Backhoe Hydraulics

[ch47dpilot]

Looking at a backhoe for my tractor. I'm very familiar with the hydraulic system as far as power beyond, closed vs open circuits ect. I've noticed most of the backhoes have only 2 hoses. Power and return. Right now my hydraulics go FEL--PWR beyond to 3 point---to tank. The FEL has its own return to tank line along with the PWR in and PWR beyond(3hoses). If I put the Backhoe in the middle, use the FEL pwr beyond to power Backhoe where does the return line go to. If to the tank I understand, 3 point no longer needs PWR and is left out of loop. But when Backhoe is removed how does 3 point get power. Line is dead end at QD for backhoe. I've seen a few system where they connect the Backhoe QD together completing the power beyond circuit to the 3point. This makes sense up to a point. When the backhoe is connected you are in essence using the backhoes return line as a power beyond line for the 3 point. Yes the 3 point isn't being used but will this cause any issues if somehow the 3 point is moved.

My thought was to have the FEL power beyond go into a tee fitting. Put a QD for the Backhoe and then QD the Power beyond line going to 3 point. With backhoe removed will work same as now. With Backhoe connected disconnect QD for 3 point so its out of system. But seems like there must be something simpler

 

[Tractor Seabee]

There is another thread on here where the OP has an L, and seems he has a different set up than you do. He has rear remotes and it appears a BH just hooks to the P and T as the p comes from one of the remotes. Has to hold the valve open with a bungee cord as the remotes do not have a detent position. He is using an after market 3PT BH. He is totally frustrated right now.

If you do not have the work shop manual (WSM) for your model get one. That was how I figured out how my BX25 hydraulics were piped. it is a 3 hose BH and you couple the P and PB when the BH is off. The fluid has to get back to T someway. either through a valve stack or direct. Does Kubota make a BH specifically for the L? That is a place to start as their should be a hydraulic diagram for it and how it connects to the tractor. Post all that info and let's sort it out.

Ron

 

[Michael In Tennessee]

Seabee, I don't think that particular thread is a good example.

The Kubota OEM backhoe does not have a tank line. Power Beyond from the FEL goes to the backhoe then to the manifold under the right floorboard. Without the backhoe, the FEL PB goes to that manifold directly.

Given this OP's backhoe will allow full pressure instead of tank pressure on the output, then plumbing just like the OEM backhoe is prudent.

In no way would one want to Tee any lines except the tank line if required.

 

[ch47dpilot]

I want to make sure I understand. The FEL PB goes to back of tractor for BH PWR. With BH not connected to FEL PB and BH return are connected and then back to manifold, PB in Port. With BH connected the BH return line is actually a PB to the manifold.

 

[s219]

I want to make sure I understand. The FEL PB goes to back of tractor for BH PWR. With BH not connected to FEL PB and BH return are connected and then back to manifold, PB in Port. With BH connected the BH return line is actually a PB to the manifold.

Correct. You're inserting the backhoe into the PB loop after the loader and before the 3-pt. When backhoe is not mounted, connect the two hoses together and everything goes back to like it was before.

 

[Michael In Tennessee]

Yep. However, your backhoe must allow its return to be high pressure.

 

[Richard]

Michael, we're almost neighbors!

I live in Greenback.

Nice to see someone nearby here.

 

[ch47dpilot]

Thanks. I figured that's what they did. I do have a question that maybe someone can help me with. I've seen a cutaway of a control valve with PB. So I understand how it works. What I don't understand is why do you need a separate PB circuit. It seems to me that the return line could double as PB. When control valve #1 is in use return line is return pressure. When it's not being used the return line would have full pressure for rest of control valves. The line would have to be able to handle full psi. It seems to me that's what they are doing with the BH. The Down stream CV get full pressure from the BH return line. Granted this is probably only the unusable 3pt. But if you have additional CV for say rear remotes or a FEL grapple they could be used with the BH attached. Would you run into any issues with the downstream CV getting full PSI from the BH return line. Or would you have to ensure that other than the 3pt all other CV are upstream from the BH. Hope I asked this without being confusing.

 

[BukitCase]

Very few control valves are rated for full pressure in their "tank" galleries - so there's a very real possibility that using a line that's a tank return as a PB line would take out the valve whose tank return you tried to use. Basically, all a PB port is is an adapter that screws into an otherwise tank return, but incorporates a blocking device that isolates the tank gallery from full pressure... Steve

 

[ch47dpilot]

Makes sense. I would think it would be easier and cheaper to just have one outlet port that can handle full pressure. Definitely would be easier for installation. Just connect outlet to inlet like lightbulbs in series. But I guess it's a better option for manufacturer to have two independent ports