[JesseK]

In 2010 we had this issue, but I think AndyMark has addressed it since then. If you use the Toughbox Nano's, make sure the final gear stage has no lateral movement on the shaft. Otherwise the output shaft bearing could pop out. It's an easy fix (2 washers), but I do believe AM fixed it already.

This was also from 2010, so double check the wheels before you buy. The 6" Mecanum wheels are sheet steel -- very very strong. Because of that, we got away with assembling 1 hub onto each Mecanum wheel, then putting that onto the output shaft of the Toughbox nano. There was roughly 0.25"-0.375" of gap between the Toughbox Nano bearing and the hub, which we filled in with PVC -- you NEED that gap so the Mecanum wheel roller bolts don't interfere with the gearbox as it spins. We then put a 1/4-20 bolt into the hold at the tip of the shaft, which kept the hub from coming off. The whole setup lasted through 2 competitions and 14 hours of little kids banging it around at the Science & Engineering Festival in Oct 2010 in DC. It went over the 12" bumps of 2010 and survived like a champ.

Toughboxes are -- wait for it -- really Tough! I've been a fan of them ever since that season.