"How Much CO2 do I need?"

[BC Pneumatics]

For all those people out there looking for a rough idea of how much CO2 they will need for a chamber of any given size-
Just multiply the volume of your chamber (In Cubic Inches) by the constant 0.008475 This will give you the ounces of CO2 needed at 120psi, 73*f, needed for each chamber fill.

Example:
3.14 x (1/2) x 3"id x 36"length chamber= 254.34ci x 0.008475 = 2.155oz of CO2.


Edit by MrC:

Thanks to Davidvaini and Ragnarok for this calculation table:


http://www.spudfiles.com/forums/viewtop ... tml#229345



Alternative Word or PDF file available below.

[A-98]

how would you calulate it for different pressures, say 250, or 100.

thanks alot though, and i could definitely use this.

[BC Pneumatics]

Ideal Gas Law

[demilus]

And I thought that I'd never use the stuff I learned in Chemistry class

EDIT: I just realized, that the calculations need fixing.
It's pi*(radius of inner diameter)^2 * length of chamber = volume of chamber

NOT diameter of chamber * length of chamber

I think you knew this but you just forgot to write the equation. (254 is the volume of your example chamber, but 3*36, which equals 108, is not)

I'll delete this when it gets fixed

Fixed it, thanks

[randompkguy]

what if your regulator is graded in psi? is there a coefficient of expansion that you can multiply the psi by to get your final psi? (at 80 degrees)

[ALIHISGREAT]

what about if i wanted to fill to 100psi?

[BC Pneumatics]

You would need .83x as much.

[ALIHISGREAT]

thanks, i found a 12g co2 adapter in the garge yesterday, it could be interesting to see what kind of pressures i can get in my 6mm sniper also what if i want to work it out for different temperatures?

[Ragnarok]

The ideal gas law again, I'm afraid.

A slightly different equation is this one:
Ounces of CO2 = Chamber volume in Cubic inches * Pressure in psi / (Temperature in Fahrenheit + 460) / 26.5

That includes temperature and pressure and gives practically the same answer.

[ALIHISGREAT]

ahh thanks i will go and get my pencil! ok so at 10 degrees c i need 41.5oz to fill my 6mm to 250psi... which is quite alot

[Ragnarok]

ahh thanks i will go and get my pencil! ok so at 10 degrees c i need 41.5oz to fill my 6mm to 250psi... which is quite alot

Wow, you have a 36.76 litre chamber.

Astounding for a 6mm sniper. I think you may have put the wrong numbers in, or mixed up the ordering of the functions. Are you sure you didn't go:
((Volume*Pressure/Fahrenheit)+460)/26.5
Rather than:
(Volume*Pressure/(Fahrenheit+460))/26.5

[)DEMON(]

So what if I had a chamber of 40 cubic inches and 12grams of liquid co2?

[BC Pneumatics]

148psi @ 73*F, though I have to point out that the CO2 will no longer be in liquid form at this point.

Luckily gases are very easy to work with. Half the volume (20 CU) will give you twice the pressure (300psi), and increasing the chamber to 50CU, the pressure drops to 118psi.

For further manipulation...
P1V1=P2V2, where P= pressure and V= volume.

[)DEMON(]

Thanks for the help

[BC Pneumatics]

Well, most of the credit goes to Clapeyron, but I'm glad I could help.