CHAPTER XXIV. THE WESTINGHOUSE AIR-BRAKE.

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INVENTION OF THE WESTINGHOUSE ATMOSPHERIC BRAKE.

In this exacting age, the traveling public are much more disposed to find fault with systems that do not provide against fatalities resulting from human fallibility, than to commend the perfection of appliances which annually save more lives than would be lost in a sanguinary war. The Westinghouse brake has performed this life-saving service, yet its great conserving merit has been but feebly appreciated outside of railroad circles. During the decade between 1860 and 1870, America became a reproach among nations for the frequency and disastrous nature of its railroad accidents. To-day fewer railroad travelers in America lose their lives by accidents beyond their own control, than the travelers in any country under the sun. The credit of this immunity from fatal accidents is almost entirely due to the successful operation of the Westinghouse and other brakes that followed the line suggested by this invention.

DISTINCT CLASSES OF INVENTIONS.

Inventions may be divided into two distinct classes. Far the more numerous class are those which effect improvements on recognized appliances. The other is the rare and more valuable class, to which belongs the original inventor who devises an entirely new method for performing a desired operation. Among this class of inventions may be noted Watt’s separate condenser, which first rendered the steam engine a commercial success; the multitubular boiler of Nathan Read, which made a high-speed locomotive practicable; and the air-brake of Westinghouse, which made fast traveling safe, by putting the train speed under the control of the engineer.

BENEFITS CONFERRED ON TRAIN MEN BY GOOD BRAKES.

To the traveling public the air-brake has proved a source of satisfaction by assuring exemption from accidents, but its greatest blessing has been conferred upon train men. Being the greatest sufferers from railway accidents, their risks of life and limb are greatly reduced; and the agonizing helplessness that used to be so often experienced with trains that could not be stopped in time to avoid a disaster, is almost unknown on our well-managed roads. Mind has become victor in its conflict with matter. When necessary, an engineer can run a train at a high velocity over crowded lines without having to shut off steam within a mile of each point where there may be another train obstructing the track, or keep up his speed at the risk of his life. People unacquainted with the inside operating of railroads have no idea of the difficulties train men had to contend with in getting fast trains over the road, before continuous brakes were supplied. The train had to be run on schedule time, and all points where trains might be expected had to be approached with care. This meant reduced speed; and speed could not be reduced in short distances, so the risk had to be taken of violating one rule to comply with another.

FIRST TRIALS OF THE WESTINGHOUSE ATMOSPHERIC BRAKE.

The Westinghouse atmospheric brake was patented April 13, 1869; and the first public trial took place on the Panhandle road about the same time. The trial was so satisfactory, that the Pennsylvania Railroad Company, which have been always noted for their liberal patronage of every meritorious device likely to promote the efficiency and safety of railroad operating, had a train equipped with the brake. This was the Walls accommodation train, a kind of service where frequent stops were required, and was therefore well calculated to demonstrate the true character of any brake. A number of public trials were made with the brake thus fitted, among which was one by the Master Mechanics’ Association in the middle of September, 1869, on the Horseshoe Bend on the Pennsylvania Railroad. Here a train of six cars, running down a grade of 96 feet to the mile, at the rate of 30 miles an hour, was stopped in a distance of 420 feet. Such a feat was unprecedented at that time, and attracted wide-spread attention.

In the following month, official trials of the train were made by the officers of the Pennsylvania Railroad near Philadelphia. The train was then taken to Chicago, where numerous tests were made in the presence of leading Western railroad officers. So convincing were these trials of the decided efficiency of the brake, that, immediately afterwards, the Michigan Central Railroad and the Chicago and North-Western Railway each ordered a train to be fitted with the brake.

FIRST ROADS THAT ADOPTED THE WESTINGHOUSE BRAKE.

The first five sets of the Westinghouse brake fittings made were got out in the shops belonging to the Pennsylvania Railroad Company at Altoona, Penn. The first railroads to adopt the brake as a regular part of their equipment, were the Pennsylvania, the Pittsburg, Cincinnati, and St. Louis, the Union Pacific, the Chicago and North-Western, and the Michigan Central Railroads.

Since the Westinghouse atmospheric brake was first tried, many changes in details have been made, and numerous improvements have been effected; but the essential points remain the same. And the best forms of brakes subsequently got out by other inventors are founded on the Westinghouse idea, just as much as the numerous types of locomotives follow the design of Stephenson’s Rocket.

OUTLINES OF THE ATMOSPHERIC BRAKE.

Although the automatic air-brake is now becoming almost universal in American railroad practice, most train men are familiar with the working of the atmospheric brake under the name of “straight air.” When first invented, the Westinghouse brake consisted of an apparatus located on the locomotive for compressing air, which was stored in an iron drum fastened somewhere about the engine. Underneath each car, and connected with the ordinary brake attachments, was a cylinder containing a piston, which operated the brake. The brake-cylinders were kept in communication with the air-drum on the locomotive by iron pipes. Connection between the cars where “stretching” and “compression” made the train vary in length, was made by means of rubber flexible hose. When the engineer wished to apply the brakes, he admitted the compressed air into the supply pipes, through a three-way cock at his hand. This air entered the cylinders under the cars, moving back the pistons which pulled the levers operating the brakes. To release the brakes, the air was permitted to escape out of the pipes into the atmosphere.

Thus, what is really a complicated operation was performed in a simple manner, and by means of machinery not liable to get out of order readily. The instant application of every brake on a long train was put in the hand of the engineer. On the first indication of danger, his hand became powerful beyond the magical forces conceived by the imagination of poets.

HOW EASTERN RAILROADS KEPT ALOOF FROM THE WESTINGHOUSE BRAKE.

The growth of the Westinghouse brake into public favor furnishes a curious commentary on the different degrees of enterprise to be found among railroad companies in the various sections of this country. It was natural to suppose that railroads in the thickly settled States, where trains had become too numerous for being safely operated with crude brakes, and no signals, would have been the first to adopt an improved appliance which gave promise of increased safety. Yet the railroads in the Eastern States, with a few creditable exceptions, were among the last to patronize the Westinghouse brake; and they adopted it only when the influence of public opinion could no longer be ignored. Western railroads that ran through sparsely settled prairies, where trains were rare, and stopping room generally ample, were among the first to encourage the inventor of the brake with their support.

LESSON OF THE REVERE RAILROAD ACCIDENT.

During the first two years after it was invented, the Westinghouse brake made slow progress into practical application, except in the West. In the ancient State of Massachusetts, it was hardly known till the Revere accident happened near Boston. This was the case of a crowded road being operated without signals or brakes, except those of the most primitive description. A fast express train ran into the rear end of an accommodation train, killing twenty-nine persons, and severely injuring fifty-seven others. The engineer of the express train, while running at a speed of twenty-five miles an hour, saw the tail lights of the accommodation train when he was eight hundred feet away. He whistled for brakes, and reversed his engine; but the train could not be stopped.

The railroad superintendents throughout the conservative State of Massachusetts then received enlightenment respecting the existence of an efficient continuous brake in a vigorous fashion. The Revere accident conveyed its lessons in a terrible way, but they were effectual in convincing railroad managers that they could not afford to dispense with a brake that proved itself to be reliable.

WEAK POINTS OF THE ATMOSPHERIC BRAKE.

Although the atmospheric brake could, with light trains, make stops within the shortest distance it was desirable to stop trains with safety to the passengers and rolling stock, it possessed certain weak points which demanded remedy. In case of a train breaking in two,—an accident which frequently happens, especially on rough track,—there was danger of the engineer applying the brake without knowing that an interval existed between the cars, and allowing the rear end of the train to crash into the forward part. The signal given by the bell-rope breaking, had a tendency to lead to an accident of this character. Another objection to straight air was, that should derailment take place, or any accident happen that would rupture the pipes or their connections, the brake was rendered useless. These weak features did not interfere with the working of ordinary traffic; and as providing special appliances to meet cases of accident which are rare, does not generally receive much consideration, the brake might have been regarded as perfect enough for all practical purposes had it not failed to meet satisfactorily a condition of ordinary train service. As the length of trains was increased, it was found that the atmospheric brake was slow in action. When a long array of pipes and many cylinders had to be charged with air from the drum on the locomotive after the necessity for applying the brake became apparent, and before it would act, some seconds were required for the operation. Every additional car put upon the train increased the length of pipes and the cylinders to be filled, and so lengthened the time that elapsed between the instant danger was perceived and the time at which the brake began to perform its retarding work. The increase of time might be only a few seconds, but they would probably be priceless moments when an accident was impending.

THE WESTINGHOUSE AUTOMATIC AIR-BRAKE.

To overcome this line of weakness, the Westinghouse automatic air-brake was invented. Where good station signals are in use, it has long been accepted as an axiom among railway authorities, that a signal must be constructed so that it will indicate danger when any accident happens to its mechanism. This principle was brought into practical application in the Westinghouse automatic air-brake. When any thing goes wrong with the brake apparatus, its tendency is to apply the brake automatically. A break in a pipe makes the brake fly on. Each car carries a supply of compressed air sufficient to apply its own brakes several times. By the new arrangement, the brakes on all the cars are applied almost simultaneously, and instantly after the engineer turns the handle of his stopping-valve. The brakes are applied by decreasing the pressure in the pipes; so the breaking in two of the train, or the fracture of an air-pipe or coupling, sets the brakes on all the cars on the train, whatever side of the break the cars may be on. That in itself is an invaluable feature in a continuous brake, and prevents cars from acting as battering-rams upon each other in cases of derailment.

LIFE-SAVING VALUE OF THE AUTOMATIC BRAKE.

Every few days, notices get into the public prints relating how frightful accidents were prevented by the prompt action of the automatic air-brake. And hundreds of narrow escapes, where this brake proves the preventive of destruction to life and property, receive no record, and are known only to the employes connected with the operating of trains. To the men familiar with train service, to those who are intimately acquainted with the life-saving effected by the automatic air-brake, it seems surprising that railroads could have been operated without this or a similar appliance. They certainly were not operated safely without it.

FIRST RAILROADS THAT ADOPTED THE WESTINGHOUSE AUTOMATIC AIR-BRAKE.

Patents for the Westinghouse automatic air-brake were granted in March, 1872. During the succeeding winter, trials of the brake were made by the Pennsylvania Railroad; and it was shortly afterwards adopted by the Philadelphia and Reading Railroad Company as their standard brake for passenger trains. The example of that company was soon followed by the St. Louis, Kansas City and Northern, the Chicago and Alton, the Toledo, Wabash and Western, and the St. Louis, Iron Mountain and Southern Railroads, all of which companies equipped their passenger rolling stock with the automatic air-brake within a few months.

ESSENTIAL PARTS OF THE WESTINGHOUSE AUTOMATIC AIR-BRAKE.

The prominent features of the Westinghouse automatic air-brake consist of the following leading parts: An air-pump, placed on the locomotive, is operated by a steam cylinder, which forces air into an iron drum or reservoir placed under the deck, or in any other convenient part about the engine. The air is compressed to the density considered necessary for the kind of train the locomotive usually pulls.

In the cab, located conveniently to the hand of the engineer, is the engineer’s brake-valve, commonly called the “three-way cock,” which regulates the flow of air from the main reservoir into the main brake-pipes for supplying the auxiliary reservoirs with air. This valve applies the train-brakes by letting the air escape from the main brake-pipes, and releases them by again admitting the pressure of air into the pipes.

From the main reservoir, the main brake-pipe connects with the engineer’s valve, and thence along the train, supplying all the brakes with the air required.

Under the floor of each car is fastened an auxiliary reservoir, which holds a supply of air necessary for operating the brakes on that car. So each car carries its own supply of air.

Connected with each car-truck is a brake-cylinder, in which is operated a piston that applies the brake. The brake-levers connect with the piston-rod in such a manner, that, when the piston is forced out by the air-pressure, the brake is applied.

Attached to the auxiliary reservoir is the triple valve, whose action connects the air-cylinder with the auxiliary reservoir.

THE AIR-PUMP.

When the air-brake was first invented, the distribution of steam within the cylinder was effected differently from what it is in modern pump-cylinders. The steam-valve consisted of a double piston, the heads having ports on their edges which admitted and released the steam. This valve did not move up and down, but received an oscillatory motion from a small auxiliary engine placed on the top of the steam cylinder-head. The movements of the auxiliary engine were regulated by a reversing-rod (popularly known as a kicker-rod), working inside the main piston-rod. This arrangement of steam distribution was somewhat complicated, and liable to get out of order; and it was superseded by the differential steam-valve movement now in use.

HOW THE AIR-PUMP WORKS.

Fig.33a.

In Fig.33a, steam enters from the boiler at the nipple 35, and fills the steam-space between the heads of the main piston-valve 15, 16, maintaining a constant pressure of steam there while the pump is at work. The upper head of the main valve being of greater area than the lower one, the tendency of the pressure is to raise the valve. A downward movement of the valve is provided for by a separate single-headed piston-valve 20, working in a cylinder above the main valve. The reversing-rod 12 operates a slide-valve 13, which regulates the admission and release of steam for the third piston.

In the cylinder shown in the engraving, the main valve is down, so that steam is passing into the lower end of the main cylinder. Two small ports can be seen close to the piston-head 16, one above the other. The upper port is open, and is the admission port; the lower port, which is closed by the small piston, is for exhausting the steam. The main piston 7 is on its upward stroke, and the upper exhaust port seen above the piston-valve 15 is open, while the steam port immediately below it is closed by the valve-piston in the same way that the exhaust port is closed at the other end. When the main piston 7 shall reach near the top of its upward stroke, the plate 10 will strike on the projection on the reversing-rod, pushing up the slide-valve 13. The upper edge of this slide-valve will cut the steam off the passage a, and open the passage b to the exhaust. This takes the steam away from the piston 20, and allows piston 15 to move upward, closing the exhaust-port, and opening the upper steam-port. The same movement makes the piston 16 close its steam-port, and open the exhaust. Piston 7 now begins to travel downward; and, when it reaches nearly to the bottom of the cylinder, the plate 10 catches the knob on the end of the reversing-rod, and pulls down the slide-valve 13 to the position it holds in the engraving. Steam then rushes through the passage a, and makes the piston 20 push down the main valve. That completes the circle of the operations in the steam cylinder.

HOW THE AIR-END OPERATES.

Fig.33b.

The operation of the air part of the pump is very simple. While the main piston (Fig.33b), which is on the same rod as the piston of the steam cylinder, is moving upward, it is forcing the air out of the upper end of the cylinder up under the discharge-valve 32, and away through the proper passages to the main reservoir. At the same time the lower end of the cylinder is being filled with air drawn through the lower receiving-valve 34. During the downward stroke of the piston, the air will be delivered through the valve 33, and the upper part of the cylinder filled by air received through the upper valve 34.

AIR-PUMP DISORDERS.

An engineer who does not understand the principles of a locomotive’s action, is not likely to prove a valuable runner. The men who are most successful in getting trains over the road with solar regularity; the men who make the best records on the mileage sheets for economy in fuel and in lubricants; who are lightest in repairs, yet keep their engine going longest,—are those who comprehend the functions of every portion of the engine, and what relation the various parts bear to each other. With this knowledge clearly established in the mind of the runner, his power to detect any thing wrong with his engine becomes instinctive. Trifling defects, which neglect would develop into serious disabilities, are rectified in time, and the whole engine is maintained in smooth working-order by the harmony of its individual sections. The mere stopper and starter is losing his hold on the locomotive service. When he drops off entirely, our mileage for each dollar expended will be decidedly increased.

The principles which apply to the running of a locomotive are equally applicable to the management of an air-brake, with all its perfected connections. This apparatus can not be properly managed unless the man who works it knows something about its action.

PUNY DIFFICULTIES VANQUISH THE IGNORANT ENGINEER.

A great many engineers who run passenger trains, and take an intelligent interest in the working of the locomotive, whose technicalities they have thoroughly mastered, display no desire whatever to understand the air-brake, and are perfectly contented with its action so long as it will stop the train. The air-pump, so wonderfully interesting to those who understand its movements, receives no more attention than is necessary to keep it going so that the required air-pressure is maintained. They know how to start and stop the machine, and they oil it regularly; but these are the limits of their attentions. Should the pump happen to stop working, the cause is mysterious, like many other mysteries; and the natural remedy suggested, is to hit the thing on the head with a monkey-wrench. Should it not respond to this treatment by renewed action, the hand-brakes are resorted to for the rest of the journey; and the round-house foreman or machinist is required to do the head-work which locates the trouble.

A belief prevails among men who labor principally with their hands, that laziness is exclusively physical. This is a mistake. It is a psychological fact, well known to metaphysicians, that mental laziness is prevalent enough to dwarf the minds of half the human race. Men who would willingly work with their hands during half their leisure time to keep their engines in proper condition for running, have to be driven, by fear or jealousy, before they will force their mental faculties to do trifling labor in a new channel.

CAUSES THAT MAKE BRAKES INOPERATIVE OFTEN EASILY REMEDIED.

Any engineer of ordinary intelligence, who will spend one hour a day for two weeks studying up the Westinghouse instruction book, will understand the brake so well, from the pump to the hind end of the train, that any imperfection happening to its working will be as readily located as an ordinary defect in a locomotive. Yet it is an intensely hard matter to induce men running passenger engines to go through this trifling mental exercise. The consequence is, that the brake sometimes becomes inoperative from causes so slight that men should be ashamed to report them; and they would be so if they only comprehended how small a mole-heap became their mountain. I knew a case where all the train men—that is to say, engineer, fireman, conductor, baggageman, and brakemen—wrestled for twenty minutes over a triple valve, trying to find out how to cut the air off a car; and, when the crowd was vanquished, a colored porter came, and showed them how the thing was done. This was on a road where straight air was generally used. One day some winters ago, a passenger train on the road I worked for was delayed an hour or more at a station, waiting for something. When the engineer tried to start the air-pump, it would not work. He fumed and fussed over it for fifteen minutes, gave it a liberal dose of copper hammer medicine, and saturated it with oil, but all to no purpose. It would not pump a pound of air, so the old-fashioned Armstrong was called into operation. In the course of its journey, this train had to pass the round-house at headquarters; and the engineer stopped to see if his pump could be given some quick remedy. I happened to be the doctor consulted. On learning the particulars of how the pump stopped working, I set fire to a piece of greasy waste, and held the flame to the check-valve of the air-drum; and the pump went right to work. All the trouble was, that the check-valve was frozen in its seat. I felt sorry for that engineer, he appeared to be so thoroughly ashamed and crestfallen at being baffled by such a small trouble.

CARE OF THE AIR-PUMP.

To run an air-pump successfully, the first requisite is that it should be managed intelligently, and its wants attended to regularly. An air-pump consists of numerous moving parts, which should operate with the least possible amount of friction: consequently, it is important that the machine should be properly lubricated,—not deluged with grease for ten minutes, and then run on the interest of the excess for two hours, but sparingly furnished with clean oil, which will keep the moving parts moist all the time. To accomplish this, the feeding-cup must be kept in proper working-order, so that it will pass the oil regularly. I have found a leading cause for air-pumps working unsatisfactorily to be in the intermittent feeding of the oil-cups. Some dirt gets into the cup, obstructing its action, and greater opening is given to make it feed; then the oil goes through by spasms, and the pump works irregularly; for at one time the steam-piston is churning the oil, and again it is working dry. There is also a common abuse of the oil-can when any thing goes wrong with the pump; for some men will then drench it with oil, expecting that to make it work smoothly. Permanent injury is often done in this way, especially where inferior oils are used, which frequently contain mineral substances in suspension. This solid matter is separated from the oil by the heat, and settles in the small passages, filling them up by degrees till eventually there is no channel left for the steam to pass through to reverse the steam-valve; so the pump stops. I once saw a runner trying to doctor a sick pump by pouring the stickiest kind of gummy valve-oil into an air-cylinder. He gave the thing its quietus, as other poor doctors sometimes do with their patients.

PUMP PACKING.

The stuffing-box packing is not generally supposed to exercise an important effect on the action of an air-pump; yet I have seen cases where irregular action of the pump, and serious loss of air, resulted from bad packing. Soapstone and asbestos, and other substances that become compact and rigid when cold, are unsuitable for packing the air end of a pump. After a little use, material of this kind becomes so hard that no amount of screwing of the gland will make it tight; and the greater part of the air at that end of the pump escapes through the stuffing-box instead of passing into the drum.

HOW STEAM PASSAGES GET CHOKED.

Around the bushings of the cylinder, where the small reversing piston 20 works, are diminutive steam passages, very liable to get stopped up when foreign matter is attempted to be run through the cylinder. Such matter is occasionally introduced in various ways. When rubber gaskets are used in the pipe connections leading to the cylinder, the rubber often peels off in shreds, or breaks off in small pieces, which lodge around the bushing in the passages, producing harassing annoyance. So soon as those passages get obstructed, or reduced below their correct size, the pump begins to work badly. Machinists not well versed in the mysterious ways of air-pump disorders will now take that pump apart, and find nothing the matter. Subsequent proceedings depend upon the nature of the man who has the job in hand. If the machinist be of a conservative disposition, he will put the apparatus together again without making any alteration, and perhaps will relieve his mind by expressing a belief that the engineer does not know when an air-pump is in good shape. Another machinist, of a more enterprising stamp, must find something to change, so he lengthens or shortens the reversing valve-rod 12 (a favorite resort of small-knowledge tinkers), which gives the pump the coup de grÂce; and it has to be overhauled by a competent machinist before it again supplies the air to stop a train. This competent man goes direct to the root of the trouble. Skill in this particular line of work convinces him, after an examination, that the moving parts require no repairs; and knowledge begotten of experience, supplemented by sound sense, directs him where to look for the cause of defective operation.

SAGACITY NEEDED IN REPAIRING AIR-PUMPS.

Men who meet with good success in repairing air-pumps, and in determining, from the action of the pump, the probable cause of defect, have to do a great deal of deep and sagacious thinking. Sometimes a defect, simple enough in itself, is extremely difficult to locate, because it belongs to the unexpected order of occurrences.

Here was an instance. Some small jobs had been done one day to the steam cylinder of a pump which had not been working quite satisfactorily. When they tried to start it, after being put together, the pump would not work at all. The machinist who did the job, an eminently competent man at such work, took the machine apart again, but could detect no defect or maladjustment about it. The steam cylinder, with all its valves and rods and bushings, was critically examined: the air-pump, with all its connections, got a thorough inspection to no purpose. When an ordinary man goes through the patient, thoughtful labor needed for an examination of this kind, and finds nothing wrong, he is apt to get discouraged, and confess himself beaten. This man did not recognize the word beaten as applied to his work. He reasoned, “This pump would work if it were all right. It will not work, so something must be wrong.” After exercising more patience and perseverance, he discovered that the bushing 23 of the reversing valve (usually called the kicking-rod valve) had become loose, and, when the cap was screwed down, it twisted the bushing round, and closed the passages that lead steam to the reversing piston. There are small grooves round the sides of the small steam passages to provide for the bushings being moved a little, but these grooves had become gummed up so that they failed to serve their purpose of keeping the ports open.

GRADUAL DEGENERATION OF THE AIR-PUMP.

The working and stationary parts within the cylinders of the air-pump are adjusted with nice exactness; and, when they remain in their normal condition, the pump works smoothly, and compresses air rapidly. When wear, or any other cause, alters the dimensions of these parts, the effect immediately becomes apparent in unsatisfactory working of the whole machine. Rods are adjusted so that valves or pistons shall cover and uncover steam passages, and no superfluous movement is provided for. The passages are so small that all the steam they convey is needed for the work of reversing the motion; and if from any cause the valve or piston only partly uncovers the opening, the necessary volume of steam does not get through. A close observer of the pump’s action can, day by day, perceive the gradual degeneration due to wear. Wear of the steam-cylinder connections is generally indicated by reduced power. The pump will not do its work satisfactorily, and has difficulty in keeping up the pressure of air. This deterioration continues till the pump will stop, unless its decay gets arrested by repairs. When the valves of the air-pump are in correct order for doing good work, the discharge-valves 32 and 33 have 1/16, and the suction-valves 34 ? lift. The continual tapping of these valves on their seats has a tendency to wear out valves and seats, making the lift greater than what is desirable. Any material increase of lift for the discharge-valve has a most injurious effect upon the motion of the pump, especially if the suction-valve should happen to be leaky. Then the movement of the pistons will become fluctuating, and subject to frequent stoppages. The up-and-down motion of the piston is of a jerky character, that makes the beholder suppose the thing is uncertain which way to go. Deterioration of air-valves is not, however, the only cause for that jerky motion so often observed in bad working pumps. A bent reversing valve stem (kicker-rod) acts on the reversing valve with oblique pull and thrust, which tend to move it away from the seat, letting the steam pass the wrong way. A broken main steam-valve ring has a similar effect; for the steam passes to the wrong end of the valve, destroying its equilibrium; and there is nothing decisive about its reversal, or about its motion after it is reversed. Its action resembles the movements of a vacillating human being. It does not want to go in that direction, but goes, then keeps trying to change its mind during the rest of the journey. Obstructed steam passages will sometimes cause indecisive action of the pump before it gets bad enough to stop it altogether.

CAUSES THAT MAKE A PUMP POUND.

Pounding on the heads is a somewhat common attribute of degenerated air-pumps. Broken or badly worn air-valves very often cause the pump to pound. If the trouble should happen to be in the upper air-valve, it will demonstrate its disorder by causing pounding on the upper head; and the lower valve’s malady will cause pounding on the lower head. When a pump is suffering from indecisive motion, or is pounding, and the machinist does not feel certain about where the trouble lies, he may safely examine the condition of the air-valves,—for they can be easily reached,—and in a great many cases the defect will be found there. Wear of the pin whereon the bottom of the main valve-rod rests, or of the rod itself, will induce pounding on the upper head by the main piston. Some runners think, that, by keeping the drain-cock of the steam-cylinder open all the time, they secure dry steam. The practice is pernicious, and injurious to the pump: for the piston receives so little cushion when the drain-cock is shut, that it can not afford the decrease made by a permanently open cock; and consequently the loss of cushion permits pounding on the lower head.

I have known of a disastrous effect being produced on a pump by putting a new gasket, which proved too thick, on the upper head. It was the thinnest copper that could be found, but it perceptibly lengthened the upper end of the cylinder so that the bottom knob on the reversing stem struck the reversing plate on the main piston before that action was due. On several occasions I have had air-pumps reported to be working badly, when all the trouble lay in the air-strainer being partly choked up by floating vegetable matter that had been sucked in with the air, and failed to pass through the meshes. In another case we had much difficulty in locating the defect, with a pump that absolutely refused to work. The boiler-makers had been working in the smoke-box, and by some means the end of the exhaust-pipe got solidly stopped up with cinders. As none of us had come across that particular cause of obstruction before, we expended a good deal of labor searching for the trouble before we thought to disconnect the exhaust-pipe from the pump.

THE TRIPLE VALVE.

This is the part whose operation gives the brake its automatic action. Those who have opposed this form of brake have made great objection to the complicated nature of the triple valve. But some familiarity with the device shows that it is far from being complex, considering the functions it performs. It is merely a piston-valve carrying a slide-valve along with it.

The arrangement of the parts of the triple valve is shown in Fig.34.

Fig.34.

The triple valve has a piston 5, working in the chamber B, and carrying with it the slide-valve 6. Air enters from the main pipe through the four-way cock 13 into the drain-cup A, and passes to the chamber B, forcing the piston up, and uncovering a small feeding-groove in the upper part of the chamber, which permits air to flow past the piston into the auxiliary reservoir, while, at the same time, there is an open communication from the brake-cylinder to the atmosphere through the passages d, e, f, and g. Air will continue to flow into the auxiliary reservoir until it contains the same pressure as the main brake-pipe.

ACTION OF THE TRIPLE VALVE.

To apply the brakes with their full force, the compressed air in the main brake-pipe is permitted to escape, when the greater pressure in the auxiliary reservoir forces the piston 5 down below the feeding-groove, thus preventing the return of air from the reservoir to the brake-pipe. As the piston descends, it moves with it the slide-valve 6, so as to permit air to flow directly from the auxiliary reservoir into the brake-cylinder, which forces the pistons out, and applies the brakes. The brakes are released by again admitting pressure into the main brake-pipe from the main reservoir; which pressure, being greater than that of the auxiliary reservoir, forces the piston 5 back to the position shown in the engraving, recharges the reservoir, and at the same time permits the air in the brake-cylinders to escape.

To apply the brakes gently, a slight reduction is made in the pressure in the main brake-pipe, which moves the piston down slowly until it is stopped by the graduating spring 9. At this point, the opening l in the slide-valve is opposite the port f, and allows air from the auxiliary reservoir to feed through a hole in the side of the slide-valve, and through the opening l into the brake-cylinder. The passage l is opened and closed by a small valve 7, which is attached to, and moves with, the piston 5, provision being made for a limited motion of these parts without moving the valve 6. When the pressure in the auxiliary reservoir has been reduced by expanding into the brake-cylinder until it is the same as the pressure in the main brake-pipe, the graduating spring pushes the piston up until the small valve 7 closes the feed opening l. This causes whatever pressure is in the brake-cylinder to be retained, thus applying the brake with a force proportionate to the reduction of pressure in the brake-pipe.

TO PREVENT CREEPING ON OF BRAKES.

To prevent the application of the brakes, from a slight reduction of pressure caused by leakage in the brake-pipe, a semicircular groove is cut in the body of the car-cylinder, 9/64 of an inch in width, 5/64 of an inch in depth, and extending so that the piston must travel three inches before the groove is covered by the packing leather. A small quantity of air, such as results from a leak, passing from the triple valve into the car-cylinder, has the effect of moving the piston slightly forward, but not sufficiently to close the groove, which permits the air to flow out past the piston. If, however, the brakes are applied in the usual manner, the piston will be moved forward, notwithstanding the slight leak, and will cover the groove. It is very important that the groove shall be three inches long, and shall not exceed in area the dimensions given above. Heretofore leakage valves have been used, and also a leakage hole. These leakage holes have been found to be too uncertain in their operation; and consequently it is recommended that these holes should be closed, and the grooves in the cylinders substituted, as rapidly as possible.

When the handle of the four-way cock 13 is turned down, there is a direct communication from main brake-pipe to the brake-cylinder, the triple valve and auxiliary reservoir being cut out; and the apparatus can be worked as a non-automatic brake, by admitting air into the main brake-pipe and brake-cylinder, to apply the brakes. When from any cause it is desirable to have the brake inoperative on any particular car, the four-way cock is turned to an intermediate position, which shuts off the brake-cylinder and reservoir, leaving the main brake-pipe unobstructed to supply air to the remaining vehicles.

The drain-cup A collects any moisture that may accumulate, and is drained by unscrewing the bottom nut.

HOW TO APPLY AND RELEASE THE BRAKE.

The brakes, as has been explained, are applied when the pressure in the brake-pipe is suddenly reduced, and released when the pressure is restored.

It is of very great importance that every engineer should bear in mind that the air-pressure may sometimes reduce slowly, owing to the steam-pressure getting low, or from the stopping of the pump, or from a leakage in some of the pipes when one or more cars are detached for switching purposes, and that in consequence it has been found absolutely necessary to provide each cylinder with the leakage groove already referred to, which permits a slight pressure to escape without moving the piston, thus preventing the application of the brakes, when the pressure is slowly reduced, as would result from any of the above causes.

This provision against the accidental application of the brakes must be taken into consideration, or else it will sometimes happen that all of the brakes will not be applied when such is the intention, simply because the air has been discharged so slowly from the brake-pipe that it only represents a considerable leakage, and thus allows the air under some cars to be wasted.

It is thus very essential to discharge enough air in the first instance, and with sufficient rapidity, to cause all of the leakage grooves to be closed, which will remain closed until the brakes have been released. In no case should the reduction in the brake-pipe for closing the leakage grooves be less than four or five pounds, which will move all pistons out so that the brake-shoes will be only slightly bearing against the wheels. After this first reduction, the pressure can be reduced to suit the circumstances.

On a long train, if the three-way cock be opened suddenly, and then quickly closed, the pressure in the brake-pipe, as indicated by the gauge, will be suddenly and considerably reduced on the engine, and will then be increased by the air-pressure coming from the rear of the train: hence it is important to always close the three-way cock slowly, and in such a manner that the pressure, as indicated by the gauge, will not be increased; or else the brakes on the engine and tender, and sometimes on the first one or two cars, will come off when they should remain on. It is likewise very important, while the brakes are on, to keep the three-way cock in such a position that the brake-pipe pressure can not be increased by leakage from the main reservoir; for any increase of pressure in the brake-pipe causes the brakes to come off.

On long down grades, it is important to be able to control the speed of the train, and at the same time to maintain a good working pressure. This is easily accomplished by running the pump at a good speed, so that the main reservoir will accumulate a high pressure while the brakes are on. When, after using the brake some time, the pressure has been reduced to sixty pounds, the train pipes and reservoirs should be recharged as much as possible before the speed has increased to the maximum allowed. A greater time for recharging is obtained by considerably reducing the speed of the train just before recharging, and by taking advantage of the variation in the grades.

There should not be any safety-valve or leaks in the main reservoir, otherwise the necessary surplus pressure for quickly recharging can not be obtained.

To release the brakes with certainty, it is important to have a higher pressure in the main reservoir than in the main pipe. If an engineer feels that some of his brakes are not off, it is best to turn the handle of the three-way cock just far enough to shut off the main reservoir, and then pump up fifteen or twenty pounds extra, which will insure the release of all of the brakes; all of which can be done while the train is in motion.

For ordinary stops, great economy in the use of air is effected by, in the first instance, letting out from eight to twelve pounds pressure while the train is at speed, taking care to begin a sufficient distance from the station.

PUMP GOVERNOR.

This is an important attachment which ought to be connected to all air-brake pumps. It not only prevents the carrying of an excessive air-pressure by the engineers, which often results in the sliding of the wheels, but it also causes the accumulation of a surplus of air-pressure in the main reservoir, while the brakes are applied, which insures the release of the brakes without delay. It also limits the speed of the pump, and consequently the wear.

The pump governor is shown in Fig.34b, the object of which is to automatically cut off the supply of steam to the pump when the air-pressure in the train-pipe exceeds a certain limit, say seventy pounds.

The operation of this governor is as follows: the wheel 8 is screwed down so as to permit the valve 10 to be unseated by the excess of pressure on the upper side of the valve, permitting steam to pass through the openings A and B to the pump. A connection is made from the train-pipe to the upper end of the governor, and the compressed air passes around the stem 14 to the upper side of the diaphragm plate 18, which is held to its position by the spring 16, which latter is of sufficient strength to resist a pressure of, say, seventy pounds per square inch on diaphragm. As soon as the air-pressure on the diaphragm 18 exceeds this amount, it forces the diaphragm down, unseating the valve 13, and allowing the steam on the upper side of the valve 10 to escape through the exhaust 6, which causes an excess of steam-pressure on the lower side of the valve 10, forcing the valve against its seat, and cutting off the supply of steam to the pump.

When the pressure in the train-pipe is diminished by applying the brakes, the diaphragm is restored to the position shown by the action of the spring 16. The valve 13 is seated by the spring 12; and the steam-pressure, passing through the port C, accumulates on the upper side of the valve 10, forcing it down, and opening the passage for steam to the pump until the air-pressure is again restored to the required limit of seventy pounds.


                                                                                                                                                                                                                                                                                                           

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