|
|
Mark;
I’m very pleased to hear it
happened while still at the airport.
There should be little or no pressure
forcing it out; and there should be no significant level of oil in the housing,
so it is just the ‘splash’ around the shaft. Given the large
quantity of oil you lost in a short time would suggest significant pressure and
a backup of oil. Do you have at least a 3/8” line for the drain-back, and
could there be some restriction?
You also might want check what kind/brand
of seal you’re using. I had an issue with that mounting plate seal on my
20B after about the first 50 hours. It worked part way out of it’s socket
(I guess it was against the damper plate hub) and resulted in some minor
leakage. I had Tracy send me a new seal, which I didn’t like because; IIRC, the
outer part of the seal did not have the coated metal flange, just hard elastomer
material. I felt that after running hot for awhile it could loosen and not stay
in place. Tracy gave me brand and part number and I got a replacement to match the
original. Unfortunately, I can’t tell you brand and part#; although
may still have the box and old seal at the hangar.
Also don’t know what I did to insure
it stay in place. May have just coated it with hardening gasket maker, or peened
a couple of dents at the edge of the hole in the plate. In any case, it has
remained where it belongs for the last 150 hours.
Al
-----Original Message-----
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Mark Steitle
Sent: Sunday,
September 19, 2010 5:19 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Check
PSRU Oil Drain-back hose was Re: Watch that psru oil seal
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
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.
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.
|
|
|