Fleet Management News & Business Info | Commercial Carrier Journal
Issue link: http://read.dmtmag.com/i/201087
in focus: AERODYNAMIC DEVICES ATDynamics' TrailerTails are lightweight thermoplastic composite fairings that can be installed on the back of dry or refrigerated semi-trailers to help reduce low-pressure aerodynamic drag behind the trailer. Crunching the numbers While aerodynamic devices are the future of efficiency, fleets must know how to do the math BY JACK ROBERTS W atching the nation's roadways these days, it's obvious that a growing number of tractor-trailers now have aerodynamic devices to help control fuel costs. The science of aerodynamics isn't new, but given the boost in commercial vehicle efficiency it delivers, it's surprising it's taken this long for the trucking industry to embrace it more fully. Even more surprising is that there remain aerodynamic holdouts – fleets and drivers who dislike the devices because they don't look "traditional." "It's a totally different world than we saw back in 2006 and 2007," says Jeff Grossmann, vice president of engineering for ATDynamics. "It is understood in our industry today that the most competitive and profitable fleets are the ones that are adopting aerodynamic technologies ahead of their competitors." Grossmann says that understanding by fleets only is going to deepen next year as the results of the U.S. Department of Energy's SuperTruck Program come to light. The goal was to boost commercial vehicle fuel economy to twice the baseline number established in 2010 when the project started. "We're already seeing releases stating that number is going to be met," he says. "Aerodynamic devices have played a huge role in hitting that number." will have an effect on the total system," says James Scarcelli, vice president and general manager for Wabash Composites, a division of Wabash National. If a gap reducer is added to a system that already has a skirt, the aerodynamic change also will affect the aerodynamics around the skirt. "In most cases, you are dealing with the law of diminishing returns – the more you add, the less each part can contribute to the total system," Scarcelli says. "You cannot take a 4 percent device and a 6 percent device and call it a 10 percent gain." To measure the gains of combined devices accurately, the configuration should be tested in a wind tunnel, at a track or on the road, he says. Another problem with calculating fuel savings accurately is understanding the maddening array of variables that come into play. Wind, weather, temperature, road surface and terrain are just a few of the conditions trucks encounter that can reset the aerodynamic calculator on a daily basis. For many fleets, it may be more accurate to measure aerodynamic efficiency gains in miles per gallon instead of drag percentages. "Air drag is a force that drains a certain amount of power from Percentage vs. cumulative The verdict may be in on aerodynamic devices, but fleets thinking about adding them to their vehicles need to have realistic expectations on the type of fuel economy numbers they're likely to see. Fuel efficiency percentage boosts based on device combinations are not cumulative. To understand the actual increases provided by adding a Avantechs' VorBlade number of different aeroWing side fairings can be purchased as individual dynamic devices, a fleet has units to use on a tractor or to look at the tractor and trailer, or as side fairings trailer as a total system. for a trailer. "Each piece that is added COMMERCIAL CARRIER JOURNAL | NOVEMBER 2013 35