They told us and I did not write it down. Mark Wrathal wrote it down

I think. Mark?

It is flame sprayed something or other. Not Nicosil. The rotor

housing is Nicosil.

It is quite thick as there is a slight recess machined in the end

housing to accept

the coating. If it were me I would just put hardened and
ground sheet steel in there.

Paul Lamar

Paul, with the small area near the pinch of the trochoid
you would probably have trouble keeping sheet steel flat.
The coating if successful, would be easier to do. Fewer machining ops.

I haven't given up on a source for coatings.
Bill Jepson

I think you could stud weld on some screws and bolt it on. I think it
would be
a lot more durable than coatings. Either that or cast it in like Mazda
does on
the rotor housings. One could also press in special serrated flat head
steel pins
in undersize holes in the aluminum casting. Then grind it smooth.

Paul Lamar

Sorry Paul, for once I must disagree with you.  If you cut a Mazda rotor
housing, you will see that the steel insert has tiny serrations to
improve structural and thermal contact with aluminum.  We have
thoroughly investigated it and the fact is that it is a very
sophisticated casting process which Mazda developed and which can be
afforded only if you have automobile-industry series.  With
aviation-industry series, you just forget about it and investigate what
coatings/seal material combination may effectively and durably replace
it.

Side housings are slightly different matter, but it's a different
chapter.

Francois Badoux

Well Nicosil has given problems. The guys at Diamond said there were two
suppliers in England. One of which put out some bad coatings. Probably the
downfall of Wankel Gmbh. Maule refuses to do it for aircraft engines.
Silicon carbide detonation coatings are very reliable but expensive as 
they must be diamond ground. 

I still think thin steel liners are the way to go. Both rotor and end housings. If it 
were me, considering the prospects for getting Cessna or Piper to convert to rotary 
engines I would say certification was not worth the huge gamble. Stick with the 
experimental market and use Mazda parts.

Paul Lamar
 
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