Courtesy of Hyundai

Behold The Hyundai Uni Wheel. Transportation May Never Be The Same

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Since the early days of the automobile, there have been some inventions that fundamentally changed the driving experience. The self starter, the automatic transmission, front wheel drive, and electronic fuel injection are a few examples that come to mind. Air conditioning and touchscreens didn’t alter how cars drove but did revolutionize the driving experience. Now Hyundai has created the Uni Wheel, a device that not only transmits power to a wheel more efficiently, it also saves space within the structure of a vehicle — space that can be used for other things, like more battery capacity, more cargo space, or more room for passengers to stretch their legs.

Of Differentials And CV Joints

The Hyundai Uni Wheel is fiendishly clever. It is also fiendishly difficult to describe accurately. What it does is move the drive reduction gear and flexible driveshaft components known as constant velocity joints inside the wheel. So it’s not an in-wheel motor, as such, but functions very much like one without adding the weight of the motor to the wheel.

Let’s start with one of the basic dilemmas that has confronted automotive engineers since the very beginning. When a rear wheel drive car goes around a corner, the outside wheel travels a slightly longer distance than the inside wheel. A direct mechanical connection between the two would put stress on the rear axle, stress that might lead to premature failure. The more power transmitted, the more stress created and the higher the failure rate.

To compensate, engineers created the differential, a device that only sends power to one wheel so the other can turn freely in corners. For decades, most cars and trucks had what essentially was one wheel drive, thanks to the compromises the differential required. That led to the invention of more complicated devices known as limited slip differentials, or posi-traction in marketing terms.

Then came front wheel drive cars. They had the motor, a differential, and two drive axles sending power to the front wheels. So far, so good. But front wheels have to be able to steer and absorb bumps as well as move a car forward. To make that possible, those drive axles need flexible joints in them.

But those joints have the same mechanical challenges as the rear axles of early cars did. When they flex, some parts have to travel a slightly longer distance than other parts, putting stress on the drivetrain, stress that can lead to failure. The answer was the constant velocity joint, a device that allows each driveshaft to bend while allowing a smooth flow of power to the wheels.

For 50 years, CV joints have done what they were designed to do and have gone from being troublesome things that needed constant replacement to reliable devices that can last for 100,000 miles or more. They are used by every vehicle that sends power to the front wheels from the cheapest sedan to the most expensive all wheel drive sports cars.

The Hyundai Uni Wheel Explained

Courtesy of Hyundai

Hyundai engineers wondered if there might not be a better way, and so they started tinkering with ideas. Eventually they came up with the Uni Wheel, a devilishly clever device that replaces the CV joint completely and heralds a new era in which each wheel has its own motor.

They say a picture is worth a thousand words but in this case a video is worth 10,000 words. And so, without further ado, here is the Hyundai Uni Wheel video that explains it all.

Hyundai Uni Wheel Introduced

In a press release, Jongsool Park, Senior Fellow at the Institute of Advanced Technology Development of Hyundai Motor Group said, “We are pleased to showcase innovative ideas that could become game changers in the future mobility market. We will perfect the technology so that customers can experience mobility in a completely different and new way.”

The press statement went on to say a conventional drive system using a regular CV joint suffers from a decrease in efficiency and durability as the angle of drive shaft deflection increases when travelling over bumpy, undulating surfaces. Uni Wheel can transmit power with almost no change to efficiency regardless of wheel movement, ensuring high durability and ride comfort.

When combined with electronic air suspension that can adjust ride height according to the driving situation, this can be increased to stabilize the vehicle on rough roads, or decreased for high speed driving to improve power and stability.

By moving the reduction gear to the wheel hub, Uni Wheel’s high reduction ratio delivers a significant torque output and allows for a more compact electric motor. With independent control of up to four efficient electric drive units, Uni Wheel also allows for unprecedented levels of torque vectoring to boost dynamic ability and deliver high levels of steering and driving stability.

The Takeaway

When I watched that video, it reminded me of when my parents took me to the Boston Museum of Science when I was a young boy. I was fascinated by mechanical things as a lad. My favorite toy was a plastic model of an internal combustion engine that showed the pistons going up and down in the cylinders and turning the crankshaft. The coolest part was a small red light that came on in the top of each cylinder when it was time for each spark plug to fire.

At the Museum of Science there was a wall of gears. Some were square and some were oblong, but they all worked just fine when you turned the crank that made them move. Watching that video reminded me of that wall of gears. I can’t explain how the Uni Wheel works in words but when I watch the video it all makes sense to me.

The explanation is very well done but what really got my attention was at the end when the video explores some of the innovations in mobility the Uni Wheel could make possible. The press release makes reference to so-called purpose built vehicles. Hyundai has recently started production at a specialized factory in Singapore that is specifically designed to manufacture such purpose built vehicles — cars and trucks that would be built in small numbers to fit a particular purpose. Hyundai also announced recently it will start selling cars online with Amazon. While other companies are whining about lower EV sales, Hyundai is busy innovating to get ready for the future.

Efficiency is the Holy Grail for electric vehicles. We simply can’t afford to continue wasting nearly three quarters of the energy in a gallon of gasoline. Anything that makes an EV more efficient is welcome news for our rapidly heating planet. The engineers at Hyundai deserve a lot of credit for thinking outside the CV joint.


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Steve Hanley

Steve writes about the interface between technology and sustainability from his home in Florida or anywhere else The Force may lead him. He is proud to be "woke" and doesn't really give a damn why the glass broke. He believes passionately in what Socrates said 3000 years ago: "The secret to change is to focus all of your energy not on fighting the old but on building the new."

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