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BMW electric a revolutionary car with revolutionary process

"Revolution" is a word worthy of the BMW Megacity, an electric vehicle that will be the world’s first volume-produced car with a passenger cell made from carbon-fibre.

That somewhat immodest quote was uttered last week by BMW head honcho, Norbert Reithofer, after revealing how and where the automaker will build its Megacity electric vehicle.


About $650 million will go to expand its plant in Leipzig, Germany, and another $100 million or so towards a new “carbon-fibre” factory in Moses Lake, Washington.


This plant will be a joint project with SGL Carbon SE, the world’s biggest manufacturer of carbon and graphite products.


The carbon plant should tip you off to why BMW is using “revolutionary” rhetoric. Megacity will become the world’s first volume-produced car with a passenger cell made from carbon-fibre.


With carbon-fibre, which is 50 percent lighter than steel, BMW figures it can offset the additional weight of an electric vehicle — typically 250-350 kilograms. A lighter car also means it can use a smaller, lighter, and less expensive battery.


Making large pieces out of carbon-fibre is expensive and time-consuming. To achieve thickness you have to keep layering or weaving thin strands of carbon-fibre, a process not unlike crocheting, and who has time to crochet a fender?


This is why, until now at least, it has remained a niche material. But automakers are chipping away at the dilemma.


A large section of the McLaren’s new sports car, the MP4-12C, is crafted of carbon fibre. For this application McLaren developed a new process, which takes about five hours. When McLaren last made such a carbon-fibre piece, for the Mercedes-Benz SLR, the process took about 400 hours.


Because the Megacity is to be a relatively affordable city car, BMW said it is going to great lengths to reduce the cost of a carbon-fibre build. For one thing, the material is actually carbon-fibre reinforced plastic (CFRP). BMW’s process also involves the reuse of scrap, enabled by a new technique of turning carbon strands into sheets of fibre, and a new “quasi-stamping process” to make some of the smaller CFRP parts.


Megacity also has a unique chassis design consisting of two modules: Drive — the battery, drive system and structural and crash crumple piece; Life — the CFRP passenger cell piece. BMW says this new-old “body on frame” architecture opens the door to totally new production processes which are both simpler and more flexible; it also uses less energy and offers more styling freedom.


With the vehicle themselves and their factories set to undergo such a revolution, what’s next? The humanoid behind the wheel? Better take cover.

 
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