Block and tackle: trading weight for time and speed
Mechanical advantage in pulley trains, with cord speeds in proportion to the load
Two half-sheets developing the mechanics of compound pulleys (block and tackle). Leonardo notes that the same rule which diminishes the weight felt at the mover also increases the time of motion, tabulating a series 128, 64, 32, 16, 8, 4, 2, 1 between the loads m and n. In a second system he shows that if the head of cord a moves one braccio, cord b moves a half and cord c a quarter, so a is four times faster than c because the proportion of motion follows that of the weights. A closing note warns that a pulley driven straight-line loses the cord's stability even when the poles are equidistant.
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Diminishing the load on the mover by stacking pulleys
Just as the rule shown here diminishes the weight upon the mover, so the same figure gives the rule for increasing the time of the motion; and in the motions from m to n the same proportion holds as between the weights n and m, tabulated as 128, 64, 32, 16, 8, 4, 2, 1.
Cord a moves four times faster than cord c
If the head of cord a moves one braccio, cord b moves 1/2 and cord c 1/4; therefore a is four times faster than c in equal time, since the proportion of the motion is like that of the weights, a being 1 and g being 4.
A pulley driven in a straight line loses cord stability
If one channel of the pulley moves the channel of the other pulley in a straight line, the cord passing over it will have no stability in their channels, even though the poles of such pulleys are equidistant.