ENGINEER'S BRAKE VALVES 139 



the brake cylinder, and the other valve is opened and allows 

 brake-cylinder air to escape to the atmosphere. 



A graduated release can be made with this brake valve when 

 desired. To partly release the brakes, move the handle to 

 release position until the desired reduction of brake-cylinder 

 pressure is made, and then move it to lap. 



The notches at the ends of the quadrant that the latch fits 

 into are intended to hold the handle in position against the 

 tension of the springs 15 and 27. If these notches become 

 worn, the force of the spring 27 is liable to return the handle 

 to lap position from release position. 



S-3-A (|-IN.) STRAIGHT-AIR BRAKE VALVE 

 Piece and Reference Numbers. The S-3-A (|-in.) straight- 

 air brake valve, shown in Fig. 2, is special and is supplied 

 instead of the S-3 brake valve where independent driver- 

 brake release is desired and when specified on orders; its 

 weight is 18 Ib. Its piece number, with brass handle, com- 

 plete, is 17,537; with a malleable-iron handle, 19,168. The 

 piece and reference numbers of the various parts are given 

 in the accompanying list. If it is desired to add the inde- 

 pendent driver-brake release feature to S-3 straight-air brake 

 valves already in service, order should specify Piece No. 16,235, 

 which includes all parts necessary to change an S-3 into an 

 S-3-A brake valve; viz., Ref. Nos. 5, 23, 25, 26, 27. 



PC. No. Ref. No. Name of Part 



2,617 2 Body. 



2.620 3 Shaft cap nut. 



2.621 4 Valve cap nut. 

 16,125 5 Quadrant. 



2,310 6 Quadrant bolt and nut. 



2.628 7 Shaft, complete, includes 9. 

 2,426 8 Leather shaft washer. 

 2,619 9 Shaft-spring washer. 

 2,616 10 Shaft spring. 



2.629 Valve, complete, includes 11, 12, 13, and 



14. 

 4,855 11 Valve stem. 



2.623 12 Valve. 



2.624 13 Valve seat. 



2.625 14 Valve-stem nut. 

 2,616 15 Valve spring. 



2,632 16 Brass handle, complete, includes 17, 18, 

 19, 20, 21, and 22. 



