Quote:
Originally Posted by Alan Anderson
a simple roller lock to improve the maximum forward torque before losing traction
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I'm assuming you mean a lock to keep the roller from rolling? In that case, if you were to lock mecanum
wheels (not rollers) from turning then try to push the robot forward/backward, or left/right, the rollers already won't roll* so the lock won't change anything*. worst case would be 45 degrees, but still with no lock you have 2 wheels resisting the push, and this would be difficult for another robot to capitalize on.
The decrease in traction comes from the fact that the mecanum wheel translates torque to a force at an angle to the plane of the wheel, which means it must necessarily create more force than a regular wheel (with the same input torque) and therefore would reach the maximum force of static friction before a regular wheel (with the same wheel material).
Somewhere on CD awhile ago, I saw someone put forth the idea of a mecanum wheel that is 20 or 30 degrees between roller axle and the plane of the wheel. This would give a larger maximum friction force with all other things being equal at the cost of some strafe performance. I wish I had the resources and manufacturing skills to create wheels like this to test...
The other option would be to change the roller angle on the fly, but at that point, it's probably easier and more effective to just build an octocanum or swerve.
*OK, roller compliance and axial free play have some effect on this, but IMO these effects are not FRC significant enough that I would spend time designing a locking mechanism.
EDIT: since I just spent a bunch of posts addressing other posts that seemed to blur fact and opinion, I'll add that this is just my hypothesis for how a lock would behave, and it includes a couple untested assumptions about locked rollers, and I'm open to being disproved!