A grader, also commonly referred to as a road grader, motor grader, or simply a blade, is a form of heavy equipment with a long blade used to create a flat surface during grading. Although the earliest models were towed behind horses, and later tractors, most modern graders are self-propelled and thus technically "motor graders". Typical graders have three axles, with the steering wheels in front, followed by the grading blade, then a cab and engine atop tandem rear axles. Some graders also have front wheel drive for improved performance. Some graders have optional rear attachments, such as a ripper, scarifier, or compactor. A blade forward of the front axle may also be added. For snowplowing and some dirt grading operations, a main blade extension can also be mounted. Capacities range from a blade width of 2.50 to 7.30 m and engines from 93–373 kW. Certain graders can operate multiple attachments, or be designed for specialized tasks like underground mining.
Function
In civil engineering, "rough grading" is performed by heavy equipment or engineering vehicles such as scrapers and bulldozers. Graders are used to "finish grade". The angle, tilt and height of the grader's blade can be adjusted to achieve a high level of precision. Graders are commonly used in the construction and maintenance of dirt roads and gravel roads. In constructing paved roads, they prepare a wife flat base course for the final road surface. Graders are also used to set native soil or gravelfoundation pads to finish grade prior to the construction of large buildings. Graders can produce canted surfaces for drainage or safety. In some countries they are used to produce drainage ditches with shallow V-shaped cross-sections on either side of highways. Steering is via a steering wheel or joystick controlling the angle of the front wheels, but many models also allow frame articulation between the front and rear axles, which allows a smaller turning radius in addition to allowing the operator to adjust articulation angle to aid in the efficiency of moving material. Other implement functions are typically hydraulically powered, and can be directly controlled by levers, or by joystick inputs or electronic switches controlling Electrohydraulic servo valves. A more recent innovation is the outfitting of graders with grade control technologies, such as those manufactured by Topcon Positioning Systems, Inc., Trimble Navigation, Leica Geosystems or Mikrofyn for precise grade control and "stakeless" construction. Manufacturers such as Deere have also began to integrate these technologies during construction.
History
Early graders were drawn by people and draft animals. The era of motorization by traction engines, steam tractors, motor trucks, and tractors saw such towed graders grow in size and productivity. The first self-propelled grader was made in 1920 by the Russell Grader Manufacturing Company, which called it the Russell Motor Hi-Way Patrol. These early graders were created by adding the grader blade as an attachment to a generalist tractor unit. After purchasing the company in 1928, Caterpillar went on to truly integrate the tractor and grader into one design—at the same time replacing crawler tracks with wheels to yield the first rubber-tire self-propelled grader, the Caterpillar Auto Patrol, released in 1931.
Regional uses
In addition to their use in road construction, graders may also be used to perform roughly equivalent work. In some locales such as Northern Europe, Canada, and places in the United States, graders are often used in municipal and residential snow removal. In scrubland and grassland areas of Australia and Africa, graders are often an essential piece of equipment on ranches, large farms, and plantations to make dirt tracks where the absence of rocks and trees means bulldozers are not required.
