After 1950s, the truck's tonnage increased. In 1951, he released the world's largest Euclid-1LLD dump truck with a capacity of 50 tons. The vehicle adopts three axle and 10 wheel chassis and carries two Cummins diesel engines with a total power of 375 horsepower. The heavy-duty dump truck has greatly improved the mining efficiency of open pit mines. However, most of the open mines are rewinding ramps, and the running cost of diesel trucks is relatively high. In order to improve the economy of heavy truck's ramp transportation, the electric wheel truck came into being. American engineering machinery legend Redono (R.G.LeTourneau) proposed the idea of a diesel engine power multi wheel drive. Each wheel is driven by an independent motor, which can improve its traction by assigning engine power to each wheel, which is similar to the concept of a railway vehicle at that time, but only steel. The wheels changed into rubber tires.
In 1958, Berkeley copper mine in Montana asked the company to provide vehicle transportation plan. Two years later, Retorno modified a TR-60 articulated electric dump truck. The car's load was 60 short tons, and a 335 horsepower Cummins diesel engine was installed. In the test, it was found that the power was insufficient when the electric power line was separated and then changed to double engine. The power of the engine was doubled and the load was raised to 75 short tons. Diesel electric wheeled vehicle is free from the shackles of electric overhead lines and can better meet the needs of mine transportation, so it has been widely applied.
In 1963, the US Unit Rege (Unit Rig) Co operated with GE company to start mass production of M85 type 77 ton (85 short ton) electric wheel dump truck. Unit Rege was founded in 1935, the founder of four oil traders, then the main production of drilling equipment. During World War II, the company produced a large number of military products. In January 1960, uni rig launched the first electric wheel truck, which was a great success in the market. As of 1983, the company's representative Mark36 (154 tons) electric wheel vehicle sales amounted to 783 units. In 1988, he joined the TEREX group in the United States; by 1998, he bought O&K in Germany and merged it with as a major branch of the group. Unit Rege's current product line mainly consists of a series of mine dump trucks and live bottom unloading trucks, whose total sales volume exceeds 4500 units.
