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
Hi!: According to non-technical info I read long ago, the clearance betweenrotor and
shaft gears was the reason why the Sachs KC-27 in the HerculesW-2000 motorcycle sounds
like a reciprocating engine close to having a molten rod-to-crankshaft connection, if
tolerances were changed to eliminatethis noise, duration of engine was compromised, I
guess the issue of gears'tolerances is addressed in the first edition of the book by
Kenichi Yamamoto 'Rotary Engine', however, this first edition has two printings, in
1969 and 1971;as I own only one of them, I can't say if the content differs from one
printing to the other. The 1981 edition of the same book by K Yamamoto, 'Rotary
Engine', doesn't deal at all with the subject of internal gear's tolerances. I read
also that if you're going to change some internal parts, but not the shaftof an RCE,
it's better keeping the old bearings instead of installing new bearings.The reason for
this remains unknown to me. SAE paper 860562 by Mark R. Culina from John Deere has the
title:'Experimental Evaluation of Rotary Engine Timing Gear Loads'. That's all I know
about this, or better said, all the papers I have on this.Hope it's useful for
somebody.Best regards, salut + Jose Gros-Aymerich E-28033 Madrid, Spain