| The landscape of American farming changed | | | | how fast the tractor can go) and through the |
| dramatically between 1850 and 1950 due in large part | | | | differential gear to the two large rear-drive wheels. |
| to the introduction of farm tractors. Initially, tractors | | | | Some farm tractors can reach speeds up to 25 miles |
| used steam engines, until these gave way to internal | | | | per hour, but slow speeds are necessary to give the |
| combustion engines in the twentieth century. The | | | | farmer more control while doing field work. |
| turn-of-the-century steam engine tractor is gigantic | | | | Farm tractors are designed to be operated with |
| and primitive looking, using chains on a rotating shaft | | | | additional weight or ballast when pulling heavy loads |
| to steer. | | | | to reduce wheel slip. Insufficient ballast can cause |
| When tractors were introduced, farmers quickly | | | | excessive wheel slip and increased fuel consumption. |
| found that engine driven tractors were more | | | | Tractors need large tires to avoid compressing the |
| economical to use, as compared to keeping animals | | | | earth, and to avoid digging in. Thus only the rear tires |
| for tillage, and tractors began selling widely. In many | | | | really need to be large and the front tires can be |
| cases agricultural machinery dealers received cattle | | | | small and smooth unless the tractor has four wheel |
| for the barter for tractors and they and in turn sold | | | | drive. Tractors used on ground of irregular contours |
| the cattle in the meat market. The Farmall is one of | | | | have tracks so mounted that their left and right |
| early tractors and the most familiar and famous | | | | front ends rise and fall independently of each other. |
| names in tractor history. Tractors were made to be | | | | However, soil undulations induce tractor and machine |
| work horses, so niceties were minimal. This included | | | | vibrations, reducing driver's comfort and their |
| foregoing a fuel gauge. | | | | capability of controlling the linked machinery. |
| Tractors are most useful for cultivation purposes, so | | | | Tractors are usually used to pull, or in some cases, |
| a tractor or tractors have been a must for farm | | | | push objects and are designed to pull either large |
| owners, but tractors are also used in excavation, in | | | | loads at slow speeds or lighter loads at higher speeds. |
| manufacturing and industry, or on construction sites. | | | | Field speeds up to 10 mph are typical, but rangeland |
| Farm size, availability of labor and custom services, | | | | applications usually vary from 2 to 5 mph. Tractors |
| crop selection, and cultural practices, such as choice | | | | can be generally classified as two-wheel drive, |
| of tillage system, all affect the selection of an | | | | two-wheel drive with front wheel assist, four-wheel |
| optimum equipment set and, ultimately, the number | | | | drive (often with articulated steering), or track |
| of tractors necessary to farm. Although demand for | | | | tractors (with either two or four powered rubber |
| tractor power generally increases with farm size, | | | | tracks). |
| many commercial farms operate efficiently with a | | | | Tractors are equipped with a hitching point below the |
| single tractor. | | | | rear axles to prevent roll over. Unfortunately, some |
| Tractors are designed to operate at different travel | | | | people will attach to a point above the rear axle in a |
| speeds, but the final drives are not designed for all | | | | foolish attempt to get more weight/traction on the |
| possible torques theoretically available. The engine | | | | drive wheels and this can lead to disaster. Also, if a |
| may range from about 12 to 120 horsepower or | | | | tractor is used to free and tow a stuck vehicle, the |
| more and tractors over the years have been typically | | | | operator should hitch the vehicles front-to-front and |
| offered in the range of 20 to 400 horsepower. | | | | drive the towing tractor in reverse, which minimizes |
| Engine power is transmitted to a gearbox typically | | | | the risk for rollover, by transmitting all the engine |
| having 4 to10 speeds (these transmissions are | | | | power of the towing tractor through the chain to the |
| manually switched via a control lever to determine | | | | other vehicle. |