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Quiet Air Cannon Possible?

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Quiet Air Cannon Possible?

Unread postAuthor: bionic » Sat Jan 23, 2010 12:03 pm

Hello all - new around here. All the gun stuff is cool as heck but I am trying to design something to shoot nothing but a slug of high volume high pressure air. Is it even possible?
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Unread postAuthor: inonickname » Sat Jan 23, 2010 12:27 pm

So you want to do damage only with the propelling fluid?

Depends. If you took a house and filled it to 3000 psi it would be destroyed. However direction the pressure at it would be a different story.

Depends on the target and range really. If you could make an exception for other gasses you could use dry ice (not a great idea).
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Unread postAuthor: bionic » Sat Jan 23, 2010 12:43 pm

No damage needed. It is for a movie effect.

I need to move a volume of air - lets say we visualize a cylinder of invisible air 4" dia. x 12"long.

The air "slug" if you will needs to be puffed reasonably quiet (silently would be best) and have some arse behind it. Now the puff is to shoot out and knock a stuffed animal off its stand down a tube on the other side.

The faster I can blow the stuffed toy off its perch the funnier it will be! :lol:
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Unread postAuthor: jackssmirkingrevenge » Sat Jan 23, 2010 12:59 pm

If noise is an issue then you're better off with high volume and low pressure. I would suggest a burst disk would be the best way to get this effect but you'll have parts of the disk flying off and these might interfere with your visuals.
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Unread postAuthor: Biopyro » Sat Jan 23, 2010 1:49 pm

Sounds like you need a vortex cannon. I would suggest something like the airzooka, scaled up so you get a bit more power. The extremely low pressure will keep it quiet, but it should have enough force for what you describe.
Have you considered fishing wire if you just need to move it invisibly and quietly?
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Unread postAuthor: D_Hall » Sat Jan 23, 2010 2:31 pm

Agree with biopyro. A vortex cannon is what's being described. It's a bit slow, but anything fast is going to be *LOUD*.
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Unread postAuthor: bionic » Sun Jan 24, 2010 4:29 pm

Thanks for the thoughts. I think I'll give the Vortex cannon another consideration. A concern though is I need the volume of air to push something like a small stuffed animal (5 oz.) into and down another tube. The vortex while reasonably quiet with focus, doesn't appear to have enough volume and follow through. Not sure I understand the theory but it appears a vortex simply makes a wave through the air and doesn't transmit a slug...

Using Boyle's law taking say a 1 cu ft storage vessel at 60psi and releasing it to atm you've got an expansion of around 4 cu ft. So I'm thinking that is the path I need to go - V1 to V2 kind of calcs and trials....

I've also got to consider nozzle sizes and types. I definitely have to ensure the stuffed animal goes into the receiving tube and not veering off into the scene.
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Unread postAuthor: ramses » Sun Jan 24, 2010 7:41 pm

Since this is a movie, do this in an echo-free environment and just cut out the "ka-F*kin BOOM" part of the sound track out. Resume in time to hear the animal hit the bottom of the pit. Record some background noise and stick it where the artificial silence would be to make it sound more natural.

That said, build this.
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Unread postAuthor: Insomniac » Sun Jan 24, 2010 8:33 pm

No, vortex cannons actually propel a ring of gas across a distance... If you put smoke into the laucher, the ring will be filled with smoke as it travels.

And yeah, if this is for a movie, why not fake it? You can record the scene and then add some seperately recorded ambient noise and sound effects, just like they do for most real films.
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Unread postAuthor: bionic » Sun Jan 24, 2010 10:36 pm

Guys thanks for thinking out of the box on this one. I'm impressed at all the multitude of designs that have been modded in this hobby and community. From all I've researched in just a day or two as an outsider I'd say we need to take this to the next level and focus the pursuit for the perfect potato launch into something bigger.

I'm talking time travel here.

So I'm enlisting you - the experts - to help with a simple problem - but put the movie part out of your heads.

Quiet is do-able. Think smaller - we just have to move the object quickly from point a to point b.
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Unread postAuthor: Ragnarok » Mon Jan 25, 2010 12:09 am

No cannon is going to be particularly quiet, nor necessarily "invisible" - cameras can see somewhat into the infrared region, so the water vapour in the muzzle blast may well show up.

While this is a cannon forum, I'm always one to look at other possible solutions to a problem. Might I suggest something like the standard "blown across the room" rig?

Just fit the thing with some kind of fine wire (fine enough that the camera can't see it...), arrange wire as appropriate with pulleys, etc... then yank hard on the other end when you want it to go flying.
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Unread postAuthor: bionic » Mon Jan 25, 2010 10:43 am

Cool, the problem with wire or string is that this is to be repeating. Right to left. I need high speed. I've thought about taking an air cylinder and removing the piston seals. This way it will be very fast pusher and somewhat quiet. Then I'll just have to use a 3 way valve to control.

What I am leaning toward is a small 3 gal tank from Harbor Freight, a sprinkler valve, and pipe to a 90 elbow. Wondering on nozzles now...


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Could also fit a suppressor on the end. Has that been done before?
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Unread postAuthor: jmadden91 » Mon Jan 25, 2010 11:10 am

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Unread postAuthor: john bunsenburner » Mon Jan 25, 2010 11:47 am

The suppressor is meant to get rid of as much extra air as possible...it would be contra-productive in this case, as it would make the sound less intense while also making the blast less intense...

Why not use an industrial size vacume(sure you can borrow one if you ask nicely) to suck the object into the tube and then a compressor to blow it back out?
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