Brake Tests

TYPE of Rigging Tested. 265. The various designs of rigging tested are referred to in this report as standard brake (single shoe), clasp brake No. 1, clasp brake No. 2 and clasp brake No. 3. These' riggings are shown diagrammatically in Figs. 3 to 7, inclusive. Standard BRAKE (SINGLE SHOE). 266. The single shoe brake shown in Figs. 4, 7 and 68, now standard for P-70 cars, was modified in the following particulars for the purpose of these tests:— The strength of various rigging members was increased to allow for the use of 180 per cent, emergency braking power. The truck dead lever anchorage was changed from truck bolster to car body center sill. The brake shoes were hung 1% inches below the standard location. 267. These changes while considerably improving the action of the rigging with respect to truck tilting and journal conditions, left the general characteristics of the standard single shoe type of rigging practically unchanged, so that the results obtained in the tests of this rigging were typical of what is experienced in service in other par- ticulars, especially with respect to the action of the brake shoes. The effect of the position of the brake shoes was to cause a noticeable com- pression of the truck springs during brake applications, resulting in a corresponding horizontal movement of the brake shoes and a consequent travel tending to reduce the effectiveness of the increase in piston travel, tendis 00 brake. 268. The rate of wear of brake shoes under single shoe conditions is discussed in Chapter VII. CLASP BRAKE Rigging. 269. In the application of the preliminary experimental types of clasp brake rigging to the existing trucks for the purposes of these tests the primary object was to provide for the use of two brake shoes per wheel with the least possible alteration of trucks, and maintain as nearly as possible the arrangement of body and truck rigging as with the single shoe brake. Certain undesirable features developed m the preliminary clasp brake designs during the progress of the tests and resulted in improvements in design. - 2 270. These tests demonstrated the fact that even though the desired brake cylinder pressure could be obtained in an average minimum time of 2.2 seconds, the stops were longer than anticipated even with this short time to develop the maximum cylinder pressure, and in the development of the later designs of clasp brake rigging consideration • , u coccihle source of loss in the transmission of forces was given to all possible source