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Interchangeble Chambers

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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Interchangeble Chambers

Unread postAuthor: Jared Haehnel » Tue Feb 26, 2008 9:22 am

In light of my new project a lot of interesting Ideas have been posted and they have been very helpful.

I thought of this after posting a remark about the amount of pressure spudders generally use in PVC. The small diameter pipes can hold a higher amount of PSI then the larger ones.

For Example.

4" =220 psi
3" =240 psi
2" =260psi
1.25" = 370 psi
1" = 450psi

So why not make interchangeable chambers that can hold higher psi or hold more volume depending on the barrel you use and the objects you are launching. Might be too much work. But that way we would only have to make one valve that can withstand a wide range of pressures, and be unrestrictive to a wide range of flow?

Does it make sense at all? And is it really worth while?
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Unread postAuthor: bigbob12345 » Tue Feb 26, 2008 9:28 am

never use sch40pvc above 150psi no matter what the diameter and rating, period.
But the interchangeable chambers idea isnt so bad it would be useful if you live in a crowded enviorment and want to fire off your gun but cant because of the noise it would make.
But it just wouldnt be worth the effort.
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Unread postAuthor: brogdenlaxmiddie » Tue Feb 26, 2008 9:37 am

the only way that I would find that effective, is if I had just built/paid a helluva lot of money/work to get the valve. Otherwise, Just do what I did, Build a couple of guns for differnt uses. :D
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Unread postAuthor: Jared Haehnel » Tue Feb 26, 2008 10:21 am

Yeah, thats what I figured, isn't worth the effort. Just thought I would post the idea.

And I would agree 150psi is plenty for sch40 pvc pipe. Just found the ratings to be interesting. Never had paid much attention before. I assumed 220psi was for all the pipes.
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Unread postAuthor: bluerussetboy » Tue Feb 26, 2008 11:01 am

while the general feeling on this forum is not to use pvc over 150 psi, it can be taken higher. but why do it? and why interchangeable chambers?
let's say you make a 1" copper chamber that you feel comfortable taking to 400 psi(i have no idea what 1" copper is rated for). why spend more time and money building another chamber when all you have to do is lower your pressure?


beside you'll stay on DYI's better side if you don't even mention high pressure in pvc :wink:
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Unread postAuthor: Jared Haehnel » Tue Feb 26, 2008 12:01 pm

Honestly I like the things I build to be versatile. For experimentation.Thats the only reason. And I don't plan on taking any of my cannons to that pressure. I design them to work the best at around 125 - 150 psi.
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Unread postAuthor: Lentamentalisk » Tue Feb 26, 2008 2:18 pm

the real reason for making interchangeable chambers is for different volumes, to go along with your different barrel lengths. It is ridiculous to fill up the tank that you use for the 10' barrel, when you are shooting out of a 2' barrel.
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Unread postAuthor: Jared Haehnel » Tue Feb 26, 2008 2:43 pm

Thats more what I was getting at...I worded it all wrong.

Build a valve/chamber system that can easily adapted for a variety applications. That way you save on the cost of building everything from scratch if you decided to launch something thats doesn't need all that push or expand a chamber to improve the performance of something that needs a bit more power.... That was more of my Idea I went too far with the PSI thing.
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Unread postAuthor: Solar » Thu Feb 28, 2008 6:08 am

The Eclipse launcher uses the interchangeable volume chambers for the very reasons above. If in use for shark repellent cannister launching it will most likely be attached to a 150-200 psi scuba regulator. To achieve enough power at those pressures to launch an 8 oz. projectile into the surf, a larger chamber is used. For paintball shot rounds at 300psi a smaller chamber is used to increase rate of fire numbers. The end caps are removable so all that is needed is to change out the length of the center tube.

Image
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Unread postAuthor: jr » Sat Mar 01, 2008 11:31 pm

correct me if i'm wrong but don't piston valves work in a certain psi range.... so changing the chamber would alow you to keep the psi to operate the valve and change the distance the projectile will travel?
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Unread postAuthor: Solar » Sun Mar 02, 2008 1:55 am

Piston valves will open with any pressure great enough to overcome the return spring and the force of the pressure holding the valve closed(which is vented to ambient). The piston valve in the Eclipse uses the difference in surface area of the piston and valve plug faces to operate. Still, only need to overcome the force of the pressure pushing the valve closed with just slightly greater force than the spring and back pressure.


Larger ballast chambers will maintain the pressure for a longer time. At some point there is no advantage once the ammo has left the barrel. I feed the 3/4" port with a .975 tube connected to a 1.5" chamber.
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