Strain gauges used for torque measurement in a gas turbine environment

A technique of measuring the torque in the shaft between the low pressure turbine and the fan of the RB211 engine was developed. The low pressure system torque is measured by three independent strain gage bridges, oriented such that they are sensitive to torsional stress in the shaft and insensitive to axial and bending loads. The system was used in three separate engine tests. Absolute system accuracy of better than + or - 1% full scale torique is achieved. Agreement between the bridges is better than + or - 0.2% of mean torque value.