Paul,

You requested photos of my OMC side plate – They are attached -

The engine had swallowed a piece of metal and seized – housing was
damaged but the sides, rotor and seals appeared to be OK except for a
few scratches on the depressions in the face of the rotor - You can see
in 1624 the overall area location of the hard area – 1627 is a closer
photo – 1630 is quite close up –

The inserted area is very hard – cannot scratch it – I have a Rockwell
tester but haven’t tried it on the part - The aluminum die casting is
quite soft and doesn’t appear to be anodized or have any hard finish on
it but it is undamaged – The black line in the photos is just a stain
where the rotor had been sitting for a long time, not damage to the side
plate -

The inserted hard area as shown in 1630 has a finish similar to that of
an Oilite bronze bearing and appears to be porous, possibly for
retaining lubricant and releasing it as required – Would be good to find
an old OMC engineer who was familiar with the process they used – Do any
of your readers know someone like that ? – Maybe a patent exists -

I’m guessing that the side plate was probably lapped flat after the hard
material was applied because there are no discernible marks of machining
on either the aluminum or the hard surfaced area -

Roland Friestad

The coating could be Nikasil.

Here is where the rotor cooling oil squirter goes.  This allows doing away
with the charge cooling and a simple tuned p-port will increase the VE to
about 120 %. (from 70 or 80% if your lucky). So the HP will increase
about 30%.

The oil squirter requires an oil pan to catch the oil drain back, a pump
and oil cooler.

Paul Lamar

Paul,

Is it possible that OMC used an alloy similar to A390 and that the 'hard' area of the side housing is actually just the silicon brought to the surface?
the Chevy Vega was the first auto that I saw which used this process and I believe that BMW presently uses it in some of it's engines - this process had been perfected by the time the OMC rotaries were built.


Ken Powell  - still here and continuing my education

Ken you had a motor mount in 2003.
You don't have that thing flying yet :-) What is it?  An RV4?


SAE 730119
OMC used Hypereutectic aluminum side housings and a piston alloy for
the rotor housing. The cooling capability was designed for organic oils.
Mobil 1 synthetic is twice as good as organic oils temperature wise.
Of course a steel trochoide will with stand higher temperatures.

The rotor bearing was another cooling problem. If a silicon nitride roller or balls are used the rotor bearing will withstand twice the temperature.

The hotter you can run an engine the better the BSFC.


Paul Lamar

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