Levers, balances and experiments on the force of screws
Compound levers where one resists a thousand, trials of screws and a windlass, and a plumb-line guide
The sheet gathers experiments in statics: a chain of three balances in which ten braccia of lever against one lets 100 pounds lift 1000, 10 lift 100 and one lift 10, so that a single weight resists a thousand. A second balance shows one weight acting against another with the beam's own weight discounted, and a large screw on a trestle is set up to test the force of screws with varying numbers of threads and turns. Leonardo also proposes comparing a screw against a windlass of equal thickness, each with a one-braccio lever, and sketches a plumb-line instrument whose ball, centred in a ring, keeps the device running level.
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Compound lever where one resists a thousand
With ten braccia of lever against one of counter-lever, 100 pounds lift 1000; likewise 10 lifts 100 and one lifts 10, marked 1 – 10 – 100 – 1000 along the beam. Chained together, experience shows that a single weight resists a thousand.
Weight against weight, beam discounted
A balance marked 10 and 100 shows what a weight does by itself against another weight, arranged so that the weight of the balance's own beams is discounted from the result.
Trial of the force of screws
A large screw on a trestle is set up to make trial of the force of screws: one thread to the nut, tested with 2, 3, 4, 5 and 6 turns using the same weight and lever, watching the variation and whether a lower screw shortens the time. Every kind of screw is to be tried this way.
Screw compared with a windlass
Leonardo proposes testing a screw and a windlass each an eighth of a braccio thick, giving each a one-braccio lever and loading the head of each with one's own weight, to see and note the difference in lifting.
Plumb-line ball as a level guide
An instrument carries a plumb-line whose ball sits inside a ring: kept in the middle of the circle it guides the device to run level, and set off-centre it runs slanted, as trial will teach. The wind must not be allowed to strike it.