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Future Forward: 'Car dieting' is back in vogue

Jørn Madslien

(Credit: iStock)
(Credit: iStock)

Weight watching is back in vogue among automotive engineers facing increasingly ambitious cost and emissions targets.

And the ongoing transition to electric motoring is a major driving force behind this.

“Lightweighting is the final frontier in any motor car, whether it’s internal combustion engine, hybrid or electric,” according to automotive guru Gordon Murray, the former Formula One racing car designer and the man behind the McLaren F1 supercar. “But it’s much more important in electric vehicles (EVs) because the battery’s weight is directly proportional to the chassis weight.”

With manufacturers having responded to consumers’ range anxiety and desire for creature comforts by offering luxurious, often large, EVs that can be driven 320km or more on a single charge, there has been an uptick in the weight of batteries.

“Lightweighting has been washed over and forgotten a bit with the rush to alternative powertrains and the amount of luxury that customers are demanding in cars,” says Murray.

To compensate, engineers have identified weight reduction as an effective way to regain some of the lost efficiency.

“If you can’t make the car body any smaller, the only solution is to use lighter materials, or less of them. Or both,” points out Thatcham, the motor insurers’ automotive research centre.

Murray believes that weight reduction can reduce both resource requirements and costs. “For every kilogram we can take out of the chassis, EV-makers can save €10 worth of lithium-ion in the batteries.”

Lightweighting brings benefits to internal combustion engine cars too, according to chemicals company DuPont. A 50kg vehicle weight reduction cuts carbon dioxide emissions by up to 5g/km and increases fuel economy by up to 2%, says the company, and replacing metal parts with parts made from high-performance polymers is a “proven strategy for weight reduction”.

Similar strategies have been adopted by at least two British start-up firms that hope to bring sports cars to the market in the next couple of years.

“Lightweighting is very much on everybody’s lips these days,” says Alcraft Motor’s managing director David Alcraft. The embryonic carmaker has designed an electric sports car around a carbon-fibre tub to ensure that its weight is 75% of that of a Tesla S, yet offering similar performance, says Alcraft.

Murray is also getting in on the act. Last month, he revealed plans of his own to start building “superlight” road cars based on his iStream manufacturing process, which has lightweight Formula One technology at its core.

His company, called Gordon Murray Automotive, has come up with a development model that he says can be manufactured, then run for 100,000km with a petrol engine, before being recycled – with the entire process using less energy than it takes to merely make an SUV.

“That should serve as a wake-up call,” says Murray. “We think this is going to be the ultimate body-in-white structure for the next couple of decades,” he says.

“Whether manufacturers like it or not, they’ll have to get back to smaller, lighter cars, because it’s not sustainable what we’re doing now, whatever the powertrain.”

Former Tata Motors chief executive Carl-Peter Forster says “it’s happening already”. “Mainstream OEMs are willing to pay substantially more per kilogram saved than they ever used to,” says the automotive veteran, who has worked for BMW, General Motors and Jaguar Land Rover. Forster is also the chairman of the London Electric Vehicle Company, formerly the London Taxi Company, a board member of Geely Automobile Holdings and Volvo Cars, and he advises Murray on his latest venture. 

Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.

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