STEAM LOCOMOTIVE ENGINEMAN’S. Manual - part 28

Chapter 12: - Westinghouse Brake 

 

 

12.7.3 

FURTHER TEST 

 
 

The train pipe cock on the front of the engine is 
opened slightly to create a leakage.  If the black 
hand on the gauge falls to 68 lb, and then 
returns to 70 lb, and continues to fluctuate 
between these points, it indicates that the feed 
valve is opening and closing correctly. 

 
 

If air is escaping from the vent port in the 
adjusting spring chamber, it indicates cracked or 
defective diaphragm plates.  If the rotary valve is 
not blowing through, a loss of excess pressure 
may be caused by leakage past the supply and 
regulating valves, by a defective gasket between 
the body of the feed valve and brake valve, by 
incorrect adjustment, or by overcharging of the 
train pipe. 

 
 

In cases where excess pressure is obtained and 
then lost, the fault can generally be traced to a 
dirty supply or regulating valve.  The trouble can 
generally be overcome by adopting the following 
method: 

 
 

The isolating cock is closed and all train pipe 
pressure exhausted by opening the cock on the 
back of tender.  The caps from the supply and 
regulating valve chambers are then removed, 
and the supply valve and spring, also the 
regulating valve and spring, are withdrawn and 
cleaned thoroughly with a kerosene soaked 
cloth. 

 
 

The valve bushes are also cleaned by the same 
method.  While these valves are out, the tension 
of the springs is checked, and the brake valve 
handle is placed in the running position and the 
isolating cock opened for a few seconds to 
remove any dirt in the passages. 

 
 

The valves and springs are then replaced, the 
cock on the back of tender closed, and the 
isolating cock opened, ready for service. 

 

Chapter 12: - Westinghouse Brake 

 

 

12.8 

AUTOMATIC SLACK ADJUSTER 

 

12.8.1 

PURPOSE 

 
 

The purpose of the slack adjuster is to maintain 
uniform piston travel, by automatically taking up 
the slack caused by wear of the brake blocks. 

 
 

It consists of a small air cylinder and piston, the 
packing leather of which is held in position by an 
expanding ring and follower, and a pawl, pawl 
spring, piston spring, cylinder head and casing, 
and a ratchet nut. 

 
 

The air cylinder is connected with a pipe that 
leads from a predetermined port on the side of 
the brake cylinder.  The ratchet engages with the 
adjusting screw, which automatically takes up 
the slack when the brake is released. 

 
12.8.2 

OPERATION 

 
 

If there is sufficient slack in the brake rigging to 
permit the brake cylinder piston to extend 
beyond the port in the side of the brake cylinder 
when the brake is applied, brake cylinder air will 
pass through the port and connecting pipe, and 
enter the slack adjuster cylinder. 

 
 

The slack adjuster piston will be forced out, 
compressing the piston spring, and the pawl 
spring will cause the pawl to engage in the teeth 
of the ratchet nut.  When the brake is released, 
air pressure from the adjuster cylinder escapes 
on the non-pressure side of the brake cylinder.   

 
 

This permits the adjuster piston spring to force 
its piston back, causing the pawl to turn the 
ratchet nut and consequently taking up the 
adjusting screw.  The effect of this is to draw the 
brake blocks nearer to the wheels.  The 
arrangement is adjusted to control the brake 
cylinder piston travel to the laid down. 

 
 

For the purpose of renewing brake blocks and 
setting the blocks correctly, hand adjustment can 
be made by turning the ratchet nut with a 
spanner. 

 

Chapter 12: - Westinghouse Brake 

 

 

  

To slacken the brake rigging the adjuster 
crosshead is moved towards the brake cylinder, 
and to tighten the rigging and shorten the piston 
travel the crosshead is moved in the opposite 
direction. 

 
12.9 

PASSENGER INTERCOMMUNICATION GEAR ON 
CARRIAGES 

 
 

This arrangement is fitted to carriages for use by passengers 
in an emergency. 

 
 

A branch pipe leads from the train pipe to a casing, which 
contains a spring loaded valve, the valve being closed in its 
normal position.  An operating rod with a cam that can 
engage the valve stem is fitted in bearings on the end of the 
carriage. 

 
 

Connected to this rod is a chain running through a tube from 
one end of the carriage to the other, the tube having an 
opening in each compartment.  A disc is attached to each 
end of the operating rod and is in a horizontal position when 
normal and a vertical position after use. 

 
 

When the chain is pulled in a compartment, the cam on the 
operating rod engages the stem of the air valve, opening the 
valve and releasing air from the train pipe, causing the 
brakes to be applied. 

 
 

To close the valve, it is necessary to turn the disc on the 
operating rod so as to release the cam from the valve stem 
and allow the valve to be closed by its spring,  thus 
preventing further escape of air from the train pipe. 

 
 

To enable the device to operate successfully, drivers must 
always have the automatic brake valve handle in the running 
position when not in use.  Discretion must be used so as not 
to allow the train to stop on a bridge where other passengers 
may alight.  All cases of interference with the gear must be 
reported on Driver’s Occurrence Sheets. 

 

Chapter 13: - General Westinghouse Brake – Questions and Answers 

 

 

 

CHAPTER 13 

 
 

GENERAL WESTINGHOUSE 

BRAKE – QUESTIONS AND 

ANSWERS