Hydraulic Thumb For L39

[JimMorrissey]

OK. I need some help here. I'm not much of a hydraulic guy, but I know just enough to get myself into trouble.

The situation is.....I want a hydraulic thumb for my hoe and I don't know how, or if it's possible to do with what I have or can purchase reasonably. I recently had my front hydraulics installed by the dealer and don't want to go through that again.

I attached three pictures of the right, left and center of the hoe valves to show you what I'm working with. Hopefully somebody has some ideas, other than bring it back to the dealer and can describe their ideas in layman's terms to start. I'd like to learn more about hydraulics and figure this would be a good project.

Thanks,

Jim

 

[JimMorrissey]

Here's the center shot. As you can see I don't really have anything to work with as far as spares ports go.

 

[JimMorrissey]

And here's the left side shot.....just to show the complete valve assembly.

What are my options?

 

[tawilson]

Not much of a hydraulic guy either, so when I wanted to change my woodsplitter valve to an autocycle, I looked up the nearest Prince valve supplier, talked to them on the phone, got excellent help, and ordered the valve. Installed and working fine. Perhaps they would suggest you buy a valve with power beyond in it already, then feed it first with the hydraulics, then use the power beyond to supply your backhoe valves.

 

[MadReferee]

There was a recent post by someone who added an additional spool to his BX23 backhoe valve bank for use to control a thumb. The spool was just a replacement part for an existing valve spool and it was purchased it directly from the dealer.

You might be able to purchase a replacement repair spool for your L39 and add it to the valve bank in a similar way. Your other options are a seperate valve plumbed in series with the backhoe valve's feed or an electric diverter of some type connected to an existing spool.

Backhoe thumb for BX23

 

[AntrimMan]

I do see what appears to be an extra set of tapped holes in the valve mounting surface. This may allow the addition of a valve module to the stack, just as was added by (NASDAQSAM?) the BX23 owner. That is definitely the way to go as far as appearance and compatibility goes. Does Kubota offer a thumb that could be plagerized? I know they have at least one spare QD on the dipper of the excavators, the valving may be the same or similar, maybe check that out on a lazy Sunday at the dealers lot, and look up the parts at Tractorsmart. Nothing like improving on an already good idea.
This will be a fun project. Research the life out of it before you start, I'm sure you will do a bang-up job. I want one for the BH90 too, so lots of pics needed please.
All the best,
Martin

 

[nasdaqsam]

Jim,

No expert here, however that valve assembly looks modular in nature, as mine was. I would go to your Kubota dealer and order another valve section. For the thumb I opted for one with the pressure relief valves (better safe than sorry). So far it works great. All you have to do is go to the local hardware store and pick up some threaded rod longer than the bolts the valve maker used to accomodate the longer assembly. You just unbolt the assembly and add the valve, slide the new rod through and put the nuts on and tighten. Cut off the excess and your done. It is that simple. My valve ran right around $200. This way you only have two hoses to buy. With the PB valves and sleeves you have to run in and out and back.....it got to be to much. This is simple.

Now you would have to remount the assembly. It's hard to tell but looking at your pictures there seems to be another set of welded nuts already in place to accept the longer valve assembly. If not it is pretty simple to just drill new holes and bolt through the housing. You will have to do some cutting of the housing to accomodate moving the assembly. I am talking about the area of the housing that faces you when you are sitting on the tractor and ready to use the BH. You will see there are small notchs to allow the use of the stabilzer levers. You have to recut those to accomodate the move. That is at least how mine was set-up.

The top plate will also have to be modified. We found it easiest to cut one side of the top plate and add to the other. It sounds harder than it is. You could touch it up after with spray paint.

I found this to be the cleanest way to add the thumb valve. You would also want to order the lever and connections from the dealer. They are a pain to try and make. I used the same set-up as my stabilizers as it is a small lever and easy to place anywhere and not be in the way. The only other thing I would recommend is get factory fittings for the hose connections.

I just finished the same thing you are going to do so if you need any assistance just ask.

From what I learned while doing my project. The valves are pass through valves. I believe they call that center open. Anyway the way I understand it is the hydraulic fluid is always passing through the valve. The design is such that as you call for use (for example raising the stick) the valve grabs the needed pressure from the passing fluid, some still goes on which allows you to say swing and raise at the same time and so on. Eventually there is no more available therefore that is the limit of what the tractor can handle. So in other words the thumb will work as long as there is fluid/pressure available which is probably always as it would be hard to swing, riase, curl and use the thumb all at once anyway. Most of the time from my experience you are over what you want to pick and curling the bucket in while pushing with the thumb the hydraulics should have no problem with that at all.

 

[JimMorrissey]

Nasdaq,

Excellent post. Thank you. I will be asking you some questions along the way. I was following your original post, then went on vacation or something and lost sight of it. I'm going to re-read and check the pics again.

Yes, there are holes already in place for a spare valve. Might be onto something good here. I really want a foot petal for the thumb. It just seems like it would be so easy to operate that way. The L39 has a seperate pump for the boom swing and the pumps are pretty high-flow for a tractor so I think I'll be fine in the flow dept. Like you said, a guy is normally not doing all these things simultaneously anyway.

 

[JimMorrissey]

Yep, Thanks for the link Mad.

 

[JimMorrissey]

Will post pics and going to stop by the local dealer (whom I did not buy the machine from and they know it /forums/images/graemlins/shocked.gif ) to check for valve availability. Going to check prince and others as well.