. The Bell System technical journal . / 1 1 / 1 / 1 1 f / / 1 1 / / 1 1/ 4 f r / 40 / / / / J / r / f / ,y y / o^y / / -/ / / ./ / 35 i r, J 1 y 1 1 / V 11 /- r f // H 30 1 i 1 ^ I 1 1 / 1 1 / 1 1 1 / 1 1 i 25 t /+ 1 / / / 1 / ^/ 1 / / / 1 / __^ i^ , 1 ?n / / / / / t J + t 1 s 7 1 .^ ^ y 10 0 20 40 60 80 100 WIND VELOCITY IN MILES PER HOUR 0 20 40 60 80 100 WIND VELOCITY IN MILES PER HOUR SPAN OF 130 FEETFig. 5-^. SPAN OF 200 FEET Fig. 5-B. 362 BELL SYSTEM TECHNICAL JOURNAL If E is the modulus of elasticity in pounds per square inch cross-section,D the diameter in inches, a the sag in feet and
. The Bell System technical journal . / 1 1 / 1 / 1 1 f / / 1 1 / / 1 1/ 4 f r / 40 / / / / J / r / f / ,y y / o^y / / -/ / / ./ / 35 i r, J 1 y 1 1 / V 11 /- r f // H 30 1 i 1 ^ I 1 1 / 1 1 / 1 1 1 / 1 1 i 25 t /+ 1 / / / 1 / ^/ 1 / / / 1 / __^ i^ , 1 ?n / / / / / t J + t 1 s 7 1 .^ ^ y 10 0 20 40 60 80 100 WIND VELOCITY IN MILES PER HOUR 0 20 40 60 80 100 WIND VELOCITY IN MILES PER HOUR SPAN OF 130 FEETFig. 5-^. SPAN OF 200 FEET Fig. 5-B. 362 BELL SYSTEM TECHNICAL JOURNAL If E is the modulus of elasticity in pounds per square inch cross-section,D the diameter in inches, a the sag in feet and m the weight of wire perlinear foot, the approximate relationship^ is: a + — (c - r)a = ttD^E As only horizontal winds normal to the line of supports are beingconsidered, the wind pressure when the loop is in equilibrium ishorizontal. The weight of the wire being vertical the two forces addat right angles, their resultant being the square root of the sum of theirsquares. This resultant lies of course in the plane of equilibrium of. Fig. 6—Test House and Line. the loop. The wind pressure component is about equal to the gravitycomponent for a velocity of 38 in the case of .104 wire and about47 in the case of .165 wire. The effective weight of the wireunder these conditions would be greater by a factor of V2 than the trueweight. In general, ni in the above formula is the effective weight ofthe wire per unit length. A wire having a sag of 5 in a 130 span with a temperature of —10°F. would have a sag of about 9 at 50° F. and about 16 at 100° F. dueto thermal expansion. The sag of such a wire would be increased bywind pressure as shown in Fig. 5-A, the wind being given in true normalvelocity. The figure shows the increase to be most marked for lowtemperatures and small diameters as would be expected. Similar ^ Due to Mr. J. A. Carr of Bell Telephone Laboratories. MOTION OF TELEPHONE WIRES IN WIND 363 results are shown in Fig. S-B for a span of 200. Both indica
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
