Eco-design and Validation of In-Wheel Concept
for Electric Vehicles

Eunice Project


Protean says electric wheel motors ready for production in 2014

While it's not reinventing the wheel entirely, Protean Electric is at least changing most of what we know about vehicle drivetrains.


Imagine being surrounded by four twin-turbo Mercedes V12 engines, their massive torque at your instant disposal, and rushing off in near silence.

That's essentially how tomorrow's electric cars could work if a new in-wheel motor gets approval from major automakers.

Protean Electric, a private British engineering firm now headquartered in Michigan, has been toying with a radical concept since 2007. Instead of routing power from a single electric motor through a transmission and differential, Protean (then named PML Flightlink) put four deep-dish motors at the wheel hubs of a Mini Cooper, effectively giving each motor direct control without any traditional power losses.

The idea has been around for awhile, as anyone who has seen an electric bicycle can attest. But Protean's motor is seriously powerful.

The company's latest in-wheel motor, unveiled at the SAE World Congress this week, is a disc enclosure that spins with the wheel and looks like a giant drum brake. It puts down up to 735 pound-feet of torque (just three shy of the Mercedes V12) and 100 horsepower, the most power per square inch of any motor on sale, Protean said. The motors also promises fewer energy losses during braking, as well as independent, instant computer control of each wheel's speed, which Protean says could make a car "unskiddable."

Engineers have already tested a prototype gas-electric hybrid, a Brabus-modified E-Class, with hub motors attached to the rear wheels that Protean says deliver up to 30 percent more fuel economy than its standard hybrid counterpart.


But even huge luxury automakers like Mercedes have budgets, and it's here where Protean thinks it could sell the technology as an easier, cheaper fit to existing cars, since there are no special clutches or other typical EV components to add beyond batteries. Protean CEO Bob Purcell, who directed the GM EV1 program in the 1990s, said at the SAE World Congress this week that his company's hub motors were the "closest the industry will ever come to a bolt-on electric drive solution."

Yet it's not so simple. Each motor, equipped with a built-in inverter, weighs 68 pounds and will add to a vehicle's unsprung weight (the weight of the wheels, tires, brakes and other components not supported by a car's suspension). In tests with a Ford Focus, the motors caused an increase in road harshness and heavier steering (.pdf), which the company said could be offset with suspension tweaks and softer springs. Further, the motors are so large that they won't fit wheel diameters smaller than 18 inches, at which point tire sidewalls and ride comfort significantly decrease on most cars.


But how a car stops, not its handling, is currently the biggest challenge. In 2007, Protean's electric Mini had no brakes, instead relying on the regenerative effects of its four motors spinning backwards. Unsurprisingly, that would prove insufficient. Now Protean is testing an "inside-out" brake (.pdf), a thin iron ring mounted directly behind the motor, that should be ready by summer.

"Whilst the packaging of this brake is not conventional, the technology used (sliding calipers, conventional iron disc, etc.) most certainly is," Andrew Whitehead, Protean's director of strategic alliances, told MSN Autos in an email. "Therefore we see this work as a re-packaging exercise rather than a total 'rethink.'"

Protean says it is talking with several automakers and expects to start production at a Chinese plant in 2014.

Source: MSN Autos

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