A sublime PVC cannon

PVC

Not to be outdone with hair spray powered PVC cannons, [William] created an even cooler device: a cannon powered by dry ice.

Once dry ice is loaded into the pressure vessel, a burst disk is placed in the breech and the barrel is screwed on. The trigger isn’t very precise – the entire gun is powered by dry ice turning from a solid into a gas – but the resulting cloudy booms more than make up for any imperfections.

Despite building a cannon and using PVC as a pressure vessel, [Bill]’s project is actually quite safe. The ‘trigger’ is a burst valve made out of a disc of aluminum foil held between two sections of PVC. When the pressure rises, the aluminum foil inevitably tears, shooting whatever is in the barrel out and hopefully not into an eye. The ‘safety’ on the gun is a ball valve connected directly to the pressure vessel, and with a pressure gauge and a release valve. We’re more than confident in saying this is pretty darn safe as far as PVC cannons are concerned.

24 thoughts on “A sublime PVC cannon

  1. Wow, I expected all of the anti-PVC nazis to come out of the woodwork and post 50 dozen “you can’t do that!” warnings…

    1. And I expected to see all the ‘who cares about safety’ idiots to post in reply. Looks like I was wrong, you got here before we did!

      1. You notice that I DID NOT say that PVC was an acceptable pressure vessel. I simply stated my surprise that I managed to get a post in before the haters.

        Congrats on being the first of the anti-PVC nazis to come out of the woodwork, JohnSmith.

    2. You can do it, this one is safer than many out there but PVC still remains an unsuitable material for pressure vessels. Drop it before the “burst disk” ruptures and boom shrapnel.

    1. I guess that’s where the word “hack” comes in. Although a real PRV would make things a notch safer (and a bit more expensive? I’m not sure).

  2. I can’t quite make it out in the pic, but hopefully he has safety glasses on. Remember, you can’t grow eyes back!

    As for exploding PVC, it’s perfectly safe if the fuel is hairspray/starting fluid. If you’re paranoid (like me) you make the combustion chamber out of a 3″ “wye” (3″ on both ends, 1.5″ coming out at a 45 degree). The walls on that section are massively thick. Always use the thick PVC (schedule 80), and never use ammo that isn’t a bit slippery. Potatoes and pears work great. Wear gloves when firing it.

        1. It does fling a metal bracket towards your face. So you still don’t want to fire it from your shoulder.
          But that’s just an implementation detail, you could use the same parts safely with a minor layout change.

  3. the ball valve is the safety, there is also a real pressure relief valve. 2 separate devices on it, you can see them in the picture.

  4. I’ve made so many of these and have never had one explode on me. Dry ice is an interesting idea though. I normally use starting fluid or hair spray paired with flint & steel (the ones that work with lanterns seem to be the best). I also stay away from pvc and just use abs, much thicker.

  5. Very cool idea. I would use a metal pressure vessel, though. My concern with plastic, even ABS, is that it gets brittle when cold. Further, because it is such a poor conductor of heat, it would tend to get very cold only in one place, which might make the brittleness even worse. Nonetheless, using dry ice is a cool (no pun intended) idea :)

  6. Would the old science fair favourite, baking soda and vinegar, build up enough pressure to work this think, no problem with cold and easier to get (with the added bonus of everything smelling like pickles!)

  7. I used PVC as a pressure vessel, and now my grandma is dead! PVC is never safe to use when any pressure at all is involved. It should only be used when both the interior and exterior are exposed to a vacuum, as in deep space, and even then with extreme caution. It could still kill everyone you know and love, and will, if given the chance.

  8. ABS — always recommended over PVC, but where do you find it? Here in the Northeast US, the only ABS I have ever even seen is the “foamed” kind (suitable for DVW use only, not pressure-rated). I believe (though I don’t know for sure) that the reason I can’t find it here, is that it’s not legal to use it, so it’s not stocked. Even the “foamed” stuff is almost impossible to find.

    Is there some place in the US where the Home Depots and Lowes stores carry solid ABS pressure-rated pipesin appropriate diameters for this sort of thing?

  9. Back in my college days I built a potato cannon that operated using a burst disk and phase transition. However I used liquid nitrogen and a scuba tank as a pressure vessel.

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