This large model allows actuating a bronze mirror rotating on a support and simultaneously a circular sector of copper that polishes the mirror by moving in alternating motion. A weight is used to cause the copper sector to exert the proper pressure. Leonardo draws two variants in which the mirror can be made to rotate either by a crank or by a connecting rod linked to a pedal that was restored to position by means of a leaf spring. The shaft for the oscillating sector needed to be about 20 braccia (12 m) long.
The model is based on the drawing:
- Codex Atlanticus f. 1103 v. (1513-1515)
Milano, Biblioteca Ambrosiana