Part 4

=Wiring of Circuit Breakers and Canopy Switches.= Figs. 33, 34, and 35 show the methods of wiring circuit breakers and canopy switches for double-end cars.

[Illustration: Fig. 33.]

In the parallel connection as shown in Fig. 33, the trolley leads after passing through the choke coils go directly to the blow-out coil of the controllers. Aside from the fact that two lightning arresters and choke coils are required, this method is preferable for automatic circuit breakers.

[Illustration: Fig. 34.]

Fig. 34 shows the hand-operated circuit breakers connected in series. This method is used where non-automatic breakers are employed, but for automatic breakers it has the objection that an overload would throw the breaker set at the lowest point. This might be the breaker on the opposite end to that occupied by the motorman and in such an event would necessitate a trip to the other end to set the breaker. Fig. 35 shows a method of parallel connection requiring but one lightning arrester. This method has the objection that the motorman on the front end would have no assurance that by throwing the breaker over him the power would be cut off. The rear breaker might have been carelessly left set.

[Illustration: Fig. 35.]

[Illustration: Fig. 36.]

=Fuses.= A fuse is placed in series with the motor circuit before it enters the controller wiring, but where circuit breakers are used instead of canopy switches, the fuse box may sometimes be dispensed with. The fuse box on street cars is usually located underneath one side of the car body where it is accessible for replacing fuses, but where a motorman’s cab is used, the fuse may be placed in the cab. The fuse may be of any of the types in common use, either open or enclosed. In the Westinghouse fuse box it is necessary only to open the box and drop in a piece of straight copper wire of the right length and size. The closing of the box clamps this wire to the terminals and establishes a circuit through the copper wire as a fuse. Of course this copper wire is of small enough size to be fused by a dangerously heavy current.

=Lightning Arresters.= A lightning arrester is used on all cars taking current from overhead lines. The lightning arrester is connected to the main circuit as it comes from the trolley base, before it reaches any of the other electrical devices on the car, so that it may afford them protection. A common type of lightning arrester is shown in Fig. 36. One terminal of the lightning arrester is connected to the motor frame so as to ground it, and the other is connected with the trolley. In most forms of lightning arrester, a small air gap is provided, not such as to permit the 500-volt current to jump across, but across which the lightning will jump on account of its high potential. To prevent an arc being established across the air gap by the power house current after the lightning discharge has taken place and started the arc, some means of extinguishing the arc is provided. In the General Electric Company’s lightning arrester, the arc is extinguished by a magnetic blow-out, which is energized by the current that flows through the lightning arrester. The instant the discharge takes place the current flows across the air gap. The magnetic blow-out extinguishes the arc, and this opens the circuit, leaving the arrester ready for another discharge. In the Garton-Daniels lightning arrester a plunger contact operated by a solenoid opens the circuit as soon as current begins to flow through the arrester. This plunger operates in a magnetic field, which extinguishes the arc. A choke coil, consisting of a few turns of wire around a wooden drum, is placed in the circuit leading to the motors at a point just after it has passed the lightning arrester tap. This choke coil is for the purpose of placing self-induction in the circuit, so that the lightning will tend to branch off through the lightning arrester and to ground, rather than to seek a path through the motor insulation to ground.

[Illustration: Fig 37. Diagram of Light Circuit.]

Often, however, the choke coil is omitted, the coils in the circuit breaker and the blow-out coil in the controller being depended upon to prevent the lightning charge from passing.

=Lamp Circuits.= The lamp circuit of a car is protected by its separate fuse box, and usually each lamp circuit has a switch. As explained before, five 100-volt or 110-volt lamps are placed in series between the trolley wire side of the circuit and ground. If one lamp in the series burns out, of course, all five are extinguished until the defective lamp is replaced with a new one. Enclosed arc lamps are sometimes used for car lighting.

Cars to be operated from either end are often wired so that by turning a switch the platform light on the front end, a light for the sign and another for the headlight on the rear end will be extinguished and corresponding lights on the rear and front ends lighted. This is accomplished by the method of wiring shown in Fig. 37. The interior of the car is lighted by six lights. Headlights of 32 candle power are used. This method requires the use of two switches. In all light wiring schemes a switch should be placed on the trolley side of the lights. This permits the current to be cut off in the event of a ground occurring in the system.

On interurban cars arc headlights are almost invariably used. The circuit for the headlight after passing through a switch in the motorman’s cab goes through a resistance frame usually underneath the car and terminates in a socket near the car bumper. The brackets on which the lamp is hung are grounded so that whenever the plug from the lamp is inserted in the socket and the switch in the cab is turned on, the circuit is made.

Usually there is a pressure of about 60 to 70 volts at the terminals of the lamp. The remainder of the voltage drop, from 500 or 600 volts (or whatever the line may be), is in the resistance under the car. The current through the lamp is usually about four amperes. With 60 volts at the arc and 500 volts on the line, this gives a consumption in the lamp of 240 watts and a loss in the resistance under the car of 2,000 watts, or about 90 per cent. The use of the headlight resistance to cut the voltage down is therefore a very inefficient method. Some schemes of wiring use the incandescent lamps used in lighting the car as resistance for the headlight. Another way is to light the interior of the car with arc lamps placed in series with the arc headlight.

=Trolley Base.= The trolley base upon which the trolley pole swivels, and which furnishes the tension that holds the trolley wheel against the wire, is designed to maintain, by means of springs, an approximately even tension against the trolley wire, whether the trolley wire is high above the track or near the car roof. This is done by changing the relative leverage which the springs of the trolley base have on the trolley pole according to the height of the trolley pole.

[Illustration: Fig. 38. Trolley Base.]

[Illustration: Fig. 39. Trolley Wheel.]

Fig. 38 shows one form of trolley base. The trolley base is bolted to a platform constructed for it on the roof of the car; and the supply wire to the motors and other electrical devices on the car, except in cases where a wooden trolley pole is used for certain special reasons, is connected directly to the trolley base. An insulated trolley wire is run down the wooden trolley pole, and connected through a flexible lead to the car wiring.

=Trolley Poles.= The trolley poles in general use are of tubular steel, which gives the greatest strength for a given weight, and which can usually be straightened if the pole has been bent by striking overhead work when the trolley wheel leaves the wire.

=Trolley Wheels.= Trolley wheels are from four to six inches in diameter over all, the small wheels being used in the city service, and the large wheels in high speed interurban service. A typical trolley wheel is shown in Fig. 39. Various companies use various forms of groove in the trolley wheels, some adopting a groove approximately V-shaped. The U-shaped groove, however, is the most common. The trolley wheel is made of a brass composition selected for its toughness and wearing qualities.

[Illustration: Fig. 40. Trolley Harp.]

=Trolley Harp.= The trolley harp, which is placed on the end of the trolley pole and in which the trolley wheel revolves, usually has some means for making electrical contact with the wheel in addition to the journal bearing. In the harp illustrated in Fig. 40, which is a typical form, this additional contact is secured by a spring bearing against the side of the hub of the wheel.

[Illustration: Fig. 41. Third Rail Shoe.]

Since trolley wheels revolve at a very high speed, some unusual means of lubrication must be provided, since there is no opportunity for ordinary oil or grease lubrication. Graphite, in the shape of what is called a “graphite bushing,” is most commonly used. This is a brass bushing, which is pressed into the hub of the trolley wheel. In this bushing is a spiral groove filled with graphite which is supposed to furnish sufficient lubrication as the bushing wears. Roller-bearing trolley wheels have been used to a limited extent, with considerable success in some cases. Some companies have done away with the graphite bushing, and have provided a very long journal for the trolley wheel instead of the usual short bushing.

=Contact Shoes.= The contact shoe most commonly used on roads employing the third rail is shown in Fig. 41. This is simply a shoe of cast iron hung loosely by links. The weight of the shoe is sufficient to give contact. The motion of the links permits the shoe to accommodate itself to unusual obstructions and variations in the height of the third rail. The shoe is fastened to the truck frame by means of a wooden plank which furnishes the necessary insulation.

[Illustration: Fig. 42. Sleet Wheel.]

The Potter third-rail shoe which has been used to a limited extent, employs a spring for giving the necessary tension to make electrical contact between the shoe and the third rail. In some ways this is superior, because a spring tension is quicker in its action than gravity, and the shoe accommodates itself better to variations in the height of the third rail at very high speed. The wear on the shoe, however, is likely to be greater.

=Sleet on Trolleys and Third Rails.= The deposit of sleet on trolleys and third rails hinders greatly the operation of cars. Often sleet wheels of the type shown in Fig. 42 are used as a trolley wheel. These cut the sleet off instead of rolling over it.

On the third rail, scrapers and brushes in advance of the contact shoe are usually effective where trains are frequent. Several roads are now melting the sleet on the rails by the use of a solution of calcium chloride. The solution is stored in a tank on the car and is led through small pipes to the rail immediately in front of the collecting shoe. About one gallon of solution is used per mile, making the cost about 7½ cents per mile. The effects of one treatment last for two or three hours during the continuance of a storm.

Solutions of common salt have been used in the same manner, but it is claimed that the corroding action on the iron of the calcium chloride is not as great as that of a salt solution.

TRUCKS.

Electric railway cars are classified generally as _double-truck_ and _single-truck_ cars. Double-truck cars are those that have a truck that swivels at each end of the car. A single-truck car is one having four wheels.

[Illustration: Fig. 43. Brill 21-E Car Truck.]

=Single Trucks.= A great many types of single trucks have been designed. It would be out of the question to discuss them all here. In general, however, it may be said that truck builders have aimed to make a truck frame in itself a complete unit independently of the car body, so that the car body will simply rest upon the trucks and there will be no strain on the car body in maintaining the alignment of the truck. Most single trucks, therefore, consist of a rectangular steel frame, either cast or forged, riveted or bolted together. This frame holds the journal boxes in rigid alignment. Usually a spring is placed between each journal box and the truck frame. This spring may be either spiral or elliptic. The principal springs, however, are between the truck frame and the car body. Most truck builders have used a combination of spiral and elliptic springs between the car body and truck frame, as this combination is considered to give better riding qualities and greater freedom from teetering or galloping than either spiral or elliptic springs alone. Fig. 43 shows a Brill single truck, which illustrates all of the features enumerated.

=Swivel Trucks.= Swivel trucks, commonly called _double trucks_, are made in many forms, but the most common is that known as the M. C. B. type of truck. This truck is similar to the standard truck which is in universal use on steam railroad passenger cars in the United States. Different truck builders have introduced many variations in this general type of truck, in adapting it to electric service. Some modifications from the steam railroad standard truck were necessary to accommodate the electric motors and to permit in some cases a low-hung car body. Such trucks are made in a great variety of sizes.

[Illustration: Fig. 44. St. Louis Car Company Truck.]

Fig. 44 shows one of these trucks built by the St. Louis Car Company. In this type of truck the car body is fastened to the truck only by the kingbolt on which the truck swivels. This kingbolt is placed in the center of the truck bolster. There are also side bearings between the car body and the ends of the bolster, to prevent tipping of the car body when it is unbalanced. The arrangement of this part of the truck is shown in Fig. 45. Under this bolster are elliptic springs which rest on what is called the _spring plank_. This spring plank is hung from the rectangular frame of the truck by links which allow a side motion. This side motion gives easier riding, especially upon entering and leaving curves. All trucks having this feature are known as _swing bolster trucks_. The weight, being transmitted to the transom and truck frame through the swinging links just referred to, is then taken by the equalizer springs that support the rectangular truck frame on equalizing bars, which equalizing bars rest on the journal box at either end and are bent down to accommodate the springs located between them and the truck frame. The truck frame holds the journal boxes in alignment by means of guides which permit an up-and-down movement without movement in any other direction, just as on all other types of truck. It is thus seen that there are two sets of springs between the car body and car journals; one set of spiral springs between the equalizing bar and truck frame; and one set of elliptic springs between the spring plank and the bolster. All shocks must be transmitted first through the spiral springs and then through the elliptic springs. The motors used on this type of truck usually have nose suspension, the nose of the motor resting either on the bolster of the truck or on the truck frame.

[Illustration: Fig. 45. Bolster, Links and Spring Plank.]

[Illustration: Fig. 46. Steel Tire Wheel.]

There are a number of swivel trucks made which have departed considerably from M. C. B. lines, but nearly all retain the features of a bolster mounted by springs on a spring plank, a spring plank hung from a transom, a transom rigidly fastened to the rectangular truck frame of which it forms a part; and a truck frame with one or more sets of spiral springs between it and the journal boxes. =Maximum Traction Trucks.= A type of swivel truck that once was very popular but has largely been superseded by the type just described is the “maximum traction truck.” This truck has two large wheels on an axle which carries 60 to 70 per cent of the weight on the truck, and two small wheels carrying the balance of the weight. The motors are on the large wheels.

=Car Wheels.= The car wheels most commonly used are of cast iron. In order to make a tread and flange upon which the wear comes, hard enough to give a good mileage, the tread and flange are chilled in the process of casting. Around the periphery of the mould in which the wheels are cast, is a ring of iron instead of the usual sand. When the molten cast iron comes in contact with this ring of iron, which is called a “_chill_,” the iron is cooled so suddenly that it becomes extremely hard. The balance of the wheel, cooling more slowly since it is surrounded by sand, has the hardness of ordinary cast iron. A steel tire wheel is shown in Fig. 46.

[Illustration: Fig. 47. Elevated Car Axle.]

Wheels with steel tires are coming into use for elevated and interurban cars because their flanges are not so brittle as those of cast-iron wheels. In wheels of cast metal there is always a liability that the flanges and tread will chip and crack. On high-speed cars the falling-out of pieces of flange may be a serious matter and result in a wreck. Steel-tired wheels have a hub and spokes either of cast or forged steel or iron. On to this wheel a steel tire is shrunk. The tire is heated in a furnace built for the purpose, and is then slipped over the wheel. It is made just such a size that it will slip over the wheel when hot, and when it is cool it will shrink enough to make a very tight fit. When the tire is to be removed after it is worn out, it is heated until it has expanded sufficiently to drop off.

An axle for elevated car is shown in Fig. 47.

When cast-iron wheels are worn to an improper shape or have flat spots upon them, due to the sliding of the wheels with the brakes set, an emery wheel grinder must be used to grind them down, as nothing else is hard enough to have any effect on the iron.

[Illustration: Fig. 48. Standard M. C. B. Flange.]

When steel-tired wheels are worn, they can be put in a lathe and the surface of the tire turned off, as this surface is of metal soft enough to be workable with ordinary tools.

[Illustration: Fig. 49. Brake Shoes and Levers.]

The types of wheel tread and wheel flange in use vary greatly among different electric railways. There is a standard Master Car Builders’ wheel tread used on steam railroads, which is shown in Fig. 48. Electric railways, however, are usually obliged to use a smaller flange and narrower tread. Street railway special work, such as switches and crossings, usually has too shallow a flange way to permit a standard M. C. B. flange to pass through. Some street railways use flanges as shallow as ⅜-inch, although ¾-inch is most common on city work. The width of the tread on street railway cars, that is, the width of the wheel where it bears on the rail, is usually from 1¾ inches to 2¼ inches. There is a tendency, however, on electric railways, on account of the increasing number of interurban cars which must use city tracks, to build tracks that will accommodate wheels approaching the M. C. B. standard of steam roads. A few roads have adopted wheel treads and flanges very near to the M. C. B. standard.

[Illustration: AUTOMATIC AIR BRAKE CAB EQUIPMENT. Westinghouse Air Brake Co.]

=Brake Rigging.= The brake rigging on a single-truck car may be arranged in a variety of ways, but should be such that a nearly equal pressure will be brought to bear on the brake shoes on all four wheels. A typical arrangement of brake shoes and levers for single-truck cars is shown in Fig. 49. The rods R terminate in chains winding around the brake staff upon which the motorman’s handle or hand wheel is mounted.

[Illustration: Fig. 50. Brake Levers and Air Brake.]

For double-truck cars the brake rigging is necessarily more complicated, as it must be arranged to give an equal pressure on all eight wheels of the car. Brake shoes are sometimes placed between the wheels of a truck and sometimes outside. The arrangement of brake shoes between wheels is apparently finding most favor, as when the shoes are applied in this position there is less tendency to tilt the truck frame when the brakes are applied, and this adds to the comfort of passengers in riding. Fig. 50 shows one form of arrangement of brake levers common on a double-truck car equipped with air brakes, with inside-hung brake shoes.

=Brake Leverages and Shoe Pressure.= The levers between the air cylinder and the brake shoes are usually so proportioned that with an air pressure of 70 lbs. per sq. in. in the brake cylinders the total of the brake shoe pressures on the wheels will be equal to about 90 per cent of the weight of the car. The diagram Fig. 51 has shoe pressures and strains in the several rods marked on shoes and rods.

The following example, based on the diagram, will explain the lever proportioning. Only round numbers are given on the diagram.

Assume a four-motor car weighing 40,000 pounds. A brake cylinder 7 inches in diameter is used. This gives 38.5 square inches and at 70 pounds air pressure a total force on the piston rod of 2,695 pounds. The weight of the car is 40,000 pounds. Taking 90 per cent of this gives a total of 36,000 pounds to be exerted by the brake shoe when an emergency stop is made. Each of the eight shoes will press against the wheels with a force of 4,500 pounds.

The dimensions of the truck are such that the “dead levers,” those fixed at one end and which carry shoes, cannot be over 13 inches long. The shoe will be hung three inches from one end, making the proportions 10 to 3, and the pressure on the strut rod between shoes will be 4,500 × ¹⁰⁄₁₃ or 3,461 pounds. To clear the truck frame the live lever extends 14 inches above the point of application of the brake shoe. To obtain 4,500 pounds pressure on the shoe, the distance between the brake shoe and the strut rod, which we will call “_x_,” will be found by regarding the upper end of the lever as fixed and the power applied at the lower end.

14 + _x_ 4500 = 3461 × ———————— or 14

_x_ = 4.2 inches.

Now to obtain the force required in the rod to the truck quadrant, the bottom end of the live lever must be regarded as the fulcrum. The equation is

4.2 _x_ = 4500 × ———— = 1038 pounds. 18.2

As the pull rods from each side of the truck are attached to the truck quadrant, the stresses in the brake rods are double this, or 2,076 pounds.