Spring winder with worm screw, and centerless wheels
Winding a one-way spring, and wheels made without a central pivot
The large drawing shows a spring-driven mechanism inside a frame, with a wheel S, a pinion n, a spring, a perpetual (worm) screw and a toothed rack: to wind the spring one turns the handle m the contrary way, so that wheel S stops with its axle while pinion n turns upon it carrying the spring, worm screw and rack. Lower on the page Leonardo demonstrates wheels a and b built without a center in the middle, supported instead by three little rollers, the only difference being that wheel a's rollers are better placed and distributed. He notes that such centerless wheels are made to show how to build a wheel with no central pivot, a case that often arises. Parts are lettered S, n, m, a and b.
On this page
Winding the spring with handle m and a worm screw
When you want to wind the spring, turn the handle m the contrary way; the wheel S stops together with its axle, and the pinion n turns upon that axle together with the spring, the perpetual (worm) screw and the toothed bar with its little wheel.
Wheels made without a central pivot
The wheels a and b are made as one and the same, differing only in that the three little rollers supporting wheel a are better placed and distributed. They are drawn to show how to make a wheel with no center in the middle, a case that often occurs.