HPA and Co2 mix- someone around here somewhere has done this...

[jpsgunworks]

I remember reading the post recently. It's not the one Gippeto posted, it's recent. I think the guy was from South America.

[rsterne]

Why not take a freshly filled CO2 tank (say a 9 oz, with an actual 9 oz. of CO2 in it) and rig up a fitting to add air to it.... The tanks are rated at 1800 psi and have a 3K burst disc.... Let it stabilize at room temperature (~20*C) to ~850 psi, and then add HPA until it is at, say 1700 (ie adding ~850 psi of air) so the pressure is half and half.... Put a gauge on the outlet and let it stabilize again and record the temperature and pressure.... Then throw it in a freezer, let it stabilize and then record the temperature and pressure again.... If the temperature drop is about 30*C, the pressure should drop about 10% to ~1530 psi if Walter is right.... If Steve is right, it should drop to about 1200 psi, depending on the exact temperatures.... To confirm, find a location that is about 40*C, and let stabilize and record the temperature and pressure again.... Should be pretty straightforward what is happening....

Bob

[Voltar1]

Why not take a freshly filled CO2 tank (say a 9 oz, with an actual 9 oz. of CO2 in it) and rig up a fitting to add air to it.... The tanks are rated at 1800 psi and have a 3K burst disc.... Let it stabilize at room temperature (~20*C) to ~850 psi, and then add HPA until it is at, say 1700 (ie adding ~850 psi of air) so the pressure is half and half.... Put a gauge on the outlet and let it stabilize again and record the temperature and pressure.... Then throw it in a freezer, let it stabilize and then record the temperature and pressure again.... If the temperature drop is about 30*C, the pressure should drop about 10% to ~1530 psi if Walter is right.... If Steve is right, it should drop to about 1200 psi, depending on the exact temperatures.... To confirm, find a location that is about 40*C, and let stabilize and record the temperature and pressure again.... Should be pretty straightforward what is happening....

Bob

Go for it Bob.

[rsterne]

Thanks for checking the math, I really appreciate it.... When I do a complicated post like that, I just work my way through it a step at a time, typing as I go.... so I have no idea what the results will be until I get to the last equals sign.... *LOL*.... Then if I look at the results and it makes no sense, or is confusing, I end up with thoughts like in the last paragraph....

It would appear to me that if the reservoir is filled with CO2 by weight, there is little room left for air (1/8th), and in fact there would be liquid CO2 (at least I believe that to be so).... It would appear that with the reservoir about half full of CO2 (by volume) there is no liquid, but a mixture of supercritical fluids.... If that is the case, then there is very likely an optimum ratio of CO2 to air to maximize the total FPE.... I have no idea if that optimum ratio would change if you played with the hammer spring and/or porting to alter the bell-curve (assuming there is one) or the FPE per shot (and therefore the number of shots).... Once the mixture is in this realm of a mix of supercritical fluids, I would guess that the gasses would be used in the same proportions as their mole fractions.... In the previous example, 5 parts CO2 to 1 part air in every shot.... All that happens is that the pressure gradually drops as the mixture is used up, the percentages stay the same.... I would also think that rapid shooting would not alter the pressure (no "boiling" taking place), and that temperature change would no longer affect the velocity, at least not any more than with HPA.... Would you agree that has to be the case?....

Bob