Size or Mass? The Technical Rationale for Selecting Size as an Attribute for Vehicle Efficiency Standards
A new era in vehicle design and manufacturing
The 2015 F150 pickup truck unveiled by Ford at the 2014 Detroit Auto Show is perhaps the most significant vehicle redesign introduced in the last century. The Toyota Prius may be just as significant technologically, but you arguably have to go back to the Model T introduced by Ford in 1908 to find a larger impact on how vehicles are designed and made.
Much of the press from Detroit today is going to the new aluminum body on the 2015 F150, and justifiably so, because this is a really big deal. 97% of the cab and pickup bed will be made up of various grades of aluminum that match the strength used by the military. In addition, the proportion of high-strength steel in the frame (pickup trucks are built with separate bodies and frames, unlike most cars, which use a unibody construction) will increase from 23% to 77%. Combined, this will reduce weight by about 660 pounds, more for supercab models, less for base cab models. This equates to a 12-13% mass reduction from the model year 2014 four-door F150, the largest mass reduction by percent that we have ever seen from a high sales volume vehicle. Ford also says the new truck will tow more and haul more, accelerate and stop more quickly, be more resistant to dents and dings and rust, and it will not be significantly more expensive to repair and insure.
This is hugely important, because it is the first use of an aluminum body in a high-volume production vehicle—and not just any high-volume vehicle: the F150 is, by far, the largest-selling vehicle in the US and has been for more than three decades running. And it’s a truck, to boot. Manufacturers have usually claimed that weight reduction and lightweight materials are far less feasible for larger light trucks. For example, Mark Reuss, GM’s president, told Automotive News just two years ago: “‘What you risk when you light-weight trucks are duty-cycle issues.’ Capability can’t be reduced because ‘there are people who use that to make a living.’”
The fact that Ford started with the F150 debunks these claims. Even more important, if Ford can do this on a pickup truck, then it shows that using lightweight materials is feasible in any vehicle. Ford has leapfrogged not just other trucks, but cars as well.
It’s also important that Ford is using the lighter weight of the F150 to downsize the engine lineup for this model. Ford will still offer four engines, but the choices will change significantly. The base 3.7L V6 engine is downsized to 3.5L while increasing performance. Ford also announced they are introducing a new 2.7L V6 EcoBoost (turbocharged) engine, which will be smaller and lighter than the current 3.5L EcoBoost engine and will include an engine stop/start system. The existing 5.0L V8 and 3.5L V6 EcoBoost engines top the engine lineup. Significantly, the current 6.2L V8 engine is being dropped from the F150. This illustrates how weight reduction can provide equal or better performance even when paired with smaller engines.
One of the criticisms of aluminum is its higher cost than steel. This is likely one of the reasons why Ford started with the F150, as the huge sales volume allows Ford to quickly gain economics of sale. Ford and its aluminum suppliers have also invested in improved techniques to make and use aluminum. Two examples pulled from one of the numerous reports from the auto show:
“Pete Reyes, the F-150’s chief engineer, said Ford expects to make up the premium by reducing its recycling costs, since there will be less metal to recycle, and by slimming down the engine and other components, since they won’t have to move so much weight.”
“Improvements in aluminum are also driving the change. Three years ago, for example, Alcoa Inc. — one of Ford’s suppliers for the F-150 — figured out a way to pretreat aluminum so it would be more durable when parts are bonded together. Carmakers can now use three or four rivets to piece together parts that would have needed 10 rivets before, Alcoa spokesman Kevin Lowery said.”
But while the weight reduction and engine downsizing on the F150 are important, they are not the main reason why this is a historically important vehicle. What makes this a really big deal is the role computers played in design and engineering. This is a breakthrough moment.
ICCT has been predicting [.pdf] for several years that lightweight materials were poised for this breakthrough because of the rapid improvements occurring in computer simulations and computer-assisted engineering. The 2015 F150 is in the vanguard of a truly radical transformation. Here’s what Ford is saying:
“Peter Reyes recalls that 15 years ago, it took nine months for Ford Motor Co to make two possible designs for a vehicle frame. Now, the chief engineer of the revamped F-150 pickup truck says he can create 100 different examples in that time.”
“Recent advances in computer-assisted engineering, or CAE, were one key factor that enabled Ford to take one of the biggest gambles in its history – making the hugely popular F-150 largely out of aluminum while retaining the brawniness of steel.”
“Ford used CAE tools to digitally experiment with more lightweight materials and test those components against “a blizzard of stiffness and strength requirements,” Reyes said.”
Ford has developed aluminum vehicles before. The company built 40 experimental Mercury Sable Aluminum Intensive Vehicles in 1993 and later put a low-volume aluminum vehicle into production, the 2003 Jaguar XJ. The key difference today is simply the orders-of-magnitude improvement in computer-assisted engineering.
Five recent studies of lightweight vehicle designs (See FEV, Lotus, EDAG, WorldAutoSteel, Aluminum Association reports) all drive toward the conclusion that weight could be reduced by 15% to 30% at low, if not zero, cost with no impact on safety. These studies, which implicitly assumed that every part would be optimized for material, shape, and thickness, have been criticized by the industry for ignoring part sharing and real world interactions with safety, noise, vibration, and harshness. The criticisms are rooted in how things used to be done. The 2015 F150 is significant because it demonstrates in practice what those studies argued in theory. This is where the industry is headed. Just like it did with the Model T, Ford has transformed the way that vehicles are designed and built.