[JesseK]

In my experiences, these drives tend to rotate about their center of mass, regardless of how offset it is. 6WD/4WD traction skid steer have more forces at play, thus the center of rotation is somewhere between the center of mass and the center of area (CoA being the intersection of the diagonals created by track width and wheel base).

All this really means is that the characteristics are different. Mecanum and 2+2 will translate slightly as they rotate if the center of mass is not co-located with the intended center of rotation.

However, in our trials, the robot is consistent in how it turns for the most part. I don't know that we'll get precision turning without some fine tuning, but we won't know until week 6 when the robot is fully loaded in its final form. Not that our autonomous ideas require too much precision turning ( < 1 degree accuracy & consistency ) without translation anyways.