Paul, i have not had the time to even take the package of o-rings you sent to
me from my office to my garage. i have been busy with some other pressing
business that is taking me away from the eng overhaul. my eng is not quite
ready to try fit the rings but i was wondering about the hardness of the oil
control o-rings. they seem harder
or more stiff than they should be. that implies that they may possibly stand
up to more heat but may not seal as effective as the original O-ring. by the
way the fc3s newsletter about the 2nd gen mazda cars that i subscribe to are
having problems with the dealers having two different color oil rings. one
may be a later part number
and i am trying to find time to check out this. the seals you sent me seem OK
for the other uses in the eng but i am Leary of trying them in my eng just
yet for oil control o-rings. not sure what i will do about that just yet. has
Bruce turrentine tried these
or had time to look at them yet. may i suggest that you send Bruce a set of
just the oil control rings or better yet a full set for his opinion which i
for one would highly
regard i think he builds up a lot of engs so he may be able to get info back
to us sooner.  i did not know that i was the first to get the new rings. if
these are indeed better rings i am sure that Bruce would be interested in
using them in his overhauls as a product improvement. what do you think about
this Bruce??  tom Kimsey

Tom the issue of the oil o-ring hardness has some explanation called for.
The main issue is the friction between the o-ring and the 
oil seal slot wall. If this friction is too high the metal oil seal will
not move in and out of the slot freely. A softer ring with a given ratio of
diameter to slot depth will have less friction, all other things being equal.

Trouble is they are not equal. The friction coefficient of teflon is reputed 
to be lower than just about any other material so therefore a harder o-ring 
can be used and still result in the same friction force. This is what I am 
counting on. Another way to reduce this force is use an o-ring that is only 10% 
larger than the slot depth rather than say 20% larger. This would result in
less force on the friction surface.

There is no pressure to speak of on these o-rings with a properly vented 
oil sump system. They  are mainly there to seal the rotor housing from oil 
seepage when the engine is stopped. Only a limited amount of oil is trapped 
in the rotor when the engine stops. It is this trapped oil they are designed 
to seal from seepage down into the rotor housing cavities.  The oil O-rings are 
above the top of the oil level in the sump when the properly installed up 
right rotary engine is stopped so no oil touches these o-rings.
When they failed in my Cosmo the smoking stoped in a few seconds after 
startup and no abnormal oil consumption was noticed by me.
In this regard the engine acted a lot like a radial engine.

Lynn I am sure you have had some experience along these lines.

The two metal oil seal rings  do all the oil scrapping while the engine 
is running.
 

Paul Lamar
 
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