[apalrd]

We had a sorta C-shaped bracket, with the shaft supported on both flanges and the motor on one, a pivot point on one end and a pneumatic piston on the other. It was a really big piston, 2" bore.

One other thing to keep in mind is the slight rotation of the output gear that is generated when you unmesh the gears. Since you are not pulling the gears straight out, you are pulling them on an angle, that action will rotate the output gear slightly. Make sure this rotation causes the kicker to go out rather than in. This way, the gears will be easier to unmesh and require a smaller piston (it is not fighting the springs to unmesh).

One final thing to keep in mind is the default state of the pneumatics. We used a double-action cylinder (air pushes both directions) but a single coil valve. We made sure that the default state (when no power is applied to the valve) left the gearbox meshed, so it kept the kicker in the box and avoid accidental firing. We left the pneumatics system full all the time to prevent the gearbox from firing (actually, we shipped the robot to Atlanta with 120psi of air in it's one air tank, and it still had 80psi in that one tank when we took it out of the crate)