Sanity Check! Mecanum wheels...

[Alan Anderson]

The two possibilities have very different turning behavior. Imagine the equivalent omniwheel drivebase with the wheels in an X shape instead of a diamond. You simply cannot turn yourself in place using that arrangement, but you also cannot prevent yourself from being turned by an outside force.

If the mecanum rollers don't all point at the same place in the middle of the robot, as would be the case with a rectangular drivebase, you actually do have a slight ability to turn. But switching them to the other orientation will give much better control.

[Lil' Lavery]

Originally Posted by Alan Anderson

The two possibilities have very different turning behavior. Imagine the equivalent omniwheel drivebase with the wheels in an X shape instead of a diamond. You simply cannot turn yourself in place using that arrangement, but you also cannot prevent yourself from being turned by an outside force.

Good point, I hadn't thought about applying a torque to your robot. I was thinking translational pushing, in which case the two configurations are the same.

[Dan Petrovic]

If you're confused about how the rollers make X's or O's, refer to the axis' of the rollers. If the axis' of the rollers make an X on top, you're in good shape.