Custom hydraulic backhoe thumb

[rbarnett]

Very nice idea, and I am copying it, sort of, for my Kubota Excavator. I have all the major parts, and will build before I start a demolition job next month. Thanks for sharing the build. I'll document mine when I get started.
Bob

[dfkrug]

Originally Posted by rbarnett

Very nice idea, and I am copying it, sort of, for my Kubota Excavator. I have all the major parts, and will build before I start a demolition job next month. Thanks for sharing the build. I'll document mine when I get started.

Thx, Bob

Many of those excavators already come plumbed for an AUX circuit at the
end of the dipper. You may even have more than 2500psi to work with.
You may get 7-8000 lbs of pulling force on the end of your dipper at the
thumb pivot....remember to build that weldment strong!

[slicktierney]

dfkrug
Excellent work on your projects! Nice 4 in 1 bucket also.
How did you size the solinoid valve on the hydraulic cylinder? I am redoing my thumb to a serrated jaw, so while I have it cut apart it would be nice to set up for hydraulics at the same time. Thank you
Slick

[dfkrug]

Originally Posted by slicktierney

How did you size the solinoid valve on the hydraulic cylinder?

Thx for the pos feedback, Slick.

My tractor delivers a max implement flow rate of 8.3 GPM. I figured that
I needed a minimum flow rate for my valve of 4-5GPM. That is based on
the fact that I am rarely running at full engine speed and the valve is in
parallel with the curl cylinder so flow is shared. A dedicated AUX valve
should be sized to the tractor's max output or greater, generally. In my
case, small size was very desirable.

What tractor are you going to be using?

[slicktierney]

Hi dfkrug;
I have a kubota 3710 with a woods 9000 that runs off a woods pto pump which is rated @ 3.8 cubic inches. The manual says it requires 8-10 gpm @ 2400 psi. I guess about the same as yours.

[dfkrug]

Originally Posted by slicktierney

I have a kubota 3710 with a woods 9000 that runs off a woods pto pump which is rated @ 3.8 cubic inches. The manual says it requires 8-10 gpm @ 2400 psi. I guess about the same as yours.

Your tractor will do 7.8GPM at PTO speed, and your PTO pump puts out
8.9 at that speed (540). 8 GPM is likely to be faster than you want to
operate that hoe, so you are fine. Your design criteria should be similar
to mine if your solenoid valve is a 2-way valve for parallel operation. If
you go with a dual solenoid full diverter setup (4-way), I suggest you get
one to accommodate the 8+ GPM it might experience. BTW, there are a
bunch of those latter valves shown on various TBN grapple bucket
projects. Unfortunately they tend to be large valves and often require you
buy a manifold (base plate).

[slicktierney]

Hi dfkrug;
I will start looking for the same valve setup, I like the component performance that you describe, The fixed thumbs are tough because you have to be placed correctly to grab effectively. The excavator isn't so bad because it moves easier. Maybe down the road I'll have to replace the footvalve on the excavator from hammer stuff to thumb stuff. Thank you for your help!

[dfkrug]

Originally Posted by slicktierney

The excavator isn't so bad because it moves easier. Maybe down the road I'll have to replace the footvalve on the excavator from hammer stuff to thumb stuff.

Happy to help if I can. I used a rented excavator before and a right
foot valve controlled the thumb. It moved FAST. It also closed
when I pushed the pedal, and automatically opened when I let go. It
was slick, but it did not provide classical grapple action (parallel).

[steveoutdoorrec]

Not really a thumb but have any of you seen something like this

There was one at a banquet here last night and I was drawn to it like a moth to a flame. Sure could use it on all the stumps the last guy left me to deal with.

[3RRL]

Hi Dave,
Sorry I didn't post sooner on your thread.
What a great idea and of course. a super build job you did.
The parallel action is fantastic. How is everything holding up? Are the function and use as designed working just as you thought? It has to be a pleasure to operate your new set up. I would be really excited about it with a lot of self satisfaction.
Great job Dave.
Rob-