Harder rubber couplings are not the way to go. Any rubber used as a torsional
damper is going to heat up when it is operated in the resonant RPM range. There
are all metal torsional dampers that don't heat up significantly and they are
used on aircraft engine crankshafts and on this rotary engine built be Everett
Hatch and Steve Beckham. A very clever thing to do as you need the counter
weights anyway. They are called pendulum dampers and they are expensive to make.
Rubber type torsional dampers will work if high temperature 500 F Silicone
rubber is used instead of the more common 200 F neoprene rubber. Also a blast
tube on the torsional damper will keep them cool. Rubber torsional dampers are
found on almost all auto engines except rotaries. Rotaries don't need them
unless they are driving a prop and then the problem is more the PSRU than
it is the e-shaft.

The Diamond engine uses a rubber coupling similar to those found on BMW drive
shafts as does Richard Sohn on his one rotor engine. They are so large and so
over kill the heat does not bother them as there is plenty of surface area to
dissipate the heat. The problem is finding them soft enough to use on a one rotor.

Tracy uses four, much smaller, rubber bushing and I can see how they could over
heat and fail under certain circumstances. They are made from neoprene and
substituting Silcone would go a long way towards reducing failures.

Paul Lamar

Paul,
The pendulum type dampers really intrigue me and thanks for the explanation,
as I could not work that out at all for myself.

My concern is that the motor and PSRU being directly connected ( with this
system), the oscillating steel dampers tuned for the engine might not be
tuned for the PSRU. However Powersport had developed their system, so it
obviously worked for their combination, but I think it's something you would
have to consider.
George (down under)

I like to hear from Steve on this subject. As far as I know they only built
one. Later engine went the full rigid route.

Paul Lamar

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