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• Aye... Where be the video?

  Posted by: dragonphyre on November 9, 2007 at 10:54 AM

• Along with the usual safety caveats know this:
  Rumor is that PVC shards don't show up very well on X-ray. So BE CAREFUL!
  - Use Schedule 40 or 80 PVC pipe & fittings for the high-pressure part of the cannon.
  - Don't exceed the maximum rated pressure when pressurizing the reservoir.
  - Leak test your air reservoir by filling almost all the way with water, then pressurizing with your bike pump.

  Posted by: jswilson64 on November 9, 2007 at 11:19 AM

• Presta valves are threaded and can be easily attached with a nut. There's a simple $.50 attachment you can get at any bike shop for your pump/compressor. The o-rings on them tend to come out though, so if you are into this, you might want to spring for a more expensive one.

  The presta valves can also often be gotten for free from the repair shop, from holy innertubes!

  Posted by: osbock on November 9, 2007 at 11:53 AM

• That should be "T-Shirt Cannon". A "canon" is something entirely different.

  Posted by: Rostov on November 9, 2007 at 1:08 PM

• Great idea with that PDF cast.
  http://www.isnare.com/?s=author&a=Jessie+Ferguson

  Posted by: jackattaway2 on November 9, 2007 at 2:02 PM

• You can find schrader valves that bolt in place in the auto parts store.

  I built something like this a bunch of years ago using 2" PVC for the barrel and reservoir. I used a lawn sprinkler valve, but hacked it to be pneumatically actuated, instead of electrically so I didn't have to mess with batteries. My valve also included a vacuum break, which involved forcing the air to make several unnecessary U-turns. I hacked that out to remove as much restriction as possible from the air flow path. The 2" pvc was rated to 280PSI, but the valve was only rated to 80PSI. I did fire it a few times with 100PSI or so. It could lob various vegetable matter a couple hundred yards.

  I also worked out a method for launching water balloons. You can't just cram a water balloon down the barrel and fire it. The friction between the balloon and the barrel will break the balloon. I figured out a 'sabot' arrangement using a paper cup to hold the balloon.

  Posted by: darus67 on November 9, 2007 at 2:13 PM

• Be Very Careful! as mentioned before PVC wont show up on xray!

  only use schedule 40(white) or CPVC (Tan) (because their pressure rated) if you use DWC (drainage PVC usually grey) your palying with fire, its not designed for pressure so it will explode

  Rainbird makes good valves and can be modded to be used with a pneumatic blowgun accessory so they open faster. for a cheaper alternative, .25 inch quarter turn ball valves may be used.

  dont used threaded PVC, glue every joint.

  Schrader valves can be had at most hardware stores as a self seating valve or a screw in. I find the screw in valves are better but if you go to a tire repair shop and ask for a tire stem most places will give them to you for free.

  a VERY good thing to buy is a Pressure release valve rated for 85 psi, attach it to the reservoir so if the pressure goes above 85 PSI it will pop and vent the pressure so you dont hurt yourself.

  I wouldn't use a "U" piece like MAKE did, I'd do a straight shot design where the reservoir is connected inline (via your valve) to your barrel

  Have fun every one and be safe with this one! also if you use a .5 Inch barrel, mini-marshmallows are very fun to shoot!

  Posted by: jerb on November 9, 2007 at 2:44 PM

• Be REALLY carefull - The Police in your area may want to take you to jail for possessing this one! They might contend that it is a class three firearm as it is capable of lauching a projectile (think of the t-shirt as wadding behind the solid object..)! Not a fantasy, I was present when a similar device was confiscated in the Seattle area about 3 years ago.

  cheers,
  chuck...
  

  Posted by: chuck... on November 9, 2007 at 3:27 PM

• As someone who works in theatre and has built several confetti guns, I'd like to reiterate that PVC pipe is not considered safe for storing pressurized air. The reason for this is the compressibility of air. Water at a certain pressure only has a small bit of springiness to it. If the pipe breaks at 120 psi when it's full of water, it just cracks and the water spills out. Air, on the other hand, has enough springiness to send sharp pieces hurtling at ballistic speeds.

  ABS (the black stuff) is a better substitute, although not quite as easy or ubiquitous.

  Also, if you'd like to forego all the electronics and make it a bit simpler, a ball valve is a good choice. One quick 90-degree turn and it's fully open. Get the biggest you can afford.

  Posted by: FredicvsMaximvs on November 9, 2007 at 5:32 PM

• By simply reversing the positions of the quick coupler components, you should be able to charge the tank and remove the pump hose with a minimum of loss.

  Yes test the final product hydro statically. I have helped installed literally miles of PVC in the oil field, manufacturing defects are not unheard of. Keep in mind that successfully passing the test doesn't mean there will not be a failure down the road. While it may be cost prohibitive, a butterfly valve would be the fastest full opening manually operate valve

  Posted by: pvlman on November 10, 2007 at 5:59 PM

• I built one with a few modifications. Mine has interchangable barrels of different sizes and hooks directly up to my air compressor, so I can shoot as fast as I can reload.

  You can see it and how it works here:
  http://www.metacafe.com/watch/923291/high_speed_stuff_accelerator_pneumatic_cannon_in_action/

  Posted by: shoomaker on November 15, 2007 at 3:14 PM

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