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Discussion Starter #1
Hello,

I am wondering if it is correct to connect 1(outlet)
to 3(inlet), if you want to add a second hydraulic
valve to your setup?

And second this valve has a 5GPM specification,
does this mean the valve restricts the flow to 5gpm,
and the excess flow is directed to the outlet?

So, if your motor is a 5gpm motor, and
the PB system has higher than 5gpm,
is this this how you do it? With a valve like this?

Thanks

 

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Quick answer: No.


The valve is rated for 5 gallons per minute because that's how big the internal passages are. If you push more than 5 gallons per minute through it, you will end up heating up your oil (and everything else with it = not good).

I'm not sure what the best option to restrict the flow would be. There's flow control valves that are designed to do this, but I'm not well versed enough to tell you an optimal way to implement it.

What are you trying to do?
 

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Discussion Starter #3
Quick answer: No.

What are you trying to do?
First, I'm only trying to get some answers, so thanks.

I'm wondering about hydraulic motors, at the moment.
It didn't seem inconceivable that this might be
some sort of 5GPM regulator valve.
But OK, no.

So, how do you get a variable speed hydraulic motor?
Is this where a proportional valve is used?

I think I'm a little, or a lot, confused about pressure and flow.
What determines how fast or slow a cylinder extends,
or a hydraulic motor turns?

Or what is a proportional valve proportioning, pressure or GPM?
I can't see how it's not flow or GPM.

In my valve above. It cannot flow more than 5GPM because of its
fixed internal passages. And my motor will turn the same speed
every time the valve is opened? And depending on the pressure,
it will stall at different loads?

I guess what I'm trying to do is confirm some things.
(Or reject.)

If this isn't too tedious, thanks.
 

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First, I'm only trying to get some answers, so thanks.

I'm wondering about hydraulic motors, at the moment.
It didn't seem inconceivable that this might be
some sort of 5GPM regulator valve.

{...}

What determines how fast or slow a cylinder extends,
or a hydraulic motor turns?
It's not a regulator, but a flow limiter. If it were an electric circuit, you'd model it as a resistor. The amount of pressure dropped across it varies with the flow. 5GPM is a meaningless specification without knowing the parameters surrounding it. Anyone can get 20GPM though a 5GPM valve given enough pressure and strong enough materials. I suppose with mobile hydraulics it is assumed to be something common like 2500 PSI and whatever is considered to be an acceptable pressure loss, but I don't know for sure. Unlike DC electric circuits, velocity of the fluid medium comes into play for some analysis and power lost in the restriction is not dissipated in the restrictor but imparted to the fluid as heat.


All else being equal, the rate at which a cylinder moves or a hydraulic motor turns is determined by the flow rate. How much force it exerts is determined by pressure.

Al
 

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A variable speed hydraulic motor can be attained only one way: varying the displacement (gpm). BUT a vane, gear, or gerotor pump speed is change by changing the gpm TO the pump, usually a variable flow control valve does this. These are called "fixed displacement pumps". A piston pump has a "swash plate" (sp?) within the pump that at a constant displacement controls the stroke/displacement of the pistons which controls the output speed...1/4" stroke = "X"speed, 1/2" stroke = "Y" speed. These are called "variable displacement pumps".

Hydraulics can...and usually is!...confusing without a basic knowledge. I'd suggest looking around online for "hydraulics for dummy's" or "hydraulics 101" and get some basic understanding of what goes on and why. That said, you can still continue here with questions and someone WILL help! Bob
 

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Discussion Starter #6
A variable speed hydraulic motor can be attained only one way: varying the displacement (gpm). ..., usually a variable flow control valve does this. ... WILL help! Bob
So, I have an old JLG lift, with, what they call, proportional controls.
I've always thought that all the control was going on in just the valves.

I thought the spool was being moved faster or slower, and that somehow
each coil of the valve was playing a sort of tug of war against each other
to either be held(stop flow) or move(open up) at the speed(flow) desired.

Is this even close to what's going on?
Are these so called proportional valves what you are calling,
"usually a variable flow control valve"?

On this machine, I didn't think the pump varied at all. I thought it just
supplied pressure and enough flow to drive everything. And I thought this
is more or less what a power beyond is as well.
 

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So, I have an old JLG lift, with, what they call, proportional controls.
I've always thought that all the control was going on in just the valves.

I thought the spool was being moved faster or slower, and that somehow
each coil of the valve was playing a sort of tug of war against each other
to either be held(stop flow) or move(open up) at the speed(flow) desired.

Is this even close to what's going on?
Are these so called proportional valves what you are calling,
"usually a variable flow control valve"?

On this machine, I didn't think the pump varied at all. I thought it just
supplied pressure and enough flow to drive everything. And I thought this
is more or less what a power beyond is as well.
Variable displacement pumps are common in closed center systems where the required functionality is more demanding - multiple hydraulic devices that need to be controlled simultaneously and independently.

From an engineering perspective, a valve spool is just like a variable resistor in an electric circuit. It's not very efficient but, more important, it does no regulation. The amount of flow and the pressure drop are entirely dependent on the motor load and setting of the valve. As the load increases, the flow through the motor and valve drops while the pressure on the motor side of the valve increases. You act as the control computer and decide whether speed or torque is what you wish to control by varying the valve.

A lot of SCVs carry a warning that they are not intended for hydraulic motor use. Why, I do not know.

Al
 

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A lot of SCVs carry a warning that they are not intended for hydraulic motor use. Why, I do not know.

Al
Because they lock the ports in the center position. Say your motor is humming along spinning something like a ditch mower, you go from full flow to stopped by moving the spool to center - all the vanes in the motor are now hydrolocked and it blows up.

Motor spools gang the A and B ports together when the valve is not applying fluid. When you take the mower in the previous example and remove power, the fluid just keeps on flowing round and round inside the motor and lines without any force applied.
 

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Because they lock the ports in the center position. Say your motor is humming along spinning something like a ditch mower, you go from full flow to stopped by moving the spool to center - all the vanes in the motor are now hydrolocked and it blows up.

Motor spools gang the A and B ports together when the valve is not applying fluid. When you take the mower in the previous example and remove power, the fluid just keeps on flowing round and round inside the motor and lines without any force applied.
Great explanation, thanks!

Al
 

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I guess to add to or, more to the point, clarify my previous post.

A proportional control valve is basically the same as a single spool on a selective control valve. Think of a water valve. You control the rate of flow by the amount you open or close the valve. The rate of flow will stay the same ONLY IF THE LOAD MOVED BY THE FLOW STAYS CONSTANT. If it varies, then for a given valve position the flow will vary inversely proportional to the load change. If the load increases, the flow will decrease and vice versa.

Al
 

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Or what is a proportional valve proportioning, pressure or GPM?
I can't see how it's not flow or GPM.
Flow, but only indirectly. It is a valve whose opening is continuously variable from closed to fully open.

A lesson in proportional control. The basic parameters are the set point, the thing you are controlling (process value), error and control input. The error is calculated by subtracting the process value from the set point. The amount of control input (correction) you introduce into the system to bring the controlled value to the set point is proportional to the error. More error, more input.

Take your automobile. That big pedal on the right is a proportional valve. You're going 30mph (process value) on the ramp to the Interstate. You want to go 80mph (set point). You slam your foot to the floor (control input) to accelerate. As you approach 80mph (error is shrinking), you start to let off the gas (reduce control input). When you reach 80mph (error is now zero) you maintain only enough control input to maintain that speed. If you start to up a grade, you will add some input (correction) and if you go down a grade, you will remove some input.

All the above is manual control - a human is the controller. Turn your cruise control on and then the control is automatic. Regulated. See Wikipedia for a technical explanation of PID control systems.

The distinction on your JLG lift is because all the hydraulic controls are electrically operated from the boom bucket. A simple solenoid valve (directional control in hydraulics) is on or off. For something that needs a higher degree of precision you need a proportional valve, which means instead of on & off you can continuously vary the size of the opening. To do this remotely requires some technology such as a stepper motor to set the valve opening to a specific size based on the position of a knob or lever elsewhere.

Al
 

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Discussion Starter #13
Flow, but only indirectly. It is a valve whose opening is continuously variable from closed to fully open.
...
technical explanation of PID control systems.
...
The distinction on your JLG lift is because all the hydraulic controls are electrically operated from the boom bucket. A simple solenoid valve (directional control in hydraulics) is on or off. For something that needs a higher degree of precision you need a proportional valve, which means instead of on & off you can continuously vary the size of the opening.
...
To do this remotely requires some technology such as a stepper motor to set the valve opening to a specific size based on the position of a knob or lever elsewhere.

Al
I have to say with a self mocking chuckle, thanks for this answer,
I've been watching explanation PID YouTubes all evening.

I found examples for controlling temperature, lighting, pressure,
and many others.

My 1990's lift doesn't have any stepper motors, I'm sure of that.
I'm not sure how the proportional controls work exactly. I've replaced
some of them, and they are mostly a lever connected to a potentiometer
and a little circuit board. I'm fairly sure there are no sensors for any feedback.

Some of the videos described ways of generating 4 to 20 milliamps. I'm wondering if
this is some sort of standard or normal convention.

There's a guy in Austria who built a six legged robot with a cab and an engine-pump
compartment big enough to carry the system in a JLG boom lift. And he is using
a PID system to smooth out the hydraulic controls. It's pretty impressive.

Thanks.

FWIW:
Understanding PID in 4 minutes
https://www.youtube.com/watch?v=wbmEUi2p-nA
(This is math heavy. But there are many practical examples.)

The Difference Between Pressure and Flow
https://www.youtube.com/watch?v=AyizWUpPt28
 

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My 1990's lift doesn't have any stepper motors, I'm sure of that.
I'm not sure how the proportional controls work exactly. I've replaced
some of them, and they are mostly a lever connected to a potentiometer
and a little circuit board. I'm fairly sure there are no sensors for any feedback.
I don't actually know how the valves (where the hydraulic action happens, not the control in the bucket) do their job. I only know that the valve opening is continuously variable and remotely controlled. In your case, the lever, potentiometer and circuit board convert lever position to some sort of electrical signal (varying voltage; current; resistance; a digital message) and the valve converts that information to an opening size. Something electro-mechanical does that. A stepper motor is the one thing I could think of that will yield precise rotational position based on an input, but I don't know if that is what is actually used.

The feedback mechanism is you! Eyes-brain-hand!

Al
 

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Since the valve the O.P. is interested in is a solenoid valve, it is either ON or OFF depending on whether the coil is energized or not. It can't be used to throttle the flow of oil.
 

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So, I have an old JLG lift, with, what they call, proportional controls.
I've always thought that all the control was going on in just the valves.

I thought the spool was being moved faster or slower, and that somehow
each coil of the valve was playing a sort of tug of war against each other
to either be held(stop flow) or move(open up) at the speed(flow) desired.

Is this even close to what's going on?
Are these so called proportional valves what you are calling,
"usually a variable flow control valve"?

On this machine, I didn't think the pump varied at all. I thought it just
supplied pressure and enough flow to drive everything. And I thought this
is more or less what a power beyond is as well.
This is not an easy thing to explain in a few words, so this is lengthy.:flag_of_truce:

First, proportional simply means it is not an on/off valve, it is a valve that variably opens. If you are using a valve to control a hydraulic motor, it should be proportional. Using an on/off valve to control a hydraulic motor is not a good idea unless you connect accumulators in the circuit to absorb pressure spikes.

The solenoid valve that you show in your original post is simply an on/off valve with a spring centered motor spool. When one coil is energized, the spool shifts one way which will cause the motor to suddenly start turning in one direction (this sudden trying to turn can cause pressure spikes in a hydraulic system). When power is released, the spool centers which will allow the motor to free spin until it stops, also not the best (It is better to use a cross over relief valve in a motor circuit. This type of valve acts as a hydraulic brake on the motor causing it to slow quicker so it doesn't free spin. It depends on what the motor is turning as to whether a cross over relief should be used). When energizing the other coil, the valve shifts the other way which will cause the motor to turn in the opposite direction.

It is possible to buy proportional solenoid coil actuated valves, such as the one that you show, that can be controlled by a "milliamp output" controller. These controllers, when turned on, slowly ramp up a milliamp output so the valve does not shift quickly. The valve will "proportionately" open. This is actually the type of solenoid valve and controller that is used to engage the PTO on electrically engaged PTO circuits. This provides for proportional engagement rather than instantaneous engagement. This is also the type of solenoid valve and control that should be used in a motor circuit.

Examples of proportional solenoid valves and the controllers that can be used to control them.
http://www.hydraforce.com/Literature/2016_HF_Electronic-Products-Guide.pdf
HydraForce Hydraulic Electro-Proportional Directional Cartridge Valves

JLG has used several types of "proportional controls" over the years. I will assume, since you said old, you have what is called "pilot pressure proportional control" valves. If your manlift actually has small (1/4") hydraulic hoses run up the boom to the platform, then you have a pilot pressure control system. I missed your last post. I noticed you said you have electronic controllers. These are 4 - 20 milliamp output controllers. See below.

This means, there is a low pressure (probably about 500 psi) hydraulic circuit that feeds the controls in the platform. A pilot pressure control circuit isn't a flow circuit, it is a dead head regulated pressure circuit. The charge pressure circuit in a tractor wheel drive hydraulic system is also a dead head system that maintains a preset amount of pressure in the system. This pressurized oil is what maintains the feed oil to the actual propel pump and motor.

What happens is, the function controls in the platform are proportional valves that regulate the pilot pressure to the end caps of the main function control valves down on the machine. These valves act like a variable air pressure regulator except they are regulating the output pilot hydraulic pressure. The further you push the controller, the more pilot pressure is directed to the main valve end cap.

Proportional pilot control valves allow for a very smooth operating hydraulic system.

Now, if you have a slightly newer JLG manlift, the platform controls are electronic proportional. (this is what you have) The earlier ones used a milliamp output, usually 4 - 20 milliamp, to the control valve. The further you push the controller, the higher the milliamp output, the further the main valve opens.

Of course, newer systems are using more high tech systems to control hydraulics. Most are now controlled by micro processing units (ECU) that are connected via CAN BUS (controller area network).
 

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Discussion Starter #17
so this is lengthy.:flag_of_truce:
...
I missed your last post. I noticed you said you have electronic controllers. These are 4 - 20 milliamp output controllers. See below.
...
Now, if you have a slightly newer JLG manlift, the platform controls are electronic proportional. (this is what you have) The earlier ones used a milliamp output, usually 4 - 20 milliamp, to the control valve. The further you push the controller, the higher the milliamp output, the further the main valve opens.

Of course, newer systems are using more high tech systems to control hydraulics. Most are now controlled by micro processing units (ECU) that are connected via CAN BUS (controller area network).
Man, thanks for this!

I had convinced myself that these controllers were varying the voltage from zero to 12vdc.
So, I was way off.

Like I said earlier, there is a guy building a freakishly scary robot vehicle,
and he is getting his 4 - 20 mAmps from an arduino to a DAC circuit with an op amp.
It's fairly simple after he explains it along with the schematic. He's Austrian, we'll probably
see something on the news eventually, after the tragic calamity.

The machine usually works, but now I can at least put a meter on it and know what to look for.
The new controller I installed, it's just a molex plug and some mounting screws, needed to be
adjusted, and have never been adjusted the right way. I gave up after getting something I
could live with. I would like to put them on the bench to adjust them. They have a ramp up,
a max speed, and a ramp down, that needs to be set reasonably for safety and utility.
And now I think I can do that.

Regards.

So, you might be interested in the version in question. It is a 1996 year model.




1996
 

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Man, thanks for this!

I had convinced myself that these controllers were varying the voltage from zero to 12vdc.
So, I was way off.

Like I said earlier, there is a guy building a freakishly scary robot vehicle,
and he is getting his 4 - 20 mAmps from an arduino to a DAC circuit with an op amp.
It's fairly simple after he explains it along with the schematic. He's Austrian, we'll probably
see something on the news eventually, after the tragic calamity.

The machine usually works, but now I can at least put a meter on it and know what to look for.
The new controller I installed, it's just a molex plug and some mounting screws, needed to be
adjusted, and have never been adjusted the right way. I gave up after getting something I
could live with. I would like to put them on the bench to adjust them. They have a ramp up,
a max speed, and a ramp down, that needs to be set reasonably for safety and utility.
And now I think I can do that.

Regards.

So, you might be interested in the version in question. It is a 1996 year model.




1996
Yep, you are on track. The ramp up and ramp down are adjustments to control how quickly changes are made when you move the control handle. Like you said, this is how you adjust how quickly, not maximum speed, but how quickly the function will speed up. The maximum output will limit the maximum speed that you desire.

In a manlift, rarely do you ever max. out the controller. You just do not want that much speed, at least I don't.:good2:
 

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Man, thanks for this!

I had convinced myself that these controllers were varying the voltage from zero to 12vdc.
So, I was way off.

Like I said earlier, there is a guy building a freakishly scary robot vehicle,
and he is getting his 4 - 20 mAmps from an arduino to a DAC circuit with an op amp.
It's fairly simple after he explains it along with the schematic. He's Austrian, we'll probably
see something on the news eventually, after the tragic calamity.

The machine usually works, but now I can at least put a meter on it and know what to look for.
The new controller I installed, it's just a molex plug and some mounting screws, needed to be
adjusted, and have never been adjusted the right way. I gave up after getting something I
could live with. I would like to put them on the bench to adjust them. They have a ramp up,
a max speed, and a ramp down, that needs to be set reasonably for safety and utility.
And now I think I can do that.

Regards.

So, you might be interested in the version in question. It is a 1996 year model.




1996
Allot of these machines used PQ Controllers. Something like this. P-Q Controls | Model 120 - Heavy Duty Throttle Joystick Control Lever
 

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Man, thanks for this!

I had convinced myself that these controllers were varying the voltage from zero to 12vdc.
So, I was way off.

Like I said earlier, there is a guy building a freakishly scary robot vehicle,
and he is getting his 4 - 20 mAmps from an arduino to a DAC circuit with an op amp.
It's fairly simple after he explains it along with the schematic. He's Austrian, we'll probably
see something on the news eventually, after the tragic calamity.

The machine usually works, but now I can at least put a meter on it and know what to look for.
The new controller I installed, it's just a molex plug and some mounting screws, needed to be
adjusted, and have never been adjusted the right way. I gave up after getting something I
could live with. I would like to put them on the bench to adjust them. They have a ramp up,
a max speed, and a ramp down, that needs to be set reasonably for safety and utility.
And now I think I can do that.

Regards.

So, you might be interested in the version in question. It is a 1996 year model.




1996
I should also point out, there were some machines that did vary the voltage output to control proportional control valves, although, most of these types of controllers haven't been used for quite a few years.

The reason is, in a variable voltage output circuit, any slight corrosion resistance that occurs over time in a wiring connector will effect the voltage to the valve coil which will cause inconsistent control. This is caused by voltage drop across resistance.

In a system that varies the milli-amp output, any slight corrosion resistance that may occur in a wiring connector over time will have no effect on the valve coil operation, as the milli-amp reading in a DC circuit is the same anywhere in the circuit.
 
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