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Old 01-26-2008, 03:34 PM #1
cmosser502
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Need Help 12 gram CO2

ok i need to know the psi and capacity of a 12 gram. i am building a rockt launcher and i just built a 2" by 3" long pvc chamber. glued it together, screwed in the 12 gram, then crack, boom, the cap blows up and now my thumbs throbing and bleeding from where the 12gram changer blew of the cap and eliated it. could have been deadly.... was my chamber to small or what?ive been using a 6" long metal chamber (3/4" in dia) and it holds the air but not big enough, olny shoots like 50 yards paralell to the ground.

thanks
cole

any suggestions?
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Old 01-26-2008, 03:37 PM #2
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it holds 12 grams of co2
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Old 01-26-2008, 03:53 PM #3
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it holds 12 grams of co2
he speaks the truth. 3/7 of an ounce if that figure works better for ya.
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Old 01-26-2008, 03:58 PM #4
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duh... ok what the psi? i almost blew my thumb off, the chamber is around 5+ times the size of the 12 gram.
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Old 01-26-2008, 04:44 PM #5
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figure 800psi at 75 degrees.

But at 5 times the chamber size the pressure will NOT be 160psi. The pressure will remain 800psi until all the liquid co2 has boiled off to gas.

Someone here posted it takes a chamber of fairly large size to drop the pressure to usable levels. A very common solution is to hook a 12gram changer into a simple ASA, then attack a cheap WGP Sledgehammer LPR to that, and feed the PVC chamber with 100psi from the sledhehammer.

nick
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Old 01-26-2008, 04:47 PM #6
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In the future be careful with messing with stuff like air under pressure if you don't know what you're doing.
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Old 01-26-2008, 04:47 PM #7
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i think 12grams are the same as other co2 tanks so... somewhere near 850 psi...

calculate the volume of your cylinder to find your pressure

use PV = nRT where n, R, and T (relatively speaking) are constant

so P1 V1 = P2 V2

850psi * 3/7oz = (x) psi * [(v) oz + 3/7oz]

where (x) is the new psi and (v) is the volume of your cylinder

make sure to keep units constant so if you switch to square inches... convert

that calculation should be correct but someone correct me if im wrong

its also a guess calculation.. temperature changes and such will affect it as well


edit: ok nevermind... lovecraft is right
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Old 01-26-2008, 05:26 PM #8
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ya...hence why almost no launchers use straight co2.
it's a pain to calc the pressure when you bring liquid into it.
reg that ****, and use a blow off(safety) valve.
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Old 01-26-2008, 05:46 PM #9
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thanks everyone, i googled some stuff andow have a larger chamber.... the problem is the liquid, i now believe that the liquid CO2 froze the back cap which is why it shattered, i think #2 will work like a charm, believe me i am taking extra precautions.
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Old 01-26-2008, 06:08 PM #10
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Dont Use Pvc!
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Old 01-26-2008, 06:49 PM #11
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^why? i just need to get the pressue down to 280 psi and rid of the liquid.
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Old 01-26-2008, 07:02 PM #12
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Make sure the pvc is rated for 280 psi. If not dont use it. I know i see a lot of pvc rated for only like 120 psi.
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Old 01-26-2008, 07:09 PM #13
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Normally speaking...

PVC + Co2 + High pressure = bloody nubs for fingers.

You got lucky.... 12 grams are considerably high pressure, Ive had some out putting 900 PSI lately so.. to make things safe.. I would make an air chamber rated to double that atleast.
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Old 01-26-2008, 07:30 PM #14
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Here's a page with all the equations to figure out what size of chamber you'll need to bring a 12 gram of CO2 down to the desired pressure (you'll want to go down to like 100 to 150psi)...

http://www.doomlabs.com/science/CO2_Science.html

If you can't understand the equations, then you probably shouldn't be monkeying with this kind of thing. Pick up an old cocker LPR and regulate that sucker.
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Old 01-26-2008, 07:51 PM #15
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Old 01-27-2008, 02:46 AM #16
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PVC isn't rated for carrying pressure. Sure it'll be fine for perhaps 30 or 40 but you're trying to stuff 280 into it with no idea at all what the pressure rating of the tubing and fittings are. If you make a larger chamber then there will just be more potential for damage in it and the next post we see from you may be with more than your thumb damaged.

This is just not a good idea. Especially since you're just making up the stuff as you go along. At least stop and do the numbers on the materials. And if you can't find pressure ratings for the materials then switch to something where you CAN find the info. The life you save will be your own. Do not underestimate how much damage that 280 psi of pressure can do if it is able to make your plastic burst into shrapnel.
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Old 01-27-2008, 02:59 AM #17
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and if you won't heed everybody else's advice, at least stay the hell away from me with your paint cannon machinery time bomb thing.
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Old 01-27-2008, 10:24 AM #18
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and if you won't heed everybody else's advice, at least stay the hell away from me with your paint cannon machinery time bomb thing.
me 2, pressure + little to no room (volume) =explosion, thats why gunpowder burns when its not in a gun, be safe, and dont kill yourself and listen to the guy giving chem equations that were just on my AP final, he = probably knows what he's doing
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Old 01-27-2008, 12:13 PM #19
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"you're doing it wrong"

dude, just make the co2 the rocket! I used to pass a good many summer days by throwing 12 grams down a c02 barrel which had a nail at the very end. Pop, PHEEEEEEEEEEEw VOOOOOOM!

nice, onomatopoeian expressions for the win!

I mean, they don't have fins and just kinda go willy nilly, but damn that's fun.


ALSO:

If you wish to keep your ambitions, ROCKETS ARE NOT MADE BY CONTAINING THE EXPLOSION! THAT IS WHAT A BOMB IS!

The ONLY difference between a rocket and a bomb is whether there is enough room for exhaust. DO NOT CONTAIN THE EXPLOSION DO NOT CONTAIN THE EXPLOSION DO NOT CONTAIN THE EXPLOSION!

Rockets don't fly because you create pressure in a chamber and pop it off from that. That's how paintballs fly. Rockets fly under their own power. The CO2 exhaust should push against the AIR, not the ground or a chamber.
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Old 01-27-2008, 12:55 PM #20
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^^ to the guy above me, can you pm me how to make one of those, i live in a small town = nothing to do : /
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Old 01-27-2008, 01:16 PM #21
cmosser502
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Originally Posted by Fubarius View Post
Here's a page with all the equations to figure out what size of chamber you'll need to bring a 12 gram of CO2 down to the desired pressure (you'll want to go down to like 100 to 150psi)...

http://www.doomlabs.com/science/CO2_Science.html

If you can't understand the equations, then you probably shouldn't be monkeying with this kind of thing. Pick up an old cocker LPR and regulate that sucker.

yes i found that, its what i used to recreate my chamber, i now use compressed air. thanks everyone.
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