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Unread 03-08-2010, 15:04
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JamesCH95 JamesCH95 is offline
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FRC #0095 (The Grasshoppers)
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Re: Drop-center drivetrains: Why?

Quote:
Originally Posted by Chris is me View Post
I caught that. 6 wheel 4 omni isn't terrible or anything but it is more easily spun and negates a lot of the advantages of a rocking drivetrain. The CG issue, while relevant, really isn't something you need computer precision to analyze. If you don't want to rock with an arm too much, you can adjust the drop a little, put the CG a bit more to one side fore-aft, or even run an 8 wheel drive if your CG is centered. You should be able to get a good enough estimate with just some napkin sketches of where the "heavy stuff" goes. CAD isn't required to figure it out.
I am aware that CG/tipping moments can be roughly estimated with napkin calculations. Chassis stiffness is not analyzed so easily.

We've also done a drive-train with two omni wheels in the middle and traction wheels on four corners these omni+traction 6wd robots, in either configuration, have all been successful.

I'm not trying to invalidate your points, Chris, they are indeed accurate. While the does trade off a little hit-and-spin stability, it also gains turning speed and virtually eliminates jitters from scrubbing the outside wheels and rocking. As with any robot design choice it has to be made in context of the teams strategy in that year's game. I feel that this disclaimer need not be made with every post though.
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