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.

Paul Lamar
--
Hi Robin,
The key to remember about the gear is its usage. Normally we always think of
a gear as a power transmission component. In the rotary, the gear is used as
a positioning device.
It puts the rotor in the correct position at a certain moment in the cycle,
it could be
likened to a timing chain sproket that puts a camshaft in the proper
position at a certain
moment during the cycle. Neither the sproket or the gear experience any
significant loading in
this type of usage aside from the miniscule amount of force required to
accomplish the
positioning of its related part. (Although the camshaft is usually asked to
press
on a valve stem simultaneously)  Dave M


Controlling the position of something does take some power..  In the
case of the rotary, the power required to locate the rotor properly is
low.  Actuating spring closed poppet valves periodically requires the
cam to deliver power enough to compress the valve spring.  This is
significant power.  It heats the spring significantly, and generates
frictional loss in the rocker, on the cam lobes, and on the cam
bearings.

Maybe the stationary gear loads are like the desmodromic valve
actuation systems.  Except the load on the desmo is momentary/periodic
where the rotary stationary gear is nearly continuous.

If the stationary gears were missing, what position would the rotor
seek as the e-shaft rotates?   I think the rotor wouldn't rotate
around the housing because the low drag rotor bearing would allow it
to not change orientation as the e-shaft eccentric moves.  It seems to
me that the gears overcome the drag load of the apex seals sliding
along the surface of the rotor housing.  There may be other loads but
I can't picture them at the moment.


Matt-