In addition to examining friction and wear that contacting elements experience, da Vinci explored the benefits that could be provided via the addition of rolling elements between the sliding plates. While it was known by ancient civilizations that rolling was more efficient than sliding, there is no evidence of the study of how and why this was true.

Leonardo began his iterative design process with disk bearings. However, his studies showed that the wear experienced in the bearings would be more evenly distributed if balls/rollers were used in place of thin disks. One error da Vinci made in his work was failing to observe the differences between roller and ball bearings. In a quote from the Codex Madrid he remarked “I do not see any difference between balls or rollers save the fact that balls have universal motion whereas rollers can move only in one direction.” In fact, balls and rollers do behave differently depending on the type of loading applied (radial or axial).

Regardless of that shortcoming, da Vinci was still very insightful in his observation of the need for individual bearing elements to be isolated. His work showed that if rolling elements contact each other during operation that the friction present between them is too great to gain a mechanical advantage. In contrast, if the elements are kept at a distance and only permitted to contact the two sliding surfaces via the implementation of cages, wear is greatly decreased and movement is much easier.

Tribologists today are still impressed with the insights da Vinci provided in regards to rolling elements.

Source: Reti, Ladislao. “LEONARDO ON BEARINGS AND GEARS.” Scientific American, vol. 224, no. 2, 1971, pp. 100–11.

 Image: Reti, Ladislao. “LEONARDO ON BEARINGS AND GEARS.” Scientific American, vol. 224, no. 2, 1971, pp. 100–11.