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Unread 10-12-2007, 16:27
meaubry meaubry is offline
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Re: Position idlers to get better chain wrap -- a question about good practices.

Madison,
We've built serpentine #35 - 6 wheel drive systems that incorporated idler / chain tensioners mechanisms in the past, along with many other types of chain drive systems.

The distance apart and the amount of chain wrap is directly related in a design like the one you are showing. We've had them as close as "the teeth almost touching", to a few inches apart with 3 teeth engaged.

So, it can be done - but, there are other issues to also consider when routing the chain this way.

The chain wrap and chain tensioning will impact the drive motor output and temperature.
Too much tension is not good and too little tension is not good. Too much wrap is not good and too little wrap is not good.

The chain tensioning can also be achieved by placing shims or blocks beneath the idler or motor mount. Thus lifting one or the other upward, taking up the chain tension and increasing the chain engagement. This can be done either in conjunction with, or seperate from, sliding fore and aft on the rail.

Also watch that the longest unengaged side of the chain (in this case it is on the bottom side) is protected. Any object that can push against the side of the loosest side will act like a derailer.

I may not have provided a specific answer to your question, but I hope this helps,

Mike Aubry