Part of my Pololu metal gearmotor shaft keeps slipping

Hey there, I recently bought a 30:1 Metal Gearmotor 37Dx68L mm 12V with 64 CPR Encoder (Helical Pinion) to use for a project, and accidentally hit the shaft of it while trying to fit in a universal mounting hub. This made a part of the shaft to be loose.

Do you guys have any ideas on how to stop it from slipping off to the end of the shaft? Here’s what it looks like when it does:

and here’s what it looks like when I push it back on.


Thank you for posting good pictures that show the problem. Unfortunately, that shaft support is critical to keeping things aligned correctly, and it is not practical to repair that damage. If you send an email to with your order information and a reference to this thread, we can probably help you with a discount on a replacement unit.

- Patrick