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OT, Skid loader boom repair, how the???

Ranchero50

Cast Iron
Joined
Jan 2, 2008
Location
Hagerstown MD, USA
'95 vintage New Holland Lx485 got dropped off today with a boom pivot point fatigue failure. I'm trying to figure out what happened and what needs done to fix it so it won't fly back apart...

The yellow bar's bottom pivot has about 3/4" of slop in it.
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The yellow bar is cracked out too
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Trying to figure out how to hold the boom pin so it's concentric with the other sides pin before welding it back together. I have a tow truck to pop the boom off so that's not too big an issue. It's used for farm duty, usually handling round hay bales for the animals.

Any suggestions other than run?
Jamie
 
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Crap design - should be reconfigured to be a clevis style design where the pin is in shear only -

Right now, the pin and the bores all have to carry huge moment loads.

If the engineer who came up with that design used that kind of judgment on a regular basis, no doubt his employer celebrated the day of his/her departure.
 
Been a while (30 yrs) but when I used to do jobs like that I found the only reliable method was to cut the cracked parts right off and make new ends for the arms, lotta work, but I'll wager a beer a simple dye penetrant test will show cracks all over the end.


X2 for Motion Guru's crap design.


If the customer wants a cheap ''weld her up'' job ask them to take it elsewhere.
 
Just this once I gotta disagree with MG. The pin did not fail. That thing
took a hard shot from the side. I would not repair the one failure before
I found the other ones.

Looks to me like the *upper* portion of the top, black arm was ripped off the
lower portion, in the upwards direction.
 
Jim, no marks of a side load. Even frontal hits on the bucket or forks would or should cause cracks in other directions. The pin pivots on the yellow bar. This one has me stumped for a post mortum. Only lifting under a load causes the crack to spread. If I load the boom going down the crack shrinks. The pivot points are free. Overall the loaders in pretty decent shape. With the slop in the bottom pivot point the boom always swings to the left before lifting off the stops. I'm just having a hard time figuring why it's fatigued so bad at the welds only at this point.

Jamie
 
get a lump of 4" or more dia and cut back the arm until the solid
can be welded in.MG is right.The design is weak,but it can be made
stronger.
 
Davo, it's got a 3/8" strap on from the factory. it already split through it too.

Jmead, I was hoping to bend the pin back straight before welding it together.

Motion, I guess it's done pretty well for being 15 years old especially under the loads to articulation sees.

Limy, I don't want to cut it off. I'm more looking at a five year repair (sadly this thing will be junk by then). Goal was to do a simple repair to make it safe to use.


Guys, Thanks for the replies, it's given me something to think about this evening. I'll post up some pics tomorrow as I get into it.
Jamie
 
Keith, the 4" was the original idea but I don't want or need another garage queen. I'm just about done the Cummins 6bt conversion on the '89 F450 tow truck.

I just want to work on my own stuff once in a while. :willy_nilly:

Jamie
 
Looks like the pin is moving in the yellow arm, and that opens up the crack in the black arm. Could be bushing wear in the yellow arm started it by allowing the pin to tilt and pry the black arm apart. Could the loader have been rolled at some point?

I agree with Motion. With all the leverage on the top arm and the cylinder, I wonder how any of them last.

I'd take the yellow arm off and fix it right or else replace it, then I'd Vee out the cracks in the black one, weld them up, then bend and weld big ugly gobs of heavy strap all around the joint and make sure it doesn't get painted so it gets good and rusty. Seems like that's how skid loader repairs get done on farms around here.

Any chance of finding used parts?
 
If this did duty with a hay spike (assuming round bales) - I can see why the pivot points are all wallered out. Their is nothing in the structure of the bucket arms to resist moment loads but the pins themselves and not a single hard pivot point in the whole design.

Typical bucket loaders pivot around a clevis captured fixed point of rotation - this bucket pivots around a virtual point of rotation that is defined by two links and a cylinder.

I bet if you lowered it and pushed on a bale spike from side to side that you have a foot of play or more at the end of the spike.

If it were mine, I would make a 3/4" thick x 4" wide x 12" long plate that attached to the yellow link (welded to a spacer so that it captured the black pivot point)

I'd repair and bore the black link and put the bushing in there. Then repair the Yellow link and line bore through the plate / link assembly for a tight fit.

Make a longer pin that spanned the 3/4" plate, black pivot point and through the existing Yellow link. Weld a tab to the pin so it doesn't rotate and bolt the tab to the plate.

A lot of work, but the repair would be one you wouldn't have to worry about ever.

I see a gusset welded in the lower link point - I bet that one is sloppy too.
 
Jamie
It looks like they were lifting to heavy or froze down hay bales.
Once the hay spike is under to heavy of bale the hyd. cly. tries to lift and can't. The cly. pushes against the pins if it can't raise the bucket.
Repair and check the by pass on the hyd pump to see if someone bumped the pressure.

Hal
 
Wonder if the farmer bought it new or used? That's the sort of cracks that are typical of regular use of a hydraulic demolition hammer on a skid steer.

There's a definite purpose to New Holland's design of the bucket arms and linkage. By allowing the pivot point to rise, they can get a lot of additional dump height. NH skid steers actually have one of the best reputations among skid steer loaders as evidenced by what they'll bring at auction as compared to other brands of similar size and condition.
 
1 New black boss.
2 Install #1, then weld cracks in original black "wrap".
3 Overlay a stout reinforcing strap onto the original wrap. Taper the ends of the new overlay from both sides at both ends.

This skid steer is in hell of a lot better shape than the '92 Alamo side-boom mower (tree trimmer?) that I am currently repairing!

locoguy
 
If this crack is not matched by similar crack or obvious distress in paint on opposite side, look for an asymmetry. Perhaps a bushing fell out on one side, causing the while boom to cock and concentrate stress on one cheek of one boom end. Also consider that perhaps one cylinder leaks. or one hose is kinked, so that one side is getting more stress than other.

For the structural repair, yes, vee-out and weld E7018, yes, add 1.4 x 2 flatiron strap wrapped hot around end of boom. Taper ends of strap so they are at least 4" longer at inside edge than outside edge, do both sides, weld all around. Use vibratory stress relief while welding if possible. Welding strap on while it is hotter than the original boom end will provide much better stress distribution, like autofrettaging gun barrel
Magnaflux unnecessary. Paint acts as brittle lacquer, will show cracks.

Do take care to weld or bush sloppy bores and align-ream or bore everything or at least use a long bar as alignment pin while welding, and straighten pins as needed, and check out cylinders, to be sure loads are balanced.

A billet end is overkill.

Possible that the overhung or cantilevered trunnion design is root cause, as it would concentrate stress at inner cheeks of boom...but look for distress on other side.
 
skid steer

Everyone is talking about the black arm, look at the top of the yellow arm sure looks like another crack to me there is a grease fitting at the top of the yellow arm that means it a pivot point which is probably means the bushing is worn out.
 
Doesn't strike me as a single blow failure mode. I would expect some racking and bent metal to go along with a set of cracks like that.

The jackhammer possibility certainly has fatigue written all over it.
 








 
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