durabol wrote:
Thanks for the responses. I meant for ultralight or light aircraft
with 20-40hp from 1 or 2 cylinders. I definitely want to copy as much
as I can since I'm not engineer. I planned to have the RPM at about
4000 in order to get enough power out of the engine but I may reduce
the rpm if I can get enough power. Also I may have to weld the crank
together to handle the propeller loads.

Brock

That RPM isn't going to give you much prop efficiency.

A more spindly engine with higher displacement may be lighter overall --
and certainly mechanically simpler -- than a little fast engine and a
speed reducer.

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com