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Unread 12-05-2010, 10:31
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Re: The Center Wheel

Whenever we've done 6-wheel designs, we've dropped the center wheel. In Overdrive, we had a forklift-like elevator that got up probably 10 feet high with dropped center wheels... and we never tipped over. We also had a giant steel plate on the bottom of the robot to lower the CG.

Dropping the center wheel a fraction of an inch does make the robot look a little unstable as it bounces between front and back wheels, this is true. But in reality, if your CG is fairly low, it introduces no risk of tipping while on flat ground (and even climbing ramps in Rack and Roll it didn't seem to matter).

You may want to create a small test bed to see the results and prove it to yourself. Create a standard robot chassis with 6 wheels, but make the center wheel's height adjustable for example, you could securely mount a screw vertically that, when tightened, pushed the axle downwards, giving you a dropped center wheel, assuming you're using dead axle's). Drive it around with both dropped center and non-dropped center, and see how it handles with each. Design some tests for stability to determine if that would be a problem. In short, get some data before you decide which way to go.
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