10-20hp 2-speed transmission. Need to find a source.

[kerosene]

This is quite off topic - but its sort of for a bike concept (in my head).

I am playing with a concept of a supreme range aerodynamic electric motorbike. Idea is to make the bike as efficient as possible so 3-4kwh battery pack could provide as good of a range as possible.

Electric bikes work ok without transmission but the currents go up and efficiency down on low speed starts and accelerating if the setup is geared for higher top speeds. Yes e-motor can work in really broad rpm range with good torque but not quite broad enough.
To keep efficiency high yet allow 70mph top speed from 72V system a transmission would be crucial.

A simple 2 speed transmission with 1:2 and 1:1 ratios would be ideal remedy for the issue.

As this forum has people of various backgrounds I was wondering if someone would know from what kind of machine one could nick such a transmission.

Planetary 2 speed would be ideal - at cruising the transmission would be efficient 1:1 straight through.

Belt systems could work but they are not the most efficient.

thanks.

[liki]

One could use e.g. ABB or Siemens AC induction servo motors, which are can be directly coupled with a 2-speed transmission available from ZF. Frequency-changing(?) inverter drive will also be the very efficient, but you will somewhere around 1.5 times the AC voltage used from the battery pack, 300V DC for 230V AC.

I think that the ZF servo transmission can be geared only at rest, but with induction motor you will get well by with direct drive. Weight could be an issue for such setup, and you'd likely need lifepo4 batteries to reach the required voltages. I've been researching DIY-EV's and that's the idea I'd use.

[WestVanHan]

Two electric clutches on the motor shaft each with it's own ratio sprocket and chain to the drive wheel.

Low gear clutch engaged,high is off-and vice versa.

[CDK]

Why not use the push belt CVT found in go-karts, snowmobiles and scooter bikes? It is very efficient and gives you the opportunity to determine the best possible ratios.