Design analysis of Pericyclic Mechanical Transmission system

The Pericyclic Mechanical Transmission (PMT) system is a high reduction ratio, high tooth contact ratio, and nutating/rotating gear mechanism which incorporates meshing conjugate face-gear pairs. The PMT kinematics, gear tooth load capacity, bearing load capacity, and mesh efficiency are investigated in this paper. The gear train kinematics and the reduction ratio formulas are identified initially. The tooth load capacities of the meshing conjugate face-gear pairs are calculated analytically as a function of gear tooth loads and dimensions. The dynamics of the nutating gear and the overturning moments produced by nutation are formulated. The effect of gear mesh loads and overturning moment on the bearing load capacity is investigated based on the Hertzian contact stress of the most heavily loaded rolling element. PMT mesh efficiency is first estimated based on Elastohydrodynamic Lubrication (EHL) theory. Then, an analytical formula is developed to approximate the mesh efficiency without lengthy EHL computations. Finally, 760 HP level helicopter transmission design spaces are investigated at different reduction ratios. The PMT system shows substantial gear weight improvement without sacrificing efficiency.