> I wonder if anyone can shed some light on this issue. I had
   assumed that
    > the rotary would have considerably less torsional vibration than a
    > piston engine -- for a number of reasons -- but I have heard this may
    > not be so.
    >
    > Also, how does the single-rotor engine fare in this regard?
    >
    > Regards,
    >
    > Gordon Arnaut
    > Ontario, Canada.
    >
    >
    > The two rotor is better than a four cylinder. About the same as a six
    > cylinder.
    > The one rotor is a real beast. See the attached graphics.
    >
    > Paul Lamar

   I had my 13B run for few seconds on one rotor and it was shaking so
   bad, my
   teeth were rattling:). If one rotor quits you'll know it.
   Bulent

   I have heard that said and on the other hand Tracy and I were watching
   Joe Schiferl start up his Power Sport 13B powered Velocity at
   OSH and Tracy supposed it was running on only one rotor from the sound
   it was making. It did not seem to be shaking.

   Many one rotors have been built and when properly balanced they don't
   apparently shake. They appear to be smooth. I don't really think you
   can feel or see torsional vibration at anything over 1500 RPM or so.
   The prop connection sees it for sure as that is why a Lycoming is so
   hard on props. In theory there is no up, down or back and fourth
   shaking forces.

   Perhaps there is something else going on in your engine.
   Its a mystery.

   next message ------------------------------------------------

   Duh! I just think I figured it out. When the two rotor runs
   on one rotor the pulse rate is below Tracy's rubber torque pulse
   isolator
   resonant frequency. Tracy's latest rubber torque pulse isolator is
   smooth down to 1000 RPM or so according to Tracy running on two rotors.
   The Power Sport PSRU uses a direct connection to the gear box. No torque
   pulse isolator.

   The old Ross clutch spring plate torque pulse isolator had a higher
   resonant frequency and therefore one had to keep the engine idle above
   1800 to 2000 RPM or it would shake and shutter badly.

   Come to think of it when we were running the p-port engine on
   the dyno recently it would occasionally run on one rotor for various
   mixture
   issues with no apparent vibration. It too of course was directly
   connected
   to the dyno water pump load with no torque pulse isolator.

   Paul Lamar


What exactly is the source of the vibration and at what rpm. I would
assume it has to do with the moment of the rotor in that elliptical path?

I was surprised to hear that the single-rotor requires the same heavy
gearbox used on the two-rotor. Why not use the proper damping tuned for
the appropriate rpm of the resonance and size the gearbox or belt
according to torque output (downsize and lighten)?

Regards,

Gordon.

First there is no elliptical motion. The CG of the rotor rotates
around the center of the e-shaft in a perfect circle while at the same
time rotating about its own center. Much as the earth rotates about the sun
while rotating about its own axis. That is why the Wankel is sometimes
called a planetary engine.

See the animations on the web site http://www.rotaryeng.net/

..... Principles of the Wankel (in German)

and also

..... An excellent movie animation of how the Wankel works created by Gene Nomicos. .

Also read;

..... How The Wankel Works Paul Lamar. Text.


The torsional vibration is caused by the two rotor engine firing twice
per output shaft revolution just like a four cylinder four cycle
engine. The firing impulses causes no vertical  or horizontal
vibration unlike what happens with all piston engines.

The rotary engine is nearly as smooth as an electric motor.

Yes a dampener specifically designed for a one rotor engine is
a good idea.

Paul Lamar

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