140 ENGINEER'S BRAKE VALVES 



PC. No. Rej. No. Name of Part 



18,721 16 Malleable-iron handle, complete, includes 

 17,18, 19, 20, 21, and 22. 



1.367 17 Latch spring. 



1.292 18 Latch. 



1.368 19 Latch screw. 



5,191 Handle clamp bolt, complete, includes 21 



and 22. 



1.293 20 Clamp bolt, only. 



1.294 21 Thumb nut. 

 1,291 22 Pin. 



16,124 23 Check-valve stem, complete, includes two 



each of 13 and 24. 

 1,738 24 Check- valve nut. 



16.121 25 Check-valve case. 



16.122 26 Check- valve cap nut. 



16,190 27 Valve spring for driver-brake release 

 attachment. 



Operation of S-3-A Straight-Air Brake Valve. The S-3-A 

 straight-air brake valve is a special valve furnished only when 

 specially ordered, where it is desired to provide for independ- 

 ent driver brake release. It is similar to the S-3 straight-air 

 brake valve, except for the addition of a device called the 

 driver-brake release attachment (reference numbers 23, 24, 25, 

 and 26), and the addition of a running -position notch to the 

 quadrant corresponding to the release position of the S-3 brake 

 valve, the release position of the S-3-A brake valve being 

 used for the independent release of the driver-brake cylinders. 

 The driver-brake release attachment is arranged to screw into 

 the body of the brake valve as shown in Fig. 2, in place of 

 the valve cap nut 4, Fig. 1, and makes possible the releasing 

 of the driver brakes after an automatic application, without 

 affecting the brakes on the train or tender, thereby providing 

 for independent operation of the driver brakes. 



The driver-brake release attachment is connected by piping 

 to the automatic side of the driver-brake double check-valve, 

 the other connections to the brake valve remaining the same as 

 for the S-3 brake valve. When brakes are applied automatic- 

 ally, the double-seated check-valve 23 will be forced upwards 

 against the upper seat, preventing escape of air through the 

 brake-valve exhaust port. To make an independent release of 

 the driver brakes after an automatic application, the straight- 

 air brake-valve handle is moved to release position, as usual, 



