JCB 512-56 Broken Axle

[Makers Acres]

Well, I did another dumb thing and bought a used machine with problems. From what I can tell so far before I tear it apart, it looks like it needs a rear axle, or maybe just a rear knuckle?

It looks like just one side snapped the rear knuckles off. I found a Facebook thread from a rental company that appears to see this a lot when someone forgets to set the parking brake and lets it roll down the hill or drops the load of the front too fast and then the machine comes crashing down on the rear. I imagine with that large counterweight that is a lot of stress on these castings. To me, the castings look too small to begin with.

Anyhow, does anyone have the service manuals for this thing?

Has anyone done this repair before? I am sure I am going to get some negative responses to this, but has anyone welded one of these back together and then line bored it? I know if this was a rental company or a company machine, this is an absolute no-no, but this is a private machine for moving things around the farm from time to time. Maybe 5-10 hours of use per year... maybe.

 

[Simon C]

Well, I did another dumb thing and bought a used machine with problems. From what I can tell so far before I tear it apart, it looks like it needs a rear axle, or maybe just a rear knuckle?

It looks like just one side snapped the rear knuckles off. I found a Facebook thread from a rental company that appears to see this a lot when someone forgets to set the parking brake and lets it roll down the hill or drops the load of the front too fast and then the machine comes crashing down on the rear. I imagine with that large counterweight that is a lot of stress on these castings. To me, the castings look too small to begin with.

Anyhow, does anyone have the service manuals for this thing?

Has anyone done this repair before? I am sure I am going to get some negative responses to this, but has anyone welded one of these back together and then line bored it? I know if this was a rental company or a company machine, this is an absolute no-no, but this is a private machine for moving things around the farm from time to time. Maybe 5-10 hours of use per year... maybe.

Maybe post some pictures for more folks to chime in.
Simon C

 

[Makers Acres]

So I bought the thing sight unseen on Tuesday, and picked it up today (Thursday). I was just going off crappy pictures before, but was so excited I wanted to get something posted so I could lay awake at night thinking about the repair. I was able to drive it 3 wheeled on and off the trailer and the engine and the rest of the hydraulics appear to be good. Attached are some pictures I took a few minutes ago. And to be clear, the other chunk is missing.

 

[llehandro]

This is how I would repair it:

• Completely disassemble the steering knuckle.
• If the broken piece is available, reuse it. If not, machine a new section.
• Grind a full V-groove on both sides of the fracture.
• Preheat the casting to around 250–300°C.
• Weld using TIG or pulsed MIG with a high-strength filler such as ER80S-D2. If the base material is uncertain, 309L is usually a safe choice.
• Keep the part in a rigid jig during welding to maintain alignment.
• After welding, machine and fit an external 4140 steel reinforcement around the ear to help distribute the load.
• Allow the part to cool slowly under insulation.Cool slowly, covered with a thermal blanket or dry sand.

If it were my machine, I would first look for a used or new steering knuckle. Welding would only be my second option if replacement parts were unavailable.

 

[Makers Acres]

This is how I would repair it:

• Completely disassemble the steering knuckle.
• If the broken piece is available, reuse it. If not, machine a new section.
• Grind a full V-groove on both sides of the fracture.
• Preheat the casting to around 250–300°C.
• Weld using TIG or pulsed MIG with a high-strength filler such as ER80S-D2. If the base material is uncertain, 309L is usually a safe choice.
• Keep the part in a rigid jig during welding to maintain alignment.
• After welding, machine and fit an external 4140 steel reinforcement around the ear to help distribute the load.
• Allow the part to cool slowly under insulation.Cool slowly, covered with a thermal blanket or dry sand.

If it were my machine, I would first look for a used or new steering knuckle. Welding would only be my second option if replacement parts were unavailable.

This is all great info! Thank you. You can get them still, but JCB wants 7500$ plus tax for just that one side. 22.5k for the full axel casing. It’s hard to justify when I got the machine for 14.5k. Seems outrageous to me. I’m looking for used ones, but I have not found any listings for them, which seems surprising to me.

 

[llehandro]

This is all great info! Thank you. You can get them still, but JCB wants 7500$ plus tax for just that one side. 22.5k for the full axel casing. It’s hard to justify when I got the machine for 14.5k.

 

[llehandro]

I completely understand. At those prices, I’d definitely consider repairing it before spending more than the machine is worth.





If the fracture is clean and the rest of the knuckle is in good condition, a properly executed repair with the correct preheat, filler material, controlled cooling, and an external reinforcement can last a long time, especially on a machine that’s only used occasionally.
.I've seen many soldiers spinning around even today.