[russell]

You would be amazed how much you can do with not much air too. Last year we had a two stage arm, the first stage used two 1.5" x 2ft long rams, and the second stage used one fatty (2"?) ram that was two feet long. We could extend all three on a tank of air, and retract them (pulling the robot off the ground in the process) all within about 6 seconds. That compressor is fast and keep in mind that you can store the air at 120 psi. Additionally depending on how you plumb your pneumatics you can draw air from other rams essentially using them as tanks.