adding a thumb to Kubota KX-018

[love2havefun]

I recently purchased the above machine with 105 hours on it, nice machine!
I want to install a hydraulic thumb, the thumb manufacturer (AMI) recommends that the auxiliary hydraulic pressure to be set to 1800 PSI , it is currently at 3100 PSI.
I am unable to find out any information on how to adjust the pressure down on Kubota's auxillary circuit, hoping you can help here. Can you please advise or point me in a direction, the dealer I contacted did not know how to do this and recommended I leave at 3100 but I am concerned because the thumb pressure is to be lower so that when curling the bucket it will overcome the thumb pressure which isn稚 going to happen at 3100. I have looked at pressure regulators but not sure if I can get a return line back to hydraulic tank and if there is anywhere to tie it in? Also if there is a regulator what is happening to the pressure in the cylinder when the bucket tries to curl it back and there is no place for fluid to go?
I look forward to hearing back

 

[oldnslo]

The auxiliary valve might have work port reliefs built into it. If not then you would have to install some form of external pressure control. This could possibly be added close to the valve which would make the tank line easier to access.

 

[love2havefun]

Hi Oldnslo
Thanks for your comments, appreciated. I think I have two issues:
- first is reducing auxiliary line from 3100 to 1800 psi, a regulator will do that provided I install return line connected to tank, you agree?
- dumping pressure from thumb cylinder created when bucket curls up back to tank tied into above, you agree here as well?
I'm not sure what will do this?

 

[oldnslo]

Love2,
There are a couple of different options for limiting clamping force - pressure on the thumb.

1) Simple relief valve installed on the cap end of the cylinder connected directly to the tank line. This would limit pressure in that line to whatever you set the relief valve to but would also dump pressure whenever this valve is actuated. This also allows the thumb cylinder to retract when you curl the bucket. Down side is that it draws a vacuum in the rod end of the thumb cylinder. Probably not a major problem but will cause the thumb to be spongy. Again your auxiliary valve might have anti-cavitation check valves to prevent this from happening.

2) Pressure reducing / reliving valve installed in the cap end of the thumb cylinder and tank line connected directly to tank. Reduces pressure to the thumb but does not dump excess flow to tank causing complete system pressure to fall. Relief function would allow cylinder to retract same as relief valve above.

Post more questions if you have them.

 

[love2havefun]

Hi and thanks for your comments. I was thinking of doing #2 and adding check valve so that when bucket is curling up the fluid in thumb cylinder can exit to tank return line. Sun Hydraulics has manifold, cartridge (PPDBLWN) and check valve. Now I need to see if I can install a return line to tank. Never done one, not sure if you have? Anything I need to look for ( hopefully an open, spare port?)

 

[oldnslo]

For tank connection you can just tee into the existing tank line of your valve stacks.

Looks like a Sun E2? would have the cavity for the reducing and check valve that allows free flow around the reducing valve so that you can open the thumb. The relief port of the reducing would connect to tank and this is what would allow the thumb to move when external load is applied from curling the bucket.

 

[Seven Gables]

Before you go through too much extra work, I would make sure you don't have work port reliefs like was mentioned. I don't know about your kubota but a lot of machines have them built in to both sides of the auxiliary control valve , makes it very easy to adjust pressure relief setting on that circuit. Find that auxiliary thumb valve and look for a Allen head bolt with a jamb nut. The important thing is to set this thumb relief pressure to less than the thumb cylinder is rated for. Hard to believe your kubota dealer doesn't know? If it has this port relief it will save you a lot of frogging around. Do you have access to hyd pressure test gauge?

 

[love2havefun]

Hi
Thanks for your email
Yes I have hydraulic pressure gauge. I looked as best as I could where valves are, took a cap off one, couldn't find anything to adjust , it's nice an easy area to find things but will be checking again tomorrow. I also have to find tank return line to see if I can tie into it.

The Sun Hydraulics pilot operated pressure reducing / relieving valve is a PPDBCWN.
I was really surprised that the dealer wasn't aware, they just said they have installed a lot of these thumbs and leave hydraulics at factory which isn't making sense to me but I have a LOT to learn in that dept.

 

[love2havefun]

As an FYI the thumb manufacturer states that thumb pressure should be at 1800 psi, the Kubota auxiliary circuit is delivering 3100psi. The way I understand it is that if the thumb isn't less that the bucket it wont move up as bucket curls.
Comments are welcome

 

[love2havefun]

I am working on plumbing layout for relief valve

 

[oldnslo]

View attachment 654276
View attachment 654277

I am working on plumbing layout for relief valve

If that is a reducing / relieving valve you do NOT need a relief. The relief function of the valve maintains the reduced pressure by relieving any external load induced pressure to tank.

Sun also makes a body that eliminates all the extra plumbing for the reverse flow check. These bodies are the E2 series.

 

[love2havefun]

Well I tried adding the pressure assembly with external check valve, no luck! Simply too much plumbing on a small arm, I need to find assembly with build in check valve. I went to Sun Hydraulics site but I simply don't have the knowledge to figure out what I need.
I feel I need to do the following on one side of the auxiliary port:
- Reduce pressure to thumb closing ( top of cylinder) to 1800 from 3100
- Allow excess pressure in thumb cylinder to release back to tank when the bucket is curling up and pushing it up
If there is anything I have missed please feel free to advise
Your help is appreciated.
Thanks

 

[ptsg]

Well I tried adding the pressure assembly with external check valve, no luck! Simply too much plumbing on a small arm, I need to find assembly with build in check valve. I went to Sun Hydraulics site but I simply don't have the knowledge to figure out what I need.
I feel I need to do the following on one side of the auxiliary port:
- Reduce pressure to thumb closing ( top of cylinder) to 1800 from 3100
- Allow excess pressure in thumb cylinder to release back to tank when the bucket is curling up and pushing it up
If there is anything I have missed please feel free to advise
Your help is appreciated.
Thanks

Excavators usually come ready for what you want to do. They have relief valves on the work ports of the auxiliary valve to allow the extra pressure to relieve to the tank.

Basically you just need to connect the thumb to the auxiliary circuit and then adjust the work port pressure relief valves at the valve bank.

After looking at your previous picture of the valves, it's a pain to check anything like that but I would try to look around a bit better.

 

[love2havefun]

Excavators usually come ready for what you want to do. They have relief valves on the work ports of the auxiliary valve to allow the extra pressure to relieve to the tank.

Basically you just need to connect the thumb to the auxiliary circuit and then adjust the work port pressure relief valves at the valve bank.

After looking at your previous picture of the valves, it's a pain to check anything like that but I would try to look around a bit better.

That's the problem, there is no adjustment, the auxiliary circuit get's same a rest at 3100psi. I need 1800 so that the bucket will overcome the thumb when you curl it

 

[ptsg]

That's the problem, there is no adjustment, the auxiliary circuit get's same a rest at 3100psi. I need 1800 so that the bucket will overcome the thumb when you curl it

No work port relief valves on the auxiliary valve? That's odd though. Do you have a hydraulic diagram?

EDIT: Just checked the parts diagram on the KX-018-4 on Messicks and it doesn't have it either. That's a bit lame from Kubota. Most excavators have relief valves at the work ports.

 

[love2havefun]

No work port relief valves on the auxiliary valve? That's odd though. Do you have a hydraulic diagram?

EDIT: Just checked the parts diagram on the KX-018-4 on Messicks and it doesn't have it either. That's a bit lame from Kubota. Most excavators have relief valves at the work ports.

I do not have hydraulic layout. I have checked hydraulic pressures with gauge and they are at 3100 like the owners manual says. It's not a big deal I just need assistance with pressure regulator / relief valve

 

[oldnslo]

If the link below works it is the page for Sun Bodies with cavity for reducing reliving valve and free flow check. Multiple ports styles and sizes to choose from.


https://www.sunhydraulics.com/model... degree with reverse flow check - reducing"]}

 

[love2havefun]

If the link below works it is the page for Sun Bodies with cavity for reducing reliving valve and free flow check. Multiple ports styles and sizes to choose from.


https://www.sunhydraulics.com/model... degree with reverse flow check - reducing"]}

I just added a thumb, the thumb manufacturer ask痴 that the hydraulic pressure be set to 1800 psi (the auxiliary circuit it plugs into is currently 3100psi) so that when you curl the bucket the bucket will overpower the thumb and both will move up accordingly. I looked at the bank of hydraulic valves but don稚 see any adjustment on the one that works the auxiliary circuit.
Then I reviewed a Kubota site to find that there are 田aps you remove to find spring and shims ,I would like more information on the shims please.
I am trying to lower not increase pressure but then need to increase pressure back to 3100 psi when I hook up post hole auger.
Is there a 田ap that has an adjustment rod/screw that can be adjusted without taking things apart? If you have details on this is appreciated so I can order from someone.
Thanks for your help

 

[Seven Gables]

Just wondering if you did in fact find this cap and the shims and spring on your auxiliary valve? If so just take one shim at a time out and re test your hyd pressure to see how much each shim removed reduces the pressure.

 

[love2havefun]

Just wondering if you did in fact find this cap and the shims and spring on your auxiliary valve? If so just take one shim at a time out and re test your hyd pressure to see how much each shim removed reduces the pressure.

I spoke with another Kubota dealer who advised me that Kubota has a valve available for this that vents excess pressure over to other side of cylinder and they use it on their thumb installations. OMG I have many hours into this with no success to hopefully have found a solution. I have ordered the valve and will install in when I receive. I will let you know once done.