Any tips on how to fix this?
Grind it out, weld it up. Don't break it again.
My goodness, shame on the mess. A busted boom and broken dreams all up in here. Looks like it’s been messed up for awhile.
Inspect it frequently and you might find the crack before it grows so big next time. As above, get all the hydraulic lines out of the way, get the boom off the machine, then take some more good photos of the damage.
Looks like an articulated boom section where the break is. Depends on age and where the machine came from. Call the dealer and demand a new boom under warranty. The break is a design failure. Another cause might be a sloppy joint that wasn't taken care of which impact loaded on a seam. The proper repair in my mind would be to dismantle the boom section from the main boom and stick, get it all pressed back in place and do the welding thing. Add fish plate on the sides when the broken stuff is all back together. Replace sloppy pins and bushings in the joints as required. Reassemble and go back to work to pay for it all.
Oh man, you guys are the best. Had a rough day but at least you guys will set me straight. It’s 100% my fault for not noticing earlier... this machine is like a red headed stepchild so I kinda just beat it up without any regard for its wellbeing. I’m a hack of a welder but I know some real professionals... should have that aspect under control. the break is right on the bushing for the pivot... will all that heat from welding distort the bushing? My guess is yes. ..
the needs to be stripped of all lines and cylinders and removed from the machine so you dealing with a single piece .pull or press that crack tight .creative use of a good porto power jack and some strong backs should accomplish that. once its tight gouge it out clean it up and weld it up . this shouldnt hurt the bushing bore judging the distance of the crack from the bore in the picture. you may want to consider a doubler plate running back to the bushing bore and tapering out maybe a foot to 18" down the boom. this reinforcing welded to the bushing hub may make the bushing go out of round,but it quite likely is beaten egg shaped already . You may need it built up and bored anyhow . If your welder works on booms he will know the procedures.If not ask in here we can all help with details as to rod type beveling and reinforcing plate design. Its only an excavator boom they arent hard to fix.Just takes a creative welder I threw this picture in of a boom off an old 172 Hitachi road builder boom with a couple of cracks in it that neede fixing. we cut right apart ,fabbed up new sections with some 50,000 yield plate and a paint job . off it went back to work
IC weld on utube has some video on repairing excavator booms.
Good day Maybe an idea to check that the machine is not over stressed by the attachments and the operator is aware of the swinging boom limitations, better to prevent that repair may be a little late with that advice. Kind regards Uffex
Good point, Uffex... This machine is gray market and kind of different. .. the cab/body/motor/hydraulics/tracks are a Deere 35d but the boom/arm are from a 40series machine that I’m having trouble identifying. The issue could be the mismatched structures...or it could be that I’m a **** operator!!
If anyone has any guesses on the boom/arm setup I’m all ears... would be nice to know where to get parts
TBH looking at the physical size of it and where it goes from and to, rather than attempting a welding repair it might be easier/cheaper to simply replace it provided you could identify the Part Number and also track one down. Personally I'd go that way first.
Airman is Japanese. I've only seen one branded mini here, that one looked Kabota like, we do see some of their Airman compressors but I think that's a whole different section. If you brought that to us we'd probably strip it, pull the boom then cut that end square and rebuild the end, little bit of new plate, a pin boss and then bevel and backer strip connection maybe plate it depending on how it looks/gets used. I'd bet that existing boss is hammered.
Should have painted it yeller when ya got it! LOL
That makes sense. I was wondering myself about the feasibility of stitching both ends of the existing boom on to a new center section.
I would get some measurements done and start checking on other makes for that articulating boom. My guess is they were all made by a sub contractor and then installed on any make that wanted one of them. Pin distance, diameter and type of bearings would be the considerations.
I wonder if you do some measuring if you could find a standard boom from a machine being parted out that would fit. You would lose the articulating boom though. I bet if you have a competent welder near you he could put it back together. Especially if you disassemble and reassemble yourself. You’ll probably need new pin and bushings though.
A little bit more time probably that way. On a lot of stuff I've found you can cut and replace just as quick or quicker then sitting there and gouge/air arc/touch out old weld trying to reuse/fix, especially if you can source off shelf bosses or use stock DOM tube sizes.
Good day Sorry, no offence to the operator. Kind regards Uffex
From the looks of the cracks developing perpendicular to the main larger crack there is going to be metal fatigue. I would not waste my time trying to grind / gouge and weld that back up. I would cut the sections of metal out, use backer plates and weld up new metal. This would be stronger than dealing with smaller cracks and metal fatigued areas that will fail yet again under load. Side note using fish plates over an existing repair weld will only cover up any new cracking / failure in the welds or metal until the issue is severe enough to cause a larger failure / break. This was done on my mini ex stick. Once I removed the fish plate just to have a look in an area thought to have no issues, well there was severe issues to deal with so no go on the fish plate.
It depends a lot on how competent the welder is. Some would grind a simple groove knowing a fish plate was going on. A proper repair would have a bevel to insure 100% penetration so theoretically the fish plate wouldn't be required but the added fish plate would give additional strength. Some of the repairs I see on the forum I wish I was closer as it would be interesting to do the repairs.
Nothing wrong with simply grinding that out and welding it up once you get it aligned. That failed from pushing sideways on the boom. The boom goes side to side so you can dig to the side, NOT so you can push stuff sideways, EVERY backhoe or excavator boom will crack if it's used like that long enough. Nothing different about that articulating boom. It's not even some highly engineered big boy, that's a very simple design, and you found the weak spot, now weld it up, don't push side to side, inspect the whole machine once in a while, and fix it again before it gets that bad.
We have done a lot of covering up existing cracks with fish plates ,once the cracks had been properly repaired and ground flush . A well designed fishplate will carry the stress away from a weak point and run it out in a more neutral area . Heres the boom from the earlier picture with fish plates on typical crack areas. The nice looking backspar was an instant failure brought on by the quest to make things lighter and lighter ,cost me a week in camp doing a bush fix making new legs out of 1/2" plate .
Just make sure to use a properly designed fish plate and welding of it. Have read the swing booms aren't common in N. America because they are much weaker than a standard boom. That said is probably referring to pushing sideways and not digging.
They are much less "handy" than the swing boom base that is common on that size of machine. Nobody makes those booms anymore for good reason. They add lifted weight and add a joint that is inherently less robust than the swing base.
They also were dangerous in that the bucket can hit the cab if the electronics don't work. Many people tamper with the system when things don't work. I used to see the scar on the front of the cab when I went to inspect them. Kick and front windows would be gone and the front window frame would be stuck in place because of the dents on the front of the cab.
Thanks for all the insight... I’m guilty as charged when it comes to being lazy and pushing dirt sideways occasionally (Although I recall about a month ago I got a bit too up close and personal with a tree and am thinking that might have been the final straw) Got things taken apart finally. A handful of bushings/pins need to be replaced. any suggestions on where to find? I believe this machine is a clone of a hitachi zx40... just not 100% which version.
There almost certainly wasn't a "final straw", maybe there was a "first big whack" but that has been cracked for a while, and getting worse with each movement even if there was no side to side. We LOVE close up pictures of the metal that failed.
High cycle fatigue. It only needs one overload, that by itself isn’t enough to break the structure, to start the rot. Thereafter loads that are within the design limits advance the crack until the structure finally fails. Who knows when that “first big whack” was.? It may even have been before you bought the machine.
When it stops raining I’ll get more pics. Machine has 5,000hrs... last 200 or so have been with me.
Thoughts on fishplate design?
I dunno what anyone else thinks but with the failure being so close to the end of the top and bottom plates I'd suggest cutting out the end bit of plate plus a bit more and replace it completely before even thinking about fishplating over the top of a repair - see the sketch below. That would put the repair weld welds in the top/bottom plates much further away from the boss at the end. it would also mean that a backing strip could be installed across the structure to get full weld penetration in the transverse weld on the bottom side of the sketch. The new weld at the top end would of course be a fillet weld so it ought to be easy to get good penetration. I think it would be far less complicated to weld if a piece of plate was cut out and replaced completely. I'd be interested to know what others think.
This is what I'm talking about. The design of your boom is different with the top/bottom plates inside the side plates as opposed to being on top of them as this photo shows, but the principle is the same. Never be afraid to cut into a structure is a good motto, but know what you're doing, and have a clear plan first.......
More than I would do, given the machine and circumstances. If he did what he suggests and it cracks through in the same place, I was wrong and he can do what you suggest then.
Nige has more experience with this than anyone probably. I don't know if you're willing to do a Nige quality job on this though. Those cracks need to be ground out to get full penetration. If you fishplate it, I would cut the side plate flush with the intersection of the round boss, and get rid of the plugs. I like the top plate. The plugs are just adding more material on top in this case, if you want to add more material on top, I could weld that up as it is, and beef up the cracked top and bottom plate where it counts, with a lot less material than the plates. Really, this has been failing for at least 2,000 hours, and you got unlucky enough to buy it like that and not catch it. No big deal, just a few more rods. If you are planning to run it another 2,000 hours, and don't push side to side, you should be fine with any repair. But grind out before welding, and check the whole boom for cracks twice a year.
Good call Nige, I was concerned with how “busy” that area is. I’m leaning towards gouging out, welding, grinding smooth and slapping fishplates on there as of now... that might change tho as I start the repair.
My suggestion is based purely on the (very) short distance between the crack and the fillet weld at the end of the top/bottom plates. Rather than put a repair weld in close proximity to an original factory weld I'd cut the lot out and start again. My 2c. YMMV. Even if you didn't go fully with my suggestion you could always cut out the short section of plate above the crack (as per photo). That would allow you to get a backing strip inside the top/bottom plates to assist with full weld penetration. There would be no fear of burning through the inside of the plate when you were welding. The way we always worked with repairs like this one was to attempt to "stagger" the repair welds and not have them all in one line of cross-section of the structure, if that makes sense. If you gouge, grind, and weld as you are proposing you're going to have all the 4 repair welds in one transverse line through the structure - not good. Well, not optimal anyway. Oh, and if you can get hold of a plasma torch it would help you big style when prepping the bevels.
Ah yes, I might do that then...would be nice to get backing plates inside. I do have a plasma cutter somewhere in my disaster of a garage
It’s a mini ex, not a gun ship going to war. It was broke when you got it. Any fix you do will be better than it was. Arc it out, weld it back up and put it to work.
That was what I was saying in so many words. If that doesn't hold, go back and hack it all off. I think the difference in philosophy is if you're getting paid to do the job, and do it once, versus a guy welding up his own machine and getting back to work.