Fleet Management News & Business Info | Commercial Carrier Journal
Issue link: http://read.dmtmag.com/i/599511
40 commercial carrier journal | november 2015 A erodynamic characteristics around the fifth wheel and the trailer's rear are difficult to manage. The trailer gap is a nec- essary open space that allows for full articulation as the rig maneuvers in tight surroundings. But in aerodynamic terms, that massive gap is a huge drag inducer on the entire vehicle. At highway speeds, as air flows past the tractor heading for the trailer, it encounters a large vacuum area created by the gap's open space. The same holds true for the back of a trailer. As air passes around it, a nat- ural vacuum forms behind the vehicle that air seeks to fill. The result is drag, which leads to aerodynamic inefficiency and makes a vehicle more difficult to move down the road efficiently. The engine must work harder to overcome it, burning more fuel as a consequence. Smart fleet managers understand the importance of reducing these large areas of turbulence and drag. Fortu- nately, tractor-trailer aerodynamics have become better understood in re- cent years, leading to new devices that help smooth airflow past the trailer gap and behind the trailer. "Until about 2000, tractors and trailers were really manufactured in isolation from each other," says Kent Smerdon, vice president of inter- national marketing for Aeroserve Technologies, which manufactures and sells Airtab vortex generators. "This concept is changing, with the indus- try appreciation that a large gap is an aerodynamic and fuel problem area." Today's aerodynamic innovations include high-rise condo – or load- height matching – full fairings and side extenders. "From the trailer side of the equation, rounded front corners and devices such as nose cones have helped with drag reduction efforts," Smerdon says. Jeff Grossmann, director of en- gineering for aerodynamic device manufacturer Stemco, believes that North American truck fleets have learned that closing the tractor-trailer gap is the easiest way to save fuel and improve fuel economy. "Just closing the gap a mere 5 inches – from 50 to 45 inches, for example – offers fleets large and immediate fuel savings," Grossmann says. Tackling the total package Smerdon says that although OEMs have improved their designs for more aerodynamic efficiency, fleet manag- ers should understand that only the separate tractor and trailer have been optimized, not the total package. "The connection point between these two items is the big variable, and the best gap is no gap at all," he says. "Add-on aerodynamic fairings and side extenders can help reduce the gap, but it still exists and will remain a sig- nificant source of drag until a practical way to eliminate it is invented." Aeroserve offers vortex generators that attach to strategic points on a tractor to help direct airflow around the gap and decrease unwanted wrap- around turbulence and crosswinds. "Vortex generators offer fleets the option of setting their kingpins for optimum axle loading for their loads without any loss of fuel economy," Smerdon says. Vortex generators are designed for easy installation and to deliver a cost-effective benefit by fitting only the tractors, and the results sound impressive. Smerdon says the current best-selling vortex generator claims a 2- to 3-percent fuel savings on a fully faired tractor-only installation for a typical dry van gap. in focus: TRAILER AERODYNAMICS Filling the holes on the highway Aeroserve's Airtab vortex generators attach on a tractor to help direct airflow around the tractor-trailer gap. Stemco manufactures TrailerTail boat-tail aerodynamic devices. Minding the trailer's gap, rear can boost the bottom line By jack RoBeRts