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there's no such thing as a "dumb question" !!! as you have by now noticed CBN is "cubic boron nitride", much longer lasting than alumina I use the method of Don Bell in "Master Cam Design" StrictlyIC Oct 1994. basically you start with a 3-arc cam design, keep the centers of the three arcs in...

first take a look at this video, then ask some questions, that way I'll know what parts need the most detailed drawings, FYI DoMore tool post grinder, 4" CBN wheel, variac for speed control, Sherline lathe bed, a micrometer head, ER-16 collet holder with long 1/2" straight shank, a couple XL...

I could probably be persuaded to clean up my plans enough that someone could use them my grinder was inspired by Bob Hettinger's (BAEM Club member), it is based on the tilting bed type (the cam shaft moves), not the type where the grinding wheel moves, and mine uses the additive master cam (see...

possibly my favorite of all the Stuarts !!! be very careful with the sole plate and don't make the mistake I made, be sure that the crankshaft bearing mounts are machined so that the cylinder will be centered in its mount at the other end, mine is off by a bit, not enough to be noticeable by...

looking good !!!, this is the point where I start grinding notches in the end of the cylinder liner and taking off some of the piston skirt, rather than weaken the con-rod, YMMV, ...

Green, NICE!, did you notice the axial cam for the ignition (I presume?) in between the radial cams for the valves, that's a neat trick !!! Pete.

the number one issue with low RPM in model engines is flywheel weight, the heavier the slower, as a certain minimum amount of flywheel inertia is required to get through the compression stroke. (also flywheel inertia doesn't scale linearly so smaller scale engines need larger than scale...

there was a fellow BAEM Club member that was going to turn my camshaft grinder drawings into something readable and/or usable by other people but that hasn't happened yet, and I can't say when I'd be able to get around to it, perhaps I can answer some questions ?

that's a good suggestion, but the ring gear should be between the crankshaft and the flywheel, and the flywheel bolts onto a large flange machined on the end of the crankshaft so no way to get the roller bearing in there (without designing a new crankshaft, argh!) that I can see

normally that would work but with the Duesey there's a ring gear that's cut directly into the flywheel. I guess I could make the ring gear separate, and if I wanted to be clever then use a one-way mechanism to engage it with the flywheel (like pawls and ratchet in a ten-speed hub, those tend to...

I didn't photo the machining of the flywheel/clutch housing, but here it is, mostly finished. basically it was a lot of rotary table work. now the engine has mounting lugs and I can start on a traditional oak wood box base to mount it on. It has a boss for a starter motor as per full size, but...

Minh-Thanh, the equations are real, the losses incurred by heat absorbed into cylinder walls is very small compared to the heat generated by compression, the problem is the definition of "auto-ignition", that was derived by an experiment that you don't really know the conditions of, that is...

Minh-Thanh, any text book on thermodynamics (I got my start designing a model turbo-jet engine made from automobile turbo-charger rotor parts, same approach as Kurt Schreckling and Thomas Kamps, so have a collection of turbine engine text books which also cover the thermodynamics) you'll have...

I have a hard time understanding what you're complaining about here, Hansen's fuel choice, his compression ratio ?, his injector design ?, his pump design ? here are some fun facts from thermodynamics, compression ratio, pressure ratio PSI, and Temp, for gasoline engines in the 6 to 12 CR range...

so from high school you should remember P x V = n x r x T, the relationship that says Pressure and Volume are inversely proportional to Temperature (for a fixed quantity of gas, EG steam). you do know the volume change of your cylinder, but that's one equation in three unknowns so is...

I think you're right, I think I messed up somewhere (wouldn't be the first time :-( !!!) the reason its to hard to reason about this is Displacement doesn't scale linearly with Bore either, and I was attempting to relate throat bore to cylinder bore, and then you might or might not want to...

OK, so 1/3 * 1.125" = .375" is the number I was looking for. (thou I'm confused by what you said, is that 4 venturis at 1.125" ?) getting back to scaling laws, the formula you gave has be be pretty much correct because you can re-work it to (throat)^2 ~~ displacement X rpm, which...

"K is a constant .65 to .90" --- ahhh, there's nothing like an empirical fudge factor :) !!! wondering how your .180 compares to 1/3 scale ?

Terry, curious about your carb throat, I have a 7.5mm RC carb on my V12 with .938" bores, started with a 6.5mm but could not get high RPM at WOT, and believe that even larger would benefit (but since I'm running with a wood prop don't actually want to see how much RPMs I can get out of it)...

stick with proven metals (grey cast iron, 1144 steel, etc, I've even had good luck with 4130 when a thin wall was required), otherwise you're the guinea pig ! I once used brass pipe to make split crankshaft bearings because it was cheap and available at the local hardware store, had to throw...