We did no chain last year and loved it!!
http://www.vandenrobotics.com/plogge...icture&id=1517
Those were Toughbox modules we made by adding a 1/2" hole in the corner of the toughbox for a dead shaft. Then mounted a gear directly on the wheel that meshed with a gear on the output shaft of the toughbox. Then used a pillowblock bearing on the opposite side of the wheel. This is a pretty straight forward direct gearing design, that most any team could do. Down side is using a gearbox for each wheel.
This year we tried belts, but didn't use the right size and couldn't get the tension right, so we reverted back to #35 chain. The most common way chain comes off is misalignment and/or lack of correct tensioning.