Backhoe piston broke

[seniornukect]

It's not tight, about 1/16th on either side. The pin looked fine, no issue removing it.

 

[ray66v]

Clearly there was a defect in casting of the piston eye.

May have been made that way, or damaged at some point.

If you find can't get a replacement, it would suggest there is a known manufacturing problem.

Good luck with your repair.

 

[SPYDERLK]

Im guessing the pin is bowing significantly and the boss sees extremely high stress from the bore trying to make the pin stay perfectly straight. Stresses would be highest with a new and tight bore - like yours. How wide spaced are the BH ears in comparison to the width of the cyl rod pin boss?

It's not tight, about 1/16th on either side. The pin looked fine, no issue removing it.View attachment 713639

I cant tell (or see) the extent of bracing around the ears where the pin connects the cyl rod to the dipper. The ears look pretty thin, and unless doubled by some more plate welded in where I dont see, there may be more flexure allowed than is prudent. Flexure will compromise support of the pin. Those hefty bosses in the ears are supported way out at the ear metal itself, so unless the ears are buttressed in some way the bosses offer little support of the pin inside the ears themselves. If the pin bows much the splitting forces on the new/close fit failed part are huge - - and may be a primary contributor. Hopefully that cyl rod eye/boss was just defective.

 

[5030]

it's forged, not cast and it's not pot metal. Don't believe you know what pot metal is. Just get a new one and carry on.

 

[panamaguy]

Anyone run into this issue with a woods bh75? I am digging a trench for water and power lines and found a good sized rock. No way to lift it out so I dug a deeper hole behind it and when I went to push it back with the bucket I heard a bang and the dipper arm swung loose. Found the half of the eyelet in the hole, no sign of the grease fitting. It looks like really cheap pot metal.View attachment 713444View attachment 713445

Having been a welder all my life and for 15 years a welder in a hyd shop in Canada I have welded thousands of cylinders. Take it apart so you do not cook the seals. If you do not have a lathe take it to a machine shop and have them machine a new rod end and tap it for a nipple and have them weld it. If you weld yourself and want to do it preheat the rod a bit and the

 

[panamaguy]

Having been a welder all my life and for 15 years a welder in a hyd shop in Canada I have welded thousands of cylinders. Take it apart so you do not cook the seals. If you do not have a lathe take it to a machine shop and have them machine a new rod end and tap it for a nipple and have them weld it. If you weld yourself and want to do it preheat the rod a bit and the

Sorry hit the wrong button. Tack it on. Preheat it a bit, not red hot but to hot to touch, turn the oxygen off on the torch and just leave the act on and blacken the chrome rod, this helps stop splatter sticking as it does not stick to carbon. Weld it and then col slowly, cat litter is good for slow cooling if you do not have floor dry for soaking up oil off the floor

 

[RancherGuy]

It's not tight, about 1/16th on either side. The pin looked fine, no issue removing it.

@SPYDERLK makes good points. The sheetmetal supporting the ends of the pin look unreasonably thin - as though the backhoe is only intended for light-to-medium duty, so be careful on how hard it is used. The pin itself may be low grade steel and might flex/bow. You might want to find a high grade replacement for all high-stress pins throughout. Most likely metric, but if this works, visit a tractor store and see if you can find a high grade hitch pin or a thick high grade bolt that can be cut to length and drilled for the retaining pin. A machine shop can reduce the diameter if you get something oversized.

The other point I was going to make is a reference to a very recent hydraulic cylinder repair by Abom79. Not that this matches your situation, but if that eye broke, the process there about welding a new eye might be a consideration. Have a machine shop make a billet steel replacement with thicker sidewalls. My guess is that the original eye is either cast iron (poor choice) or cast steel then welded to the rod. They they induced failure by drilling a big hole for the zerk fitting where tension is the highest. Abom79:

 

[SPYDERLK]

it's forged, not cast and it's not pot metal. Don't believe you know what pot metal is. Just get a new one and carry on.

Could it be some eyes are cast steel? It would fit with the calamitous cracking. Cracking a forging is significantly harder and longer term in development.

 

[5030]

Never seen one but anything is possible today Being a high stressed part, a casting would always be suspect.

 

[Dmacleo]

those sides do (IMO ) look thin and susceptible to flexing.
with cylinder on do you have room to weld a cross piece in to support those ends?