Weight-driven grain mill with a gear train and pendulum
A 20,000-lb weight on a 30-braccio lever turns a millstone 960 times per wheel-turn through lantern gears
On blue prepared paper Leonardo lays out a grain mill powered by an enormous falling weight rather than by water. A weight of 20,000 pounds hangs from a 30-braccio lever against a one-braccio counter-lever, and a train of toothed wheels and lantern-gears steps the motion up so that one turn of the first 200-tooth wheel drives the millstone exactly 960 revolutions. Struck-out notes describe how the first two lantern-gears sit and how to start the stone spinning free before lowering it by a screw and feeding in the grain. A small pendulum scheme carries the maxim that no more power can be drawn out than was put in, unless one spends time to build it up.
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Gear train stepping one wheel-turn to 960 millstone turns
The first lantern-gear (rocca) of one braccio carries 25 spindles under a wheel 8 braccia across with 200 teeth; the second wheel has 150 teeth, the third 100, each lantern keeping 25 spindles. With the last lantern reduced to 5 spindles, a single turn of the first wheel drives the millstone exactly 960 times.
Counter-lever a strikes and draws back lever b
A lever pair is labelled a and b. When the stone strikes the counter-lever a, it pulls the lever b backwards, coupling the swinging weight to the mechanism it drives.
Starting the mill: spin free, then lower by screw
A struck-out procedure directs that the millstone first be turned raised half a braccio clear of its companion; once it reaches full speed it is lowered with the screw beneath the pole of the stone, and only then is the grain fed in.
No power greater than what you generate
A small pendulum scheme lettered a, b carries the principle that no power greater than the one you have generated can be obtained from you, unless you spend time to build it up, and states that this is demonstrated.