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Propane is better than you thought

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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Propane is better than you thought

Unread postAuthor: VH_man » Sun May 27, 2007 1:52 pm

Ever wondered how airsoft guns can get through 25 rounds without loosing pressure untill the last one?

heres the answer. in the clip of the gun, the propane is liquid. the small space above the propane is in gas form. the valves on the airsoft guns release only the gas, and when the valve closes the propane then once again evaporates into gas, in which you can siphon it right off again.

(btw, propane liquefies at 100 PSI, so its completely safe for homade things. just dont get the liquid propane on any plastic, that wouldnt turn out to good)

Im thinking of making a select fire airsoft rifle based of this principle, and will be filled by plain old Airsoft Green Gas. (green gas IS propane.... ) does anyone see any objections to my principle? or the fact im going to be carrying around a 2 lb tank of liquified propane?
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Unread postAuthor: hi » Sun May 27, 2007 1:55 pm

DR made one.....

i knew that airsoft guns ran off propane, but never knew how they lasted.

anyway, no i have no objection because even if there was a flame in the chamber it would be impossible for it to ignite.

edit- dont use green gas, buy a propane adaptor, it is much cheaper to fill airsoft guns that way.
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Unread postAuthor: VH_man » Sun May 27, 2007 1:59 pm

yeah, airsoft guns dont run down on pressure that much at all............. only when you hit the last few shots does it rapidly decrease. CO2 works the same way, however it requires a regulator because it is a much higer pressure than propane is.....
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Unread postAuthor: BC Pneumatics » Sun May 27, 2007 3:04 pm

If you Chrony a gas gun, you will notice a few FPS drop after every rapid shot. This is becasue the propane that is stored in the magazine cools, and boils at a lower temperature.

Also, dont belive this 100psi thing. I have usde propane in pneumatics at well over 160psi. (Bottomed out my gauge.)

BTW, this is right on the the verge of common knowledge, and certainly is such around here :P
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Unread postAuthor: VH_man » Mon May 28, 2007 6:36 am

oh, 160 PSI is alot......... ill just use all metal parts...........

anyone know if the MCmaster QEV's can take the kind of pressure propane gives off? they are full metal.........(besides the diaphram)

is there any way to stop the cooldown effect? i noticed this on my gas rifle today, the mag gets really cold and it doesnt fire at all. mabey slow down the ROF? or use less gas per shot?

whatever it is, im still gonna try to make this. my freind just gave me a crappy CYMA mp5 and im gonna rip the barrel out of it and use it to make this thing.
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Unread postAuthor: chaos » Mon May 28, 2007 7:48 am

wow wow wow hold up a second people.

Image

i think u guys are forgetting the temperatures that effect propane's pressure

i just wanted to point that out


i go now

~chaos
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Unread postAuthor: VH_man » Mon May 28, 2007 7:53 am

wow thanks chaos that helps alot. it never gets above 110 where i live, so thats perfect! thanks
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Unread postAuthor: chaos » Mon May 28, 2007 8:05 am

from my findings

http://www.spudfiles.com/forums/pnuemat ... t7934.html

make sure you check it out
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Unread postAuthor: VH_man » Mon May 28, 2007 9:09 am

yeah, i dont mind aobut the smell that much. and remeber im not releasing a crapload of it at once. im thinking of using a hammer valve to blow air through the barrel/actuate the blowback mechanism (yes, my select fire gas rifle will have blwoback, aka someting that mimics the kick of a real gun). that way, i dont waste any gas. also, im going to use VERY small amounts of propane per shot, so i dont htink smell is a problem.

i honestly would rather buy a 3 dollar coleman propane tank than spend 5 bucks getting a CO2 tank refilled ever 5 days, as well as buying the tank by itself (did i mention the regulator a CO2 setup would cost?) also, you can use the coleman propane tanks to fill up normal airosft gas gun mags, so hey, my sidearm can get filled from the same tank of gas! (when i get it, that is).

i gotta say i will use propane to power my select fire airsoft rifle. my freind might be albe to hook me up with a regulated CO2 tank, but for now, ill stick with screwing a coleman propane tank to the back of my gun. if i dont like that ill jsut make an internal gas resivoir, or mabey even implemnt the hammer vailve into a clip, so its jsut like an airosft gas gun......
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Unread postAuthor: BC Pneumatics » Mon May 28, 2007 10:02 am

Thanks for the table Chaos, great resource to have laying around
When I get a chance (Maybe later today) I will chart up CO2 vs Propane for shots/oz (and for shots/usd as well) at one or a variety of temperatures. Interesting to look at, if nothing else.
When using propane pneumatics, make sure you don't use anything that is being eaten by the propane, or that will crack/contort from the cold. Easy thing to overlook.
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Unread postAuthor: jimmy101 » Mon May 28, 2007 3:29 pm

VH_man wrote:wow thanks chaos that helps alot. it never gets above 110 where i live, so thats perfect! thanks


You have to be careful about "never gets above 110". It almost certainly gets above 110F where you live. The inside of a closed car on a sunny day can get to 150F.

A dark colored tank sitting in the sun, particularly if it protected from the wind, will easily get to more than 110F.

I regularly use butane lighters, the cheap 99 cent ones, for small guns. Butane has a higher boiling point then propane, hence lower pressure in the lighter at a given temperature. Still, in a hot car they will explode from over pressure.
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Unread postAuthor: iknowmy3tables » Mon May 28, 2007 3:43 pm

how does the valve alow gas only
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Unread postAuthor: pyrogeek » Mon May 28, 2007 4:19 pm

The gas is less dense than when it's in liquid form. So when the tank is held in the upright position, only gas will come out. Although, you would want liquid in the air soft guns, so you would invert it.
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Unread postAuthor: FeLeX » Mon May 28, 2007 4:27 pm

Hmm I was thinking about this for a long time and what I thought was:
Would you get as many shots from the 3 dollar propane tank using it for pneumatic as you would using it for combustion. Because the power is almost the same you know...
Tell me what you think...
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Unread postAuthor: VH_man » Mon May 28, 2007 4:34 pm

yes! also, propane allows small chambered guns to go semi/full auto without expensive regulators.........
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