[Alex1072]

If you only have one wheel, the you run into the problem of having to control motor outputs to go straight. I think I might not be understanding what you're saying though.


EDIT: I get it now. There is no inner/outer wheel speed problem because each truck has a differential in the gear box. Having the 2 wheels makes it so that there is no weight on the castors normally. With 2 wheels the castors are only used when you the angles of the trucks get too close to 90 degrees from the robot frame.

BTW I made slight mistake with that ASCII diagram:


the turn in place would look like this:

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with castors on the left and right for support