Brake Tests

45 have become so great that the limit of satisfactory operation of the type P triple valve is closely approached even under favorable conditions. Under unfavorable conditions, either of installation, or maintenance or of manipulation, even though none of these may be bad enough in themselves to become noticeable, the triple valve may be sluggish in its response or erratic in its operation. This has been noticed par- ticularly with reference to the uneven application and failure to release of brakes toward the rear end of long trains and the troubles which have been experienced in this direction are a sufficient proof of the limitation of the type P triple valve for the service required of it under modern operating conditions. Provision for Extension to Cars of Heavier Weights or to Greater Effectiveness as Circumstances MAY Require. 94. In addition to the considerations mentioned in the preceding paragraphs, the fact that the PM equipment possesses no margin for future increased demands is shown by the fact that the severest require- ments (of the heaviest cars) have been met in a temporary manner by the application of two complete PM equipments per car. This has not proved entirely satisfactory as is well known and plainly admits of little or no further extension to meet future requirements of greater severity as they may arise. MODERN OPERATIVE Requirements.* 95. Briefly stated, present day railroad service requires that a brake equipment which will insure maximum safety, adaptability and economy of operation, shall provide: (a) Maximum stopping power available at all times and to a degree limited only by excessive wheel sliding with average bad rail conditions. (b) Maximum protection against undesired operations in service brake applications, in emergency applications and when releasing. (c) Protection against entire loss of braking pressure due to ac- cident or oversight. (d) Certainty of response to manipulation by the engineman at any time. (e) Flexibility in service operation, the braking force being cumu- lative by small increments throughout its range from zero to service maximum. (f) Uniform and simultaneous operation of all units in the train, which eliminates slack action and insures maximum smooth- ness in stopping. _ ____________- --------------- --------— — - ------ — or n ----- * Paragraphs 95 to 109 inclusive, are extracted from a paper by W. V. Turner, Chief Engineer of the Westinghouse Air Brake Co., before the Altoona Railroad Club.