It is tiresome to wind up the rubber motors by hand, so mechanical winding devices have been made. A drill with a hook in the place of a drill-bit is quite satisfactory. It is best to have a ring on the rubber motor where it is attached to the anchoring hook. This ring can be hooked on the hook of the drill. This winds but one at a time, so they should be changed about in the winding process, first on one and then on the other back and forth, until tight enough. A very good winder can be made of a revolving egg-beater. The egg-beating part is cut off, leaving two shafts instead of one. If there is a hook on each, both motors can be wound at once and as they should be wound in opposite directions, the device works all right.