Work done by da Vinci both to understand friction and to design devices to overcome it were documented in his notebooks written between 1493 and 1497. He made observations on principles such as wear and coefficient of friction. These observations led him to understand the value of lubrication, cages, and the impossibility of perpetual motion.

Most of what is known regarding da Vinci’s work on ball bearings comes from the Codex Madrid I. These works were found in 1967 and were written by da Vinci between 1493 and 1497. Previously, scholars had the Codex Atlanticus, which was a more random collection of writings and sketches created between 1483 and 1518. Material in the Codex Atlanticus is considered as drafts upon which da Vinci expanded and improved in Codex Madrid I.  

In these notebooks, da Vinci makes observations and predictions of system interactions that are not far off from the empirical values still used by tribologists today. The designs he proposes are novel and truly innovations that greatly influenced designs that are still considered the most efficient bearing designs today. 

Source: Reti, Ladislao. “LEONARDO ON BEARINGS AND GEARS.” Scientific American, vol. 224, no. 2, 1971, pp. 100–111., www.jstor.org/stable/24927729.

Image: http://ebooks.library.cornell.edu/k/kmoddl/toc_leonardo1.html