OH SNAP! Belt failures 2014

[Thad House]

We snapped 6 belts as of now. We snapped one on the practice bot, one on the competition bot at our second competition, and 4 on our competition bot at our 3rd competition.

We are using belts on our drive train. It is a 6 CIM 6WD WCD setup with 4" wheels. We are using 9MM 130T belts, using 24T pulleys at each end. The robot only weights 100 lbs, so it is fairly light.
At our 3rd competition, the belt going to each wheel snapped once each. The practice bot snap and the 1st competition bot snap were both on the same wheel.
All of the breaks were very similar. The were all very rough and messy, with alot of jagged edges. We emailed Vex, and they said that we were over torquing the belt, because we have too small of pulleys, with too much power on the drive. Didn't seem like a tension error, because the teeth were all fine, and the belts looked like stress snaps.
The pulleys never failed, and still look brand new.
The belts were under the load a 6 CIM drive would give. I don't have exact numbers.
We had 15MM pulleys in the center, and then 9MM pulleys on each end. The 2 belts shared the 15MM in the middle.

For worlds, we plan on putting chain back on so we don't have to worry about snapping. This summer, we will put more work into doing calculations, and redesign the chassis so it will fit larger pulleys.
But otherwise, we loved how quiet and smooth the belts were. We are glad we tried them this year, and will use them again next year if we can fix the snapping issues.