As the purpose of a locomotive engine attached to a train is to take that train along on time, and as engines are generally rated to pull cars according to their size, it is of the utmost importance that they should make steam freely enough to keep up an even pressure on the boiler while the cylinders are drawing the supply necessary to maintain speed. A locomotive that does not generate steam as fast as the cylinders use it, is like a lame horse on the road, a torture to itself, and to every one connected with it.

To steam freely, an engine must be built according to sound mechanical principles. The locomotives constructed by our best manufacturers, the engines which keep the trains on our first-class roads moving like clock-work, are designed according to proportions which experience has demonstrated to be productive of the most satisfactory results for power and speed, combined with economy. There are certain characteristics common to all good makers. The valve-motion is planned to apply steam to the pistons at nearly boiler pressure, with the means of cutting off early in the stroke, and retaining the steam long enough in the cylinders to obtain tangible benefits from its expansive principle. Liberal heating-surface is provided in the boiler, its extent being regulated by the size of the cylinders to be supplied with steam. With a good valve-motion, and plenty of heating-surface served with the products of good coal, an engine must steam freely if it is not prevented from doing so by malconstruction or adjustment of minor parts, or by the wasting of heat in the boiler or in the cylinders.

An engine of that kind will steam if it is managed with any degree of skill. But as the best lathe ever constructed will turn out poor work under the hands of a blundering machinist, so the best of locomotives will make a bad record when run without care or skill. Regular feeding — the water supplied at a rate to equal the quantity evaporated, which will maintain a nearly level gauge — is an essential point in successful running. It is hardly second in importance to skillful firing.

When an engine is steaming badly, almost the first action of an experienced engineer is to examine the petticoat-pipe. The influence which this pipe exercises on the steaming qualities of an engine has already been adverted to, but its importance can not be too strongly urged upon the attention of the young engineer. It is one of the most successful devices invented for regulating the vacuum in the smoke-box, so that the currents of hot gases shall flow evenly through all the flues. Any thing which interferes to disturb the flow of these currents, crowding them away from any section of the flue-surface, will have a prejudicial effect upon the steam. The pipe may be set too high to produce an even draught, or the fault may be in the opposite direction. Its diameter may not be suitable for the conditions of smoke box and stack, or its shape may be at fault. Not unfrequently the pipe is fastened obliquely, so that the blast impinges on the side of the stack, producing evil results; or the braces which keep it in position occasionally break, and the draught is permitted to shoot in every direction but the direct way to the atmosphere, and the effect is immediately apparent on the steam-gauge.

The petticoat-pipe performs, in relation to draught, functions of a similar nature to those performed by the tubes of an injector in inducing the flow of water; and its efficiency is reduced by the same disturbing agencies. The pipe must have a size in proportion to the diameter of stack, and it must be set so that it shall deliver the exhaust-steam to make a straight shoot through the stack. When these conditions are properly arranged, the exhaust-steam goes through the stack like a piston, leaving a vacuum behind. The petticoat-pipe is a device confined mainly to American locomotives; and its purpose is to regulate the draught in the smoke-box so that the currents of hot gases are drawn uniformly through the flues, the top, bottom, and sides getting about the same heating intensity as passes through the middle rows. The opportunity for the exhibition of good firing depends greatly upon the petticoat-pipe being constructed properly, and secured at the right position. It is impracticable to lay down a positive rule for dimensions and best position of these pipes, for engines of the same proportions frequently require different petticoat-pipe arrangements to make them steam freely. For our 17 x 24 engine, there is a petticoat-pipe 112 inches in diameter, with a flare, at bottom, 17 inches wide. The pipe reaches within 3 inches of the bottom of the stack, and is set one inch above the nozzle. This gives good results in our case. When engines with sufficient heating-surface do not steam freely, the trouble nearly always lies in malproportioned or badly set petticoat-pipes. Sometimes a very small change in the position of this pipe will have a wonderful effect upon the steaming qualities of the engine. If the pipe is set too high, most of the draught will pass through the lower flues; and the upper rows will become filled with soot, and many of them are likely to get choked with fine ashes, which remains there for want of draught to force it out. Should it be too low, the bottom rows of flues will suffer from the effect of defective draught. When the petticoat-pipe is just right, the flues will look uniformly clean inside, which can be ascertained by a close inspection of the smoke-box. In addition to making the engine lose the benefit of its full heating-surface, a badly arranged petticoat-pipe concentrates the draught so much that it tears the fire to pieces at one particular point; and the only resource for the man who wishes to keep up steam is to fire heavily, thereby preventing cold air from being drawn through the crevices. Many engines will not steam with a light fire, and yet do well with a heavy body of coal on the grates. In nearly every instance of this kind, the fault lies in the petticoat-pipe; and, if this is properly adjusted, the engine will be found capable of carrying a light fire, and will show far more economical results than could be reached with heavy firing. Some engineers assume that the petticoat-pipe must be right when an engine steams freely, even though a heavy fire is necessary to produce this result. This is a mistake. It may be badly set or badly proportioned, only a degree smaller than it is where the engine will not steam to keep the train going. By closely watching the action of the blast on the fire of an engine that calls for heavy firing, the engineer learns where the fault lies. When the engine is laboring on a hard pull, he should open the door; and if he finds, that, in a particular section of the fire-box, the smaller pieces of coal are dancing and glowing with an incandescence more brilliant than the other parts, and if he finds that this is repeatedly the case, he may conclude that the nozzles are too small, or the petticoat-pipe is working the mischief with his coal-account. Should the nozzles be the proper size, he had better lose no time in beginning to experiment with this pipe. He can lower it a quarter of an inch at a time, and mark the effects of the change on the fire. Should that produce no improvement, he may try raising it; or, if there is a movable sleeve on the top, that may be set in different positions. An engineer can test a petticoat-pipe much better by manipulating it on the road than in the round-house. If no change of position will improve the working of the pipe, one of different dimensions should be tried. Perseverance in this line will bring the right thing in the end. I knew an engineer who tried five different petticoat-pipes before the proper one was reached. Such a thing causes labor, and needs patience; but it pays when the fuel-account for running ten thousand miles comes in.

The ordinary purpose of the smoke-stack is to convey the smoke and exhausted gases to the atmosphere. If it is intended to perform its functions in a straightforward manner, it is made about the same diameter as the cylinders, and its highest altitude rises from 14 to 15 feet above the rail. The stack is a simple-enough article to look at, yet a vast amount of inventive genius has been expended upon attempts to expand its natural functions. Attempts have been made to utilize it as an apparatus for consuming smoke, and hundreds of patents bang upon it as a spark-arrester. Patentees, in pushing their hobby, seem occasionally to forget that a locomotive requires some draught, as a means of generating steam; and stacks are frequently so hampered with patent spark-arresters that the means of making steam are seriously curtailed. Were it not for the danger of raising fires by spark throwing, it would be more economical to use engines with clear smoke-stacks; and the extended front end, with open stack, is a good move in this direction.

Every obstruction to free draught entails the use of strong artificial means to overcome it. The usual resort is contracted nozzles, which induce a sharp blast, and use up more fuel than would be required with an open passage to the atmosphere. Among the obstacles to free steaming, that come under the category of obstructed draught, may be placed a wide cone fastened low, and netting with fine meshes. When the draught passage is interrupted to a pernicious extent by spark-arresting appliances, their effects can be perceived on the fire when steam is shut off; for the flame and smoke prefer the fire-box door to the stack as a means of exit. Sometimes steam-making is hindered by the netting getting gummed up with spent lubricants and dirt from the cylinders. Cases occur where this gum has to be burned off before free draught can be obtained. Waste soaked with coal-oil will generally burn off the objectionable coating.

Gumming of the netting is usually caused by carelessness in oiling the valves. Some runners will shut off for a minute while the fireman oils the valves, and the lubricant scarcely gets time to reach the steam-chest when the throttle is opened wide again; and instead of soaking over valves and cylinders, and into the remotest part of piston-packing, the oil goes through the stack with the first puff of steam. It is best, in oiling the valves, to leave the cup-plugs open long enough for the oil to be sucked out of the pipes. Then, when steam is applied, it should be done by slightly opening the throttle, so that it will work the oil into the piston-packing; and, after a few turns run this way, there will be no loose oil left to defile the netting.

Certain kinds of coal deposit a hard, silicious substance upon the back flue-sheet, which gradually accumulates till the draught is seriously impeded. This, of course, prevents the full benefit of the hot gases being obtained; and consequently the steam goes down. Flues stopped up with cinders produce a similar effect. The flues getting choked up with cinders is not always an indication that the petticoat-pipe is performing its duty improperly. Stopping up of flues is often caused by wild, unskillful firing. A shovelful of coal pitched high, deposits part of its load direct in the flues; and some pieces that are a close fit do not go through. They stick half way; and small cinders soon follow, that quickly close up the entire passage.

By this arrangement, the spark-arresting device is transferred from the smoke-stack to the smoke-box, and the exhaust steam escapes direct to the atmosphere, without meeting obstruction from a cone or netting. The netting is generally an oblong screen, extending from above the upper row of flues to the top of the extended smoke-box, some distance ahead of the stack. This presents a wide area of netting for the fire-gases to pass through. The draught through the flues is regulated by an apron or diaphragm-plate, extending downwards at an acute angle from the upper part of the flue-sheet. With the long exhaust-pipe used with the extended smoke-box, the tendency of the exhaust is to draw the fire-gases through the upper row of flues. The diaphragm-plate performs the same duties here, of regulating the draught through the flues equally, as the petticoat-pipe does with the diamond-stack. It is of great consequence, for the successful working of the engine, that the draught should be properly regulated: otherwise there will be trouble for want of steam.

When an engine having an extended smoke-box does not steam properly, experiments should be made with the diaphragm fastened at different angles, till the point is reached where equal draught through the flues is obtained. Closing the nozzles, as a means of improving the steaming of such an engine, is certain to make matters worse.

The blowing of steam-pipe joints in the smoke-box is very disastrous to the steaming qualities of a locomotive. This has a double action against keeping up steam. All that escapes by leaking is so much wasted, and its presence in the smoke-box interrupts the draught.

If the steam-pipe joints are leaking badly, they can be heard when the fire-door is open and the engine working steam. Some experienced engineers can detect the action of leaky steam-pipe joints on the fire; but the safest way to locate this trouble is by opening the smoke-box door, and giving the engine steam.

Grates that are fitted so close as to curtail the free admission of air below the fire prevent an engine from steaming freely. The effect of this will be most apparent when the fire begins to get dirty. This is not a common fault. I once knew of an engine's steaming being very seriously impaired by two or three fingers in one section of grate being broken off. The engine steamed well with a light fire, till, in dumping the fire at the end of a journey, the men knocked some of the fingers off. Next trip, it seemed a different engine. Nothing but heavy firing would keep up an approach at working-pressure. I experimented with the petticoat-pipe without satisfaction, assured myself that no leaks existed among the pipes; the stack, with its connections, was faultless; and the engineer was puzzled. The defect was discovered by watching the effect of the blast upon the fire. Signs of air-drawing were often to be seen at the point where the broken fingers were. This was where the mischief lay. Too much cold air came through, unless the opening were bedded over by heavy fire.

A drop-grate that did not close properly had a similar effect upon another engine which came under the author's notice; and a change, which shut the opening, effected a perfect remedy.

In calcareous regions, where the water-supply for locomotives is drawn from wells, the most common cause for bad-steaming engines is leaky heating-surfaces, or water-surfaces incrusted with lime deposits. When he sees water pouring from flues and stay-bolts, an engineer has no difficulty in divining the reason why his engine steams poorly; nor need he be far-seeing to perceive a remedy in the boiler-maker's calking-tools skillfully applied. The case of incrustation is, however, more difficult to comprehend in all its bearings. When water containing lime-salts touches the hot flues or fire-box, evaporation takes place; and the solid substance previously in solution is left behind, and adheres to the heating-surfaces, gradually forming a refractory scale which is an indifferent conductor of heat. As this scale becomes thick, it stands up, like a non-conducting barrier, between the water and the hot sheets; and it takes a much greater expenditure of heat to evaporate the water inside, just as a kettle coated with scale is much harder to boil than a clean one. When a boiler gets badly fouled with scale and mud, these impurities exercise a pernicious effect upon the steaming qualities of a locomotive.

Mud-drums, with blow-off cocks attached, serve to check the growth of this evil when the engineer is careful to make frequent use of these appliances; and a strong pressure of washing-out water, poured frequently through the boiler, has an excellent cleansing effect: but some kinds of scale defy mud-drums and the best methods of washing out, leaving the only resort to be the removal of flues for cleansing. The filling up of a boiler with scale and mud, so as to prevent the engine from steaming freely, is necessarily a gradual process; and an observant engineer has time to note the change, and recommend the proper remedy.

Leaky flues or stay-bolts may sometimes be dried up temporarily by putting bran, or any other substance containing starch, in the feed-water. Care must be taken not to use this remedy too liberally, or it will cause foaming. It is, however, a sort of granger resort, and is seldom tried except to help an engine to the nearest point where calking can be done.

No engine steams so freely but that it will get short under mismanagement. The locomotive is designed to generate steam from water kept at a nearly uniform temperature. If an engine is pulling a train which requires the evaporation of 1,500 gallons of water each hour, there will be 25 gallons pumped into the boiler every minute. When this goes on regularly, all goes well; but if the runner shuts the feed for five minutes, and then opens it to allow 50 gallons a minute to pass through the pump, the best engine going will show signs of distress. Where this fluctuating style of feeding is indulged in, — and many careless runners are habitually guilty of such practices, — no locomotive can retain the reputation of doing its work economically.

The case of Fred Bemis, who still murders locomotives on a road in Indiana, is instructive in this respect. Fred was originally a butcher; and, had he stuck to the cleaver, he might have passed through life as a fairly intelligent man. But he was seized with the ambition to go railroading, and struck a job as fireman. He never displayed any aptitude for the business, and was a poor fireman all his time through sheer indifference. But he had no specially bad habits; and, in the course of years, he was "set up." He had the aptitude for seeing a thing done a thousand times without learning how to do it. All his movements with an engine were spasmodic. Starting from a station with a roaring fire and full boiler, the next stopping-point loomed ahead; and to get there as soon as possible was his only thought. He would keep the reverse-lever in the neighborhood of the "corner," and pound the engine along. The pump would be shut off to keep the steam from going back too fast, till the water became low: then the feed would be opened wide, and the steam drowned down. In vain a heavy fire would be torn to pieces by vigorous shaking of the grates. The steam would not rally, and he would crawl into the next station at a wagon pace. A laboring blower and shaker-bar would resuscitate the energies of the engine in a few minutes if the flues and fire-box were not leaking too badly, and the injector would provide the water for starting on; but no experience of delay and trouble seemed capable of teaching Bemis the lesson how to work the engine properly. He soon became the terror of train men, and the boiler-makers worked incessantly on his fire-box. But he is still there, although he will not make an engineer if he runs for a century.

On one of our leading railroads a locomotive was rebuilt, and fitted with the extension smoke-box, which was an experiment for that road, and consequently was looked upon with some degree of distrust. When the engine was put on the road, it was found that it did not steam satisfactorily. Of course, it was at once concluded that the draught arrangements were to blame; and experiments were made, with the view of adjusting the flow of gases through the tubes to produce better results. The traveling engineer of the road had charge of the job, and he proceeded industriously to work at locating the trouble. He tried every thing in the way of adjusting the smoke-box attachments that could be thought of, but nothing that was done improved the steaming qualities of the engine. He then proceeded to search for trouble in some other direction. The result of his examination was the discovery that the engine was working with three-fourth inch clearance at each end of the cylinders. This, he naturally concluded, entailed a serious waste of steam; so he had the clearance reduced to one-fourth inch. When the engine got out after this change, it steamed very satisfactorily; and the extension smoke-box is no longer in disrepute on that road.

Mistakes are frequently made when the open stack is adopted, as is practicable with the extended smoke-box, of making the stack too wide for the exhaust. This leads to deficiency of draught for the steam that is passing through the stack, because the steam does not fill the stack like a piston creating a clean vacuum behind it. Where an engine fails to steam freely after being equipped with an extended smoke-box, attention should be directed to the proportion of stack diameter to the size of cylinders.

Locomotives, with their limited heating-surface, require intense artificial draught to produce steam rapidly. Many devices have been tried to stimulate combustion, and generate the necessary heat; but none have proved so effectual and reliable as contracted exhaust orifices. As the intermittent rush of steam from the cylinders to the open atmosphere escapes from the contracted openings of the exhaust-pipe, it leaves a partial vacuum in the smoke-box, into which the gases from the fire-box flow with amazing velocity. As the area of the exhaust nozzles is increased, the pressure of steam passing through becomes lessened, and the height of the vacuum in the smoke-box is decreased. Consequently, with wide nozzles, the velocity of the gases through the flues is slower than with narrow ones; for there is less suction in the smoke-box to draw out the fire products: and, where the gases pass slowly through the flues, there is more time given for the water to abstract the heat. Any change or arrangement which will retain the gases of combustion one-tenth of a second longer in contact with the heat-extracting surfaces, will wonderfully increase the evaporative service of a ton of coal. Experiments with the pyrometer, an instrument for measuring high temperatures, have shown that the gases passing through the smoke-box vary from 400 degrees up to 900 degrees Fahrenheit; and they show that increase of smoke-box temperature keeps pace with contracted nozzles. From this, engineers can understand why lead gaskets do not keep blower-joints in a smoke-box tight, the melting-point of lead being 627 degrees.

Inordinately contracted nozzles are objectionable in another way. They cause back pressure in the cylinders, and thereby decrease the effective duty of the steam. Double nozzles are preferable to single ones; because with the latter the steam has a tendency to shoot over into the other cylinder, and cause back pressure.

Engineers anxious to make a good record, try to run with nozzles as wide as possible. Contracted nozzles destroy power by back pressure: they tear the fire to pieces with the violent blast, and they hurry the heat through the flues so fast that its temperature is but slightly diminished when it passes into the atmosphere. The engineer, who, by intelligent care, reduces his smoke-box temperature 100 degrees, is worthy to rank as a master in his calling.

The other day an engineer came into the round-house, and said, "You had better put 32 inch nozzles in my engine: I think she will get along with that increase of size." He had been using 34 inch nozzles. The change was accordingly made. When he returned from the next trip, he expressed a doubt about the advantage of the change. But it happened that his own fireman was off, and a strange man was sent out, who, although a good fireman, failed to keep up steam satisfactorily. On the following trip, however, the fireman who be-longed to the engine, returned, and found no difficulty in getting all the steam required. But this fireman is one who would stand far up among a thousand competitors. Considerable practice and intelligent thoughtfulness, combined with unfailing industry, have developed in this man an excellence in fire management seldom attained. He follows a unique system, which seems his own. It is the method of firing light carried to perfection. His coal is all broken down fine, and lies within easy reach. His movements are cool and deliberate, no hurry, no fuss. When he opens the door, his loaded shovel is ready to deposit its cargo over the spot which a glance shows him to be the thinnest portion of the fire. On the parts of the run where the most steam is needed, he fires one shovelful at brief intervals, keeping it up right along. In this way the steam never feels the cooling effect of fresh fire, for the contents of the fire-box are kept nearly uniform. This plan is a near approach to the automatic stoker which mechanical visionaries predict will effect perfect firing in the vague future. To follow out such a system requires perseverance and self-denial, but these are well rewarded to the man whose work is his pride.

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