Custom hydraulic backhoe thumb

[arkydog]

I have the Ansung model BH76 which is similar size to kb77 I think. From info I got here, I ordered from Surplus Center one that measures out to work to convert my thumb from manual to hydraulic. Item # 9-8760, '2.5x13.25x1.25 DA Hydraulic Cylinder' 159041 XHo411. Price was $70.

thank you ron50. i will check my length and stroke to see if its the same, should be.

my sister used to live around phoenix but now lives in payson, its a beautiful area out there.

 

[cic317]

Although it has a similar Yanmar engine as does the JD110, I don't see anything else it
might share with the Deere. It did compete in the same segment, smaller industrial TLBs.

AUX valves were optional, as I recall.

I knew the CBL40 has HST drive, and a 2-pump hoe, but doesn't the implement hyd pump
that powers the FEL also power the hoe?

I am not a fan of bolted-on thumbs, and esp not a hyd one with all that force at your
command.

As I pointed out near the beginning of this thread, I would get a welded cyl of the same
diameter as your bkt cyl, and design the thumb around it. That way, you do not have
to modify the cyl, and you can decide where to put the thumb pivot to achieve
the open/closed geometry you need. You have to fabricate a thumb anyway.

On that machine, I would use pivot pins of 1.5" diameter and 1/2" plate steel.

Another question, since you seem to have cornered the market on thumb fabrication...HAHA, what width is the thumb you settled on? The bucket on my hoe is 24" and suits most of what I needed. I was thinking 12" wide w/ 2 tines, or would you say to wide?
Thanks

 

[Aquamoose]

I have the Ansung model BH76 which is similar size to kb77 I think. From info I got here, I ordered from Surplus Center one that measures out to work to convert my thumb from manual to hydraulic. Item # 9-8760, '2.5x13.25x1.25 DA Hydraulic Cylinder' 159041 XHo411. Price was $70.

Ron50,

I also have the same backhoe, did you confirm that it's the right cylinder? I want to do the same setup on mine. Hopefully you can advise me as you progress?

 

[Ron50]

Aquamoose,
Surplus Center just shipped yesterday for some reason. Due to me UPS this comming Monday. This should give cylinder and I already have a pressure relief valve from Ken's BoltOn Hooks to protect thumb from being over powered by curl function of bucket. I've used excavators that have this relief so for $100 I thought it was worth it. Pay now instead of repairing later.
I"m adding a valve to the control stack to power it. I'll split the stack between the stabilizer vlaves and insert the new one. This is the hardest part of the install to get the stabilizer valve. I hope tomorrow that with the help of a local hydraulic shop I'll get it done. Walvoil distribution center gave me three choices, just have to get it right. Then I'll get hoses made. No diverter or 3rd function, just another valve block. Ansung was nice but they never called back, so no help.
I'll keep you posted, Ron

 

[bumperm]

maybe your not understanding me or I'm not understanding what you are trying to say.... i already have the bh77 back hoe with the factory kubota mechanical thumb installed on the backhoe. I'm wanting to convert the mechanical thumb to a hydraulic thumb and am wanting some help figuring out which hydraulic cylinder to get to convert to hydraulic. i just can't figure what hydraulic cylinder to start with. does that make more sense.

This is the cylinder I used to convert my BH77 thumb to hydraulic:

Chief WX Hydraulic Cylinders | Bore 2in. Bore - 3000 PSI 2 X 10 WLD CYL 1.125 ROD 207-384

This cylinder, with the BH77 and Kubota mechanical thumb, allows full retraction and more extension than the stock manual link. Without the 1/2" spacer (see below) the thumb hits the cylinder upon retraction and the rod lacks full retraction by about 5/8". With the spacer, the thumb retracts fully and stops its swing about 1/8" from hitting cylinder in its storage position. Upon full extension, the ram stops with the piston rod about 1/8" away from hitting the end of the dipper stick - so max extension and travel is had at both ends of the cylinder stroke.

An advantage of this cylinder is that you can change how the ports are oriented. But, like most cylinders you might purchase, this one too is just "almost" right. It can be used as is, and I did so for awhile. But to be absolutely perfect for the job, it needs to be 1/2" longer. I cut off the cylinder end fitting and welded it back in with a spacer. I tack welded this in place mounted to the hoe to correct for a slight misalignment that existed, probably in the hoe brackets (it amounted to a hair over 1/8" off set in the rod end so no big deal - - but if you're welding it anyway . . .

BTW, not necessary to take apart the cylinder to weld or cut - unless you want to. When I was welding the spacer I extended the rod all the way to get the seals away from the heat, then wrapped a wet rag around the cylinder near the weldment. No problems at all.

There are other threads on this endeavor with more info. Dfkrug is one of the pioneers and instrumental in getting a number of us off our butts and doing this mod which is seriously worthwhile!

 

[Aquamoose]

Thanks Ron!

 

[dfkrug]

what width is the thumb you settled on? The bucket on my hoe is 24" and suits
most of what I needed. I was thinking 12" wide w/ 2 tines, or would you say to wide?

the width you decide on is influenced by what you plan to use it for. If you are trying to hold looser
materials inside your bkt, then making the thumb nearly as wide as your bkt makes sense. If, however,
you are grabbing rocks, logs, or branches, a narrower width will reduce the twisting forces on the
thumb without adversely affecting the grabbing action.

To make things simplest, I went with a width that was the width of the dipper + 2x the width of the
steel sides of the thumb, plus some clearance.

 

[cic317]

the width you decide on is influenced by what you plan to use it for. If you are trying to hold looser
materials inside your bkt, then making the thumb nearly as wide as your bkt makes sense. If, however,
you are grabbing rocks, logs, or branches, a narrower width will reduce the twisting forces on the
thumb without adversely affecting the grabbing action.

To make things simplest, I went with a width that was the width of the dipper + 2x the width of the
steel sides of the thumb, plus some clearance.

Thanks, It seem this will be a piece meal project, will be working on it as time allows. Will post update

 

[arkydog]

bumperm. thank you so much for the response. the cylinder looks real close to a kubota cylinder which i thought wouldn't be a big deal but seams like might as well get something that looks close. thanks for your reply.

rob

 

[Ron50]

Aquamoose
The cylinder from Surpuls Center was to long. I mistook reracted length for overall length. My solution,since I don't weld, is to have a hydraulic shop shorten it 2 1/2". I found one from Bailey Hydraulics, but it too would have to be modified because the ports are on the top or bottom and they need to be on the side. It would be nice if Ansung could just stock a cylinder for those who want to convert to hydraulic. They make all the other cylinders already anyway.
I am getting another valve block from Walvoil that is the same as the stabilizer valve. I'll insert the new valve between the stabilizer valves with a longer handle and reassemble with longer bolts. There is enough room to do this and curl and thumb can both be active together. Probably be one to two weeks before I can assemble and post some pictures.