Motor graders come in all sizes, with the largest currently being the Caterpillar 24-H, weighing nearly 137,000 pounds with a 24-foot moldboard. But several large noteworthy motor graders preceded Cat's machine.
In 1975, Dominion Road Machinery, later called Champion Road Machinery, introduced the world's largest production-model grader, the 80-T, which later became the 100-T. It was powered by a 700-hp Cummins engine and had an operating weight of 202,000 pounds. Like Cat's 24-H, it carried a 24-foot moldboard. Intended for use in surface mines to maintain haul roads or to reclaim large expanses of land, the 100-T was offered for some 14 years, but few were sold.
RayGo Inc., best known for its compactors, ventured into the super grader market in 1969 with the introduction of the RayGo Giant. Weighing 53 tons, it featured double articulation and GM 318-hp engines at both ends, each driving a single axle. Although it was suitable for heavy-duty leveling and reclamation of surface mines, its blade was fixed to the central frame instead of the usual circle mounting. The operator's cab was mounted on the rear frame and suspended over the rear articulated joint, giving the operator a panoramic view of the blade and the front power unit. CMI purchased RayGo in 1985. Rights to RayGo products passed to Caterpillar in 1987.
The same year that RayGo came out with the Giant, CMI introduced the Autoblade. It, too, was a double-articulated unit with a power module at each end consisting of a 225-hp engine driving four wheels through hydrostatic drive. Measuring 40 feet alone, the Autoblade had a cab module that could swing 180 degrees, so the operator could face the direction of travel. CMI promoted the machine as a precision grader, suitable for fine grading. The 65,000-pound machine could be guided in both alignment and grade from a fixed stringline attached to pins on the ground.
Other good-size motor graders were built by Galion and O&K. The Galion T-700 was introduced in 1955 and incorporated the new "Grade-O-Matic" control system consisting of a torque converter drive and powershift transmission. The biggest grader of its day, the T-700 weighed 40,000 pounds. The O&K machine, the G-350, weighed 90,000 pounds yet had all the blade movements of a smaller grader.
The prize for the largest motor grader ever built goes to an Italian contractor named Umberto Acco around 1980. This one-of-a-kind grader had a 1,000-hp engine in the rear and a 700-hp unit up front to push the 33-foot blade, using traction from the machine's 12 tires.
Information taken from "Giant Earthmovers" and "Colossal Earth-movers," both written by Keith Haddock and published by MBI Publishing. If you are interested in historical equipment, consider a membership in the Historical Construction Equipment Association. Visit its website at www.hcea.net.