[Mechvet]

I've got a drive base in our shop from 2010 with the original belts still on it. We use to practice having a defender harassing the current season's robot. Brecoflex belts are indestructible ONLY if they're very carefully designed around.

That drive base also has no adjustable tensioner.

EDIT: Here's our guidelines for a tank track system:
1. Sideloading is the quickest way to kill a belt system not built for sideloads. All pulleys will need their center groove accurately machined, and wherever the belt is not contacting the ground some sort of rigid plane should be present to stop the belt from tracking too far out of center.
2. The belt loop length needs to be very accurately machined. The system we were using had 0.25" 6061 plates for each side of each track module. This didn't allow for the possibility for either too loose or too tight a loop. Multiple components retaining your track hardware will allow for misalignment, and each time you split the system into multiple parts you add more possibility for either lengthening or tightening the belt loop.
3. A tight belt is just as responsible for failure as a loose belt. Overtensioning a steel belted system will make it fatigue and tear. Once the plastic and tread around a seam has torn free, all the fatigue and stress moves to the steel belt for that section, which will fail in short time. On our 2010 system each belt has maybe .01" of vertical flex when the belts were new. Turnbuckle style belt tensioners lead to 'crank-er-down' practices which will overstress the belts and lead to premature failure.