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Motor mounting hubs easily come loose


Hi there,

I am experiencing difficulties with the Pololu Universal Aluminum Mounting Hub on my 25D gear motors on my robot.

It seems like the set screw comes loose over time. I’ve had this happen in warm temperatures and colder temperatures. The robot itself experiences a lot of vibrations, so I guess the set screw loosens over time. I did try ‘small’ strength thread lock… but I still worry that one day it’s going to give way like the others.

Do you know of any possible solutions? Or a better mounting hub? Maybe something with not as small of a set screw?




In general, adding thread lock can be a reasonable solution to keep the set screws from loosening. If a stronger thread lock does not work for those set screws, you might consider switching to a high hold cone point set screw like this. Cone point set screws have a greater clamping force than the cup point set screws that come included with those hubs.

We do not have any other mounting hubs for 4mm shafts that would also allow mounting the same wheels.



Thanks for your reply Jonathan

Interesting about the cone point set screw. Will the tip deform under the pressure to make a smooth contact with the axel surface?

Hmm… one more question. If you were to design a new version of a mounting hub to make it stronger, what would you add? Maybe it might be possible to cnc a custom new one…


No, the purpose of the cone point is to force the point into the shaft. The more the set screw is tightened, the deeper the cone is inserted into the shaft, making it more and more difficult to uncouple the motion of the adapter and shaft.

If you had the ability to create an adapter that had a D-shaped cutout with the same dimensions as the D-shaft of the 25D mm motor, then that would be an improvement.

By the way, have you considered that you might not be tightening the set screws enough? If you are using the small Allen wrench we include with the mounting hubs, you might try increasing the lever-arm of the wrench to give yourself more mechanical advantage.