Aluminium Tube Pressure Rated?

[Gippeto]

Hey Mitch. Might be a good find there.

Is this seamless tube?

Did some quick numbers. Used 2 mm for wall thickness, and 15 mm for od.

No way of knowing the alloy or heat treat I suppose, but as you cannot bend it, I don't believe it is annealed.

6061-0 (annealed) has a yield strength of 8000psi, which gives a burst pressure of 2138.75psi.

6061-T6 has a yield strength of 35000psi, giving a burst pressure of 9333.33psi.

200psi seems to be pretty conservative.

[Mitchza89]

Yeah mate it's seamless tube, hence why I reckon it could be able to hold enough pressure to satisfy my hunger .

Thank you so much for the help with this mate. I reckon I'll be making the first aluminium piston gun on spudfiles pretty shortly. I'm gonna have the chamber as 25mm aluminium tube, all copper fittings, and a 20mm copper tube barrel. It's all gonna be nicely polished.

...Thats the plan anyway .

Cheers mate.

[Gippeto]

Sounds good, I look forward to it!

20mm is going to have plenty of power! Watch the fence.

[Mitchza89]

Hmm I'm a bit concerned... I got most of the parts for the gun. The 25mm aluminium tube is the slightest bit loose in the copper fitting. I'm gonna be using epoxy putty to keep it all together. Do ya reckon this very slight looseness will make a difference in how it's all going to bond?

[Gippeto]

JSR is the epoxy "expert" , maybe pm him.

My suggestion would be to rough both sides of the joint with some 40 grit before you epoxy it together.

Do you have any info on the epoxy? Specifically the shear strength and/or tensile strength?

Might be able to make a better call with those numbers.

[Mitchza89]

Well the tensile strength of the epoxy putty I have is 3000psi. It's a metal epoxy so it might be alright. I'm still worried that the pipe wobbles a tad because the pipe has an OD, about a millimeter smaller then the ID of the copper elbow so it's not quite a tight fit.

Cheers mate.

[Gippeto]

Ok.

Jb weld has a tensile strength of 3960psi, and a lap shear strength of 1040 psi.

Calculated for a 1" tube with a joint length of 1".

Surface area of joint= 3.14in2

Surface area x shear strength =3265.6 (we'll divide by 4 for safety)

= 816.4 pounds (maximum allowable force on joint)

Area of 1" tube =.785 in2

Max pressure = 816.4 pounds / .785 in2

Max pressure = (oddly enough!) 1040 psi

Should double check for the shear strength of the epoxy you will be using though.

What kind is it?

[Mitchza89]

Wow... You really know your stuff Gippedo. I'm very, very impressed...

I can't remember the name of it, but it's an automotive metal epoxy putty... I don't actually have it yet. I just know that I'll be getting it tomorrow . Ehh it should be fine mate. I won't kill myself because I won't be taking this gun high enough to start with.

[dongfang]

Hi

I just want to say - good luck with using aluminium! I just made a pump out of the same tube that you found.

Some time I will try get some aluminium welding rods, and see if I can weld it just with propane. If it works as easily as announced, that would be great for a hybrid..

Why don´t you also use aluminium for the barrel? It´s a much nicer material (IMO) for that than copper: It´s light, it doesn´t get bent as easily, it won´t corrode and look ugly, and no smelly fingers!

Regards
Soren

[Mitchza89]

My thoughts exactly Soren . I really am generally surprised that more people have not gone into Aluminium tubing much at all. I reckon it's a great material to use. The only reason that I can think of, is that it's quite hard to bond together and find fittings for but if you have some decent epoxy or you know how and have the equipment to aluminium weld, then even better!

I saw your pump yesturday. It looks really well built. You should be able to get much more then 20 bar out of it though. I've taken my pump up to 350psi with no worries at all. I could have gone alot higher I think but my guage only goes up to 300psi and so I didn't want to risk breaking it.

Do you have any plans of making an all aluminium gun Soren?

Cheers mate,

Mitch.

[dongfang]

Hi Mitch, thanks for the nice words.

I am sure my pump could take a lot of pressure, but I just made it for taking a gun up to 10-15 bar without breaking my wrists. With a piston area of about 3.33 sq cm, it will go up to about 15-20 bar with a reasonable effort / comfort. If I once need more, I'll make another, smaller bore pump! Of aluminium again...

Yes I have a plan of making an all-aluminium gun! Something like a burst disk free hybrid. Just a small scale experimental thing, to get a little experience with hybrids. My ultimate goal is the sonic GB

Regards
Soren

[Mitchza89]

That's a great plan! It's going to be a beast of a gun . I only just realised that your pump has dimentions different to mine. I use 3/4'' copper as the cylinder. It would explain why I'm able to get to 400psi quite easily. The strong advantage of your pump, is your able to fill up your guns much, much quicker so it all depends on the pressure your after, and the size of your chamber. To get a decent marble gun up to 300 psi, I'll have to use a pump thats the same size as yours otherwise I'll be pumping all day...

When do you think you'll have this Aluminium weapon of mass destuction all writen up and designed?

[dongfang]

Hi Mitch,

What is the exact (actual not nominal ) ID of your pump cylinder?

Yeah I'm already looking around for parts for one more pump. Maybe with a 16 mm (OD) cylinder. Just for some materials strength tests that I want to make, and publish here.

The aluimium gun is just in the planning stage right now. I have a few other things ahead in the queue. BUT in the lunch break today I could not resist going to the hardware store, and look at propane torches and aluminium welding (soldering) rods. They have it all!

Regards
Soren

[Mitchza89]

I honestly couldn't tell you off the top of my head. ID is probably 21 or so mm and the ID would be about 18mm. These numbers are just total estimates.

Ahh I've got the same problem. I'll get bored so I'll duck to the hardware. I'll be poor as hell but I'll still walk out with 40 bucks worth of parts, ending up more broke...

[DYI]

Contrary to the opinion on the first page of the thread, tubing is generally higher quality, and made to higher tolerances, than pipe. I have a .25" ID SS tube with walls only 0.03" thick, which is RATED to 2000psi.

Good luck on using the aluminum tube, it really is one of the best materials for spudgun construction.