Jeremy wrote:Ideally a simple two speed gearbox would do the job, as few road going EVs need more than two gears, often quite widely spaced.
Three gears; reverse is quite useful too!
I know it's easy to do electrically, but you get it for free with a standard gearbox and you can remove the unused gears to reduce drag if you want to go to the effort.
I've wondered about using an external overdrive unit instead of a gearbox. The main snag with some of these would be whether the internal clutch could take the torque. I managed to break a couple of Laycock overdrive units years ago (fitted to a 3 litre Scimitar), in both the cone engagement clutch failed.
It's been a common discussion on the EV list over the years. The ratio change is often relatively small, just designed to to drop a thousand rpm or so at cruise in top gear. There are drag race units that work on a similar principal, but they tend to be quite heavy (and expensive).