Lightweight electric motors

The lightweight electric motors developed to power the wheels of the Morgan Motor Company’s concept fuel-cell car are now being prepared for mass-market commercialisation.

The motors were devised by Oxford University researchers for the 2008 Morgan LIFEcar — a fuel-cell electric vehicle project being undertaken by Morgan Motor and start-up Riversimple.

The concept car is equipped with four electric motors to power each wheel. The design is similar to the whispering wheel concept, which involves housing the electric motor used for propulsion in the wheel itself.

The researchers’ spin-out company, Oxford Yasa Motors, recently received government and private investment totalling approximately £3.4m to redesign its motors for the wider automotive and industrial market.

Tim Woolmer, head of technology at Oxford Yasa Motors and a co-developer of the Morgan LIFEcar motor, said the new motor has significantly more torque for the same power output.

The extreme requirements of the Morgan LIFEcar project prompted Woolmer and co-developer Malcolm McCulloch, head of Oxford’s Electronic Power Group, to realise they could push the design further to the limit.

’With the Morgan LIFEcar, we were told the car was required to do an emergency stop from 70mph to 0mph in less than 75m,’ he said. ’When you do the sums you find you need 0.7G worth of acceleration just to stop the vehicle at that speed, and you need 350 Newton-metres per wheel to do that. We were given a budget of just 20kg per motor.’ In the end Woolmer and McCulloch were able to achieve a 13kg motor and 7kg gearbox that could deliver 360 Newton-metres. While good enough for the LIFEcar, Woolmer said they knew a greater power density could be achieved.

Oxford Yasa Motors worked with engineering firm Delta Motorsport over the past eight months on a new lightweight motor. Woolmer said the group found the best way to reduce the weight was to take out the gearbox. The new direct-drive motor weighs 23kg, which he admits is slightly more than the LIFEcar motor, but it has a peak torque of 500 Newton-metres.

’The motors have a peak power of around 50kW but it could be extended to around 75kW,’ said Woolmer.

Oxford Yasa Motors and Delta Motorsport have configured the motor for a new four-seat coupe, which is scheduled for track tests scheduled at the end of 2009.

Woolmer said the new direct-drive motor will be less expensive to manufacture. It should also be more reliable, he added, because the only moving part is the rotor of the motor.

Oxford Yasa Motors is aiming to sell a low volume of the motors over the next few months, but Woolmer said they hope to scale up production and develop new models over the coming year.

He added the company plans to adapt the motor for aerospace and industrial applications.

Siobhan Wagner