When repairing a broken arm on a backhoe or excavator boom or stick, should nice heavy reinforcing plates be added to the sides or is plating the top and bottom of the boom more important.
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Engineering Question for repairing broken excavator booms.
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No engineer here but just my thoughts. I think it all depends on the original crack & where it formed & how/why it cracked. Most repairs seem to be different & one fix won't fit all.
Anytime you add a plate over the top it will transfer the stress to somewhere else. It can also become a stress point itself as the boom/stick can not flex evenly throughout it's length. If it is just a crack then I gouge it out & weld it up. Maybe a really big crack I might cut a slot & insert a backer for the weld. If it is completely broken & bent then I just use my judgment. Again I don't think one type of fix is right for all situations.
I think the important thing is to get a good repair before you plate it. I don't know how many times I have fixed something that has been plated & when I cut the old plate off I find bird crap underneath.
Here is a mini I did last year. Completely broke so I welded it up & plated it. You can see why it broke as this was the weakest point right where it transitioned & the thumb base plate ended. I plated both sides & extended the thumb plate up to spread the load. A larger machine I would probably do the same way.
Last edited by MMW; 05-06-2015, 08:10 AM.MM250
Trailblazer 250g
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Lincoln ac/dc 225
Victor O/A
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Whitney 30 ton hydraulic punch
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To try & answer your original question I would say this. If the crack started on the sides only & was limited to the sides I would only add side plates. If the inside/bottom plate cracked first then I would plate the inside/bottom also. I have never seen a cracked boom/stick start on the top so I don't think that would need it as it almost always under compression. I never plate the top.
Again each job may require a different approach.MM250
Trailblazer 250g
22a feeder
Lincoln ac/dc 225
Victor O/A
MM200 black face
Whitney 30 ton hydraulic punch
Lown 1/8x 36" power roller
Arco roto-phase model M
Vectrax 7x12 band saw
Miller spectrum 875
30a spoolgun w/wc-24
Syncrowave 250
RCCS-14
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Originally posted by Portable Welder View PostWhen repairing a broken arm on a backhoe or excavator boom or stick, should nice heavy reinforcing plates be added to the sides or is plating the top and bottom of the boom more important.
KevinLincoln ranger 305g x2
Ln25
Miller spectrum 625
Miller 30a spoolgun
Wc115a
Lincoln 210mp
F550 imt service truck
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Tragn5 and MMW, thanks for the input.
Where I was going with this question is where is the most stress on the boom at!!!
The sides or the top and bottom, Many of the owners that I deal with have it in their head that they want a big plate on the side.
The way I have fixed them is to cut the side of the boom out so I can gusset the top and bottom from the inside, Tryagn5, you are right about some of them having a hidden gusset plate on the inside, on the last one I did I cut it out and replaced it with a new one, I then weld the side plate back in.
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Originally posted by Portable Welder View PostTragn5 and MMW, thanks for the input.
Where I was going with this question is where is the most stress on the boom at!!!
The sides or the top and bottom, Many of the owners that I deal with have it in their head that they want a big plate on the side.
The way I have fixed them is to cut the side of the boom out so I can gusset the top and bottom from the inside, Tryagn5, you are right about some of them having a hidden gusset plate on the inside, on the last one I did I cut it out and replaced it with a new one, I then weld the side plate back in.
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