CCJ

February 2018

Fleet Management News & Business Info | Commercial Carrier Journal

Issue link: http://read.dmtmag.com/i/936627

Contents of this Issue

Navigation

Page 29 of 67

28 commercial carrier journal | february 2018 Upfit strategies, impacts can vary BY JASON CANNON W hile much effort has been made to improve the aerodynamics of heavy trucks over the years, the same hardly can be said for the trailer. While the improved airflow coming off the tractor has a positive impact on the box behind it, the responsibility of improving trailer drag has fallen largely on upfits and add-ons such as skirts, tails and fairings. e three areas on a trailer where aerodynamic drag is the greatest are the front above the tractor's air dam, the bogie and the negative pressure pocket behind the doors. But the strategies used to attack those three areas can vary, as can their impacts on efficiency and overall effectiveness. "Generally speaking, if you have one thing, and then you add another thing, it's not always a '1+1=2' all the time," said Josh Butler, FlowBelow president. "Two things that affect the same spot aren't necessarily going to be additive," said Steve Ingham, SmartTruck chief executive officer. Redirect or deflect Ingham said there are two basic ways to improve aerodynamics – redirect airflow, or deflect it – because there's not much you can do with air aer it hits a moving vehicle. "e challenge of deflecting air is that it creates forces that have to be overcome," Ingham said. "e drag created by the structure to support the deflection is usually bigger than the benefit of the deflection." FlowBelow's tractor AeroKit works with the trailer by filling the gap between the truck's drive axles. e kit's rear panel, which is flared outward, helps the air jump the gap between the last fairing and the trailer skirt. "It also helps to pull out the underbody flow of the truck," But- ler said. "You're trying to get that air out and get it to go around the skirt. Most importantly, it prevents [air] from going under the skirts." According to the North American Council for Freight Efficiency's Annual FleetFuel Study, trailer skirts have soared in popularity since 2008, with deployment of the devices reaching more than 80 percent over a six-year period. Skirts reduce aerodynamic drag under the trailer where air hits the rear axles by streamlining and guiding air around the sides and to the back of the trailer. Trailer tails, another familiar add-on, create a vacuum and suck the air around the trailer's rear corners before air can be forced into the low-pressure pocket that causes rear drag. Tails also provide perks beyond aerodynamics, said Prashanth Kamath, leader of Stemco's Innovative Tire & Mileage Solutions segment. "It also goes a long way to increasing safety, stability and visi- bility," he said. "It does a lot to streamline airflow and makes for a smoother drive, leading to lower driver fatigue." Making a choice For fleets struggling to decide between tails and skirts, choosing the industry's most popular aero add-on is a logical first step, Kamath said. "If you've got nothing, go with a skirt," he said. "If you have a skirt, go with a tail. If you have a tail, go with an auto-deploy- ment device [for the tail]." SmartTruck's TopKit is shaped like airplane wings and mounted to the trailer top and sides. It works similar to a tail by compressing, accelerating and redirecting airflow around the trailer's rear corner. "By pushing that flow around those corners, it fills that low-pressure pocket more effectively and lessens the amount of low pressure that is pulling on those doors," Ingham said. Last year, the U.S. Environmental Protection Agency shelved plans to include trailer efficiency in its Phase 2 Greenhouse Gas regulations that would have required all trailers to use some combination of efficiency technologies, which could have included aero upfits and low-rolling-resis- tance tires, among other options. in focus: TRAILER AERODYNAMICS Trailer skirts have soared in popularity since 2008, with deploy- ment of the devices reaching more than 80 percent over a six-year period, according to NACFE.

Articles in this issue

Archives of this issue

view archives of CCJ - February 2018