Ignorant First Question about adding Hydraulic operated Accessories

[hill]

I'd like to eventually add a backhoe thumb, a FL grapple, and turn and tilt contrl of my hitch. To me that sounds like four additional hydraulic circuits.

The Surplus Center is featuring the valve shown in this link:

Surplus Center Item Detail

Would that valve be a good starting place and could it be brought into play one spool at a time, blocking the remainder, as I add a feature at a time and keep my tractor operating while I proceed? If not, why not?

 

[Bird]

[QUOTEWould that valve be a good starting place ][/QUOTE]

Not in my opinion (but keep in mind that we have many members who know a great deal more about hydraulics than I do, so I could be wrong).

The reason I say not is: (1) that's a closed center valve and I think you would need an open center valve, and (2) that's rated for far more hydraulic flow (20 gpm) than your tractor will ever put out; maybe just overkill for that part.

 

[hill]

Thanks Bird,

It's heavy at 34 lbs. and is described as a 'motor control valve' but given their prices on one and two spool valves by Eaton/Cessna it seemed like a bargain if it would do the same things. Admittedly I don't know enough about how this all works to know whether closed center position would disrupt the whole system flow or only the flow to the particular implement each valve would control. There are separate oil intake and exhaust ports with the working in and outs for each valve separated from the mainline flow....maybe?

I did see that the flow capability exceeds my 9.6 gpm by a large margin but don't know whether that would affect it's ability to interact with my tractor system or not.

something did occur to me after posting the question though, and that is that I might find it easier to keep the controls straight in my head if I had two separate valves - one set for turning and burning the other for biting front and rear.

 

[DannyLobster]

Thanks Bird,

It's heavy at 34 lbs. and is described as a 'motor control valve' but given their prices on one and two spool valves by Eaton/Cessna it seemed like a bargain if it would do the same things. Admittedly I don't know enough about how this all works to know whether closed center position would disrupt the whole system flow or only the flow to the particular implement each valve would control. There are separate oil intake and exhaust ports with the working in and outs for each valve separated from the mainline flow....maybe?

I did see that the flow capability exceeds my 9.6 gpm by a large margin but don't know whether that would affect it's ability to interact with my tractor system or not.

something did occur to me after posting the question though, and that is that I might find it easier to keep the controls straight in my head if I had two separate valves - one set for turning and burning the other for biting front and rear.

I am new to hydraulics too, but I believe you want a directional control valve rather than a motor control for the functions you describe. The other thing which occured to me was I could not see how you could use more than three of those functions ata time?

A motor control would be used for like a winch

 

[MJPetersen]

I'd like to eventually add a backhoe thumb, a FL grapple, and turn and tilt contrl of my hitch. To me that sounds like four additional hydraulic circuits.

Would that valve be a good starting place and could it be brought into play one spool at a time, blocking the remainder, as I add a feature at a time and keep my tractor operating while I proceed? If not, why not?

1. It not only would not be a good choice it would not work. You need open center valves in the 10-15 gpm range.

2. It would not be easy to use. It would be hard to place a valve that would be convenient to use for a grapple on the FEL and a hydraulic thumb on the bh, besides the top and tilt function.

What you need is to have separate valves for each of those functions. The grapple is often powered with an electric solenoid diverter valve that allows you to close the grapple with flow from the curl function. The top and tilt should be close to the 3pt control. The thumb should be with the controls for the bh. (a stationary thumb is also possible as well as a mechanical actuated with the curl function.

The flow in the hydraulics of most tractors is in a continuous circle. All of the valves are in series to the others. Flow from the pump enters the loader valve out the power beyond port to the 3pt valve and back to the sump. When you want to do something else you break that circle and insert, what are esentially diverter valves to the tool. Let's say you pull the control to rais the lift arm. Flow from pump to FEL control does not flow through, but rather is diverted to the bottom of the lift cylinder and as it presses on the cylinder it forces oil out the upper port of the cylinder, which returns to the FEL valve and then is dumped back into the sump. The control valve "short circuits" the oil flow. If the lever fully diverts the flow, then nothing down stream from that valve has hydraulic power. You cannot operate your FEL and your bh at the same time.

I hope that make sense and helps get a general picture of the workings of your hyd system.

Mike in Warsaw

 

[patrick_g]

A real simple example:

If I run my 3PH arm hydraulic control from lowest to highest position and at the same time try to use the hydraulic top to raise the 3PH implement, you DO NOT get both motions at the same time. When I release the self centering top lift control then the lower arms come up. You can't do both at the same time.

Not being able to use certain controls at the same time would be quite limiting in some situations.

Pat

 

[hill]

What you need is to have separate valves for each of those functions. The grapple is often powered with an electric solenoid diverter valve that allows you to close the grapple with flow from the curl function. The top and tilt should be close to the 3pt control. The thumb should be with the controls for the bh. (a stationary thumb is also possible as well as a mechanical actuated with the curl function.

The flow in the hydraulics of most tractors is in a continuous circle. All of the valves are in series to the others. Flow from the pump enters the loader valve out the power beyond port to the 3pt valve and back to the sump. When you want to do something else you break that circle and insert, what are esentially diverter valves to the tool. Let's say you pull the control to rais the lift arm. Flow from pump to FEL control does not flow through, but rather is diverted to the bottom of the lift cylinder and as it presses on the cylinder it forces oil out the upper port of the cylinder, which returns to the FEL valve and then is dumped back into the sump. The control valve "short circuits" the oil flow. If the lever fully diverts the flow, then nothing down stream from that valve has hydraulic power. You cannot operate your FEL and your bh at the same time.

I hope that make sense and helps get a general picture of the workings of your hyd system.

Mike in Warsaw

Thanks a lot Mike, that was a concise and understandable post.

Where is pressure regulated, and are different pressures used at different points in a system? It would seem to me that for a grapple, a device that would not need anywhere near the power that an FEL does, could be operated hydraulically by teeing the line to either ram and directing fluid through reduced diameter lines to a valve and on to the relatively small grapple ram, thereby bleeding off only the smaller amount of pressure and only for tha amount of time needed to close the device. Would a closed center valve be appropriate in such a scenario in order to maintain pressure until released by opening the valve to return it to the FEL circuit? (Grapple opened by a spring maybe?)

In other words, is it feasable to construct low pressure subsystems which use one or another of the installed tractor operation systems as parent - both source and sump, and wouldn't the parent system remain operational, albeit at a reduced rate during bleedoff to the subsystem but still operational whenever the bleedoff valve was centered to closed?

It seems to me that tractor systems are simpler than need be and that they extend only to providing one full loop drive for each large user installed. The method of adding additional systems seems to be limited to establishing yet another full bore system with flow back to nuetral at the sump when the original larger systems might carry enough fluid/pressure to operate more than one small system alongside.

 

[MJPetersen]

OK one thing at a time. There are others who are a whole lot more knowledgable than I who can jump right in at anytime.

Where is pressure regulated, and are different pressures used at different points in a system?

In an open flow system like what we have on most of our tractors there is one pressure through out the system (of course return lines and suction lines not included. that is the beauty of "hydraulics" and the principle that makes it work. Fluids are not compressible and therefore a 10psi force in one place exerts a 10 psi force everywhere.

The pressure is regulated in the valve bodies with a "relief valve". You will have one main pressure regulator connected to the valve of the 3pt and then often there are relief valves in the other valve bodies. Normally you set the ones in the valves that control attachments a bit lower than the main one in the 3pt.

It would seem to me that for a grapple, a device that would not need anywhere near the power that an FEL does, could be operated hydraulically by teeing the line to either ram and directing fluid through reduced diameter lines to a valve and on to the relatively small grapple ram, thereby bleeding off only the smaller amount of pressure and only for tha amount of time needed to close the device.

If I understand this correctly that you are proposing to try to get hyd flow for a grapple from the output to the FEL lift or curl cylinders? That would not work. 1. A smaller diameter line reduces the flow volume, but NOT the pressure. 2. you control the force of a cylinder by the pressure (set by the relief valve), the geometry of its attach points and the size of the cylinder. (at 1500 psi a 2 in cylinder will have about 4,718 lbs of force and a 4 in cylinder will have about 18,874 pounds of force.) The sq in surface of the piston X system psi).

Would a closed center valve be appropriate in such a scenario in order to maintain pressure until released by opening the valve to return it to the FEL circuit? (Grapple opened by a spring maybe?)

You cannot mix open and closed circuit valves. In an open system you have oil flow all the time. With all valves centered the pump is producing the maximum flow through the system and almost 0 psi. When a control valve is moved and the oil is diverted to work a cylinder then there is resistance and pressure builds until the cylinder moves or the relief valve opens.

A closed center system is very different. The pump here maintains a constant pressure but there is no flow until a control valve is moved. The system tries to maintain the pressure. The pumps are more complicated variable displacement pumps. Some JD have such a system and the BIG rigs but for us guys in the normal realm of things it is usually the open center variety.

You can use an electric diverter valve like I mention previously to change the valve out put from one function to another. For example you can put an electric diverter valve in the curl line of your FEL and when activated the curl movement of the control lever closes the grapple.

Hope that helps.

Mike

 

[hill]

OK one thing at a time. There are others who are a whole lot more knowledgable than I who can jump right in at anytime.

You cannot mix open and closed circuit valves. In an open system you have oil flow all the time. With all valves centered the pump is producing the maximum flow through the system and almost 0 psi. When a control valve is moved and the oil is diverted to work a cylinder then there is resistance and pressure builds until the cylinder moves or the relief valve opens.

A closed center system is very different. The pump here maintains a constant pressure but there is no flow until a control valve is moved. The system tries to maintain the pressure. The pumps are more complicated variable displacement pumps. Some JD have such a system and the BIG rigs but for us guys in the normal realm of things it is usually the open center variety.

You can use an electric diverter valve like I mention previously to change the valve out put from one function to another. For example you can put an electric diverter valve in the curl line of your FEL and when activated the curl movement of the control lever closes the grapple.

Hope that helps.

Mike

Yes, it does help a lot, Mike, and Thanks again. You teach hydraulics somewhere, maybe?

It hadn't occured to me that the installed system would be constant flow with little or no pressure. That would make the addition of a 'feeder' system that bled smaller amounts of line pressure to operate mechanisms which don't need the full capability much more problematic, to say the least, since there would usually be nothing to bleed. It would simply fill to the closed valve like backwater behind a rock in the river and sit there. ("steam, not live").

Ok then. Solenoid gates or diverter valves will reroute the flow on demand, but once rerouted it needs to go to an open centered valve to operate a two way cylinder in a chosen direction? Thiss could be done several times in a single circuit creating multiple usage paths for, presumably, the chosen underused original device making that circuit supply say four cylinders no two of which can be operated simulteniously? Or can a multipath system be built new from a tractor's single "power beyond" outlet from the main loading valve?

Is this all touching on how these systems are normally done? Is part of it touching?....None of it? What? This stuff is getting fascinating.

 

[kennyd]

Hill, you have gotten some very good advice so far...let me highlight some points:
1. You need a Open Center, Double Acting, Spring Return To Center spool vavle, NOT a Motor Spool valve.

2. You CANNOT "T" into hydraulic pressure lines, you can only "T" the Return To Tank line.

3. That valve you linked is WAY to big for a CUT.

And here is more food for thought, The way I read your initial post:

I'd like to eventually add a backhoe thumb, a FL grapple, and turn and tilt contrl of my hitch. To me that sounds like four additional hydraulic circuits.

You only need 3 additional circuits. Remember when your BH is on, the T&T on the 3PH will not be on the tractor. So the most you'll use at once is 1 spool for the grapple, and 2 spools for the T&T.