Power Split Device and Method

A power split device and method is disclosed. The variable ratio power split device, comprises: radially inner and outer races, each comprising at least two axially spaced parts; a plurality of planetary members arranged for rolling contact between the inner and outer races; a planet follower carrier engaging with the planetary members; a first rotatable power element spindle connected with the planet follower and operable to couple power between the planet follower carrier and a first power element; a second rotatable power element spindle connected with the inner race and operable to couple power between the inner race and a second power element; a third rotatable power element spindle connected with the outer race and operable to couple power between the outer race and a third power element; and means for adjusting an axial separation of the axially spaced parts of at least one of the races to vary a power split ratio between the first, second and third rotatable power element spindles. By adjusting the axial separation of one of the races, the ratio of power distributed between the power element spindles is varied which improves the operability of the device.