Motor in axle

[Rimrock]

Can advice using a tube setup. Best thing is to put a suitable tube in a lathe and machine the internal diameter close to the diameter of the motor/gearbox. I use 4 off set screws to keep the motors in position. Drill some holes in the motor/gearbox somewhere, not going through, where the set screws will 'dig in'. One have to select the points where set screws will hit the motor with care to not damage the motor cache