Schroff has developed a special VARISTAR cabinet with shock absorbers, adapted to the demanding conditions of operation at sea and suitable for use on frigates, aircraft carriers and submarines. The cabinet, containing approx. 150kg of electronic components, has been tested to the MIL-STD-901D standard, which tests shock resistance under simulated conditions of impacts from water bombs.
The shock absorbers used are available in two versions: wire rope springs and elastomer absorbers. The standard sized VARISTAR cabinet (1800mm x 600mm x 800mm) was tested with both types of shock absorber. The dimensioning of the shock absorbers is based on the weight of the components housed in the cabinet, the position of the centre of gravity within the cabinet, the cabinet dimensions, the position of the shock absorbers and the intended areas of application.
With the co-operation of Schroff’s partner Socitec Vibrations of Sartrouville, France, the required shock absorbers are calculated exactly and designed individually for each application. In addition to the MIL-STD-901D shock test, Schroff can also perform a vibration resistance test to the MIL 167 standard on request, with the customer’s actual electronics mounted in the cabinet.
The basis of the VARISTAR MIL 901D is the Seismic/EMC frame, built to meet the high demands for robustness and stability required for mobile applications. Four shock absorbers are fitted to the welded base plate and two more are positioned at the top to the rear of the cabinet. The rear panel is divided into three parts: at the top, a robust plate on which the shock absorbers are mounted; in the centre, a standard rear panel; and at the bottom, a connecting plate in stainless steel for cable ducting.
The top cover is solid and the front door is provided with a locking mechanism. The cabinet features EMC protection (60dB at 1GHz, 40dB at 3GHz) and IP protection (IP55). The frame and all cladding parts both galvanised and powder coated (RAL 7032) to protect them against corrosion (salt air). The standard, VARISTAR-based cabinet described here can be modified to specific customer requirements by means of simple modifications.