Heres a quick drawing. The dimensions and proportions are way off, but it illustrates the idea well. Al, I did think about the friction between robots and the fact that you would still be locked in somewhat if you changed direction while pushing, but we normally have so much pushing force that I doubt it would be a problem. But even if we did get stuck, you could just back away slightly before switching direction.
The other nice thing here, that I can't really illustrate without a full drawing, is that you aren't turning the wheel in place like a traditional crab, you are instead turning it in an arc, so the force required to swing the module should be far less, especially with a high traction wheel.
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