4 CIMs in 3 stage VEX Pro ball shifters. We might switch to 3 CIMS in 1 stage gearboxes after our first event, based on how well these work.
The more interesting thing is a completely custom tread drive system. See video for some
footage of it driving. The tread is a
Brecoflex conveyor with the drive cog run by chain from the gearboxes. Two 3/16 side plates hold each drive module together; the idlers are made from round delron stock and the last one can move to tension the tread.
Why treads this year? It is part of our team credo never to lose a pushing match, even with Trucktown (we were on an alliance with them last year, we never got a chance to test their mettle unfortunately). Speed is reasonably good and they are quite stable.