I can motorize a ball and make it roll--but it tends to lose its head!
Print the wheel and put the washer "tire" into the slot.
Push the motor into the motor carrier.
Add the wheel (friction fit) onto the motor shaft.
Add the idle wheel onto the shaft.
Press fit the hub onto the end of the idle shaft axle.
Insert the bar magnet into the magnet holder. Add the spring from a ball point pen onto the shaft.
Remove the nubs from the holder.
Use superglue gel to attach the battery holder to the bottom of the motor base.
Solder the motor wires to the battery holder.
Insert the round magnet (friction fit) into the head.
Insert the battery, then join the two sphere pieces with tape.
The ball will run around on a smooth floor. The head seems to be too heavy and it falls off every chance it gets.