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self filling gas

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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self filling gas

Unread postAuthor: partyars » Sat Jul 25, 2009 8:06 pm

hi y all,
im pretty new to this and maybe this cold be posted somewhere else in this forum but i wanted to be sure,
so here's my idea:

cant you maybe put a mix, like dry ice and hot water, or sink cleaner and alumineum foil, into a pneumatic gun so it will refill your tank?
warning, best not to use explosive mixtures

notice: i dont know the max pressure these mixes can give so be careful if you want to test, if this works, a pressure meter is an absolute must so you know the pressures all time

greetz
me
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Last edited by partyars on Sat Jul 25, 2009 8:34 pm, edited 1 time in total.

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Unread postAuthor: irisher » Sat Jul 25, 2009 8:10 pm

Read the forum rules before posting!
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Unread postAuthor: partyars » Sat Jul 25, 2009 8:14 pm

oh i see
srry for this
it wont happn again

grtz
me
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Unread postAuthor: KineticAmbitions » Sat Jul 25, 2009 8:26 pm

There's nothing against the forum rules about using chemical reactions such as Al/HCl, or phase changes such as off-gassing dry ice as pressure sources.

There IS something against the rules about exploding containers with them.

The CO2 method has been used before, and works, although it is rather dangerous compared to more conventional means. As for the HCl / Al reaction... if it can rupture a pop bottle (150psi or so), it should be able to fill a chamber. The problem there would be corrosion of parts due to the liquid and gaseous HCl, and the hydrogen as well to a lesser extent (hydrogen embrittlement).
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Unread postAuthor: inonickname » Sat Jul 25, 2009 8:31 pm

If you just edit out the part about making the bomb then there won't be an issue seen as you have a valid question.

The reaction between sodium hydroxide and aluminum produces hydrogen. It's really too low of a pressure to be used in spudgunning applications, and sodium hydroxide is of course extremely corrosive, so it won't agree with your chamber.

Bicarbonate and vinegar can create higher pressures but it is almost useless as under pressure the gas will dissolve into liquid.

Dry ice (solid CO2) can create very high pressures after sublimination in water. If you calculate the amount of water to ice correctly there won't be an issue. These pressures will require a strong chamber (such as steel). Dry ice is also extremely cold, and will make any plastic chamber brittle.

There are numerous others, such as liquid nitrogen also.
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Unread postAuthor: partyars » Sat Jul 25, 2009 8:37 pm

ok, i put the bomb part away, i think the dry ice method here works best for me, i got fire extinquisher as chamber, i think that would be enough

grtz me
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Unread postAuthor: mikemurph » Sat Aug 01, 2009 4:48 pm

how about vinegar and baking soda, i have recently drwn up plans for it. it has two small chambers, a large mixing chamber and a burst disk. each small chamber has a ball valve leading to the mixing chamber. each ball valve is opened, then the vinegar and baking soda mix, and at a certain pressure the disk breaks and the projectile is fired. I would like to see how powerful these other chemical reactions are in comparison to vinegar and baking soda


P.S.
this sounds kind of dumb but how about mentos and diet coke?
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Unread postAuthor: Hotwired » Sat Aug 01, 2009 5:01 pm

Vinegar and bicarb fails, you get a bit of pressure but inside a hell of a lot of froth which then goes on to cover everything.

Carbonated drinks... are pretty much the same except stickier.
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Unread postAuthor: mikemurph » Sat Aug 01, 2009 6:29 pm

darn, im gonna need a new fuel
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Unread postAuthor: inonickname » Sat Aug 01, 2009 8:02 pm

Hotwired wrote:Vinegar and bicarb fails, you get a bit of pressure but inside a hell of a lot of froth which then goes on to cover everything.

Carbonated drinks... are pretty much the same except stickier.


It can actually produce respectable pressure. However, before that pressure is reached the carbon dioxide dissolves back into the water, similar to a carbonated drink.

Vinegar and bicarb is best used for synthesis of sodium acetate/ethanoate.
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