Brake Tests

44 Length of Emergency Stops. 90. The result of using the PM equipment with the large (16-inch) brake cylinders necessary on modern heavy cars is to (a) Render less effective both in time and in amount the air vented from the brake pipe to the brake cylinder during quick action appli- (b) Materially lengthen the time to reach maximum brake cylinde pressure. ,. , t ble (c) Reduce the maximum brake cylinder pressure obtainable. The capacity of the equipment is limited to a maximum percent- age of braking power less than is required to e ectively control modern high-speed trains. The emergency blowdownfeature (high- speed reducing valve) is no longer necessary oi desira e on future cars, considering the amount of energy to be controlled and th brake shoe limitations of such cars. UNIFORMITY or BRAKE APPLICATIONS ON DIFFERENT VEHICLES COMPRISING THE Train. 91. The action of the equipment, being affected materially by the length of train and condition of the valve devices and associated appa- ratus, is less uniform or dependable in action under modern conditions . , • oirernents were less severe. This applies than when the service requirements w 1 indesired especially to light.service reductions and the tendency to undesired quick action. Safety and Protective Features Demanded by Severe and Complex Service Conditions. 92. The volume of air to be handled makes it difficult to obtain effective service brake applications in quick succession and renders a ---------- feature of great importance and is not P : fluctuations equipment. The creeping on of brakes due to unavoidable fluctuations in brake pipe pressure is undesirable and becomes more and more troublesome as the PM equipment is pushed to the limit of its capac- ity. The emergency functions of the equipment which depend up the service functions can be interfered with by improper ac 10 service parts of the apparatus. The entire loss o air on without warning to the engineman, though only possi e we manipulation is improper and no doubt infrequent, is some mg be eliminated. FLEXIBILITY AND CERTAINTY IN APPLYING AND RELEASING BRAKES During Service Applications. 93. With the advent of long trains of heavy cars, especially cars having two complete PM equipments, the volumes of air to be han e