Quote:
Originally Posted by joeweber
If you layout your sprockets and chain flat on a table you can get the dimensions center to center of the axels and you will not need tensioners. We did this on our test bot and it worked pritty good.
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Unless you plan on pre-stretching it, 25-pitch chain will "stretch" under a high enough load to the point where it will start skipping. Over very short chain runs (a few inches, max), it often won't be enough of a problem. But over anything longer than a few inches it'll be noticeable enough to cause the chains to pop off.
This past season I experimented with super lightweight floating idlers to much success. The floating idlers I used were polycarbonate sprockets (milled from 1/8" sheet) that were inserted into the roller chain. The tension of them kept them in place. I made several sizes, so that over the course of the competition season the chain could be re-tensioned as it stretched by either moving the sprockets closer to the end sprockets, or by replacing it with a larger idler sprocket.
After our first or second competition, the chain stopped stretching and the sprockets have remained untouched since, where they've lasted through a half dozen competitions. They've worked flawlessly, and have never popped out of the chain or failed in any way, all with a tensioner that weighs a fraction of an ounce.