Instructables user [birdycrazy] built a winding rig from a PVC pipe and a bunch of K’Nex. He had recently started a Tesla coil project and needed an efficient way to wind the secondary coil.

Anyone who has ever wound a toroidal coil by hand can tell you that it ... That obviously requires a winding ring that can be opened up to allow the toroid form to be inserted; [Sandeep] chose ...

Winding up the backswing is basically a simple turn -- whilst at the same time stretching the elastic bands so that when you swing down and through the ball, it's as fast as possible, all the while ...