Here are some dwgs I had on file. Not sure where they
came from but they originated in June 2008.
They look like your style George.

The pictures are of Richards Sohn's cut down one rotor shaft.

The largest problem one would have installing this engine in a helicopter
is dealing with the severe torque pulses. A one rotor looks like a really
big 120 HP two cylinder engine in that it fires once per 360 degrees
of revolution. This will require a really large and soft rubber coupling
to get the torsional resonant frequency down below 2000 RPM idle.
Last picture.

Paul Lamar

Paul,
Yep! same set of drawings. Richard has done his differently as he uses the
front bearing for his particular set-up, whereas most use the rear bearing.
You have hit upon the last and not least significant  problem of the single
rotor and that's the large reversals of the single ( torsional Vibrations).
Perhaps Martin can chime in here and give some advice.

My research suggests a more centralized and harder rubber coupling is the
way to go. I remember reading where a chap had problems with a 4 cylinder
engine and tried soft rubber couplings and they disintegrated in short order
( rubber turned to dust) so he tried the harder synthetic material used in
4wd leaf spring bushings and they worked perfectly. His suggestion was that
with the large reversals, the softer rubber wasn't able to keep up with the
large fluxuations, whereas the harder material didn't move as far. This
seemed logical to me and it worked out ( in the real world application) for
him as well.

Given that Tracy Crook suggests that wider and softer ( the softer the
better) for the 2 rotor ( very little reversals), it would seem logical that
the opposite is true for the single. However I would be happy either way if
Martin could throw some light on this matter.
George (down under)

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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