Bulldozer
A bulldozer is a very powerful crawler (caterpillar tracked tractor) equipped with a blade. The term "bulldozer" is often used to mean any heavy engineering vehicle, but precisely, the term refers only to a tractor (usually tracked) fitted with a dozer blade. That is the meaning used herein.
History
The first bulldozers were adapted from farm Holt tractors that were used to plough fields. Their versatility insoft ground for logging and road building, lead directly to them becoming the armoured tank in the first war.
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 thick 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 specialised 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-1930's, and the addition of powered down force made them the preferred excavation machine for large and small contractors alike by the 1940's, by which time the term "bulldozer" referred to the entire machine and not just the attachment.
Over the years, when engineers needed equipment to complete large scale earthworks, firms like the CAT, Komatsu, Fiat-Allis, John Deere, International Harvester, Case, Liebherr, Terex and JCB started to manufacture large tracked-type earthmoving machines. They were large, noisy, and powerful, and therefore nicknamed "bulldozer".
Through the years, bulldozers got bigger, more powerful, and more sophisticated. 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 a rear ripper claw to loosen rocky soils or to break up pavement (roads).
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.
History of the word
- 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.
- 1886: "bulldozer" meant a large-caliber pistol and the person who wielded it.
- Late 1800s: "bulldozing" meant using big force to push over or through any obstacle.
- Later: applied to the vehicle.
These appeared as early as 1929, but were known as "bull grader" blades, the term "bulldozer blade" does not appear to come into widespread use until the mid 1930's and now refers to the whole machine not just the attachment.
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 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.
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) or in groups or 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 very best land in the California wine country consists of old lava flows: with heavy bulldozers such as the Caterpillar D9 and the Caterpillar D11 the lava is shattered allowing practical agriculture for the wine industry. Also, hard earth can be ripped and decompacted to allow planting of orchards which otherwise could not grow on the land.
Blade
The bulldozer blade is a piece of heavy metal plate, installed on the front of the tractor, with the aim of pushing things, handle rough obstacles and shoving sand, dirt and debris. The dozer blade on front of the tractor usually comes in 3 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.
Modifications
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: see the image at this link and this link.
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.
Uses
Bulldozers can be found on large and small scale construction sites, mines, roadsides, military bases, heavy industry factories, and large governmental projects.
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 most famous armored bulldozer is probably the IDF Caterpillar D9, used by the Israeli Defense Forces for detonating explosive charges and demolishing structures under fire. Caterpillar does not make nor install the armor—that is entirely the work of the IDF. However, various users including the US military buy armor kits from the IDF and fit them onto their own D9s. The design varies but the armor kit on average adds 10 tonnes to the weight of the bulldozer, which weighs about 49 tonnes without the armor.
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. See: Marvin Heemeyer, 'Killdozer'.
See also
- Killdozer
- Engineering vehicle
- Grader
- Front loader
- Caterpillar D9
- Caterpillar 60
- Caterpillar D6
- Caterpillar D11
- Caterpillar Inc.
- Civil Engineering
- Benjamin Holt
- Komatsu D-475
- Tractor
- Backhoe
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 bulldozer shrimp is a tropical sea shrimp so named because it spends much of its time pushing sand out of its hole.
- Tracked Loaders (also known as Crawler Loaders) are sometimes incorrectly referred to as bulldozers because of the similarity in design.
External links
- Construction Equipment and Methods Photographs
- Construction Vehicles Reference CD
- The mechanism of a bulldozer (Short illustrated explanation, with GIF animations, fit for kids)
- Quick Reference Equipment Specs
- German page with photos of engineering vehicles: bulldozers, graders, etc
- Van Naatta Bulldozers
- Configure a Caterpillar Bulldozer - from the official website
- Pictures and photographs
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