[EricH]

Originally Posted by donkehote

Why not run belts/chains to the middle wheels only from one end This would allow you to turn front/rear wheels separately, allowing mecanum strafing, but would still drive all 6 when on the traction wheels. Seems a bit more simple than using a ball diff.

Unless you happen to be on a hill in the field while trying to strafe, when you'l end up doing who-knows-what when the traction wheels hit. And the last game I can think of with a completely flat field is Aerial Assist; before that I'd have to go clear back to 2007 (if you didn't climb the on-robot ramps, which most teams did) or 1999 (if you weren't a puck-climber, which most teams were). Every other game has at least had raised surface under the carpet. If you have a way of neutralizing the motion of the center wheel, you can at least get predictable results, which will be a lot easier to plan for.

And yes, I can think of situations over the years where strafing on a hill or irregularity in the field would provide an advantage.