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Old 07-15-2019, 07:43 AM
turboimark turboimark is offline
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Quote:
Originally Posted by itsid View Post
BUT..
roller wear and chain stretch are two very different and mostly unrelated topics.

chain stretch is not due to rollers wearing down,
it wouldn't allow the chain to snap it wouldn't even stretch the chain at all
O-ring chain takes up for some of the wear to still protect the pin with worn rollers
and has nothing to do with manufacturing tolerances.

what stretches and thus weakens the chain is pin wear or fatigue for that matter
and at times plate stretch (on low quality chain)

So personally I'd say measure both roller diameter (averaging over the entire section of links) and actual length of segment
and decide based upon both independently..
and if you find any individual roller having excessive lateral play
you'd better order new chain now to be prepared next week.

a low load high abuse chain might not stretch past the 1% mark but can still have fully worn rollers which cause the sprocket to wear eventually start jumping etc.
and taking the slack out only makes it worse (the wear not the jumping part).
so such chain also needs to be replaced before it wears on the sprocket teeth,
no matter if stretched or not.
Since a worn sprocket prematurely wears the next chain rollers..

So the only thing to go by is roller wear at times..
Since once a pin is allowed to collect rust or dust
(O-rings offers some protection remember?)
it grinds down the pin hidden from view
and you cannot see or predict it's failure really

excessive play on the roller can be a sign of such hidden wear
since the pin and roller should wear evenly when ground against each other,
half of the play comes fromt he worn inside of the roller the other half is the outside of the pin
(which must be prevented)

'sid
Right, elongation and fatigue are two separate things.


In my experience in the field people mostly conflate "stretch" and elongation so just to be colloquial I call them the same thing in this post since 99% of people will never know the difference.

If the chain is fatiguing (actually stretching sidebars without wearing rollers) then there is definitely overloading happening and another problem entirely with the design (i.e. you need a bigger chain or a dual strand setup).

IDK about measuring the rollers separately. The only time I've ever seen worn rollers but low elongation was in cases of long flat conveyor chains where the roller for some reason was dragging along a long flat surface and locked up instead of rolling. Something like an plywood kiln chain or a car body assembly conveyor. It's extremely odd to see rollers wear but no elongation on drive chain unless the customer just bought absolute oddball Chinesium garbage.


Anyways, I didn't want to get too off into the weeds. I'm writing a Chain stretch 101 forum post for amateur go kart builders, not teaching a graduate level course in material science.

Peace
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Last edited by turboimark; 07-15-2019 at 07:48 AM. Reason: edited for sarcasm
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