Harder rubber couplings are not the way to go. Any rubber used as a torsional
damper is going to heat up when it is operated in the resonant RPM

range.

There
are all metal torsional dampers that don't heat up significantly and

they

are
used on aircraft engine crankshafts and on this rotary engine built be

Everett
Hatch and Steve Beckham. A very clever thing to do as you need the

counter

weights anyway. They are called pendulum dampers and they are

expensive to

make.
Rubber type torsional dampers will work if high temperature 500 F

Silicone

rubber is used instead of the more common 200 F neoprene rubber. Also

a

blast
tube on the torsional damper will keep them cool. Rubber torsional

dampers

are
found on almost all auto engines except rotaries. Rotaries don't need

them

unless they are driving a prop and then the problem is more the PSRU

than

it is the e-shaft.

The Diamond engine uses a rubber coupling similar to those found on

BMW

drive
shafts as does Richard Sohn on his one rotor engine. They are so large

and

so
over kill the heat does not bother them as there is plenty of surface

area

to
dissipate the heat. The problem is finding them soft enough to use on

a

one rotor.

Tracy uses four, much smaller, rubber bushing and I can see how they

could

over
heat and fail under certain circumstances. They are made from neoprene

and

substituting Silcone would go a long way towards reducing failures.

Paul Lamar

Paul,
Quite obviously I don't know what is best, but I'm always willing to
learn
from the experts. I've seen the BMW dampers and I tried to find one that
was
on a Diesel 4 cylinder. I figured there wouldn't be anything with more
Torsional Vibrations than a 4 cylinder diesel, but haven't found one
yet.

The size of the one large damper was what I was referring to, their big
but
smaller in diameter than, the widely spread diameter of Tracy Crook's
unit.
The BMW type however gives only 3 connecting points each side of the
power-in side and the power-out side. I was hoping to make something
with 6
connections ( in and out) - like Tracy's.

I guess we won't know for sure without a definitive test, over a period
of
time. However if the Diamond engines are running them, my guess that
they
would be good. Now if we could identify the exact one they were using!?
George (down under)

--------------------------------------------------------------------

Here is a company that makes something similar in a range of sizes.
This is the one used on the Rotamax 2 rotor engine. The unit Rotamax
chose was 60 durometer and the resonant frequency was about 2000 RPM.
We ordered a 50 durometer version and that lowered the resonant RPM
to about 1800. Next step would be to drill some holes in it to lower
the idle RPM lower still. Or one could try the next smaller size.

Paul Lamar



Paul and George,

Sorry for the late reply; today is my first day back in the office after
the Christmas closure.

Unfortunately I don't have any records of what exactly was used on the
MWE/Diamond engines. I do recall though that we were using Centaflex
couplings on the gearbox of MWE-twins as depicted, size unknown though.
We used exactly the same couplings to couple the 300cc single rotor
engines without a gearbox directly to the pass-off dyno as well. They
worked ok for quite some time as long as we kept the engines above
2.800rpm.
I do remember as well, that, in the past, when we were using larger
diameter couplings, we had more problems!
Interesting enough those very couplings exploded within seconds (!) when
we had the first R7 (400cc single rotor engine, now officially called
IAE75R) on the same dyno. We tried to run the engine at elevated
tick-over, 2.500 - 3.000rpm several times with and without load.
Eventually we had to disconnect the engine from the power take off and
ran it without any coupling (hence without applying any load!) for a
quick first demonstration run. The engine was then shelved until I left
Diamond, so I don't have access to any more recent information.

Maybe it's worth getting in touch with Austro Engine and order a new
Centaflex coupling for a GIAE110R engine! I can clearly visualize loads
of them in the ex-Diamond Engine stores. That would get you at least a
sample and a guideline of what size to go for.

Regards and good luck!

Martin.

The Austro part will only work for the small displacement Austror engines.
A one rotor Mazda is a monster by comparison. More like the big Austro.

Here is the Centaflex catalog.

Also a couple of picture of the torque isolator found in all moto cross
off road dirt bikes. Probably near ideal for a large one rotor engine.

Paul Lamar