Custom hydraulic backhoe thumb

[bumperm]

Wetmoose,

Well, it's true that the valve will act as a check valve stopping flow in one direction when off and allowing flow in the opposite direction above a certain cracking pressure. That's not important for this application, though. You are simply using the valve as an on-off switch, to allow to extend or retract the ram to move the thumb when the valve is energized. When not energized the valve will keep the ram at whatever position it is in.

 

[cic317]

Wetmoose,

Well, it's true that the valve will act as a check valve stopping flow in one direction when off and allowing flow in the opposite direction above a certain cracking pressure. That's not important for this application, though. You are simply using the valve as an on-off switch, to allow to extend or retract the ram to move the thumb when the valve is energized. When not energized the valve will keep the ram at whatever position it is in.

perfect, as far as rating on the valve necessary to bump up to the SV10, or does the SV8 have enough cushion to handle the additional flow?

 

[bumperm]

Flow should not be an issue, remember when the valve is activated and the thumb and bucket are moving, flow is split between the bucket and thumb cylinders. When one meets resistance, even gravity, then the cylinder with the least resistance will get more flow. In practice it works just fine - you quickly get used to pre-positioning the thumb where you want it by touching the bucket to ground or object to increase resistance.

When plucking you big tap root weeds, like sage brush, you put the bucket on the far side, the thumb on the near side, push down, squeeze!! and pull up. Weed and roots yank out clean. Pretty darn amazing!

 

[Aquamoose]

I have a new SV8 valve with ORB ports to sell. I've decided to take a mechanical approach by fabricating a foot switch to open/close the valve rather than the electrical solenoid route if anyone's interested.

It comes complete with

- Valve SV08-24-0-N-0-0 (normally closed 4.5 gpm)
- 6306012 connector body
- 7151010 #8 body, #6 ORB 5k psi rated

 

[dfkrug]

I think I might be better with the Hydraforce SV10 VS SV8, any opinions?
Next questions has anyone done anything about pressure relief valves? I have to get time to read
the entire post but I didn't remember seeing anything there.

Your industrial tractor does have more flow than CUTs like mine, so I can see bumping up a size.
But don't forget that your flow is intermittant, and shared with thumb and bkt cyl if you follow
my design.

As for a pressure RV in the work lines, I did mention that, but it is also discussed in some other threads.
It bears repeating: I designed everything to work with my system pressure, so I did not need an
RV. This is not going to be the case if you do not follow my design. I made my cyls the same size,
and my system pressure was only 2500psi. Those with industrial machines need to be careful, as you
may have pressures north of 3000psi to deal with.

 

[Ron50]

Aquamoose. I finally finished my hydraulic thumb conversion. I added another stablizer valve betwween the two stablizer valves. Part description: SDS100/7/Q-101-8L, Working section "Q" style w/o Rings Cyl. Spool Spring Center. Price was $224.37 from Hydraulic Controls Inc. Phoenix, Az.
The cylinder I used was from Bailey Hydraulics. 2" Bore x 10" stroke x 1.25 rod. This folds back the thumb to the right place without hitting the cylinder. SKU #207384. This cylinder allows you to rotate the ports 90 degrees from each other which helped with the install. Price was $175.00.
I also installed a double relief valve under the controls stack on the side to be on the safe side. Boltonhooks.com price $100.
The mechanical thumb just didn't work for me. I'm probably into this beween $650 and $700 when fittings and hoses are added in. You have to trim the sheet metal cover a bit to acomodate the wider valve stack and drill new mounting holes 3/4" wider on each side of existing holes. You also have to get 1 1/2" longer bolts to hold the stack together because of the valve you add in the middle being 1 1/2" thick.
All and all I think it was worth it, it is just like an excavator now. This was done on an Ansung BH65 which is one of the brands Branson uses for their backhoes.
If I ever figure out the picture loading on my Samsung Note Pro I'll load some for you.

 

[dfkrug]

All and all I think it was worth it, it is just like an excavator now.

Congratulations. I would like to see the pix. How do you control it?

The last excavator I operated had a factory hyd thumb. To close it, you pushed
a foot pedal, and it closed all the way. When you released it, it opened all the
way. It used some sort of electro-hydraulic control.

 

[Ron50]

Excavators have electric solenoid operated valves. To operate this backhoe thumb I installed a valve just like the stabilizer valves between the two stabilizer valves. I t makes the stack one valve longer, 1 1/2", which requires three new bolts to hold them all together and some sheet metal modification. It is just one more open center valve in the stack. I installed a handle that is two inches taller than the stabilizer handles right in the middle of all the handles. It is easy to operate with either hand and it is always available. No diverter solenoids, just another valve.

 

[Aquamoose]

Hey Ron50, cool! I'd be interested in your pics when you have the chance. Since then, I've decided to go with a mechanical on-off valve to avoid the 12vdc wiring so I plan to rig some type of mechanical valve for the foot but my options are always open.

 

[Ron50]

Here's a few pictures . Maybe.