Real-world on-road testing conducted by Mercedes-Benz showed that a tractor/semitrailer combination with a gross weight of 40 tonnes consisting of a Mercedes-Benz Actros—currently offering the best aerodynamics in a series production truck—and the aerodynamically optimized Aerodynamics trailer can achieve fuel savings of 4.5% in long-haul usage.

In the case of an average annual mileage of 150,000 km for a long-distance truck, this means a reduction in diesel consumption of around 2,000 liters and more than five tonnes of CO₂ annually. In real terms, trucks which are subject to toll charges on German motorways (12 t and above) cover around 25 billion kilometres which corresponds to 300 million litres of diesel that can be saved in a year, as well as more than 800,000 tonnes of CO₂ emissions.

The tractor unit, here the new Mercedes-Benz Actros with StreamSpace cab, remains unchanged. The new Actros is already aerodynamically optimized. It will merely be equipped with an air deflector on the roof, cab side deflectors and side trim panels between the axles. This aerodynamics package is already available ex-factory for heavy-duty Mercedes-Benz trucks in long-haul transport.

The Mercedes-Benz Aerodynamics trailer is ready for everyday use, without any restrictions. It is based on a conventional 13.6 m freezer box body, with a refrigeration unit at the front end. Whether for ground clearance, approach/departure angle or ease of loading at the rear, the Aerodynamics trailer meets all the usual requirements of everyday haulage. The box body remains unchanged despite the aerodynamic measures.

The development partners in the IAA project were Daimler Trucks and trailer specialist Schmitz Cargobull. They ensured focus was on everyday suitability. Working closely with designers and engineers from Daimler Trucks, Schmitz Cargobull developed the attachments on their own, based on designs furnished by Mercedes-Benz. These were transformed by Schmitz Cargobull into the actual Aerodynamics trailer using computer surface data.

The Aerodynamics trailer began as a study presented by Mercedes-Benz last autumn at the “Trailer” trade show in Kortrijk, Belgium. (Earlier post.) Going beyond the Actros, Mercedes-Benz had set its sights on the entire tractor/semitrailer combination.

As the Aerodynamics trailer shows, Mercedes-Benz suggests, ultimate efficiency in a semitrailer is only achieved with the perfect combination of tractor unit and trailer. Based on the results of the Record Run, a realistic fuel consumption of less than 25 l/100 km (9.4 mpg US) is possible for a 40-tonne tractor trailer when a Mercedes-Benz Actros is combined with an Aerodynamics trailer.

The vehicle combination is producible, upholds the framework of coming legal requirements and is realistic for everyday use under tough road transport conditions.

The Aerodynamics trailer at the IAA corresponds largely to the Mercedes-Benz study. The basic model is a refrigerator trailer, a typical vehicle for long-distance haulage. Measuring 13.6 m long and 2.6 m wide with a total height of 4 m including the chassis, the familiar box body remains unchanged for the Aerodynamics trailer.

Numerous individual measures on the Aerodynamics trailer lower the air resistance of the entire tractor unit.

• A spoiler on the bulkhead of the trailer reduces the distance to the tractor unit, and this itself lowers air resistance by 1%. The spoiler frames the refrigerator unit, with air slots providing the necessary ventilation.

• The plastic side trim panels on the Aerodynamics trailer contribute an 8%improvement to the air resistance. As in the design study, they are slightly drawn-in at the front and characterized by an opening at the rear. This steers the air in the direction of the rear diffuser.

• The diffuser has the shape of a parallelogram and links up with the underbody panelling. Also made of plastic, it improves the wind resistance by a further 1–2%. The diffuser surrounds the rear underride guard and serves as a mount for the tail lamps.

• An important component of the complete aerodynamic system is the “boat tail”, a rear taper measuring up to 400 mm in length. It improves the air resistance of the entire tractor unit by a full 7%. Its elements can be folded away, ensuring the usual easy access to the cargo compartment. The wings of the rear taper are made of aluminium sections and the sides are curved.

  In May of this year, the EU Commission recommended an extension of the maximum length by up to 500 mm for aerodynamic measures at the rear. Prerequisites: the loading length must not be restricted; when the vehicle is stationary, the extension must fold in to the permitted maximum length of 16.5 m for semitrailers and must not adversely affect use in combined operation. The Mercedes-Benz Aerodynamics trailer meets these requirements.

  The flaps on the rear extension fold in automatically by means of an electric motor when the vehicle is at a standstill. This does not impair the vehicle’s maneuverability. It is anticipated that the change in length regulations in the EU will become law by early next year.

The developers of Mercedes-Benz and Schmitz Cargobull paid particular attention to the everyday usability of the Aerodynamics trailer. Its rear airfoil automatically swings approximately ten degrees upwards during loading and unloading, providing clearance for the doors of the loading portal. When the trailer unit is stationary, electric actuators automatically fold the side wings of the taper onto the door sections. This ensures an opening angle of around 245 degrees when opening up the doors. It also enables the trailer to negotiate bollards when maneuvering at loading/unloading docks and to dock at the loading bay for loading and unloading.

A ground clearance of 350 mm for the side trim panels and the approach/departure angle of the Aerodynamics trailer likewise correspond to the requirements of companies, important for example when negotiating ferry ramps. Engineers and developers also focussed on easy accessibility of the landing legs as well as operation of the control valves and easy operation of the loading portal. A practical pallet box is provided, as are the required side marker lamps. The hinges on the loading portal are standard parts, as too is the frame structure of the side trim panels. It will soon be possible to manufacture the Aerodynamics trailer on a commercial scale.

The Aerodynamics rigid truck for long-distance haulage and short-radius distribution operations. It Click to enlarge.

Rigid truck. In the rigid truck project, the aerodynamic engineers and development engineers at Mercedes-Benz took ideas from the Aerodynamics trailer and applied them to the rigid truck, with vehicle-specific enhancements.

The new Mercedes-Benz Antos was used as the basis vehicle and then developed to offer the best aerodynamic figures possible. Compared with conventional box-type rigid vehicles, the Aerodynamics truck improves aerodynamics by approximately 12% percent. This means a consumption reduction of approximately 3% on trunk roads. In the case of an annual mileage of 50,000 kilometers, this results in a saving of around 350 l per year, or just under one tonne of CO₂. These projections from the development engineers have been confirmed in practice in initial test drives.

The cab side deflectors are from the accessories range from Mercedes-Benz and fit almost flush with the structure. There is no need for a spoiler on the bulkhead, but the air deflector on the roof is necessary.

The body is a conventional box with an outside length of 6.5 m, a width of 2.55 m and an inside height of 2.20 m. The outer skin is made of smooth Alucobond plates, which provide little resistance to the wind. In contrast to many aerodynamically unfavorable box bodies, the Aerodynamics truck has an edge radius of 80 mm at the transition of the side walls to the roof and an edge radius of 200 mm at the bulkhead. This ensures a streamlined airflow.

The side trim panels are reminiscent of the Aerodynamics trailer. Their upper edge fits nearly flush with the box body. On the Aerodynamics truck as well, the trim panels at the rear are drawn in and direct the air towards a rear diffuser, which fully encompasses the underride guard. An edge radius of 200 mm at the bottom end of the side trim panels provides a soft transition without separation of air flow towards the underside.

The entire underside of the Aerodynamics truck is covered in panelling. The almost entirely closed body this creates approximates the aerodynamic ideal and is interrupted only by slots for dissipating heat from the engine.

The Aerodynamics truck also features a “boat tail” similar to the Aerodynamics trailer. The folding elements of the portal are largely the same as those of the Aerodynamics trailer. In this case, however, the spring-actuated elements fold open as needed towards the side, since a tail lift behind the flaps provides access to the load compartment.

The side trim panels can be folded away, providing easy access to the fuel and AdBlue tank for instance, as well as to the rear wheels. The ground clearance and approach/departure angles also meet the requirements of everyday use.

The body of the Aerodynamics truck was developed and produced by Daimler Trucks. While the work was under way, the engineers implemented a further idea: the operating panel for the loading tailgate is integrated into the side wall and can be easily operated from a standing position.

Further extensive consumption measurements and driving trials for both the Aerodynamics trailer and truck will be conducted this autumn by the vehicle testing division at Mercedes-Benz. In the next step, selected customers will test the Mercedes-Benz Actros and Aerodynamics trailer combination in everyday haulage operations.

The Mercedes-Benz Aerodynamics truck will first undergo thorough testing as a laboratory vehicle. If there is sufficient demand, the Aerodynamics trailer and Aerodynamics truck will be able to be transitioned to large-scale production relatively quickly. Also conceivable are extensions to the Aerodynamics truck by means of an appropriately equipped trailer, thus creating an Aerodynamics truck/semitrailer combination.