Chapter XXXVIII.—The Locomotive

VOL. II. AMERICAN FREIGHT LOCOMOTIVE PLATE XXIX.

In Fig. 3326 is shown a modern freight locomotive, the construction being as follows:

For generating the steam we have the boiler, which at the front end is firmly bolted to the engine cylinders, which are in turn bolted to the frames, while at the back end the boiler is suspended by the links b (one at each end of the fire box on each side of the engine).

The starting bar is shown in position to start the engine, and it is seen that the rod a and bell crank b are in such a position as to open the valve t, and thus admit steam from the dome to the pipe e, whence it passes through pipes f, g and r into the steam chest i, the slide valve v distributing the steam to the cylinder. The exhaust occurs through the exhaust port d, whence it passes up the exhaust pipe and out at the smoke stack.

The boiler is fed with water as follows:

The feed pipe from the tender supplies water to the injector, which is forced by the injector through the feed pipe to boiler and into the latter.

In the figure the parts are shown in position for the engine to go ahead, hence the reversing gear is in the extreme forward notch of the sector, and the valve gear is in full gear for the forward motion.

The lever m is for opening and closing the cylinder cocks, which are necessary to let the water of condensation out of the cylinder when the engine is first started and the cold cylinder condenses the steam.

To supply steam to the injectors (of which there are two, one on each side of the engine) and to the steam cylinder of the pump, there is a steam pipe leading from the dome to the steam drum, the pipe k supplying steam to the injector, and pipe j supplying steam to the steam cylinder of the air pump. The pipe for supplying oil to the slide valve and cylinder is furnished with a sight feed oil cup, the oil being carried by steam from the steam drum.

This pipe passes beneath the lagging until it reaches the smoke box, which is done to keep it warm and prevent the oil from freezing, while the steam pressure enables the oil to feed against the steam pressure in the steam chest.

The slide valve is balanced by means of strips let into its back, and bearing against a plate fixed to the steam chest cover.

The frame on the side of the engine shown in the engraving is shown broken away from the yoke a to the fire box, so as to expose the link motion to full view, the shaded portion of the frame being that on the other side of the engine.

The yoke or brace a carries one end of the guide bars. The safety valve s may be raised to see that it is in working order, or to regulate the steam pressure, by the lever o, which has a ratchet tongue engaging with the notches at l.

In addition to the safety valve with spring balance, however, a pop safety valve is employed on the part of the dome that is shown broken away, the construction of this pop valve being shown in the outside view, Fig. 3326a, and a sectional view, Fig. 3326b, the casing being removed from the latter. In the valve seat b is a recess a, and upon the circumference of the valve is a threaded ring c′. When the valve lifts, the steam is somewhat confined in the annular recess of the valve, and the extra valve area thus receiving pressure causes the valve to lift promptly and the steam to escape freely. The degree of this action is governed as follows:

The sleeve c′ is threaded upon the upper part of the valve, so that by screwing it up or down upon the valve the amount of opening between the annular recess a a, and the lower edge of the sleeve c′ c′, is increased or diminished at will; the less this opening, the more promptly the valve will rise after lifting from its seat.

To secure the sleeve or ring in its adjusted position, the ends of the screws l, l seat in notches cut in the upper edge of the sleeve. In many engines pop valves alone are used, and in some cases levers are provided by means of which the pop valve can be raised from its seat to test if it is in working order.

Referring again to Fig. 3326, h is the handle for operating the injector, and w a rod for opening the injector overflow.

We now come to the automatic air brake; steam for the steam cylinder of which, is received from the steam drum through the pipe j, passing through the pump governor, or regulator g. The exhaust pipe for the steam cylinder of the air pump passes into the smoke box. The air cylinder receives its supply of air through the small holes at k, k, and delivers it through the pipe c into the air reservoir or tank, from which it passes through the tank pipe up to the threeway cock or engineer’s brake valve, whose handle is shown at m. The brakes are kept free from the wheels and out of action so long as there is air pressure in the air reservoir and in the train pipe, hence the normal position of the handle m is such as to let the air pass from the air reservoir up the pipe x and into the train pipe. When the brakes are to be applied, handle m is moved so that there is an open connection made between the train pipe and the pipe to open air, which releases the air pressure and then puts on the brakes not only on each car, but also on the engine, because the engine brake cylinders receive their air pressure from the pipe shown leading to the train pipe. From the tank pipe x a pipe h leads to the top of the pump governor g, whose action is to shut off the steam from the steam cylinder of the air pump whenever the pressure in the air reservoir or tank exceeds 70 lbs. per square inch. A small pipe leads up from pipe h to the air pressure gauge.

For regulating the draught of the fire there is a damper door at each end of the ash pan, and to increase the draught, a pipe leads from the steam drum into the smoke box, where it passes up alongside of the exhaust pipe, its end being shown at z. This is called the blower, and its pipe is on the other side of the engine. The plate shown at p, p in the smoke box checks the draught in the upper tubes, and therefore distributes it more through the lower ones.

There are two sand valves, both of which are operated by one rod, the construction being shown in Fig. 3327, which is a plan showing the bottom of the sand box broken away to expose the gear for moving the valves. The two valves v, v for the sand pipes are on raised seats e, e, and are fast on the same shafts as the segments s, s, but the valves are obviously above, while the segments are beneath the bottom of the sand box. The gear wheel w is pivoted to the under side of the bottom of the sand box, and the arm l is fixed to the wheel. At t are pieces of wire, which, being fast in the spindle, revolve with it and stir up the sand when the valves are moved. As shown in the figure, the two sand pipes a, a are open, but suppose the rod is moved endways and l will revolve w, which will move s, s and the valves v, v, causing the latter to move over and cover the pipes a, a, and shut off the sand from the pipes.

VOL. II. AMERICAN PASSENGER LOCOMOTIVE PLATE XXX.

Fig. 3328 represents an American passenger locomotive with a steam reversing gear, or in other words, a reversing gear that is operated by steam.

The link motion is substantially the same as that shown in Fig. 3326 for a freight locomotive, the eccentric rods in this case being straight, as there is no wheel axle in the way.

The injector for feeding the boiler is the same as that shown on the freight locomotive.

The ash pan is provided with two dampers, one at each end, and the front one is operated by the bell crank a c.

The sand boxes are here fastened to the frame, both sand valves being operated by the lever m, which at its lower end connects to a rod, u, which at its back end connects to an arm, p, on a shaft that extends across the fire box and connects to a rod corresponding to rod u, but situated on the other side of the engine and connecting with the other sand valve.

The steam pump for the automatic air brake is on the other side of the engine, and the air reservoirs, of which there are two, are horizontal and situated beneath the front end of the boiler. The air pipe to the triple valve here connects to the front pipe of the three beneath the triple valve, the middle pipe being that which is open to the atmosphere, which is the usual construction. The engine brake receives its air from a pipe on the other side of the engine which feeds the pipes g, v, for the brake cylinder shown in the figure. When the engine is running backwards, the train brakes are operated through the medium of the “pipe to air brake and to front end of engine” which is shown broken off.

The construction of the steam reversing gear is shown in Fig. 3328a. a is a steam cylinder and b a cylinder filled with oil or other liquid. Each of these cylinders has a piston, the two being connected together by their piston-rods c c′. These rods are also connected to a lever d e f, which works on a fulcrum e. The lower end of the lever is connected to the reverse rod f g, the front end of which is attached to the vertical arm of the lifting or reverse shaft. It will readily be seen that if the piston in b is free to move and steam is then admitted to either end of the steam cylinder a, the two pistons will be moved in a corresponding direction, and with them the lever d e f, and the other parts of the reversing gear. A valve, h, is provided, by which communication is opened between the cylinder a and the steam inlet pipe. Another valve, i, is placed between h and the cylinder a, by which the steam may be admitted either into the front or back end of the cylinder. It will be apparent, though, that if the piston in a is thus moved, and the reverse gear placed in any required position, some provision must be made to hold it there securely. This is accomplished by the oil cylinder and piston b. To it a valve, j, is provided, by which communication between the front and back ends of the cylinder may be opened or closed. It is evident that if the piston b is in any given position, and both ends of the cylinder are filled with liquid, the former will be held securely in that position if the liquid in one end cannot flow into the other. If, however, communication is opened between the two ends, then, if a pressure is exerted on the piston b, it will cause the liquid to flow from one end of the cylinder to the other, and thus permit b to move in whichever direction the pressure is exerted.

r is the reverse lever, made in the form of a bell crank, the short end of which works in a slot c, in the upper end of a shaft or spindle d. This shaft is inclosed by a tubular shaft s, to which the fulcrum of r is fastened. The tubular shaft has an arm b. The reverse lever has two movements, the one to raise the end up, and the other to turn on the axis of the tubular shaft. The arm b on the latter is connected by a rod, f, with the valves j and h. The lower end of the shaft d is connected with a bell crank, f′, which, in turn, is connected by a rod, k l, with the valve i. Therefore, by turning the lever r so as to partly revolve the shaft s, the valves j and h may be opened or closed, and by moving the lever r up or down, the valve i is moved to admit steam to the front or back end of a. To reverse the engine, therefore, the lever r is turned so as to open the valves j and h. This opens communication between the opposite ends of b, and h admits steam to i. Now, by reversing the end of the reverse lever r, the valve i is moved so as to admit steam to either end of a, the pressure in which will move the reverse gear to the desired position. When this is done, the valves j and h are closed. This prevents the fluid in b from flowing from one end of the cylinder to the other, and thus securely locks the piston b in the position it may happen to be in, and at the same time the valve h shuts off steam from the cylinder a.

The bar k is graduated, as shown in the plan of r, k, to indicate to the locomotive runner the position of the reversing gear.

This apparatus enables the reversing gear to be handled with the utmost facility, and with almost no exertion on the part of the engineer. The engine can be reversed almost instantly, and it can be graduated with the most minute precision.