Ed,
You and Lynn may have hit on something regarding the crankcase vent line being too small. It may have been marginally acceptable with the side port engine, but way undersized for the fire-breathing p-port. First time I ran it real hard, out came the seal. I am using the stock vent line, but will go ahead and up-size it while I'm fixing the psru seal.
Mark On Sun, Sep 19, 2010 at 8:10 AM, Ed Anderson <eanderson@carolina.rr.com> wrote:
Mark, here's another thing to check for - the oil drain
back hose from the PSRU
The PSRU typically has its oil drain-back to the oil pan
which can be "pressurized" by blow-by of the rotors. This back
pressure could impede the flow back of oil from the PSRU because by
the time the oil in the PSRU is ready to drain back it has dropped the oil
pressure from its 80 psi input to practically zero. So it basically
gravity feed back to the oil pan. I guess the oil pan pressure
could get to the point of serioulsy impeding the oil blow - but I would think
that much crank case pressure would have given other indications - such as
blowing your dip stick out {:>)
Now if the PSRU oil drain-back became
plugged/restricted/crimped for some reason then the pressure on the seal
might eventually reach near the 80 psi input mark and that would put
considerably force on the seal. So (as I know you already planned) check
out the drain back hose.
But, in any case mechanically restraining the seal
sounds like a smart ideal in any case
Ed
Sent: Sunday, September 19, 2010 8:39 AM
Subject: [FlyRotary] Re: Watch that psru oil seal
Lynn,
Am I reading you right in saying that it it was crankcase
pressure, not oil pressure. And to relieve said pressure, one needs a
larger relief tube than the factory one on the oil fill. (call it perhaps
3/16" without going to the hanger and measuring)
Ben --- On Sun, 9/19/10, Lehanover@aol.com <Lehanover@aol.com>
wrote:
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
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