I'm not saying it wouldn't work. It was just too different from what I had finally got to work with my V-4, and I didn't want to take any chances with the some 500 hours of work I had accumulated on all the heads. I was especially afraid of not getting the seat concentric with the integral guide since that always seems to be a model engine builder's nemesis. Instead, I designed a valve cage with an integral seat and guide in a single part. Getting the seat concentric with the guide in a valve cage isn't easy either, but I had honed a process that seemed to work for me. And then there was the lure of being able to check the valve seal before committing my heads. There wasn't much space to work with in the original head design, and I began wishing I had designed the valve cage before I had machined the heads. There was no way I was going to re-make the heads. I eventually got a valve cage design I was satisfied with. It would require a slight re-sizing of the valves which I hadn't yet made. The plan was to machine the cages out of 544 phosphor bronze, cut the seats by hand to .010" width with a precision piloted seat cutter that I had already made, check for concentricity, install them in the head, and finally double check them for leaks. Two things went wrong. First, even though I had a theoretical easy slip fit between the head and the guide, when the high temp bearing retainer was added, the fit became snug and due to the conical shape of the combustion chamber all seats went slightly oblong in the same direction. To solve this I had to re-cut the seats in the head, and now my seat width was .020" which I knew was going to be more problematic to seal than .010". I really lost sleep over the second problem. After the seats were installed, I realized that the 544 phosphor bronze material that I thought I was using was, in fact, mismarked SAE 660 bearing bronze. SAE660 is much softer than 544. In fact, it is softer than aluminum or brass. I still don't know if this will be a problem in the short or long term. I tried calculating the expected worst-case pressure on the seat during combustion to compare it with SAE 660's yield strength, but I had to make some assumptions about the combustion pressures and I could not find values for its yield strength as a function of temperature. Hodgson recommends aluminum bronze for the seats, but I've been told by some experienced modelers that it is too hard and causes heavy wear on stainless valves. Maybe I will get lucky and the softer 660 material will quickly conform to the valve during actual use, effect a perfect seal, and last forever.
The head and cylinder are screwed permanently together with an aluminum head gasket washer using yet another special tool, and then the cylinder mounting holes are drilled. Drilling these mounting holes is the point of no return on the head cylinder pair and so I procrastinated for days before doing it.. After screwing them together but before drilling, I pressurized each cylinder/head pair with 40 psi air and measured a 20 psi leakdown after aboout a minute or so. I expect this should be fine although the real test will be a compression test after the piston is added After I built a compression tester, I did some calculations from the dimensions in the planset and came up with a compression ratio of 5 for this engine instead of 6.7. This lower value of compression ratio seems to be verified with pressure measurements others have made on their cylinders. - Terry


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## mayhugh1

Since the beginning of this build I have always thought that the biggest improvement to this engine's appearance would be new rocker arm supports. That is, unless one were going to change the entire head design. I didn't feel comfortable at all with changing the head design at the beginning of the project since at that time I still couldn't figure out how the stock heads were supposed to look. Many others have added rocker boxes and covers, and I think these improve the appearance 100% over the simple brackets used in the original Hodgson design. I spent a lot of time modelling other types of rocker arm supports while maintaining the original pushrod geometry. I wanted the open geometry of the original supports so the movement of the rocker arms was not hidden since I liked seeing all the moving parts while running. I finally settled on the supports shown in the photos. I like the vintage appearance it adds to the engine and it makes my version look much different from the others out there. The rocker arms themselves are aluminum instead of steel as called out in the drawings. I did, however, add a bronze bearing for the rocker arm shaft and I also added a bronze insert for the pushrod. I studied the compound geometry of the pushrod motion with a CAD simulation, and I machined a spherical cavity (with conical sides for clearance) so the spherical pushrod end would mate nicely in this cavity. I also deepened the cavity (and lengthened the pushrod) since I had heard reports of pushrods sometimes jumping out of their rocker arms. The contact point with the valve stem is a hardened socket head setscrew with a spherical end secured with a locknut. This gives a lash adjustment scheme similar to that used on full-size engines.
The photo of the rear of the cylinder also shows the intake/exhaust pipes. The original design called for these to be soldered up from brass/copper, but I wanted all white metal. I bent annealed 304 stainless tubes using a Rigid 600 series tubing bender and then silver soldered them in a custom fixture to a re-designed flange having more meat on it than the original design. The tubing bends easily without having to be filled with Cerrobend or sand. The soldering fixture was desgned to draw heat away from the tubes so they only discolored slightly. In fact I was going to leave the straw discoloration on them until I realized that it wouldn't be realistic for the intake pipe to also be colored. An overnight session in a tumbler filled with tiny ceramic balls polished these assemblies right up. I also milled a slight draft around the circumference of the tube ends that protrude beyond the gasket so they fit snugly into the holes in the heads. All of this gives a neat and leak-free seal. I have since machined looms which fit nicely against the exhaust flanges and which will support the plug wires at each cylinder. These will be shown later in the assembly process when the plug wiring is added. The gaskets were cut from auto store gasket material on my Tormach using their new vinyl cutter and they match the flanges perfectly. - Terry


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## mayhugh1

The first photo is of the 'engine stand' I built to hold the engine during assembly. It is welded up from steel and is similar in design to Hodgson's display stand. When the engine is completed this stand will bolt down behind a 'firewall' that I built to hold all the ancillary components required to actually make the engine run. Note the milled cavity below the engine that I expect will be needed to collect the oil drips. The fuel, oil, Hall sensor, and coil HV lines will eventually run from the firewall to the engine.
The second photo shows the components on the rear of the firewall. I separated the oil and fuel tanks to give me more flexibility in carburetor choice. (More about this later.) The oil from the oil tank to the pressure pump is regulated with a drip feed system at the left side of the tank as these engines are known to pump more oil into the engine than the scavenger pump can keep up with. The scavenger return line enters the tank to the right. I also added a sight glass to keep track of the oil level in the tank. There is also a sight glass on the drip feeder. The fuel pump is an RC airplane tank available at any hobby store. It is located below the expected carburetor intake port. I plan to use a fuel pump to pump fuel to the carb bowl. Unused fuel is returned back to the tank through a return hose. My fuel pump is a repackage of the internals of an RC fuel filler available at any hobby store.
This pump is used in two different ways depending upon the carburetor I finally decide upon. The most recent Hodgson design recommends the carb designed by Jerry Howell. I've built three of these for my other engines; and although I might have to build a fourth, I want to try something different. The first thing I want ro try is a Walbro carb operating on gasolene. These diaphragm pumps require a pressurized fuel source for operation. My fuel pump will supply some 15 psi fuel to a carb bowl I made for the Walbro. This carb bowl has a 5psi pressure regulator built into in it and so it will supply 5psi pressurized fuel to the carb and return the excess back to the fuel tank. The Walbro I have is one that I salvaged from a yard tool but it's possible that the venturi might be a little large for this engine. We'll see. 
The second carb I plan to try is a Super Tiger carb salvaged from my son's crashed helicopter. This carb will run methanol (+10% WD-40) - the same fuel my other two engines have run. The venturi on it is even bigger than that of the Walbro, but I think others have been successful in getting a similar carb to run on their engines. The carb bowl I built for this engine just maintains a constant level of fuel just below the throttle shaft of the carb while returning excess fuel back to the fuel tank. When I finally settle on the fuel I will be using, I may have to change out a few components in order to remain compatible with the fuel. I plan to start with gasolene, however. 
The control panel at the bottom has three switches and a rheostat to help regulate fuel flow if needed. One switch is to turn on the low voltage for the ignition so I can see the Hall effect trigger without firing a plug. This will be used to check the ignition and verify engine timing. The second switch turns on the fuel pump. The third enables the high voltage section of the ignition so the plugs can actually fire. The module to the upper right is a TIM-6 ignition. I made the pcb, heatsink, and enclosure for it. Those with experience with the TIM-6 know that it doesn't like the engine to stop with the Hall device enabled as the output transistor can overheat. Two leds - one on each side of the firewall - shows when the Hall device is enabled. I've never had any ignition issues with any of my other engines, and so I'm using the same design here. The big black thing in the upper right hand corner in an older version of an "Exciter" model engine coil. I hear that the newer and smaller ones are more prone to overheating. This is the first time I've not jumped through hoops to hide the coil. In fact the big circular thing around its bottom is a bracket I made to support it. 
The handle in the middle is throttle lever. I was able to design a throttle with ball joint linkages that will work with either of my carbs.
The whole thing will be quite heavy and so I made a cut-out at the top for ease of transport. - Terry


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## mayhugh1

These are photos of the two completed carb assemblies I plan to try with my H9. The first is a Walbro 345 carb that I salvaged from an old yard tool, cleaned up, and rebuilt. I designed a simple bolt-on linkage adapter to work with my throttle control on the firewall. The carb bowl contains a ball-and-spring pressure requlator to supply 5 psi fuel to the carb and return the excess to the fuel tank. I wish it had a choke or primer, but I drilled a small hole in the top cover so I can press down on the diaphragm with a small tool which I think will prime it while under fuel pressure.
The second carb is a Super Tiger RC helio engine. This bowl simply regulates the level of fuel with a drain hose back to the fuel tank. Again the linkage is compatible with my throttle control and the adapter at the rear matches the back of my engine - Terry


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## kvom

Liking this series a lot!


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## ozzie46

Oh lovely,lovely,lovely. th_wavth_wav


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## Ramon

Absolutely superb all round - workmanship, images and text .

Truly informative posting - brilliant

I only have time for a quick look now having to go out but am looking forward to reading it in more depth later

Thanks for taking the time Terry

Thm:Thm:Thm:


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## ronkh

Terry.

That is a work of art, thank you for showing.

Well done!

Ron.


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## petertha

What a build & incredible journey. Thanks so much for sharing. Im interested in radials & posted some newbie questions. So it's awesome to have someone like yourself on the forum. Best of luck on the home stretch.


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## petertha

mayhugh1 said:


> until I stumbled across Tom Blough's website detailing his head machining steps.....


 
I'm sure by now you found this website re Hodgson build (and other engines) but just in case..
http://homepage2.nifty.com/modelicengine/


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## mayhugh1

Petertha,
      Yes, I came across his website sometime ago and found it to be a remarkable, persistent, and heart-breaking saga. That man has no lack of patience. I noticed he has returned to his Hodgson build to take care of some loose ends. The initial thrill of finally just getting it to run seems to have worn off and now he wants to make it really right. I was particularly interested in his heat exchanger to heat the fuel for better atomization. I'm hoping the larger impeller design of the later plansets take care of this. - Terry


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## vcutajar

Terry, I will be following your progress and learning new things as you move forward with your build.  Thanks for sharing all this information.

Vince


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## kuhncw

Terry, congratulations  on a beautiful engine and a very well documented build.  When you have a moment, would you please post a few photos showing the internals for your distributor?

Thanks.

Chuck


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## mayhugh1

Here I've installed the rear main bearing, crankshaft, the oil pumps, the rear seal, impeller, and the distributor drive gear. This was just to verify the fit that I had when I machined my crank. During trial fitting of the crank it came in and out of the crankcase many times as my goal was to center the crank for a max .002" without the use of shims and to also set near-zero backlash with the distributor also without shims. - Terry


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## mayhugh1

Here is a photo of my setup to time the camshaft. I made a generic degree wheel and positioned my height gauge to act as a pointer for it. I made a fixture to support a plunger style DTI in the spark plug hole in order to indicate TDC. A second DTI rests against the intake and/or exhaust lifters to probe for the centerlines of the cam lobes. My technique was to probe for the .015" cam lobe heights and then divide by two to find the center. I was careful to always approach the measurements with the crank turning CCW to avoid backlash errors. The goal here is to move the cam ring in relation to the crank in order to center TDC between the intake and exhaust lobes. This is done by carefully lifting the cam ring jackshaft up and out of engagement with the crank shaft and then rotating the cam ring for the best result. Trial and error is at work here. Unfortunately, with the gears used in this design it turns out that the resolution in terms of cam degrees is at best 2.8 degrees per cam ring tooth. This is reflected over in crank degrees by a factor of 8 giving a whopping 22.4 degrees resolution in crank degrees. Fortunately, the phasing of the two gears on the jackshaft, 32 tooth and 12 tooth, can be used to advantage to cut down this resolution error. This means the jackshaft has to be disengaged from both gears and then rotated and then the lobe center is re-found as described above - a bit more complicated trial and error. I called it quits when I had TDC centered between the lobe centers by +/-4 crank degrees. This was equivalent to the resolution to which the cam ring was designed. The cam timing I measured is a pretty common result for a mild street engine. The exhaust valve opens 43 deg before BDC and closes 7 deg ATDC. The intake valve opens 2 deg before TDC and closes 35 deg ABDC. The intake duration is 208 deg and the exhaust duration is 221 deg. The distance between lobe centers is 222 deg. I've done cam timing on full size engines before, but the hardest this thing for me to wrap my head around on this step was remembering that the crank on this engine is turning 8 times faster thatn of the cam instead of 2 times faster. The distributor timing still needs to be set up but that will be one of the last steps in my assembly. - Terry


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## mayhugh1

Here is a photo of the cam timed and finally installed. Also, the slave rods are installed. As it turned out I thought I could install the slave rods with the front main bearing installed, but that wasn't possible. And so I had to do a bit of disassembly to install them. Hopefully the crank will not have to come back out. Even with the clamp arrangement I used to tie the front and rear sections of the crankshaft together, the fit is so close that it is difficult to pull the front section out even with the clamp screw removed. The second photo is a trial fit of the front cover and I couldn't resist adding the prop and spinner temporarily. As mentioned before, the spinner is polished aluminum with a stainless hex pressed in the rear. The stainless insert is tapped for a reverse thread so the prop won't loosen while the engine is being started. If you look closely, you might notice I engraved a warning about the LH thread on the side of the stainless insert. I always do this on left handed parts as a courtesy to the next person who might need to loosen the part. Hodgson design vents the crankcase through a hole drilled through the center of the crankshaft and a second intersecting holed cross-drilled hole in the crankshaft inside the crankcase. I would have guessed that the oil scavenging pump would have done away with the need to vent the crankcase since it would be sucking in this area and venting into the oil tank which is also vented. But just in case, I kept his ventilation system. Since his design was expecting a simple nut on the end of the crankshaft, I had to provide a path for the venting through my spinner. That is what the radial holes in the hex portion of the spinner are for. The diameter of the portion of the crankshaft extending through the front cover sure looks small for that big 23" prop. Another thing about radials is that our model engines typically don't drive loads and so really don't develop much actual horsepower unless connected to a dyno or some other load. A radial, on the other hand, is turning a propeller and trying to fly. - Terry


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## aonemarine

People like to give thier engines names, and if I were to name your radial I would call it "dedication".   That is some beautiful work.  Maybe some day I will make it to your level of workmanship.


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## mayhugh1

Chuck,
Here are some construction photos I took while I was building my distributor. The slot in the bottom of the metal housing is where the Hall device is placed. There is another slot on the opposite side of the housing. Only one is visible in this photo. The Hall device leads come out this slot at the bottom of the distributor. The white Delrin disk in the unassembled parts photo - the one with the large center hole and small perimeter hole - goes into the metal housing on top of the Hall device and sandwiches it between the aluminum housing and this disk. The dark shadow on this white disk directly opposite the perimeter hole is a milled cavity for the Hall device. The small perimeter hole is actually tapped for a 2-56 screw. A screw comes up through the other slot in the bottom of the housing and secures the disk and Hall device in place. When loosened, this screw can be used as a handle to slightly adjust the angular position of the Hall device in order to tweek the timing. This is necessary because the resolution of the positioning of the rotor and the number 1 high voltage tower is set by the finite number of teeth on the distributor gear. - Terry


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## tony_m_baker

Do you have any drawings for this engine? I am really only interested in the parts show here. I want to do something similar in a sculpture I am doing and the radial engine is a perfect model.


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## mayhugh1

I thought I might comment on the valves in this engine. I really like Hodgson's valve design with its beefy .187" stem diameter necked down only behind the head where it is needed to unshroud the valve and increase flow. The valves on the other two engines I have built had tiny .125" stem diameters and were difficult and tedious to machine. Hodgson's valves turned out to be a breeze to machine. 
I'm fortunate enough to have a 9x20 cnc converted lathe. It has its issues, but I've learned to work around most of them; and with the right amount of babysitting I can hold .001" or so for a while. What I did was to saw off 15 half-inch diameter 303 stainless blanks which were 4-1/2 inches long. I generated 2 cnc programs - one to rough out the valve but to leave .020" stock along the entire profile of the valve. I used somewhat aggressive feeds and speeds because I wasn't interested in surface finish at this point. And, because I was leaving a good bit of stock I didn't have to continually monitor the tool calibration in order to hold cutting accuracy. I ran this program 30 times - once on each end of each blank with the same cutting tool. I was able to rough out 30 valves in 3 hours or so by just zonking out and feeding blanks to the machine. My plan was to then to stress relieve them overnight at 450F in my oven before running the finishing program. Well, we took a one week vacation between the roughing and finishing steps and I forgot to do this step. I'm not sure if it is really necessary but Bob Shores recommends it and I figure it can't hurt. 
Calibrating my lathe's x-axis for sub .001" accuracy is touch and go and when cutting multiple parts like this I don't like to change tools because it adds another set of variables to the accuracy of the cutting. From past experiments I have found a Kennametal DCMT2151UF light finishing insert can give a great surface finish on 303 in my lathe even when cutting as little as .002" off the diameter. The DCMT insert is required for this valve to get access to the entire profile of the valve. Again, after calibrating the x axis and touching off z, I just feed parts into the machine. Only this time, after every run, I measure the diameter of the valve stem in the area where it will make actual contact with my valve guide. (This is the only part of the valve whose diameter is really critical.) After every run I reset the x-axis calibration to agree with the measured diameter of the stem in preparation for the next run. Much less agressive feeds and speeds more than triples the finishing time, but that gives me more time to surf the web while the lathe does the tedious work. I was able to finish all the valves in an evening on a single insert and the wear on the insert was negligible. I normally aim for .0005" valve stem clearance with the guide and this is what I was able to more or less achieve. I programmed a very slight taper at the top of the valve stem so there would be no issues with inserting it through the valve guide. I later had second thoughts about whether or not this engine depends on a larger valve stem clearance (Hodgson spec'd .005") in order for the guide to get some blow-by for lubrication in addition to the slop added to help the valve find its own sealing position. There is no top end lubrication except for oil that makes it way into the combustion chamber and out past the valve. So, later I came back and in a secondary operation I polished another .0005" off the completed valve stem. After the finishing program was run, I sawed the valves off each end of the blanks and then performed all the tedious individual operations to face the valve to length and to add a keeper groove. The valve retaining scheme was my only departure from Hodgson's design (plus a small reduction in diameter for my valve cage). He uses a tiny pin in a cross-drilled hole in the stem to retain the valve. Instead, I machined c-washers that slip into a groove I cut into the top end of the valve stem and then retaining cups to secure the c-washers. It's a lot neater looking, but is one of those things that no one notices since they are hidden out of sight under the rocker arm supports. - Terry


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## mayhugh1

Tony,
       Drawings are available from the original designer at

agelessengines.com


Regards,
Terry


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## kuhncw

Terry, thanks for the information on your distributor.  That is a nice design.

Chuck


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## swilliams

Awesome Terry, really top notch workmanship.  I'll get back and read all of this carefully when I have some time      

 Cheers Steve


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## mayhugh1

Here, I've installed the rings on the pistons and, miraculously, didn't break a single one. I ended up with lots of spares of compression rings but only 1 extra oil ring. Hodgson's oil ring design is fairly complex with a shallow circumferential groove cut into the outside of the ring and a number of tiny radial drilled holes. The theory is that oil is scraped into this groove between the ring and cylinder wall, forced through the holes in the ring, and then through a second set of radial holes cut into the piston where the oil can return to the crankcase. Hodgson evidently changed the piston/ring design in the later versions of this engine because I've seen others that had only a single compression ring. The drawings I have call for two compression rings. They are cast iron and only .045" wide and so they look pretty fragile compared with the ones I made for my V-4. I had to make all new fixtures to fabricate and heat treat these rings because they were a different diameter from those on the the V-4. 
One thing about this project is that fixtures are a way of life. I think I ended up building, on the average, one unique fixture for every three unique parts built for the engine; and I didn't even build all the recommended ones. This weekend I will install the cylinders and the pistons on the crankcase. I have marked each cylinder and piston with a unique number so I can keep track of them should I need to later disassemble the engine. I have three spare cylinders and ringed pistons. Their measurements, leakdown test, etc are all recorded in a notebook to help me keep track of what works and what doesn't work later when/if the engine is running. This step will be tedious and take a bit of time as there are 72 small pattern 4-40 nuts that have to be tightened a fraction of a turn at a time to secure the cylinders. I also need to add a washer and lock washer on each stud with my fat fingers without dropping anything into the engine. I cut out some .004" linen-paper gaskets on my Tormach using their vinyl cutter to help seal oil leaks between the cylinder and crank case. This will reduce the compression ratio even more. I'll take a break from nut tightening this weekend to include a section on compression ratio calculations for this engine. - Terry


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## petertha

mayhugh1 said:


> Instead, I turned the whole crank from a single scrap round of mild steel and drilled the hole for the crank pin before sawing the result into two pieces with guaranteed alignment. The cheeks were slit so the master rod journal could be clamped into place with an 8-32 SHCS in each cheek.


 
I'm really interested your alternate procedure of constructing the crank shaft. Do these sketches roughly represent the machining sequence up until slitting part? By 'guaranteed alignment' you mean drilling the crank pin hole through the entire segment of what will be become front & rear counterweight pieces when sawn apart? What is the crankpin itself made of? Do the ends have a reduced diameter step which engages the web holes?


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## mayhugh1

Petertha,
       You have it exactly right in your drawings. My crankpin is hardened O2 tool steel (and I added a bronze bearing to the main rod). My crankshaft is 12L14. I drilled and reamed the hole through the cranshaft blank for the pin after turning the ends but before sawing the crank into two pieces. In my radial engine I turned the crankpin only a few tenths below the diameter of the hole for a snug sliding fit. This was in case I might have to later disassemble the crankshaft within my crankcase due to some problem. This clearance would make it a bit easier to separate the two pieces within the crankcase. (Remember, in this radial the master rod captures the crankshaft within the crankcase.) In my radial, I locked both cheeks to both sides of my crank. I was able to do this because my main bearing alignment ended up pretty good and I had no binding. I don't think it is necessary to lock both of them. One is sufficient to keep the oil passages aligned and to keep the pin in place. In my V-4 I only locked the rear section. I reamed the crank cheek in the front section in this engine .001" over-size and did not clamp it. I did this to relieve a small crankshaft bind due to a small misialignment in the main bearings in this engine. This engine had 5 main bearings and a center section high pressure Babitt oil seal, and my machining just skills weren't up to the task of getting them all perfectly aligned. -Terry


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## mayhugh1

I finally got all the cylinders installed on the crankcase. It wasn't as tedious as I thought it would be, but I did have to make a special wrench to tighten the nuts on the two lower cylinders on either side of the oil sump. After 1-1/2 years of accumulating parts in plastic bags, this engine is finally starting to look like one. I trial fitted a pair of my rocker covers to check the length of the pushrods that I made. I'm going to shorten them by .050" to get the valve adjusters in a better looking position. I'm also having second thoughts about my rocker covers. I'm not sure I like their looks as much as I thought I would. I might redo these.
I have now put the engine into an ugly but effective setup to "motor it in." I'm using an electric drill and my starter adapter to spin the crankcase to check for any last minute problems before I ask it to produce its own power. I want see the oiling system in action and check for leaks that are easier to fix now. This will be my first real test of my drip-feed oil tank as well as the scavenging oil pump's ability to evacuate the sump. I was able to check the pressurized oil side earlier when I finished installing the crankshaft. I've opened the closed loop oiling system for this test so I'm not recirculating dirty oil during this test. I'm just collecting the oil from the scavenger pump for disposal and refilling the oil tank as needed. My plan is to run about a quart of oil through the engine in a number of start and stop runs at various speeds. I'm not expecting this step to seat the rings without the forces of combustion pushing the rings against the cylinder walls. It should start the process, though, by wearing off any high spot imperfections in my rings. I may be able to see this debris collected on the magnet that I embedded in the sump cover.
I'm amazed at how much oil is being moved through this engine. Even at 1 rpm the outlet hose of the scavenger pump is evacuating oil at a rate that I would have expected at idle. I now see the importance of adding the oil drip feed system as recommended by Hodgson. I've left the screws out of the front cover so I can watch for oil build up in the front portion of the engine which is a known issue with this design. I enlarged the area of the drain-back system some 50% and I'm curious to see if this at least partially cures it. The collected scavenger oil is pretty black, but I think this may be the bluing inside the cylinder being scrapped off by the rings. - Terry


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## mayhugh1

While 'motoring-in' the engine I decided to try to quantatively check the compression in each of the cylinders. For this engine build, I made the compression tester in the photo. I designed it for use with a model engine with negligible volume below its check valve. The chrome center portion of the gauge was robbed from a $5.00 peak reading tire tester from a local auto store. I added a spring-loaded ball check valve in the bottom portion which is threaded to screw into a 10mm spark plug hole. At the top I adapted a 0-100 psi gauge that I bought at the NAMES show last year. Since the pushrods and rockers aren't yet installed, I have to manually pump one of the valves with my finger about once per crank revolution to allow fresh air into the chamber while the engine is spinning. After a half dozen or so revolutions, the peak compression pressure is accumulated by my peak reading gauge, and the reading should approach what I would obtain from a conventional compression test.
After passing 125 mL of oil through the engine during 'motoring,' I obtained the following measurements:
#1 = 83 psi
#2 = 68 psi #9 = 83 psi
#3 = 72 psi #8 = 72 psi
#4 = 72 psi #7 = 72 psi
(I did not have enough clearance in this setup to screw my gauge into cylinder numbers 5 or 6.)
Taking an average reading of 75 psi, this would make the average dynamic compression ratio = 75psi/14.7psi = 5.1
The compression ratio spec'd by Hodgson for this engine is 6.7. I computed the static c.r. for this engine using Hodgson's drawings since measurements of all my parts that affect the c.r. agree almost exactly with his drawings. 
Here's what I obtain: 
Head volume due to conical section of head = (pi/3)(r^2)h = (pi/3)(.6025^2)(.281) = .107 cu.in.

Head cylindrical volume due to thread relief = (pi)(r^2)h = (pi)(.6025^2)(.030) = .034 cu.in.

Head cylindrical volume due to aluminum washer offset = (pi)(r^2)h = (pi)(.6025^2)(.030) = .034 cu.in.

Cylindrical volume from piston top below top of cylinder at TDC = (pi)(r^2)h = (pi)(.5^2)(.062) = .049 cu.in.

Total volume at TDC = .107 + .034 + .034 + .049 = .224 cu.in.

Volume at BDC = .224 + (pi)(r^2)(stroke) = .224 + (pi)(.5^2)(1.125) = .224 + .884 = 1.108 cu.in.

Static c.r. = 1.108/.224 = 4.9
I believe Hodgson left out the excess volumes due to the thread relief and the aluminum washer used as the head gasket in his calculations because the result is 6.7 if these are ignored.
I plan to make a final compression test after the motoring is finished and the pushrods are installed to see if the extra motoring time improves any of the pressure readings.
Terry


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## swilliams

Nice Terry. Will be interesting to see what happens after more motoring. With a little luck the rings may bed in making things more consistent between all cylinders.  So are you using the 10mm spark plugs as sold on the Jerry Howell site?   

Cheers Steve


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## Lakc

I didn't have time to jump in on the mailing list when this subject came up, but I have a few moments now to comment. 
 There are a lot of factors that go into a compression test that makes the values obtained less then useful for determining compression ratio. 

 Leakage is probably the biggest one, and that is what makes it a useful test in servicing engines when something goes wrong. It will take actual run time to help the rings and valves seal and you should see compression rise slightly after its run. Oil itself will mask sealing issues at cranking speeds, so you end up with a spread based on where your oil has sprayed/dripped/collected. Leakage in your compression tester from your check valve may not be as repeatable as you would like.

 Throttling and pumping losses due to restrictions and pressure variations in the intake and carburation. Air is a fluid, and any non-laminar flow involved will vary the amount of intake each stroke. At higher running rpm's this air has mass and momentum that will tend to lessen those effects. Although not applicable to round engines as far as I can tell, some V engine designs can have two cylinders trying to draw air simultaneously from relatively confined spaces which lead to less intake. In our "minimal area" type model compression gauges this adds even more reduction of the "true" pressure in the cylinder

 Cranking speed variations will also vary your compression readings. Unless your driving a crank with a very large mass at an exact speed every time the work of compression will slow the crankshaft a different amount.

So, in a perfect world the math would work out, but its not going to cooperate that simply.  To do a proper compression ratio check you use liquid to measure the volume of surfaces involved. Much less variables to affect your readings that way. Dont sweat the differences too much either, due to manufacturing tolerances stacking up the compression can vary by a significant amount. One auto manufacturer listed a delta spread of compression ratios for its V10 engine as 8.9-10.1:1.


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## mayhugh1

Jeff,
      Points well taken. 

Steve,
      I bought my CM-6 plugs from a vendor at Names last year. Cncengines.com sells them for $5.00 which is as cheap as I've seen them. They're really big and way out of scale for this engine, but they have better resistance to oil fouling and this will probably be welcomed for cylinders 5 and 6 at the bottom of the engine. If I'm lucky and my engine doesn't have a lot of oil fouling issues after it is running and dialed in, a possible option is to make some adapter inserts for 1/4-32 plugs which will fit the scale a lot better. - Terry


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## mayhugh1

Petertha,
Here are some photos I took during the construction of my crankshaft. - Terry


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## kvom

So how did you drill the hole so as ensure it would be precisely parallel to the shaft?


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## mayhugh1

Kvom,
Sorry I didn't have a photo of that setup. I held the crankshaft by the front turned bearing in a 5C collet holder, and indicated it vertical in my mill vise. The spotting, pre-drilling (carbide drill), drilling, and 2 step reaming was done on my mill all in the same set-up. - Terry


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## vihatch

Thank you for a very enjoyable thread.  I am currently 95% finished with a Howell V twin.  Your comments about valve testing and lapping coincide exactly with my experience.  It's good to know I am not the only one who doesn't get a perfect valve seal.  I am going to try the 1200 grit lapping compound on my next build.


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## seagar

wow!!!!!


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## mayhugh1

These are photos of the assembly stand that I built for the Hodgson. It is really necessary to have something like this to hold the engine while it is being assembled. The engine is awkward to hold and very heavy, and it must be held in some a number of positions while several fussy assembly steps are performed. This is no time to drop the thing on the floor. Some have even built a special rotating engine stand for the engine. I decided on the simple design in the photos which lets me get to most areas during assembly and, so the work wasn't throw-away, I integrated it into the final running display of the engine. The support ring that bolts the stand to the rear cover uses the rear cover mounting holes to mount the engine to the stand, but it leaves three of them free so that the distributor timing isn't disturbed when the engine is taken on and off the stand. The stand is designed to temporarily support the engine from its front also so that the distributor/rear cover section can be taken on and off easily when it comes time to time the distributor. - Terry


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## mayhugh1

I've called it quits on the "motoring-in step." I ran about 250 ml oil thru it in a large number of short runs over several days while I take care of some other things. I had to re-charge the batteries in my 18V drill three times in the process. I took a photo of the sump magnet after moving about 200 mL of oil through the engine which took about 30 minutes total run rime. There is a very fine layer of metal over a portion of its surface which is probably coming from the rings. I had the oil drip feed system set at about two drops of oil per second for this test. This seemed to keep oil moving through the scavenger at the slowest rpms my drill was turning over the crank. At any fixed drip setting the actual flow rate varies with engine speed and so I expect this is going to be a critical setting with the engine running. I never saw the scavenger pump lose its prime in the 3-4 days this test ran. Behind the front cover the entire cam is wet with oil and so the front portion of the engine is getting well lubricated even it low rpms. The is no oil leaking past my rear seal into the fuel diffusing area and this is good news. The best news though is that the engine does not seem to be pumping significant oil into the combustion chambers of the cylinders. There is nothing leaking out the spark plug holes of the bottom cylinders and looking with a flashlight into the other cylinders shows only a few drops of oil in the combustion chamber. This was not the case during a similar test on my V-4. The engine pumped quite a bit of oil out the cylinder decks even with the crankcase well vented. I may finally have made a decent set of rings. I had to plug the lower lifter bushings with silicone plugs to keep oil from pouring out them during this test. When I finally install the lifters I'll select the ones with the closest fit to the bushings at these low positions. Leakage at these lifters is a known problem with this engine design and is the reason why I milled the oil-catching trough in the bottom of my assembly stand. The next step is to install the rockers, intake and exhaust pipes and to time the distributor. Al though totally unrelated to this step in the assembly, I'm also including some photos of the construction process during the past 18 months. - Terry


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## Lakc

Is that the newer design diffuser or the older one?


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## mayhugh1

Lakc,
    I believe this is the latest one. The planset supplement that I bought 2 years ago contained this large diffuser. - Terry


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## danthompson58

Very nice build, excellent workmanship and pictures with descriptions.
Dan


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## mayhugh1

The next step is to time the distributor and button up the rear of the engine including the rear cover and air guide. The "motoring-in" test showed the oiling system is working well with no engine oil leaking into this area, and so now it should be safe to assemble the rear of the engine for the last time. 
There are two separate timings involved with the distributor. In the first, the trigger signal of the Hall device with must occur when the rotor is directly below one of the high voltage terminals in the distributor cap. I established this in my distributor when it was finally assembled and tested about 9 months ago. In my design, the Hall device is buried in the bottom of the aluminum distributor housing and attached to a Delrin plate that can be rotated +/- 30 degrees with respect to the distributor cap and then locked permanently in place. This has already been done and tested. 
The second timing requirement is to time the Hall device to TDC on the crankshaft comprerssion/firing stroke of cylinder #1. The only way to do this in this engine is by trial and error by repeatedly mating the rear section containing the distributor onto the main crankcase section to engage the distributor pinion gear with the crankshaft pinion and then checking that the Hall device triggers at TDC of cylinder #1. The rear section is then removed, the distributor pinion gear rotated one tooth, and the rear section is re-mated onto the crankcase until the best result is obtained. I included a stationary timing pointer and a set of 10 degree (crank) timing marks on either side of TDC on my distributor housing. So, I located the best pinion gear engagement that gave me a Hall device trigger at TDC as indicated by my dial indicator in the sparkplug hole of cylinder #1 simultaneously with my TDC timing pointer on the distributor housing. In addition, since I engraved cylinder numbers on my distributor cap beside each HV tower the rotor also has to be beneath the tower maked #1. (I added these distributor cap numbers in order to make it easier to keep track of my plug wires later.) Once this is done, the timing can be advanced as needed for best engine performance by loosening a locking screw on the distributor housing and rotating it. This will advance or retard the Hall trigger with respect to TDC on the crank but not disturb the relationship of the trigger with respect to the HV towers in the cap. In addition, it will rotate the calibrated timing marks on the side of the distributor housing with respect to the stationary timing pointer so the amount of the advance can be read. There are two blue leds - one of either side of my firewall - which turn ON when my Hall device is ON. The length of time the Hall device is ON is the dwell time. This is the time during which the ignition coil charges. For my TIM ignition the dwell time is fixed and is established by the radius of the mounting circle of the nine magnets (and their diameters) that make up my trigger disk. For my radial engine I've set the dwell at about 22 crankshaft degrees. The dwell of my V4 was 25 crankshaft degrees and this was sufficient for a useable spark at 1700 -6200 (measured) rpm without excessive overheating of my coil or output transistor. I decided to maintain about the same dwell for my radial since I will be firing 5 more cylinders and the additional power dissipation could be a problem. I don't plan to rev this engine much above 3000 rpm anyway as I expect that will be scary enough with a big 23" prop. Of course my choice of dwell is very dependent upon the inductance and resistance of the coil being used as well as the maximum charging current of my output tansistor. Since the 'old' style Exciter coils that I have been using are no longer available, this will have to be re-thought for any future engines.
In my other two engines I have found these dwell leds to be invaluable when setting up and troubleshooting the ignition. The secondary or high voltage portion of my TIM ignition is enabled by a separate switch and so it is not necessary to attach a dummy sparkplug or sparkgap when checking timing or troubleshooting the low voltage section of the ignition. Once the distributor is timed it is attached for, hopefully, the final time and secured with three SHCS at the rear of the engine. The assembly/display stand clears these screws so the timing will not be disturbed when the engine is taken off or attached to the stand. I am attaching a SolidWorks cross-section of my distributor. The actual machined components shown in an earlier post can be located in this drawing. - Terry


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## mayhugh1

I'm now installing the intake and exhaust pipes. In the photo you can also see the wire loom that I've added to help organize the plug wiring that will encircle the engine behind the heads. I've also added a photo showing the fixture I used to silver solder the stainless steel pipes to the beefy flanges I made to fit the rear of the heads. This was the first silver soldering that I've ever done of any consequence and I was surprised at how easy it really was. I used 3/8" annealed 304 stainless tubing and it bent very easily and cleanly using a Rigid 600 series hand bender without heating or filling the tubing. This is a 3 roller bender that I was preparing to build myself, but Santa ended up bringing it for Christmas instead. I made the wood gauges to check the tubing bends before they went into the soldering fixture. The intake/exhaust manifold gaskets were cut from 1/64" automotive gasket material on my Tormach using their new vinyl cutter. I created a cutting program for the gaskets using my CAD model of the flange itself to guarantee a perfect fit. I was having so much fun learning to solder the pipes that I made almost twice as many as I needed. Everyone of them dropped into place with no interference. - Terry


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## johnl

Great work on your 9 cylinder. I recently received my set of plans from Lee H. and am gathering materials.
I hope mine turns out as well as yours did.  John


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## mayhugh1

Here are some photos I took during the machining of the crankcase. There are 137 holes that must be drilled and tapped - most of them are 4-40's. If I had been more brave I would have cnc tapped them on my Tormach, but I chickened out at the last minute and decided to tap them all by hand. I'm proud to say I didn't break a single tap. One of the photos contains the fixtures that I had to make to support the crankcase in my rotary while I machined the crankcase. This photo also contains the first crankcase that I built and screwed up during its last maching step. If you look closely, you can see that the cylinder mounting bolt hole pattern is off-center from the cylinder deck. I had the tailstock tightened up ridiculously tight against the crankcase while it was on the horizontal rotary for this machining step. This caused the rotary to lose steps as it rotated the crankcase under the spindle and caused the error. I thought about trying to salvage it by plugging the holes and re-drilling, but I hate to start out a project on a questionable foundation. - Terry


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## mayhugh1

Here are photos of some more of the fixtures that I constructed to build the Hodgson 9 radial. This first group of fixtures were used to make pistons and rings. The heat-colored parts go together to form the annealing fixture used to heat treat the cast iron rings. The tool in the back is a cleaver for cleanly breaking the rings for their gaps. The wrench-tool in the second photo was used to screw the heads onto their cylinders with a .030" dead soft aluminum head gasket between them. This tool was also used to hold the completed assembly in my mill vise in order to locate and drill the mounting holes for the cylinders to the crankcase. Once this drilling is done the cylinder is married to that particular location on the crankcase and likely cannot be salvaged after disassembled for repair. In my case that represents about 100 hour chunk of time that would be discarded if, for instance, a valve seat would need to be repaired. This is why I made three complete spare assemblies. The third photo is a number of tools I used to fabricate and install my valve cages. - Terry


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## metalmad

Top job Terry
Love your work ;D
Pete


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## petertha

mayhugh1 said:


> Static c.r. = 1.108/.224 = 4.9 I believe Hodgson left out the excess volumes due to the thread relief and the aluminum washer used as the head gasket in his calculations because the result is 6.7 if these are ignored.
> Terry


 
Very interesting Terry. FWIW, I went through a similar calculation exercise on my own cad project. Another potential source of head 'volume add' that further reduces CR is the valve bottom superimposed into the cone shaped combustion volume. Depending on dimensional variables like how deep the seat/cage sits in the head, valve shape, valve seating depth, head cone angle etc... the resultant true head volume also develops those extra little stubby 'antlers'. It wouldn't seem like much when you see a typical drawing section view cut through the valve center & the valve bottom appears to connect closely across the head cone line. Its easier to visualize in 3D.  

In my case it wasn't much. But a steeper cone angle + larger diameter valves + deeper seating... potentially adds up a little here, a little there. Mostly I was trying to get a feel for how much CR would vary just by expected newbie machining & assembly inaccuracies. My planned remedy was utilizing different thickness head shims to balance the cylinders CR, I guess after doing accurate liquid volume measurement. But I'm not there yet so cant tell you how it turned out.


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## mayhugh1

Petertha,
         I agree with you. This number is very sensitive to machining errors especially when talking about c.r.'s of 8 or 9. In this radial I actually have the opposite case to the one you are looking at. My seats aren't fully recessed and so the valves actually rob some volume in the combustion chamber and will tend to raise the c.r. a bit. I didn't think to calculate its contribution when I did my c.r. calculations. - Terry


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## mayhugh1

Here, I've installed the intake and exhaust pipes, the pushrods, and the rocker arm supports. The engine is now completely assembled except for the carburetor and the sparkplugs and plug wiring. I shortened all my pushrods a bit to get the lash adjusters in the center of their adjustment range. I counted a total of 19 different machining operations that affect the length of this rod. My push rods end up about .130" longer than the stock rods due to changes I made in the valve design in order to accommodate my valve cages and keeper design as well as the changes to the lash adjuster that I made. The pushrods act at compound angles between the lifters and the rocker arms. These angles are different for the intake and the exhaust rockers. I studied the geometry of their movements and designed spherical cavities with conical walls for clearance in both the rockers and the lifters. The stainless steel pushrods have turned hemispherical ends to match these cavities. I hardened the lifters, and before milling the cavities into the aluminum rocker arms I pressed in phosphor bronze inserts. The rocker arms also rotate on bronze bearings. I was not able to convince SolidWorks, the CAD modelling program I'm using, to mate my pushrod with my lifters and rockers in an assembly so I could easily design the 'ball-and socket' connections. This was all done manually by trial and error and prevented me from getting a complete animated assembly of the entire valvetrain. I figured it was because the version I'm using is 6 years old but I was recently able to speak to a SW rep at a local demo and learned that this is a limitation of the tool. This is why I decided to make the pushrods a little longer and then trim them at final assembly. I made compression tests in each cylinder before putting the engine back into my 'motoring-in' setup. 
The compression test results were:
#1 = 70psi #9 = 72psi
#2 = 63psi #8 = 72psi
#3 = 66psi #7 = 72psi
#4 = 66psi #6 = 80psi
#5 = 77psi
These readings are repeatable and reasonably consistent especially since the engine hasn't yet been run and the rings have not been seated. The maximum I should theoretically expect for this engine is 72psi. The two cylinders at the bottom of the engine give somewhat higher than expected readings. This may be because oil has drained into them (known problem with radials) and reduced the volume of the combustion chamber somewhat. These readings are not consistent which those I made earlier before the pushrods were installed and when I manually pumped one of the valves to get air into the combustion chamber to get a compression reading. The reason for this is probably one of those mentioned by Lakc in his comments to my first compression measurements. It is certainly likely that I didn't open the valve manually the same amount that the cam is now opening it.
I also connected a sparkplug to my coil to exercise the ignition with multiple firings while the drill is turning the engine. So far, I am getting nice fat sparks at the test plug that seemed to be properly timed with the position of the rotor under the HV towers. The fat sparks are expected at low rpms since the coil is having a lot of time to saturate. More on that later. 
I'll run another 200 ml or so of oil through the engine with another series of short runs driven by my drill and starter adapter in order to start the run-in of the cam and lifters. I'm also curious to see what the oil seepage around the lifters on the lower cylinders is going to look like. I hate making engines that leak oil but I knew the reputation of this engine before I started. I'm finally happy with the appearance of the rocker covers now that they are finally all installed and don't plan on re-designing them. - Terry


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## petertha

mayhugh1 said:


> The compression test results were...
> These readings are repeatable and reasonably consistent...
> The maximum I should theoretically expect for this engine is 72psi.
> The two cylinders at the bottom of the engine give somewhat higher...
> Terry


 
I am really enjoying your detailed build/assembly report!

Is the Hodgson master rod compensated to acheive equal CR's for its link rod pin layout? (as opposed to 360 deg / 9 cyl = 40 deg equal nominal radial spacing). I'm sure he thought of that, but was just curious because of the pressure readings. Does your 72 psi theoretical max come from CR calculatiion using your TDC/BDC volumes? (Pmax = CR * 14.7 psi atmospheric)

link & post 4&5 has related info FWIW. This notion didnt even occur to me until I somehow stubled onto the topic.
http://www.homemodelenginemachinist.com/f26/master-rod-layout-15156/


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## mayhugh1

Petertha,
        In my post I'm estimating my max pressure readings from my calculated compression ratio and assuming 14.7 psi for atmospheric pressure. 
        No, the master rod is not compensated. The slave rods are all at 40 degrees. I went through the calculations to see what would be required for compensation but found there was not enough room for eight compensated and reliable slave rods on the diameter master rod that would fit this crankcase. If there had only been five cylinders I could have done it. I briefly thought about arranging the ignition trigger magnets and high voltage towers on the distributor in irregular intervals, but at that point in time I didn't feel confident about drifting too far out of the box on my first radial. - Terry


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## mayhugh1

I have finished the 'motoring-in' step with the pushrods installed in order to get a bit of initial wear on the cam and lifters and to check that they are all getting lubed. The two bottom-most lifters in #5 and #6 continue to leak oil. I found the cause and there doesn't seem to be practical fix for it at this late date. What's happening is that oil is accumulated behind the front cover of the engine where it is drained through a trough (that I enlarged by 50%) into the sump where it is removed by the scavenger pump. The inlet tube for the scavenge pump is about 1/8" from the bottom of the sump and so theoretically there would be a constant 1/8" level of oil left in the sump. However, air is trapped in the sump with no place to go when the engine is stopped because the only vent for the sump is the oil line going to the scavenger pump and this, hopefully, remains full of oil to maintain the pump's prime. Therefore the oil behind the front cover cannot drain into the unvented sump and it leaks around the lower lifters. Drilling a hole in the sump to vent this air might result in a more serious leak when the engine is running at speed. If I had known about this earlier I would have added a third tube to the sump and vented it into the crankcase. Hodgson recommends draining the sump after running the engine and so this should reduce this leakage. Hopefully this won't cause the scavenger pump to lose prime which is the reason that I was planning to not drain it.
I've finished the plug wiring. It took me longer than it probably should have because I'm anal about the appearance of the wiring in my engines. The wire looms that I designed for each cylinder keeps the wires away from the exhaust pipes and helps organize a radial harness around the back of the engine. Beside giving a better appearance, it also keeps the plug wires at right angles and away from the Hall effect sensor cable to reduce electrical noise in the trigger circuitry. I used 20kV wire and made up boots for the distributor towers from several layers of shrink tubing. I used simple low-profile clips for attaching the wires to the plugs instead of boots because the CM6 plugs are already too tall for the scale of this engine and adding boots to them will increase their heights. After inserting all the plugs I was glad to still be able to feel the compresion bumps when the engine was manually turned over. Having nine cylinders places them pretty close together. - Terry


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## mayhugh1

I thought I might mention a possible problem that has been on my mind and that may be waiting for me when the engine is fired up. I have a very big unknown and that is the Walbro carb that I intend to use on this engine. I have zero experience with these carbs and I don't even know if the one I have is capable of working on this engine. So, I have been trying to be very careful up to this point to eliminate as much uncertainty in the areas of compression and spark so that if the engine has issues with running I can be reasonably certain it is in the fuel system. 
I'm using the same TIM ignition in this engine as I used in the Jerry Howell V-4 that I built. An important parameter for this transistorized Kettering type ignition is the dwell since it sets the amount of energy that will stored in the coil for discharge across the plug gap. It also affects the relibility of the ignition components since significant power is dissipated in the output transistor and the coil and the dwell is a 'duty cycle' for this dissipation. I could easily calculate what I need to know if I knew the specs of the coil I'm using; but I don't and I don't have any equipment to measure the primary inductance in either the fequency or time domains. I do know, however, the resistance of the coil I'm using. Once the primary inductance is known, the slope of the rise of the current through the coil can be computed by L/R and knowing the saturation current I can compute the time it takes for the coil to just reach saturation. If I'm going strictly for performance I calculate the required dwell in degrees at the maxiumum rpm I want to run with full spark power. At lower speeds where the dwell angle is the same but the dwell time is longer, I waste power and decrease reliability of the ignition components by dissipating power in them after the coil saturates. If I'm going strictly for reliability I choose an idle rpm and compute the dwell ini degrees at that rpm. At higher rpms, the coil does not have time to saturate and the energy in the spark falls off until the rpms are increased to the point where the plug is not capable of firing at all. 
I built my Jerry Howell V-4 to his specs and used the TIM ignition and 'Exciter' coil that he sold. Only the resistance of the coil was spec'd but Jerry had evidently massaged the dwell so that the combination would work with his engine. The dwell in this engine was chosen to be 40 degrees (I'll always refer to crank degrees when speaking about dwell). This dwell is set in the distributor by the time the rare earth magnets that activate the Hall effect sensor spend over the active area of the chip. This time is, in turn, set by the diameter of the magnets and their radial distance from the axis of the distributor. Jerry chose 2mm magnets and .3 inches radial distance to get the 40 degrees. When I built and first tested this engine I verified the dwell at 40 degrees. This ignition combination was adequate to support 1200 rpm to 6200 rpm and I never had any problems with overheating the output transistor of the coil. 
For my Hodgson-9 I decided to use the same ignition since I had a spare original Exciter coil. This coil was designed by Bob Shores and is no longer available although a smaller cousin with different specs from the original (whatever they are.) is being sold from the Howell website. I have never wanted to make my own ignition coil because it is really difficult to do properly.) Anyway with 5 more cylinders power dissipation might become an issue for the electronics and so I decided to cut the dwell in half from my V-4 since I didn't forsee running the radial with its big prop at 6000 rpm. I went to the drawings for the V-4 magnetic disk and increased the radial distance for the H-9 magnets to .58" instead of .3". After the distributor was completed I verified the dwell measured 21 degrees which is close to what I wanted. Anyway, a few days ago I took the V-4 down off the shelf to run it. I decided to make a dwell measurement and I measured only 24 degrees! I rechecked my notes for that engine and verified that I had measured 40 degrees at various times just after finishing the engine 1-1/2 years ago. I still had several of the rare earth magnets left over from the V-4. They had been stored on a steel 'keeper' plate all this time and easured 40 deg dwell in a dummy magnetic disk that I rigged up. Evidently, over time, those magnets in the V-4 have lost strength. It is not temperature problem. The magnets are inside the distributor at the front of the engine which is water cooled with a radiator fan. The distibutor housing barely gets warm when the engine is run. I think the opposing fields of the adjacent magnetts locked in close proximity are causing the magnets to degrade over time. The four magnets on the V-4 disk are not distributed evenly around the distributor axis. This engine is actually two single pin crankshafts in tandem with an irregular firing order. This places the magnets in two closely adjacent pairs around the distributor axis whose od's are only .129" apart. The good news is that this problem offers some support for the 20 dwell choice I arbitrarily made for the H-9. The magnets in the H-9 distributor are spaced .32" apart at their od's which, hopefully, is enough so that they will not degrade and reduce the dwell even further. 
The photo shows my valve cage design. I was surprised to find out that the bottom cooling groove in the valve towers that intersects of the body of the head limited the diameter of the cage. Since I hadn't thought out the design of my cages before machining the heads I had to reduce the diameter of the valves slightly to be able to use a cage. I could have kept the original valve size if I hadn't cut this bottom cooling groove. - Terry


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## mayhugh1

OK, after 18 months and an estimated 3000 hours of work I've finished my radial to the point where all I can now do is add the prop and gas and then spin it up to see if it will run. The engine has been sitting fully assembled for a day and even though I did empty the sump, oil continues to drip pass the lifters in the two lower-most cylinders. There is only .0003" clearance between them but overnight a puddle of oil collects under them. Some oil is also dripping out of the #5 exhaust pipe. The engine happened to be left sitting with the #5 exhaust valve open and oil has drained past the rings and into the open valve. The rings fit the cylinders at installation such that light doesn't pass by the fit, and so the oil must be finding its way past the .004" ring gaps and the clearance between the ring i.d. and piston in the piston groove. Hodgson warns that it is necessary to remove the #5 and #6 plugs after running this radial in order to prevent hydrolock in these cylinders at the next start-up. I'm hoping mine will be 'special' and not require this because the clips I used for the spark plug wires are a hassel to remove from these two cylinders.
I've installed my Walbro WT-237 carb. (This carb is no longer available but its replacement WT-345 is available on Ebay for $10-$20.) I really want to make this carb work. And I really want to run this engine on gasolene instead of the methanol that I have been running on my other engines. The problem with methanol is that it's volatility is pretty low and so something has to be added to it to get a small IC engine to start expecially when the temperature is below 65F-70F. Jerry Howell recommended 20%-30% Coleman camp fuel. My experience with the Coleman in my V-twin has been that it will not stay dissolved in the methanol. If you vigorously shake the mixture you can get it to temporarily dissolve and it works OK if you immediately use it. The Coleman that I bought also has a lot of fine fibers in it that will clog the Howell carb and so I had to filter it before using it. I went looking for something else when I built my V-4. I found a similar product Crowne Camp fuel. This stuff readily dissolved in the methanol and didn't have to be filtered. It appeared to work well. I finished this engine in mid-November 2011. I ran it for a total runtime of an hour or so over a period of two weeks or so in my reasonably well ventilated garage - door open and exhaust fan running. When the blood tests for my annual physical came back in mid-December I was told that I had a low hemoglobin count that I had not had the year before. I wasn't anemic. For some reason my body suddenlt wasn't producing the proper level of hemoglobin. For some reason, I wondered if the camp fuel had something to do with it. My doctor suggested a re-test in three months. From that point on I only ran my engines outdoors. Three months later the re-test showed that my hemoglobin had not fallen any lower but was still at the level measured in December. At that point I decided to only run my engines outdoors. When I got my blood test results back for my December 2102 physical, my hemoglobin level was back to normal. I don't know know if the Crowne camp fuel had anything to do with this but I have quit using it altogether. Some model engine builders mix WD-40 with methanol to increase its volatility. I've tried this and at a 15% misture it seems to work even better than any of the camp fuels. The only issue with it for me has been with the Jerry Howell carb on my V-4. I have to make a final run with methanol only before putting the engine away because the WD-40 will clog this carb if any trace of it is left to dry up and scum over.
I was happy to see that there is enough carb vacuum when spinning the engine with the drill to suck my thumb hard into carb intake. I shouldn't have a problem with drawing fuel from my carb bowl. 
I added two photos of the internals of my fuel pump. The pump and motor were scavenged from a $20 electric fuel filler for fueling RC cars and planes and is available at hobby stores.
I've also added a photo of a neat device I bought at an auto parts store years ago to sanity check an ignition system. It is nothing more than a neon bulb with a pick-up loop. You place it near a plug wire with the engine running, and it will flash if the wire is being pulsed with high voltage. The leds I built into my firewall will tell me if my Hall device is working and this little device will tell me if the high voltage is actually firing without having to pull a wire to test it for spark. Pulling a wire in these model engine ignitions can be tricky since if you don't get it to close enough to engine ground when it fires you can damage your coil or output transistor.


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## swilliams

Well done Terry. 

It's looking great and so many small touches you've added that all sum up to make such an impressive outcome. I really like what you've done with the nut that holds the prop on and stand you've made up to hold everything.  

On another note, what do you think about the prospect of using a full size 6v coil with the Hall effect ignition you have employed? I imagine one of these can store significantly more energy than the small exciter, but will this make things easier or not? I guess with a bigger coil you need to reduce the dwell in order to avoid frying the power transistor. Is that how you see it? 


 Cheers Steve


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## petertha

mayhugh1 said:


> I was happy to see that there is enough carb vacuum when spinning the engine with the drill to suck my thumb hard into carb intake.
> 
> The pump and motor were scavenged from a $20 electric fuel filler for fueling RC cars and planes and is available at hobby stores..


 
This is incredible. Best of luck on the home stretch. 

Re the carb suction, can you elaborate on the Hodgson overall induction flowpath. In an earlier picture it looked like some sort of vaned cetrifugal 'booster-looking' device off the crankshaft. This gets fed by the carb outlet AF mixture, right?. Do the blades & chamber shape actually further compress intake charge by reduced chamber volumer? Ive heard people say this provides more equal distribution to the cylinders so the uppers dont run lean & lowers not more rich. That makes sense. But maybe I just dont understand the principle. It would seem to me with a centered carb, any one open inlet valve would receive almost a direct feed from carb to its inlet pipe in about the same path/distance. And at typical rpm this would happen in a blink. 

I can see there is something equivalent to a hydrostatic head difference between the upper & lower-most cylinders, but does intake mixture gas actually densify or coallesce or something that much that would cause the upper/lower lean/rich? Or is it moreso slinging the charge giving centrifugal push?

Re the RC pump, that is a great idea. Im not sure if its the type I've used but typically they make a glow (methanol) & gas (-oline or exhaust smoke feed). Just mentioning because sometimes internal gaskets, o-rings, plastic parts etc. dont like one fuel or another & can swell or degrade.


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## R Degen

What size prop are you going to use?


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## mayhugh1

Steve,
       That's pretty much how I see it. I haven't been able to get too quantitative about the performance of my ignition because I don't have a way to measure the inductance of my coil and he Lpri/Rpri are key factors in determining how much energy one can store in a the coil. Guess-estimating my Exciter coil primary inductance from its physical size and taking some liberties with how I think the potted case is filled with wire I get about 5 mH using a freshman physics equation for the inductance of a solenoid

L=(core permeability) (#turns^2)( core cross sectional area)/(core length)

This combined with the measured resistance of 1 ohm gives a current rise which I think is longer than it should be for the dwell time I'm using. I plan to get hold of an oscilloscope and make measurements on my ignition system soon, and especially if I have problems with getting it to run. I hate having such an important component of this project be such an unknown. I plan to stay with the same coil but may have to make some changes to the dwell time or the TIM circuit itself. I've already ordered some new magnets of various diameters so I can re-do the trigger disk in the distributor if necessary. I'm pretty sure the older style automobile coils have inductance values on the order of 25 mH or so because I measured some a long time again using equipment at a former employer's lab. (I'm a retired engineer.) They also have resistances lower than 1 ohm which means they draw quite a bit more current than I'm willing to put up with in a model. The other big unknown is how much energy is required to fire a plug in the combustion chamber. Part of my testing on my ignition will be placing a plug in a chamber under 70-80 psi and see what energy is required to fire it. - Terry


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## mayhugh1

Petertha,
        I disassembled the fuel pump I'm using to see if there were any o-rings in there to worry about with fuel compatibility. The one I'm using is just a some sort of plastic pump with no seals. The way they seal the shaft is with a close fit in a very long neck. The fuel lubricates the pump shaft and so it probably would like the RC glow fuel better than the gasolene. The testing I did on it showed some minor seepage here and so I just added a drain tube so any seeped fuel would not accumulate in the housing. So far my testing has showed no problems but it is a bit of a question mark in my mind also. 
      The impeller is meant to just keep the air/fuel mixture stirred up for better diffusion. There have been three iterations of the fuel distribution system in this engine. The first had no impeller, then a small impeller was added, and in this design there is a full size impeller. These were done to improve starting and to try to get an even distribution for all cylinders especially the #5 and #6. From what I understand these have progressively helped but not fully solved the problem. Most of the engines I have actually seen running have so many oil control issues with the lower cylinders that they fuel distribution issue is in the noise. In normal operation the bottoms of those cylinders behind the piston rings are filled with oil. The oil-drip system and a recommendation of straight 50 wt oil are attempts to try to reduce this. The impeller chamber has drain holes so that accumulated liquid fuel in this area is drained into the oil sump. - Terry


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## mayhugh1

R Degen,
    I have two props - a 26x10 two blade and a 24x10 three blade. I chose the diameters purely for esthetics and to allow me access to the throttle at the rear while holding the starter in the front with getting clipped in the face. - Terry


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## Lakc

Its just not a round engine if it doesnt leak oil, its part of the charm. 
As to fuel, E85 has been the easiest to get here. 15% gasoline 85% methanol. No oil to worry about like model engine fuel.


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## mayhugh1

Lackc,
        I haven't seen any E85 around here. (I think you meant ethanol.). This is Texas and we don't use no stinkin' corn gas down here.  - Terry


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## Lakc

http://e85vehicles.com/e85-stations.html

It aint worth nothing in cars, but for models it is fine


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## mayhugh1

This was a very bad day...
Today, I tried for a first pop. I've started with the Walbro WT-237 carb and both the high and low speed adjustment screws are 1 turn open from full closed. I'm running 87 octane pump gasolene and timingset at 10 degrees BTDC. I thought I had set the fuel pressure at 5 psi but I later learned it was set for 10 psi. I didn't get a single indication of firing on the first spin-up with my drill starter. So, with the fuel pump running, and ignition OFF I pushed down on the diaphragm on top of the carb to prime the metering circuitry while turning the prop a few rotations by hand. (On this carb I had drilled a small hole through the center of metal cover over the diaphragm.) This time I did get a first 'pop' but not kind of sustained running. Basically after a few minutes of playing, I decided that gas is probably not getting drawn past the inlet valve on the metering diaphragm due to insufficient manifold vacuum. The venturi on this carb is .310" which I think is close to ideal for this engine. I eventually got the engine to sustain running a couple times but only for a few seconds on primed fuel. To get even this I had to close the throttle almost completely and excessively richen both fuel screws 1/2 to 3/4 turn. This is a tricky maneuver, because at the angle I have to stand to fuss with the throttle or carb adjustments while holding the drill starter, the prop is only inches from my face. When the engine first started there was a glorious cloud of blue smoke as the lower cylinders cleared the oil that had drained into them but the smoke quickly dissipated a second or two later just before the engine died. I spent a good bit of time playing with the carb screws and engine timing because it seems pretty much everything is working except for the carb and I'm not going to be able to fix that with mixture adjustments. After an unsuccessful hour or so and running down the battery on my drill starter I decided to call it quits. I was able to determine was that I could force the engine to draw fuel from the carb, and probably puddle it in the horizontal venturi, by placing my thumb over the venturi and turning the prop over by hand. The only thing this meant though was that my fuel pump was getting fuel into the metering circuits.
While my battery was charging I decided to check the fuel pressure and found it was 10 psi and so I reset it to 5 psi and made sure it was a consistent 5 psi this time. Of course if the engine isn't getting fuel, decreasing the fuel pressure is the wrong direction to go. I also double checked my ignition to make sure I was getting a spark. Even with my limited dwell I expect to be getting fat sparks at starting and idling rpms and I am getting them as expected. 
Since I had tried everything else I could think of, I decided to shorten the spring behind the metering diaphragm. This is the spring that holds the inlet seat closed. My interpretation of the Walbro service manual is that manifold vacuum pulls fuel out of the carb that has been let into the metering circuitry by atmospheric pressure acting on the diaphragm which, in turn, has to overcome the force of a spring located between it and the inlet seat in order to open the seat and let in more fuel. The fuel pump seems to be doing its job. I took the diaphragm cover OFF several times, and there was always fuel under the diaphragm. I studied the Walbro carb service manual some more and to me it was just too simple. It just seems like it has to work.
This is the point where I decided, right or wrong, that the carb may not be getting fuel into the metering circuit because my vacuum signal was not strong enough to overcome the force of the stck spring. And so I decided to modify the spring.
The Walbro stock spring in this carb is .008" brass wire wound at a .125" od and free height of .330". For my first test I trimmed the spring to .255", but I couldn't get any better result trying to sart the engine. In fact I couldn't get much popping at all. Trimming again to .200" was too much and the result was gas puddling uncontrollably in the venturi. The engine wouldn't even pop off this flooding. 
I figured that perhaps something is wrong with this particular carb or my re-build job or whatever. I had a second carb that I found listed as 'new' on Ebay, but I suspect it was also rebuilt. It was a Walbro WT-345 which is listed as the replacement for the WT-237 and looks identical to it. I installed it with its stock spring, but I got the same no start results as before. I pulled all the sparkplugs and cleaned them. They were all wet with gas and some had some black carbon deposits that told me they had at least briefly seen a too rich fuel mixture. While all these starting attempts are going on I'm also fiddling with the oil drip regulator because the engine is blowing alot of oil out of the exhausts of the lower cylinders and between all the fuel collecting on my baseplate from my priming efforts, I can't tell if there is also gas in the oil. I'm afraid to limit the oil flow too much because I don't want to create a bearing problem on top of everything else. 
At this point I'm out in the deep weeds. I've tried many things in a reasonably systematic order that may not be apparent from my description, and nothing seems to be making sense. I seem to be able to move from no fuel flow to a flooding condition with very little small changes. Also in the mix along the way I turned a .250" reducing bushing for the venturi of the WT-345 to see if more carb vacuum was the problem and, again, no joy. I can not honestly diagnose what is going on. If I had to summarize what I'm seeing it would be that the engine isn't drawing fuel from the carb unless it is primed, and then when it is primed it draws an excessive amount and floods the engine.
At this point I decided to change to the Super Tiger carb and go back to my methanol and campfuel mix just to see if I can make any difference at all. In the back of my mind are the comments I've heard from model engine building experts that say "carb problems usually turn out to be electrical problems" and then there's the other one "electrical problems usually turn out to be carb problems." I installed the Super Tiger - I don't like this carb as much because the .350" venturi just seems too big - and changed out the fuel. In this carb setup my pump merely filIs a carb bowl to a pre-defined level and recirculates the remainder back to the tank. The carb sees no fuel pressure - just a fuel level below the venturi to draw from. I started my drill starter and on the second revolution I felt a thud and the starter stalled. The prop was locked up tight. I pulled the sparkplugs from the #5 and #6 cylinders and gasolene (not methanol) poured out of the #6 sparkplug hole. After draining the cylinder the prop turned very tightly and so something is wrong deep inside the engine. On one of my previous tests with the Walbro I had evidently managed to flood the engine and the excess fuel got sucked into the intake pipe of #6 and hydrolocked the cylinder. I was aware of the potential for this happening with oil and had been careful to check for hydrolocking after the engine has set for a while, but I wasn't expecting to see this happen with fuel literally minutes after previously cranking the engine. 
So, the engine will have to come apart to see what has happened. I may have bent a slave rod or even the entire main rod assembly. Either of those would be much preferable, though, to damaging the crankshaft. I'm just hoping the crank is OK. It's a complicated part with lots of machining operations, and it will be very tough to duplicate the fit that I had achieved with all the other mating components already completed. 
Now, I have to go start on my income taxes. I'm trying to decide if I should throw up before or after. - Terry
p.s.
I got to talk with Ron Colonna on the phone today after all the fuel fumes had a chance to dissipate. It turns out that Ron and I are almost the same age, grew up in the same town, went to the same high school and technical school and shopped at the same neighborhood hardware store for parts for our projects when we were kids. Ron has some experience with a Walbro-type carb on his Challenger V-8. After explaining what I had just been through, Ron suggested that my method of priming the engine by pressing down on the diaphragm was probably letting too much fuel into the engine. And now, after thinking about it, I can see his point. While I have the diaphragm depressed the fuel pump is just pumping fuel into the engine and where will it go? Of course, it will go into the bottom two cylinders. Ron also suggested that with the rpms I am likely to be turning with this engine it will probably never be drawing fuel from the high speed idle circuit and so I might try to turn that screw completely off. I studied the Walbro manual some more and noticed that when the throttle is closed, the carb is designed to also pull fuel from the high speed jet to enrich the mixture for starting when choked. Shutting off this path would elimimate another source of flooding while I am priming the carb by choking it with my thumb. I reviewed some 'first pop' videos that my wife took. (She was more excited about starting it up than I was.) They showed that with the stock carb and 10 psi fuel pressure the engine almost wanted to run. I did prime it for the first pop but possibly my mistake was re-priming it and flooding it thinking that I wasn't getting enough fuel. Holding down the diaphragm while turning the prop was a big mistake. A better way of priming it would be to partially cover the intake with my thumb. Very likely, the completely dead re-start attempts were due to massive flooding. If I had allowed the flooding to clear before trying to restart the engine perhaps my attempts to adjust the idle screw would have been more effective. Oh and one other thing: for the first several starts when I thought I was turning the idle screw I was actually turning the high speed screw. The carb that Ron used actually had .625" venturi so he made a .25" reducing bushing that went through the carb. It was cross drilled for the fuel holes and he had to make a new butterfly. At .310" Ron felt my carb was probably about the right size for this engine. After all my careful prep work I let things go to Hell in the heat of battle.


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## agmachado

Fantastic!!!

Congratulations... very, very nice job !!!

Cheers,

Alexandre


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## keith5700

Hope crank is ok.
The very first fire-up is always the worst because you have no idea where the fueling is set to.
When I eventually got mine to run I realised the settings I'd been previously using  to get it to start were waaaay too rich.
The only way I could get mine to run was to pre-heat the engine to around 50 degrees c with a fan heater.
After this first run, with much different carb settings, it will now start cold (just).

Lovely engine by the way.
Keith.


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## mayhugh1

Keith,
      What carb and fuel are you running?

Terry


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## keith5700

Terry, my situation is a bit different to yours in that I am hoping to go to fuel injection ultimately, so the carb setup is just temporary, just to see if the engine would run. So, I bought a small twin needle carb from a small rc aero engine. The bore is 5mm, and my engine is 40cc V8.
The engine will rev high, and also tick over at about 700rpm, although not at the same carb setting.
It served it's purpose in getting the engine to run but it's far from a permanent solution.

Fuel is ordinary petrol/gasoline.
Cheers.


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## Swede

Hi Terry - VERY nice build, and your descriptions of the carburetor issues and difficulties in a first run mirror my own to a certain degree.

First, I'm not sure why you feel that you need to use methanol with a stock RC model carb like the super tigre.  True, often the needle valves, venturis, and carb throat diameter are engineered for methanol, but they will work with gasoline.  The problem most people see when using a RC model carb is an overly lean mixture due to a large throat and low air velocity, and this can be corrected by selecting a smaller carb or sleeving the throat of a larger carb.  Additionally, of course, some sort of float bowl setup needs to be engineered so that negative head pressure of the fuel line to the carb remains consistent, as needle valve adjustments using gasoline are more sensitive than the same carb when using methanol and oil.

I started with a full hall-effect transistor setup, and a carb similar to your Walbro, with almost zero success.  I went to a local hobby store, and simply purchased a number of O.S. and Super-tigre carbs (3 or 4) and machined adapter plates for them, and I found that as the carb-size dropped, performance improved.  In the end, the best carb I found was from a .30 sized glow engine, a very simple unit.  It seems ridiculous that a carb from such a tiny engine would work well with a massive radial engine using gasoline, but for me, this was the case.

The tiny throat produces a nice air velocity, sucking and atomizing the fuel very well vs. the larger carbs.  And in the end, isn't reliable running the goal, vs. wringing a few hundred extra RPM out of the engine?

If you do end up with a simple/small carb, priming requires quite a few turns of the prop with a finger over the air inlet.  When mine fails to start, it's almost always insufficient prime.

The process from final assembly to a solid, running engine with no missing cylinders did take a while, and in almost every case, I found simpler was better.  I went from large, complex carbs to small, simple ones, and I also changed my ignition from 6 to 12V, installed a large coil, got rid of hall chips, and used a breaker with a tool steel cam, and this has been running now for many years, starting up with two hand flips.

I'm guessing your hall system is better engineered than mine, so I suspect it'll work fine, but right now, I'm guessing your problems are fuel and carb.  I hope there was no damage - rather than tear it down, I'd simply drain all fluids from it and check rotation and compression.  If all is good, I'd say go for it!

You've done a beautiful job of it - keep plugging away, and you will be rewarded with a sweet running engine.


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## mayhugh1

Kieth,
      I'm sorry I didn't recognize your screen name before. I've been following your build ever since it started. Your attention to detail and the workmanship in your V-8 totally blew me away. I don't know how many non-engine-builder friends I've pointed to your site just so they could see the realism. Some of them even thought it was a Photoshop creation. I've been especially interested in your start-up progress and am still eagerly following it. - Terry


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## mayhugh1

Swede,
        Thanks a lot for the advice. Once I get the engine running on methanol with the Super Tiger carb I will certainly give gas a try. I've been a fan of your website for many years. I first found it when I built my oven to give metalcasting a try. I spent several hours studying your H-9 project before I started my own, and some of the changes I made to the design were based on your experiences. Lee told me at one of the shows that the changes he eventually recommended for the ignition system were a result of your experiences. - Terry


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## mayhugh1

Day1...
Well, I opened up the front cover - it was very difficult to pull off. I had to rig a puller. I removed the cam ring assembly and cylinders #5 and #6. It turned out that the problem was that when cylinder #6 hydrolocked, the rear crank half could no longer rotate, but my drill starter was powerful enough to rotate the front half of the crankshaft a few degrees (this front crank cheek is clamped to the crank pin with a SHCS). This rotating slip around the crank pin caused the axes of the front and rear portions of the crankshaft to move out of alignment and bind in the main bearings as well as the front cover bearing. The bearings don't seem to be harmed. Loosening the front cheek SHCS clamp allowed the two halves of the crank to self-align in the bearings and the crank could rotate freely once more. This was a great relief. Fortunately, the rotational energy of the starter was slowly dissipated in the front clamp instead of being abruptly dumped as would have happened if had pinned the sections together. If I had used a pin it might have broken or, even worse, I might have broken a rod. I decided to check the rear cheek clamp in order to see if that section had also rotated. The front and back have to be aligned in order to align the oil passages through the crank. 
When I built the crankshaft I was able to easily tighten the rear cheek clamp with the crank in my hand. I then considered this a permanent assembly. When I tightened the front clamp, though, that had to be done within the engine during assembly, and I had only a small hex key that would fit through a cylinder opening in the crankcase to do it. It was difficult to put a lot of torque on the screw with the 1/2" long handle of the hex key. In order to get to get the rear section out I need to pull the seal plate and rear main bearing out. I've decided to just completely disassemble the entire engine, though, and start over. 
A quick look at a couple cylinders showed something amazing (to me, at least). When I annealed my rings a light straw oxide formed on them which I did not polish off. And, my 12L14 cylinders were internally lapped and hot-blued. When I looked at two of my cylinders I expected to see the bluing worn off where the rings had been rubbing. The amazing part is that there was absolutely no wear on the cylinders. The bluing was untouched. But the straw oxide on the rings was worn nicely around the entire circumference of the rings and they were a bright and shiny bare metal. I realize that without some actual runtime and combustion pressures this is only saying that the cast iron oxide is softer than the 12L14 mild steel but even still this was pretty unexpected. I've heard many builders comment that 12L14 is not a suitable cylinder material.
I can see why the bottom cylinders are so stressed with oil in these engines and why ring sealing is so important in them. When I removed the front bearing I could see that those two upside down cylinders were completely full of oil. There is no place for that oil to go since the skirts of the cylinders sit above the drain path to the sump. The sparkplugs of those cylinders will certainly have to be removed for long term storage so that this volume of oil, which is more than enough to hydrolock the cylinder, can drain out the spark plug holes. This is also a Lee Hodgson warning.
I didn't get very far into the complete teardown since my stomach was bothering me, but I wanted to make a little more progress so I decided to make another ignition test. Since I had the distributor off the engine already anyway, I hooked it back up to the radial ignition and spun the distributor as fast as I could with a dummy sparkplug connected and the sparks looked very healthy. Then I brought down my Howell V-4 and connected my radial ignition to it to see if it would run the V-4. I'm still using the V-4 distributor, of course, but the all-important coils and dwell times are the same for both engines. The V-4 fired right up and ran at full rpm and sounded even better than I remember it sounding on its own ignition. All this testing did not actually test the plug firing path through my radial distributor and so I plan to eventually rig up a plate with nine sparkplugs and connect it to the beautiful radial ignition harness that I will have to remove. If it passes that test OK, I'm finally putting the question of any ignition problem to bed. - Terry


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## jixxerbill

I dont know about model engine carbs but I know plenty about Holley's.. I do know for sure that a carb set up for gas will not work for alcohol.. It takes almost two times as much alcohol compared to gas to go thru the carb.. Im only mentioning this wondering if the problems people have with using a carb designed for use with nitromethane and trying to run gas thru it. Just wondering.. Maybe the search for the RIGHT carb is actually a search for a carb that has enough adjustment to get the air/fuel mixture correct.. I have wondered about this since seeing a thread back a couple months ago...Bill


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## RonC9876

Terry: Glad to hear the engine wasn't seriously damaged and that you are getting it back to where it needs to be. I was thinking it might be better to hand crank the engine until you get more familiar with the fuel flow. You would be less lkely to do damage to any internal parts that way. I have had some experience with model airplane diesel engines and you never use any type of starter with those due to the danger of hyraulic lock. Of course it requires a good glove on your hand to protect the fingers from backfire. With spark ignition and a four stroke engine, backfire is not likely. You mght wear your arm out cranking though until the thing actually starts. Best of luck. Ron Colonna


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## Lakc

Full size rule of thumb is count 6 or 8 blades rotation by hand before using the starter. (3 or 4 blade prop). This basically means you rotate it twice by hand, but 4-6 times would be better. If you ever had the pleasure of hand propping a real radial over you can feel the bottom cylinders when they hit tdc.


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## swilliams

Thanks for your thoughts on the ignition Terry, they are very helpful.

Looks like better days with your engine are just around the corner 
Good luck, I'm hoping it goes well for you

Steve


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## mayhugh1

Day2 ...
I tore the engine completely down and am now in the process of re-assembly. I did alot of thinking about what, if anything, I should do about the cheek clamp screws. I started thinking about the ugly possibility of tightening them so tightly that I broke one of them. I'm not a mechanical engineer, and so I'm learning as I go, but after a little research I was surprised to find out that common stainless steel screws are half as strong as those made of steel. I used 18-8 stainless steel 6-32 SHCS for the cheek screws in my mild steel crank mainly because I bought an assortment of them at a show and they look cool. I found the maximum recommended torque for 18-8 SHCS published at 9.6 in-lbs. This number goes all the way up to 30 in-lbs for a common steel SHCS. I borrowed a miniature torque wrench and ran some experiments in a 3/8" thick steel plate in which I had drilled and tapped a number of 6-32 holes. What I found was that for oiled threads all the 18-8's consistently broke at 30 in-lbs and all the steel screws broke at 50 in-lbs. The steel SHCS that I have on hand are military spec parts and they have a tiny fillet under the head instead of the sharp corner of the hardware store variety. I used the torque wrench to do some comparative measurements with the hex wrench I had used to tighten the front screw. I estimate that I was hand tightening the 18-8 stainless SHCS at 12-15 in-lbs. I replaced the rear screw with a steel screw and tightened it to 30 in-lbs. I also used blue (medium strength) threadlocker. I also did some experiments on both the purple and blue threadlockers and found that neither seemed to increase the break-away torque above the 30 in-lbs for a steel SHCS tightened to 30 in-lbs. They did add friction for much of the unscrewing process, however. For the front screw I bought a steel Torx SHCS because I had a long Torx driver that would fit through the crankcase to finally tighten this screw using the torque wrench inside the engine.
After assembly, the the crank turns freely in the front and rear main bearings but when the front cover is added there is still a slight bind. I have always had this bind even before the crash. I believe it comes from the fact that when the detail in the front crankshaft section forward of the front bearing is machined the shaft deforms from relieving stresses in the metal. Some of this detail is not symmetrical around the crank center axis and includes a keyway and a transverse flat needed for assembly clearance of the jackshaft. This bind is still about the same after my crash, and so I don't think the crank was tweeked during the crash. I thought about trying to straighten it - it's real tempting - but I finally decided to leave well enough alone.
After re-installing the rear spacer and impeller I temporarily added the rear section containing the distributor to verify the near zero backlash I originally had in the distributor drive. What I found now was some 10-20 degrees of backlash. After checking I found that the screw securing the magnetic disk and rotor to the distributor drive shaft was loose allowing the trigger disk and rotor to slip on the distributor shaft. There is no reason for this screw to loosen on its own. There is near-zero load on all the rotating components of the distributor. I suspect that when I originally timed the magnetic disk to the Hall device when I built the distributor over a year ago I did not finally tighten this screw after aligning it. There is a very good chance that the inertia of the disk and rotor allowed them to rotate and take the whole engine out of time sometime while I was trying to start the engine. It might have been when the engine first fired and tried to run but wouldn't sustain, or it may have happened when the engine was abruptly stopped by the hydrolock. Anyway, I'm glad I found it now because it would have been a big problem later. On the fronts of both of my other engines I engraved timing marks with which to compare with my flashing dwell led when the flywheel is turned over by hand before attempting to start them. I don't have these marks on this engine because of the prop and so I felt blind when it came to verifying the timing 'in the field'. I learned this evening though that comparing my dwell led with the position of the rotor as seen through my transparent distributor is just the thing I'm looking for. 
When I originally timed the camshaft I marked the cam ring, the integral cam drive gear on the crank and the jackshaft gear with witness marks so I could re-assemble the engine, if necessary, without going through the trial and error process of centering the cam between the intake and exhaust lobes on the intake stroke. I lined up my marks and checked the centering and the timing agreed within 1 degree of my original value.

I'm also adding some construction photos that I had taken during the machining of my oil pump because if you're like me you like to see pictures instead of boring text. 

- Terry


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## petertha

mayhugh1 said:


> Once I get the engine running on methanol with the Super Tiger carb I will certainly give gas a try.... Terry


 
Terry, I wish I could offer something more tangible than sideline cheering & admiration of what you've accomplished thus far. But I'm confident you will solve the issues one by one in the same methodical manner you built it.  

Not sure if you've seen this link or maybe the fellow visits this forum, but its a double row Hodgson. Looks like he selected an RC-ish looking carb for whatever reason, or at least for initial running. 

https://plus.google.com/photos/111407870409657577971/albums/5278304464310065009?banner=pwa
https://plus.google.com/photos/111407870409657577971/albums/5311594071549777217/5592492649961509586?banner=pwa

I think Ive seen others too, so maybe there is more than one way to skin this cat. I must confess I've hydro-locked the odd fuel flooded inverted 4S RC engine in my day, especially with pressurized fuel systems. Sometimes with a bent rod or sheared crankpin to show for it if the starter battery or gear ratio was strong. Those engines are nowhere near as complicated to dismantle, so the procedure was remove the glow plug, spin it up & behold the shooting fuel spray geyser. I wonder if a starter assembly using a cordless drill could be adapted & use its adjustable clutch to 'spin out' at some set point you deemed below an unsafe torque level?


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## mayhugh1

Petertha,
       You make a great point. My drill does have a variable torque setting. When I bought it I just set it for its maximum and forgot about it for normal use. It never occurred to me to drop the setting down to the minimum needed to turn the engine over. Thanks!!! - Terry


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## t.l.a.r. eng

Just thinking out loud, most if not all radial engines have updraft carburetors if they don't use fuel injection, and that prevents hydro locking for the most part. If you ever witness a flooded radial on the ramp at the local airport, you will see excess fuel running out the cowling, but not the exhaust.
 I used an updraft on my 1/6 Kinner and it is virtually impossible to flood.


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## mayhugh1

Day 3...
The main bearings, the oil pump, rear seal, impeller, timed-cam, and front cover are now all installed and the crank once again turns freely. Next I'm re-installing the pistons and cylinders. When I disassembled the engine after the crash, I bagged the piston and cylinder/head assemblies together and marked them so they can go back into their original positions. Here is a photo of the tools I use to re-assemble the cylinders and the 72 small pattern 4-40 nuts, washers and lock washers back onto the studs in the extremely limited space I have to work. The object is to not drop a fastener into an opening in the crankcase. I borrowed the idea for one of the tools from Ken-ichi Tsuzuki's website.
http://homepage2.nifty.com/modelicengine/h9index.htm
He's the extremely patient guy who had to remake his crankshaft four times (and he just finished finally finished his engine a week ago). Its is a simple but remarkably effective tool to start the 4-40 nut onto the stud in the limited space around the stud. At it tip is a short 4-40 stud (enough to to capture two threads and hold the nut. The tool is held above the cylinder stud and then with a toothpick the nut is spun onto the stud and then tightened with a tiny 3/16" open end wrench. For the bottom cylinders the sump interferes with tightening a pait nuts on each cylinder and so I ground down a closed-end box wrench for those two nuts. Also shown in the photo is the socket I use to tighten the sparkplugs. In order to get clearance around the 10 mm sparkplug the socket has to be ground down to its very minimum diameter even with the extra clearance aI added to the head. It is also important when designing the stand that there is sufficient room for the ratchet and plug socket to be able to remove plugs 5 and 6. My stand supports the crankshaft 6.6" above the deck and this gives just enough clearance for my tool.
When I installed my spark plugs during my orginal assembly I used a dab of copper-laced anti-seize lubricant (sold for this purpose) on the threads of the spark plug. I've always used this on my full-size engines but it doesn't look like such a good idea here. Nearly all the heads ended up with some of this on the inside surface of the combustion chamber. I cleaned this off with a long reach Q-tip. I don't think I want it ending up embedded in the valve seats. 
I re-assembled all the cylinders to the crankcase and while doing so I examined the rings with a jeweler's loop. Except for one piston, both compression rings show shiny wear patterns 360 degrees around them where the annealing oxide had worn off. The cylinders, themselves, are mirror polished but there is no sign of wear in the bluing. The one piston showed less than a 10 degree area of little or no wear, so fa,r on one of the rings. The oil control rings, however, all had two small 5 degree or so non-wear areas at the 5 o'clock and 7 o'clock positions with respect to the ring gap. Since these results were consistent among all the oil rings, this must have something to do with their construction. My lathe on which I bored the cylinders has a slight taper, and so when I bored the cylinders I made sure the larger diameter was at the bottom of the bore. Therefore, I expect the oil rings will take longer to seat because the diameter of the cylinder over a good bit of their travel is slightly larger in diameter than optimum; and, of course, the oil rings don't see much combustion pressure.
After installing the rockers and pushrods I re-measured the compression to compare with my original measuremens:
        now       previous
#1    71 psi    70 psi
#2    66 psi    63 psi
#3    67 psi    66 psi
#4    64 psi    66 psi
#5    70 psi    77 psi
#6    72 psi    80 psi
#7    75 psi    72 psi
#8    65 psi    72 psi
#9    71 psi    72 psi
The largest changes seem to be in cylinders which took a real beating with fuel flooding during the 'first pop'. I decided to not change the rings at this time but instead to wait to see if they improve after the engine is actually running. I have three spare head/cylinder/piston assemblies as well as a number of spare compression rings.
I'm stopping with any further assembly at this point. I'm making arrangements to get access to a scope to properly examine the operation of my ignition. I'm still bothered by the low dwell that I chose, and I may make a new trigger disk. But, I want to look at my primary coil current and secondary arc-burn waveforms with a scope to help me decide before I add the rear section, distributor, and wiring. This scope has the capability of recording waveforms and dumping them to a flash drive as a .jpg, and so I hope to include them in my next post.


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## Swede

A few thoughts - carbs designed for glow fuel will work with gasoline, but some caveats must be kept in mind.

Most of us at one time or the other in our lives have operated a glow engine on an RC plane or similar.  They behave well, and are generally easy to start.  Importantly, the mixture needle allows operation over a pretty healthy range, usually a turn or three.  When used with gasoline, the needle valve becomes much more sensitive, and the range in needle valve clicks or motion narrows considerably.

That was one of the problems I faced when experimenting with a new/different glow carb and gasoline fuel... where to set the darned needle valve.  If the needle is over a turn off from where it needs to be, the engine simply won't sustain, and the standard glow procedure of getting a rough run, then tuning the mixture for best running by ear, doesn't work as well with gasoline.

Probably the easiest method would be to open the valve two turns or so, prime, and crank. If the engine fires on the prime, then dies, open the needle another 1/4 turn.  Try again.  Eventually, it runs a bit more than just the prime fuel. When this happens, you're getting close. begin working with smaller increments, like 1/8 turn.  Eventually, the engine sustains, and more often than not, just a few clicks of the ratcheting needle valve will find the sweet spot.

One good part I've found - if your fuel pressure is constant, such as from a bowl, the needle valve will hardly ever need to be touched again.  Much better behaved than when using glow fuel.  I don't think I've messed with my needle valve more than two or three times since I found the sweet spot.

Oil - the H9 oil pump is extremely effective.  Now what I am about to say is pure opinion, so take it with a grain of salt - the scavenge pump, being larger, should in theory do its job.  But if the metering to the pressure pump is open too much, there's too much oil being delivered... the path that the used oil takes to get to the scavenge tank is very tortuous, and what happens is that oil rapidly accumulates in the front cover area, and in the lower cylinders.  During some early runs, I found oil being blown out the front ball bearing, just behind the prop.  Waaay too much oil, and as you have seen, you can hydraulically lock the engine.

Now, I run with my oil supply needle valve open only 1/2 to 3/4 turn or so.  In fact, here is how I start and run my engine w/regards to oil, and guys are going to cringe, but it works.

Engine is cold.

1) Open oil needle supply valve 4 or 5 turns.  
2) Switch off.  Hand prop a dozen turns or more.  We're pre-oiling a bit.
3) CLOSE the oil supply valve.
4) Prime the engine.
5) Crank it.  Yes, we start with the oil supply OFF.
6) Once idling, open the oil needle valve 3/4 turn.  

More open than that, I notice smoke, sometimes significant, from the bottom exhausts.  This tells me I've got too much oil entering the engine.

I've been running this way for years, with no noticeable wear.  When I miked a cylinder after this time, the wear was close to zero.  My cylinders are also 12L14.

Every engine is different.  Maybe my oil rings aren't as good as yours, maybe my pumps are different.  My point is that the design seems to run fine with less oil than our instinct wants to give it.  If you use transparent plastic lines for pressure and scavenge, you can see the oil flowing, and rather than seeing solid oil in the tube, I am seeing oil, then air, then oil, or a frothy mix of air and oil.

This engine (at least my example) does not get very hot.  I've been running it a bit leaner than I normally do lately, and have been rewarded with hotter cylinders and heads, especially the lowers, which pleases me.  I found that a larger prop also improved running and heat characteristics.

As you're discovering, it can take some time to get the engine running.  May I respectfully suggest skipping the drill starter.  Wear a leather glove, and hand prop.  It's more labor intensive, but when dialed-in, the engine starts with 2 to 3 hand flips.

Good luck with it!  You'll have it running soon.  One last thought - consider a large external battery for these early attempts... it removes one variable from the equation, namely, weak current and voltage to the ignition.


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## Swede

For reference, here is the carb I am currently running with... it is a Super Tigre carb, but I don't remember the exact model.  Off a .30 or so glow engine.  It looks ridiculously small, but works very well.

Over the years, I have measured full-throttle RPM with various ignition and carb schemes, and with the original prop, which was way too small, BTW, the highest I saw was 6,200 RPM.  That was using a larger carb and hall-effect ignition.  But mid-range and idle suffered... there was not adequate air velocity at idle to properly feed/atomize the fuel.  By going with a smaller carb, I lost about 400 RPM off the top, but it idles nicely.






This is your thread... I don't want to distract from it, but some of the issues you are having were identical to mine.  In the end, you know what is best for your engine, and how you want to operate it.  You've done a tremendous job with it, and I especially like how you packaged it all into a neat, tidy setup.


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## PeterB

This is amazing!!!
I can feel my breathing frequency change when I'm looking and reading your posts :bow::bow::bow:


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## mayhugh1

I was able to get hold of a Tektronix TDS2012C digital scope and a compatible current probe. This scope is capable of recording one-shot events and is nearly ideal for what I am trying do. I made a capacitive coupler for one of the x10 probes in order to sample the voltage signal from the high tension secondary winding of the ignition coil during an actual sparkplug firing. I experimentally sized the coupler to give a reasonable amplitude without damage to the scope or probe. The distributor is electrically connected to my radial engine's TIM ignition, but physically it is currently unattached to the engine. In these measurements I'm not passing any high voltage through the distributor. I have a sparkplug connected between the ignition coil secondary and system ground. The plug will fire nine times per revolution of the distributor rotor. The only part of the distributor I'm using in these tests is its magnetic trigger disk and Hall sensor. In order to capture the waveforms I want to study my plan is to arm the scope and just spin the pinion gear of the distributor with my finger while the ignition is powered. The current probe is around the lead going to the primary winding of the coil and will measure the current waveform of the primary winding. I'm using a third, ordinary, x10 scope probe to capture the coil primary voltage waveforms. I'll trigger the scope data collection with the rising edge of the coil primary voltage or current. This scope is capable of displaying only two channels at a time but can record and save them to a USB flash drive. - Terry


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## Lakc

It takes a very brave friend to loan you a scope to work on potentially damaging voltages.


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## cfellows

Terry, I hadn't seen this string of posts before and didn't realize you were so close with the hodgson.  All I can do is shake my head at the work you've done.  Hope to see you at Rudy's tonight!

Chuck


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## mayhugh1

The first pair of waveforms that I captured is the coil primary voltage and current. It takes a little trial and error to capture the information that I'm looking for because, being manually spun, the rotor rpms are constantly changing as it spins up to a high speed and then spins down. And, I want a time scale that optimally shows the waveform detail while the sensor is in dwell. "TEK0003.BMP" shows the coil primary voltage in green at the top and the coil primary current in yellow at the bottom. When the output TIP42C transistor switches ON the voltage across the coil's primary instantaneously switches to just over 5 volts. As can be seen later in TEK0000.BMP the leading edge of this voltage waveform appears in the secondary voltage waveform transformed by the coil turns ratio into a harmless low energy glitch. In a Kettering ignition with mechanical points this glitch would not occur because the capacitor across the points would slow the rise of this edge so that it would not be seen by the coil. The coil current rises exponentially toward its maximum which, in this case, is about 4.4 amps. Dividing the coil voltage by the coil current at the end of the dwell, after the effects of the inductance have died out, gives the coil resistance which, also measured independently with an ohmmeter, is about 1 ohm. The exponential current rise gives me an opportunity to finally calculate the primary inductance of my 'old style' Exciter coil. The time constant of this rise is the time it takes for the current to reach 63% of its final value. From the current waveform this time measures to be about 1.8 ms. The time constant for a series LR circuit is tc =L/R and so L = 1.8ms x 1 ohm = 1.8 mH. The time for the coil to reach its maximum (for all practical purposes) current is 4-5 time constants, and from this waveform we see this takes about 6 ms. We can also calculate the energy stored in the coil at the end of the dwell period as E = 1/2(L * I^2) = (1/2)(1.8mH)(4.4^2) = 17mJoules. This will be important later because this is the energy that will be available to the sparkplug to ignite and burn the air/fuel mixture in the cylinder. This will be a key parameter that will be used later to determine my dwell requirements. We can also calculate the power dissipated in the TIP42C during the dwell period. In my circuit this is (.6V vce x 3.5 amps avg) = 2.1 watts (I'm roughly eye-balling the average dwell current). I'll correct this dissipation for duty cycle as a function of engine rpm later. There is also a series diode in the emitter of the output transistor of Jerry Howell's TIM design whose only job is to limit the coil voltage and take some of the dissipation away from the output transistor. I need to keep an eye on the dissipation of this diode also. This dissipation = .75 Vd x 3.5 amps avg = 2.6 watts and, again, I'll correct the dissipation for the duty cycle later.
When the output transistor switches OFF at the end of the dwell period, the coil primary voltage spikes to about -26 volts as the coil tries to continue the primary current flow. This is the so-called flyback voltage and its value depends upon how quickly the output transistor switches OFF. To a first order, the amplitude of this spike can be as high as L x (delta I)/(delta t) where delta t is the switching time of the output transistor. Plugging in values for L, delta I and .5 us for the switching time for the TIP42C and ignoring strays we get a maximum of almost 16kV! However, this voltage is clamped to a much lower value when the plug fires. Without an sparkplug connected to the secondary it is this high voltage spike that destroys a solid state ignition when the flyback occurs. What is the value of this clamped primary voltage? To find this out we must use an important physics work called the Paschen Curve which is a curve of the breakdown voltage of an air gap as a function of the gap length and pressure of the gas surrounding it. Plugging in .018" for my spark plug gap, and 14.7 psi air pressure into this curve gives 2500 volts for the plug firing voltage. This means that the plug will fire as soon as the secondary voltage rises to 2500 volts. Dividing this initial firing voltage by the coil turns ratio of 100, gives 25 volts which is very close to the observed 26 volt primary clamped flyback. Assuming a compression ratio of 5, a resulting cylinder pressure of 73 psi, and the same plug gap the Paschen curve predicts a plug firing voltage of 8kV. Dividing this by 100 gives a primary clamped flyback voltage of 80 volts. The Vce and Vcb breakdown voltages for the TIP42C are 100 volts and so we are safe but with little margin.
The coil current drops to zero when the output transistor is switched OFF, and this marks the end of the dwell time. There is some additional structure in the primary voltage waveform that occurs after the end of the dwell. This 'noise' is coupled back through the transformer from the high voltage secondary to the now high impedance primary and is created by the electrical storm going on in the plug gap.
I selected this waveform pair out of many that I captured because they represent an engine rpm where the dwell is such that the coil just reaches its maximum possible current. If the engine is running faster, the coil current will peak out at a value limited to less than its maximum possible, and the energy available to burn the fuel in the cylinder will be lower. If the engine is running slower, the current will not be significantly higher; and the net result will be the output transistor and the coil run warmer. 
The waveform "TEK0000.BMP" shows this effect. Here, the top green waveform is now the secondary voltage. Although the vertical scale says 50V/div this is relatively meaningless because of the the uncalibrated capacitive coupler that I made to pick up the high voltage secondary. We can estimate the attenuation of my coupler by assuming the actual peak secondary voltage is the Paschen value of 2500 volts. Since the scope is recording this spike at 155 volts, my coupler is therefore attenuating the signal by a factor of 16. The bottom yellow waveform is the coil primary current as before. In this waveform, the distributor rpms are rapidly slowing down after being manually spun up; and we can see two adjacent primary current pulses. In the first pulse the coil has enough time to reach the full 4.4 amps, but the second pulse has only enough dwell time to reach only 4 amps. (It seems to be common jargon to refer to the maximum possible current that the coil can reach as the 'saturation' current; but technically the flux density of the core is not actually reaching its saturation point and so I just refer to it as the maximum possible current.)
The large positive spike in the green secondary waveform when the output transistor switches OFF is, of course, the voltage that fires the plug. As explained above, this voltage will rise to whatever the cylinder conditions require (up to the max possible flyback voltage times the turns ratio) to jump the plug gap. The air/fuel mixture is NOT instantaneously ignited at this time. Just after the plug fires the voltage waveform quickly falls to about 150 volts which is the voltage needed to sustain the arc across the plug gap. The voltage remains at this value for about one ms while the total stored energy in the coil (the mJ we calculated before) is dissipated in the plug gap. It is during this time, called the spark time or spark zone, that the air/fuel mixture starts to burn as the energy necessary for ignition is transferred to the mixture. This spark time continues until the coil runs out of energy to sustain the arc in the gap. Hopefully the mixture is explosively ignited before the end of the spark zone. The time it takes after the plug first fires to transfer enough spark energy to the mixture to cause it to explode is dependent upon a number of complicated factors; but this delay is the reason why we typically have to advance the timing in an engine (even our small unloaded models) to get them to run optimally. Statically timing an engine so the plug fires at TDC means only that the plug will instantaneously fire at that time. Additional time is required for the coil to transfer sufficient energy into the mixture to reliably light it up. And this happens during the 1 ms interval after the initial plug firing. In a V-8 running at 5000 rpm this 1ms spark time is equivalent to up to 30 degrees of timing.
The green secondary voltage waveform in "TEK0000.BMP" shows a relatively large negative spike after the arc extinguishes and then a noisy decay back to zero. What is happening here is that when the coil current is once more interrupted but this time by the extinguished arc and another flyback spike occurs, this time in the secondary, as the coil tries to maintain the sparkplug current. In a Kettering system with mechanical points and a capacitor this shows up as another nicely damped sinusoid as the remaining coil energy oscillates back and forth between the coil and the capacitor. 
The final goal is to put all of this together in order to come up with a value for the dwell time. This dwell time will determine how much energy is required to reliably ignite the air/fuel mixture over a reasonable range of engine rpms and cylinder conditions. To do this we must know, after the plug fires, how much coil energy is required to start and continue the mixture burn. There have been several white papers written on this subject especially over the past 40 years when the auto manufacturers have been interested in cleaning up engine emissions. What I have found is that a minimum of 0.2 mJ is capable of reliably burning fuel at a stoichometric ratio of 14:1. For very rich or very lean mixtures as much as 3 mJ may be required. The high energy ignitions in modern full-size engines can produce as much as 70 mJ or more, but those high values are required to reduce emissions under demanding cold start and high load conditions. Supercharged race engines use ignitions capable of producing more than 100 mJ. For my model radial I'll likely set an energy requirement of 1 mJ or so. I hope my next installment will have the final data to tell me if my present trigger disk is adequate. - Terry


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## Lakc

Its nice to have the right toys, its downright frustrating to use my old analog scope with a broken trigger circuit. Nice writeup, thanks.


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## mayhugh1

From the waveform measurements I compiled two tables - one for a 10 (distributor) degree dwell trigger disk and one for a 20 degree dwell trigger disk. My radial currently has a 10 degree trigger disk. Each table shows the spark energy, the output transistor dissipation, and the coil dissipation as a function of engine rpm. I realized that I have not yet shown a schematic of the TIM ignition and so I am including a sketch of it also. This circuit was first published in the June/July 1992 issue of Strictly IC magazine and has been successfully used by many model engine builders. Jerry Howell added the series diode in the emitter of the output transistor in order to reduce the coil current so that a 6 volt battery could be used for a power source. This exact circuit is in both my V-twin and V-4 engines. (In fact the V-twin uses two of them instead of a distributor.) My tables also include the power dissipation of this diode as a function of rpm. From our last discussion a 1mJ spark energy should be adequate to ignite an air/fuel mixture that this engine is likely to encounter (once the carburetor problems are sorted out). The tables show that either 10 or 20 degrees of dwell should be capable of running this engine beyond 5000 rpm with the 20 degree dwell providing some healthy margin. And so, the component dissipations will be considered next. 
Ignoring, for a moment, the issue of zero rpm i.e. if the engine is stopped with the Hall device triggered ON, the heat-sinked output transistor and the dropping diode dissipations are within reason. Things get a bit toasty for the non-heat-sinked diode at idling and mid-range rpms with the 20 degree dwell, however. The coil dissipations are markedly higher with the 20 degree disk. The coil is rather physically large, but the epoxy potting likely has a high thermal resistance, and so the core and windings will likely see high transient thermal stresses that will affect the reliability of the coil. 
And so my conclusion is that I will, for now, stay with the 10 degree disk that is currently in the distributor. My engine will likely spend most of its time between 2000 and 4000 rpm and this seems to be a sweet spot for this ignition combination at 10 degrees of dwell (and assuming all this theory is correct :wall.
The real concern is being careful to not allow the engine to sit still with the coil current ON. With my brief experience with this engine so far, the compression bumps tend to cause it to settle in a position with the coil current OFF. The diode and coil seem to be the biggest at-risk components. I am going to look at replacing the diode with a higher current version or adding some kind of heatsink. 
It would seem that ideally this circuit could be further optimized for this engine by adding a second dropping diode and then changing the dwell to 20 degrees to compensate for the drop in current caused by the second diode. The second diode would divide the dissipation between two devices and it would limit the coil current at zero rpm with the output transistor ON. The increase in dwell would compensate for the lower maximum coil current at higher rpms.

One last comment concerns the gap between the rotor tip and the high voltage tower contacts of the distributor. The tip of the rotor generally doesn't actually touch the tower contacts as this could leave metal particles in an area where they can cause a lot of havoc. And so the distributor must designed so there is a gap between the rotor and the tower contacts. It is important to make this gap as small as possible because there are two gaps to which the ignition must supply energy. The energy in the spark zone will be divided between the rotor gap outside the engine and the sparkplug inside the engine. The rotor gap energy does nothing to help burn the air/fuel mixture in the cylinder. It just erodes the rotor and tower electrodes over time and widens the gap to make the problem even worse. My plug gaps are about .018" and so my design goal was to have a maximum rotor gap less than .002". Jerry Howell's otherwise great distributor was designed to use the Satra distributor cap which uses metal rivets for contacts which stick down vertically from the towers. The rotor must be designed so that its flat top surface rotates below these rivets. The problem with this design is that it is difficult to maintain a consistent vertical clearance between the rotor and the tower contacts. This clearance is affected by the bearing scheme used for the distributor shaf, but even more important it is affected by the run-out of the meshed pinion gear set driving the distributor shaft. A much better design for the cap is the one used by full-size distributors back in the days when distributors were used. In these caps the tower electrodes extend down from the tower insulators at the periphery of the cap. After the electrodes are pressed into the towers, the cap is put in a lathe (or on a mill and rotary table); and the electrodes are bored out to about half their diameter for a depth sufficient to clear the total height of the rotor. The diameter of this bore is equal to the diameter of the rotor. In this scheme it is not important to maintain a consistent or non-varible vertical clearance of the rotor since the rotor gap is now horizontal instead of being vertical. It is only the run-out of the rotor and the centering of the tower boring operation that determines the maximum gap. I made my cap in this manner and included a registered periphery to insure consistent mounting to the distributor base.

The next step is to finish the assembly and try for a 'second pop.' - Terry


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## mayhugh1

I've included the Paschen curve I used in my previous post. I forgot to add it to my previous discussion of the dwell requirements for my ignition. 
I finished the re-assembly of the engine, timed the distributor, and made sure the trigger disk screw was tight this time. I've decided to use the Super Tiger carb for this second start attempt since I think my chances for success are higher. I'm also going to start with a 15% mix of methanol and Crowne camp fuel since I will be safely outdoors. The methanol I'm using is from an Auto parts store. It is sold as a fuel line dryer called 'Heet'. The yellow bottles are nearly pure methanol while the red bottles are nearly pure rubbing alcohol. If I can get the engine running to a point where I'm satisfied with it I'll then try gasolene in this carb per Swede's comment. I hope to return to the Walbro later. The carb that I have is a Super Tiger model 12163146. It was salvaged from a second hand RC helicopter that my son didn't have much success in learning to fly. It was designed for high revving glow engines with displacements between .60 and .90 cubic inches. This sounds like an ideal carb for this engine but it this carb was designed for engines that rev up to 16,000 rpm. As others have pointed out in this thread, a carb this size is likely a bit large for this radial which has a per cylinder displacement of just under .9 cubic inches and maximum rpm of 5k to 6k rpm. This carb is spec'd with an internal throat diameter of .41" but I measure a venturi diameter of .35".
So I decided to pre-set the needle adjustments to the lean side before mounting the carb to the engine. To do this I connected a length of clean plastic tubing to the fuel inlet on the carb. With the throttle wide open I blew into the other end of the tubing and adjusted the high speed needle while listening for air flow through the throat of the carb. My goal was to find the point at which the air flow stopped and then open the needle 1/2 turn as a starting poin for my radial. However, I could not stop the air flow no matter how far in I turned the needle. I couldn't see any damage to the needle itself and so I don't know if this is the wrong needle or if the carb was designed so the high speed mixture cannot be completely turned off. I performed the same test with the low speed needle but this time with the throttle nearly closed. I was able to then set the needle 1/2 turn open from the point that the air flow ceased.
At this point I'm beginning to remember that the engine on that helicopter didn't actually run all that well, and so I went down to the local hobby store to buy another carburetor. The only one they had in stock was a Super Tiger 12163145. It is designed for glow engines with displacements between .40 and .51 cubic inches. It has the same .41" internal throat diameter as my salvaged carb but, for some reason the outer diameter of the throat is .050" smaller than the carburetor around which I designed my adapter. So I made a .025" brass bushing for my adapter so I wouldn't have to make a new one. With this carb I was able to completely shut off the air flow using the high speed needle with the throttle wide open. In fact, I tried this needle in my first carb and it also shut off the air flow in that carb. This makes me think the stock needle on the first carb was designed to always allow some mimimum amount of fuel flow past the high speed needle. This is probably something I really don't want for this engine. With the throttle fully open I opened the high speed needle 1/2 turn from the point at which I could here no air flowing through the carb. With the throttle nearly closed I opened the idle needle 1-1/2 turns from the point where I could here no air flowing when I blew softly into the tube. I marked both needles with dabs of paint so I can keep track of their settings.
Next, I attached the bowl to the carb and hooked it up to my fuel pump before bolting the combination onto the rear of the engine. My last experience has made me overly sensitive to potential flooding problems and so I wanted to make sure I don't at least have this problem. Unlike the Walbro, in this set-up the fuel pump just pumps fuel into the bowl which tries to maintain a constant level with the excess being returned to the tank through a return line. The level in the bowl is set by the height of a vertical return tube soldered to the bottom of the bowl. I moved the bowl to its lowest position on the carb adapter to reduce any chance of flooding and this position sets the fuel level .25" below the carb spray bar. Unfortunately when the fuel pump was turned on and the carb primed the carb flooded. with no air moving through the venturi. The fuel pump has a rheostat so I can adjust the voltage to the pump, but I had only a very narrow range of voltage around three volts where the pump would pump without flooding the carb. I had not done much testing on this set-up since I expected to be using the Walbro with the pressure regulating bowl that I had designed and thoroughly tested. This Super Tiger was pretty much an after thought and a very distant plan B.
The cause of the flooding was the turbulent high speed flow of fuel into the carb was causing the fuel level to rise all the way to the top of the carb in one single corner of the bowl. And this corner happens to be where the outlet to the carb is located and so the fuel level seen by the carb was above the spray bar. I think the carb was probably even seeing pressurized fuel when the fuel in this corner hit the lid on the bowl. This was happening even though my fuel line to the bowl contains a .022" restricter. I tried adding various baffles to the bowl to try to drop the fuel level in this corner, but I could not find a solution in the small volume of the bowl. Eventually I shortened the height of the drain pipe inside the bowl. This allowed me to get a non-flooding pump zone over a range of 3 to 5 Volts pump voltage - not perfect but good enough. - Terry
&#12288;


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## Lakc

I appreciate all the work you have put into the math involved regarding ignition systems, its very timely.


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## mayhugh1

Success !...
I bolted the engine down to a workbench in my backyard to try for a 'second pop'. I'm currently running the oil system open loop. I am pumping fresh oil into the engine from my oil tank; but instead of allowing the scavenger pump to return the oil to the tank I am just pumping it into a waste container for disposal. I put my thumb over the carb intake and turned the prop over by hand two turns to prime it using the idle and high speed settings I came up with in my shop last night. The priming wetted my thumb with fuel and I took this to be a good sign. I opened the throttle half way and turned the ignition ON making sure the prop wasn't resting in a position with the coil current ON. I had the drill starter in my hand; but, just for the heck of it, I gave the prop a slap with my hand. I couldn't believe it. The engine started right up and ran and it sounded great. It appeared to be running on all cylinders as I could feel hot exhaust gases coming from all the exhaust pipes including #5 and #6. Even more astonishing to me was the fact that I was getting no oil smoke out of any of the exhausts. My brain was in a such a startled state that I couldn't decide what to do next. I had a notebook set up so I could record various carb and timing settings and their results as I went through what I thought was going to be a laborious process to get the engine to run. But this I wasn't ready for. I decided to use up the fuel remaining in the tank using the existing carb settings with short runs of a minute or so each and to allow the engine to cool down completely between these runs in order to help start the seating process for the rings. I only got three short runs because this engine really uses up fuel quickly. Part of this, of course, is related to the fact that I'm using methanol, but right now it seems to be using about an ounce per minute at half throttle. Because of comments I had heard from other builders I wasn't expecting the high temperatures at the heads and exhaust pipes that I'm seeing. After a minute of running, mine are much too hot to touch. Lee had told me the exhausts would be cool to the touch and so maybe when I optimize the carb settings I'll find I need to richen the carb. I spot checked the #2 plug and it looked like new, but frankly methanol isn't going to color the plug in any meaningful way.
The engine started easily by hand for all three one minute runs, and so I decided to quit and celebrate. My next step will be to optimize the carb settings for methanol/Crowne camp fuel. I plan to continue using short runs with cool down between for the first half hour or so of running. I'll also continue to run the oil system open loop for the first hour or so of running.
After I get the carb and timing settings to a point where I can't seem to make any further improvement, I'll take and post a short video before changing over to gasolene or perhaps going back to the Walbro (yeah, ... like that's going to happen). - Terry


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## kuhncw

Congratulations, Terry!  Glad to hear your radial fired up on the first flip.

Regards,

Chuck


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## RonC9876

Terry: Way to go! You must have been smiling from ear to ear when it fired right up. Glad you decided on hand cranking. Less chance of doing damage. Congratulations on a job well done. Ron Colonna


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## petertha

mayhugh1 said:


> ...I had heard from other builders I wasn't expecting the high temperatures at the heads and exhaust pipes that I'm seeing. After a minute of running, mine are much too hot to touch.- Terry


 
First off... YAAAY! So glad to hear its running!

I cant speak for your exact fuel methanol mixture but it's not uncommon for typical RC 4-stroke methanol burners to be pretty hot in my experience. Some of the exhaust hardware we happily ran on 2-strokes sometimes melted or fatigued on 4-S. 

Its been too many years to remember exactly, but head temps north of 400F ring a bell & exhaust headers temps higher yet (influenced by prop blowback cooling &  other variables). You probably have seen these cheapy temp gauges, but they are kind of handy for checking different spots quickly.
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXEMG5&P=ML

I will be interested to see your cylinder temp variation once its broken in and up & running, Congrats!


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## mayhugh1

Thanks all for your congratulations. The tips that many of you gave me during the past weeks were greatly appreciated and helped me get it running.

Petertha,
Your comment on your experiences with 4-strokes running hotter head and exhaust temperatures when burning methanol instead of gasolene caught me by surprise. I thought the opposite was true. I'm not at all familiar with its chemistry, but I thought methanol had a cooling effect in the combustion chamber because of it higher heat of vaporization and that fact that almost twice as much is required to produce the same power. I figured its cooling effect was also one of the reasons it is a popular fuel in air-cooled RC engines? Do you have any references you could point me to?
I run methanol in my other two model 4-stroke engines, but I don't like it because it corrodes aluminum (you need to make the carb and fuel tank out of brass). It's expensive, and its volatility is so low you have to mix it with something more volatile in order to reliably cold start a small engine. I expect the oil or some other corrosion inhibiter in two stroke fuels limits the corrosion in (lightweight) aluminum R/C carbs. The only advantage I can see in using it for model engines is that the carb settings are less sensitive; and so the sweet-spot is maybe twice as wide as when using gasolene. I tried gasolene in the Jerry Howell carbs on my V-4 and V-twin engines when I built them and could not get a consistent combination to run. 
Now I'm curious. I'm going into the shop and make a new set of needles for the carb on the V-4 to see if I can get it to run on gas. I'm going to lengthen the taper by a factor of two and see what happens. - Terry


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## Lakc

Congratulations, it sounds like you have it dialed pretty dead on!
Alcohol as you know has half of the heat energy of gasoline, but if you burn twice as much its just as hot as gasoline, minus the latent heat of evaporation difference. This tends to effectively lower cylinder temperatures, but more fuel beyond that leaves more leftover cooling benefits further down the exhaust valve, port, and tube. As I said, the way it looks, it seems pretty dead on.


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## ozzie46

Congrats on getting it to run.Thm:Thm:Thm:Thm:

  When can we expect a video??  Hmmm.  ;D;D;D

Ron


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## GailInNM

A great milestone Terry. One you can be very proud of.  I have followed from the first post and very happy for you, but there was never really any doubt of the final outcome.  Congratulations.
Gail in NM


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## Niceonetidy

What a marvelous experience to see the engine run, congratulations, well done

Kind regards

Colin




mayhugh1 said:


> Success !...
> I bolted the engine down to a workbench in my backyard to try for a 'second pop'. I'm currently running the oil system open loop. I am pumping fresh oil into the engine from my oil tank; but instead of allowing the scavenger pump to return the oil to the tank I am just pumping it into a waste container for disposal. I put my thumb over the carb intake and turned the prop over by hand two turns to prime it using the idle and high speed settings I came up with in my shop last night. The priming wetted my thumb with fuel and I took this to be a good sign. I opened the throttle half way and turned the ignition ON making sure the prop wasn't resting in a position with the coil current ON. I had the drill starter in my hand; but, just for the heck of it, I gave the prop a slap with my hand. I couldn't believe it. The engine started right up and ran and it sounded great. It appeared to be running on all cylinders as I could feel hot exhaust gases coming from all the exhaust pipes including #5 and #6. Even more astonishing to me was the fact that I was getting no oil smoke out of any of the exhausts. My brain was in a such a startled state that I couldn't decide what to do next. I had a notebook set up so I could record various carb and timing settings and their results as I went through what I thought was going to be a laborious process to get the engine to run. But this I wasn't ready for. I decided to use up the fuel remaining in the tank using the existing carb settings with short runs of a minute or so each and to allow the engine to cool down completely between these runs in order to help start the seating process for the rings. I only got three short runs because this engine really uses up fuel quickly. Part of this, of course, is related to the fact that I'm using methanol, but right now it seems to be using about an ounce per minute at half throttle. Because of comments I had heard from other builders I wasn't expecting the high temperatures at the heads and exhaust pipes that I'm seeing. After a minute of running, mine are much too hot to touch. Lee had told me the exhausts would be cool to the touch and so maybe when I optimize the carb settings I'll find I need to richen the carb. I spot checked the #2 plug and it looked like new, but frankly methanol isn't going to color the plug in any meaningful way.
> The engine started easily by hand for all three one minute runs, and so I decided to quit and celebrate. My next step will be to optimize the carb settings for methanol/Crowne camp fuel. I plan to continue using short runs with cool down between for the first half hour or so of running. I'll also continue to run the oil system open loop for the first hour or so of running.
> After I get the carb and timing settings to a point where I can't seem to make any further improvement, I'll take and post a short video before changing over to gasolene or perhaps going back to the Walbro (yeah, ... like that's going to happen). - Terry


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## cfellows

Congratulations, Terry!  I guess I can breath again.  After seeing all the work you've put into this project I probably would have been as heartbroken as you if for some reason you couldn't get it running.  But, the truth is, I was pretty sure you would stick with it until you got it going and going well, even if you had to rebuild it from scratch!  

Chuck


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## petertha

mayhugh1 said:


> .. your experiences with 4-strokes running hotter head and exhaust temperatures when burning methanol instead of gasolene caught me by surprise.


 
To clarify, my experience/comment was 4-S engines seemed to run hotter on the exhaust assembly components vs. 2-S engines, but both were typical RC methanol based fuel (+nitro +oil), not gasoline. I do recall measuring this temp increase directly with gauges & thermal crayons because we were struggling with exhaust bits burning up way more frequent than 2S. As to why... the thinking was 2S benefited by cooling from the fresh induction charge even though it was firing less often than 4S. But this is off topic to your gasoline vs methanol point, sorry for any confusion. 

I'm trying to find links of (methanol based) temperature & this is about what I could muster FWIW. I don't think my rusty recollection of ~400F is very far off at the exhaust header, but as mentioned, subject to numerous assumptions & variables (engine type, load, avg head temp vs exhaust area temp, prop cooling blast, lean/rich setting, oil content, rpm, boost.... etc.) 

http://www.rcgroups.com/forums/showthread.php?t=1598160
http://www.teamflyingcircus.com/forum/f23/cylinder-head-temp-5982/index14.html

http://www.rcgroups.com/forums/showthread.php?t=715078


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## Art K

Terry,
Good job getting the radial running. Not surprised it started on the first flip, you seem to be the thorough sort. Nice job, I'm looking forward to the video! I've been following your thread for a bit now, good luck with the minor sorting out.
Art


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## mayhugh1

Lakc - good point on the 2x fuel volume and thanks Petertha for your clarification. I mis-interpreted your post.
I spent a few hours making a new but ugly looking set of needles for the Jerry Howell carb on my V-4 to see if I could have any better luck running gasolene. I was hoping to reduce the taper by a factor of two, but there wasn't enough room in the carb for such a shallow taper and so I was only able to reduce it about 20%-30%. I figured any amount would be better than nothing. The bottom line is that I was able to get it to run just fine on gasolene. The new idle needle seemed to have about the same setting sensitivity as my original needle, and so I put the original one back in; and sure enough I got it to idle and run mid-throttle just fine. I found a narrow setting, about a quarter turn, with the new high speed needle where the transition from idle to high speed was acceptable. I put my original high speed needle back in at its original methanol setting, and the transition from idle to high speed stumbled badly. In order to correct this I had to reduce the high speed setting by a full half turn which almost completely shut fuel off to the high speed spray bar. I let the engine cool for several hours and then cold started it. It immediately fired up and ran, probably as good as it ever did on methanol, and the throttle response was as also as good as I'd seen it. I plan to run gasolene in that engine from now on. 
Meanwhile, I put some more runtime on the radial. I'm still running a 15% mix of methanol and Crowne camp fuel because I want to see how well I can get it to run on methanol first. I'm continuing to run short 1-2 minute cyles with complete cool down in between and I'm resisting the urge to rev it up to full throttle. The engine starts everytime with just a flip of the prop. My timing is 10 deg BTDC and some cursory checks show that the performance, so far, doesn't seem to be very sensitive to timing advances between 10 and 30 deg BTDC. But then I'm not revving the engine up yet either. Using an IR probe I measured the head and exhaust temperatuures after several mid-throttle runs and never saw them to be over 140F. I'm sure this is probably the 'cool' running exhaust temperature that the other builders have described. I guess I was just too excited yesterday when I was measuring it with my uncalibrated finger and thought the temperature seemed excessive. Still in the back of my mind is my construction error of using SAE-660 bronze for the valve cages, and I don't feel comfortable using this material at 400F-500F.
With a whopping 10 minutes total run time so far I made some rpm measurements so I could calibrate my ear. I was able to get the engine to idle down to 800 rpm while still hitting on all cylinders, and the sound at that speed is incredible. At about half throttle the engine runs at 2600 rpm. At this speed I played with the high speed needle and was able to get the rpm to peak by closing it OFF another 1/4 turn. This means that the high speed needle is now only 1/4 turn open from its full OFF position. It sounds like when I shift over to gasolene I'll probably have to nearly close off the high speed needle as I did with my V-4. I also played some with the idle needle some but +/- 1/4 turn didn't seem to make any difference in engine speed. The fuel consumption is more like 2 ounces per minute at mid throttle.
I'm happy to see that the engine doesn't seem to be spitting or blowing any oil. If I remove the #5 and #6 plugs after shutting down for the day as Hodgson recommends, and then put them back in before starting the engine again the next day the firewall is completely dry. If I leave the plugs in I will get a bit of initial blow-by from the #6 exhaust, and then the engine exhausts run clean. There seems to be a bit of oil seeping past the rings in #6 and dropping onto the plug. 
I've included a few photos of the engine running. I want to wait until I'm on gasolene and comfortable with revving it up before I try to make a final video. - Terry


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## Henry

Nice, nice , nice .... but now we want to hear it, there is nothing like a radial music!!!!

Congratulations!!!


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## mayhugh1

Today I decided to give gasolene a try. 
I think I have the carburetor idle and half throttle performance pretty much dialed-in for methanol at this point even though admittedly I haven't yet made any full power runs with it. In summary, my final settings for the Super Tiger model 12163145 carb running on methanol on this engine are: low speed needle is set 1-1/2 turns open from fully closed position and the high speed needle is set 1/4 turn open from its fully closed position. I determined the fully closed starting positions by blowing through a length of clean fuel line connected to the carb fuel nipple (carb off the engine) and listening for air flow through the carb to stop when I turned each of the needles clockwise. The throttle was 95% closed for the low speed test and wide open for the high speed test. I also determined that anywhere between 5-20 degrees of timing advance seems to work equally well at midrange. 
If a model engine builder is looking for a reason to change from methanol to gasolene I have two photo pretty convincing photos. In my last post if you look at the photo taken from the rear of the engine while it is running methanol you can see the waste oil container in which I'm collecting the scavenged oil for disposal. If you look closely you will see it is a yellow frothy emulsion. This comes from the fact that the beneficial extra oxygen in the alcohol produces a lot more water during combustion. If the engine (model or even full-size) isn't run long enough and hot enough to get the engine oil up to a temperature where this water can evaporate and escape through the crankcase ventillation system it will remain in the crankcase where it will eventually corrode the steel components inside the engine. And, model engines are hardly ever run up to this point. Compare this photo to the one I took today while running on gasolene and making similar 1-2 minute runs with engine cooling down in between. The oil in this case is cloudy but there is no excessive water emulsion. This is one of the reasons why I have been running the oil system open loop. If the Hodgson's reputation for running 'cool' is legitimate then you definitely don't want to run it on methanol unless you're willing to add a mandatory oil change to your engine post-run maintence list.
I filled the tank with 87 octane and began with the carb settings as they were for methanol. The engine wouldn't start by hand, but it did fire up with the starter. It idled and ran at half throttle, but I had some misfiring and I was getting some oil and fuel out the exhausts indicating that I was (surprise!) running too rich. I played some with the needles, and the combination that I tentatively settled on was: 1) the low speed needle closed another full turn from the methanol position (the needle is now only 1/4 turn open), and 2) the high speed needle closed almost another 1/4 turn from the methanol position (it is now nearly completely shut off). Even though the engine is idling down to a very low speed (still sounds like 800 -900 rpm but my optical tach isn't working in the bright sunlight and so I couldn't get an actual measurement), I now have to keep the throttle open a minimum of about 20% to keep the engine running. With methanol and my previous carb settings the engine idled with less than 5% or so throttle opening. This is likely happening because the low speed needle is now so nearly closed off that I'm just not getting any fuel flow at all with a nearly closed throttle. I stopped the engine and let it cool down. For the next cycle and these needle settings the engine did start by hand and I finished running the gas out of the tank. There was now only a bit of oil/fuel coming out of the exhausts; but no smoke, and so I'm probably close with these settings. The only thing is that both needles are so close to being shut completely off that I'm starting to wonder how consistent these settings will remain over time. If a model engine builder is looking for a reason to not run gasolene in his engine with a methanol carburetor, this will be at least one of them. 
I blipped the throttle a few times and the throttle response is there. In fact, maybe it feels better than when I was running methanol. The engine wants to rev up but I'm still not ready. I played with the timing a little, and now the engine seems to want some timing. Right now, I have it tentatively set at 15 deg BTDC. The timing requirements may change again later when I rev it up. My engine now smells like an old gasolene engine. There was never any fuel odor with methanol. After the engine cooled down, I pulled all the plugs and cleaned them. All were sooty black showing a too-rich mixture. Some were also a bit wet with oil. I've never seen soot on the plugs of my other two engines even when the methanol mixture was overly rich. These plugs were probably loaded up when I first started and ran the engine with the methanol settings before I had leaned down the mixture. I guess I've also proven that my ignition dwell, at least at mid-throttle, is adequate to ignite an overly rich air/fuel mixture. I'm going to add a healthy stripe of reflective tape on the back of the prop so I can use my optical tach toe measure the engine rpms on tomorrow's runs. - Terry


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## mayhugh1

For the past few days it has been very cool down here; and with the much needed rain we're getting, I decided to wait before doing any more carb tuning. I used the time to re-make the banjo nuts on my oil transfer tubes which have been seeping oil. I originally made a nice pair of decorative nuts from black Delrin, but I did a poor job of threading them; and they were a sloppy fit to the banjos and couldn't be properly tightened. I made new ones out of steel that solved the problem. I also made a simple bracket on the firewall to hold the #5 and #6 sparkplugs for safekeeping during long term storage of the engine. I also made a nameplate that officially delares this project finished this month. I inspected and cleaned all the plugs from my last run. They were all sooty rich but since the needles had been adjusted over such a wide range during the last session it was impossible to tell if the final settings were still too rich. All plugs seemed to be equally sooty and none were wet with oil.
I decided it was time for a video and set up my camera to capture my first start after the engine was allowed to sit for two days.

[ame]http://www.youtube.com/watch?v=oQeuXqu_Gw8[/ame]

The sequence is to 1) turn on the fuel pump, 2) set throttle to w.o.t. and prime the engine by turning the prop over a few times with my thumb over the carb intake, 3) repeat number two but this time with the fuel pump ON dummy:hDe:, 4) set throttle to half open, and 5) turn on the ignition and give the prop a slap. I'm still running the oil system open loop, but I intend to close it after another 20 minutes or so of running. As you can see in the video, the engine starts right up with a temporary cloud of blue smoke as the oil that settled in the lower two cylinders over the past few days is cleared out. In the video I'm tweaking the idle and high speed needles a bit around the settings I ended up during my last session. Before starting the engine I placed a large piece of reflective tape on the rear of the prop so I can use my optical tach to measure rpms. In this video the engine eventually idled down to just over 800 rpm. However, I could not get it to rev up past 3000 rpm. I later found out that I was too focused on the carb mixture and not paying enough attention to engine timing. In a later run after the video was made I discovered that the 2-56 grub screw in the rear engine section that bears against the distributor body and keeps it from rotating had sheared and allowed my timing to shift to ATDC. I have a huge pointer mounted on the rear of the distributor to indicate the timing - I just wasn't looking at it. Unfortunately this grub screw rides in an internal groove cut around the circumference of the distributor tail, and so the distributor is now captive to the engine rear section. If I ever have to remove the distributor body from the rear section I'll have to perform some careful surgery on the still-remaining piece of grub screw. When I manually rotated the distributor back to 20-30 degrees BTDC the engine rev'd up to the point of being scary. So, my next task is to come up with some kind of linkage to allow me to easily adjust the timing and hold it in place. A first look tells me it will be difficult to link it to the throttle lever in the space I have. It probably also means that the carb settings I've come up with so far are suspect. So far the exhausts are not spitting oil. I think Hodgson's oil control rings are doing their job. - Terry


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## vcutajar

BEAUTIFUL just BEAUTIFUL.

Vince


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## metalmad

Like she said
WOW;D
Pete


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## ozzie46

YeeHaaawww! Absolutely beautiful.Thm:Thm:Thm:

Ron


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## Henry

That is music sir!!!! I love the sound when idle:bow::bow:th_wav.


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## rythmnbls

One of the finest examples of a Hodgson I have ever seen. The sound of the engine idling gave me goosebumps.

Congrats.

Steve.


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## vihatch

Your work is an inspiration to me as I work on completing the Howell V2.  My ultimate goal model engine would be the Hodgson radial.  Don't know if I will ever get there but it will be fun trying.  Great job.


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## keith5700

Just had to say how nice this looks. There's some lovely engineering going on there. Seeing the video makes me want to make one for myself, especially hearing it with the headphones on! I'd love to see it with a big fat 3 blade prop.
Great job. 
Keith.


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## mu38&Bg#

Congratulations!

Regarding the carb settings, does the engine run the same if you shut off the fuel pump and let it burn off the fuel in the bowl? The needle settings seem as though there is excessive fuel pressure. I assume the fuel bowl is vented to atmosphere? 1/2-3/4 turn is what I found is typical on glow RC engines converted to spark and gas. These carbs require the main needle to be set first at Wide Open Throttle, then the low speed at idle to achieve a reasonable idle and transition to high speed.

Greg


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## mayhugh1

Dieselpilot,
       Yes, it seems to run the same when I shut the fuel pump off. My fuelpump just maintains a constant level of fuel in the external carb bowl, and returns excess fuel back to the tank through a return line; and so the carb shouldn't be seeing any fuel pressure. And, both the bowl and tank are vented to the atmosphere. When I shut down the engine for the day I kill the fuel pump so the engine will use up the fuel in the bowl. For the next 7 or 8 seconds the engine runs normally and then speeds up as it leans out just before dying. I was just getting ready to set up the high speed needle at w.o.t. and then come back and touch up the idle when I notice my distributor was loose and the timing was ATDC. I needed three hands to hold the distributor, work the throttle and adjust the needle so I just shut it down. I'm working on the timing linkage now and will try your suggestion for setting the needles when I get that worked out. - thanks, Terry


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## RCW

I am in awe of your workmanship.

--Bob


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## swilliams

Top notch job Terry, it really has turned out superb.

I haven't looked in at your thread for a little while, and boy have you put some great stuff in. I really appreciate the detailed analysis you have done of your ignition system and lots of great info about the fuel and carb etc. You have really created a great resource for those who have the journey in front of us, which is much appreciated. 

Cheers
Steve


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## kvom

I always fee a bit down after getting an engine to run and making the video.  Time to think about the next project!


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## seagar

Congratulations !!!!!! Wonderful workmanship ,beautiful result.

Ian(seagar)


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## mayhugh1

I made a few minor modifications to the engine since my last post. First, I've added a control so I can easily vary and hold the ignition timing. When the grub screw that I was using as a friction device for the distributor sheared, it allowed the distributor to freely rotate under the vibration of the engine and allowed the timing advance to wonder about uncontrolled. (The screw is still in the rear section of the engine and keeps the distributor from rising up vertically.) This rotating lever solves that problem and in addition has adjustable stops that currently limit the timing between 5 deg BTDC for starting and 35 deg BTDC for w.o.t. running. I came up a workable design that linked the timing to the throttle, but I decided at the last minute to keep the two separate until I better understand the engine's timing requirements. 
The next addition was a start-up checklist that I've posted on the firewall and which I hope will help with any future senior moments. A day after completing the little storage rack for the #5 and #6 plugs, I started up the engine and noticed that although it had started very easily, the rhythmic idle sounded differently from what I had become accustomed to. I also noticed that the #5 and #6 exhausts were spitting raw fuel and; sure enough, I had forgotten to install the two lower plugs. I was more worried about was happening with the ignition as I hit the kill switch, though, as the spark had no where to go for those two cylinders. The ignition seemed to function normally after the incident and so either the coil arc'd internally or the output transistor clamped at its Vcb breakdown voltage without catastrophic damage. My next and hopefully final step will be to dial in the carb needle settings. This time I will first set the high speed needle at wot and then set the idle needle. - Terry


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## metalmad

That is just the Ducks Guts Buddy!!
Pete


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## xjs

Truly inspirational, Mr Mayhugh. Well done, and thank you.  I have enjoyed and appreciated your detailed narrative, and share (what I hope is) your joy in the result.


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## Flopearedmule

Does anyone know how far off the timing would be in degrees on the slave rods if the spacing in not corrected on this engine?  Also is there anywhere we can find what the correct hole positions would be to hit TDC every 40 degrees?
Just curious
Thanks

Nice job Terry!!  The pictures you gave us in this thread are awesome!!


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## stevehuckss396

dmh13433 said:


> Does anyone know how far off the timing would be in degrees on the slave rods if the spacing in not corrected on this engine?  Also is there anywhere we can find what the correct hole positions would be to hit TDC every 40 degrees?
> Just curious
> Thanks
> 
> Nice job Terry!!  The pictures you gave us in this thread are awesome!!



I have done the calcs but it was some time ago. I have modeled the correct slave positions and found that the rods hit the bottom of the cylinders. Bottom line is unless you want to redesign you will get a fine running engine the way it is designed. I can provide all the details if you want. PM me with any questions.


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## Flopearedmule

stevehuckss396 said:


> I have done the calcs but it was some time ago. I have modeled the correct slave positions and found that the rods hit the bottom of the cylinders. Bottom line is unless you want to redesign you will get a fine running engine the way it is designed. I can provide all the details if you want. PM me with any questions.




Thanks Steve,  I know it runs good.......I've seen quite a few on you tube.  I was just being curious if anyone held a timing light on all the other cylinders to see where they were at.  
Dennis


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## mayhugh1

Dennis,
       Your question got my curiosity up, and so I used my SolidWorks simulation to try to measure the timing errors you asked about. There is also a small height error as well. That is, the pistons on the slave rods don't actually come up to the same height as piston #1 which is on the master rod. My simuation is built around my actual machined dimensions, and so these results will likely vary some from their theoretical values. The values below are listed as #N(xxx"/xx.xdeg) where xxx" is the height difference with respect to #1 at TDC, and xx.xdeg is the crank angle error with respect to nx40 deg.

#1(.000"/0deg)
#2(-.006"/3.9deg)
#3(-.014"/2.9deg)
#4(-.010"/3.6deg)
#5(-.010"/-5.2deg)
#6(-.001"/2.6deg)
#7(-.010"/-2.8deg)
#8(-.014"/-6.4deg)
#9(-.006"/-4.3deg)

As Steve said, for a model display engine the errors are really not important. It would suggest a minimum timing of 10 deg BTDC, though, as Hodgson recommends. If the locations of the slave rod pins were altered to attempt to correct the errors (there is really no room for this in the current design) you would then introduce errors into the valve opening and closing times with respect to TDC for each cylinder and compression differences between cylinders would now occur. I haven't thought this fully through but it seems like the distributor could be designed to correct for this as an academic exercise by altering the position of the trigger magnets and the locations of the HV towers. - Terry


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## Flopearedmule

I'm not seeing the valve timing difference.  with the 4 lobes exactly 90 degrees apart, they should open cylinders every 20 degrees.??
I think it was the guy on 5bears that made his master rod compensated, but he used steel instead of aluminum for more strength.  maybe it was somebody else????

thanks for posting how far off in degrees.  I have always been curious how far off in degrees it would be.


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## mayhugh1

What I meant was if the location of the TDC's were changed, but the valve opening positions remained the same as set by the cam, then the valve open times relative to the new compensated TDC's would be altered. For example if the TDC of one cylinder was delayed by 5 deg and there was no change to the cam then the intake would effectively be open for 5 deg longer before TDC but after TDC it would close 5 deg sooner. - Terry


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## mayhugh1

I thought I would make a final post on this build/assembly to wrap things up. The engine has been running for about a month now and I have run about a full gallon of gas through it. The engine starts easily by hand nearly everytime I run it. I learned that the secret to easy hand starting is to adequately prime the engine by placing my thumb over the wide-open throttle intake and then rotating the prop four times to suck in fuel to the point that my thumb gets pretty wet. Then I close the throttle to about 1/4 open and slap the prop with my finger. My distributor cap is transparent and so I can see the location of the rotor when I am ready to start it. I found that the best place to start the engine is with the rotor pointing to cylinder #8 or so. This allows me to get 3 or 4 cylinders fired by my hand strike before the distributor reaches the bottom two cylinders which in my engine usually are a bit wet with oil after the engine sits for several days. I'm not detecting any misfires in any of the cylinders. The plug colors look good and are uniform except for cylinder #9 which is a bit more sooty than any of the others. I may swap in one of my completed spare cylinders into this location someday to see if it makes any difference. The plug insulators all have a nice tan color with my current carb settings, but all the ground electrodes are always sooty. I think this is because the relatively high mass of these electrodes sticking out of the plug shell is cooling the charge in this area and the electrode is not getting hot enough to burn off the fuel. I've run the engine in the dark looking for misfires in the distributor but can see none. What I did see, though, is the heat of the rotor arc was slightly carbonizing the lexan around the tower contacts and I've had to clean this out after the initial quart of gas was run through the engine. This erosion seems to have abated and I haven't had to clean out the cap a second time. I closed the oil loop several days after my last post and ran into a surprise. The engine would start OK but would die after 10 seconds or so. As it turned out the scavenger pump is a great crankcase ventilator. After increasing the size of the vent hole in my oil tank cap from .030" to .080" that problem was solved. My oil lines are transparent tygon tubing and so I can see the oil flowing into and out of the engine when it is running. The crankcase pressure pulses are very noticible in the return line. My over-size oil tank works as a nice phase separator and pretty much all the gasses in the scavenger line are dissipated from the oil before being returned to the pressure pump. I've been experimenting with a new (to me) product called Tru Fuel. It is sold by Lowe's and is intended for use in small engines which are may see long storage periods. It is supposed to be equivalent to 92 octane gas (no alcohol) and is formulated for a long shelf life. I've run about a quart of this in my radial and in my V-4. What I'm seeing on the V-4 is that after starting I don't need to get on the carb adjustments to find a new stable running point to keep the engine running optimally. After dialing in the carb on the radial it, too, always has started and run without messing with the carb adjustments and so I don't know if the fuel is helping it. But I'm pretty sure it is making a significant on the V-4. 
For my next project I became inspired when I ran across this link:

http://picasaweb.google.com/18.cyl.radial.engine/HodgsonRadial18#

Studying these pictures it appears that the twin version of this engine is just two 9 cylinders mounted back-to-back. I'm thinking about trying my hand at merging two of these together to make a twin. The guy that did this posted enough pictures that I think I'm going to try build a CAD model of the crankcase and then see if I'm still interested enough to start making chips. - Terry


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## metalmad

All I can say is WOW!!
That is some piece of work.
Pete


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## dmac

Terry,

Most impressive build you have there.

Why not stretch yourself and go for a triple row radial.

Dave


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## gbritnell

First off a very hearty congratulations on the completion and running of your engine. The sound is incredible! Although I've seen a number of the Hodgson radials built I've never talked at length to many of the builders. Here is something I found on my little radial, as the crankcase gets hot it conveys the heat to the carb which in turn starts to vapor lock or at least cause erratic running. I ended up making an insulator bushing to go between the carb and crankcase and it's seems to have helped immeasurably. 
Once again, outstanding work. 
gbritnell


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## Septic

I would honestly like to say that I really don't like it.....

But as that would be a grossly unfair and untrue statement, based purely upon my own limited attention span and lack of patience, I can only express my admiration at your dedication and attention to detail...  A beautifully crafted rendition of the type and a truly praiseworthy winner of the award in every respect...


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## capin

Beautiful !Terry, everything you've built has been first rate but you have outdone yourself. Brian


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## Blue_Rock

What a beautiful work of art Terry! Congrats


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## mayhugh1

I was surfing YouTube recently and stumbled across some videos by an Australian company called Rotec. This is a relatively small company that builds and sells full-size radial engines to homebuilt aircraft enthusiasts. I had previously been only vaguely familiar with Rotec, having seen a video of one of their engines running in a custom-buit motorcycle. The video that I stumbled across was probably made early in the company's history. It's a video of a quarter scale nine cylinder engine that, if you don't look carefully, you will swear is another Hodgson model with the optional rocker boxes. 
[ame]https://m.youtube.com/watch?v=bP3-WSvnGIY[/ame]
The heads are essentially identical to stock Hodgsons with the main visual difference between the engines being the location of the distributor which, in the Rotec design, is on the crankshaft axis. The video of the 350 (cc) is evidently an early run of the small scale prototype built to test their design before starting the full scale build. If you listen carefully at the end of this video you'll hear someone in their group watching the test say "OK, but it will never work in a real plane."
There are several other videos including this one showing some highlights of their manufacturing process:
[ame]https://m.youtube.com/watch?v=CVu6vjPvxkg[/ame]
that was probably made sometime later. Those who have built a Hodgson-9 will see some steps eerily similar to those performed during their own builds. You'll also notice the familiar intake/exhaust flange milled into the rear of the heads. A change in the head design to note, though, is a modification they made to support two spark plugs per head. As it turns out, the full-size Rotec design includes redundant ignition systems - spark and magneto. 
This video will bring a smile to the faces of all who have actually built a Hodgson or similar model radial:
[ame]https://m.youtube.com/watch?v=jwpnucBidGQ[/ame]
where the technician, who looks a lot like the guy in the 350 video, is explaining how to troubleshoot failures in the spark ignition system. If you watch carefully you'll see him holding a familiar red, white, and black three wire cable while explaining how to ohmmeter test the Hall sensor inside the distributor. - Terry


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## Stieglitz

Hi Mayhugh1,
                  Thanks for sharing your project,a real work of art.
Cheers.


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## DickInOhio

Where did you get your propeller? Nearly finished with my 9.  Beautiful build. I followed along as I built mine.


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## mayhugh1

Dick,
You can find them here:
http://www.aircraftinternational.com/Products/Propellers/BielaCarbonProps.aspx

Terry


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## Bentwings

mayhugh1 said:


> These are photos of the two completed carb assemblies I plan to try with my H9. The first is a Walbro 345 carb that I salvaged from an old yard tool, cleaned up, and rebuilt. I designed a simple bolt-on linkage adapter to work with my throttle control on the firewall. The carb bowl contains a ball-and-spring pressure requlator to supply 5 psi fuel to the carb and return the excess to the fuel tank. I wish it had a choke or primer, but I drilled a small hole in the top cover so I can press down on the diaphragm with a small tool which I think will prime it while under fuel pressure.
> The second carb is a Super Tiger RC helio engine. This bowl simply regulates the level of fuel with a drain hose back to the fuel tank. Again the linkage is compatible with my throttle control and the adapter at the rear matches the back of my engine - Terry
> 
> View attachment 60994
> "K
> 
> View attachment 60995


Nice work and thanks fir the tips. I’m just getting started on modeling parts for review.  I’ll have to read this over several times to take it all in. .i especially like the metallurgical comments.i still don’t really follow the cylinder head work. I guess I’ll just have to work on it myself.  I’ll save this and review it  later. I may even have some to add myself as I progress.

byron nelson

byron


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