The general idea is that a QEV only is open when the pressure in the pilot is less than the pressure in the chamber. With this setup, the pilot pressure only lowers by a small percentage, so the same is true with the chamber.
To fire, you make sure that the ball valve is closed, then pull the trigger.
To reset it for firing, simply open the ball valve to let out the air, and close it again

This could work with a home made piston, but I have my doubts, since they generaly are not as sensitive as manufactured QEVs.









