PART II.

OVERHEAD CONSTRUCTION.

=Trolley Wire.= The trolley wire is suspended from the span wires or brackets in such a way as to permit of an uninterrupted passage of an upward pressing trolley wheel underneath it. The trolley wire itself may be either round, grooved, or figure 8 in section. Where a round wire is used, No. 00 B. & S. gauge is the most common size. Figure 8 wire, so called from its section, which is shown in Fig. 64, is designed to present a smooth under surface to the trolley wheel, which will not be interrupted by the clamps or ears used to support it. Clamps are fastened to the upper part of the figure 8. The grooved wire is rolled with grooves into which the supporting clamps fasten. This wire also presents a smooth under surface to the trolley wheel.

=Trolley-Wire Clamps and Ears.= The trolley is supported either by clamps or by soldered ears. One type of clamp grasps the wire by virtue of screw pressure. A soldered ear is shown at E, Fig. 65. This ear has small projections at each end, which are bent around the wire to assist the solder in holding the wire to the ear. Another form of ear, used to some extent, holds the wire by virtue of having the edges of the groove offset or riveted around the wire.

The ear or clamp screws to a bolt which is insulated from the metal ear through which passes the span wire. A cross-section through a common type of trolley-wire hanger is shown in Fig. 66. Here there is an outer shell of metal, which is adapted to hook to the span wire. In this shell is an insulating bolt, that is, a bolt surrounded with some form of insulating material which is very strong mechanically and not likely to be cracked by the hammering action of the passing trolley wheel. Most of the insulating compounds used in making trolley-wire insulators are trade secrets. Another kind of insulator called the “cap and cone” type is shown at C, Fig. 65. In these insulators, the metal part B which fastens to the span wire does not completely surround the insulation C. Wood has sometimes been used for the insulation of trolley-wire hangers.

=Span Wires.= In city streets, the trolley wire is commonly suspended from span wires stretched between poles located on both sides of the street. These span wires are of ¼-inch or ⅜-inch galvanized stranded steel cable. In order to add to the insulation between the trolley wire and the poles at the side of the street, what is called a _strain insulator_ is placed in the span wire. This is an insulator adapted to withstand the great tension put upon it by the span wire. One of these is shown in Fig. 67. Means are usually provided for tightening the span wires as they stretch and as the poles give under the strain. The insulator in Fig. 67 has a screw eye for that purpose.

=Brackets.= In the bracket type of overhead construction, a trolley wire is fastened to brackets placed on poles near the track. This construction is used on suburban and interurban lines where the presence of poles near the track is not objectionable. It has been found that a rigid connection of the trolley wire to a bracket is likely to result in the breaking of the trolley-wire insulators. For this reason the brackets now commonly used provide for a flexible suspension of the trolley-wire hanger from the bracket. A bracket employing such flexible construction, made by the Ohio Brass Company, is illustrated in Fig. 68.

An example of standard straight-line bracket construction is shown in Fig. 69.

=Feeders.= Where additional conductivity is needed beyond that furnished by the trolley wire itself, feeders are run on insulators along the poles at the side of the track. Such feeders are connected to the trolley wire at regular intervals. Where span-wire construction is used, the feed wire may be substituted for the span wire at the pole where the connection between feed wire and trolley wire is made. In such a case, of course, a trolley-wire hanger is used which has no insulator, so that the current feeds directly through the hanger. Another method is to run the feed connection parallel with a span wire and a short distance from it.

=Section Insulators.= Section insulators are usually placed in the trolley wire at regular intervals. Such a section insulator is shown in Fig. 70. Its purpose is to insulate one section of trolley wire from the next, so that in case the trolley wire of one section breaks, or is grounded in any other manner, that section can be disconnected and the other sections on either side kept in operation. In large city street-railway systems, each section of trolley wire usually has its own feeder or feeders, independent of the other sections. This feeder is supplied through an automatic circuit breaker at the power house. In case a certain section of trolley wire is grounded the large current that immediately flows will open the circuit breaker supplying that section; but, unless the ground contact is of an extremely low resistance, it will not affect the operation of the other feeders. Should it be of sufficiently low resistance to cause all the generator circuit breakers to open, it would, of course, interrupt the entire service temporarily; but usually the circuit breaker on any individual feeder will cut that feeder out before all the circuit breakers will open.

=High-Tension Lines.= Where high-tension alternating-current wires are run, as in the case where the road is of such length as to require the establishment of several substations, these high-tension circuits are usually carried some distance above the 500-volt direct-current trolley and feeders. An example of interurban overhead construction is shown in Fig. 69. Here the high-tension wires are carried on large porcelain insulators of a size necessary for 26,000 volts. These insulators are placed 35 inches apart. High-tension wires are kept so far apart because of the danger that arcs will in some way be started between the lines, as the high-tension current will maintain an extremely long arc. The blowing of green twigs across the lines, or birds of sufficient size flying into the lines, is likely to establish arcs which will temporarily short-circuit the line. The greater the distance apart of the wires, the less danger that such things will occur.

Both glass and porcelain insulators are successfully used on lines of very high tension. Glass is the cheaper and porcelain has the greater mechanical strength.

High-tension wires are usually of hard-drawn copper or of aluminum made up in the form of a cable of several strands. Aluminum is lighter for a given conductivity than copper; and, at the market price controlling at the present time, is cheaper. It is, however, more subject to unevenness of composition, which leaves weak spots at certain points in the wire; and that is the reason why aluminum is now always used in the form of a stranded cable rather than as a single conductor. Aluminum, being considerably softer than copper and melting at a lower temperature, is more likely to be worn through as a result of abrasions or to be melted off by a temporary arc. These slight objections are balanced against its smaller first cost as compared with the cost of copper.

The calculation of the proper amount of feed wire for a given section of road is somewhat similar to the calculation of electric light and power wiring as already outlined. It is first necessary to estimate approximately the amount of current required at different portions of the line. The amount of drop to be allowed between the power house and cars must be decided arbitrarily by the engineer. A drop of 10 per cent is probably the one most commonly figured upon in designing feeding systems. The resistance in ohms of the copper feeders required to conduct a given current with a given loss in volts, can be calculated by dividing the volts lost by the current, according to Ohm’s law. By the aid of a table which gives the conductivity of various sizes of wire according to the methods outlined in connection with “Electric Wiring,” the proper number and size of the feeders can be determined. The most difficult thing to determine is the load that will be placed upon any section of the line. Of course, there will be times when cars are bunched together owing to blockades. It is out of the question to provide enough feeder copper to keep the loss in voltage within reasonable limits at such times. The ordinary load upon any feeder is used as the basis of calculation in most cases. The amount of current required per car depends on the weight of the car and the character of the service. This will be taken up later under the head of “Operation.”

THIRD RAIL.

=Location.= The third-rail system of conducting current to electric cars, as most commonly employed in the United States, follows the example set by the Metropolitan West Side Elevated Railway of Chicago. All the elevated roads in the United States are now operated by means of third rails located at one side of the track. The third rail is an ordinary T-rail and is located with the center of its head 20 inches outside of the gauge line of the nearest track rail, and 6³⁄₁₆ inches above the top of the track rail. On a few interurban roads this distance has been increased in order to accommodate certain steam railroad rolling stock which must at times be operated over the line.

=Insulators.= The third rail is supported every fifth tie on an insulator. These insulators on first construction were made of wooden blocks boiled in paraffine, but at the present time more substantial forms of insulation are being used.

One form of third-rail insulator, known as the “Gonzenbach,” has a base of cast iron resting on the tie. Over this is placed a cap of insulating material similar to that used in strain and trolley-wire insulators. Over this insulating material is another cast-iron cap upon which the third rail rests. The weight of the third rail holds it in position, and there is no clamping together of the various parts of the insulator.

Another form of third-rail insulator is made of what is called “reconstructed granite,” and another of vitrified clay. Fig. 71 shows one of the latter.

=Switches.= Where the third rail is used, a contact shoe is placed on each side of both trucks of the motor car. At switches it is necessary to omit the third rail for a short distance on one side of the track, and place a short section of third rail on the other side of the track so that the current supply to the car will be uninterrupted.

=At Highway Crossings.= Where the third-rail system is employed on interurban surface lines, it is necessary to omit a section of it at every highway crossing. If the crossing is too wide to be bridged across by a car, the car must have sufficient momentum to drift over such crossings when it comes to them. To connect across the break in the third rail at such points, an underground cable is generally used. This cable must be thoroughly protected against leakage of moisture into the insulation where it comes to the surface for connection to the third rail.

Another form of third rail, laid several years ago on some of the lines of the New York, New Haven & Hartford Railroad, was of an inverted V-shape, and was laid midway between the track rails with its top 1 inch above them and its bottom only 1⅝ inches above the ties. It was supported on wooden blocks. This location of the third rail has never been popular, because of the poor insulation with the rail located so close to the ties between the rails.

=Conductivity.= The conductivity of a steel rail varies considerably. A rail of the ordinary composition used on steam railroads is too high in carbon to give the best conductivity. Such a rail has about one-tenth the conductivity of the same cross-section of copper. Steel can easily be obtained, however, which will have one-seventh the conductivity of copper, and the additional cost of obtaining such special steel is quite low, so that the majority of roads installing the third-rail system have seen fit to pay the extra cost and thereby secure a softer rail than that usually employed in track rails.

=Cost.= The cost of the third-rail system is less than an overhead trolley system, provided enough copper is placed in the trolley feeders to make the conductivity of the trolley system equal to that of the third-rail system. It is very seldom, however, that a trolley system is so constructed on an interurban road; and hence the trolley system, as usually constructed, is cheaper than the third-rail system, because it is not of equal conductivity to a third-rail system.

=Advantages in Operation.= Where very heavy cars or trains are to be operated, the third-rail system is decidedly an advantage, for two reasons. In the first place, it affords the cheaper method of conducting a given heavy volume of current; and in the second place, the contact shoes that conduct the current from the third rail to the moving car or train are built to carry a much larger volume of current than the trolley wheel, which has only a small area of contact on the trolley wire. Ordinarily there are two of these contact shoes in multiple for every motor car.

Another advantage of the third rail over the trolley is that the trolley may leave the wire at high speeds or in passing switches. On well-constructed roads, where the trolley wire is kept in good alignment and the track is smooth, there is little trouble from this source; but it is undoubtedly a convenience to be able to operate cars or trains without giving any attention to a trolley pole.

CONDUIT SYSTEMS.

The underground conduit system, in which the conductors conveying the current to the cars are located in a conduit under the tracks, is in use in two cities of the United States—New York City and Washington, D. C. The cost of this system, and the danger of interruption of the service where the drainage is not excellent, have prevented its more extensive adoption.

The New York type of conduit is a good example of this construction. The conductors consist of T-bars (CC) of steel supported from porcelain cup insulators located 15 feet apart in the conduit. A cross-section of the conduit is shown in Fig. 72. At each insulator a handhole is provided (Fig. 73), so that access may be had to the insulator from the street surface. Manholes are provided at intervals of about 150 feet, so that the dirt which collects in the conduit can be scraped into these manholes and removed at intervals. The manholes also serve as points of drainage to the sewer system.

=Contact Plow.= Current is conducted to the car through a pair of contact shoes commonly called a _plow_ (Fig. 74). This plow has the two shoes insulated from each other, and from the frame of the plow. They are provided with flat springs that hold the shoes against the conducting bars in the conduit. The shank of the plow is thin enough (⁹⁄₁₆ inch) to enter the slot of the conduit. The conductors pass up through the middle. These plows can, of course, be removed only when the car is over an open pit.

=Cost.= A conduit system of this kind is very expensive to build because of the fact that a very deep excavation must be made in the street to accommodate the conduit. The track rails, slot rails, and sheet-steel conduit lining are held in alignment by cast-iron yokes placed 5 feet apart. The entire space around and underneath these yokes is filled with concrete in order to give rigidity and a permanent track. Three expensive items, therefore, enter into the construction of a conduit road—namely, the deep excavation, which may call for the changing of other underground pipes or conduits in the street; the large amount of iron and steel needed for the yokes and slot rails; and the large amount of concrete needed.

On American conduit roads the slot and conduit are placed under the middle of the track. Some of these roads are simply reconstructed cable-conduit roads in which the old cable conduit has been used for electrical conductors. In the conduit road at Buda-Pest, Hungary, the slot is placed alongside one of the track rails.

=Current Leakage.= The leakage on an underground conduit road is considerable, because the insulators are necessarily located in a damp, dirty place, which causes leakage over the surface of the insulators. This leakage, however, is not prohibitive so long as the conductor rails are not under water. If on account of poor drainage the conductor rails become submerged, the leakage becomes so great that it is impossible to operate the road.

It will be noticed that the conduit system as illustrated here employs two conductor rails—one for the positive side of the circuit and the other for the negative. The track rails, therefore, are not used as conductors, and one side of the circuit is not grounded as in the ordinary trolley system, although the leakage to ground may be considerable from one or both conductor rails.

TRACK CONSTRUCTION.

=Girder Rail.= A great variety of track rails are used in electric railways. The most common at one time was the girder, a typical section of which, with joint, is illustrated in Fig. 75. This is an outgrowth of the old tram rail used on horse railways. It has a tram alongside of the head, on which vehicles may be driven. Its chief advantage from the standpoint of the railway company is that there is plenty of room for dirt and snow to be pushed away by the flanges of the cars. If the company maintains the paving, it may be to its advantage to have teams use the steel track rather than the paving, although this advantage in maintenance is probably more than compensated for by the delay of cars through the regular use of the track by teams.

=Trilby Groove Rail.= A modification of the girder rail, known as the _Trilby_, and sometimes as the _grooved girder_, is shown in Fig. 76. A rail similar to this is used in several large cities of the United States. It has a groove of such a shape that the flanges of the car wheels will force snow and dirt out of it instead of packing it into the bottom of the groove, as in the case of the regular European narrow-grooved rail. A narrow-grooved rail in which the grooves correspond closely to the shape of the car-wheel flanges is sure to make trouble in localities where there is snow and ice, as the grooves become packed and derail the cars.

=Shanghai T-Rail.= In some systems a T-rail is used. Where the T-rail is to be used with paving, the popular form is the Shanghai T, shown in Fig. 77. This rail is high enough to permit the use of high paving blocks around it.

=Common T-Rail.= The T-rail used by steam railroads is known as the A. S. C. E. standard T-rail, because it follows the standard dimensions recommended for T-rails by the American Society of Civil Engineers. A standard 65-pound T-rail of this kind is shown in Fig. 78. Other weights of this rail have the same relative proportions. Such a rail is used for interurban roads, and for suburban lines in streets where there is no block paving. The high rails are used to facilitate paving with high paving blocks.

=Track Support.= The greater portion of track is laid on wooden ties. These ties, in the most substantial wooden tie construction, are 6 inches by 8 inches in section, and 8 feet long. They are spaced two feet between centers. Sometimes smaller ties, spaced farther apart, are used in cheaper forms of construction; but the foregoing figures are those of the best construction known in American railway practice. In paved streets, ties are usually employed, although sometimes what is known as “concrete stringer” construction is used instead of ties to support the rails. A strip of concrete about 12 inches deep is laid under each rail, and the rails are held to gauge by ties or tie rods placed at frequent intervals. Sometimes the concrete is made a continuous bed under the entire track. In most large cities the concrete foundation is used under all paving; and consequently, when concrete is used instead of ties to support the rails, this concrete is simply a continuation of the paving foundation. Where ties are used, they are laid sometimes in gravel, crushed stone, or sand, although frequently, in the largest cities, they are embedded in concrete. Sometimes this concrete is extended under the ties, and sometimes it is simply put around the ties.

=Ballast.= A ballast of gravel, broken stone, cinders, or other material which is self draining and which will pack to form a solid bed under the ties, should be used to get the best results under all forms of tie construction, whether in paved streets or on a private right of way, as on an interurban road. Of course, if concrete is placed under the ties, the gravel or rock ballast is not necessary. If ties are placed directly in soft earth, which forms mud when wet, they will work up and down under the weight of passing trains, and an insecure foundation for the track will be the result.

=Joints.= The matter of securing a proper joint for fastening together the ends of rails so as to make a smooth riding track without appreciable jar or jolt when the wheels pass a joint, has been given much study by electric railway engineers. A section through an ordinary bolted angle-bar joint is shown in Fig. 75. This joint is formed by bolting a couple of bars, one on each side of the rails. The edges of these bars are made accurately to such an angle that they will wedge in between the head and base of the rail as the bolts are tightened; hence the name _angle bars_. This is the form of joint generally used on steam railroads and on electric roads in exposed track, or in track where the joints are easily accessible, as in dirt streets. In paved streets, the undesirability of tearing up the pavement frequently to tighten the bolts on such joints, has led to the invention of several other types, which will be described later. Nevertheless very good results have been obtained in recent years with bolted joints laid in paved streets where care has been given to details in laying the track, and where the joints have been tightened several times before the paving is finally laid around them.

=Welded Joints.= Several forms of welded joints are in use. All these welded joints fasten the ends of the rails together so that the rail is practically continuous—just as if there were no joints—so far as the running surface of the rail is concerned. It was thought at one time that a continuous rail would be an impossibility because of the contraction and expansion of the rail under heat and cold, which, it was thought, would tend to pull the rails apart in cold weather and to cause them to bend and buckle out of line in hot weather. Experience has conclusively shown, however, that contraction and expansion are not to be feared when the track is laid in a street where it is covered with paving material or dirt. The paving tends to hold the track in line, and to protect it from extremes of heat and cold. The reason that contraction and expansion do not work havoc on track with welded joints, is probably that the rails have enough elasticity to provide for the contraction and expansion without breaking.

It is found that the best results are secured by welding rail joints during cool weather, so that the effect of contraction in the coldest weather will be minimum. In this case, of course, there will be considerable expansion of the track in the hottest weather, but this does not cause serious bending of the rails; whereas occasionally, if the track is welded in very hot weather, the contraction in winter will cause the joint to break.

=Cast-Welded Joints.= The process of cast-welding joints consists in pouring very hot cast iron into a mould placed around the ends of the rails. These moulds are of iron; and to prevent their sticking to the joint when it is cast, they are painted inside with a mixture of linseed oil and graphite. Iron is usually poured so hot that, before it cools, the base of the rail in the center of the molten joint becomes partially melted, thus causing a true union of the steel rail and cast-iron joint. This makes the joint solid mechanically and a good electrical conductor. To supply melted cast iron during the process of cast-welding joints on the street, a small portable cupola on wheels is employed. Fig. 79 gives an idea of the process of making cast-welded joints.

=Electrically Welded Joints.= An electrically welded joint is made by welding steel blocks to the rail ends. A steel block is placed on each side of the joint, and current of very large volume is passed through from one block to the other. This current is so large that the electrical resistance between the rail and steel block causes that point to become molten. Current is then shut off, and the joint allowed to cool. There is in this case a true weld between the steel blocks and the rails and joint. An electric welding outfit being expensive to maintain and operate, this process is used only where a large amount of welding can be done at once. Current is taken from the trolley wire. A rotary converter set takes 500-volt direct current from the trolley wire, and converts it into alternating current. This alternating current is taken to a static transformer which reduces the voltage and gives a current of great quantity at low voltage, the latter current being passed through the blocks and rails in the welding process. A massive pair of clamps is used to hold the blocks against the rails, and to conduct the current to and from the joint while it is being welded. These clamps are water-cooled by having water circulated through them so that they will not become overheated at the point of contact with the steel blocks.

=Thermit Welding.= A process of welding rail joints which was developed after the cast-welding and electric-welding processes, is known as the _Goldschmidt process_, which makes use of a material called “thermit” for supplying heat to make the weld. A mould is placed around the joint and the thermit is put in this mould and ignited. The heat produced by the thermit is so intense as to reduce the iron in the thermit mixture and make a welded joint. The thermit consists of a mixture of finely powdered aluminum and iron oxide. When this is ignited, the aluminum oxidizes, that is, absorbs oxygen so rapidly that an intense heat is the result. In the process of oxidation, the aluminum takes the oxygen from the oxide of iron, leaving molten metallic iron, which metallic iron makes the weld by union with the molten rail ends. This process has the advantage over other welding processes, of not requiring an elaborate apparatus and a large crew of men to operate it; and consequently it can be used where but a few joints are to be welded.

=Bonding and Return Circuits.= When the track rails are used as the conductors, as is usually the case, it is necessary to see that the electrical conductivity of the rail joints does not offer too high a resistance to the passage of the current. For this reason, when bolted or angle-bar joints are used, the rails are bonded together by means of copper bonds. It was soon found after electric roads were in use a short time, that unless the rail ends were so bonded, the resistance of the joints was so great as to cause great loss of power in the track. First, small iron bonds were used; but these bonds were so insufficient that large copper-wire bonds soon began to be used; and at the present time, on large roads, bonds of heavy copper cable are common. The resistance of a steel rail, such as used in city streets, is about eleven times that of copper. In order to secure as great carrying capacity at the rail joint as is afforded by the unbroken rail, it is therefore necessary to install bonds having a total cross-section ¹⁄₁₁ that of the rail. Where welded joints are used, bonding is unnecessary, except at crossings and switches where bolted joints are employed. Where track is welded, however, cross bonds should be put in at frequent intervals from one rail to another, and, if the track is double, from one track to the other, so that if one of the track rails breaks at a joint there will be a path around the break for the current.

A great many schemes have been devised to insure good contact between the copper bond and the rail, as the terminal is the weak point in any bond. One of the earliest and most efficient of small bonds was made by the use of channel pins, Fig. 80. This bond consisted of a piece of copper wire having its ends placed in the holes in the rail ends. Alongside this wire, a channel pin was driven in. The objection to the channel pin was the small area of contact between the copper bond and rail.

Next after the channel pin came the Chicago type of bond, Fig. 81, which is a piece of heavy copper wire with thimbles forged on the ends. These thimbles were placed in accurately fitted holes in the rail ends, and a wedge-shaped steel pin was driven into the thimbles to expand them tightly into the hole in the rail. Several other bonds using modifications of this principle are in use.

A type of bond in very common use consists of solid copper rivet-shaped terminals, Fig. 82. Between these terminals is a piece of flexible stranded copper cable, made flat to go under the angle bars. In one type the terminal lugs are cast around the ends of the cables, and in another type the cables are forged at their ends into solid rivet-like terminals. These terminal rivets were first applied as any other rivets, with the use of a riveting hammer. Because of the difficulty of thoroughly expanding such large rivets into the holes made for them in the rails, it has become customary to compress these rivets either with a screw press or a portable hydraulic press, which brings such great pressure to bear on the opposite ends of the rivet that it is forced to expand itself so as to fill the hole in the rail completely. This expansion is made possible by the ductile character of the copper. This great ductility characteristic of copper, however, has been the source of one of the difficulties in connection with rail bonding, because the soft copper terminal has a tendency to work loose in the hole made for it in the rail. It is practically impossible to maintain good bonding where the rail joints are so loose as to allow considerable motion between the rail ends.

Several types of bonds have been introduced, in which the contact between the rail and bond is made by an extra piece or thimble.

Another method of expanding bond terminals into the holes made to receive them, is that employed in the General Electric Company’s bond. In it a soft pin in the center of the terminal is expanded by compression of the terminal so that it forces the copper surrounding it outward. The copper terminal, in expanding to fill the hole, is therefore backed by the steel center pin.

All types of bonds must be installed with great care if they are to be efficient. Unless the bond terminal thoroughly fills the hole and is tightly expanded into it, moisture will creep into the space between the copper and the iron, and the copper will become coated with a non-conducting scale which destroys the conductivity of the contact. The _plastic_ rail bond, so called because it depends for the contact between the rail and the bond upon a plastic, putty-like alloy of mercury and some other metal, is applied in a number of different ways. One form consists of a strip of copper held by a spring against the rail ends under the fish-plate. The rail ends at the point of contact with this strip of copper are amalgamated and made bright by the use of a mercury compound similar to the plastic alloy. These points of contact are then daubed with plastic alloy, and the copper bond plate applied. It is not necessary, with any form of plastic bond, that the mechanical contact be unyielding, as the amalgamated surfaces with the aid of the plastic alloy between them, maintain a good conductivity in spite of any slight motion. The plastic alloy can be applied in a number of other ways, one of which is to drill a hole forming a small cup in the rail base in adjacent rail ends, fill these cups with plastic alloy, and bridge the space between them with a short copper bond having its ends projecting down into the cups.

=Resistance of the Track.= The resistance of the return circuit is usually much higher than it should be owing to the bad contact of the bonds. The resistance of rails varies greatly with the proportions of carbon, manganese and phosphorus. The following figures, however, may be regarded as the average.

Weight per Yard. Resistance Single Rail per Mile. 50 .0253 ohms 60 .0211 ” 70 .0180 ” 80 .0159 ” 90 .014 ”

A track laid with continuous rails as in the case of welded joints, would have one-half the resistance given since there are two rails to be considered.

Tests of new unbonded track constructed with rails 60 feet long show that the joints cause an increase of .25 ohms or more per mile.

Several roads in testing bonds consider a bond good when the bond and one foot of the rail over it have a resistance equal to five feet of the solid rail.

=Supplementary Return Feeders.= On some large roads it is necessary to run additional return feeders from the power house to various points on the system, to supplement the conductivity of the rails. Otherwise the track rails near the power house would have to carry all the current, and in some cases there are not enough such lines of track passing the power house to do this properly. Sometimes these feeders are laid underground in troughs; sometimes they are laid bare in the ground, and sometimes on overhead pole lines. When laid in the ground, frequently old rails are used instead of copper or aluminum cables. The old rails are, of course, thoroughly bonded together with bonds giving a conductivity nearly equal to that of the unbroken rail.

FEEDER SYSTEMS.

There are two general schemes of direct current feeding in common use. One of these is shown in Fig. 83. Here the trolley wire is continuous and is fed into at different points. The long feeders supplying the more distant portion of the road are larger than those supplying the trolley near by, so as to maintain as nearly as is feasible the same potential the entire length of the line. With such a system of feeding, in order to maintain absolutely the same voltage at all points, it would be necessary to have just one trolley feeder and that feeding into the extreme end of the line farthest from the power station and further to make the resistance per 1,000 ft. of trolley and feeder the same as the resistance per 1,000 ft. of the track return circuit. The plan shown in Fig. 83 evidently does not fully carry out these rather impracticable requirements but is in the nature of a compromise, giving a higher potential near the power station than at distant points but nevertheless much more even potential than if the heaviest feeders were feeding into the trolley near the power house.

The other plan, shown in Fig. 84, divides the trolley wire into sections and feeds each section through a separate feeder which is calculated of such size as to maintain the same voltage on all the sections with the ordinary load.

In calculating a feeder system a certain probable load is assumed at certain points along the line. This load will manifestly depend on the size and number of cars in operation, grades and many local conditions.

The following example will show the method pursued. The figures resulting from the calculations are placed immediately below the sections to which they refer in Fig. 84. The rails are assumed to be 70 pound to the yard. These have a resistance of about .018 ohms per mile. Adding one-sixth for additional resistance of bonds gives .021 and since the track is composed of two rails the resistance of the track will be one-half of this or .0105 ohms per mile.

The maximum drop in any section occurs when the car is farthest from the power house. Each car is assumed to take 50 amperes and the feeders are to be so designed as to allow a 10 per cent or 60 volts drop.

The current in the two miles of track nearest the power house is 150 amperes, in the next section 100 amperes, and in the last section 50 amperes. The drop in each section is as shown. The drop in the trolley which is 00 wire is, in each section, 20.5 volts. Subtracting from 60 volts the drop in the return circuit and trolley, gives the allowable drop in the feeder.

The resistance of each feeder can be calculated, since the current in each one is 50 amperes. The first feeder is one mile long, the second 3 miles and the third 5 miles, and with these figures the feet per ohm can be computed. The size of wire may be obtained by reference to a table of copper wire resistances.

BLOCK SIGNALS FOR ELECTRIC RAILWAYS.

The simplest block signal used by electric roads is a hand-operated one constructed on the principle shown in the diagram Fig. 85. A double throw switch is placed at each terminal of the section of track that is to be protected.

The switches have no central position, the knife blade always making contact with one or the other of the terminals shown. If the lamps are lighted, throwing either one of the switches will put them out. If they are not burning, they will be lighted by throwing either one of the switches.

A motorman on reaching a section of track finding the lamps not burning throws the switch. Lamps now burn in each switch box and show that the section is in use. On arriving at the other terminal of the block the switch is thrown, extinguishing the lights and showing that the block is clear.

Automatic signal systems have been devised on the same principle, in which magnets, operated by contacts made by the passage of the trolley wheel, cause the lamps to be lighted and extinguished automatically.

ELECTROLYSIS.

Much has been said about the possibilities of electrolysis of underground metal by the action of the return current of electric railways, when such railways are operated with grounded circuits, as they usually are. If electric current is passed through a liquid from one metal electrode to another, electrolysis will take place; that is, metal will be deposited on the negative pole, and the positive pole or electrode will be dissolved by becoming oxidized from the action of the oxygen collecting at that pole.

In an electric-railway return circuit, there is necessarily a difference of potential between the rails at outlying parts of the system and the rails and other buried pieces of metal located near the power house. Just what this total difference of potential is, depends on the loss of voltage in the return circuit. Thus, suppose there is 25 volts drop in the return circuit between a certain point on the system and the power station. There is, therefore, a pressure of 25 volts tending to force the current through the moist earth from the rails at distant portions of the line, to the rails, water pipes, and other connected metallic structures located in the earth near the power station. The amount of current that will thus flow to earth in preference to remaining in the rails, depends on the relative resistance of the rails, the earth, and the other paths offered to the current to return to the power house.

To take a very simple case, let us suppose a single-track road, Fig. 86, with a power house at one end, and a parallel line of water pipe on the same street passing the power house. If the positive terminals of the generators are connected to the trolley wire, the current passes, as indicated by the arrows, out over the trolley wire through the cars and to the rails. When it has reached the rails it has the choice of two paths back to the power house. One is through the rails and bonding; the other is through the moist earth to the line of water pipe and back to the power house, leaving the pipe for the rails, at the power house. Should the bonding of the rails be very defective, considerable current might pass through the earth to the water pipe.

Remembering now the principles of electrolysis, we see that the oxidizing action of this flow of current from the rails to the water pipes at the distant portion of the road will tend to destroy the rails, but will not harm the water pipe at that point, as it will tend to deposit metal upon it. When, however, the current arrives at the power house, it must in some way leave this water pipe to get back to the rails, and so to the negative terminals of the generators.

Here we see that there is a chance for electrolysis of the water pipe, because at this point the water pipe forms the positive electrode, which is the one likely to be oxidized and destroyed. This very simple case is taken merely for illustration. In actual practice the conditions are never so simple as this, for there are various pipes located in the ground running in various directions, which complicate the case very much; but we can see from this simple example that the principal place electrolysis of water pipe is to be feared is at points where a large volume of current is leaving the water pipe to take to some other conductor.

As an indication of how much current is likely to be leaving the water pipes at various points, it is customary to measure the voltage between the water pipes and the electric railway track and rails. When this voltage is high, it does not necessarily mean that a large volume of current is leaving the water pipes at the point where these pipes are several volts positive with reference to the rails; but such voltage readings indicate that, if there is a path of sufficiently low resistance through the earth, and if the moisture in the earth is sufficiently impregnated with salts or acids, there will be trouble from an electrolytic action due to a large flow of current. There is obviously no method of measuring exactly the amount of current leaving a water pipe at any given point, since the pipe is buried in the earth. Voltmeter readings between pipes and rails simply serve to give an indication as to where there is likely to be trouble from electrolysis. The danger to underground pipes and other metallic structures from electrolysis has been much overestimated by some people, as the trouble can be overcome by proper care and attention to the return circuit. Trouble from electrolysis, however, is sure to occur unless such care is given.

=Prevention of Electrolysis.= Remedies for electrolysis may be classified under two heads—general and specific. The general remedy is obviously to make the resistance of the circuit through the rails and supplementary return feeders so low that there will be but little tendency for the current to seek other conductors, such as water and gas pipes and the lead covering of underground cables. This remedy consists in heavy bonding, in ample connections, around switches and special work where the bonding is especially liable to injury, and in additional return conductors at points near the power house to supplement the conductivity of the rails.

It is important that all rail bonds be tested at intervals of six months to one year in order that defective bonds may be located and renewed, as a few defective bonds can greatly lower the efficiency of an otherwise low-resistance circuit.

The specific remedy for electrolysis which may be applied to reduce electrolytic action at certain specific points, consists in connecting the water pipe at the point where electrolysis is taking place, with the rail or other conductor to which the current is flowing. Thus, for example, if it is found that a large amount of current is leaving a water pipe and flowing to the rails or to the negative return feeders at the power house, the electrolytic action at this point can obviously be stopped by connecting the water pipe with the rails by means of a low-resistance copper wire or cable, thereby short-circuiting the points between which electrolytic action is taking place. There are certain cases in which it is advisable to adopt such a specific remedy. It should be remembered, however, that a low-resistance connection of this kind, while it reduces electrolysis at points near the power house, is an added inducement to the current to take to the water pipes at points distant from the power house, because of the decrease in resistance of the water-pipe path to the power house resulting from the introduction of the connection between the water pipe and the negative return feeder at the power house. With the water pipes connected to the return feeders in the vicinity of the power house, the current which flows from the rails to the water pipes at points distant from the power house will obviously cause electrolysis of the rails but not of the water pipes, since the current is passing from the earth to the pipe, and the pipe is negative to the earth. In this case the principal danger is that the high resistance of the joints between the lengths of water pipe will cause current to flow through the earth around each joint, as indicated on some of the joints, Fig. 86, and will cause electrolytic action at each joint. It is evident, however, that the conditions of the track circuit and bonding must be very bad if current would flow over a line of water pipe, with its high-resistance joints, in sufficient volume to cause electrolysis, in preference to the rail-return circuit, especially since ordinarily the resistance offered to the flow of current over the water pipes back to the power house must include the resistance of the earth between the tracks and water pipes.

It is usually considered inadvisable to connect tracks and water pipes at points distant from the power house, because of the danger of electrolysis at water-pipe joints, as just explained.

Methods of testing rail bonds in the track will be explained under the head of “Tests.”

POWER SUPPLY AND DISTRIBUTION.

=Direct-Current Feeding.= As already explained, the majority of electric railways are operated on a 500-volt constant-potential direct-current system with a ground return. A constant potential of 450 to 550 volts is maintained between the trolley wire and track. Where the trolley wire is not sufficient, additional feeders are run from the power house and connected to the trolley wire, the number of feeders depending on the distance from the power house and the traffic.

=Booster Feeding.= Boosters are sometimes used on long feeder lines where there is a heavy load only a small portion of the time. These boosters are direct-current dynamos that are connected in series with the feeder upon which the voltage is to be raised above the regular power-house voltage. The booster may be driven either by a small steam engine or by an electric motor. The simplest form of booster is a series-wound dynamo. A booster armature must, of course, be of sufficient current capacity to pass all the current that will be required on its feeder. The voltage yielded by this dynamo, plus the power-station voltage, is the voltage of the boosted feeder as it leaves the power house. Supposing that a series-wound booster will give 125 volts at full load; it is obvious that being series-wound it will give no voltage at no load. The voltage will increase approximately as the load on the feeder increases; and since the drop in voltage on the feeder for which the booster is to compensate also varies with the load, the action of the booster is simply to add sufficient voltage to its feeder at any instant to compensate for the line loss upon that feeder and to maintain approximately constant potential at the far end of the feeder. Boosters raising the power-station voltage of a feeder more than 250 volts above the normal power-station voltage, are not common, though cases are on record where a feeder has been boosted as high as 1,100 volts above the power-station voltage. Since all the power used in driving a booster is wasted in line loss, this method of feeding is not economical; but where used only a few days out of the year it is sometimes to be preferred to a heavy investment in feeders. The investment in feeders might involve more interest charges than the cost of power wasted in booster feeding would amount to.

=Alternating-Current Transmission.= High-tension alternating-current transmission _to_ substations, with direct-current distribution _from_ substations, is extensively used on long interurban roads, and on large city street-railway systems where power is to be distributed over a wide area. In such cases the power house is equipped with alternating-current dynamos supplying high-tension three-phase alternating current to high-tension transmission lines or feeders. These high-tension feeders are taken to substations located at various points on the road, where the voltage is reduced by step-down transformers; and these transformers supply current to operate rotary converters, which convert from alternating to direct current for use on the trolley.

The advantage of this system of high-tension distribution is that, owing to the high transmission voltage, there is but a small loss in the high-tension lines, which lines can be made very small, and will thus involve but little copper investment. The substations can be located at frequent intervals, so that the distance the 500-volt direct-current must be conducted to supply the cars is not great. Current from one power house can thus be distributed over a very large system in cases where, if the 500-volt direct-current system of distribution were used, the cost of feeders for distributing such a low-voltage current would be prohibitive. Were the alternating-current high-tension scheme of distribution not used, it would be necessary to have a number of small power houses at various points on the system instead of one large power house. The cost of operation of several small power plants per kilowatt output, is likely to be much greater than that of one large power plant. The first cost of the alternating-current distributing system, including power house and substations, is likely to be considerably higher than would be the cost of a number of small power houses; but in cases where alternating-current distribution has been installed, it has been figured that the cost of operation of the central power house with alternating-current distribution would be sufficiently low as compared with several small ones to pay more than the interest on this extra investment.

=A System of Distribution for an Interurban Railway.= The typical features of a high tension system of distribution for an extensive interurban railway system are shown in Fig. 87, which represents the electrical transmission and distribution system of the Indiana Union Traction Company. The central power station at Anderson feeds into thirteen rotary converter substations from 7 to 65 miles distant from the power house. The substations east of Indianapolis are fed at 16,000 volts and are placed about 11 miles apart. The substations due north of Indianapolis are located at intervals of about 17 miles and are fed at 30,000 volts.

The power station at Anderson has a total capacity of 5,000 K. W. The substations vary in capacity from 250 to 1,500 K. W.

=Efficiency of Transmission Systems.= The average efficiency of a high tension transmission system for a certain interurban electric railway system are given below. Current was generated at 380 volts. The step-up transformers raised it to a potential of 16,000 volts at which pressure it was transmitted to eight substations at distances from 10 to 40 miles from the power station. It was then stepped down to 380 volts and converted to direct current by a rotary converter. The tests extended over a period of three days. The efficiency of the step-up transformers was 95 per cent; of the high tension line 92.9 per cent; of the step-down transformers 95 per cent; and of the rotary converters 88 per cent; giving a total efficiency of the transmission system of 73.5 per cent.

=Power House Location.= A power house is usually located where coal and water supply can be cheaply obtained. For this reason it is placed either on some line of railroad or where coal can be taken to it over the electric railway.

As it is always desirable to operate the engines in connection with condensers, on account of the saving in fuel, which is approximately 20 per cent with condensers, power stations are located, when possible, near rivers and ponds from which a large supply of cold water for condensation of exhaust steam can be obtained. Where no such natural water supply is available, it has become customary to provide means for artificially cooling a sufficiently large supply of water for condensation. One method is to erect a number of towers, so constructed that the water when pumped to the top will fall through a structure that breaks the water up into fine spray as it falls, thus allowing it to cool by evaporation so that it can be used again for the condensers when it arrives at the bottom of the tower. Where more room is available, ponds are sometimes excavated near the power house, and the water is made to flow back and forth through a series of troughs located above the pond, and it is thus cooled.

Where a power station is of the direct-current type, operating at 500 to 600 volts, it is desirable to have it as near the center of electrical distribution as possible, in order to keep down the amount of investment in the feed wire; but it is more important to have it located near a cheap coal and water supply than exactly at the center of distribution.

It is also desirable to have the station located where there is room for coal storage, on account of the chances for interruption of the coal supply by strikes, railroad blockades, and other causes beyond the company’s control. The continuity of the coal supply is also another argument against placing the station where dependence must be placed upon wagons or inadequate railroad facilities.

Coal handling, after the coal has reached the station, is done by hand in the smaller power stations; but in larger power stations it has come to be the general practice to do as much of the handling as possible by means of automatic coal conveyors. The most elaborate power stations have means for dumping coal from cars into hoppers, from which it is conveyed by an endless chain provided with buckets, called a _coal conveyor_, to storage bins. Coal conveyors also take the coal from the storage bins, and deposit it in the hoppers of mechanical stokers in front of the boilers. Ashes are conveyed from under the boilers by the same kind of conveyors, and are dumped into hoppers, whence they are drawn into cars or wagons to be hauled away. The coal, having been deposited in hoppers at the boiler front, is automatically fed into the furnaces by automatic stokers. One type of automatic stoker in common use is of the chain-grate or link-belt type, which is constructed like an endless sprocket chain, with links composed of heavy cast-iron blocks that serve as grate bars. This link belt or chain is kept in constant, slow motion by a small stoker engine or motor which operates all the stokers of a line of boilers. The coal is fed from the hopper on to the chain grate, and the chain is slowly moved under the boilers. As the coal on that part of the grate under the boilers is on fire, the fresh coal as it enters the furnaces is soon ignited. The grate is run at such a rate, and the thickness of the coal is so adjusted, that the coal is burned to an ash by the time it has traveled to the back of the furnace. There the grate turns down over a sprocket wheel, and the ashes are dumped into the ash pit as the grate revolves.

The boilers in most common use in large American electric-railway power houses are of the water-tube type, in which water is contained inside of a bank of tubes, the ends of these tubes being connected to drums or headers. The horizontal return-tubular type of boiler is used in many of the smaller power stations, and vertical boilers are also in use.

The engines in the larger and more economical stations are generally of the Corliss compound-condensing type, running at speeds of from 60 to 120 revolutions per minute, according to the size of the unit. The smaller the unit, the higher the speed. In the smaller and older stations, simple Corliss engines belted to generators are frequently found, and high-speed engines also are used. It is the almost universal custom now, to place the generator directly on the engine shaft, making a direct-connected unit.

Steam turbines, in which the steam acts in jets against the blades of a turbine wheel, are beginning to come into use at the present time. These turbines rotate at very high speed, the largest and slowest speed-units running 600 r.p.m., and others at higher rates. As the output of any generator varies directly according to its speed, a very much smaller generator can be used when coupled to a high-speed steam turbine, to obtain a given output, than if the generator must be coupled to a Corliss steam engine which revolves at very low speed. The economy of the steam turbine at full load is about that of a compound-condensing Corliss engine, but is better on light loads than the engine. The turbine requires less building space and a much less expensive foundation.

Railway generators or dynamos for direct current are usually built with compound-wound fields, so that, as the load increases, they will automatically raise the voltage at their terminals to compensate for the drop in the feeders and to maintain a constant potential at the cars. Thus, if the line loss on a system is 10 per cent, or 50 volts at full load, the generators will be provided with shunt fields of sufficient strength to give 500 volts at no load, and with series field coils which will add to the field strength enough to give 550 volts at full load. The amount of “compounding”—which is the term applied to this method of increasing voltage—may be any amount within reasonable limits. The pressure maintained at different companies’ electric-railway power houses varies, but is usually between 500 and 600 volts.

=Alternating-Current Generators.= Alternating-current generators used for generating alternating current to be distributed at high tension, are generally constructed to give a three-phase current at 25 cycles per second. The voltage of these alternating-current generators is sometimes the voltage at which the power is to be transmitted, if the distances are not too great. A number of stations have alternating-current generators giving 6,600 volts at their terminals, which is a voltage well adapted to high-tension distribution within the limits of a large city. However, generators giving 11,000 volts at their terminals are now becoming common. For higher voltages than this, it is considered necessary to use step-up transformers, in order to raise the voltage to the proper pressure for transmission over long distances. In such cases there is no object in having a high generator voltage. At such stations the voltage of the generators adopted may be anything desired, and it varies according to the ideas of the constructing engineer. Voltages of 400, 1,000, and 2,300 are among those in most common use.

=Double-Current Generators.= Double-current generators are sometimes used, which generators will give direct current at a commutator at one end of the armature for use on a 500-volt direct-current distribution system supplying the trolley direct. The other end of the armature has collector rings from which the three-phase alternating current is obtained, which can be taken to step-up transformers and raised to a sufficient pressure, for high-tension transmission to substations at distant parts of the road. The same generator can therefore be used on both the direct-current and the high-tension alternating-current distribution.

=General Plan of Power Stations.= The general plan of an electric-railway power station is usually such that the building can be extended and more boilers, engines and generators added without disturbing the symmetrical design of the station. Thus, the boilers and engines are placed as in Fig. 88, in parallel rows, although almost invariably in different rooms separated by a fire wall. By adding to the row of engines and to the row of boilers, the station capacity can be increased. Other arrangements are sometimes required by circumstances; but this is the most common arrangement and gives the greatest capacity with the minimum amount of steam piping. Large stations are sometimes constructed with a boiler room of several floors and with boilers on each floor, in order to save ground space and bring the boilers near to the large engine units so that there will not be an excessive amount of steam piping.

=Switchboards.= Direct-current stations have switchboards, which may be considered under two general classes—_generator boards_ and _feeder boards_. Each board consists of panels.

=Generator D. C. Panels.= The generator panel usually contains an automatic circuit breaker which will open the main circuit to the generator in case of an overload due to a short circuit. These circuit breakers consist of a coil in the main circuit, which acts upon a solenoid. When the current in the coil exceeds a certain amount, the solenoid is drawn in, and a trigger is tripped which allows the circuit breaker to fly open under the pressure of a spring. In the General Electric circuit breaker, the main contact is made by heavy copper jaws, but the last breaking of the contact is made between points which are under the influence of a magnetic field. This magnetic field blows out the heavy arc that would otherwise be established. On the I-T-E, the Westinghouse and most other types of circuit breaker, the breaking of the contact takes place between carbon points, which are not so readily destroyed by an arc as are copper contacts, and which are more cheaply renewed. The main contact through the circuit breaker, in either type, is made between copper jaws of sufficient cross-section for carrying the current without heating. These jaws open before the current is finally broken by the smaller contacts which take the final arc.

In Fig. 89_a_ is seen a General Electric circuit breaker with the magnetic blow-out coils at the top, the solenoid at the left, and the handle for resetting the circuit breaker at the bottom. The small handle for tripping the circuit breaker, when it is desired to open the circuit by hand, is shown just under the solenoid.

An I-T-E circuit breaker is shown in Fig. 89_b_. This is of the type previously mentioned, in which the break occurs between carbon contacts and there is no magnetic blow-out.

In addition to the circuit breaker there is usually an ammeter, to indicate the current passing from the generator; and a rheostat handle, geared to a rheostat back of the board, for cutting in and out more or less resistance in the shunt field coils of the generator so as to reduce or raise the voltage. There is a small switch for opening and closing the circuit through the shunt field coils.

The main leads from the generator pass through two single-pole quick-break knife switches. The most recent practice is to have the switches on the switchboard in only the positive and negative leads from the generator, leaving connection to the equalizer to be made by a switch located on or near the generator. However, all three leads may be taken to the switchboard, and a three-pole knife switch may be used instead of the positive and negative switches spoken of.

In Fig. 90 is given a simple diagram of the general relative connection of generators and feeders in a direct-current railway power station. It is seen that the generators are connected in parallel across the positive and negative bus bar. There is a third bus bar—called an “equalizing bus”—which connects in parallel the series coils of all the generator fields. The object of this equalizer is to prevent the weakening of the series field of any one generator, so as to allow it to take current and to act as a motor instead of as a generator.

=Starting Up a Generator.= Suppose that a new generator is to be started up and connected to the bus bars in addition to others already in operation. The engine of that generator is first brought up to speed. The switch controlling the shunt field circuit is then closed, causing current to flow through the shunt fields; and the generator begins to “build up,” its voltage gradually rising until it approximates that upon the bus bars. Before the generator is thrown in parallel with the others by connecting it with the bus bars, it is important that its voltage be nearly the same as that of the bus bars. Otherwise, when connected to the bus bars, it might take more than its share of the load; while, on the other hand, if its voltage were too low, it might act as a motor, taking current from the bus bars. The voltage of the bus bars in a railway station is constantly fluctuating, owing to the varying load and to the fact that generators are often compounded, as before mentioned, in order to compensate for the line loss.

In order that the voltage of the generator to be thrown in shall vary in accordance with the bus bar voltage, the next step in the operation is to close the positive switch, assuming that the equalizer switch on the generator has already been closed. This throws the series field of the new generator in parallel with the series fields of the other generators. The voltage of the new generator will therefore vary just as the voltage on the bus bars; and, by adjusting the resistance of the shunt field, this voltage can be adjusted so as to be the same as that on the bus bars. The voltages on the bus bars and on the new generator are measured usually by a large voltmeter on a bracket at the end of the generator switchboard. By means of a voltmeter plug or of a push button on the generator panel, the voltmeter can be connected either to the bus bars or to the new generator. When the two voltages are the same, the negative switch of the new generator can be closed, and it will operate in parallel with the other generators, taking its share of the load. If the attendant sees that any generator is not taking its share, he can raise its voltage by cutting out some of the resistance in series with its shunt field, and this makes that generator take more load.

=Feeder Panel.= The feeder panel is simpler than the generator panel, since it usually handles only the positive side of the circuit. Frequently two feeders are run on a single panel side by side. The feeder panel has an automatic circuit breaker, an ammeter for indicating the current on that feeder, and a single-pole switch for connecting the feeder to the bus bar. All generators feed into a common set of bus bars; and the positive bus bar continues back of the feeder panels so that all feeders can draw current from the bus bars. Fig. 91 shows a railway switchboard with 7 feeder panels at the right; 4 generator panels at the left; and, in the middle, a panel with an ammeter and recording wattmeter for measuring total output.

In some stations two and even three sets of bus bars are used, as it may be desired to operate different parts of the system at different voltages or to feed a higher voltage to the longer lines than to those near the station. In such a case double-throw switches are provided for connecting feeders and generators to either set of bus bars.

=Alternating-Current Switchboards.= In an alternating-current station, generator switchboards are radically different from those in a direct-current station. Practice in alternating-current generator switchboards has not yet been so fully standardized and is not so uniform as in direct-current railway switchboards. There is always, however, a three-pole main switch for opening and closing the main three wires from the three-phase generator. Automatic circuit breakers are usually provided, as well as indicating ammeters and wattmeters to show the output.

Indicating wattmeters, recording the number of watt hours passing through them, are frequently used both on alternating and direct-current generator panels.

A station usually has what is called a “total load” panel, which has a recording wattmeter measuring the total output of the station in kilowatt hours. This panel also has an ammeter indicating the total station load.

=High-Tension Oil Switches.= Alternating-current generators for high voltages usually have oil switches to interrupt the main circuit, that is, switches in which the contact is made and broken under oil. These switches have been found very efficient in preventing the formation of a destructive arc upon the opening of a high-voltage circuit, on circuits up to 60,000 volts. Some of the larger oil switches are operated by electric motors or solenoids. The machine-type oil switch of the General Electric Company has the motive power for operating the switches, stored up in a spring. The spring is wound up by a small electric motor. This motor operates every time the switch is opened or closed, and winds up the spring enough to compensate for the amount it was unwound in operating the switch. Each circuit is broken under oil in a long tube, and these tubes are mounted in individual cells, each cell being separated from the next by a masonry wall so that there can be no flashing across from one leg of the circuit to another in case of any defect in the switch. All the high-tension wiring to and from such switches, is taken either in lead-covered cables, or on bus bars separated from each other by masonry walls to prevent the spread of short circuits. These precautions are necessary because of the great length of arc that may be established between adjacent high-tension conductors.

Where alternating-current generators of low voltage are used in connection with step-up transformers, one practice is to have the switches for each generator directly in the generator leads, between the generators and the step-up transformers, in the low-voltage circuit.

Another practice which has recently been introduced, is to consider each generator with its step-up transformers as a unit and to connect the generator permanently with its bank of transformers, and to control this unit by a single three-pole machine-operated oil switch. In this case there are no switchboard switches between generators and transformers, and this simplifies the switchboard considerably. There must be switches on the high-tension side of the transformers in any event. The switchboard for rotary converters in the substations is, of course, a combination of alternating and direct-current apparatus. The direct-current ends of the rotary converters are treated almost exactly like direct-current railway generators; and their switchboard panels are similarly equipped, except that usually there is a rheostat that can be connected in series with the armature whereby a rotary converter can be brought up to speed from a state of rest by connecting it with the direct-current bus bars of the substation.

The alternating-current end of the rotary converter is supplied through switches in the alternating-current leads from the step-down transformers. A rotary converter can be started from a state of rest by connecting it to the alternating-current leads through the medium of compensating coils which reduce the voltage. A very heavy current is required to do this, as the motor thus starts as a very inefficient induction motor with a very low power factor.

There are usually but two direct-current feeder panels in a substation of an interurban electric road. One of these feeders is to supply the trolley or third rail extending in one direction from the substation, and the other feeds that extending in the other direction from the substation. The trolley or third rail has a section insulator directly at the substation. When both feeders are connected to the bus bars, it is evident that this section insulator is short-circuited through the medium of the substation bus bars, every substation on the line being connected in this way, as indicated in Fig. 92. It is seen that, should a short circuit occur on any section, it would open the circuit breakers at the substations at both ends, and that section would not interfere with the balance of the road. At the same time, when the road is in normal operation and there is an unusually heavy load between any two substations, the other substations along the line can help out those nearest to the load by feeding through the bus bars of the nearest substation. The high-tension apparatus at a substation consists usually of a bank of high-tension lightning arresters; high-tension switches, for shutting off the high-tension current; and step-down transformers, for reducing from the high transmission voltage to the 370 volts commonly fed to the alternating-current end of railway rotary converters.

=Storage Batteries in Stations.= Storage batteries are frequently used both in substations and in direct-current power stations. They may be connected directly across the line and allowed to “float,” as it is termed; or they may be used in connection with storage-battery boosters, which will cause the storage battery to take the fluctuations in the load and to give a constant load on the rotary converters or power station. The action of storage-battery boosters which cause the storage battery to be charged automatically at light loads and to discharge and assist the station at heavy loads, is explained in the paper on “Storage Batteries.”

ALTERNATING-CURRENT SYSTEMS.

So far this paper has been devoted almost entirely to electric railway systems employing 500-volt direct-current motors on the cars, since this is the system almost universally employed on electric railways at the present time. There are, however, several systems employing alternating-current motors on cars, which have already been used experimentally and to some extent commercially. Some of these give promise of coming into extensive use.

=Three-Phase Motors.= On several roads in Europe three-phase induction motors are employed. These induction motors are operated by three-phase alternating current taken direct from the trolley wires. As three conductors are necessary, two trolley wires are used, with the rails as the third conductor. The two principal objections to the system are the necessity of two trolley wires, and the fact that the induction motor operates very much like a direct-current shunt motor in that it is a constant-speed motor and not adapted to variable-speed work. The power factor is low in starting; that is, a great volume of current is taken, although, owing to the voltage and the current not being in phase, the actual energy consumed is small.

=Single-Phase Motors.= The Westinghouse Electric & Manufacturing Company has brought out a railway motor adapted to operate on single-phase alternating-current circuits. This motor is very similar in construction to the ordinary series-wound 500-volt direct-current railway motor. It has, however, more field poles than the ordinary direct-current motor; and the pole pieces are laminated to avoid heating of the iron by eddy currents caused by the influence of the alternating current. There are also other special features in the design that reduce the sparking at the commutator, which sparking was for several years the greatest obstacle to the use of alternating-current motors of this kind. In the Westinghouse system the current is taken from the trolley wire at high potential, and is reduced by an auto-transformer on the car. This auto-transformer is connected with an induction regulator so arranged that a low voltage can be supplied to the motor in starting or for slow running, and this voltage increased to increase the speed. There is thus no need to reduce the trolley voltage by wasting part of it in a rheostat, as is the case with direct-current motors; and the efficiency during acceleration is, therefore, higher with this alternating system than with the direct current. Several other single-phase railway motors are also being worked out at the present time, including that of the General Electric Company.

=Alternating-Current Motor Advantages.= There are two great advantages secured by the use of an alternating-current railway motor. The first is a reduction in investment and operating expenses by doing away with substations containing rotary converters. Such substations are necessary on long lines of railway operating with direct-current motors. The second advantage is that, owing to the fact that a high tension current can be used on the trolley wire and reduced by a transformer on the car, the difficulties of collecting a large amount of energy from a trolley wire are much reduced.

First, in regard to the substations, it will be seen that with the alternating-current motor system, high-tension current can be conducted from the power house to substations along the line which contain nothing but static transformers. Since these transformers have no revolving parts they do not require the constant attendance that a rotary converter does. Furthermore, the investment in rotary converters is entirely dispensed with, and this makes a considerable reduction in the total cost of the distribution plant. With the alternating-current system, current is fed direct to the trolley wire from the secondary terminals of the transformers at the substations.

As regards the advantages of carrying a high voltage on the trolley wire, it will readily be seen that, since the amount of power, or the watts required by a car, is equal to the product of the voltage and current, an increase in the voltage reduces the volume of current necessary. By having high voltage on the trolley wire, even a large car can be operated with a small volume of current, and this current can be taken through an ordinary trolley wheel without difficulty. Where 500 volts is the pressure used on the trolley wire, there is considerable flashing and burning of trolley wheel and wire when large cars and locomotives are run, owing to the heavy current conducted; and this has been one of the principal reasons for the adoption of the third rail instead of the trolley on certain roads. Even with the third rail, the volume of current that must be conducted to large electric locomotives involves some difficulties in the way of heated contact shoes and considerable loss of energy. The use of high voltage on the trolley wire, with transformers on the car to reduce the voltage to a safe pressure for use on the motors, overcomes many of the difficulties that would otherwise be found in the use of electricity for heavy railroad work.

OPERATION.

=Power Taken by Cars.= The amount of power required in the practical operation of a car depends upon so many variable elements that many of the calculations sometimes given for determining the power required by a car are of little value. The theoretical horsepower required to maintain a car at a certain speed on a level, is evidently the tractive effort in pounds multiplied by the speed in feet per minute and divided by 33,000. What the tractive effort per ton of car will be, depends on the condition of the rail and on several other uncertain factors. For street-railway motor cars, 20 pounds per ton is the usual tractive effort assumed as necessary. A calculation of this kind, however, takes no account of the losses in the motors and gears, nor of the fact that the greater part of the power required to propel a street car in practical service is used in accelerating the car from a state of rest to full speed. In interurban service, of course, the power required in acceleration is not so great a proportion of the whole.

The safest figures to use in engineering calculations as to the amount of power required, are those taken from actual results obtained in everyday commercial service. The power required by an eight-ton car in service in a large city like Chicago, is in the neighborhood of one kilowatt hour per car-mile run. On outlying lines this figure may be reduced to .7 kilowatt hour, and in the down-town districts may run up to 1.5 kilowatt hours per car mile. Double-truck cars in city service, weighing from 20 to 25 tons, take from 2½ to 4 kilowatt hours per car mile at the power station. Interurban cars around Detroit, weighing about 32 tons, in interurban service, making 25 miles per hour, including stops, in level country, and geared to 43 miles per hour, take about 3 kilowatt hours per car mile at the power station. However, interurban railway conditions are extremely variable.

The reports of several Indiana electric railways show an average power consumption of 1.48 kilowatt hours per car mile for city cars and 5.18 kilowatt hours for interurban cars, including line and distribution losses.

An interurban car weighing 31½ tons and equipped with two 150 horsepower motors, on a test run of 50 miles at an average speed of 39 miles per hour consumed 2.20 kilowatt hours per car mile. This car made 18 stops. A similar car under the same conditions made the same run at an average speed of 26 miles per hour with 44 stops, consumed 2.44 kilowatt hours and a third car, making 12 stops and at a speed of 33 miles per hour, consumed 2.10 kilowatt hours per car mile. These individual car test figures are from measurements taken at the car and do not include line losses.

=Road Tests of Electric Cars.= Of late considerable attention has been given to making road tests of electric cars. The results of the tests are usually plotted in the form shown in Fig. 93. Time is plotted horizontally in seconds, while volts, amperes, speed and per cent grade are plotted vertically. The diagram referred to is the result of a continuous run of 6 minutes of a 32.5 ton car equipped with two motors. The line voltage, motor consumption and other readings may be obtained for any instant of time. The acceleration in miles per hour per second may be obtained by noting the increase in height of the speed curve in one second. In making such a test the necessary instruments, voltmeters, ammeters, wattmeters and speed indicators are mounted direct on the car and are read at intervals of a few seconds.

The curve of motor consumption gives an idea of the abnormal current required to get the car under headway.

=Economy in Power.= As already stated, a large part of the energy taken by a car in city service is used in accelerating the car. Much of this energy must be destroyed or used up in the brake shoes at the next stop. The energy stored up in a car by process of acceleration is represented by the formula: Mass in lbs. × (Velocity in ft. per sec.)² Energy in ft. lbs. = ——————————————————————————————————————————, which 2 is the formula for kinetic or live energy, the derivation of which is found in any Instruction Paper on Mechanics. In performing any given schedule with frequent stops, the more rapid the acceleration the lower the maximum speed required to make the schedule, and the less the energy required in acceleration. For city street and elevated service, therefore, rapid acceleration and low maximum speeds are desirable because not only more economical but safer.

For economical operation with any given equipment and schedule, it is important to use as much of the energy stored up in the car as possible, before wasting it by applying the brakes. Motors are built of a size to yield the large horsepower required in acceleration, and consequently are lightly loaded when operating the car at maximum speed. To economize in power, current should be shut off as soon as possible after the car has attained full speed; and the car should be allowed to drift without current as long as possible before the brakes are applied. In this way the energy stored in the car will propel it at nearly maximum speed for a considerable distance between stops; there will be the smallest possible waste of energy in the brake shoes; and the losses of energy which take place when the current is in the motors will be prevented as far as possible. Practical tests as well as theoretical calculations show a possibility of very material saving in energy in the operation of an electric railway car or train, by the observance of this simple rule of drifting as much as possible and using the brakes as little as possible. Whatever energy is used up in the brake shoes is necessarily wasted. The smaller this waste can be kept while performing a given service, the greater the economy secured.

=Cost of Power.= The reports of 85 per cent of the railway power generating stations in Indiana show the average cost at the station per kilowatt hour to be .755 cent. This was divided as follows: Fuel .526 cents, labor .158 cents, lubricants and miscellaneous supplies .032 cents, repairs .039 cents. The lowest cost reported was .505 cents.

During 1901 the average cost of power generated at the power house of the Indiana Union Traction Company was .443 cents per kilowatt hour at the switchboard. Distributed from the substations it was .765 cents per kilowatt hour. Natural gas was used for fuel. On occasions when this failed, coal at $1.50 per ton was burned.

=Sliding and Spinning Wheels.= In accelerating a car, however, there is no economy in turning on current so rapidly as to spin the wheels. As mentioned in the section on “Brakes,” the tractive effort between wheels and rails falls off about two-thirds when the wheels begin to slip; and this slipping of wheels, therefore, reduces the chance of securing the acceleration which is possible. For the same reason, in making emergency stops either by the use of brakes or by reversing the motors, care should be taken not to slide the wheels, as by so doing the time required to stop the car is much increased.

In the ordinary straight air-brake equipment used on heavy electric cars, there is much higher pressure carried in the storage reservoir than it is permissible to turn into the brake cylinder, since, if the full pressure were turned into the brake cylinder, it would result in sliding of the wheels—which, it has just been shown, is something to be avoided, not only on account of making flat spots on the wheels, but also because of the reduction in the braking force as soon as the wheels begin to slide. An experienced motorman can tell from the feeling of the car when the wheels are sliding, and will instantly release the brake sufficiently to allow the wheels to begin to revolve as soon as he notices that this has taken place.

The friction between brake shoes and car wheels decreases as the speed increases. A certain pressure applied to the brake shoes upon a car running 50 miles per hour, therefore, exerts much less retarding force than the same pressure at ten miles per hour. In order to give the same braking or retarding force at higher speeds, the brakes must be applied harder than at the lower speeds. If they are applied at the maximum pressure possible without sliding the wheels at higher speeds, it is evident that this pressure must be reduced as the speed of the car is reduced, or the wheels will be “skidded.” In the Westinghouse high-speed automatic air brake used on steam roads, this reduction of pressure is automatically accomplished.

TESTING FOR FAULTS.

=Bond Testing.= It is important to test the conductivity of rail bonds from time to time in order to determine if they have deteriorated so as to reduce their conductivity and introduce an unnecessary amount of resistance into the return circuits. One way of doing this is to measure the drop in potential over a bonded joint as compared with the drop in potential of an equal length of unbroken rail. To do this, an apparatus is employed whereby simultaneous contact will be made bridging three or more feet of rail and an equal length of rail including the bonded joint, as shown in Fig. 94, which illustrates the connections of a common form of apparatus where two milli-voltmeters are employed that measure the drop in voltage of the bonded and unbonded rail simultaneously. If the current flowing through the rail due to the operation of the cars were constant, of course one milli-voltmeter might be used, being connected first to one circuit and then to the other. The current in the rail, however, fluctuates rapidly, so that two instruments are necessary for rapid work. The resistance of the bonded joint is usually considerably more than that of the unbroken rail, and the milli-voltmeter used to bridge the joint consequently need not be so sensitive as that bridging the unbroken rail.

In another form of apparatus, a telephone receiver is used instead of the milli-voltmeter, the resistance of a long unbroken rail being balanced against that of the bonded joint, as in a Wheatstone bridge, until, upon closing the circuit, these two resistances when balanced give no sound in the telephone receiver.

Bond tests of this kind can be made with satisfaction only when a considerable volume of current is flowing through the rails at the time of the test, because the drop in voltage is dependent on the current flowing, and in any event is small. It has sometimes been found necessary or advisable to fit up a testing car equipped with a rheostat which will itself use a considerable volume of current, so as to give a current in the rail which will give an appreciable drop of potential across a bonded joint. Some of the latest forms of testing cars carry motor generators which will pass a large current of known value through a bonded joint, and so cause a drop of potential across the joint large enough to be easily measured.

=Motor-Coil Testing.= Testing for faults in the motor armature and field coils is done in a great variety of ways. The resistance of these coils can be measured by means of a Wheatstone bridge employing a telephone receiver in place of the galvanometer used in such bridges in laboratory practice; but other less delicate tests are also in use.

Another method is to pass a known current through the coil to be tested and to measure the drop in the voltage between the terminals of the coil, the voltage divided by the current equaling the resistance.

A simple method, and one which involves no delicate instruments, has lately been introduced into railway shop practice very successfully. This is known as the _transformer test_ for short-circuited coils. It requires an alternating current which can easily be supplied either by a regular motor generator or by putting collecting rings onto an ordinary direct-current motor and connecting these rings to bars of opposite polarity on the commutator.

The method of testing for short-circuited armature coils employed in the shops of the St. Louis Transit Company is indicated in diagram in Fig. 95. A core built up of soft laminated iron is wound with 28 turns of No. 6 copper wire. This coil is supplied with alternating current from a 110-volt circuit. The core has pole pieces made to fit the surface of the armature. When one side of a short-circuited coil in the armature is brought between the pole pieces of this testing transformer, as in Fig. 95, the short-circuited armature coil becomes like the short-circuited secondary of a transformer, and a large current will flow in it. This current will in time manifest itself by heating the coil; but it is not necessary to wait for this, as a piece of iron held over that side of the coil not enclosed between the pole pieces, as indicated in. Fig. 95, will be attracted to the face of the armature if held directly over the coil, but will be attracted at no other point.

This testing can be done very rapidly, and does not require delicate instruments or skilled operators.

Tests for short circuits in field coils can be made in a similar manner, by placing the coils on a core which is magnetized by alternating current. The presence of a short circuit, even of one convolution of a field coil, will be apparent from the increase in the alternating current required to magnetize the core upon which the field coil is being tested. The insulation resistance of armatures and fields is frequently tested by means of alternating current, about 2,000 volts being the common testing voltage for 500-volt motor coils. One terminal of the testing circuit is connected to the frame of the motor, and the other to its windings. Any weakness in the insulation insufficient to withstand 2,000 volts will, of course, be broken down by this test. Alternating current is generally used for such tests because it is usually more easily obtained at the proper voltage, as it is a simple matter to put in an alternating transformer which will give any desired voltage and which can be controlled by a primary circuit of low voltage.

Open circuits in the armature can be easily detected by placing the armature in a frame so that it can be rotated, the frame being provided with brushes resting 90° apart on the commutator. If either an alternating or direct current be passed through the armature by means of these brushes, and the armature be rotated by hand, a flash will occur when the open-circuited coils pass under the brushes. A large current should be used.

The tests just mentioned are among the best of the methods used by electric-railway companies for systematic work in the location of certain classes of faults. A large number of other methods of testing have also been evolved.

The following are some of the most common faults experienced with electric railway car equipments:

=Grounds.= As one side of the circuit is grounded, any accidental leakage of current from the car wiring or the motors to ground will cause a partial short circuit. Such a ground on a motor will manifest itself by blowing the fuse or opening the circuit breaker whenever current is turned into the motor. In case the fuse blows when the trolley is placed on the wire and the controller is off, it is a sign that there is a ground somewhere in the car wiring outside of the motors. Moisture and the abrasion of wires are the most common causes of grounds in car wiring. In motors, defects are usually due to overheating and the charring of the insulation.

=Burn-Outs.= Burning out of motors is due to two general causes: First, a ground on the motor, which, by causing a partial short circuit, causes an excessive current to flow; second, overloading the motor, which causes a gradual burning or carbonizing of the insulation until it finally breaks down.

Short-circuited field coils having a few of their turns short-circuited, if not promptly discovered, are likely to result in burned-out armatures, as the weakening of the field reduces the counter-electromotive force of the motor, so that an abnormally large current flows through the armatures. Cars with partially short-circuited fields are likely to run above their proper speed, though, if only one motor on a four-motor equipment has defective fields, the motor armature is likely to burn out before the defect is noticed from the increase in speed.

=Defects of Armature Windings.= Defects in armature windings probably cause one-third the maintenance expenses of electrical equipment of cars. Almost all repair shops have men continually employed in repairing them. The most frequent trouble with armatures is through failure of the insulation of the coils and consequent “grounding.” This term is used in connection with armatures and fields and other electrical apparatus where a direct path exists to ground. As the armature core is electrically connected to the ground through its bearings and the motor casing, a break down of the insulation of the coils in the slots permits the current to pass directly to ground. This shunts the current around the fields and an abnormal current flows because of their weakness. The circuit breaker or fuse is placed in circuit to protect the apparatus in such an emergency, but usually before such devices break the circuit, several of the coils of the armature are burned in such a manner as to make their removal necessary. The coils are so wound on top of one another that in order to replace one coil alone, one-fourth of the coils of the armature must be lifted.

With the armature of No. 1 motor grounded the car will not operate and if the resistance points be passed over, the fuse will usually blow. When No. 2 motor is grounded the action of No. 1 motor is not impaired and this latter motor will pull the car until the controller is thrown to the multiple position. But if the motors are thrown in multiple, the path through the ground of No. 2 motor shunts motor No. 1. A study of Fig. 18 will make this evident.

Next to grounding, open circuits are the most serious defects of armatures. These are usually caused by burning in two of the wires in the slot, or where they cross one another in passing to the commutator. Sometimes the connections where the leads are soldered to the commutator become loose.

The effect of an open circuit is shown in Fig. 96. The circuit is open at n. The brushes are on segments _a_ and _d_. By tracing out the winding it will be found that no current flows through the wires marked in heavy lines. Whenever segments _c_ and _d_ are under a brush the coil with the open circuit is bridged by the brush and current flows as in a normal armature. As segment _c_ passes out from under the brush the open circuit interrupts the current in half the armature and a long flaming arc is drawn out.

In Fig. 97 is shown the result of a short circuit between two coils. The short circuit is at _b_, _c_, the two leads coming in contact with each other when they cross. The effect is to short-circuit all of the winding indicated by the heavy lines.

=Mistakes in Winding Armatures.= The armature winder is given very simple rules as to how to wind the armature, but the great number of leads each to be connected to their proper commutator segment sometimes so confuse him that misconnections are made. The effect of getting two leads crossed is shown in Fig. 98. The leads to segments _b_ and _c_ from the right are shown interchanged. This short-circuits the coils shown in heavy lines. The abnormal current resulting in these would usually cause them to burn out.

Fig. 99 shows the results of placing all of the top leads, or all of the bottom leads one segment beyond the proper position. This causes the circuit starting from _a_ and traveling counter clockwise around the armature to return on segment _m_ instead of on segment _b_ as is the case in Fig. 97.

The only result of such connections is to change the direction of rotation of the armature. It may be noticed by comparing the two figures that with the positive brush on segments _a_ the arrows show the currents to be in opposite directions in coils similarly located with reference to the position of the brushes. Some armatures are intended to be wound as in the last case mentioned.

=Sparking at the Commutator.= As railway motors are made to operate, and usually do operate, almost sparklessly, sparking at the brushes may be taken as a sign that something is radically wrong.

The pressure exerted by the spring in the brush holder may not hold the brush firmly against the commutator.

If brushes are burned or broken so that they do not make good contact on the commutator, they should be renewed or should be sandpapered to fit the commutator.

A dirty commutator will cause sparking.

A commutator having uneven surface will cause sparking, and should be polished off or turned down.

Sometimes the mica segments between commutator bars do not wear as fast as the bars and when this is the case, the brushes will be kept from making good contact when the commutator bars are slightly worn. The remedy is to take the armature into the shop, and groove out the mica between the commutator bars for a depth of about ¹⁄₆₄-inch below the commutator surface.

A greenish flash which appears to run around the commutator, accompanied by scoring or burning of the commutator at two points, indicates that there is an open-circuited coil at the points at which the scoring occurs as in Fig. 100.

The magnetic field may be weakened by a short circuit in the field coils, as before explained, and this may give rise to sparking.

Short circuits in the armature may give rise to sparking, but will also be made evident by the jerking motion of the car and the blowing out of the fuse.

=Failure of Car to Start.= The failure of the car to start when the controller is turned on may be due to any of the following causes:

Opening of the circuit breaker at the power house.

Poor contact between the wheels and the rails owing to dirt or to a breaking of the bond wire connections between the rail on which the car is standing and the adjacent track.

One controller may be defective in that one of the contact fingers may not make connection with the drum. In this case try the other controller if there is another one on the car.

The fuse may be blown or the circuit breaker opened. The occurrence of either of these, however, is usually accompanied by a report which leaves little doubt as to the cause of the interruption in current.

The lamp circuit is always at hand for testing the presence of current on the trolley wire or third rail. If the lamps light when the lamp circuit is turned on, it is a tolerably sure sign that any defect is somewhere in the controllers, motors, or fuse boxes, although in case the cars are on a very dirty rail enough current might leak through the dirt to light the lamps, but not sufficient to operate the cars. In such a case, the lamps will immediately go out as soon as the controller is turned on. Ice on the trolley wire or third rail will have the same effect as dirt on the tracks.

LOCATING DEFECTS IN MOTOR AND CONTROLLER WIRING.

Defects in the wirings are those due to (1) open circuits, (2) short circuits. Open circuits make themselves evident by no flow of current, short circuits usually by a blowing of the fuse or opening of the breaker. The point of the short circuit or “ground” can be located roughly by noting on what point the fuse is blown. Accurate location can be made by cutting out the motors, disconnecting, etc., according to directions in the following pages. The tests outlined apply particularly to the K type of controller with two-motor equipment.

OPEN-CIRCUIT TESTS.

No current: On 1st point, Open circuit but not located. On 1st point multiple, Motors most probably O. K. On series-resistance points after trying 1st point multiple, Open circuit outside controller and equipment wiring.

With an open anywhere between trolley and ground no current will flow on the first point. Opens are most likely to occur in the motors and these may be tested first. However, as will be explained later, one open in an armature will not stop the current. To test the motors open the breaker and put the controller on the first point multiple. Then flash the breaker quickly. Current flowing indicates that one or the other of the motors has an open circuit. In the series position this open prevented the flow but in multiple the current flows through the other motor. Which one is at fault can be quickly determined by returning the controller to the off position and cutting out one or the other of the motors by means of the cut-out switch and then trying for current. The car can in any event be run on the remaining motor. On returning to the shop the open can be determined definitely by the use of the lamp bank.

But should no current flow when the breaker is flashed on the 6th point it is reasonable to presume that the motors are O. K. and that the open is elsewhere. The ground for such a supposition is that as there is a path through each motor normally, there would necessarily be an open in each one to stop the current. It is hardly probable that such a coincidence would occur.

After failure to find fault with the motors, doubt as to the resistance may be removed. The controller should be placed on progressive series-resistance points and the breaker flashed on each one. If current is obtained on any point, the open is in the resistance or the resistance lead just behind the one being used. Special care should be used to flash the breaker quickly for otherwise the fuse may be blown.

The tests indicated are sufficient for the motors, controllers and resistance wiring. If no current is obtained on either of them, the trouble is evidently caused by a bad rail contact, ground wire off if both motors are grounded through the same wire, an open in the blow-out coil, at the lightning arrester, circuit breaker or on top of the car.

None of the tests applied locate the open definitely, but this can easily be done in the shop or wherever a lamp bank is at hand. Connect one terminal of the lamp bank to the trolley just behind the circuit breaker and the controller on the 1st point series, then with the other terminal begin at ground and trace backwards up the circuit until the lamps fail to light. The path in a K type of controller is readily traced with the help of Fig. 22.

SHORT-CIRCUIT TESTS.

The location of short-circuits is much more tedious. The blowing of the fuse or opening of the breaker will locate them as shown below. The separate tests can then be followed until location is definite.

These tests it must be kept in mind are more especially adapted to cases on the road or where no facilities for testing are at hand.

Rather than blow fuses as frequently as indicated it would in most cases be better to place a lamp bank across the open circuit breaker and note the flow of the current by the lights.

=Fuse Blows=: I. When overhead is thrown on may be due to: 1. Grounded controller blow-out coil. 2. Grounded trolley wire or cable. 3. Grounded lightning arrester. II. On first point: 1. Grounded resistance near R 1. 2. Grounded controller cylinder. 3. Bridging between the insulated sections of cylinder. III. Near last point series: 1. Grounded resistance near R 3, R 4 and R 5. 2. No. 1 motor grounded. IV. Near last point multiple: 1. No. 2 motor grounded. 2. Bridging between lower sections of cylinder. 3. Armature defective.

CASE I.

=Fuse Blows= when overhead is thrown on: 1. Grounded controller blow-out coil. 2. Grounded trolley wire or cable. 3. Grounded lightning arrester.

The blowing of the fuse immediately on closing the overhead switch or circuit breaker, when the controller is on the off position, indicates that the fault exists somewhere between the overhead and the upper or trolley finger of the controller.

Should the defect occur during a thunderstorm, it may be presumed at once that lightning has grounded the blow-out coil of the controller.

CASE II.

=Fuse Blows= on first point: 1. Grounded resistance near R 1. 2. Grounded controller cylinder. 3. Bridging between sections of cylinder.

When the controller is on the first point all of the wiring of the system with the exception of the ground wire for No. 1 motor is connected with trolley. But a defect in the wiring beyond the resistance will not show itself on the first point by an abnormal rush of current because the resistance of the rheostats is sufficient to prevent any excessive flow of current.

The resistance and leads and the controller cylinder are the only parts to be tested when the fuse blows on the 1st point.

CASE III.

=Fuse Blows= on 3rd or 4th point: 1. Grounded resistance near R 4 or R 5. 2. No. 1 motor grounded.

With either of the above defects the car will most probably refuse to move as the current is led to ground before passing through the motors.

No. 1 motor may be tested by cutting it out of service by means of its cut-out switch. If this removes the ground, the motor is at fault.

CASE IV.

=Fuse Blows= near last point multiple: 1. No. 2 motor grounded. 2. Either armature short-circuited.

The fact that the fuse did not blow on the series positions excludes the resistances and No. 1 motor from investigations for grounds.

Cut out both motors. If the ground still exists the controller is defective. If not, the fault may be located in either one of the motors by cutting out first one and then the other.

ARMATURE TESTS FOR GROUNDS.

With a lamp bank at hand tests for grounded armature can be made as follows:

Throw the reverse on center. Attach one terminal of the lamp bank to the trolley. Put the other terminal on the commutator of the armature to be tested. No current shows the armature O. K. If current flows remove brushes and try again, to be certain that the ground is not in the leads.

FIELD TESTS FOR GROUNDS.

Disconnect field leads and put test point of the lamp bank on one side of the terminals. No current indicates that the fields are O. K.

REVERSED FIELDS.

In placing new fields in the shell it often happens that one or more are wrongly connected. Reversed fields make themselves known by excessive sparking at the brushes in each case.

In Fig. 101 all of the fields are connected correctly. The flow of magnetism is in one pole and out of the adjacent one. Some of the magnetism leaks out of the shell and affects a compass held near the outside. The direction taken by the compass needle in the different positions is shown. The needle should point in opposite directions over adjacent coils and should lie parallel to the shell in positions half way between two coils.

Figure 102 shows the flow of magnetism when one field is reversed. In such a case the compass will take the position shown. The field marked “X” is the one reversed.

With one reversed field a machine will usually operate, as the magnetism in three of the poles is in the normal direction. But an excessive flow of current that has no effect in turning the armature will take place on that side of the armature next to the reversed field.

CAR REPAIR SHOPS.

Every electric railway system has a repair shop in which the cars are overhauled. Hardly two shops are built alike. In those shops where only a few cars are cared for, the work is sometimes all done in one room. The shop plan shown in Fig. 103 was presented to the American Railway Mechanical and Electrical Association by W. D. Wright. It contains the idea upon which the larger shops are now being constructed, having a transfer table between the separate departments on either side. In the general design of shops the blacksmith shop, machine shop and truck shop or equipping shop should be close together as a great deal of heavy material is carried between these departments. The paint shop should be separated as much as possible from the other departments in order that flying dust and dirt be avoided. The wood shop may occupy a position at a considerable distance from the other departments as no heavy material is carried from this shop to them.

The tracks of the motor and truck repair shop are usually provided with pits so that trucks and electrical equipment may be repaired and inspected from below. The tracks in shops are usually about 15 or 16 feet between centers. This gives a clearance of about 6 or 8 feet between cars when adjacent tracks are occupied.

A large portion of the work done in the average shop consists of the repairing of trucks and the motors mounted on them. With the smaller car, especially those with single trucks, much of this work is done from the pit below while the trucks are in position under the cars. In this case the armatures are either removed by letting them down with the lower half of the motor shell by means of a pit jack, or the lower half of the armature shell is swung down by the use of a chain and block placed in the car and the armature rolled out on a board.

The trucks of double truck cars are usually taken out from under the car body when repairs are to be made. In this case the motor leads, the sand box connections and the brake rigging are disconnected and the car body either raised or the trucks lowered from it. Several methods of raising the car body are in use. Where no special apparatus is at hand, this is done by means of jacks, hydraulic or mechanical, placed under the side sills of the car near the end to be raised. Sometimes an overhead crane is employed to lift the car body. A special apparatus to raise the body is employed by the St. Louis Transit Company. This consists of four screw jacks located below the floor of the shop. An I-beam extends over the tops of the two located on the same side of the car. The jacks are motor driven by means of one sprocket chain so that they rise at the same speed. When a car is to be raised it is run on the track between the jacks, bars are placed under the car resting across the I-beams and the jacks raise the car off the trucks. The trucks are then rolled out from under the car and the repairs made.

Sometimes, as has been stated, the trucks are dropped from the car body. In this case the car is so placed that the truck rests on an elevator or section of track that drops to the floor below. After the car is blocked up the trucks are dropped and the repairs made. This method is also used in changing wheels in small shops. The old pair of wheels is dropped by a hand-operated drop section of track. A new pair is then elevated into position. This saves jacking up one end of the car.

THE SINGLE-PHASE ELECTRIC RAILWAY.

In no other line of electrical activity have developments during the last few years been so rapid as in that of electric railway work, and from all indications the limit has not yet been reached.

Until recent years all electric traction has been dependent upon direct current as a motive power. This is due principally to the fact that the series direct-current motor is admirably adapted for such work, and no alternating-current motor had been developed which could be substituted for it. One of the great advantages possessed by the direct-current series motor is its large starting torque, which may be several times greater than that required to propel a car at full speed. This type of motor is also essentially a variable speed machine, and lends itself very well to wide variations in speed control; consequently, for many years, in this country at least, all advance was made along direct-current lines.

The trolley voltage used at first was from 450 to 500 volts, this being supplied directly to the cars by means of a trolley wire, the rails being used for the return circuit. It is evident from the outset that the comparatively low voltage, necessitating as it did a correspondingly large current for a given amount of power, would place a definite limitation on the use of such a system for anything other than purely local distribution. To overcome this difficulty as far as possible, the trolley voltage was gradually raised to 600 or 650. This of course decreased the required current, thus increasing the scope of the system accordingly. The limit of increase of direct-current voltage on the trolley was reached at about this point, and the fact was recognized that some means must be devised for using a still higher voltage, since there are difficulties to increasing the trolley voltage beyond 600 or 700, due to flashing of the motors, which seems to increase directly with the voltage.

It may be mentioned in passing that one prominent electric traction expert has stated that a direct-current trolley voltage of 1500 can be used, but it remains to be proven whether or not he is correct. A very satisfactory solution of the problem for large city street railway systems and long interurban roads, consists in the use of a combination alternating-current direct-current system in which three-phase high tension alternating current is generated and distributed on high tension lines to substations along the road. It is here stepped down by means of transformers, and then changed to direct current by rotary converters, and supplied to the trolley wire as direct current at the usual voltage of say 600. This system has many advantages, as there is but small loss in the high-tension lines, and these lines can be made comparatively small, thus effecting a considerable saving in investment for copper.

The above mentioned system of distribution is very generally used, and has been found quite satisfactory. The substations can be located at frequent intervals, and the distance that the 600-volt current must be conducted to supply the cars is not great. By this means current can be distributed over wide areas with a small loss, where it would be impossible to use the straight direct-current system of distribution.

While, as stated, this furnishes a fairly satisfactory solution of the problem, it is far from perfect, as it necessitates the intervention of the rotary converter substation, in which the investment must be large; and moreover the cost of operation is high, as such a station requires skilled attendance on account of the somewhat intricate nature of the rotary converter. The ideal system, therefore, is one which does away altogether with the use of direct current, the power being generated, distributed, and utilized by the motors, as alternating current.

Three-phase induction motors have been used quite extensively and with considerable success in Europe for many years past. The three-phase motor, however, is not entirely adapted for railway work, since it possesses the characteristics of the shunt rather than of the series motor, being a constant speed, not a variable speed machine. Moreover, two trolley wires are necessary instead of one, and still another disadvantage consists in the low power-factor of the three-phase induction motor at starting.

The recent application of the single-phase alternating current to railway work has opened up a new field, which bids fair to supplant all other forms of distribution to a great extent at least, and it is impossible to predict at the present time just what its limitations may or may not prove to be. This has been made possible by the development of a _practical commercial_ single-phase motor, which permits of the use of alternating current on the trolley wire with all its advantages, and yet sacrifices few, if any, of the advantages of the direct-current series motor on the car.

This motor, which is the latest and most important development in the electric railway field, is of the series commutator type, and does not differ in principle from its direct-current contemporary. It is called the _commutator type single-phase motor_, and is the one type of alternating-current motor which has the same desirable characteristics for railway work as the direct-current series motor.

At first thought it may seem strange that a motor built fundamentally on the same lines as a direct-current machine would operate on an alternating current, as it might appear that the motor would tend to turn first in one direction and then in the opposite direction with no resultant motion. This, however, is not the case, because the direction of rotation of a motor depends upon the relative direction of its field and armature currents. If now the field were maintained in a constant direction and the armature supplied with alternating current, then the tendency would be to rotate first in one direction and then in the other, it is true, but as a matter of fact the alternating current is supplied to the field in series with the armature, so that when the direction of current in the armature changes it also reverses in the field. The result is that the relative direction of current in the field and armature is constant and the motor has, therefore, a tendency to turn continuously in one direction as long as the alternating-current power is supplied.

This being true, the question may arise as to why the single-phase motor was not brought to the front for railway work long ago. The answer is that there were certain inherent difficulties to be overcome, and the development of the single-phase motor has been simply the removal of these difficulties, rather than the design of an entirely new type of machine.

The most serious obstacle to overcome is the sparking at the commutator, due to the fact that when the terminals of a coil are bridged by a brush, the coil acts like the short circuited secondary of a transformer of which the field winding constitutes the primary. Also there is an iron loss due to the alternating magnetic flux through the magnetic circuit; while another objectionable feature is the counter E.M.F. induced in the field coils.

In order that it may overcome these difficulties, to some extent, at least, the single-phase motor presents certain modifications from the direct-current type, in that it has more field poles, and the entire magnetic circuit of field frame, cores, and pole pieces, is carefully laminated. The number of commutator segments is also increased, thus reducing the number of armature turns per coil, and there are special features introduced to prevent sparking, such as compensating windings which neutralize the effect of armature distortion; the use of narrow brushes; a type of armature winding which gives a low reactance per coil; the use of high resistance leads between the armature coils and commutator segments, etc.

The single-phase motor is then a refined and highly perfected type of direct-current motor, and this explains the fact that it will operate on either alternating- or direct-current circuits. In fact some claim that it will operate even more efficiently on direct current than the regulation direct-current motor itself.

The field for which the single-phase motor seems particularly adapted is that of heavy service and interurban work, where it has many distinct advantages, among which may be mentioned the following:

The alternating current on the trolley allows the use of a high voltage and correspondingly smaller current, which reduces the line loss and permits of the use of smaller wire, which of course means a saving in the investment for copper. Moreover, the difficulty of collecting a large current from the trolley wire is overcome. Rotary converter substations are eliminated, being replaced by simple and cheap transformer substations, which require no attendance. The capacity can be easily increased by merely increasing the number of these transformer substations.

The efficiency of speed control is a point particularly worthy of mention. In direct-current speed control, the series-parallel method is used almost exclusively. This consists of putting the motors in series for low speed and in parallel for high speed. This permits of two, and only two, economical running points; the one at full speed, and the other at approximately half speed. All intermediate points must be obtained by the insertion of dead resistance in which the voltage is simply wasted as heat, thus causing a large loss particularly at starting.

With the single-phase motor the current is supplied to the car with a voltage of say 3300. It is then stepped down by means of transformers on the car to the voltage of the motors, which may be 200 or 250 volts. The speed is, of course, dependent upon the voltage applied to the motors, and this voltage is cut down from the maximum, to obtain various gradations, by means of an induction controller, or by taps from an auto-transformer. Thus the motor takes from the trolley only slightly more power than is actually required to operate it at any given speed, instead of taking full voltage from the line and absorbing part of it in dead resistance.

The effect of electrolysis upon neighboring water pipes paralleling an electric road, which is the cause of so much trouble with direct current, is entirely eliminated, as electrolysis evidently will not take place with alternating current.

In connection with this system a sliding contact device or bow trolley has in many cases been substituted with considerable success for the ordinary current collecting device, or trolley wheel, one advantage of this being that the car can be run in either direction without reversing the contact device. Another very satisfactory form of trolley is of the pantograph type with sliding shoe, shown on the New York, New Haven and Hartford locomotive.

A new form of trolley suspension known as the catenary has been developed to meet the demand for more substantial construction necessitated by the high trolley voltage. This consists of a stranded galvanized steel messenger or supporting cable, from which the trolley wire is suspended at intervals of about 10 feet, thus keeping it at a uniform distance above the track.

The multiple-unit system of control can be used in connection with single-phase motors, this being the scheme which has been in use for a long time on elevated and other roads using direct current, whereby several cars can be operated in a train from a single point, each car being equipped with its individual motor and controlling apparatus. The entire system is then controlled as one unit by a single motorman stationed usually in the front of the first car. This method of control has become of such tremendous importance that any system to which it cannot be applied would be seriously handicapped. Cars equipped with single-phase motors can be operated on either direct-current or alternating-current lines, with high or low tension, with trolley or third rail.

It must not be supposed, however, that with all the above mentioned advantages, the single-phase system has no disadvantages, as such is not the case. The car equipment, due to the transformers and the nature of the motors, is considerably heavier. The motors themselves are more expensive on account of their special construction. The equipment is not always adapted for operation on existing lines. There is a slight increased “apparent” resistance of the trolley line and a considerable increased “apparent” resistance of the rails, due to reactance caused by the alternating nature of the current. There is also an active electro-motive force between the field coils, which is objectionable, and there is a possibility of interference with neighboring telephone lines. Furthermore, there is slight loss in power in the transformers on the car, while the power-factor of the motors is less than unity.

Summing the matter up as a whole, however, the advantages seem to overbalance the disadvantages, at least for many kinds of work, and it is safe to predict that this new system of operation will have a very wide and increasing application in the near future.

As to the operation of the system in general, the current may be developed by single-phase, two-phase, or three-phase generators, and supplied to the transformer substations just as it was formerly supplied to the rotary converter substations. Only a single phase is used on any section of the trolley line. The voltage on this transmission line will depend upon the existing conditions, and can be figured out like any other problem in power transmission.

Three-phase generators would ordinarily be used, as less copper is required to supply a given amount of power. The common frequency is 25 cycles per second. At the transformer stations, the voltage is then stepped down to that required on the trolley, which may be 2,000, 3,300, 6,600, or even 11,000 volts. While we cannot speak yet of a standard voltage, 3300 seems to be finding considerable favor. The voltage for which the motors are wound is 200 or 250, the General Electric motors using the former voltage, and the Westinghouse the latter. When operating on alternating current the motors are connected in parallel, and when running on direct current they are connected in series. Motors have been constructed from 50 to 225 horsepower, and there is no apparent reason why larger ones could not be made to operate with equal satisfaction.

Among the roads in this country which are either using, or planning to use single-phase current, may be mentioned the Ballston-Schenectady line, which was one of the first systems to be equipped and has been in successful operation for some time. This road uses the alternating-current motor developed by the General Electric Co. The motors are adapted for operation on the 2,000-volt alternating-current trolley between cities, and on the standard 600-volt direct current in Schenectady. They are wound for 400 volts, and are operated in series on the 600-volt direct current. The frequency used is 25 cycles. Current is supplied by an overhead trolley, no feeders being used.

A second road of importance is one in Georgia between Atlanta and Marietta, which is 15 miles in length. This uses the Westinghouse equipment. The current on the trolley is 2,200 volts and 25 cycles. It is transmitted at a voltage of 22,000.

Another road of importance is the Indiana and Cincinnati interurban line, 41 miles in length, which has been in operation on regular schedule since July 1st, 1905. For 37 miles the road is operated from alternating current, and for 4 miles, from direct current. Four 75-horse power motors per car are used, capable of a maximum speed of 65 miles per hour.

The Bloomington, Pontiac and Joliet Electric Railway is a single-phase road equipped with General Electric apparatus, and has maintained a regular schedule over a distance of more than 10 miles since March, 1905.

The plans are now being laid for a single-phase road, which will run south from Spokane, Washington, a distance of 150 miles. The current on the transmission line is 45,000 volts, which is stepped down to 6,600 on the trolley. The car will be capable of operating on current from a 6,600-volt alternating, a 700-volt alternating, or a 575-volt direct-current supply.

Perhaps the most important move which has been made in the direction of single-phase traction thus far is the decision of the New York, New Haven, and Hartford road to establish a long-distance passenger traffic on the single-phase system. According to the latest plans this road will operate between the Grand Central Depot and Woodlawn, N. Y., over the terminal tracks of the New York Central road, on direct current taken from the trolley. From Woodlawn, N. Y., to Stamford, Conn., the road will be operated on the single-phase system.

The equipment is being supplied by the Westinghouse Co. The current is generated by revolving-field type turbine-driven alternators. The armatures are designed for either three-phase or single-phase connection. The current is generated at 25 cycles and 11,000 volts, being delivered directly to the trolley, and thence to the cars, without the intervention of any transformers. The double catenary suspension from messenger wires is used to support the trolley. The locomotives are each equipped with four 200-H. P. gearless motors, designed to operate on 235-volt alternating current and 275- to 300-volt direct current. The armature is not mounted on the shaft direct, but is built upon a quill through which the axle passes with about ⅝-inch clearance all around. There is a flange at each end of the quill from which seven pins project and fit into the hubs of the driving wheels. On the direct-current part of the line, current is delivered to the car through eight collecting shoes from a third rail. On the alternating-current section, current is delivered through two pantograph bow trolleys. On the direct-current section the series-parallel method of speed control is used, current being fed directly to the motors which are connected two in series permanently and the series-parallel control is applied to the motors in groups of two. The alternating-current speed control is accomplished by six taps from an auto-transformer for the corresponding running points. The cars weigh 78 tons and are capable of a speed of 60 to 65 miles per hour. The electro-pneumatic unit-switch type of control is used. At each end of the cab is a master controller from which the main controller is operated. Several locomotives can be operated together on the multiple-unit system, if desired.

The Washington, Baltimore and Indiana single-phase road is the latest in the field, contracts having been placed very recently. The current will be transmitted at 33,000 volts and 25 cycles, then being stepped down to 6,600 volts on the trolley. The road will be 60 miles long and will be equipped with General Electric apparatus. Four 125-H. P. motors capable of operating on either alternating current or direct current will be used, and the cars will be capable of a speed of 60 miles per hour.

INDEX

Air brakes, 56

Air compressors, 57 automatic governor for, 57 Westinghouse, 58

Alternating-current generators, 105

Alternating-current switchboards, 110

Alternating-current systems, 113 single-phase motors, 114 three-phase motors, 113

Alternating-current transmission, 99

Armature coils, 8

Armature leads, 9

Armature tests for grounds, 133

Armature winding, 5 defects of, 124 mistakes in, 126

Automatic governor for air compressors, 57

Ballast, 85

Bearings of railway motors, 13

Block signals for electric railways, 94

Bond testing, 120

Bonding and return circuits, 88

Booster feeder, 98

Brackets, 75

Brake leverages and shoe pressure, 54

Brake rigging, 53

Brake shoes, 64

Brush holders, 10

Brushes, 10

Burn-outs, 123

Canopy switch, 39

Car, failure of to start, 127

Car bodies, 67

Car circuit breaker, 39

Car construction, 67

Car equipment, 3

Car heaters, 34 electric, 34 hot-water, 36

Car painting, 72

Car repair shops, 134

Car weights, 72

Car wheels, 51

Car wiring, 37

Cast-welded joints, 87

Coefficient of friction, 65

Common T-rail, 84

Commutator type single-phase motor, 139

Compressors, 57

Conductivity of steel rail, 80

Conduit systems, 81 contact plow, 82 cost of, 82 current leakage, 83

Contact plow, 82

Contact shoes, 45

Controller construction, 19

Controller notches, 27

Controller wiring, 20

Controllers, 16

Cost of power, 119

Couplers, 66

Current required to heat cars, 35

Current leakage, 83

Defects of armature windings, 124

Direct-current feeding, 98

Double-current generators, 105

Drawbars, 66

Economy in power, 118

Electric car accessories, 39 canopy switch, 39 car circuit breaker, 39 contact shoes, 45 fuses, 41 lamp circuits, 43 lightning arresters, 41 trolley base, 44 trolley poles, 44 trolley harp, 45 trolley wheels, 44

Electric cars, road tests of, 117

Electric heaters for cars, 34

Electric railway, 1

Electrically welded joints, 87

Electrolysis, 95 prevention of, 97

Feeder panel, 110

Feeder systems, 92

Feeders, 75

Field coils, 8

Field tests for grounds, 133

Four motors, 19

Fuse blows, 130

Fuses, 41

Gearing, 12

G. E. electric brake, 61

G. E. train control, 29

Generator, starting up, 108

Generator D. C. panels, 106

Generators, 105

Girder rail, 83

Grounds, 123

High-tension lines, 77

High-tension oil switches, 111

Highway crossings, 80

Hot-water heaters for cars, 36

Insulators, third rail, 79

Interurban railway, system of distribution for, 101

Joints for rails, 86

Lamp circuits, 43

Lightning arresters, 41

Locating defects in motor and controller wiring, 128

Location of power houses, 101 third rail, 79

Lubrication of railway motors, 13

Magnetic blow-out, 26

Maximum traction trucks, 51

Momentum brakes, 59

Motor leads, 9

Motor suspension, 14

Motor-coil testing, 121

Motors, 3 as emergency brakes, 63 of the New York Central electric locomotive, 15

Multiple-unit control, 29

Oil switches, high tension, 111

Open-circuit tests, 128

Opening cases for inspection, 10

Overhead construction, 73 brackets, 75 feeders, 75 high-tension lines, 77 section insulators, 76 span wires, 74 trolley wire, 73 trolley-wire clamps and ears, 73

Potter third-rail shoe, 46

Power cost of, 119 economy in, 118 taken by cars, 115

Power house location, 101

Power stations, general plan of, 105

Power supply and distribution, 98

Railway motors bearings, 13 brushes, 10 characteristics of, 3 gearing of, 12 lubrication of, 13

Rate of retardation in braking, 66

Resistance of track, 91

Resistances, 38

Return feeders, 92

Reversal of motor, 26

Reversed fields, 133

Rheostat control, 17

Road tests of electric cars, 117

Sectional insulators, 76

Series-parallel control, 17

Shanghai T-rail, 84

Short-circuit tests, 130

Single trucks, 48

Single-phase electric railway, 136

Single-phase motors, 114, 139

Sleet on trolleys and third rails, 46

Sliding and spinning wheels, 119

Span wires, 74

Sparking at the commutator, 127

Sprague multiple-unit system of control, 29

Steel car framing, 71

Storage air brakes, 58

Storage batteries in stations, 113

Street railway motors, general data on, 6

Supplementary return feeders, 92

Swing bolster trucks, 49

Switchboards, 106 alternating-current, 110

Switches, third rail, 79

Swivel trucks, 48

T-rail, 84

Thermit welding, 88

Third rail, 79 advantages in operation, 80

Third rail conductivity of, 80 cost of, 80 highway crossings, 80 insulators for, 79 location, 79 switches, 79

Three-phase motors, 113

Track brakes, 63

Track construction, 83

Track resistance, 91

Track sanders, 65

Track support, 85

Transmission systems, efficiency of, 101

Trilby groove rail, 84

Trolley base, 44

Trolley harp, 45

Trolley poles, 44

Trolley wheels, 44

Trolley wire, 73

Trolley-wire clamps and cars, 73

Trucks, 46 maximum traction, 51 single, 48 swing bolster, 49 swivel, 48

Type L controllers, wiring of, 24

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Transcriber’s Notes:

• Text enclosed by underscores is in italics (_italics_). • Text enclosed by equals is in bold (=bold=). • Text enclosed by pluses is in small caps (+small caps+). • Obvious typographical errors have been silently corrected.