BH77 - has anyone considered converting mechanical thumb to hydraulic?

[jim_wilson]

This is what I've been wondering. And where do you put it?

How is it done on the B26? Do they come stock with the extra valve in the stack already and the option of the aux lines gives you the linkages to the valve and the boom lines?

I've been throwing around some ideas in my head about how the add a hydraulic grapple onto the BH77 too - and I think it just came to me how to add the valve in - put a foot pedal on - and not have to do any real big modifications to the hoe itself.

If you look at the online Kubota parts manual for the BT820 hoe on the B26 - what they do to add the hydraulic grapple is just add another valve into the existing stack. That's not really an option on the BH77 because the room just doesn't exist on the BH77 to do that. I've already sat there looking at that valve stack a lot trying to figure out how to do it - and I just don't see how to make it work - without major modification.

on the B26 the foot pedal goes on the side of the control tower - and then it just actuates that added on valve in the stack directly - because the valve appears to be the last (or first) - in the stack - and sits right below the pedal - so the linkage goes from the pedal right down the valve.

The easiest way to add a valve onto the BH77 - is to put it under the operators platform and plumb it into the existing valve stack with hoses. That means you have to actuate it somehow. I think I just figured out how to do it - I just need to think on it a little bit more - and see if there is an appropriate valve that would work for that position. I actually think the valve that Woods supplies with their BH80-X hydraulic grapple kit would work well - and if anybody knows what that valve is - I'd love to get the information.

If that Co. that bandit67 is dealing with doesn't come thru - I think this is coming together in my head how to make this complete system work. I've just got to do a little more research. I've got the number for the local Parker sales tech and I'm going to be making a phone call next week to see what the options are on hydraulic cylinders. I've got to do some measurements this weekend on the retract and extend dimensions on the thumb so I can give him something to work with. If I can track down that Woods valve - I think I'd have the full picture of the components needed for all of this.

 

[CDN Farm Boy]

Ok, you and I are both looking at the valve stack the same and there just isn't any room for an additional section but lots of room under the platform. How do you figure tying it in to the existing? Plumbing it in series seems like the only way but I thought that was bad for the valves

 

[CDN Farm Boy]

I'd guess that something as simple as this valve could be made to work:

https://www.surpluscenter.com/item.asp?item=9-7861&catname=hydraulic

 

[jim_wilson]

Ok, you and I are both looking at the valve stack the same and there just isn't any room for an additional section but lots of room under the platform. How do you figure tying it in to the existing? Plumbing it in series seems like the only way but I thought that was bad for the valves

Well the only way I can think of doing it is to use hoses - or maybe dedicated hard lines. Basically put the new valve inline with the existing stack somehow by just plumbing it in. I'm not completely familiar with hydraulics - why is that bad for the valves?

I'm doing some reading to try and get an education on hydraulics (more than my current basic understanding) - but from what I'm reading maybe the valve for the grapple needs to be plumbed in such a way that it's the first in the series - and it's setup for power beyond to feed the existing valve stack for the hoe?

 

[jim_wilson]

So - after doing a little reading - and from my cursory understanding of hydraulics - it looks like the way this additional valve for the grapple would need to be plumbed in would be like so (somebody please correct me if I'm wrong on this):

This is from my B3200 (may be different on other tractors)

- the existing BH77 valve stack has a pressure in from the power beyond coming from the FEL valve on the tractor. The "out" coming from the BH77 valve stack then feeds back to the 3 point hitch valve.

- from some of the stuff I just read - it sounds like putting an additional valve inline on that "out" line coming from the valve stack on the BH77 could be a bad idea because it might introduce back pressure into the BH77 valve stack. Which is actually warned against in the BH77 manual because it talks about NOT operating the 3pt while the BH77 is attached - because it can introduce backpressure and damage the valves in the hoe.

- So..... just adding another valve for the grapple on the OUT line would probably not work - maybe unless that added on valve had a dedicated tank return port and a pressure relief that was lower than that of the BH77 pressure relief. If I understand the way a valve with a pressure in, pressure out - and dedicated tank return port works - the pressure relief (if it goes off) - dumps directly to the tank. I think a setup like this would protect the BH77 valve stack. A setup like this would necessitate adding another line (tank return) - from the hoe. I'm actually thinking of modifying the hydraulics on my tractor for some added functionality and adding a connection for a dedicated tank return - but for the sake of this BH77 discussion I don't think that type of setup is likely the best way to go.

- so it seems as if that leave only one other option: the added grapple valve needs to be mounted "before" the BH77 valve stack and needs to have a power beyond function to supply pressure to the BH77 stack.

The problem is the diagrams of valves with power beyond that I have found - all still have a tank return line in the circuit. So it looks like maybe an added tank return line is going to be part of the picture no matter what.

If the added valve was part of the existing valve stack , from what I'm reading - none of this would be an issue because the integrated stack setups have internal passage designs that handle the fluid flow properly when the different valves are operating.

Adding a tank return line - if another valve is added in series - appears to me at the moment the way this has to be setup to avoid damage. I've got some plans to add one anyway like I said - but I don't know what you do if you don't add that return line.

 

[CDN Farm Boy]

I wonder if you could use a valve like the one I linked earlier mounted before the BH77 stack, use the PB port of the new valve to power the main stack as you suggest and T the 2 returns together?

No extra lines to mess with mounting/dismounting the hoe.

 

[CDN Farm Boy]

We need J_J and MtnViewRanch to chime in here.......I'm sure they'd have some valuable insight to the plumbing

 

[jim_wilson]

I wonder if you could use a valve like the one I linked earlier mounted before the BH77 stack, use the PB port of the new valve to power the main stack as you suggest and T the 2 returns together?

No extra lines to mess with mounting/dismounting the hoe.

Not sure if you can tee the return lines. My understanding is that the "Out" lines - are different from the tank return lines in that the "Out" lines may have higher pressure - whereas a dedicated tank return line is lower pressure. On the FEL valve on my B3200 for instance - the port that is marked as being the "return" line - is just plumbed back into the side of the resevoir with some low pressure rubber hose that is only held on with some simple hose clams.

Whereas - the "out" line coming from the backhoe is a full pressure line with crimped fittings - and it is feeding the 3pt valve on the tractor.

 

[CDN Farm Boy]

I know what you are saying, my B3300 is the same. However, I"m not sure there is a difference between "Out" and "Return". I think the "out" of the BH has full pressure fitting because it runs the 3pt. To me, that just means that when the new valve "out" is T'd into the existing "out", full pressure fittings need to be used.

I could be way off, it does seem a bit too simple.

 

[jim_wilson]

I know what you are saying, my B3300 is the same. However, I"m not sure there is a difference between "Out" and "Return". I think the "out" of the BH has full pressure fitting because it runs the 3pt. To me, that just means that when the new valve "out" is T'd into the existing "out", full pressure fittings need to be used.

I could be way off, it does seem a bit too simple.

There is a difference between a "return" and an "out" line. The terminology appears to be all over the place - but basically one is a pressurized return - and the other is a "drain" line which is not under pressure.

This document has some explanation on page 4:

http://www.greatplainsmfg.com/manuals/pdf/CDMR101209.pdf

The BH77 setup the way it comes from the factory - has a pressurized return and no case drain setup. My thought is that adding another valve in to feed the grapple - would necessitate adding a "drain" line - so that the added valve's pressure relief would have somewhere to dump. And the added valve needs a pressure relief because it cannot rely on the pressure relief in the factory valve stack - and also needs to pressure relief to avoid damage to the factory stack.

There's some explanations and diagrams here: Hydraulic valve power beyond or high pressure carry over