The mechanism is very simple. A 6 volt motor with 200:1 gear box is glued to one end of the block and a pulley wheel is glued to the motor's spindle so that it lies horizontally on top of the block. A hole is drilled into the middle of the block, just large enough to allow a length of dowel to turn easily inside the hole. A pulley wheel is glued to the piece of dowel just above where it leaves the block so that it is at the same height as the other pulley. A rubber band is used to link the two pulleys. The model is then put over the protruding length of dowel.