Abstract: An electromagnetic vibration generator or shaker comprises an armature suspended from a stator and having a coil carried by the armature located in an air gap in the stator. A D.C. magnetic field is produced across the air gap and when an alternating current is fed through the armature coil the armature virbrates along its longitudinal axis. According to the invention the armature is suspended at its periphery by a plurality of suspension members which are arranged in pairs and allow free movement of the armature along its axis of vibration. However the two members of each pair are arranged at an angle to each other and exhibit a stiffness to lateral movement of the armature so as to restrain turning forces acting on the armature in either direction of rotation.

Abstract: An armature structure for an electrodynamic shaker comprises an armature support and an armature coil assembly mounted on the support. The coil assembly includes a cladding, or alternatively a spine, of a carbon fibre material. Preferably the carbon fibres extend generally longitudinally of the armature, that is to say in its direction of motion.

Abstract: Vibration testing apparatus comprises a vibration generator coupled to a horizontal slip plate by means of a driver bar, having limbs which embrace opposite sides of the slip plate. The lower limb of the driver bar is separable from the remainder of the driver bar so as to enable the vibration generator and the remainder of the driver bar to be pivoted away from the slip plate without lateral displacement of the slip plate along its horizontal axis.