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precisely, the term refers only to a tractor (usually tracked) fitted with a dozer blade.

Most often, bulldozers are large and powerful tracked engineering vehicles. The tracks give them excellent ground hold and mobility through very rough terrain. Wide tracks help distribute the bulldozers weight over large area (decreasing pressure), thus preventing it from sinking in sandy or muddy ground. Extra wide tracks are known as swamp tracks. Bulldozers have excellent ground hold and a torque divider designed to convert the engine s power into dragging ability, letting the bulldozer use its own weight to push very heavy things and remove obstacles that are stuck in the ground. The Caterpillar D9, for example, can easily tow tanks that weigh more than 70 tons. Because of these attributes, bulldozers are used to clear areas of obstacles, shrubbery, burnt vehicles, and

Сremains of structures.

иremoving the soil from the cut and depositing it elsewhere on shallow ground (fill). Many dozer blades have a reinforced center section with this purpose in mind, and are called «bull blades».

Sometimes a bulldozer is used to push another piece of earthmoving

equipment known as a «scraper». The towed Fresno Scraper, invented in 1883 by

James Porteous, was the first design to enable this to be done economically,

(single shank/giantбripper) or in groups of two or more (multi shank rippers). Usually, a single shank is preferred for heavy ripping. The ripper shank is fitted with a replaceable tungsten steel alloy tip.

The bulldozer s primary tools are the blade and the ripper. The ripper is the

long claw–like device on the back of the bulldozer. Rippers can come singly

А to handle and transport, which canДthen be removed so grading can take place.

Ripping rock lets the ground surface rock be broken into small rubble easy

Agricultural ripping lets rocky or very hard earth be broken up so otherwise unploughable land can be farmed. For example, much of the best land in the California wine country consists of old lava flows. With heavy bulldozers the lava is shattered, allowing agriculture. Also, hard earth can be ripped and decompacted

can optionally be fitted on other vehicles, such as artillery tractors like the Type 73

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or M8 Tractor. Combat applications for dozer blades include clearing battlefield obstacles and preparing fire positions.

The first bulldozers were adapted from Holt farm tractors that were used to plough fields. Their versatility in soft ground for logging and road building led directly to their becoming the armoured tank in World War I.

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 Сcity park in Morrowville, Kansas where the two built the first bulldozer. By the1920s, 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 metal plate (it got its curved иshape later) is called a «blade». The blade peels layers of soil and 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 tree stumps. In some early models the driver sat on top in the open withoutбa 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 timeАthe 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 Caterpillar, Komatsu, Fiat–Allis, John Deere, International Harvester, Case, Liebherr, Terex and JCB manufactured large tracked–typeДearthmoving machines.

Bulldozers grew more sophisticated as time passed. 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 rear ripper claw(s)Иto loosen rocky soils or to break up pavement (roads). A more recent innovation is the outfitting of bulldozers with GPS technology, such as manufactured by Topcon Positioning Systems, Inc., Trimble Inc., or Mikrofyn for precise grade control and (potentially) «stakeless» construction.

The best known maker of bulldozers is probably Caterpillar which earned its reputation for making tough durable reliable machines. There are however other manufacturers of bulldozers for instance Fiat, Komatsu or Allis Chalmers. Although these machines began as modified farm tractors, they became the mainstay for big civil construction projects, and found their way into use by military construction units world–wide. Their best known model, the Caterpillar D9, was also used to clear mines and demolish enemy structures.

2.Write down a plan of your report.

3.Find in the text:

• supporting factual data (structural, historical, statistical);

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• analytical findings;

• solutions (or conclusion);

• recommendations or predictions.

4. Find the terms in this text. Were they explained enough?

components, Japan made main pump, multi–circuit valve, swing motor, walking motor, South Korea made gasoline tank On–line digital monitoring and control system GPS satellite position (optional) and remote diagnose system(optional) Full opened engine hood and easy up–forward–lifted cab rubber track (optional, or steel track), no damage to the ground of road cold & warm air conditioner(optional).

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Now the best–seller model is ZL50G, this loader feature is fully hydraulic powered steering with flow–amplified system. Pilot operated control for loader hydraulic system, power shift transmission makes convenient and flexible operating. XCMG new Z–bar linkage, high breakout force, shorter hydraulic cycle time, automatic leveling on any position, and greater productivity. Special quadrate type transmission shaft of construction machinery. Power transmission is more reliability. EG–TM combination is supported on three points by dual directions,

Сvibration–isolators. Reducing resonance and fatigue failure of structure. Optimized structure of diesel engine air intake system reduces dust into air filter. Prolonging the durability of engine, convenience the service of air filter element. Optimized cooling system, drops overall heat balance temperature. Integral operable hood, иmade by compound material, reduces noise and vibration, makes convenient and flexible operation and service.

Equipped with SHANGHAI STYRE, CAT or CUMMINS diesel engine, electric starting, electric stopping, having excellent performance and reliability.

1. ZL50Gбwheel loader features fully hydraulic powered steering with flow– amplified system, Pilot operated control for loader hydraulic system, power shift and electric shift optional transmission makes convenient and flexible operating.

2. XCMG wheel loader new Z–bar linkage, high breakout force, short hydraulic cycle time, automatic leveling on any position, and higher productivity.

3. Special quadratАtype transmission shaft of construction machinery. Power transmission is more reliable for heavy equipment.

4. Integral new luxury cab, excellent visibility, safety and reliability for wheel loader.

5. EG–TM combination is supported on three points by dual directions, vibration–isolators. Reducing resonanceДand fatigue failure of structure.

6. Optimized structure of diesel engine air intake system reduces dust into air filter, Prolonging the durability of the engine and conveniencing the service of air filter element. Optimized cooling system drops overall heat balance temperature.

7. Integral openable hood made of compoundИmaterial reduces noise and vibration, and makes operation and service more convenient and flexible.

8. ZL50G wheel loader Equipped with SHANGHAI, STYRE, or CUMMINS diesel engine, which is of electric starting, electric stopping and excellent performance and reliability. It approves to be one of the best wheel loader in China.

Graders are the necessary construction machinery in the construction of national defense project, mining construction, urban and rural road, and water conservancy construction and farmland reconstruction.

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