Loose shaft on HPCB Micro Metal Gear Motor

I recently purchased four 298:1 gear ratio HPCB micro metal gear motors. I am using them for a robotics project, and the motors are currently being employed by attaching 3D printed wheels directly to the motor shaft. 3 of the motors function fine and run as expected. The fourth, however, has a loose shaft that wiggles back and forth. As a result the fourth wheel of the robot cannot be driven in a straight line, instead it constantly wobbles and as such it is difficult to keep all four wheels on the ground (the robot is running over uneven, sandy terrain). I have taken off the gearbox to attempt to find a way to tighten the shaft but this does not appear to be possible. What should I do?


I am sorry you are having problems with your gearmotors. Have you tried swapping the wheels to make sure the problem follows the gearmotor? If you already checked that, could post pictures or video showing the problem?

- Grant