Pivot bearings and gear-tooth lever engagement
Low-friction pivots, a four-ball thrust support, and how a wheel tooth trips a lever
A page of pivot and bearing studies drawn in pen: compass-like lever arms swung inside circles at the top, a rosette of four balls forming a thrust bearing at the lower left, a small roller assembly, and a dense column of gear-tooth, screw and bearing components on the right lettered a through g. The notes examine how a wheel tooth engages and releases the end of a lever, arguing the motion is best when the engagement angle n and release angle f differ least. Another jotting describes a pivot on which a 'mother' (nut) threads itself. The repeated word 'pigro' (lazy) is written inside one figure.
On this page
A wheel tooth engaging and releasing the end of a lever
When a wheel's tooth catches the extremity of the lever, the smaller the difference between the angle n, where it takes up the lever, and the angle f, where it lets the lever go, the better that motion will be. Leonardo is seeking the tooth geometry that gives the smoothest transfer of force.
Four-ball thrust bearing drawn as a rosette
At the lower left four spheres are arranged in a ring around a central hub, a thrust-bearing rosette that lets an axle turn on rolling balls rather than a sliding pivot. Below it a small stacked-disc roller assembly is sketched in the same spirit of reducing contact friction.
A pivot threaded by its 'mother' (nut)
A short note describes one of the pivots as the one on which the 'mother' (the nut, la madre) moves to thread itself upon it, treating the male pivot and its female counterpart as a screw pairing. The sentence breaks off as Leonardo starts to define another pivot.