How tight should a flywheel be?

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Ian McMillan - 12 Aug 2003 14:52 GMT

Hello all,

I have an OS 50 that has only had about two gallons of fuel through it and
the rear bearing has failed. My question is, could it be due to the flywheel
being overtightened? If so, how tight should the nut on the crank be
tightened?
There does not seem to be any evidence of corrosion. The engine has never
had a lean run or been overheated and it has been running beatifully until
just now.

Thanks

Ian

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Beav - 12 Aug 2003 20:37 GMT

> Hello all,
>
> I have an OS 50 that has only had about two gallons of fuel through it and
> the rear bearing has failed. My question is, could it be due to the flywheel
> being overtightened?

Not in a million years Ian, not IF the flywheel was installed correctly. The
flywheel/fan-hub, should ONLY come into contact with the INNER race of the
front bearing and behind the inner race there's a "step" on the crankshaft,
so you're only bearing down on that inner race. There's no "pulling the
crank right through the engine" thing going on, so there's nothing pulling
on the rear bearing AT ALL.

If so, how tight should the nut on the crank be

> tightened?

> There does not seem to be any evidence of corrosion. The engine has never
> had a lean run or been overheated and it has been running beatifully until
> just now.

You wouldn't by any chance be running something blue through the motor with
something less than 30% nitro would you?

Either that or your fan/clutch assembly was wildly out of balance.

Signature

Beav

Please note my E-mail address is "beavis dot original at ntlworld dot com"
(with the obvious changes)

Beavisland now lives at
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Model Forum / Radio Controlled / Helicopters / August 2003

How tight should a flywheel be?