Gears, worm-screws and clock movements; where a rope breaks
Male-and-female gear teeth, pinion-versus-screw force, spring-driven clocks, and why to use large pulleys
This densely drawn verso surveys machine elements: a large toothed wheel engaging a worm-screw labelled 'teeth of wheels, male and female,' lantern gears, a crane hauling a weight (200/100) with a man pulling the rope, a scissor-spring, and two clock movements — one noted as driven by a cord or spring (tenpo d'orilogio con corda). A question compares which yields more force from the same power: turning a pinion (rochetta) or a screw (vite). A lettered study (e, b, d a c f, m o g n) of a cord over pulleys argues it will break not at c g, e f or a b c but at point f, and advises making the pulleys large because the cord's middle stretches and weakens most. Small captions beside several of the sketches carry further untranscribed notes.
On this page
A worm-screw driving a toothed wheel (male and female teeth)
A large toothed wheel meshes with an endless screw, the engagement labelled 'teeth of wheels, male and female.' It is one of several gear trains — including lantern pinions — laid out across the sheet.
Clock movements driven by a cord or spring
Two mechanisms are labelled as clock movements (tenpo d'orilogio), one explicitly driven by a cord or spring. They are drawn among gear wheels, a coiled scissor-spring and barrel-drums that make up the going train.
More force from a pinion or from a screw?
Leonardo poses the comparison directly: with one and the same power, which produces more force — turning by the pinion (rochetta) or by the screw (vite)?
Where a cord over pulleys breaks; use large pulleys
The cord will not break at c g, e f or a b c but at point f, being of equal strength throughout. Make the pulleys large, because the cord grows in length on its outer side as much as it shrinks on the inner while the centre keeps its natural length — so its middle, at e, is weaker than at d or f.