Burst Disk or Ball valve

[rsgpit]

I was about to go get materials for a ballvalve cannon, but just made a mini burst disk cannon out of a 1liter gatorade bottle and bikepump(shoots AAA batteries 200 yards), and was thinking should i make a burst disk cannon or a ball valve cannon.

And, how is the best way to make a burst disk union without ripping tin foil, cause i had to move to glad wrap for my mini.

[spudshot]

a burst disk cannon will outperform a ball valve cannon if it bursts at the same pressure, what i do is take a piece of aluminum foil, and the side of the union with the O-ring, and trace around the union with a sharpie marker, then cut out the circles, do that about 100 times, and cut them out while watching TV, you wont notice how long it takes you to cut them out

[julz]

can someone draw a pic of how burst disck work plz. i still dont get them properly.
thanks.
---Julz

[rsgpit]

A burst disk is a piece of material that acts as a valve. It sits between the barrel and compression chamber of a simple BD cannon. When the pressure gets high enough, it rips the material, or you can send a sharp object in to do that job.

I think im gonna get a spring loaded popping device to do that, or should i just do ball valve.

[spudshot]

why use a ball valve? they're just about the worst valve you can use, try getting a hold of a sprinkler valve or a QEV, or build yourself a diaphragm or piston valve, anything would be better than a ball valve

[julz]

i get it now. i thought it was like that and it just bursts when it gets x pressure but i thought that would be a little dangerous and unpredictable. a pin make a lot of sense. thanks Rsgpit.
---Julz

[Aaron ?????]

you could have both like the ball valve then the burst disk after that

[spudshot]

julz, most burst disk launchers do just burst at any pressure, andeh found a way to control it look for his launcher under pneumatics. i dont see why it would be dangerous because you should always have your gun pointed in a safe direction anyway

[Rambo]

Will there be any differense between tha ball valve and sprincler valve if the barrel is 1'' and 1m long.The projectile is from lead at lest 150gr.Will the preformance be better for ball valve if there is deth spase?Did some one try to use a rubber band for a ball valve ?What is the maximum preshure of a sprincler valve? And what's price of the cheapest spr. valve?

[theregoesthewindow]

One of the reasons a ball valve is so bad is because it has a human element to it. It depends on how quickly you can flick the valve open. Another is because there is almost no possible way for you to flick it open as quickly as a piston or diaphragm valve opens, I think. *enter BLB* But most likely the sprinkler will be better.
I don't really know what you mean by "deth spase" but you might be refering to space after the valve and before the projectile? If so then I don't think that dead space helps any valve.
Someone used a spring for a ball valve here http://www.spudfiles.com/forums/viewtop ... &lighter=&
Sprinkler valves usually go up to 120, but one brand goes to 150 and there are special ones that go even higher (I think)

[dragon finder]

Yeah ones made of metal.

[spudkid22]

can someone tell me how to make the gatorade burst disk cannon

[theregoesthewindow]

If by gatorade burst disc cannon you mean a:
1. hybrid, no do some research *look in the hybrid section*
2. burst disc pnuematic that uses gatorade bottles as a disc source, yes just build something like this http://www.spudfiles.com/forums/viewtop ... &lighter=&
3. combustion burst disc, don't think it'll work but you can try

next time please be more specific/do your homework

[boilingleadbath]

Rambo, why can't you run GGDT?
Just in case there is an acctual reason you can't, I'v done it for you this time...

Using a reasonable geuss for the chamber (23 in^3), a burst disk at 100 psi will get your 150gr (~9g) projectile to 530 fps.
At 150: 636 fps, at 200: 714 fps.

Using a ballvalve (same chamber), opening time 90ms:
100 Psi yeilds the highest velocity with a full 14 in^3 of dead space - 321 fps.
150 gives 364 fps @ 14 in^3
200 gives 397 fps @ 14 in^3

Some people have done spring-actuated ballvalves, and I personly just tie a string to the handle - yanking it gives me fast enough actuation for a pilot valve.

Sprinklers cost anywhere from 10-20$ (roughly) plus shipping for a 1" valve. Note, however, that that's American - our costs are a bit inflated over here.

[Brian the brain]

I think he is best off just using the ball valve to actuate a home made piston.

Rambo, look up piston valve in the Wiki.
Ballvalves are slow.Also with a spring.( opening must be in milliseconds.
If you use it with a piston it will open a lot faster.
The piston pops open.
If you just use a ballvalve it's more of a ...woooooshhh
The projectile will leave the barrel at minimum pressure that way.
Piston valves pop open very fast and the projectile gets full pressure almost instantly.