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



Paul,

I couldn't tell for sure if you were the one who saw the flying wing
or you
were responding to someone's email who saw the wing.   But, what a great
concept--fluid coupling.  If that wasn't you're email, do you think it
would
work?  Wow.  I think you can build them to set the stall speed about
wherever you want it as per drag racers.  If you could set it as low as
possible and still accomplish the purpose, seems like great solution.
What
say you.


Van

That was me. I took the pic of the flying wing.

Paul Lamar

Hi  Paul,
               Fluid couplings are no good for transmitting power, too
much losses in slippage, there are losses in a torque converter, but, at
least one gets a torque increase when the output shaft is turning slower
than the input shaft. If anyone doubts that check-out the old GM
hydramatic trans. If you put a piece of timber on the ground in front of
the front wheel,(one) and attempt to drive over it, one could not, with
the accelerator flat to the floor!! As soon as they changed to the
later Powerglide with torque converter, there was no trouble to climb
over a little stick like that, and if it was bigger the rear wheels
would spin, the old Hydramatics could not spin their wheels from a
standing start.
             John Burey

We had a lot of experience with torque converters in Chaparral racing cars. It all
had to do with stall speed and the number of gears. The stall speed is inversely
proportional to the diameter of the torque converter. Smaller higher stall speed.

Early PowerGlides had only two gears.
Some of the latest from MB and others have as many as six gears. Stall speed could be
anywhere from 1500 to 3000 RPM. When it was actual converting torque it could be as
bad as 60% efficient. After it got up to about 4000 RPM or 5000 RPM it was essentially
one to one and efficiency could be 97% or 98%. If you want the last 2% you install a lock
up clutch which most of the recent auto tx with torque converters already have.

A pure fluid coupling operates more or less the same way at high RPM.
The same lock up clutch can be used.

Fortunately we don't need a lot of power or torque transmission
below 5000 RPM for aircraft operations.

I don't think I would try a heavy off the shelf torque converter or fluid coupling
because of the weight. It is probably possible to NC machine a smaller pure fluid
coupling out of aluminum that starts to lock up about 4000 RPM. Perhaps reinforced with
uni directional carbon fiber and high temp epoxy. What one is looking for is a material
with high tensile strength to weight ratio.

http://en.wikipedia.org/wiki/Torque_converter


Paul Lamar