BULLDOZER (EN: bulldozer; DE: Planierraupe, Bulldozer; FR: bulldozer; ES: excavadora de empuje, bulldozer; RU: бульдозер) is the self-propelled excavating-transporting (earth-digging) machine, which is representing by itself the tracked or wheeled pulling machine (tractor), with the hinged (sometimes trailing) deflecting frontal blade, which is curvilinear in the cross-section, or with the flat pushing shield, which is situated outside of the base of the chassis of the machine. They use bulldozer during the development of the placers, at the waste dumps, during the recultivation, as the auxiliary machine at the open pit mines. Besides these purposes, they use bulldozer during the construction and repair of the roads, and also as the pusher machine (for example, during the loading of the self-propelled scrapers), and so on. Bulldozers are provided with the replaceable equipment (soil-loosening teeth, deflecting wedge-shaped blades, deflecting wing-shaped blades, and so on), which are expanding the field for the usage.
They distinguish the bulldozers: with the non-rotating deflecting blade, which is installed perpendicular to the longitudinal axis of the base machine; with the rotating deflecting blade, which may be installed within the horizontal plane at the angle (up to 30 degrees) along both sides of the longitudinal axis, or perpendicularly to this longitudinal axis; universal with the deflecting blade, which comprises two hinge-joint halves, which are placed within the horizontal plane at the different angles to the longitudinal axis of the machine (the shrub-cutting machine), or perpendicularly to this longitudinal axis (the track-laying machine). The deflecting blades of all the types of bulldozers are provided with the mechanisms with the hydraulic (see the Figure) or rope mover for the lifting-lowering, rotations along the horizontal plane, tilts along the transverse plane, inclination forward and backward along the movement.
The advantage of bulldozer is the high specific performance (per 1 tonne of its mass), which depends on the distance of transportation, on the parameters of the working organ, on the power and mass of the tractor; for the tracked tractors, with the distance for transportation of up to 100 metres, the performance is 4-6 cubic metres per hour-metre on average, while for the powerful tractors (300-735 kilowatts), the performance is 8 cubic metres per hour-metre during the development of the rocks within the massif, and 13 cubic metres per hour-metre during the leveling of the waste dumps. For the increasing of the traction ability of the tracked tractors, they use the serial and parallel connection of two (tandem) or more traction aggregates, which are controlled by the single operator, who is using the common remote control board. The tandem, which comprises two bulldozers with the power of 300-385 kilowatts each, can move the deflecting blade with the length of 12-18 metres during the work at the leveling of the waste dump rocks with the performance of 7-8 thousand cubic metres per hour. Within the USSR, there have been created the bulldozers with hydraulic control; for example, the DET-250 with the engine with the power of 220 kilowatts (300 horse powers), with the mass of 26.5 • 10^3 kilograms, and with the size of the deflecting blade of 4.5x1.4 metres, and the D-701 with the power of 243 kilowatts (330 horse powers), with the mass of approximately 45 • 10^3 kilograms, with the non-rotating and rotating deflecting blades. There are being created the hydraulic bulldozers, which are mounted onto the tracked tractors, and also onto the wheeled tractors with the power of up to 885 kilowatts (1200 horse powers).
Abroad, the most powerful tracked bulldozers are issued within Japan (the "Comatsu" firm, the 555 = Au model) and within the USA (the "Caterpillar" company, the D10 model), the wheeled bulldozers are issued by the "Marion" firm (within the USA, the V220 model).
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