The H-6 Brake Valve lease position only long enough to insure a releasing movement of the triple valves of the cars, and then moved at once to lap position; in this "lap-fromrelease" position the locomotive brakes will release; the brake-pipe recharge had put the distributing valve in release position, and the application-cylinder pressure reached port in the rotary-valve seat, ready for release; in the lap position a supplemental cavity channelled in the face of the rotary valve connects port with port q in the seat, through which the application-cylinder pressure is discharged to the atmosphere, resulting, as is already understood, in the release of the locomotive brakes; then the brake-valve handle is moved to service position and the second application is begun. If a third application is made, it should be in the same manner. From the moment the handle is pulled from release position until it is placed in service position again, the brake valve is in lap position, giving the longest possible time for brake-pipe air to be absorbed by the. auxiliary reservoirs, so that when the following application is begun the triple valves will be prompt in responding. THE SG TYPE COMPRESSOR GOVERNOR The SF type of air-compressor governor is described on pages 161 to 168, and illustrated in Fig. 45. That type of governor, while brought out as a part of the ET equipment, may be used on a locomotive with automatic brake equipment if the air pipe connecting with the spring case of the excess-pressure governor head has its other connection made with the brake pipe direct. The SG Governor functions exactly the same as the SF style, but has fewer pipe connections and is more consolidated in construction; and it must be used only with the ET equipment-will not control the pump's action properly, except in association with the H-6 brake valve. The SG Governor is illustrated in section in Fig. 54. It has been explained that main-reservoir pressure must go to the high-pressure governor top at all times; and must go to the excess (low)-pressure governor top when the brake-valve handle is in release, running or holding position, but not in lap, service or emergency position; therefore, while the diaphragm body of the high-pressure top is in direct pipe connection with the main reservoir, the corresponding part of the excess-pressure top is piped to the automatic brake-valve, and from which the main-reservoir pressure is delivered only when the brake valve is in one of the three positions first noted. The object is to make the excess-pressure governor top inoperative from lap to emergency positions, inclusively, but it happens that this effect occurs in those positions (where the H-6 brake valve is used) although main-reservoir pressure be present in the diaphragm body of the excess-pressure governor top. This is explained fully on pages 127, 128, and 129. Therefore, with the SG Governor the pipe formerly used between brake valve and diaphragm body of governor is here discarded; there is but one, common, diaphragm body, and it is piped direct to mainreservoir pressure, and carries the usual portions comprising both the high-pressure and excess-pressure tops. Fig. 54 illustrates this very plainly. Tests and readjustments are made the same as directed for the SF Governor. It will be noted that in the SG Governor there is but one air vent port to the atmosphere, and which should always be kept open; while in the SF style there are two such ports, one of which is required to be kept closed with a screw plug, and the other one open and clean. If the above is understood, Fig. 55 will show very clearly how the SF type of governor may be converted into the equivalent of the SG type. |