Slipping Pinion Gear

We are using the AM-2964 NeveRest motors on our FTC robot this year. They have worked great for us until yesterday. One of our drive motors would only work going forward. Upon further examination, we realized that the motor would freely spin in reverse and would engage with the motor when going forward.

NeveRest AM-2964 with Gearbox Removed
NeveRest AM-2964 with Gearbox Removed

When the motor was stripped down, the pinion gear was found to be detached from the drive axle. The pinion gear only mounts to the axle in one direction. There is no flat surface or groove on the drive axle and no set screw on the pinion gear. It appears the the pinion gear on these motors is compression mounted on the drive axle.

Following the failure of this motor, we wrote it off as an isolated event. We mounted a new motor onto the robot and resumed testing. During the testing, our other drive motor suffered an identical failure. While the first motor that failed had nearly 20 hours of drive-time on it, the other motor had less than 5 minutes on it!

Short of using Loctite, I’m at a loss on how to secure this pinion gear to the drive axle. Has anyone else has this issue with the NeveRest motors from AndyMark? If so, how did you resolve it?