Hi Adam! Interesting question here. If I understand you correctly, you like the geared hubs that use pedal power (verses cassettes and chain rings) and are wondering why they are not so common on ebikes (aside from the NuVinci continuously variable transmission CVT product). You suggest that a mid-drive motor system would be required and that is partially correct, you could also use a front hub motor.
I was just visiting Optibike today and speaking with their founder, Jim Turner. He started out with an interest in hub motors but soon settled with middrive systems because they are more efficient, leveraging bicycle gears in much the same way that a rider does when they pedal. Many Optibikes actually do use geared hubs. In particular, the R series (including R8
) use the 14 speed internally geared Rohloff Speedhub. I think this might be exactly what you're looking for, though it is a more expensive product.
One other bike that uses a geared rear hub (the eight speed Shimano Alfine) in combination with a less powerful, though lighter weight, front hub motor is the Faraday Porteur
. The benefits of this design include being very balanced from front to rear, very quiet and clean (it uses a belt drive in combination with the geared rear hub) and staying cleaner... no gears are exposed as they would be with a cassette and there is no chain to get squeaky or bounce around and slap the chain stays when going over bumps. It's a very elegant application of a geared hub and one I really enjoyed riding
There are a couple of other bikes out there that use geared hubs with fewer gears in them (usually just two or three) including the Electra Townie Go
and OHM XU450
that auto shifts as cadence increases (system by SRAM), the Juiced Riders ODK V3
, all EZ Pedaler ebikes
, all of the Hebb ElectroGlide ebikes
, the Grace Easy
, the VeloMini folding ebike
and the Bodhi ebikes
and EVELO ebikes
which use the NuVinci hub.
is another ebike company that uses internal gearing for their pedal systems. Instead of using geared hubs however, they actually build the gearing right into the bottom bracket. Their Fighter
has two speeds and the Bomber
has nine! The two speed system is a bit like the Outrider electric trikes
which uses a silver button embedded in the bottom bracket that you click in with your heel when pedaling, it's pretty neat and convenient, reminds me of using the clutch on a motorcycle.
As I was doing research to provide this response for you I realized just how many ebikes actually are using internal gearing systems (or offering them as optional). My favorite parts about these designs are that they allow the chain or belt to stay tighter, as there are no ring sizes to accommodate, and this means they don't fall off as easily or slap and chip the metal frame tubing when riding over bumps. They also keep the gears cleaner, seem to shift very smoothly and don't require as much maintenance as a result. Some of them can even be shifted at standstill which is nice if you have to stop at a stop sign or traffic light and need to change to an easier gear to get going again. I was just in San Francisco testing out some Kalkhoff ebikes and tried this going up a steep hill however and it did not work. Some internally geared bicycle hubs have a system that does not let them shift over a certain load limit to keep them from wearing out.
I realize I haven't touched on the actual engineering hurdles here for you (as I am not an engineer and really not that experienced with geared hubs) but I hope these resources help you! If you'd like to know more I could ask one of the guys from Optibike to chime in and share their thoughts as they have been using them for many years for high stress off-road bicycling applications.