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captlloyd · 12-06-2017, 15:29

Been welding for 60 years. After studying the picture I see what the problem is. It's the old "hooking up a water hose to a fire hydrant" issue. Note the thickness of the tang and the massive weld. At best, I would guess the thickness of that mast section to 3/16 at most. Do you see the disparity? My answer would be an external band at least a 1/4 inch thick with the tang welded to the band. Now you have the stresses spread out over a much larger area. The reinforcement could also be a partial band, 3/8 thick would be even better. Gussets are very good if clearance allows. Now we are getting the mast strength to match the gusset strength.
I don't think heat is the problem here. Think of that tang as a lever with that wide weld being an opposite leg. And think of years of minute flexing, that weld has to eventually crack. Us old time welders are the best engineers. We have seen many things break. You might look at some wooden mast gooseneck designs to get some ideas.

Cheechako · 12-06-2017, 15:51

Quote:

Originally Posted by captlloyd

Been welding for 60 years. After studying the picture I see what the problem is. It's the old "hooking up a water hose to a fire hydrant" issue. Note the thickness of the tang and the massive weld. At best, I would guess the thickness of that mast section to 3/16 at most. Do you see the disparity? My answer would be an external band at least a 1/4 inch thick with the tang welded to the band. Now you have the stresses spread out over a much larger area. The reinforcement could also be a partial band, 3/8 thick would be even better. Gussets are very good if clearance allows. Now we are getting the mast strength to match the gusset strength.
I don't think heat is the problem here. Think of that tang as a lever with that wide weld being an opposite leg. And think of years of minute flexing, that weld has to eventually crack. Us old time welders are the best engineers. We have seen many things break. You might look at some wooden mast gooseneck designs to get some ideas.

Yep as I mentioned back in post #7...

Cherod · 12-06-2017, 16:42

Quote:

Originally Posted by Cheechako

Yep as I mentioned back in post #7...

I would have thot as a welder for 60 years you would have commented on the puss poor weld !! Remember that a mast ( like many production processes ) are built to very close tolerances , mostly due to financial constraints, and rely on all parts / processes complying to certain standards , if even one part does not then the card pack can collapse , in this instance the designer would rightly and understandably expect that the weld would be completed in a satisfactory manner by a competent operator , not as in this case by some jack of all trades factory operative who fancies him self as a bit of a welder . That " weld " would surely not pass any reputable QC check and the fact that it held for 15 years is testimony to the design , it is the process which has let the product down not the design . If this crack were to be ground out and rewelded properly then the repair will probabably last twice the original 15 yrs , just get a welder to do it not some jack of all trades .

Cheechako · 12-06-2017, 16:55

Quote:

Originally Posted by Cherod

I would have thot as a welder for 60 years you would have commented on the puss poor weld !! Remember that a mast ( like many production processes ) are built to very close tolerances , mostly due to financial constraints, and rely on all parts / processes complying to certain standards , if even one part does not then the card pack can collapse , in this instance the designer would rightly and understandably expect that the weld would be completed in a satisfactory manner by a competent operator , not as in this case by some jack of all trades factory operative who fancies him self as a bit of a welder . That " weld " would surely not pass any reputable QC check and the fact that it held for 15 years is testimony to the design , it is the process which has let the product down not the design . If this crack were to be ground out and rewelded properly then the repair will probabably last twice the original 15 yrs , just get a welder to do it not some jack of all trades .

The picture isn't too clear, but that weld looks pretty good to me, at least visually. But as mentioned, it's a thick piece needing more heat being put onto a thin piece. To me that's a potential design failure. There are ways to weld that thick piece to the thin, but distortion is a potential result as well as possible heat effected zone issues.
The trouble is, it already has a large heat effected/low strength zone...(HAZ), grinding out and adding more weld will add even wider heat effected zone... there will come a point where you reach the point of diminishing returns.

Cherod · 12-06-2017, 17:09

No , sorry mate , that does not look even half decent let alone pretty good , it is not even what it is supposed to be , a cheap production mig weld , even that has to comply with certain standards which this one surely would not have , look closely and I think the crack has originated in the finish crater in the poor end " turn " and has emigrated from there , yes the rest ( secondary) would seem to be in the haz area and not actual weld failure as such , grinding out and rewelding a proper , slightly bigger , weld would eliminate the original haz and without any defects would be less likely to fail again .

Captain Bill · 14-06-2017, 09:43

Well it looks like the rewelders have it. The machinist says it would have to be rewelded anyway before he could do anything else. His welder(machine) is not portable but he has a welder (human) that he uses for mobile stuff who can TIG weld and makes custom arches and other aluminum structures for boats. The mast manufacturer agrees that this is what needs to be done.

Cherod · 14-06-2017, 10:37

No surprise there then ,,,, and be sure to post a pic of the repair

Captain Bill · 14-06-2017, 13:50

Quote:

Originally Posted by Cherod

No surprise there then ,,,, and be sure to post a pic of the repair

Will do. Since I know little about welding can anyone give me some pointers on how I will know if is done correctly. From what's been said already I would expect to see a slightly bigger weld and it should cover the area of the original weld plus the crack. How far should I expect it to go beyond the crack? You mentioned the finish crater and turn in your previous post. Am I understanding that this was the finish point for the horizontal portion of the weld, before beginning the vertical portion? If there is a finish crater in this position, does that imply that the weld was done in two steps rather than one continuous weld? I'm not asking for a course in welding, but I could sure use a few pointers on how to know if it was done correctly.

Thanks
Bill

Cherod · 14-06-2017, 14:19

Quote:

Originally Posted by Captain Bill

Will do. Since I know little about welding can anyone give me some pointers on how I will know if is done correctly. From what's been said already I would expect to see a slightly bigger weld and it should cover the area of the original weld plus the crack. How far should I expect it to go beyond the crack? You mentioned the finish crater and turn in your previous post. Am I understanding that this was the finish point for the horizontal portion of the weld, before beginning the vertical portion? If there is a finish crater in this position, does that imply that the weld was done in two steps rather than one continuous weld? I'm not asking for a course in welding, but I could sure use a few pointers on how to know if it was done correctly.

Thanks
Bill

The prev weld was not done in one continuous pass , it does not really need to be so long as the stop starts fuse together properly , with your previous " weld " the end turn just seems to be a blob put on wighout any great care , without going into detail a quick judge of a weld is if it looks good it usually is , it should be uniform in shape all round , the corner turns ( actually a very important part of the weld ) should be of same dimensions as the rest of the fillet , the weld should be totally all round the fitment and should blend in at all edges , for good visual images of tig welds google is your friend , cheers

Cherod · 14-06-2017, 14:22

Ps , you are only looking at another 2 mm or so bigger than that original one , not some massive thing !!

**a64pilot** · 14-06-2017, 16:04

TIG if done well, will be a work or art compared to what you have, it should look like a line of continuous drops of little puddles connected together, not piled on top of the parent metal, and no undercutting either.
MIG is fast and requires not much skill. TIG is much more precise and is more difficult to do.
MIG is how bush hogs and other farm equipment is made, Aircraft, race cars etc. are often TIG welded.

model 10 · 14-06-2017, 16:15

Quote:

Originally Posted by a64pilot

MIG is how bush hogs and other farm equipment is made, Aircraft, race cars etc. are often TIG welded.

The gas welding job on my 1940 Stinson fueselage is a work of high craft. Are modern Ag plane fuselages still gas welded?

**estarzinger** · 14-06-2017, 17:43

I'm going to comment once more and then leave it . . . .

I spent about a decade looking for a "permanent" solution to this exact problem. I tried a lot of different options from highly skilled metal workers and riggers. I found two such "permanent" solutions - and neither is just rewelding that tang - no matter how good the welder is. The welders (some of the best on three continents) always said they could make it good, and I gave them several opportunities to do so . . . But they all edge cracked - significant peeling loads and fatigue stress riser concentrated right at the weld edge . . . . It is just not the best approach for this very particular application.

For me it is just somewhat frustrating seeing the industry repeat mistakes like this without learning.

However, that said, you will definitely get some extra time from a reweld, and a bit more time if you add "H" gussets to the ends of the tang. Good luck with it. Remember me when you redo it next time

Captain Bill · 14-06-2017, 19:11

I have some more information about the welder. Besides his core business of building custom aluminum arches and other structures for boats, he does custom contract welding for a local aerospace company where his specialty is welding heavy aluminum parts to thin aluminum parts on satellites and aircraft. This seems to be the skill set I need for this job. I will discuss adding some gussets with him as I see that as a pretty good idea. I'll post pictures when it's done. Thanks for all of the pointers.