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Dołączył: 11 Maj 2011
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Wysłany: Śro 6:05, 18 Maj 2011 |
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landscape of American farming changed dramatically between 1850 and 1950 due in large part to the introduction of farm tractors. Initially, tractors used steam engines, until these gave way to internal combustion engines in the twentieth century. The turn-of-the-century steam engine tractor was gigantic and primitive looking, using chains on a rotating shaft to steer.
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 in turn sold the cattle in the meat market. Farmall was one of the early tractors and its name was the most familiar and famous name in tractor history. Niceties were minimal on tractors as they were made to be work horses. Many of them did not even have 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. The selection of an optimum equipment set and ultimately, the number of tractors necessary to farm. Is driven by farm size, availability of labor and custom services, crop selection, and cultural practices, such as the choice of tillage system. Even though the demand for tractor power increases with farm size generally, many commercial farms operate efficiently with only one tractor.
Tractors are designed to operate at different travel speeds, but the final drives are not necessarily designed for all torques theoretically available. Engine power, which typically ranges from about 12 to 120 horsepower or more and over the years have ranged between 20 and 400 horsepower, is transmitted through a gearbox usually having from 4 to10 speeds (these transmissions are manually controlled via a lever to determine how fast the tractor can go) to the differential gear which drives two large rear-drive wheels. Slow speeds are necessary to give the farmer more control while doing field work although some farm tractors can reach speeds up to 25 miles per hour.
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.
Usually tractors are used to pull, but in some cases,Cheap Air Jordans Rocawear Clothing Line Continues,[link widoczny dla zalogowanych], push objects and are designed to pull either large loads using slow speeds or lighter loads at higher speeds. Field speeds up to 10 mph are may be used, but rangeland applications usually vary from 2 to 5 mph. Tractors are generally classified as two-wheel drive,Jordan 13 Just Enjoy Life - A Beginner Crochet Pro, two-wheel drive with front wheel assist, four-wheel drive (often with articulated steering),[link widoczny dla zalogowanych], or tracked tractors (with either two or four powered rubber tracks).
The hitching point for tractors is below the rear axles in order to prevent roll over. Unfortunately, some people have attached to a point above the rear axle in an attempt to get more weight/traction on the drive wheels but this can lead to disaster. When a tractor is used to free and tow a stuck vehicle, the vehicles should be hitched front-to-front with the towing tractor in reverse. This method minimizes the risk for rollover by transmitting all the engine power of the towing tractor through the chain to the other vehicle.
A drawbar or three-point hitch is used to attach most farm implement
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