The art of aerodynamics

In March 2014, US retail giant Walmart unveiled a futuristic concept truck that has since caused a stir in the North American commercial vehicle design community. The Walmart Advanced Vehicle Experience (WAVE) is said to be 20 per cent more aerodynamic than any current truck/trailer combination in the vast Walmart fleet and reignited the age-old debate on the importance of streamlined equipment design.

“The key to continued improvement is through technology. We need to use the most efficient equipment available – and we need to pursue and test the technologies of tomorrow,” says Walmart’s Elizabeth Fretheim , revealing that the privately funded study could be more than just a show vehicle.

According to Fretheim, the futuristic semi was built by Great Dane and is made almost exclusively of carbon fibre, saving almost 4,000 pounds (1.8 tonnes) on tare weight. While details on the material’s impact resistance have not been revealed as yet, Walmart did expose the convex nose cannot only help improve on aerodynamic performance, but also increase storage space on the inside. A comparable concept has been used in truck body design for quite some time now, albeit mostly as a bolt-on feature with no added functionality.

In that sense, Walmart’s latest design experiment is bringing a new element – added functionality – to the aerodynamics discussion, which has been rumbling on for almost 80 years now. Canadian company J. B. Baillargeon Express came up with an aerodynamic concept truck as early as 1925, and NASA’s Dryden Flight Research Centre (now known the Armstrong Flight Research Centre) began re-interpreting the classic truck shape in the 1970s, followed by a range of research projects all across the globe that continue to attract attention today.

NASA’s Dryden team and those who followed realised early on that all components of a vehicle’s design interact with each other, and that understanding truck and trailer as one unit of mutually supporting elements was essential. 

Today, another driving force for the design of more aerodynamic trailers is environmental concern. That’s why California and the US Environmental Protection Agency (EPA) have been pushing ‘aero equipment’ aggressively recently, and why the US is leading the movement from the front.

Walmart’s WAVE concept is adding to that proud tradition, again putting North American ingenuity in the spotlight after the country pioneered the use of aerodynamic trailer ‘tails’ and efficiency-enhancing side skirts over the past decade. 

Europe’s transport equipment industry is equally creative, yet less conclusive in regard to adapting the legal framework required to make modern trailer design a reality. Only recently, a draft law to allow for a more aerodynamic truck design – officially a revision of EU Directive 96/53 – was backed by the European Parliament’s Committee on Transport (TRAN), but the EU still needs to agree on a formal wording, which could delay the implementation of the new law indefinitely.

While the committee followed the European Commission’s announcement to add an additional 50cm to the standard length of a semi, allowing for the installation of aerodynamic fairings at the rear, it rejected the proposal to liberalise the movement of so-called ‘Gigaliners’ across Europe, pending further research. The Committee asked the Commission to further assess the impact of lifting the ban on cross-border usage of oversized combinations, which can measure up to 25m in length and weigh 60 tonnes, by 2016.

Future commercial vehicle design in Europe will therefore have to focus on  small-scale aerodynamic improvement only – at least until the Commission has assessed the impact of oversized vehicles on competition, modal shift, the cost of adapting roads, the environment and overall safety.

But, the lack of legislative support has hardly ever stopped the aerodynamics community to re-think modern vehicle design – at least theoretically. Back in 2008, for example, a public-private partnership platform was established in the Netherlands to evaluate the viability of improving the aerodynamic shape of semi-trailers by mounting side skirts and boat tails comparable to those used in the US. Trials confirmed the effectiveness of both systems, with the Delft University of Technology stating a cut in fuel consumption and emissions of up to 15 per cent. 

In 2011, Mercedes-Benz presented a futuristic design study named Aero at a trade show in Kortrijk, Belgium – claiming it would be able to reduce wind resistance by 18 per cent and decrease fuel consumption by five per cent – and trailer expert Krone presented an equally impressive concept vehicle at the IAA 2012. Scania also experimented with aerodynamic optimisation at the time, trialling a rear air deflector on trucks shuttling between the company’s two main European truck manufacturing plants in Sodertalje, Sweden and Zwolle, Holland.

At the same time, UK trailer brand Lawrence David had already been selling the Fuel Saver model – a semi in the shape of a teardrop that is tapered at the front and back to improve airflow and connect to the roof spoiler of the truck in front – for about half a decade. The trailer – developed in line with current legislation – is now also available in a double deck, extra long version to work under the UK’s own high performance vehicle design scheme. It is also one of the few streamlined semi-trailers that have actually gone into serial production.

In the virtual world, additional work on aerodynamic truck design with a special focus on trailing equipment has been published by industrial design consultant Jeremy Singley from the US and his Kenyan colleague, Arnold Kioko Muthui, to name a few. Singley actually went to great lengths to make the concept as practical as possible.

“I’m seeing a lot of concepts out there that require changes to regulations, changes to the dry van box dimensions, impossible windshields, wacky styling that truckers – a very conservative lot – wouldn’t be caught dead in and hard-to-handle boat tails,” he says. “The box dimensions are particularly important. The whole product world is dedicated to how many widgets fit into how many boxes onto how many pallets into an 8 1/2 x 9 foot trailer. So, you cannot change the trailer.” 

However, Singley is well aware that more work has to be done to make his SuperTruck a reality. “Regarding the trailer aero add-ons I’ve designed, there are details there that remain to be worked out,” he says, pointing out that future research may be crowd-funded, depending on public feedback.

He adds, “For the first prototype, we would probably keep the fifth wheel and the trailer wheels in dedicated positions, allowing for adjustability of those positions in a subsequent trial. For the boat tail, we are looking at designs that should be easier and more practical to use than existing boat tail designs, though possibly a bit more pricy.”

While Singley is still trying to fund the actual build of the SuperTruck, solvent transport companies like Walmart will continue to push the envelope, primarily driven by the need to become more cost-effective. Despite being restricted by current legislation, the European competition will certainly not stand idle, and it’s safe to say a new, hungry generation from Asia and the Middle East will soon join the vibrant truck design scene as well.

The result will be a highly energetic marketplace of innovation that could lift truck design as we know it to a whole new level. What is needed, though, is a supportive framework that will help make the work being done at the ground level visible on the political agenda.

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