Debating POSITION CONTROL. What is it to YOU?

[Singalo]

First let me lay out the most common theories of what position control is that I have run into most frequently.

Theory #1: Position Control is nothing more or less then the ability to stop the 3pt hitch at any point in the length of it's travel. For the sake of this discussion this will be referred to T#1

Theory #2: Position Control is the mechanism or scheme by which the 3pt hitch can be set to a predetermined height repeatedly with out the need to make fine adjustment. Think, set it and forget it. For the sake of this discussion this will be referred to as T#2

Theory #3: Position Control is a "Self Regulating Circuit", that automatically adjusts the height of the 3pt hitch. This automatic adjustment is needed in order to correct "Drift", that is the droop of an implement, that occurs due normal and acceptable leakage. For the sake of this discussion this will be referred to as T#3


I hope we can all agree that these three theories are expressing completely different ideas, and are mutually exclusive.

This topic has been discussed in several diffident threads. But to me, it always seems that there are folks that weigh in that feel that they are absolutely correct in their understanding of what Position Control is. This is not a criticism. I say this only to illustrate the problem it creates for folks that don't yet understand. If I, as a representative of the group that "Does not Know", accepts the certainty of Authority #1 that T#1 is correct. Then what am I to make of Authority #2 and #3 who are equally as certain that T#2 and T#3 are correct. From my perspective, and although I respect the experience of each of these authorities upfront, I can't reconcile the Fact, that all 3 theories can not be simultaneously correct. So although Authority #1,2 and 3 are "Certain", I am not.

Id like to respond to some comments made in another thread that sparked me to create this one.


Bullitt said:

With position control with the tractor running and 3PH lever left in one place the 3PH will not drift down.

The question is, what do you mean by "Position Control". If, by position control, you mean T#1. Then That is saying one thing.

IF however, when you say "Position Control", you are speaking about T#3, then that is saying something totally different.

So, I take this:

With a neutral lift after hours with a heavy load you may notice some leakage but very very very minimal if everything is working properly.

To mean that you consider "Position Control" as something that is Void of this "Self Regulating Circuit". Or at the very least, does not require such a circuit to be considered position control.

Further, I take this quote from Grandad:

+1 What he said. Any tractor, regardless of what type of lift control the 3 pt has, should not "drift" down so you have to re-adjust it all the time. If it's doing that, there is something worn or leaking in the hydraulics.

To be supporting testimony.

If I am understanding both of you (Correctly), Bullitt and Grandad4, then there are a few things that can be taken away from this.

1) Pretty much all modern tractors have the ability to stop the 3pt hitch at any point in the full length of it's travel, thus pretty much all modern tractors have "Position Control". I try not to speak in absolutes, so that's why I say "Pretty Much".

2) Drift, or the process of drooping due to "Acceptable Leakage", is normal, but in a properly working system should be very slow, on the order of days at least to have any noticeable or significant movement, which essentially means in practical terms, there is no need for a "Self Regulating Circuit". Because any operation you may be doing, be it raking, tilling and so on, will not be done on a time scale where "Normal Drift" will have any appreciable affect on that operation.

That said, I feel that at least Grandad4 and Bullitt are proponents of T#1. I too feel, or at least felt at one time, that this was an accurate description of PC. Now, I simply can't be certain. and the reason why is this. I have heard supporting testimony from a fair selection of people that "SHOULD" understand the true nature of PC. Dealers and Brand Representatives that subscribe to one or a combination of the 3 theories listed above. The only certainty that I have is that they are NOT all on the same page.

I am not here to personally prove what the true nature of PC is. But I would like to see a constructive conversation from the various proponents of the differing theories above. Depending on what you choose to accept as factual, I have heard convincing explanations for at least two of the theories listed above.

 

[Singalo]

As a follow up, I'd like to point out that part of the argument between theories hinges on ones notion of how fast "Normal Drift" occurs.

Proponents of T#1 believe that "Normal Drift" happens over a long period of time, such that during normal operation, this drift does not have, or should not have any appreciable affect on the operation. If it does, this means there is a problem with the hydraulics. Meaning that there is considerably more leakage then would otherwise consider to be normal or acceptable.

Proponents of T#3 believe that "Normal Drift" happens over a much shorter period of time, such that during normal operation, this drift can and will affect on the height adjustment of the 3pt hitch, which in turn requires those without PC to make frequent manual adjustments during normal operation. PC is intended to deal with this drift by automatically adjusting for it. Few of the dealers I spoke to share this idea. Still other dealers claim T#2 is all PC is.

 

[murphy1244]

I chose T-3

 

[MasseyWV]

Having recently rebuilt the hydraulics on my MF-135 tractor as part of a complete restoration project, I fully comprehend how position control works. However, I prefer to look at it like this...

A: I pull the little lever back and the implement goes up.
B: I push the little lever forward and the implement goes down.
C: I stop moving the little lever and the implement stops too.

 

[J_J]

This is your basic definition.

It enables your three-point hitch to stay at the height you set.

How different tractor achieves this is the real question.

 

[Singalo]

Having recently rebuilt the hydraulics on my MF-135 tractor as part of a complete restoration project, I fully comprehend how position control works. However, I prefer to look at it like this...

A: I pull the little lever back and the implement goes up.
B: I push the little lever forward and the implement goes down.
C: I stop moving the little lever and the implement stops too.

I don't know about anyone else, but this sounds pretty much like T#1 to me.

 

[Singalo]

This is your basic definition.

It enables your three-point hitch to stay at the height you set.

How different tractor achieves this is the real question.

So are you saying that Position Control actually has no one set definition?

 

[Gary Fowler]

Ideally you want position control and Draft Control. Most all tractors have position control. How well they work is taken in by the three T's that you described. If they aren't T3 then they really aren't position control because if it drops for ANY reason and doesn't auto-correct, then it is not position control.
Then you add in draft control to the position and you have a workable 3 PH implement. Lets say you are pulling a plow of some sorts that is set by position control at 6" depth which is about all your tractor can handle in the normal soil conditions. You encounter heavy clay soils at some point that loads the tractor heavier. With draft control, it would sense this excess load and automatically raise the implement so you regained traction or speed as the case may be. This has to be set as you are doing the operation but once set it automatically raises when excess load is encounter and then lowers the implement back to preset height of the position control lever when the load is normalized.
I would say that T1 isn't position control if it doesn't compensate for drift.
I don't see a distinction between T2 and T3 as it seems both are the same "set and forget"

 

[Gary Fowler]

I just looked at all the LS models and none of the smaller tractors have draft control until you get to the Rxxxx series, Then they all seem to have it. The J series and G series only have position control and since I have never been in the seat of one that small, I couldn't begin to say how well they work. As far as that goes, I cant tell you how well my Kubota B26 position control works either as I have never used a 3 PH implement on it, maybe never will but I can tell you that it doesn't have draft control as it only has one lever to control the 3 point linkage (draft control would have 2).

 

[MasseyWV]

I don't know about anyone else, but this sounds pretty much like T#1 to me.

Actually, it's a combination of all three, and then some. I could get technical, very technical, but I'm tired and simply don't feel like it at the moment. However, I will say this... The entire system is a marvel of engineering that seems very complicated at first glance, but once you understand how it all works it's actually very simple.

 

[J_J]

So are you saying that Position Control actually has no one set definition?

Don't believe so , as you can do the same thing in different ways. Could probably be done with a torque tube, spring, lever principle, electronics,etc.

So what is the real question. is it a good thing, a bad thing, not useful, useful with draft control.

You will probably find different ways to achieve the results you desire. IE, position control.

You can elaborate on the words [ positional control ], with some extras thrown in, but it is still positional control.

 

[oldnslo]

Is this a matter of definitions from manufacturer to manufacturer. I.e. Kubota calls there a 1/4 inching valve. Is this the same as a JD position control?

With out seeing a accurate and complete hydraulic schematic does a position control hold position under load or just move the 3PH arms to a similar spot when the control lever is moved to the same position?

My belief is that there are two many description variables to give a cart blanche answer on position control.

Draft control I believe is pretty universal and Gary Fowler gave a very good description of how it operates.

 

[Singalo]

Is this a matter of definitions from manufacturer to manufacturer. I.e. Kubota calls there a 1/4 inching valve. Is this the same as a JD position control?

With out seeing a accurate and complete hydraulic schematic does a position control hold position under load or just move the 3PH arms to a similar spot when the control lever is moved to the same position?

My belief is that there are two many description variables to give a cart blanche answer on position control.

.

Ahhh, Now you are getting into a perspective that I am personally warming to. And it has implications of course.

Everyone, that is every brand of tractor wants to use position control as selling feature. Heck, even not mentioning PC at all in the brochure for a given tractor is saying something one way or the other. But what does it all mean to the consumer? Your "Selling" me this "Feature". But finding anything more then fuzzy vagaries explaining what this "Feature" is hard to come by. I will give you two examples.

LS puts in the brochure for the J under standard features, "Position Control". Ok,,,,,,,,, so WTF is it? I mean exactly? I asked this of my LS dealer I am working with. You will never guess what. Ok, maybe you will. I got no solid answers. But it gets better.

In a review of the Boomer 25 from Tractor.com, one of the Con's was that the Boomer 25 lacked Position Control. Now wait just one second. I know for a SOLID FACT, that the LS J and the Boomer 25 are the same tractor. So does the tractor have PC or not? Or is this all dependent on the individuals understanding of what PC is? LS says the J has it, Tractor.com says it does not. So what is a consumer supposed to make of it all? PC as a feature under these circumstances has NO MEANING.

If we are to accept that there is in fact, NO concise definition of what PC is, then rather or not a tractor has this as a "Feature" is irrelevant. Because as some posters have said in this very thread so far, PC is what the owner makes of it. If you can achieve "Position Control" by a variety of methods, then you can make an argument that ALL tractors have PC.

Another example is when a person on TBN says, I much prefer my tractor with PC over Kubota's quarter inching valve. Really? What exactly do you like better I wonder? When a person says this, you have to also ask, what is PC to you? Do you have a self regulating circuit? How do you know that you have this circuit? If the LS J has PC as the company says it does, and you think a self regulating circuit is what PC is, I can tell you that there is NO documentation readily available to me the consumer, or the dealer that is selling me the tractor. I think as long as there is no specific definition of what PC ACTUALLY IS, then the notion of PC is irrelevant, because much the same as religion, it can be what ever you want it to be.

 

[oldnslo]

I can't speak for other brands but I know my Kubota BX 1850 had none of the above. It was a spring centered valve and you manually raised the lever to raise and let it return to center in the position you desired. It would NOT hold the load in this position.

My Branson 2400H says it has PC. My interpretation of PC is that the control lever stays where you put it. Ie. part way down and the arms drop part way and stop. What I am not sure of is if this system tries to keep the arms at this height. I.e. suspend a load a few inches off the ground and will try and keep the arms in that position.

 

[s219]

Having used several different systems in the past year or so, I can't understand why there is confusion or the need to turn this into a drawn out discussion.

If your lever has numbers and moving the lever to a number sets and maintains the height of the 3-point repeatably, then it's position control. This lever directly controls "position" of the hitch (in a physics sense).

If your lever just has up/down directions and pushing it in either direction moves the hitch without setting or maintaining a specific position, then it's not position control. The lever controls "velocity" of the hitch (speed and direction in a physics sense).

I think your theory #1 is generic, applying to either case. Theories #2 and #3 constitute position control in my experience.

There are analogous control modes for aircraft controls, computer input devices (mice/joystick/etc), machinery, and many other controls you'd come across in human interface design. It comes down to whether the control directly sets the position of the device, or whether it simply controls the motion of the device.

Kubota's 1/4 incher is not position control. In fact, it's nothing fancier than a range limiter stop on the up/down lever that moves the hitch in small increments (slower velocity) for fine adjustment.

 

[Singalo]

Ok, what follows is an excerpt of a position control explanation as given by Johnson City Kubota And Equipment LLC. Believe it or not, =), I will give a brief breakdown of the supplied explanation.

If you have a 3pt hitch control lever that has an up, down AND NEUTRAL position, in order to place the implement repeatedly to the same adjustment height, you must for example lower the implement by pressing the lever "Down". BUT,,, you have to guess when to return the lever to the neutral position when you want it to stop. The problem is, stooping the 3pt hitch is not instantaneous. The lift will have a bit of residual movement after you want it to stop, as well as the fact it takes a certain amount of time to get the lever back to the neutral position, making putting the implement back at an exact position nearly impossible.

Position Control however does not have this "3 Position Lever", allowing you to move the lever to an infinite number of positions along the length of travel. SUCH, that if you had a mechanical stop, something as simple as a bolt and a nut to stop the lever at a certain place along the arc of travel, whala, you have position control.

In this explanation from what should be an "Authority", this notion of there being a "Self Regulating Circuit" that counters "Drift" is not even mentioned, let alone being some kind of prerequisite. For the record, THIS is what the four different dealers I talked to that had any kind of clue stated.

here is a link to the full page: http://www.johnsoncitykubota.com/Three Point Lift Types.htm

If we accept the Johnson City Kubota and Equipment, LLC explanation, then the Notion that a "Self Regulating Circuit" defines PC is false. NOT that such a circuit does not exist. I would not argue that this technology does not exist. BUT,, and this is hugely important. If Johnson City Kubota is correct, it has NOTHING to do with what PC is.

Johnson City Kubota & Equipment, LLC

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Tractor Three Point Lift Types

Let's start by defining what a three point hitch is. Tractor three point hitches are so named because they consist of three major components. They are; the left and right lower lift arms (those long things with the balls in the end that are sticking out the back of the tractor) and the top link; usually a three piece adjustable apparatus with a central body and two threaded ends with balls, one of which attaches to the tractor, and the other which attaches to the implement. The overall length of the top link is adjustable via the threaded ends. The sole purpose of the three point hitch is to place, and hold, the mounted implement in the desired position to accomplish the job at hand. As you may have guessed, there are many different types of systems available to get this done. Some are quite simple, while others are extremely complex. In the simplest form, a hydraulic pump supplies oil to a control valve. The position of the control valve determines where the oil goes next. If the control valve is in neutral, the oil is simply directed back into the reservoir (transmission housing). If "raise" is selected, the oil from the pump is directed, by the control valve, into the lift cylinder, causing the lift arms to rise. If "lower" is selected, the oil from the pump is directed, by the control valve, to the reservoir (just like neutral); however, a passage is also opened which will allow oil to escape from the lift cylinder, allowing gravity to lower the lift arms. Many of the smaller compact tractors are, in fact, just that simple in lift control. They use what might be termed;

"Non position" control. This type of lift is simple to build, easy to troubleshoot/repair, and potentially very aggravating to use, depending on the implement. Let's assume you are using a rear "grooming" mower that is supported, while in mowing position, by four caster wheels (one at each corner of the deck). No sweat. Just shove the lift lever to the "down" position, and the casters take care of it from there. Now, suppose you want to put your box scraper on and put a nice "finish" grade on a yard. In order to do a good job, it is important to have "finite" control of the height of the box scraper. The problem is, you must manually return the control valve to neutral at the very instant the box scraper arrives at the correct height. What usually happens is that the "box" has already gone past where you want it to be before you can "jerk" the control valve into neutral. Need something more user friendly for box scraper work? Enter….

"Position control". This lift type has some extra parts called "feed back" linkage. This linkage can be either internal or external, yet it's purpose remains the same. Feed back linkage serves to return the control valve (automatically) to the neutral state as soon as the lift arms reach the point selected by the relative position of the lift control lever. Whereas the "non position" control type only has three positions (raise, lower or neutral), the position control type allows an infinite number of lift arm positions, from all the way down, to all the way up. If you regularly perform tasks that require precise, repeatable lift arm height control, definitely get the position control type of lift. Next we take a look at….

 

[Singalo]

Having used several different systems in the past year or so, I can't understand why there is confusion or the need to turn this into a drawn out discussion.

There ABSOLUTELY IS a Necessity for a "Long Drawn out Discussion", because as evidence by the varied responses in this thread, there are very REAL and DIFFERING ideas of what PC is. I fully accept the fact that maybe in the end, it's just not that big of a deal. But regardless of how important it is to the overall operation of your tractor, in order to speak intelligently about it, we must all have some kind of standard definition with which to work from. Otherwise, any discussion outside of that definition has just about ZERO meaning. Especially when tractor brands are using the "Notion" of Position Control as some kind of selling feature that " Other Brands do not have".

 

[s219]

There ABSOLUTELY IS a Necessity for a "Long Drawn out Discussion", because as evidence by the varied responses in this thread, there are very REAL and DIFFERING ideas of what PC is. I fully accept that fact that maybe in the end, it's just not that big of a deal. But regardless of how important it is to the overall operation of your tractor, in order to speak intelligently about it, we must all have some kind of standard definition from which to work with. Otherwise, any discussion outside of that definition has just about ZERO meaning. Especially when tractor brands are using the "Notion" of Position Control as some kind of selling feature that " Other Brands do not have".

Well I can't help it if everyone else is an idiot!

Seriously, if you look at and use enough tractors, it will basically boil down into two different types of levers, and they correspond to the classes of HID controls I mentioned. You're either controlling position or velocity of the hitch with the lever. I don't think there's a need to make it more complicated than that. You might have to physically look at the lever on the actual tractor to cut through marketing BS, but that is no different than many other things in product sales.

Speaking from my own experience, I have never run across a tractor spec'd as position control that was anything different. Generally if they are bragging about it being position control, it's position control.

 

[Baby Grand]

My theories:
T#1 : Moves in noticeable increments up or down. AKA Inching Control.
T#2 : Stops moving when you stop moving the lever. AKA Position Control.
T#3 : Has feedback loop & adjusts to changes in soil contour and implement depth: AKA Draft Control.

T#0 : Either all the war up or all the way down?

 

[Singalo]

Well I can't help it if everyone else is an idiot!

Seriously, if you look at and use enough tractors, it will basically boil down into two different types of levers, and they correspond to the classes of HID controls I mentioned. You're either controlling position or velocity of the hitch with the lever. I don't think there's a need to make it more complicated than that. You might have to physically look at the lever on the actual tractor to cut through marketing BS, but that is no different than many other things in product sales.

Speaking from my own experience, I have never run across a tractor spec'd as position control that was anything different. Generally if they are bragging about it being position control, it's position control.

Id like to ask you then what you make of the Johnson City Kubota LLC explanation I posted a couple posts above. If I am understanding you, then you essentially agree with that explanation.