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Zumo 32U4: one of the wheels does not rotate smoothly


It worked very well till yesterday, and I don’t know what’s happened (no shocks, I think, but of course I cannot swear).
The right wheel is not rotating freely and smoothly, above all in CCW direction.
I don’t think the wheel was forcedly pushed towards the robot: it does not look jammed though it is. Perhaps some small debris somewhere?
Should I try and unmount the wheel?
It happened just during a class… one robot out of six is now out of order…



There are two sprockets attached to the right tread on the Zumo; is it the Zumo’s drive sprocket that you are having issues with? (This is the sprocket attached to the gearmotor). What is the gear ratio of the gearmotors you are using? You mentioned the sprocket is not rotating freely and smoothly in the counterclockwise direction, but is it working normally in the clockwise direction? Is the behavior the same if you remove the tread? What about if you prop up your zumo on a box or otherwise suspend the treads in the air? Does that sprocket still have issues rotating?

If you are not already using new or fully-charged batteries, can you try replacing them? If that doesn’t fix the issue, can you post a link to a video showing the behavior you are seeing?



Dear Tony,
thank you very much for your kind reply!
I had to leave for a congress so I could neither reply nor try your suggestions (some of them I had tried myself so I can already give an answer). I’ll soon do some tests and come back to the forum.
Thanks again!