Giant machines :Bulldozer

A bulldozer is a crawler (continuous tracked tractor) equipped with a substantial metal plate (known as a blade) used to push large quantities of soil, sand, rubble, or other such material during construction or conversion work and typically equipped at the rear with a claw-like device (known as a ripper) to loosen densely-compacted materials.
Bulldozers can be found on a wide range of sites, mines and quarries, military bases, heavy industry factories, engineering projects and farms.
The term "bulldozer" is often used erroneously to mean any heavy equipment (sometimes a loader and sometimes an excavator), but precisely, the term refers only to a tractor (usually tracked) fitted with a dozer blade.

Description 

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

A crawler bulldozer (crawler dozer,sometimes referred to as tracked or caterpillar) has a traction mechanism like that of a semi-rigid suspension car. It uses a two-plate dry primary clutch, which makes maintenance easy. The steering is hydraulically assisted. Most all crawler bulldozers are powered by diesel engines, which makes the work energy efficient, and relatively low polluting. It can be used in road building, hydro-electric construction, field modification, port and mine development. Sludge constructions and soft ground work also commonly utilize crawler bulldozers.
The other type, a wheeled bulldozer, is also called a wheel dozer. The principle of the machine work is to push outfitted dozer blades by essentially tractors, so as to clearing and grading land or paving the roads. These machines use a drive system of military industry technology, which is of big tractive force, high efficiency and good performance. It is with full hydraulic articulated steering and all wheel drive, which is easy and flexible to operate.
The bulldozer's primary tools are the blade and the ripper.

Blade

The bulldozer blade is a heavy metal plate on the front of the tractor, used to push objects, and shoving sand, soil and debris. Dozer blades usually come in three varieties:

1. A straight blade ("S blade") which is short and has no lateral curve and no side wings and can be used for fine grading.
2. A universal blade ("U blade") which is tall and very curved, and has large side wings to carry more material.
3. An "S-U" combination blade which is shorter, has less curvature, and smaller side wings. This blade is typically used for pushing piles of large rocks, such as at a quarry.

Blades can be fitted straight across the frame, or at an angle, sometimes using additional 'tilt cylinders' to vary the angle while moving. The bottom edge of the blade can be sharpened, e.g. to cut tree stumps.
Sometimes a bulldozer is used to push another piece of earth moving 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, removing 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".

In military use, dozer blades are fixed on combat engineering vehicles and can optionally be fitted on other vehicles, such as artillery tractors such as the Type 73 or M8 Tractor. Dozer blades can also be mounted on main battle tanks, where it can be used to clear antitank obstacles, mines, and dig improvised shelters. Combat applications for dozer blades include clearing battlefield obstacles and preparing fire positions.

Ripper

The ripper is the long claw-like device on the back of the bulldozer. Rippers can come as a single (single shank/giant ripper) 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. Ripping rock breaks the ground surface rock or pavement into small rubble easy to handle and transport, which can then be removed so grading can take place. With agricultural ripping, a farmer breaks up rocky or very hard earth (such as podzol hardpan) which is otherwise unploughable, in order to farm it. For example, much of the best land in the California wine country consists of old lava flows. The grower shatters the lava with heavy bulldozers so surface crops or trees can be planted. A less common rear attachment is a stumpbuster, which is a single spike that protrudes horizontally and can be raised to get it (mostly) out of the way. A stumpbuster is used to split a tree stump. A bulldozer with a stumpbuster is used for landclearing operations, and probably has a brush-rake blade.

Manufacturers

Industry statistics based on 2010 production published by Off-Highway Research showed Shantui was the largest producer of bulldozers, making over 10,000 units that year or 2 in 5 crawler-type dozers made in the world The next largest producer by number of units is Caterpillar Inc., which produced 6,400 units.

History of the word

• 19th century: term used in engineering for a horizontal forging press.
• Around 1880: In the USA, a "bull-dose" was a large dose (namely, one large enough to be literally or figuratively effective against a bull) of any sort of medicine or punishment. 'Bull-dosing' meant a severe whipping or coercion, or other intimidation such as at gunpoint.
• 1886: "bulldozer" meant a large-caliber pistol and the person who wielded it.
• Late 19th century: "bulldozing" meant using brute force to push over or through any obstacle.
• 1930s: applied to the vehicle.

These appeared as early as 1929, but were known as "bull grader" blades, and the term "bulldozer blade" did not appear to come into widespread use until the mid-1930s. "Bulldozer" now refers to the whole machine not just the attachment. In contemporary usage, "bulldozer" is often shortened to "dozer".