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Old 08-24-2019, 09:46 AM
Snaker Snaker is offline
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Great writeup Turboimark. I've worked with a lot of chain through the years, both on my stuff and industrial. But haven't gotten into the technical end, more of a change it when it needs it. Some thing I want to add is how the stress (load) is transferred, using a dirt bike as a easy to "see" example.

Looking at a dirt bike from the left side (engine drive sprocket to the left, rear wheel driven sprocket to the right), the stress is only at a couple links near entry on the drive and a couple links near exit on the driven. A very stretched chain makes it glaringly obvious.

I could put the bike in gear, roll the bike back till the top of the chain was tight between sprockets and yet easily pull the chain outward away from the driven sprocket teeth just a few links in from the exit.
So the last link to exit has the full load which it transfers to the next link in line to exit.

A new chain will have this transition happening but the transition will happen when the tooth is just starting to roll out of the last link, so the stress is deeper into the bottom of the tooth. As the chain stretches the transition happens later and the chain stress moves further out towards the tip of the tooth, which accelerates the wear .

Some of these characteristics also happen with drive belts.

On your 2-3% general wear I have a question. About the only chain I deal with these days is on my bicycle. I have a go - no go tool

That tool specs out no go choices of .5% or .75% depending on how far one wants to push it.

Question is how do those small tolerances jive with your 2-3% general specs?