Motorsport aerodynamics saves precious fuel for truckers

Tom Shelley reports on how advanced aerodynamics is bringing significant cash benefits for truck owners and operators

Tom Shelley reports on how advanced aerodynamics is bringing significant cash benefits for truck owners and operators

Greatly improving the aerodynamics of commercial tractor-trailers combinations is able to reduce fuel consumption by 14%, which latest road trials show may be improved to 20%.

The additions to the cab bodywork, which achieve about 7% reduction are relatively conventional, but the most striking enhancements are those made to trailer units, whose methods of functioning are far from obvious.

The technology to do this has been developed and proven in Formula 1 and other branches of motorsport, but is nonetheless to made available to all, at initial prices that can be expected to ensure payback within 12 months or less.

The company that has done all this is Piper International Design Group, an engineering design consultancy based in West London specialising in design and build projects within the motor sport and automotive industries. The team has experience that includes working with Reynard Motorsports, the Williams, and Benetton Formula 1 teams, Jaguar Group C sports cars, Cadillac and Ferrari.

The technology it is now offering is called Fuel Saving Aerodynamics (FSA), and has been trialed over 1 million kilometres. It is now being fitted to more than 85 lorries owned by Marks & Spencer. When fitted to the cabs, it is said to have produced fuel savings of 7.5% over and above those already achieved by the company. Further trials have shown that fitting up trailers achieves an additional 7%, with the tentative results from tests with the latest version kit showing a 12% reduction.

Shown round a test truck at a just held press conference by Piper Design's chief aerodynamicist, Ben Wood revealed a number of innovations.

As well as deflectors on each side of the radiator grilles, which are now almost universal on truck cab bodies, there are also A-pillar deflectors on either side of the windscreen. The deflectors are turning vanes attached to the cab unit which help guide the air round the A-pillars in a managed manner.

An air dam or 'chin spoiler' tidies airflow underneath the cab unit. It is fitted below the vehicle's front bumper. It allows the cab to work normally, without restricting cooling capacity or access for servicing.

A collar fitted at the rear of the cab unit closes the gap between it and the trailer and manages the air flow onto the sides of the trailer. The collar also has to allow access to all connections on the front of the trailer and full tractor-trailer articulation.

Fairings on the side of either the cab or trailer unit manage airflow away from batteries, fuel tank, suspension and chassis elements.

Looking under the trailer revealed a large boat bow in front of the back wheels. The sides of the rear wheels were enclosed by lift up fairing. The rear of the trailer unit was surrounded by a rubber skirt, which, we were told, also helped reduce damage when the trailer was backed into something. We assume that its effect was provide an air cushion for turbulence round the rear of the vehicle. Streamlining the rear end of the vehicle has been achieved without interfering with cargo access or increasing overall length.

The rear of the trailer roof was equipped with a row of vortex generators taking the form of open wishbones, with the openings towards the front. Vortex generators come from the aircraft industry and have the effect of reducing boundary layer thickness. If used to reduce drag, aircraft engineers place them at the point where the boundary layer flow changes from laminar to turbulent, otherwise they can increase drag.

We asked Mr Wood whether the design owed anything to computational fluid dynamics. He said not, even though he owned up to being a writer of CFD code in a previous employment. Instead, the designs were based on lessons learned designing for motorsport, followed by the construction of a 1/3 scale wind tunnel model in the Summer of 2002. During these tests, the Piper configured cab with a standard trailer showed a 20% reduction in drag coefficient. Prototype parts were made in the Autumn of that year. A standard cab with factory fitted kit was tested against the Piper designed cab, each pulling a wide variety of trailers during the course of the trials which lasted six weeks, on a night run between Leicester and Tunbridge Wells. Drivers were chosen for the consistent driving styles and they swapped vehicles regularly over the course of the trials. The result was the 7.5% average fuel saving mentioned earlier. Later tests using a Piper Design configured cab and trailer which wind tunnel model tests had showed to have a drag coefficient reduction of 40%, produced fuel savings of around 14%.

Percentage fuel savings are much less than the reduction in drag coefficient because aerodynamic drag is only one of the sources of resistance to motion, and because of times when the vehicle is stopped, or driving slowly.

Piper Design chief engineer Nick Carpenter reckons that a 10% fuel reduction could produce a fuel cost saving in excess of £2,400 per year. The initial target had been to reduce drag by 12.5% and save 4 to 6% fuel expenditure.

The intellectual property in the technology is protected by patent applications and registration of designs. The kits cost about £3,000 and are presently made in the UK by a subcontractor. Piper Design, however, also intends to earns income from the development by licensing it to OEMs.

The same technical approach can potentially be applied to buses, coaches and other vehicles.

Piper International Design Group

Eureka says: Since there are around 450,000 registered heavy goods vehicles in the UK, the possible fuel savings that could be achieved by aerodynamically designed trucks is staggering, even if each one were to only use 10% less fuel. The sum is more than enough to justify all the money spent on motorsport, from which the technology comes, for many years to come.

Pointers

* Aerodynamically redesigning a truck cab can be made to reduce fuel costs by 7.5%, and aerodynamically redesigning the trailer as well reduces costs by a further 7%

* With the latest refinements to the design, it looks likely to bring the overall saving figure up to 20%

Author
Tom Shelley

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