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68
MOTORINDIA
l
January 2012
burden on the environment to the
tune of over five tonnes of CO
2
per
annum.
The fundamental feature of the
revolutionary aero trailer is to be
found in its load compartment,
whose dimensions remain totally
unaffected. The familiar box, meas-
uring 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 measure-
ment exceeds the currently permissi-
ble 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. 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.
The “Truck and Trailer 7plus”
initiative
The aero trailer is the flagship of
the new “Truck and Trailer 7plus”
initiative being launched by Mer-
cedes-Benz.
The basis of the “Truck and
Trailer 7plus” formula is the fuel
consumption of the new Mercedes-
Benz Actros, which is proven to be
more than seven per cent lower than
its predecessor model, itself rec-
ognised as being frugal. This con-
sumption advantage was achieved
by the Actros earlier this year: dur-
ing the “Record Run” it totalled 7.6
per cent less consumption, with 25.1
to 27.1 litres/100 km. The values
were determined by Mercedes-Benz
under neutral supervision: semitrail-
er tractors bearing 40-tonne loads
were each driven 10,000 km in iden-
tical conditions between Rotterdam
in the Netherlands and Szczecin in
Poland. “Truck and Trailer 7plus”
stands for the fact that Mercedes-
Benz wants to extend the consump-
tion advantage achieved here by
closely co-operating with the trailer
manufacturers.
Intensive tests in the wind tunnel
and on the road prove that consider-
able further consumption progress is
possible for semitrailer tractors. By
way of example, measurements tak-
en in the wind tunnel at Mercedes-
Benz have shown that a side trim
panel on the trailer cuts wind resist-
ance by eight per cent.
During test drives on the Record
Run route this translated into a real-
life consumption benefit of some
two per cent for a semitrailer tractor
weighing 40 tonnes. In the case of an
average annual mileage of 150,000
km in long-distance transport this
results in a saving of around 750 l of
fuel and relieves the burden on the
environment to the tune of approxi-
mately 2000 kg of CO
2
emissions.
“Boat tail” saves 1000 l of
diesel
In addition to this, at the instiga-
tion of Mercedes-Benz a working
group of truck and trailer manufac-
turers under the umbrella of the Ger-
man Association of the Automotive
Industry has carried out further tests
on the aerodynamics of semi-trailer
tractors. In the framework of this
study, measurements in the wind
tunnel at Mercedes-Benz concluded
that modifications to the cab such as
a supposedly aerodynamic exten-
sion result in merely minimal im-
provements where wind resistance
is concerned.
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.
Four flaps measuring just 400 mm
in length and positioned at an angle
reduce the wind resistance of the en-
tire semi-trailer tractor by nearly 10
per cent. In arithmetical terms this
focus on trailers
By taking a holistic approach
to the tractor unit and trailer it
aims to considerably cut fuel con-
sumption, and thus also the CO
2
emissions of semitrailer tractors