Here is a good article from Mazda Sport Magazine.


Excerpt from:
Slippery Business by Royce Branch
Mazda Sport Magazine May/June 2004

Still another key factor is film strength, a measurement of the amount of pressure needed to force a film of the oil out from between two flat pieces of metal. Some synthetics post film
strength of over 3000 pounds per square inch; for petroleum oils, the average is less than 500.

Fred O. asks:

Does the ability of a journal bearing to sustain side loads relate
directly to film strength?
For example, does 3000/500 = 6 times the side load capability?

Paul replied:

Yes is if you are using a plain bearing thrust bearing but the Mazda rotary
uses a needle thrust bearing. I am not sure what you mean by side load?
The rotor and main bearings see only radial loads. In other words loads
only in the radial direction.

I also don't know if this applies to ball or needle bearings.

Fred O. wrote:

Sorry Paul, in my early morning fog the proper term just could not
penetrate the haze. My "side load" should have been "radial load". So
my question should have been is the radial load capability proportional
to the film strength?

Yes. In theory this leads to the conclusion that you should be able
to rev the rotary higher without damage to the rotor bearing using 
synthetic oil.

Paul Lamar
 
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