Modern Locomotive Valves and Valve Gears

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Griffin & Winters, 1917 - Locomotives - 339 pages
 

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Page 241 - Walschaert valve gear, the radius rod is directly connected to the lift shaft arm by means of a slip block or crosshead. It is common practice in such cases to make the lift shaft arm in two pieces so that the radius rod may be easily disconnected from it, as shown in Fig.
Page 212 - Fig. 14, except that the valve has one inch outside lap and the eccentric crank has been advanced to more than a quarter of a revolution ahead of the main pin. If then the link block is at the bottom of the link, as in position "A...
Page 212 - ... eccentric relative to the main pin; if there is to be any method of reversing the engine. In the Walschaert valve gear the motion for providing lap and lead to the valve is derived from the main pin by suitable connections with the crosshead. This brings us to the next step in the development of the Walschaert valve gear and the introduction of the lap and lead lever.
Page 208 - ... back center. In order to make the engine run backward, the eccentric would have to be in the opposite position from that which it occupies, or on the lower quarter ; in which case as the wheel was turned to the left or backward the eccentric would be a quarter of a revolution ahead of the main pin and move the valve forward, opening up the back port and admitting steam behind the piston as is necessary. The first thing to do in the development of this simple form of engine, therefore, is to introduce...
Page 207 - ... position on its seat with all ports closed. Although it is apparent that if the throttle were open this engine could not start of itself, with another engine of the same kind connected to the wheel on the other side of the axle, and with the main pins at right angles to each other, as is the case in the locomotive, the valve of the left hand engine would be in a position to admit steam behind the piston and start the wheels turning to the right. The eccentric crank on the engine which is shown...
Page 287 - ... neither had there been one cent spent on repairs to the valve gear parts. All bearings, pins and bushings of the Southern valve gear are of such size as to insure long usage with very, little wear. The forward end of the eccentric rod is supported by a bell crank hanger, which has at its top two bearings spaced widely apart, thus absolutely preventing any side slap on the eccentric rod. Fig.
Page 247 - ... lap plus the lead which gives a port opening equal to the amount of the lead. This permits of leaving the main rod up and running in with both sides, as the cylinders can b*e lubricated, and though the cut-off will be very short on the disabled side, the steam that will be admitted will do a certain amount of work and the engine can be reversed.
Page 208 - ... same position, the valve stem was connected to the upper end of the link, as shown in diagram "B," the valve would be moved to its extreme position to the left and the front port would be opened and steam admitted ahead of the piston and the engine would run backward. With a flexible valve stem, or radius rod, connected to a block which slides in a curved slot in the beam, or link, as shown, and with the necessary mechanism for raising and lowering the block, it is evident that we now have an...
Page 133 - ... the valve to lift it is necessary to force the cone up into this taper ring ; and since the ring is held, by the steam chest pressure, from opening, the valve cannot lift without first overcoming the entire friction of the beveled face besides opening the ring against the chest pressure.
Page 205 - The favorable results for starting are, however, obtained at the expense of the distortion of the valve events in back motion by robbing one to favor the other. For this reason the Walschaert valve gear, with variable lead, is suitable only for passenger and fast freight locomotives and not for slow freight or switching locomotives. With a variable lead, so arranged that the lead increases as the reverse lever is hooked up, the eccentric crank lags behind the correct position for a constant lead...

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