Power train or transmission

A power train variable from substantially a 1:1 ratio to a higher ratio, comprising a driving member and a driven member, a pair of planetary gear assemblies, each including a sun gear, a ring gear and a planetary carrier having at least one planetary gear operatively connecting the associated ring and sun gears, said gear assemblies having different gear ratios, both planetary assemblies having their sun gears rotatable by said driving member, said driven member being operatively connected to the planetary carrier of one of said assemblies, means connecting said ring gears for rotation as a unit, and means for selectively rotating the planetary carrier of the other of said assemblies at desired speeds with respect to the driving member, whereby the overall ratio between the driving and driven members is variable in dependence upon the relative speeds of said driving member and said planetary carrier of said other of said assemblies.