Hyundai and Kia present a new powertrain for electric cars. The main components move to the wheel hub

While car manufacturing is slowly but surely moving towards an all-electric future, many design processes and necessary mechanical components have changed and in many cases been minimised. However, one key component of internal combustion engine vehicles has remained relatively the same in the transition to electric vehicles – the powertrain.

Universal Wheel Drive drive system

In vehicles with an internal combustion engine, the power is transmitted from the engine through the gearbox and on to the wheels via drive shafts and CV joints. In electric cars, the engine and gearbox are replaced by an electric motor and a reduction gearbox, but the way the power is transferred to the wheels is still the same.

Electric motors are more compact and, in combination with flat platforms, have made it possible to obtain much more interior space with the same vehicle footprint compared to cars powered by an internal combustion engine. However, the motors still take up space in the front and/or rear of the EV. Hyundai and Kia have introduced a new powertrain solution that can create even more space while maintaining the efficiency necessary for effective range.

Kia and Hyundai shared details regarding the new Uni Wheel technology in a press release following Wednesday’s Tech Day event. The Uni Wheel system is described by its creators as “paradigm-changing vehicle propulsion system”. The main idea is moving the main components of the drivetrain to the free space in the wheel hub of the electric car.

It’s not new, but it’s unique

It should be added that this is not a completely new approach – other manufacturers of passenger electric cars, such as Lordstown Motors, have also tried in-hub motors, but failed (and, in the case of Lordstown Motors, went bankrupt). A similar approach is also being taken by start-up companies specializing in commercial electric vehicle technology, such as REE Automotive with its patented REEcorners.

For its Uni Wheel system, Hyundai has chosen a similar, but unique solution in its own way, which uses a special planetary gearbox consisting of a central gear in the middle, four gears on each side, and an outer gear which surrounds the whole.

Traditional internal combustion vehicles use CV joints, but moving them closer to the wheels during driving requires shortening the length of the drive train and, as a result, reducing efficiency and durability – especially on rough terrain. In contrast, the Uni Wheel system can transmit power with almost zero change in efficiency regardless of wheel movement.

More space in the interior

“The power generated by the electric motor is transmitted to the central gear, which then engages the pinions and turns the outer gear. It is connected to the wheel and drives the vehicle. The pinions of the Uni Wheel are interconnected and form two linkages and this one the multi-element mechanism enables multi-axis movement of the wheel A Uni Wheel that offers a wide range of motion.” describes in the Kia press release.

The result is more space on the platform and thus more space in the interior of the electric car, including luggage compartments. The technology also opens the door to wider possibilities for unconventional seating arrangements in the cabin, which could prove beneficial as autonomous driving technologies are further developed and integrated.

Hyundai and Kia state that for the future they plan to continue improving the Uni Wheel systemso that customers can enjoy mobility “in a completely different and new way”. The timeline for when we’ll see this system integrated into an actual electric car remains unclear at this point, but the two automakers say they’ve already applied for eight patents related to the technology in South Korea, the U.S. and Europe.