Bent bucket cyl on model 48 backhoe

[DanMc77]

Wow, that’s pretty amazing how you got the same exact bend! Definitely a weakness in the machine here, which supports going with the larger diameter rod.

I don’t have an exact measurement on how much I had to shorten the rod on the new cylinder. I think I would have taken measurements off the machine. Why not cut off both ends and use the original pins? I wanted to make it easier in the future to change out the cylinder if I ever have to change it again, for whatever reason.

BTW: I have probably put 20-30 hours on the machine since my repair. All is well and I can’t tell that it ever happened.

 

[loggin]

Was wondering if a pressure test was ever performed on either machine? Could be pressure relief valve malfunction or set too high. Or could just be soft metal used in the rod.

 

[beenthere]

It isn't a weakness in the machine, but is a result of using the bucket wrong.
That cylinder when all the way out is to be correctly used pulling in on the cylinder (as in under tension) rather than pushing out as in compression.
Will function pushing out, but has to done very carefully or the bent rod can be the result.

 

[bindian]

It isn't a weakness in the machine, but is a result of using the bucket wrong.
That cylinder when all the way out is to be correctly used pulling in on the cylinder (as in under tension) rather than pushing out as in compression.
Will function pushing out, but has to done very carefully or the bent rod can be the result.

Looking at the last two photos, it looked like the straps links or the "H" link are too long. But wrong bucket with the rod end out of the designed travel axis can do that. My Bradco backhoe buckets have 3 positions I can attach to. One is digging, one is for loading dumptrucks, and I forgot what the middle holes are far. All designed for my Bradco 511 backhoe.
hugs, Brandi

 

[al20hp]

nks for sharing the info on the bushings. Those might come in handy

ll length of the pin looks to be 7 3/8" while the width of the dipper measures 7 1/16". If you want photos let me know.

Wow, that’s pretty amazing how you got the same exact bend! Definitely a weakness in the machine here, which supports going with the larger diameter rod.

I don’t have an exact measurement on how much I had to shorten the rod on the new cylinder. I think I would have taken measurements off the machine. Why not cut off both ends and use the original pins? I wanted to make it easier in the future to change out the cylinder if I ever have to change it again, for whatever reason.

BTW: I have probably put 20-30 hours on the machine since my repair. All is well and I can’t tell that it ever happened.

This is my first time repairing a hydraulic cylinder (besides replacing hoses).

Two questions


1)What did you use to cut the rod? Metal chop saw ?

2) Also, guessing I'm going to to be cutting somewhere between 6-8 inches of the replacement rod off. Prior to cutting it, I'm figuring the best way to determine where the cut should be would be to place the hydraulic cylinder on the backhoe and extend and retract the rod to determine the proper area to cut?


Thanks
Al

 

[DanMc77]

I think we may have used a cutoff wheel.

As for me, I was pulling on a tree root. I had the bucket curled in a little, and the boom/dipper both fully extended. I hooked the bucket teeth into the root and then began to pull with the boom and dipper. That obviously overstressed the bucket cylinder rod. But the new cylinder has a 1/4” larger rod diameter, so hopefully that won’t happen again.

In my opinion, a machine should be capable of handling a situation like this.

 

[ROUSTABOUT]

Yes it's bent.

 

[loggin]

I think we may have used a cutoff wheel.

As for me, I was pulling on a tree root. I had the bucket curled in a little, and the boom/dipper both fully extended. I hooked the bucket teeth into the root and then began to pull with the boom and dipper. That obviously overstressed the bucket cylinder rod. But the new cylinder has a 1/4” larger rod diameter, so hopefully that won’t happen again.

In my opinion, a machine should be capable of handling a situation like this.

Agreed. Your machine should be designed to handle that sort of situation. Did you ever check the pressure of the hydraulics to see if it is within specifications?

Also wondering if you have put a different bucket on other than what came with the backhoe?

 

[al20hp]

Agreed. Your machine should be designed to handle that sort of situation. Did you ever check the pressure of the hydraulics to see if it is within specifications?

Also wondering if you have put a different bucket on other than what came with the backhoe?

My JD 4700 with 48 backhoe is all factory

 

[DanMc77]

Agreed. Your machine should be designed to handle that sort of situation. Did you ever check the pressure of the hydraulics to see if it is within specifications?

Also wondering if you have put a different bucket on other than what came with the backhoe?

No. Mine came with a 4 tooth bucket and that’s fine. I have not checked hydraulic pressure. But what I was doing could create some very high pressures. Having the boom fully extended, then pulling creates some tremendous mechanical advantage. Couple with the cylinder being close to fully extended, then add some torque being applied to the rod by the pin. I don’t think that there’s a work-port relief valve on the bucket cylinder.

Look closely at my initial posts, you may notice that I have a hydraulic thumb. The valve for the thumb was specifically chosen with a workport relief so the bucket can push back the thumb when grasping rocks and stuff. I’m sure the bucket valve has no relief.

 

[DanMc77]

Relating to the comment about straightening the rod. All I can say is wow. Straightening that out would be very impressive. But in my case, the rod surface has millions of microcracks in the bend, which would probably eat the seals.

I find it a bit disappointing that a stiffer steel would not be used for the original cylinder rod. I’m my opinion, that is a defect in the machine.

If this ever happens again, I think there’s a good chance that Magister would replace the cylinder for free (but not after cutting off the rod end). Whatever, the replacement cylinder was inexpensive enough to not lose any sleep over.

 

[DanMc77]

@al20hp:​

I just measured the modified Magister bucket cylinder on my machine.

Extended: 43 7/8"
Retracted: 25 5/8"

With this, you should be able to figure out how much to cut off. However, I would still recommend that you make measurements on your machine with the cylinder disconnected to confirm the extended and retracted limits.

Oh by the way, before I could get the rod end pin out, I had to cut off the cylinder rod close to the cylinder body. There was a great deal of pressure on the pin from the rod being jammed up against the dipper, so that needed to be relieved before the pin would come out. I saved that bent rod section. It's a good conversation piece.

 

[al20hp]

Thanks for the measurements. My new cylinder is scheduled to arrive today. I removed the old cylinder & pins the other day with no difficulties. The pins came out with minimal effort. Hopefully I can get it to the welder tomorrow.

Thanks

Al

 

[DanMc77]

What will you do about the cylinder end cross tube bore?

 

[al20hp]

What will you do about the cylinder end cross tube bore?

 

[al20hp]

I purchased a 1.25 “ x 8” piece of stock steel and some bushings. I’m not sure if I’m going to use the original bolt hole to hold the pin. When the new cylinder is in place I can determine if I need any shims

 

[al20hp]

 

[al20hp]

@al20hp:​

I just measured the modified Magister bucket cylinder on my machine.

Extended: 43 7/8"
Retracted: 25 5/8"

With this, you should be able to figure out how much to cut off. However, I would still recommend that you make measurements on your machine with the cylinder disconnected to confirm the extended and retracted limits.

Oh by the way, before I could get the rod end pin out, I had to cut off the cylinder rod close to the cylinder body. There was a great deal of pressure on the pin from the rod being jammed up against the dipper, so that needed to be relieved before the pin would come out. I saved that bent rod section. It's a good conversation piece.

Are your measurements from end to end of the cross tubes. Or from the center of one cross tube pin, to the center of the other cross tube pin?

Thanks again

Al

Hopefully, I will have this thing running again soon!

 

[DanMc77]

Center of pin to center of pin.

BTW: be careful of rocks rolling on the the stabilizer cylinders. Been there done that too. I’m still thinking about some shields to protect the chrome rods. Maybe I’ll build a wood prototype before getting into steel. Sometimes wood prototypes work so well that they become permanent.