Originally Posted by
HillRider
To date nobody has been able to design an acceptable CVT for bike use. The attempts have all been either mechanical failures or unacceptably heavy and inefficient. So it's not a "more feasible solution", at least not so far.
The pie-in-the-sky electronic shifting system proposed by the OP may indeed be possible some day but current prototype electric shifting systems by Shimano and Campy (and Mavic's two failed commercial attempts) are just electrically shifted versions of current derailleur systems. They replace the shift lever, cable and hosing with servo motors and a battery. The only advantage I can see is you can install the shift buttons anywhere and have them in more than one location.
I built an electronic shift system using off the shelf parts from
www.mouser.com. It consists of two stepper motors with gears and clutches pulling the cables. The clutches allow manual friction shifting if you allow the batteries to expire. I recently upgraded it to Bluetooth so the rider shifts it with buttons located in either the right or left glove. Bluetooth also allows someone following in a SAG to read Heart rate, Watts, speed, cadence, gear ratio, and body temp. It also allows the rider to talk to the SAG with a wireless Bluetooth headset. Electronics are here and you'll love it, eventually.