. Electric railway journal . e taken asillustrating widely differing characters of service, curve Xrequiring one stop every 3 minutes, curve Y one every 90seconds, and curve Z one stop every 70 seconds, allowing 10seconds duration for each stop. On the basis of these three V / X , Car Weights—Fig. 2.—Energy Curves for Cars of VariousWeights Operating on Schedules Shown in Fig. 1 curves, changing the dimensions in the manner above de-scribed, the energy curves of Fig. 4 have been show the energy in watt-hours per ton mile requiredfor cars of various weights from to 50 tons,
. Electric railway journal . e taken asillustrating widely differing characters of service, curve Xrequiring one stop every 3 minutes, curve Y one every 90seconds, and curve Z one stop every 70 seconds, allowing 10seconds duration for each stop. On the basis of these three V / X , Car Weights—Fig. 2.—Energy Curves for Cars of VariousWeights Operating on Schedules Shown in Fig. 1 curves, changing the dimensions in the manner above de-scribed, the energy curves of Fig. 4 have been show the energy in watt-hours per ton mile requiredfor cars of various weights from to 50 tons, operatingon various schedule speeds, and on speed-time curves ofshapes similar to the curves X, Y and Z of Fig. 3. These curves are all very nearly straight lines representedby the equation B=a+bW, when E=the energy per car mile, a is the intercept of thecurve on the Y axis, and b is the slope of the curve. This equation will therefore be adopted as correctly rep-resenting the relation of weights of car to power consump-. 0 10 M M 40 GO 60 70 80 30 100 110 120 180 110 150 IliO 1,0Seconds Car Weights—Fig. 3.—Calculated Speed-Time Curves forVarious Kinds of Service lion in all cases of like schedule, the constants a and bbeing dependent upon the frequency of stops and schedulespeed attained. This formula may be expressed:P P = — (ap + bpW).n where P—cost of power per car mile in cents; p cost of power per kw-hour in cents; and n = efficiency of trans-mission, power house to car. For ordinary frequent stop service, when the schedulespeed is forced up to about the highest point permitted byfrequency of stops, probably conditions intermediate be-tween those of curves Y and Z would obtain, and the powerconsumption would be about that indicated by the brokenline on Fig. 4. The equation of this line is: E=.500+.075 WIf we assume that the cost of power per kw-hour is onecent, and the efficiency of transmission to the car 75 percent, this becomes: p=.667+.l W, which is believ
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