Toplink Can hydraulic top link exert downpressure?

[powerscol]

Neighbor uses suitcase weight on his. He hangs them off the back top lip of the blade. I think he has added about 400 lbs if I remember correctly. Does a great job.

 

[Fallon]

The problem with adding weight to many implements, especially a box blade is that wright is a good proxy for strength. Adding weight makes the box work harder when it might not be built with enough steel to be up to the extra work.

Not always the case, but I'd rather start with the heavier implement from the get go even it costs more.

 

[powerscol]

Fallon - very true. However in his case it is a strong Land Pride unit and he needed the weight to get it to bite on his gravel drive and not bounce along. He has gotten very good using the 3pt to control the depth of cut.

 

[RalphVa]

If you get the top link longer than two lift arms, it'll exert down pressure. It's just geometry. I had this happening on my 4010. They installed the lift pins in the wrong location on the LX-4 bush hog. The top link ended up extending longer than the lift arms. You raise the "hog", and the rear wheel is driven more to the ground before the front is lifted.

Ralph

 

[TomSeller]

If you get the top link longer than two lift arms, it'll exert down pressure. It's just geometry. I had this happening on my 4010. They installed the lift pins in the wrong location on the LX-4 bush hog. The top link ended up extending longer than the lift arms. You raise the "hog", and the rear wheel is driven more to the ground before the front is lifted.

Ralph

Understand what you are saying, but in regards to a blade, I would say that would make the blade dig in due to the angle, but not apply actual down pressure.

My Case backhoe has a 3 point hitch kit which is no more than an external hydraulic cylinder, linkage and lift arms. It applies actual down pressure but as has been mentioned, decreases traction.

 

[Tomtint]

I understand the newtons law thing. However, I believe that if you have a hydrolic top link and can add 2-300 pounds of down pressure using it, it will be almost unnoticeable is the uplift at the rear wheels. I think it would certainly *** to the effectiveness of the implement

 

[LD1]

I understand the newtons law thing. However, I believe that if you have a hydrolic top link and can add 2-300 pounds of down pressure using it, it will be almost unnoticeable is the uplift at the rear wheels. I think it would certainly *** to the effectiveness of the implement

Nope. Hitch is free to float up, you cannot add down pressure with a TL except in rare cases as mentioned. Like a really long TL that messes with the geometry of the hitch, or it the hitch is already as high as it can go, or you chain it down to the drawbar. But Lengthening or shortening a standard toplink within its normal range doesnt change the pressure

 

[Threepoint]

Down pressure in any form lifts rear tires an equal amount so you net ZERO. (Newton's Law: Equal and Opposite Reaction.)

This is why HEAVY ground engagement implements are necessary, gravity is all you have.

Actually, I have to disagree with this. If there is down pressure applied to the hitch sufficient to lift the rear of the tractor, it has indeed increased the "weight" (technically the ground reaction force) on the implement. It does this by transferring some of the tractor's weight to the box blade, etc. What Newton's third law of motion means though, and I think this is probably Jeff's meaning as well, is that the net overall weight of the implement and tractor combined does not change (assuming the tractor is not moving forward under power, see below).

I also agree with comments that a hydraulic top link, wonderful as it is, won't by itself add down pressure on the implement so long as the 3pt upper lift arms and lower link arms float (as they do on virtually all current CUTs, I believe). But again, this is assuming the tractor is not moving forward under power. If it is, then some downforce can be achieved even with a floating hitch by using the top link to change the angle of attack of the blade. By increasing the attack angle of the cutting edge and box, the blade will tend to dig deeper, depending on the material being worked, thus effectively converting some of the kinetic energy of the tractor's forward motion downward. So, in a sense, greater down pressure caused by the engagement with the ground itself.

 

[Fallon]

Actually, I have to disagree with this. If there is down pressure applied to the hitch sufficient to lift the rear of the tractor, it has indeed increased the "weight" (technically the ground reaction force) on the implement. It does this by transferring some of the tractor's weight to the box blade, etc. What Newton's third law of motion means though, and I think this is probably Jeff's meaning as well, is that the net overall weight of the implement and tractor combined does not change (assuming the tractor is not moving forward under power, see below).

I also agree with comments that a hydraulic top link, wonderful as it is, won't by itself add down pressure on the implement so long as the 3pt upper lift arms and lower link arms float (as they do on virtually all current CUTs, I believe). But again, this is assuming the tractor is not moving forward under power. If it is, then some downforce can be achieved even with a floating hitch by using the top link to change the angle of attack of the blade. By increasing the attack angle of the cutting edge and box, the blade will tend to dig deeper, depending on the material being worked, thus effectively converting some of the kinetic energy of the tractor's forward motion downward. So, in a sense, greater down pressure caused by the engagement with the ground itself.

That is why Henry Ferguson designed the 3pt in the first place. When pulling a plow, the 3pt converts some of the drag force of the plow into additional down force on the tractor through the toplink. It was quite revolutionary back in the day & made the 3pt hitch tractors able to pull/plow circles around similar sized tractors & plows using just a towed plow.

 

[like2wheel]

Actually, I have to disagree with this. If there is down pressure applied to the hitch sufficient to lift the rear of the tractor, it has indeed increased the "weight" (technically the ground reaction force) on the implement. It does this by transferring some of the tractor's weight to the box blade, etc.

Thanks.
Thought I was in another dimension there for a moment