I think what we really need for the torque damper is a fliud
 coupling. I was at the Camarillo air show yesterday and they had
 an unprecedented collection of war birds. No less than two flying
 P38's among many others.

 They also had a restored early Northrop flying wing.

 I turned the prop both ways  and it rotated freely.
 I asked some of the CAF types if it flew in :)
 They said yes. They said it had torque converters but
 what I really think they meant were fluid couplings.
 Maybe they were really torque converters Northrop got in a
 junkyard :)

 The torque converter is closely related to a fluid coupling
 and is widely used in automatic transmission. The stall
 speed is about 2000 RPM so the engine can rotate freely
 up to about 1500 RPM before a lot of torque is transmitted.

 Our problems are not so much torsional resonance but
 gear box chatter.

 I think a fluid coupling will solve the problem once
 and for all.

 http://pt.rexnord.com/products/couplings/true_torque_fluid_couplings/fluid-couplings.asp

 Falk True Torque Fluid Couplings

 A fluid coupling allows the motor to accelerate independently to full speed,
 the driven load has been isolated by the fluid coupling.

 Paul Lamar

        
So would an automotive torque converter be suitable? At least the mass would
give you some desirable flywheel effect:) The fluid fly-wheel would have
more chance of dissipating heat build-up than those poor little bits of
rubber!
What about the prop now free-wheeling to give windmill drag with the engine
out?:(


John Evans
           

Probably weigh 10 or 12 pounds. On the up side if you used the Mazda auto tx
torque converter it would bolt right up to the stock flex plate :) Ironically the
Mazda auto tranny is a scaled down version of the Ford C6, A4OD, etc., etc. which
we now use the planetary gears out of.  Made in Japan by Jatco transmission.

Paul Lamar