When tractors were introduced, farmers quickly found that engine driven tractors were more economical to use, as compared to keeping animals for tillage, and tractors began selling widely. In many cases agricultural machinery dealers received cattle for the barter for tractors and they and in turn sold the cattle in the meat market. The Farmall is one of early tractors and the most familiar and famous names in tractor history. Tractors were made to be work horses, so niceties were minimal. This included foregoing a fuel gauge.
Tractors are most useful for cultivation purposes, so a tractor or tractors have been a must for farm owners, but tractors are also used in excavation, in manufacturing and industry, or on construction sites. Farm size, availability of labor and custom services, crop selection, and cultural practices, such as choice of tillage system, all affect the selection of an optimum equipment set and, ultimately, the number of tractors necessary to farm. Although demand for tractor power generally increases with farm size, many commercial farms operate efficiently with a single tractor.
Tractors are designed to operate at different travel speeds, but the final drives are not designed for all possible torques theoretically available. The engine may range from about 12 to 120 horsepower or more and tractors over the years have been typically offered in the range of 20 to 400 horsepower. Engine power is transmitted to a gearbox typically having 4 to10 speeds (these transmissions are manually switched via a control lever to determine how fast the tractor can go) and through the differential gear to the two large rear-drive wheels. Some farm tractors can reach speeds up to 25 miles per hour, but slow speeds are necessary to give the farmer more control while doing field work.
Farm tractors are designed to be operated with additional weight or ballast when pulling heavy loads to reduce wheel slip. Insufficient ballast can cause excessive wheel slip and increased fuel consumption. Tractors need large tires to avoid compressing the earth, and to avoid digging in. Thus only the rear tires really need to be large and the front tires can be small and smooth unless the tractor has four wheel drive. Tractors used on ground of irregular contours have tracks so mounted that their left and right front ends rise and fall independently of each other. However, soil undulations induce tractor and machine vibrations, reducing driver’s comfort and their capability of controlling the linked machinery.
Tractors are usually used to pull, or in some cases, push objects and are designed to pull either large loads at slow speeds or lighter loads at higher speeds. Field speeds up to 10 mph are typical, but rangeland applications usually vary from 2 to 5 mph. Tractors can be generally classified as two-wheel drive, two-wheel drive with front wheel assist, four-wheel drive (often with articulated steering), or track tractors (with either two or four powered rubber tracks).
Tractors are equipped with a hitching point below the rear axles to prevent roll over. Unfortunately, some people will attach to a point above the rear axle in a foolish attempt to get more weight/traction on the drive wheels and this can lead to disaster. Also, if a tractor is used to free and tow a stuck vehicle, the operator should hitch the vehicles front-to-front and drive the towing tractor in reverse, which minimizes the risk for rollover, by transmitting all the engine power of the towing tractor through the chain to the other vehicle.
