> >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

   Yes I think you are right as the center of the housing is where the
real damage is may be do to the lack of lube rather expansion that is
causing the seizure and this simply seizes before the bearings, just
got to keep the life blood in there and wont have this problem.

  Using Kendall 20-50 oil, I don't see any signs of coking.

   Ken

Try some Mobil One in the "crankcase" typically. It does not break down
until about 500 F while regular oil starts breaking down at about
250 F. I have been using Mobil One in all my engines for 10 years and the
Dodge Caravan engine has 200,000 miles while still passing smog tests.
Everything else in the transmission, drive line and chassis has failed at
least once and sometimes more than once.

Paul Lamar

Paul,

This seems like a good time to add $0.02:)

I ran Mobil 1 oil in an '85 Monte Carlo SS, 305 HO, noted for camshaft failures among others, for 277,000 miles before I parked it.  Changed oil and filter at 15000 mile intervals.  Engine never opened.  Still runs.

I followed that up with a '94 Chrysler Concord for 244,000 miles, change interval 12000 miles (six cylinder is a little harder on the oil), then gave the car to my youngest daughter, who is still driving it at 275,000 miles.  Engine never opened.  Runs like new, as a matter of fact.

Current vehicle is a Chrysler 300M, 151,000 miles, change interval 12000 miles, no engine problems (no other problems either, for that matter, other than replacing the cooling fans about a month ago, and a transmission input speed sensor).

My wife's old car-- '90 Plymouth Laser 2 litre Turbo- 287,000 miles, change interval 10000 miles (4 cylinder, really hard on oil), engine never opened except to change head gasket.  Our son is still driving this one.  Mobil 1 gear lube in the transmission on this one-- shifts like butter.

All these vehicles were purchased new and filled with Mobil 1 at the first recommended oil change.  You can't beat the stuff.  My brother has or has had several vehicles in the same mileage ranges, same stories, including some rotaries.

Bob Lemings

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