3 Pt. question?

[MikeFLA]

Why can't (doesn't) a 3 pt. system have the ability to exert down-force, i.e. the hydraulics on an FEL?

 

[Bird]

Mike, I think it's simply a lack of demand for it, and the increased cost of building them. There are some of them in existence, but I don't remember just which makes and models.

 

[Anonymous Poster]

My IH 300 has down force. Works good with scraper. My Kubota doesn't works good to pile up snow.

 

[gator]

In the case of my 750, my tech manual shows fluid on one side of the rockshaft piston only,air on opposite side, nothing to push it in the opposite direction (ie:down force).Hope this helps.

 

[hayden]

Isn't that what Draft Control does? Bigger tractors have it, but I've never used one.

 

[Youare]

Most 3PH hydraulic systems are put together in a similar fashion. There is a cylinder that looks like a can, open at one end closed at the other.

Inside the cylinder is a piston. As hydraulic fluid is feed into the closed end of the cylinder it pushes the piston in the opposite direction which is connected ultimately to the lift arms
outside the tractor.

This cylinder arrangement is called a single acting cylinder in that it can be powered in only one direction. Gravity moves it the other direction when you operate the lift control lever to release the fluid in the cylinder.

I guess some tractors do have double acting cylinders, powered in both directions. The 3PH as we have it today was invented by Henry Ferguson. It was designed to transfer the pull on the tractor from the drawbar to more towards the middle of the tractor. Early tractors without the "modern" 3PH arrangement had a bad habit of rearing up as the immplement met more resistance from the ground.

The Ferguson 3PH placed more weight on the tires as the immplement, then it was mostly for plowing, dug into the ground. This arrangement also allowed the immplement to "float" better over hard objects in the ground.

If you could put donward pressure on the 3PH it would reduce the weight on the rear tires giving you less traction. I agree sometimes it would be nice to put a little more pressure on the 3PH.

Randy

 

[MikeFLA]

I appreciate the responses. I now have a working knowledge of this system. I can see where down force would give you less traction. Had not thought about that.

The next obvious question is...can it be retro-fit. Probably not, but I just thought I'd ask.

 

[frank_f15]

probably can not be retro fitted but not sure. also not sure if u really would want to, to much downward pressre on 3ph would not be good,it might have a tendency to cause u some problems, like stand your tractor on it's rear wheels/w3tcompact/icons/eyes.gifiam sure there are reasons why they don't build them that way, have to ask the experts for that ans.

 

[Anonymous Poster]

<font color=blue>....Why can't (doesn't) a 3 pt. system have the ability to exert down-force, i.e. the hydraulics on an FEL?...</font color=blue>

Because of the inherent design of the "rockshaft nature" of the 3-point system...
{on the very large Ag tractors they use auxiliary "boosters" or single action cylinders to help lift up to 15,000 lbs. on the Cat V hitches}

Looking at another way... it would have the similarities of using a loader with "single action" hydraulic cylinders versus our "double action" cylinders now mostly used...

The single action only "lifts"... it "free falls" or retracts with "natural weight" attached...

{If you notice- most all older "trip loaders" use single action hydraulic cylinders... hence no "down pressure"...}

 

[Anonymous Poster]

...another common example I forgot to mention would be a hydraulic jack... upon release... it "free falls"...