Wendel, One suggestion I have is to bend a
paper clip so that an leg is sticking straight out (or any other such) then
insert it into the keyway. I forget now but I think it should not go in
much more than 1/4" IF the key is present, I'll check on a pump I have in the
shop tomorrow. If you find the paper clip going in more than 1/2" (I'll
check tomorrow) you key is likely missing.
Further amplification on what Leon said about the
key - it is easier than you may think to put the key in the keyway and slide
the sprocket on the shaft and push the keyway out. Normally when that
happens you hear the "ping" as the metal key hits the floor. But in this
case, It appears that when I push the key out the back side as I slid on
the sprocket, I actually clamped the key between the sprocket and the pump
housing. The reason I am confident that is what happened is the mark of
the key was impressed into the soft aluminum housing. The first
spin of the sprocket then threw the key into the bottom of the
pan.
Fortunately I had torqued the nut to the books
specs (which many think is a bit high for that small a nut) and flew with it
for 10 hours. One evening when I was at Tracy's we were looking into the
throttle bodies and I had push my throttle in all the way to open the
butterfly. Forgot to close it. Next more was cool and when I
started the engine it immediately (wide open throttle ) fired and zoomed to
5000 rpm with cold 50 weight oil. That broke the clamp of the nut and it
started to turn the sprocket faster than the shaft and actually wore a small
circular place around the sprocket shaft as it rubbed against the shoulder of
the shaft.
Tracy, Finn and I were going flying. A very
lite breeze from the north, but Tracy and Finn elected to take off to the
south. Unless an unusual situation exists, I always take off into the
wind, so I elected to taxi to the south end for my up wind take off. One
the way taxing I noticed that my oil pressure was only reading 20 psi when it
normally reads 30 - 50 psi.
I tried telling myself it must be a bad sensor or
gauge and nothing was really wrong, but I just couldn't ignore that anomaly
and decided to abort the take off and taxied back to the hangar.
Fortunate decision as I doubt the oil pressure would have stayed as high as 20
psi had I decided to fly.
After much "try this, try that" it finally
because apparent the engine would have to come off.
Tracy's is the best place in the world (other
than perhaps your home hangar) to have a problem. He had a replacement
oil pump and helped me get it all back together using his hangar for my
repair. A great place to have to spend time down for
repair.
FWIW.
Ed Anderson
----- Original Message -----
Sent: Friday, January 07, 2005 7:22
PM
Subject: [FlyRotary] Re: Oil Pump Drive
Key was Re: [FlyRotary] Re: Some things to check
----- Original Message -----
Sent: Friday, January 07, 2005 2:46
PM
Subject: [FlyRotary] Oil Pump Drive
Key was Re: [FlyRotary] Re: Some things to check
Wendell,
Ed Anderson had a problem where the oil pump
Wooodruff key wasn't in the keyway. The drive was just taken by the
friction of the tensioned nut. Worked for a while. Sooner or
later, the sprocket will slip on the shoulder of the pump
shaft. The symptom is intermittent loss of oil pressure, which
gets worse as the sprocket wears on the shaft shoulder.
So, as I said in the post below,
always make sure that the key is actually in the keyway before fitting to
nut & lockwasher. The key itself is very tiny, and it
requires a bit of juggling to get it in the keyway in the sprocket.
I normally gently stake the keyway in the shaft so that the key can't slip
out.
Hope this makes sense!
Leon
Thanks Leon, can proper installation be
checked by inspection or do you have to remove the pump and start
over?
Wendell