The motor turns the helical lift at only 5 rpm, so I had to gear up the speed. I ended up with 18rpm, and an arm that is about 20" long. There is a belt that is around the shaft on the lift extending to a secondary shaft to the right. The large white bearing just behind the belt is there push into the back side (the slack side) of the belt and keep tension on it. The tension keeps the teeth in the belt well seated into the grooves on the gears, and it fits the belt around the gear a little more than 180 degrees. The flat blue gear then turns a small gear on the end of the long 15" shaft, turning it. The marbles in the end of the arms are loose so they roll around as the arms rotate, and look as nice as possible! (this is also part of #64)