Nice break
I have seen the same problem on a 972H , but the bucket was high tip and far too big , the customer changed the arm , he bought an arm out of a burned machine How big is your bucket ?
Ouch! Don't you hate it when that happens? Guess they don't make them like they used to! Years ago we had a 988 87A vintage machine that had a high wall collapse on it bent the right side of arm a couple inches. Dealer sent a guy out with a hyd. press set up and they tried to bend it back, no luck even with lots of heat! As a last resort the dealers guy told us he could not do it but if we wanted to give it a try it was our call, cut about 75% of the way through the boom from top to bottom then bend it back to place. Then vee it out and weld it back together. Then heat till red and let it cool. We had a very good welder working for us at the time and when he was done it looked like nothing had ever happened and machine was working for years after with no failures.
Do you have any really good close-up photos of the break ..? I'd like to see them. ksh - there are some loader arms (on the larger machines mainly) that are a special aluminium-killed alloy steel that would not respond to the procedure you mention above. In face trying to straighten an arm that way would actually cause a sudden total failure of the arm in the same way as this 966 about 6-12 months after the repair.
I guess I should have included a disclaimer say I would not attempt this kind of repair without information on the type of alloy the boom is made from and proper means to make repairs to it. I know we had some 988B's that developed cracks in the tubing connecting the two boom arms. They would crack in a nice even X. Saw a few that people tried quickie repairs on that lasted maybe a week before the crack reappeared. Finally one plant had a welding expert look at the problem who gave them instructions on what rod to use and a detailed procedure to prep and do the welding. After that was done the cracking never returned. Knowing what you are working on and the proper methods can go a long way to a successful repair!
Thanks for your interest guys. It did have an over size bucket on it. It's not my machine and don't know if I'll do...or want to do the repair. Nige. I,ll see if I can get a better pic when I get out that way. That machine is resting now as the owner has other machines. I'm definitely interested in feedback from you guys on how to repair the problem or welding procedures on this. Thanks. Ps: or "stay away from that job "
Presently the only other picture of the break
Fix, I need a really good close-up of the face of the break. Either piece will do, either what's left on the loader or what fell off with the bucket. To give you an idea here's a lift arm I was intimately involved with (one of many TBH) that let go. Check out the photo, you can see the dark area that was a crack that was slowly developing due to fatigue, the "beach marks" as the crack developed over time are clearly visible. The silver area below it is where the final sudden failure occured. The root cause of this failure could be traced back well over a year to when the owners had a machining company recondition the pin bores to the left but out of shot in the first photo, and to install new bushes. The machinists used a piece of steel I-beam or channel and welded it across the lift arm to hold everything in position while they did their boring operation. Unfortunately when they removed it they failed to completely remove all traces of their welding. The small "snot" of weld seen in the photo is what triggered the start of the fatigue crack that led to the final failure. The bill for a new lift arm was close to $200k. To quote a famous TV show - "Let's be careful out there" .............
Serious!, not yet seen a failure on a lift arm like that. Would really like to see a repair process.
So would I. There isn't one........... the whole lift arm which weighs about 18 tonnes is put in an oven and stress-relieved at 700 degrees for 12 hours after welding when it is manufactured. That kind of rules out field repairs because ovens that big are not found in most welding & fab shops. I've seen a number of customers attempt to repair breaks like this one (I have a file full of photos of at least a dozen that have failed this way), the record for how long a repair lasts currently stands at 3 months - and that after investing probably somewhere around $30-40K in the repair as a minimum, often a lot more than that but a customer with egg on his face is never going to admit to you exactly how much he spent after you advised against attempting a repair in the first place. Economically it's not worth it but as I always tell them when they insist on having a bash - "crack on, it's your money" ..........
Jeez... Cheers for the info Nige.
I use photos like these to encourage people to look after the Lift Arm and to show them just what can go wrong when their d1ckhead welders going slapping additional brackets and stuff on to a structure where they know Jack Schitt about its metallurgy ....... The reason I posted the photos was really to show the OP of this thread the type of photo I'm looking for on his 966 Lift Arm. If we had those photos we might just be able to come up with a reason why it failed in the first place. Knowing why it failed is half the battle of coming up with a repair process or making a decision if said process is even possible. BTW the 966 Lift Arm is not so complex metallurgically-speaking as the one in my photos. However anyone harbouring thoughts of trying to glue the broken bits of something like this back together really ought to know potentially what they are up against.
Thanks for the head's up Nige! I want no part of that now. I saw no heat or welding marks on it, but that doesn't mean they weren't ground off. I believe the break to be clean and consistently even, a light even silver like in the picture. If I go by there again I'll get a close up and check for grinder marks.
Wow didn't know it's a real money repair! Looks like it's got a fine future to look forward to pushing snow or pulling a wagon on the farm.
Nige I will definitely try to get you a close up picture. It's got me wondering why it failed too! Thanx again, fix
This is a 966f I don't know the year. Makes me wonder if this one was line bored too?
Remember that the 966 Lift Arm is NOT a heat-treated alloy steel structure like the photos I posted. However it still bears careful thought before going anywhere near it to try to repair, and figuring out why it failed in the first instance is key to answering the question "Is it repairable and if so - just exactly how do we go about doing it ..?"
That reminds me of something I was shown many years ago at a Cat school in Peoria. They had what I believe was track recoil spring out of a D8 that broke. The root cause of that failure was a tiny dot of weld that fell on the unprotected spring. The dot was maybe about twice the size of the period at the end of this sentence.
SWAG: first picture, hard to see but it looks like the crack started at the bottom and the bottom of the lift arm is deformed a bit. Picture of the bucket from a distance... looks pretty big to me for 966, and the OP did say it was oversize. First impression, maybe the oversized bucket slamming the bottom of the lift arm hard enough to find the weakest stress spot? Especially if one side hits before the other..... :my2c
Nige makes a very good point that is well worth heeding. Even a seemingly simple arc strike can lead to a catastrophic failure. Many people wave welding torches around like fairy wands and don't give much thought to the component they are working on. Often there is a detailed repair procedure listed by a manufacturer for a very good reason and some parts are just not designed to be repaired. I can only begin to imagine the commotion caused on a mine site if a loader broke an arm in service. There would be clipboard wielding safety guru's, witches hats, barricade tape, not to mention the obligatory statements and photographs. I sure wouldn't want my name to be connected to working on it without knowing a procedure or the type of material involved. Plus I would want to be able to demonstrate a documented competence to attempt the repair. So many unknowns and so many pineapples to receive (rough end first!).
Well we probably got some folks checking their loader arms now. What struck me (prompting me to seek Good counsel) was that The break looked like broken Cast Iron. ***? Also I wonder the proper procedure for line boring a similar hoist. Makes me shake my head and say Oh F* model
The steel for the main plate of a lift arm is usually a very fine-grained steel, that's why when it let's go the fracture face can look a little like cast. It's not though. For reconditioning/reboring a complete (i.e. unbroken) lift arm we're talking about a fairly standard process that is almost a sure-fire repair if it's done right. I have all the data regarding Lift Arm measurements of every Cat Wheel Loader ever made. All you have to do is ask....... The procedure for boring is a fairly simple 3-step process. It requires a mobile line-boring machine, or take the lift arm to a machine shop. 1. Centre the boring bar and bore both bores on a axis (i.e. pin bores on both sides) maybe 3mm (1/8") oversize. 2. With the automatic wire welder that's part of the boring machine, build up the bores with weld until they are undersize. 3. Bore to size. The reason you don't weld straight to an existing bore is two-fold. First it's a good idea to run the machine tool through the bore and clean out the crap to give your build-up weld a good uncontaminated surface to stick to. Second if you go well oversize then the heat-affected weld zone where you have the penetration between original steel and your repair weld is well away from your final surface level. RayF of this parish could likely explain it better than I can but he's on vacation right now. If you want to see some super-duper line boring check out this thread. This is how it SHOULD be done, but a lot of machine owners do not realize it's such a complex process.
You mean you can't just wash out the bushing bore and coat the inside of the boom with a thick layer of Devcon Iron filled epoxy and let it set overnight? Don't laugh we had a boss who thought that would work. Actually tried it and it lasted a couple minutes! Gee why did I doubt that repair? Same guy who when welder was repairing bucket and told boss we were out of 1/2 inch steel plate tried to convince welder he could just use two layers of 1/4 inch!
Thanks for your interest guys. ... I really appreciate the information Nige I don't think I'll be doing any line boring soon. But hey you never know. They had a portable rig where I worked but i never used it. I use a 966 here on a little dirt ranch but mostly as a tool carrier and ride around. K S I was thinking of starting a Devcon or adhesive post but maybe it would be under. .. "What have you done in a number nine bind" Ps...has anyone seen a walking chain binder?
Nige, thanks for that link - Ray is some craftsman - Me, I think i'll stick with the old Trojan.............
Fix, the point I was trying to make is that anyone who wants to glue that lift arm back together has to be prepared to do a reboring job on the bucket pin bores at the end of it all because it's guaranteed they will be out of line when the welding repair is completed.
I dusted off a few of my files. Here's another one, again back to a botched boring job. In this case it was again the A-Pin that failed, but this time it was the actual rebuilding weld done inside the bore. It was welded by hand and done with beads running along the line of the bore instead of circumferentially as an automatic bore welder would do them. At a couple of points the weld penetration was, shall we say, less than optimal - and that's putting it diplomatically, at the time I stated I had a 9-year-old son who could weld better...!! The result was a crack started inside and by the time it got to the surface the whole boss burst apart. Result - another scrap lift arm.
And another two, just to show how some "welders" (and I use that word under advisement) shouldn't be allowed loose with a welding machine - EVER. Both from the same customer and both with the same result. First - the grease line guards. The holes in the guards are to weld them to the structure dumbass, not to make them pretty and save weight ............. you can't just weld anywhere you want on this thing and get away with it.
Second - if you need more material on the bucket stops to protect your tilt cylinders FFS weld it on the back of the bucket, not on the Lift Arm............
Thanks for the scary pics Nige. Great photography. Maybe it's time for a welding section. Or a "Don't try this at home" section. Now we know why they make those "DO NOT WELD **" stickers
Can you see now why I would love to see some similar photos from the 966 Lift Arm..? It all adds to the store of accumulated knowledge at the end of the day.
Nige, as a Boilermaker, I am both amazed and dismayed at those photos, although I probably shouldn't be. I worked on a mine site with a "Boilermaker" who on paper was really well qualified, only problem was he had spent his entire career to that point where the heaviest section was 5mm and most jobs were downhand. His first week on the job was cut short after he hit himself in the face with a 12 pound hammer, (trying to remove shrouds of a Cat 2900 bucket). He nearly destroyed a charge up basket by drilling holes in the frame to mount new door hinges, not to mention the full hypercharge unit on the back while he was merrily cutting and welding. We could also mention the numerous wear strips etc lost because he only put a single run on them. He blew the computer on a Volvo loader because he didn't follow the disconnection procedure before welding on the machine. He found a crack in the lift arms of a 2900 one day while doing bucket repairs and eagerly grabbed the arcair torch. Thankfully he was stopped before he was able to arc up. Rushing in to jobs that you know nothing about will bring you unstuck every time. Those photos of yours really illustrate how critical maintenance procedures are on highly stressed components and the need to know your stuff before you commence operations.
I had a 994F articulation hitch to rebuild not long ago that got a lot of bearing play very suddenly and was nowhere near the hours we would expect for normal bearing replacement resulting from wear. On disassembly we could see the arc track marks through the bearings where some jolly welder had been too lazy to drag his ground cable right to where he was working and as a result had run his ground current right through the hitch while he was working. If I'd have found out who did it his ass would have gone into the hole along with the new pins when we put it all together ...........
I hope to be out that way soon for a few better pictures. Providing they didn't do anything hasty (thought I may have heard talk of a trailer) I haven't spoken with the owner of the machine. I looked for the stub of the lift arm when I was there and didn't see it. I'll see what I come up with this week and let you know.
Some interesti g pics there. Some of Niges bought a tear to my eye From a line borers point of view its a good reminder to take care where our support brackets are welded with a view to the future potential problems. I was once accused of being the cause of a 994 Liebherr boom breaking through a bore I had machined. A very big dollar item. It cost me an arm and a leg to get a proffessional crack analysis report done which proved I was in the clear but it was a close shave. With that 66 boom, I have seen quite a few successful repairs done on them. Its not something to rush into but if a proper procedure is followed its simple enough. The correct consumables, run off strips,proper preheats and it can be stress relieved locally by building a small furnace around the repair area to also get rid of the fusion zone embrittlement. Then as Nige says a proper line boring job after sorting out all the misalignment issues. Remember these arms always bend in service. Anyone who works on those small Cats will know as the arm is lifted out of the top bores the arms will spring together. Its normal for us to address that. Depending on what they have been used for they will normally twist. Sometimes to the point where they have to be pressed before line boring. Ray in Scotland
You do some really nice work Ray I didn't even think of run off strips but did give some thought to the preheat and cool down.
IMHO run-off strips are an absolute essential when welding any structure. They allow the welder to establish a stable arc outside the structure and to terminate it the same way. Afterwards you just cut them off - albeit carefully. We did a front chassis on a 16M not long ago. I'll see if I can find the photos.
I second that Nige. Run on and run off strips are the cheapest insurance against lack of fusion and crater cracking you will get. As you say though, it's no good doing a perfect weld, then destroying the job by gouging holes cutting the strips off.
Fix, if you do get back there again as well as taking photos take a look at the back RH side of the bucket. If it's a Cat bucket it will have a data plate on it just under the spill guard. Get any numbers that you can from it and we can figure out how big it is.
Will do Nige. I did meet the owner of the machine a couple years ago and he told me where his outfit was. I happened by there about a week ago to see if he was there. He wasn't bu an operator was and he showed me the machine I asked to see the stub but we couldn't locate it. I called the owner got the secretary. Left a message and didn't hear from him. As I was scratching my head a pickup pulled up guy was about 65 and owns a welding shop. We chatted a bit turns out his dad and mine were friend's. Now passed) So I thought I'd call him yesterday see what I could find out. He said the owner never returned his call either. That's another reason I'll drive by there again. If a cat bucket would it be on the right side in the middle? When I did meet the owner it was at a greasy spoon we talk over coffee. ..seemed like a good guy. Maybe he has more pressing problems. .. I'll take a ride over there. Thanks again Steve
If it's a Cat bucket the data plate will be all the way over to the RH side and about a foot below the spill guard. If the plate is missing often there are numbers stamped in the same location where the welders stamped them before the "Plate Guy" rivetted the data plate in position.
I thought that while I was on a roll I ought to post another one for Karl and all the welders on here. This was a classic case of "doing right by doing wrong" where cracks had appeared in the factory welds of the lift arm at the bucket end in what we commonly refer to as the "teardrop" reinforcements around the pins. To repair these cracks isn't hard, all you have to do is carefully gouge out the crack, take the last bit out with a small die grinder or Dremel, pre-heat correctly, weld with E7108 or the equivalent wire, needle peen each pass after welding, and finally grind the welds smooth, especially where they tail out beyond the teardrops on to the main plate. Well these guys did "none of the above" and worst of all they terminated every one of the repair weld passes one on top of another slap bang on the end of the teardrop. So it was no wonder that the lift arm developed not one but THREE high-cycle fatigue cracks which when they developed far enough led to the structure letting go catastrophically.
Here's what I think a half-way decent weld repair of cracks in the weld seams between the lift arm main plate and the teardrops ought to look like. Not 100% perfect IMHO but a lot better chance of living to a ripe old age than the one above.
Knowing the steel, rod material, pre-heat temp, post-heat temp, and stress relief temp/time is critical for certain alloy steels. I was a Tool and Die maker and did repairs on large Die-Casting dies. The dies were subjected to temp swings from 120F die lube sprays to 1300F molten aluminum every few seconds or minutes (depending on the volume of the casting, cooling time, etc.). This created surface cracks that would deepen, fill with aluminum flash, and eventually crack all the way through several inches of alloy steel to the internal cooling passages. Our repair routine: Disassemble, clean, die-grind/machine entire crack out, pre-heat to 800F, TIG weld with matching alloy rod, heat for min. 4 hours at 1100F, slow cool (8hours in oven with lid on), machine/grind to original contour/shape, stress relieve again (4hours at 1100F, slow cool), reassemble die. That's several shifts without any product going out the door. Very minor repairs were done in the machine, but when the die was pulled for other maintenance we would usually give it the Full treatment. At the other end of the spectrum (Farm work): cracked main lift arm on JD trackloader, grind out Polyester Body Filler (yup, somebody did a previous repair), grind out crystallized steel and 6011 filler (looked like 6011 beads when i got the Poly out of the way), Multiple-pass 7018 (peening and wire wheeling), grind smooth, add several Fish-plate gussets. Worked for years. It was the old style welded box-beam arm that was easier to work with than the new alloys.
Back to the subject of runoff tabs. Here is a crack we welded on a 16M front chassis right next to the lift cylinder brackets (where they always crack). Actually we put 2 sets of runoff tabs on it, outside and inside. The inside ones were inclined upwards to at the narrow end of the groove the weld bead could be run upwards off the chassis. Unfortunately I didn't get any photos of them so you'll have to imagine what they looked like. The final job looks pretty neat though I say so myself.
Yair . . . Nige . In your #45 post is there any reason the repair wasn't plated? Even though it is a massive section I have always assumed (at best) a weld repair will only be as good as the original uncracked material . . . it won't be any stronger, meaning the section will crack again. Does that make sense? Cheers.
Scrub, the problem was not with the crack itself, but in a vertical welded seam quite close to it. The horizontal crack was actually a consequence of a vertical crack underneath a stiffener plate (so unseen) in the frame caused by a dodgy factory weld in the frame right behind the lift cylinder mounting. The vertical crack developed unseen until it broke out at the top and the horizontal crack was the first sign of trouble. We fixed the vertical crack, updated the stiffener plates in the frame as per the latest generation of frame design (designed to help prevent the vertical crack coming back again in the future, despite the reason that bad welding was the root cause) and then simply welded up the crack in the top frame rail. The horizontal crack in the frame was a pretty minor detail in the grand scheme of things compared to the rest of the cracks that we fixed. I posted the photos more to show the use of the runoff tabs than anything else. Personally I'm a great believer in NOT using plates over frame repairs apart from in certain specific circumstances like excavator sticks and booms. From experience the doubler plate usually hides a pretty dodgy welding repair underneath it.
Yair . . . Nige . As always, thanks for explanation. A lot of truth in what you say but, generally speaking, if something broke or cracked during normal operation the thing wasn't strong enough in the first place and, as mentioned a weld repair without reinforcement is unlikely to be any stranger than the original. I always abided by that philosophy, but as mentioned on other threads, always tried to make repairs look like "factory" and part of the component. I am a completely self taught bush welder with knowledge gained from books. I was never shy to use a grinder and sanding disks down to 120 grit. I copped a lot of flack over the years from "tradesmen" commenting on ground and polished welds in high stress areas . . . pin bosses and the like. Cheers.
This failure, IMHO, was something a bit different - when we removed the stiffening plates to expose the frame underneath them there was at least 3" of vertical weld that when we gouged/ground it out had no penetration. it didn't fail because it wasn't designed strong enough, it failed because of poor weld quality. We cut the dodgy weld out and re-did it, updated the design by using the latest stiffeners, and lastly attended to the external crack. To me if we'd just fixed the original dodgy weld properly and used the original stiffener plates it would never have cracked again, but the parts for the upgrade were available at no cost to us so we did it at the same time. To me no repair weld is finished until it is ground back to the original profile and painted .......... so here's a typical example of a repair weld that I would consider (as it stands in the photo) to be "unfinished".
Yair . . . good one Nige! . We are poles apart in in background but obviously have come to the same conclusions on this subject . . . but if that component failed in normal service do you believe that even if that weld was dressed and polished it would not fail again with out some reinforcing? It is a competent weld but if you look closely at the last run on the right hand side bottom there is a slight discontinuity there that in a high stress/flex situation could propagate a crack. Cheers.
Tell me something, when you weld these plates of the lift arms of wheel loaders that are broken and must be joined with welding, is it advisable or not advisable to place a reinforcement plate?
Personally if the leg of a Lift Arm breaks clean through, like the photos in Post #42 above, then it's scrap and not repairable. This opinion is mostly because in order to find a welder with the skill levels (and the necessary equipment for stress-relieving after the repair) necessary to do a good job is somewhat like looking for a needle in a haystack. Others may have differing opinions. If anyone wants to have a bash at repairing a completely failed lift arm leg, let me refer them to the words of the famous @RayF ............. With that 966 boom, I have seen quite a few successful repairs done on them. Its not something to rush into but if a proper procedure is followed it's simple enough. The correct consumables, run off strips,proper preheats and it can be stress relieved locally by building a small furnace around the repair area to also get rid of the fusion zone embrittlement. Then as Nige says a proper line boring job after sorting out all the misalignment issues. Remember these arms always bend in service. Anyone who works on those small Cats will know as the arm is lifted out of the top bores the arms will spring together. Its normal for us to address that. Depending on what they have been used for they will normally twist. Sometimes to the point where they have to be pressed before line boring. @Mario Leon Try posting a few photos of the broken structure if you want better quality advice.