New Thumb Build

[lcgoatboy]

The way your thumb pins are secured is not enough. Those presto pins will fly off in no time! Best to use 5/16" bolts, with nylon lock nuts.
If you don't know the rated pressure of your third function, be carefull when putting the new replacement cylinder. Its rated PSI may be too low for the third function pressure delivery. You may want to undo the cylinder lines, install a pressure guage, and plug the end of the line. Run a test and see for yourself. Industrial equipment do run at higher pressures.:2cents:

Your right about the presto pins but I was so excited to use the thumb. I will bolt after I get the pressures right.

 

[lcgoatboy]

Thumbs looks great, you don't appreciate it until you have to use a machine without one. Did you send your build to the Princess Auto projects site?

No I didn't know about the Princess Auto project site. I'll have to check it out. Thanks

 

[skyhook]

No relief yet,I'm going to pm firemanmike69 to see if he knows if my machine already has relief install. I do know the thumb and curl cylinders have the same pressure because they fight each other.

I can bet you it does, but at what pressure is what you need to find out.

 

[lcgoatboy]

Found out today relief valves are 250 a piece. I need 2 if I don't already have them installed. I'll get a pressure reading tomorrow.

 

[lcgoatboy]

So I do have relief valves on the excavator,that's good. The pressure was 3000psi we lowered it to 1800,that's good! The bad is the thumb ram creeps down quite fast,15 seconds or so. What did I do wrong?

 

[firemanmike69]

So I do have relief valves on the excavator,that's good. The pressure was 3000psi we lowered it to 1800,that's good! The bad is the thumb ram creeps down quite fast,15 seconds or so. What did I do wrong?

Does it basically just fall down ? Look to see if the hammer valve is shut. If it's open it will let the oil on that side of the ram mostly bypass the valve and return to tank
To isolate the cylinder from the rest of the machine close the valves on the stick and see if the problem persists

 

[lcgoatboy]

Does it basically just fall down ? Look to see if the hammer valve is shut. If it's open it will let the oil on that side of the ram mostly bypass the valve and return to tank
To isolate the cylinder from the rest of the machine close the valves on the stick and see if the problem persists

http://youtu.be/H2f5QPlnyiQ?list=UUITlsGgm9QnGqjHU6u-7IzQ This is what happens. Love technology!

 

[skyhook]

I don't know, but maybe that relief pressure of 1800 is too low and its relieving.
That does sound like it would be a low relief setting for a thumb.

 

[pmsmechanic]

I'm guessing from your video that there is something wrong inside the valve that operates the thumb. Or there is an electrically operated valve somewhere that's not working properly.

 

[ptsg]

Maybe the machine has a motor valve to fit hydraulic breakers and attachments that use hydraulic motors, that can cause this problem.

 

[lcgoatboy]

I have my own theory,the 2 relief valves are not exactly the same pressure 1700 ish and 1800ish. I want to balance the 2 with the machine running and watching the reaction of the thumb. I think???

 

[ptsg]

I dont think that the thumb has enough weight to open the relief valve

 

[firemanmike69]

I have my own theory,the 2 relief valves are not exactly the same pressure 1700 ish and 1800ish. I want to balance the 2 with the machine running and watching the reaction of the thumb. I think???

I'd try the machine running while I slowly raised the setting on the relief and see if it stops. Then check the pressure

 

[firemanmike69]

Looked in the service manual today here's the layout of the valve and the functions




And if you're not reading the pressure directly at the attachment here's where you can read them on the pump

 

[CNC Dan]

So I do have relief valves on the excavator,that's good. The pressure was 3000psi we lowered it to 1800,that's good! The bad is the thumb ram creeps down quite fast,15 seconds or so. What did I do wrong?

Did it start when you adjusted the relief valves. If not, it sounds like your valve for the thumb has a 'motor spool' in it, rather than the usual type of spool.

 

[lcgoatboy]

I had no time today. I hope tomorrow.
The Takeuchi said they adjust their thumbs to 1800 psi,it seems a bit low to me??
Also the thumb only started this creeping after I adjusted the relief valves.

 

[lcgoatboy]

Looked in the service manual today here's the layout of the valve and the functions


View attachment 410954

And if you're not reading the pressure directly at the attachment here's where you can read them on the pump


View attachment 410955

Thank you Mike. I'll be on this tomorrow.

 

[firemanmike69]

Thank you Mike. I'll be on this tomorrow.

No problem sorry it took me so long to get back to you

 

[lcgoatboy]

No problem sorry it took me so long to get back to you

Ok,so today I adjusted one of the relief valves until the ram stopped lowering. That worked but there is not much clamping pressure. I was told 1800 psi was the number to set the thumb at. Is this at an idle? Thanks.

 

[David Devuono]

I would like to see a picture of the relief valve. I am pretty sure mine has a cross over relief valve near the base of the main boom. Its quite a large unit but I have purchased cross over relief valves from Princess auto for other projects and they where not $250. PA has a 10GPM Poppet style for 99 bucks.