Consortium Building Safe Lightweight E-Car Body, Drivetrain

Visio.M prototype e-car (A. Heddergott / S. Rauchbart, Technische Universität München)

A consortium of German manufacturers and Technical University Munich (Technische Universität München) is building a prototype concept car that provides a lightweight, yet strong body for electric passenger vehicles. The consortium known as Visio.M is led by car maker BMW and includes Technical University Munich as the group’s scientific partner, as well as 15 other companies and government agencies.

The consortium’s challenge is to develop a structure for an electric car that is extremely light to conserve the vehicle’s battery life, while providing solid protection for the car’s driver and passengers. Up to now, manufacturers and buyers had to chose between light weight to extend vehicle range, and heavier frames and crumple zones for safety, when considering electric cars. Visio.M, however, is expected to achieve a level of protection equal to that offered by conventional cars with internal combustion engines.

The engineers and scientists building the concept car are using a different kind of structure for the car, as well as advanced materials to meet this goal. The Visio.M prototype has a monocoque — French for “single shell” — structure where the body is combined with the chassis as a single unit. Racing cars often use a monocoque structure to reduce weight and increase speed.

The prototype’s passenger compartment will be made of carbon-fiber-reinforced plastic, similar to composite materials of this type found in aircraft and luxury sports cars. The problem with these materials is their difficulty to produce and, as a result, their high cost. While still a work in progress, Visio.M engineers are looking into adapting carbon fiber materials already used in ultra-compact cars as a potential solution.

The car’s engineers are reducing weight as well in the drivetrain, that combines the vehicle’s engine and system to deliver power to the car’s wheels. The Visio.M prototype will have a compact asynchronous electric motor, also known as an induction motor, a common technology for converting electrical energy into mechanical power. The transmission system will use lightweight gears on hollow shafts that are exptected to reduce the transmission’s weight by 15 percent.

Testing on the research prototype vehicle has already begun at a site near Munich. The car has passed initial chassis tests, and is undergoing tests of its anti-lock brakes  and torque vectoring system that transfers torque to the car’s wheels that need extra power.

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