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burst disc bouncy ball cannon

Unread postPosted: Tue Jul 13, 2010 10:45 am
Author: skishoot
My friend and I built this cannon is it a triggerable burst disc, it uses two one inch unions and a ball valve for the valve and has a 24in by 2in chamber. The barrel is 1in pvc about 50in long and the whole gun is 8' 3" long. I assembled the piolit valve so that there is a 1/2in endcap after the 1/2in valve with a hole in it so that all of the air doesn't rush out of the piolit after the first disc breaks and this still does happen with low pressure. At 35 psi I can't even see the ball go out of the barrel. I am hopefully going to paint it red and name it something better that "burst disc bouncy ball cannon" my whole valve is one inch threaded on both sides so I can replace it with a 1in sprinkler valve or a ball valve which I wont ever do. Firing video soon. does anybody know any other ammo that fits in 1in pvc I will post a video of me firing it if I like the idea. Oh yeah by the way this is my first good cannon so any critisism is welcome

Unread postPosted: Tue Jul 13, 2010 11:32 am
Author: c11man
nice cannon but there are some improvements than can be made. first of all cant quite tell bu the coupler on the chamber appears to be DWV but only a better pic would confirm this.

also the MASSIVE dead space between the burstdisks is killing your preformace. you want that area to be as small as possible and if its small the gun will fire faster after opening the ball valve and with less wasted power.

<a href="http://s696.photobucket.com/albums/vv321/c11man/?action=view&current=100_8630.jpg" target="_blank"><img src="http://i696.photobucket.com/albums/vv321/c11man/100_8630.jpg" border="0" alt="Photobucket"></a>
this is a example of a a setup with less space but its even this example could be i proved

otherwise i bet you are having fun with the preformace of burstdisk :D

Unread postPosted: Tue Jul 13, 2010 11:34 am
Author: Technician1002
does anybody know any other ammo that fits in 1in pvc


I used 1 inch quite a bit in my Mouse Musket, and later with the 1 inch barrel for the Marshmallow cannon.

Some of my favorite ammo is Lemonheads;
Image

Jawbreakers;
Image

Gumballs and marshmallows.
Image

Unread postPosted: Tue Jul 13, 2010 5:37 pm
Author: Zeus
I'll back up what c11man said, it would be quite simple to reduce that
dead space with very few modifications.

Technician1002, you truth omitter. What else fits remarkably well in 25mm PVC? Deceased rodents.

I'm just having a joke, I don't endorse the projection of rodents,
deceased or otherwise.

Have fun with the BD launcher, it's the third best performing valve
that has been designed so far.

Unread postPosted: Tue Jul 13, 2010 5:48 pm
Author: skishoot
I'm keeping the pressure low until I get a better coupler on the chamber, I am aware that it is not pressure rated and am not going to take it over 50 psi until I can rebuild the chamber. I will try to rebuild the valve adventually if I can get a threaded schrader.

Unread postPosted: Tue Jul 13, 2010 5:58 pm
Author: Zeus
A good place to get threaded schrader valves is old fire extinguishers, they are 1/4 NPT. Or you can do this

I've had some fun with one lately

Unread postPosted: Tue Jul 13, 2010 6:13 pm
Author: c11man
if you change over to quick connects you can save space because you can exhaust through it

Unread postPosted: Tue Jul 13, 2010 7:31 pm
Author: skishoot
what pressure can a dwv coupling hold? Will it be ok at 60psi?

Unread postPosted: Tue Jul 13, 2010 9:57 pm
Author: Technician1002
Zeus wrote:
Technician1002, you truth omitter. What else fits remarkably well in 25mm PVC? Deceased rodents.


I listed my favorite ammo for the 1 inch size. I didn't list everything I have stuffed in there. Mice fly poorly, don't have the best barrel seal and most of the time they are limited in supply. I simply listed some of my more common projectiles that fit well. Truth be told, the deceased mouse broke on launch so that was a one time trial. I don't recommend them. They make lousy projectiles.
:lol:

I have personaly tested 4 inch ABS DWV couplings to 100 PSI.

Unread postPosted: Tue Jul 13, 2010 11:07 pm
Author: Zeus
Ok, I'll let you off with that one.

In regards to DWV PVC, it may be fine, then again it could turn you into a
PVC pincushion. I've never built anything from PVC, though I'm
considering it for a casting system for fishing.

I won't recommend DWV PVC because from what I've read.

u get ded frum dwv


You can correct me on that.

Note I make a point of DWV PVC as opposed to just DWV because
of this

Thank you to Technician1002 for posting directly above so I
don't have to find the link.

Unread postPosted: Wed Jul 14, 2010 9:39 am
Author: skishoot
Does anybody know if lowes sells 2in couplings that are sch 40?

Unread postPosted: Wed Jul 14, 2010 9:43 am
Author: skishoot
Have fun with the BD launcher, it's the third best performing valve
that has been designed so far.[/quote]

does a piston valve perform better than a burst disk? what are the better performing valves???

vid soon

Unread postPosted: Wed Jul 14, 2010 5:41 pm
Author: Zeus
Well the "ideal" valve is to make a valveless launcher, most people
would do that with a detent system. The second best is a ball valve,
rather suprising really, considering their reputation.

The trick with ball valves is to open them fast enough.

The reason that burst discs aren't the best is because when they burst,
some material from the disc either goes with the projectile and
slows the flow, or the disc blows out in the middle, and the
remains of the disc around the edge restrict flow.

Burst discs are the simplest high performance valve, but reloading isn't
very fast.

Piston valves are quite good, but they don't perform as well as a burst disc, still they aren't that hard to build, so if you want to make one, go ahead.

I hope that helps, but I've got a habit of writing essays for simple questions.

Unread postPosted: Thu Jul 15, 2010 10:47 am
Author: skishoot
thanks for the advice zeus.