Building for robot wars may not be a valid target any more with the likely demise of Robot Wars as an institution, although building for robot combat (i.e. live events) is a valid aim. If youre building something light e.g. a 12kg featherweight bot you may be able to follow the original Rexs Robot Challenge idea of using a bike pump at max pressure around 50psi (I imagine it could go higher), although I couldnt tell you exactly how they modded the pump for this (Id be interested to find out however.)

I bow to the more superior knowledge of others (Mario?) on the specifics of pneumatic ram building however.

-- Kev