Paul,
There are two methods in common use for applying the Teflon coating to a
cylindrical substrate.  An older method involves a spiral or helical
wrap of  Teflon ribbon.  When the wrap is complete, the adjoining edges
of  ribbon are fused someway to form a continuous covering.  If one
examines a variety of Teflon insulated wire samples some will clearly
show this helical wrap pattern in the insulation.  A newer method that
is more difficult and more costly involves extruding the Teflon onto the
surface of the substrate to form a continuous and seamless coating.

The cracks that are apparent in these two photos that Brian posted seem
to indicate a helical pattern.  Rotary Aviation could have received a
batch of defective O-ring material or received the wrong material
(wrapped instead of extruded).  It may be worthwhile to destructively
test some samples of  TES O-ring material to see if cracks similar to
those shown in Brian's photos can be produced.

Aubrey Thompson

In the case of Creavey I think the Teflon is extruded first and the
silicone
is
injected in the liquid state. This is probably done in a mold so the
pressure
required to inject the silicone does not expand the Teflon. I could be
wrong.
On the  other hand I think air may be required to convert liquid silicone
to
the rubber state. That is why they call it RTV or Room Temperature
Vulcanizing
I think.

These picture you attached look like very poor workmanship was used to
make
these O-rings.
I have never seen a TES O-ring that looked anywhere near that bad
including
the
ones we bought from McMaster car. Creavey quality control on the other
hand
is
excellent. It is on the cool side of the engine as well. The O-rings look
to
be the proper cross section size however. Perhaps they were well under
diameter
and somebody stretched them to fit. If you try to do this one section of
the Teflon will yield while the rest of it remains the same. Perhaps this
is what happened some where along the line.

I have always thought of rubber, and that includes silicone, as being
"compressible".
What has been brought home to me after reading some bad O-ring experiences
years ago
is; rubber is no more "compressible" than hydraulic fluid. Furthermore
silicone expands
greatly when heated. If it is contained in a closed chamber without
expansion room such as an
O-ring slot it will generate tremendous forces. Enough to crack cast iron
and bend steel.
Therefore it is extremely important to have the right section diameter
when
installing
O-rings.

If the O-ring is oversize for the slot the process of tightening down the
tension
bolts will cause the hydraulic force of the rubber to break the cast iron
end housings.
The problem will compound itself when the engine is warmed up to operating
temperature
as the silicone expands.

The last picture is what happens when the TES O-ring is too large in
section
diameter for the size of the slot. You can see that the Teflon was cold
extruded
into the space between housings prior to final torquing of the tension
bolts.
The date on this photo is March 2003.

Paul Lamar ...No rotor no motor.



Now I'm getting very concerned! I've installed these o rings in my 20B and
now I'm wondering if I should tear it down and replace them with factory o
rings. I'm getting very close to my engine installation and would rather
do
it now than after the installation. Do we know of success stories with
these
o rings? Or should I just change them...

Bob Mears
Supermarine Spitfire

Bob,
I installed Creavy TES o-rings about 4-5 years ago.  While I've only got
about 25 hours on the engine, there is no sign of leakage to date.  We'll
see how things develop.  Where did you get your TES o-rings?

Mark St.

I am about to put an engine together, so I need some TES o-rings as well as
the full overhaul kit (engine only). I have searched the web, but without
any assurance that I will get Creavy o-rings. Can anybody recommend a vendor
who sells the full overhaul kit with TES o-rings and stock Mazda apex seals?
Or can I get the stock apex seals only from Mazda?

Doc Custer
Retired Software Engineer and sometime Audiologist

I don't think there is one. Buy the stock overhaul kit from Bob Mears
Mazda or Mazdtrix and buy the O-rings from Creavey. You might be able to
sell the stock O-rings on ebay. Mazdatrix also sells the stock apex seals
and stock overhaul kit for that matter.

BTW TES O-rings are not essential for aircraft use.

They just give a bit of a better over heating margin and are reusable.
The knowledge on what it takes to improve the rotary cooling system has
advanced greatly in the past ten years so airplanes are now flying
with no cooling problems from the get go. The stock inner water cooling
ring is coated with Teflon on one side with the rest silicone. They work
fine in most cases.

One place that they could still pay off is in the oil scraper rings
on the sides of the rotors. Chuck Dunlap has been flying with those
for a few years. That is a compromise with all TES O-rings.

I drove my Cosmo for years with these melted out. Smoked like
a smelter for years when I started it up but other than
a little extra oil consumption I experienced no other problems.