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CpTn_lAw's 5th pneumatic

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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CpTn_lAw's 5th pneumatic

Unread postAuthor: CpTn_lAw » Fri Nov 07, 2008 5:04 pm

Hey guys! well well well...it's been a long time since i last posted a cannon here...guess what? time for a new round!!

So..."what gave you the idea of making this? :D "
Simple my good man !! I wanted a powerfull, steel, burst disc cannon, without having the crap of not exactly knowing when it would fire...so, i thought i could add a ball valve behind the union where stis the burst disc!

Results?
Amazing! the burst discs i use can hold up to 15 bars, so...plenty of air!! I filmed my self shooting in slow motion (600 fps) to see when the air comes out. Well, burst discs explode when i have opened the ball valve at its 3/4 th.

Power is here, no need to search for really more, almost 900 fps (slow motion helps for estimations) with a 4 gram (60 grains) marble, 600 fps with a 10 gram lead sinker, 400 with a 15 grams sinker. (big 7/16" lead balls) that is with a burst disc. When i get tired of changing the disc i simply use extreme tight fit projectile (usually need to push them with a hammer) so that gives me quite the time to open the valve.
Stiil, efficiency is way better with a burst disc. (8 layers of alluminium foil)


The chamber is 1" wide, 1' long. barrel, 1/2" wide, 3,2 ' long.
All materials with nominal pressure of 25 bars. (± 400 psi) i am below the nominal working pressure of the components.

Here is a video i made, be sure there will be more. (i have bought glow sticks, and i'm gonna shoot them against targets in 300 fps slow motion)

[youtube]http://fr.youtube.com/watch?v=1ui1vDT9aXo[/youtube]
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Re: CpTn_lAw's 5th pneumatic

Unread postAuthor: jackssmirkingrevenge » Fri Nov 07, 2008 6:34 pm

CpTn_lAw wrote:[youtube]http://www.youtube.com/watch?v=1ui1vDT9aXo[/youtube]
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Unread postAuthor: CpTn_lAw » Sat Nov 08, 2008 4:54 am

thanks for the link, i couldn't get it right ;)
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Unread postAuthor: elad311 » Sat Nov 08, 2008 6:08 am

Very cool cannon! :D
But, does it works with a ball valve?!
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Unread postAuthor: starman » Sat Nov 08, 2008 10:34 am

Sounds like a pretty elegant idea although you're still going to have to open the ball valve quickly and completely to make sure you don't have a flow restriction. Keeping the disk at a high psi rating will offset this to some degree.

Maybe someone else has done this before but I haven't seen it .... nice work Cptn! Also, replacing the ball valve with a sprinker valve may offer a small benefit.
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Unread postAuthor: CpTn_lAw » Sat Nov 08, 2008 11:34 am

I thought of it, but most sprinklers can only safely go up to 150 psi...I'm thinking of a spring-loaded trigger system...but i can't find how to make it clean...
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Unread postAuthor: grumpy » Sat Nov 08, 2008 11:37 am

ignore me i'm on meds right now, going to bed.
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Unread postAuthor: starman » Sat Nov 08, 2008 12:09 pm

CpTn_lAw wrote:I thought of it, but most sprinklers can only safely go up to 150 psi...


True enough. Even so, if you limited a gun to 150 psi but with a burst disk transition, you could have a very good performer indeed.
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Unread postAuthor: CpTn_lAw » Sat Nov 08, 2008 3:41 pm

Yeah, sure, but without the big "bang" all the smoke due to high pressure, and well, 300-400 psi gives more power than 150 even with a burst disc...and i have the luxury of having a bust disc AND 300-400 psi. I think a strong spring loaded mechanism will do just fine


Edit:
Here is one 225 grains lead sinker i shoot. Image

I've just done a test shot against a phone book...lol, i don't have the pic, i'll have it as soon as my camera is charged up, but it's pretty self-explanatory about the power compressed air can have...
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Unread postAuthor: FishBoy » Sun Nov 09, 2008 9:25 am

Nice build and all, but where did you get a round lead sinker??
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Unread postAuthor: Fnord » Sun Nov 09, 2008 9:45 am

What kind of camera is that, by the way?
I've been looking for a decently priced high frame rate camera for a long time.
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Unread postAuthor: CpTn_lAw » Sun Nov 09, 2008 10:09 am

my camera is a casio EX-F1. you can get it for around 750 $.
I get these sinkers at "decathlon" a sports store near my house. they range from .2 gram to 20 grams. they have ogival sinkers, round balls, etc...
it's here that i get the glowsticks too. They have .45 cm ones, 6mm ones, and big fishing ones, like 10cms long, glow for 9 hours...but they are not cheap.
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