Friday, November 25, 2011

New Freight Trailer Study by Mercedes Cuts Drag 18 per cent

Belgian Show Launches Latest Fuel Saving Project
Shipping News Feature

BELGIUM – GERMANY – EUROPE – Always the way, you wait weeks for a decent Mercedes Benz story then two come along at once. Freight trailers are not the first thing one comes up with when the archetypal German car and truck maker is discussed but now the marque is making some pretty bold claims for a new breed of trailer they have come up with in a comprehensive design study which investigates ways of reducing the enormous drag a 13.6 metre articulated vehicle produces. Mercedes-Benz will be presenting its ideas for the first time on the occasion of the “Trailer 2011” show taking place between the 25th and 29th November in Kortrijk, Belgium.

The ‘Aero Trailer’ study takes a typically efficient look at established design features, many of which have already been improved elsewhere, and assimilates them into a package which Mercedes says cuts wind resistance by 18 percent and fuel consumption by virtually five percent. The aero trailer encompasses the tremendous amount of know-how contributed by the developers and aerodynamicists at Mercedes-Benz cooperating with the Commercial Vehicle Design department which has already succeeded in cutting the wind resistance of their new premium truck, the Mercedes-Benz Actros, bringing it down to 12 to 15 percent lower than that of its predecessor, depending on the model in question. The designers have now created a trailer with corresponding properties.

Numerous individual measures drastically lower the wind resistance of the entire articulated tractor/trailer unit. A front airdam on the trailer reduces the distance to the tractor unit and lowers the wind resistance by one percent. Meanwhile side trim panels contribute an eight-percent improvement. They are slightly drawn-in at the front and characterised by an opening at the rear which 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. This improves the wind resistance by one to two percent whilst a rear end taper measuring slightly more than 400 mm in length forms a crucial part of the aerodynamic concept. It features folding elements to facilitate access to the load compartment and improves wind resistance by a further seven percent.

Overall the aero trailer lowers the wind resistance of the entire semitrailer tractor by approximately 18 percent. In the experience of Mercedes-Benz this results in a reduction in fuel consumption amounting to almost five percent in real-life road traffic. In the case of an average mileage of 150,000 km a year this means a saving of some 2000 litres of diesel fuel and relieves the burden on the environment to the tune of over five tonnes of CO2 per annum.

The fundamental feature of the revolutionary aero trailer is to be found in the trailer’s load compartment, whose dimensions remain totally unaffected. The familiar box – measuring 13.6 m in length, 2.55 m in width and with an overall height of four metres – remains available for the freight, just as before. The aero trailer’s only restriction is the fact that its length measurement exceeds the currently permissible limit by almost half a metre, due to the tail-end extension. That said, the handling and manoeuvrability are not in any way compromised by the taper.

There is much more potential in aerodynamic measures at the tail end of the trailer; a minor extension of the tail end in the form of a “boat tail” brings significant benefits a subject we have written on previously but with ramifications for the ease of offloading from the rear. In the case of the Mercedes project four flaps measuring just 400 mm in length and positioned at an angle reduce the wind resistance of the entire semitrailer tractor by nearly ten percent. In arithmetical terms this corresponds to virtually three percent less fuel consumption or more than 1000 litres of diesel a year. At the same time it saves the environment over 2600 kg of CO2 emissions. This is also proven by the simulations which have been carried out for the aero trailer.

Mercedes says it is here that changes to legislation are necessary, as in the case of tail lifts and transportable fork-lift trucks, for instance, where exceptions of a similar magnitude are already granted and, with a ten year test already under way in the UK for larger trucks, the German group will be looking for a common sense compromise for vehicles that plainly have a beneficial effect on emissions and fuel consumption yet vary so little from the accepted current norm.