Adding Hydraulic Thumb to Backhoe

[labbe001]

Hi Guys...new member here.
I have an old Ford 555D that I'm wanting to add a hydraulic thumb to. There are currently no provisions (that I'm aware of) for adding an auxiliary hydraulic attachment. The machine specs lists an open center hydraulic system with a pump flow rate of 30 GPM. I'd like to utilize a 12V electric solenoid with a switch to operate the hydraulic thumb. I don't intend to operate the backhoe at max rpm while utilizing the thumb.
My question is, would I need a 30 GPM solenoid valve or could i down size to a 25 GPM. I'm having trouble finding a 30 GPM and when i do, they are VERY expensive. Thanks in advance for the help.

 

[HarleyHappy]

You can use a lower gpm valve of course.
For my front hydraulics, I used a 15 gpm valve for a plow mount, with the possibility of adding a grapple in the future.
Understand, the lower the gpm, the smaller the fittings.
When I put my thumb on my case backhoe, I tied into the bucket lines at the control valve and used a auction house valve with a pressure relief valve and ran them out to the thumb.
Was considerably cheaper at the time.
Just bolted the valve to the tower.

 

[Swetz]

Some on here have tapped into the stabilizer circuit for hydraulics. Of course you would need a diverter valve to switch between the 2 functions. Tinkerer has posted pics of his install. If you run a search it should come up. His was a Case, but it was an open center machine like yours.

 

[labbe001]

Gotcha...thank you guys for the great info.
Ideally I'd like to plumb into the main 30 GPM circuit of the machine instead of using a diverter valve. That way, I can mount a toggle on one of the joysticks and operate the thumb. Just like a 3rd function kit on a tractor. would I be able to plumb a 25 GPM solenoid into the main 30 GPM circuit so long as i don't run near max RPM....or am I thinking about this completely wrong?

 

[Tinkerer]

You will need a pressure relief valve in the circuit to avoid bending the rod on the thumb.
The thumb cylinder has to be on a two way circuit.
It is a fairly complex plumbing situation.
If you could add an extend-a-hoe valve section to the backhoe control valve it would be a lot simpler. IMHO

 

[labbe001]

You will need a pressure relief valve in the circuit to avoid bending the rod on the thumb.
The thumb cylinder has to be on a two way circuit.
It is a fairly complex plumbing situation.
If you could add an extend-a-hoe valve section to the backhoe control valve it would be a lot simpler. IMHO

OK...I think I'm tracking what you're saying. So if I get a 25 GPM solenoid, it might be pumping more than what the thumb cylinder can handle? So would I need to size the valve that operates the thumb (whether electric solenoid or manual valve or diverter valve) based off of the specs of the thumbs cylinder?

I was under the impression that I would need a valve with similar GPM to overall flow rate of the machines hydraulic pump. But it sounds like the GPM of a hydraulic control valve refers to what is delivered to the cylinder that the valve is controlling.

So if I'm thinking about this correctly.....in talking about the existing backhoe hydraulic control valve: The GPM of each spool on backhoe control valve is sized per the cylinder it's serving...would this be a correct statement?

Thanks guys for helping me understand.

 

[Tinkerer]

Flow rate will have an effect on the speed that the thumb cylinder opens and closes.
The factory designs the control valves to meet the needs of the circuit.
A hydraulic cylinder can handle a huge flow rate. An excessively high flow rate delivered to the cylinder could make it open and close so fast it would be hard to control.
The size of the hose comes into the speed factor also.

 

[franklin2]

You can buy flow control valves like these to make the speed adjustable.

3/8 NPT 8 GPM Wolverine by Prince WFC-600 In-Line Flow Control | Inline & Needle Valves | Flow Control Valves | Hydraulic Valves | Hydraulics | www.surpluscenter.com

3/8 NPT 8 GPM Wolverine by Prince WFC-600 In-Line Flow Control, Inline & Needle Valves, 3/8 NPT 8 GPM PRINCE WFC-600 IN-LINE FLOW CONTROL, 3/8 NPTWolverine by Prince Mfg,WFC-600 ,

www.surpluscenter.com

 

[labbe001]

So does the GPM of a hydraulic valve refer to the flow rate to the rate produced for the cylinder it’s operating?

 

[franklin2]

So does the GPM of a hydraulic valve refer to the flow rate to the rate produced for the cylinder it’s operating?

I know enough about hydraulics to get myself in trouble, but I would think the flow rate of the valve would be at a rated pressure, wide open ports with nothing connected to it. The lines and fittings would reduce this flow rate depending on their number and size.

Someone can correct me if I am wrong, but you can generally get in the flow ballpark by observing the port fitting sizes. Smaller flow rate valve will have small ports and take smaller fluid lines correct?

 

[Welder Dave]

It's the maximum continuous flow the valve is designed for. You can buy flow restrictors to put in line or on the cylinder to slow the speed. Flow restrictors for a thumb wouldn't cause issues because a thumb isn't normally used continuously. The problem if you put a lower GPM valve that oil is constantly flowing through is it will create heat because it has smaller oil passages. A 25 GPM valve on a 30 GPM max. system/pump might be a non issue unless your running full throttle all the time. From what I've read actual flow is less than the pump rating because you have to take friction losses and pressure into consideration. A simple example is a 30 GPM pump will flow more through a 2ft. hose than through a 20ft. hose.

 

[Swetz]

It's the maximum continuous flow the valve is designed for. You can buy flow restrictors to put in line or on the cylinder to slow the speed. Flow restrictors for a thumb wouldn't cause issues because a thumb isn't normally used continuously. The problem if you put a lower GPM valve that oil is constantly flowing through is it will create heat because it has smaller oil passages. A 25 GPM valve on a 30 GPM max. system/pump might be a non issue unless your running full throttle all the time. From what I've read actual flow is less than the pump rating because you have to take friction losses and pressure into consideration. A simple example is a 30 GPM pump will flow more through a 2ft. hose than through a 20ft. hose.

What Welder Dave has said above is incredibly important!


If you install parts in the system that are not rated for the flow of the system, you will create heat...incredible amounts of heat...heat that will damage your system. There are ways to control flow other than the color flow valve that franklin pointed out above. When you use a color flow, or small hoses, or even a bank not rated for the flow rate, they all introduce heat. The color flow, as pointed out above is made to be used in a portion of the system that does not operate continuously, like the thumb. Again, because of the heat that they generate. If you plumb this type of valve in the main flow, it would be active all the time.

The reason for the heat being caused in a color flow valve is the restriction (you are basically cranking a pressure rated valve closed to obtain desired flow). The oil must pass over an orifice. This creates back pressure (pressure behind the restriction), which will in turn cause the pressure relief valve to open, which is another orifice, and generates more heat in your system.


Tinkerers suggestion (see below) solves most of your problems, granted it is not simple. The extend-a-hoe valve section, when not in use, does not introduce any heat into the system. Granted actuation will need to be fabricated, especially if you are dead set on an electrically operated toggle switch...not impossible tho!

If you could add an extend-a-hoe valve section to the backhoe control valve it would be a lot simpler. IMHO

 

[labbe001]

Tinkerers suggestion (see below) solves most of your problems, granted it is not simple. The extend-a-hoe valve section, when not in use, does not introduce any heat into the system. Granted actuation will need to be fabricated, especially if you are dead set on an electrically operated toggle switch...not impossible tho!

Yeah I thought about doing this initially and replacing the whole unit. However, I couldn't find a 7 spool for an extend-a-hoe....everything I came across was a 6 spool like the one currently on the machine.

It's the maximum continuous flow the valve is designed for.

So when you say maximum continuous flow, do you mean when the valve is actuated? I guess I'm assuming that since the main circuit flow is 30 GPM, that i need a valve rated for around 30 GPM. I think what I'm having trouble comprehending is when I look online at a hydraulic control valve, and it says 30 GPM, does that refer to the flow when actuated or does it refer to the flow when not actuated (The continuous flow on an open center circuit)...or does it refer to both? In theory, if i were tapping into the main circuit, would i need to get a valve rated for 30 GPM and reduced the flow on the cylinder side (actuated side) of the valve.


I apologize for my ignorance on hydraulics. it seems simple yet complicated at the same time..lol

 

[franklin2]

There are some good threads on here somewhere with people talking about doing other hydraulic shenanigan's to get a thumb added without all the added hydraulic line. I think someone added tee fittings into the bucket curl lines with shut-off valves? When you wanted to use the thumb you got out and opened the valves and the thumb came in when you curled the bucket, went back up when you uncurled the bucket. I seem to remember since both cylinders would be parallel when the valves were opened, it was a race when they opened and closed, depending on which cylinder hit the object first that you are picking up.

I think when you were done with the thumb you uncurled the bucket till it stopped and kept going till the thumb was all the way up, and then get out and valve it off.

I think there were several other ideas people were using to get a thumb added on.

 

[Swetz]

labbe001,
Are you married to the idea of a hydraulic thumb? I have an Amulet Hoe Clamp on my machine and love it!
I am installing it in this pic, but it gives you a good idea of what makes it work.


Here it is at work. I have never had a rock that the machine could lift that the hoe wouldnt grab. I am in rock country too! Same with trees that I have felled.

I purchased my online at equipment land. Below is a quote for a 555D with extend-a-hoe, from them. I am not affiliated with them. You can go on their site and find a dealer near you. Not sure what you have (regular hoe or extenda-a-hoe) but it is available either way.


The bottom line is that this thumb is well made and will do almost anything you want a thumb to do. The price looks a bit high, but figure in a hydraulic thimb, the hoses, and valving and I predict this route is cheaper, and much easier. I struggled with hyd vs this, and went the hoe clamp route and have no regrets.

Just more to think about

 

[Welder Dave]

Yeah I thought about doing this initially and replacing the whole unit. However, I couldn't find a 7 spool for an extend-a-hoe....everything I came across was a 6 spool like the one currently on the machine.

So when you say maximum continuous flow, do you mean when the valve is actuated? I guess I'm assuming that since the main circuit flow is 30 GPM, that i need a valve rated for around 30 GPM. I think what I'm having trouble comprehending is when I look online at a hydraulic control valve, and it says 30 GPM, does that refer to the flow when actuated or does it refer to the flow when not actuated (The continuous flow on an open center circuit)...or does it refer to both? In theory, if i were tapping into the main circuit, would i need to get a valve rated for 30 GPM and reduced the flow on the cylinder side (actuated side) of the valve.


I apologize for my ignorance on hydraulics. it seems simple yet complicated at the same time..lol

On an open center system fluid is generally flowing through the valve all the time. That's where the flow rate comes into play. There can be set ups where an accessory valve is added to a system that doesn't have fluid flow through it constantly. Maybe another valve needs to be opened let fluid flow to an accessory valve.

 

[Joe H]

I found this years ago when I was searching for how-to for mine----> https://www.tractorbynet.com/forums/threads/custom-hydraulic-backhoe-thumb.125912/

There's a lot of info there, helpful to you who knows.

Joe H

 

[NH575E]

Yeah I thought about doing this initially and replacing the whole unit. However, I couldn't find a 7 spool for an extend-a-hoe....everything I came across was a 6 spool like the one currently on the machine.

It's my understanding the spools are stacked. You wouldn't have to replace the whole unit. Just add a section. I think they had a kit with longer bolts for adding a spool.

 

[Tinkerer]

the parts book----------------------------on Messick's website

New Holland Construction | Schematic, Manuals, Specifications and Diagrams for control valve, hed or auxiliary valve | MyCNHi US Store

Find schematics, manuals, specifications and diagrams for CONTROL VALVE, HED OR AUXILIARY VALVE. Find genuine OEM parts for your needs.

www.mycnhistore.com

 

[Tinkerer]

Adding a stabilizer section is another way to get a valve installed for a thumb.
If you could find a complete used control vavle you would a nice supply of spare parts for your existing control valve. IMHO