Torque measurement in flexible drive coupling plate

A drive coupling system comprises a shaft, eg. a crankshaft, drivingly coupled to a flexible disc / flexplate for transmitting drive from the shaft, the disc having a plurality of circumferentially spaced apertures 8 extending therethrough, each pair of adjacent apertures 8 defining a radially extending web 9 therebetween, a plurality of circumferentially spaced fastening holes 4 for attaching to an output member, a plurality of radially extending slots 10, and a strain sensor located in a countersunk recess 13 on an axial surface of on one of the webs such that the sensor lies on the local neutral axis of the disc. Three or four apertures may be provided which correspondingly form three or four webs. The strain sensor/s may be a surface acoustic wave (SAW) device and may be symmetrically located on the webs. Ring gear 6 may be provided for meshing with a gear of a starter motor.