Three-speed hoist

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Working model after Leonardo da Vinci, Codex Atlanticus (BAM), fol. 1083v

Invented by Brunelleschi ca. 1420, this device is assembled in a sturdy frame firmly anchored into the ground. Two joined horizontal wheels operate on an alternating basis. Each bears revolving cylindrical gears to reduce friction wear. Via the pair of wheels, a vertical shaft drives a horizontal cylindrical shaft of two different diameters. By means of a pinion and toothed wheel system, the vertical shaft also drives another horizontal cylindrical shaft of a third diameter. The ropes for lifting the load are wound around the horizontal shafts and pass through an overhead pulley. The horizontal shafts rotate at three different speeds, each providing a different force and selected according to the load to be lifted.

The machine is driven by a pair of oxen and is fitted with a safety device to prevent the shafts from rotating in the reverse direction.

A worm-screw mechanism at the base of the driving shaft serves to raise or lower the shaft. This causes one of the two horizontal wheels to mesh with the drum teeth. One can thus reverse the rotation of the horizontal cylindrical shafts (and hence shift from load-raising to load-lowering mode) without having to unhitch the animals from the yoke and re-hitch them facing the other way.

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