FWIW, CP's got an interesting thread going in the 1/2A forum...he's checking the timing figures of several engines.


I'm just wondering now if maybe it's the carb and/or the size of the venturi that would limit the r.p.m. in a dive? (pumping losses or words to that effect? )...the engine couldn't suck in enough air to allow it to spin any faster? That in conjunction with the timing.

I think that's what keeps some engines from blowing when they have a shaft run...the venturi size is such that it gets to a certain r.p.m. then chokes. (I know there are other considerations such as cross sectional area of the port runners, runner saturation, crank's I. passage, the pipe, etc. etc. )

Just out of curiosity, does anyone have the timing #'s for the Rossi .53? Being a Rossi, I don't think it's outside the realm of possability that it could turn to 20K (give or take a little ) in a prolonged WOT dive and not fly apart?

Maybe Speedboy could do another video, and do some dive tests...gradually increasing the angle of the dive, and you could do the analysis of the r.p.m. (right now, I'm picturing Clark Gable in "Test Pilot" or maybe Fred McMurray in "Dive Bomber" )