[–] Amalek666_ 3 points -2 points 1 point (+1|-3) ago
Look at this. Every shape of gear imaginable.
[–] NassTee 0 points 1 point 1 point (+1|-0) ago
Borromean - it comes from the name of a family. https://en.wikipedia.org/wiki/Borromean_rings
[–] the-gerbil-in-my-bum 0 points 3 points 3 points (+3|-0) ago
[–] thrus ago
Pretty much any number of teeth will work the trick is to get them to move smoothly so there is minimal wear and thus minimal maintenance.