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Cold weather gun - What to make it out of?

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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Cold weather gun - What to make it out of?

Unread postAuthor: Panzerfaust » Mon Oct 22, 2007 2:50 pm

This might belong in the construction materials section but since i am interested in a specifically pneumatic gun so i put it here.

I live in michigan, and with our nice, long, cold winter approaching, i am looking for something to entertain me while my pvc guns are disabled by the cold. I have access to both iron (i think its called black iron, it is black) and galvanized steel pipe in low diameters from local hardware stores. Im thinking of making a QEV gun similar in shape (but longer) to this:
http://www.spudfiles.com/forums/sawed-off-riot-gun-redone-t1342.html
Can these materials handle 100PSI in below freezing temperatures? Can a QEV handle these temperatures? Can your average compressor work in these conditions? If these materials cant take the cold, is there anything that can?
Thanks.
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Unread postAuthor: ShowNoMercy » Mon Oct 22, 2007 2:58 pm

You could always make a ball valve cannon out of wrought iron and then have a C02 setup, although the C02 and the cold would play well together. But other than efficiency that would work well.
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Unread postAuthor: ALIHISGREAT » Mon Oct 22, 2007 3:34 pm

the qevs i have seen can handle -10 degrees.

you could make a gunt like the winter wonder rifle http://www.spudfiles.com/forums/wwr-winter-wonder-rifle-t9985.html
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Unread postAuthor: MisterSteve124 » Mon Oct 22, 2007 6:30 pm

or copper, people use that in qev cannons a lot a lot.
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Unread postAuthor: Marco321 » Mon Oct 22, 2007 7:33 pm

Make a piston valved metal gun
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Unread postAuthor: Panzerfaust » Mon Oct 22, 2007 8:14 pm

Im looking to know if metal can handle these temperatures, telling me to build a cool gun or telling me "hey build one like this" dosent help, however good your suggestion may be. I just need to know if iron or galvanized steel can handle 100+psi and less than freezing temperature. I cannot use copper as it is expensive and i do not know how to solder it. I am thinking of making something with a 2" ish air chamber, which would be insanely expensive with copper.
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Unread postAuthor: DYI » Mon Oct 22, 2007 8:20 pm

The steel pipe will be fine, you really can't make it fail with any pressure and temperature that can be easily generated.
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Unread postAuthor: Panzerfaust » Mon Oct 22, 2007 8:24 pm

Thank you. (The steel pipe says either 150 or 125 max psi, but for the thickness of it and fact that its steel ive always thought that absurd)

Ive also had a question about check valves, ive always thought how convenient it would be to have a check valved fill system instead of a ball valve, just hook the hose on, it auto fills, and disconnect. However mcmaster carries like 6 different kinds of check valves, and im not sure on thier capabilities. I would need a check valve that has absolutely no chance of failing if it is shaken/hit, as on a piston/QEV fill system the check valve opening in reverse would cause the gun to fire. Are there any check valves that have that kind of impact assurance?
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Last edited by Panzerfaust on Mon Oct 22, 2007 8:26 pm, edited 1 time in total.
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Unread postAuthor: Marco321 » Mon Oct 22, 2007 8:26 pm

If its under 1" copper will be way too expensive, you can sue compression fittings or metal epoxy, ill just put it out there. Copper can also handle 300psi and laughs at cold temperatures.

I would go with threaded steel, its much cheaper than copper and just threads in. It also can hold more pressure than copper, about 400psi. It also laughs at cold temperatures.

You can make a piston using epoxy, it should handle the cold temperatures, but you might want to check with JSR.

But don't lick or kiss it if its cold or you tongue and or lips will stick :wink:
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Unread postAuthor: DYI » Mon Oct 22, 2007 8:51 pm

The main reason for the low pressure rating is the roughly cut threads which may leak at higher pressures. I've had threaded steel pipe up to 450 psi with no problems other than the launcher springing a really bad leak.
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Unread postAuthor: battlemonkey » Tue Oct 23, 2007 2:46 am

you could make something with a large ball valve and a chamber like a truck air chamber to shoot at snowmen :D
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Unread postAuthor: ALIHISGREAT » Tue Oct 23, 2007 3:47 am

DYI wrote:The main reason for the low pressure rating is the roughly cut threads which may leak at higher pressures. I've had threaded steel pipe up to 450 psi with no problems other than the launcher springing a really bad leak.


if the threads have leaking problems then you should use the yellow gas ptfe tape which is thicker and better, it think you can use it up to 3000psi.
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Unread postAuthor: Panzerfaust » Tue Oct 23, 2007 2:44 pm

Does any1 know about the safety of check valves in a fill system?
And thanks for the materials info.
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Unread postAuthor: TurboSuper » Tue Oct 23, 2007 4:37 pm

I'd like to see the evidence that PVC-based cannons will rupture in below freezing temperatures.

I'm pretty sure that the ratings from the manufacturer are given under the assumption that it will be outside permanently.

Not only that, but pressure-rated PVC (and needless to say, metal) is usually rated for a much higher pressure than you'd have a reason to charge the cannon up to for most cases, so you should have plenty of slack.

That being said, this is just my reasoning, I'd just like to see some anecdotes is all.
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Unread postAuthor: Panzerfaust » Tue Oct 23, 2007 5:19 pm

PVC pipe says right on it "240PSI@73 degrees F" so yeah, the pipe says right on it what temperature is meant for that rating. HOWEVER, back when i was an uber-noob i used a 3" nsf-dwv chamber charged to 60 PSI in less than freezing weather, in fact i let it sit in the snow (thank god im still alive). However, with what i know now i am not going to risk life and limb on plastic that is known to be weakened by cold.
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