paper: Belt Driven VersaChassis WCD - Step by Step guide

[Oblarg]

449 ran 9mm belts last year without any issue on their WCD.

Looking at the belt specs (which are conservative - you can get more than the rated torque out of them given how short the lifespan is in FRC compared to industrial applications), if I were running an 8WD I'd probably be happier with 15mm between the two lower wheels. For a 6WD, where the vast majority of the robot's weight is on the center wheel to begin with, I don't think it's a likely problem.

As for why bother with 9mm, it allows one to use the WCP gearboxes with pulleys-in-gearbox just as one would do with chain. Personally, I'm not a huge fan of that setup - if a belt does break (admittedly unlikely but it's better not to tempt Murphy if you can avoid it) it's a royal pain to fix - but even in other setups it's nice and much more compact to be able to fit 2 9mm belts on one pulley than have two pulleys.