A system of signaling by which signals can be sent to the engine room from any point along the haulage road is shown in Fig. 15. The bare conductors a and b leading from the battery are supported on insulators parallel to each other along the roadside, and about 6 in. apart. A short iron rod, placed across the wires a, signals to the engineer, or by simply bringing the two wires together a signal may be sent. When the engineer hauls from different roads, the signaling system should be supplemented with indicators, so that when the bell rings the indicator will show from which point the signal came, and in case several signals were given at the same time, the engineer should not heed any until the indicator shows that a complete signal came from one place.

FIG. 15

A system of signaling for showing whether or not a section of track is occupied by another motor is shown in Fig. 16. White lights indicate a clear

track and darkness an occupied section. A single-center hinge, double-handle switch at each signal station is used and a touch of the handle throws the switch in the desired direction. The switches are placed in the roof, 4 ft.

above the rails within easy reach of the motorman. Each switch is provided with a spring (not shown in the figure) which, drawing across the center hinge when the handles are in their central position, insures a perfect contact when the switch is inclined toward either the trolley or rail-terminal plug.

DYNAMO AND MOTOR TROUBLES

SPARKING AT BRUSHES

Faults in dynamos and motors may be classed as follows: Sparking at the brushes; heating of armature, field coils, and bearings; noise; too high or too low speed. Besides, a motor may stop, fail to start, or may run backwards or against the brushes and a dynamo may fail to generate electricity.

Brush Faults.-Sparking at brushes may be due to some fault with the brushes.

1. The brushes may not have been set diametrically opposite one another because they were not set properly while at rest by counting the bars, by measurement, or by the use of reference marks on the commutator. Brushes can be set properly, if necessary, in an emergency while the machine is running by bringing the brushes on one side to the least sparking point by moving the rocker-arm, and then adjusting the brushes on the other side to the least sparking point by moving in or out the brush holder and clamping in new positions.

2. The brushes may not have been set at a neutral point. In this case, move the rocker-arm slowly back and forth until the sparking is stopped or reduced to a minimum.

3. The brushes may not have been properly trimmed. If sparking begins from this cause and the dynamo cannot be shut down, bend back and cut off the loose and ragged wires; retrim as soon as possible after the machine is shut down. If there are two or more brushes in each set they may be changed one at a time on a low-voltage machine while it is running. If there is a singing or hissing at the brushes apply a little mineral oil or better yet vaseline, or hold a piece of stearic-acid candle on the commutator a moment and then wipe off, leaving just a faint trace of oil or grease. To eliminate noise, it may be necessary to lengthen or shorten the brushes in the holders until a firm but gentle pressure is maintained free from vibration. Use only a cloth, never waste, to wipe off commutator.

4. The brushes may not be in line. In this case, adjust each brush until the brushes rest on the same line and square with the commutator bar, bearing evenly throughout their width, unless purposely staggered. In case of a broken circuit in an armature winding, it is sometimes necessary to bridge the break temporarily by staggering the brushes until the machine can be shut down,

when it should be repaired; this is only a temporary makeshift to reduce sparking during a run when the machine cannot be stopped for repairs.

5. The brushes may not make good contact. In this case, clean the commutator of oil, dirt, or grit so that the brushes will bear properly on it and adjust by the proper tension screws and springs until a light but firm and even contact is secured.

Commutator Faults. Sparking at the brushes may also be due to some fault with the commutator.

1. The commutator may be rough, worn in grooves and ridges or out of round. In any case, the commutator should be ground down with fine sandpaper (never emery in any form) laid in a piece of wood curved to fit the commutator, or a curved suitable stone, and finally polished with soft, clean cloth. If the commutator is too bad to grind down, it may be turned down with a special tool and rest while the commutator is turning slowly in its own bearings or the armature may be removed from the machine, placed in a lathe, and the commutator turned off with light cuts. An armature should have from toin. end motion so as to distribute the wear of the brushes evenly and to prevent their wearing ruts in the commutator. Brushes may be shifted sidewise occasionally to assist in the distribution of wear. If there is no end motion, the shoulders should be turned off of the shaft or filed or turned off of bearings until the armature has some free end play while in motion.

2. One or more commutator bars may be too high. A high bar should be forced down carefully with a wooden mallet or block of wood, care being taken not to bend, bruise, or injure the bar, and then tighten the clamping rings; if this does not remedy the fault, the high bar should be filed or trimmed down to the level of the other bars, or the commutator ground or turned down a little. High bars may cause the brush to jump or vibrate so as to sing. 3. One or more commutator bars may be too low. In this case, the commutator may be ground or turned down until no bearings are below a true cylindrical surface.

HEATING OF ARMATURE, FIELD COIL, AND BEARINGS

Heating of Armature.-The heating of an armature may be due to the machine being overloaded, to a short circuit, a broken circuit, or a crossconnection; the causes and remedies for such conditions are given under the head of Miscellaneous Troubles. Moisture in the armature coils should be removed by drying out the coils with a slow heat secured by sending through the armature current that is regulated so as not to exceed the proper amount. If the moisture is so bad as to cause a short circuit or a cross-connection or to heat the armature too much, it may be dried out by the heat produced by its under current while running.

The heating of an armature may also be due to eddy currents in the armature coil. If the iron of the armature is hotter than the coils after a short run, the faulty armature core should have been more laminated and the laminations should have been better insulated from one another. There is no remedy but to rebuild the armature.

Heating of Field Coils.-The heating of field coils may be due to excessive current in the field circuit, eddy currents in the pole pieces, or moisture in the field coils. Excessive currents in the field circuit of a shunt machine may be reduced by decreasing the voltage at the terminals by reducing the speed or increasing the resistance of the field coils by winding on more wire, by rewinding with finer wire, or by putting a resistance in series with the field. Excessive current in the field circuit of a series machine may be reduced by shunting a portion or otherwise decreasing the current in the field coils or by taking off one or more layers of wire or rewinding the field coils with closer wire. Excessive current in a shunt or series machine may of course be due to a short circuit or from moisture in the coils acting as a short circuit.

Eddy currents in pole pieces may cause the pole pieces to become hotter than the coils after a short run. This is due to faulty construction or to fluctuating current; if due to the latter, the current should be regulated.

Moisture in the field coils may cause the coils to be lower in resistance than normal or it may cause a short circuit or a contact between the coils and the iron of the machine. The coil should be dried out, as already explained. Excessive current may be due to a short circuit or to moisture in the coils acting as a short circuit.

Heating of Bearings.-Heating of bearings may be due to not enough or a poor quality of oil. The remedy is to use plenty of oil and see that it is fed properly. Only the best quality of mineral oil, filtered clean and free from

grit should be used, and care must be taken not to flood the bearings so as to force the oil upon the commutator or into the insulation of the brush holders, as it will then gradually char and gather copper dust and form a short circuit. Vaseline, cylinder oil, or other heavy lubricant may be used if the ordinary oil fails to remedy the hot boxes; such lubricant should be used until the run is over, when the bearings should be cleaned and adjusted.

When ice is used to cool the bearings, care must be exercised not to let it get into the commutator or armature, which it may ruin unless they are waterproof as in the case of street-car and some other motors. A machine must never be shut down because of a hot bearing until all the remedies given therefor have been tried and proved of no avail. If it is absolutely necessary to shut down a machine, take the belt off as soon as possible, do not allow the shaft to stick in stopping, get the bearings out and cool off as soon as possible, but not in water, as this may ruin them. Then scrape, fit, clean, and polish the bearings and shaft and see if it can be turned freely by hand before putting on the belt and starting again. Use none but the best of mineral lubricating oil. New oil and oil from self-oiling bearings should be filtered before being used.

Heating of bearings may be due to dirt, grit, or other matter in bearings. In this case wash out the grit by flooding with clean oil until the run is over; then clean out the bearings, being careful, however, not to flood the commutator or brush holders. When the run is over, remove the cap of the bearing and clean the journals and bearings very carefully, then replace caps and lubricate well. Allow bearings to cool off naturally. It may be necessary to entirely remove the bearings and clean the grit away, polish all parts, and set up again.

Should rough journals or bearings cause hot bearings, polish the bearings in a lathe, remove cuts, scratches, and marks; then fit new bearings of Babbitt or other metal.

If journals are too tight in bearings, loosen the bolts in the cap of the bearing, put in very thin pieces of packing or sheet metal between the caps and the base, retighten the bolts until the run is over; then make the journal bearing smooth and so it can be rotated by hand. If necessary, turn down, smooth, and repolish the journal or scrape the bearings to a proper fit.

In the case of a bent or sprung shaft, bend it by carefully springing the shaft or turning it in a lathe.

If a bearing is out of line, loosen the foot of the bearing until the armature can be turned freely by hand with the belt off, being careful to keep the armature in the center of the polar space. Ream out the bolt in dowel-pin holes and fit new dowels to allow the new position to be retained when the bolts are drawn up tight. If the shaft must be raised or lowered, pack up or trim down the feet of the bearing to allow the proper setting.

Heating of bearings may be caused by end pressure of the pulley hub or shaft collars against bearings. The foundation should be level and the armature should have a free end motion. If there is no end motion, turn or trim off the ends of the bearings or hub on the shaft until the proper end motion is secured. Line up the shaft pulley and belt so that no end thrust is maintained on the shaft by a sidewise pull of the belt. The armature should have free end play while in motion.

If the heating of the bearings is caused by too great a load or strain on the belt, reduce the load so that the belt may be slackened and yet not slip; avoid vertical belts if possible. Use larger pulleys, wider and longer belts, run slack on top to increase adhesion and pull of belt without excessive tightening, so that a full load may be carried. Belts should be tightened just enough to drive a full load smoothly without that vibrating or flapping which may cause the lamps to flicker.

An armature out of center in polar space may cause hot bearings. The bearings may be worn out, thereby allowing the armature to move out of the center and to need replacing. Center the armature in the polar space and adjust the bearings to a new position, as already explained. File out the polar space to give equal clearance all around or spring the pole pieces away from the armature and secure it in place; this will be a difficult, if not an impossible, job in large machines.

NOISE

If the armature strikes or rubs against the pole pieces, bend or press down the projecting wires and secure strongly in place with tie-bands or wire. File out the pole pieces where the armature strikes. The bearings may be worn

out, thus allowing the armature to move out of the center and may need readjustment. It is sometimes, though seldom, necessary to file out the polar space to give equal clearance all around, or to spring the pole pieces away from the armature and to secure it in place. This is a difficult, if not an impossible, job on large and rigid machines.

Collars or shoulders on the shaft or the hub or web of the pulley may strike or rattle against the bearings, because the bearings are worn out and too loose. New bearings may be required if the remedies given for bearings out of line and for loose screws, bolts, or connections do not remove the trouble. If the noise is caused by loose screws, bolts, or connections, tighten them all to a firm bearing and keep them so by daily attention. The jar and movement of the machine tends to work screwed connections loose when they are not held by check-nuts, cotter pins, or some other device designed for that purpose.

Singing or hissing of the brushes may be stopped by the remedies described for brushes not properly trimmed. Sometimes, it may be necessary to apply a little mineral oil, preferably vaseline, or a piece of stearic-acid candle against the commutator and then wipe it off; just a faint trace of oil or grease is all that is necessary. The brushes may be adjusted in the holders until a firm, but gentle, pressure free from any vibration is secured. The trouble may be due to a faulty commutator, the remedies for which have already been given. Flapping or pounding of belt joints will be remedied if the ends of the belt are properly laced or joined together, or an endless belt used.

If belts slip from overload, use larger pulleys, wider and longer belts, and run with the slack side of the belt on top.

To stop the humming of armature lugs, or teeth as they pass the pole pieces, slope the ends of the pole pieces, in order that the armature teeth shall not pass the edges all at once. Decrease the magnetism of the field or increase the magnetic capacity of the teeth.

REGULATION

Speed Too High-Too high a speed may cause the engine to fail to regulate with a varying load, in which case adjust the governor or other means of regulation. If this cannot be accomplished, get a better engine. The engine should regulate closely with proper steam supply from no load to full load.

A series motor may run too fast on account of receiving too much current for the load that it carries, and hence the motor runs away. In the case of a series motor on a constant-potential circuit, insert a resistance in series with the motor in order to cut down the current; or use a proper regulator or controlling switch, or change to automatic speed regulating motor.

The regulator may not be properly set, the proper amount of current may not be used, or the motor may not be properly proportioned and, therefore, may fail to regulate properly. The regulator should be adjusted to control the speed, the proper current, voltage, and rheostat should be used or get a motor properly designed for the work.

Speed Too Low. It may be necessary to drive the dynamo with a better engine that will regulate better with proper steam supply from no load to full load. The motor may be overloaded, the causes and remedies for which have been previously given. There may be a short circuit in the armature, a striking or rubbing of the armature against the pole pieces, or an unusual amount of friction, all of which have been explained.

MOTOR STOPS, FAILS TO START, OR RUNS BACKWARDS OR AGAINST THE BRUSHES

The stopping of a motor or its failure to start may be due to no load. The stopping may also be due to the motor's being greatly overloaded. In this case reduce the load to the proper amount that the motor is rated to carry.

Sometimes the stopping is caused by excessive friction, due to the heating of the bearings, the cause and remedies for which have been given. Open the switch and keep it open and the arm of the rheostat on the off-position while locating and eliminating the trouble; then close the switch and shift the arm gradually to the on-position to see if everything is correct. With a series motor no great harm will result from the motor stopping or failing to start; with a shunt motor on a constant-potential circuit the armature may and probably will burn out or the fuse will blow.

The stopping of the motor may be due to the circuit being open on account of the safety fuse being melted, a broken wire, a broken connection, the brushes not being in contact with the commutator or brush holder, or an open switch.

If the

In any case, see that the switch is in good order and makes its connections properly. Then, if necessary, open the switch, locate and repair the trouble, and replace. A melted fuse should not be replaced until the fault is corrected, for otherwise the fuse will melt again when the motor is started up. open circuit is caused by a fault in the armature or with the brushes, the remedy has already been given. If the current should fail or be shunted off from the machine, open the switch, return the starting lever to its off-position, and wait until the current is again supplied to the line, testing from time to time by closing the switch and moving the starting lever to close the circuit. When the trouble is due to a short circuit of the field, armature, or switch, test for and repair the trouble if possible, carefully looking over the insulation of binding posts and brush holders for poor insulation, oil, dirt, or copper dust. Such causes and remedies are given more fully under Armature Faults due to short-circuited coil.

When the trouble is due to wrong connections through the motor, connect up the motor properly, referring to a correct diagram of connections; if same is not to be had, try reversing the connections to brush holders or make other changes until the correct connections are secured for the direction of rotation desired; then connect up permanently.

FAILURE OF DYNAMO TO GENERATE

Reversed Residual Magnetism.-The dynamo may fail to generate because the residual magnetism is reversed, owing to reversed current through field coils due to earth's magnetism, proximity of another dynamo, or too weak residual magnetism. In this case, a current should be sent from another dynamo or from a storage or primary battery through the field coils in the proper direction to correct the fault. The polarity may be tested by holding a compass needle as near as convenient to the center of each pole piece and the connections of any or all of the field coils may be changed until the proper polarity is obtained.

When the reversed residual magnetism is caused by reversed connections, connect properly for the direction of rotation desired, referring to proper diagram of connections if obtainable. See that connections for series coils (in compound dynamo) are properly made as well as those for the shunt coil. Make such changes in connection as may be necessary to give the desired and correct rotation.

If the brushes are not in their right position, shift them until evidence of improvement is secured. The position of the brushes for the best generation of energy should be clearly understood and is generally at or near the neutral point, as has already been stated.

Short Circuit in Machine.-When the failure of the dynamo is due to a short circuit in the machine, the procedure is the same as when a similar fault occurs in the motor.

Short Circuit in External Circuits. If a lamp circuit or other device or part of a line is short-circuited or grounded, it may prevent the building up of the shunt, or compound, field of the dynamo. In this case, look for and remedy the short circuit before closing the switch. This fault, also, should be treated the same as similar faults in motors.

Field Coils Opposed to One Another.-If some of the field coils should be opposed to one another, reverse the connections of one or more of them and test the pole pieces with a compass. Alternate poles should show opposite polarity. If the pole pieces are found to be of proper polarity or are so connected as to give the proper polarity, and if the dynamo does not build up, try the remedies given under reversed residual magnetism due to a reversed current through the field coils, earth's magnetism, proximity of another dynamo or to too weakened residual magnetism. If current is not then produced in the proper direction, reverse field connections or recharge in proper direction. Open Circuit. When the failure of the dynamo to operate is due to an open circuit, it may be that the brushes are not in contact. The remedy for this fault has already been given.

In the case of a broken or melted safety fuse, open the switch, look for and repair the trouble and replace the fuse. A dead short circuit should blow the fuse and a new fuse should not be put in until this fault is removed, as it will simply blow the fuse-again when the switch is closed. The remedy for this trouble is obvious.

If the external circuit is open or not properly connected, locate the trouble and repair it while the dynamo switch is open. The remedy for an open circuit in the armature has already been given.