The chatter marks in the Wankel are a result of the needed gearing for
proper piston orientation, any play in the gearing causes chatter marks.
The presented engine concept has no gearing, hence no chatter marks
 similar
to vane pumps.

Rolf Pfeiffer


Wankel chatter marks. Apex seal history.

http://www.rotaryeng.net/history.html



You don't get chatter marks with silicon nitride apex seals.

 Paul Lamar


Yes. That is because the silicon nitride seals are light having very
 little
inertia. The force they generate is not high enough to penetrate the
trochoide surface. (The force is their vibrational acceleration times
 their
mass and they hardly bounce having next to no vibrational distance.)

Also, that steel does not make a good apex seal material I would agree
with. Too heavy and mainly too elastic which is their more detrimental
feature.

Rolf

 That is not what Mazda said in this official history of the apex seal.
 Friction is a strong factor. I will agree the modulus of elasticity
 of the wear surface is a factor. Steel being 3 times stiffer than
 aluminum.

 http://www.rotaryeng.net/history.html


 Paul Lamar


 Friction is also a factor, of course, but only one of the many, and in my
 opinion not as strong as made out to be. Your attachment is very
 informative and provides the history of development.

 The drilling of bores into the apex seals was mainly to reduce weight which
 can be had for free with a lighter gravity material such as silicon nitride
 that also has low friction. With thinner seals longitudinal drilling is not
 practical. Although the seals get lighter with reduced width they are still
 heavy per volume which needs to be reduced.

 Another factor to reduce the vibration aspect was mounting the gear not
 rigid but holding it by hollow, cut open pins that provide a little give to
 build down the vibration peaks. Even the number of pins plays a role in
 smooth running without chatter Mazda found out. If I remember right either
 9 or 11 pins gave the best results.

 There are many factors that affect seal chatter. Avoiding it completely is
 likely not possible but it can be reduced to within allowable limits as
 proven by Mazda.

 Coming back to friction, we all know that pulling a rubber eraser slanted
 along a table top is smooth but pushing it causes the eraser to 'dig in'
 due to friction and the eraser jumps or vibrates. The area of the trochoide
 housing where the chatter marks occur is similar to the puling condition,
 not the pushing. That is why I believe that friction is a minor issue.

 Rolf