The requirement would be for a motor have a fast enough response time and enough torque to overcome the release spring. The motor would also need to return to the zero position (with the help of the spring) when no voltage is passed through is case of an emergency.
Sounds a bit dangerous to me, unless other means of safety is involved (Like a brake made like a Dead Mans Handle).
How much force (N/kg/Lb) is needed to press the pedal down?
Three questions I have:
1) Firstly which would be best for this application a stepper or servo. I am leaning towards stepper because I believe it rotates freely with no voltage (is this correct?).
A regular gear head DC motor with a magnetic clutch to disengage the shaft in an emergency (loss of radio signal) would be a possibility.
2) My major concern is how much power the stepper will take. I am looking at the one below:
Would something like this be able to run for over 30 minutes with constant use with a small 12V lead acid battery (14Ah)?
It takes 0.33A so it should be able to run it for (very roughly) 32 hours.
However, this stepper does not have the power to overcome a speeder pedal.
3) Would this stepper be able to be powered directly through the arduino board (I am using an arduino Mega)?
You will need a driver no matter what motor you wanna run (except for an R/C servo which has got one built-in, but which I don't think will work).