System of Joints and a Lever Analysis of a Rod
Red-chalk joint studies with a lever and counter-lever calculation.
Drawn largely in red chalk, the sheet studies a system of mechanical joints, several fitted with springs and labelled with letters. One figure is used for a lever analysis: a rod slides up along its pin at the contact a, and Leonardo argues that the longer the rod, the easier the motion. Treating c–a as a lever and c–n as its counter-lever, he reasons that 20 of power applied at a yields 20 of resistance at n, while the opposite holds at c–g.
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System of joints with a spring
In red chalk Leonardo draws a system of joints, one member labelled as carrying a spring. The joints connect rods and blocks that can move against one another. The spring returns or steadies the moving part.
Lever and counter-lever of the sliding rod
A related figure carries the labels r — c x — a n — m — o — f — g — f. Leonardo states that if the rod is moved up along its pin by the contact a, the longer the rod, the easier the motion. Taking c–a as a lever and c–n as a counter-lever, he concludes that 20 of power at a produces 20 of resistance at n, while at c–g the reverse holds.
Analogous joint figure with lettered points
To the left, a similar figure repeats the joint with its points of contact marked by letters n–f, o–r and a–S. The lettering keys the figure to the lever reasoning worked out alongside it.