Broken Pin - BH77

[Mac in PA]

Well it finally happened, the pin that holds the two cylinders on the boom broke Wednesday night.

I latched on to a rock in the ditch trying to pry it loose. I was working the bucket, boom and dipper at the same time, which had worked many times before to pry a rock loose. I heard a loud crack even over the roar of the engine at full throttle and ear protectors on. I then noticed that the boom cylinder and dipper cylinder were wiggling in two different directions at the anchor point. Checked it out and the pin had broken. Luckily there wasn't any weight in the bucket so it didn't damage the boom at the pin anchor holes.

The first picture shows the broken pin, which broke at the weak point, the grease groove. The second picture is the new pin. It may not be visible but it looked like the heat treating was different at the grease groove and 1/2 inch on either side of it. Improvement? ? ?:confused3:
Picture three is before the broken pin was removed. No evidence that it was broke. The last picture is with the new pin installed.

Before I assembled everything I pulled the cylinders back and made sure the new pin could be slid in place easily by hand. This verified that the pin anchors were not twisted or damaged.

I ordered the part Thursday from Messick's and asked them to get it UPS Next Day Air and I would pay the freight.
Warranty covered the cost of the part. Everything worked out as planned and I had the BH up and running the next day. :applause::applause::applause:

 

[Deano]

Wow! :confused2:

 

[KennyV]

You could view it as a fuse failure...
At some point things are overstressed... it is good to have an affordable & easily replaceable part fail, before something major breaks.... KennyV

 

[sal64]

the pin was heattreated to hard thats why it snaped.

 

[Verticaltrx]

You could view it as a fuse failure...
At some point things are overstressed... it is good to have an affordable & easily replaceable part fail, before something major breaks.... KennyV

The only problem with that is that most of these I've seen bend the cylinders ears and the tabs on the boom with it.


Was this one of the early 'problem' pins or one after the recall? I've been thinking about a BH77 for my B3200 but this issue has worried me all along.

 

[magicheater]

Was that a 3/4" or 1" diameter pin?

 

[Mac in PA]

Was that a 3/4" or 1" diameter pin?

The pin is 1.172" in diameter or a little over 1 1/8"

The only problem with that is that most of these I've seen bend the cylinders ears and the tabs on the boom with it.

Was this one of the early 'problem' pins or one after the recall? I've been thinking about a BH77 for my B3200 but this issue has worried me all along.

I bought the BH77 new January of this year. I was not notified of a recall if there was one for my unit.

I believe I was very lucky that I caught it before any major damage was done. I'm not sure what caused it to break but it looked like the pin was partially broken or cracked. There was a dark area on the one side of the break about 1/8" wide, which indicated to me that it was cracked for a while before breaking.


Mac

 

[Tomtint]

Mine broke the second time I used my BH. I was digging a pine stump out of sandy soil and SNAP. It mangled the ears on the dipper and the dealer replaced everything under warranty.

 

[magicheater]

Well it finally happened, the pin that holds the two cylinders on the boom broke Wednesday night.

I latched on to a rock in the ditch trying to pry it loose. I was working the bucket, boom and dipper at the same time, which had worked many times before to pry a rock loose. I heard a loud crack even over the roar of the engine at full throttle and ear protectors on. I then noticed that the boom cylinder and dipper cylinder were wiggling in two different directions at the anchor point. Checked it out and the pin had broken. Luckily there wasn't any weight in the bucket so it didn't damage the boom at the pin anchor holes.

The first picture shows the broken pin, which broke at the weak point, the grease groove. The second picture is the new pin. It may not be visible but it looked like the heat treating was different at the grease groove and 1/2 inch on either side of it. Improvement? ? ?:confused3:
Picture three is before the broken pin was removed. No evidence that it was broke. The last picture is with the new pin installed.

Before I assembled everything I pulled the cylinders back and made sure the new pin could be slid in place easily by hand. This verified that the pin anchors were not twisted or damaged.

I ordered the part Thursday from Messick's and asked them to get it UPS Next Day Air and I would pay the freight.
Warranty covered the cost of the part. Everything worked out as planned and I had the BH up and running the next day. :applause::applause::applause:

View attachment 271678

IMHO: The shared mounting point allowing the cylinders to apply force against each other is probably the problem. If this is a common problem on the backhoe the only relatively inexpensive "fix" would be to retro for a larger diameter pin.

 

[Mac in PA]

IMHO: The shared mounting point allowing the cylinders to apply force against each other is probably the problem. If this is a common problem on the backhoe the only relatively inexpensive "fix" would be to retro for a larger diameter pin.

Replacing the pin with one that has no grease groove will probably fix the problem also. I don't believe that this groove is necessary.

Mac