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Bulldozer
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A bulldozer is a crawler (caterpillar tracked tractor), equipped with a substantial metal plate (known as a blade), used to push large quantities of soil, sand, rubble, etc, during construction work. The term "bulldozer" is often used to mean any heavy engineering vehicle (frequently loaders and in particular track loaders), but precisely, the term refers only to a tractor (usually tracked) fitted with a dozer blade. That is the meaning used here.
first bulldozers were adapted from Holt farm tractors that were used to plough fields.
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A bulldozer is a crawler (caterpillar tracked tractor), equipped with a substantial metal plate (known as a blade), used to push large quantities of soil, sand, rubble, etc, during construction work. The term "bulldozer" is often used to mean any heavy engineering vehicle (frequently loaders and in particular track loaders), but precisely, the term refers only to a tractor (usually tracked) fitted with a dozer blade. That is the meaning used here.
History
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 city park in Morrowville, Kansas where the two built the first bulldozer.
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 metal plate (it got its curved shape 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 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 Caterpillar, Komatsu, Fiat-Allis, John Deere, International Harvester, Case, Liebherr, Terex and JCB manufactured large tracked-type earthmoving 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) to 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[www.mikrofyn.com] 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.
History of the word
- 1800s: term used in engineering for a horizontal forging press.
- 1886: "bulldozer" meant a large-caliber pistol and the person who wielded it.
- Around 1880: In the USA, a "bull-dose" was a large and efficient dose of any sort of medicine or punishment. 'Bull-dosing' meant a severe whipping or coercion, or other intimidation such as at gunpoint.
- Late 1800s: "bulldozing" meant using big 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, and now refers to the whole machine not just the attachment. In contemporary usage, "bulldozer" is often shortened to "dozer".
Description
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 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 areas of obstacles, shrubbery, burnt vehicles, and remains of structures.
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, 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."
The bulldozer's primary tools are the blade and the ripper.
Ripper
The ripper is the long claw-like device on the back of the bulldozer. Rippers can come singly (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 lets the ground surface rock be broken into small rubble easy to handle and transport, which can then be removed so grading can take place. 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 to allow planting of orchards where trees could not otherwise grow.
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:
- A Straight Blade ("S-Blade") which is short and has no lateral curve, no side wings, and can be used for fine grading.
- A Universal Blade ("U-Blade") which is tall and very curved, and has large side wings to carry more material.
- A "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.
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.
Modifications
Bulldozers have been further modified over time to evolve into new machines which can work in ways that the original bulldozer cannot.
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.
Some light weight form of bulldozer are commonly used in snow removal and as a tool for preparing winter sports areas for ski and snowboard sports.
Nevertheless, the original earthmoving bulldozers are still irreplaceable as their tasks are concentrated in deforestation, earthmoving, ground levelling, and road carving. Heavy bulldozers are mainly employed to level the terrain to prepare it for construction. The construction, however, is mainly done by small bulldozers and loader tractors.
Armored bulldozers
Some bulldozers, especially bulldozers in military usage, have been fitted with armor to protect the driver from enemy fire, enabling the bulldozer to operate in battle zones. The best-known use of an armored bulldozer is probably the use by the Israeli Defense Forces (IDF) of the IDF Caterpillar D9, for earthmoving, clearing terrain obstacles, opening routes, detonating explosive charges and demolishing structures whilst under fire. The extensive use of armoured bulldozers during the Second Intifada drew controversy and criticism from human rights organizations while military experts saw it as a key factor in reducing IDF casualties.
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. This has also been done by civilians with a dispute with the authorities, such as Marvin Heemeyer to then demolish government buildings.
Education
The National Association of Heavy Equipment Training Schools (NAHETS), established 2002, uses practical tests and theory training schools as a method to teach bulldozer users safe and practical operational skills.
Uses
Bulldozers can be found on a wide range of small scale and large construction sites, mines and quarries, military bases, heavy industry factories, and large governmental and public Engineering projects as welll as farming.
See also
Derivative word uses
- The "Bulldozer" is a popular mixed drink consisting of one shot of Jägermeister and a half can of Red Bull. The drink is also known as a "Jäger Bomb".
- The is a tropical sea shrimp so named because it spends much of its time pushing sand out of the hole in which it stays.
- Tracked Loaders (also known as Crawler Loaders) are sometimes incorrectly referred to as bulldozers because of the similarity in design.
External links
- (Short illustrated explanations, with flash animations, fit for kids)
- Further information about working bulldozers
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- - Russian bulldozer
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