Harry Ferguson had been making and selling tractors for years in the early 30s. He finally invented a hydraulic lift that had 3 points for attaching his specially built 3 point implements such as turning plows and cultivators. He incorporated an automatic device that allowed you to set the amount of draft or pull on the plow and it would automatically raise the plow if a harder piece of soil was encountered with the plow or let it down a little if an easier place to pull the plow was encountered. This is accomplished by being able to set the control valve link inside the lift closer or farther away from the plunger rod that is attached to the top link which is in turn attached to the top of the turning plow or cultivator linkage. When a hard place in the ground is contacted the spring is compressed till it comes in contact with the linkage to the control rod and pushes the control valve in till the plow is raised to the point where the pressure on the big spring on the top link is slightly released thus letting the control rod move back toward the down position and stabilizing the draft of the plow. Thus it is called automatic draft control. The lower you put the touch control handle the harder it is to cause the draft to raise the plow and the plow will go deeper as the touch control lever is gradually lowered.
Draft control is the automatic depth control of a ground engaging implement such as a turning plow or a cultivator. When you let the lift down so that the plow touches the ground and begins to go into the ground the plow tends to rotate on the two points of the draw bar of the plow/implement. When the plow point tries to pull back on the tractor this is what the word "draft" means. When the plow point engages the ground and the plow starts to try to rotate on the drawbar hook up pins at the ends of the lift arms the top link then begins to push in towards the back of the tractor and compresses the big spring on the lift housing. The lower you have the touch control handle set on the quadrant the more the big draft spring has to compress in order to push against the internal linkage that will try to make the control valve in the pump start to lift the plow. As the plow is lifted the stress on the top link becomes less on the big draft spring and this in turn lets the pump tend to drop the plow to the preset position you have selected on the quadrant touch control handle. The deeper or more draft you want to put on the plow/tractor the lower you are required to lower the place on the quadrant where the touch control handle/lever is placed.
The Ford tractor has a very effecient "Draft control"
The way it works is you move the touch control handle until the plow begins to drop. Do not lower the touch control any further and try the plow at this position of the touch control handle. It should go into the ground only slightly and no further. To make the plow go deeper just move the touch control lever a fraction of an inch lower on the quadrant. This will increase the distance that the draft plunger spring on the back of the tractor at the top link connection has to be compressed. This will allow the plow to go a little deeper. Continue to lower the touch control on the quadrant in fractions of an inch until the depth you desire is reached. Then set the quadrant lever stop to the bottom of the touch control lever so it will not drop any further down.
This is "Draft control"
Added on Date: 16:43:10 09/01/04
Position control is being able to maintain a selected height of the lift arms or "position control"
The 9N/2N Ford and The TO Fergusons that have the Ferguson system lift did not have position or height control. Only draft control and my device adds this much needed option to the original Ferguson system lift. When these tractors were first manufactured they were primarily used in farming and plowing and the need for a height/position control was not needed but as more and more equipment was invented to use with the farm tractor the need for position/height control came about. Such things as the Bush Hog, boom pole. box blade and snow plow need to be able to be controlled as to the height of the implement. So I invented the "position control" ZANE THANG and have sold over 600 to satisfied customers.
See my web site below for more information on the position control
DRAFT NOT WORKING WHEN TOUCH CONTROL MOVED ALL THE WAY UP THE QUADRANT.
When the lift gets to where it will not lift the implement when in draft and the touch control handle is raised all the way to the top of the quadrant something in the draft linkage has either been bent or worn to the point that the lift control valve is not being engaged sufficiently to raise the lift when the lever is raised.
Most of the time this is caused from shock loads being put on the draft linkage through the top link to the big draft sensing spring. Lots of tractors have the two and three hole top link rocker hookups. These specialty rockers were for specific applications and were never meant to be used in such operations as using a turning plow or bush hog or box blade. They were made primarily for use with light draft implements such as the two row cultivator and some mowing machines etc.
If one of the upper holes are used while doing something like heavy plowing and something immovable is struck by the plow the excessive leverage of having the top link in one of the upper holes has a tremendous mechanical advantage on the top link and this is transmitted into the big draft sensing spring and on into the internal linkage. The internal linkage is actually bent in this manner and after it gets bent in this manner it will not lift anymore in the draft mode until the damage is corrected.
Also the draft sensing spring seat can become convex from the action of carrying too great a load on the lift and having it jump up and down while being transported over uneven terrain. Just think of the force being applied to the draft spring seat while doing this. This is also multiplied by using one of the top holes in the top link rocker connector.
Unless you are going to use a row crop cultivator you should cut off the upper holes in the rocker or put a bolt in them to discourage them being used for anything other than what it was designed for.