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Material for snowball cannon?

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
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Material for snowball cannon?

Unread postAuthor: JEK3 » Mon Dec 21, 2009 10:14 pm

I am looking to make a snowball cannon (just got 15-18" over the weekend). I would prefer to work in PVC, but that would be kind of dangerous in the cold weather. It would have to withstand up to 100psi at about 30 degrees F., and I would like the barrel to be on the order of 1.5" to 2" in diameter. I have access to the normal hardware-store variety of materials. What do you recommend I use as a material?
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Unread postAuthor: kjjohn » Mon Dec 21, 2009 10:21 pm

Copper, steel, or aluminum. Black or galv steel pipe and fittings can be bought at most hardware stores, as well as copper.
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Unread postAuthor: Lockednloaded » Mon Dec 21, 2009 10:24 pm

definitely go with metal, PVC is VERY dangerous with cold. I think one of BTBs cannons blew up just by using ice ammo. If you can't work with metal i would probably go with sch 80, I'm not totally sure, but it seems less prone to exploding in the cold, but I have never worked with sch 80 so I may not be right
@kkjohn- copper fittings in the 1 inch and up range tend to be very very pricy, wouldn't recommend it
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Unread postAuthor: SpudBlaster15 » Mon Dec 21, 2009 10:47 pm

I fire PVC cannons in low temperatures (0 degrees Celsius and below) quite often, though that's not typically recommended. I find that if you don't shock the launcher by dropping it or opening a very fast valve into the barrel, PVC cannons are fine in the cold.

However, if you prefer something with greater safety, a different material may be in order. It sounds like you want to build a pneumatic cannon, and in that case, I would recommend using 2" malleable iron fittings for the chamber, and 1.5" ABS for the barrel. ABS is MUCH tougher than PVC, and will resist shock loading at low temperatures.

For the valve, you don't want something overly fast, as that would simply destroy the snowball in the barrel. A brass ball valve of suitable diameter would likely work well for this application.
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Unread postAuthor: JEK3 » Mon Dec 21, 2009 11:22 pm

Thanks for the input so far. I kind of knew the answer already before I posted my question, but I still wanted to get some input.

I would prefer to use a barrel- or chamber-sealing design, rather than a ball valve. I was planning to slow down the shot by reducing the pressure, although I could also shorten the piston travel to throttle the flow.

How about a copper valve body, with an ABS barrel?
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Unread postAuthor: SpudBlaster15 » Mon Dec 21, 2009 11:31 pm

That will work, but as I'm sure you know, large diameter copper fittings are very expensive. If that's not a problem for you, it should be a viable route.
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Unread postAuthor: Biopyro » Tue Dec 22, 2009 5:24 am

The pressure rating of PVC actually increases when it's cold, but it's shock resistance decreases as it becomes more brittle. Something like a piston slamming into it, a lot of recoil force focused on one joint or dropping it might be enough to crack it and the pressure would do the rest. Best to steer clear for something like this, but it doesn't mean PVC is unusable in cold weather.

High acceleration will give you a useless mist of snow, so you'll be best off with a slow valve at low pressure, not more than 50psi. I think the safest route would be to have a foam sabot behind the projectile to stop air rushing through the air gaps in the snow and tearing it apart.
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Unread postAuthor: bradisfun » Tue Dec 22, 2009 6:23 am

i think that u dont want to be carrying around a heavy canon
so....................
i think that u sould make it out of PVC but then get some 4-5" PVC and sleving in that and then inbetween the 2 u can fill it with expandable foam
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Unread postAuthor: psycix » Wed Dec 23, 2009 1:53 pm

I'd go with metal construction, because I do not like surprises when pulling a trigger.
Stuffing the whole barrel full of densely packed snow (because you can't resist) might blow a PVC gun that survived hundreds of normal snowball shots.
You will never be safe with a subzero PVC cannon.


Large diameter thin wall metal pipe, ball valve (or just slap on a QEV), start at a low pressure, slowly work your way up.
Small chamber, onboard pump.
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Unread postAuthor: SpudBlaster15 » Wed Dec 23, 2009 3:26 pm

psycix wrote:Stuffing the whole barrel full of densely packed snow (because you can't resist) might blow a PVC gun that survived hundreds of normal snowball shots.


Stuffing the barrel full of densely packed anything has a good chance of breaking a lightweight PVC cannon from recoil force alone, regardless of whether it's at room temperature or subzero. Even on an average summer day, PVC is below its glass transition temperature, and is thus still susceptible to brittle failure if you knock it too hard.

It should be common sense to avoid firing very heavy projectiles from a launcher constructed with such materials.
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Unread postAuthor: psycix » Fri Dec 25, 2009 6:12 am

Which is one of the reasons I switched over to metal cannons. :)
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