Abstract: A variable power transmission mechanism including a first disc rotatable about a first axis and having a flat surface perpendicular to the first axis, a second disc rotatable about a second axis and providing a flat surface perpendicular to the second axis, apparatus positioning the first and second discs in spaced apposition so that the flat surfaces define planes intersecting at an acute dihedral angle and including a ratio varying arrangement for causing displacement between the discs in a direction aligned with the vertex of the dihedral angle, a ball which makes contact with the surfaces along circles concentric with the respective axes and is resiliently urged toward the vertex of the dihedral angle, a guide for causing displacement of the ball in a direction aligned with the vertex, and an interconnection between the ratio varying arrangement and the ball guide for causing displacement of the latter simultaneously with and proportional to displacement between the discs.