Jerry wrote:

Yes, but I've seen some of these engines run at the NAMES show.
There was a guy with a 4-cyl in-line Bentley model that ran nicely, but
another guy had a 4-cyl rotary of his own design that was a total
screamer, turning a 12"+ prop at over 7000 RPM.
I was worried that people were standing to the side of this thing and if
it lost a prop blade there would be a BIG mess to clean up. Fortunately,
no such thing happened.

Jon


Hi Jon

I was under the impression that Rotary (radial) engines needed to be an
odd number of cylinders. Have I remembered this wrong??
Well, most radials of the Pratt & Whitney variety were based on
7 or 9 cyls. per bank, but there really is no reason it has to
be that way. It may balance more easily or run a little
smoother that way, but there's no reason it has to be like that.

This guy's rotary was nothing like the traditional rotary
engines, though, I think the pistons were linked to the "crank"
by a cam and a roller bearing. The pistons clattered against
the cam when turning it over by hand, they apparently needed
centrifugal force to hold them out against the cam.

Jon