Reinventing the Wheel

Reinventing the Wheel

The race is on! Instead of chasing speed, auto manufacturers today are chasing reduced carbon emissions. One solution is electric traction.
 
In the push to reduce carbon emissions and meet government targets quickly enough, vehicle manufacturers are looking for ways that allow them to incorporate new elements into existing designs.

In-wheel motors
One such innovative element comes from Protean Electric. The company’s electric motor is housed inside the wheel hub.

The technology is a modern development of an old idea. Ferdinand Porsche sold 300 cars using electric in-wheel motors more than a century ago. The ready availability of cheap gasoline put an end to that. Now, however, the escalating economic and environmental costs of gasoline are bringing the potential for in-wheel motors back.

Ken Stewart, Vice President, Business Development at Protean Electric, says the philosophy behind the idea is simple: “Why not put the torque at the wheel? That’s where you need it.”

Saving space and improving carbon footprint
The idea also has the advantage of freeing up space inside the vehicle. “Not only does the motor fit inside wasted space,” Stewart says, “you don’t need drive shafts, transmission, differential or any mechanical connections. You just press the throttle pedal, which sends a command along a wire to provide more torque at the wheel.”

Protean is still testing the motor on prototypes and expects to go into serial production in 2014.

The motor would be ideal for retrofitting on a car to augment the existing powertrain. One of the main uses Protean sees in the medium term is for fleet operators who can improve the carbon footprint of their fleet by making all their cars into hybrids with two electric-driven and two conventionally driven wheels, all controlled by smart software.

Meeting future requirements
It will also be useful for manufacturers that are redesigning existing models. “Companies realize they can meet the increasingly tough environmental norms over the next two or three years with their own technology, but after that they need larger reductions,” Stewart says.

And looking to the future, wheel-based power could lead to the total redesign of the automobile, with, for example, pod-like vehicles moving sideways into parking spaces.

But if the wheel is an ideal home for the motor in some ways, in others it’s the worst possible place. It’s subject to vibrations and road irregularities, it gets splashed with water, and it is often knocked against curbs. So the seals within the in-wheel motors have a difficult job to do. They have to keep foreign matter out of the gap between the rotor and the stator. Says Tony Fagg, a Key Account Manager at the Trelleborg marketing company for sealing solutions: “This application requires that the seals meet a combination of thermal and physical challenges. It has needed a number of design and material iterations during development to meet these demands.”

Overcoming challenges
The challenge is the wide variety of conditions under which the seal has to work. “The car could be parked in a puddle in Alaska that freezes overnight,” Fagg says, “but when the motor starts, the seal quickly reaches a potential friction heat of 160 degrees Celsius.” 
Tests are ongoing. Fagg says that with the current design “nothing has failed yet,” but he expects that small changes will still be necessary. Comments Stewart: “This is a critical design point for the motor, and I’m confident it’ll work.”

The Motor Within Protean Electric has been making in-wheel motors since 2005. The company has featured in a variety of prototype vehicles, from a Mini Cooper to a Brabus Mercedes and a Vauxhall delivery van. Though now based in Detroit, Michigan, in the U.S., its engineering is in Farnham, England, and there are plans for a production facility in China.

Worldwide network of specialists 
Fagg is pleased with the way this project has come together. “This has been a real international affair, combining our expertise from around the world,” he says.

“The Trelleborg manufacturing and development facility in Malta has the knowledge of materials to engineer the right elastomer and will be carrying out volume production,” Fagg continues. “We’ve been able to call on the assistance of our facilities in England in the initial stages. Tewkesbury has the skill to manufacture prototypes, and our site in Bridgewater has the specialist test equipment needed. In addition, we’ll be able to serve the factory in China with our Global Supply Chain Management network and give local support from our marketing company there.”