Brake Tests

171 Diagrams of Comparative Stops. 385. The general averages, pages 300 to 317, have been shown graphically in the diagrams of Figs. 93 to 100. Whenever possible an average was taken of a series of tests in which the variables (Par. 379-1) were present. In certain cases all of the tests under a given set of con- ditions were made with one or more of these variables present. In such cases the tests have been averaged and shown in the diagrams (Figs. 93 to 100). The common to a series variables have been shown. 386. The variables which existed in the tests of any series are indi- cated as follows:— 1 .—Car stop affected by locomotive. 2 .—Braking power decidedly lower than on tests of other brake rigging or of the same brake rigging at other speeds, with the same air brake equipment. 3 .—Braking power decidedly higher than on tests of other brake rigging or of the same brake rigging at other speeds, with the same air brake equipment. 4 .—Speed 4 m.p.h. or more, less than the nominal. 5 .—Bad shoe condition. 387. The comparisons which may have been affected by any of the above variables have been marked by the proper symbol. The actual value of any of these variables is a factor for which correct allowance cannot be made. Before making an absolute comparison between the results shown in Figs. 93 to 100, the individual tests making up the aver- age should be studied. 388. In making comparisons of the various percentages of braking power it should be remembered that the nominal braking power shown on the various Figs. 93 to 100 represent the braking power of the cars. In train tests due to lower braking power of the locomotive and tender the per cent, braking power of the train, as a whole, is somewhat reduced. 389. For example, with a K2. locomotive and tender half loaded the following table shows the braking power of the cars and of the train as a wliole:— BRAKING Power. Twelve Cars. 90 per cent. 113 " " 125 « " 150 “" 180 « « Twelve Cars and K2. Locomotive and Tender (Half loaded). 90 per cent. 100 " " 117 « " 137 " « 160 “ «