. The strength of materials; a text-book for engineers and architects. relative safe stresses for the twocases. Time of Vibration of a Spring.—The vibration of aspring follows the laws of simple harmonic motion, so thatthe following general formula will enable the time of vibra-tion to be obtained. Time of complete vibration = ^ _ 2 TT / Weight of spring ^ _ ^ ^^^ y g X Force to cause unit deflection . •. number of complete vibrations per second == - z TORSION SPRINGS Close-Coiled Helical Springs.—If a helical spring is soclosely coiled that each turn is practically a plane, the stressesupon t
. The strength of materials; a text-book for engineers and architects. relative safe stresses for the twocases. Time of Vibration of a Spring.—The vibration of aspring follows the laws of simple harmonic motion, so thatthe following general formula will enable the time of vibra-tion to be obtained. Time of complete vibration = ^ _ 2 TT / Weight of spring ^ _ ^ ^^^ y g X Force to cause unit deflection . •. number of complete vibrations per second == - z TORSION SPRINGS Close-Coiled Helical Springs.—If a helical spring is soclosely coiled that each turn is practically a plane, the stressesupon the material will be almost pure torsion. The twistingmoment. Fig. 147, will be W R and the spring will be equiva-lent to a shaft of diameter d and of length I equal to the totallength of wire in the spring, ^. e. if n are the number of turns,I =. 2 TT R ?^ (approx.); the torque applied to this equivalentshaft will be W R as indicated. 338 THE STRENGTH OF ]\L\TERIALS By our general torsion formnla we have s _T _Gf 2 /T nvR •*• ^ GI,, Gjd^3232nVR~ GVci^ (2). LUILUIL turns Jlllli in L = 27rR ^^ d
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