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1/2 galv steel gun

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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1/2 galv steel gun

Unread postAuthor: Clutch » Sun Apr 19, 2009 9:16 pm

Hi i was at Lowes and had a bit of an impulse to make a galvanized steel gun. I bought:

1/2 x 32in black steel(for barrel)
(2) 1/2 elbows galvanized steel
1/2 x 8 in black steel (for chamber)
(2)x 1/2 galvanized steel threads (A 2 inch piece of pipe with nothing but thread)
1/2 galv steel endcap
and finally a 1/2 inch threaded Ball valve (YEA i know ball valves SUCK)

It's all threaded pipe so it was easy to connect with some thread sealer and some force. The only problem is filling it with air!?!?! I cut a valve off a bicycle innertube and burned off the rubber, so it left me with a brass(?) fill valve, i drilled a hole in the end cap that matches the valve. Shoved the valve in the hole (With a hammer, no dought) and sealed it with some silicone.


Only problem is the fill valve leaks REALLY bad, constant filling with an air compressor only holds about 80 psi. leaking out air really fast.

HOW can i seal (Or can i just buy a threaded fill valve?) that valve up. I want this steel pipe to hold like 500+ PSI!! :twisted:

(Btw how much CAN galv steel/black iron hold before it fails..)
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Unread postAuthor: jmccalip » Sun Apr 19, 2009 9:28 pm

I wouldn't go above 100PSI. I think black iron is rated to 150PSI of steam.


What you are looking for is a schrader valve.
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Unread postAuthor: Clutch » Sun Apr 19, 2009 9:39 pm

You do realize black "iron" is steel pipe with a black finish, right?


"STANDARD GALVANIZED STEEL PIPE
# A-53-A Schedule 40
# Steam to 600 PSI,
# Water, air, oil to 720 PSI
# -20 to 400 Deg F "


720 PSI. A little bit higher than 150 :)
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Unread postAuthor: Clutch » Sun Apr 19, 2009 9:41 pm

And also, a "bike" valve is a schrader valve coated in rubber, which i burned off. So i have a brass schrader valve, but it's not threaded. I was needing to know how i could seal it.

(steel pipe + brass fittings? ) I don't know if you can weld/solder that. . .
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Unread postAuthor: c11man » Sun Apr 19, 2009 9:47 pm

i wuld just buy a threaded one
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Unread postAuthor: Clutch » Sun Apr 19, 2009 9:51 pm

It seems to me i have to buy a threaded valve ( i guess the kind for an air-compressor quick connect)?)

because a schrader valve apparently fails at 70 psi, anyway.
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Unread postAuthor: MountainousDew » Sun Apr 19, 2009 9:55 pm

Clutch wrote:because a schrader valve apparently fails at 70 psi, anyway.


Umm, no they don't. I have taken mine way passed 120 psi, with no leaks or failure...

And also quick connects don't seal when you disconnect the thing filling up the gun with an awesome invention called, "air".
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Unread postAuthor: inonickname » Sun Apr 19, 2009 9:58 pm

No, they don't fail at 70. They CRACK at 70 psi, which means they open and act like a check valve at 70 psi from the fill side. It leaks because you either didn't use teflon tape on the threads OR didn't glue the valve in well..or both.
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Unread postAuthor: jmccalip » Sun Apr 19, 2009 10:04 pm

Clutch wrote:You do realize black "iron" is steel pipe with a black finish, right?


"STANDARD GALVANIZED STEEL PIPE
# A-53-A Schedule 40
# Steam to 600 PSI,
# Water, air, oil to 720 PSI
# -20 to 400 Deg F "


720 PSI. A little bit higher than 150 :)


Seamless pipe has a MUCH higher pressure rating. 1" Pipe that has a seam is 150 psi. Look for a line/weld on the side of the pipe. I'd assume 1/2" is a little more, but not 500psi.

You could have a steel grenade on your hands, so be careful! :o
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Unread postAuthor: frankrede » Sun Apr 19, 2009 10:16 pm

jmccalip wrote:
Clutch wrote:You do realize black "iron" is steel pipe with a black finish, right?


"STANDARD GALVANIZED STEEL PIPE
# A-53-A Schedule 40
# Steam to 600 PSI,
# Water, air, oil to 720 PSI
# -20 to 400 Deg F "


720 PSI. A little bit higher than 150 :)


Seamless pipe has a MUCH higher pressure rating. 1" Pipe that has a seam is 150 psi. Look for a line/weld on the side of the pipe. I'd assume 1/2" is a little more, but not 500psi.

You could have a steel grenade on your hands, so be careful! :o
I have taken 1 1/4" seamed pipe to over 500 psi and it is fine, a member of this site actually did a pressure test to discover when it would fail.
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Unread postAuthor: dudeman508 » Sun Apr 19, 2009 10:21 pm

frankrede wrote:
jmccalip wrote:
Clutch wrote:You do realize black "iron" is steel pipe with a black finish, right?


"STANDARD GALVANIZED STEEL PIPE
# A-53-A Schedule 40
# Steam to 600 PSI,
# Water, air, oil to 720 PSI
# -20 to 400 Deg F "


720 PSI. A little bit higher than 150 :)


Seamless pipe has a MUCH higher pressure rating. 1" Pipe that has a seam is 150 psi. Look for a line/weld on the side of the pipe. I'd assume 1/2" is a little more, but not 500psi.

You could have a steel grenade on your hands, so be careful! :o
I have taken 1 1/4" seamed pipe to over 500 psi and it is fine, a member of this site actually did a pressure test to discover when it would fail.



When did it fail?
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Unread postAuthor: Cosmic Muffin » Sun Apr 19, 2009 10:40 pm

if it leaks from the valve, you probably melted the rubber o-ring sealing the valve when you heated it up to remove the outside rubber.
in future just cut it off with a knife or get a special spanner and remove the inside of the valve :wink:
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Unread postAuthor: jmccalip » Sun Apr 19, 2009 10:42 pm

frankrede wrote:
jmccalip wrote:
Clutch wrote:You do realize black "iron" is steel pipe with a black finish, right?


"STANDARD GALVANIZED STEEL PIPE
# A-53-A Schedule 40
# Steam to 600 PSI,
# Water, air, oil to 720 PSI
# -20 to 400 Deg F "


720 PSI. A little bit higher than 150 :)


Seamless pipe has a MUCH higher pressure rating. 1" Pipe that has a seam is 150 psi. Look for a line/weld on the side of the pipe. I'd assume 1/2" is a little more, but not 500psi.

You could have a steel grenade on your hands, so be careful! :o
I have taken 1 1/4" seamed pipe to over 500 psi and it is fine, a member of this site actually did a pressure test to discover when it would fail.


Hmm, well I was just going by the rating. I personally wouldn't risk it since each batch may be different, but it's your call.
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Unread postAuthor: jackssmirkingrevenge » Mon Apr 20, 2009 12:12 am

Cosmic Muffin wrote:if it leaks from the valve, you probably melted the rubber o-ring sealing the valve when you heated it up to remove the outside rubber.


My thoughts exactly :roll:

In future just cut it off with a knife or get a special spanner and remove the inside of the valve :wink:


What I do is put it in a drill and file down the rubber.
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Unread postAuthor: jook13 » Mon Apr 20, 2009 12:24 am

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