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Galvanized steel maximum pressure?

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
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Galvanized steel maximum pressure?

Unread postAuthor: daniele tn » Sat Jan 22, 2011 6:00 pm

Hi guys,
I was thinking about making another medium piston gun, all copper and galvanized steel, does anybody know if it is safe to use 1" galvanized tees and pipes at 30-40 bar?
Thanks
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Unread postAuthor: saefroch » Sat Jan 22, 2011 6:04 pm

Yup, you'll be quite safe. You could run up to 70 bars without much reasonable fear.
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Unread postAuthor: daniele tn » Sun Jan 23, 2011 5:28 am

Thanks saefroch!
When I will be done with my exams expect some true POWER :twisted:
(if I can find a fridge....)
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Unread postAuthor: jackssmirkingrevenge » Sun Jan 23, 2011 5:44 am

daniele tn wrote:expect some true POWER :twisted:
(if I can find a fridge....)


Out of context, it's almost like you're going to compete in a flatulence contest :D
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Unread postAuthor: saefroch » Sun Jan 23, 2011 3:06 pm

There are other ways to get a really high pressure system. Mine certainly isn't the only two-stage on the site, look around and you'll find other designs.
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Unread postAuthor: FighterAce » Sun Jan 23, 2011 3:13 pm

My interest in two stage pumps jumped ~3 hours ago... I've been designing one with 3/8 NPT threaded parts and aluminum cylinders until now :D

Check this out. Mine will basically be a copy of his pump but without copper parts :D
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Unread postAuthor: saefroch » Sun Jan 23, 2011 10:14 pm

It's a very effective design, but I don't have the machining ability to make a pump with a head that wide. Luckily, you do. Just make sure you have a significant difference in head diameter. With a 1" diameter head and a .5" diameter head, it's about 1.5 strokes on the 1" diameter head to one stroke on the .5" head to maintain the pressure between them.

Two-stages are amazing. Flat-out amazing.
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Unread postAuthor: Brian the brain » Mon Jan 24, 2011 4:28 pm

40 bar is never safe.
Never treat it as if it is safe...
Doublecheck everything!!

What thickness is the material?
Are there welds involved?
How far do you thread it in?
What's the diameter???? As diameter goes up, pressure rating goes down..

Are there other forces involved: long reservoir hanging on a single brass fitting for instance? support the structure if needed.
Even if it seems strong enough, over time you can create metal fatigue at a point that vibrates at every shot.Even if you don't see it.

If you know what you're doing, you can hold 40 bar in galvanised steel, but it depends on a lot of factors to just answer " yes"

I have made cannons using unregulated CO2 at roomtemp ( assuming 55-60 bar) but that is no guarantee.

I understand the quest for power, but I must emphesise the need for safety.
First hydrotest it.
Fill up the cannon with water instead of air and then pressurise it to at least 50% over your required firing pressure.
Water is (almost) non compressable, so it will store far less energy.
In case it blows, you're better off with a water filled cannon..

You really need to know if it will hold before you fill it up with air at 40 bar and hold it in your hands..
Also...treat it like it may go off any time, so always point it somewhere safe!
Piston valves CAN fail resulting in an unintended shot.
Not something you'd want ,especially at those pressures
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Unread postAuthor: daniele tn » Tue Jan 25, 2011 4:37 pm

Thanks for the help everyone.
Yes, I could go for a 2 stage pump, I have already build one that cold take my old 16 mm piston gun to 18/20 bar but it really was time consuming, and for this gun I am planning for a large resorvoir in order to have multishot capability.

The maximum diameter I planning to use is 1" for both tees and pipes.

BtB, I live in Belgium so the tees should be the same as in the Netherlands, the ones you can get from Brico.
Once I have my compressor I will pressure test the materials in a safe area first, and then (if they are still in one piece) use them safely.
Don't worry about "pointing in the right direction", I am used to different airguns, homemade and not, and my 70lbs bow, which really is dangerous...
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