Friday, December 12, 2008

Future trends: weight reduction strategies

One of the main improvements in future cars and associated global platforms is weight reduction. This trend has already started, or at least, new cars have stopped to gain significantly on weight. Weight reduction has not been more actively pursued because it’s expensive and people didn’t really care a lot. Reduction of emissions and fuel consumption is now mandatory so manufacturers are finding cost effective ways to reduce weight. Several strategies are being adopted and we can expect more than 100kg of weight reduction in future generations of the European compact class (Focus III, Golf VII, for example).

Body structure…
The increased use of high strength steels is one of the ways of achieving weight reduction, allowing the use of thinner sheet-metal, although this poses other issues in stiffness, vibration modes and welding processes, for example. The key factor is that one can not just replace steel grades but an holistic approach must be used including changes in manufacturing process as well: expect more hydroformed parts and hot stamping of Ultra high strength steel grades.

Other (more expensive) trend in the body structure is the use of both aluminium and steel in panels and other parts. BMW will make use of this strategy in future cars (it already does so in the current 5-series). Other more advanced mix of materials can be expected in two car generations: a recent joint-research project of several European manufacturers previews an aggressive mix of different materials (see figure below) although this still poses many challenges in cost and robustness of manufacturing.

… and everything else
Of those 100kg referred previously one can expect about 30kg reduction in the body structure and the rest from basically everything else. And car manufacturers are finding an easy way of achieving this. They are saying to suppliers that they must make new parts that are both cheaper and lighter than the old ones. And that can be achieved with careful design and the cost-leverage of global platforms. That’s how the new Ford Fiesta achieves part of its weight reduction.

The virtuous cycle
One of the interesting bits of weight reduction is that once it is started we can enter a virtuous cycle that allows further weight reduction. For example if the overall structure and components are lighter the suspension parts can be made even lighter because these are not so stressed anymore. And in the end one can even effectively do engine downsizing while keeping the same performance, or better yet, make it more fun with the same engine size and some turbocharging…

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