Brake Tests
År: 1913
Forlag: Pensylvania Railroad Company
Sted: Altoona, Penna.
Sider: 401
A Report Of A Series Of Road Tests Of Brakes On Passanger Equipment Cars Made At Absecon, New Jersey, In 1913
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36
CHAPTER III.
AIR BRAKE EQUIPMENT.
PRESENT EQUIPMENT ON P. R. R. P-70 CARS.
73. The Westinghouse quick action automatic brake (PM equip-
ment) used on P-70 cars, is illustrated in Fig. 22. It comprises a
16-inch brake cylinder with automatic brake slack adjuster set for
8-inch running piston travel, a 16 in. by 42 in. auxiliary reservoir for
increased capacity for service applications, a quick action triple valve
(Type P-2, Fig. 23), which controls the flow of compressed air:—
(a) From the brake pipe to the auxiliary reservoir for charging the
system.
(b) From the auxiliary reservoir to the brake cylinder for applying
the brakes.
(c) From the brake cylinder to the atmosphere when releasing.
(d) From the brake pipe to the brake cylinder, as well as from the
auxiliary reservoir to the brake cylinder when a quick action
application of the brakes is desired.
74. A high-speed reducing valve designed to perform the functions
of a safety valve during service brake applications, limits the brake
cylinder pressure to a maximum, predetermined as satisfactory for
service operations (62 pounds). In emergency applications the high-
speed reducing valve retains the maximum cylinder pressure practically
constant for a period of time and then by an accelerating blow down,
reduces the brake cylinder pressure as the stopping point is approached,
this reduction compensates for the increased effectiveness of the brake
shoes as the speed diminishes.
75. The characteristic functional features of this type of brake
equipment are given in paragraphs 76 to 88.
Charging and RECHARGING AFTER Brake Application.
76. The compressed air required to charge the auxiliary reservoir
is all supplied from the' brake pipe through the feed groove around the
triple valve piston when in release position only.
Service Brake Application.
77. In response to a given reduction in brake pipe pressure the
triple valve automatically reduces the pressuie in the auxiliary reservoir
an equal amount. The total volume of compressed air thus measured
out from the auxiliary reservoir is delivered to the brake cylinder, where
it produces a pressure on the brake cylinder piston proportional to the
volume of the brake cylinder as determined by the piston travel.