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SFX Cannons

Discussion in 'Special Effects' started by MHSTech, Jul 21, 2005.

  1. MHSTech

    MHSTech Active Member

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    Location:
    Ohio
    Just courious about what you guys have built or bought in the way of special effects cannons.

    The last musical we did was Beauty and the Beast. At the end of "Be Our Guest" our director wanted a shot of confetti over the audience. So I built this beast...

    http://img.photobucket.com/albums/v654/fiestakid88/DSC00597.jpg

    It's a 7 gallon tank with a 2 inch nipple welded into it. And before you go all over me about this not being safe because I ruind the integrity of it...I tested this before it was used in a show and there is a guage on it. On the end of the nipple was a 2 inch ball valve and then a barrel. It worked out pretty nice, now I use it for launching golf balls into my neighbors field. For the musical I rented a 20 pound tank of CO2, but now I use my air compressor here at home. I fill it through the original fill that was in the tank.
     
  2. Mayhem

    Mayhem Senior Team Emeritus Premium Member

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    Not trying to cut you down, as this is not that far from what is used professionally over here but I am wondering what you did to test the weld?

    Professionals should do welding in this application (although you were not clear on who did the welding) and some would expect an x-ray to certify the integrity of the weld for insurance purposes.

    Most of our cannons would have threaded adaptors and ½” fittings work well. I assume that the gauge is to prevent the pressure in the tank form exceeding the pressure rating of the PVC tube (I assume that you used high pressure rated PVC). Good idea and something that would be required here in terms of safety. I would also have the regulator set on the air compressor as a double safety when filling the system.

    Your next modification might be to replace the ball cock valve with an electronic solenoid, which will give you greater flexibility for firing. And a swivel coupling would also be of assistance.

    I would skip the CO2 gas as it really isn’t the best thing to use and is a cost that you could do without. Compressed air is all you need.

    Nice effort and just keep an eye on the integrity of the PVC and replace if there are any signs of fatigue.
     
  3. MHSTech

    MHSTech Active Member

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    My father in law works for CAT, he welded it for me.

    I pressure tested it with the CO2 at what the ball valve was rated (around 150 PSI). And also, the CO2 was free.

    There is no pressure put on the PVC except for when firing it. I didn't even need to go high pressure because when you have a 2 inch opening in the tank you hardly need anything over 30 or 40 PSI. The CO2 was only used for a conveinence. It was right there, and it didn't make a noise when you filled it.
     
  4. Mayhem

    Mayhem Senior Team Emeritus Premium Member

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    Do you use lifting cups and end caps (closed tube system) or are you leaving the PVC tube open?

    If you are using a closed tube system the PVC should be pressure rated. Looking at the picture, I am unsure as to how you would change your tubes. Are they screw fittings or is the tube glued into place. We use ½” connectors so the tubes can be interchanged quickly if needed.

    I am guessing that you are not using a closed tube system in which case you are relying upon a steady stream of air to expel the payload. A closed tube system will use less air but requires that the tube be pressurised in order to distribute the payload as the lifting cup compresses the payload up against the end cap, which breaks, releasing the contents. This is the best way to shoot streamers.

    Using a closed tube system, a tank that size should allow you to do a couple of shots without having to fill the tank again. We fill our tanks and then position them and sometimes they are flown.
     
  5. LDSFX

    LDSFX Member

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    Location:
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    If you are looking for some great pre-made cannons, the Big Shots are the way to go. Each unit features 2, fully aimable cannons and in internal air tank that can be refilled with a household compressor! The barrels are 2" so you really aren't limited as to what you can shoot out of them. Trigger is provided by standard 110v, just plug in the units, and they fire. I just used 6 of them at a football game and the results were amazing!
    Here for pics: http://homepage.mac.com/ldsfx/PhotoAlbum12.html
     
  6. sandals1621

    sandals1621 Member

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    Location:
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    The Big Shots Are nice compact well working units... but can be expensive.

    I was able to build exact replicas of the Big Shot's for about $150/piece (this included all the Aluminum (for the frame) Steel for the tank, fittings, solenoid etc) And they work great.
     

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