. Electrical world. rived in this particular case, by theuse of aluminum in preference to copper cables; and the precedingmaterial was selected: Aluminum wire, rods and bars will be furnished of 63 per cent,electrical conductivity, which will have an equal tensile strength perunit of area with the copper, and, therefore, with the electrical con-ductivity equivalent of 48 per cent, of the weight of the copper andsectional area of 160, against the area of the copper section 100. Thetensile strength of aluminum conductors will be as 100 for the copperis to 160 for the aluminum. This would mean, i
. Electrical world. rived in this particular case, by theuse of aluminum in preference to copper cables; and the precedingmaterial was selected: Aluminum wire, rods and bars will be furnished of 63 per cent,electrical conductivity, which will have an equal tensile strength perunit of area with the copper, and, therefore, with the electrical con-ductivity equivalent of 48 per cent, of the weight of the copper andsectional area of 160, against the area of the copper section 100. Thetensile strength of aluminum conductors will be as 100 for the copperis to 160 for the aluminum. This would mean, if a square inch ofcopper conductor was used of, say, 32,000 pounds per square inchtensile strength, the equal conductivity area of i 6/10 in. of aluminum used for convenience of construction) ; sag allowable at212° P., 35 ft. ; maximum wind probable pressure, 40 pounds per ; minimum temperature, 20 F.: pnibable ice coating, 4 in. tensile strength of hard-drawn aluminum wire is 35,000 pounds. -959-7?i; Straifht Line Lcugth of Cahle- 366-95s C. to C. L£ FIG. 2.— per sq. in.; its conductivity, 63, as compared with copper at 100; andthe coefficient of expansion, .0000231 per degree Fahrenheit. The problem to be considered is, what is the maximum tension inthe cable under the most severe conditions as noted above, as com-pared to the ultimate strength of the cable? When a wire is suspended between two supports it takes a curveknown technically as the catenary. In the case at hand, the catenarycomes very dose to the parabola, which gives the following relations:L^ w T = - (I) 8rfWhere T = tension in cable at ends,L = length of span in feet,tt ^= weight per foot of wire,d = the central deflection in T will be a maximum when H is at its maximum and dat its minimum. The wire will have its greatest weight per footwhen coated with ice and is withstanding a heavy wind pressure; andthe deflection will vary flirectly as the temper
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectelectri, bookyear1883
