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Aerodynamics | CV Dealer Feature

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Do aerodynamic packages genuinely cut fuel usage and CO2 emissions? No question about it say Mercedes-Benz and trailer manufacturer Krone.

mercedes-benz krone trailer

Mercedes-Benz and Krone have been collaborating on an aerodynamic curtainsider semi-trailer, which debuted at the IAA Hanover Commercial Vehicle Show 2016

At the recent IAA Hanover Commercial Vehicle Show in Germany Mercedes-Benz and Krone jointly exhibited an aerodynamic curtainsider semi-trailer which has delivered fuel savings of over 5% under test conditions.

Making its world premiere at Hanover, Krone’s Profi Liner Efficiency trailer is equipped with panels or skirts that cover the sides below the load bed – including the three axles – and are said to reduce drag by 5.2%. Low-rolling-resistance tyres are fitted too.

A four-part wing is installed at the back which Krone says cuts drag by a further 6.3%. It extends by a comparatively modest 500mm – considerably less than some of the wings now being fitted to trailers in the USA – but Mercedes points out that European legislation does not allow it to project any further.

The wing has to be folded away before the back doors can be opened but this only takes a few seconds, say Mercedes and Krone.

The test referred to involved five German hauliers who hauled Profi Liner Efficiency trailers using standard Actros tractor units in what the two manufacturers style as ‘Efficiency Run 2016’.

krone four part wing

Krone claim their four-part wing, which is fitted to the back of trailers, can reduce drag by 6.3%

Critics of aerodynamics point out that side skirts and rear extensions are vulnerable to expensive damage. The side skirts fitted to the Krone trailer are solidly constructed and appear to have been designed with ease of repair in mind, and the operators concerned say that no harm came to them during three months and some 95,000 miles of testing, despite the fact that the trailers were regularly side-loaded by forklifts. Nor did the rear wings come to grief.

“A trailer with side panels is just as usable as a conventional trailer,” says Rudiger Elflein, Managing Director of Elflein Spediton & Transport, whose company took part in the trial.

The five artics were used on a mixture of short- and long-haul work moving car engines, steel, paper, timber products and building materials.

At the show the trailer was exhibited coupled to the latest Actros 4×2 powered by the OM 471 six-cylinder diesel and equipped with low rolling Predictive Powertrain Control – a cruise control system that anticipates the highway ahead and responds accordingly. It is a combination that promises a fuel saving of up to 20%, says Mercedes.

“Our optimised tractor and semi-trailer pay off for the environment and our customers, and the cost can be amortised in about 18 months,” says Dr Wolfgang Bernhard, the Daimler Board of Management member responsible for Daimler Trucks and Buses.

Savings to be Made

Detractors contend that while aerodynamic treatments may be beneficial if you are travelling at a steady 56mph on the motorway hour after hour, they are of little help if you are involved in stop-start city centre distribution. If that is the sort of work you are on, they add, then you should save fuel by reducing the un-laden weight of your vehicles by, for example, specifying bodies with aluminium side raves, floors and cross-members.

Aerodyne contends that while the impact of aerodynamics is without a doubt less if you are on urban delivery work rather than intercity runs, it cannot be dismissed entirely. It argues that useful fuel savings can be achieved at surprisingly low speeds – 20mph to 35mph – if steps are taken to smooth the airflow around the bodies of light and medium trucks on distribution runs.

It cites examples of firms that have fitted items such as 3D cab top fairings and cab rear sidewings to 18 tonners – which tend not to be used on long-haul intercity trunking work – and have seen fuel consumption tumble by anywhere from 5.8% to 8.4%.; more than one might expect. The return on the investment required to fit side skirts, radiused body cappings and so on to trucks can vary from four to fifteen months; it adds depending on what is specified, the work the vehicle is on and the mileage covered.

Wide Variety of Products on Offer

While Mercedes-Benz and Krone clearly had aerodynamics in mind from the beginning, for others it can be an afterthought.

“A lot of people only consider fitting aerodynamics after the vehicle is built or do not bother. In a completive business, owners need to consider how they can get extra money,” explains Kevin Hawes, Aerodynamic Specialist for Hilton Docker Mouldings. “Those that invest time and effort into researching their fleets and the best package for them will reap a good return. Those that do not and adopt the policy that it will have one fitted from wherever they source their vehicle stand to lose.”

Kevin suggests that it is companies’ and peoples’ resistance to change that is holding the trade back: “Without change you can only guarantee you will get the same you had yesterday. Those that do not wish to change will get the same from their business and will not improve for the future, let alone the impact on our environment.”

For those looking to make that change and improve the aerodynamics of their vehicles, there are options out there. Aerodyne offers a wide variety of aerodynamic packages and is constantly adding to the line-up. Earlier this year for example it introduced more air management kits for Actros, its sister model Antos and the Renault T-range.

Meanwhile, Hilton Docker Mouldings offers a broad assortment of products for both trucks and light commercials, including cab top deflectors and spoilers for models such as Citroen’s Relay and Vauxhall’s Movano.

A key problem with cab top spoilers on tractor units in particular is that they do not always align with the roof of the trailer, which means that their effect is dramatically diluted. One benefit of Kuda’s iAM line-up of air management kits is that the spoiler for the cab roof is adjustable and can cater for trailer heights of up to 4.8m.

“Just 400mm of exposed trailer bulkhead increases drag on the vehicle by a massive 12% and therefore increases fuel consumption by 6%,” says Tim Vincent, Head of Product Market Development and Type Approval Consultant. With this in mind Kuda offers LaserEye.

“It intelligently detects the coupled trailer height and automatically adjusts the spoiler on the roof to the correct height for optimum fuel efficiency,” he says.

Roof-mounted spoilers can be affected by motorway cross-winds. In response, Hatcher has worked in conjunction with Cranfield University to develop Active Freddie.

Pressure sensor monitoring while the vehicle is in motion ensures that the deflector constantly optimises its position in relation to the yaw angle. As a consequence, it provides consistent drag reduction and additional fuel savings, Hatcher says.

“The external aerodynamic shape is maintained as close as possible to that which results in the lowest drag for the given conditions throughout the trip,” says Cranfield’s Professor Kevin Garry. “The resulting additional fuel saving can be as much as 3% on a typical journey.”

Active Freddie can be adjusted to the height of a trailer and can be complemented by Under-trailer Freddie, a shaped fairing that sweeps rearwards from the landing legs. It can deliver a fuel saving of up to 3%, reports Hatcher.

New Products


OptiFlow™ AutoTail represents the next generation of WABCO’s OptiFlow Tail, the best performing tail in Europe as validated by fleets, that features automatic deployment and retraction of aerodynamic tail panels based on driving speed. (Image: WABCO)

Hatcher was at the Hanover Show, as was automotive components giant WABCO, which gave OptiFlow AutoTail its global premiere. It is a rear-mounted wing that deploys and retracts automatically depending on the speed at which the truck is travelling.

Automatic deployment occurs at 75km/h (47mph) and the wing folds away again at 15km/h (9mph) which ensures the device is consistently used at speeds that maximise aerodynamic fuel savings, says WABCO. Under test conditions it has delivered savings of up to 1.1 litres per 100km (62 miles) at 85km/h (53mph), the company says, and reduced CO2 emissions by up to 2.8 tonnes per trailer per year.

On show too, and for the first time in Europe, was OptiFlow TrailerSkirt, which WABCO acquired when it bought Canadian aerodynamics specialist Laydon Composites last April. It has demonstrated savings of over 1.8 litres per 100km at US highway speeds of 105km/h (65mph), WABCO states.


OptiFlow™ TrailerSkirt provides a lightweight aerodynamic system available to commercial vehicle fleets in the North American market. It has demonstrated fuel savings of more than 1.8 litres per 100 km at U.S. highway speeds (Image: WABCO)

An aerodynamically-styled rigid body or trailer can of course bring marketing benefits, especially if you are a high-profile retailer; something businesses that have opted for dramatically-sculpted products such as Don-Bur’s Teardop trailer have doubtless found. They get your brand noticed on the motorway and in a positive way.

Add their visual impact to the fuel savings and CO2 cuts they can deliver, and for many fleets the investment is likely to be a wise one.

For those now thinking how they could improve their own vehicles or perhaps wondering if they have the products fitted, Hilton Docker’s Kevin Hawes recommends that people do not leave their savings to chance, and to contact someone deals and specialises in aerodynamics to help them make an informed decision.