Water-blob Launcher

This rifle-shaped water cannon looks great and packs a big punch. We guess you could say that it’s a water balloon launcher, but the balloons are torn off and drop like the wad from a shotgun shell when fired. So we think this launches water blobs, or orbs, or something along those lines.

[Wolf] built it using PVC and some brass fittings that allow for the injection of compressed air. There’s a slick valve system that he developed which we don’t get a great look at in the build pictures. Fortunately, there’s an animated GIF that shows the various stages. Using his valve there’s no need for any electrical system like a lot of other pneumatic launcher systems use.

Just like the water-filled ping-pong gun, you’ve got to be careful with this thing. As you can see in the clip after the break there’s lethal force behind these projectiles. Especially when [Wolf] swaps out the water balloons for big steel darts.


39 thoughts on “Water-blob Launcher

  1. The thing you see falling away is wadding so that the air force doesn’t make the balloon pop. He says as much at one point in the video. Not water orbs definitely water balloons.

  2. while the application might be dangerous because it’s built from pvc, the concept is awesome. The way the ball maintains it’s form through flight is great. I imagine it could leave some decent bruises too.

  3. Hmm, if you pressurize PVC to 100+ PSI willingly you’re either crazy or stupid or both. But a PVC backpressure release tank like that would be useful for making a mondo nerf gun where pressures would stay below 40 PSI.

  4. No… the balloons don’t tear off and drop, that’s wadding you’re seeing. He even mentions the wadding in the video. Besides, think about it for a second, do you honestly think a water “drop” that size would stay intact on its own when blasted out the end of a cannon?

    If you still don’t believe me, take a look at the slomo clip when he fires it straight up. See that thing that goes off to the side? Looks awfully similar to a sabot, doesn’t it?

  5. interesting but i don’t like the advertising part of this. he really doesn’t show anything that has to do with the valve really or trigger mech all he does is show it off then say if you want one give me 300 on ebay. might as well just had a big paid ad for this dude on the front page. sorry but IMHO remove this as it adds nothing at all to this site.

  6. Wow, I made something like that in college – should have put it on the internet first. I could never figure out how to make a good stock for it like this guy did. So pretty cool from that standpoint…

    160 PSI though? That’s too close to the burst strength for my taste – I don’t think I ever pumped it past 80 or so. You don’t really know how well it was manufactured or if there are scratches.

  7. “That is not PVC, its ABS. Even worse under pressure.
    Posted at 3:42 pm on Dec 3rd, 2010 by macona”

    Because its black? Nope….Its PVC. He painted it….see page 2 step 4 of his “build” where he “styles it up”

    now, go regulate.
    if they ain’t violating, ass shot is warning shot. if they need some sense knocked into their thick skulls, go for the headshot..

  9. Since when does plastic shatter? Sure it ruptures or breaks, but shattering…eeh probably not. It’d have to be some serious hardened sheit i don’t think pvc comes close to this – pvc is still quite bendable. ABS i believe would be more likely to shatter. Also he says it handles up to 160 psi, if it would “shatter” over a 100 psi then i’m pretty sure 160 would have done it. I want solid evidence on the pvc “shattering”, not this “i heard someone say, he heard someone say this 12 years ago”.

    “the less you know the more assumptions you have” – whether this applies to me or the people i comment, i don’t know.

  10. The valve…thats a piston exhaustive valve, it was adapted for air cannon use a long time ago and is used for high volume, quick releases of air; usually to blow out grain silos and the like.

    ABS has a higher PSI rating than basic PVC of the same thickness.

    Shooting liquids out of an air cannon atomizes it quite well. Try putting someone against a concrete wall. Instant silhouette and wet t-shirt contest winner in one.

    120 PSI in a SCH 40 pipe made in the United States or Canada isn’t a worry…just don’t drop it as the pipe can and does shatter, shooting large sharp bits across the yard and hitting my-err a potential neigbor’s house.

    And finally if you think this is crazy and dangerous to do in plastics… look up hybrid cannons. They use compressed air and compressed propane in the right ratio. Personally it is alot more fun to use oxygen but it is hard to get the mixture right as it is self igniting(think two simultaneous valve releases).

  11. Try this out. Don’t actually DO it – this is a thought experiment only.

    Take two PVC caps and a length of 3 or 4″ PVC. Drill out one end and put a nipple and a ball valve on it. Fill it up to 160 PSI.

    Brand new PVC (even schedule 40) can technically *handle* it. It will not leak or explode. But then drop it on the ground. Or hit it with a hammer. Or get it cold so it gets a bit more brittle and then smack it around. As soon as a stress crack of any type forms – boom. Everybody has cracked PVC – it isn’t that hard to do. And that is without 160 PSI (which in a 3 or 4″ tube can be literally tons of pressure) of air behind it.

    My point is, at some point it is going to fail. Catastrophically. And in a fraction of a second. Like a small bomb would. Only the PVC crates sharp edges. Which act like shrapnel.

    Anything can explode under pressure an nobody is arguing we can’t or shouldn’t have fun. Hell, I have fired potato cannons and I loved it. But if you want to do something like that, please do it right. Don’t use 160+ psi of air inside a large volume of PVC. Because it will very possibly shatter catastrophically and when it does it will very likely hurt you very badly.

    This is the same reason when I have put on firework shows that I use fiberglass tubes and not PVC.

  12. PVC definately shatters even when it’s not containing compressed gasses. You can try it yourself just by smacking a section with a hammer, the pieces chip off.
    This is why they use HDPE(which doesn’t shatter) or parallel wound paper tubes to launch mortars for professional fireworks shows

  13. Steel, stainless steel, fiberglass, brass, aluminum, cast iron… even PVC would be “fine” if it was wrapped in epoxy and fiberglass. Other things would work too – magnesium (really, really light weight) titanium, etc.

    If we are talking about less than 200 psi, my personal suggestion would be for a fairly thin bored aluminum.

    Glass reinforced polypropylene might work too.

  14. Teflon might work – not sure its failure mode in this condition though? Duct tape reinforced PVC to protect it from impacts and attempt to contain the shards if it failed? Copper tubing would work.

    Anything that has a high enough tensile strength, isn’t brittle and obviously is non toxic and can withstand water and the elements and be affordable.

    The first supersoakers used PET plastic, the kind used on nearly all soda bottles. Then they switched to…. don’t quote me on this… thick walled HDPE plastic.

  15. To address some of the complaints about building the cannon out of PVC: 2″ sch40 pvc has a rated pressure of 166psi but I wouldn’t exactly call this cutting it close. Based on a quick google search the actual minimum burst pressure is nearly 900psi.

    I’d be more worried if the air chamber had any protrusions or joints, but aside from throwing the cannon around there’s really no way to put leverage on it, so I don’t feel like I’m stressing it too much.

  16. Over at Spudfiles this kind of valve would be known as a “toolie-style” piston valve.

    As long as you take care of the PVC (don’t drop it, don’t expose it to extreme temperatures or conditions) the pressure rating on it will hold. That way you can avoid PVC’s pretty bad failure mode better.

  17. Fine naysayers, stick an arduino on the side and call it a hack then, or maybe some brass bits, and call it steampunk.

    Has everyone here blown up an pressurized pvc pipe? or are you all parroting the safety patrol?

    Seriously, you kids must solder in welding aprons and face shields.

    I think it’s sweet. Nice work.

  18. It’s not the intended impacts on the PVC that concern me, it is the accidental ones. You are correct that 2″ PVC really isn’t likely to burst at 160ish PSI. That’s the working pressure. The burst is several times as much, typically 3 – 6. But those are perfect world conditions, assuming no physical damage is going to happen to the PVC. But you can’t reasonably guarantee that. Drop it from about 5 feet onto a sharp rock and it might literally explode under only 160 PSI. Because it cracked. Nothing is there to contain said blast, hence the danger. It’s the same reason why you don’t run air lines in your shop in PVC. I run mine in aluminum.

    I design and build 1″ NPT 10,000 PSI systems that are braided stainless steel and pressure rated to handle the pressures the equipment is rated to produce (which in that case maxes out at about 7,500 PSI – and my waterjet puts out 60,000 PSI. Both machines have pressure relief valves as well as use material appropriate to the application (in both cases stainless steel double braid and solid tubing respectively).

    If there was a properly set pressure relief valve and either the correct material or at the minimum quite a few layers of duct tape to protect and attempt to contain any explosion, I would consider a device like this marginally safe to use. With neither of those in place, this is, in my opinion, an intrinsically unsafe device.

    I suppose if you had a pressure regulator feeding air into the device it would be a BIT safer but what if it is set wrong or fails to operate properly? At least most air compressors can’t generally produce more than about 160 PSI.

  19. He ought to get himself a defense contract, improve the design for mass production, and make a bajillion dollars. I could see these used as a non-lethal weapon at riots or heavy border crossings.

  20. http://www.spudfiles.com/forums/files/s10314451_128.jpg
    Granted this is from a Hybrid cannon, and not a strictly pneumatic one, but the evidence still stands. and this is Sch 80(hence the grey color) which is much stronger than Sch 40 pvc

    These guys took what looks to be 3″ sch 40 and did drop tests on it at 140psig with a 2lb(?) weight and it survived everything but a hit from 12ft after it had been removed from a domestic freezer.

    A few things to keep in mind is that the blows were over a rather larger surface, so if you drop your cannon and it lands on a sharp edge a smaller fall could lead to catastrophic failure. And all of the experiments were done with ‘new’ pipe. ‘New’ pipe meaning it hadn’t been toted around for a year, dropped during your move or exposed to years of UV rays to degrade the PVC.

  21. I have to say I’m actually a bit worried about this HAD post. I love the fact they feature this stuff, but this one needs several safety warnings!

    This isn’t a hack, for one, it’s a well-known method of making air-launchers. The design isn’t unique to the author, it was developed years ago. He hasn’t really done anything unique, or hacked anything.. he *did* do a good job on the internals and the woodstock.. that’s about it.

    Anything using a pressurized chamber needs pressure relief valves/burst-discs. It’s a fail-safe measure for the ‘oops’ moments or the Murphy’s Law problems.

    Regardless of the pressure-rating stamped/printed on the PVC, nobody here (including the author) has taken into account pressure-DE-rating which you need to do!

    With a maximum operating pressure of 166psi and an ambient air temperature of 80F, your max psi drops to 149, and at 90F drops to 124. This doesn’t take into account the fittings.. merely the piping itself.

    There’s no gauge to show actual pressure on the pressure chamber, you’re relying on the air-supply’s regulator. Pressure vessels should always have a gauge of some sort.. coupled with relief valves.

    Another reccomended item, but not required, is a way to dump the air from the vessel without firing it.

    For his previous model, the LAW1 (Light Antitank Weapon btw, a common paintball term), I didn’t read any info on it.. but hopefully he wasn’t using high pressure on that either.

    A lot of people forget those valves have maximum operating pressures as well, and most of the cheaper valves use ABS for the pressure-body. The higher-end units used pressure-rated ABS or fiberglass-reinforced plastics, with operating pressures 160-200psi. Rainbird Industrial models are known for this quality.

    I build PVC/Metal-styled LAW units as a hobby, have been doing it for a decade. Safety isn’t overlooked in my units, and I encourage others to focus on safety when they build these. I have seen PVC shatter (contrary to what some people think), and have known someone to almost die as a result of it. The shrapnel missed his jugular by about 1/8″.

    This was a result of not using a safety-relief valve or a pressure gauge, and his air-source-regulator was apparently inaccurate.

    HAD editors: You really should post some basic safety warnings such as ‘at your own risk’ with these sorts of things, or get someone on the staff who knows what to look for regarding this particular category.

    I love the quality of the author’s work on the internals, and I love seeing air-cannons, but there should be some measure of safety involved on this.

    One final note, a properly-designed pressure-chamber/barrel can do the same or better with regard to velocity/distance, using less pressure.

  22. I completely missed the fact he put screws into the sidewall of the PVC, another DO NOT. It puts a weak spot into the sidewall of single-wall PVC. If you need to do such, you are supposed to use a PVC slip-over coupling, glued in place.

    This strengthens the wall from hairlike-fissures which do develop from the threads.


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