Replaced Hydraulic Hoses...Bucket Issue

[bobframe]

I started this thread at 2:02PM on 10/9/17 asking for help.

Fearing that the hoses were incorrectly attached, at 3:46PM 10/9/17 (PAGE 2) I supplied numerous photographs showing EXACTLY how they were attached. I reference the photographs and asked "Isn't this correct?"

At 4:03PM, in reference to the above, I was told "The hoses look good visually".

It was at this point that the suggestions began focusing on air blocks, crimped fittings, plastic plugs blocking hoses, closed valves and mud dobbers. I thought, "If the hoses look good, then the problem lies elsewhere."

I should note that earlier in the day I showed the same photos to the service manager at the local Kubota dealer and asked him explicitly whether the hoses were correctly attached, to which he replied in the affirmative.

At 8:09PM (same day), having tried numerous techniques to clear the lines, I asked (Post #31), "Is there a chance that I have the hoses attached to the wrong ports?" and supplied a photo of the hoses which were, in hindsight, plainly attached to the WRONG PORTS. No one suggested that they were incorrectly attached.

In summary, I asked TWICE about whether the hoses were attached incorrectly.

 

[LD1]

I started this thread at 2:02PM on 10/9/17 asking for help.

Fearing that the hoses were incorrectly attached, at 3:46PM 10/9/17 (PAGE 2) I supplied numerous photographs showing EXACTLY how they were attached. I reference the photographs and asked "Isn't this correct?"

At 4:03PM, in reference to the above, I was told "The hoses look good visually".

It was at this point that the suggestions began focusing on air blocks, crimped fittings, plastic plugs blocking hoses, closed valves and mud dobbers. I thought, "If the hoses look good, then the problem lies elsewhere."

I should note that earlier in the day I showed the same photos to the service manager at the local Kubota dealer and asked him explicitly whether the hoses were correctly attached, to which he replied in the affirmative.

At 8:09PM (same day), having tried numerous techniques to clear the lines, I asked (Post #31), "Is there a chance that I have the hoses attached to the wrong ports?" and supplied a photo of the hoses which were, in hindsight, plainly attached to the WRONG PORTS. No one suggested that they were incorrectly attached.

In summary, I asked TWICE about whether the hoses were attached incorrectly.

Which is why I wished I saw this thread earlier to advise. But by the time I saw it you had the problem figured out.

With the photos you supplied, its impossible to tell if they are hooked backwards. Because we need the COMPLETE picture from VALVE to CYLINDER to determine that. Simply seeing which hard steel line the hoses are hooked to isnt sufficient, because we need to know WHICH port on the valve that the hard lines go to.

Had I seen the thread earlier, I would have asked for more pics showing the routing of the lines up the loader frame all the way to the valve. Dont know how anyone can say the hose routing looks good other than it does confirm that one side matches the other.

But again, even without the pics of the routing, simply showing the bucket at full dump and knowing that it wont move (it physically cannot move further in the dump position).....I suspected a regen/backwards hose problem. And would have asked for more pics, or just advised you to swap and try. Because there is no harm gonna be done if they are on backwards. So there would be no risk to swapping and trying.

All this just shows how little I know about hydraulics in general and "regen" specifically!

Regen quite simply opens BOTH cylinder ports to full pressure. When you do this, the cylinder will STILL extend. Because a cylinder has more force extending than retracting, because the surface area of the piston is bigger on the base end because it doesnt have a rod attached to it. So you have the full area of the piston multiplied by the system pressure (~2500). The rod side has the full area of the piston MINUS the area of the rod.

So....lets say a 2" cylinder and a 1" rod and 2500 PSI. The cylinder can PUSH with 7850# of force when 2500 PSI fluid is applied.Subtract the area of the rod, means it retracts with less force. 5900# or so retract.

Well, when you are trying to extend with 7850# and trying to retract with 5900# of force.....the end result is the cylinder still extends. But only with the difference. ~1850#.

Two main reasons why regen is beneficial.

1. It operates a cylinder FASTER. Faster with less force. Since you dont have to wait on the pump to fill the full volume of oil in the cylinder. By opening both ports to P, the oil on the rod side, rather than being expelled and pushed back to tank, it simply combines with the flow going into the base end of the cylinder. So instead of having to fill a whole 2" diameter cylinder.....you only need the pump to replace the volume of fluid that the 1" rod occupied.

2. In the case of the loader bucket....when dumping a load of whatever....gravity can dump the loader FASTER than the pump can fill it with oil. This creates air in the system and what is know as "floppy bucket syndrome". Where when you just dumped a load and want to backdrag it to feather it out and the bucket wont hold its position. Well....regen prevents this by pressurizing BOTH ports and preventing gravity from causing an air pocket.

 

[bobframe]

Which is why I wished I saw this thread earlier to advise. But by the time I saw it you had the problem figured out.

With the photos you supplied, its impossible to tell if they are hooked backwards. Because we need the COMPLETE picture from VALVE to CYLINDER to determine that. Simply seeing which hard steel line the hoses are hooked to isnt sufficient, because we need to know WHICH port on the valve that the hard lines go to.

Had I seen the thread earlier, I would have asked for more pics showing the routing of the lines up the loader frame all the way to the valve. Dont know how anyone can say the hose routing looks good other than it does confirm that one side matches the other.

But again, even without the pics of the routing, simply showing the bucket at full dump and knowing that it wont move (it physically cannot move further in the dump position).....I suspected a regen/backwards hose problem. And would have asked for more pics, or just advised you to swap and try. Because there is no harm gonna be done if they are on backwards. So there would be no risk to swapping and trying.




Regen quite simply opens BOTH cylinder ports to full pressure. When you do this, the cylinder will STILL extend. Because a cylinder has more force extending than retracting, because the surface area of the piston is bigger on the base end because it doesnt have a rod attached to it. So you have the full area of the piston multiplied by the system pressure (~2500). The rod side has the full area of the piston MINUS the area of the rod.

So....lets say a 2" cylinder and a 1" rod and 2500 PSI. The cylinder can PUSH with 7850# of force when 2500 PSI fluid is applied.Subtract the area of the rod, means it retracts with less force. 5900# or so retract.

Well, when you are trying to extend with 7850# and trying to retract with 5900# of force.....the end result is the cylinder still extends. But only with the difference. ~1850#.

Two main reasons why regen is beneficial.

1. It operates a cylinder FASTER. Faster with less force. Since you dont have to wait on the pump to fill the full volume of oil in the cylinder. By opening both ports to P, the oil on the rod side, rather than being expelled and pushed back to tank, it simply combines with the flow going into the base end of the cylinder. So instead of having to fill a whole 2" diameter cylinder.....you only need the pump to replace the volume of fluid that the 1" rod occupied.

2. In the case of the loader bucket....when dumping a load of whatever....gravity can dump the loader FASTER than the pump can fill it with oil. This creates air in the system and what is know as "floppy bucket syndrome". Where when you just dumped a load and want to backdrag it to feather it out and the bucket wont hold its position. Well....regen prevents this by pressurizing BOTH ports and preventing gravity from causing an air pocket.

GREAT response! Wish you'd seen this sooner...suggesting that I swap lines is exactly what we did and it instantly solved the issue. I could have done a better job describing the initial symptom...push joystick right and it dumps, pull stick left and it dumps.

Anyway, problem solved. I learned several things. Thanks for the lesson on hydraulics and regen.

BTW, can you suggest a place I can go to see diagrams of how a hydraulic cylinder is constructed? I've never seen one.

 

[LD1]

I could have done a better job describing the initial symptom...push joystick right and it dumps, pull stick left and it dumps.

If that indeed was the initial symptom.....then yea if you had posted that I am sure someone would have figured that out long before page 4 or 5 whenever you swapped hoses. I was going off assumption seeing that your bucket was dumped ALL the way. And that with hoses backwards both directions tries to make it dump....which it physically cannot....thus you describe the symptom as doing nothing.

But yea, glad its working for you. And I am sure you learned a valuable lesson......either change hoses one at a time....or mark them so you dont mix them up.

I had to tear apart my backhoe valve last year. Hard to get to, and 6 work-port hoses, a return that has a TEE and two hoses, a PB, and a pressure line. And there is only one possible order that 10 hoses can come off and go back on. I Marked them all with coding electrical tape (colored). Too oily of a mess and a few fell off. Got two reversed. And had to take of 6 of the hoses just to get to the two that were backwards. And being under a floor pan under the seat in a tight area anyway......there were a few choice words said.

 

[Spanner]

As I recall, when I first attempted to operate the bucket I though it was operating weirdly...like it was doing the opposite of what I wanted it to do.

Lesson learned (again) is that when you are disassembling an unfamiliar device either take notes or take photos. I knew better.

This would have been pertinent to the Page 1, Post #1 information.

:2cents:

 

[bobframe]

This would have been pertinent to the Page 1, Post #1 information.

:2cents:

Yup...I get that now. At the time I'm not sure I realized what was happening...just that the dump and curl functions weren't working. It took seconds for the bucket to reach its fully extended position and at that point NOTHING I did had any effect. It took me a while to reconstruct what I'd experienced and to put it into words.

I thought that simply seeing how the hoses were connected at their termination points would reveal whether they were correctly connected. Now I understand that its necessary to trace the circuits all the way to the valve. Oh well, great learning experience for me.

Thanks again to all who offered assistance and I apologize if my ham handed description caused any of you to waste your time....certainly not my intent.