Of Tackles: More Pulleys, More Mechanical Advantage
Each added pulley eases the load but the mover must always exceed it
Leonardo continues "of tackles" with three lettered pulley figures drawn in the right margin. He argues that the ropes descending from the pulleys feel more heaviness than the rope that rises, since the mover must always be more powerful than the load. Working along a chain of pulleys, each rope must be more powerful than the next (a c above c d above d e), so the more pulleys are joined in one arrangement the harder the load is for its mover. Conversely, the more pulleys interposed between load and mover, the more the load's weight is diminished and the mover's power increased.
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Descending ropes feel more weight than the rising rope
The ropes that descend from the pulleys feel more heaviness than the rope that rises, since the mover is always more powerful than the load. Though ropes n m and n p seem to carry the same weight of the heavy body m, if p n becomes the mover it must be more powerful than the load.
Each rope in the chain must exceed the next
In the second and third figures the mover b a must be more powerful than rope a c, and a c than c d, and c d than d e. So the more pulleys joined in the same order, the greater the load's difficulty for its mover and the more the mover diminishes in power.
More interposed pulleys, less load and more mechanical power
Conversely, the load's weight diminishes and the mover's power grows as the number of pulleys set between load and mover increases. The many ropes running up and down each diminish resistance, so the mover struggles to move the load on the last rope when the penultimate rope has far less power than the antepenultimate.