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Unread 26-01-2010, 02:38
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Mechanical Engineer
AKA: Craig Boezwinkle
FRC #2811 (StormBots)
Team Role: Mentor
 
Join Date: Oct 2008
Rookie Year: 2009
Location: Chicago, IL
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Re: Spinning the Robot with Mecanum Wheels

Quote:
Originally Posted by Alan Anderson View Post
Yes. It'll actually work best that way.

(...unless you have your wheels swapped, in which case it won't be able to rotate itself at all.)
For wheels mounted in the correct configuration, I don't think that it's possible to rotate a bot about center if they are mounted in a square configuration. When summing moments about center they all cancel out when length = width. Only when you have a rectangular bot, where length != width, can you create one pair of moments not offset by the other pair.

This seems to be unconventional thinking, and I can't seem to find anywhere on CD that this has ever been stated. Am I missing something? Would anyone be willing to provide a vector analysis of a square 'bot rotating about center?

(It can be done using four identical wheels, but thats not what I'm after. Two "RH" and two "LH" wheels, mounted in an "O" configuration, cannot seem to create a moment about the center of a square bot).