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"How Much CO2 do I need?"

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: LikimysCrotchus5 » Fri May 16, 2008 3:19 pm

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


So im guessing he is the one who made one of these laws?

I am actually surprised to see that i am learning this now in chemistry and it pops up again in the forum.

For anyone who is curious, you can manipulate this formula to solve for different variable but this is the basic equation i leanred.

PV = nRT where:
P = pressure (usually in kPa or atm)
V = volume (usually in Liters)
n = amount of gas (usually in moles)
R = ideal gas constant (8.31 kPa or 0.0821 in atm)
T = Temperature (usually in Kelvin)

So as long as you have all of these variable but one, you cant solve for the missing variable.

And if anyone needs to find the how much pressure, volume or temperature changes depending on what you change, you can use the combined gas formula which is:

P1*V1/T1 = P2*V2/T2 where:
P1 = pressure of first container (usually in kPa)
V1 = volume of first container (usually in Liters)
T1 = temperature of the gas (usually in Kelvin)
P2 = pressure of second container (kPa)
V2 = volume of second container (Liters)
T2 = temperature of second container (Kelvin)

And if one of those variables is missing, then you can solve for it by manipulating the equation.

This was my dollar and 2 cents.

:D
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Unread postAuthor: BC Pneumatics » Fri May 16, 2008 5:16 pm

Well Liki, he came up with 'PV=nRT', which is the base from which everything else you wrote is derived. There are also tons of forms you didn't mention, but they are not particularly helpful to us. They are mostly forms where things like 'n' (moles of gas) are substituted out and replaced with stuff like 'mass/molar mass' You can make tons of substitutions and get very complex, the only advantage of which is a better fit for your application.
He did other stuff too, but none of it is terribly relevant to us.
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Unread postAuthor: LikimysCrotchus5 » Fri May 16, 2008 5:22 pm

BCPneumatics wrote:There are also tons of forms you didn't mention, but they are not particularly helpful to us. They are mostly forms where things like 'n' (moles of gas) are substituted out and replaced with stuff like 'mass/molar mass'


Hence the reason i wrote usually :wink:

But really to make these suited for our needs, all one must do is convert from different measurements of pressure, volume, and temperature and then we can apply it to what we do. :)
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Unread postAuthor: BC Pneumatics » Fri May 16, 2008 5:24 pm

It may also be noted that what I posted in this topic to begin with, is nothing more than PV=nRT, rearranged, and with some variables replaced with constants. Not to mention a bunch of unit conversions.
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Unread postAuthor: LikimysCrotchus5 » Fri May 16, 2008 5:31 pm

Too bad this ideal gas law wont be accurate in areas of in areas of high temperature, because ideal gasses cannot become solid or liquid, which is why they dont exist and are only used to predict.

But im sure you already know this.
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Unread postAuthor: BC Pneumatics » Fri May 16, 2008 6:03 pm

Liki, you are completely correct, the 'ideal gas' does not exist. That is why we must use V=((nRT)/P)+nb where 'n'= moles of gas and 'b'= a constant intrinsic to each gas to account for non ideal gas volume.

And corrected for intermolecular forces, it is P=((nRT)/V)-(a(n/V)^2)). Here 'a' is a constant intrinsic to each gas.

We of course owe a great deal of gratitude to Van der Waals for figuring these corrections, and combining them into the Van der Waals equation. (No one ever said he was humble.)

Equations are very jarbled in regular text, so I used an image to represent that equation in it's common form.
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Unread postAuthor: LikimysCrotchus5 » Fri May 16, 2008 8:58 pm

BCPnuematics wrote:That is why we must use V=((nRT)/P)+nb where 'n'= moles of gas and 'b'= a constant intrinsic to each gas to account for non ideal gas volume.

And corrected for intermolecular forces, it is P=((nRT)/V)-(a(n/V)^2)). Here 'a' is a constant intrinsic to each gas.

We of course owe a great deal of gratitude to Van der Waals for figuring these corrections, and combining them into the Van der Waals equation. (No one ever said he was humble.)

Equations are very jarbled in regular text, so I used an image to represent that equation in it's common form.


Now i may not go into that with a chem 1 class, but i never knew that. So thats what you use here then, right?

My hats off to you sir :salute:
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Unread postAuthor: Davidvaini » Sat Jan 24, 2009 12:47 am

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Unread postAuthor: c11man » Fri Feb 13, 2009 5:33 pm

I am not going to use co2 for my cannon but i put in the numbers for the chamber and i would need 17 cartages to fill it to 80~100psi. not practical for huge cannons lol :lol:
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Unread postAuthor: Technician1002 » Tue Apr 07, 2009 3:08 am

BC Pneumatics wrote: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.


Don't forget that Half the volume = twice the pressure is true for Absolute pressure, not relative.

In short, in space at 0 PSI halving the size doesn't increase pressure. On earth, at 0 PSI, would double the absolute pressure from about 15 PSI to 30, or a reading on the tire gauge of about 15 PSI.
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Co2 Fill Program

Unread postAuthor: Davidvaini » Mon Jul 13, 2009 10:02 pm

hey guys, I decided to make a program version of the quick reference chart.

It allows the user to put in temperature, Size of Pipe, and Size of co2 Container, so its not just limited to 70 Degrees, with a 12g.

Again thanks, to Ragnarok for help with the equations.

Image

I'm also going to make a new post about this to see what people think!
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Unread postAuthor: THUNDERLORD » Mon Jul 13, 2009 10:29 pm

When i try to download it I get an error.
It all goes back to when I removed spyware I picked up on accident.

If anyone's interested, I am raising an army to smash entire families of people with anything to do with spyware...
you know, rip their teeth out with pliers burn them alive and impale them through the bum on pikes etc.
This is not a joke. Seriously, it could become a decent career. :roll: :twisted: :twisted: :twisted: 8)
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Unread postAuthor: Davidvaini » Mon Jul 13, 2009 10:49 pm

Well I can guarantee there is no spyware or viruses in this program or any program that I create.
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Unread postAuthor: THUNDERLORD » Mon Jul 13, 2009 10:57 pm

Well I can guarantee there is no spyware or viruses in this program or any program that I create.


Hope you didn't take that the wrong way.
Had nothing to do with yourself.

The thing is, I got some nasty e-mail that I would've deleted immediately,
But my mouse clicker gets stuck all the time, so when I moved across the mssg. to delete, it opened and infected my personal computer.
really P's me off.

I paid my security provider to remove it, but by then , i had cut the heck out of important programs,
and also wondered why I need to pay my security to remove a program it should've protected my PC against, in the first place.

There was a known spammer who not too long ago died and it was strange because all the news reports were very cheerfull about his death.
It was sort of funny really. 8)

EDIT: Wish I could download that program...looks good. :(
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Unread postAuthor: c11man » Mon Jul 13, 2009 11:03 pm

i havent downloaded yet but it looks good
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