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

 Cary,

 Thanks for the Presentations. I have been thinking about building and
 was really worried about the mechanical issues. That clears up many
 doubts.

 I do have a question for you. Since you are interested in Rotary, do
 you know how much Torsional Damping will be needed for 13B 3 rotors?
 In the presentation, it talked about Ross's PSRU failure. Do you know
 what it looks like? Is it similar to the flex plate failure or it is
 more like broken gears, etc. Thanks!

 Henry Nee



 How about using the magnetic fluid like they are using in some shocks
to vary
the damping response. More magnetic field increases the stiffness.
Could vary
with a rheostat on the panel. Might be possible with testing to use a
PLC to
control it according to engine and flight parameters. Use in a housing
like
Cary showed.

Dale Davies

Hey Dale;
Maybe, I don't know.
Martin ran the numbers and discounted it at the time as a viable damper.
IIRC, being an EE, he was quite interested in that possibility...
~Cary