Bulldozer

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The first bulldozers were adapted from farm Holttractors that were used to ploughfields. Their versatility in soft ground for logging and road building, lead directly to them becoming the armoured tankin the first war.

In 1923, a young farmer named James Cummings and a draftsman named J. Earl McLeod made the first designs for a bulldozer. A replica is on display at the city park in Morrowville, Kansaswhere the two built the first bulldozer.[1]

By the 1920s, tracked vehicles became common, particularly the Caterpillar 60. To dig canals, raise earth dams, and do other earthmoving jobs, these tractors were equipped with a large thick metal plate in front. This thick metal plate (it got its curved shape later) is called a "blade". The blade peels layers of soiland pushes it forward as the tractor advances. Several specialized blades have been developed: for high volume loads such as coal, rakes to remove only larger boulders, or blades with razor sharp edges to cut treestumps. In some early models the driver sat on top in the open without a cabin. These attachments, home built or by small equipment manufacturers of attachments for wheeled and crawler tractors and trucks, appeared by 1929, widespread acceptance of the bull-grader does not seem to appear before the mid-1930s, and the addition of powered down force made them the preferred excavation machine for large and small contractors alike by the 1940s, by which time the term "bulldozer" referred to the entire machine and not just the attachment.

Over the years, bulldozers got bigger and more powerful in response to the demand for equipment suited for ever larger earthworks. Firms like Catepillar, Komatsu, Fiat-Allis, John Deere, International Harvester, Case, Liebherr, Terexand JCBstarted to manufacture large tracked-type earthmoving machines.

Bulldozers grew more sophisticated as well. Important improvements include more powerful engines, more reliable drive trains, better tracks, raised cabins, and hydraulic(instead of early models' cable operated) arms that enable more precise manipulation of the blade and automated controls. As an option, bulldozers can be equipped with a rear ripper claw to loosen rocky soils or to break up pavement (roads). A more recent innovation is the outfitting of bulldozers with GPStechnology, such as manufactured by Trimble Inc.orMikrofyn [www.mikrofyn.com] for precise grade control and (potentially) "stakeless" construction.

The best known maker of bulldozers is probably the Caterpillar Tractor Company, which earned its reputation for making tough durable reliable machines. Although these machines began as modified farm tractors, they became the mainstay for big civil construction projects, and found their way into use by militaryconstruction units throughout the world. Their best known model, the Caterpillar D9, was also used to clear minesand demolishenemy structures.