Custom hydraulic backhoe thumb

[bumperm]

Yeah, Photobucket did a real number on very many. I'll see if I can post a link that works on all my pics. I quit using them but left the pics there. Most won't have labels, but are self explanatory.

Kubota Tractor by John Morgan | Photobucket

 

[Aquamoose]

Thanks! Originally, it didn’t show the pics at first but now they do. How are they plumbed? That’s the only part I can’t figure out.

 

[bumperm]

The thumb cylinder is plumbed in parallel with the bucket cylinder so that if there were no other valving, if you curl the bucket in, the thumb would move down. Conversely, lifting the bucket up will raise the thumb. Obviously this won't work that way as we need to be able to "lock" the thumb down at various positions so the bucket can curl or close into the thumb. This is accomplished by adding an electrically operated, normally closed, hydraulic valve. There is a button on the control stick to open that valve.

In use, if the bucket has resistance to its movement (i.e. it is touching the ground or an object), then pushing the button to open the thumb cylinder valve will cause the thumb to extend. Releasing the button will close the valve and the flow (pressure) then goes to the bucket curl cylinder to curl the bucket into the thumb. Thumb is retracted by pushing the button and "extending" the bucket - the bucket's weight gives primacy to the thumb retract so it moves first.

In use, this all comes easily and naturally. There is but one limitation I'm aware of. If you have picked up an object, rock, log etc. you cannot pivot it's position by say opening the bucket further while extending the thumb to follow and maintain grip.

 

[Outlawmoon]

Ron50 - would happen to know if the valve you selected for your Ansung BH65 to match the stabilizer valves the same as the stabilizer valves on the Ansung BH86 model?

Thanks!!

 

[ning]

I know this is an old thread, but I'm hoping some knowledgeable folks from its past are still around as I'd like to do this conversion to my BH.

The pins for this BH's (ansung bh76) manual thumb are a nice 1" w/ zerks already.

I'm trying to find what the right cylinder size would be for this application and would greatly appreciate a hand here.

At full retraction - thumb tucked back against the dipper as far as it goes away from the bucket - the measurement from center of one thumb pin to the other is 18" (exactly).

At full extension, which looks like this - the thumb extension tube hits the dipper with the bucket as far open as it gets -

at this full extension the measurement is 32" center to center.

Just for more information, if I retract the thumb a bit, here's what things look like with a 28" center-to-center measurement; bucket is fully opened still:

Other measurements, if they matter - bucket cylinder as a ~1.184" diameter rod and the exterior of the bucket cylinder is ~2.345".

 

[ericm979]

I did the research for this a while ago and then didn't get around to doing it. I don't think its possible to get a cylinder that's 18" closed and 32" open. I couldn't find one anyhow. But you could get something like (for example) 19.5" closed and 31.5 open.
(2x12x1.25 Double-Acting Hydraulic Cylinder Wolverine by Prince Mfg WWSB2012-S | Double Acting Hydraulic Cylinders | Hydraulic Cylinders | Hydraulics | www.surpluscenter.com)

I think that you might want the ports on the side rather than on the top/bottom so the hoses are out of the way. There's a few cylinders that let you rotate the cylinder end eye, or a hydraulic shop could cut and weld the eye back at the right orientation.

You probably found the thread in the Branson section where someone added a valve for a thumb to the existing valve stack. It's really clean and just needed a bit of modification to the sheet metal cover for the extra handle in the center. I'm assuming your BH76 has the same valve stack as his did- mine does. Of course I didn't take notes so I don't have the URL handy.

 

[dfkrug]

.....the exterior of the bucket cylinder is ~2.345".

The most important dimension is the ID of the bucket cyl. Your thumb cyl has to match that. Then the most important dimension it closed length, so you can retract your thumb up against the dipper adequately. The open length is less critical since the fully open position of the thumb should not be critical. If you let it open too far, the bucket will exert too much pressure on the thumb cyl when it is OFF.

You can buy cyls on eBay or SurplusCenter and cut off the cross tubes to match. I would not use tierod cyls since they are usually lower pressure vs. welded.

When I started this thread 16y ago, one of my goals was to avoid adding 2 more hoses along my hoe boom and dipper. All my posted pix are still there since I did not use some "free" photo posting site.