3pth position control

[W5FL]

Looks like you got all of the right answers already.

It is a true position servo valve that moves the 3 point to match the position control lever. Usually has arbritrary markings and a couple of stops so you can repeat (for instance) where the mower will lower to when you mow. The difference in a tractor position servo and other types (such as steering) is that at any time the position is controlled in a down direction, but the 3 point is free to move in an up position so when you hit something with a disc or mower, your tractor won't be knocked up into the air. /w3tcompact/icons/smile.gif

As Bird said when you push the lever all the way down, the 3 point provides only minimal resistance to both up and down motion of the 3 point so when using a tiller or disk, the implement can move up and down in the soil and not jerk your tractor or the implement around.

Third point is that (most) 3 points DO NOT put any down pressure on the 3 point. The down force is strictly dependent on the weight of the implement, which is why a lot of box blades don't dig very well. They are not heavy enough to not just bounce around.

Use the stops to limit the height you want to raise the 3 point and the lower stop to set the lowest down postion. My 3 point also has an adjustment to limit the rate you can drop an implement to the ground from very very slowly to very fast. It can also give you heart failure if someone plays with it and the 3 point will no longer move! /w3tcompact/icons/smile.gif

 

[GaryK]

You forgot to mention the flow control valve, that controls not only the rate of drop etc but can be closed to "freeze" the 3pt in position so the implement cannot be moved up or down.

 

[W5FL]

Gary,

This is the first tractor I have ever had that had a rate of drop valve. I really don't find it really useful for most things. It is nice to not drop a 1000# mower or box blade quite so fast. I guess it would be a theft deterrent to lock it down, but I have never seen or heard of anyone actually doing that.

 

[Bird]

Wen, I agree with you in that I don't adjust the knob very often at all for the rate of drop; however, it really is handy in some situations. If you have it adjusted so that it drops a light weight implement as fast and smoothly as you want, then put a heavy weight implement on and try to lower it slowly, it tends to be rather jerky, but you can adjust the knob to a slower drop rate and lower the heavy implement smoothly. One place I found it handy was to get it adjusted just right for a post hole digger in order to lower it slowly and smoothly without the jerking.

Bird

 

[Keoke]

Most tractors don't have a presure done on the three point.
But has any one out there with a hydraulic center link tried this.
1. Pull center link ram to it's mid travel position.
2. Drop the implement (eg. rear blade) to the ground.
3. Lock drop flow control in the closed position, which I gather from previous posts, keeps it from moving either up or down.
4. To the extent of it's travel, could the center ram now be used to give a pivoting DOWN and up force feature to the blade????????

 

[MChalkley]

Keoke - In theory this should certainly work, but I don't see how you could get any significant of down force because the only thing you have to push against is ground and that would be forcing the implement to raise up, which you can already do. Or did I misunderstand the question?

Mark

 

[Keoke]

Mark, since the lower arms are locked, wouldn't having the center hyd ram pushing in a downward arc on the blade apply more downward force then the weight of the blade alone generate?
I have a Woods/Dual trencher with it's own center link ram that goes from center point to trencher. This ram is used to shift the weight of the tractor to the drive wheels of the trencher. The tractor is then put in neutral and a variable speed hyd motor on the trencher propels both tractor and trencher together. PTO runs the cutter chain. The ram is used to lift the rear tractor just enough to get the deflection off the tires. This gives good traction to the trencher drive wheels allowing it to drive both units easily. By the way this is the only sensible way to run a trencher on a non-hydro trans tractor.
I am thinking, but don't really know, that forcing the center link out, with lower arms locked, will try to cause the rear of the tractor to rise. This in turn, should apply considerable more downward pressure to the blade then the blades weight alone. Does this make any sense??
regards, george
By the way "Keoke" is Hawaiian for George. Registered to late to get a lock on "george".

 

[Bird]

Keoke (or George), I understand the theory; haven't ever tried it, but yes, it should put some downward force on an implement, but since it would also mostly be pushing back on the top link, and tilting the bottom of the implement forward toward the tractor, I haven't figured out how it would have any practical application except for something like the trencher.

Bird

 

[Keoke]

Bird, on your point of the front of the blade lifting up as you run the ram back.
Wouldn't this depend on where the ram starts the blades arc?
If, for example, you start the ram with the blade off vertical, with a slight tilt to the rear at bottom, then feeding the ram out would drive the blade bottom down to the ground first before starting it's end of cycle upward climb after passing vertical.
Eg. the distance from pivot point (lower arms) to ground is the longest when the blade is at true vertical. Consequently, shouldn't approaching true vertical increase downward pressure and getting away from vertical decrease the same? Bird, I am not sure that I am making my point clearly.
regards,
george

 

[MChalkley]

Keoke - Ok, I did misunderstand. Yes, it should work as you describe. I don't think it would be very practical except in very limited applications, though. But, for applying downforce in situations where you didn't need much travel, it could be useful.

Mark