Understanding draft control

sixdogs · Oct 25, 2021

Here's what draft control on a tractor is, what it does and why it does it. It's easy but there is a lot of confusion because the instructions are often poorly written.

1. "Draft control" merely causes the three point arms to maintain a constant amount of resistance, or "draft" as farm people call it. For example, if you had a grader blade on the back and drove though a tilled farm field, when the front wheels dipped into a hole, the rear blade would raise and dump a pile of dirt. Also the reverse when the front wheels hit a ridge and the rear blade will dig into the ground. Since rear linkage just naturally "floats", without the use of draft control, what happens is you add holes and humps and make a grading task worse.

2. Enter draft control. All it does is cause the rear linkage to not float but instead operate with a degree of resistance and you choose that amount with the levers. So when the front wheels hit a hole, the draft control tells the linkage and the rear arms and blade will then keep the same amount of resistance as though the front wheels were on flat ground. And the reverse; hit a hump with the front wheels and the draft control tells the rear arms to lessen resistance and keep the same amount as before hitting the hump.

3. That's all there is to it. The 3pt arms lever (position control) and draft lever are interrelated and you have to fiddle with both until you get what you want. In plowing, if you hit a front hole, the plow will lift and you won't have the depth of cut wanted. And the reverse if you hit a hump and get a too-deep cut. Plowing would be more, meaning more draft control needed.

*******

A. That's about it, short of experience. You could read 50 pages on how to ride a bike or instead learn by falling off twice. For me, I use draft control mostly with an 8' rock rake and sometimes a blade. Through repeated passes, I can leave a graded area so smooth and flat that strangers stop and take pictures. I need lighter draft control for this while plowing or cultivating would take more draft control.

B. Another practical example is using cultivators. You might be just cultivating along and suddenly bog down and nearly stall the tractor. We now know that's likely because the front wheels hit a small rise and caused the cultivators to sink in. With the use of draft control, kiss that issue goodbye.

C. For extra credit, look up Harry Ferguson and the so-called 3 pt and draft control "Handshake Agreement" with Henry Ford that went south. That caused the growth of Ferguson tractors, the eventual origin of Massey- Ferguson and then on to Agco. All of this because of Harry's innovation and development of draft control.

oosik · Oct 25, 2021

My Kubota M6040 has draft control. I used it ONCE with my single bottom moldboard plow. Too many large rocks in the particular field I choose.

I suppose it might come in handy when I use the rear blade on my driveway. I've found it a whole lot easier to just drag my LPGS.

CausticUrbanCoast · Oct 25, 2021

sixdogs said:
Here's what draft control on a tractor is, what it does and why it does it. It's easy but there is a lot of confusion because the instructions are often poorly written.

1. "Draft control" merely causes the three point arms to maintain a constant amount of resistance, or "draft" as farm people call it. For example, if you had a grader blade on the back and drove though a tilled farm field, when the front wheels dipped into a hole, the rear blade would raise and dump a pile of dirt. Also the reverse when the front wheels hit a ridge and the rear blade will dig into the ground. Since rear linkage just naturally "floats", without the use of draft control, what happens is you add holes and humps and make a grading task worse.

2. Enter draft control. All it does is cause the rear linkage to not float but instead operate with a degree of resistance and you choose that amount with the levers. So when the front wheels hit a hole, the draft control tells the linkage and the rear arms and blade will then keep the same amount of resistance as though the front wheels were on flat ground. And the reverse; hit a hump with the front wheels and the draft control tells the rear arms to lessen resistance and keep the same amount as before hitting the hump.

3. That's all there is to it. The 3pt arms lever (position control) and draft lever are interrelated and you have to fiddle with both until you get what you want. In plowing, if you hit a front hole, the plow will lift and you won't have the depth of cut wanted. And the reverse if you hit a hump and get a too-deep cut. Plowing would be more, meaning more draft control needed.

*******

A. That's about it, short of experience. You could read 50 pages on how to ride a bike or instead learn by falling off twice. For me, I use draft control mostly with an 8' rock rake and sometimes a blade. Through repeated passes, I can leave a graded area so smooth and flat that strangers stop and take pictures. I need lighter draft control for this while plowing or cultivating would take more draft control.

B. Another practical example is using cultivators. You might be just cultivating along and suddenly bog down and nearly stall the tractor. We now know that's likely because the front wheels hit a small rise and caused the cultivators to sink in. With the use of draft control, kiss that issue goodbye.

C. For extra credit, look up Harry Ferguson and the so-called 3 pt and draft control "Handshake Agreement" with Henry Ford that went south. That caused the growth of Ferguson tractors, the eventual origin of Massey- Ferguson and then on to Agco. All of this because of Harry's innovation and development of draft control.

Nice description of the sensing draft control. How about one for the non-sensing draft control?

JimB77 · Oct 26, 2021

sixdogs said:
Here's what draft control on a tractor is, what it does and why it does it. It's easy but there is a lot of confusion because the instructions are often poorly written.

1. "Draft control" merely causes the three point arms to maintain a constant amount of resistance, or "draft" as farm people call it. For example, if you had a grader blade on the back and drove though a tilled farm field, when the front wheels dipped into a hole, the rear blade would raise and dump a pile of dirt. Also the reverse when the front wheels hit a ridge and the rear blade will dig into the ground. Since rear linkage just naturally "floats", without the use of draft control, what happens is you add holes and humps and make a grading task worse.

2. Enter draft control. All it does is cause the """"rear linkage to not float""" but instead operate with a degree of resistance and you choose that amount with the levers. So when the front wheels hit a hole, the draft control tells the linkage and the rear arms and blade will then keep the same amount of resistance as though the front wheels were on flat ground. And the reverse; hit a hump with the front wheels and the draft control tells the rear arms to lessen resistance and keep the same amount as before hitting the hump.

3. That's all there is to it. The 3pt arms lever (position control) and draft lever are interrelated and you have to fiddle with both until you get what you want. In plowing, if you hit a front hole, the plow will lift and you won't have the depth of cut wanted. And the reverse if you hit a hump and get a too-deep cut. Plowing would be more, meaning more draft control needed.

sixdogs
Please explain how a single acting(one way) cylinder or cylinders such as most farm tractors 3 pt hitches possess when at a height other than fully raised not float whether control is utilizing "draft control or no draft control".
Thanks Jim

MossRoad · Oct 26, 2021

Draft control doesn't have anything to do with the front tires dipping into a hole or riding up a hill. It works on flat ground as well. It only "cares" about the rear end of the tractor.

It works by sensing the load on the implement that's engaged in the ground. Pull a plow, box blade, or other implement into tough soil. That load causes the rear tires to spin, which digs a hole, which lowers the rear end of the tractor. When the rear end lowers, that tries to change the triangle angles that are formed between the 3pt arms, the implement, the top link, and the rear of the tractor. All that puts pressure on the rock shaft that the top link is connected to. The rock shaft operates a valve that raises the 3pt arms to try and maintain the proper angles in triangle. As the 3pt arms lift the implement out of the tough soil, that causes less resistance to the tractor. The tractor is able to climb out of the tire holes in the ground. The load on the top link pulls back, moving the rock shaft in the opposite direction, which lowers the implement back toward the pre-set location.

Tinhack · Oct 26, 2021

And to just make it more complex; Most tractors with draft control also have multiple top-link and sensing holes for the pin. The location of the pin determines how sensitive the draft will be or to lock it out entirely.

Tinhack · Oct 26, 2021

Oh yeah, did I mention the draft speed adjustment?

LD1 · Oct 26, 2021

Think of draft control as maintaining a constant compression force on the toplink.

Some have different settings. some the settings are just choosing a different toplink hole.

With a plow or blade or anything that digs in the dirt on the 3PH, as you drive forward with the implement in the ground....the ground is trying to push backwards on the implement. This causes the implement to want to rotate around the lower pins and in turn it tries to compress the toplink.

Draft control is to sense this "compression" force of the toplink and want it to remain constant. Exceed watever "compression" force is desired and the 3PH will automatically raise the hitch to try and lessen that compressive force (lessen the draft load). Example would be plowing and hitting a patch of hard ground....or even as he eluded to...front tires go over a mound and the rear implement tries to dig in.

Whenever it senses too little compressive force it reacts and LOWERS the hitch to try and increase the draft load.

All of this draft mechanism like on old 8n fords were connected to a spring and rod. The different toplink mounting positions changed the leverage that the top-links compressive force had on the spring and rod....thus either making the draft control more sensitive or less.

This was great back in the day of plowing acres of field with an 8n and a 2-bottom....because you would never spin-out. How many people with our modern compact tractors that do plowing or pulling a rear blade are constantly fidgeting with your 3PH lever. Get too agressive of a bite and start loosing traction and you raise it the hitch a little to keep moving.....then lower it again when you need more bite. Thats sorta what draft control does automatically.

For me, I dont have draft and never had a want or need for it. When I am plowing my garden or my 2-acre corn plot....I want constant depth....NOT constant draft load. I have sufficient tractor to pull 3-14 plow. I dont want the plow deciding on its own that I am in a hard patch of ground and deciding it only wants to plow at 4-5" instead of my desired 7-8". I want my plow to maintain depth. And with a properly set plow.....it wont plow TOO deep. SO I just lower the lever ALL the way and go. The frot going over a bump or incline does NOT make the plow dig deeper if it is set right. And fronts dropping into a hole or depression....with the hitch in float it stays at depth

oosik · Oct 26, 2021

I've come to notice something about Owners Manuals. If they were written by people whose first language was YOUR first language - we would be a whole lot better off.

Just imagine an east African - bought his brand new Ford tractor - trying to comprehend his OM that's written in Simbutu.

And the more difficult it is to put into words - the more difficult it is to understand.