Chapter VII: Part II: Overhead Construction (3)

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.

Note the two pantograph bow trolleys for collecting the current.]

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.

The three-phase current is delivered to the transformers where it is stepped down to the voltage required for the rotary converter. In this machine it is transformed to direct current and delivered to the trolley wire.]

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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Latest and best American methods. Price =$1.00=

=WATER SUPPLY. By F. E. Turneaure.= 150 pp., 40 illus. An
exhaustive compendium for Sanitary and Waterworks Engineers and
all interested in matters affecting public health. Price =$1.00=

=HIGHWAY CONSTRUCTION. By Phillips and Byrne.= 140 pp., 80 illus.
Modern methods for Road Builders and all interested in better
ways of communication. Price =$1.00=

=REINFORCED CONCRETE. By Webb and Gibson.= 150 pp., 140 illus.
A manual of practical methods for Architects, Builders.
Contractors, Civil and Sanitary Engineers. Information for the
first time made known to the world. Based on recent construction
work, special tests, etc. Price =$1.00=

=MANAGEMENT OF DYNAMO-ELECTRIC MACHINERY. By F. B. Crocker.= 130
pp., 65 illus. For all who have to do with electric light or
power plants. Price =$1.00=

=STEAM ENGINES. By Leland and Snow.= 170 pp., 63 illus. A practical
guide. Field covered in a way anyone can grasp. Price =$1.00=

=ELECTRIC RAILWAYS. By J. R. Cravath.= 150 pp., 103 illus. Trolley
and third-rail systems. Electric Locomotive, etc. Price =$1.00=

=ESTIMATING. By Edward Nichols.= 140 pp., 35 illus. For all workers
in Building trades. Tells how to estimate intelligently. Price
=$1.00=

=CONTRACTS AND SPECIFICATIONS. By James C. Plant.= 130 pp.,
fully illustrated. Forms of public and private contracts,
specifications, bonds, etc., duties and responsibilities of
Architects, Contractors, and Owners. Price =$1.00=

=STAIR-BUILDING AND STEEL SQUARE. By Hodgson and Williams.= 130
pp., 180 illus. Only up-to-date work on these subjects. Price
=$1.00=

=VALVE GEARS AND INDICATORS. By Leland and Dow.= 150 pp., 105
illus. Two books in one. Types of valves, gears, etc., fully
explained. Price =$1.00=

=STRENGTH OF MATERIALS. By E. R. Maurer.= 140 pp., 58 illus. For
Architects, Builders, Steel and Concrete Workers. Enables one to
avoid mistakes. Price =$1.00=

=THE ELECTRIC TELEGRAPH. By Thom and Collins.= 150 pp., 81 illus.
Carries along by easy steps to complete mastery. Multiplex and
Wireless telegraph explained. Price =$1.00=

=MECHANICAL DRAWING. By E. Kenison.= 160 pp., 140 illus.
Complete course in projections, shade lines, intersections and
developments, lettering, with exercises and plates. Price =$1.00=

=POWER STATIONS AND TRANSMISSION. By G. C. Shaad.= 160 pp., 43
illus. For Electrical Workers. Up-to-date practice. Price =$1.00=

=PATTERN MAKING. By James Ritchey.= 150 pp., 250 illus. For Wood
and Metal Workers and Molders. Methods of building up and
finishing, fully described. Price =$1.00=

=SURVEYING. By Alfred E. Phillips.= 200 pp., 133 illus. For Civil
Engineers and Students. All details of field work explained.
Price =$1.50=

=STEEL CONSTRUCTION. By E. A. TUCKER.= 300 pp., 275 illus. Covers
every phase of the use of steel in structural work. Based on
actual experience, special tests, etc. For Architects, Bridge
Builders, Contractors, Civil Engineers. Price =$1.50=

=BUILDING SUPERINTENDENCE. By E. Nichols.= 200 pp., 250 illus.
Costly mistakes occur through lack of attention at proper time,
hurtful to Owner and discreditable to Architect and Builder.
Gives thorough knowledge of methods and materials. Price =$1.50=

=ARCHITECTURAL DRAWING AND LETTERING. By Bourne, von Holst and
Brown.= 200 pp., 55 drawings. Complete course in making working
drawings and artistic lettering for architectural purposes. Price
=$1.50=

=MACHINE SHOP WORK. By F. W. Turner.= 200 pp., 200 illus. Meets
every requirement of the shopman, from the simplest tools to the
most complex turning and milling machines. Price =$1.50=

=TOOL MAKING. By E. R. Markham.= 200 pp., 325 illus. How to make,
how to use tools. Profusely illustrated. Price =$1.50=

=MACHINE DESIGN. By C. L. Griffin.= 200 pp., 82 designs. Written by
one of the foremost authorities of the day. Every illustration
represents a new device in machine shop practice. Price =$1.50=

These volumes are handsomely bound in red art Vellum de Luxe,
size 6½ × 9½ inches. Sent prepaid to any part of the world, on
receipt of price. Remit by Draft, Postal Order, Express Order, or
Registered Letter.

AMERICAN SCHOOL OF CORRESPONDENCE, CHICAGO

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.