. American engineer . ears of proportioning braking poweron passenger cars to 90 per cent, based on a brake cylinderpressure of 60 lbs. is no longer tenable and must become ob-solete in the immediate future. Even though our methods havegiven good results in the past under other conditions, the situ-ation today has so changed that practice must now be madeto agree with known facts. If we wish to operate our passenger JlXK. AM ICRICAN ENGI \ EKR. 317 trains wiili siiuiutliness and safely \vc must adopt a rationalsliding scale for proportioning the braking power. Diagram 1 shows the amount o
. American engineer . ears of proportioning braking poweron passenger cars to 90 per cent, based on a brake cylinderpressure of 60 lbs. is no longer tenable and must become ob-solete in the immediate future. Even though our methods havegiven good results in the past under other conditions, the situ-ation today has so changed that practice must now be madeto agree with known facts. If we wish to operate our passenger JlXK. AM ICRICAN ENGI \ EKR. 317 trains wiili siiuiutliness and safely \vc must adopt a rationalsliding scale for proportioning the braking power. Diagram 1 shows the amount of braking power required tomake machine test stops from a speed of 60 miles per hourin a certain distance with different wheel loads. These curveswill vary, of course, with different shoes, and had shoes oflower frictional qualities than plain cast iron or Diamond Sbeen used, they would have been further to the right and have per cent, is a satisfactory braking power for the light carshaving a wheel load of PowycR (7S^ EFFICltNCv) ita*7. Fig. 1—Braking Power Required to IVIal<e Stops from 60 m. p. h. forVarious Wheel Loads; Steel Tired Wheels. shown the necessity of higher percentages of braking powerfor the same length of stop. The general character of thecurves would have been the same, however. Similar curvesfor stops from a speed of 40 miles per hour might have beenincluded, but they would not have brought out the facts anyclearer as the angle of slope is essentially the same, althoughthe distances in feet are less. Diagram 2 shows the percentages of braking power which arenecessary to insure essentially the same retarding force orlength of stop with cars of different weights. To illustrate theway the diagram should be used we will assume that we havean eight-wheel coach weighing lbs. By consulting thediagram we find that the braking power should be 110 percent. If, on the other hand, we had an eight-wheel coach weigh-ing 104,000 lbs., we find that t
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectrailroa, bookyear1912
