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Henry Ford’s Model T was the 20th century’s boldest automotive stroke. Like Lotus’s Colin Chapman and every other shrewd motorsports engineer, Ford—even way back when—identified weight as the enemy. Model T frames were made of steel containing vanadium for extra strength, and millions of T hoods were aluminum long before that metal entered the car-material mainstream. With only 20 horsepower under the hood, the T needed its weight to be kept below 2000 pounds to meet Ford’s ambitious performance goals. Now that 2015 Ford F-150s are finally in customer hands, inquiring minds wonder why it took a century for aluminum to leap from Model T hoods to the cabs and beds of America’s bestselling vehicle. Let’s explore that topic, shall we?
One reason is because steel is affordable, easy to shape, and, except for some obvious shortcomings such as its lack of corrosion resistance, an ideal material for automotive use. On a per-pound basis, aluminum costs roughly twice as much. Affordability will always be the prime concern in any industry that produces millions of units per year. It’s only when improved performance and fuel-efficiency goals enter the equation that alternative materials can be seriously considered. Aluminum’s prime attraction is its density (mass per volume), which is only one-third that of steel. Unfortunately, aluminum also offers only one-third the stiffness, so gauge increases are usually needed when aluminum replaces steel. Ultimately, the weight savings come from choosing aluminum alloys that approach steel’s tensile strength—the load a component can bear without sustaining permanent deformation. Ford managed to make the math work for its new F-150, and we’ve compiled everything you need to know about the new truck’s aluminum, from how it is used to where it comes from.
Where Does It Come From? Where Does It Go?
Ford’s aluminum-body research began in earnest two decades ago. Forty experimental Mercury Sables were constructed using the light metal; a photo shows two engineers easily lifting a body-in-white (bare car minus closure panels). One of the first lessons learned was that fresh approaches to joining stamped-aluminum panels were needed. Collaborating with Jaguar, Ford engineers developed various mechanical fastener and adhesive techniques to replace spot welding. In 2003, Jaguar launched the XJ sedan, which was made up of a creative mix of aluminum stampings, castings, and extrusions held together with epoxy adhesive, steel rivets, and a few nuts, bolts, and spot welds. Even though the XJ was significantly larger than the outgoing model, Jaguar claimed its unibody was 60 percent stiffer and 200 pounds lighter.
Although Ford enjoys touting the military or aerospace grades of aluminum comprising the F-150’s cab and bed, these materials have been in general use for decades. The aluminum formulations chosen for their mechanical properties and ready availability through suppliers Alcoa and Novelis are 5000- and 6000-series alloys. The 5000 series—containing small amounts of chromium, copper, iron, magnesium, manganese, and silicon—has adequate strength for low-stress areas such as the cab’s floor, cowl, and inner door panels. 6000-series aluminum’s strength is increased by heat-treating after the forming process. The F-150’s inner-hood panel achieves the desired state during paint baking. Maximum yield strength 6000-series aluminum is used in high-stress cab, sill, and A-pillar areas. In addition to the alloying ingredients listed above, 6000-series aluminum contains a small amount of zinc.
Spot welding aluminum requires higher electric currents and some means of removing the oxidized coating that covers this metal’s surface. General Motors has made recent strides in this area and reported that it will continue using spot welds to join its aluminum body panels. The new F-150 also has a few spot welds in its bodywork, but lessons learned from the Sable and Jaguar experiences convinced Ford that special fasteners and adhesives were the way to go in most instances. When there’s easy access to the rear side of a joined surface, self-piercing rivets are used. Instead of erupting through the opposite side, each rivet’s tip spreads inside the panel and locks permanently in place, leaving only a slight mushroom bump visible on the back surface.
In many instances, there is no access to the backside for a tool to apply the necessary clamping pressure. Here, the solution is to use what’s called a flow-drill screw: a sharp-pointed and threaded steel fastener is spun at high speed while pressed firmly against the panels to be joined. The underlying aluminum material is pierced, heated by friction, and formed into a cylindrical jacket that grips the joining fastener’s threads.
The new F-150 also has more than 350 feet of structural adhesive beads to supplement the joint strength provided by fasteners. The adhesive also blocks noise and moisture and enhances collision performance. Like the use of aluminum and special fasteners, these adhesives are well proven after years of reliable service. In the past decade, the amount of structural adhesives in car and truck bodies in general has increased by 50 percent.
Steel is still an important part of the F-150’s makeup. The massive ladder frame supplied by Metalsa is 60 pounds lighter than the 2014 design thanks to a significant increase in the use of high-strength steel. Most of the anti-intrusion door beams are steel tubes, there are several small tapped steel plates in the bed sides, the bottom edge of the tailgate is steel, and all of the aforementioned fasteners are zinc-coated (for corrosion resistance) steel pieces.
Rethinking the core materials that comprise this pickup required upward of $3 billion in investments in Ford’s Dearborn, Michigan, and Kansas City, Missouri, stamping and assembly facilities. Thus far, workers have applauded the reduction in noise and sparks associated with the move to aluminum. To help offset the cost of the more expensive metal, the same trucks that deliver coils of aluminum to the plants haul the valuable scrap back to suppliers for recycling.
The bottom line, or at least the intended one, is lighter and more fuel-efficient pickup trucks. Comparing the curb weight of an F-150 we tested five years ago with the 2015 edition reveals a net weight savings of about 300 pounds. Unfortunately, the validity of such comparisons are undermined by the move to smaller and lighter engines, more lavish creature comforts, and ever-rising haul and tow ratings. It’s an unspoken law of nature that each new pickup must be larger, more comfortable, and more capable than its immediate predecessor.
Assessing the fuel-economy gains is equally difficult. In addition to lighter weight, Ford claims the 2015 F-150 boasts a 23-percent aerodynamic-drag improvement attributable to the use of grille shutters and cleaner cab and bed shapes (though frontal area is slightly larger). In EPA tests, the most fuel-efficient 2015 F-150 scores 19 mpg in city driving and 26 mpg on the highway, versus 16 and 22 mpg for last year’s efficiency leader. That’s a 22-percent improvement in combined mileage and there’s more to come. Work is underway on a hybrid powertrain, and you can expect additional aero refinements such as the active wheel shutters that Ford showed in prototype form two years ago to eventually trickle into the F-150.
Don’t be surprised if Ford’s hybridized F-150 takes a whack at the mpg king in this segment, the diesel-powered Ram 1500 EcoDiesel, which achieves 20 mpg in EPA city testing and 28 mpg on the highway exam. Ford is quick to note that diesels make no economic sense. The one in the Ram adds $4000 in initial cost and consumes fuel that, per gallon, costs about 30 percent more than gasoline. But there are hard-core diesel enthusiasts quite happy to spend extra to own and operate their kind of engine. That conviction and the success of the Ram EcoDiesel are too significant for Ford and GM to ignore, just as the effect of Ford adding so much aluminum to the F-150 is something every pickup maker is studying very closely.