Over the centuries, closely related to the transmission of motion was the problem dell'attrito, produced by the various stresses that the machine suffered, up to be impeded in its functionality, especially in the presence of a heavy load. Therefore, in order to optimize the yield of machinery in motion, limiting the effect usurante dell'attrito, Leonardo, driven in his search for designer and engineer to solving practical problems, ideò, with great advance of the modern mechanics, bearing ball. An extraordinary plan outlines the system and structure, proposing the view that the plant in cross section, for its possible construction. The ring scroll bearing is composed of eight spheres, with free bikes, and interspersed among many bobbins incastrate concave, instead revolving around oneself and perfectly acceding to them. Leonardo spent this device at the theatre of Fable of Orfeo for Charles d'Amboise in Milan.
C. 1497. Code of Madrid