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Max PSI

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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Max PSI

Unread postAuthor: storm33229 » Tue Jan 09, 2007 10:27 pm

I'm not too sure how the modified sprinkler valves actually work. So if someone could also shed some light on that as well... but my question is: what is the max PSI a modified sprinkler valve can handle before it just 'goes off'?

-Storm
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Unread postAuthor: SpudBlaster15 » Tue Jan 09, 2007 11:19 pm

They are rated to 120psi, so I wouldnt go over that.

A sprinkler valve is a basic diaphram valve. When you pressurize your chamber, air bleeds through an opening in the diaphram, into the "cavity" in which your blow gun is mounted. A much larger surface area is exposed on this side of the diaphram, causing it to seat against a stop, sealing off airflow through the barrel. When you actuate the valve, (sqeeze the blowgun) you dump all the pressure on that side of the diaphram in a fraction of a second, and because the air pressure on the other side is now large enough to overcome the surface area deficit, the diaphram is pushed upward, enabling the air to flow into the barrel.
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Unread postAuthor: storm33229 » Tue Jan 09, 2007 11:24 pm

SpudBlaster15 wrote:They are rated to 120psi, so I wouldnt go over that.

A sprinkler valve is a basic diaphram valve. When you pressurize your chamber, air bleeds through an opening in the diaphram, into the "cavity" in which your blow gun is mounted. A much larger surface area is exposed on this side of the diaphram, causing it to seat against a stop, sealing off airflow through the barrel. When you actuate the valve, (sqeeze the blowgun) you dump all the pressure on that side of the diaphram in a fraction of a second, and because the air pressure on the other side is now large enough to overcome the surface area deficit, the diaphram is pushed upward, enabling the air to flow into the barrel.


Ah, well my target PSI is around 200. I've played with 120 and it's just a bit too slow for my liking. So is there any way to buy a pre modified air valve that will hold >= 200 PSI?

-Storm
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Unread postAuthor: squeaks » Tue Jan 09, 2007 11:30 pm

#1 where are you getting a compressor that goes up to 200?

#2 Few people sell them that are rated to that high. You're better off making your own out of sch 80 pipe and sch 80 fittings.
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Unread postAuthor: storm33229 » Tue Jan 09, 2007 11:33 pm

squeaks wrote:#1 where are you getting a compressor that goes up to 200?

#2 Few people sell them that are rated to that high. You're better off making your own out of sch 80 pipe and sch 80 fittings.


Well, I've yet to look for a compressor that goes that high...I was kinda assuming that home depot would have one; if Sch. 80 PVC 1/4" can hold around 600+ PSI, then I was assuming that there would be a air compressor that would pump up to 200 PSI. But yeah, I guess I might have to stick with 120 PSI then... Main reason for that is because I really don't want to have to construct my own air valve.

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Unread postAuthor: sergeantspud2 » Tue Jan 09, 2007 11:42 pm

Your going to have a problem finding a 200psi air compressor. But 120 is more than enough to give you sufficient power to a pnuematic cannon.
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Unread postAuthor: squeaks » Tue Jan 09, 2007 11:43 pm

Well, it depends on your chamber and barrel size. If you have a 1' long gun you aren't going to get a lot of power.
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Unread postAuthor: sergeantspud2 » Tue Jan 09, 2007 11:53 pm

Thats why there isnt much of a point for making mini pnuematics... you dont see pill bottle pnuematics (not pill bottle but similar in size chamber) pnumatics are designed to be BIG! :P
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Unread postAuthor: storm33229 » Tue Jan 09, 2007 11:56 pm

squeaks wrote:Well, it depends on your chamber and barrel size. If you have a 1' long gun you aren't going to get a lot of power.


Chances are that I will be shooting 1/4" or 1/2" marbles out of a 3/4" ID x 2' barrel @ around 120-125 PSI.

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Unread postAuthor: squeaks » Tue Jan 09, 2007 11:57 pm

yeah, just get like a 1.5' 2" chamber. Should work good, I think.
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Unread postAuthor: SpudBlaster15 » Wed Jan 10, 2007 12:15 am

I would aim for a 1:1 - 1.5:1 C:B ratio. After you go above that point, performance does not increase by a noticable amount, and all you are doing is wasting air. For a barrel that small, (.75" x 24") you only need a chamber measuring 1.5" x 6" to acheive a 1:1 volume ratio.
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Unread postAuthor: akaddis » Tue Jan 16, 2007 4:23 pm

my sprinkler valve has a max of 150psi...you can buy it an any hardware store for like 15 bucks....I didn't even mod mine i just used it how it is and used 3 nine volt batteries with 2 switches to make it have an electric trigger. Works PERFECTLY!!
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Unread postAuthor: Bluetooth » Tue Jan 16, 2007 4:27 pm

Pneumatics aren't designed to be big. Have you seen BTBs Sawn-off?
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Unread postAuthor: akaddis » Thu Jan 18, 2007 1:30 am

Bluetooth wrote:Pneumatics aren't designed to be big. Have you seen BTBs Sawn-off?


yeah its pretty small!!
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Unread postAuthor: Hotwired » Thu Jan 18, 2007 9:27 am

If you have pipe to take this 200psi pressure you're after then use a QEV.

I'm using one at 160psi in my copper design that ought to be done by this weekend :)

A few hand/foot pumps go up to 200psi. I'm sure the track pump I've got can do that but the gauge stops qat 160psi and its not a good idea to keep going past it in my opinion :wink:
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