Backhoe attachment

[Vigo327]

Don't I lose my loader function by doing that ?

No.

The PB port is an outlet from your loader valve, not an inlet. The loader will function exactly as it already does. The only caveat to feeding the backhoe from your loader PB port is that pulling a loader valve will cut power to the backhoe, which is a total non-issue because you never HAVE to use both simultaneuously.

If you think about where that hose starts at your loader PB port, and ends at your hydraulic block, you are basically inserting your backhoe valve between those two points.

 

[rScotty]

Well here it is. Picked it up today. He claims no top link used with this sub frame and he didn't have one hooked up ?

It looks nice. Next step would be to make the sub frame fit.
You might want to contact Woods to conirm the top link. That subframe looks very strong, but without a top link it needs to fit the tractor very well. I don't see a downside to a top link.

rScotty

 

[rScotty]

No.

The PB port is an outlet from your loader valve, not an inlet. The loader will function exactly as it already does. The only caveat to feeding the backhoe from your loader PB port is that pulling a loader valve will cut power to the backhoe, which is a total non-issue because you never HAVE to use both simultaneuously.

If you think about where that hose starts at your loader PB port, and ends at your hydraulic block, you are basically inserting your backhoe valve between those two points.

Don't you think that plumbing the system that way also depends on having a PB port on the backhoe valve stack? I think it needs a path to take the high pressure flow from the backhoe back to the hydraulic block.
rScotty

 

[Vigo327]

So this is an assumption..but MOST backhoe valves are sectional valves where you can stack up more valve sections. On a monoblock unless you can find documentation that says so you have to wonder if the ‘return’ or tank port passages can handle full line pressure without cracking the housing. But my ASSUMPTION is that on a sectional type valve set, for SURE all the galleys in the valve sections are designed to hold full pressure and the only part that MIGHT not be rated to that pressure is the outlet housing, but i suspect it would be fine in nearly all cases.

So even though it is not always a good idea to subject a valve set’s tank port/passages to high pressure, im suspecting that on a backhoe sectional valve set that usually is fine.

I replumbed a backhoe on a small kubota tractor to work this way and it has been fine so far. I put a gauge on it and im subjecting the backhoe valve outlet to ~1400psi, no problems yet.

 

[rScotty]

Best of all would be if we could find both a PB and a return port on the sectional valve - and it might have that configuration already - or be available. Sectional valves tend to have every option.
It would help if we had a fluid schematic for the Woods sectional valve. Woods might be able to help out on that & someone ought to ask. They have probably seen every configuration there is.

 

[John1550]

Best of all would be if we could find both a PB and a return port on the sectional valve - and it might have that configuration already - or be available. Sectional valves tend to have every option.
It would help if we had a fluid schematic for the Woods sectional valve. Woods might be able to help out on that & someone ought to ask. They have probably seen every configuration there is.

Does this help

 

[Vigo327]

So the way i recommended plumbing it would technically put pressure on the outlet port of the backhoe IF you put the 3pt under pressure somehow. But if you didnt, or if the tractor has position control i dont think you even could (because it would just hit the target and stop pushing?), it is simply routing the backhoe exhaust flow through the 3pt plumbing before returning to tank, just as that flow currently does now. I recommended to do it this way because it is the simplest in terms of making or moving connections. Just ‘put the backhoe valve in series between the loader and 3pt on the power beyond line’.

 

[John1550]

So the way i recommended plumbing it would technically put pressure on the outlet port of the backhoe IF you put the 3pt under pressure somehow. But if you didnt, or if the tractor has position control i dont think you even could (because it would just hit the target and stop pushing?), it is simply routing the backhoe exhaust flow through the 3pt plumbing before returning to tank, just as that flow currently does now. I recommended to do it this way because it is the simplest in terms of making or moving connections. Just ‘put the backhoe valve in series between the loader and 3pt on the power beyond line’.

Huh ? Lol

 

[Vigo327]

Dont worry, I didn’t know much about hydraulics a year ago either but ‘look at me now’

 

[John1550]

Dont worry, I didn’t know much about hydraulics a year ago either but ‘look at me now’

Maybe a sketch would help

 

[Vigo327]

We'll see!!

 

[rScotty]

Huh ? Lol

I believe that Vigo327 is saying that since the 3pt hitch is not going to be used at the same time as the backhoe is installed, then it is possible to use the 3pt hitch's internal circuit as a path for the backhoe fluid return flow. (backhoe fluid OUT).

He is drawing attention to the fact that there is a return path that already exists within the 3pt fluid circuit that has the right characteristics to be able to accept flow from the backhoe and directing it to the sump. It is the same bypass pathway that the tractor uses when the hydraulic pump is running but the 3pt is not in use.

Tractors all have some position on the 3pt control that selects that bypass path and directs incoming high pressure flow directly to the sump. On most tractors - not all, but most - this is the path selected by the 3pt control when the control is pushed all the way forward.

Some Kubotas even have a thumb screw designed to hold the control in the full forward bypass position.

He is also saying that if you plumb things that way, you do have to be careful to leave the 3pt control in the bypass position and not to actuate that 3pt control when the backhoe is connected.

I think that might work. It's worth a try. It has the advantage of simplicity.

If you are going to try it that way, I'm thinking the sketch needs to have some more detail so that everyone is on the same page. There are some high pressures in this solution, so be sure to use hydralic connectors, not standard plumbing connectors.
rScotty

 

[John1550]

This valve under the seat I believe locks the 3 pt so it won't move ? Should I use that

 

[John1550]

I ran out of welding gas so I can't complete the front bracket just yet but the rear hooked up rather easy. I had to take the hitch off though. My only concern is I had to remove a bolt on each side to get the frame to slide on. Deciding if I want to remove the frame and grind that section away to get the bolts in ?

 

[rScotty]

This valve under the seat I believe locks the 3 pt so it won't move ? Should I use that

No. Leave that valve as it is. It is the "stop/lock valve", a needle valve to "fluid lock" movement of the 3pt piston.

Which way do you move the 3pt control lever to lower an implement? Move the lever all the way in that direction and leave it there.

And please get yourself some hydraulic flow diagrams and study up. Most service manuals have several chapters on the hydraulic system.

3pt systems haven't changed much since they were invented. To get you started, here are some views of the 3pt on an old Yanmar. It's about as basic as they come. Most Service manuals have better views than this. But if you can follow this, you can follow them. .
rScotty

 

[rScotty]

I ran out of welding gas so I can't complete the front bracket just yet but the rear hooked up rather easy. I had to take the hitch off though. My only concern is I had to remove a bolt on each side to get the frame to slide on. Deciding if I want to remove the frame and grind that section away to get the bolts in ?

I'd remove just enough metal to get the bolts to slide in for now. It won't clamp all that well with half a washer worth of compressive force missing, but you want what you can get. Looks like it will probably need longer bolts, too. Metrics will fit tighter in the hole.
Then when you get acet. gas you can weld on an extention to that ear that will cover the hole and drill new holes in the extention.

 

[rScotty]

BTW, when you hook the BH to your hydraulic system you will be mixing all the BH hydraulic oil retained in the cylinders with yours system.
HST transmissions are real sensitive to oil type and often have an additional filter as well. So you may want to consider what his tractor looked like and if you want to change oils and filters. Some do; some don't.

 

[Vigo327]

I don't think the missing bolt is intended to be part of securing the subframe so i would just notch out that part of the bracket that is interfering with the bolt. My .02.

Thanks rScotty for giving my hydraulics comments the benefit of the doubt. I'm sure im not doing the best job explaining my ideas, but you definitely 100% got what i meant.

 

[rScotty]

I don't think the missing bolt is intended to be part of securing the subframe so i would just notch out that part of the bracket that is interfering with the bolt. My .02.

Thanks rScotty for giving my hydraulics comments the benefit of the doubt. I'm sure im not doing the best job explaining my ideas, but you definitely 100% got what i meant.

Yes, not the way I would normally do it - but I'm glad for your idea and think it is definitely worth a try.

The problem is whether or not the backhoe will work right using the high fluid resistance return path through the 3pt valve.
Even when the 3pt control is wide open as a bypass, that 3pt return path seems specifically designed to slow the returning fluid down and dissipate the pressure. That makes sense, tractors don't want a lot of quick movement on the 3pt piston.

So I'm not sure what effect that high resistance path will have on the backhoe return. Maybe nothing, or it might slow the backhoe down too much. Worth a try.

 

[John1550]

Well there is always this option. Not sure if he'll ship though he's 4 1/2 hrs from me