Editing Tractor (section)

== Hitches and power applications ==
The power produced by the engine must be transmitted to the implement or equipment to do the actual work intended for the equipment.  This may be accomplished via a drawbar or hitch system if the implement is to be towed or otherwise pulled through the tractive power of the engine, or via a pulley or power takeoff system if the implement is stationary, or a combination of the two.

=== Drawbars ===
[[Plows]] and other tillage equipment are most commonly connected to the tractor via a [[Drawbar (haulage)#Agriculture and horse-drawn vehicles|drawbar]].  The classic drawbar is simply a steel bar attached to the tractor (or in some cases, as in the early Fordsons, cast as part of the rear transmission housing) to which the hitch of the implement was attached with a pin or by a loop and [[clevis]].  The implement could be readily attached and removed, allowing the tractor to be used for other purposes on a daily basis.  If the tractor was equipped with a swinging drawbar, then it could be set at the center or offset from center to allow the tractor to run outside the path of the implement.

The drawbar system necessitated the implement having its own running gear (usually wheels) and in the case of a plow, chisel cultivator or harrow, some sort of lift mechanism to raise it out of the ground at turns or for transport.  Drawbars necessarily posed a rollover risk depending on how the tractive torque was applied.<ref>{{Cite journal|last1=Irwin|first1=Amy|last2=Poots|first2=Jill|date=12 Apr 2018|title=Investigation of UK Farmer Go/No-Go Decisions in Response to Tractor-Based Risk Scenarios|journal=Journal of Agromedicine|volume=23|issue=2|pages=154–165|doi=10.1080/1059924X.2017.1423000|pmid=29648955|url=http://aura.abdn.ac.uk/bitstream/2164/12160/1/JAg_tractorpaper_revision.pdf|hdl=2164/12160|s2cid=4783478|hdl-access=free}}</ref> The Fordson tractor was prone to roll backward due to an excessively short wheelbase.  The linkage between the implement and the tractor usually had some slack which could lead to jerky starts and greater wear and tear on the tractor and the equipment.

[[File:Modern John Deere Tractor IMG 0401.JPG|thumb|left|A large, modern John Deere model 9400 four-wheel drive tractor with tripled wheels and a drawbar-towed tool chain, including one-pass tillage equipment, planter and fertilizer applicator with tanks]]

Drawbars were appropriate to the dawn of mechanization, because they were very simple in concept and because as the tractor replaced the horse, existing horse-drawn implements usually already had running gear. As the history of mechanization progressed, the advantages of other hitching systems became apparent, leading to new developments (see below).  Depending on the function for which a tractor is used, though, the drawbar is still one of the usual means of attaching an implement to a tractor (see photo at left).

=== Fixed mounts ===
Some tractor manufacturers produced matching equipment that could be directly mounted on the tractor.  Examples included front-end loaders, belly mowers, row crop cultivators, corn pickers and corn planters.  In most cases, these fixed mounts were proprietary and unique to each make of tractor, so an implement produced by John Deere, for example, could not be attached to a Minneapolis Moline tractor. Another disadvantage was mounting usually required some time and labor, resulting in the implement being semi-permanently attached with bolts or other mounting hardware. Usually, it was impractical to remove the implement and reinstall it on a day-to-day basis.  As a result, the tractor was unavailable for other uses and dedicated to a single use for an appreciable period of time.  An implement was generally mounted at the beginning of its season of use (such as tillage, planting or harvesting) and removed when the season ended.

=== Three-point and quick ===
{{main|Three-point hitch}} 
 
The drawbar system was virtually the exclusive method of attaching implements (other than direct attachment to the tractor) before [[Harry Ferguson]] developed the [[three-point hitch]].<ref>Ferguson's patents for three-point hitch:
*  Ferguson, Harry. British patent no. 320,084 (issued:  3 July 1928)   
*  Ferguson, Harry [https://pdfpiw.uspto.gov/.piw?docid=01916945&PageNum=1 "Tractor-drawn agricultural implement"] U.S. patent no. 1,916,945 (filed:  6 June 1929; issued:  4 July 1933)</ref> Equipment attached to the three-point hitch can be raised or lowered [[hydraulic]]ally with a control lever. The equipment attached to the three-point hitch is usually completely supported by the tractor. Another way to attach an implement is via a quick hitch, which is attached to the three-point hitch. This enables a single person to attach an implement quicker and put the person in less danger when attaching the implement.

[[File:Tractor3pointhitchDubMay04.jpg|thumb|left|A modern three-point with a quick hitch attached]]

The three-point hitch revolutionized farm tractors and their implements. While the [[Three-point hitch#History|Ferguson System]]  was still under patent, other manufacturers developed new hitching systems to try to fend off some of Ferguson's competitive advantage. For example, International Harvester's [[Farmall]] tractors gained a two-point "Fast Hitch", and John Deere had a power lift that was somewhat similar to the more flexible Ferguson invention. Once the patent protection expired on the three-point hitch, it became an industry standard.

Almost every tractor today features Ferguson's three-point linkage or a derivative of it.  This hitch allows for easy attachment and detachment of implements while allowing the implement to function as a part of the tractor, almost as if it were attached by a fixed mount.  Previously, when the implement hit an obstacle, the towing link broke or the tractor flipped over.  Ferguson's idea was to combine a connection via two lower and one upper lift arms that were connected to a hydraulic lifting ram.  The ram was, in turn, connected to the upper of the three links so the increased drag (as when a plough hits a rock) caused the hydraulics to lift the implement until the obstacle was passed.

Recently, [[Bobcat Company|Bobcat's]] patent on its front loader connection (inspired by these earlier systems) has expired, and compact tractors are now being outfitted with quick-connect attachments for their [[loader (equipment)|front-end loaders]].

=== Power take-off systems and hydraulics ===
In addition to towing an implement or supplying tractive power through the wheels, most tractors have a means to transfer power to another machine such as a [[baler]], [[swather]], or [[mower]].  Unless it functions solely by pulling it through or over the ground, a towed implement needs its own power source (such as a baler or combine with a separate engine) or else a means of transmitting power from the tractor to the mechanical operations of the equipment.

Early tractors used [[Belt (mechanical)|belts]] or cables wrapped around the [[flywheel]] or a separate belt pulley to power stationary equipment, such as a threshing machine, buzz saw, silage blower, or stationary baler. In most cases, it was impractical for the tractor and equipment to move with a flexible belt or cable between them, so this system required the tractor to remain in one location, with the work brought to the equipment, or the tractor to be relocated at each turn and the power set-up reapplied (as in cable-drawn plowing systems used in early steam tractor operations).

[[File:TractorPTOshaftMay04.jpg|left|thumb|An implement connected to a tractor's [[power take-off]] (PTO) shaft]]

Modern tractors use a [[power take-off]] (PTO) shaft to provide rotary power to machinery that may be stationary or pulled. The PTO shaft generally is at the rear of the tractor, and can be connected to an implement that is either towed by a drawbar or a three-point hitch.  This eliminates the need for a separate, implement-mounted power source, which is almost never seen in modern farm equipment. It is also optional to get a front PTO as well when buying a new tractor.

Virtually all modern tractors can also provide external [[hydraulic fluid]] and [[electric]]al power to the equipment they are towing, either by hoses or wires.