This could be a game-changer.
The Hyundai Motor Group has unveiled the Universal Wheel Drive System (Uni-Wheel), a new wheel design that's claimed to revolutionize the design of future mobility products, particularly electric vehicles.
In a nutshell, the Uni-Wheel integrates an EV's reduction gear (its transmission) inside the hollow part of the wheel. It eliminates the need to engineer ways to package CV joints and drive shafts neatly while ensuring the motor can transmit power more efficiently to the wheel. So, by using the Uni-Wheel design, EVs may get more interior room and more space for batteries.
The Uni-Wheel compromises a special planetary gear configuration made out of a central "sun gear," orbited by four pinion gears and a ring gear. The power generated by an EV motor is sent to the sun gear, which turns the pinion gears, which then engages the outer ring gear.
As the Uni-Wheel system goes over road surfaces, the entire gear set is designed to move in various directions like a gyroscope, eliminating the need for traditional suspension systems and a conventional CV joint.
Apart from potentially making the brand's future EV models better packaged and more spacious, the Korean carmaker says it might also make EVs even more efficient. No details were provided regarding how much, but we suspect it cuts down on the power loss between the electric motor/s and the wheels.
This phenomenon is also seen in internal combustion engines, where an engine's output rating and dyno reading differ as the latter is measured at the wheels. For example, the Ford Mustang Dark Horse sends 428 horsepower to the wheels, lower than the official output of 500 hp on paper.
But due to the design of the Uni-Wheel, an EV's motors can likewise be placed nearer to the wheels. This shortens the length of the power transmission and may reduce driveline power losses.
While this sounds good in theory, the Uni-Wheel design raises plenty of questions. Does it need a specialized wheel design? Where will manufacturers mount the brakes? How will this affect car design as a whole? Can we expect future Kia and Hyundai vehicles like a theoretical second-gen Kia EV9 equipped with the Uni-Wheel to detract even more from typical car designs?
Hopefully, the Korean car giant can answer those questions soon, but as far as efficiency and packaging go, the new system appears promising.