Metal rocker concedes to quiet cover versions

A centre-bolted thermoplastic rocker cover on Mercedes Benz light trucks is to cut costs by 50%, weight by 40%, and lower noise compared to the aluminium version. Designed by Mercedes Benz, Mann+Hummel and supported by DuPont Automotive, the Zytel glass-reinforced nylon cover protects four and six cylinder diesel engines. The design further proves the future of under-bonnet plastic applications.

The size of the rocker cover (800mm) was a challenge for centre bolt design. Traditional problems of centre bolt design have been in reducing creep to maintain enough sealing force from the centre of the part to the outside gasket. Dozens of interlinking arch supports under the cover combined with the good flexural modulus of DuPont’s Zytel ensure a tightly maintained seal.

Prototyping was eliminated using CAD/CAE with mould flow and structural analysis. Cost savings were realised by integrating the oil separator within the rocker cover (not possible using aluminium). The system also produced a noise reduction of two decibels over the aluminium design.

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