Air Tank Materials?

[Hurricane Air Arms]

Greetings once again.

Most of us started with coke bottles and stuff when we were churning out out first projects when it came to air tanks. For the most part the 2-litre bottles cold safely hold 80psi and had the ability to spit out in excess of 100 BB's which is great for beginners.

Looking at today's most advanced air guns, cylinders of high grade are used and are typically pretty safe, which is my number 1 concern - safety and I think it should be everyone's. SO when I see people pressurising PVC I think back to when my older brothers PVC tank exploded and how lucky he was not to actually be impaled by the subsequent shrapnel.

I'm here to ask what everyone else here uses as an intermediate tank - respectable price and plenty of safety and volume is what I'm thinking. Lots of people use thick copper, some use steel tubes, what do you guys use for your pressures exceeding 100, 150, 200 PSI?

[Doodmens]

http://www.copper.org/applications/plum ... burst.html
If you click on the tables you'll see that copper is a pretty good material, and steel is even stronger of course. The critical part here is the joint, so I'd recommend not going above 1000 psi without welded joints

[Hurricane Air Arms]

Thanks Man. Very helpful.

What's the best way to seal the ends of a copper tank? Threads?

[wdr0]

For lower pressures standard soft plumbing solder would be fine especially for smaller sizes. Brazing would definitely be best for pressures near the max rating for the pipe.

[Hurricane Air Arms]

I'm not confident in soldering nor my abilities, I was thinking of more of a threaded cap?

[Gippeto]

Threaded connections are VERY strong, but sweating copper is a good skill to learn and the equipment (torch, pipe cutter, emery cloth, flux and solder) does not cost a whole lot or take up a lot of storage room.

First off...brazing copper LOWERS the safe working pressure...brazing temperatures anneal the drawn copper tube. Ratings for brazed joints are at the bottom. Copper Tube Handbook is a great resource...suggest downloading the pdf.

http://www.copper.org/applications/plum ... able4.html

Can use 95/5 Tin/Antimony to sweat the copper together...joints have higher strength than 50/50. That said...50/50 is a little easier to use, flows a little better, and might provide a better quality joint for someone with less experience sweating copper. At low pressure, entirely adequate.

Flux is your friend...

IMHO...the best way to seal the end of a copper tube is with a sweated tube cap.

[Hurricane Air Arms]

Ahh nice. Thank you.

Let's say I use a length of copper and thread it at both ends, (Basic) what could I expect for maximum safe working pressure? Just off the top of your head.

[mrfoo]

As close to infinite as you're likely to get. After all, you're talking about a length of solid copper bar, right?

No?

In that case, it will depend on, variously but probably not exhaustively :

- Pipe diameter
- Wall thickness
- Thread type, pitch and depth
- How much of the pipe you're threading
- end cap form

Not knowing the answers to any of the above, off the top of my head the answer would be "some, but no more than that".

[farcticox1]

- seamless (extruded) or welded ?

And you wouldn't thread copper ? I guess a compression fitting to thread