

TRIPLE VALVES 195 



PASSENGER-BRAKE TRIPLE VALVES 



DEVELOPMENT OF PASSENGER TRIPLE VALVE 



The governing factors in passenger-train control are speed, 

 weight, and frequency of trains. The limits of time and dis- 

 tance in which a train must be stopped in emergencies to 

 insure safety in train operation were worked out in connec- 

 tion with the quick-action automatic brake at the time when 

 the weight and speed of trains were moderate and the fre- 

 quency of trains was not such a controlling factor. The prob- 

 lem today is to devise a brake that will enable the modern, 

 heavy, high-speed trains to be stopped in approximately the 

 same time and distance as were the lighter trains of the past. 



Since the introduction of the quick-action brake, a growing 

 yearly increase in passenger traffic has brought with it a grow- 

 ing increase in the length and weight of passenger trains, in 

 the train speed, and in the frequency of the service. Each 

 increase reduced the comparative efficiency of the existing 

 brake system and necessitated improvements to compensate 

 for this inefficiency, in order that stops could be made within 

 the limits prescribed by safety. These improvements con- 

 sisted in additions of apparatus to the existing quick-action 

 brake systems that resulted finally in the brake known as the 

 high-speed brake. For a time, this brake accomplished its 

 purpose, but later changes in operative conditions so reduced 

 its efficiency as to neutralize partly the improvements that 

 had been made on the older forms of brake, and further improve- 

 ments were imperative. 



In order to determine the necessary improvements, exhaust- 

 ive tests and experiments were conducted to ascertain the 

 limitations of the standard passenger triple valves when 

 used in the latest modern service. These tests emphasized 

 the facts that to fill the present requirements the improved 

 brake not only would have to meet the requirements for 

 emergency stops, but also would have to be flexible enough 

 to make service stops with due regard for other factors, such 

 as the comfort of the passengers; economy of time in making 

 stops; necessity of accuracy and smoothness in making stops; 



