<< 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 stopped 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
I had a disabling "O" ring failure after running the same engine for three
years with oil temps of 230+. I ran the engine at home with no problem. We
took it off the trailer at Indianapolis Raceway Park and it started smoking
big time. I thought I might have mixed too much oil or mixed it twice over
the two weeks between races. I ran it on fuel with no oil at all and it kept
getting worse. I mean big white clouds of smoke like W.W.II. We went home. On
inspection, I found the "O" rings on the front side of the rear rotor had
decomposed into pieces about 1/2" long. There was little wear on anything so
I replaced the "O" rings and put it back together. Since it is unlikely that
both "O" rings failed at the same time, (we may have been running for some
time with just one ring working) I have wondered if I could get away with
just running the inside scraper and do away with some drag. Also I notice
that the center hole in the iron could be larger, and maybe the single
scraper with less spring pressure would be more effective. The scrapers have
to deal with all of the oil expended from each bearing and the oil spray
holes in the crank. This, and a big centrifugal load on the oil. Since we got
the oil temp down to 190-200 we have had no additional problems.
Lynn E. Hanover.
I forgot about the centrifugal oil load on the oil rings. Very good point Lynn.
Thanks for bringing that up.
BTW I just bought some O-rings for the wiggins coupling from McMaster
Carr. They did not have the size and material I needed in the catalog but
they got them to me anyway by UPS Red Label. So I think we can get the
teflon encapsulated silicone oil control o-rings from McMaster Carr as well.
The size I think we need for the outer ring is 4 3/4 ID 3/32" section
which should have an AS568A-158 number. The inner ring should be
an AS568A-157. That would be a 4 1/2 ID with a 3/32" section.
I could be wrong on this. Tom Kimsey has a set so we shall see.
I think we can up the temperature of the oil going into the engine out of the
oil cooler to 250 degrees F if these 500 degree F oil O-rings are used
and are successful.
BTW This is the oil temp Continental used on the Voyager engine the
Rutans used to fly around the world non-stop in 216 hours. Patrick Swayzes
Cessna 414 with water cooled turbo Continental six's also, I suppose, use
this oil temperature limit. The benefits are less heat loss to the oil,
less fuel consumption and a smaller oil cooler hence less cooling drag.
The stock gen II oil cooler would then be more than adequate for over 200 HP.
Paul Lamar
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