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Luke Tonachel’s Blog

The Quiet Revolution in Vehicle Lightweighting

Luke Tonachel

Posted November 21, 2012 in Moving Beyond Oil, Solving Global Warming

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The company that brought American consumers the heavyweight Hummer SUVs, as well as the maker of the perennially best-selling truck in the U.S. are both “getting religion” on the benefits of manufacturing its vehicles to be lighter in weight.  In recent years, General Motors, Ford and virtually every other automaker have been preparing to meet stronger fuel efficiency standards by taking a page out of motoring legend and the founder of Lotus Cars Colin Chapman’s philosophy of automotive design: “Simplify, then add lightness.” 

Most people, when confronted with the idea of lightening a vehicle, automatically assume that less weight will make for a less safe vehicle, but this is not so, and particularly not under the fuel efficiency standards.  Vehicle size is what matters when it comes to safety. In 2008, federal regulators first implemented size-based standards and rejected a weight-based system.  Size, they found, is the critical factor for designing vehicles with needed crumple zones and strategically-placed high-strength materials that protect drivers and passengers.  Simply adding weight does not necessarily improve safety, but conversely, removing weight while maintaining size can make a safe car use less gas. Under the current and new fuel efficiency standards, automakers are encouraged to maintain the size of vehicles in their fleets and add fuel-saving engines, transmissions and strong, lightweight structures that cut fuel consumption but keep vehicles safe.

Automotive engineers have been aware of the benefits of building lighter vehicles since the dawn of the automobile, but with the new fuel efficiency standards, the concept of lightweighting is undergoing a revival among the CAD-and-blueprints crowd.  Reflecting this renewed interest in auto lightness, the Society of Automotive Engineers (SAE) released the results of an in-depth survey of SAE members conducted from mid-July to early August 2012, just prior to the release of the final fuel efficiency rules. 

According to the 516 respondents to the online survey conducted by independent research company Signet International on behalf of 3M and Automotive Engineering International, two main technology trends will have the greatest impact on vehicle fuel efficiency: lightweight structural materials (72%) and engine downsizing (65%).  The survey authors also noted that “nearly three-quarters (72%) of the respondents believe that the level of commitment to lightweighting within their organization is greater than it was five years ago.”

As I noted above, GM is taking a fresh look at lightweighting.  For example, the ATS, Cadillac’s new sport sedan, was designed from the ground-up to be the class leader in weight savings, and getting to that target required a major rethinking of how the team developing the ATS operated compared to standard GM procedures. 

“Our (mantra) was ‘Every gram, by every engineer, every day,’” [vehicle chief engineer-performance cars Ken Kelzer] says. “When an engineer would come in on a design meeting, we would ask, ‘What does this mean from a gram standpoint? What sort of mass are we talking about?’”

Along with the redesign of the Cadillac ATS, GM has been investing in new technologies to reduce the cost of using lighter materials. The company announced recently that it has developed a method to efficiently weld aluminum onto aluminum, meaning that the lightweight material will be used more extensively and cheaply than before.  GM also announced the development of a new process for molding magnesium from a proprietary corrosion-resistant magnesium sheet metal that has passed strict durability testing. 

My focus on GM today is in no way meant to take away from the great advances in materials research and development other automakers are currently engaged in.  Honda’s new Ohio-manufactured Accord, for instance, uses a new technique they call “friction stir welding” to join aluminum and steel together seamlessly in the front suspension subframe, the first time the two metals have been joined in a major structural element of an automobile.  At the other end of the price range, the new Range Rover uses an all-aluminum chassis to help save 700 lbs., a first for a SUV chassis. 

Automakers are also continuing to take advantage of advancements in high-strength steel components that maintain rigidity for safety but enable less material, and therefore less mass, to be applied to the vehicle.

But a huge change in the automotive landscape may be yet to come, as according to the Wall Street Journal, the next-generation Ford F-150 appears set to radically adopt the use of aluminum throughout its body, with the goal being to save 700 pounds, or 15% of its total weight.  As the article notes, the production shift marks a risk for Ford to take, as there may be a perception among truck buyers that aluminum lacks “toughness” compared to steel, but the company is betting the radically increased fuel efficiency that will result will open minds and wallets.

Such engineering and manufacturing advances will become more and more commonplace as companies innovate to meet the new standards, if no less amazing and inspiring to learn about.  The increased costs of these materials compared to standard steel will surely dictate the range of applications of these new materials and processes to the vehicles we buy, but with fuel efficiency competition heating up between automakers, and as these processes scale up and become more widespread, automakers will be forced to keep prices in check.  As usual, the consumer wins out in the end, as we will all benefit from lighter, more fuel-efficient cars and trucks that provide better performance, handling and braking while maintaining safety. 

Just remember to thank the automotive engineers in Detroit and elsewhere who are sweating away over every gram of weight to help you go that much farther for your fuel dollars.

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Comments

Guybrush ThreepwoodNov 21 2012 04:23 PM

I have to say this blog post is terrible. It reads like a big sign that says "Keep buying SUVs they're getting lighter and will have good mpg, it doesn't mater if they are big!"

This is not true. You will never make a 4600 lb SUV weight the same as a small 1800 lb car, ever. Ever.

Luckily it's ok to buy a small car. Your wrong about size determining safety, look at an F1 car, super super safe and small. Look at the crash rating for some vehicles you'll see a lot of small cars can rate just as high or higher than larger cars.

Small cars also have a huge advantage over the big cars your pushing. You may have noticed a car is slower to accelerate from 60 mph to 80 mph than it is from 10 mph to 30 mph. This is because of Drag, a force that works against the car's Velocity. The more drag there is the more power the car needs to accelerate or maintain speed, the power of course comes from burning gas. Here is a simple equation for Drag = Cd * .5 * r * V^2 * A. Cd is the co-efficient of drag, how aerodynamically sculpted a car is. r is the density of air. V is velocity, and A is....... here's the big one.... AREA, the frontal area of the car, as you can see drag is directly related to the size of the car. Notice in this equation there is no weight.... because guess what weight doesn't mater, it only maters when you accelerate.

Don't buy big SUVs with poor aerodynamics, and big tires. Buy small aerodynamic cars with efficient engines, and narrow tires. Please for the good of saving the planet take your blog post down.

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Switchboard is the staff blog of the Natural Resources Defense Council, the nation’s most effective environmental group. For more about our work, including in-depth policy documents, action alerts and ways you can contribute, visit NRDC.org.

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