http://www.torque-online.co.uk/news/?p=3631
     --

     Paul Lamar

  Paul,

  Did this kart have ceramic bearings and if not when (if ever) will
  the AIXRO folks add them?

  I have not seen any reference to it, but do they have the liquid cooled
  shaft per the paper you have linked to i.e., the "LCCR" ?

  Also,
  I see the Cubewano UAV Wankel is using Ceramic Coatings on the
Rotor  and the epitrochoid surface, as well as claims of lower BSFC.

  Any comments?

  My best,
  Anthony

  Those questions are above my pay grade :) Send your questions
  directly to:

  Poul Henrik Woelfle AIXRO <ph.woelfle@woelfle-engineering.com

  I will say IMHO ceramic coatings on the rotor are not worth the
risk  of damaging your rotor housings when it comes off.

  BTW they have a new very nice web site.

  http://www.woelfle-engineering.com/index.html

  Paul Lamar
  --

  Hi there,

  First, thanks to Paul for publishing the links.

  Now to the questions:
  The engine may have had ceramic apex seals, but there is not so
much  of a difference to standard seals. The biggest difference is above
  8000rpm, where the ceramic seals produce less friction and allow
for  some more top-end power. Even if it's about 3hp (that's 6% on a
 45hp engine), the average karter will not really notice the
 difference though. On a side note: We hardly ever see any wear, but
 we do see some "running in" with the standard seals. Therefore
changing from standard to ceramic on a used engine is no good unless
 the trochoid housing is exchanged as well.

  We have tried ceramic rotor needle bearings, which were good for
  lower bearing temperatures. These things are very sensitive though.
  If anything manages to get into the bearing (dirt, etc.), the
  needles will dissolve and destroy the e-shaft, rotor, seals and
  housing, i.e. the complete core engine. The apex seals are much
less  sensitive to such occasions, because they can wipe potential
dirt or  the like out the p-port exhaust. For this reason we don't
use  ceramic bearings. Ceramic coating of the rotor and housing is surely
  interesting, and when it works it's great. But I agree with Paul
  that getting it right is a difficult exercise, especially in aircraft.

  Our trochoid housing and side plates are from aluminium and water cooled.
  The E-shaft is charge cooled. Of course a liquid cooled shaft (or a
  completely different rotor cooling/lubrication system) would allow
  for more power, but it would also add to the cost, weight and
  complexity of the system. The charge cooling system we are using
  works fine in the intended power range.

  Best Regards,
  Poul

  Let me put on my devil's advocate hat here for a few minutes with
  some assumptions and questions. The devil is always in the
  details... especially with a rotary engine.

  Since the kart engine is limited to 10 seconds at full power for
max  HP, what percentage of max HP can it run at full power for 5 minutes?

  A certified aircraft engine must run at full power for 5 minutes at
  a time according to the FAA.

  I assume this is due to the rotor bearing temperature in the charge
  cooled rotary engine.

  Lets also assume for the moment that the dirt particle capable of
  shattering a ceramic needle bearing is made from diamond, being the
  hardest particle I can think of right at the moment.

  What diameter of diamond particle relative to the diameter of a
  ceramic needle causes the needle to shatter?

  Can we come up with a filter that will remove particles that size
  and above in the premixed oil/fuel mixture before it is added to
the  fuel tank?

  Can we come up with a filter that will remove particles that size
  and above in a filter on the engine located in the fuel/oil feed system?

  What is the best place to put a thermal couple to measure the temperature
  of the rotor bearing if that is in fact possible?

  Paul Lamar

  Paul,

  My experience with WOT running problem was self ignition, once on
an  air cooled engine motorcycle I switched the ignition off and
rode a  full lap to make the point to our Chief Engineer, I tossed
the keys  to him as I passed, we switched to water cooled shortly
after. Even  on water cooled we had the problem but this was plug
orientated, a  nodule would build up on the plug and this acted like
a glow plug, scraping  the nodule off gave a further say 100 odd
mile of High speed WOT running.

  On Rotor bearings we had special ones with low skew grade, and in
  fact we used to use a skew test rig, this consisted of a ground
  shaft spinning at a set RPM with a loaded bearing the axial thrust
  being measured. On WOT work we had the Eccentric shaft grow by

  0.0001" per 1000 miles, and the new build clearance did not help
the  noise emitted by a air cooled engine, we Cryogenically treated the
  Shafts to stabilize and speed up the Growth prior to final grinding
  and in so doing we was able to reduce the new build clearances and
noise.

  Bob
  UK

  A few years ago it was determined most engine wear was caused by
particles of 5 to 25 microns size. At the time and I suspect even
today, that most filters only removed particles larger than 40 microns.
  With charge cooling, dirt in the intake air will be the culprit.
The fuel/oil should be fairly clean and not be the start of a
problem unless care has not been taken transffering the liquids.

Dale Davies

Poul, Suppose for the moment you built a two rotor with a full
pressure fed oil system and a planet gear box. What would you have
to charge for it at a quantity of one per week for the non certified
Light Sport Aircraft market and the US experimental market.

We need a light weight 2 rotor 100 HP engine for aircraft service.

Take a guess.

Paul Lamar

Poul,

Out of curiosity, are the rotor housings and end plates hyper-eutectic
aluminum, with the aluminum lapped out to let the seals ride on the silicone
or do they use a steel liner? I realize intellectual property is involved and
the lightness for a kart engine is a factor in the design. Thank you for what
answer you can provide.

Dale Davies