. The Street railway journal . r ton train friction, are shownin Fig. 5, and the limiting values of maximum speeds forall other rates, thus affording a means of ascertaining themaximum speed reached for any rate of acceleration andany length of time for completing a run of 5,280 ft. withthe assumed constants of train friction and braking ef-fort. As the relative speed when brakes are applied is ameasure of the energy input for a given run, the run end-ing with the lowest speed on the braking line is evidently the one requiring the least energy input, and this leastspeed occurs when a train coa
. The Street railway journal . r ton train friction, are shownin Fig. 5, and the limiting values of maximum speeds forall other rates, thus affording a means of ascertaining themaximum speed reached for any rate of acceleration andany length of time for completing a run of 5,280 ft. withthe assumed constants of train friction and braking ef-fort. As the relative speed when brakes are applied is ameasure of the energy input for a given run, the run end-ing with the lowest speed on the braking line is evidently the one requiring the least energy input, and this leastspeed occurs when a train coasts the entire distance witha retarding force equal to train friction and ends at zerospeed in the specified time, hence the longer the coastingthe less the energy required to propel a train with a givennumber of stops per mile. The relative amount of energy required for the differentrates of acceleration is better shown on curves in Fig. 6, ACCELERATION CURVES TRAIN FRICTION 20 LBS. BRAKING EFFORT 150 LBS. DISTANCE 5280 SO 100 120 Time in Seconds FIG. 5 100 ISO Street giving the energy consumed in accelerating a train withany rate making any speed over a distance of 5,280 ft.,the speed given being the average speed while train isin motion and tractive effort, including 20 lbs. train fric-tion. An inspection of curves shows that the least en-ergy that can be expended is 40 watt hours per ton mile,and this is the amount of energy expended in moving atrain at any speed with a tractive effort equaling a trainfriction of 20 lbs. per ton. The benefit of a rapid rate ofacceleration for the higher speeds is here shown veryclearly, and the curves bring out most forcibly the pooreconomy resulting from having the rate of accelerationand schedule speed so proportioned that power must beapplied up to the moment of applying brakes, that is atthe minimum rate and allowing no time for coasting. Forinstance, with an average speed of 25 miles per hour whiletrain is in motion,
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectstreetr, bookyear1884
