Part 2

=Opening Cases for Inspection.= Accessibility for inspection and repairs is essential in all railway motors. A lid is always provided directly over the commutator to facilitate inspection of the commutator and brushes. To open up the motor casing for more extensive inspection or repairs, three general schemes are employed. One is to have the lower half of the casing swing downward on a hinge as in Fig. 9, which illustrates the Westinghouse No. 38 B motor. The armature may be placed either in the lower half, as shown in Fig. 9, or in the upper half. When a motor of this type is to be opened the car is run over a pit, and the repair men work entirely from below.

Often the hinge pins are removed and the lower shell containing the armature is dropped down by means of a jack placed underneath.

Two handholes are usually provided in the bottom shell for observing the clearance between the armature and the pole pieces and also for removing dirt that may collect in the bottom of the shell. Another scheme is to have motors open from the top, either by hinging the upper part of the motor casing, as in Fig. 3, or by having the top part of the casing lift off. Where this form of motor is used, the car body is hoisted clear of the truck, and the trucks are run out from under the car body before work is done on the motors. In this case, all the work can be done from above without the use of pits.

[Illustration: Fig. 9. Railway Motor. Lower Half of Casing Swung Down.]

A third design is the box-frame motor casing, from which the armature can be removed endwise only. Such an arrangement is shown in Fig. 10, which is a view of a No. 66 motor of the General Electric Company. In this motor a sufficiently large opening is provided in the ends of the motor casing to permit of the armature being removed endwise. A plate or head, which accurately fits into this opening, carries the armature bearing. In removing armatures from motors of this kind, the usual method is to take the motor out of the trucks and stand it on end with the pinion up. The bolts being removed from the end plate, the armature can then be hoisted out of the case by means of a special hook attached to the pinion. Another plan that has been used in removing armatures from such motors, is to place the motor in an apparatus where the armature shaft can be held between centers, as in a large lathe. The motor casing is then moved along in a direction parallel to the armature shaft, until the armature is exposed.

This latter box-frame type of motor is very compact; a stronger casing can be made for a given weight and space than if it were divided horizontally. Moreover, the magnetic circuit cannot be disturbed by imperfect contact between two parts of the casing. Where this type of motor is used, the bearings project inward under the commutator and armature, thus getting long bearings with a short motor, which is important where the room is limited, as, for example, in the case of a large motor mounted on a standard-gauge truck.

[Illustration: Fig. 10. Box-Frame Motor.]

=Gearing.= In most cases, spur gearing is used to transmit power from the armature shaft to the car axle, although a few motors with armatures mounted directly on the car axle are in use. Various gearings other than the simple spur gear have been tried, such as worm gears, chain and bevel gears. Practically all have been abandoned in favor of the single-reduction spur gearing, which is the most satisfactory from the standpoint of wear and efficiency. This gearing is shown in Figs. 3 and 9. The gearing is covered with a gear case (Fig. 9), which is usually of steel, though gear cases of thin sheet metal and wood are sometimes used. A solid gear is shown in Fig. 11, and a split gear in Fig. 12. The gear ratios in common use vary from 5 to 1 to 2 to 1, the larger ratio being common on the smaller motors. A ratio often used on motors of 30 to 50 horsepower is 4.78 to 1, the gear having 67 teeth, the pinion 14 teeth.

Street car wheels are usually 33 inches in diameter. This makes necessary 612 revolutions per mile. With a gear ratio of 4.78 the armature revolves 2,925 times per mile. At 15 miles per hour, this gives 731 r.p.m.

[Illustration: Fig. 11. Solid Gear.]

[Illustration: Fig. 12. Split Gear.]

=Lubrication.= The lubrication of railway motors was for a number of years carried on almost exclusively with grease, which it was customary to place in the gear casing and in grease boxes over the armature and car-axle bearings. Grease becomes most efficient as a lubricant only when the bearing is heated sufficiently to make the grease run like oil. Oil is now being used to a considerable extent, especially for larger motors. It is fed to the bearings by various devices that allow a very slow feed, such as wicks and lubricators adjusted to pass a small amount of oil per hour.

=Bearings.= Railway motor bearings are usually of Babbitt metal, which metal is cast into a steel shell. This shell fits into receptacles in the motor casing, which can be seen in Figs. 3 and 9. A steel shell is used so that the worn-out bearings can be easily renewed and the shells taken to a Babbitt melting furnace to have new Babbitt poured into them.

The motor has two sets of bearings, those for the armature and those for the axle upon which the motor is mounted. The axle bearings are always split diametrically to avoid removing a wheel when a bearing is replaced. On the later designs of motors these are of brass, no Babbitt metal being used. The armature bearings are distinguished by the terms “gear end” and “commutator end” bearings. The gear end bearing is usually of larger diameter and of greater length because of the thrust of the gears it must take in addition to the weight of the armature. This bearing is split so that it may be removed and replaced without the removal of the gear. The commutator end bearing is in one piece. Armature bearings are shown in Fig. 13.

[Illustration: Fig. 13. Armature Bearings.]

=Motor Suspension.= Two methods of suspending motors flexibly on trucks are in common use. That end of the motor which has bearings on the car axle cannot, of course, be flexibly suspended with regard to the axle; but the other end of the motor can be placed on springs, or rest on a bar supported on springs, as shown in Fig. 14. This suspension is commonly called _nose suspension_. Instead of having a special bar and special springs for the nose of the motor, the nose may rest upon some part of the truck that is carried upon springs. Thus, on the M. C. B. type of swivel truck, the nose usually rests on the truck bolster, and thus gets the benefit both of the bolster springs and of the equalizer springs of the truck. Another general plan of suspension is that known in one form as _cradle suspension_, and in another form as _side-bar suspension_. A side-bar suspension is shown in Fig. 15. Here a larger percentage of the weight of the motor is evidently taken by the springs than in the case of nose suspension. It is desirable to relieve the car axle of as much dead weight as possible. By dead weight is meant weight resting upon it without the intervention of springs.

[Illustration: Fig. 14. Nose Suspension.]

[Illustration: Fig. 15. Side-bar Suspension.]

=Motors of the New York Central Electric Locomotive.= These motors are a radical departure from the usual type of railway motors. The locomotive on which they are mounted has four driving axles, upon each of which is mounted an armature, direct, no gears being used, Figs. 16 and 17. The motors are remarkable for three special features: The method of mounting the armature, the shape of the pole pieces, and the path of the magnetic flux. [Illustration: Fig. 16. Longitudinal Section of New York Central Locomotive.]

[Illustration: 95 TON ELECTRIC LOCOMOTIVE FOR NEW YORK CENTRAL RAILROAD. General Electric Company.]

The mounting of the armature upon the driving axle and the motor fields on the truck frame makes it necessary to have flat pole pieces in order that the armature may play up and down as the journal box and axle slide in the guides of the truck frame. The shape of the pole pieces may be observed in the drawing Fig. 16. When in the central position there is a ¾-inch air gap between the armature and pole pieces. The magnetic flux is continuous through the fields of all four of the motors. It returns through the cast steel side frames of the truck and two bars placed in the path.

The brush holders are so mounted that the brushes occupy a fixed position relative to the armature. The armature is removed by lowering it with the wheels and axle upon which it is mounted. This can be done without disturbing the fields of the motor.

CONTROLLERS.

In an ordinary electric car, current is taken from the wire through the trolley wheel and pole, and is first led from the trolley base through overhead switches or a circuit breaker, and then to the controller, from which it passes through the motors and thence through the motor frames, car truck, and wheels to the rails and ground. If the car is designed to be operated from either end, an overhead switch or circuit breaker is placed over each platform of the car so that current can instantly be cut off entirely from the controllers by throwing the switch or circuit breaker at either end of the car.

[Illustration: Fig. 17. Armature Axle and Wheels.]

The lighting circuit is run from the trolley base independently of the motor circuit, and has its own switch and fuse box. Current for the lights is taken from the trolley circuit before it reaches the main switches or circuit breakers. Current for electric heaters, if such are used, is likewise taken from a separate circuit. On a 500-volt system five 100-volt lamps are usually connected in series for car lighting. As many multiples of five can be employed as are necessary to light the car.

=Rheostat Control.= The simplest form of controller is that employed where only one motor is used on a car. A rheostat is placed in series with the motor when started, just as on a stationary motor; and the function of the controller is to short-circuit this resistance gradually until it is entirely cut out and the motor operates with the full voltage. The controller also has a reversing switch by means of which the relative connections of the armature and fields are reversed, which, of course, changes the direction of rotation of the motor armature. Such a simple equipment as this, however, is rarely to be found in practice.

=Series-Parallel Control.= Single-truck cars usually have two motors, one on each axle; and on such cars a series-parallel controller is the kind usually employed. Diagrams of connections on the various points of a series-parallel controller (Type K6) of the General Electric Company, are given in Fig. 18.

[Illustration: Fig. 18. Diagram of K6 Controller Combinations.]

From these diagrams it is seen that the motors are first operated in series until all the resistance is short-circuited by the controller. When this has occurred, the cars are running at about half speed. The next point on the controller puts the two motors in multiple, with some resistance in the circuit, which resistance is cut out upon the following points, until at full speed the two motors are in multiple, without any resistance in the circuit.

=Four Motors.= Where four motors are used on a car, as is frequently the case with double-truck cars, the motors on each truck are usually controlled just as in case of the two-motor equipment that has been described; but each pair of motors is operated in multiple. That is, on the first points of the controller, the two motors of a pair are in series, as in Fig. 19, and the two pairs are in parallel; and on the last points of the controller, all the motors are in parallel, as in Fig. 20.

[Illustration: Fig. 19. Motor in Series.]

[Illustration: Fig. 20. Motor in Parallel.]

=Controller Construction.= The controller (Type K) shown open in Fig. 21, which in its various forms is the type most commonly used on street cars in the United States, has a contact cylinder or drum mounted upon the main shaft of the controller. This contact drum carries contact rings insulated from the drum, and is suitably interconnected, as indicated in Fig. 22, which shows the contact rings of the controller as they would appear if rolled out flat. Contact fingers are placed along the left side of the controller, as seen in Fig. 21, one for each ring on the drum; and as the controller handle is turned to revolve this drum, the contact fingers make contact with the rings on the drum and give the various connections. Alongside the main controller drum is a reverse drum which simply reverses the armature connections of the two motors. =Controller Wiring.= The connection between motors, controllers, and resistances, with two motors and a K6 controller is shown in Fig. 22. A careful study of this will show the combinations to be the same as indicated in the diagram, Fig. 18. The wiring is rather complicated; and in practice, to avoid confusion, the ends of each wire are labeled with tags showing the terminals to which they belong.

[Illustration: Fig. 21. Controller.]

[Illustration: Car Wiring for K-6 Controllers with two Motors Fig. 22]

[Illustration: Fig. 23. Motors in Series.]

[Illustration: Fig. 24. Motors in Parallel.]

With the aid of Figs. 22, 23 and 24, the wiring of a type K6 controller with two motors may be followed. Figs. 23 and 24 are for a different controller but can be used to assist in an understanding of the complicated diagram 22. The current leaves the choke or kicking coil of the lightning arrester and passes through the blow out coil of the controller. It then goes to the top finger T of the controller. On the first point the circuit is as shown in Fig. 23. The top segment A makes contact with the top or trolley finger. All but the lower five segments of the cylinder are electrically connected together by means of the iron cylinder upon which they are mounted. On the first point then the current passes from the cylinder over R₁, and with straight series connections of the resistances, it goes through all of the rheostats under the car, and returns to the controller over the last resistance lead, R₇. Behind the motor cut-out switches at the base of the controller this lead is tapped into a wire one end of which leads to finger 19 of the controller, and the other end through the cut-out switch and reverse cylinder to No. 1 armature. The current takes the latter path, passes through the armature of the motor and returns by way of the reverse cylinder, thence through the fields of No. 1 motor and then through the cut-out switch of No. 1 motor and to finger E₁, of the controller. Segments O, M, N and L, shown in Fig. 23, and corresponding segments of Figs. 22 and 24, are insulated from the remainder of the controller cylinder. From finger E₁ and segment O (Fig. 23) the current passes over finger 15 through No. 2 cut-out switch and the reverse cylinder to the armature of No. 2 motor. Returning it passes through the reverse cylinder, then back through the fields of No. 2 motor and to the ground, which is usually through a connection on the motor casing.

On points 2, 3, 4 and 5, the successive series points of the controller R₁, R₂, etc., make contact with segments B, C, etc., Figs. 23 and 24, until finally finger 19 rests on segments J, the resistance is all cut out and the motors are connected in series directly across the line. A further movement of the controller handle changes the motors from series to multiple connection and inserts in the circuit a portion of the external resistance. There are four separate stages in making this change. First, the resistance fingers slide off their segments and the resistance is inserted in the line. Second, fingers E₁ and G make contact with segments P and Q. Motor No. 1 is then across the line in series with the resistance; the circuit being from E₁ to ground over G. When the lower finger E₁ makes contact with P, the upper one has not yet left segment O. This short-circuits No. 2 motor, the path being from the ground, up wire G, thence by way of segments P and Q and through connecting clip V, between the two E₁ fingers back through finger 15 to the motor.

A further movement of the controller handle causes the fingers to leave segments M and O and No. 2 motor is open-circuited until finger 15 makes contact with segment N. When this takes place the motors are in multiple. On the successive points after this the external resistance is cut out in the same manner as previously described.

By reference to Fig. 22, it will be noticed that the leads to the motors and the resistances are tapped on wires of the cables connecting the two controllers on the ends of the car. The two ends of these wires, with the exception of the armature wires, lead to similar binding posts on the two controllers. The armature wires are interchanged connecting at one controller into binding post A A, while the other end connects into binding post A. This change of connection is necessary in order that the reverse handles be forward for forward direction of movement of the car.

[Illustration: Fig. 25. Forward Position of Reverse.]

To reverse a series motor it is simply necessary to reverse the direction of flow of the current in either the armature or field. For several reasons, it is advantageous in the case of the street railway motor to reverse the current in the armature rather than in the field. Figs. 25 and 26 show how this is accomplished. The squares shown in the figures represent the lugs on the reverse cylinder as shown in Fig. 21. With the reverse handle in one position (Fig. 25), the large lugs are under the reverse fingers, and current passes from finger 19 to finger A₁, and from finger 15 to finger A₂. Fig. 26 shows the relative position of reverse fingers and lugs for the reverse position of the controller handle. In this case the current passes from finger 19 to A A₁, and from finger 15 to finger A A₂. The effect is to change the direction of flow in the armatures while that in the fields remains the same as may be observed by the arrows.

[Illustration: Fig. 26. Reverse Position of Reverse.]

=Wiring of Type L Controllers.= The type L controller, shown in Fig. 27, while accomplishing the same results as the type K, is wired in a radically different manner. The circuit is opened in changing from series to multiple connections. The controller handle makes two complete revolutions in moving from the series to the multiple position. It is geared to the rheostatic cylinder in such a manner that the first half of both the first and second revolutions gives this cylinder one complete turn. During the second half of the revolution the cylinder is returned to its original position. The controller handle is so connected to the commutating arm that this stands in a central position for the off position of the handle. At the beginning of the first revolution it is swung to the left, throwing the motors in series. At the beginning of the second revolution it is moved to the right, putting the motors in multiple.

The rheostats instead of being wired in series are connected in multiple. Current passes from the blow-out coil to the bottom fingers of the controller S, and thence to the rheostats. On the first point the current returns over R₁ to the controller cylinder. It passes off through a collar at the base of the cylinder through No. 1 cut-out, and the reverse, which is shown in the central position, to No. 1 motor. On returning to the controller over E₁ it passes to the upper section of the commutating arm. In the diagram this is shown in the central position. In series it is thrown to the left. The current then passes from the commutating arm to No. 2 cut-out, and to No. 2 motor. Movement of the controller handle further multiplies the paths through the rheostats and finally, when fingers S rest on the cylinder, the rheostats are short-circuited. If the controller handle is moved still farther, the rheostat cylinder is returned to the off position and the commutating arm is thrown to the left. With the arm in this position the current divides, one portion passing to No. 1 motor as before and to ground by way of the upper section of the commutating arm; while the other branch goes by way of the lower section of the commutating arm to the cut-out switch for No. 2 motor and thence to the motor.

[Illustration: +Diagram of Connections+ _for_ L2 +Controller+ Fig. 27.]

Reversing is accomplished by one-quarter revolutions to the right and left of the segments shown. It is evident that this will connect either A₁ or A A₁, to the trolley. And likewise connect the other armature leads.

=Reversal.= The reversing handle and the main controller handle are made interlocking so that the motors cannot be reversed without first throwing the controller to off position. This is to prevent damage to the motors through careless or inadvertent throwing of the reverse handle when the controller is on some of its higher points. Such a reversal would cause an enormous current to flow through the motors, and would be likely to damage them and to open all the circuit breakers and fuses in that circuit. The reason for the enormous flow of current is, of course, that the counter-electromotive force of the motors, when reversed with the car going at some speed, would materially add to the electromotive force of the trolley line, instead of opposing it as when the cars are in operation. The current flowing through the motor circuit would then be equal to (_electromotive force of line_ + _electromotive force of motors_) ÷ (_resistance of motors_), which would result in a very large current.