Mercedes S500 Carphone Armrest – Brief

Design replacement armrest compartment with roller shutter cover enabling a telephone to fit inside. product required to fit into position of standard armrest and look as per original equipment.

Design Assesment

We accessed the existing components to determine whether parts of the original could be incorporated. The overall shape was to remain the same, but the new requirements for the interior were such though that none of the original armrest parts could be used.

Production Report

It was estimated that sales would be hundreds rather than the thousands, so injection Moulding was ruled out due to high tooling costs. It was decided to manufacture using vacuum forming, a process with low tooling costs

A design was drawn up from the original Mercedes armrest and moulds for the external shapes were cast in resin, the moulds for the roller shutter housing, were machined in aluminium.

the first pulls from the new moulds were produced, routing and trimming jigs were then made to machine the components to their final dimensions.

There were two components which were impossible to produce by vacuum forming. – the trim which
retains the roller shutter, – the handle of the roller shutter itself. The styling and shapes
specified by the client, and the requirement for these parts to have a smooth finish as moulded,

To produce the best finish by soft feel painting, it was decided that the only satisfactory method of production would be to injection mould.

First tests of the finished armrest revealed that some reinforcement was required in the area of the hinge, because the large recess necessary for the phone had taken away some of the strength that the original had in that area. This problem was satisfactorily resolved by riveting a shaped steel brace into the structure.

The roller shutter was taken from stock, the extrusion having been designed for earlier projects.
All that was necessary was to cut the slats to length and assemble.

Dynamic tests in a car revealed the need for a catch to prevent the roller shutter from sliding open under heavy braking. This problem was resolved by building in 2 small powerful magnets into the slats of the roller shutter which were gripped by two others in the body to hold the shutter firmly in the closed position.

The finishing of the armrest required that the inside of the telephone compartment was flock sprayed black, the roller shutter and its retaining trim spray painted and soft feel lacquered, in the colour to match the trim of the vehicle in which it was to be fitted, and the body upholstered in matching leather; this last operation being carried out by the client.

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