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New Project: Wire-Controlled Air Burst Cannon

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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New Project: Wire-Controlled Air Burst Cannon

Unread postAuthor: SEAKING9006 » Fri Jun 27, 2008 5:18 pm

UPDATE July 24: Cannon complete. Please see the thread on the CA3 PDAB, the completed version.




My next project will be a launcher that fires a round containing flour packed into a clamshell inside a 1-piece sabot. The sabot is attached by a spool of pre-cut high-load fishing line on the rear of the launcher, housed in a small piece of PVC at the rear of the breach. The ammo will be a plastic bottle 1-piece sabot, with a two piece clamshell, made from a soda can. there will be about 6" to 1' of twine attached to the inside of both the clamshell and the sabot. Inside of that, will be loose-packed flour. Future designs will incorporate a trigger mechanism to allow for controlled bursting. This design concept is mostly intended to increase my skills in working with modified fittings and making multi-part ammo. I will begin working on the prototype as soon as I get the fittings I need. On a side note, the tank will probably end up being two sections of 2" on a tee, due to a lack of access to pressure rated fittings above 2".


I have added the third revision of the concept drawing. There is no longer a vulnerable breach hole for the line.

EDIT July 1: The first prototype should be operational by the 17th, depending on when I receive the proper fittings. The design has been finalized and is in the production queue.


EDIT July 22: I will be going to Home Depot today, and I will get all of the necessary fittings and pipe to build this thing. I got a sack of flour yesterday, and the bottles are air-drying as we speak. Gun should be complete in three days, and firing by the end of the week.
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Attachments
WC-AB_Concept1.gif
This is the original concept sketch. It shows the basic configuration with the barrel on the top, the breech behind, followed by the spool assembly, and the tank on the bottom of the tee. Not shown is the type of valve or control system.
WC-AB_Concept1.gif (3.67 KiB) Viewed 1175 times
WC-AB_Ammo.gif
Here is a diagram of the ammo. Self-explanatory.
WC-AB_Ammo.gif (12.92 KiB) Viewed 1175 times
WC-AB_Concept2.jpg
Wire-Controlled Airburst Project, 2'nd Revision.
WC-AB_Concept2.jpg (20.29 KiB) Viewed 1044 times
Last edited by SEAKING9006 on Thu Jul 24, 2008 10:23 pm, edited 4 times in total.
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Unread postAuthor: pizlo » Fri Jun 27, 2008 5:45 pm

It either won't burst until impact, or it will burst right as it leaves the barrel.
Well maybe not, but thats what seems reasonable. Even if it only burst on impact it will still be cool. And realy its just for experience so you can't lose.
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Unread postAuthor: SEAKING9006 » Fri Jun 27, 2008 5:48 pm

Well, it's not meant to impact. It's meant to fly out until the wire runs out, pull taught, and the front part of the shell keeps going for about a foot, thanks to the inertia of the flour. The main sabot keeps it together until then, as it's nothing more than a cup.
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Unread postAuthor: MaxuS the 2nd » Fri Jun 27, 2008 5:48 pm

The clamshell will need to be packed tight enough to not just fall out, but loose enough that when the sabot reaches the end of it's teather, then the shock will force it out.
What happens when you want to fire another shot?
Do you reel it back in and reload?
Would be a bit of a [female doggy] to reel it back in over rough terrain.
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Unread postAuthor: SEAKING9006 » Fri Jun 27, 2008 5:53 pm

No, it won't be reeled in. The breech (either a union or a threaded plug) will be removed. The entire reel assembly is removable. You just pick up another round/reel, slip the sabot into the breech, close the breech, and pressurize the tank. It will be cumbersome, but it's not meant to be used as a combat weapon is airsoft or something. THAT launcher will come later. :wink:
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Unread postAuthor: jrrdw » Fri Jun 27, 2008 5:53 pm

I don't think you will be able to stop the air leak where the string enters the pilot chamber. Air leaks in pilot chambers can cause a miss fires.

I would mount the spool of string/thin wire underneath the mussel and feed the atched down the barrel on top off the loaded ammo. Might yank when the slack takes up out of the string, but if your broad casting your ammo, that might make the yank a plus, I don't know.
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Unread postAuthor: SEAKING9006 » Fri Jun 27, 2008 5:55 pm

It won't leak, because the valve isn't there. That's not the pilot. That's the breach.
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Unread postAuthor: MaxuS the 2nd » Fri Jun 27, 2008 5:57 pm

The Tee gives the impression of a piston valve. I think that's what Jrrdw is referring to.
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Unread postAuthor: SEAKING9006 » Fri Jun 27, 2008 5:59 pm

Yeah, me too. It's just a tee so I can mount the reel assembly behind the breach.
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Unread postAuthor: jrrdw » Fri Jun 27, 2008 6:00 pm

Ok, I want to see what valve your going to use. Are we to understand that the main/firing valve is placed below the tee?
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Unread postAuthor: SEAKING9006 » Fri Jun 27, 2008 6:03 pm

Most likely a modded sprinkler. And yes. That a bad thing?
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Unread postAuthor: MaxuS the 2nd » Fri Jun 27, 2008 6:07 pm

I'd agree with Jrrdw on this one. If you mount the reel underneath the muzzle then it'll both be easier to reload and also the pressurised gas won't vent out the back through the string hole instead of down the barrel.

You will also need to account for the amount of friction. There will be more friction on the twine if it were coming through the back rather than be set underneath the muzzle.

Thats how the pro's do it.
http://www.antennalaunchers.com/csv19/index.html
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Unread postAuthor: SEAKING9006 » Fri Jun 27, 2008 6:15 pm

I was planning to reduce friction by rounding the edges of the hole. Also, I placed it behind the breech to avoid the -yank- that occurs on types with muzzle mounted spools. If that happened with this ammo, it could cause it to burst early. And also to reduce friction, I was planning on using heavy fishing line.
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Unread postAuthor: D_Hall » Fri Jun 27, 2008 7:03 pm

Your string is going to break. As the projectile begins to move forward the string will pull taught. The inertia of the reel trying to spin up will be too much for the string. SNAP.

How to fix?

Don't use a reel. Use a spool. Set it up such that the string is pulled off the top of the spool (so that the spool doesn't have to spin to let string out).

You may still find yourself snapping strings though.

Best bet? Incorporate the spool into the projectile; not into the gun.
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Unread postAuthor: SEAKING9006 » Fri Jun 27, 2008 7:08 pm

How's that going to happen? As long as I use strong enough fishing line, it should work.
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