Commercial vehicles are traditionally big and heavy. But, with diesel prices skyrocketing, the industry is hungry for fuel-efficient vehicles. Truck manufacturers are responding with aluminum, composites and other lightweight, corrosion-resistant materials. This trend is forcing assemblers to use new joining methods, such as structural adhesives.
Caterpillar Inc. is world-famous for its bulky construction equipment containing lots of cast-iron parts. But, when it launched a line of on-highway trucks last year in conjunction with Navistar, engineers turned to lightweight materials.
For instance, the Cat CT660 vocational truck features an aluminum cab and a composite hood. The cab, which is 250 pounds lighter than traditional welded steel construction, is riveted and bonded.
“The primary trends at the moment are in aluminum and various new composite sidewall materials and plastics,” says Dan Tuerk, ground transporation leader at Infastech. He predicts that other lightweight materials, such as magnesium, will be used by commercial vehicle manufacturers in the future, as the technology trickles down from the automotive industry.
Demand for lighter materials among truck and trailer manufacturers has slowly evolved over the last decade. “Thinner and lighter weight sidewalls are the primary challenge facing us today vs. 10 years ago,” he points out.
The typical Class 8 truck weighs about 17,000 pounds. According to a recent study conducted by the National Academy of Sciences, the powertrain accounts for 24 percent of the weight, while the body structure is 19 percent. Other heavy components on big rigs include drivetrain and suspension (17 percent) and chassis (12 percent).
“Lighter weight is not the challenge in and of itself, but thinner joints require fasteners to work in new conditions,” adds Tuerk. “Lighter materials can be more subject to deformation when placed in compression. These require innovative solutions like shouldered lockbolt pins combined with large flange collars to increase the footprint and avoid crushing soft materials.”
“Certain segments of the [trucking] industry have always been weight-sensitive, but the real push only began in the last few years, as diesel fuel prices rose dramatically,” explains Steve Tam, vice president of the commercial vehicle sector at ACT Research Co. “New fuel economy standards that will be phased in over the next five years will make [cutting vehicle weight] de riguer.”
“Meeting tough new federal fuel and emission standards on medium- and heavy-duty trucks will require them to be lighter, cleaner and more fuel efficient,” adds Randall Scheps, chairman of the Aluminum Association’s Aluminum Transportation Group. “If newly built Class 8 trucks and trailers [used more] aluminum, it could save 3,300 pounds for each unit, in turn saving 1 billion gallons of diesel fuel and 10 million tons of carbon annually across the fleet.”
The Environmental Protection Agency and the National Highway Traffic Safety Administration recently collaborated on a fuel and emission reduction mandate. Their proposed standards cover not only engines, but the complete vehicle, which Tam says allows greater latitude for vehicle manufacturers to achieve reductions.
The standards, which cover model years 2014 to 2018, will reduce greenhouse gas emissions by nearly 250 million metric tons and save approximately 500 million barrels of oil over the life of these vehicles.
“In an industry where less vehicle weight means more company profit, strategic weight reduction is a smart business tool that is rising in importance,” say Scheps. “It’s simple physics and basic economics. Heavier vehicles need more fuel to operate and [have less] payload capacity, both of which waste money. That’s why the average Class 8 truck today already uses more than 1,000 pounds of aluminum in the form of forged wheels, trailer structure, cabs, fuel tanks and other critical components.”
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