Mechanics of engineeringComprising statics and dynamics of solids: and the mechanics of the materials of constructions, or strength and elasticity of beams, columns, arches, shafts, etc . s. per minute, or =396,000inch-lbs. per minute ; or = 550 per second. Usuallythe rate of rotation of a shaft is given in revolutions perminute. But eq. (8) happens to contain Pa the moment of torsionacting to maintain the constant value of the angle of tor-sion, and since for safety (see eq. (3) § 216) Pa=/S/p-4-e,with 7P= y27ZT^ and e=r for a solid circular shaft, we havefor such a shaft (Safe), fl.
Mechanics of engineeringComprising statics and dynamics of solids: and the mechanics of the materials of constructions, or strength and elasticity of beams, columns, arches, shafts, etc . s. per minute, or =396,000inch-lbs. per minute ; or = 550 per second. Usuallythe rate of rotation of a shaft is given in revolutions perminute. But eq. (8) happens to contain Pa the moment of torsionacting to maintain the constant value of the angle of tor-sion, and since for safety (see eq. (3) § 216) Pa=/S/p-4-e,with 7P= y27ZT^ and e=r for a solid circular shaft, we havefor such a shaft (Safe), fl. ^_ ... (9) which is the safe H. P., which the given shaft can trans-mit at the given speed. S may be made 7,000 lbs. per for wrought iron ; 10,000 for steel, and 5,000 for cast-iron. If the value of Pa fluctuates periodically, as whena shaft is driven by a connecting rod and crank, for (H. P.)we put raX(H. P.), m being the ratio of the maximum tothe mean torsional moment; m = about V/2 under ordi-nary circumstances (Cotterill). 240 MECHANICS OF ENGINEERING. 222. Autographic Testing Machine.—The principle of ProlThurstons invention bearing this name is shown in Fig,. Fig. 317. 217. The test-piece is of a standard shape and size, itscentral cylinder being subjected to torsion. A jaw, carry-ing a handle (or gear-wheel turned by a worm) and a drumon which paper is wrapped, takes a firm hold of one endof the test-piece, whose further end lies in another jawrigidly connected with a heavy pendulum carrying a pen-cil free to move axially. By a continuous slow motion ofthe handle the pendulum is gradually deviated more andmore from the vertical, through the intervention of thetest-piece, which is thus subjected to an increasing tor-sional moment. The axis of the test-piece lies in the axisof motion. This motion of the pendulum by means of aproperly curved guide, WR, causes an axial (, parallelto axis of test-piece) motion of the pencil A, as well as anangular deviati
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectenginee, bookyear1888
