Abstract
Examination of the operational requirements of agricultural tractors, combine harvesters, loading shovels, road rollers, dumper trucks, etc., and a comparison of the characteristics of various transmissions, shows that the hydrostatic type provides a stepless range of ratios which allows vehicles to operate with advantage relative to other transmission systems. Experimental work has proceeded over a number of years on two alternative systems: (1) hydraulic motors mounted in the wheels fed by an engine driven pump and giving maximum vehicle design freedom; and (2) an integrated pump and motor system driving into the conventional rear axle (gearbox replacement). These units are described and the relative operating characteristics have been established. The method of control of the transmission can have a major effect on work output, and field work in conjunction with the N.I.A.E. has been used to establish control requirements. Extensive field testing with agricultural tractors and other vehicles has shown the improvements in work rate and work quality that are obtainable, together with reliability and life characteristics.
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