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Good point, Jim
Also the nut on the sprocket takes a lot more torque per
spec than you might think from its size. Do torque it to specs -
When I rebuilt my engine, I unknowingly pushed the shaft key out and
pinned it between the sprocket and the aluminum pump housing - so it did not
fall to the floor and warn me. I flew 10 hours with the key missing - the
proper torque kept the sprocket from spinning on the shaft.
However, at Tracy Crooks, Finn Lassen and I were comparing
intakes and I left my throttle pushed full open. Next morning we
were going to measure exhaust loudness - you guessed it - when I fired up
on this cool 50F morning my engine immediately revved to 5000 rpm before I could
get it shut down. Did I mention I use 50 weigh oil??
During taxi to the far end of the runway (because I was a
wimp and would not take off down wind even thought it was only a less than 5 mph
breeze) I noticed my oil pressure was on the low side like around 20 psi.
That caught my attention. Even when I revved the engine it did not go much
above that - must be the sensor or the gauge - right? Well, I
could not bring my self to take off even though I "knew" it has to be the sensor
or gauge.
Well, you know the answer, when I disassembled the engine
at Tracys I found the beat up key in the bottom of the oil pan. I also
discovered the impression in the soft aluminum oil pump housing where tightening
the sprocket nut had pushed it - until after I had buttoned up the engine and
ran it the first time. The immediate zoom to 5000 rpm on a cool morning
undoubtedly was too much torque for the nut alone to hold against. When I
examined the sprocket, the shoulder of the pump shaft had started to wear a
grove in the sprocket. A few more turns and I probably would not have been
able to get 20 psi. Fortunately, Tracy had a lot of replacement
parts including an oil pump.
Soooo the message is make certain that key is in
there. I use a paper clip bending out one leg - if it goes in more than
1/4" that key is not in the slot. It turns out I was not the first to have
this happen - for the key to get pushed out. But, apparently no body else
flew that way {:>)_
Ed
----- Original Message -----
Sent: Wednesday, February 20, 2008 6:34
PM
Subject: [FlyRotary] Re: Rebuild
kit
Ernest,
While you have the oil pump drive exposed it would be a good idea to
assure
that the nut that holds the drive sprocket on the pump has the locking
washer
installed properly.
Mine did not, and it only took about 8 hours of run time for the sprocket
to fall off
and chew a hole in the cover.
Lehanover@aol.com
wrote:
> So now the chain is too long, but it has no affect on
performance. The spec
> is for droop when the chain is off the engine
and held side ways to check for
> wear in the link joints. Still
doesn't matter. Even warn out they work just
> fine. Up to 115 pounds
of oil pressure. There is a tiny hole in the pump that
> sprays lube
oil into the pulley to lube the chain. Have never seen one break
>
since 1980.
>
> Lynn E. Hanover
>
>
Thanks,
Lynn.
Woohoo! One part down. 64 more to go 8*)
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