Bevel and spur gear speed changer

In these devices, a lantern gear drives three toothed wheels. Their different diameters cause them to rotate at different speeds. Leonardo’s study compares two possibilities: in one case, the lantern gear is cylindrical, the three wheels have identical teeth, and each has its own axis of rotation. In the second case, the conical shape of the lantern gear results in different teeth for each wheel, but allows the use of a single common axis of rotation. A similar principle is applied in modern automobile gearboxes.

The model with the conical lantern gear is presented in two examples, reflecting two different interpretations: the first from 1952, and the second from 1983.