Is it possible to have a drive and driven gear on the same shaft? Rookie question, I know. I've been doing a lot of googling and sometimes I think I understand that they can, but reading the definitions, I don't understand how that's possible.
Yes, if one gear is keyed to the shaft and the other on a bearing or sleeve - has been used in aftermarket overdrive units by Fairey for example.
Edit : also old belt-driven equipment had fixed / sliding pulleys which could be locked together or unlocked to provide a "neutral" as most were driven from a common shaft in machine shops.