Hydraulics limitations

[soulasphil]

The problem is as soon as I open the 3rd SCV to activate the hedge trimmer, the log splitter or the dump trailer, all other hydraulic devices like FEL or 3pt are cut off, that is very annoying and I wonder why Deere designed it that way.

 

[J_J]

The routing of the hyd fluid could probably be modified to accomplish what you want to happen. The first valve after the pump should have priority. Valves downstream use what is not used by upstream valves. Steering hyd is a high priority. Do you have a hyd schematic to see the routing of the fluid.

 

[kennyd]

The problem is as soon as I open the 3rd SCV to activate the hedge trimmer, the log splitter or the dump trailer, all other hydraulic devices like FEL or 3pt are cut off, that is very annoying and I wonder why Deere designed it that way.

Deere didn't "design" it that way, it's just the nature of the system for the money you spent. To have a system that would supply all of the different functions at once would cost more money.

 

[soulasphil]

Unfortunately, I only have the owner's manual and no hyd schematic, pity that would certainly help. Besides it is difficult to understand the plumbing from looking at the tractor as many links are internal. Steering and other utilities have their own separate hydraulic pump, so I'm only looking into implement hydraulics.
I don't think it's a question of money. For instance I can use the FEL and 3 pt hitch at the same time, but I cannot use the FEL and 3rd SCV at the same time. There clearly is a difference and I would like to know why.

 

[J_J]

Can you determine where the fluid goes first? Otherwise, does it go to the FEL first, or go to the back first? Is the tractor open center, and can you follow the flow through the system. If in fact it goes to the FEL, and then to the 3rd SCV, and then the 3pt. If the hyd hedge trimmers are running, they would be using all the fluid in the series loop, and the 3pt would not get any. If you ran the hedge trimmers at half speed, then the 3pt should work, although not as fast. Probably as soon as you turn off the hyd hedge trimmers, you should have 3pt. If you are only using some of the flow for one circuit, there should be some flow left for another circuit.

Does your 3rd SCV have PB?

You could put hyd gage in the circuits to test and trouble shoot the system.

JD 3520

Hydraulics
Type Open Center

Pump Rated Output, gpm (L/min.) 13.9 (52.5)

Steering 5.3 (20)

Implement 8.6 (32.5)

Pump Type Dual gear

Maximum Operating Pressure (PSI) 2500

Draft Control Type Position control

Remote Control Valves Available 5

 

[soulasphil]

Thank you very much J J for trying to help me understanding those mysteries. I'll go under the 3520 some more to try and follow the hyd lines. I do not have power beyond but am thinking of having it installed.
From the beginning, you take for granted that the different outlets share the available oil and some of them have to slow down when others are turned on. That is exactly the case with the positioning cylinders of the hedge trimmer and its motor. But it is not the case with the 3rd SCV. As soon as it is in one of the 2 active positions (not the float position far forward) the rest of the tractor's hydraulics is cut off, the controls dead. And this is true even if no oil is used (log splitter stopped for instance). I find it difficult to understand how this can be achieved.

 

[J_J]

soulasphil

I noticed that your avatar is a sailboat, but did you know that a ferro cement sailboat was built, and is operational. Here are some pictures of the hull with a steel grid frame, the finished cement hull, and the fitted out sailboat.

 

[soulasphil]

Yes I know there are concrete hulls for sailboats. I have seen a few and even had drinks aboard one of them. I don't know about America, but in Europe they are no longer in fashion.