installing hydraulic thumb

[J_J]

If your machine is strictly a BH, it will not have a 3pt.

3pt is the lift mechanism for a tractor.

We are talking about open center hyd system here correct?

If it is closed center hyd, things are different.

 

[Uamauka]

Yes it is a backhoe, strictly. This is one of the ingersoll rand/bobcat types. I do believe we are talking open center, however, I am not 100% sure of myself. I do know the loader/backhoe hydraulics run off a single gear pump.

 

[J_J]

If it has a gear pump a and the fluid is flowing all the time, it is an open center system,

 

[Uamauka]

flow restriction? sizing solenoid valve for hydraulic thumb

It is the Ingersoll Rand BL-570 backhoe with 56hp Kubota v2003T engine and separate piston hydrostatic pump for drive system. The steering and loader hydraulics run off a single gear pump so it is open center and apparently has a flow capability of 18 gpm.

I was planning to use the 10 gpm solenoid control valve referred to earlier. But I am concerned about restricting flow back to tank when hydraulics are idling. The hoses and fittings on the original one way breaker solenoid are about 3/4 inch and on the new one the ports are sae -6. I feel like I am squeezing things quite a bit adapting down to this port size. Should I be looking for a 20 gpm valve instead?

 

[J_J]

Yes, match up the flow to the valve..

 

[Uamauka]

Right! so that means returning this which I bought but have not installed, which uses D03 subplate, -6sae ports (as well as returning a bunch of sae -06 to 10 jic adaptors- which attach to jic to 30mm din adaptors):

12 VDC 10 GPM OC DA SOLENOID VALVE



and perhaps getting something like this, which uses d05 subplate, sae -8 ports:

D05 Hydraulic Solenoid Valve 4 Way 3 Position Tandem Center 12VDC | eBay

or if I could find one, something that uses D07 subplate would more accurately match the existing hoses. I know I don't need this kind of flow for the thumb, but I would hate to reduce efficiency of the whole machine by doing a substandard thumb installation. Or is the d05 size going to be enough of an improvement over the D03?

Or, I could go back to the switching solenoid and plumb off the bucket valve. This option would not be as slick operationally, I think, but it would leave the power beyond output flow untouched.

Opinions?

 

[J_J]

You might rethink this as the thumb does not require a lot of flow. You could still use a divider valve and a DO3 valve and subplate.

This valve has a fixed priority flow of 3 GPM and the rest is passed on to the next circuit.

3/30 GPM PRINCE PRIORITY FLOW DIVIDER W/RELIEF

Whichever is more economical to you.

 

[Uamauka]

Well this is a new twist I hadn't thought of. Let me see if I understand how this divider valve setup would work.
- Do I put the divider valve's 3/4" input and excess ports in the place where my breaker solenoid currently is; then run the priority 3gpm port to the d03 subplate/solenoid valve; then T the tank line from the subplate and the relief port from the divider valve in to the excess port return?

Then can I do away with the relief cushion valve that I was going to place on the workport lines out to the thumb?

I can see how this would give me the most unrestricted flow back to tank, (which by the way instinct tells me is better but is it a significant concern?).

Cost wise there doesn't seem to be much difference between this divider valve route and the d05 valve route. Setup wise not too much difference either since in one case I need the relief cushion valve and the other case the extra divider valve. Either way I have to return some stuff and buy some other stuff before the installation happens, and wait for stuff to come in the mail.

That leads to this question. Assuming a d05 (not d07) solenoid valve, along with the relief cushion valve on the work port lines on the one hand--

and this divider valve without additional relief valve, and feeding into the D03 solenoid valve on the other hand--

Which is the better installation for overall performance and reliability?

Or if I misunderstood how this installation would work, where did I go wrong?

Thanks.

 

[J_J]

I believe I would redraw the open center circuit flow and see if there is any conflict.

All valves should be in series, but you can have two or three series circuit.

The master relief in the first section of the flow path will handle the overall relief, except the relief across the thumb cyl, and that operates when the pressure on the thumb cyl equal the set pressure.

Each series path should return to tank.

Show circuit drawing when complete.

 

[Uamauka]

I'm not sure I understand about redrawing the circuit. Is it because I asked too many questions in one post? Are you suggesting I draw the two proposed alternatives to determine if I am about to make any mistakes? If I decide to add the diverter 3gpm valve, do I still have to add the inline relief valve across the thumb? If so, then I would prefer to skip that step, as long as a -08 sae port/tank flow is sufficient.

 

[J_J]

You need the relief across the thumb in case the bucket cyl over rides the thumb cyl.

If you use a large cyl for the thumb, you might not need it.

Actually I am not sure what you are dong now.

I have given you suggestions and alternatives, you do not have to use them.

 

[Uamauka]

Ok this first drawing shows the existing setup above, and alternative 1, using a D05 sized solenoid valve and subplate, relief valve, and shows where old aux hose Ts shall be plugged. These hoses will mount to ports A and B with metric adaptors.

The in hose to breaker solenoid will go to P with metric adaptor, and the out hose from breaker will go to T w/ metric adaptor.




This drawing shows alternative 2, using an additional valve (diverter) and a few more hoses, but using the D03 size control valve.

In hose from solenoid will go to input on diverter valve. Out hose from solenoid will go to excess port. 3gpm port will lead to P on D03 subplate. T on this subplate will lead to tank via a T adaptor at excess port on diverter valve. A and B ports will lead to relief as in alt 1. In this drawing I am not sure what to do with the diverter valve relief port (if it can be plugged or must run also to tank). This alternative has the drawback of greater installation complexity and cost, as well as needing to find space to mount one extra valve, (if I understand the installation recommendation correctly)

But this alt 2 has the advantage of larger port size for freer flow when hydraulics are idling, and perhaps also a more controllable (slower) thumb movement.

 

[Uamauka]

In my last post I guess I forgot to ask specific questions:

--What would be the result of alt 1 vs alt 2 installations? I gave my guess but that is speculation on my part.

--For alt 2 (with divider valve), what do I do with pressure relief port if I don't need pressure relief here?

--What would actually happen if I just installed the 10gpm (D03 subplate) solenoid valve without adding the divider valve?

--Other suggestions different from what is described in either of these alts? If this was covered earlier than I missed it or did not understand.

I know a lot of people install hydraulic thumbs, some of them may be as daft as myself and benefit from the distinctions spelled out here. If successful I will be happy to post pictures of results.

Thanks.

 

[J_J]

Why would you not want relief?

The divider valve is to allow a lower GPM flow to the thumb.

The DO3 would work, as you are probably using the thumb intermittently.

If you use the subplate and not the divider valve, you lose your flow downstream of the thumb until you release the thumb.

You also restrict the flow somewhat.

You don't have to run the engine at full rpm and reduce max flow until you need it..

 

[Uamauka]

This is great help. Thanks!

Why would you not want relief?

I meant no relief on the divider valve because I will be using a cushion valve across the thumb. Something I don't understand here?

If you use the subplate and not the divider valve, you lose your flow downstream of the thumb until you release the thumb.

Wouldn't this be OK since this is the last circuit in the line?

You also restrict the flow somewhat.

This has been my primary concern, but I didn't know if I was just being a worry wart or how much of a difference does it make?

Also how much of an improvement in this category would going to the D05 subplate make asuming no divider valve?

You don't have to run the engine at full rpm and reduce max flow until you need it..

Yes I appreciate this sentiment. In fact being new to heavy machinery I like to take my time and I have been running with just enough rpms to keep her from bogging down, which probably about 1/4 to 1/3 throttle. Plenty of power to to move just about everything. The Kubota engine has a nice governor that does a good job of keeping engine speed steady at different loads.

And it runs much quieter and is less fatiguing this way.

 

[J_J]

You really don't need much flow for a thumb.

If you run the engine slow, then the DO3 subplate would work. It is your choice as far as which DO# valve to use.

If your thumb valve will be the last valve in the circuit, you could use the divider valve and send the EF flow to tank. The relief valve for the divider valve is only functional when using the cyl.

You still need a relief valve or a cushion valve across the cyl.

Here is what may happen when a 3000 psi 3 in cyl is pushing against a 2 in thumb cyl.

You might blow a hose of the cyl seals with over pressure.

 

[Uamauka]

You still need a relief valve or a cushion valve across the cyl.

Here is what may happen when a 3000 psi 3 in cyl is pushing against a 2 in thumb cyl.

You might blow a hose of the cyl seals with over pressure.

If understand correctly then, the cushion relief across the cylinder is going to save my cylinder rod and allow the bucket to push in the cylinder safely AND I need relief at the divider valve to protect the hoses and seals, since the cushion valve does not go to tank? So, for instance I couldn't use this divider valve instead?

3/4" NPT 30 GPM ADJ PRIORITY DIVIDER VALVE RD575

Or If I chose not to use the divider valve at all, then is my cushion valve sufficient relief or is there something about the power beyond that requires relief valve to tank in addition to main relief valve?

As you can see there is something in your explanation that I am not understanding, but I am trying.

Thanks.

 

[J_J]

I thought I had explained the situation fairly well, but here it is again.

The implement pump has to be protected, so when you first get a tractor, the 3pt is the only relief.

Then some people add a FEL, and the FEL relief becomes the main protection.

Some people then add a remote valve, and it has a relief.

Then some people add a BH, and it has a relief.

Those relief all protect the pump.

When all valves are in neutral, the relief across the cyl will protect the cyl.

Now, you should set all the reliefs the same unless you want a lower pressure for a particular circuit.

When you use a valve upstream, you lose hyd capability downstream.

You can however only use half lever to allow some flow downstream, except for a solenoid valve, which will always pass full flow.

You can also slow the flow by using restrictors, either fixed or adjustable.