This combination of qualities means that bulldozers are often used in situations that require powerful, mobile and stable major earth moving capabilities. A second type of bulldozer is the wheeled and articulated model. These will generally have four-wheel drive and an articulated steering system, with the blade mounted to the front of a hydraulically actuated articulation joint.
The bulldozer\'s main weapon is the blade and this comes in a number of configurations. An S, or straight, blade is straight and short with no curve or side wings. It is usually used for fine grading work. The U, or universal blade, is tall and curved with extensive side wings, which means it can move more material. There is also a combination, SU blade, with a slight curve and short wings, which is often used in quarrying applications.
The bulldozer has a long history, initially being an adaptation of a ploughing tractor and patented as a tractor attachment by two American inventors in 1923. Caterpillar was an early adopter of the technology, and the design was soon altered so that the bulldozer was to become a distinct machine in itself.