"Brian D. Cain" wrote:
 >
 > While we've been on the subject of general engine reliability

lately

 > (especially
 > with the o-ring thread a week or two back), I've been thinking alot

about

 > the
 > corner seal rubber insert "problem".  Just three weeks back when I

was in

 > sunny Lancaster, CA rebuilding a 4-port 13BT for a comrade of mine,

I

 > noticed
 > yet again that the rubber inserts on all 12 corner seals were

turned into

 > mush.

The engine builder likes the rubber plug style. I use only the solid

style. I

have cracked one of the plug types and had one turn back into powdered

iron.

I have never lost a solid one. You stomp on the thin ice long enough,

you get

wet.
Lynn E. Hanover

I have heard of that happening. John at Mazdatrix mentioned they
were having trouble with those things. As I said somebody ought
to try replacing the whole works with a slotted teflon cylinder.

Paul Lamar

"Brian D. Cain" wrote:

What I don't completely understand is their original purpose. Obviously,
as history has demonstrated, plain ol' rubber right inside of the engine
doesn't
seem to last very long (ala the older stock oil control ring o-rings) so I'm
still wondering why Mazda continues to use these instead of an alternative.
My guess at their use has to do w/ having some "cushion" in the apex seal
to ride on at their respective very corners as well as provide an "elastic"
combustion gas seal at the same place.  Otherwise, I don't have a clue
why they're there and don't understand the efficacy of using solids over
non-solids.  Any care to explain this, please?

B

I think the rubber is in there to damp the vibration. Hard to fathom
I know but I suspect that tiny little C shaped corner seal is resonating
like a tuning fork. That is why it shatters. It will be intersting
to see what Mazda does on the RX8.

Paul Lamar

I think that Mazda changed to the new corner seals with the elastomer insert to improve sealing
and reduce emissions. The theory behind the design is that the seal is drilled out to give it some
diametral "spring." The seal can then be made a closer fit in the bore without fear of binding.
This reduces leakage around the seal. Then, the elastomer insert fills in the drilled hole to
reduce crevice volume. Crevice volume is all the little volumes inside an engine's combustion
chamber that are too restrictive to support combustion of gasses that get trapped. In a piston
engine it is mostly the volume around the piston circumference above the top ring. It is also to a
lesser extent the volumes of the ring to groove clearances and the volumes behind the rings.
Crevice volumes trap unburned hydrocarbons which ultimately find their way out the exhaust or into
the crankcase.

Jon Lauter
Rotary Power Marine Corporation

The AirCraft Rotary Engine NewsLetter.  Powered by Linux.
ACRE NL web site. http://home.earthlink.net/~rotaryeng/            
Copyright 1998-2002 All world wide rights reserved.