Shipbuilding and Shipping Record . shaft is equal to the angle between thetwo beams of light. If this angle is small, it is approximately pro-portional to the scale reading. We have seen that H P0 = constant X -^ (iv) above, , H P = constant X N 0 ; and since 0 is proportional to the scalereading, H P = constant X revs, per min. X scale reading. The value of the constant is best determined for different valuesof the twisting couple, these being in approximate agreement, andthe average value taken for use when the instrument is in serviceon board the ship. If, however, the torsionmeter is a
Shipbuilding and Shipping Record . shaft is equal to the angle between thetwo beams of light. If this angle is small, it is approximately pro-portional to the scale reading. We have seen that H P0 = constant X -^ (iv) above, , H P = constant X N 0 ; and since 0 is proportional to the scalereading, H P = constant X revs, per min. X scale reading. The value of the constant is best determined for different valuesof the twisting couple, these being in approximate agreement, andthe average value taken for use when the instrument is in serviceon board the ship. If, however, the torsionmeter is applied toexisting shafts, where it would be impossible to make direct readingsin order to obtain the constant, this can only be determined bycalculation, as shown above. By a combination of mirrors it is possible to obtain more than onereading of the torque in the shaft during each revolution, but it?will be apparent that this instrument is only suited to deal withshafts in which the twisting movement is uniform, as in tiu-bine. Fig. S.—Denny-Edgecombe Torsionmeter with Indicatorand Recorder. shafts, as in the event of a reading being made when the torque wasvery much chfferent from the average value, the shaft horse-powerarrived at would be correspondingly inaccurate. Another form of instrument is the Denny-Edgecombe torsion-meter, made by Denny Brothers, of Dumbarton, the principle ofwhich is the same as that already described, but which differs inthe means adopted for measuring the relative displacement of thetwo flanges. Each of the flanges carries two similar and similarlysituated arms, and when the shaft is twisted, the sleeve remamingrigid, there is a transverse chsplacement of the arms carried by theflange attached to the sleeve, relatively to those carried by the otherflange, the displacement corresponding to the t^vist of the shaftbetween the two collars. One of the arms has a short rack of in-volute teeth on its periphery, the other carries an enclosed multi-plying
Size: 2195px × 1138px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, bookpublisherlondon, bookyear191
