alt Hacker NewsA fun simple gear related concept is "hunting tooth".
https://en.wikipedia.org/wiki/Gear_train#Hunting_and_non-hun...
Basically you don't want any common denominators in teeth count, otherwise the same sets of teeth will engage at some frequency. If there is a small imperfection on a tooth it'll wear out quicker. E.g. a set with 5:14 teeth will theoretically wear better than a set with 5:15 teeth.
It's cool to learn the term for this, I have used the same principle before with bicycle gearing, so the chain would wear more evenly. Not sure if it makes much difference but it was worth doing anyway.