Hi Dave,

There are too many factors here to draw any firm conclusions.  Possible reasons for the broken side seal are detonation, flawed seal or installation damage.  Being sintered iron and only .7 mm thick, they are fairly delicate.  Were they fitted properly when installed?  New side seals are slightly too long as furnished and must be individually fitted to the groove by carefully grinding to length.

 

 BTW, what apex seals were you using?  These are usually the first thing to go with detonation.  RA seals will frequently not break leading many racers to conclude that they did not have detonation.  The failure mode of our seals in detonation is heat damage which eventually causes them to sag into the groove and have low compression when hot.  Better than a fractured seal that typically takes out a rotor and rotor housing.

 

Lots of carbon?  You call that lots of carbon?   (I've seen lots of carbon and that isn't it : ) 

But the really important thing about carbon is the nature of the carbon buildup.  If it is the "fluffy" type that is easily scrapped off it is not really a problem.

  Typical 4 stroke oil leaves an almost varnish like carbon deposit that is very difficult to remove and causes seals to stick in the groove.  This is the really significant difference between 2 & 4 stroke oil.  Also remember that 99+ percent of what is being burned in the combustion chamber is gasoline.  It leaves carbon deposits especially if the mixture is too rich.

 

Tracy

----- Original Message -----

From: David Leonard

To: Rotary motors in aircraft

Sent: Monday, October 10, 2005 1:47 AM

Subject: [FlyRotary] Carbon Build up.

 

The first picture is the front rotor with the stuck and broken side seal with a piece missing. Wouldn't fit in the last message.

 

So the big question now is why.  Note the picture of the rotor face.  There is LOTS of carbon build-up.  So much for 2-stroke oil burning very cleanly.  I am mixing less than 1:100 (about 5 oz per 6 gal gas can).  I have thought of the following possible causes:

 

1 My oil may be running a little cool.  It maxes out at 160 and is usually closer to 140-150.  This could keep the rotors too cool and prevent burning of the oil.  Add in the modification to the oil bypass and this may be it, but it seems unlikely to me.

 

2 Running rich.  Because it is so hard to get the engine tuned, I am probably running very rich (the only way to keep it running), especially at low RPM.

 

Some of both?  Poor quality 2-stroke?  I have noticed that the 2-stroke oil does accumulate in the crank case.  That of course indicates that it does not all burn, and what doe burns does not necessarily burn cleanly.  Maybe using crank-case oil would burn less, and there would be less needed and less residue. 

 

Anyone else seen this?  Any ideas?

--
Dave Leonard
Turbo Rotary RV-6 N4VY
http://members.aol.com/_ht_a/rotaryroster/index.html
http://members.aol.com/_ht_a/vp4skydoc/index.html

--
Dave Leonard
Turbo Rotary RV-6 N4VY
http://members.aol.com/_ht_a/rotaryroster/index.html
http://membersaol.com/_ht_a/vp4skydoc/index.html --
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