Paul,

When I was at the Seven Stock Show, I noticed that all of the rotors were
cast iron.  Has anyone made aluminum rotors?  Is there too much thermal
expansion to use aluminum?  I was also thinking that the rotors could be
made of a ceramic--low expansion, lighter weight, and possibly lower cost.

Steve Brazil

I think it is  a heat issue. The rotors can run 500 F or more.
Titanium seems to work but it is expensive.


-- 
Paul Lamar ...No rotor no motor.

Paul,

That's interesting.  Titanium likes heat and it's highly corrosion
resistant, although it has problems around metals like cadmium.  It does
very well with investment casting.  I have some very large investment cast
Ti parts around the shop at work--on the order of 50 lb.  I would think a
rotor would be easy.  Do the rotors wear out?

I heard somebody at the show talking about a ceramic either rotor or seal
that they were using in a Formula Mazda car.  I think one of the new
ceramics would be worth looking at.

I don't know if anyone has done this, but the rotor could also be machined
in halves out of stainless steel, electron beam welded together then finish
machined.  This would make a very light, strong rotor although a precision
investment casting in stainless steel would be very close to this.

Steve

Yes rotors wear in the apex seal slots. They are good for 300,000 miles
in a car and well over 2000 hours in aircraft service. They are hardened only
at the ends of the slots. A chrome plated or totally hardened slot would
reduce the wear further. I don't know what the situation would be with
titanium rotors. I always thought that a aluminum rotors with steel
inserts  for the apex seal slots might work. This is done on heavy duty
aluminum pistons with the piston ring slots in some aircraft engines.

I also don't know what the life would be with ceramic apex seals.
I suspect it would further extend the life of the rotor slots.

Also worn rotor slots can be ground out for 3 mm apex seals.

Paul Lamar ...No rotor no motor.

Steve,
I believe I read somewhere that Ti doesn't wear well, if that's the case the
apex slot could wear quickly. It is already a problem in steel - however a
steel insert could be the solution. A replaceable slot insert would also be
the solution in the steel rotor.

BTW apart from the slot, I've never heard of a rotor being worn out, Ti
would be a good investment.
George (down under)

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