Reinventing the wheel – Protean puts electric motor inside wheel hub


Car wheel

The auto manufacturers of today are chasing reduced carbon emissions, and one company has found a solution in 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.

This innovative element comes from Protean Electric, which houses an electric motor inside the wheel hub.

The technology, now in the final stages of testing, 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.”

The idea also has the advantage of freeing up space inside the vehicle. “Not only does the motor fit inside wasted space,” Mr 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 next year.

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.

It will also be useful for manufacturers redesigning existing models. “Companies realise 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,” Mr 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.

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,” Mr Stewart says, “but when the motor starts, the seal quickly reaches a potential friction heat of 160oC.”