From: Lehanover@aol.com <Lehanover@aol.com>
Subject: [FlyRotary] Re: Watch that psru oil seal
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Date: Sunday, September 19, 2010, 7:14 AM

In a message dated 9/19/2010 5:41:35 A.M. Eastern Standard Time, msteitle@gmail.com writes:

Kelly, 

My custom adapter plate was built on a Bridgeport mill.  The hole spacing (and sizes) were obtained from a drawing for the actual RD-2C plate.  Could it be a thou or two oversize?  I guess that's possible, but I don't think so.  The machinist that did the work is very meticulous.  However, before reassembly, I'll definitely check it to be sure.  The bottom line is that there is 90-100 psi trying to push it out of place.  So, I feel that a mechanical fastener is the only real way to guarantee that it stays put 100% of the time.  

Mark

Anything not positively retained in aircraft, will eventually fall off. Garlock style lip seals will just barely hold back oil splash with little to no pressure. You see Garlocks  pressed into cavities that are cast or formed with retaining lips at the end. Not into smooth bores. More than a few pounds against a lip seal over heats the seal and fails the lip allowing a leak. Note the oil drainback paths in the rotary, so seals see no pressure even beside a main bearing other than from crank case gasses..

 

I had a weaver Brothers three section dry sump pump that had the pressure section in the blind end of a casting so no high pressurized oil was exposed to a seal of any kind. The drive shaft extended from the scavenge pump end, so any pressure pulses would of minimal size against the Garlock seal pressed into a smooth bore in the end plate. Each session the seal would be found dancing along the shaft with oil dripping off of everything. A competitor told me to retain the seal with a plate of some kind. Once that very long weekend was over I did that with a plate and three little screws. I replaced the single lip seal with 2 half width lip seals and the plate and never had another problem. I also cut a tiny groove from the suction side of the pump to the center of the shaft cavity. Oil drain-back to a lower pressure area. 

 

Lip seals are the most freedom loving seals of all. If pressurized they turn their lips inside out and leak on you.

 

If you persist, they will escape the bore and dump your oil out on the ground. They have been that way since the first day. Thought should be expended on the release of crank case gasses. The street engine has a tiny tube sticking out of the oil filler neck. This is way too small for operation above about 3500 RPM.

 

Lynn E. Hanover