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Converting Oxygen Cylinder

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: theBOOM » Thu May 06, 2010 4:47 am

Thanks for the info -_-, if I can get a machinist to make me the proper adapter I'll use a big fire extinguisher that's in my house too.
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Unread postAuthor: boyntonstu » Thu May 06, 2010 8:25 am

theBOOM wrote:Well, I'm just saying, it's not a wise decision to exceed a fitting's pressure rating by 4, so just a word of warning.
Kinda off topic but after doign a search, I figuired that Dry chemical fire extingiushers can hold up 250 or 300 psi just fine right??

Edit, for a piece of mind I would swap out that brass fittings for galvanized steel 1/4" fittings, I would trust it more at these pressures. Just my opinion though.


1/4" brass NPT fittings are the strongest fitting size.

The smaller the diameter, the smaller the fitting.

Note, the 3,000 psi gauge with its 1/4" brass fitting.

http://tinyurl.com/24y774n

That should give us some confidence.
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Unread postAuthor: boyntonstu » Thu May 06, 2010 8:40 am

jackssmirkingrevenge wrote:Sounds like a good excuse to make a semi-automatic :)


I believe that it may be possible to fire 4 nail dart shots in a minute using the converted cylinder, quick disconnects, and the Trom-Boyn action.

OTOH I have a 4 foot length of 4,000 psi hose.

Using the cylinder on the ground, and a repeating design would be nice.

AAMOF I am working on a completely new gun design that is a natural repeater.

When I get 'er done, you may be surprised.
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Unread postAuthor: POLAND_SPUD » Thu May 06, 2010 9:47 am

1/4" brass NPT fittings are the strongest fitting size
somethign tells me that 1/8" is even stronger than that :wink:

Nice setup, have you considered building a semi ?
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Unread postAuthor: spudamine » Fri May 07, 2010 1:52 am

Spudamine, I used the wrong words, they don't actually say "rated to 600 psi" but from tests members of this site have made, I can assure you that 1/4" galv. fittings can hold 600 psi safely.

http://www.spudfiles.com/forums/me20h-4 ... 14452.html

I'm sure that creates more pressure than fridge compressors
They wheren't even 1/4", yes brass might look shiny and cool but I trust galvanized more when it comes to pressure. Oh, and they have them in my ace hardware store along with some zinc plated fittings too.


You're example isn't the best there's a big difference between holding a high peak pressure for such a short time and maintaining it permanently. However Gippeto has done hydrotesting on similar malleable iron fittings and from memory they held up to well over 1000psi so I've no doubt such fittings are suitable for most spudding purposes.
What I don't understand is why you think brass is inferior, I use it in my 600psi cannon, not because it looks shinier but because it's designed for use in pneumatics not plumbing and I think the manufacturing process is more reliable. Also show me one high pressure hydraulic fitting made out of malleable iron, galvanised or otherwise. :lol:
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Unread postAuthor: theBOOM » Fri May 07, 2010 2:25 am

spudamine wrote:
You're example isn't the best there's a big difference between holding a high peak pressure for such a short time and maintaining it permanently. However Gippeto has done hydrotesting on similar malleable iron fittings and from memory they held up to well over 1000psi so I've no doubt such fittings are suitable for most spudding purposes.
What I don't understand is why you think brass is inferior, I use it in my 600psi cannon, not because it looks shinier but because it's designed for use in pneumatics not plumbing and I think the manufacturing process is more reliable. Also show me one high pressure hydraulic fitting made out of malleable iron, galvanised or otherwise. :lol:


Spudamine, to achieve a 20x hybrid mix you would still need about 360 psi, enough for this application.
Uh, I think you got confused inferior means higher, or better, but anyway :lol: I really don't know why I favor galvanized fittings over brass fittings, I've never seen brass fittings rated to 150 take anything close to 1000 psi, I'm not saying brass isn't a good material to construct a cannon out off, I myself ordered myself some brass fittings rated to 1600 psi from McMaster, now those DO have thick walls.

Also what do you mean by the manufacturing process being more
reliable, I really don't see any defect on how galvanized fittings and pipe are made. (Except for that annoying weld line in pipe, but you can buy seamless ones)

I believe this is getting a bit out of hand though, it's just a personal opinion of mine, lets leave it at that.
Edit- I haven't seen any hydraulic fittings made out of malleable iron, but I do know of forged steel fittings that can hold up to 6000 psi, would that count?
Edit 2- Maybe gippeto can do some high pressure tests on brass fittings as he did with the malleable iron ones.
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Unread postAuthor: inonickname » Fri May 07, 2010 5:02 am

Uh, I think you got confused inferior means higher, or better, but anyway

Inferior:
1. Lower in place, rank, value, excellence, etc.; less important or valuable; subordinate; underneath; beneath.


Perhaps you meant superior?
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Unread postAuthor: Ragnarok » Fri May 07, 2010 6:44 am

Lucky you.

I can't exactly say I'm jealous though, given I have seven empty 2kg CO<sub>2</sub> fire extinguishers around. Safety mechanism on that limits them to 190 bar (2750 psi), but as I don't have the means to get anywhere close to that yet, I'm hardly restricted.

I'm still converting five of them into a 15 litre bulk tank, which should be able to take 100 bar (1450 psi) easily.
Downside is that actually using it for rapid fire fun will have to wait a while, as it turns out that the new dog doesn't particularly like loud bangs (and ironically, it's a gundog breed. :roll:)
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Unread postAuthor: theBOOM » Fri May 07, 2010 8:20 pm

inonickname wrote:
Uh, I think you got confused inferior means higher, or better, but anyway

Inferior:
1. Lower in place, rank, value, excellence, etc.; less important or valuable; subordinate; underneath; beneath.


Perhaps you meant superior?


Yeah sorry, inferior in spanish means higher... Hm how odd.
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