An experimental aerodynamic trailer from Great DaneTrailers, International Truck & Engine Corp. and Wal-Mart is an integrated approach to smoothing airflow for drag reduction and fuel savings.
Reduction of consumption of diesel fuel by fleet operators is a critical need from both an economic and environmental perspective. The Wal-Mart Experimental Trailer has external geometric features designed to improve trailer aerodynamics and reduce fuel consumption by the tractor. According to the US Department of Energy, Class 8 trucks account for 11%-12% of total US petroleum consumption and 50% of energy expenditure by Class 8 trucks is in overcoming aerodynamic drag at highway speeds
The trailer utilizes improvements in three key areas to reduce drag and at the same time meet necessary design and functional criteria. Reductions in frontal, underbody and base (rear) drag are designed to accompany efficient tractor aerodynamic design leveraging the benefits of both and leading to significant improvements as compared to conventional equipment.
Reduced overall height contributes to an 8% reduction in frontal area. Cargo volume is maintained by utilization of a drop deck configuration, while a "maxi lift" suspension allows the trailer to adjust to a normal dock height for loading and unloading.
Deployable underbody "skirts" are employed to improve aerodynamics particularly in the presence of crosswinds. Below 35 mph, the skirts are raised to improve ground clearance. Above 35 mph, they automatically deploy to improve aerodynamics and reduce drag.
The aft section of the trailer is tapered to help keep airflow attached to the trailer body better than conventional square construction. A "cavity back" increases pressure behind the trailer. Both design details effectively reduce the trailer's "wake" contributing to reduced drag and improved economy.
The experimental trailer also makes use of single-wide tires to reduce weight, reduce rolling friction, and reduce fuel consumption. Additionally, the Wal-Mart Experimental Trailer is equipped with smooth wheel covers to reduce drag associated with the wheels and tires.
"After many years of working on trailer aerodynamics, the design for our corporate partner Wal-Mart is particularly rewarding because of the leadership role they are taking on energy efficiency," said Charlie Fetz, vice president of research and development at Great Dane Trailers. "Wal-Mart's environmental concern and request for an experimental trailer as a way to save fuel is both the motivation and the momentum behind the project."
"The culmination of Great Dane's work with International Truck Engine Corp. under the TMA validates the research we have conducted over many years. Our goal is to design practical aerodynamic solutions which would lead to immediate fuel savings. Our effort with International shows significant progress toward this goal, incorporating important aerodynamic concepts into a very functional trailer."