[lasereyes]

Our team was originally going for a 'center-drive 4-caster bot'. When we made the prototype, we took it out into the parking lot to try to drive it. The robot ended up doing donuts. After a while we found that one of the gearboxes had a problem, so they fixed it. After that, it no longer did donuts, but it still tracked left. We found that the problem was the distribution of weight on the robot. It tracked to whichever side that the battery (and therefore, most of the weight) was on.

Our team ended up abandoning casters because we found it to be too complicated and too prone to problems.