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 | NHnewt
Join Date: Posts: 1 
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2002-03-22 36605
Can someone help me out with this. I saw a post that made reference to the B2410 having position control while the B7500 does not. What is position control and how is it usefull?
Thanks.
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| Bird Senter
Join Date: Jun 1999 Posts: 962 
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2002-03-22 36608
Position control? I'll see if I can give you an explanation that makes sense (I've had a B7100 without it and a B2710 with it).
Without position control, the lever is centered and when you raise or lower the 3-point by moving the lever forward or backwards, it continues in an up or down movement until you center the lever again. The distance you move the lever may affect the speed with which it raises or lowers, but not where it stops. So you have to just go by visually watching to stop it where you want it.
With position control, the slot for the lever is usually numbered (1 to 8 in my case), with 1 being all the way down and 8 being all the way up. If you want to lower it to 4, move the lever there, the hitch stops at that point and the lever stays where you left it. It's much easier to make small adjustments in the height of the hitch, and if you raise it, it's much easier to lower it back to the same height again.
In other words, position control is a VERY NICE feature and I really like it, but it's not absolutely necessary. ....
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| NHnewt
Join Date: Posts: 1
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2002-03-22 36609
thanks Bird, I can see why it would be a nice feature. This is one more reason why I may go with the B2410 over the B7500! ....
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| Dan Bessette
Join Date: Posts: 1
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2002-03-22 36611
In regards to position control, Bird you mentioned that the 3ph should stay where you leave the lever. I have a JD 4600 with position control. The other day I had a post hole digger on the machine. I had raised it and was off the tractor cleaning out one of my newly created holes when I noticed the hitch reposition itself. I watched more closely and every few minutes the weight of the digger was making the hitch drop far enough to engage the positioner. Is this a problem or normal operation? The tractor was running by the way. ....
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| Bird Senter
Join Date: Jun 1999 Posts: 962
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2002-03-22 36613
Dan, I might ought to leave this question to a better mechanic than I am, but for a personal opinion, sounds to me like something (3-point hitch cylinder)is slowly leaking down OR the valve is letting it leak down. Won't it do the same thing with other implements (at least those of comparable weight) left raised on the 3-point? ....
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| Dan Bessette
Join Date: Posts: 1
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2002-03-22 36617
I'm not sure about other implements as the only thing I have is the digger. The only other rear attachment I have is a frame mount backhoe. ....
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| Rubintropfen
Join Date: Posts: 1
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2002-03-22 36618
Some lift adjustment is normal with position control. There is a feedback mechanism that tries to bleed and/or add fluid as required to hold the set position. Excessive adjustment means something is leaking down too much. The old rule of thumb is that if it takes more than 10-15 minutes for a raised implement to reach the ground when you shut off the engine then the lift is working "well enough".
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| Stan
Join Date: Feb 2002 Posts: 87
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2002-03-22 36621
I'll ask the next logical question in the series - what is DRAFT CONTROL. I assume it is the next step up, but what is it and how does it work? ....
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| Bird Senter
Join Date: Jun 1999 Posts: 962
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2002-03-22 36627
Stan, I've never even used a tractor with draft control, but have a farmer neighbor who has it on his big John Deere tractors. It "senses" when the load gets hard to pull (pulling plows through the ground) and raises the implement to lighten the load. If the load gets too easy to pull, then it lowers the implement deeper into the ground. From what I hear, it's great for serious tillage, although it seems to me that you'd be plowing some parts of a field more deeply than other parts, and that doesn't sound all that great to me. I've also heard that some "sense" the load through pressure on the top link and that some sense it through a loss of rpm. So now, someone who knows more tell me and Stan both more about it. ....
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| ROB IN MASS.
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2002-03-22 36631
Guys I have been reading the posts & hope I can help.I have a 1988 John Deer 1050 with 36 hp. considered a compact by all standards. Maybe at the higher end but a compact.The machine does have draft sensing. I will give you the verbage as it reads out of my owners manual. JD can word it better than me anyways, so here goes!
USING DRAFT CONTROL
Rockshaft is equipted with a draft control system. rockshaft raises automatically as load increases. Draft control lever regulates amount of load required before hitch responds. With lever placed fully down there is no draftsensing.
(A). USING POSITION CONTROL
When draftsensing lever is pushed back, rockshaft "holds" a constant position regardless of load. Use "position contol" when you do not want rock shft to to adjust automatically to draft load; as for implements operating on guage wheels.
(B). USING DRAFT CONTROL
When draft sensing lever is pulled forward Rockshaft senses draft load and automatically raises and lowers to maintain a "constant" depth. Use "draft control" in tillage work to keep depth of implement fairly constant: It transfers weight to rear wheels for improved traction.
POSITIONING CENTER LINK
For light draft loads, install center link in lower hole of center link bracket. In this position, less draft load change is required for automatic sensing.
for heavy draft loads, install center link in upper hole. In this position, more change in draft load is required for aotomatic sencing.
__________________________________________________________
Ok thats the way JD printed it in my manual. please note that this draft lever they spoke of is seperate from the
other two controls that operate the rockshaft, that operates the three point hitch. The other two controls on the machine is a valve that regulates the speed or rate of drop for the rockshaft/3ph. And obviously the last contol is the rock shaft lever itself. so, this may help clear the air a bit I hope! now mabey I will throw in my own verbage.
The way I see it is, in addition to what the manual says there is a semi crude but visually good way of showing what the tractor does going over uneven ground pictured in the manual. The picture shows the tractor using draft control both over even and uneven ground. The picture showing the tractor going over uneven ground in posion control mode, depicts the tractor implement not removing enough material as the tractor just starts to go down grade. And just the oposite, too much material removed just as the tactor start to go up hill. Keep in mind it would eventually go to correct depth if the up hiil / down hill grade continued long enough because both tractor and implemnt would be folliwing the same straight line up or down hill. It is these more abrupt quick changes in grade ie: smaller irregularities that if it is in between the tractor and the implement, if you could picture a tractor with implement attatched, ballanced on a mound of dirt, the tractor pointing downward on the left of the mound. and the attatched implement travelling up hill on the right, with the peak of the mound in between the tractor and implement you can see that the mound of dirt will be torn off on one side and the other side will be under cut. sooooo! after all this,you can see that in a sense no pun intended, the draft contol works much like a cars shock absorber. Wheels of good luxery car bouncing up an down over railroad tracks but car and ocupants staying at same level. this is much like our situation, but in our case we want our hydrolic rockshaft to go up and down with the ground changes and dial that change into the height of the implement vrs: height/angle of the tactor. now as if we all are not totaly confused including myself just kidding, all this daft sensig is not needed if you are using gauge wheels because there is another sense point being used to sort of do what the draft sensing is doing I hope that I did not confuse any one. in short draft sensing can be very usefull but not absolutely needed.
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley 
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2002-03-23 36636
Regarding the 3ph that lowers while the tractor is running. Most 3ph quadrant levers have a tension adjustment on them and I'd check that. There's a good chance that vibration is shaking the quadrant lever down and placing the hitch into lower mode. Most leaky valve/cylinder problems result in a hitch that cycles up and down when the tractor is running and the quadrant lever stationary.
My repair manual also refers to draft control as: maintaining a constant depth and keeping a constant draft. However, virtually the next paragraph talks about varying soil conditions and changing the depth to maintain a constant draft in response to changing soil conditions. I think the description may foster some inaccurate ideas about what draft control actually does, or at least how I understand it.
I can see that draft is going to increase when a plow first starts up a hill and raising the hitch might be thought of as maintaining a constant depth. However, going down a hill is the reverse, and draft control does nothing to lower the 3ph below its position setting in response to low drafts. Hit a hard spot while plowing on a level and the wheels will slip and burrow in unless the hitch is raised. Draft control will lift automatically and then return to its position level after the hard spot is passed. That's what you want it to do, but that's not maintaining constant depth.
Another problem I have with the manual language is the idea that constant draft constant draft is maintained. At least the systems I'm aware don't do that. There is a draft threshold above which lift is triggered. It's not a continuous feedback mechanism. I believe the threshold is adjustable on most systems, but the system doesn't react at all to changes in draft below the threshold. That's a long way from the idea of constant draft, at least to me. Still, draft control is very useful for plowing, because a plow is designed to take itself into the ground. They don’t need to be held down, but they sometimes can use some lifting when they can’t float up on their own.
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2002-03-23 36644
This discussion caused me to do some reading. What I thought was clear in my mind doesn't seem to be. Sorry if I created some confusion, although thinking about it may clarify thinking in more minds than my own.
After reading my repair manual, it seems that the draft control lever is used to select depth. The lever adjusts sensitivity of the draft feedback mechanism to the control valve. A sensitive setting triggers lift with a light draft so a sensitive setting equals a shallow depth relative to soil condition, implement type etc. Meanwhile, the manual indicates that the position control lever sets the minimum operating depth for an implement while operating under draft control. Under position control, it sets the maximum depth.
My reading indicates that draft control operates pretty much the way I didn't think it did. Essentially, implement depth floats on feedback provided by a small leaf spring behind the top-link bracket. With medium sensitivity settings, the depth is somewhere in the middle of the lift range, and the control can respond to changing draft conditions by either raising or lowering. The design is a continuous feedback idea that is capable of responding to draft increases or decreases.
Of course, given the small success I have with trying to feather my position control, I don't know how continuous the feedback mechanism is in practice. That’s the difference between book learning and experience I guess. Too bad I edited out a comment similar to Bird's that I haven't used a tractor with draft control from my first post.
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| Rob in Mass
Join Date: Posts: 1
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2002-03-23 36657
Bird & Tom great take re: position & draft control Just a few things Tom mentioned that I should have touched on. Toms dead on right, the term constant depth is used rather loosely especially by mfgs. They would like to make you think of it as auotmatic sense both up and down & that the slightest deviation in implement angle/hieght change would cause exact output to compensate. this is not 100% the case there is a bit more to it than that. while they are not totaly wrong the device can and does work but like all things there is some limitations. Toms right about lowering to a certain point & if the 3ph needs to go lower because of a out of range condition-(beyond physical ability of the travel limits and the limits of the mechanicle sensing device. But hey it's not a perfect world nor are we or our machines. another thing tom pointed out is he mentioned soil conditions or hard objects, he is right about that a good portion of draft sence is based on that objective... lifting the hitch to a point where wheels grab more as the implement is lifted. I supose my previous post wasn't to indicate its a full featured automatic closed loop control, it does have a few traits of a open control loop the more I think about it there is a base setting as mentioned regarding selecting the proper ratio of the center link. Positiong the top middle or bottom hole for the top link. This not only dials in the varing geometry to the imlement/tractor relationship but it also trims out or amplifies the varying sensing signal for the mechanical to hydrolic relationship a s.p.f.b (set point feed back) if you will. simply stated hit or dig into a hard object or as implement digs in due to geomety change from irregular surface contors than there will be a compensating out put proportional to the input signal. But then goes back to a certain point because of gravity on the implement.
So what I think it all comes down to is some mfgs publications hit more on continuos depth control. Vrs: hieght of varying terain, & should point out a bit more of what tom had said reguarding load change, force aplied to implement and depth contol. But in real world there are both factors to be considered, force on implement and geometry of implement sensed back to draft control. Both are a function of one another. Because if the implement is engaged with the ground either one of these variables- hieght/angle of implement or force applied to implement will cause an output to 3ph. So if we want a dead on accurate depth regardless of any condition I think it would be god awfully expensive to employ on a compact tractor. Maybe on a ultra slick grader but not a 10 to $30,000 compact tractor. Not to mention the tractor would most likely need to move much slower to keep pace with what is going on in back of the machine and stay at a
consistent depth. so now that I have looked at this
feature and thought about it more I have suddenly gained a great respect for this rather simple looking device, although not simple once you consider all the components to actually perform draft control ie: sensing spring, linkage rods, cam plates,and extra hydrolic interface on the rock shaft. Ajustments looks like living nightmare to set up without shop manual at hand.
Please more input on this if I have missed something. Great
board topic I usually don't write in, only read posts.
I find it interesting and always learning from different topics. ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2002-03-24 36671
If the main interest is in the mechanical workings of draft control, I might be hooked. It will take me awhile to figure it out to my satisfaction from my manuals. In the meantime I'll be prone to posting barely coherent comments, so I'll try to take thing in small bites.
A couple of comments: My manual only gives one adjustment specific to draft control. It's the draft control rod, and adjustments is similar to the position control rod, which has to be adjusted first. The procedure doesn't seem too bad. I recall seeing a picture of a top-link bracket for draft-control, but I can't remember if it had several pin position. From your comment they must have similar to ordinary brackets. The position probably does affect compression applied to the bracket the amount the draft control rod moves.
I'm guessing that any difference feedback due to different pin positions would be within the range of the draft control sensitivity adjustment. A different pin position would use a different setting on the draft control lever to achieve the same operating depth. As far as I know, the different pin positions are provided for safety reasons. top-link compression applies leverage to help keep the front wheels on the ground. Without top-link compression, a tractor under heavy draft can climb its own rear wheels. The upper pin positions apply more leverage and are intended for use with heavy draft implements.
One of the main differences between position and draft control parts is that position control lowers by means of a poppet valve while draft control uses a lowering spool. Poppet valves open solely due to the relationship between lift arm level and quadrant lever position. High lift arms, low lever positions or a combination of the two can open a poppet valve. Lowering is entirely position dependent. Lowering in draft control is more complex since both position and draft affect lowering. Hence the lowering spool and a bunch of additional parts. As I noted, it'll take me awhile to figure the 'why fors' on this one. I also have to keep these posts shorter.
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| JimTN
Join Date: Posts: 1
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2002-03-24 36688
Dan: For what it is worth.
I have a new Kubota B2410HSD with FEL and 456 pound flail mower on the 3ph. I left it raised with the engine running for 5 or 10 minutes and did not notice any repositioning. When I parked, I left the mower fully raised for close to an hour (engine off) and could not tell that it had lowered any.
Perhaps your tractor needs some adjustment.
Jim ....
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