(Article published in L’Automobile Mechanic magazine, February 2024)

By Piero Facchin

Hyundai Motor Company and Kia Corporation recently presented a potentially revolutionary approach to electric vehicle (EV) drivetrain design at the Uni Wheel Tech Day event in Seoul.

The Universal Wheel Drive system, or “Uni Wheel,” moves major components to the wheel hub, creating additional space in the passenger compartment. As the global mobility market evolves towards an all-electric future, many of the design techniques and mechanical components required have changed, or have been minimized.

However, one key element of internal combustion (ICE) powered vehicles has remained relatively unchanged in this transition: the transmission. The power created in ICE vehicles is transmitted from the engine to the transmission, and then to the wheels via drive shafts and constant velocity joints (CV joints). In electric vehicles (EVs), the motor and transmission are replaced by a motor and gearbox, but the method of transmitting power to the wheels remains the same.

Electric motors are more compact and, when combined with flat EV platforms, create more interior space, while the vehicle footprint remains the same as that of ICE cars. However, these engines still take up space at the front or rear of an electric vehicle.

Improved Efficiency 

In short, the system eliminates internal and external CV joints. As a result, it considerably shortens the drive shaft, offering greater efficiency at both ends of its course. To use it, individual electric motors are positioned close to the “Uni Wheel” assembly, requiring two motors per axle to operate. But these motors remain mounted on the chassis, eliminating the unsprung weight from another method of eliminating CV joints—wheel-mounted motors.

On the positive side, drive reduction is managed internally in the “Uni Wheel” system, enabling two functions to be combined within the same space (CV joint and drive reduction).

Greater Design Scope

The technology also opens the door to greater design opportunities for unconventional seating configurations in the cabin, which could prove fruitful as we continue to integrate more autonomous driving technologies into our vehicles.

Hyundai and Kia plan to keep perfecting the “Uni Wheel” system so that future customers can experience mobility in a “completely different and new way.” The timetable for integrating this system into a real EV remains uncertain at this stage, but the two automakers said they have already applied for eight patents related to this technology in South Korea, the USA and Europe.

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