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SPEED IN LOCOMOTIVES.
Scribner's—January to June, 1892


THE LIMITATIONS OF FAST RUNNING.
By M. N. Forney.—Editor, Railroad and Engineering Journal

 

RACING seems to be a natural instinct in human beings as well as in other animals. In our natures this instinct seems to be stimulated, and not satisfied, by the means which science has supplied for achieving rapid movement, and modern appliances are now put into requisition for the gratification of this natural bent. Whole nations are now interested in the "records" of transatlantic steamers, and in the time made by the Flying Dutchman or the Columbian Express. Each gain in speed, in both land and water, seems to add to the eagerness with which people inquire about future possibilities.

When Stephenson's Rocket, on its trial trip, made a speed of nearly thirty miles an hour, doubtless those who saw and heard of it were as anxious then to know how much faster a locomotive could run as we are to-day when we travel more than twice as fast.

In speculating on this subject a sort of single-rule-of-three logic is sometimes applied to it which is apt to lead to erroneous conclusions. Mechanical dialecticians assume as a premise that the improvements which have been made in locomotives in sixty years have resulted in doubling the speed, therefore in sixty years more we will be able to travel twice as fast as we do now. Or, in other words, sixty years ago we travelled 30 miles an hour and now we travel 60, therefore as 30 : 60 :: 60 :120= the speed at which we will travel sixty years hence. There are, however, greater difficulties in the way of doing this than appear from this arithmetical syllogism. The aim of this brief discourse on railroad speed will be, to use words of Mr. Carlyle which referred to quite a different subject, "to tell practically, in reasonable words, what the possibilities, limitations, difficulties, laws, and conditions of the enterprise are."

It may be said, in the first place, that to move an ordinary car on a level railroad track requires the exertion of a horizontal pull of from four to five pounds for each ton (of 2,000 pounds) of its weight. That is, if it weighs twenty-five tons and a rope is attached to it, it will be necessary to exert a pull of from one hundred to one hundred and twenty-five pounds on the rope to keep the car moving at a slow speed after it is started. As the speed increases, the "resistance"—as it is called—of the car also increases: that is, more force or pull must be exerted to keep it moving. The exact rate with which this resistance is augmented when the speed is accelerated, and the laws governing it, are still imperfectly understood. Our knowledge of the subject—especially that relating to the higher speeds—is only approximate, and probably not a very close approximation either. Tables have been compiled—from such data as are available—showing the resistance of trains at different speeds. The accompanying diagram is constructed from such a table, in which the resistances have been plotted, so as to show graphically the rate at which they increase. The speed in miles per hour is laid off on the base line 0-100, each space between the vertical lines representing five miles per hour. The spaces between the horizontal lines represent the resistance in pounds per ton. The resistance per ton for the speed represented by each vertical line is laid off from the base line, and a curve, A B C, is drawn through the points thus laid down. Its vertical distance, as 40 B above the base line, at any point 40, thus represents the resistance at the speed indicated by that point. At sixty miles an hour, it will be seen the curve shows that the resistance is twenty-five pounds per ton.

No data exist to show how much power is required to pull a train at a speed greater than seventy miles per hour; but if the curve in the diagram is continued beyond the vertical line representing seventy miles per hour, as shown by the dotted line C D, it will indicate approximately the rapid rate at which the resistance probably increases above that speed.

It must be remembered that to maintain a high rate of speed there must be a continuous pull exerted on the drawbar of a locomotive, and that the relative amount of this pull at different speeds is indicated by our diagram.

This propelling power of a locomotive is due to the pressure which is exerted on the pistons of two cylinders by the expansive action of the steam. Each piston makes two strokes, or moves twice through the whole length of the cylinder during each revolution of the driving-wheels.

It will be assumed that we have a locomotive with driving-wheels six feet, and cylinders eighteen inches, in diameter, and pistons which have two feet stroke. Such an engine with its tender would weigh about ninety tons. Each cylinder would have a capacity of about three and a half cubic feet. Excepting in starting a train, these cylinders are filled only partly full of steam from the boiler, for two reasons—first, because it would be a very wasteful use of steam to fill them entirely full, and second, it would be impossible for the boiler to supply enough to fill them when running fast. Therefore steam is "cut-off," as it is termed—that is, it is admitted to the cylinder during a third or a fourth or some other fraction of the stroke, and the opening which admits it to the cylinder is then closed, and the steam which has been admitted is allowed to expand while the piston is moving to the end of its stroke.

To show how the speed and load of a locomotive are limited by the supply of steam, it will be supposed that for each stroke of the pistons the cylinders are filled one-third full of steam of the boiler pressure of one hundred and sixty pounds. This is expanded in the cylinder during the completion of the stroke of the pistons. For each revolution of the wheels, therefore, four-thirds of a cylinder full of steam would be used. Wheels six feet in diameter would turn 280 times in running a mile, and at 60 miles an hour they would turn 16,800 times in that period, and would consume 79,161 cubic feet of steam. On making comparisons of the quantities of steam of varying pressures used, it is best to do it in terms of its weight, because that will represent the actual quantity irrespective of its pressure or volume; 79,161 cubic feet of steam of 160 pounds pressure per square inch will weigh 31,094 pounds.

It has been found that the greatest amount of coal which can be burned in an hour, on each square foot of grate of a locomotive, is about two hundred pounds. A locomotive such as we have described would have about twenty-four square feet of grate area, so that 4,800 pounds of coal is the maximum amount which could be burned in its fire-box per hour. At this high rate of combustion each pound of fuel would not evaporate more than about six pounds of water, and, therefore, not more than 28,800 pounds of water could be evaporated in such a boiler per hour. This, it will be seen, would not be sufficient to supply the cylinders under the conditions of working described. Consequently, in running an engine at 60 miles an hour we would be obliged to reduce the quantity of steam admitted to the cylinders, which would either diminish the load which could be hauled or the speed of running. If instead of cutting off the steam at 8 inches and filling the cylinders one-third full of steam during each stroke, it was cut off at 7 inches, the consumption per hour would be reduced to 27,207 pounds, which is somewhat less than the maximum quantity which it is possible for the boiler to supply. Not counting any back pressure or any other losses or waste, the maximum tractive or pulling force which this quantity of steam would exert would be equal to 10,700 pounds. As the resistance at this speed, as shown by the diagram, is 25 pounds per ton, the maximum load which could be hauled would be 428 tons, including the weight of the engine and tender, or 338 tons without. Practically, an ordinary locomotive would not do nearly as much work as this, on account of the back pressure in the pistons, waste, friction of the machine, and losses of various kinds in the engine.

If the speed were increased to 90 miles an hour, then the number of strokes made by the pistons would also be increased in like proportion. The capacity of the boiler to generate steam would, however, be no greater at this high velocity than it was at 60 miles an hour. Therefore, instead of cutting off the steam at 7 inches of the stroke, we would be obliged to cut it off at about 5 inches. The tractive force exerted by this steam could not be more than 8,494 pounds. The resistance of the train would, however, according to our diagram, be about 51 pounds per ton. The maximum load which could be hauled would therefore not exceed 166 tons, including the weight of engine and tender, or 76 tons without. In practice this could not be done with an ordinary engine, on account of the losses and waste of various kinds already referred to.

These calculations therefore indicate that at a speed of 100 miles per hour on a level track, an ordinary locomotive would do tittle more than pull itself and its tender, and maintain the speed for any considerable time. Of course, on an ascending grade it could not do this.

Before considering the possibilities of the future, some of the other obstacles in the way of making very fast time must be referred to.

If the driving-wheels of a locomotive are three feet in diameter, their circumference will be nearly nine and a half feet long, and in travelling a mile, or 5,280 feet, they must turn 560 times. A speed of thirty miles an hour is equal to one mile in two minutes, so that, at that velocity, wheels three feet in diameter must be turned 280 times per minute. We may double this speed by turning the wheels twice as often in a given time, or by making them twice as large, or six feet in diameter, and turn them the same number of revolutions in any given period. To quadruple the speed—that is, to run 120 miles per hour—wheels three feet in diameter would have to turn 1,120 times per minute, or if they revolve only 280 times, they must be 12 feet in diameter to make that speed. Big driving-wheels in a locomotive always excite popular admiration; but in designing a locomotive an engineer cannot allow his imagination to guide him. He is absolutely confined to certain limits, such as the weight which can be carried on each wheel, the space between the rails, or the "gauge" of the track, as it is called, the length of the wheel-base which will permit the engine to run around curves, the height of tunnels overhead, bridges, etc.

As a practical illustration of this, we may take the limitations which would be imposed on a designer of an express locomotive of the heaviest and most powerful type now used. The maximum which is now allowed in this country on each driving-wheel is 20,000 pounds. More than this would be considered injurious to both the rails and wheel-tires, and would be likely to cause the axles to heat, owing to the excessive friction due to the weight on the journals. The whole length of the wheel base must not exceed 24 or 25 feet, and if a truck is placed in the usual position under the front end of the engine, it will carry about a third of the weight of the engine, or one-half as much as the four driving-wheels. The total weight of such a locomotive, without its tender, will therefore be as follows:

20,000 pounds on each of four driving-wheels 80,000
10,000 pounds on each of four truck-wheels 40,000
Total . . . . . . . . . . . . . . . . . . . . . . .120, 000

A still more powerful locomotive could be constructed if we used six driving-wheels, but for the present only the eight wheeled engine will be considered.

The problem the designer, then, has to solve is to proportion the parts of his locomotive so as to produce the most efficient machine of that weight. During each revolution of the wheels the pistons must be moved backward and forward through their whole stroke. At 70 miles an hour a six-foot wheel of a locomotive would revolve more than five times in a second. During every revolution each piston and its connection must start and stop twice. They come to a state of rest at the end of each stroke, and must be started and their motion accelerated to a speed of nearly 35 feet per second, in less than one-tenth of a second, and then come to a state of rest again in the same time. When it is remembered that each of the pistons, with their moving connections, weighs considerably over 500 pounds, the amount of power required to move them, and the disturbing effect which they exert on being started and stopped twice during each revolution at these high speeds may be imagined. To neutralize these disturbing effects balance-weights are placed in the wheels opposite the cranks. These accomplish their purpose, however, only partially, for the reason that they move in a circle, while the piston and other reciprocating parts have only a horizontal motion. Consequently, while the balance-weights may be made to neutralize the horizontal motion and momentum of the pistons, etc., the weights themselves thus produce a vertical disturbing force which at high speeds has been said to be so great as to bend the rails on which the locomotives are running. For these reasons a compromise is usually made by balancing the reciprocating parts only partially, which lessens the vertical disturbance but does not entirely compensate for the horizontal momentum of the reciprocating parts. Therefore, a locomotive at best is an unstable machine at high speeds.

The obvious expedient for getting over this difficulty is to increase the size of the wheels of fast engines, and it seems like a very simple inference to assume that, if a locomotive with wheels 3 feet in diameter will run satisfactorily at speeds of 30 miles per hour, therefore, to run at 60 miles an hour all we need do is to increase the wheels to 6 feet, and then with the same number of revolutions we shall make double the speed, and, with wheels 7½ feet in diameter we can run 75 miles an hour as easily as we can travel 30 miles with 3-foot wheels. But in enlarging the size of wheels we soon reach limitations, owing to their increase in weight and in that of other parts. The weight of a wheel increases about as the square of its diameter. If its diameter is enlarged, the size of the cylinders and their connections must all be larger and heavier. This makes necessary stronger frames and an increase in size and weight of many of the other parts. Now, the importance of having ample boiler capacity has been explained. If, then, the weight of our hypothetical locomotive is limited to 120,000 pounds, every extra pound of weight which is put into the wheels, cylinders, frames, etc., means that the weight of the boiler must be that much less. In other words, the bigger the wheels are, the tighter and smaller must be the boiler. The problem which the locomotive designer, then, has to consider and determine, is the sum of the advantages which will result from an increase in the size of the wheels, and a diminution of that of the boiler, or vice versa.

It may be said that no common agreement with reference to the size of locomotive wheels has ever been reached by locomotive engineers. Practice seems to vacillate: at one time wheels as large as 10, and we believe 12, feet in diameter were employed, but these excessively large sizes have now been abandoned. At present American practice seems to incline toward larger sizes. In running the Empire Express on the New York Central road, engines with wheels 6 feet, and others of 6 feet 6 inches diameter have both been used, with the result that the service of the engines with the larger wheels has been decidedly the most satisfactory.

As an essential thing to do in running fast is to turn the wheels rapidly, it might be thought advisable to increase the power available for this purpose by enlarging the cylinders. Here, too, we encounter a difficulty. If the cylinders are larger than a certain size, the force which will be exerted by a given steam pressure to turn the wheels will be greater than their "adhesion" or friction on the rails, and they will slip, and we shall have what engineers call a "slippery engine." The cylinders, driving-wheels, the weight on them, and the steam pressure must, therefore, bear such proportions to each other that the pistons can exert what is called a "rotative effect" on the wheels equal to, but not much in excess of, their adhesion or friction on the rails.

Another obstacle in the way of running at high speeds is that of getting the steam into the cylinders, and have it exert the requisite pressure on the pistons, and then get it out again, so that there will not be any, or as little, back pressure as possible in front of the pistons. The quickness with which the steam must act may be understood from the figure on next-page, which represents a section of a locomotive cylinder with its piston. As already remarked, at 70 miles per hour this action must begin and be completed in less than a tenth of a second. What adds to the difficulty is the fact that, in order to stimulate the fire, the opening in the ends of the exhaust-pipes through which the steam escapes must be more or less contracted, so as to produce a blast in the chimney to stimulate the fire. This, of course, obstructs the free flow of the escaping steam from the cylinders, and produces more or less back-pressure on the pistons.

The mechanism for admitting the steam to, and exhausting it from, the cylinders, performs a very important part in fast-running engines, as the action of the steam in the cylinders depends very much on that of the slide-valves, and no problem connected with locomotive construction has been the subject of so much thought and invention as that of "valve-gear," or the mechanism for working the valves. It has been analyzed mathematically, elucidated graphically, demonstrated mechanically, and tested experimentally in every conceivable way. Numberless inventions have been made of mechanism for this purpose, but what is called Stephenson's "link motion," which was adopted by him, although he was not its inventor, still holds its supremacy among valve-gears, and there are at present no signs that it will soon lose it.

There is much less difficulty, however, in getting the steam into the cylinders than there is in getting it out, because there is a pressure in the boiler of from 150 pounds to 200 pounds per square inch to force it in; but after it has done its work in the cylinders it has been expanded and its pressure and temperature very much reduced, so that it is partially condensed or liquefied, and consequently does not move with as much celerity as "live" steam, as it is called, fresh from the boiler does. The result is that at high speeds there is always an increase of back pressure in front of the pistons, which has a retarding effect, at the time when it is essential that the maximum power should be exerted by the pistons. If the engineer tries to compensate for this by admitting more steam in front of the pistons, then the demand on the boiler becomes so great that it cannot supply it. Besides this, the escaping steam then has not had sufficient opportunity to expand, and escapes up the chimney with such violence as to "tear the fire to pieces," as firemen express it. An engineer who is running an engine must therefore be careful, at high speeds, not to use more steam in an engine than the boiler can supply, and generally the limitations to speed in a locomotive are the same as those of a horse—want of wind.

A writer on this subject has formulated the maxim, that "within the limits of weight and space to which a locomotive boiler is necessarily confined it cannot be too big." Certainly the larger it is the greater will be the efficiency of the engine, and the more economical will it be in the use of fuel.

The limitations in the weight of a locomotive have been explained. Its size is necessarily confined by the distance between the rails, or their "gauge," as it is called. This on ordinary roads is 4 feet 8½ inches. The flanges of the wheels are inside of the rails, so that the distance between the tires is 4 feet 5-and-three-eighths inches. The frames of the engine are ordinarily inside of the tires and the fire-box inside of them. Therefore, as usually constructed, it can be only about 3 feet 7 or 8 inches wide. The result is that this part of the boiler is contracted in one of its vital parts, and it has been remarked that the back end of a large locomotive boiler looks like a broad-shouldered woman in tightly-laced corsets. Under these conditions the vital parts of both the woman and the locomotive are contracted. To partly obviate this difficulty in locomotives, their fire-boxes are now often placed on top of the frames. This allows them to be about 8 inches wider than they could be if they were between the frames, but the height of the firebox must then be reduced. In the Wootten locomotive—named after its inventor—the fire-box is located entirely above the wheels, and can then be made as wide as the widest part of the locomotive. This necessarily raises the centre of gravity of the boiler and reduces the depth of the fire-box.

From what has been said it will be seen what an exceedingly difficult problem is presented to a locomotive engineer in designing an engine for very high speeds. It is largely a matter of relativity and proportion. A maximum speed can be attained only when the different organs, as—they may be called, hear the proper proportion to each other, and the ability of the designer is shown by his recognition of the relative value and importance of the proportions of the different parts.

The question whether we shall ever be able to travel on railroads at a regular speed of 100 miles per hour is often asked. Most railroad managers are disposed to answer the question as David Copperfield replied to the disparaging remark about the inability to swing a cat in his room. He replied that he didn't want to swing a cat, and so most managers say they don't want to travel at the rate of 100 miles per hour. Those who know most about the risks of such speeds seem least inclined to encounter them. Every school-boy knows that after a kite has reached a certain height, no amount of added string will allow it to fly higher. The span of a bridge may be so long that it will not carry its own weight. So our diagram of train resistance shows that when we get above 70 miles per hour, the resistance of the locomotive and that of the cars becomes so great that it will do no more than pull itself and its tender. When this point is reached, further increase of speed becomes impossible with the locomotives we are now using.

Besides the difficulties which have been pointed out, there is the risk, at high speed, of the breakage of the coupling-rods—by which the cranks on adjoining wheels are coupled together—owing to the strain to which they are subjected by centrifugal force. This danger increases with the distance apart of the wheels and the length of the rods, and the centrifugal force which acts on the rods increases with the number of revolutions of the wheels; and consequently, as large wheels make fewer revolutions at a given speed of train, the centrifugal force exerted on the rods is then inversely to the diameter of the wheels, or, in other words, the larger they are the less is this force.

With high speeds and the heavy express engines which are now used, a good deal of trouble is also experienced from the heating of the journal bearings of the driving-axles, owing to insufficient bearing surfaces. Their size is limited when the fire-boxes are placed between the frames, because in order to make the former as wide as possible, the frames are placed as far apart as the wheels will permit. This shortens the journals, and consequently diminished the surface of their bearings. The cure for this is to bring the frames nearer together and thus lengthen the journals. There is no objection to doing this when the fire-boxes are not between the frames.

It may therefore be inferred that there is not much probability of attaining regular and continuous speeds of 100 miles per hour with our present locomotives. Their fire-boxes—which perform the same functions for the machines that their stomachs do for animals—are, with the present system of construction, necessarily contracted in size. The weight of the whole locomotive being fixed, the dimensions of the different parts are also limited.

It is proverbially dangerous to prophesy when you are not quite sure, and if prognostications are based upon calculations the mendacity of figures may rise up hereafter to deprive the prophet of all honor.

From what has been said, however, it will be seen that fast running is largely a question of steam production. Given a boiler which will generate enough steam, and the other problems are of comparatively easy solution. The difficulty is to get the boiler sufficiently large within the limits of size and weight to which it must be confined.

It will be safe to say that to be able to travel continuously at 100 miles per hour we must have either boilers or fuel which will generate more steam in a given time than those we are using now do, or our engines must use less steam to do the same work, or, what is more probable still, we must have all three of these features combined. In the locomotive of the future the action of the reciprocating parts will probably be more perfectly balanced than it now is; coupling-rods will either be dispensed with altogether or their risk of breakage will be lessened by placing the driving-wheels near together, and both this danger and the disturbing effect of the reciprocating parts will be lessened by increasing the size of the wheels. To enable the engine, or, rather, its journals, to "run cool," the journals and their bearings will be increased in size so as to have ample surface to resist wear.

Just how these improvements will be made, it is perhaps too early to predict. Coming events are, however, already casting their shadows before them, and there are indications that the improvements which are here foreshadowed, or some of them, are in process of evolution. In Mr. Webb's new engine, Greater Britain, recently built for the London & Northwestern Railway, the boiler has been materially increased in size, and he reports the remarkable performance of evaporating nearly eleven pounds of water per pound of coal while pulling a heavy train at the rate of over 44½ miles per hour. This engine is compounded so as to use steam with the greatest economy, and is without coupling-rods. These are dispensed with by using three cylinders—two high pressure and one low pressure. The two former are connected to the back pair of driving-wheels and the latter to the front pair. By this means both pairs of wheels are driven by separate cylinders. A new express locomotive is now in process of construction in this country with a fire-box about twice as wide as those ordinarily used. The problem of improving the balancing of engines is attracting much attention, and the bearing surfaces of many recent locomotives have been materially increased. Driving-wheels have been enlarged in size with the increase in speed, and if the march of improvement continues—and there is no reason for thinking it will not—the anticipation that we shall travel at the rate of 100 miles per hour may be fulfilled while some of us are left here to see it.

 

 

 

TRAIN-SPEED A QUESTION OF TRANSPORTATION.
By Theodore N. Ely.—General Superintendent of Motive Power
—Pennsylvania Railroad

IT is a pleasing sign of the times to witness the growing interest taken by the general public in railway matters. This demand has caused the daily press and magazines to give considerable space to a presentation of such of the problems as can well be treated by them. As a supplement to the more detailed and technical discussions of the scientific journals, the opinions of the press will be welcome to all professional railway officers; and without doubt will go far toward securing high standards of management. Much has been written relating to speed of trains, the different phases of which have been so well explained that anything to be said at this time must in a measure go over oft-trodden ground.

But what is a fast train? The very difficulty in giving a proper definition here helps to prove that speed is a relative term.

"Will you walk a little faster?" said a whiting to a snail,
"There's a porpoise close behind us, and he's treading on my tail."

This couplet suggests to me, as it probably did not to its author, a perfect description of a slow-moving train—even to the necessity for, and evident absence of, the Block System! But it is not so easy to say what speed entitles a train to the distinction of being called fast.

It can hardly be said that the possible speed of locomotives has improved in the last fifteen or twenty years. The records would no doubt show that the locomotives of that period made, on occasions, as fast runs with trains within their capacity as those of the present day. It is indeed reassuring when we recall the high-speed journeys taken safely over the tracks and alignment which existed twenty-five years ago. We were either very brave or very ignorant in those days; for, from our present point of view, we would regard the running of trains at such speed over such tracks as extremely hazardous. There were accidents, to be sure, but not of such frequency as the railroad engineer of today would predict.

Briefly, the radical improvements which have been accomplished may be comprised under three general heads—Roadway, Equipment, and Signals.

ROADWAY.—Some twenty-five years ago the Pennsylvania Railroad adopted broken stone as best meeting the conditions of a good track foundation; at the same time the dimensions and number of ties were fixed, and finally the rails and turnouts were laid according to carefully considered rules. The weight of rails has been increased, with a corresponding improvement in fastenings; the old turnouts have given place to those of more modern design; but the foundation is much the same as that first adopted. Closely related to the roadway are crossings at grade. These have, from time to time, been abolished as detrimental to the safe passage of trains.

EQUIPMENT.—In equipment, the locomotive has been thoroughly redesigned and made stronger in all its parts. The air-brake applied to its driving and tender wheels, has made it possible not only to stop itself quickly, but assist in retarding the train, as well. The strength of passenger cars has been increased, until they have reached a weight of 27 tons, and the couplings and platforms have been greatly improved. Sleeping-car construction has likewise advanced, until the more modern ones have reached a weight of nigh 50 tons. The air-brake has become indispensable as a condition of safety in fast-moving trains.

SIGNALS.—In the early days of railways there was nothing that could properly be dignified by the name of signal. By slow degrees, as is usual in matters involving questions of safety, a high state of development has at last been reached. The best systems of signalling and interlocking are marvels of mechanical skill and ingenuity, and command the respect due to their wonderful reliability.

The pirate of the Mediterranean would be flattered, indeed, if he could know that the semaphore signal of warning he was wont to display from the rock of Gibraltar had become the recognized danger signal of modern railways.

It may be interesting to note in passing, a few instances of train movements which have come under the writer's observation. Nearly sixteen years ago, or to be exact, in June, 1876, a Pennsylvania Railroad standard locomotive drawing a train of two sleeping-cars and a dining-car, covered the distance between Jersey City and Pittsburgh, 438.5 miles, without a stop, in 605 minutes, or an average rate of 43½ miles an hour. This journey is interesting as the longest known continuous run; and one which involved thorough transportation arrangements for its movement, and great endurance on the part of the locomotive. The special train was en route to San Francisco, which city was reached in 84 hours and 17 minutes after leaving New York.

The train which conveyed our lamented President Garfield from Washington to Elberon, September 7, 1881, was run under conditions of great excitement and anxiety. His life hung upon a thread, and any detention to the train would have resulted disastrously. The heat was intense and prostration was imminent. The physicians had fixed upon 30 miles an hour as the speed which would give the least discomfort to the patient. After the train was well under way, and without warning, an increase in speed was determined upon, which reached 65 miles an hour before the journey was completed. The orders for the transportation of this train were contained in one message, and so skillfully was it worded that, despite the changed conditions, there was not the slightest detention from any cause.

A most noteworthy accomplishment was that of the Pennsylvania locomotive which drew the special train of the delegates to the International American Conference on their tour to the principal cities east of the Rocky Mountains. This engine traversed the rails of twenty distinct lines of railroad, and covered 10,000 miles in its course, without accident of any kind or unreasonable delay.

Another example of endurance may be mentioned—the 126,000 miles made by one locomotive between Philadelphia and Washington in the year 1891—equal to five complete journeys around the world.

From the lessons of the past we may forecast the future, for certainly we have reached that stage in railway progress where we may assert with confidence that our acts and opinions are based upon accumulated experience and not upon prophetic inspiration. Guided by this light, let us consider what factor will control the limit of speed in the passenger-trains of the future.

In the road-bed we shall have to demand that the alignment be almost free from curvature, and the width between the tracks be increased; that the foundation shall be stable and well-protected from rain and frost; that land-slides and other accidental obstructions shall be provided for; that the ties shall be firmly embedded; that the rails shall be heavy—one hundred pounds, or more, if necessary—and securely fastened; that all frogs and switches shall be proof against accidental misplacement or rupture; that all drawbridges shall be made secure beyond question, and, finally, that all crossings at grade be abolished. We must further insist that a thorough system of supervision and inspection shall be carried out.

With a fulfillment of these conditions, which, professionally speaking, are perfectly practicable, trains, so far as the road-bed is concerned, may be run in safety as fast as any locomotive can be made to haul them.

Of the locomotive, it may be said that, only with the improvements in road-bed referred to, can its highest attainable speed be utilized.

The measure of the speed and capacity of the locomotive rests in the fire-box, the length and breadth of which cannot exceed certain dimensions. It therefore follows that when this furnace is arranged to burn the maximum quantity of fuel, the steam-producing limit will be reached, and with it the limit of speed. But this steam must be used to the very best advantage, as relating to the proportions of the locomotive, as well as to its type; the first of these are already well known, and it will probably be found that some form of compounding will suggest the type. With these limitations the speed of locomotives with passenger trains will not fall far short of 100 miles an hour; by which is meant a sustained speed at that rate, as, for instance, a trip between New York and Philadelphia in about one hour, or between New York and Chicago in ten or eleven hours.

As to car equipment, it is probable that, with some change in size and proportions of wheels, journals, and other parts of the trucks, the best class of cars in present use would be suitable for the highest speed. They should be made to run as noiselessly as possible, that the occupants may be relieved from any feeling of insecurity or nervous strain. The air-brake should be applied in its best form to both locomotive and cars, so that every pound of braking weight would become instantly available.

The above conditions have been cited in detail to show that they all must be fulfilled in order to make possible our future travelling at the rate of 100 miles an hour. Make possible, yes, but only upon the fulfillment of one other condition, namely, a clear track ahead; and this it is which brings us to the real measure of speed, which is the question of transportation in its strict sense. This limit will vary with the number of trains already on the line and with the facilities for handling them. First of all, we must know how soon after receiving warning of danger a train, running a mile in 36 seconds, can be stopped. It is estimated that if running at 60 miles per hour, with the full braking weight of the train utilized, and the rails in the most favorable condition, this train could be brought to a full stop in 900 feet; at 80 miles per hour, in 1,600 feet; at 90 miles per hour, in 2,025 feet, and, finally, at 100 miles per hour, in 2,500 feet. These figures at once establish the fact that under the best possible conditions the track must be kept clear of all obstruction for at least 2,500 feet in advance of a train running at the highest limit; but we must estimate the clearance for the worst conditions, such as slippery rails, foggy weather, and unfavorable grades; the personal equation of the engineman must also be considered in a train covering 145 feet each second.

Would it, therefore, be too much to ask that the engineman receive his warning at least three-quarters of a mile before he must halt ?

The difficulties of arranging for the passage of trains of this character are manifest; we are not speaking of special trains, but rather of regular trains, running as frequently as may be desired. It should be remembered that, in a two-hour run, the fastest trains of to-day would require a leeway of an hour, and slower ones would have to start proportionately earlier, or be passed on the way.

The most improved forms of signalling and interlocking, be they mechanical, pneumatic, electric, automatic, or otherwise, which are so necessary to the safe movement of passenger trains, may be introduced, but cannot be placed nearer together than three-quarters of a mile. The very presence of these signals, while giving the maximum safety, has in practice made prompt movement more difficult. They are governed by fixed laws, which, if obeyed, make chance-taking impossible, for trains must keep a prescribed distance apart, and increase in speed involves greater intervals. This state of affairs would point to the necessity for an increase in the number of tracks, so that passenger trains could be grouped on the basis of speed just as it has been found necessary already, on crowded lines, to separate the freight traffic from the passenger.

If this be done, and unlimited track facilities are furnished, the prompt despatching of trains would not be the ultimate measure of speed; but such an outlay would be beyond all reason. It is fair, therefore, we think, to rest the burden upon the transportation shoulders, and predict that with it, and it alone, lies the practical limit of the speed of railway trains drawn by steam locomotives.

 

 

A PRACTICAL EXPERIMENT.
By H. Walter Webb.—3rd Vice-President—New York Central Railroad

 

ON September 14, 1891, a train, consisting of a locomotive and three large private cars, made a run over the New York Central & Hudson River Railroad, from New York to Buffalo, on a schedule the most extraordinary on record, and which is destined to exert an important influence on railroad travel during the next few years.

The engine was of a new class, especially designed for fast passenger service by Mr. William Buchanan, the Superintendent of Motive Power of the road, and built by the Schenectady Locomotive Works, its total weight in working order being 100 tons. The aggregate weight of the cars when empty was over 130 tons.

The journey from New York to East Buffalo, a distance of 436-and-32/100 miles, was made in 439-and-45/100 minutes. Allowing for time lost in changing engines at Albany and Syracuse, and for cooling a hot journal at Fairport, the run of 436.32 miles was made in 426 minutes, or at the rate of 61.44 miles per hour.

Previous to this run there were scores of records of fast time made by passenger trains, special and regular, both in this country and in England. Records of fast runs of 10, 15, or 20 miles were exceedingly plentiful, but there were few records of long distance runs that had attracted any special attention. The most remarkable on record, and the ones that until last September were unequalled in railroad history, were those made between London and Edinburgh, in the summer of 1888, when the "race to Edinburgh" was in progress between the London & Northwestern and the Great Northern Railways of England. The distance over the former is 400 miles, and the run was made daily on a schedule calling for a speed of 53-and-one-third miles per hour. On the Great Northern the distance is 393 miles, and the schedule in this case called for a speed of 54 miles per hour.

These trains were run daily for many weeks, and were generally punctual and within their schedule time. On several occasions, however, they exceeded the schedule, and made what at that time were regarded as phenomenal runs.

On August 13, 1888, the Northwestern train covered the distance of 400 miles in 427 minutes, or at a rate of 56-and-one-fifth miles per hour, and on August 31st the Great Northern train made the run of 393 miles in 412 minutes, or at the rate of 57½ miles per hour. These individual runs were both remarkable, but the daily running of the trains on their published schedules were regarded by railroad men as still more extraordinary, and at that time there were no schedule trains in this country that approached them in point of speed. It must be remembered, however, that these English roads are possessed of many advantages not enjoyed by railroads on this side of the water, as, for instance, the long and numerous tangents, the entire absence of grade crossings, and, more especially, the light weight of the cars, 80 tons being the maximum weight of the trains used in the "race to Edinburgh."

With equipment of the character required and used in this country, provided as it is with all luxuries, conveniences, and comforts, and a rate of two cents per mile, a train limited to the above weight could not carry a sufficient number of passengers to enable it to earn its running expenses.

Three years previous to these English records a special train weighing 64 tons made a run on the West Shore road from Buffalo to Weehawken in 9 hours and 23 minutes. In the published accounts different allowances for stops were made, making the average rate per mile vary from 51 to 54 miles per hour; either rate, however, making it the best long-distance run on record in the United States, until the run from New York to Buffalo, over the New York Central & Hudson River Railroad, described in the beginning of this article.

That remarkable run eclipsed and left far behind all records for long-distance runs formerly made in this country or England. And to fully appreciate the importance of what was demonstrated by it, we must remember that within six weeks after it was made a passenger train was running between those cities on a schedule two hours shorter than had at any time previously been made by the fastest limited or mail train, and the air is even now full of rumors of shorter time to be made on important lines between great cities during the coming spring and summer, so that it is not at all improbable, in view of the power now to be obtained and the public demand for faster service, that in the near future we shall see trains from New York to Buffalo in 7½ hours, from New York to Boston in less than 4 hours, and from New York to Washington in the same time.

But to railroad men and to those familiar with the characteristics of the New York Central Railroad, between New York and Buffalo, the record of the trip referred to was far more significant than was indicated by the mere statement that the run had been at a speed averaging 61-and-44/100 miles per hour.

They appreciated the fact that the journey out of the Grand Central Depot, through the Fourth Avenue tunnel, over the Harlem drawbridge, following the winding curves along the Harlem River to Spuyten Duyvil, along the banks of the Hudson, through Yonkers, Peekskill, and Poughkeepsie, rounding the curves of the Highlands, and taking water twice from tanks between the tracks, meant frequent reductions of speed in order to make the run in comfort and ease; and from Albany, west, the long and heavy grade over the hill, the thriving and prosperous towns of the Mohawk Valley, the slow, tedious run through the streets of Syracuse, the viaduct at Rochester, and the 11-mile grade at Batavia, all furnished reminders that the train must have at times attained a high degree of speed to have made the average mile at a rate of over 60 miles an hour.

A careful schedule of the running time of each mile was kept, an analysis of which shows the following:

Four hundred and thirty-six miles were run in 426 minutes.

One hundred and thirty miles were run at a rate of less than 60 miles per hour.

One hundred and eighteen miles were run at a rate varying from 60 to 65 miles per hour.

One hundred and fifty-one miles were run at a rate varying from sixty-five to seventy miles per hour.

Thirty-seven miles were run at a rate varying from seventy to seventy-eight miles per hour.

The schedule and analysis certainly indicate a radical change in the conditions affecting fast passenger train service in this country. For many years the problem has been to obtain power sufficient to draw heavy trains long distances at high rates of speed. The above figures make it evident that steam will without difficulty furnish power sufficient to take a train heavy enough to be profitable over a long distance at a rate of speed very much in excess of an average of 60 miles per hour; and attention is now diverted from the motive power to other departments of the railroads and a consideration of whether the roadbed, bridges, tracks, and safety appliances are such as to permit the use of this power and speed with entire safety and comfort to passengers.

The question then naturally arises, and is repeatedly asked: If it is incumbent on most roads to raise their standards of roadways, tracks, and bridges in order to permit of the use of the best and most effective power, if the motive-power department is now in advance of the other departments of railroads, wherein has there been a change? On what lines and in what particulars has the locomotive so developed in the past few years as to become so much superior to what it was before?

The best and most complete answer is a comparison of the distinctive features of the type of engine now in use on the New York Central road for fast passenger service with those in use in the same service two years ago. To fully appreciate the comparison it must be remembered that the ability of a locomotive to draw a heavy load a long distance at a high rate of speed is limited.

First, by the capacity of the boiler to furnish steam rapidly enough and in volume sufficient to supply the demand.

Second, by the adhesion of the engine; that is, the resistance which prevents or opposes the slipping of the driving wheels on the rails, and,

Third, by its tractive power; that is, the force by which it is urged onward by the pressure of steam in the cylinders.

The problem, therefore, presented to Mr. Buchanan in designing the new type of passenger engine was to obtain greater boiler capacity, greater adhesion, and greater tractive power. The engine in use on the New York Central two years ago for the movement of its fast passenger trains is a fair exponent of the best type then in use or known. It rendered excellent service and attracted frequent attention from motive-power men, both here and abroad, on account of the work it did.

The fire-box of this engine was as large as it was possible to make it, located where it was between the frames and driving-axles, its width and length thereby being limited. The problem of increasing the boiler capacity was for that reason a difficult one, and also because the weight of the boiler itself in a locomotive and the space it occupies is necessarily less in proportion to its capacity than that of any other boiler, and for this reason it must produce much more steam in a given space of time, in proportion to its size, than a boiler of any other kind of engine.

To obtain the desired increased boiler capacity and heating surface, Mr. Buchanan located the fire-box, which formerly was between the sides or frames of the engine and between the axles of the driving-wheels, on top of these frames and axles, and by so doing obtained an increase in the width of the fire-box of 5½ inches and an increase in its length of 25 inches, being an equivalent of nine and three-quarter square feet of additional grate area. The boiler flues, which in the former engine numbered 238, he increased to 268, and by the change in the fire-box he was enabled to lengthen them 4½ inches, thus obtaining an increased heating surface of two hundred and twenty-one and a half square feet, the diameter of the boiler being increased from 51 to 58 inches. With this increase in the grate area and heating surface, the desired increase in boiler capacity was obtained.

To secure the adhesion the weight on the four drivers, which formerly was limited to thirty tons, was increased to over forty, or, over ten tons' weight on each driving-wheel.

Here, however, came in the question of road-bed, rail, and bridges, as there are but few roads in the country that would permit the use of an engine with such weight located on four drivers. In this case, however, the matter had been fully provided for and extensive alterations had been made to many bridges, a large amount of work done on the road-bed, and the old and lighter form of rail removed and replaced with the standard 80-pound section. To increase the tractive power of the engine the cylinders were enlarged 1 inch in diameter; being formerly 18 x 24, they were now made 19 x 24.

All these changes had vastly increased the height and weight of the engine, and by some faint-hearted friends the criticism was freely made that its use would be destructive of roadway, tracks, and bridges. These objections, however, were more than met by a departure from the usual and by original methods of suspending the engine on its springs. Formerly the springs were placed on top of the driving-boxes; in this case they were located beneath them and connected with equalizing bars, thus allowing the use of a longer and more elastic spring than was formerly used, and it has been demonstrated that these engines are less destructive to road-bed and rail, are freer from the swaying motion usually found in engines hung from above the driving-boxes, and ride smoother and more comfortably than any in the service.

Of course, to obtain the speed that was sought, it was desirable to increase the diameter of the driving-wheels; but this was not done at first, nor until it was ascertained how successful had been the efforts to increase the boiler capacity of the engine. When it was found that this increase was ample, and even more successful than had been hoped for, the driving-wheels were changed and the new ones of 6 feet 6 inches in diameter, or 8 inches larger than the old ones, were attached. The gain in speed is most apparent and can well be appreciated when it is remembered that the large driver makes 29.51 less revolutions in a mile than the small ones. On a trip from New York to Albany the decrease in the number of revolutions by the large 6 foot 6 inch wheel would be 4,219.93, an equivalent of 86,154.09 feet, or a saving of nearly 16-and-one-third miles. From New York to Buffalo the saving would be nearly 50-and-1/100 miles.

With a locomotive such as this for motive power it is not a difficult matter to run profit-paying passenger trains over long distances at a running rate of over a mile a minute; this, of course, assuming we have proper character of roadbed and rails and approved appliances to insure safety and rapid speed.

That the speed of passenger trains in this country is destined to rapidly increase in the near future seems certain. There is nothing in railroading that renders such large and quick returns to the management as catering to the wants and desires of the travelling public. Nothing so fully exemplifies this as the immense change that has taken place in the past five years in the equipment of through express trains from the seaboard to the West and Southwest.

The luxury and comfort that can today be obtained on one of the many limited trains passing over any of the great trunk lines, is in strong contrast to what was furnished five or six years ago, and it would seem that there was not much room for further improvement in that direction. What the public are now seeking, and what will certainly be furnished, is fast time; and that this is appreciated by railroad managers is well evidenced by the large sums that are now being spent to perfect the roadways of the more important lines.

One word, in closing, in regard to the alleged danger of the fast train. It is most emphatically untrue that it is more dangerous than other trains. Those familiar with the subject will agree that the very reverse is the case. As an eminent English authority writes, "With picked engineers, trainmen, and firemen, with the best and newest rolling-stock and the most perfect engines the company possesses, with every signalman and flagman all down the line on the qui vive, it is difficult to see where there comes in any special source of danger." And in addition to this, it must be remembered that fast trains such as are now being run on many roads in this country would be simply impossible without the vigorous discipline, the constant energy, the keenest exactitude, and the care and attention to the details of the service that is the surest and most effective guard against accidents.


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