Mailing List flyrotary@lancaironline.net Message #42077
From: <Lehanover@aol.com>
Subject: Oil pan design
Date: Wed, 26 Mar 2008 11:12:02 EDT
To: <flyrotary@lancaironline.net>
Years ago Many rotary racers discovered quite painfully that the entire oil supply of the engine would move into the front case under hard breaking. Since the driver would be very busy during this part of the lap, he would seldom notice the total lack of oil pressure. Once through the turn and the G load was removed, oil returned to the pan and oil pressure would return to normal. But screaming the engine for the downshift with no oil pressure, would take out the rotor bearings before the end of the season.
 
However at higher RPM there is no need to have the surface of the oil at a 45 degree angle (one "G") to subvert the oiling system. In hot oil you can pull enough vacuum at the pickup to create a vortex in the oil. 
 
The tornado looking thing from the bathtub drain. When flow rates are high as on climb out, the pressure in the oil pan near the pickup becomes less than the local air pressure, combined with a little centrifugal load as the vortex forms and provides a supply of air for the pickup to inhale instead of oil, the oil pressure will sag a bit. In race cars that can brake at more than one "G" it is fatal to the bearings after long exposure.  
 
The rotary adds more foam to the oil than does a piston engine, from oil squirted into the spinning rotors for cooling. Air in the oil makes the problem worse. Air is an insulator. Oil cooling becomes more difficult.
 
In race cars the addition of a flat plate style baffle cures the problem. But the longer time spent at climb attitude may not allow for just a baffle to get it to work. But maybe so..........
 
I suggest that since the engine is backwards in the plane, and oil can run into that front case on climb-out, it would be good to check the oil pressure now and again.
 
I have in mind an oil pan that would preclude any such shenanigans. Complex, difficult to build, takes up too much space, probably not needed, but it is stuck in my head.......
 
Lynn E. Hanover  
 
 




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