Let's start by defining what a three point hitch is. Tractor three point hitches consist of; Tada! three major components. They are:  the left and right lower lift arms (those long things with the balls in the end, that are sticking out the back of the tractor), and the top link; usually a three piece adjustable apparatus with a central body and two threaded ends with balls, one of which attaches to the tractor, and the other which attaches to the implement.  The overall length of the top link is adjustable via the threaded ends.  The sole purpose of the three point hitch is to place, and hold, the mounted implement in the desired position to accomplish the job at hand. As you may have guessed, there are many different types of systems available to get this done.  Some are quite simple, while others are extremely complex.  In the simplest form, a hydraulic pump supplies oil to a control valve.  The position of the control valve determines where the oil goes next.  If the control valve is in neutral, the oil is simply directed back into the reservoir (transmission housing). If raise is selected, the oil from the pump is directed, by the control valve, into the lift cylinder, causing the lift arms to rise. If lower is selected, the oil from the pump is directed, by the control valve, to the reservoir (just like neutral); however, a passage is also opened which will allow oil to escape from the lift cylinder, allowing gravity to lower the lift arms. Many of the smaller compact tractors are, in fact, just that simple in lift control.  They use what might be termed...

Non position control. This type of lift is simple to build, easy to troubleshoot/repair, and potentially very aggravating to use, depending on the implement.  Let's assume you are using a rear grooming mower that is supported, while in mowing position, by four caster wheels (one at each corner of the deck). No sweat. Just shove the lift lever to the down position, and the casters take care of it from there.  Now, suppose you want to put your box scraper on and put a nice finish grade on a yard. In order to do a good job, it is important to have finite control of the height of the box scraper. The problem is, you must manually return the control valve to neutral at the very instant the box scraper arrives at the correct height. What usually happens is that the box has already gone past where you want it to be before you can yank the control valve into neutral.  Well dang, I don't want to go through that.  Enter….

Position control.  This nifty lift type has some extra parts called feed back linkage. This linkage can be either internal or external, yet it's purpose remains the same.  Feed back linkage serves to return the control valve (automatically) to the neutral state as soon as the lift arms reach the point selected by the relative position of the lift control lever. Whereas the non position control type only has three positions (raise, lower or neutral), the position control type allows an infinite number of lift arm positions, from all the way down, to all the way up.  If you regularly perform tasks that require precision, repeatable lift arm height control, definitely get the position control type of lift.  Now, take a deep breath and get ready for….

Draft control.  Draft control, while not essential, makes life a little easier when plowing, sub-soiling, or using other ground engaging implements. For illustration purposes, let's assume we want to go plow up the back forty.  We've mounted our plow to the three point hitch and adjusted things so that the plow will run straight and track properly behind the tractor. A note about plowing- if you have adjusted the plow properly, you should not have to use the stabilizer system to keep it running true behind the tractor. As you let the lift arms down, and begin to move forward though the field, the plow will start to enter the ground. As the plow continues down, traction and horsepower requirements increase. The natural tendency is for the plow to continue down until the tractor either loses traction, runs out of power, or the lift arms reach their lower limit. It is very unlikely that the latter will happen.  We want to be able to plow at a reasonable depth without straining the engine or having excessive tire slippage.  We also do not want to have to continually fiddle with the lift controls, raising and lowering the plow by small amounts, as ground conditions vary throughout the field. That's where draft control really helps. Draft control senses the amount of strain that the tractor is being subjected to from the plow. If the strain exceeds a predetermined level, the draft control will automatically raise the plow just enough to restore normal loading of the tractor.  After you get past the hard spot in the field, the draft control automatically returns the plow to the pre-selected, ideal depth. There are two main types of draft sensing in wide use today. They are: lower link draft sensing, and top link draft sensing.  Both achieve the same end result, and much discussion could be made over which is the best method.  Generally you will find lower link sensing on larger, higher horsepower tractors.  In the case of lower link sensing, the front of the lift arms are attached to a common bar that flexes with variable loading to impart movement to linkage that is ultimately connected to the control valve.  There are also tractors on the market that incorporate an electronic lift control system.  With these, the lower draft bar contains a strain sensor which sends a signal to an onboard computer.  Movement of these electronic bars is almost undetectable to the eye.  For tractors that utilize top link draft sensing, there are several methods in use to transmit draft load information to the control valve.  For a large portion of North American style tractors, there is a rather large (usually internal) coil spring, which is compressed (by the top link) as draft load increases, and relaxed as the load diminishes. This compression/relaxation causes movement in the draft control linkage, thus changing the position on the control valve, raising and lowering the lift arms as needed.  Other tractors (namely European style) have a massive leaf type spring between the top link and the lift cover.  Still others use a torsion bar that is actually twisted as the top link moves toward and away from the tractor.  Now, with all of this draft action going on, we've got to slow the lift system down some, or we'll end up with a rapid, out of control oscillation of the lift arms going up and down. This is accomplished with something called….

Response control.  Response control (in most systems we know of) simply serves to control the rate at which hydraulic oil is allowed to escape from the lift cylinder. By slowing this rate, we minimize undesirable oscillations that would otherwise occur. Response control has no effect on rate of lift, and that is good, because we want the plow to raise quickly when we hit a hard spot.  However, if we let the plow go back into the ground at an uncontrolled speed, we will end up pulling a plow that jumps into and out of the ground.  We have to give the system a little time to settle down somewhere in the raise/lower cycle, and that is the function of the response control.

To get the maximum benefit from draft control, you must use it the way the manufacturer intended for it to be used.  Do you need draft control?  On the smaller tractors, probably not, as these tractors are rarely used to do much plowing.  On larger tractors, it is pretty much standard equipment anyway, so the choice is made for you.

Regardless of what tractor you now own, or may be considering as a future purchase, take a little time to completely familiarize yourself with it's operating characteristics. You'll enjoy it much more!