Quote:
Originally Posted by Dunngeon
It's possible, but you'd have to use 2x2 tubing to get both of the belts to fit into the interior. From what I've read on Delphi, chain in tube is better than belt since chains (rarely) snap and don't stretch over time, eliminating the need for a tensioning system.
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You have it backwards - chain *does* stretch over time, and belts do not. Chains generally do need a tensioning system, and belts generally do not. My team has run 15mm belts in tube with exact center distances for now four seasons in a row without ever having a belt failure or need to tension. Belts just don't stretch in the liftetime of an FRC robot.
If you undersize your belt drive, it can break - generally failures I've seen involve 9mm wide belts with 24t or smaller pulleys. This just isn't up to snuff. 15mm wide is a safe bet if you're using small, west coast drive friendly pulleys. If you are using larger tooth count pulleys such as the bolt on VersaPulleys that are 36 or 48 tooth, 9mm is generally fine for those.
The reason "chain in tube" drivetrains with no tensioning work is because the chain and sprockets are sized so that they just barely fit in the tube at all. Chain in tube does stretch, but since the chain on the sprocket is such a close fit with the tube, the chain can't jump the sprocket since there's just nowhere for the chain to go. It works well, but it is very much an edge case with chain drives.