How would you repair this crack in aluminum tube?

[Noidea87]

Long time lurker here and have been in the marine rigging business all my life. I say keep it up, give yourself a little more time to do you're homework (which your doing), to think about the repair process and practice a bunch more on similar condition sections (slice open practice welds afterwards to inspect your work) and to think about if this is the right solution and what can happen if things go wrong during the operation?

Sounds like some people here sitting at their desk being critical and demanding idealistic perfection instead of helping out more with your task at hand, its your property and project that you want to see out and complete yourself, sounds like you understand the impact and responsibility of doing it yourself. Having a good contingent plan B is a really idea if Plan A goes south and sounds like you already have done that. My only advice is to think about more what could go wrong during your welding repair, if it will fix the issue and what the impact (costs) it will have on the tower and its usage if things don't go according to plan?

Based on the very limited pictures and info, there is some additional work on the tower you can do afterwards that can hopefully help mitigate more failure like the one you're dealing with now to make the tower last longer, a lot more info, specs & pics is needed about what's on top but that's for a later conversation and more overall pics are needed but as of right now you first have to deal with this specific spot and repairing it.

Thanks, i do have some time. Earliest we will be there is mid April and I've been putting down beads whenever I can. Next I plan to order some small 4x4 sections and mock up the joints, and also practice on some heavily oxidized pieces.

I also looked into taking a 3F or 3G test on aluminum if I could practice enough. Just to have documentation that I have the skills to weld the joint properly. May ask my supervisor if they'll pay for it. I'm a long way off now but it may be useful to have in the future

[BillE.Dee]

You are basically committed to finish the weld once you start. And you will MOVE as the aluminum will retain the heat and the heat will increase as you continue the weld. Kind of like a jet engine....the more horsepower it makes the faster it goes and the faster it goes the more horsepower it makes, etc etc. You should practice on like material and see exactly how it will react to your procedure and set up your machine so you won't get outrun. Capiche??

[Avie]

It's outside so argon coverage becomes a big problem.

The trick with doing this stuff outside I've found is hang moving blankets (or other heavy blankets) around your work area with those spring clamps (.99c each at home depot) or failing that buy a bunch of cardboard boxes and cut them open and build a box around your work area with same clamps. I've had the unfortunate opportunity to do a lot of TIG welding outside (don't ask) and these tricks have worked. Gas lenses are also great if you're tigging.

[William McCormick]

The bright spot is that the only defect is where the hole is at the base. The rest of the structure including all of the welds show no signs of failure. Could be the OP is right, that a defect was inherent in only that section of tube. Something looks to be installed behind that crack.

The bottom supports of the tower take the most force when the tower moves, that is why we see the total failure there. But that does not mean the other higher supports are not already cracked on the inside of the tube. This is really a failure of "modern engineering". Some distributors call square inner and outer corner box tubing structural which is criminal and shows a total lack of engineering skill.

I myself have welded up square corner tube for people but I mention it is not meant for structural purposes, usually for a special use tool for special moving equipment, where the guys know what they are using and know its limitations. They are looking for it to give or break. Or we support the Architectural box tubing in a way that does not let it flex.


Sincerely,

William McCormick

[William McCormick]

Long time lurker here and have been in the marine rigging business all my life. I say keep it up, give yourself a little more time to do you're homework (which your doing), to think about the repair process and practice a bunch more on similar condition sections (slice open practice welds afterwards to inspect your work) and to think about if this is the right solution and what can happen if things go wrong during the operation?

Sounds like some people here sitting at their desk being critical and demanding idealistic perfection instead of helping out more with your task at hand, its your property and project that you want to see out and complete yourself, sounds like you understand the impact and responsibility of doing it yourself. Having a good contingent plan B is a really idea if Plan A goes south and sounds like you already have done that. My only advice is to think about more what could go wrong during your welding repair, if it will fix the issue and what the impact (costs) it will have on the tower and its usage if things don't go according to plan?

Based on the very limited pictures and info, there is some additional work on the tower you can do afterwards that can hopefully help mitigate more failure like the one you're dealing with now to make the tower last longer, a lot more info, specs & pics is needed about what's on top but that's for a later conversation and more overall pics are needed but as of right now you first have to deal with this specific spot and repairing it.

The weld the OP is asking for help to perform cannot even be done to any standard of repair or acceptable weld. Even if the OP ground out a V-groove without a pass inside it will never even be back to the original incorrect engineering design.

If someone wanted to put the tower back to the incorrect original spec they found it in, they would just cut out the damaged, expanded, mechanically hardened support and put in a new one. If he is afraid he does not have the skill to do that, take the time to learn how to weld in a new diagonal support, or leave it to someone else's liability insurance. Anyone that welds professionally would say that if you cannot weld in a new diagonal support, you certainly should not attempt the impossible weld repair.

That whole tower should have been condemned after the storm damage it received. I would bet the other tubes already have internal cracking. The OP could use a veneer caliper to check for swelling on the other tubes that would prove they have cracked internally at the sharp corners as well.

Sincerely,

William McCormick

[William McCormick]

Do you mean you aren't supposed to stop with aluminum until you finish the joint? I was able to stop and restart in my test piece once I figured out how to get the crater to fill. Or do you just mean you can't slow down? I definitely figured that out haha, I got the feel for watching the puddle and figuring out when I should stop completely or start moving fast to keep from burning through

Any quality MIG weld to form a complete seem is done with a run-in-strip that is later ground off. The problem with stick welding is a similar problem you cannot stay in one spot and preheat the material after you restart without creating a non-uniform weld and heating pattern. If you look at penetration marks you will see when stick welding that you get an uneven pattern of heating. Making the only type of weld I would trust doing something like that a TIG weld. In fact, if I was told the future of earth depended on me making that weld you wish to do, I would grind the corner off completely and TIG weld and build up the corner with weld. Then I would feel as if I returned a poorly engineered tower to its original poorly engineered state. Or I would just weld in a new diagonal support and return it to its original poorly engineered state.

You have to make the call, ask yourself could a hurricane come next year and take the tower down in five minutes in its obviously weakened condition and if it came down what would the consequences be. I mean if it is on your land and no one would get hurt and the insurance would replace it maybe that is the way to go just patch it up and collect the insurance next hurricane.

Sincerely,

William McCormick

[William McCormick]

Let's recap some of the things that have been said and the ideas put forth so far.

We have had the idea that the diagonal support may have been manufactured incorrectly and was just defective, which means you cut it out and replace it. It does not mean you try to weld the defective aluminum material in the diagonal back together.

We have had the wall thickness of the tube being used as a possible reason for using it as a structural tube. The thicker the wall of the architectural box tubing actually increases the rate of cracking in the sharp square corner box tubing upon flexing.


We have had many individuals state that the weld is possible, but if we look at the way the tube destructed, we see that the inside corner was the weakest point. Why would you attempt a MIG weld that I highly doubt would be as good as the extruded inside factory corner that has already failed?

We have had some say to start and stop MIG it. MIG is bad enough on old aluminum but to start and stop MIG on a structure that is already questionable in its perfect state seems like really bad advice.

Others have suggested TIG welding and although it will not help the poor engineering design in any way, it could probably return the beam closely to its original failed engineering condition after annealing the beam completely in the area.

A few have said to replace the diagonal, which would be the only sane advice, to return the tower to its failed engineering state.

All of the above, do not take into consideration that the engineer that used architectural tubing for a structural job did not also send the tower out to be heat treated making all the repairs extremely questionable with effects unknown.

I am suggesting that the OP buy a couple thousand in structural aluminum tube and rebuild it.


Sincerely,

William McCormick

[shovelon]

Let's recap some of the things that have been said and the ideas put forth so far.

We have had the idea that the diagonal support may have been manufactured incorrectly and was just defective, which means you cut it out and replace it. It does not mean you try to weld the defective aluminum material in the diagonal back together.

We have had the wall thickness of the tube being used as a possible reason for using it as a structural tube. The thicker the wall of the architectural box tubing actually increases the rate of cracking in the sharp square corner box tubing upon flexing.


We have had many individuals state that the weld is possible, but if we look at the way the tube destructed, we see that the inside corner was the weakest point. Why would you attempt a MIG weld that I highly doubt would be as good as the extruded inside factory corner that has already failed?

We have had some say to start and stop MIG it. MIG is bad enough on old aluminum but to start and stop MIG on a structure that is already questionable in its perfect state seems like really bad advice.

Others have suggested TIG welding and although it will not help the poor engineering design in any way, it could probably return the beam closely to its original failed engineering condition after annealing the beam completely in the area.

A few have said to replace the diagonal, which would be the only sane advice, to return the tower to its failed engineering state.

All of the above, do not take into consideration that the engineer that used architectural tubing for a structural job did not also send the tower out to be heat treated making all the repairs extremely questionable with effects unknown.

I am suggesting that the OP buy a couple thousand in structural aluminum tube and rebuild it.


Sincerely,

William McCormick

Not the approach I would take. The failed tube looks to have some corrosion as well as a crack. That could be why it failed. I see no reason the section could not be replaced with additional reinforcement where the cutout is.

[William McCormick]

Not the approach I would take. The failed tube looks to have some corrosion as well as a crack. That could be why it failed. I see no reason the section could not be replaced with additional reinforcement where the cutout is.

When you flex aluminum you crack it, fracture it, and then salt water soaks into it like a sponge furthering the corrosion. If you have worked in a marina you have bandsawn new two by two-inch solid aluminum to replace totally salt destroyed sail boat rigging mounts, that have turned to total composite inside, or bandsawn them out of stainless steel or fabricated them out of stainless steel or titanium.

We have been through this exact scenario the OP posted over 40 years ago, no one cares really and often the same people do the same thing again and again. If that was a radiused corner square tube it would still be there and not corroded. That sharp inside corner is a magnet for corrosion. And once the tubing is flexed that corner opens up and lets the corrosion in and you get what you see in the OP's picture.


Sincerely,

William McCormick

[Yofish]

"If you have worked in a marina you have bandsawn new two by two-inch solid aluminum to replace totally salt destroyed sail boat rigging mounts, that have turned to total composite inside, or bandsawn them out of stainless steel or fabricated them out of stainless steel or titanium."

Pzzzt! Sorry, my decoder ring isn't working tonight. I don't know why you are jabbing so much about a simple repair. I get your Jones but sometimes it's best to just stow it...

[Spectator]

Thanks, i do have some time. Earliest we will be there is mid April and I've been putting down beads whenever I can. Next I plan to order some small 4x4 sections and mock up the joints, and also practice on some heavily oxidized pieces.

I also looked into taking a 3F or 3G test on aluminum if I could practice enough. Just to have documentation that I have the skills to weld the joint properly. May ask my supervisor if they'll pay for it. I'm a long way off now but it may be useful to have in the future

Go for it! Get your company to sign off on it and get ready for the test, why not? Sounds like its a good fit and if you pass; it will be a feather in your cap and you'll be more valuable to your company.

Let us know how it goes with your 4x4 mockups.

[William McCormick]

"If you have worked in a marina you have bandsawn new two by two-inch solid aluminum to replace totally salt destroyed sail boat rigging mounts, that have turned to total composite inside, or bandsawn them out of stainless steel or fabricated them out of stainless steel or titanium."

Pzzzt! Sorry, my decoder ring isn't working tonight. I don't know why you are jabbing so much about a simple repair. I get your Jones but sometimes it's best to just stow it...

I was saying that if you have done fabrication in a marina you have probably replaced solid 2"x2"x14" sailboat rigging blocks that have corroded completely through, they become a total composite. It starts at some little crack or metal mismatch. In other words aluminum corrodes by saltwater we get that, but it almost always needs a place to start and that happens inside a non-radiused corner non-structural tube that cannot ever be allowed to flex or it will crack in that sharp corner every time. I have seen this for decades and people just realize it and do it again a few years later. That could not have happened with radius corner structural box tubing ever.

Sincerely,

William McCormick

[William McCormick]

[QUOTE=Noidea87;8804920]

Next time I'm in the office I plan to practice on some old aluminum scrap we have that had been installed out on a platform for probably 10 years around salt water. Try my cleaning method out and see how it works.

The back up plan is to replace the whole cross member. The more I think about it that might actually be easier than trying to repair these cracks. We are meeting with our engineers for suggestions here soon. They may recommend just replacing the whole cross member instead of repairing. He was surprised to see it fail like this. Thought maybe it was bad section of tube from the get go. If we do go that route I'm trying to figure out a good way to rig up a temporary support. Any ideas there?

I would get a piece of bar stock, perhaps 1" x 4" and some nice heavy C-clamps, and cut out the old one. If it is not windy it will not be under a load. Bar stock is pretty cheap, extrusion is much more expensive.

Sincerely,

William McCormick

[William McCormick]

And aluminum bar stock comes in 12-foot lengths making it even more affordable.


Sincerely,

William McCormick