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Codex Forster II — 097r

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© Victoria and Albert Museum, London

Peso sollevato da grossa vite, con:

a o n m

Se 'l centro del peso sarà fori del perpendiculare del centro della vite, che lo move, esso1 peso si mosterrà più grave al suo motore e i denti della vite insieme con quelli della madre che li veste, saranno oppositamente affaticati da due contrarie forze.

a sia il centro del peso, n sia quello della vite; e per la quinta della 'Teorica' diremo che tanto quanto n m entra in n a, tanto il peso si dimostra maggiore al suo motore che esso non è.

E i denti della vite che sono dal lato di o, toccan colla parte inferiore la superiore della sua madre, e i denti che sono dal lato di m, fanno per l'opposito.

Weight raised by a thick screw, with:

a o n m

If the centre of the weight lies outside the vertical through the centre of the screw that moves it, this weight will show itself heavier to its mover, and the threads of the screw together with those of the 'mother' (nut) that sheathes it will be oppositely stressed by two contrary forces.

Let a be the centre of the weight and n that of the screw; and by the fifth of the 'Theory' we shall say that by as much as n m enters into n a, so much does the weight show itself greater to its mover than it really is.

And the threads of the screw that are on the side of o touch, with their lower part, the upper part of its mother; while the threads that are on the side of m do the opposite.

Weight Raised by a Large Screw

An off-centre load stresses screw and nut with two contrary forces

Machines & Devices Physics & Mechanics

A large vertical screw is drawn passing through a horizontal nut-block and pressing down onto a weight that rests on a solid block; the members are lettered a, o, n and m. The note observes that if the centre of the weight lies off the vertical through the screw's centre, the load feels heavier to whoever turns it, and the threads of the screw and of the 'mother' (nut) that sheathes it are stressed oppositely by two contrary forces. Citing the fifth proposition of the 'Theory', Leonardo says the weight shows itself greater in the ratio by which n m enters into n a, the threads on the o side pressing one way and those on the m side the reverse.

On this page

Screw and nut lifting a weight

The drawing shows a thick threaded screw running through a nut-block and bearing on a weight set atop a solid block. The screw's centre is marked n and the weight's centre a, with the threaded sides at o and m.

Opposed forces on the threads of an off-centre load

When the weight's centre a lies off the vertical of the screw's centre n, the load feels heavier in the ratio by which n m enters n a. The threads on the o side touch the nut with their lower part while those on the m side do the opposite, so screw and nut are stressed by two contrary forces.

Reader's Edition — described with AI from the e-Leo transcription.