gear for LEGO DUPLO train motor

Often cause damage of trains Lego hollow - split gear on the motor shaft.
This is not a problem, if you have a 3D printer.

Especially for repair of my locomotive I modeled this gear.

Gear must be worn tight on the motor shaft.
To put the gear on the shaft, I wasted edge of the inner hole of printed gear a little by using stationery knife and push it onto the shaft with force.