Dipper snapped

[North Idaho Wolfman]

Side loading them can cause them to fail like that.

 

[chim]

I'm not an engineer, nor do I have any experience with repairs like that. I do recall discussions on how the shape of reinforcing plates can affect the strength / longevity of the repair. Hopefully someone who understands such things will drop by. BFreaky built his own backhoe and discussed some theory on that over on TBN.

 

[dirtydeed]

Wow. That really sux.

Broke right below the reinforcement.

 

[selftot]

I'm an amateur but this is what i came up with. Probably overkill and wrong shape. And wrong location. lol.
Would appreciate any feedback.

 

[selftot]

Side loading them can cause them to fail like that.

I am guilt of that - especially in earlier years.
When it happened, i was grabbing a rock when the tooth slipped - pulling the bucket away from the side where it failed.

 

[McMXi]

I'm an amateur but this is what i came up with. Probably overkill and wrong shape. And wrong location. lol.
Would appreciate any feedback.

View attachment 168461

CAD to the rescue!! Cardboard Aided Design. Your repair would almost certainly improve the strength of the part but there are lots of ways to complete this repair.

I worked as a welder for years and have numerous certifications including 5G pipe and repaired hundreds of Cascade forklift parts when I lived in Oregon so I know more than a little about welding repairs. Access to a plasma table and press brake would make this repair easy for sure. Home repairs are often more limited, but plating each side and even a puddle weld on either side of the failure (via holes in plate) would help.

Personally, I'd do some weld prep, get the part back in alignment, weld it up, plate it on at least both sides and possibly a third side, paint it and never worry about it again. Your template is perhaps a little more elaborate than I'd make but it's still a good concept.

 

[Hugo Habicht]

I'm an amateur but this is what i came up with. Probably overkill and wrong shape. And wrong location. lol.
Would appreciate any feedback.

View attachment 168461

This would be my suggestion. The strain is mainly on the right hand side when digging, hence the original reinforcement. People with finite element software can propably calculate a better shape.

And of course v-groove and weld before attaching the plates, as suggested earlier.

 

[ruger1980]

As Stated that has been broken for quite some time and should have been noticed. That would have made the repair much easier.
I would probably just cut whatever is holding the stick in one piece and put backer plates behind the cracks and vee the broken areas back to clean metal. Weld where the cracks are to make the stick whole. Reinforce the side with a pattern similar to what @Hugo Habicht drew and you can probably put a plate to and bottom as well.

Never weld perpendicular to the length of the stick. This is a sure way to crack the stick again. Always weld on a diagonal either the entre way as drawn or using a pint or fish mouth pattern on the reinforcement. You do o not have to weld fully around the end of the plates. You can terminate the weld before the end of the plate. If you do weld to the end of the plate, extend the weld past it and join the 2 weld. I would then grin the end of the puddle flush with the base metal.
Make sure you have enough welder to do the job.

 

[JohnDB]

If you need to get it up and running quickly, some good solutions above. If you have more time to plan, IMHO you should consider it's highly unlikely that its made out of mild steel, more likely something like ASTM A656 Grade 80. So would expect low hydrogen electrode/pre/post heat treatment. The reinforcing would need some thought to avoid adding stress raisers - which is more of an issue with high strength steels like the Gr 80. Depends on how long you aim to keep the machine doing the same sort of work.

 

[selftot]

I appreciate all the positive comments and repair suggestions.

I was going to give it a try myself but decided to take it to my welder tomorrow. My welding skills are limited. If i screw it up and find out later - it's not just a "grind it down and try again" thing.

Thanks guys !

I'll post pictures when he's done

 

[D2Cat]

I appreciate all the positive comments and repair suggestions.

I was going to give it a try myself but decided to take it to my welder tomorrow. My welding skills are limited. If i screw it up and find out later - it's not just a "grind it down and try again" thing.

Thanks guys !

I'll post pictures when he's done

That's a good choice!!

 

[Runs With Scissors]

I appreciate all the positive comments and repair suggestions.

I was going to give it a try myself but decided to take it to my welder tomorrow. My welding skills are limited. If i screw it up and find out later - it's not just a "grind it down and try again" thing.

Thanks guys !

I'll post pictures when he's done

 

[Yooper]

3/8” T1 steel would be my first choice for the fish plate. The shape I would choose would look like a football. Preheat to about 400 Fahrenheit to prevent thermal shock.

I believe Wolfman is on to something with the side loading. That makes sense looking at how this crack started.

 

[hagrid]

I'm curious about the pressure at which the relief valve begins to open.

 

[Motion]

In addition to repairing the damage, I'd suggest removing the manual thumb and welding some ears to accept a hydraulic cylinder and properly place the thumb and a couple of brackets to mount hoses.

 

[TheOldHokie]

I'm curious about the pressure at which the relief valve begins to open.

Which one? The valve has an inlet relief and the swing, boom, dipperstick, and bucket circuits all (I think) have two different port reliefs each.

Dan

 

[John T]

Considering this is technically a 'compact' tractor its hard to believe it has enough nut to rip open like that.
Me thinks it had a ding'er in it from over-enthusiastic use..... eventually turning into a crack.
(especially if you are ham fisted with the controls)

It's been a long time coming.
A careful inspection would have most likely shown signs...

That damage didn't happen in one use.

OR,

It could just be an 'Act of God' .....

 

[ruger1980]

My guess is that the end of this weld created a stress riser that was the origination of the crack as @Yooper mentioned. It looks like they started their beat out past the reinforcement plate instead of ending there like they should have. Best practice would have been to end the bead extended form the reinforcement and then grind the puddle flush.

I would also guess that the steel used is nothing more than an average structural steel. No special or high strength alloys. using anything more than that is overkill in this repair. The The reinforcement does not need to be any heavier than what is there. Anything heavier is only adding weight and reducing the capacity of the attachment.

They don't use anything other than standard structural steels in large excavators so I doubt they use anything more than that on a small Kubota attachment.

I would probably use a 7018 rod in the repair, and make sure it is fresh out of a rod oven. Wire feed could be used if done properly and you have a welder that has the capacity to weld it properly, but it is not my preference.

 

[selftot]

I showed it to a fabricator at an excavation company. He was convinced that original welding technique was to blame. He suggested the arm was not properly pre-heated when welding the reinforcement which caused stress when it cooled.

I was inclined to believe him - mainly because it exonerates the operator (me).

 

[hagrid]

Which one?

Dan

All.