Adding hydraulic thumb to Hew Holland 935GBH Backhoe

[Dave1953]

I just purchased a brand new New Holland Boomer 55 with the GBH 935 backhoe and it came with a manual thumb. I want to add a hyd. thumb. NH does not offer a hyd. thumb kit for this backhoe. There is a removable plastic cover on the side of the pedalstal just to the right of the BH control valve and you can access hyd. pressure right off the valve. It looks to be an easy swap from the adjustable rod on the thumb to a hyd. cylinder. I thought of mounting a hand valve to the side of the pedalstal to actuate the thumb then I saw a video of the Kubota BH 92 foot operated valve and that looks like the cat's meow but Kubota would want a mint for that valve while a suitable hand valve can be had for around 100.00. I would like to hear from some of you guys who has added a hyd. thumb and what kinda valve setup works best. Thanks in advance.

 

[RNeumann]

I have an electric switch from Scorpion that opens and closes my grapple. The electric over hydraulic valve is a Hyvair DO3.

 

[ericm979]

This thread is really good: https://www.tractorbynet.com/forums/build-yourself/125912-custom-hydraulic-backhoe-thumb.html

There's a lot of other threads on this that the search function can bring up.

Is that port where hydraulic is available a power beyond port? Some BH valves can't handle full system pressure on their tank ports.

The full hydraulic thumb kit with foot valve is expensive for Bransons.

 

[Dave1953]

Now if that port is a power beyond port is a question I can't answer. I just don't have a clue and don't even know wo to ask.

 

[Dave1953]

Do you have a switch that has to be held in place then returns to center when released? I see those valves are about 110.00 on Ebay and there are various versions of it.

 

[RNeumann]

Do you have a switch that has to be held in place then returns to center when released? I see those valves are about 110.00 on Ebay and there are various versions of it.

My “switch” is two buttons. Open/close or left/right depending on the implement. Yours would be same. Hold one button to send the thump to the bucket (close) and the other button to send the thumb away (open) from the thumb.

 

[Dave1953]

I see. Can you tell me the model of Hyvair DO3 you are using ?

 

[ericm979]

It's an electronically operated directional valve, where there's two work ports and the valve can switch between them when it's not in neutral. You'd want one where neutral blocks both work ports so the thumb stays in place. These are often used for loader "3rd function" valves to operate grapples. You can't feather this kind of valve, it's full on only. You can use restrictors to slow the movement of the thumb if its too fast but you'll be limited to one speed. You'll also need electrical power to the BH.

The thread I linked also details some other methods of operating a thumb. One interesting one is to tee the bucket curl cylinder to an on/off solenoid switch. When off, flow goes to the curl cylinder like normal. When on it goes to both the curl and the thumb. With hydraulics if you have flow to two cylinders, the one with the least resistance moves. So you can curl the bucket to the object then the thumb cylinder will move in. (read the thread for a better more realistic description). The advantage to this is that plumbing is minimal and cost is low.

Another option is to add a mechanical valve to run the thumb. You can use a mechanical diverter valve to divert flow from a stabilizer, but you'll have to switch it between thumb and stabilizer each time you position the tractor (and want to use the thumb) and switch it back the next time.

Another way to add a thumb valve is to add it to the BH's valve stack. BH valves are usually an assembled stack of valves, and you can disassemble the stack and put another section in. I can't find the post (it may be in that thread) but someone here did that to add the thumb valve between the stabilizer valves, in the middle of the stack. This was on an Ansung BH for a Branson. He had to drill new mounting holes for the stack and modify the sheet metal cover, but it looks totally factory and it's always ready to use.

 

[RNeumann]

I see. Can you tell me the model of Hyvair DO3 you are using ?

I’m not the expert but something like a DO3 S2C 12D but someone will need to double check that! Scroll down to page 7.


https://www.cfwheelock.com/amfile/file/download/file_id/325/product_id/463/

 

[Dave1953]

Hopefully someone can confirm this. Thanks