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.