Belts 9mm or 15mm?

[zuzoom101]

We have been using 15mm belts for the last couple of years on the drivetrain, and they have been working great. As long as the alignment is correct, no belts should be broken. We have had to tension them a couple of times through the season, but nothing too worrying.

We tried using 9mm belts on a test drivetrain that we built. It weighed only around 50lbs, and after only 30 minutes of use, we ripped one of the belts. We replaced it and haven't ripped one yet. I would go with the 15mm to be safe, but you have to take the extra width into account when designing the robot.