I still remember my reaction to my first view of the
inner-workings of a
Wankel engine close to 50 years ago.  My immediate
thought was "Boy, those
gears in those rotors will probably wear out fast!"

I have never heard/read much about such gear wear, other
than being assured
that there was no problem.

During the life of a modified rotary engine, the rotor will
make on the order
of one-billion revolutions. That is a lot of
potential  metal-to-metal
contact on the teeth of those rotor gears.  Just what
does one find when one
tears down an old engine?

I realize that drivetrain gearing, cam gearing, and such on
regular  IC
engines outlive a similar number of revolutions (ie My
300Kmile Honda
Accord), but somehow the dynamics of gearing within the
rotor of a
high-performance Mazda engine seems to be more
metalurgically challenging.

Robin

In theory there is no load. In practice there is some sort
of mechanical
vibration going on. Mazda instrumented the gear set and
measured
the loads. A simple change in the number of roll pins
drastically
reduced the loads and the failure rates.
---------------------------------------
Opss failed to attach all the needed graphics.
Here is the most important.

Paul Lamar



Paul

Why is the loading different in reverse rotation? And why would they even bother testing it?

Robert

First the load is reversing on the gears due to the rotor torsional vibration.
If you look at a three tooth situation the center rotor tooth bounces off
one stationary tooth and hits the S. tooth on the other side.  You need to know this
to determine the fatigue life of the gear. Apparently it is below the fatique
limit of the material used as I have never heard of a gear failing short
of boosting the engine to over 800 HP or 400 HP per rotor.

Paul Lamar