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Chain and chainwheel don't mate?!?!

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Chain and chainwheel don't mate?!?!

Old 06-05-11, 10:52 AM
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Roll-Monroe-Co
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Chain and chainwheel don't mate?!?!

I was helping some folks fix up a 50s Norman 3-speed at the coop. It's not certain that the crank (with swaged chainwheel) or the chain are original. Certainly, the chain could be a replacement.

They seated up the chain on the chainwheel and cog and tensioned it by affixing the rear wheel in the proper way. It looks completely normal.

Then you turn the crank and something weird happens: The chain and the teeth of the chainwheel do no stay synched up. Instead, the chain processes on the chainwheel until some or all of the rollers are sitting on top of the teeth of the chainwheel. (The only time I've ever seen anything like this is with an Atom freewheel and an Allvit derailleur, when a shift is incomplete and the chain is skidding along the tops of the teeth of the cog, but there's no derailling going on on this bike and there's no extra chain in play.)

The only thing I can think is that they somehow got hold of a chain with a different pitch (like a chainsaw chain or something). The solution would be just to replace the chain.

Can you think of any other reasons this might be happening? (My concern would be severely worn chainwheel or cog teeth, but I've never seen this kind of behavior before.)
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Old 06-05-11, 11:04 AM
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well off the top of my head I can't recall the measurements... 1/8 and 3/32 I believe one is BMX and single speed the other 3/32 is for multispeed bikes with a derailleur did some one put a multispeed chain on it?


(yes I know these rules are not hard and fast today but I would think it appliaes to this bike)
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Old 06-05-11, 12:14 PM
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Can you measure the chain and check the wear? 12 links should be fairly close to 12 inches. When I got my Raleigh, the chain on that was at just under 12 1/4 inches for 12 links, and that still ran fine on the chainring, so that must be one seriously worn chain if that's what's going on. Pitch mismatch would be the only other reason I can think of, because the chain must be wide enough if it seats initially.
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Old 06-05-11, 03:41 PM
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The Norman uses 1/8" chain; I suspect the co-op put 3/32" chain on by mistake.
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Old 06-05-11, 03:49 PM
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Originally Posted by JohnDThompson View Post
The Norman uses 1/8" chain; I suspect the co-op put 3/32" chain on by mistake.
+1

I doubt it was pitch error since the next commercially available pitch is 3/8" and the difference is glaringly obvious. Probably the chain is too narrow to seat properly on the teeth.

The other possibility is very poor chainline, and the chain is hanging on the teeth as it comes around.
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Old 06-05-11, 04:54 PM
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Hmm. Thanks guys. I never really eyeballed the chainline, though the chain seems to stay lined up on the chainwheel--it's just that the rollers won't stay between the teeth.

Next time I see them I'll just recommend checking out the chainline and trying a new single-speed chain.
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