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

 

[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

 

[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

 

[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

 

[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

 

[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

 

[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

 

[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

 

[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

 

[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

 

[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

 

[kvom]

Liking this series a lot!

 

[ozzie46]

Oh lovely,lovely,lovely. th_wavth_wav

 

[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:

 

[ronkh]

Terry.

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

Well done!

Ron.

 

[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.

 

[petertha]

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/

 

[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

 

[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

 

[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