XStream Trucking has introduced its TruckWings active cab-to-trailer aerodynamic system to the North American market. In its prototype form, called GapGorilla, it won the company first prize in the 2016 First Look West (FloW) competition run by Caltech's Resnick Sustainability Institute. Now its shape-shifting approach to reducing drag is heading for the highway with the promise of fuel savings of up to five percent.

With fuel accounting for a significant proportion of truck running costs these days, the quest for fuel efficiency has been attracting increasing attention. While engine, transmission and tire efficiencies continue to improve and yield useful gains, several research studies have indicated that reducing aerodynamic drag can contribute fuel savings of as much as 12 percent. Consequently, cab-forward designs on long-haul trucks have dwindled as flowing lines have been adopted on engine-forward cabs, and side skirts, under-body fairings, wheel covers and trailer tails have become mainstream equipment. Alongside those, there have been several products designed to reduce the substantial drag introduced by the gap between the cab and the trailer.

Because the rig must be able to turn tightly with the cab rotating at an angle to the trailer, there has traditionally been a large gap there that creates a zone of low-pressure turbulence. Attempts to reduce this problem have included trim tabs installed around the cab periphery to smooth the air flow across the gap, curved bulkheads that extend forward from the trailer, fixed skirts mounted around the cab sides and roof, and telescoping fifth-wheel dollies that automatically reduce the gap at highway speeds. XStream Trucking's approach is to literally close the gap at highway speeds and, according to the company, TruckWings can reduce fuel consumption by between three and five percent.

"TruckWings is the first device which completely solves the turbulence problem created by the open area between the tractor and trailer that contributes significantly to a truck's overall aerodynamic drag," says Daniel Burrows, XStream Trucking's founder and CEO. "Since two thirds of a truck's fuel bill is spent overcoming that drag, there is a huge savings to be had by reducing it."

The patented TruckWings design incorporates folding panels made of impact-resistant, glass-reinforced composites attached to the rear sides and roof of the cab that automatically swing out to close the cab-to-trailer gap at highway speeds, and retract against the rear of the cab at lower speeds to leave room for turning maneuvers.

XStream Trucking has developed the technology during the last few years, initially validating the concept using computational fluid dynamics and then conducting wind tunnel modeling at the Environmental Protection Agency (EPA) SmartWay-approved Automotive Research Center in Indianapolis. With the wind tunnel tests suggesting a fuel saving of up to four percent on sleeper cabs, on-track tests were conducted with independent supervision by Canada's sustainable transportation organization, the PIT Group, and then real-world fuel saving tests were run on public highways and witnessed by the North American Council for Freight Efficiency (NACFE).

"The exciting thing about TruckWings is that it is the first solution to automatically and completely enclose the sides and top of the tractor trailer gap," says Mike Roeth, Executive Director of NACFE. "This gap area presents as much as a five percent opportunity with little to no other solutions available for truckers today."

As well as the option to purchase the equipment outright, XStream Trucking is offering a shared savings program to customers who, the company claims, could achieve full payback after 18 months of normal use. Several freight carriers, including two of the US's largest trucking fleets, are currently running private tests using TruckWings.

See TruckWings in action in the following video.

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