We were waiting for a trailer to be delivered so we could take
the 650 HP 2 rotor powered Harmon Rocket [real Rocket] to Cal City to
test fly for the attempt on the world record 0 to 10,000 feet Time To Climb
in 91 seconds. Now held by the Grumman Bearcat. The power to weight ration
of this airplane is 8 TIMES the power to weight ratio of a C172.
The turbo charged two rotor, mostly Mazda under 200 pound engine, is
making 650 HP on Methanol at 8000 RPM. The Bell 47 PSRU is 3:1.

The Bell prop shaft looked a little marginal but we had already run it up to
more or less max power at 7500 RPM with a 68 inch prop on the ground.
Not the 84 inch TTC prop. That has never been higher than 6700 RPM
on the ground. When Dan hopped it off the SZP runway  it got off the ground
in two seconds! YES TWO SECONDS!!!!  Half throttle! We have Motec
logged data to prove it.

I calculated the contribution of the prop shaft spline at 1400 foot pounds.
The four 3/16th dowel pins contributed another roughly 1000 foot pounds.

That gave us a safety factor of 1.5. Not really enough with that huge
84 inch diameter  TTC prop IMHO.

 So John Lync set it up in his NC mill and he installed
four more .25 inch diameter dowel pins. That gave us 4500 foot pounds total  in
theory. That gave us a safety factor of nearly 3 which I am now more comfortable
with.

Paul Lamar

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