Just about every powertrain configuration has been offered in recent production vehicles except one: the wheel hub motor.It’s not been for lack of trying. General Motors early this century tinkered with a Chevrolet S-10 pickup powered by an electric motor in each wheel. The effort was abandoned when engineers couldn’t solve three problems: reducing unsprung weight, effectively sealing out the elements and maintaining a proper temperature.The technology has advanced since GM’s trial, and if all goes as planned, the four-wheel-drive Lordstown Endurance electric truck will introduce wheel hub motors a year from now.It will be the only truck without a transmission, axles, transfer case, driveshaft, U-joints or gears — saving about a thousand pounds.An Endurance engineering mule performed admirably during a brief ride, delivering smooth, torque-y acceleration and, from my perch in the passenger seat, reasonable performance.Lordstown Motors will build the wheel hub motors at an Ohio plant, but the design came from Slovenia’s Elaphe Propulsion Technologies, which has been working for a dozen years to solve riddles that have kept wheel hub motors on the sidelines.
Elaphe’s chief technology officer, Gorazd Gotovac, via phone from the company’s Ljubljana headquarters, shared how engineers have improved the wheel hub motor, starting with weight. Electric motors can be heavy. They often have a steel outer frame — similar to the crankcase on an internal combustion engine — and a steel rotor, magnets, bearings, copper windings and other parts. The frame on Elaphe’s motors is aluminum.Because a wheel hub motor is mounted outside the springs on the suspension system, the weight affects steering, handling and braking.”Our approach is a little bit different,” Gotovac said. “We developed an electromagnetic body that is very light and has a very small footprint, so not a lot of volume. It has a very high volumetric torque density. With that you solve a lot of things.” On the Endurance, each wheel — including motor, disc brakes and related parts — weighs about 74 pounds. That’s heavier than wheels on most vehicles, but manageable.The other big bogey is ensuring the electric motor seals out water, can take a pounding from potholes and runs cool under duress. For that, Gotovac said, Elaphe engineers are testing motors the old-fashioned way: in the real world. A lot can go wrong. The motors are liquid-cooled. And electric motors in most vehicles are not subject to road bumps. But Gotovac said the motors are designed to last the life of the vehicle; the only part that might need replacing is a seal or two.
Joe Bakaj, product development head at Ford of Europe before retiring two years ago, said wheel hub motors are a “game changer.”From his home in Germany, Bakaj said packaging and space freed up by placing electric motors in the wheels could be used to enhance ground clearance, improve aerodynamics, enable larger battery packs and improve handling by lowering the center of gravity. It also provides the flexibility to add 4wd without reengineering a platform, he said.Gotovac says interest in wheel hub motors is growing and other automakers are testing the company’s technology: “We have more than 50 vehicles around the world in different stages of R&D, so definitely a lot of interest. But there’s also a lot of old myths to bust.”