Removing the return spring of a rear derailleur I am trying to turn my standard shifting bicycle into an automatic shifter using a motor to increase and decrease the tension in the shifter cable. The problem is that a lot of torque is required to do this, so I was considering cutting the return spring off. 

I know this is permanent, so I want to make sure that I am doing the right thing before making the cut. I am planning on installing a spring with a much lower spring constant on the cable itself (see image).



This is another thread with a similar topic. Móż suggested cutting this spring.

(Automatic Bike Project) amount of torque required to change gears?

I am really new to bicycle engineering, so please excuse my lack of knowledge on the topic.
It is called the return spring.  Without that spring you don't have return.

Without a return you would need a push / pull (stiff) activator.

Looks like commercial electronic use a cable (pull) activator.