A drive system for a tiltrotor aircraft includes a first gearbox rotatably mounted to the airframe and rotatable about a longitudinal axis to operate the tiltrotor aircraft between helicopter and airplane modes. A second gearbox extends generally normal to the longitudinal axis of the first gearbox. A common shaft, rotatable about the longitudinal axis, transfers torque from an output gear of the second gearbox to an input gear of the first gearbox. A support assembly couples the second gearbox to the airframe and includes a fixed joint proximate the longitudinal axis, a first directional reacting joint remote from the longitudinal axis providing a first radial growth degree of freedom to the second gearbox and a second directional reacting joint remote from the longitudinal axis providing a second radial growth degree of freedom to the second gearbox that is not parallel with the first radial growth degree of freedom.

An involute gear bracket system includes first and second involute gears. Each includes a circular base and a plurality of gear teeth extending outward from an outer region of a surface and evenly spaced apart from each other along a plurality of locations on the outer region of the surface. The shape of each gear tooth is defined by a varying cross-sectional involute profile, wherein starting from a first involute profile that is in a plane parallel to the surface of the circular base and extending outward from a center of the circular base, each location on the first involute profile is rotated about a corresponding axis while traversing a path defined by a corresponding imaginary ray extending from the center of the circular base to that location, the corresponding axis being tangential to an imaginary circle that encompasses the inner region of the surface and perpendicular to the corresponding imaginary ray. A first bracket is coupled to a first pivot located at a first distance from the central axis of the first involute gear. A second bracket is coupled to a second pivot and rotatable about the second pivot at least within a second range of angles. The first and second pivots are arranged relative to each other and relative to the central axes of the first and second involute gears, respectively, such that the gear tooth of the first involute gear meshes with the gear tooth of the second involute gear at a corresponding angle within a second range of angles.

An involute gear is disclosed. A circular base has a surface that includes an inner region and an outer region. A gear tooth extends outward from the outer region of the surface. A shape of the gear tooth is defined by a varying cross-sectional involute profile. Starting from a first involute profile that is in a plane parallel to the surface of the circular base and extending outward from a center of the circular base, each location on the first involute profile is rotated about a corresponding axis while traversing a path defined by a corresponding imaginary ray extending from the center of the circular base to that location in the first involute profile. The corresponding axis is tangential to an imaginary circle that encompasses the inner region of the surface and is perpendicular to the corresponding imaginary ray

A universal driving device includes a ring gear, a sun gear having a variable inter-axis distance with respect to a rotation shaft of the ring gear, a gear train including a series of gears configured to connect the sun gear and the ring gear, link mechanisms configured to accommodate a change in an inter-axis distance between the sun gear and the ring gear and rotatably connected with respect to each other to continuously maintain a power transmission state between the sun gear and the ring gear, a carrier configured to support a rotation shaft of a final gear engaged with the ring gear, among the gears constituting the gear train, a sun gear bearing positioned between the rotation shaft of the sun gear and each of the link mechanisms, and a sleeve positioned between the sun gear bearing and each of the link mechanisms.

An adjustable idler gear assembly comprises an idler gear that meshes with a mating gear and is driven to rotate by a pinion directly or indirectly via at least one intermediate gear, and an idler positioning body having an idler gear shaft with which the idler gear is rotationally coupled. The idler positioning body is configured to change a position of the idler gear shaft along a circular path at a range of distances from an axis of rotation of the pinion to selectively engage and disengage from being driven by the pinion while maintaining a consistent mesh with the mating gear.