What Is a 3PH Designed To Do?

[KennK]

This may sound like a silly question, it occurred to me after reading all the posts about hard-pulling backward.

I that the draw bar is designed for hard-pulling forward. I understand that it is placed below the axle such that a hard pull straight backward on the draw bar will actually pull the front of the tractor downward - and that is good.

I know that a 3PH can carry implements in a fairly static position (such as a spreader).

Some primarily lift implements upward without any real significant backward force - such as rear pallet forks and mowers.

But some implements would clearly have a backward force - such as rear blades, and implements that pull through soil. To much backward pull, and the tractor flips - right?

So it seems that the primary function of the 3PH is to lift and carry - rather than to pull. Am I correct?

 

[Duffster]

This may sound like a silly question, it occurred to me after reading all the posts about hard-pulling backward.

I that the draw bar is designed for hard-pulling forward. I understand that it is placed below the axle such that a hard pull straight backward on the draw bar will actually pull the front of the tractor downward - and that is good.

I know that a 3PH can carry implements in a fairly static position (such as a spreader).

Some primarily lift implements upward without any real significant backward force - such as rear pallet forks and mowers.

But some implements would clearly have a backward force - such as rear blades, and implements that pull through soil. To much backward pull, and the tractor flips - right?

So it seems that the primary function of the 3PH is to lift and carry - rather than to pull. Am I correct?

NO

How would pulling a 3point attachment flip a tractor when said attahment is on the ground.

 

[Soundguy]

Nope.. pretty much opposite of that.

the 3pt hitch geometry actually is designed to keep the tractor planted when pulling.. say.. a plow.. or other ground engaging implement...ie.. keeping traction to the ground...

moldboard plow was probably one of the first implements for the 3pt hitch equiped tractors..

now.. that is not to say that you can't make a tractor front come up with a 3pt implement on back.. you can.. the shorter the implement.. the higher the angle the tractor will come up befor ethe lift range maxes out.. then it's a question of traction, geometry and material strength as to whether the implement buckles and the tractor goes over..

soundguy

 

[Foton404]

An 8n Ford uses the 3pt hitch for a draw bar. But I see your point. I always question which is better; to use a 3pt for a relatively heavy mower deck or, a pull type brush rotary mower of the same size?

 

[Stimw]

A 3pt lets you adjust the working height of the implement and raise it to transport.
I can't just drop my box blade or brush cutter and go to work. I have to set the proper height for them to work.

 

[Farmwithjunk]

Here's the guy who designed and patented the first 3-point hitch

Ferguson Company - Wikipedia, the free encyclopedia


More


http://www.geocities.com/MotorCity/Downs/9828/


And one more....Good visual on how the 3-point hitch works.


http://www.livinghistoryfarm.org/farminginthe40s/machines_0204.html

 

[Soundguy]

An 8n Ford uses the 3pt hitch for a draw bar. But I see your point. I always question which is better; to use a 3pt for a relatively heavy mower deck or, a pull type brush rotary mower of the same size?

An 8n is setup to use a swinging drawbar. It's a bolt on bracket that goes on the bottom of the diffy.

soundguy

 

[Baby Grand]

KennK-
A lot of confusion is caused if you don't consider the line of action of the applied force. The line of action is usually independent of where the attachment point are. Consider this:

Weld a bracket to the underside of the diff and apply a rearward load that is parallel to the ground - the result will be to pull the front wheels down, onto the ground.

Using the same bracket, construct a mast that sticks up vertically, above the top of the tractor's ROP. Again, apply a rearward load (to the top of the mast) that is parallel to the ground - the result will be to lift the front wheels off of the ground.

Even though the two loads are transmitted through the very same bracket the resulting load on the tractor is very different - all because the line of action in the first example is beneath the diff and the line of action in the second case is up above the diff.

When a turning plow is engaging the earth the line of action is actually down in the dirt somewhere and well below the diff. But if you hook a chain to the top link of the same plow and apply a large, rearward load the front will start to lighten and lift.

-Jim

 

[Reg]

This may sound like a silly question, it occurred to me after reading all the posts about hard-pulling backward.

I that the draw bar is designed for hard-pulling forward. I understand that it is placed below the axle such that a hard pull straight backward on the draw bar will actually pull the front of the tractor downward - and that is good.

I know that a 3PH can carry implements in a fairly static position (such as a spreader).

Some primarily lift implements upward without any real significant backward force - such as rear pallet forks and mowers.

But some implements would clearly have a backward force - such as rear blades, and implements that pull through soil. To much backward pull, and the tractor flips - right?

So it seems that the primary function of the 3PH is to lift and carry - rather than to pull. Am I correct?

I think you have either mis-read or mis-understood a few things.
Attend a tractor pull some time; It isn't about WHERE the drawbar actually IS and it certainly doesn't bring the front down.
The geometry PERMITS the front of the tractor to come UP - to a point of maximum traction and stability.

Unlikely that a tractor would flip backwards from a blade or plow encountering a major obstruction.
Not saying it couldn't happen, just that the speed would have to be way higher than would be prudent for the task.

Yes, (if I am to believe the Ferguson story) the original purpose was to lift and carry ground engaging implements..... which would be "pulled" in the next row after the turnaround.
Whatever pattern you drive you are faced with sharp turns and having to at least drive over the same ground more than once.
Lifting the implement from the ground during the turn makes so much sense in so many ways, too many to list.

 

[pitt_md]

This may sound like a silly question, it occurred to me after reading all the posts about hard-pulling backward.

I that the draw bar is designed for hard-pulling forward. I understand that it is placed below the axle such that a hard pull straight backward on the draw bar will actually pull the front of the tractor downward - and that is good.

I know that a 3PH can carry implements in a fairly static position (such as a spreader).

Some primarily lift implements upward without any real significant backward force - such as rear pallet forks and mowers.

But some implements would clearly have a backward force - such as rear blades, and implements that pull through soil. To much backward pull, and the tractor flips - right?

So it seems that the primary function of the 3PH is to lift and carry - rather than to pull. Am I correct?

The short answer is no. They are designed to pull all kinds of things. When engaging the ground you lower the 3ph so that you are pulling from below the axel.