Canadian Airgun Forum

On another forum, I read a post that indicated that a SCUBA tank (88cf) had a captured energy
potential in excess of a quarter million ftlbs.

In an earlier thread, I had suggested that there may be a potential of 130 shots at ~485fps in a
modified 22XX Rifle. I still haven't ruled it out, but I'm beginning to believe the goal, may
be more lofty than I'd previously estimated.

For six carts I've recorded pellet velocities and converted it into ftlbs of energy. For every cart,
the gun has been tuned to a different velocity, ranging from a low of 435 to a high of XYZ(PM me).
It currently appears, that the greatest efficiency of conversion(expansion of gas to pellet momentum),
occurs at lower velocities, but I still haven't been able to measureably extract the amount of
energy required to shoot 130, 7.9gn pellets at ~485(roughly 540ftlbs).

My research certainly hasn't been exhaustive, and I've formed a few theories to explain my
current results, but it has suddenly hit me, that I really don't have a clue, as to the energy
potential of a CO2 cart.

Has anyone ever come across the figure as it relates to 12gm CO2 Cartridges? I understand
the answer has a significant temperature variable, let's assume 'room temperature'. Roughly, how
many ftlb of energy are contained/stored in 12gm of CO2?

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I like to shoot my gun To much thinking ruins that for me

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Jonathan

Moderator

Found this http://www.combro.co.uk/nigelh/diver/tank.html could possibly be converted to CO2 assuming your carty was gas only, no liquid,

Just a guess....

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I think you'd have to talk to a 12g cartridge manufacturer to find out if, in fact, there really is 12 grams of Co2 in a cartridge- and then find out the exact interior dimensions of the cartridge to figure anything out with any sort of accuracy.

Once you have this info, you can determine how much liquid vs. gas is in the cartridge, plug in the temperature and expansion rates and get the answer.

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You told to read about energy in the SCUBA tank. As far as I know it is simply PxV (bolume times pressure, use metric units), but I am not quite sure about it. Or let say, it depende how energy is released qnd what extend of the total energy can be converted to work in the barrel.

The case of CO2 is probably more complex bacause phase transition from liquid to gas phase.
I am not familiar with CO2 guns, so I'll ask. Is there a gas reservoire or is gas evaporated from the liquid during the shot.

-FinnishVisitor-

perhaps you will need to understand this

http://www.chem.arizona.edu/~salzmanr/4 ... vwork.html

You can also determine the work done (in ft.lbs) experimentally. how about this setup : make the 12gm Co2 expands along a constant temperature (i don't know how to do that) and the expansion will move a piston against a known friction force for some distance to be measured. Work=Force x Distance.

That's correct. When gas is expanding it can do some work.
The amout of the work is not the same as energy stored in the gas whatsoever.
When gas expands it cools. This cooling is loss of energy too. But I don't really know if this energy can be used to drive your pellet?

Keeping CO2 cylinder in constant temp during the expansio is not easy. Just think about the liquid natural gas cylinder you use in your barbeque. When gas is used for prolonged period, cylinder cool and even frost can be found from the surface of the gas cylinder.

-FinnishVisitor-

I posed similar question over on the Green, where I know Steve in NC hangs out quite often. He was kind enough to share, that liquid CO2 has approximately 59FPE/gram of stored energy potential. This equates to somewhere around ~700FPE in a 12gm cart. I clearly understand that "12grams", is likely an averaged approximation, of the actual amount of CO2 in each cart, and additionally, much is lost to thermodynamics.

Thanks for the help guys; or at least being interested enough to weigh-in.

I'm not any closer to my goal, but at least I now know, that it's potentially theoretically possible.

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Don't Be Sexist - Broads Hate That.