[Brandon_B]

Hi All – I've really been enjoying the forum and I'm blown away by the expertise here. If anyone has a few minutes, I'm looking for a sanity check on my repair technique. First, a look at the cracks I usually see on our old farm equipment (this front end loader is a good example - I think it's mostly 3/16" steel)...





I wire-wheeled these welds to see this crack better. Can't see it in the pic, but it extends down along the toe of what looks like a 6010 or 6011 bead. There are several cracks (and many previous repairs, probably as old as I am) along where this attaches to both loader arms. We move a lot of round bales and the load is constantly shifting side-to-side as we drive over uneven ground, which really tweaks this thing.


My go-to fix is to grind out a bit along the crack, lay a first layer of 6010 or 6011, then cover with 7014 or 7018 (only just recently picked up a DC machine so 7018 is a recent possibility for me). This was always “grampa’s fix”, but is there a better technique for this? Is there a need to run that first pass with 6010/6011? Or since 7018 is more ductile, can I just make the whole repair with that? Finally, if there's an entirely better procedure or technique, I'd love to hear it!

Thanks,
Brandon

[cj737]

If you grind and clean the old, failed weld out, no need for 60xx at all. 70xx is obviously stronger and would be my choice.

[Coldman]

And put more than one pass on it


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[Homemade]

Grind it out. Make sure you go a little farther then then end of what you can see. The crack can be very fine near the edges. 7018 the whole way is ok.

Try and find why it cracked in the first place. Are the pins and bushings all bagged out? Maybe you can add some gussets to strengthen it up or it will probably crack again. That is an obvious high stress point.

[Poland308]

Even if you end drill the cracks and grind them out your dealing with a different issue. Those are stress cracks from the metal flexing as it’s used. You can fill in those weld joints till there more filled. IE if the joint is a lap joint, most of them are in the pictures. You need to fill the fillet up till it’s got more of a flush filled look. Then you need to make sure your welds don’t start or end at a corner. Those are focus points for stress. Even with the best welds those arms will still crack from flexing. Over time the metal gets more brittle from the stress. You can also weld out a few stringers along side those welds( like padding beads) to spread out the load. But remember if you reinforce those arms the stress will just be born in another point. Make sure it’s one you can fix.

[Brandon_B]

Thanks for all the comments, guys - this is all really helpful. I’ll stick with 7018. The best I can figure is that the cracks happen when the bucket shifts violently from side to side. We mostly move round bales with a bale spear attached to the bucket (which has suffered too), and it’s so far out in front of the tractor that a 500lb. bale can really muscle those arms from side to side on rough ground. I guess the most cost-effective fix would be driving lessons for my family.

I’m glad to hear that a few more beads won’t hurt anything. I’m never sure how much is too much. I read warnings about the heat affected zone and residual stresses until my head spins. I’ve seen a lot of cracks right next welds and I figure when the weld cooled, it pulled like the dentist on the metal next to it. Then a sudden stress came along and popped it free. Did I do that by welding too much or too little?

On that subject, does anyone know of a good book (or any book) on diagnosing and repairing failed welds? I see countless books on learning to weld, but not so much on understanding structures and stresses. Things like case studies on why things failed.

This one caught my eye, but maybe you guys know of others?

[tweake]

have a closer look as to why it failed.
for eg the 2nd pic shows a design issue or a missed weld. its broken of at the end due to a small poor looking weld and the rest of it is not welded. that allows movement and constant flexing will crack that weak design.

can't really see much on the 3rd pic as really need to see how its constructed.

so many times you see things broken because someone ignored basic engineering principles.
tho with farm gear i know how it goes. you quickly make something for a one off use, but temporary becomes permanent.

[cj737]

Butted welds of structural steel are never very strong and always susceptible to cracking. That’s a hefty load on that thin, long stress point. Because the metals are so thin, and you’re only welding the outside edges, it’s very difficult to prevent that stress from loading up over time.

Add to that, “no great” welds, and you have a recipe for repair work. I’ve repaired stuff like this many a time. There have been situations that provided me the opportunity to drill through the faces and add “plug” welds throughout the field of the pieces. This provides some added support to the edges. I won’t say it is the solution, but those pieces have not returned for repair since (might have gone elsewhere though...). Best you can do is grind it all out (even where it’s not cracked) and add quality welds over top all the way around. Metal fatigues over time from use. Be relieved you have the skills to fix it and continue using it

[Brandon_B]

Thanks for all the feedback, guys. Lots to ponder.

Be relieved you have the skills to fix it and continue using it

I hope I do… I sure as hell don’t have any money for new equipment

I've re-injured my back so I've been laying low, which has given me time to think. I got looking at loader designs and realized that the newer loaders we have all have a big piece of tubing that goes through the arms, which can be welded onto both sides of each arm. The design on this old loader only has the stiffener welded to the insides of both arms, and is where the majority of fatigue cracks are.

These aren’t my pictures, but I put them together to illustrate:



I’m considering cutting some holes in the arms and putting a piece of tubing through mine, above where the existing stiffening/connector is. Am I nuts?

[cj737]

That was kind of my point about the plug welds. In my opinion, you are not nuts to add that stifferner. Sorry to hear about your back. I just went through the same damn thing. Thank God for my acupuncturist!

[Brandon_B]

That was kind of my point about the plug welds. In my opinion, you are not nuts to add that stifferner. Sorry to hear about your back. I just went through the same damn thing. Thank God for my acupuncturist!

Thanks - I seem to be on a 2 year cycle. Good for a couple years, then out of nowhere I bulge that same disc. Never thought of acupuncture. Out of curiosity, how big of a hole do you usually drill for the plug welds? And do you drill through both pieces where they overlap, or just the top one? I would think just the top one, if possible, but this is my sanity check post after all I'm going to hobble out and start working on this tomorrow if the weather's good.

[cj737]

Several 5/8” or up to 1” depending on the piece. 3 or 4 for the piece I see in your photos should do. They won’t be as strong as the cross brace, but it does add support and rigidity to the plate weld. You don’t need to drill thru both, but into the bottom so you get some penetration in the lower/backer and fuse the plate to it.

[Poland308]

Hole saws work great for cutting plug holes.

[Brandon_B]

You guys are awesome, I appreciate all the tips and info. I got nicely started on the fixes this weekend. Dragged a nice 4" tube out of the junk pile and stuffed it between the loader arms. I cut the end plate off and found it was 5/16" wall thickness. Couldn't ask for a better piece




Laid out and cut my holes:




Nice snug fit:




I got nicely started welding it in, but ran out of 7018. Boy is that a trick, welding around a tube like that What's a good sequence for that? 6 o'clock to 12 o'clock on each side? I ended up trying a bunch of starting/stopping points, but nothing felt "right".

[cj737]

Uphill only, Baby, uphill only. 7018 doesn’t weld downhill like 6010 will. I weld from 5:00-1:00, then start at 4:55 and weld back to 1:15 if you get my drift. Of course welding beyond for decent tie ins. A decent spot tack in 4 quarters, then let it eat.

[Homemade]

Lots of pipe welding videos out there. You can do a little review before you tackle it. Even try a coupon on some plate first. Just cut a 4” long piece off and attach it to some plate to get the hang of it. I would tack at 12,3,6,9 o’clock and burn it in.