off-season launcher

[Bryan Herbst]

Originally Posted by Da Kid

Tanis, by the way you answered the questions it seems you have a different set up than we plan.

this is what we are planning to do:
Main tank(120 psi)-->pressure regulators-->A secondary tank for each of the three barrels(different psi's)-->Sprinkler valve-->actual barrels.

Ah, you are correct there. We have one barrel hooked up through a sprinkler valve to our tank. On the other end of the tank we have a compressor with regulators.

Though I am by no means an expert in pneumatics and the underlying physics, I am fairly certain that a pre-charged 5 gallon tank would prove just as problematic. Keep in mind that 120 PSI means 120 pounds of pressure per square inch. As you have 5 gallons worth of volume, you still have far more total stress on the compressor.

I could be wrong there though, so don't quote me!

[PAR_WIG1350]

Originally Posted by Tanis

Ah, you are correct there. We have one barrel hooked up through a sprinkler valve to our tank. On the other end of the tank we have a compressor with regulators.

Though I am by no means an expert in pneumatics and the underlying physics, I am fairly certain that a pre-charged 5 gallon tank would prove just as problematic. Keep in mind that 120 PSI means 120 pounds of pressure per square inch. As you have 5 gallons worth of volume, you still have far more total stress on the compressor.

I could be wrong there though, so don't quote me!

Now, I know you said not to quote you, but I just wanted to clarify something(s). I don't know if this is what you were trying to say, but if it is, then it is just an extension on that.

1) The piston in the compressor has a set (frontal) surface area [which for the sake of simplicity we will say is one square inch]. If the compressor is filling a 1-inch cube to 120 psi, it would need to push with 120 lbs of force to move the piston (1x120=120). Now, if we increase that to 5 gallons, 1x120 still comes out to be 120 lbs. The volume of the tank doesn't change the amount of force needed to push the piston in the compressor. The (frontal) surface area of the piston and the pressure are the only factors involved in this.

2) Volume and surface area are not related in any particular manner, without specifying a specific shape such as a sphere. Thus, the total force applied to a vessel at any given pressure not directly related to the vessels volume, while it is directly related to its surface area.

3) The compressor will still have to do more work to compress a larger volume of air simply due to the fact that more air must be moved, however, at a given pressure, work per compressor cycle (piston stroke) is constant.