ing brake-pipe air to unseat check valve 15 and pass by the emergency valve into the brake cylinder. At the same time, port S in the slide valve registers with port in the seat and allows auxiliary reservoir air to flow through these ports to the brake cylinder. (Art. 1.) r 12. Q.-How long does the brake-pipe air flow into the brake cylinder? A. Until the brake-pipe and brake-cylinder pressures equalize, when the check valve is forced to its seat by the check-valve spring. (Art. 1.) 13. Q.-Does auxiliary-reservoir pressure flow into the brake cylinder at the same time? A. Yes. (Art. 1.) 14. Q.-After the brake-pipe and brake-cylinder pressures equalize, does the brake-cylinder pressure continue to rise? A. Yes, as air from the auxiliary reservoir continues to flow to the brake cylinder until their pressures equalize, when a full emergency application is obtained. (Art. 1.) 15. Q.-Why does not this rising pressure flow back into the brake pipe? A. This is prevented by the check valve being seated. (Art. 1.) 16. Q.-How long does the emergency valve remain open? A.-Until the auxiliary-reservoir and brake-cylinder pressures equalize, when the emergency valve and emergency piston are seated by the check-valve spring. (Art. 1.) 17. Q.-In what two respects do the results obtained in an emergency application with a quick-action triple valve differ from those obtained with a plain triple valve? A.—The air taken from the brake pipe into the brake cylinder helps to rapidly reduce the brake-pipe pressure at each triple valve, thus causing the reduction to pass from car to car through a long train in a very short time; it also materially increases the pressure at which the brake cylinder and auxiliary reservoir become equalized. (Art. 1.) 18. Q.-About how much more brake-cylinder pressure is obtained in emergency than in service with a quick-action triple valve? A.-A gain of about one-fifth in braking pressure. (Art. 1.) 19. Q. Can an emergency application be obtained when the brakes are already applied in a service application? Why? A. No, unless the service application is very light, because in a service application the brake-pipe pressure is reduced while the brake-cylinder pressure is increased; this leaves the difference between these two pressures less than normally and, if the quick-action parts do operate, the amount of air that can flow from the brake pipe at its reduced pressure into the brake cylinder, which already has some pressure in it, is usually not enough to cause the quick-action parts of the triple valve on the next and following cars to operate. (Art. 1.) 20. Q.-What is the general rule in handling brakes in case an emergency arises during a service application? A. The brake-valve handle should be placed in emergency position at once, as it is possible that some brakes in the train have not fully applied, and the result will at least assure a full-service application. (Art. 1.) 21. Q-How many sizes of standard quick-action triple valves are in common use, and what are they called? A.-Four, the H-1, H-2, P-1, and P-2. (Art. 2.) 22. Q.-With what sizes and types of brake cylinders are they used? A. The H-1 is used with 8-inch freight-car and passenger tender-brake cylinders, the H-2 with 10-inch freight-car brake cylinders, the P-1 with 8- and 10-inch passenger-car and 10-inch passenger tender-brake cylinders, and the P-2 with 12-, 14- and 16-inch passenger-car and passenger tender-brake cylinders. (Art. 2.) 23. Q.-How can you tell them apart? A. By the raised letters "H-1," "H-2," "P-1," or "P-2," on the side of the body casting and under the exhaust opening. (Art. 2.) 24. Q.-What is the purpose of the vent valve? A.—It is a device that is used with the plain triple valve on the tenderbrake equipment, so as to obtain quick action on the tender just as if a quickaction triple valve were used, and is so designed that there is no possibility of obtaining undesired quick action on the tender because of its nearness to the brake valve. (Art. 3.) 25. Q.-What does the vent valve practically consist of? A. The quick-action parts of the triple valve placed in a separate valve. (Art. 3.) 26. Q.-What are the principal parts of the vent valve? A.-A pipe bracket, which is bolted to the under frame of the tender to support the valve; a body, and a cylinder cap. (Art. 3.) 27. Q.-To what part are the pipe connections made? A. To the pipe bracket. (Art. 3.) 28. Q.-How many and what are the pipe connections? A.-There are three pipe connections; namely, the brake-pipe, the brakecylinder pipe, and the vent-valve reservoir connections. 29. Q-What are the operating parts? (Art. 3.) A. The emergency piston, emergency slide valve, check valve, check-valve spring, graduating sleeve, and graduating spring. (Art. 3.) 30. Q.-What two pressures are separated by the piston? 32. Q-When charging the brake system, what occurs in the vent valve? A. Air pressure admitted from the brake pipe forces the piston firmly against the cylinder-cap gasket, thereby preventing air from flowing through two large feed grooves in the top of the piston bushing, and compelling the charging of the vent-valve reservoir to occur through a small port drilled through the piston just above the stem. (Art. 3.) 33. Q.-What occurs during a service application? A. When a service reduction is made, the gradual fall in pressure on the slide valve side of the piston causes it to move slightly away from the cylinder-cap gasket until the end of the piston stem strikes the graduating sleeve, preventing any further movement. This opens the feed grooves in the piston bushing and allows air from the vent-valve reservoir to pass around the piston into the slide valve chamber and brake pipe in about the same time that air from the auxiliary reservoir passes to the brake cylinder. (Art. 3.) 34. Q-What effect does this have on the brake application? Why? A. It has no effect, because the difference in pressures on the two sides of the piston in a service application never becomes sufficient to compress the graduating spring, consequently the port in the slide-valve seat remains closed. (Art. 3.) 35. Q.-What occurs during an emergency application? A. When an emergency application is made, the sudden reduction of pressure in the slide valve chamber allows the pressure in the vent-valve reservoir to force the piston out the full length of its stroke, compressing the graduating spring and opening the port in the slide-valve seat, thus allowing brake-pipe air to force down the check valve and flow into the brake cylinder. As soon as brake cylinder and brake-pipe pressures equalize, the check valve is forced to its seat by the check-valve spring. The pressure in the vent-valve reservoir reduces by feeding through the small feed port in the piston into the slide-valve chamber and brake pipe until the graduating spring is able to move the piston and slide valve back to service position, thus closing the port in the slide-valve seat. (Art. 3.) 36. Q.-What effect has this on an emergency application? A. It causes a greater brake-cylinder pressure and a local reduction in brake-pipe pressure, the same as is obtained from a quick-action triple valve. (Art. 3.) 37. Q.-Then why not use a quick-action triple valve instead of a plain triple valve and the vent valve with its additional reservoir? A. Because the vent valve has no duties to perform in service applications, and consequently the parts can be arranged so as to be less sensitive to variations in the rate of brake-pipe reduction than the quick-action triple valve, which has certain duties to perform in service as well as emergency applications. Thus, the use of a quick-action triple valve may cause the brakes to apply quick action when only a service application was intended. (Art. 3.) 38. Q-How many sizes of vent valves are there? Why? A. There is only one size, as it is suitable for use with any size of plain triple valve. (Art. 3.) 39. Q.-What is the object of the auxiliary reservoir? A. To store a supply of air for use in applying the brake on the vehicle so equipped. (Art. 4.) 40. Q.-What determines the size of an auxiliary reservoir? A. The fact that its volume should always be such that when stored with air at 70 pounds pressure it will equalize in a full-service application with its brake cylinder at 50 pounds pressure, when the brake-cylinder piston travel is six inches for engine-driver and truck-brake cylinders, and eight inches for all other brake cylinders. (Art. 4.) 41. Q.-What two different types of auxiliary reservoirs are used? A.-Wrought-iron and cast-iron auxiliary reservoirs are the two types in (Art. 4.) use. 42. Q.-Upon what vehicles is a wrought-iron reservoir used? A. On all engines, tenders and pas enger cars. (Art. 4.) 44. Q. How is the wrought-iron reservoir connected with a plain triple valve? A. One end is connected by piping to the slide-valve chamber in the top of the triple valve; the other end is closed by a pipe plug, and a drain plug or cock is screwed into the bottom of the barrel. (Art. 4.) 45. Q.-How is it connected when a quick-action triple valve is used? A.—To the triple valve seat on the brake-cylinder head. (Art. 4.) 46. Q.-Explain how the auxiliary reservoir is placed in the combined freight set. A. The auxiliary reservoir has a seat on one end for the triple valve and is arranged on the other end for direct connection with the brake cylinder; there is a tube inside the reservoir connecting the triple valve with the brake cylinder. (Art. 4.) 47. Q.-What is the purpose of the detached freight set? A. It is for use on cars where the space is limited, such as on a hopperbottom car. (Art. 4.) 48. Q.-How does the detached set differ from the combined set? A. The cylinder and reservoir are furnished detached instead of being combined, as in the combined equipment. (Art. 4.) 49. Q.-In the detached set, how is the triple valve connected with the brake cylinder? A. A pipe is used to connect the outlet of the reservoir tube with the brake cylinder. (Art. 4.) 50. Q.-How can the cast-iron auxiliary reservoir be drained? A. By removing a plug, placed in the bottom of the reservoir for that purpose. (Art. 4.) 51. Q.-What valve is placed in the top of a cast-iron, or freight, auxiliarv reservoir, and what is it for? A. A release valve, for the purpose of discharging air from the auxiliary reservoir so as to release that brake when for any reason it cannot be done by the engineer. (Art. 4.) 52. Q.-How is this accomplished with passenger and engine equipments? A. By opening the drain cock in the bottom of the auxiliary reservoir. (Art. 4.) 53. Q.-Why does this release the brakes? A. It reduces the pressure in the auxiliary reservoir below that in the brake pipe, thus allowing the greater brake-pipe pressure to move the piston to release position. (Art. 4.) 54. Q.-How long should air be discharged from the auxiliary reservoir to cause the brakes to release? A. Until air commences to exhaust from the triple valve. (Art. 4.) 55. reservoir? A.-It may cause the brakes to apply on the other cars near the brake that is being released, as the air will continue to flow from the brake pipe to recharge the auxiliary, thus causing a reduction in brake-pipe pressure. (Art. 4.) 56. Q.-In driver-brake equipments, how many cylinders are used with one auxiliary reservoir? A.-Ordinarily two cylinders are used. (Art. 4.) 57. Q.-What is the brake cylinder for? A. To deliver the power or force, created by the compressed air admitted into it, to the levers and rods to be transmitted to ine brake shoes. 58. Q.-What are the operating parts of the brake cylinder? (Art 5.) A. The piston and its packing leather, the piston follower to hold the packing leather in place, the piston-packing expander to hold the packing leather out against the cylinder wall, the push rod which is held in place by the push-rod-holder pin, the crosshead, which is fastened to one end of the cylinder lever, and the release spring which tends to hold the piston in release position. (Art. 6.) 59. Q. How does it operate during an application? A. When air is admitted to the brake cylinder from the triple valve, it fills the space between the piston and pressure head, and as soon as the pressure is sufficient to overcome the resistance offered by the release spring and the friction, the piston is forced away from the pressure head until the brake shoes are against the wheels and all lost motion in the brake rigging is taken up. (Art. 6.) 60. Q.-When the brakes are released, how does it operate? A.-Air pressure being released by the triple valve, the release spring forces the piston back to its normal position, thereby pulling the brake shoes away from the wheels by means of the levers and rods connecting them. (Art. 6.) 61. Q.-What is the brake-cylinder leakage groove for? A. It is for the purpose of allowing any air that might get into the brake cylinder, due to brake-pipe leakage, to flow by the piston and out through the non-pressure head and to the atmosphere, without moving the piston out to apply the brake. (Art. 6.) 62. Q.-What is the principal difference between various types of brake cylinders? A. The general design of all brake cylinders is the same, but they differ in detail according to the requirements of the equipment with which they are used, and also for convenience in installation. In the tender and freight-car brake cylinders the push rod fits loosely inside the piston rod so that when the brake is applied by the hand wheel the piston will not be pulled out. In the passenger-brake cylinders the piston rod is solid, having the crosshead firmly attached to it. The driver-brake cylinder has a hollow piston rod riveted to the piston, the push rod being placed inside the piston rod and held in place by the push-rod holder pin. (Arts. 5, 6 and 7.) |