How wheels drive one another and their turning
Direction of rotation of meshing wheels, on and off their poles
This closely written page sets out how two wheels of different sizes drive one another: the smaller moves the larger more easily than the reverse on a level line, while equal wheels transmit motion equally. Leonardo distinguishes wheels turning off their poles, which then turn the same way, from wheels turning on their poles, which must turn contrary. To make two pole-mounted wheels turn the same way one must be received inside the other like a ring on a finger, leaving a crescent- or lunar-shaped gap, or else a third wheel of any size is inserted between them. Small marginal diagrams show pairs, nested rings and rows of wheels illustrating these cases.
On this page
Small wheel drives the larger more easily
When two wheels of different sizes drive one another on a level line, the smaller moves the larger more easily than the larger would move the smaller. Wheels of equal height and weight transmit motion equally in either direction.
Turning off the poles versus on the poles
Two wheels whose motion drives each other while off their poles turn in one and the same direction. But when they turn upon their poles their motions must be of contrary course, so the two spin opposite ways.
The lunar gap, or a third wheel between
To make two pole-mounted wheels turn the same way one must receive the other within it, as a wide ring receives a slender finger, leaving a lunar-shaped gap outside their contact. Failing that, a third wheel of any size is set between them to restore the same direction.
Marginal diagrams of paired and ringed wheels
The right margin carries small sketches of the cases discussed: two circles touching, two circles nested with a crescent gap, rows of three wheels, and four small wheels ranged around a central one. They serve as visual keys to the text.