Abstract: A mechanically variable transmission is provided by a novel arrangement of sheaves in combination with a power ring which can be utilized with a planetary device to smoothly varying output speed from maximum rotational speed in one direction to maximum speed in the opposite direction while passing through or maintaining zero output speed or any other speed in a forward or reverse direction while the input speed is varied or remains constant. The novel arrangement provides changes in the output speed over the entire range of engine power and under all load conditions since declutching is not necessary to shift gears allowing the engine to operate at a constant horsepower over the entire range of throttle settings and can enhance engine efficiency by allowing the engine to operate at the lowest possible speed and highest torque.