Bridging the gap

A new continuously variable transmission system that allows an engine to operate at its most efficient speed is the first to bridge the gap between hybrid and nonhybrid vehicles, its UK developer claims.

Created by London engineering start-up Nexxtdrive, the DualDrive system takes power from a vehicle’s engine and splits it between a mechanical drive path through an epicyclic gear train, and an electrical path through two generator/motors. The gear train is then used to combine the motion from the engine and power from electric motors.

While the majority of power is transferred through the gearbox, the electrical power path is used to precisely control the speed and torque of the transmission’s output shaft. This according, to the systems’ developer, makes it extremely efficient.

Movable arm Epicyclic, or planetary, gear trains typically consist of a number of outer ‘planet’ gears that rotate about a central ‘sun gear’. The gears are mounted on a movable arm, which can also rotate relative to the sun gear. This means that epicyclic gear trains are very useful for combining power from different sources and splitting power from different outputs.