Caterpillar D9



The Caterpillar D9 is a large track-type tractor designed and manufactured by Caterpillar Inc. It is usually sold as a bulldozer equipped with a detachable large blade and a rear ripper attachment.

The D9, with 354 kW (474 hp) of gross power and an operating weight of 49 tons, is in the upper end of Caterpillar's track-type tractors, which range in size from the D3 57 kW (77 hp), 8 tons, to the D11 698 kW (935 hp), 104 tons.

The size, durability, reliability, and low operating costs have made the D9 one of the most popular large track-type tractors in the world. The Komatsu D275A is one of its most direct competitors.

Engineering and technical description
The D9 is a series of heavy tracked-type tractors, propelled by Caterpillar tracks and usually used as bulldozers. The series began in 1954 with a prototype tractor called the D9X. Ten D9X prototype models were built in 1954. In 1955, the 286 hp D9 was introduced to compete against the more powerful Euclid TC-12. The D9 came equipped with a 1,473 cid D353 which powered the D9 right up until the 1980 introduction of the D9L. In 1956 the D9 had its engine power raised to 320 hp. The new 335 hp D9E replaced that model in 1959. Two years later, in 1961, the legendary 385 hp D9G was introduced, that remained in production for 13 years. Over its 13-year life the D9G became the main crawler on many job sites, testifying to its sturdiness and design.

In 1965, West Coast businessman Buster Peterson hooked up a pair of D9Gs to pushload the largest wheel tractor scrapers built. In 1986 Caterpillar bought the rights to this concept and thus the 770 hp DD9G was created (D stands for Dual D9G). Peterson also built the first SxS D9G which has two D9Gs side-by-side, pushing a 24 ft wide bulldozer blade.

In 1969, Caterpillar introduced this new SxS D9G. In 1974, the improved 410 hp D9H was introduced to replace the D9G. The D9H is still the more powerful conventional track-type tractor in company history. The DD9H and the SxsD9H would soon follow.

In 1980, the 460 hp D9L was introduced. The unit featured the same new type of elevated-sprocket undercarriage as was used in the larger D10. The D9L was the first variation of the D9 to employ elevated-drive-sprocket design in which the drive sprocket is elevated above the track, and not on the ground. The new undercarriage design reduced strain and shock loads on the final drives and gave the "belly pan" more ground clearance. The elevated-drive-sprocket undercarriage is a modular design. To repair the machines one breaks down the tracks and pulls the drive sprockets out. As a result, one can pull the powershift transmission out the rear. The 370 hp D9N replaced the D8L in 1987.

In 1988, Caterpillar produced their 25,000th elevated-drive-sprocket track-type tractor, a D9N. The 405 hp D9R replaced the D9N in 1996. The 410 hp D9T replaced the D9R in 2004. The D9T has a low-emissions ACERT diesel engine. The current model is the D9T; however, older models such as the D9R, D9N, and D9L are still commonly used. The L, N, R and T models of the D9 are visually very similar, differing primarily in the design of their internal systems.

The D9L was replaced by the 520 hp D10N in 1987. The 370 hp D9N replaced D8L in 1987. The main difference between the D9T and the D9R is the installment of the new Cat C18 ACERT engine. The D9L is the most powerful D9 in history, with a flywheel power of 460 hp. The D9L is also the heaviest D9 in history at 130,000 lbs.

The D9's primary working tools are the blade, affixed to the front and controlled by six hydraulic arms, and an optional ripper, which can be attached to the back. The blade is mainly intended for earthmoving and bulk material handling: pushing up sand, dirt, and rubble. It also can be used to push other heavy equipment such as earthmoving scraper pans, and in military applications, main battle tanks. The dozer blade usually comes in three variants: Like many other bulldozers, the D9 can be fitted with other devices such as mine plows.
 * 1) A Straight Blade ("S-Blade") which is short and has no lateral curve, 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) 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.

The rear ripper is intended for use in loosening rocky ground and ripping out larger stones. It can also break frozen ground and excavate small ditches. The ripper can be replaced with a multi-shank ripper, allowing the bulldozer to comb the ground.

The size, power and weight of the larger track-type tractors dictate that they are used primarily for major projects. The D9 is most commonly found in use in construction, forestry, mining, waste, and quarry operations.

Military applications


Caterpillar Inc. does not manufacture a military version of the D9 per se, but the attributes that make the D9 popular for major construction projects make it desirable for military applications as well, and in this role - with Israeli modifications and armor - it has been particularly effective for the Israel Defense Forces (IDF) and also used by KBR in Iraq.

The US Army used D9 bulldozers to clear forest in the Vietnam war but after the war they were replaced with smaller and cheaper Caterpillar D7G bulldozers. D7G dozers are still very common in US combat engineering battalions, but there is an series of oft-recurrent suggestions to replace the lighter D7Gs with the newer and more heavily armored D9s.