Sean Graham's engineering quest began as many do — completely by happenstance. While finishing a degree in mechanical engineering at Penn State University, he did some aerodynamic “wind tunnel” work on cars and trucks and was struck by the contrast between the blunt and boxy shape of the trailers and the sleek and round-edged shape of the tractors that pulled them.
During his drive out West to pursue a graduate degree in wind tunnel engineering, Graham passed tractor-trailers mile after long mile and grew more and more convinced that there had to be a way to improve the aerodynamic “footprint” of trailers to match that of their tractor counterparts, thus reducing drag and fuel consumption.
Graham discovered there were already hundreds of patents for a huge range of aerodynamic trailer innovations. “It's a big list of very expensive attempts to solve this problem.”
This did not deter him, however. Graham was convinced he could develop a solution to trailer aerodynamics for fleets would find cost effective. He knew that the key was to be aware of how real-world needs might change what he designed in the lab.
Four years ago Graham formed Freight Wing, with the goal of developing a design prototype for a “boat tail” that would attach to the rear of a trailer, tractor-trailer gap fairing, and belly fairing. He was awarded a $75,000 grant from the Dept. of Energy to conduct computer simulations confirming drag improvement and fuel savings.
The next step was to talk to fleets about conducting field tests. Fleets had a very short list of needs when it came to the design criteria for trailer aerodynamic improvements: fuel savings; durability; retention of vehicle operating characteristics. “Fleets also said they wouldn't pay attention to us if we didn't get a respected third party to test our invention using accredited industry standards.”
Graham tested three fairing prototypes at the Transportation Research Center (TRC) in East Liberty, OH, using SAE and TMC fuel economy tests. Fuel economy improvements by type were: belly fairing, 4%; gap fairing, 2%; and boat tail 1%.
“We expected the boat tail to perform the best, but the belly fairing came out on top,” he points out. The silver lining was that they could now drop the problematic boat tail design. Creating a durable design for the rear of the trailer, as well as minimizing its impact on opening and closing the doors, had proved very difficult.
Transport Corporation of America was Freight Wing's first test fleet, putting fairings on five of its trailers. As expected, says, Graham, those field tests forced new design changes.
“First, the rivets we used to attach the fairings to the trailer were too small,” he says. “Then we tried thinning the fairings down to reduce weight. We went to a 0.04 mm thickness [trailer siding is typically 0.05 mm] but that proved too light to withstand daily operations. So now the ‘wings’ are 0.06 mm.”
A second DOE grant helped spur more fleet tests since it enabled Freight Wing to cut by half the cost of buying and installing the fairings. One fleet is Whole Foods Markets, which outfitted 20 of its reefer trailers at its Munster, IN, distribution center with the belly fairing product. Steve Burse, Whole Food's team leader on the project, reported that it took just three days to get all the fairings installed and that fuel savings were achieved from the get-go. Based on annual mileage of 2.58 million, he projects a 16,900-gal. fuel savings. At $2.50/gal, that's $42,200 savings.
“Though we're more than confident in the engineering, the real world challenges remain the biggest hurdle,” Graham explains. “There's still a lot of skepticism, especially about the fuel savings. The TRC results get us in the door, but fleets still want to conduct their own tests, not only to gauge fuel savings for themselves but to look at durability and operational issues,” he adds. “Yet fleet trials are producing a return on investment in less than 50,000 miles of operation.”