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Tech Briefs
Steel vs. 'exotic' materials
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The ULSAS twistbeam design features a unique U-shape swept section that provides continuity of structure from hub to hub.
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"Intelligent application of the latest steel technologies can match the weight savings of so-called 'exotic' materials while offering significant cost savings," said Peter Rawlinson, Program Director of the UltraLight Steel Auto Suspension (ULSAS) study. Lotus Engineering completed the study on behalf of a global consortium of 34 steel companies from 15 countries. The work complements the UltraLight Steel Auto Body (ULSAB) study completed two years ago, and the UltraLight Auto Closure (ULSAC) study now nearing completion. Rawlinson says of the ULSAS conclusion that while steel is a relatively dense material, it is also very stiff and strong, and that appropriate engineering can take advantage of these properties to produce lightweight, cost-effective solutions. But the challenge for the industry, he warns, will be "to change the mindset of engineers" now designing suspension systems for future cars.
The ULSAS project had two phases. Initially, Lotus engineers carried out a benchmark study by assessing vehicles from around the world. Subsequently, based on those assessments, Lotus undertook a holistic review of suspension-system requirements and identified opportunities for application of new steel technologies. The design phase encompassed five types of steel suspension systems across a range of vehicle sizes, resulting in the creation of a comprehensive range of suspension-system designs. The objective was to reduce the mass of a new steel design by at least 20% vs. benchmarked conventional steel suspensions without a cost penalty, and to match the mass of a benchmarked aluminum system with a steel suspension system, while demonstrating a cost saving of at least 20%. In the process, the ULSAS study opened new avenues in suspension design, material applications, and technology.
Nick Hampson, Chief Engineer for Chassis Design at Lotus, says ULSAS transcends a mass reduction study and moves into the realm of reference work for vehicle dynamic factors and priorities. "While much of the technology applied by ULSAS could not be considered ground-breaking by itself, the application of the technology and the mindset for using it and advanced steels effectively, are key messages from the study," he said.
Lotus regards the most significant design as a result of the study to be that of a twistbeam suspension - often a type used for smaller cars rather than for performance vehicles. Lotus developed a design that reduced mass by 32% with no cost penalty. According to the company, the design also improves many other performance parameters.
Stuart Birch
AEI September 2000
For more information, circle 222 & 223
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