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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...

BINGO!!!, me too, I also use a sharpie to write on the part to be machined what some of the dimensions are and double check before cutting, otherwise I tend to end up in the "measure once cut twice" club :) !!!

Teflon (your frying pan) also contains fluorine and if you leave it on the stove empty on HIGH will start fuming it in a short time, and many many other products contain it like Gortex (your jacket), and even non-stick pizza box lining paper. toxic is everywhere, the irony of "better living...

Very Cool :) !!! I've always wanted to model a snow cat ! but haven't liked any form of continuously-variable-differential that I've seen so far and I'm guessing yours isn't CV, if not what is it ?

Terry, (first putting on my asbestos flame suit :) ) am puzzled by the choice of CDI, neither D.K.Grimm nor anyone else has been able to come up with any compelling reason or evidence that it works better than LDI, either way you charge up a device (either capacitor or inductor) with a certain...

in 1992 the book "Strahlturbine fur flugmodelle I'm Selbstbau" by Kurt Schrekling came out, I absolutely HAD to build that engine, I didn't know a word of German, I didn't have any machine tools, but I simply HAD to. after a year or two of researching bench-top machine tools, reading text books...

https://www.homemodelenginemachinist.com/threads/lawrence-merlin-v12.34432/

Green, most of the folks that are really good have been at it so long they've simply forgotten that phase of their life, next to my Rolls Royce Merlin V-12 I have two shoe boxes overflowing with "wall parts" just from that one engine :) !!! yes, "first pop" is magical :-) !!! best, Pete.

don't know if Ken I is still reading his thread, I do have a couple questions, about the bearings, up front there's just the thrust bearing, are that thrust bearing's grooves deep enough that they keep the tool bit holder centered, IE there's no need for a radial bearing at both ends of the...

I like this thread, very informative, since my mini-lathe only has an MT-2 tailstock and all the commercially made rotary broaches seem to be MT-3 or 3/4" shank, am considering a re-scaling of this design for MT-2, probably a fools errand, but I'm also only hoping to make pretty small broaches...

From Machinery's Handbook, table of dimensions for National Unified Threads 10-TPI, pitch 0.100", depth of external thread Sharp Vee 0.0866, depth of external thread National Unified 0.06134 so the pitch is 0.1000", if your cross slide is at 30-deg and you feed in 0.075" on the cross slide...

cosine (30-deg) == 0.866, sine(30-deg) == 0.500, neither is 0.750, it is the sine or cosine that determines the depth of cut based on moving a compound slide at an angle. Also a 60-deg triangle has all equal sides, so the pitch of the thread and the depth along the direction of the...

I think the metric/scientific unit for that is the "OhNoSecond" (the time it takes between doing something and realizing "Oh No" I should not have done that) :) !!!

IMHO and experience, the only way to get smooth finish threads when single-point cutting on a lathe is to start with leaded-steel or leaded-brass, in my experience everything else leads to unacceptable crap (and either way 30-deg, 29.5-deg, and 29-deg doesn't seem to matter, I stick with 90-deg...