A windlass in a block: power a against weight b
The winding barrel edges toward side m, pressing it more than side n as power a overcomes weight b.
A windlass barrel sits in a broad semicircular cavity cut into a rectangular block, its cavity sides marked n and m; long turning bars project from one end, one cord suspending the weight b and another leading down to the power a. Because of the direction of winding, the barrel edges toward side m. Leonardo reasons that as the power a overcomes the weight b, the barrel presses on m more than on n in proportion to how much a exceeds b, moving downward and sideways along an oblique line.
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Windlass in a semicircular cavity, sides n and m
A windlass barrel is set in a broad semicircular cavity of a rectangular block, its sides marked n and m, with long turning bars at one end; one cord carries the weight b and another leads to the power a. The direction of winding makes the barrel approach side m.
Barrel drifts toward m as power a overcomes weight b
Leonardo reasons that when the power a prevails, the weight b is overcome and the windlass turns toward a. It then presses on side m more than on n in the same proportion as a exceeds b, gaining ground downward and transversely along an oblique line.