Quote Originally Posted by mattsdragons View Post
You would be better off with a scooter motor powered system I think. I'm all for different ideas but even using twin motors and a bloody huge solenoid would be easier!

But... if you want to go down the spring route, car springs would be a good shout. If you can compress them they should have a good amount of bounce and just add a bump stop to limit the travel (I work in parts supplies if you can't tell haha)
Completely ignore my diagram from before, I'd have to put the CAM above the axe arm. The CAM would push the bar down, raising the axe up and stretching the spring, then the spring being used to pull the axe down with something more than the force of gravity.

I'll probably use a scooter motor to power the CAM, with high torque gearing. If not a more powerful motor like an Ampflow.