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MOTORINDIA
l
May 2012
Magnesium for better mileage through
vehicle weight reduction
Volkswagen’s beetle, pro-
duced more than 21 million times
from 1938 until 2003, already
contained a lot of magnesium
– engine block, gearbox hous-
ing and other components – in
order to save weight. The vehi-
cle’s promoters were concerned
about a sufficient mileage and,
challenged by the rear-mounted
engine, a well balanced struc-
ture. Eventually, the car made
14 km to the litre. Its net weight
was approximately 600 kg: with-
out magnesium the weight would
have been 50 kg more and mile-
age five-eight per cent less.
Peak annual consumption of
the magic material for this car
has been 42,000 tons in 1971.
When its air-cooled engine was
substituted by a liquid-cooled one,
the magnesium-made engine block
had to be substituted and consump-
tion dropped. Corrosion from con-
tact with water was one of magne-
sium’s critical weaknesses before
modern alloys had been developed.
A vehicle’s mileage is affected by
many factors: structural weight, air
resistance, way of driving, road pat-
tern, number of passengers and load,
efficiency of driveline, usage of AC,
recuperation of kinetic energy, qual-
ity of tyres, and so on. In urban low-
speed stop-and-go traffic the largest
part of energy is consumed in bring-
ing the vehicle up to whatever little
speed after every stop. This is the
mobility pattern today of the major-
ity of Indian vehicles. Over and over
again the mass of e.g., a passenger
car is accelerated and, shortly after,
brought to a stop again: fossile en-
ergy first transformed into kinetic
energy and then (mis)used to heat
the brake discs. In this type of traffic
a vehicle’s mass is key to fuel con-
sumption. Slightly overstating the
effects one can say that 10 per
cent less weight will improve
the mileage by 10 per cent.
From a design point of view
weight reduction opens the door
to a highly attractive feed-back
cycle. Less structural weight
will, other things remaining
equal, allow to use e.g., a small-
er engine or brake system which
in turn allows a lighter structure.
The “down-sizing” spiral will
be a dominant theme for the fu-
ture for better mileage, less CO2
and improved dynamics. Audi’s
CEO lately has asked for “most
aggressive light-weight design”.
In the context of commercial
vehicles one kg saved in struc-
tural weight is one kg gained in
payload. The CO2 targets set by
the European Union as per 2015 will
demand a serious slimming diet. It is
safe to assume that today not many
new specification sheets are released
to the design engineers without pre-
scribing a massive weight reduction.
And the necessities of electrically
driven vehicles will very soon ac-
celerate this trend.
Magnesium is a powerful, well
explored option to reduce weight.
The metal is very light, 36 per cent
lighter than aluminium, the other
widely used non-ferrous metal in
technology
* The author is CEO of UBF.B Management Consultancy, a service company with its focus on the automotive indus-
try and Indo-German business. Its has offices in Berlin, Chennai, Pune and Stuttgart. For details, contact: andreas.
waldraff@ubfb.de.
By Dr. Andreas Waldraff*
Dr. Andreas Waldraff