A theoretical study has been made to determine the rigidity and performance of a helicopter gearbox with a cantilevered housing and two taper roller bearings. Due to the interaction of the deflection of all component parts such as gears, shafts, bearings, casings, spacers, etc., it was necessary to consider these in combination rather than individually. A computer program has been developed for analyzing a typical helicopter type input pinion assembly in which the pinion is supported by a pair of taper roller bearings. This program is suitable for determining the influence that various factors exert on the rigidity of the pinion and the performance of the bearings and which would be difficult to consider by other means. Typically the influence of endfloat or preload, misalignment of the races, casing and shaft deflection, wall thickness of the casing and the hollow shaft, and the spacing between bearings are all considered. The program is now being used as a basis for design optimization in terms of bearing lives and pinion stiffness.

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