flywheel ring gear/balancing flywheel & crankshaft
06-09-2007, 08:05 PM
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flywheel ring gear/balancing flywheel & crankshaft
Could I first give you the background to my 911 query:
Couple of years ago I had to do something about missing teeth on the flywheel of my 356. Decided on a new flywheel. Mechanic installed a new clutch at the same time. Suffered noticeable vibration in the rear view mirrors while working up to 3000rpm. Had the clutch and new flywheel balanced. Better, but not perfect. Noticed on the DVD "Built by Hand" (taken in Porsche factory circa 1959/60) that they were balancing flywheels attached to crankshafts. Then saw in Factory Workshop manual for 912 motors that flywheel and crankshaft should be balanced together.
Ok - forget about the 356 - I am looking at a very presentable 911 SC which has some missing teeth on the flywheel. You know the old trick, roll it until the starter can attach to some good teeth.
Is it a simple solution to just replace the ring gear? Will that so affect the balance that the set-up should be rebalanced? If either a new flywheel or new ring gear leads to a need for re-balancing, is it desirable that (in the case of a 911 SC) this be done with the flywheel and crankshaft attached as a unit?
I don't have access to the Factory workshop manuals for the 911SC yet as I am only about to embark on 911 ownership.
many thanks
Couple of years ago I had to do something about missing teeth on the flywheel of my 356. Decided on a new flywheel. Mechanic installed a new clutch at the same time. Suffered noticeable vibration in the rear view mirrors while working up to 3000rpm. Had the clutch and new flywheel balanced. Better, but not perfect. Noticed on the DVD "Built by Hand" (taken in Porsche factory circa 1959/60) that they were balancing flywheels attached to crankshafts. Then saw in Factory Workshop manual for 912 motors that flywheel and crankshaft should be balanced together.
Ok - forget about the 356 - I am looking at a very presentable 911 SC which has some missing teeth on the flywheel. You know the old trick, roll it until the starter can attach to some good teeth.
Is it a simple solution to just replace the ring gear? Will that so affect the balance that the set-up should be rebalanced? If either a new flywheel or new ring gear leads to a need for re-balancing, is it desirable that (in the case of a 911 SC) this be done with the flywheel and crankshaft attached as a unit?
I don't have access to the Factory workshop manuals for the 911SC yet as I am only about to embark on 911 ownership.
many thanks
06-11-2007, 01:07 PM
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It should only get better with a ring gear that has all its teeth. The ring gear is pretty thin section, not much chance for it to get out of balance unless teeth are missing, so a replacement should not create problems.
06-11-2007, 03:35 PM
#5
"a lot" - well do the math!
- the crank weighs about 30 lbs. & the throws are several inches from the centerline - add the flywheel & clutch too!
compare that with several things that weigh less than a nickel each, located less than a foot from the center
we can argue whether 1% is a lot or whether 0.1% is a lot, I suppose.
and, as noted above, adding back teeth may well tend to restore balance, not hurt it
- the crank weighs about 30 lbs. & the throws are several inches from the centerline - add the flywheel & clutch too!
compare that with several things that weigh less than a nickel each, located less than a foot from the center
we can argue whether 1% is a lot or whether 0.1% is a lot, I suppose.
and, as noted above, adding back teeth may well tend to restore balance, not hurt it
06-11-2007, 07:40 PM
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Thanks guys.
My gut feeling is that if the new ring gear is the same as the old one then logically it should not make a difference to the balance. But what the hell would I know?
Appreciate your comments.
My gut feeling is that if the new ring gear is the same as the old one then logically it should not make a difference to the balance. But what the hell would I know?
Appreciate your comments.
