> It causes no vibration but it does generate a centrifugal force
     > on the rotor bearing. It is also balanced by the second rotor
     > 180 degrees out of phase on a two rotor engine. What is left
     > is known as a "couple". The couple is caused by the two rotors
     > not being in the same plane. That is the function of the front
     > and rear counter weights. They remove the couple completely.
     > A similar situation arises when balancing a tire. The balance
     > weights must be centered on the rim width (in and out) or a couple
     > will be generated. This is sometimes referred to as
     > dynamic balance.
     >
     > In the case of the one rotor the front and rear counter weights
     > balance the weight of the rotor. In all cases the Wankel rotary
     > engine is in complete balance unlike a piston engine that always
     > has parts rocking back and fourth such as connecting rods and valves.
     >
     > Here is a mathematical balance chart for rotary engines.
     >
     > The two rotor engine does not dip below zero but the one rotor
     > engine does indeed dip below zero as does a four cylinder four
     > cycle engine.
     >
     > Paul Lamar


    Good dissertation Paul.
    I cover Static, Force, Couple, and Dynamic in my seminars
    at OSH.
    Archie
--
Thanks, Paul.
-*

You mention the four-cylinder piston going into negative torque, but the
six-cylinder piston will too, although at about half the amplitude
(approx -50 percent of mean torque, compared to -100 percent on four).

Only when you get to the eight-cylinder with its power pulse every 90
degrees does instantaneous torque stop going into negative territory. So
in that respect, the 2-rotor is better than a piston six and closer to
an eight.

Regards,

Gordon.

No I think you are wrong about that. Here are some more charts from
Kenichi Yamamoto's 2nd book, also called  Rotary Engine, published
by Mazda in 1981.

BTW I forgot to mention the fact that the rotary engine, in all
of its configurations, one, two, three or four rotors has never
required a torsional dampener. Almost all six cylinder and above
piston engine are equipped  with torsional dampeners. Even the
vee eight cylinder engines. My original six cylinder O-470 engine
in my C182 had only two. With the second 1500 hour overhaul the
crankshaft was a mass of cracks. When I traded it in
to Continental and picked up my newer version I specified the 2000 hour
TBO engine version with four dampeners instead of just two.

The last chart is of the Merlin which was a night mare for RR
to develop.

Paul Lamar

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