[eclipsed78], built an automatic toroid winder (Internet Archive). The drum splits in order to load the toroid. Then wire is wound on the drum, much like any other coil would be wound. The drum rotates as a slider pulls the wire off the drum, while revolving in and out of the toroid. A side tension keeps the slack out of the wire during operation. The winding coil is stepped as the drum rotates, in order to control the turns ratio. [eclipsed78] created a stepper driver from a schematic, so he could drive the motors. You can watch the winder in operation as a series of videos. The first of which is embedded below. If you have ever needed to wind a massive toroidal transformer, this is the project for you.