Building in Safety

Come and see how Harry Ferguson’s ingenious 3-point hitch used traction to put an end to tractor flip-overs about 100 years ago.

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courtesy by Robert Pripps
Harry Ferguson and Henry Ford in Dearborn, Mich., during the famous “handshake agreement.”

The 3-point hitch: What’s the big deal? That is a question that might be raised by younger readers who can’t envision a farm tractor without a 3-point hitch. About 100 years ago, though, integration of the tractor and implement was a new idea. It was also about 100 years ago that the first tractor flipped over backward when its plow struck an immoveable object.

It is just a matter of physics. Engine torque and flywheel inertia multiplied by the overall gear ratio means that, if the drive wheels are held stationary, torque on the axle will be enough to rotate the entire tractor backward around the axle. Of course, if the tractor was designed so that its drive axle was in front (front wheel-drive) this would not happen, but that configuration, while good for automobiles, is obviously not so good for tractors.

Continuing with the matters of tractor physics, the force of the tractor applied to the implement is called draft load, or simply draft. The way draft is reflected from the implement (whether it’s a plow or a wagon) to the tractor, and vice versa, can be expressed as a vector, known as the line of draft. If the line of draft passes below the center of the rear axle, it tends to pull down on the entire tractor, increasing traction. When traction reaches the point where there is no slippage of the rear tires, then the front end begins to rise. And that is where the 3-point hitch comes in.


As civilization developed, animal power was adopted on a massive scale to pull plows, rakes, disks, wagons, and buggies. Then, at the turn of the 20th century, the new mechanical “horsepower” arrived on the scene, to be hitched to plows and implements in the same manner as it had been with the horse. One form of motive power was substituted for another. When a horse plow struck a rock or some other immovable object, it simply stopped. When the same thing happened to a tractor-drawn plow, engine torque and flywheel inertia flipped the body of the tractor around the rear axle in rapid fashion.

Enter Harry Ferguson, inventor of the 3-point hitch. Henry George “Harry” Ferguson was born in 1884 in Northern Ireland. Harry was a spirited child with a penchant for confrontation and irritating his father, siblings, and schoolmasters. He left school at age 14 and went to work for his brother, who had set up a car and motorcycle repair business in Belfast. His activities included work as a mechanic and driver, and he actively promoted the business by racing cars and motorcycles. Although Ferguson’s early education had been curtailed, he was an avid reader and was fairly well versed in a variety of subjects.

Harry Ferguson became quite famous for his racing exploits, and for having designed, built and flown the first airplane in the British Isles. With his fame, he founded May Street Motors, a successful car and tractor dealership. He was also awarded patents for improved carburetors. He was not, however, the type of inventor who took to the workbench. He needed someone who could translate his ideas into working models. In 20-year-old Willy Sands, he found exactly what he was looking for.

Meanwhile, May Street Motors, as agents for the Overtime tractor (a British variation of the American Waterloo Boy), gained national recognition by putting on plowing demonstrations. Harry Ferguson knew how to capitalize on his personal fame.

“We’ll design a better plow!”

In 1914, at the beginning of World War I, Great Britain’s Ministry of Munitions (MOM) became concerned by the country’s reliance on imported food. Since young farmers and horses were being absorbed by the military, older farmers were encouraged to embrace tractor farming. As an incentive, the government bought and distributed all the British- and American-built tractors they could get, leasing them to farmers at very favorable terms. Ireland, in particular, had much untilled grassland. Because of Ferguson’s renowned demonstrations of the Overtime tractor, he was selected by the Ministry of Munitions to monitor the program in Ireland.

Ferguson and Sands began touring the country in a government-provided car. They encountered farmers who were unfamiliar with the internal combustion engine and who did not know how to set up multi-bottom plows. Moreover, the equipment’s design and attachment to the tractor made it dangerous to use. In frustration, Ferguson declared to Sands, “We’ll design a better plow!”

To start with, the new Ferguson plow weighed about half as much as previous tractor plows. It was designed for use with the popular Eros tractor conversion of the Ford Model T car. Its ingenious feature was the way it was hitched under the belly, forward of the rear axle and thus tending to draw all four wheels onto the ground. Excellent traction was provided and any tendency for rearing was eliminated. Unfortunately, the market for the Eros tractor dried up when Henry Ford announced his low-cost Fordson tractor in 1917.

Creation of the Duplex Hitch

In 1917, the British MOM ordered import of 6,000 Fordsons to speed the country’s tillage needs. Through Ford’s tremendous manufacturing capability, the tractors were delivered in a few weeks. The Fordsons immediately went to work in Ireland. The tendency to back-flip was especially evident in the Fordson tractor, which had rather poor weight distribution.

With that, Ferguson and Sands revised their plow design to work with the Fordson. Rather than the under-belly hitch, which was difficult to attach, Sands devised a completely new arrangement for coupling the plow to the Fordson, which he called the Duplex Hitch.

In that application, the plow was attached to the Fordson by two parallel links, one above the other, above and below the rear axle. Thus, draft loads pushed down on both the front and back wheels. If the plow struck a rock, the load tended to tip the plow with all the force going to the top link, stopping the tractor in its tracks without flipping. Sands also added a “floating-skid” device that helped to keep the plow running at an even depth. Ferguson’s company in Ireland made plows for Great Britain, while Sherman Bros. of New York made them for America.

Designing a tractor for a new system

Meanwhile, Ferguson and his expanding team, which by then included Archie Greer and John Chambers, worked on hydraulic actuation of the plow for raising and lowering and controlling depth. While the floating skid worked well enough for the plow, it was ineffective for other implements. Further difficulties arose in steering with an implement in the ground.

Sands realized that the force vectors in the upper and lower links of the duplex hitch reflected a virtual hitch point where these two vectors met, and that the draft (or pulling forces) were proportional to implement depth. As loads increased or decreased, the implement should be raised or lowered proportionately. Sands and Ferguson then obtained a patent on the hydraulically actuated 2-point hitch entitled “Apparatus for coupling agricultural implements to tractors and automatically regulating the depth of work,” known simply as draft control.

Draft control solved only part of the problem, however, as the 2-point hitch was semi-rigid laterally. If the front wheels were steered to the left, the rear-mounted implement would swing to the right. In the case of the cultivator, that would be detrimental to the plants you were steering away from. “Ah ha,” thought Sands, “if the two vectors of the 2-point hitch moved the virtual, or perceived, hitch point forward in the vertical plane, replacing the bottom link with two links angled forward toward the same virtual point, all links equipped with ball joints, the tractor could maneuver left or right without the adverse reaction of the implement. The automatic draft control sensor was then incorporated into the single upper, or third, link.</br

Not finding a suitable tractor on which to incorporate the new 3-point hitch system, Ferguson and his team designed and built a demonstrator tractor with the system built in, rather than added on. The transmission and rear axle were ordered from British gear maker David Brown, who, after a season of successful demonstrations of the system on the prototype tractor, agreed to join forces with Ferguson on a production version.

Production of the Ferguson-Brown tractor began in 1937, but sales remained sluggish. The price was somewhat high for such a small tractor, and to realize its benefits, a farmer had to buy all new implements. Nevertheless, Ferguson pressed on. In January 1938, a Ferguson-Brown was entered in a comparative plowing demonstration in Aberdeen, Scotland.  Fortunately, snow fell the night before the trials and only the Ferguson-Brown and a four-wheel drive outfit were able to plow. Farmers who witnessed the demonstration were amazed!

The legacy of the handshake agreement

Another person amazed by the performance of the diminutive Ferguson-Brown was Eber Sherman, former partner in Ferguson’s Fordson plow venture, whom Ferguson had invited to witness the demonstration. When things began to go south between David Brown and Ferguson over slow sales and high prices, Ferguson imposed upon Sherman Bros. to arrange for a demonstration with auto magnate Henry Ford. In September 1938, Ferguson, with a crated Ferguson-Brown tractor and implements, sailed for America.

Henry Ford, who had halted production of the Fordson in the U.S. in 1927, had continued searching for an ideal replacement for it. He also kept in contact with the Sherman Bros. as they had continued in the tractor business by importing British Fordsons. They were also involved with Harry Ferguson through the Fordson plow business. So it was through the Shermans that Ferguson eventually got his audience with Henry Ford.

In early fall of 1938, Ferguson, his aides and a meticulously prepared Ferguson-Brown tractor took the field at Ford’s Fair Lane Estate. The demonstration was convincing. The Ferguson-Brown, about eight-tenths the size of the Fordson, clearly outperformed both the Fordson and an Allis-Chalmers with the same size plows.

With that, Ford and Ferguson made the famous “handshake agreement,” wherein Ford would make tractors with the system and Ferguson would make the implements and do the marketing. The resulting Ford-Ferguson tractor, with the 3-point hitch system, went on to be the largest-selling single tractor model since the ubiquitous Fordson.

And the rest, as they say, is history.  As soon as the patents expired or could be circumvented, other manufacturers adopted the system, even on their garden tractors up to their largest four-wheel drive monsters. FC

After 36 years in the aircraft industry, Bob Pripps returned to his first love and began writing about tractors. He has authored some 30 books on the subject and several magazine articles. Pripps has a maple syrup farm near Park Falls, Wisconsin. In harvesting the maple sap, he relies on a Ford Jubilee and a Massey Ferguson 85.

Tracing the Evolution of Hitch Design

After World War II, the benefits of the 3-point hitch were undeniable, but patent problems and the desire of competing manufacturers to avoid the appearance of endorsement by copying led to the development of proprietary hitch designs. International Harvester announced its 2-point Fast Hitch; Allis-Chalmers, the Snap-Coupler; Case, the Eagle Hitch; and Deere, the Yakima Tool Bar.

All worked but had shortcomings, and farmers complained about having to get specialized implements for each type. In the late 1950s, with Ferguson’s patents running out, the Farm and Industrial Equipment Institute (FIEI), in cooperation with the American Society of Agricultural Engineers (ASAE), persuaded tractor manufacturers to agree on use of the basic Ferguson 3-point hitch design with standard categories depending on horsepower:

Category 0: Up to 20hp

Category 1: 20-45hp

Category 2: 40-100hp

Category 3: 80-225hp

Category 4: More than 180hp

Meanwhile, after-market suppliers developed 3-point conversions for tractors with hydraulic cultivator lifts. These did not have any type of draft control, but the operator could provide the function manually. As time passed, Ford, Ferguson and others made refinements to the system, largely copied by others, such as lower-link and electronic draft sensing.

Today, the 3-point hitch is virtually standard on all but the smallest riding lawn mowers. Some have offered 3-point hitches on both front and back along with PTO outlets, such as the Ford Versatile Model 9030. Industrial and construction machines are also 3-point equipped unless backhoe and end loader options are selected.

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