I do not know all of the restrictions to the application of the fluid
  coupling, but if you are looking for something that will absorb
 "chatter"
  and does not generate a lot of heat, have you considered the Dodge
 coupling
  that Molt Taylor used in the IMP and mini-IMP?

  http://www.dodge-pt.com/products/pt_components/flexidyne/flexidyne.html

  I had heard at one time the company was not "aviation" friendly due to
  liability issues.

  Just a thought.

  K. Carl Milbrodt PE


  As far as I can figure it out they are limited to 1800 RPM
  and they are very heavy. We need something that will survive 7500 RPM


  Paul Lamar
  --

  A Flexadyne is a centrifugal clutch.
  Bud Warren used a centrifugal clutch on his gear drives. A single plate
 with weights with ramps and rollers to clamp up instead of the springs
 in a
 normal clutch.
   Most centrifugal are drum type rather than disc. Disc is likely better
 for high rpm.  The SGF coupling is the lightest, simplest, least
 expensive
 and quickest way to deal with the drive line vibration.  Do you think
 that
 Porsche, M-B, BMW, General Motors and the other car companies that use
 them
 are guessing?

 Murry I Rozansky



 The rubber couplings really don't deal with low RPM aircraft gear box
 chatter.
 Their real function is to mitigate the torque pulses effect on the gears.
 What we need is both but I have not come up with a light weight
 fluid coupling or a centrifugal clutch yet. In the mean time we will
 continue to idle the rotary at 1800 engine RPM or higher. After all the
 prop is only turning 632 RPM.

 Paul Lamar

The Molt Taylor flexidyne is a centrifugal dry fluid clutch by
Dodge-PT.  They use a steel shot sandwiched between wavy housings/plates
to transfer power.
They are not light.
Flexidynes apparently worked well for many folks using 0-200's or less.
One Cirrus VK-30 owner mentioned a MTB Failure of a few hours with an
IO-550?   I believe they are using an off the shelf Lord LCD damper now
with many hundred successful hours.

There are a lot of engineered industrial and marine dampers out there to
choose from...

Here is a viscous torsional damper redrive project I was involved with
years ago.  The prototype was built and flown.
Many additional variations and concepts were discussed.

  http://www.eaa245.org/Presentations/EA81Torsion/Torsion/sld028.htm
  http://www.eaa245.org/Presentations/EA81Torsion/Torsion/sld022.htm

Cheers
Cary