Aerodynamic concept of the Transformers prototype

This article is about the aerodynamic measures which will be installed in the Transformers energy efficiency prototype. This includes measures which are already available on the market as well as newly developed features like the movable roof and the optimized bulkhead cover, which you can see in Figure 1. 

Figure 1: Overview about all aerodynamic measures

Within the Transformers project the Schmitz Cargobull AG developed a movable roof for the energy efficiency trailer. The fully standard fixed roof which consists of only one segment is driven by a hydropneumatic pump and hydraulic cylinders and can be lowered at front and rear. The goal is to reduce the frontal area and the drag coefficient as much as possible. Depending on the cargo height the roof can be lowered up to 500 mm at the front and 800 mm at the rear. Four different positions are possible (compare Figure 2).  


Figure 2: Possible positions of the movable roof

Position “A” is called “high-flat” and represents the common standard. In position “C” (“low-flat”) the roof is lowered parallel to the ground at front and rear for about 500 mm. In positions “B” and “C” the roof is tapered and the rear is lowered to 3200 mm total height. In these cases the front is not lowered (“B”) respectively lowered for about 500 mm. If we take position A as reference and if we assume that the roof deflector of the tractor unit is adjusted correctly to the trailer height, the drag coefficient for position B is reduced by 9,4 %. In Position D the drag coefficient is even reduced by 12,3 % and additionally the frontal area is reduced due to the lowered trailer (assuming again that the roof deflector is adjusted correctly ant the cabin height of the used tractor unit is not higher than 3,5 m). The biggest advantage of position C is again the reduced frontal area. All figures for the drag coefficients have been evaluated with CFD (computational fluid dynamics) simulations in the Transformers project performed by Virtual Vehicle.

In addition to the movable roof other aerodynamic measures are installed. At the rear the OptiFlow Tail from Wabco will be installed. In the standard version the tail helps to safe up to 1,1 l/100 km fuel (manufacturer information from Wabco). Due to the movable roof the tail needs to be shortened for the Transformers Trailer. Another feature from Wabco which is installed are the OptiFlow Sidewings. The wings are standard and a fuel consumption reduction of about 1,5 l/100 km can be achieved at high speeds (manufacturer information from Wabco).

The last part is the aerodynamic shaped bulkhead cover (Figure 3). The bulkhead cover was designed by Schmitz Cargobull AG and helps to make the whole aerodynamic system more robust against not well adjusted roof deflectors at tractor units for example. Due to the round edges and the curves the wind flow has a smooth transition from tractor to trailer unit.  

Cargobull_3 Cargobull_4

Figure 3: Aerodynamic bulkhead cover and Wabco Sidewings (left) and the Wabco Tail

Please note that Graz University of Technology (https://www.tugraz.at/en/institutes/ftg/homepage/) developed a similar movable roof concept for a trailer which is described in patent EP 2570283 B1.



HoD Trailer awarded [SCB]
TRANSFORMERS Final Conference


Facts & Figures

  • Full name: Configurable and Adaptable Trucks and Trailers for Optimal Transport Efficiency
  • Duration: 4 years
  • Start date: 1 September 2013
  • Total budget: 7.9 M€
  • EC Funding: 5.2 M€


  • Develop and demonstrate Hybrid-on-Demand Driveline for Truck-trailer Combination
  • Develop innovative complete vehicle aerodynamic measures
  • Develop innovative loading efficiency measures