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Unread 05-05-2012, 23:18
Kris Verdeyen's Avatar
Kris Verdeyen Kris Verdeyen is offline
LSR Emcee/Alamo Game Announcer
FRC #0118 (Robonauts)
Team Role: Engineer
 
Join Date: Jun 2001
Rookie Year: 2001
Location: Houston, TX
Posts: 699
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Red face Re: Mechanum Wheel Sizes

It's perfectly natural for a team your age to feel things like this. Many of us have experimented with holonomic drive trains at one time or another. It's nothing to be ashamed of, and it's good that you've come to us for help. With hard work, focus and determination, you'll come through this, better than ever.

The thing to remember is this: every single person on every single team, including the best teams in FIRST, have, when first presented with them, looked at mechanum drive trains, and said, "Whoa, cool!", and not one robot built with them has made it to Einstein in at least 2 years (because that's how far back I've checked).

It's not because they suck inherently, it's because it's hard to make them run to their full potential. So, because you'll ignore this warning and build it anyway (because, "Whoa, cool!"), the best advice I can give you is this:

1. Encoders on all 4 wheels
2. Only run it closed loop (typically velocity mode)
3. Make sure each one of the (48) little rollers is free spinning before each run. Bent wheels can cause these to bind.
4. Understand what the code needs to make the math work, especially any code you don't write yourself.
5. It still probably won't work great on anything but a flat floor.

People below me will contradict points 1,2,5, and maybe 4. They will have counterexamples. They also probably have a grandfather who smoked 4 packs a day and lived to be 100. Ignore them, believe me.
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