Ken Welter wrote:

   Here is the final report on the seizure I had when I blew a oil line.

    As I predicted there is no damage to the e-shaft or bearings and in
 fact I will use the main bearings over again but the side housings
 and rotors are trashed do to the expansion of the rotors do to loss
 of cooling to the rotors.

   Also the corner seals, apex seals and rotor housings are in good
 shape but the side seals and the oil rings are also trashed.

   Ken

This is a new one on me. One would think if you did not have enough
oil to cool the rotors you would not have enough oil for the bearings
either. How much rotor clearance did you start with Ken?

Paul Lamar

   I taper clearance the rotors by cutting off .015 at the tip of the
rotors and zero out the cut just before the oil seal, you can see it
on the earlier photo you have that you have with the bluing on it.

  Besides the engine that seized because of the ross gearbox
hamburgering itself and plugging the oil intake the other two that I
lost the thrust bearings due to the ross gearbox had the same outcome
as the oil pressure dropped when the thrust bearing went out and the
rotors seized.

  Also note that on closer examination I found that the front rotor is
salvageable and the rear one is toast which was consistent with the
first two that I lost due to thrust bearings but the one with the
plugged oil intake toasted both but the rear was the worst off.

  This may support the theory that 6000 rpm is the sweet spot for very
little bearing loading on the rotary.

   Ken

Only the rotor bearing load is low at 6000 RPM. The main bearing load
only depends on the torque being generated. 

Looking up the rate of thermal expansion on cast iron gives: 
.059 inches x 10 -4 per degree F
or .0000059 inches per degree by moving the decimal to the left by
four places.

If we start with room temp 72 F and go up to 500 F that is 430 degree F change
in temp. So the rotor should be only about .0025 wider if my numbers are correct. 
Somebody please check these numbers for us.
That is NOT taking into account the much higher expansion of the rotor housing.
The same coef. of thermal expansion for aluminum is 50% greater or .094 x 10 -4.

I think there may be something else going on here. Could be the lack of oil
is overheating just the area around the center of the end housing causing some high
local heating which results in some local spin welding. Could be tapering the 
face of the rotor is hurting in this situation rather than helping as it 
concentrates the rubbing in a much smaller surface area. Do you see signs
of metal pitting and galling in this area? I think the spin welding
theory is much more likely in this situation.

Do you see any signs of heat discoloration around the center of 
the end housing and on the center face of the rotor? At 500 F you should also see
some signs of oil coking as well. What kind of oil are you using?
Mobil One still works at 500 F. If the whole rotor was 500 F the rotor bearings
would definitely show some signs of distress. Lead in rotor bearings starts
to melt at less than 500 F. Aluminum bearings lose half their strength at 500 F.

Paul Lamar
 
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