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Air tank construction ( Only 1.5" ID ) ? Aluminum

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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Air tank construction ( Only 1.5" ID ) ? Aluminum

Unread postAuthor: tatfree » Fri Mar 12, 2010 7:12 pm

I am wanting to construct my air chamber using a 6061 Aluminum tube that will be .125" side Wall X 1.5"ID and 22" long .
I will be pushing 200 PSI Max into this chamber.

I know the weekest point of the chamber will be the ends, since I am assuming the sidewalls of this tube can handle over 900psi.

I am an experianced Tig welder, but have never constructed a tank before. I will weld one end of the tube closing it up and the other end will have a plate welded on that will have the proper threads on it.

Can anyone guide me to the correct info for how to make this or is this something that is looked down on ?

Thanks
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Last edited by tatfree on Fri Mar 12, 2010 7:38 pm, edited 2 times in total.
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Unread postAuthor: Gippeto » Fri Mar 12, 2010 7:29 pm

Working pressure calculator...use yield strength and minimum safety factor of 3.

http://www.engineersedge.com/pipe_bust_calc.htm

As to the ends...welding is a crap shoot from where I sit...of course I can't draw a bead worth s**t. :) With sheet metal ends, unpredictable penetration....there's really no way to do it safely without hydro testing a sampling....and you'll only want to make one.

Threading such a thin tube also leaves very little material remaining to handle loads.

I would make end plugs to fit inside the tube, and cross bolt with socket head cap screws sealed with quad rings or o-rings. It's relatively easy to determine the strength of such an arrangement with simple calculations.

Shear strength = (Ts*.60) * area (calculated using minor diameter of the object in question...the screw or pin)

Most calculations are usually done using UTS (Ultimate Tensile Strength)...I prefer to use yield strength for any calculation, as it increases the safety factor, and in the "event" it's better to stretch a part than have it give out completely. JMO.

Force on the plug... Pressure * exposed area of the plug
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Unread postAuthor: tatfree » Fri Mar 12, 2010 7:36 pm

Gippeto wrote:Working pressure calculator...use yield strength and minimum safety factor of 3.

http://www.engineersedge.com/pipe_bust_calc.htm

As to the ends...welding is a crap shoot from where I sit...of course I can't draw a bead worth s**t. :) With sheet metal ends, unpredictable penetration....there's really no way to do it safely without hydro testing a sampling....and you'll only want to make one.

Threading such a thin tube also leaves very little material remaining to handle loads.

I would make end plugs to fit inside the tube, and cross bolt with socket head cap screws sealed with quad rings or o-rings. It's relatively easy to determine the strength of such an arrangement with simple calculations.

Shear strength = (Ts*.60) * area (calculated using minor diameter of the object in question...the screw or pin)

Most calculations are usually done using UTS (Ultimate Tensile Strength)...I prefer to use yield strength for any calculation, as it increases the safety factor, and in the "event" it's better to stretch a part than have it give out completely. JMO.

Force on the plug... Pressure * exposed area of the plug


Actually I edited my post because I typed the wrong thing. The ID will be 1.5" and the side wall is much thicker @ .125".
In my experiance a weld is WAY stronger than threading .
Thanks
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