How much does compressed air weigh?

[Thordic]

I did the math a few years ago.

http://www.automags.org/forums/showthread.php?=21839

Using this formula:

Air has an average molecular weight of 29 (28 for N2*.8 + 32 for O2 * .2)
1 mole of gas at STP occupies a volume of 22.4 L, therefore, 29g {~1 oz)of air at STP occupies 22.4 L

Take you tank volume in Liters (ft3X28.3 or cu in X .0164) and correct to STP (forget the temperature, just multiply the volume by 204 or 306{3000psi/14.7psi; 4500/14.7psi}. This gives you the gas volume at STP.

Divide this volume by 22.4 and you get the weight of air in oz.

Using that, you get the following information:

3000 PSI = 204 atm
4500 PSI = 306 atm

47ci = 0.77 L
68ci = 1.11 L
88ci = 1.44 L
114ci = 1.87 L

So now, just plug it into what I said above, and you get these weights:

47ci 3000PSI tank: 7.0 ounces of air
68ci 3000PSI tank: 10.1 ounces of air
88ci 3000PSI tank: 13.1 ounces of air
114ci 3000PSI tank: 17.0 ounces of air

47ci 4500PSI tank: 10.5 ounces of air
68ci 4500PSI tank: 15.1 ounces of air
88ci 4500PSI tank: 19.7 ounces of air
114ci 4500PSI tank: 25.5 ounces of air

As you can see, the weight of compressed air is not negligible, especially in higher pressure setups.

[68magOwner]

not enough to make a difference

You honestly cant feel the difference between a full and empty tank?

My setup actually balances completley different with a full 45/45 vs the same 45/45 empty

[MANN]

[Thordic]

You're off a decimal place. The math I posted above was done by a chemical engineer and then verified.

[MANN]

You're off a decimal place. The math I posted above was done by a chemical engineer and then verified.

Where? I am a senior engineering student, and work with many chem/mech/civil engineers. They make mistakes too

[Paintchucker]

I don't have any scales, but I have a full 68/4500 and an empty 88/4500 and there is a noticable difference in that the full tank feels heavier... Maybe a pound, which would about match the calculations above...

Dang it, now I am curious... I am off to find a scale at a self service post office station. You can't get in trouble with just tanks in the post office can you??? If I am not back in an hour, someone call the Norcross Police Station.

[MANN]

You honestly cant feel the difference between a full and empty tank?

My setup actually balances completley different with a full 45/45 vs the same 45/45 empty

nope. I will take tanks to work tomorrow and verify. I know my scale sucks, and is hard to tell the difference. The one at work is accurate to .0001 g.

[onedude36]

I talked to a guy last weekend about it. He claimed 2 oz difference between full/empty on a 68 bottle.

[paintballfiend]

I would solve the question with my massive brain power but my calculator is out of batteries.

[MANN]

I talked to a guy last weekend about it. He claimed 2 oz difference between full/empty on a 68 bottle.

which ~.12 lb

[SR_matt]

its down in the ounce range (depending a lot of how much moisture and dirt is in the air)

had to argue with a guy at the field and he eventualy admited i was right
-matt

[Paintchucker]

let me finish my pizza, and ill go weigh. is it ok that I do 3000 instead of 4500? and it should be the same weight.

Huh??? Shouldn't the 4500 weigh 50% more ???


So I got to the post office, and it wouldn't let me get to the screen to weigh the tanks, because the main office is closed and they can't accept a package...

But if you hack around on the menus a bit, you can find it.



Both tanks have a black Rase Cover on them. Arguably, the carbon fiber on the 88 weighs more, but I flunked calculus, and think that weight is negligible...

Empty on an 88/4500 with pure energy reg = 3# 2.8oz

3500 psi on a 68/4500 with bulldog reg = 4# 2.2oz

so about a pound...


I guess to be truly scientific about it, I need to weigh the 68/4500 empty, but I just paid $6.50 this afternoon to fill the dang thing, so that will have to be later! I have some guns to get shooting again from collecting dust too long.

[bentothejam1n]

http://www.pbnation.com/showthread.php?t=1977780

eh?

[MANN]

Huh??? Shouldn't the 4500 weigh 50% more ???

sorry. I should have typed that we will see the diff in an empty and full 3k tank.

I have read ^^, and it seems that his calcs are right. im not sure on some of the conversions.

Either way I feel that weight does not make that much difference. 2-4 lb diff in a marker shouldnt make you better/worse.

[Paintchucker]

Thanks for the PbNation link. That was interesting. Another thread had the actual weights of the tanks and the regs on it.

So I guess the next question in line is how much does a full hopper weigh ???

And does one brand of paintball vary in weight vs. another ???



I do agree on the weight difference to a degree. If I start complaining, I know it is time to work out a bit more. But I will tell you that on a hot JULY Saturday afternoon down here in GA, playing the ION with a 45/45k is a little easier than with the Emag on an 88/45k.