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Reducing features not key to saving weight
Developing lighter cars will not come at expense of content, say Detroit designers
21 May 2012
HIGH customer expectations for equipment and safety mean car companies will be forced to think smarter about how to design vehicles – especially for the mass-market – while continuing to reduce weight in response to the pressure of ever-increasing fuel-efficiency requirements.
This was the consensus among a panel of leading designers from the big three Detroit car-makers at a recent Auto Press Association lunch.
It also echoes the efforts of companies like Holden, which is working to reduce the weight of its next-generation (VF) Commodore, Mazda, which is introducing its SkyActiv technology, and Volkswagen Group, which will save weight and cost with its new MQB platform.
Cadillac exterior design director Bob Boniface does not believe manufacturers will reduce the content of their cars in order to save weight.
“They won’t sell (if content is removed),” he said.
“There is an expectation on the customer’s behalf of more and more feature content, more and more safety content – that’s always going to be there, that’s a fact of life.”
Mr Boniface pointed to the lack of success Indian car-maker Tata has so far experienced with its no-frills Nano, the world’s cheapest car.
“I don’t think there is any market on earth that has embraced a car like that yet,” he said.
“I think it’s an admirable pursuit, but the expectation is always going to be for more and more and more.
“There are smart ways to (save weight) and I don’t think we are ever going to start de-contenting vehicles.”
Ford chief interior designer Mike Arbaugh said customers “want everything” in terms of equipment and interior ambience, regardless of segment.
From top: Ford's Mike Arbaugh Cadillac's Bob Boniface Chrysler's Mark Trostle.
“It’s a challenge you want it to look good, you want it to feel good, you want it to be comfortable, you want the cup-holders, you need the USB ports … it’s just a big balancing act,” he said.
Mr Arbaugh suggested one feature that could be dispensed of in the near future is the CD player, due to the number of people now using USB music storage or Bluetooth streaming, which would result in a weight saving of more than two kilograms.
He described how the days of saving weight by fitting an instrument panel made from 3.5mm thick hard plastic were over “because nobody liked it”, and how engineers have achieved the now de-rigeur soft-touch vinyl or leather surface finishes without increasing weight.
Part of the solution was reducing the thickness of the underlying substrate by 1mm, but engineers went a step further by injecting tiny bubbles of nitrogen into the polyurethane.
Chrysler’s head of SRT, Viper, Mopar and Motorsports design, Mark Trostle, said the adoption of weight-saving technologies and materials in premium and exotic vehicles will eventually trickle down to mainstream cars once they become more widespread.
Mr Trostle said taking more than 45kg out of the new Viper used a lot of materials that are not yet cost-effective, but the company benefited from the project as it allowed for experimentation with new processes.
“We are looking at those things in our future products where can we start to use those things on hoods, fenders … where it makes sense,” said Mr Trostle.
“Doing supercars or exotic cars is a great way for us to learn as a company as well … there are things that will hopefully trickle through and we can get them into the mainstream world.”
Mr Boniface described the weight-saving measure of reducing complexity and the number of components, such as replacing a steel dashboard support that uses several welded brackets with a one-piece tubular magnesium assembly that also serves as the ventilation ducting.
However, Mr Arbaugh suggested customers preferred to be able to see where the car-maker had invested money in weight-saving technologies and said Ford had previously used magnesium for dashboard supports but later decided to spend the money elsewhere.
“That’s a lot of money for a very esoteric type material that the customer never sees,” said Mr Arbaugh.
“In the past we have taken (magnesium) out and gone to materials that were not quite as heavy as they were before and put the money to where the customer sees it.”
Mr Trostle said the continuous reduction in size and weight of some components is helping, using the example of airbags.
“Even though there is weight, they (airbags) are getting smaller,” said Mr Trostle.
“If you look at the size of a steering wheel airbag and you remember when they first came out … now you would never guess what is packaged in there.”
With the larger budgets – and usually size – of premium cars, lightweight construction materials are more viable, but the real challenge is finding cost-effective ways of reducing the weight of mass-market vehicles, on which fuel-saving measures are even more important in terms of corporate average fuel economy (CAFE).
Mr Boniface said that, on premium vehicles like the Cadillacs on which he oversees the design, keeping weight down while increasing features was easier.
“It is a little tougher on a Ford or Chevrolet because those are the very vehicles where you need to reduce the mass because there are a lot more of those vehicles (on the road),” said Mr Boniface.
“Yet the price point doesn’t allow you to spend money on carbon-fibre, a lot of magnesium castings and so forth.”
Mr Boniface said studies undertaken during development of the Chevrolet/Holden Volt showed that ten counts of aerodynamic improvement (for example from a drag coefficient of 3.1 to 3.0) is equivalent to reducing weight by 22kg.
“Reducing a vehicle’s mass by 22kg costs a lot of money,” he said. “Aerodynamics in some ways is free, it’s testing time and an impact on how the car looks.”
However, aerodynamic improvements such as active radiator vents or underbody smoothing have weight implications and can impinge on interior space and visibility for the driver.
Mr Arbaugh spoke of the challenges facing an interior designer when aerodynamics dictates the form of a car.
“We have to do everything we can to make those pillars look thinner, to keep the vision of the customers,” he said.
“It is a challenge to deal with when you have A-pillars creeping in so the air flows around them better, and with safety the pillars are getting thicker.
“Eventually it all finds itself (encroaching) into the interior, and on the interior you want spaciousness.”
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