The Potowitzer: A Rapid Fire Potato Cannon

If you’ve ever fired a potato cannon, you’ll know that they are a raucous good time, but are somewhat clumsy to reload after each shot. Seeing an opportunity to improve on the design and minimize the delay between launches, [Danger First] have concocted a fast reloading potato cannon — or should I say — Potowitzer.

The key here is that they’ve gone through the extra effort of designing and building honest-to-goodness artillery rounds for their Potowitzer’s manual breech-loading mechanism. Foregoing the inconsistency of potatoes, they’ve 3D printed a bevy of bullets and sealed them with propane gas into PVC pipe cartridges. Metal contacts around the base to carry current from a BBQ lighter to the inside of the cartridge to ignite the propellant. Seeing it fire at about 18 rounds per minute is something special.

This home-made piece of artillery looks like a blast to fire. The only issue appears to be that the rapid salvos are offset by the necessity of fabricating more ammunition — something that isn’t an issue with regular potato cannons. Remember to exercise all necessary precautions if you plan on using any kind of combustible.

If you want to get an idea of what’s going in inside these rounds — or the chamber of a regular potato cannon — check out this tennis ball cannon with a clear combustion chamber.

[Thanks for the submission, Ivan Owen!]

38 thoughts on “The Potowitzer: A Rapid Fire Potato Cannon

    1. Too bad the center bolts stop the combustion spike at the half way point. And “look in at the science” is a melon twistingly marine-biology-researcher type ridiculous thing to say.

        1. i use a t fitting as my expansion chamber, this with slip fittings and working a 1 1/2 chamber to 1/2 barrel seems to not have issues, and by not gluing the slip in fitting on three sides leaves me with pressure let offs if i over pressure ( air restrictors from a nerf bolt caused this to work one already and the system worked great.)

      1. The useful temperature window is only about 10…60 C beyond which it’s either too brittle or too soft to contain pressure safely. It gets brittle with age, with exposure to sunlight, and with exposure to solvents such as the hairspray they’re using for fuel.

        Then there’s the danger that if you get the mixture just right, right on the lower explosive limits, it’s prone to exploding. It’s really difficult to ignite but if it goes, it just turns the whole thing to shards.

        In my own experiments, I made a pilot igniter by pushing raw butane in through a little hole next to the spark gap, while the rest of the mixture was right on the lower explosive limits, and that really made it go. I used a 1 L aluminium bottle for the testing, and as I dialed the mixture leaner and leaner, at some point it just went to pieces; everything popped out, the gas injector was in the ceiling and the barrel flew across the floor with a loud crack instead of the usual pop.

        2% isobutane in 1 Liters of air contains 2.4 kJ of energy which is similiar energy to a rifle shot. The only reason it’s “safe” is because it normally burns relatively slowly, and the heat of the combustion will only raise the pressure in the bottle to about 10 bar, but because it deflagrates/detonates it makes a huge shockwave, and I was trying to see if I can use that to make the projectile go faster.

      2. You don’t get a perfect fuel mixture with the spray and pray loading style. That’s probably the only thing that saves most people from hurting themselves. When you start optimizing fuel mixtures and using things other then hair spray or static guard you will appreciate ABS. I’ve seen both products fail and as mentioned above PVC can create a lot of shrapnel. ABS will just burst open and rip like paper. It’s much safer (safety being relative) then PVC.

  1. Big power trade off there.
    By making the Chamber:Barrel ratio so barrel heavy it never has a chance to build up any power. It looks like they still get +50yds out of it. Fun to be had for sure, it just seems anemic compared to the chamber favored ratios usually used. I suspect this was done intentionally since their chamber ‘lock’ seems mostly to be a friction/inertia lock. I don’t quite understand why they didn’t use smaller diameter pvc instead of spending hours of printing to get a giant daisy pellet printed out, I suspect sadly the answer is perhaps related to the native advertising in their video.

    That video could have been a lot shorter even if they had left their sponsored content commerical in there (though I find it distasteful). A lot of unnecessary verbiage to communicate a simple problem, interesting solution, and just plain awkward moments. We don’t need to see 2.5 min of loading shells.

    1. LOL, just read your comment. I commented on their YouTube channel about needing an extractor too. With the time they put in what were they thinking? Five extra minutes and they could have an extractor.

    1. It’s ummm just the first stage for my nano-satellite launcher… then it goes through a coilgun then railgun accelerator stage, then I start hitting it with a high powered pulse laser and augmenting photonic thrust by ablating an aluminum plate on the bottom so that thrust is produced from the expansion of gaseous aluminum…. and I paint go faster stripes on the projectile.

  2. I nearly stopped the video the moment I saw that guy wearing a vest outside of an ironic steampunk bar. I made it all the way until he said that his projectiles were 3D printed before I shut it off.

    C’mon guys. I’m sure if you spent 5 more seconds thinking about it, you could have shoehorned an Arduino, IoT functions, and a penny farthing in there too.

  3. Wow . . . I hope these guys realize just how dangerous that thing is to any copycat builders. Is that schedule-20 PVC? And what happens when some kid does the math and tries a balanced fuel mix? Their shells are so overfueled the lackluster results are a given. Put it this way – Less than half of a “five count” of propane a cannon with a 2′ x 4″ chamber blew the endcap 6″ into the ground and shattered the front end at the reducing coupler to a 2″ barrel when I was a kid. . . A proper mix and this design would blind and maim the operator in the best case scenario.

    . . . As for the other comments, why not? I’ve been debating working on some of my childhood fantasy cannons lately, for a few reasons, namely the fact that I’m in NY – In all their infinite wisdom with our other firearms laws, it’s only a firearm if it uses a solid propellant (condensed version of the laws). Somewhere I’ve got a letter in response from the ATF stating essentially the same on the federal level. Nice little grey area of the laws that allows for some fun toys in the meantime, with the bonus being >.5″ is not a “destructive device” if it doesn’t use a solid propellant.

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