Abstract: A method of measuring long shaft torque by pre-recording two magnetic tapes, through air gaps, with similar continuous sine wave signals; and by fixing the pre-recorded tapes spaced longitudinally apart as loops around the long shaft at no torque load, and with the continuous sine wave signals of the respective tape loops in approximate phase; and by each tape loop being opposed by a pair of air-spaced, diametrically positioned playback heads, one pair being rotationally adjustable to precisely synchronize the phases of the sine wave signals of both tapes, and both pairs of playback heads cooperating to pick up sine wave signals from both tape loops; and by transmitting the sine wave signals for each side, respectively, to an associated electronic circuit, each circuit for producing an analog voltage proportional to half of the transmitted torque of the long shaft as it rotates under a torque load and plus and minus voltage errors due to rotating long shaft skew; and by finally summing and integrating the hal

Abstract: A dynamometer in which a signal generator provides a repetitive signal of adjustable frequency, to record-playback heads fixed adjacent to similar magnetic recording mediums that are non-magnetically mounted and spaced axially apart on a drive shaft rotating without loads. Simultaneous recordings are made by the heads on the mediums and the signal generator switched off. With the rotating shaft loaded, the recordings are played back by the axially spaced recording-playback heads, and a phase difference between the recorded signal from each head is a measure of torque on the shaft. The frequency of recorded signal from either head is a measure of the speed of rotation of the shaft. The playback signals drive an electronic computer of well know design that multiplies the measure of torque by the measure of speed of rotation to provide a voltage proportional to shaft horsepower to a voltmeter that may be calibrated to read directly in horsepower given the elastic modulus of shaft material and shaft dimensions.