Hydromechanical Transmissions as Applied to Mobile Equipment

A direct hydrostatic transmission was tested in a grader in 1961 and 1962. Certain difficulties experienced led to the development in 1963 of a novel hydromechanical transmission using the same pump and motor units. Fifty graders using this new hydromechanical transmission have been placed in service since 1964. Some of these transmissions have now recorded over 8000 hr operation in the field. The development and operating principles of the new transmission are described.