. Electric railway journal . of a heavy current heatingit sufficiently to destroy its hard-drawn properties. A careful study was made of suitable messengercables composed of hard-drawn copper, phosphorbronze, and aluminum with a steel center. These werecompared on the basis of a 400,000 circ. mil coppercable, the sizes being enough larger to give the sameconductivity. A strand of phosphor bronze wasfinally decided upon, composed of nineteen wires, andhaving an over-all diameter of in. This cablehas an ultimate breaking strength of 22,000 lb. and anelastic limit of 18,600 lb. It weighs ap
. Electric railway journal . of a heavy current heatingit sufficiently to destroy its hard-drawn properties. A careful study was made of suitable messengercables composed of hard-drawn copper, phosphorbronze, and aluminum with a steel center. These werecompared on the basis of a 400,000 circ. mil coppercable, the sizes being enough larger to give the sameconductivity. A strand of phosphor bronze wasfinally decided upon, composed of nineteen wires, andhaving an over-all diameter of in. This cablehas an ultimate breaking strength of 22,000 lb. and anelastic limit of 18,600 lb. It weighs approximately1353 lb. per mile-ohm at 68 deg. Fahr. This messenger is supported every 90 ft. from theroof of the tunnel by a combination of iron yokes held 7000 0000 \ 5000) 4000\ ; 3000i 20001000 / / / =„_ / JLI GO 11 .W y . r. 0* inc ■Vy 1. 1. ViL Jo I if . > „ 1 32003100JOOO 2 3 3Sag in Feet Fig-. 3 210021002300220021002000WOO130017001000150011U0 A- 50 c 0 ° /00 t 1 no in FeetFig. 2. Temperature, Deg. Fahr. Fig. 4 CANADIAN NORTHERN OVERHEAD CONSTRUCTION — CATENARYCHARACTERISTIC CURVES—FIG. 2—UNSTRESSED LENGTHCURVES,- FIG. 3—TENSION-SAG CURVES; FIG. 4—SAGAND TENSION PLOTTED AGAINST TEMPERATURE in the concrete by four 1-in. bolts. The cross yoke car-ries the messenger insulator and is supported on twoinsulators carried on the two end yokes, so that thereare two insulators between the messenger and theground. The insulators are of glazed porcelain and,have a wet flashover test of 20,000 volts. All clampsand small parts of the messenger supports are of mal- December 8, 1917] ELECTRIC RAILWAY JOURNAL 1029 Tbmperature-Sag-Tension Data forMessenger. Temperature ,—Messenger Only^, Deg. Fahr. Sag Tension —20 5y2 in. 3,150 lb. —10 5% in. 2,910 lb. 0 6% in. 2,690 lb. 10 7 in. 2,460 1b. 20 7% in. 2,250 lb. 25 8 in. 2,143 1b. 30 8% in. 2,045 lb. 35 8% in. 1,945 lb. 40 9 4 in. 1,850 lb. 45 9% in. 1,755 lb. 50 10% in. 1,657 lb. 55 10%
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