Electric Traction When all electric traction cars were operated singly, straight air brakes were used almost exclusively in this service. After two cars were employed as a unit, air' became dangerous be cause, whenever the cars broke apart, no brak ing force could be maintained due to the brake cylinders being connected direct to atmosphere through the open straight air pipe. As a conse quence in 1905 there was developed the semi automatic equipment with the 'IA" emergency valve. With this device straight air applica tions were secured as heretofore, but the straight air connection was made through only the straight air pipe to be filled from the brake valve while the brake cylinders were charged by a reservoir located on its respective car, and controlled by a valve actuated through the medium of the air in the straight air pipe. This arrangement overcame to a considerable extent the serial time difference in the appli cation of the various car brakes. It also de veloped the proper brake cylinder pressure irre spective of the brake cylinder piston travel and maintained this pressure against brake cylinder leakage. A late development of this particular type of equipment was of electro-pneumatic semi-automatic character, having as its main new feature the electrical control of straight air, with provision for a brake application in case any portion of the electrical equipment failed. A special phase of this type of equipment, recently developed, is the one-man car, or safety control equipment (Fig. 9). With this equip ment the entire control of the car can be effi ciently handled by one man. The opening and closing of the doors, as well as the folding and unfolding of the door steps, is controlled from the brake valve. The incapacitation or negli gence of the operator, or breakage of any of the pipes at either end of the car, will cutoff the power, make an emergency brake apphca tion, sand the rails and unlock the car doors.
the emergency slide valve. The emergency brake application was obtained by reducing the pressure in the ((emergency° pipe, thus enabling the main reservoir pressure to force the emergency slide valve piston outward, which thereby cut off the straight air pipe from the atmosphere and thereupon connected the main reservoir direct to the brake cylinder. The accidental separation of cars produced a similar brake operation.
When more than two cars began to be oper ated as a unit, the serial time difference re quired to develop the braking force on the different cars was objectionable. The CD" type of emergency valve (Fig. 8) was therefore provided in 1906 to meet this new condition. This valve possessed substantially the same emergency feature as the "AD type of emergency valve; but for service' application required Another phase of the electric traction-road de velopment consisted in the use of purely auto matic devices as in steam-road service. Some
roads which operated a number of cars as a unit at times ran the individual cars separately. To obtain flexibility of brake control realized with straight air in single cars and also to operate the head car of the train separately, when desired, a combined straight air and auto matic system was developed in 1906. A recent development for electric traction service is the universal type of valve with an exhaust cut-off valve. This valve possesses all the features previously outlined for the universal valve for steam-road service and. in addition, permits the simultaneous delivery of air, for service appli cations direct from the reservoirs to their respective brake cylinders and simultaneous ex haust of brake cylinder air direct to the atmos phere without the actuation of the piston which ordinarily controls this service brake applica tion and release. Any failure of electrical equipment produces a brake application. This latest device is a safe, highly flexible, instan taneously responsive brake. Another important development in the electric traction field is the variable load brake with the universal type of valve. With this equipment the weight of the passengers automatically adjusts the cylinder pressure obtainable for emergency, and per pound brake pipe reduction for service brake application so that the same emergency and service stopping distances are realized for a given speed irrespective of the load carried. Many other inventions used with these equip They are connected with the respiratory sys tem, and are situated in the cavity of the thorax and abdomen, and sometimes extend into the bones. They are most fully developed in birds of powerful and rapid flight, such as the albatross.
a reservoir in a hy draulic apparatus, in free communication with the water. The chamber or reservoir is filled with air, which by its elasticity diminishes the shocks that would otherwise be produced by sudden changes in the speed of flow of the water, and also equalizes the flow. When the pressure in the pipes is momentarily greater than the normal pressure, water enters the air ments have been developed. One of particular note is the type up electro-pneumatic governor for electrically- riven air compressors,— the first satisfactory electro-pneumatic governor ever developed for electric compressor control. Consult in Air Brakes for Rail roads' ; 'The Air Brake as Related to Progress in Locomotion' ; 'The Vital Relation of Train Control to the Value of Steam and Electric Railway Properties' ; 'The Development of the Electro-Pneumatic Brake' ; 'Brake Perform ance on Modern Steam Railroad Passenger Trains' ; also various other publications issued by the Westinghouse Air Brake Company, Pittsburgh, Pa.