Anyone with a l47? Need help with mine. Wondering About the backhoe functions, on my machine anytime I pull in the boom and then use any other function the boom stops. Does your l47 do this too?
Anyone have a L47?
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I don't have an L47, but I have an L35 which is the original L size TLB. I understand there have been some improvements made on the consequent models. I notice you also have a Case 580. I've never operated a 'real' backhoe, but the hydraulic systems are significantly different. The L35, and I think the L47, uses an open center system. This puts all the functions in series and no pressure is developed until a function is selected. If more than one function is selected, the following ones get starved. On the L35, the boom is next-to-last, followed by the swing. So it tends to get starved. This can be mitigated somewhat by carefully feathering the controls. But it'll never match a 'real' backhoe. The L35 only has one pump for everything. I think the 47 has a second pump, but I'm not familiar with it. If you could post the hydraulic diagram from your WSM, probably the backhoe section, someone here might can help more.
thanks for the input. I will post the diagrams from the wsm. What interesting to me is that neither my 2620 or 3301 had this problem. I took can feather the controls and operate say the boom and dipper at the same time but as soon as I throw in bucket curl the boom stops. Really hoping it’s not just “how it is”
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Right now my L47 is in for service. When I get it back I'll double check, but I'm pretty sure I can pull in both boom and dipper stick at the same time (rotate too, I think).
What rpm are you running at?
I believe L47s have three pumps. One is for PS, the other two supply the hydraulics. The left stick functions are supplied by one pump and the right stick by the other.
I just found this Messick's video which explains the setup. It says M62, but the L47 is the same. You can skip ahead to around the six minute mark where he starts talking about the backhoe controls.
What rpm are you running at?
I believe L47s have three pumps. One is for PS, the other two supply the hydraulics. The left stick functions are supplied by one pump and the right stick by the other.
I just found this Messick's video which explains the setup. It says M62, but the L47 is the same. You can skip ahead to around the six minute mark where he starts talking about the backhoe controls.
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My machine isn't back from the shop yet, but I do have an update.
I pulled out my WSM and looked up the hydraulic circuit diagram.
Bad news is, I don't understand how to interpret the drawing.
Good news is I can read. :- ) At the bottom of the page it says.
P1: From Main Hydraulic Pump
P2: From Swing Hydraulic Pump
I'm guessing that the swing has it's own pump,P2 and everything else runs off P1.
If I had the ability, I'd post a copy of the diagram, but alas......
I have one with about 400 hours of experience on it. The separate pump runs the swing so that you can swing and boom at the same time. However, the main pump runs all of the boom functions and there is a clear priority in the connections so if you fully open all of the valves you only get one function at a time.
However, from experience I can tell you that if you "feather" it carefully you can move the boom, stick, and bucket at the same time but they are not equal so it's tough. For example,. to cut a flat bottom takes about 10% up boom, 40% crowd, and 10% curl or something like that. The boom has first priority and if I recall right, curl is next so getting a smooth bottom really takes some practice.
However, from experience I can tell you that if you "feather" it carefully you can move the boom, stick, and bucket at the same time but they are not equal so it's tough. For example,. to cut a flat bottom takes about 10% up boom, 40% crowd, and 10% curl or something like that. The boom has first priority and if I recall right, curl is next so getting a smooth bottom really takes some practice.
So this is what I figured out...like you mention yes one pump to run everything except the swing. As far as priority goes it has more to do with which function is closest or furthest from the incoming port. Don’t know about y’all but no other backhoe I’ve run is like this and in the case of other open center systems the pump usually speeds up to keep up with the multiple functions being operated. As a work around I’ve installed a needle check valve on the extension side of the dipper valve. By restricting flow, there is more available fluid to push out to the boom. So far so good and cautiously optimistic.
I have an M62 which has basically the same architecture in most respects as the L47. They have a common shop manual, and without looking it up, both versions use the same three pumps. One is for the loader and tractor motion and the other two operate the backhoe. I forget which pump handles the power steering. Unfortunately, they have the swing feature on the second pump and the third pump runs the boom and the stick as well as the curl function. Since they all fight for flow, as mentioned above, it is a challenge to operate the boom function smoothly while bringing the stick back in. I imagine a real pro can work this better than me, but what makes it worse is the fact that I'm trained on CAT control which gets me really frustrated when I use my M62 which has the opposite functions. An excavator has three pumps and devotes one to the boom and one to the stick while motion has its own pump. The absence of a loader and power steering makes for less pressure conflict while digging. In order to eliminate the issue, Kubota would have to design a more expensive and heavier machine which misses their price point and the ability of users to trailer with existing equipment.
TheOldHokie
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My understanding is the M62 has three hydraulic pumps
- One is dedicated to PS
- One is dedicated to the backhoe swing function
- One supplies the loader and all backhoe functions except swing
The HST transmission is a fourth separate system altogether. I would have to check the WSM but Kubota often uses the return from the PS control valve to supply the HST charge circuit. I believe that would be the only interaction between those two systems and its so small as to be negligible.
Dan
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TheOldHokie
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Th
The swing cylinder is totally independent of the boom, crowd, and bucket cylinders,
Boom, crowd, and bucket cylinders are all in parallel so they have equal priority but the cylinder with least load will always move before the heavier loads which will stall until cylinder loads equalize.
Work port flow diagram with all cylinders active below.
Dan
Its an interesting but pretty conventional valve. It has two inlet sections which share a common tank outlet.
The swing cylinder is totally independent of the boom, crowd, and bucket cylinders,
Boom, crowd, and bucket cylinders are all in parallel so they have equal priority but the cylinder with least load will always move before the heavier loads which will stall until cylinder loads equalize.
Work port flow diagram with all cylinders active below.
Dan
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fried1765
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