Editing Bulldozer (section)

== History ==
[[File:Cat45-mojave.jpg|thumb|alt=A train of over fifteen wagons crossing the desert, a flat sandy expanse with scrub-like bushes and a mountain range in the distance.|Two [[Holt tractor|Holt 45]] gas [[Continuous track|crawling-type]] tractors team up to pull a long wagon train in the [[Mojave Desert]] during construction of the [[Los Angeles Aqueduct]] in 1909.]]
[[File:Fiat Allis 41B Dozer.jpg|thumb|Heavy 1970s bulldozer [[Fiat Allis]] 41-B, the largest of its day]]

The first bulldozers were adapted from [[Holt Manufacturing Company|Holt]] farm tractors that were used to plough fields. The versatility of tractors in soft ground for logging and road building contributed to the development of the armored [[tank]] in [[World War I]].

In 1923, farmer James Cummings and draftsman J. Earl McLeod made the first designs for the bulldozer. A replica is on display at the city park in [[Morrowville, Kansas]], where the two built the first bulldozer.<ref>{{cite book|url=https://books.google.com/books?id=OZVrxulVBtoC&q=James+Cummings+J.+Earl+McLeod+bulldozer&pg=PA189 |title=Kansas Curiosities: Quirky Characters, Roadside Oddities & Other Offbeat Stuff|isbn=9780762765799|access-date=2012-04-01|last1=Grout|first1=Pam|date=15 June 2010|publisher=Rowman & Littlefield }}</ref> On December 18, 1923, Cummings and McLeod filed U.S. patent #1,522,378 that was later issued on January 6, 1925, for an "Attachment for Tractors."<ref>[https://patents.google.com/patent/US1522378?oq=1522378 Patent 1522378, Attachment For Tractors, John E McLeod and James D Cummings, Filed December 18, 1923.]</ref>

By the 1920s, tracked vehicles became common, particularly the [[Caterpillar 60]]. Rubber-tired vehicles came into use in the 1940s. To dig [[canal]]s, raise earthen [[dam]]s, and do other earth-moving jobs, these tractors were equipped with a large, thick, metal plate in front. (The blade got its curved shape later). In some early models, the driver sat on top in the open without a cabin. The three main types of bulldozer blades are a U-blade for pushing and carrying soil relatively long distances, a straight blade for "knocking down" and spreading piles of soil, and a brush [[Rake (tool)|rake]] for removing brush and roots. These attachments (home-built or built 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. The addition of power down-force provided by hydraulic cylinders instead of just the weight of the blade 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 (engineering)|earthworks]]. Firms such as [[Caterpillar Inc.|Caterpillar]], [[Komatsu Limited|Komatsu]], [[Clark Equipment Company|Clark Equipment Co]], [[Case CE|Case]], [[Euclid Trucks|Euclid]],<ref>{{cite web|last=Haddock|first=Keith|title=Euclid-General Motors' Crawler Tractor|url=http://pendergast.ca/antiqueengine/euclid.htm|publisher=PEI Tractor Club|access-date=11 September 2011|url-status=dead|archive-url=https://web.archive.org/web/20120319094927/http://pendergast.ca/antiqueengine/euclid.htm|archive-date=19 March 2012}}</ref> [[Allis Chalmers]], [[Liebherr]], [[LiuGong Construction Machinery, LLC.|LiuGong]], [[Terex]], [[Fiat-Allis]], [[Deere & Company|John Deere]], [[Massey Ferguson]], [[BEML]], XGMA, and [[International Harvester]] manufactured large, tracked-type earthmoving machines. [[R.G. LeTourneau]] and Caterpillar manufactured large, rubber-tired bulldozers.

Bulldozers grew more sophisticated as time passed. Improvements include drivetrains analogous to (in automobiles) an [[automatic transmission]] instead of a manual transmission, such as the early Euclid C-6 and TC-12 or Model C Tournadozer, blade movement controlled by [[Hydraulics|hydraulic]] cylinders or electric motors instead of early models' cable winch/brake, and automatic grade control. Hydraulic cylinders enabled the application of down force, more precise manipulation of the blade, and automated controls.

A more recent innovation is the outfitting of bulldozers with [[GPS]] technology, such as manufactured by [[Topcon]] Positioning Systems, Inc., [[Trimble Inc]], or [[Leica Geosystems]], for precise grade control and (potentially) "stakeless" construction. As a response to the many, and often varying claims about these systems, the Kellogg Report<ref>The Kellogg Report LLC (2010). Article: The Kellogg Report. Retrieved December 15, 2010 from [https://web.archive.org/web/20110111000139/http://www.kelloggreport.com/index.html kelloggreport.com]</ref> published in 2010 a detailed comparison of all the manufacturers' systems, evaluating more than 200 features for dozers alone.

The best-known maker of bulldozers is Caterpillar. Komatsu, Liebherr, Case, [[Hitachi Construction Machinery|Hitachi]], [[Volvo Construction Equipment|Volvo]], and John Deere are present-day competitors. 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 worldwide. The best-known model, the [[Caterpillar D9]], was also used to clear [[Landmines|mine]]s and [[demolition|demolish]] enemy structures.