Pneumatics Help

[dtengineering]

Although I remember that there are some horrible entropy and enthalphy type calculations that I really didn't get in third year thermo, and have even less appreciation for now, the main rule governing how much air is consumed is your good old high-school p1v1=p2v2 ideal gas law. (And, yeah, I left out the t1 and t2 divisors since it isn't too unfair to assume everything stays about the same temperature...)

So what this means is that when you compress a clippard tank (6" x 2" dia = 6 pi cubic inches) to 120 psi, you have (120psi * 6 pi cubic inches) = 720 pi pound inches of air.

When you use that air to fill a 1.5" x 8" stroke cylinder (4.5 pi cubic inches)with 60 psi of air, you will "use" (60 psi x 4.5 pi cubic inches) = 270 pi pound inches of air.

Remember that this will also cause a pressure drop in the clippard tank. In this case the pressure in the tank will drop to 720 pi - 270 pi = 450 pi pound inches, which will occupy a volume of 6 pi cubic inches, with a resulting pressure of 450/6 = 75 psi.

So consider that one clippard cylinder can pressurize a 2" x 6" cylinder to 60 psi before the pressure in the cylinder drops below 60 psi. (Not that there is anything wrong with that... it just means that if you make a second stroke before the compressor re-charges the clippard cylinder that the second stroke will be at lower pressure and thus reduced force.)

It would take the compressor several seconds (probably less than ten, though) to recharge the clippard cylinder back to roughly 120 psi, although this depends on battery charge and other current draws to the electrical system. So really, it isn't a question of how many cylinders you put on the robot... but rather how big they are and how often you "fire" them.

Jason