Great Dane Chooses Smart Way to Go Green
When Wal-Mart pledged to double fuel efficiency on its trucks within 10 years, the retail giant turned to Great Dane for a greener solution.
Of the four designs presented by Great Dane engineers, Wal-Mart chose an aggressive drop-frame 53-ft. trailer with a rounded nose and underskirts that dropped down automatically when the vehicle exceeded 35 mph. The rear section, including sides and top, was tapered inwards and the roll-up rear door was recessed inside the trailer about two feet, resulting in an aerodynamic "boattail" effect without any added length. Comprised of lightweight components, the trailer's 16-inch drop frame compensated for any loss of cube volume.
Road tested by International Truck and Engine Corp., the Great Dane trailer's aero design yielded promising results - a 20 percent reduction in drag and double-digit fuel savings (achieved without super-single tires).
Though pleased with the overall design, Great Dane engineers were troubled by the pneumatically powered drop-down skirt and the lifting suspension required to bring the trailer up to dock level, as it sat only 12'6" high.
The result was Aero 2, a 13’6" tall 53-footer featuring a full-length fixed skirt and wide-based single tires. Tested again by International, Aero 2’s results were comparable to Aero 1.
The almost full-length, flexible skirt keeps the slipstream and crosswinds from dragging along the trailer cross-members and rear wheel bogies. A removable panel fitted over the wheel-well allows service access to the tires and axles for servicing. The parabolic shaped nose lessens resistance by shortening the gap between the tractor and trailer.
The boattail effect, achieved by tapering the sides and top of the trailer and recessing the back door inward two feet, provides an air cavity which increases the air pressure behind the trailer and significantly reduces drag. The tapered rear end channels the air stream into a narrower air-corridor behind the trailer.
Though the parabolic front end, tapered rear section, and recessed door results in a loss of cubic capacity, the increased fuel economy should more than compensate for the slightly decreased volume.
Great Dane's aero trailer will go a long way to help Wal-Mart meet its ambitious fuel economy targets. It already meets and exceeds US EPA SmartWay trailer criteria by having low resistance tires, side skirts, weight-saving technologies, and a gap-reduced front end and rear boat tail.
Already a partner in the EPA SmartWay Program, Great Dane is committed to develop products and strategies that result in increased fuel efficiency. Such options include: aerodynamic devices for trailers, which reduce drag and in turn engine load, and fairings added to the front, sides, underside and rear of trailers to improve airflow.
Some of these options, which have already been showcased by Great Dane on experimental trailers for customers like Wal-Mart, are undergoing evaluation. Still, other fuel-saving technologies are already available from Great Dane. For example, single wide-base tires that replace traditional dual tires save fuel by reducing weight and rolling resistance, and there is a slight aerodynamic benefit to this technology as well.
Automatic tire inflation systems, such as the Meritor Tire Inflation System (MTIS) by P.S.I., eliminate fuel efficiency losses caused by underinflated tires. Tools developed by EPA can help quantify the benefits of these fuel-saving options.
By 2012, the SmartWay Transport Partnership and its counterpart, Natural Resources Canada's (NRCan) FleetSmart (a component of the ecoENERGY for Fleets program), aim to eliminate between 33 and 66 million metric tons of CO2 and up to 200,000 tons of nitrogen oxide (NOx) emissions per year. At the same time, the effort will result in fuel savings of up to 150 million barrels of oil annually.
The benefits are clear. By participating in these programs Great Dane and its customers are helping improve fuel efficiency to reduce their environmental footprint, an effort that brings about well-deserved distinction and recognition.