GM`s `breakthrough` wheel hub motors boost torque by 60%

General Motors has demonstrated a hybrid petrol-electric vehicle propulsion system with electric motors embedded in the vehicle`s wheel hubs. GM is hailing the system, which delivers high efficiencies and starting torques, as "a potential breakthrough technology".

"We believe that this technology will lead to the industry`s first practical application of wheel hub motors for consumers," says Larry Burns, GM`s vice-president for r&d and planning. He adds that the motors are "a critical element in making affordable and fuel-efficient all-wheel-drive and advanced technology vehicles for the future".

To demonstrate the technology, GM has incorporated two 25kW wheel-hub motors, made by the Italian firm Lucchi R Elettromeccanica, into the rear wheels of a front-wheel-drive pickup truck. The motors (shown above) add just 15kg to each wheel, yet boost the vehicle`s start-up torque by 60%.

"This enables a four-cylinder engine to perform like a six-cylinder engine," says Burns.

The wheel-hub drives have several other attractions. They avoid the power losses (of about 10%) that conventional vehicles suffer while transmitting power from the engine to the wheels. And, unlike conventional engines, which take time to get up to speed, all of the hub motors` torque is available immediately.

The motors are also said to improve steering as well as traction and anti-skid control. "The wheels don`t slip," explains Bill Slomski, managing director of GM`s Advanced Technology Centre in California, which developed the technology. "We have the ability to control each individual wheel with a better response than today`s high-end traction control systems." This could be particularly useful in wet or icy conditions, he points out.

Burns says that the technology "may enable us to build some pretty exciting future vehicles that have the potential to be as quick as a sports car, while providing significant fuel economy improvements". Another possibility is to allow the wheels to turn through 90 degrees to make parking easier.

The electronic control system and software for the demonstration vehicle were developed by the alternative vehicle specialist, Quantum Technologies, in which GM has a 20% stake.