I emailed Rexnord rep to see if he had any fluid coupling ideas for
 me...guess not...

 Begin forwarded message:

 From: Brian Clark <Brian.Clark@rexnord.com
 Date: August 24, 2011 2:14:57 PM CDT
 To: gene kahn
 Subject: RE: question about fluid coupling

 Gene, spoke with some engineers about your application, the HP is no
 problem, but
 the max speed for a fluid coupling is 1800 rpm.
 If you are looking for soft/start flexibility you might want to
 look at a inverter for the motor.
 Thanks
 Brian Clark

 Brian,

 I am investigating the use of fluid couplings for applications
 of up to 600 HP, at 6-8 thousand rpm.  The diameter could
 be up to 14 inches or so, and the length [the thinner the
 better] could be up to 6 to 8 inches.  Do you have anything
 like that?  Thanks.

 Gene Kahn



 If one reads the article on the Fluidamper harmonic balancer that someone
 put on this cite, it says the silicon in it never wears out and heat
 doesn't
 bother it.  It will turn to several thousand rpm.  Seems like the silicon
 is
 coupling one piece of metal to another to allow minute rotatational
 reversals.  Hope someone can use engineering voodoo to make something like
 that work.

 Van

 Hi, there are such couplings used in some all wheel drive cars/trucks.

 Murry


Hi all,

Paul has mentioned that fluidamper type dampers have so far been
designed for "crankshaft" type applications.  I took that to mean lower
frequency range, stronger torque pulses and probably larger amplitude
torsional twisting of the crankshafts.  The Fluidamper article
says that they have designed their product specifically for DIESEL
engines, which we know operate at lower rpm range from piston
gasoline engines, and could also exhibit different torque pulses and
crankshaft twisting depending on the specific design.

All I was thinking is that the basic idea behind the fluidamper might be
adapted somehow for our uses...for smaller, more frequent torque
pulses etc.  Perhaps a stock fluidamper could be drilled and lightened,
or different fluid could be substituted, etc etc.  If not, there is so much
talent on this newsletter we could possibly design our own from
scratch.  Even if we have to buy a new fluidamper, cut it open to see
how it is made, it could be done.

Paul tells us that our big problem is with "gear chatter".  I do not know
if the primary source of gear chatter is intrinsic to the gears themselves,
or if they chatter a lot more with whatever torsional vibrations come from
the rotary itself [probably both].  If some come from the rotary itself,
perhaps those could be largely attenuated by some adaptation of the
fluidamper or whatever.  If some gear chatter is intrinsic to the gearbox
itself, then that might have to have its own separate solution...immersing
the gears in viscous oil to simply damp the vibrations, or perhaps by
changing the moments of  inertia of the gears through addition or sub-
traction of weight in gear(s), or changing the materials out of which
one or more of the gears are made ($$) thereby altering the torsional
coefficient and affecting the primary frequencies of vibration etc.

I also was thinking that we have not actually tried Paul's new design
damper/flexplate.  Heck, the stock flexplate sort of works, but develops
cracks over time.  Could be worse.  And we don't have much time using
the aftermarket flexplate.  I thought the idea of using larger
rubber bushings was good, and Paul's redesign great.  If heat dissipation
is a big issue for the rubber pieces, perhaps a housing could be
designed allowing an oil spray to be directed onto the rubber bushings
and collected for circulation through a heat exchanger.

Just food for thought, I hope.

Gene Kahn


I have total confidence in the engineers on this cite that they will figure
out a way to use fluid/viscous couplings if it is even remotely possible.
Just seems to me that if silicon is impervious to heat and wear (as per
Fluidamper ad), then silicon sure is worth pursuing as the coupling agent.
Only question is, why is it limited to 1800 RPM.  If you could just build a
BIG fluidamper type PSRU (forget about the harmonic balancing aspect and
just use the design aspect) filled with a very stiff silicon so that there
wasn't any slip but only allow micro rotational reverses (like the rubber in
the current damper/flexplate allows) it would work????  But, I don't know if
I'm all wet.

Van