Unfortunately, there are no smaller glowplugs. You have either 1/4"-32 or turbo. With having to make room for the plug, I don't think you'll have more valve area with 4 than you will with two.

You've probably run into this in your research.

http://www.radiocontrolmodels.co.uk/...n/Page2852.htm

Greg

I had that thought too. The .40 jug is pretty small. It may have to be a 3 valve head with the glow plug where the 4th would normally be. 2 small intake, 1 large exhaust. I'm pretty sure I would want it to be OHC too.

It is more of a backup plan anyway. Thanks for all the cool links! If nothing else, I will have seen all kinds of really neat engines because of this project.

It's been a while... but I've scheduled to get some machine work done Sunday! It's just to fit the sleeve to the block and to make the small-end of the rod fit the FS40 piston pin, but it's SOMETHING.... Bathroom remodels and that pesky real life keep getting in the way, so I'm happy that I'll finally have something CUSTOM to hold in-hand and analyze.

Oh, and I've been thinking alot lately about all the different valving designs I've contemplated. I'm pretty sure I'm going with the slotted sliding design with the centered glow plug. I'm currently contemplating making the cylinder head a larger diameter than the bore to allow more room for the valve opening. Since it will be flat and I can make the piston come all the way to the top of the sleeve, I can expand the squish chamber to the side instead of up, gaining some valve area on the outside where it counts most.

One down-side of the valve design I've chose is I have to choose between an equal number of intake and exhaust slots, or having them differ by 2. The more slots, the harder the whole thing becomes to manufacture and also I lose valve opening area to allow for sealing area for each opening, so I've been throwing around 5/7 and 6/6 which makes 30 degree slots. 5/7, makes for an intake/exhaust ratio of .71 which I've read is too low for supercharged engines - it's more of a number you'd want to make more torque at the low end on a normally aspirated engine. From what I can gather, numbers closer to .9 are better for higher revving supercharged engines. These are the things that keep me up at night.

Here's the .40 sleeve and piston in its new home. The wristpins on the FS40 and VG30 are the same size, so I didn't need to modify the rod at all to make it fit. You can't really see it in this picture, but the exhaust port is no longer. Now I have something real to start designing the head for.

Great! Keep going. I'm almost done setting up a "new to me" lathe and working on a 4th axis fro my mill. I hope to be building some engines this winter!

Cool! I wish I had one of those kicking around.

I finished drawing the lower cylinder head/valve part as far as the combustion chamber is concerned. I calculated compression ratios and I can go up to 9.13 without a domed piston. After doing some research, it seems like I could use anywhere from 7.5 to around 9, so I'll go ahead with the current design.

Here's the latest in odd engine designs.

http://www.simplicitymotorworks.com/index.html

That is REALLY cool! I assume it would still have the same problems all rotary valve engines have (they can only open and close their ports at a linear rate equal to half the angular velocity of the crankshaft), but when you're not looking for nose-bleed RPM, that works!

It looks to me like an RCV engine, but done right so the cylinder liner and piston don't rotate in relation to eachother.

What's the latest?

Oh, I'm still drawing cylinder head parts. I honestly don't get to do it as much as I would like. Racing season is quickly approaching, so that may give me the bug seriously enough to really get moving on the project.

I got to do some CAD work last night. I'm spending lots of time revising things and re-drawing stuff. It's funny when you're putting a never before done concept into actual 3D space how much stuff you hadn't thought would matter really ends up mattering alot.
I'm hoping all this preemptive revisioning will help cut down on the physical prototype revisions. Those are much more expensive!

Recently I noticed that some large online vendors have OS four stroke .40 parts for the car version of that engine. Parts I have found are camshaft, valve set, valve springs and complete cylinderheads. I have thought about purchasing a used FS40 airplane version and installing the FS40 car version of a new camshaft, carburator, intake, valve setup and possible a whole cylinder head.

Does the FS40 car version respond well to the improvements that enthusiast have developed for the FS26 car version ? I read thru the thread for the FS26 for cars and some of the developments that I can recall offhand are changing to a two or three needle carburator, straight-short intake, Perry fuel pump regulator, and aircooling fan.

Thumper do you make a flywheel for the FS40 car version ? I think your straight thru cylinder head modification is awsome.

Parts for the FS26 car version are difficult to find now and the FS40 car version engine have been discontinued for several years so I don't think I will be able to find a new engine.

I've never really researched that... I seem to remember the cylinder head being different from the aircraft FS40 to the FS40S-C... When in doubt, look in the manuals and compare part numbers. They don't lie - if a certain part number is the same on both engines, it is the same part. The block is likely the same, except for the color. The crank, cam, valve springs and spring seats will be different, but other than that, I'm not sure.

I have no experience with the 40... I know the 52 and Alpha 56 responded well to a 3 needle slide carb, but I don't think a smaller displacement engine would work the same with those larger carbs. Playing the carb game is kinda like roulette. You never really know how well one is going to work until you try it, and try it with all possible fuel system setups - from no pressure to pumped/regulated. Every carb responds differently to each situation. I would start out by trying a small-bore .21 carb, or possibly a big-bore TZ-18 carb, or maybe a Traxxas 3.3 carb.

I don't currently have a flywheel for the 40. My .26 flywheel would probably be too small.. Your best bet is to have someone with a metal lathe make a steel flywheel for you that's the right size for your application. That same guy would likely have a drill press to make the clutch pin holes, and be able to press in the pins. The alternative is to adapt a .21 flywheel to fit and have a steel sleeve pressed or bolted to the outside of it to bring the overall diameter and weight up to what you need.

The head and valves are different than the airplane version. Both valves are the exhaust valve from the FS-52 which is slightly larger than the FS-40 valve. If doing the conversion, buy the whole head and valve assembly.

I've not looked inside my FS-40S-C but I have been working on a parts cross reference chart for OS engines and that's what the part numbers say.

I'm also making some headway in my four stroke engine design. I have to sit down and plot valve lift in the OS to see how the numbers are going to stack up.

I have a bunch of pics saved on my computer with OS Wankels in cars. I think most were posted on Rctech. There are a couple youtube clips out there too.

I've been sick almost this whole week - crappy colds... However, it has given me plenty of time to dive back into my "Thump 8" drawings. I've attached a teaser of the intake side of the cylinder head. It is very first rough draft - for instance, I leaned back, looked at it, and thought "Why did I put the carb clamp there? It would be better on the bottom... and the exhaust port can't go straight out the front like the intake, because the carb will be in the way."

Anyway, thought you guys might like to see I'm feeling motivated again.