As the cylinder actuated by the air moves forward though, the force exerted rapidly decreases as the volume behind it increases (same volume of air in a bigger container), whereas in a spring, the force is (ideally) constant.
Edit: I'll try this next part again.
Also, it may not entirely be the fault of the friction (you did lube it though right?), but the fluid dynamics from the air cylinder.
The gun needs to build up pressure behind the dart, and the pressure will equalize in each chamber. It would be a hard
exact equilibrium to find without calculus, since the dart may or may not be accelerated, thereby increasing the volume, among other factors. Basically though, 1ci at 80 psi, and then the whole volume of the gun's plunger tube at atmospheric pressure will equalize somewhere above what I suspect your pre-primed, pressurized air column is at. This would slow the moving pump shaft if the dart has not left the barrel yet. If it has, then this is irrelevant. Just something to keep in mind when working on it though. You'd want a looser dart fit and a barrel too short if anything, just like an air gun.
Very creative idea though.
An air tank on this principal would be pretty cool I think. A couple of pumps that would be a lot easier to do (than taking a normal tank up to 80psi), to get a column up to 20psi, then reducing the container volume to get a greater pressure. Would be an interesting experiment to see how volume and pressure change how the gun works (as in, titan tank at low pressure <?> range than a 2k at a higher pressure).
Edited by Splitlip, 22 January 2009 - 02:47 PM.
