Cracked boom repair

How many time as your fixxin something has someone said.... So what did you brake now...

I watched a dealer wrench pick himself off the ground after he said that to the owner operator of an excavator. That brand never made it on another job site of that owner.

Engineering is about cutting costs and weight while adding production. Excavator booms today are nothing like when I started or even ten years ago. Three sixteenths mid alloy plate put together in jigs and auto welded by robots. Maybe something in the jig slips and you get ten or fifteen booms with fatal flaws before anyone catches the problem. Maybe a miscalculation in the math and fifty booms go out with the flaw and don't show up for a year and out in the field. Go ahead and gouge and re-weld. The crack will be back. Some call it job security.

Nige said:

Regarding structural cracks experience has taught me that, like the iceberg that sank the Titanic, it's the 90% you can't see that you should be worried about.
From the outside lovely-looking repairs have been known to come unzipped very rapidly and very catastrophically with no prior warning - see the example below. That's why I'd always cut into the structure and repair from the inside to the outside. YMMV.

View attachment 195094

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Forgot to ask . Did you end up repairing the boom or toss it out ?


We had a little challenge on a 215 Cat excavator boom .

Customer called & said needed a welder . Showed up on site and found the end of the boom not cracked but split open on all four corners .

The stick swung back & fourth sideways like a pendulum . LOL!

Top & side sheets were not cracked but gaping open at the corners . We threw some chains & wood blocks around in and sucked it back in with screw type ratchet binders .

Welded it up with 7018 electric glue from the outside .


If memory serves me correct I think member Mitch504 had a similar situation on a repair job .

It was actually a truck frame and yes it was repaired (and some factor-optional strengthening added at the same time). This is what it looks like when it's opened up.