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


Hi Henry;

Sorry, I have not modelled the 3-rotor 20B at all.
The damping required has a lot of variables beyond just the engine.
Fortunately, a lot of solutions seem to work.

The Ross redrives had at least 4 failure modes I can think of off the
top of my head.
1.  drive plate cracks/failures
2.  lack of a anti-thrust bearing in early models
3.  need for stacked thrust washers and bearings (there were related
posts on 6/08/11, 6/28/11 here)
4.  standard issues with Ford C6/E40D broken/chipped gear teeth

Note that there were quite a few different versions of the Ross redrive
from what I have heard.
I have only heard of 1 that used a 6pinion rear planetary.

Cheers
Cary

The gear failures were traced to poor machining.

Paul Lamar

Sounds familiar.  I seem to also recall hearing there were more
machining problems and quality issues after Lou Ross.

I saw another case of multiple broken gear teeth this spring on an
unused Ross redrive.
The Ford gears sets seems to be more susceptible to chipped teeth.

~Cary

Dozens are flying built by Tracy with no problems.

Paul Lamar