Torque Measurement Flexplates

A torque measurement flexplate 20 includes a substantially planar body 54 which defines a plurality of circumferentially distributed axial through apertures 22 and a radial web or arm 24 extending between each pair of adjacent axial apertures 22. The flexplate 20 further defines a plurality of circumferentially distributed axial outer fastening holes 26 for attachment to an output member. The flexplate 20 includes a SAW surface acoustic wave strain sensor (28, fig. 2) for measuring the shear strain field on the flexplate 20. The flexplate 20 defines a recess 30 in which the strain sensor is located, the recess 30 being defined in an axial surface 32 of one of the radial webs 24. The sensor is positioned at a depth within the recess such that, in use, the sensor lies proximate to the median thickness of the flexplate in order to compensate for twisting forces. Radial slots 40 are provided to further isolate the sensors from twisting forces. Longitudinal bending forces are cancelled by arranging the strain sensors at 90 degrees in a bridge arrangement along the radial web as shown in figure 3.