Off-highway vehicles

Abstract

Industrial, agricultural, and military vehicles are classified as "off-highway vehicles"; the class includes tractors, ore trucks, scrapers, and military tanks. These vehicles have prime movers in the 100-to-1000- and-higher horsepower range, generally have top speeds up to 35 mi/h, and operate from low speed at the traction limit to maximum speed over a wide constant-horsepower range. To date, diesel enghtes with gear-shift and torque-converter transmissions have been used. Now, however, the gas turbine has become attractive because of its low weight and bulk per horsepower, particularly for those vehicles whose performance can be raised with higher power. An electric drive system is well suited to a gas turbine prime mover as a means for utilizing the high turbine speed, for handling the large horsepower, and for distributing power to many wheels. On some special heavy vehicles, dc drive systems, patterned after diesel-electric locomotives, are used. Several ac systems using solid-state converters and induction wheel motors have been built experimentally for military vehicles. When all factors are considered, it appears that the combination of the gas turbine and an ac electric drive will become the heavy off-highway vehicle drive system of the future.