Plumbing remotes - need help

[Jay4200]

I want to plumb a couple of rear remotes on my L4200 to run hydraulic chute controls for my snowblower. My tractor only has a single set of 'power beyond' lines in the rear (used for my backhoe), and I have to unplug the hydraulics from the 3pt hitch to run them, so I can't run a 3pt implement and have rear hydraulics at the same time.

I don't have any specific plans yet, but I think the best place to tap in would be my FEL controls, since I'll never be using the bucket and blower at the same time. Does that sound reasonable, or should I be looking somewhere else? Should I consider re-plumbing the machine completely (power beyond vs. 3pt hydraulics is kinda stupid), or just kludge in specifically what I need? I guess I need a couple of dual-acting valves and some hoses and connectors. Sound right? If I find a set of feed hoses, how do I tell which is supply and which is return? How do I tell what size/type connectors that I need to tap into existing stuff? Is there a link with connector dimensions somewhere?

Where is the best place to buy the equipment that I need? I found Surplus Center a while back for valves and such, and found a guy on the 'net a few years ago that did hydraulic lines for something like $1/foot + connectors, but I don't know if I still have the URL for that one.

I have zero experience with mucking around with hydraulic systems, and don't know anything about this type of project, so I have a lot to learn, and I'm looking for any and all information and/or suggestions.

thanks much - JayC

 

[kennyd]

Jay,
When your backhoe is removed you plug two hoses together correct? These are the hose you can plumb your new valve into and not loose 3PH operation.

 

[Jay4200]

Jay,
When your backhoe is removed you plug two hoses together correct? These are the hose you can plumb your new valve into and not loose 3PH operation.

Hey Kenny - how's it goin'?

I don't think I am supposed to plug two hoses together (never ran w/o the backhoe, so I'm not sure). I would assume that if I connected the BH connections together, I'd short-circuit the hydraulic system and nothing would work. Is that not correct? The BH 'power beyond' is not valved, and has two female quick disconnects, so when I disconnect the BH they just sit there. The way it is plumbed now, at least as far as I know, the high-pressure hose that powers 'power beyond' the in the back is disconnected, and another is plugged in, which powers the 3pt. I called the shop that had it last before the PO a few years ago when I messed with it the last time - I think that they plumbed it, and they told me that the BH take the 3pt hitch hydraulics. I've never actually connected and run the 3pt, so I'm not sure.

Assuming all above is correct, it seems to me that I could simply stick a tee in where the BH and 3pt high-pressure hoses connect, which would power them both at the same time. Then I could just plug a couple of remote valves into the rear 'power beyond' hoses.

JayC

 

[kennyd]

I don't think I am supposed to plug two hoses together (never ran w/o the backhoe, so I'm not sure). I would assume that if I connected the BH connections together, I'd short-circuit the hydraulic system and nothing would work. Is that not correct?

100% backwards. The fluid has to go somewhere, so the hose MUST be connected together if the BH is removed. The pump is always pumping fluid if the engine is running. If the fluid can't flow then your PRV (pressure relief valve) will pop open and your engine will lug down-the fluid will overheat if you let it run this way.

The BH 'power beyond' is not valved, and has two female quick disconnects, so when I disconnect the BH they just sit there.

Are you SURE they are both female? One should be, but the other should be male so they can plug together. I understand it's not valved,that is what a PB circuit is-a constant flow of hydraulic oil.

Assuming all above is correct, it seems to me that I could simply stick a tee in where the BH and 3pt high-pressure hoses connect, which would power them both at the same time. Then I could just plug a couple of remote valves into the rear 'power beyond' hoses.

No, you cannot Tee into any high-pressure hydraulic lines. The fluid will "take the path of least resistance" and nothing would work well.

Can you take some detailed pictures of your setup?

 

[Chilly807]

If it were me, and I'm just a rookie at this mind you... I'd start from scratch and take the return line from the loader valve, which should be "power beyond" capable to run the 3 ph as well, and run that to another power beyond capable valve (two spool would be ideal, 4 way 3 position) One spool would be detented in all three positions. You really only need a two position spool, but I'm not sure if you can get one combined with a 3 position as well. Anyway, the first spool runs your backhoe connections in one detented position, and is in neutral in the center position. The second spool is a straightforward 3 position, spring centered spool, to operate the snowblower chute. The return (power beyond) from the new valve will go to the 3 ph inlet, and the return from that will go to your tank connection. No tees anywhere except possibly on the tank return line, no pressure there so it doesn't matter.

I may be all wrong on this, if I am please show me the error of my ways, I'm still learning.

Chilly

 

[Jay4200]

100% backwards. The fluid has to go somewhere, so the hose MUST be connected together if the BH is removed. The pump is always pumping fluid if the engine is running. If the fluid can't flow then your PRV (pressure relief valve) will pop open and your engine will lug down-the fluid will overheat if you let it run this way.

Why does the fluid have to go somewhere? It doesn't go anywhere when the backhoe is connect and I'm not pushing any controls, at least I don't think it does. The high-pressure side should just sit there at high pressure (?). Or, does a valve actually run in bypass-mode until you push it one way or the other?

Are you SURE they are both female? One should be, but the other should be male so they can plug together. I understand it's not valved,that is what a PB circuit is-a constant flow of hydraulic oil.

Definitely both female. They are also hard-mounted to the tractor with a quick disconnect sleeve, so if you forget to unplug the hoses, they pop off by themselves as soon as they are yanked - good thing too, since it only took me twice before I drove away with them connected.

No, you cannot Tee into any high-pressure hydraulic lines. The fluid will "take the path of least resistance" and nothing would work well.

I don't understand this either. There surely isn't a pump for each path, so all of the paths have to be teed somewhere. Since I'll never use the bucket and rear remotes at the same time, I figured that would work fine.

Maybe my base understanding of the system is flawed. I am assuming that the hydraulic pump creates a high-pressure side, so all of the supply hoses sit at full pressure (2500PSI or so) all the time. When a valve opens, that pressure forces fluid into a cylinder, and the fluid from the other side gets pushed through the low-pressure side into a reservoir, to be sucked up by the pump to maintain the high-pressure. Is this not how a hydraulic system works? Are you saying that a pump runs as a circulator, and only builds pressure when the return path is closed off? Maybe I'm confused between an open vs. closed center system - don't know what my Kubota has.

JayC

 

[mmurphy]

I left a post on MTF but here is a simple reply. I would assume you have open center hydraulics, so hydraulics does not stay in 2500 psi or you will be running in relief causing oil to heat up. If you had a closed loop then you would be staying at 2500 psi with propably a variable piston pump used on construction equipment. The valve on open center when actuated will close off flow down stream and redirect it to cylinder allowing you to get up to 2500 psi or what ever pressure it takes to move to that point. May only take 1200.

 

[Jay4200]

I left a post on MTF but here is a simple reply. I would assume you have open center hydraulics, so hydraulics does not stay in 2500 psi or you will be running in relief causing oil to heat up. If you had a closed loop then you would be staying at 2500 psi with propably a variable piston pump used on construction equipment. The valve on open center when actuated will close off flow down stream and redirect it to cylinder allowing you to get up to 2500 psi or what ever pressure it takes to move to that point. May only take 1200.

Thanks - I read them both. I guess I misunderstood the fundamental theory behind the system. I found a couple of good descriptions on the web, so I'm starting to get it. I'll have to get some verification on that hose jumper though. I'm going to call the dealer that plumbed it today and see what I can find out.

thanks again - JayC

 

[kennyd]

Why does the fluid have to go somewhere?

Because the pump will blow up if doesn't. You have a constant displacement pump so it is ALWAYS pumping.

It doesn't go anywhere when the backhoe is connect and I'm not pushing any controls, at least I don't think it does.

Your valve are "Open Center", which means that the fluid flows through the valve when it's in neutral.

The high-pressure side should just sit there at high pressure (?). Or, does a valve actually run in bypass-mode until you push it one way or the other?

See above description.

Definitely both female. They are also hard-mounted to the tractor with a quick disconnect sleeve, so if you forget to unplug the hoses, they pop off by themselves as soon as they are yanked - good thing too, since it only took me twice before I drove away with them connected.

Then you would need a jumper to "complete the circuit" when the backhoe is removed.

I don't understand this either. There surely isn't a pump for each path, so all of the paths have to be teed somewhere. Since I'll never use the bucket and rear remotes at the same time, I figured that would work fine.

Remember, the valves are OPEN CENTER so the fluid flow THROUGH them when it in neutral. If you Tee a valve in-then try to get pressure from it the fluid will "take the path of least resistance" and flow through the another valve. All valve MUST be in series.

Maybe my base understanding of the system is flawed.

It is. I suggest you search some in the Hydraulics forum. ALL this has been discussed 100's of times. Terms like "power beyond" and "remote" will return hours of reading.

I am assuming that the hydraulic pump creates a high-pressure side, so all of the supply hoses sit at full pressure (2500PSI or so) all the time.

When all valves are in neutral, there is very little pressure developed-about 500 to 800 PSI or so due to the resistance the hoses, fitting and valves create to the flowing fluid. Only when the fluid is forced to due work and meets resistance (like from trying to move a cylinder) is pressure developed.

Are you saying that a pump runs as a circulator, and only builds pressure when the return path is closed off?

Basically, yes-that is what I am saying. It's because your system is "open center" and has a constant displacement pump.

Maybe I'm confused between an open vs. closed center system

I have been describing OC systems. What you are describing is a CC (closed center) system that uses a variable displacement pump.

don't know what my Kubota has.

Open center.

Again, I ask you to search some-maybe you will read another description that explains it better than me.

 

[kennyd]

Jay,

A good reference is the Army Hydraulics Manual. Also the Principles of Hydraulics has some good reading.