Originally Posted by
IrishBrewer
To make this practical, you would probably have to remove the springs on the derailleur so the servos can be reasonably small and don't continuously have to hold tension (a huge drain on batteries). Also, you would want some sort of mechanical lock on the derailleur position, again so it can locked into gear between shifts without consuming batery power.
No, no, no. The whole idea is for it to be compatible with any derailers. The return springs on the derailers can simply be countered on the other end of the cable, like many shifters do. Except that to do it accurately enough to minimise the net tension on the actuator, the spring would have to be non-linear, like so:
Obviously stepper motors would be the go, but that's for a bespoke actuator. In the meantime, RC servos will cut it on the prototype.