The Caterpillar D7 is a medium bulldozer manufactured by Caterpillar Inc.. The first D7 appeared in 1938. The D7C came next in 1955. The D7D came in 1959. The 160 hp D7E in 1961. The 180 hp D7F 1969.The 200 hp D7G in 1974.The 215 hp D7H in 1986.The D7H was the first D7 to come with the exclusive elevated drive sprocket undercarriage.The D7R replaced the D7H in 1996, followed by the D7R Series 2. The electric drive D7E entered service in early 2009.
In March 2008, at Conexpo 2008 held every 3 years in Las Vegas, Caterpillar introduced the D7E. This 235 hp D7E comes with an electric drive system powered by a 537cid C9.3 diesel engine. The C9.3 powers a generator that turns out electricity that supplies power to a pair of AC drive motors. Compared to the Caterpillar D7R Series II, the D7E was projected to deliver 25 percent more material moved per gallon of fuel, 10 percent greater productivity and 10 percent lower lifetime operating costs.
The D7R Series II at 240 hp power and an operating weight of around 20 tons, is in the middle of Caterpillar's track-type tractors, which range in size from the D3 57 kW (77 hp), 7 t (8 short tons), to the D11 698 kW (935 hp), 112 t (124 short tons). It is primarily used to move material short distances or through challenging terrain. The vehicle is powerful, yet small and light (16 to 20 t (18 to 23 short tons) depending on configuration). This makes it ideal for working on very steep slopes, in forests, and for backfilling pipelines safely without risking damage to the pipe.
The US Army used armored D7G to clear mine fields and unarmored D7G and D7H for earthworks. The armor was developed by the Israel Military Industries (IMI). Later, the US Army developed a remote controlled version of the D7G for mine-clearing applications.
ARTICLES SOURCES : https://en.wikipedia.org/wiki/Caterpillar_D7