The report presents applicable helicopter and harmonic drive parameters, feasibility comparisons, data concerning the engineering and designing of a test unit, results of the test program, and recommendations for further research for improved efficiency. As a result of preliminary studies, parametric analysis, and actual testing of a harmonic drive unit designed for 250 horsepower at 30,000 r.p.m. input speed with 85:1 reduction ratio, it is concluded that: (1) from the standpoints of compactness, quietness, vibration level, simplicity, reliability, and cost, harmonic drive appears to be not only feasible but superior to conventional planetary gearing, and (2) in the present state of the art, power losses associated with the hydrodynamic wave generator bearing result in significantly lower efficiency than conventional gearing.

"May 1964." "Contract DA 44-177-TC-716." "Task 1D121401D14414."