Measuring twist due to torque in a ratating shaft

A method of measuring twist in a rotating shaft of an engine which shaft is subjected to torque, the method including sensing and recording a datum time moment when a datum point on the shaft passes a fixed datum station;

• sensing, at a fixed measure station, an arrival time moment of a measure point on the shaft, longitudinally spaced from said datum point by a predetermined distance;
• measuring a measure time period between said datum time moment and said arrival time moment;
• measuring rotational speed of the shaft;
• comparing the measure time period with a computed time period under a no load condition;
• and calculating the twist in the shaft on the basis of the time lag and the rotational speed including ameliorating the effects of vibrations and resonances in rotating or reciprocating components of the engine to isolate at least to a degree data relating to said measure time period, and said rotational speed, by means of a pre-programmed processor.

A measuring apparatus for measuring twist in a rotating shaft of an engine which shaft is subjected to torque, the measuring apparatus including

• at least one datum trigger at a datum point on the shaft;
• a datum sensor at a stationary datum station arranged to sense said at least one datum trigger when said at least one datum point is in register with the datum station and to generate correspondingly at least one datum signal;
• at least one measure trigger at correspondingly at least one measure point on the shaft longitudinally spaced from said at least one datum point;
• a measure sensor at a stationary measure station arranged to sense said at least one measure trigger when said at least one measure trigger is in register with the measure station and to generate correspondingly at least on measure signal;
• a clock keeping time;
• a rotational speed meter for measuring and recording rotational speeds of the shaft against time respectively as the datum speed and as the measure speed;
• recording means for recording said datum and measure signals against time;
• a processor programmed to establish
• correspondingly at least one datum time period between a time moment said at least one datum point passes the datum station and a time moment said at least one measure point passes the measure station under no load conditions and recording the rotational speed of the shaft as the datum speed,
• correspondingly at least one measure time period between a time moment said at least one datum point passes the stationary datum station and a time moment said at least one measure point passes the stationary measure station when the shaft is subjected to torque and recording the rotational speed of the shaft as the measure speed, and
• the twist in the shaft on the basis of the difference between said at least one measure time period and said at least one datum time period, the measure speed and a length of the shaft over which torque is applied, the processor being pre-programmed to ameliorate the effects of vibrations and resonances in rotating or reciprocating components of the engine to isolate at least to a degree data relating to said at least one datum time period, said at least one measure time period, said datum speed of the shaft, said measure speed of the shaft and said length of the shaft over which torque is applied.