RE: Why the Speedboy Patriot went 170 mph
I remember a few post from Bob recommending a low load prop on a particular Jett engine and magic will happen. What I remember is the low load let the engine jump to the next harmonic tuning level and add a couple thousand rpm. This may be what is happening during a shaft run and the engine skips through the harmonic levels until something gives. If this is the case then it would only make sense that the same thing would happen in a full power dive IF the terminal velocity was high enough.
It would be interesting to put a 9x6 on a normally timed Rossi 53 and see what the rpm's would be. If that light load would let it go to the next level up in rpm then a high speed dive should take it past my prediction of 17,000 rpm. I doubt the engine would explode until well past 20,000 rpm.