Converting manual thumb to hydraulic thumb

[liberty2701]

I am in the process of converting my manual thumb to hydraulic thumb on my 18klb excvator. I will be using the hydraulics from the hammer function to power it. The only problem is that the pressure is full and not regulated. To buy two pressure regulators for the Rexroth sx14 valve would be $700. I was going to bring the pressure to the hydraulic cylinder down to 2000 psi. What are my options since I will not spend $700 on two little valves. Thanks

 

[oldnslo]

Your option is to externally plumb a relief valve or valves if doing both sides of the thumb cylinder vented to tank. These valves will have to be plumbed into the line to the cylinder with the tank line of the valve teed into the tank line of the valve stack. Using a relief in this manner will allow the thumb to move when you curl the bucket.

 

[Peter 315]

Is there a valve to switch from hammer to thumb under the engine cover I know komatsu has it because the hyd oil on a hammer only can go one way look on the valve body or near the oil tank. Did you get the BOOKS yet

 

[Peter 315]

The valve looks like this one with 2 hoses on it and a handle

 

[liberty2701]

I just enclosed some pictures.

 

[liberty2701]

I think I can use the foot pedal to retract and extend the cylinder by setting that valve in the correct position. I do not see a pressure relief/adjust valve on the control block. Under the yellow cap there is a pressure adjust valve for the boom, stick and bucket function. I do not have one for the hammer function. Although the pilot line for the hammer looks different than all the others since it has a taller nut on it. It is the lower pilot in the picture.
It looks like there are some kind of shut offs on the hammer metal hydraulic lines on top and at the end .

 

[Peter 315]

The valve has 2 positions one way flow or two way flow The foot pedal will work like you said But it should have a valve someplace Like I said the hammer can only have hyd oil flow one way That valve on the Komatsu has a picture on it of a hammer and a thumb grapple. Does the peddle have a lock so that it will only go one way when locked

 

[Peter 315]

That big nut with the lines on it is the handle so the pedal will work looks like its set right already

 

[Peter 315]

You don't need any other valves Its all set up from the factory You have to open the valves up at the bottom of the stick

 

[liberty2701]

It is locked or unlocked only. My manual has a page for activation of auger . it says to put two way valve into two way position. Unlock pedal and then use the auger via the foot pedal in both directions. I think this setting is what would be needed for the hydraulic cylinder to operate properly. This allows fluid to flow in both directions with the pedal. I guess i will have to measure the pressure to see what is is set at since there is no adjustment valve. What do you think?