Lesson 2 the reading module

Read the text: Modifications of Bulldozers

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, Terex and JCB started to manufacture large tracked-type earthmoving machines.

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 military construction units throughout the world. Their best known model, the Caterpillar D9, was also used to clear mines and demolish enemy structures. 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 bulldozer's 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 remains of structures.

Bulldozers have been further modified over time to evolve into new machines which are capable of working in ways that the original bulldozer can not. One example is that loader tractors were created by removing the blade and substituting a large volume bucket and hydraulic arms which can raise and lower the bucket, thus making it useful for scooping up earth and loading it into trucks. Other modifications to the original bulldozer include making it smaller to let it operate in small work areas where movement is limited, such as in mining. A very small bulldozer is sometimes called a calfdozer.

Nevertheless, the original earthmoving bulldozers are still irreplaceable as their tasks are concentrated in deforestation, earthmoving, ground leveling, and road carving. The heavy bulldozers are mainly employed to level the terrain to make it fit to construct on. The construction, however, is mainly done by small bulldozers and loader tractors. Some bulldozers, especially bulldozers in military usage, have been fitted with armor in order to protect the driver from enemy fire, thus enabling the bulldozer to operate in battle zones. The best-known armored bulldozer is probably the IDF Caterpillar D9, used by the Israeli Defense Forces (IDF) for earthmoving, clearing terrain obstacles, open routes, detonating explosive charges and demolishing structures under fire. Some bulldozers have been fitted with armor by non-government civilian operators to prevent bystanders or police from interfering with the work performed by the bulldozer, as in the case of strikes or demolition of condemned buildings.

In military use, dozer blades are fixed on combat engineering vehicles and can optionally be fitted on other vehicles, such as artillery tractors like the Type 73 or M8 Tractor. Combat applications for dozer blades include clearing battlefield obstacles and preparing fire positions.