Hello all,
Just back from vacation (Colorado, so beautiful I had to
buy some dirt there). I talked to Al and it is obvious that his rear
prop shaft bearing did not get drilled prior to delivery. I've made many
screw-ups but this was a new one. Gave him instructions on how to drill
but forgot to tell him that an AN fitting screwed into the port helps guide the
bit to center of bearing groove (not critical though).
I don't think he could have spun the bearing in the time and rpm he ran
it. I have had the pleasure of spinning that bearing (on the prototype
drive) while in-flight. It was just a press fit at that time
and the higher rate of expansion of aluminum allowed the bearing to spin.
Amazingly, I flew the drive for 1.5 hours after it spun. The symptom was a
momentary unexplained sag in power, much like spark plug sag that long time
rotary fliers are familiar with. All production drives have pinned
rear bearings.
Tracy (still recovering from vacation lag)
----- Original Message -----
Sent: Sunday, August 29, 2004 6:16
PM
Subject: [FlyRotary] Re: Engine run -
Good news/bad news
Al, Sounds like you are looking at the brass
"sleeve" bearing around the prop shaft. Should, of course,have an
opening for the oil. If this PSRU was run on the dyno it sounds that
like either:
1. This condition existed before the dyno
runs (could be a missed step in manufacturing) or
2. The sleeve has sheared its pins and spun in
the casting.
Ed
Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC
----- Original Message -----
Sent: Sunday, August 29, 2004 5:36
PM
Subject: [FlyRotary] Re: Engine run -
Good news/bad news
Subject:
[FlyRotary] Re: Engine run - Good news/bad news
Took the fitting
out; soaked out the oil. Shining a light in reveals a nice smooth
surface of brass seated tight to the casting. No place for the oil to
go.
Al
Al,
check for foreign debris in the inlet too.
2. The joy was short-lived
because it was only a one minute run while I had the redrive drain line
disconnected. Taking the drain line off gave the first clue.
No sign that a drop of oil had ever been there. The amount of oil
in the container after the run – zippo; not a drop. I took off the
feed line and there was oil sitting in the fitting. Feeding to a
container, I ran again for less than 30 seconds, and sent more than a
pint into the container. Complete blockage inside the drive.
The prospect of removing the prop, drive and disassembly is not a happy
one.
Al, something
you might try before taking the gearbox off (a pain to say the
least). Its been know for such stuff as the silicon grey sealant
to plug up the drains. Yes, unlikely that it would have plugged up
the front one. But, short of taking off the gear box you might try
removing the drain fittings - just in the remote chance they could be
plugged.
Ed
With two exits and 100 psi oil; my
guess is it’s highly unlikely that the explanation is ‘foreign
matter’. I think there is no oil going into the drive. It
appears to me from the diagram that the oil goes in through a bushing
via a hole and/or groove. Most likely a misalignment there giving
the oil nowhere to go. I’ll check further later
today.
Al