[combyy]

Hi all, I've undertook a project that is seemingly impossible to have a good outcome. The main purpose of this project is for self education and possible reuse of this part. It is a broken main boom from a Case backhoe. The break is located near the lower pivot point where the boom connects to the cradle. (a very high stress point) Outside of telling me it's not worth the money expense, buy a new one, wasting my time, I'd like to hear some idea's that could possibly be applied to this major problem. I grew up learning the more information you have the greater the chance of success.

First of all, someone else, besides myself, started to take this repair on. One side of the boom is completely broken off and a bevel was ground on both the parent and the broken piece. The bevel grind is completely wrong, about 45°, on both front and back sides. To much metal was taken off the most part of the mating surfaces that when the piece is lined up, or in it's proper place, there is as much of a gap between the two mating point as 3/8". The length of the break is approx 10" long.

My first thoughts was how in the world am I going to get a good root weld in that? Can I use a filler? Do I use pieces of the parent metal or de-fluxed rods that I'll be using?

I don't want to use pre-heat and long post cool for this job, the boom is just to big. I'd like to use the cold weld method, weld one inch, peen, move to another location and do the same, keeping the parent metal cool enough to touch. (I know, It's going to take a long time.) I'd like to use stringer bead for the whole job, no weaving. My boom will be flat for all welding positions, no verticals.

I chose the 321-16 rod over Nichol or the 7018 to do this job. Although this rod cost a lot more, I think I'll have better success in this situation.

There is probably some details you may want to know that I left out...if so....please ask.

Any help or ideas will be greatly appreciated.

[RamboBaby]

The only time i ever welded iron was in a gate fab shop. I ask the guy I'm working with:
So Doug-E-Fresh, if these pickets are cast iron then how are we gonna keep it from cracking when we weld it? His reply was the same as yours.....peen it with a hammer.
I can't imagine trying to do what you're attempting.

[combyy]

That was the way I was taught and it's really important when working with ductile iron because of the metal carbon structure. Depending on how other cast irons are welded, peening isn't always needed. Peening the weld helps relieve the stresses that can cause potential cracks.

[MinnesotaDave]

I would call Case directly and ask them for the welding procedure and rod recommendation.
If they say it's not weldable (some are not I've been told) then your work is done unfortunately.
But, if it is weldable, they likely can give you the correct process - which will hopefully be faster than welding 1" at a time.

[Skylineauto]

Construction company I worked for in the past always repaired the booms on the excavators. I cant comment much on getting rid of the gap but I do know they would always put a piece of fish plate over the repair to give that area of the boom to make it stronger.

[combyy]

I would call Case directly and ask them for the welding procedure and rod recommendation.
If they say it's not weldable (some are not I've been told) then your work is done unfortunately.
But, if it is weldable, they likely can give you the correct process - which will hopefully be faster than welding 1" at a time.

The boom has casted into it the words "DO NOT WELD".
After doing some research on this I found that CASE was required to do this to protect the company from law suites. Case will repair the boom but will cost as much as a new boom. They use big ovens and a fusion welding technique to make repairs.

I have welded this kind of iron in the past on pin knuckles that had cracks and clean breaks with great success but nothing like the project I'm wanting to do. I'm kinda stuck with I" at a time if I want to do this project.

I do understand what your saying though. tks

[combyy]

Construction company I worked for in the past always repaired the booms on the excavators. I cant comment much on getting rid of the gap but I do know they would always put a piece of fish plate over the repair to give that area of the boom to make it stronger.

That idea is not out of the question Skyline. I have mixed feelings about it. Some heavy equipment welders I've talked to said fish plating won't work with this kind of boom. Others have said they didn't have a problem. I'm not able to make a clear judgment about those statements because I didn't see the jobs they did and where the repair was or what they used for fish plate.

What I was considering to make a type of shoe out of some good high strength steel, slip it over the end of the boom and plug weld selected area's and maybe some stitch welds in others. Then make what modifications needed to mount the boom back into the cradle.....just an idea.....like I said, it's not out of the question.

My biggest problem right now is getting a good root weld, Never have tried to fill the Grand Canyon on this kind of stuff.

Tks

[Coldman]

What is the shape/profile of the boom?
Is it possible to get a removable backing plate in there to help fill the big root gap?

[combyy]

What is the shape/profile of the boom?
Is it possible to get a removable backing plate in there to help fill the big root gap?

In the most part, yes. It's not a flat surface on the back side plus they beveled the brake on that side too.

I was thinking about using big motor brush carbons or copper for a backing but haven't figured out how to keep it in place yet. Gonna have to figure out some sort of bracing to hold the backing from dropping out.

I'm worried about getting a good root doing it this way.