mecanum wheels on frame

[Steve_Alaniz]

Originally Posted by 7-11number1

This is team 1711 and our robot is having "minor" technical difficulties. Were using 8'' diameter mecanum wheels and it has issues when it comes to driving around. The robot handles forward, backwards, and strafing side to side perfectly well. But the wheels lock up when attempting a turn or circling around on its center of axis.
The wheels are position with the left and right wheels 20'' apart and the front and back being 19''. I know a perfect square is recommended for mecanums but would a small difference like an inch cause the wheels to lock up when attempting turns? We need an experts advice or some links that provide good information on how to properly mount and place mecanum wheels.

http://www.flickr.com/photos/23220170@N07/
(ignore pic with tread and mecanum wheels)

Vikesrock is correct. I looked at the picture of your bot and the wheels are the problem. you need to swap them.
Why... ok if you think about it, the bottoms are opposite the top. This will help picture what's happening.
When you rotate, you are gripping into the center and rotating out away, this doesn't do you any good. You want the gripping to go outward and any rotation to cancel anything going into the center.
I know this because last year we used mechanums and had them backwards... and guess what? It would go forwards, backwards and strafe but wouldn't rotate without jumping, vibrating... what ever you want to call it.

Steve