When designers from Tesla Motors Inc. began planning the company's all-electric Roadster, they had to add up the 900-pound weight of its lithium-ion battery pack with the speed performance of a sports car and ultralow-production-volumes and came up with a lightweight car-body equation of carbon-fiber panels.
But the math has changed for the Model S five-passenger sedan, set to debut in late 2011. Tesla will make up to 20,000 sedans annually, compared with 1,500 Roadsters, said Barrie Dickinson, director of body engineering for Tesla, during the Society of Plastics Engineers annual Automotive Composites Conference & Exhibition, held Sept. 15-16 in Troy.
With higher volumes, we could look at different manufacturing methods, Dickinson said.
When the Model S goes into production, it will still have extensive plastics in its batteries and other key parts, but the skin will be made of metal, including aluminum blends, he said. The Model S also will be far cheaper than the Roadster, with a base price of about $50,000, compared with $109,000.
Tesla supplier Sotira, part of France's Sora Group, makes up to 40 sets of Roadster body panels each week using carbon-fiber-epoxy resin-transfer molding. Each part requires a 20-minute cure time, with up to 30 minutes for hand layup of the carbon fiber.
That process is too long and too expensive for the higher-volume sedan, he said.
It's not a question of the cost of the [raw material] carbon fiber, he said. It's all about processing and using that material in a way that can reduce the cost at volume.
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