Diverter valve for thumb

davecampbell · Dec 26, 2019

I have a komatsu pc150-5 that is not plumbed for a thumb. Is it feasible for to put a diverter valve on the stick and switch hydraulic flow from curl to thumb to adjust thumb? There is a valve on ebay for only $100 that is rated for 13gpm. Im not worried about the speed of the thumb, but would that inhibit the speed of the bucket curl?
https://www.ebay.com/i/233046711131...MbwLoPIwCf2dSKTt4ec5SpWN1cgaau78aAhHhEALw_wcB

Ronsii · Dec 27, 2019

Measure the cylinder and rod then time the curl rates in/out... easy to figure out what it's doing now, if it's close to 13 then ought to work....

Ronsii · Dec 27, 2019

And you'll probably want to add a crossover relief also so you don't blow the thumb cylinder or lines when you have it switched out.

funwithfuel · Dec 27, 2019

The right answer is install a bidirectional option kit. What you are suggesting may be cost effective and functional now, it won't last. Thumb cylinder ,depending on mfr, usually want to see no more than 2500 psi. Your bucket curl circuit wants to relieve at almost double that. Not to mention the fact with a divert valve it's one or the other, bucket or thumb. You don't want to get out and flip 2 valves every time you make a pick? HKX makes very good and detailed aftermarket option kits for Komatsus. Good luck in whatever path you choose.

davecampbell · Dec 27, 2019

Ronsii said:
And you'll probably want to add a crossover relief also so you don't blow the thumb cylinder or lines when you have it switched out.

so with the thumb stationary, I could blow the ram by putting too much pressure on the thumb?

funwithfuel said:
You don't want to get out and flip 2 valves every time you make a pick? .

I was going to use an electric solenoid valve and put a switch on the right joystick.

jonno634 · Dec 27, 2019

davecampbell said:
so with the thumb stationary, I could blow the ram by putting too much pressure on the thumb?

If u set the thumb and curl the bucket into the thumb, if there is no by-pass, you will break something. Most likely the thumb cylinder (either bend it, or blow seals). Typically the bucket hyd will over come the pressure of the thumb and the thumb will move.

davecampbell · Feb 13, 2021

I found a 24gpm unit
https://www.amazon.com/Hydraulic-Solenoid-Diverter-selector-Valve/dp/B07KMCP6NX

Tinkerer · Feb 13, 2021

That is valve would be a good choice Dave. But, it has BSP threaded ports. NPT is what you want.
I'm in the middle of putting a hydraulic thumb on my T/L/B. I'm using 1/2inch hose with 1/2 inch pipe threads.
The reason is that I can buy pre-made, 3000 psi rated hose in increments of 1 foot for a fraction of the cost of hoses with crimp-on ends.
That may or may not work for you tho.
By all means install a pressure relief by-pass in the circuit. Some dump the oil back to the hydraulic tank and some let the oil swap sides of the cylinder piston when forced.
I don't need one because I am using a stabilizer circuit and it already has the pressure relief in it.

davecampbell · Feb 13, 2021

Tinkerer said:
By all means install a pressure relief by-pass in the circuit. Some dump the oil back to the hydraulic tank and some let the oil swap sides of the cylinder piston when forced.
I don't need one because I am using a stabilizer circuit and it already has the pressure relief in it.

What is a stabilizer circuit?

catman13 · Feb 13, 2021

what about a manual/ fixed thumb , cheaper faster

davecampbell · Feb 13, 2021

catman13 said:
what about a manual/ fixed thumb , cheaper faster

I might should settle for that.

I found one that has 10 SAE ports. What is that? It is 12V but I could probably swap out the solenoid.
https://www.amazon.com/Hydraulic-So...cphy=9026759&hvtargid=pla-1154628544952&psc=1

Tinkerer · Feb 13, 2021

An SAE 10 port has 14 threads per inch 7/8". Might be a problem getting fittings.
I purchased most of my fittings here -- https://www.surpluscenter.com/Hydraulics/
I used NPT to NPT mostly. My thumb cylinder required "O" ring boss to NPT fittings
My mechanical diverter valve has SAE 16 (1") ports. I used bushing reducers to be able to use 1/2" inch fittings. They have to be forged bushings. You cannot use hardware store (plumbing) bushings. They are not able to withstand hydraulic line pressures.

Tinkerer · Feb 14, 2021

davecampbell said:
What is a stabilizer circuit?

It is the resolver (section) of the backhoe valve bank that controls the stabilizers on the unit.
I always used to refer to stabilizers as outriggers. I guess it was from old memories when I first spent time on cranes.
I don't know if this helps any, but here is image of a PC150 with a thumb on it.

John C. · Feb 14, 2021

FYI, the number system is based on sixteenths. A number 10 fitting is 10 sixteenths which is a fraction that can be reduced to 5/8". A number eight fitting is eight sixteenths and reduced to 1/2". The system is universal for all standard tubing, hoses and pipe sizes used in the United States. It is also kind of standard for the rest of the world to some extent as well.

lantraxco · Feb 14, 2021

I see talk of crossover reliefs and such so I'll jump in here: DO NOT USE CROSSOVER RELIEFS IN CYLINDER CIRCUITS, NOR A LINE TO LINE SINGLE RELIEF. Thank you for reading. Now, you DO need to add reliefs if the circuit you tapped into on the machine doesn't already have them, best setup is two in a block with a tank port venting back to the return line before the return filter.

The problem in the most likely situation will be that you overpower the thumb with the bucket curl, the relief connected to the piston end opens to the rod end and due to the rod taking up space, within a fraction of an inch you run out of room for oil. The difference in areas creates a pressure multiplication and can reach many thousand PSI in a half a second and then the weakest link, often the cylinder tube, will catastrophically fail. Like the sound of thunder right in front of you, with hot oil moving extremely fast.

davecampbell · Feb 14, 2021

lantraxco said:
The problem in the most likely situation will be that you overpower the thumb with the bucket curl, the relief connected to the piston end opens to the rod end and due to the rod taking up space, within a fraction of an inch you run out of room for oil. The difference in areas creates a pressure multiplication and can reach many thousand PSI in a half a second and then the weakest link, often the cylinder tube, will catastrophically fail. Like the sound of thunder right in front of you, with hot oil moving extremely fast.

That makes perfect sense. That is probably why you do not see diverter valves to operate the thumbs. It would seem it would be better to have no relief than one that would relieve to the shaft side. At least then you would not have pressure multiplication. Seems my choices are build full system, settle for a fixed thumb, or trade off the machine.

lantraxco · Feb 14, 2021

Oh, there's no problem using a diverter valve, you just need to install crossover manifold block with tank drain on the cylinder side of the diverter, or at least a single relief valve teed into the cylinder butt port relieving to tank. If you use the single relief technically you should also tee a check into the rod end port also connected to the tank line to allow oil to fill the rod end so you don't suck air and dirt in, but I've seen it done without that.

Something like this works great: https://www.sunhydraulics.com/model/YRDK/LWNAJ_S

davecampbell · Feb 14, 2021

lantraxco said:
you just need to install crossover manifold block with tank drain on the cylinder side of the diverter, or at least a single relief valve teed into the cylinder butt port relieving to tank.

I guess the return line could be relatively low pressure line, so that would lower the cost somewhat.

lantraxco · Feb 14, 2021

davecampbell said:
I guess the return line could be relatively low pressure line, so that would lower the cost somewhat.

I've actually used Parker Push-Lok, typical bypass on return filters is 25psi and there's no need to plumb it in on the hot side of the cooler. 3/8" or 1/2" single wire would be a better installation, or Synflex.

Tinkerer · Feb 14, 2021

sae100r4 single wire hydraulic hose is a very affordable for return lines. Many vendors sell it on the internet.
I have used it for suction lines.

Diverter valve for thumb

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