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Unread postPosted: Tue Nov 03, 2009 10:51 am
Author: qwerty
Bonus points on how the photo was taken. Most likely a helium balloon or RC aircraft. Due to the clarity, I would guess balloon.


My guess is still a balloon but a not a heluim balloon. Solar balloon?

Unread postPosted: Tue Nov 03, 2009 11:45 am
Author: Lentamentalisk
psycix wrote:Why do you have to use a burst disk? I'd go for the convenience and the reliability of a premade valve, like a sprinkler or QEV.
Heck, if you use a hammer valve as pilot, you might close the valve right before the projectile exits, leaving some pressure in the chamber, way more silent launcher.


Exactly my thoughts, but based on my previous experiments with a
compact portable antenna launcher, I have decided against it. It is just really hard to get it to be small enough, without limiting the flow too much. A burst disk would provide me with no restriction what so ever, in a tiny, collapsible form.

Unread postPosted: Tue Nov 03, 2009 12:05 pm
Author: psycix
If you want it to be portable, why not go coaxial? Very compact.
It also makes it look like a piece of pipe.
You give me the impression that you want to make it stealthy, silent and disguise-able for shooting in an urban area so coaxial might make it easier to carry it through town.

Unread postPosted: Tue Nov 03, 2009 12:11 pm
Author: kenbo0422
Make the outside all the same size, put a shoulder strap on it with easy to remove end caps, and tote it around like its a protective case for large documents like maps or blueprints. :idea:

Unread postPosted: Tue Nov 03, 2009 12:34 pm
Author: Technician1002
psycix wrote:If you want it to be portable, why not go coaxial? Very compact.
It also makes it look like a piece of pipe.
You give me the impression that you want to make it stealthy, silent and disguise-able for shooting in an urban area so coaxial might make it easier to carry it through town.


I haven't posted it here, but I made one. I didn't post it because it is entirely thinwall PVC. I'll have to grab photos later. It launches golfballs. The ends are recessed inside the chamber so there are no protrusions. The ends are assembled by gluing couplers inside the ends of the chamber. The muzzle is a GB pipe in a coupler (not filed out) with the coupler glued inside the chamber. The breech is a female threaded coupler glued in the other end. A recessed end with a 1/4 inch ball valve with a really short handle is inside the pipe plug as the hidden trigger. Some custom modifications were needed to get the parts to fit in this unapproved manor. :D In operation, it can hardly be called stealth. It's noisy.

Unread postPosted: Tue Nov 03, 2009 12:44 pm
Author: Lentamentalisk
I will give the burst disk method a try, and if that doesn't work for me, then I will definitely give a coaxial a try. My concept is just that you shouldn't make something more complicated than it needs to be, and nothing is more simple than a burst disk.

Unread postPosted: Tue Nov 03, 2009 12:49 pm
Author: Technician1002
Lentamentalisk wrote:nothing is more simple than a burst disk.


Until you go shooting a lot. :) Releasing the trigger and adding air is about as simple as it gets. No disassembly needed to reset.

Unread postPosted: Tue Nov 03, 2009 3:34 pm
Author: psycix
nothing is more simple than a burst disk.

nothing is less of a hassle than a burst disk.

Unread postPosted: Tue Nov 03, 2009 5:09 pm
Author: Lockednloaded
i have made a 1.5" burst disk cannon using DavidVanini's method, it has a tiny chamber volume, i charge it up to 120psi with a CO2 tire inflator, it is nearly silent and packs quite a punch with key limes :lol: . I wish you good luck with yours, and hope to see it soon

P.S. I did not have a 1.5" union for this project so instead it uses a 1" union, which i think is ideal because if my math isn't incorrect you don't need as thick of a burst disk, 5 layers of Aluminum Foil holds pressures up to 120psi (where the disk pops)

Unread postPosted: Tue Nov 03, 2009 5:09 pm
Author: Lockednloaded
accidental double post (pressed submit twice)

Unread postPosted: Thu Nov 05, 2009 2:03 am
Author: Lentamentalisk
Well I went out and bought the 1.5" SCH80 threaded union, with an o-ring, only to find that my PVC cement had completely dried, in the nearly two years since I last opened it. The same was true for the ABS cement. Maybe that is what has been making my asthma act up... It turns out I don't have any specialty glues in the entire house other than some Zap-a-Gap. The epoxy is all used up, and my Plumbers Goop is nowhere to be found. I will have to find the time to stock up again...