IRLF 
 
 E7E 
 
 HHBB^B 
 
 
 
REESE LIBRARY 
 
 oi i HI: 
 
 UNIVERSITY OF CALIFORNIA. 
 
 
 No.(P*Lsi) /O . C/JSS No. 
 
ELECTRIC RAILWAY MOTORS 
 
 THEIR 
 
 Construction, Operation and 
 Maintenance 
 
 AN ELEMENTARY PRACTICAL HANDBOOK FOR THOSE EN- 
 GAGED IN THE MANAGEMENT AND OPERATION 
 OP ELECTRIC RAILWAY APPARATUS 
 
 WITH 
 
 RULES AND INSTRUCTIONS FOR MOTORMEN 
 
 BY 
 
 NELSON W. PERRY, E. M. 
 
 OFTHE 
 
 UNIVERSITY 
 CALIFORNIA 
 
 . NEW YORK 
 
 THE W. J. JOHNSTON COMPANY 
 253 BROADWAY 
 
 1896' 
 
COPYRIGHT, 1894, 
 
 BY 
 STREET RAILWAY GAZETTE COMPANY. 
 
r/ 
 
 
 UNIVERSITY 
 
 CALIFORNIA. 
 
 CONTENTS. 
 
 CHAPTER PAGE 
 
 Preface, . v 
 
 I. Introduction, ...... 1 
 
 II. Technical Terms, etc., 9 
 
 III. Ohm's Law ; Rate of Work ; Examples, . 16 
 
 IV. The Electric Current and its Properties, . 28 
 V. The Electric Current and its Properties (con- * 
 
 tinned) ; the~&en<jid, . . / . 39 
 VI. Measuring the Current ; Magnetism and Elec- 
 tro-Magnetism, 48 
 
 VII. Lines of Force ; the Closed Magnetic Circuit ; 
 
 Magnetic Leakage, ; .... 59 
 VIII. Polarity, Magnetism and Current, . * . 67 
 IX. Electro-Magnetic Induction ; The Continuous 
 Current Dynamo ; Increase of Electromo- 
 tive Force ; Eddy Currents in Armature, 75 
 X. Shifting of the Armature Wires ; Open and 
 
 Closed Coil Armatures, ;..-". . 96 
 XI. Drum and Ring Armatures ; Consequent Poles 
 
 and Multipolar Field Magnets, . 102 
 
 XII. Multiple Arc and Series Arrangement ; Cur- 
 rent Characteristics of Multiple and Series 
 Arrangements in Generators, . . . . 109 
 
 XIII. Current Characteristics in Translating De- 
 
 vices ; Multipolar Fields, '. k . V'- . . 116 
 
 XIV. The Dynamo Electric Principle; Series, 
 
 Shunt and Compound Winding ; the Re- 
 tersibility of the Dynamo. . * . 129 
 
 iii 
 
IV 
 
 CONTENTS. 
 
 CHAPTER PAGE 
 
 XV. The Electric Motor, 139 
 
 XVI. The Electric Motor (continued] ; Torque, 145 
 XVII. The Line of Commutation ; Counter-Elec- 
 tromotive Force, ..... 151 
 XVIII. Counter-Electromotive Force and Speed 
 Regulation ; Requirements of Speed Reg- 
 ulation, 157 
 
 XIX. The Sperry and Johnson-Lundell Systems, 169 
 XX. The Leonard, Perry and Other Systems ; 
 the Perry System of Series Electric Trac- 
 tion ; Storage Battery Traction ; Conduit 
 
 Systems, 177 
 
 XXI. The Management of Street Railway Motors ; 
 Sparking at the Commutator ; Motor 
 Stops Ox Fails to Start, . . . . 191 
 XXII. Specific Directions to Motormen, . . 201 
 
 XXIII. Instructions to Inspectors and Superintend- 
 
 ents, 213 
 
 XXIV. Locating Faults ; Commutators ; Drop 
 
 Method of Testing for Faults ; Insulation 
 Test ; Bearings ; Gears and Pinions ; 
 
 Controllers, 220 
 
 XXV. Trolley Wheels; In can descent Lamps; Con- 
 
 elusion, . . - /" : , . . . 229 
 
OF THE 
 
 UNIVERSITY, 
 CALIFORNIA 
 
 PEEFACE. 
 
 THE m&ttei' contained in this book first ap- 
 peared as a serial in the /Street Railway Gazette, 
 beginning with the first issue in January and ex- 
 tending through succeeding issues until that of 
 July 21. The ostensible object of the series was 
 to provide for motormen an intelligent elementary 
 exposition of the principles upon which are founded 
 the apparatus which they, too often without any 
 conception of their character, are called upon to 
 handle. It has been assumed by the author that 
 the audience is entirely ignorant both of the 
 nomenclature and principles of applied electricity, 
 but is anxious to gain a foothold, as it were, on 
 the science. To this end he has avoided the use 
 of all technical terms, except such as necessarily 
 form the very alphabet of the science, and these 
 have been met boldly the principle being fol- 
 lowed, however, of first explaining by simple ex- 
 periments, such as are readily within the scope of 
 a child of fifteen years, the phenomena themselves, 
 and then assigning to these phenomena their proper 
 names. 
 
 In the study of a new language, a new science 
 or a new branch of mathematics it is the first 
 principles that are almost always the most difficult 
 to acquire. Few of us, probably, recall the task it 
 
VI PREFACE. 
 
 was for us to learn the alphabet of our language. 
 More of us will remember the difficulty experi- 
 enced in acquiring the multiplication table, and all 
 who have pursued the higher mathematics will 
 remember how, after passing through algebra, 
 geometry, and trigonometry, they were perplexed 
 by the very rudiments of the differential calculus. 
 As each step was taken the mind had to be pre- 
 pared for the new study by means of analogies 
 which, though never exactly true, enabled the 
 mind to grasp ideas approximately correct only, 
 but which served as stepping-stones to other 
 ideas which approached more nearly the truth. 
 In this work free use has been made of analogy, 
 but by extending the analogies over a somewhat 
 extended range, and by making use of some which 
 are believed to be new, it is thought that the 
 ideas inculcated by them will be as free from 
 error as is possible under such circumstances. 
 
 The author has insisted upon a full understand- 
 ing of Ohm's law the fundamental law of the 
 flow of currents as a prerequisite to a further 
 understanding of the subject. This law, however, 
 is not sprung at once upon the student, but is led 
 up to by the series of simple and inexpensive ex- 
 periments before referred to, in the performance 
 of which the student at last finds himself sur- 
 prised that he has not only practically worked out 
 for himself the law, but has actually constructed 
 an elementary dynamo and motor for himself, 
 together with instruments for measuring electrical 
 currents. The law is then enunciated and further 
 illustrated by a number of concrete examples, in- 
 volving only the simplest mathematics, but at the 
 same time 'practically covering every problem in 
 electrical distribution by direct currents that the 
 
tBEFACB. Vll 
 
 electrician is ever likely to be called upon to solve. 
 The extreme simplicity of these operations all 
 depending upon Ohm's law will doubtless be a 
 revelation to most of those for whom this book is 
 intended. 
 
 The dynamo and motor are treated as one and 
 the same machine, as they really are, and it is 
 shown that they all, of whatever type, are built 
 upon exactly the same principles, and these are 
 explained and developed from the simplest forms 
 by the aid of numerous cuts and diagrams leading 
 up to the finished multipolar machine of to-day. 
 The intricacies and refinements of the completed 
 machines, are, however, avoided as tending in 
 a book of the scope of this one to undesirable 
 confusion. 
 
 The theory and methods of speed control of 
 railway motors are treated in as comprehensive 
 manner as seemed desirable, the aim being always 
 to explain the why and wherefore of a given 
 arrangement, rather than to describe in full a 
 specific device. Following this comes a brief 
 description of some of the newer electric railway 
 systems which promise to come into more or less 
 general use, but which are not now generally 
 known to the lay public. 
 
 Thus far it is believed that the book will be of 
 service to others than motormen that it will be 
 of interest to that large class of intelligent Ameri- 
 cans who desire to acquire a somewhat definite 
 knowledge of this mysterious agent that they see 
 working around them daily, who wish to know 
 something more definite of electricity, either with 
 the view of taking up its study more systematically 
 in the future, or for the purpose solely of getting 
 a more intelligent idea of its workings.^ 
 
Vlll PREFACE. 
 
 The last part of the work is devoted to direc- 
 tions for the care of street railway motors, the 
 detection and remedy and prevention of their 
 faults. These suggestions come from a most ex- 
 tended and varied practice, not of the author's 
 alone, but of other engineers and of the manu- 
 facturers of the motors themselves. This portion 
 of the book is especially intended for those whose 
 business it is to handle the motors. The -author 
 hopes that this portion of the book will be found 
 particularly useful to those for whom it is in- 
 tended by reason of the fact that he has en- 
 deavored in the earlier chapters to so lead up to 
 the subject that the reason for the various rules 
 and precautions laid down will be at once apparent 
 to the motorman, and that they will thus appeal 
 to his intelligence much more strongly than they 
 would if given empirically. 
 
 In conclusion the author wishes to acknowledge 
 the assistance he has received by free reference to 
 Crocker and Wheeler's " Practical Management of 
 Dynamos and Motors," Crosby and Bell's "The 
 Electric Railway," Silvanus Thompson's "Dynamo- 
 Electric Machinery," and " The Electromagnet," 
 and especially to the kind response to inquiries of 
 The Westinghouse Electric and Manufacturing 
 Co., The General Electric Co., The Short Electric 
 Railway Co., The Sperry Electric Railway Co. 
 
ELECTRIC RAILWAY MOTORS, 
 
 THEIR 
 
 CONSTRUCTION, OPERATION AND 
 MAINTENANCE. 
 
 CHAPTER I. 
 
 INTRODUCTI ON. 
 
 SOME years ago I became acquainted, as a 
 boarder, with a bright young man who introduced 
 himself to me as an electrician. It happened that 
 we were placed at the same table, and as he was 
 of an affable disposition we soon became veiy well 
 acquainted. Whenever the subject of electricity 
 came up, he was accustomed to speak in such a 
 way as to impress all his hearers with the idea 
 that he was an authority on all such subjects 
 whose opinions were not to be questioned, and as 
 he was generally correct in his statements I also 
 became somewhat impressed with his knowledge, 
 and would often ask questions sometimes for in- 
 formation, and sometimes to see how nearly his 
 opinions coincided with my own. 
 
 I found that he had been sent out by the then 
 
2 ELECTRIC RAILWAY MOTORS. 
 
 leading company engaged in electrical railway 
 construction, and his business in that city a 
 Western one was the construction of its first elec- 
 tric railway. We soon became quite good friends, 
 and when the power house was nearing completion 
 I was a privileged character within its walls, for 
 visitors were rigidly excluded as a rule ; and later, 
 when the first tests of the operation of the road 
 were made, I was one of the fortunate few invited 
 guests. 
 
 The first car over the line started out from the 
 barns at ten o'clock at night, and carried as pas- 
 sengers, besides myself and the gentleman referred 
 to, but three others all officials of the road. 
 Everything went smoothly until the further ter- 
 minus about three miles distant was reached, 
 when something gave way and we were stalled. 
 
 I must add here that my friend had not yet dis- 
 covered that I was myself an electrician. I had 
 had no other object in concealing the fact than 
 that, as I had not been asked my business, it had 
 never been necessary for me to declare it, and I 
 felt that he would talk with me more freely if he 
 did not know it. He knew that I was an engineer, 
 however, and he attributed my ability to solve 
 certain questions which arose to that fact to that 
 combined with what he took to be a smattering of 
 electricity which he supposed I had acquired in 
 some way or other. 
 
 As a matter of fact, however, I considered my- 
 self a full-fledged electrical engineer, and was, as 
 electrical engineers went in those days; for besides 
 having had a pretty thorough training on the 
 purely theoretical side of electricity, I had worked 
 in two of the largest shops in the country in all 
 the departments of electrical manufacture. I 
 
had wound armatures and fields, and assisted in 
 making and dressing down all the other parts of 
 machines, both large and small ; had assembled 
 these various parts, connected them up, soldered 
 the connections and finally tested the completed 
 machines. I had also assisted in installing one 
 road myself, and had inspected every road but 
 one that was at that time in operation in the 
 country, so that I was pretty familiar with electric 
 railroad construction as then developed. I knew 
 that my friend's experience had not been nearly as 
 wide as my own, and I was glad to be with him on 
 the occasion of the opening test of this, which I 
 suspected was the first road over whose construc- 
 tion he had been completely in charge. 
 
 Well, as I say, something had happened, which 
 was only really discovered when the attempt was 
 made to run the car back. There was a consider- 
 able grade at starting, and this the car failed to 
 ascend. We backed down to the level and tried 
 it again. The car worked all right until the grade 
 was reached, when she stopped again. This was 
 repeated a number of times, and always with the 
 same result. My own experience made me suspect 
 at once the true trouble, but it would not do for 
 me to suggest. My friend had been playing the 
 role of a great authority on electric railroad mat- 
 ters for the special benefit of his invited guests on 
 the car. He was in very high feather, and not 
 without reason, that night, because the work of 
 his hands was finished, and now he was showing 
 his admiring guests how immeasurably better it 
 worked than even his own anticipations had led 
 him to hope. 
 
 For me to have suggested the cause would have 
 been considered a piece of impertinence of the 
 
4 ELECTEIC RAILWAY MOTORS. 
 
 highest order, not only by him, but by the other 
 guests, who looked upon my friend as a wonderful 
 man ; so I kept quiet. 
 
 My friend was a man of great self-confidence 
 and equal to the emergency. In reply to inquir- 
 ing glances, he said it was due to " something or 
 other " using a term not down either in Web- 
 ster's or Houston's dictionary that it was a very 
 trivial matter and could easily be fixed ; he would 
 back down to the level again and fix it. He did 
 so that is, he backed down, and, after making an 
 examination, said : " Yes, that's it, just as I 
 thought ; the * something or other ' was just what 
 caused the trouble ; " and he straightway pro- 
 ceeded to correct the thing. In the meantime 
 I had had an opportunity of verifying my suspi- 
 cions, but of course kept my counsel. When all 
 was declared ready we entered the car again, and 
 my friend, who really had done nothing, as far as 
 I had been able to see he certainly hadn't 
 touched the root of the trouble turning on the 
 current to the last notch, said, " Now we go ; " 
 and we did until we had gotten even a little way 
 beyond the point on the grade where we had 
 always stalled before, and then we stalled again. 
 We had gained a few feet over previous attempts 
 simply because we had gained a little more 
 momentum on the level. I think my friend 
 understood this as well as I, but he pointed to the 
 small gain with apparent pride, and with unblush- 
 ing assurance stated that that proved that he 
 was right in locating the trouble, and that now 
 he would run back and fix the thing for good. 
 We went back and he got under the car again. 
 I watched him closely this time, and after doing 
 absolutely nothing more than fumble around a 
 
INTRODUCTION. 5 
 
 little he came out and announced that " Now I've 
 fixed her for good, and I'll show you how we can 
 mount that grade." 
 
 I have often heard it claimed by horsemen, and 
 have seen several instances myself where good re- 
 sults seemed to follow the plan, that to start a 
 balky horse, the best way is simply to jump out of 
 the wagon and pretend to fix the horse's bridle, 
 then get in, and on giving the signal the horse, 
 which neither whip nor oaths could budge before, 
 would start right off as though nothing had 
 happened. This was exactly what my friend 
 seemed to have done and nothing more, and when, 
 after we had all followed the injunction to get 
 " aboard," and he commenced to turn on the cur- 
 rent I could not but be astounded at the cheek, or 
 rather the assurance, which enabled him to keep 
 up the appearance of entire confidence in the suc- 
 cess of another attempt which he knew must fail 
 for exactly the same reasons the others had. It is 
 needless to state what the result was, further than 
 to say that we did not get quite as far this time as 
 we had before, and it is also needless for me to 
 state how, with equal composure, he gave some 
 excuse for going back again to the starting point. 
 I think he said he had forgotten his monkey- 
 wrench or something else. 
 
 I determined this time to speak, and when we 
 stopped at the bottom I got off and commenced 
 looking around as if hunting for something, and 
 stooping down, some distance from the car so as 
 to get him alone, cried out, " I've found it," and, as 
 I expected, he rushed over, leaving the others be- 
 hind, and I whispered, " Look at your positive brush 
 on the front motor." He heard me and under- 
 stood. He stooped down, though, as if to examine 
 
6 ELECTEIC RAILWAY MOTORS. 
 
 what I pretended to have found, and then, in tones 
 loud enough to be heard by the others, said, " No, 
 that's not it, but I've got something that will do 
 as well," and lost no time in getting under the car 
 and repairing the broken connection which had 
 rendered useless one of our motors. 
 
 When we got on to the car again and he grasped 
 the controlling switch, I know I had more confi- 
 dence that we could ascend the grade, but his 
 appearance betrayed not one whit more than it had 
 on the two previous attempts. As for the other 
 parties, I am sure there was never a suspicion. 
 We completed the return trip in great shape, and 
 the trial trip was pronounced a success, and my 
 friend was the hero of the hour. We returned to 
 the car barns, and after he had seen everything 
 safe for the night we walked home together. He 
 seemed buried in deep thought for some distance, 
 but finally broke the silence by, "You played me 
 a darned mean trick." I was very much surprised 
 at his attitude, thinking that he should rather 
 have thanked me for helping him out of his diffi- 
 culty. I knew that he would have found the 
 difficulty after a while if left to his own resources, 
 but thought I had saved him some embarrassment 
 which further delay might have caused him, so 
 I laughingly asked, " How ? " to which he replied : 
 " By not letting me know before that you were an 
 electrician." 
 
 The above anecdote is related now merely to 
 show how a little bravado, judiciously used, may 
 save a reputation where entire candor would have 
 been fatal. However reprehensible this practice 
 may be in the abstract, it is one that pervades all 
 walks in life, and is nowhere more prevalent, per- 
 haps, than in the medical profession. It is, in fact, 
 
INTRODUCTION. 7 
 
 often used there to advantage, for if the physician 
 should fail to inspire his patient with confidence in 
 the beginning, it would be almost impossible for 
 him to succeed later, and it is conceded that confi- 
 dence in one's physician, as well as in the remedies 
 one takes, is of the greatest help in curing disease. 
 
 If we find this practice so general in such an 
 honorable profession as medicine, it is not surpris- 
 ing if we find it among the motormen, nor can we 
 disparage it there while we uphold it elsewhere. 
 In fact, I believe the motorman or electrical artisan 
 is really less to blame than many others by the 
 circumstances of his position. Most often the 
 electric motorman has obtained his position as a 
 reward for faithful services as a driver or con- 
 ductor of a horse car. In his previous occupation 
 his hours have been long and his work exhausting 
 both to mind and body, and when his day's work 
 is done he is in no condition for study or more 
 work. Besides, as a driver, he has probably mas- 
 tered his business, and there has been no incentive 
 to further study. 
 
 With this habit of mind he is transferred with- 
 out any special preparation to the responsibilities 
 of the care of the electrical equipment of his car. 
 He is broken in by someone who has had a little 
 more experience than he has had, and after having 
 been shown the various parts of his apparatus, 
 and how they are intended to operate, is given a 
 set of rules whicli tell him that he must do this 
 and must not do that, and is allowed then to shift 
 for himself. He is expected to talk about a cur- 
 rent which he can't see, and to guard against 
 results which he knows only by name. A new 
 language is placed in his mouth which he' does 
 not understand, but which he understands some- 
 
8 ELECTRIC RAILWAY MOTORS. 
 
 how is intimately connected with his business. 
 His hours are no shorter than before, and books 
 which would explain matters are too expensive, 
 even if he had time to read them, or entirely inac- 
 cessible. His companion motormen are using this 
 new language familiarly, and he soon acquires 
 that habit almost unconsciously, and as soon as he 
 is thus initiated into the charmed circle which 
 speaks this foreign language he becomes with his 
 brother motormen a class distinct from that class 
 from which they have all sprung. If he knows 
 little of electricity, he still knows more than his 
 former companions, and they treat him with a 
 respect due to his superior knowledge. It will 
 not do for him to admit ignorance, and he has an 
 answer ready for every question. Nor does he 
 care to show his ignorance among his companions 
 by asking them questions or by asking questions 
 of others in their presence, and in this way too 
 often stands in his own light. That the average 
 motorman is anxious to inform himself, when he 
 can do so under circumstances which are not em- 
 barrassing, I know well from personal experience, 
 for I have had individuals ply me with questions, 
 when they could get me alone, who would rather 
 have died almost than to have asked the same ques- 
 tions in the presence of fellow- workmen. 
 
 No one blames them for this. It is human 
 nature, and, as I have stated before, they have 
 shining examples in the same practice in members 
 of professions considered more dignified than 
 theirs. 
 
CHAPTER II. 
 
 TECHNICAL TEKMS, ETC. 
 
 WHENEVER we undertake the study of a new 
 subject, it becomes necessary to, in a measure, 
 break away from old things old thoughts, old 
 names, old tools, and oftentimes accustomed 
 methods, and to adopt in their place new ones 
 which those who have had experience in the sub- 
 ject have found more suited to the new. It is 
 this first breaking away from the old and accus- 
 toming ourselves to the new that is the greatest 
 stumbling-block in the path of the student. We 
 can best describe a phenomenon or a thing to 
 a person unfamiliar with it by likening it to some- 
 thing with which he is familiar, and then, after 
 conveying to his mind a clear idea of how the 
 new resembles the old, impress upon his mind as 
 well as we can that the resemblance is not com- 
 plete, and that the manner in which the familiar 
 differs from the unfamiliar is really the essential 
 difference between the two we cannot at first 
 explain this difference clearly ; he must take that 
 much on faith and assume at the outset that what 
 is said is true. As the student becomes more and 
 more familiar with the thing described, by han- 
 dling it and seeing it used, he will begin to appre- 
 ciate more fully its nature, and the peculiarities 
 of the new object itself. It is, therefore, well 
 in the beginning to substitute for the new thing 
 
10 ELECTRIC RAILWAY MOTORS. 
 
 an entirely new name instead of continuing to 
 describe it by the names of things which it partly 
 resembles, so that the mind may associate with 
 the new name the actual qualities of the new 
 thing rather than be misled by the name which 
 the resemblance would indicate. This is true of 
 all sciences, and it is true of electricity. Each 
 branch of science presents some phenomena pe- 
 culiar to itself, and therefore must Jiave names for 
 them, and it is the names peculiar to this science 
 that constitute its technical terms. If a branch of 
 science which we are about to take up is full of 
 phenomena new to us, it will be full of strange 
 names, and it is the mastery of these that is most 
 formidable to us, for the meaning of each sentence 
 is or may be obscured by their presence. It is 
 frequently said that scientific men delight in 
 obscuring their meaning behind technical terms, 
 whereas the fact is they are using that language 
 which is most intelligible to them, and is only 
 unintelligible to us because of our ignorance of 
 the subject. 
 
 If the student could only appreciate the fact 
 that technical language is really the simplest and 
 most direct that can be used, much of the difficulty 
 of the subject at the outset would be removed, and 
 it is therefore deemed wise to add a few words 
 here with the hope of impressing upon his mind 
 the truth of this statement. 
 
 In our everyday life we are constantly making 
 use of technical terms as a matter of convenience; 
 we do it unconsciously, it is true, but are im- 
 pelled to it by the same necessities as is the elec- 
 trician, the geologist or the astronomer. As an illus- 
 tration, suppose we were to try to describe a dog 
 to a person who had never seen one, or any animal 
 
TECHNICAL TERMS, ETC. 11 
 
 of that "family. We would have to describe it in 
 some such vague terms as this : that it had four 
 legs and a tail, was covered with hair, made a 
 peculiar noise when angry or excited (imitating its 
 bark), ate meat as its chief food, etc., etc, rehears- 
 ing many of its characteristics, which, however 
 well described, would apply equally well to some 
 other animal. Supposing, after having failed to 
 convey in this way any adequate idea of the ani- 
 mal, we should secure a specimen and tell him that 
 that was a dog ; the story would be told a great 
 deal better, and ever after the technical term " dog " 
 would have a definite meaning to him a much 
 more definite meaning than any description that 
 we could give. If his education stopped there if 
 he had seen but one breed of dog, and perhaps but 
 a single specimen, all dogs to his mind would be 
 about the same. . If the one examined had been a 
 great, shaggy-haired Newfoundland, he would not 
 recognize in the hairless Mexican dog an animal of 
 the same family at all; so that even after he had 
 seen a dog of one breed it would be almost as diffi- 
 cult to describe to him another of a different breed 
 as it was in the first place to tell him what kind 
 of an animal a dog of any kind was. On the other 
 hand, among dog fanciers how definite the phrase 
 "Irish setter" is, for instance. Those two words 
 that technical phrase convey to the mind more 
 definite information than could be imparted in 
 pages of printed matter, or perhaps more than in 
 hours of discourse. To the person who was very 
 familiar with dogs it would give an idea not only 
 of the size and color, but of the general character, 
 and yet how meaningless it would be to one who 
 was not familiar with the term. To him it would 
 not even convey the idea of a dog of any kind. 
 
 ^^eSE L!BR^J>^ 
 
 f CFTHE ^^ \ 
 
 (UNIVERSITY) 
 ^. OF ; 
 
12 ELECTRIC RAILWAY MOTORS. 
 
 Thus it is that a technical term only has a mean- 
 ing for us as we associate with it certain ideas. 
 It seldom describes the thing itself, for it is im- 
 possible, as we have shown, to fully describe to 
 another something he has never seen. The best 
 we can do is to liken it to something that he has 
 seen, and then caution him that the likeness is not 
 exact. So that in describing electrical phenomena 
 it must be understood that while our explanations 
 and descriptions are the best we can give, they are 
 not always exact, but only approximately true. 
 
 It will be apparent to everyone that there is 
 more power available in a waterfall in which the 
 volume or quantity of water flowing is great than 
 in one where the quantity is small, and that the 
 amount of power will be still greater if the water 
 falls a great distance than if it falls but a short 
 distance. In describing a waterfall, therefore, it 
 is not sufficient to state either that it is of great 
 height or that it is of great volume. We must 
 state both the height and the volume. It is not 
 sufficient to say that a waterfall is five hundred 
 feet high, or that the water flows at the rate of 
 one thousand gallons per second, but when it is 
 said that a stream falls over a precipice five hun- 
 dred feet high, at the rate of one thousand gallons 
 per second, we know exactly how large the fall is 
 and can figure out just how many horse power can 
 be developed. Electricity is most often likened to 
 a stream of water falling over a precipice, and the 
 energy of an electric current is described in ex- 
 actly the same way, only instead of measuring the 
 height of its fall in feet, as we usually do water, 
 electricians have decided to use the term " volt," 
 and instead of measuring the flow in gallons per 
 second they measure it in " amperes." 
 
TECHNICAL TERMS, ETC. 13 
 
 It is not necessary at this point to state just how 
 much a volt or an ampere is the terms are mean- 
 ingless in themselves, and are the names of men 
 who early did much to advance the science of 
 electricity, that is all ; but we must now try to 
 give them a meaning. Using these terms in the 
 above example, the waterfall would be described 
 as falling five hundred volts at a rate of one 
 thousand amperes. Perhaps we would better 
 represent the volt as the equivalent of a pound of 
 pressure, and then we can say of the water in a 
 water pipe that it flows at the rate of so many 
 amperes at a pressure of so many volts. 
 
 Now, for our purposes, we may consider the 
 trolley and feed wires as copper pipes conveying 
 water from a pump at the power station to a tur- 
 bine or other water wheel beneath the car. The 
 pressure of the water in this pipe is kept by the 
 pump at five hundred pounds, and more or less 
 gallons of it per second are used on the motor as 
 we turn the controlling lever (faucet) on or off. 
 
 Everyone knows that if we twirl a wheel on an 
 axle, be it ever so well greased, it will stop before 
 long unless we continue applying power. It stops 
 by reason of friction. Every carman also knows 
 that, if his journals are not kept well greased, his 
 car will pull harder and he will get a hot box. 
 This is because there is more friction and the heat 
 is generated faster than the rubbing parts can be 
 cooled off, and therefore it accumulates to such an 
 extent as to become not only apparent, but often- 
 times troublesome. Now water, in flowing through 
 a pipe, be it ever so smooth, encounters friction 
 against the inside of the pipe. Heat is not ob- 
 served in the case of water friction, because the 
 water carries it away so rapidly, but the main 
 
14 ELECTEIC RAILWAY MOTORS. 
 
 effect is to retard the flow of water. Thus un- 
 der a given pressure a pipe of a given size, say 
 one hundred feet long, will deliver much more 
 water per second than it will if the pipe were a mile 
 or two long ; and again, more water will be deliv- 
 ered through a smooth pipe than through an equal 
 length of a rough or rusty pipe, for the same rea- 
 son that in the former there is less friction. 
 
 Now in the electric current we have pretty 
 much the same state of affairs. Every conductor, 
 however good, offers some resistance, in the way 
 of friction, to the flow of current, and of two wires 
 of the same diameter that will offer the greatest 
 resistance which is longest. If one wire be twice 
 as long as another, it will offer just twice the re- 
 sistance, and that which is the smoothest inside, 
 or in other words the best conductor, will offer the 
 least resistance. Copper is the best conductor of 
 electricity we have (except silver), and therefore 
 our copper feeder wires and trolley wires may be 
 likened to polished metallic pipes carrying water 
 from our pump to our water wheel (motor) under 
 the car, and the poorer conductors, such as iron or 
 brass or zinc, may be likened to rusty pipes which 
 produce more friction than the copper ones do. 
 But the electric current cannot carry off heat in 
 the same manner that water does, so, as in the 
 case of the car axle, if the conductor be over- 
 worked it will get hot. Electricians have a way 
 of measuring the resistance to the flow of current 
 in conductors and express this resistance in 
 " ohms." The word " ohm," like volt and ampere, 
 has no meaning in itself, and is also the name of 
 an early investigator, but to the electrician, who 
 uses it to express the resistance due to friction, it 
 has a definite meaning. Thus we have the three 
 
TECHNICAL TERMS, ETC. 15 
 
 fundamental units of electricity : the volt, equiv- 
 alent to a water pressure of say a pound to the 
 square inch, or to a head of water of say one foot ; 
 the ampere, equivalent to a rate of flow of water 
 of so many gallons per second or minute ; and the 
 ohm as the unit of resistance to a flow of water in 
 a pipe, which for present purposes we may con- 
 sider our conductors to be. We must bear in 
 mind that as there are all sorts of pipes for con- 
 veying water large ones, small ones, smooth and 
 polished ones and rusty ones, all of which differ 
 in the amount of water which they will deliver 
 under a given pressure in a second or minute, ac- 
 cording as they offer more or less frictional resist- 
 ance to its flow so are there different kinds of 
 electrical pipes or conductors, which likewise differ 
 in their carrying capacity of the electric current 
 as they are large or small, smooth and polished 
 (good conductors, silver, copper) or rusty ones 
 (poor conductors, iron, brass, zinc, carbon, etc.); 
 and although all of these units bear strange names 
 names of men who have distinguished them- 
 selves in scientific research they are very closely 
 equivalent to other units with which we have long 
 been familiar 
 
CHAPTER III. 
 
 OHM'S LAW. 
 
 THESE three units bear a definite relation to 
 each other also. Although common sense would 
 seem to tell us that with a given pressure more 
 water would be delivered through a short pipe in 
 a given time than through a long one of the same 
 diameter ; that of two pipes of the same size and 
 length that which was smooth inside would deliver 
 more water in a given time than that which was 
 rough or rusty or partly obstructed, and that of 
 two pipes of the same kind, either smooth or rusty 
 inside, that would deliver the greater quantity 
 of water which was of the greater diameter al- 
 though, as I say, common sense would seem to tell 
 us all this, electricians were a long time in finding 
 out that it was true for electricity as well as for 
 water. 
 
 It was George Simon Ohm who first discovered 
 this simple relation of the flow of a current of 
 electricity, but when he announced that the amount 
 of current that would flow through any conductor 
 was equal to the pressure (volts) divided by the 
 frictional resistance (ohms), although he had really 
 only stated that the electric current obeyed the 
 same laws essentially as the flow of water through 
 pipes, there were few who believed that it was 
 true. Other investigators had imagined that the 
 relation between the flow and the pressure and 
 
 16 
 
17 
 
 resistance was a much more complex one, and had 
 gotten up long mathematical formulae to express 
 this supposed relation. Ohm's law, as it soon 
 became called, was entirely too simple for them, 
 and for a long time they would not accept it. 
 Further experiment fortunately proved it to be 
 strictly true, and this law, which is that the rate 
 of flow of an electric current through a con- 
 ductor, or the amperes, is equal to the pressure, or 
 electromotive force or volts (all of which terms 
 mean the same thing), divided by the resistance, 
 or ohms, has become the very foundation of the 
 science of electricity. It is usually written : 
 Electromotive force 
 
 Current , 
 
 Resistance 
 
 or, for the sake of brevity, the initial letters are 
 used only and the expression becomes: 
 
 E 
 C= . 
 
 ft 
 
 Nothing could be simpler than this when one 
 understands it, and yet those who do not know 
 any better imagine that the science of electricity 
 is an exceedingly abstruse one. The contrary is 
 really the fact, but unless one understands the 
 A B C's he cannot read. It is worth while, there- 
 fore, that we devote some time in making Ohm's 
 law entirely clear, for upon it is constructed prac- 
 tically the whole of the science with which we 
 have to deal. The three letters 
 
 E 
 C= 
 
 R 
 
 (amperes equals the volts divided by the resistance 
 or ohms) constitutes the whole alphabet of our 
 
18 ELECTRIC RAILWAY MOTOKS. 
 
 science, and we only need to know how to use 
 these letters to solve any electrical problem with 
 which we are confronted. 
 
 Let us illustrate the use of this law by a few 
 numerical examples. Scientific men have very 
 carefully determined the resistance in ohms of 
 different sizes of pure copper wire, and have found 
 that at the ordinary temperature a No. 10 B and 
 S wire, which is a trifle over -fa inch in diameter, 
 offers a resistance of a trifle over 1 ohm per 
 thousand feet. (The exact figures are iWjftftr 
 inch in diameter and ITH$TT hm resistance 
 per thousand feet.) Let us discard the fractions 
 and use the whole numbers. If we were designing 
 a dynamo or buying one, we could obtain one that 
 would give us any voltage we desired. In street 
 railway practice a pressure of 500 volts or there- 
 abouts is always used, and we will assume that we 
 have a dynamo that will generate that pressure, 
 and we have a circuit of No. 10 B and S wire of 
 10,000 feet, and we desire to know what rate of 
 flow (how many amperes) can be sent over that 
 circuit. 
 
 One thousand feet of No. 10 wire offer a resist- 
 ance of 1 ohm ; 10,000 feet will therefore offer a 
 resistance of 10X1, or 10 ohms. The voltage or 
 electromotive force at our disposal is 500. Ohm's 
 law says that the current that will flow will be 
 equal to the voltage or electromotive (in this case 
 500) divided by the resistance (in this case 10 
 ohms), and therefore the answer is that C (or 
 amperes) = *f, or 50 amperes. Now if we should 
 make our circuit twice as long, or 20,000 feet, the 
 resistance would be just twice as great (20X1 = 
 20) and our equation would be C 5 g/ = 25. That 
 is to say, with the same size wire of double the 
 
19 
 
 length the rate of flow of current would be only 
 half as great, or 25 amperes instead of 50 amperes. 
 In the same way we find that if our circuit were 
 only half as long, or 5000 feet, the resistance 
 being also cut in two, the flow of current would 
 be twice as great, or 100 amperes. Now if we 
 double the amount of copper that is, use two No. 
 10 wires instead of one each of these will carry 
 the same amount of current, and at 10,000 feet 
 could deliver 2X50 amperes, or 100 amperes. 
 That is to say, if we double the weight of our 
 copper, either by using two wires of the same 
 size or a single one of the same weight as the two 
 combined, we will reduce our resistance by half, 
 and consequently be enabled to deliver twice as 
 much current at the same distance. 
 
 But supposing we have other data given. Sup- 
 pose it is required to determine what sized wire 
 to use to transmit say 1000 amperes to a distance 
 of 20,000 feet the electromotive force being, as 
 before, 500 volts. Referring to Ohm's law 
 
 E 
 
 C= 
 R 
 
 we have C, the amperes, equals 1000, and E, the 
 pressure or electromotive force, is 500. Substitut- 
 ing these in the equation, it becomes 
 
 500 
 
 1000= . 
 
 R 
 
 By simple arithmetic this may be changed to 
 
 500 
 
 1000 R=500 andR= =%. 
 
 1000 
 
 Thus we find that the resistance of the conductor 
 in ohms for 20,000 feet is J. The resistance of 
 
20 ELECTRIC RAILWAY MOTORS. 
 
 this same wire per 1000 feet will be -g 1 ^ of J, or -fa 
 ohm. A No. 10 wire has a resistance of 1 ohin 
 per 1000 feet, and the required wire, which has a 
 resistance of but fa ohm per 1000 feet, must be 
 forty times as heavy as a No. 10 wire, or equivalent 
 to 40 No. 10 wires, which by reference to any 
 wiring table will be found to be equal to two 0000 
 wires. 
 
 Or supposing we have our wire already strung 
 say a No. 10 wire and must deliver 1000 amperes 
 over a circuit 20,000 feet in length, what electro- 
 motive force must we use ? 
 
 The resistance of 1000 feet of No. 10 wire is 
 1 ohm. The resistance of 20,000 feet will be 
 20X1 ohms. The amperes or current which we 
 have to deliver is 1000. By Ohm's law 
 
 E 
 
 C= 
 R 
 
 Substituting for C its value 1000 and for R its 
 value 20, our equation becomes 
 
 E 
 
 1000=. 
 20 
 
 or by simple arithmetic 20,000 =E, which is to 
 say that the electromotive force will have to be 
 20,000 volts to force a current of 1000 amperes 
 around a circuit of 20,000 feet of No. 10 wire. 
 
 Examples have now been given of all possible 
 cases of wire calculation in their simplest form, 
 and these illustrate the way in which Ohm's law 
 is used in electrical calculations. Of course others 
 may and usually do arise in which some compli- 
 cations are introduced for instance, it is usually 
 required not simply to determine what is the small- 
 est wire that can possibly carry a given number of 
 
OHMS 
 
 amperes a certain distance, but to determine what 
 pize wire will carry that current the required dis- 
 tance with a given drop or loss of potential or 
 electromotive force or pressure; but we will not 
 discuss that question now, merely passing it by 
 with the statement that it is a very simple matter 
 to do, and requires no more knowledge of arith- 
 metic than is involved in the examples already 
 given. 
 
 It is strongly urged upon all who are not famil- 
 iar with the use of Ohm's law, and who wish to de- 
 rive benefit from the succeeding articles, to work 
 out these problems over and over again until they 
 are thoroughly familiar with the use of the law, for, 
 as before stated, it is the key to the whole science 
 of electricity. It will be observed that in Ohm's 
 law there are three elements involved, viz., the 
 pressure or electromotive force or voltage, which- 
 ever we choose to call it, the rate of flow of the 
 current, or amperes, and the resistance which 
 that flow encounters in the conductors, which is 
 measured in ohms. These same three elements 
 are involved in the flow of all other fluids as well, 
 but are simply disguised under different names. 
 As before stated, the flow of water in pipes in- 
 volves pressure (usually measured in pounds per 
 square inch or head in feet, corresponding to 
 volts in electric currents), rate of flow (usually 
 measured in gallons or barrels or cubic feet per 
 minute or second, corresponding to amperes) and 
 frictional resistance (usually measured in loss of 
 feet or inches in head or in pounds pressure, 
 corresponding to ohms in electricity), and, as 
 shown by the examples, if any two of these 
 three elements are given, the third may be de- 
 termined. 
 
22 ELECTRIC RAILWAY MOTORS. 
 
 RATE OF WORK. 
 
 In mechanics we say that when energy is 
 expended at such a rate as to lift a weight of 1 
 pound 1 foot in 1 second it is doing work at the rate 
 of 1 foot pound per second, and when it is doing 
 an amount of work equivalent to raising 550 
 pounds 1 foot high per second, or, what is the 
 same thing, raising 33,000 pounds 1 foot high per 
 minute, the work done is equal to 1 horse power. 
 A mechanical horse power 'is therefore defined as 
 that expenditure of energy which will raise a 
 weight of 550 pounds 1 foot high in 1 second, or 
 33,000 pounds (60X550) 1 foot high in 1 minute. 
 
 Since the raising of a weight usually conveys to 
 our minds the idea of a lift or pull, rather than of 
 a pressure, and we have heretofore been speaking 
 only of pressures, it may be well, in order to make 
 clear the exact similarity between the mechanical 
 and electrical units of work to translate the " pull " 
 or "lift" into a pressure. That "pull" and 
 " pressure " are really equivalent will be apparent 
 from a familiar example. When it is desired to 
 move a car in the barns it is immaterial whether 
 we get behind and push or get in front and pull. 
 One method may be more convenient than the 
 other, but the amount of work done in either case 
 if the car be moved the same distance in the same 
 time will be exactly the same, and if the work 
 thus performed is the same as that required to 
 lift or press upward a weight of 550 pounds 
 through a height of 1 foot in 1 second it will 
 be exactly a mechanical horse power. Thus we 
 see that in the measure of rate of mechanical work 
 which we call the horse power four elements are 
 involved^ viz., pressure, weight or quantity, dis- 
 
BATE OF WOBK. 23 
 
 tance and the time occupied in lifting or pushing 
 the given weight or quantity through that distance. 
 Now in electrical language it will be remem- 
 bered that the volt or electromotive force has been 
 defined as the equivalent of mechanical pressure. 
 We might also now say that it is the equivalent 
 of mechanical pull or lift. We have denned the 
 ampere as a rate of flow of current and likened it 
 to the flow of so many gallons of water per second. 
 While electricity is not supposed to have weight, 
 we may for present purposes suppose that it has. 
 A gallon of water weighs about 8 pounds, and if 
 it is lifted through 1 foot in 1 second, 8 foot 
 pounds of work will have been done. If we lift it 
 or push it so fast that- in 1 second we have lifted 
 it through -S-f ^ 68 j- feet in one second instead, we 
 will have done work equivalent to 550 foot pounds 
 in 1 second, which is equivalent to 1 horse power. 
 Therefore, since the ampere is a similiar electrical 
 expression to the mechanical expression of a flow 
 of so many gallons per minute, and since the volt 
 is equivalent to the mechanical expression of so 
 many pounds pressure, and the product of pressure 
 into gallons per second gives us foot pounds per 
 second, 550 of which make a mechanical horse 
 power, we ought to expect that the product of 
 electrical pressure (the volts) into the rate of flow 
 of the electrical currents (the ampere) would give 
 us something similar to the foot pound per second, 
 and that a certain number of these would be 
 equivalent to a mechanical horse power, and so it 
 is. If we have an electric current of 1 ampere 
 flowing under a pressure of 1 volt, we have elec- 
 trical energy expended at the rate of 1 watt, 
 and this unit is of such a size that 746 of them 
 are equivalent to 1 mechanical horse power. Or 
 
24 ELECTRIC RAILWAY MOTORS. 
 
 in other words, if 746 amperes under 1 volt pres- 
 sure, or 1 ampere under 746 volts pressure, be 
 wholly expended on an electric motor, that motor 
 will be capable of lifting a weight of 550 pounds 
 1 foot high in 1 second, or 1 pound 550 feet 
 high in the same time, or 33,000 pounds 1 foot 
 high in a minute, or will be equivalent to a horse 
 power. Thus while the watt is not exactly the 
 same thing as a foot pound per second, it is a unit 
 of exactly the same kind, but of a different size, 
 just as although an ounce is not the same thing as 
 a pound, it is a unit of the same kind. But 746 
 watts are exactly the same thing as a -horse power, 
 just as 16 ounces are the same thing as a pound. 
 
 Thus we have the electrical unit of rate of work 
 or expenditure of energy also named after a distin- 
 guished early investigator, and it has no meaning 
 whatever except that which electricians have 
 assigned to it as described. The watt is equivalent 
 to T J-g- of a horse power, and the foot pound per 
 second is -^-5- of a horse power, so that the watt is 
 somewhat smaller than the foot pound per second ; 
 but the electrical horse power and the mechanical 
 horse power are exactly the same thing. The watt 
 is also sometimes called the volt-ampere, because 
 it is obtained by multiplying the volt by the 
 ampere. The kilowatt is merely a thousand watts, 
 the word kilo meaning thousand. Since 746 watts 
 equal a horse power, a kilowatt is equal to *f-, 
 which is equal to nearly 1 J horse power. 
 
 EXAMPLES. 
 
 How many electrical horse power can be deliv- 
 ered over a No. 10 wire whose length is 20,000 
 feet, the electromotive force being 500 volts? 
 
 Ans. The resistance of No. 10 wire is 1 ohm 
 
EXAMPLES. 25 
 
 per 1000 feet. The resistance of 20,000 feet will 
 therefore be 20 ohms. According to Ohm's law 
 
 E 
 
 C= . 
 R 
 
 According to the problem the electromotive force 
 or E=500, and the resistance orR=20. Substi- 
 tuting these in the equation, it becomes C =- 8 ^= 25. 
 That is to say that 25 amperes can be delivered 
 over 20,000 feet of No. 10 wire if the pressure is 
 500 volts. 
 
 The watts delivered will be equal to the electro- 
 motive force multiplied by the current in amperes, 
 or 25X500=125,000 watts. Since 746 watts 
 equal 1 horse power, the horse power delivered 
 will be J-|f $=lfrff horse power. 
 
 The current passing over a given circuit is 800 
 amperes, and the resistance of that circuit is 
 known to be 15 ohms. What is the horse power 
 expended ? 
 
 Ans. In this case C = 800 and R=15. Sub- 
 stituting these values in Ohm's law the equation 
 becomes /* 7 ?*^' 
 
 E 
 800= , or E = 15X 800 = 12,000. 
 
 15 
 
 That is to say, the electromotive force on that 
 circuit is 12,000 volts. The number of watts = 
 CxE (amperes multiplied by volts), which in this 
 case is 800X12,000=9,600,000 watts. Since 746 
 watts equal one horse power, 
 9,600,000 
 
 =12,8684Jf horse power. 
 746 
 
 The electromotive force of a given current is 500 
 
26 ELECTEIC EAILWAY MOTORS. 
 
 / 
 
 volts, and the resistance of the circuit is 25 ohms. 
 How many horse power can be delivered ? 
 
 Ans. E=500, 11=25. Substituting these values, 
 in Ohm's law the equation becomes 
 500 
 
 C = =20. 
 
 25 
 
 That is to say, the current that will flow under 
 these conditions will be 20 amperes. Watts= 
 CxE = 20X500 = 10,000 watts. (This may also 
 be called 10 kilowatts.) 
 
 watts 10,000 
 
 Horse power= = = 13f Jf horse power. 
 
 746 746 
 
 Six hundred horse power are delivered over a 
 given circuit, the electromotive force of which 
 is 500 volts. What is the current ? 
 
 Ans. Since 1 horse power is equal to 746 watts, 
 600 horse power will be equal to 600X746 = 
 447,600 watts. 
 
 Since watts are equal to the volts multiplied by 
 the amperes, there will be as many amperes as 500 
 is contained times in 447,600 watts : 
 447,600 
 
 = 895 amperes. 
 
 500 
 
 A street car motor is generating 10 horse power 
 while taking 35 amperes. What must be the 
 electromotive force of the current ? 
 
 Ans. 1 H. P. = 746 watts. 10 H. P. = 10X746 
 watts =7460 watts. Watts=CxE = 7460. But 
 C = 35. Substituting for C its value, 
 7460 
 
 E= = 213-^ volts. 
 
 35 
 
EXAMPLES. 27 
 
 With these examples the use of Ohm's law anfl 
 the conversion of electrical into mechanical units 
 and vice versa will have been sufficiently illus- 
 trated to show the extreme simplicity of the 
 operation. It would be well for those desiring to 
 really familiarize themselves with electrical prob- 
 lems to take figures which they may obtain from 
 the actual operation of the roads with which they 
 are connected and attempt their solution in the 
 same manner. By watching the ammeter and 
 voltmeter in the power house they can obtain an 
 endless variety of problems as to how much work 
 is being done on the line, and other data usually 
 obtainable at the office will enable them to ring in 
 changes on these problems which it will be not 
 only interesting but exceedingly instructive to 
 investigate. 
 
CHAPTER IV. 
 
 THE ELECTRIC CURRENT AND ITS PROPERTIES. 
 
 WHILE all fluids resemble each other in some 
 respects, each has some peculiarity of its own by 
 which it is distinguished from every other fluid, 
 and while we may partially describe one by show- 
 ing its resemblances to other liquids or fluids, if 
 we go no further than this, we will miss the very 
 characteristics by which this particular fluid 
 ^differs from the others. If we cannot liken these 
 peculiarities to anything else, we can only become 
 familiar with them by experimenting with the 
 liquid itself and observing the peculiarities, and 
 perhaps that will be the best way for us in this 
 case. I think we can select a few experiments 
 which will cost us little to perform and require 
 little skill to prepare which will not only familiarize 
 us with many of the peculiarities of the electric 
 current, but will at the same time greatly assist us 
 in understanding the principle upon which the 
 electric motor operates, and it is proposed in this 
 chapter to give a few of these, with full instruc- 
 tions how to prepare and perform them. 
 
 A word of advice here is that two or three 
 motormen perform these experiments together 
 and divide the expense of the material. This 
 method will have several advantages, one of which 
 is that where several work together it results in 
 mutual benefit through discussions of the " whys " 
 and " wherefores " of the phenomena, and this, it 
 
 28 
 
THE ELECTRIC CURRENT. 29 
 
 must be understood, is what we must strive after in 
 all cases ; to know why a thing is so, as far as it is 
 possible to know it, and in those cases where it is 
 impossible to know why a thing is so we must 
 endeavor to satisfy our minds whether, if it is so, 
 it is always so or only occasionally or accidental!} 7 
 so. If it is always so, and we are satisfied of that 
 fact, it is then a law. If it is only occasionally 
 so, then there is surely some reason why it is ever 
 so or why it is not always so, and we must not be 
 satisfied until we have discovered this reason. 
 That is the scientific way of doing things, and in 
 fact the only satisfactory way. Another advan- 
 tage in working together is that by sharing the 
 expense of the material among two or three it 
 need not exceed an amount which any motorman 
 can spare. If there be three together, seventy- 
 five cents apiece should buy everything that is 
 needed, and I feel sure that the entertainment and 
 benefit that will be derived from this investment 
 will many fimes repay the outlay. 
 
 Thus far the flow of an electric current in a 
 wire has been likened to the flow of water in a 
 pipe, and in fact the resemblance is so strong that 
 many electrical phenomena may be clearly pre- 
 dicted if we assume that our conductor is a small 
 pipe and the electric current is a current of water 
 flowing through that pipe urged along under a 
 given pressure. 
 
 Some years ago the writer became acquainted 
 with a German mechanic who was at that time 
 in charge of the shops of one of our largest elec- 
 trical factories, and who had already gotten 
 out a number of inventions on minor details of 
 electrical apparatus that were of the utmost 
 benefit to the concern that employed him and 
 
30 ELECTRIC RAILWAY MOTORS. 
 
 which are in use to-day. In conversation with 
 this mechanic one day he told the writer that 
 he had never had any instruction in electricity 
 whatever. Upon being asked how it was pos- 
 sible, then, for him to devise such excellent elec- 
 trical apparatus, he replied that he had been 
 educated as a hydraulic engineer and understood 
 the mathematics of the flow of water through 
 pipes thoroughly, and that when he wanted to 
 know how the electric current would act under 
 new conditions he simply assumed that he was 
 dealing with water, figured out his problem ac- 
 cordingly, and was pretty sure to find that his 
 results with electricity would correspond. 
 
 But while the flow of electricity corresponds 
 closely in many respects with the flow of water, 
 it differs radically from it in many others, and it 
 is some of these differences that the following ex- 
 periments are intended to show. 
 
 To start with, we must, of course, have a gen- 
 erator of electricity, and for this purpose any 
 cheap primary battery will answer. If it is de- 
 sired to make the battery one's self, it can be done 
 very simply and cheaply and will prove both in- 
 teresting and instructive. The galvanic battery 
 depends upon the simple principle that if two 
 unlike substances that are conductors of electric- 
 ity are immersed at one end in a liquid capable of 
 acting upon or corroding one of them more than 
 the other, and the other ends of these (the two 
 ends not immersed in the liquid) be connected to- 
 gether by a wire, a current of electricity will at once 
 flow through that wire. Since almost all chemicals 
 corrode metals to at least some extent, and hardly 
 ever corrode any two metals to exactly the same 
 extent, it would be almost impossible to select any 
 
THE ELECTEIC CURRENT. 
 
 31 
 
 two metals or any two conductors of electricity 
 which would not form a battery if immersed in 
 any solution we choose to employ. We therefore 
 have an almost infinite 
 variety of materials z 
 to choose from with 
 which to make our 
 battery, but of course 
 they do not all make 
 equally good batteries. 
 If we can find two sub- 
 stances, one of which 
 is very rapidly and 
 easily corroded by our 
 solution and the other 
 not corroded at all, 
 then we have the ele- 
 ments of a good bat- 
 tery. If the solution 
 and both of the sub- 
 - stances which are im- 
 mersed in it are cheap, 
 so much the better. 
 Now it happens that 
 zinc is both cheap and 
 readily soluble in a 
 large number of solutions, and carbon is also cheap 
 and practically insoluble in all solutions, so zinc 
 and carbon are usually employed in all modern 
 batteries. It is a peculiar fact that a solution of 
 table salt in water will not corrode zinc when 
 acting upon it alone, nor will it corrode the zinc if 
 there be placed in the same vessel with it a stick 
 of carbon, so that the two might remain together 
 in the same solution almost indefinitely, if they 
 do not touch, without the zinc being corroded at 
 
 FIG. 1. 
 
32 ELECTRIC RAILWAY MOTORS. 
 
 all, but if their outer ends be connected by a 
 wire, the salt water will at once begin to attack 
 the zinc, and an electric current will commence 
 to flow, and continue until either the zinc is used 
 up or the salt water has dissolved so much of it 
 that it cannot dissolve any more that is, provid- 
 ing the zinc and carbon remain connected by the 
 wire, but the corrosion of the zinc will at once 
 cease if this connection be broken. This property 
 of salt water and zinc renders thempecularily suita- 
 ble substances to employ in electrical batteries, 
 because if the carbon and zinc be disconnected 
 when the battery is not in use, there is no waste 
 of material and the battery is always ready for 
 use, requiring only that the zine and carbon be 
 connected again to start the current to flowing. 
 
 While an excellent battery may be made with a 
 solution of ordinary table salt, there is still a bet- 
 ter substance for this purpose, sal ammoniac, which 
 is almost equally cheap and quite as harmless to 
 handle. 
 
 To make a battery, procure a wide-mouthed jar 
 either of earthenware or glass, and buy a stick of 
 battery carbon about two inches wide, one-fourth 
 inch thick and eight inches long, and also a " pen- 
 cil zinc." These may be procured of any electrical 
 supply dealer, and should both be provided at their 
 upper ends with binding posts or means to facili- 
 tate the attachment of wires. The carbon will 
 cost ten cents and the zinc five cents. At the 
 same place or at the nearest drug store five cents' 
 worth of sal ammoniac should be purchased, and 
 we have all that is necessary to make a fairly 
 good electric battery. 
 
 Empty the sal ammoniac into the jar and fill it 
 three-quarters full of water, and when it is dis- 
 
THE ELECTRIC CURRENT. 33 
 
 solved insert the carbon and zinc with their bind- 
 ing posts up. If we had an electric bell, and should 
 connect one of its binding posts to the binding 
 post of the zinc and the other to the binding post 
 of the carbon, the bell would ring vigorously and 
 continue to ring for a long time, showing that 
 quite a strong current was flowing. If we had 
 used table salt instead of sal ammoniac the only 
 difference would have been that the battery would 
 not last so long and the current would not be quite 
 so strong. 
 
 Fig. 1 shows a battery such as described above, 
 the zinc pencil being marked Z and the carbon 
 marked C. In using such a battery, or " cell," as 
 it is more properly called, it is better not to let the 
 zinc and carbon touch each other in the liquid, and 
 they must not be allowed to touch each other out- 
 side the liquid, for if they do it is the same as 
 though they were connected by a wire, and if 
 allowed to remain this way when not in use the 
 battery will soon become entirely exhausted. For 
 the reason that a little jarring might cause the zinc 
 and carbon to come in contact with each other 
 when the cell is not in use, it would be a wise pre- 
 caution to remove either one or both from the 
 liquid before setting the jar away. 
 
 It may perhaps be found more convenient to 
 buy a battery, and if so a good dry battery, which 
 can be bought for fifty cents, will be found as con- 
 venient as any. With the dry battery there is no 
 danger of spilling any liquid, and the zinc and car- 
 bon are fastened in so that there is no possibility 
 of their coming in contact with each other. 
 
 In a galvanic cell such as either of the above, 
 the current is supposed to flow through the wire 
 from the least soluble element to the one most 
 
34 ELECTRIC RAILWAY MOTORS. 
 
 readily corroded by the battery fluid. Where the 
 elements are carbon and zinc as above, the current 
 must always be considered as flowing from the 
 carbon through the wire to the zinc. The carbon 
 is therefore called the positive pole, and the zinc 
 the negative pole, and correspond respectively to 
 the positive brush of the dynamo, from which the 
 current is supposed to flow, and the negative 
 brush, through which it returns to the dynamo. 
 
 In addition to procuring the foregoing, an eight- 
 ounce spool of No. 24 cotton-insulated copper wire 
 should be purchased to complete the equipment 
 for the following experiments. This can be had 
 wherever the other supplies are purchased for forty 
 cents. 
 
 In preparation for the experiments, cut out a 
 piece of brown manilla or ordinary writing paper 
 about two inches square, and wrap this carefully 
 into a cylinder around an ordinary lead pencil. A 
 round lead pencil is better for this purpose than 
 an octagonal pencil. Next take the spool of in- 
 sulated wire, and while the paper is still on the lead 
 pencil, beginning at the left-hand end of the paper, 
 overwind it tightly and closely with the wire until 
 the right-hand end of the paper is reached. Then 
 overwind this laydr again with another layer, pro- 
 ceeding to the left, and then with a second layer 
 winding to the right, and to prevent the wire from 
 becoming loose at either end wind them with a 
 few turns of strong thread or string and tie tightly. 
 The wire may now be cut from the spool, leaving 
 an end beyond the coil of three or four inches. 
 There should be about the same length of loose 
 wire left at the beginning of the coil. The paper 
 cylinder with its overwrapped coils may now be 
 slipped from the pencil and we have a hollow 
 
THE ELECTRIC CURRENT. 35 
 
 cylinder of paper overwound with three layers of 
 
 insulated wire, the two ends of which, each some 
 
 three or four inches long, extend out loosely, as in 
 
 Fig. 2. The in- 
 
 sulation should > 
 
 be carefully re- 
 
 moved with a 
 
 knife from about ______ _ 
 
 an inch of both j^ g 
 
 ends of the wire 
 
 to enable the coil to be placed in the circuit of 
 
 the battery. 
 
 Cut off "from the spool two more pieces of wire 
 each about a foot long, and after removing the 
 insulation from both ends of these for an inch or 
 two, fasten one end of one in the zinc binding post 
 and one end of the other in the carbon binding 
 post. To the loose ends of the two wires twist 
 the two loose ends of the small coil just made. If 
 this is properly done, the carbon and zinc will be 
 connected by wire, and the current will flow from 
 the carbon around the various windings of the coil 
 to the zinc. But as yet we have no evidence of 
 this fact. Procure a large darning needle and 
 insert it point first into the hollow coil, and after 
 allowing it to remain there a few minutes take the 
 needle out and examine it. No change will be 
 observed it is apparently exactly like the needle 
 that was put in there a moment before, and yet one 
 of the most remarkable changes known to science 
 has quietly taken place. Cut a small piece of cork 
 (about the size of a good-sized pea) large enough 
 to float the needle in water, run the needle through 
 this until the cork is in the middle and drop the 
 needle with its float into a saucer full of water. 
 
 The needle will swing around untiUt-points exactly 
 
 '^ 
 
 OF THE 
 
 UNIVERSITY 
 
36 ELECTRIC RAILWAY MOTORS. 
 
 north and south. Reverse the position of the 
 needle, or point it in any direction we choose, it 
 will swing around so that it points north and south 
 
 FIG. 3. 
 
 again. If on first trying, the point of the needle 
 turns toward the north and the eye toward the 
 south, it will always take up the same position again, 
 the point always turning toward the north and the 
 eye toward the south. The act of passing the cur- 
 rent around the needle while inside the coil has 
 given ib this remarkable property, that ever after- 
 ward when free to move it will take up a north and 
 south position, and the same end will always point 
 
THE ELECTRIC CURRENT. 
 
 37 
 
 north. "We have magnetized the needle, and by 
 rendering it free to move whichever way it likes 
 have made one of the most remarkable instruments 
 the world has ever seen, viz., a compass. 
 
 Place another needle in the coil in the same 
 way point first and then float it on water. If 
 the first needle took up a position with its point 
 
 FIG. 4. 
 
 toward the north the second one will do the same, 
 and when it has come to rest its point will be 
 toward the north and its eye toward the south. 
 
 Try a third needle, but introduce this into the 
 coil eye first. Float this and the eye will be 
 toward the north instead of the point. We have 
 discovered two laws, one, that a needle which has 
 been placed in a coil through which an electric 
 current is passing acquires the property of taking 
 up a north and south position when free to move, 
 the same end always turning toward the north; 
 and second, that every needle which is placed in 
 that coil in the same way will act in the same way, 
 and the end which goes in first will always be the 
 one to point north if that was the one that pointed 
 north in the first experiment. For these reasons 
 the north end of the needle is called the north-seek- 
 ing pole and the other the south-seeking pole. 
 
38 ELECTRIC RAILWAY MOTORS. 
 
 While one of the needles is floating in the water, 
 if we bring the north-seeking pole of another 
 needle near its north pole, it will rapidly repel it. 
 If, on the contrary, we bring a north pole near a 
 south pole, the two will attract each other strongly, 
 and the floating needle will rush to and attach 
 itself to the other so strongly that it may with 
 care be lifted out of the water. In fact, we have 
 two magnets with which we can produce all the 
 phenomena of magnetism with which everyone is 
 familiar. 
 
 Now let us remove our coil from the battery 
 circuit and insert in its stead a straight piece of 
 wire, say a foot long, by twisting its two ends to 
 the battery wires, and then stretch it in a north 
 and south direction directly over our floating 
 needle or compass. It will be observed that the 
 latter is deflected through a considerable angle 
 from its former north and south position, and if the 
 wire be over the needle the deflection will always 
 be in the same direction. If we examine closefy, 
 we will find that if the current is flowing from 
 north to south the needle will always be deflected 
 to the east. If we reverse our wire, however, so 
 that the current is flowing from south to north, the 
 deflection will be to the west. Place the wire 
 under the saucer, or even under the table upon 
 which the saucer rests, and if the distance be not 
 too great the needle will be again deflected, but in 
 the opposite direction, viz., if the current flows 
 through the wire from north to south under the 
 needle, its north pole will be deflected to the west, 
 and if the wire be reversed so that the current 
 flows from south to north, the north end of the 
 needle will be deflected to the east. 
 
CHAPTER V. 
 
 THE ELECTRIC CURRENT AND ITS PROPERTIES. 
 
 T (Continued.) 
 
 WE have now discovered one radical difference 
 between the flow of water in pipes and the flow of 
 an electric current in a conductor. In the case of 
 water its flow within a pipe produces absolutely 
 no external effect, but in the case of electricity we 
 find that its flow produces quite a marked influence 
 within the space surrounding the wire. In the 
 case of the coil by which we magnetized the nee- 
 dles none of the current could possibly have gotten 
 to the needles, first, because the wire of which the 
 coil was composed was carefully insulated with 
 cotton thread, which effectually prevented the 
 escape of current from the wire, and second, there 
 were several thicknesses of paper between the 
 needle and the coil, and dry paper is one of the 
 best electrical insulators known. We might have 
 inclosed our needles in India rubber or glass before 
 inserting them in the coil as a further protection 
 against the current, but the result would have been 
 the same exactly. We have also shown that if a 
 wire in which a current is passing is held either 
 above or. below a compass needle the influence of 
 the current upon the needle is manifested by a 
 deflection either to the west or east of its normal 
 north and south direction, and further, that we can 
 not only thus tell whether a current is flowing in a 
 
40 ELECTRIC RAILWAY MOTORS. 
 
 wire or not, but we can tell in which direction it is 
 flowing. 
 
 We have seen that if a current flows from north 
 to south over the needle it deflects it to the east, 
 and that it also deflects it to the east if it flows 
 from south to north under the needle. If, there- 
 fore, we form a loop of our wire, in the center of 
 which we place our saucer of water and needle so 
 
 that the current flows 
 first from north to 
 south over and then 
 from south to north 
 under the needle (Fig. 
 
 \i 5.), the effect of the 
 ) one current is just 
 doubled. If two loops 
 are made, so that the 
 current passes over 
 FIG. 5. the needle twice from 
 
 north to south and 
 
 twice under the needle from south to north, the 
 effect of the current will be multiplied four 
 times. By increasing the number of loops in this 
 way we are enabled to produce quite percepti- 
 ble deviations with such feeble currents that they 
 could scarcely be detected in any other way. We 
 hav.e, in fact, actually made a galvanometer. As 
 winding the wire above the needle in many turns 
 would hide the needle so that we could not see its 
 deflections, it is more usual in making galvanom- 
 eters to wind the wire in a flat coil and place it 
 under the needle. While the multiplying effect 
 of a coil thus arranged is not as great as in the 
 arrangement described, the instrument itself is 
 much more convenient to use. To make such a 
 coil cut out a piece of cigar box, or other lumber of 
 
THE ELECTEIC CURRENT. 
 
 41 
 
 about that thickness, about 2 inches wide and 
 2J- long (Fig. 6). Cut away a seat on both 
 ends for the wire and at opposite corners of one 
 end bore a small hole about the diameter of a 
 
 PIG. 6. 
 
 pin to hold the ends of the wire. Into one of 
 these insert the end of the wire from the spool and 
 pull it through about five or six inches and plug up 
 the hole with a piece of wood so as to hold the 
 wire tightly in place. Then wind on tightly eighty 
 to a hundred turns of the wire and end it off 
 through the other hole, plugging it up and leaving 
 an end of about five or six inches as before. Now 
 place the coil under the saucer and its floating 
 needle and you have a very delicate galvanom- 
 eter by which currents that would otherwise 
 scarcely be suspected can be detected. Connect 
 the two ends of the coil with the battery wires 
 and the deviation of the needle will be found to be 
 much greater and more rapid than in the previous 
 experiments. 
 
42 ELECTRIC RAILWAY MOTORS. 
 
 It must be borne in mind that the tendency of 
 a current passing either above or below a compass 
 needle is to place that needle at right angles to the 
 direction of the current. The strongest current 
 will therefore only cause the needle to take up 
 a position at right angles to it it will never cause 
 it to deviate further or to reverse itself. 
 
 THE SOLENOID. 
 
 Now let us return to our first coil of wire (Fig. 2, 
 see page 35). A hollow coil of wire such as this is 
 called a solenoid, and it has some very peculiar 
 properties which it will be necessary for us to 
 understand before we can thoroughly comprehend 
 either the dynamo or motor, and as we now have 
 all the apparatus necessary to investigate these 
 properties we will begin at once. 
 
 Take one of our magnetized needles and sus- 
 pend it at its middle point by a very fine thread, 
 so that the needle will hang horizontally and be 
 free to move. Now connect up the solenoid with 
 the battery and present first one end of the sole- 
 noid and then the other to, say, the north pole of 
 the needle. It will be found that one end attracts 
 and the other repels this pole just as would a real 
 magnet, and that the end that repels the north 
 pole attracts the south pole. In fact, although 
 there is no iron or other magnetic material in the 
 solenoid, it acts exactly like a magnet, and is one 
 so long as the current flows through it. If the 
 pole of the needle which the solenoid attracts be 
 properly directed, the solenoid will suck the 
 needle almost entirely within itself, and if the 
 needle be reversed and pushed inside of the coil, it 
 will be expelled again as soon as the fingers are 
 removed from it so as to permit of it. Thus it 
 
THE SOLENOID. 43 
 
 will be seen that a solenoid has a north and south 
 pole, just as has a steel magnet, so long as a cur- 
 rent is passing through it. Now detach one of the 
 battery wires from its binding post, so that the 
 current can no longer pass through the solenoid, 
 and repeat these experiments. It will be found 
 to be entirely inert, and will neither attract nor 
 repel either pole of the needle. The magnetic 
 property of the solenoid is therefore evidently 
 entirely due to the current which is passing 
 through it. 
 
 The phenomenon of sucking in or expelling a 
 magnetized needle may be better illustrated, per- 
 haps, by partly inserting the needle in the solenoid 
 while one of the battery wires is disconnected, and 
 then suddenly closing the circuit by touching the 
 binding post with the disconnected wire. Thus 
 far we have been experimenting with a highly 
 tempered hard steel needle. We have found that 
 when it is once magnetized it remains a magnet 
 permanently. Now let us repeat our experiments, 
 using a short piece (two or three inches long) of 
 soft iron wire. Before we attempt to magnetize 
 it let us try it with our compass needle. We find 
 that it attracts both ends equally well. There 
 is under no conditions any repulsion, because it is 
 not magnetized. Place it in the solenoid as we 
 did when magnetizing the needle, and while still 
 in the solenoid test it with the compass. We 
 find that one end attracts and the other repels 
 either end of the compass needle just as did our 
 permanently magnetized needle before, and even 
 more strongly. Remove the wire from the sole- 
 noid and try it again. We find it repels neither 
 end, but attracts both, as it did before it was mag- 
 netized. Suspend the wire in the middle and 
 
44 ELECTEIC EAILWAY MOTORS. 
 
 approach the solenoid to it. The latter will attract 
 both ends equally well and suck in either end 
 with equal facility. The soft iron wire is no 
 longer a magnet. It was a stronger magnet while 
 in the solenoid than the needle^ was, but imme- 
 diately it is taken out or the current in the sole- 
 noid is broken it loses its magnetism. This may 
 be more clearly illustrated by causing the wire, 
 while in the solenoid, to pick up another small 
 piece of the same wire, and then detaching one of 
 the battery wires from its binding post. Imme- 
 diately the current is broken the wire will drop 
 its load, and it will remain incapable of picking 
 it up again until the current is started in the 
 solenoid. 
 
 There is, therefore, this very great difference 
 between hard tempered steel and soft annealed 
 iron, that the former when once magnetized retains 
 its magnetism permanently, while the latter loses 
 it immediately the encircling current is stopped. 
 
 There are also other minor differences, among 
 which may be mentioned the following : Tem- 
 pered steel requires an appreciable time to mag- 
 netize, whereas soft iron seems to assume the 
 property instantaneously. It is somewhat difficult 
 to change the direction of magnetism of steel 
 that is, after having magnetized a steel bar, so that 
 one end is north and the other south, to demag- 
 netize it and magnetize it again, so that the ends 
 which were formerly north and south will become 
 respectively south and north while with soft iron 
 the change is made with the greatest facility. A 
 given current flowing through a solenoid of a 
 given number of turns will make a much stronger 
 magnet out of a soft iron bar than it will out of a 
 steel bar of the same dimensions. 
 
THE SOLENOID. 45 
 
 Within certain limits the amount of magnetism 
 that can be imparted to a bar of iron or steel in- 
 creases with the number of amperes of current 
 passing through the solenoid and the number of 
 turns in the coil. A limit is finally reached, how- 
 ever, beyond which neither an increase of current 
 nor an increase in the number of turns or windings 
 in the solenoid will materially increase the mag- 
 netism. With tempered steel this limit is much 
 sooner reached than with soft annealed iron. For 
 this reason, of two magnets of iron and steel of 
 exactly the same size the one of soft iron can be 
 made by far stronger than it is possible to make 
 the one of steel. Cast iron, which partakes more 
 of the nature of steel than of soft or wrought iron, 
 is also inferior to the latter for magnetic purposes 
 and loses its magnetism less readily. In fact, the 
 best wrought iron that has been rolled or drawn, 
 and not subsequently softened again by annealing 
 processes, possesses the property of retaining some 
 of its magnetism for quite a while and is less suit- 
 able for magnetic purposes, especially where it is 
 desired to have the magnetism undergo rapid 
 changes either of direction or intensity. All of 
 these points have an important bearing upon motor 
 and dynamo construction, and will be referred to 
 again later on. 
 
 Another point which has also a bearing upon a 
 subject to be taken up in a subsequent chapter 
 may be referred to here. 
 
 As everyone knows, a knife or a piece of steel 
 may be magnetized by rubbing it against another 
 magnet. It may also be more slowly magnetized 
 by laying the two side by side for some time even 
 without touching each other. Now the earth itself 
 is a huge magnet with a north and a south pole 
 
46 ELECTEIC RAILWAY MOTORS. 
 
 just like the small magnets we have made, and it 
 is the attraction of the earth's north pole for the 
 compass needle that causes the latter to point 
 always to the north. Since two north or two south 
 poles never attract each other, but repel, the end 
 of the needle that points to the earth's north pole 
 is really a south pole, and should not be called a 
 north pole at all ; this is the reason that when it 
 was first referred to in this book, particular care 
 was taken to call it the " north-seeking pole." It 
 is, however, usually called the north pole, because 
 it points toward the north, and will hereafter be 
 referred to by this name. 
 
 But to return to our subject. If the earth is 
 really a magnet, we would expect bars of iron lying 
 approximately parallel with the line joining its two 
 poles to become in time magnetized, and as a mat- 
 ter of fact they do. Bars standing in a vertical 
 position seem to become magnetized more rapidly, 
 perhaps, than those lying horizontal^, but those 
 ^^j^^' lying in a north and south direction, in clinging 
 'downward toward the earth at such an angle as 
 to point directly toward the north pole, become 
 magnetized still more quickly, and the magnetiza- 
 tion is rendered almost instantaneous if the bar 
 while held at this angle is smartly struck on either 
 end with a hammer. 
 
 This experiment may be easily tried with an 
 ordinary poker. After hitting it a tap on the end 
 bring the end which was pointed toward the earth 
 near the compass needle. It will smartly repel 
 the north pole and attract the south pole. Reverse 
 the poker and hit it another tap and test it with 
 the compass ; the polarity will be found to have 
 been reversed. The end which at first repelled 
 the north pole will now attract it and repel the 
 
THE SOLENOIP. 47 
 
 south pole. Now there is a curious thing that we 
 can do. We have literally knocked magnetism 
 into the poker in the first place, and we have by 
 reversing the poker and striking it again knocked 
 a north pole out of one end into the other, and 
 now we can knock the magnetism entirely out of 
 the poker if we know how to do it. Hold the 
 poker, which we will say is already magnetized, 
 horizontally in an east and west direction and hit 
 it one or two smart raps on either end. Now test 
 it with the needle and it will be found to attract 
 either end equally well, thus proving that the 
 magnetism has entirely disappeared. 
 
CHAPTER VI. 
 
 MEASURING THE CURRENT. 
 
 BEFORE passing on to another subject it may be 
 well to call attention to something else we have 
 accomplished in the simple instruments we have 
 made. We have talked of amperes and volts and 
 ohms, the three yardsticks by which we measure 
 electrical phenomena, and have solved a number 
 of problems involving these terms, but have said 
 nothing, as yet, as to how the volts and amperes 
 of a current' or the ohms of a circuit are deter- 
 mined. We are all probably aware that the 
 amperes are measured by an ammeter and the 
 volts by a voltmeter, but we may not know on 
 what principle either of these instruments is con- 
 structed. We do know, however, that if we have 
 the volts and amperes we can determine the re- 
 sistance in ohms by Ohm's law, but, as a matter 
 of fact, we have constructed a device which, by 
 slight modification, is capable of measuring both 
 the volts and amperes. 
 
 We have already stated incidentally that the 
 
 magnetizing power of a solenoid is equal to the 
 
 /number of amperes flowing through it multiplied 
 
 N^y the number of convolutions or windings. To 
 
 state it in another way, the amount of pull which 
 
 a solenoid will exert upon a soft iron core partly 
 
 inserted is also proportional to the product of the 
 
MEASURING THE CURRENT. 
 
 current in amperes multiplied by the number of 
 turns. It may be well to prove this roughly, 
 which we can do by suspending again our short 
 piece of soft iron wire by a thread tied to its 
 center and proceeding as follows : Connect up 
 
 FIG. 7. 
 
 the battery with a few feet of wire and bend its 
 center into a loop of one turn (Fig. V) and present 
 this loop to one end of the wire. We have here a 
 solenoid of one turn, and it will tend to suck the 
 wire into itself. The attraction will be compara- 
 tively feeble, to be sure, but much stronger than 
 one would suppose who had not tried it ; but note 
 as carefully as possible its strength. Next bend 
 another loop so that we have a solenoid of two 
 
50 
 
 ELECTBIC EAILWAY MOTORS. 
 
 turns (Fig. 8). The pull will be perceptibly 
 stronger. A third loop will increase the suction 
 still more, and so on. If it were convenient for us 
 to do it, we could show that if we could double the 
 
 FIG. 8. 
 
 current in the single loop the increase of pull would 
 be exactly the same as that obtained by adding a 
 second loop. Now if we have a solenoid of any 
 number of turns it does not make any difference 
 how many and pass a known current through it, 
 and measure the pull on the dial of a spring 
 balance, or in any other convenient way, marking 
 the point where the dial hand rests when the cur- 
 rent is on full, and then measure the pull when 
 
MEASURING THE CURRENT. 51 
 
 twice this current and three times and four times 
 this current are passing, marking each time the 
 point where the dial hand rests, we will have a 
 meter which will measure the current passing in 
 terms of the unit used. If the first current used 
 was one of one ampere and the second one of two 
 amperes, etc., we will have an amperemeter or 
 ammeter. Many of the ammeters used in street 
 railway power stations are constructed after this 
 plan, only the solenoid is made to lift a weight 
 instead of pulling against a spring. Since the 
 ammeter is intended to measure the full current, 
 it is always placed in the circuit, so that all of the 
 current passes through its coils just as we have 
 placed it in our experiments thus far. 
 
 A voltmeter may be regarded as a more delicate 
 instrument of the same kind, intended, however, 
 to measure only a very small portion of the cur- 
 rent. For this reason it is made of very high 
 resistance, for, we know from Ohm's law, that of 
 two circuits having the same electromotive force 
 or voltage that will have the least current which 
 has the highest resistance. Resistance alone would 
 not be sufficient, however, for with the exceedingly 
 small current used there would not be sufficient 
 pull to operate the dial hand if the coil were made 
 up of but few turns of a high resistance wire such 
 as German silver. The coil is therefore made up 
 of the best conducting copper wire, and the resist- 
 ance is obtained by making this wire very long 
 and bending it into a large number of loops or 
 turns. 
 
 In operating an electric motor the latter does 
 not consume amperes any more than a water 
 wheel consumes or eats up gallons of water, but 
 it does consume volts just as the water wheel con- 
 
52 ELECTRIC RAILWAY MOTORS. 
 
 sumes pounds of pressure. In the water wheel 
 the water arrives at the wheel under a certain 
 number of pounds pressure, and after it has gone 
 through the wheel and done its work it flows 
 away under a lessened pressure. The amount of 
 pressure consumed by the wheel in doing its work 
 will evidently be the difference of pressure at 
 which the water arrives at the wheel and that 
 under which it flows away. So with the electric 
 motor if we wish to know the amount of electro- 
 motive force (volts) consumed in its operation, we 
 measure the difference of potential at which the, 
 
 Line Wire 
 
 current arrives at and leaves the motor. The volt- 
 meter is used to make this measurement, and is 
 placed in a derived or shunt circuit, one end of 
 which is connected with the main circuit at the 
 positive side of the motor, and the other is con- 
 nected with the same circuit at the negative side 
 of the circuit, and the amount of current which 
 will flow through the voltmeter and its circuit will 
 be proportional to the difference of the potentials 
 between the positive and negative sides of the 
 motor. In Fig. 9 the method of placing the volt- 
 meter and ammeter in circuit is shown. 
 
MEASURING THE CURRENT. 53 
 
 From this it will be seen that all of the current 
 which goes out to the car line passes through a few 
 turns of the coil A, which, with its plunger and 
 weighted lever, index hand and graduated dial, 
 constitutes the ammeter, while a very small por- 
 tion of the current is diverted from the outgoing 
 wire to the return wire or the earth through 
 the fine wire and coil of many convolutions, B y 
 which, with its plunger, weighted lever, index 
 hand and graduated dial, constitutes the voltmeter. 
 
 Of course there are many other kinds of volt- 
 meters and ammeters constructed on nearly as 
 many different principles, but we have not space 
 nor is it worth while to describe them here. There 
 is such an instrument as an ohmrneter, which 
 reads directly the resistance of a circuit, but it is 
 never used, so far as the writer knows, in street 
 railway or electric lighting equipments. Resist- 
 ances are more often measured by means of an 
 instrument known as the Wheatstone bridge, by 
 which the unknown resistances are compared 
 with coils of known resistances, enough of the latter 
 being added to just balance the unknown resist- 
 ance, exactly as we weigh an unknown quantity 
 of sugar or butter by placing the latter in one pan 
 of our scales and adding pound and ounce weights 
 to the other until the scales are exactly balanced. 
 But as the motorman is not likely, as such, to ever 
 have the handling of a bridge or be required to 
 determine very accurately the resistances either of 
 his circuits or his apparatus, and as it would only 
 needlessly complicate matters at this time, its 
 description will be omitted. But we already have 
 the means of determining resistances with con- 
 siderable accuracy in our voltmeter and ammeter, 
 as before stated, for if we introduce these two 
 
54 ELECTRIC RAILWAY MOTORS. 
 
 instruments properly into our circuits and take 
 their readings we learn the number of amperes 
 flowing and the pressure or voltage under which 
 that flow takes place, and by substituting these 
 values in Ohm's law, 
 
 E 
 ^\ 
 
 ~R 
 
 the resistances are readily calculated. 
 
 MAGNETISM AND ELECTROMAGNETISM. 
 
 In discussing the electric current we likened it 
 to a flow of water or other fluid through pipe, 
 and showed that this flow is retarded in both cases 
 by obstructions, and that in both cases these obstruc- 
 tions produced like results, which might be pre- 
 dicted by the simple relation between the flow, 
 pressure and resistance expressed in Ohm's law. 
 We further found that in the case of electric cur- 
 rent the influence of the flow within the wire 
 extended to the space surrounding the wire, and 
 that the effect of this influence was to produce 
 magnetism in that space, or, as electricians would 
 say, to produce a magnetic field. Thus every con- 
 ductor carrying a current of electricity produces 
 in the space surrounding it a magnetic field. 
 That this is true our experiments first showed by 
 the magnetizing effect which the solenoid had 
 upon the needle placed within it, and further, by 
 the tendency of the floating magnetic needle to 
 take up a position at right angles to a current 
 passing in a north or soutli direction either above 
 or below it. That the magnetic field thus gener- 
 ated by the current has a definite north and south 
 pole, which will be later shown is dependent upon 
 .the direction in which the current flows in the 
 
MAGNETISM AND ELECTROMAGNETISM. 
 
 wire, was proved by the fact that one end of the 
 solenoid repelled one end of the needle, while it 
 attracted the other, just as did another mag- 
 netized needle this being the test of magnetic 
 polarity. 
 
 It has also been shown that a piece of hard 
 tempered steel, and to a less extent cast iron and 
 even wrought iron which has become somewhat 
 hardened either through drawing or forging or too 
 rapid cooling from a high temperature, retained 
 the magnetism indefinitely which had been im- 
 parted to it by the magnetizing current, but that 
 the magnetism of the solenoid, as well as that of 
 soft annealed iron surrounded by a solenoid, lost 
 its magnetism the moment the flow of current 
 ceased. These two phenomena give rise to two 
 classes of magnets, viz., permanent and electro- 
 magnets, which differ from each other only in 
 the fact that in one case magnetism when once 
 produced continues practically unchanged after 
 the magnetizing current has been withdrawn, and 
 in the other it is wholly dependent upon the con- 
 tinuance of the current for its existence, and the 
 strength of the magnetism varies with every in- 
 stantaneous change of the strength of the current. 
 
 Since magnetism is produced whenever an elec- 
 tric current flows through a conductor, and in the 
 case of the electromagnet varies instantaneously 
 with the variations in that flow, it is readily sug- 
 gested that the two, electricity and magnetism, 
 are closely related and may follow somewhat 
 similar laws, and experiment has demonstrated the 
 correctness of this idea. 
 
 While from the fact that a permanent magnet 
 continues to be magnetic even after the magnetiz- 
 ing force is withdrawn we do not associate the 
 
56 ELECTRIC RAILWAY MOTORS. 
 
 same idea of flow in a magnet that we do in the 
 case of an electric current, and while there really 
 may be no flow or motion of the thing which we 
 may for the want of a better name call the "mag- 
 netic fluid," still the greatest advance that has 
 ever been made in the science of electricity (of 
 which magnetism is a most important part) was 
 due to this conception that an actual flow of force 
 does take place in the magnet, its direction being 
 from the north pole through the air to the south 
 pole, and thence through the magnet back again 
 to the north pole. This idea involved the idea of 
 a magnetic circuit similar to that of the electric 
 circuit, which must contain resistances. And, as 
 in the electric circuit, in order to maintain the flow 
 of current there must be some pressure to force 
 the fluid through these resistances. It would 
 logically follow from these assumptions that if a 
 certain flow could be forced to take place against 
 a given resistance by a given pressure, a greater 
 flow could be maintained through the same resist- 
 ance by a greater pressure, and we would have 
 for magnetism another Ohm's law expressing the 
 relation between the amount of flow (strength of 
 magnetism), the pressure, and the resistance offered 
 to the flow. Experiment has fully verified this 
 hypothesis, and we have the law of magnetism that 
 the strength of a magnet is equal to the pressure 
 divided by the resistance of the circuit. While 
 the pressure in the flow of water is usually spoken 
 of as hydrostatic pressure, and that in the flow of 
 electricity is called electromotive force, the pressure 
 which causes magnetism in a magnetic circuit is 
 called magnetomotive force. 
 
 It has already been stated, and the experiments 
 illustrated in Figs. 7 and 8 (pp. 49 and 50) have 
 
MAGNETISM AND ELECTROMAGNETISM. 57 
 
 shown, that the magnetic field produced by a cur- 
 rent flowing through a solenoid consisting of two 
 turns of a wire is twice as strong as that produced 
 by its flowing around a solenoid consisting of but 
 one turn. It has also been stated, and it is equally 
 true, that the magnetizing effect of a coil of wire 
 of any number of turns will be doubled if the cur- 
 rent in amperes flowing through the wire is 
 doubled, and it will be three times as strong if 
 the current is increased threefold. The law of 
 the magnetizing effect of a solenoid or hollow coil 
 of wire may therefore be stated as follows : It is 
 proportional to the current flowing and to the 
 number of times it flows through or around the 
 space which constitutes the magnetic field. Or 
 in other words, it is proportional to the product of 
 the amperes multiplied by the number of turns 
 or convolutions in the solenoid. Since an electric 
 current is always measured in amperes, and a coil 
 of wire may be definitely described by the number 
 of turns of which it is composed, it is a convenient 
 way of expressing the magnetizing effect of the 
 combination of the two by the product of these 
 two, and the magnetic effect produced by a current 
 of one ampere flowing around a coil consisting of a 
 single turn of wire, usually called an "ampere 
 turn," has been adopted as the unit of magneto- 
 motive force. Thus the magnetomotive force of 
 a solenoid may be said to be that of 100 ampere 
 turns. It matters not how these 100 ampere 
 turns are made up whether a current of 1 
 ampere flows through a coil of 100 turns, 2 
 amperes through 50 turns, 25 amperes through 4 
 turns or 100 amperes flow through a coil of a 
 single turn provided only that the product of the 
 amperes and the number of turns in the coil is 
 
58 ELECTRIC RAILWAY MOTORS. 
 
 equal to 100, the magnetomotive force will always 
 be the same. 
 
 But we have seen that the quantity of electricity 
 (amperes) that will flow through a circuit is not 
 alone dependent upon the electromotive force, 
 but is also dependent upon the resistance of the 
 circuit, being greater where that circuit is short 
 or has little resistance, and less where it is long or 
 has greater resistance. Ohm's laws says that it is 
 always equal to the electromotive force divided 
 by the resistance. This is equally true of mag- 
 netism. When we have expressed the magneto- 
 motive force of a magnet, we have not yet 
 defined its strength, because we have not men- 
 tioned the resistance of the circuit through which 
 the flow is assumed to take place. 
 
CHAPTER VII. 
 
 LINES OP FORCE. 
 
 WE have the greatest possible variety of con- 
 ductors of electricity, from silver and copper, which 
 conduct it with the greatest facility and offer the 
 least resistance, down through all of the other 
 metals and carbon to substances which are non- 
 metallic in character which offer very great re- 
 sistances, and are usually termed " non-conduct- 
 ors." But of conductors of magnetism that is, 
 magnetic substances we have but three : iron, 
 nickel, and cobalt, of which iron possesses the 
 property in a pre-eminent degree. All other sub- 
 stances, including the air, stand about upon a par 
 with each other ; hence it is that a magnet acts 
 quite as well through the top of a table, through 
 a teacup or saucer full of water, as it does through 
 the same space of air. 
 
 If, therefore, we increase the air gap between the 
 north and south poles of a magnet, we increase 
 the resistance to the flow of magnetism, for the 
 latter has to traverse this length of non-conduct- 
 ing or poorly conducting substance, and with an 
 increased air space it will, as in the case of an 
 increase in the resistance of an electric circuit, 
 require a corresponding increase of magneto- 
 motive force or, what is equivalent, an increase in 
 the number of ampere turns of wire to produce 
 
60 ELECTRIC RAILWAY MOTORS. 
 
 through this increased resistance an equal flow of 
 magnetic fluid. 
 
 With the conception of a flow of magnetism, or 
 " flux," as it is technically called, it became neces- 
 sary to have some unit corresponding to the 
 ampere as used in the flow of electricity. For 
 the magnetic flow or flux the unit adopted is " the 
 
 FIG. 10. 
 
 line of force," which is an imaginary line passing 
 out of the magnet at the north pole and into it at 
 the south pole. 
 
 Thus in Fig. 10, which represents a solenoid, 
 the lines of force emerge at the north pole and 
 pass around through the air and re-enter at the 
 south pole. In the case of the solenoid the whole 
 of the magnetic circuit is through the air. The 
 resistance to the flux is therefore very great, and 
 the number of lines of force, or, in other words, the 
 strength of the magnet, will therefore be very 
 small. 
 
 In an electric circuit, if we substitute a good 
 conductor for a poor one, we will get, with the 
 same electromotive force, more amperes, so if in 
 
LIIfES OF FORCE. 61 
 
 the solenoid (Fig. 10) we substitute a bar of iron, 
 a good conductor, for the air inside of the coil, 
 we will have greatly reduced the total resistance 
 of the circuit, and the number of lines of force 
 that will flow around the magnetic circuit will be 
 enormously increased, which means that we have 
 
 FIG. 11. 
 
 a magnet of enormously greater strength from the 
 same number of ampere turns. 
 
 We have here (Fig. 11) a bar electromagnet. 
 But strong as this is it is evident that in any bar 
 magnet at least one-half the magnetic circuit must 
 be in air, and the longer the bar the longer will 
 be the portion of the circuit which must traverse 
 the high-resisting air. If we bend the bar around 
 in the shape of a horseshoe, bringing the two 
 ends near together, we may greatly reduce the 
 distance which the lines of force must traverse 
 the air, and this means a still greater number of 
 lines that will be caused to flow by the same 
 number of ampere turns. Thus in Fig. 12 the N. 
 and S. poles are brought close together, so that 
 the air space between them is very short. The 
 lines emanating from the face of the N. pole and 
 entering the face of the S. pole will therefore 
 be very dense much denser than was the case in 
 Fig. 11, where the iron bar was the same length 
 
62 
 
 ELECTRIC RAILWAY MOTORS. 
 
 and was excited by the same number of ampere 
 turns. 
 
 In making these sketches to any given scale 
 there is, of course, a limit to the number of lines 
 of force that we can draw. We can draw a cer- 
 tain number, but there is no room for more. 
 
 The same conditions 
 exactly exist as regards 
 the number of actual 
 lines of force that can 
 be made to thread 
 through any given bar 
 of iron. Up to a 
 certain point the num- 
 ber of lines remains 
 very closely propor- 
 tional to the magnet- 
 izing force (ampere 
 turns) divided by the 
 magnetic resistance, but a limit is finally reached 
 beyond which the increase of ampere turns has 
 very little additional effect upon the strength of 
 magnetism produced new lines of force are not 
 added, siriiply for the same reason that we can- 
 not draw any more in our sketch, viz., that there 
 is no room for them. When this condition is 
 reached, the iron is said to be "saturated." 
 
 We have heretofore spoken of these lines of 
 force as purely imaginary lines. They have, how- 
 ever, a more real existence than this, for they can 
 be traced or made visible in various ways. If a 
 plate of glass be sprinkled with fine iron filings, 
 and then held close to a magnet and be gently 
 tapped so as to allow the particles of iron to take 
 up any position they desire, they will arrange 
 themselves in curved lines emanating from the 
 
THE CLOSED MAGNETIC CIRCUIT. 63 
 
 north pole and re-entering the south pole, which 
 correspond in length and direction with, and, in 
 fact, are, the visible representatives of what we 
 have been speaking of. They may also be traced 
 with a small compass needle, which, in whatever 
 position it may be held with reference to the 
 magnet, will have exactly the same direction as 
 the line of force which passes through it has at 
 that place. Thus a compass neeple points in a 
 north and south direction, simply because all lines 
 of force passing between the two poles of the 
 earth have a north and south direction. If, how- 
 ever, we bring another magnet near the needle, the 
 lines of force emanating from it will overpower 
 those of the earth's magnetic poles, and the needle 
 will take up a position in accordance with the 
 stronger, or rather in a position which is a compro- 
 mise between the two. 
 
 THE CLOSED MAGNETIC CIRCUIT. 
 
 By reference to the lines of force shown by the 
 iron filings it will be seen that they emerge from 
 and re-enter the magnet only at the poles. We 
 may therefore define the magnetic poles as those 
 portions of the magnet where the lines of force . 
 emerge from and re-enter the magnet. We have 
 also seen that as we decrease the air distance 
 through which these lines have to pass, by bend- 
 ing the magnet around so that the poles come 
 closer together, the magnet increases in strength. 
 It would be logical, therefore, to assume that if 
 we brought the two poles into actual contact, or, in 
 fact, made a closed ring of the magnet, we would 
 have a magnet of maximum strength, because the 
 air resistance would be reduced to nothing, and 
 such is really the case, and the smaller the diameter 
 
64 ELECTRIC RAILWAY MOTORS. 
 
 of the ring the stronger will be the magnet, be- 
 cause the lines of force will have a less distance of 
 iron to traverse, and hence meet with less resist- 
 ance due to that cause. 
 
 But according to our last definition a magnetic 
 pole is that surface whence the lines of force either 
 emerge or where they enter the magnet. Since 
 iron is such an enormously better conductor of mag- 
 netism than the air, the lines of force will continue 
 in the iron even though they may have to go con- 
 siderably out of the shortest path to do so. There 
 will in this case be no surfaces from which the lines 
 will emerge or into which they will enter, and 
 therefore there will be no poles. If there are no 
 lines of force external to the magnet, there will be 
 none to direct a compass needle, and the latter 
 will not be deflected as by an ordinary magnet, 
 nor will this ring magnet attract other particles 
 of iron or steel. This is entirely contrary to the 
 popular conception of a magnet, and it is only in 
 the more modern works that a magnet is not de- 
 fined by the unqualified statement that it possesses 
 both north and south poles which have the prop- 
 erty of attracting to themselves other magnetic 
 substances. We have, however, learned that we 
 obtain the strongest magnet with the least ex- 
 penditure of energy in an absolutely closed mag- 
 netic circuit and by making that circuit as short as 
 possible, and yet this strongest magnet has neither 
 north pole nor south pole, nor will it attract or 
 repel other pieces of iron or steel. 
 
 MAGNETIC LEAKAGE. 
 
 It is seldom, however, that we can realize fully 
 these ideal conditions. Although our iron ring 
 may be of the softest iron, and there may be plenty 
 
MAGNETIC LEAKAGE. 65 
 
 of it to carry all the lines of force that are gener- 
 ated by the ampere turns used, some of these 
 lines are apt to wander outside the iron, and to 
 take a short cut across the air space. These may 
 be readily detected and their direction indicated 
 by the deviation of the compass needle. To such 
 straying lines the term " leakage lines " or " mag- 
 netic leakage " has been given. 
 
 Wliile the unbroken ring or closed magnetic 
 circuit gives us by far the strongest magnet for 
 the material and energy employed, there are many 
 uses of the magnet which require that it should 
 have polarity that its lines of force should pass, 
 for a portion of the distance at least, through an 
 interval into which may be introduced substances 
 to be acted upon by these lines ; but it is a cardi- 
 nal law of magnets that that magnet which most 
 nearly approaches the closed magnetic circuit will 
 be the most efficient. For this reason magnets, 
 whether permanent or electro magnets, are usually 
 bent around so that their poles approach each 
 other, and the object to be magnetized is intro- 
 duced into the gap between the two poles. In 
 order to concentrate the lines and make them as 
 dense as possible in this gap it is usual to wind 
 the substance to be acted upon on a core of iron, 
 or imbed it in its mass, and this is introduced into 
 the gap, reducing by that much the air resistance. 
 Of course all leakage lines, or those which do not 
 pass through the path intercepted, are wasted, and 
 whatever of current was required to generate the 
 leakage lines was uselessly expended. Exactly 
 parallel would be the case were we pumping water 
 through a long pipe to operate at its other end a 
 small water wheel. If the pipe were full of small 
 holes along its length, just as much more water 
 
66 ELECTRIC RAILWAY MOTORS. 
 
 would have to be pumped into the pipe to do the 
 same amount of work as leaked out through these 
 holes. -That is to say, the water that leaks out will 
 cost us just as much to pump, per gallon, as that 
 which issues from the nozzle, and yet it does no 
 useful work. The economical man will therefore 
 not use a sieve for a water pipe, and the builder 
 of magnets will avoid shapes which tend to mag- 
 netic leakage. In designing magnets it is always 
 desirable to keep the two sides the north half 
 and the south half as far away from each other 
 as possible except at the poles, so that the air gap 
 between the latter where we want to utilize the 
 lines of force will be the path of least resistance, 
 and the great distance between all other portions 
 of the magnet of different polarity will offer too 
 great a resistance for lines of force to jump across. 
 Sharp angles or points should also be generally 
 avoided, because magnetism leaks more readily 
 from a point or angle than from a smooth surface. 
 A magnet of a circular ring shape best meets the 
 required conditions, although a strict adherence 
 to that form is not always practicable or even 
 desirable. 
 
CHAPTER VIII. 
 
 POLARITY, MAGNETISM AND CURRENT. 
 
 FOR the purpose of showing the lines of force 
 I bought for ten cents a small horseshoe magnet 
 2|- inches long. Laying this on its side on a table, 
 1 placed over it a piece of glass which had been 
 varnished on one side and allowed to become per- 
 fectly dry. Upon this I sifted as evenly as pos- 
 sible some fine iron filings, and then tapped the 
 plate gently on the edges in order to permit the' 
 filings to arrange themselves. The beautiful curves 
 shown in Fig. 13 were the result. The glass was 
 then carefully lifted from the magnet and heated 
 over a gas flame. This softened the varnish so 
 that the filings were stuck to the plate, and when 
 the varnish had hardened again were preserved 
 for the making of this cut. Fig. 13 shows the 
 lines of force emanating from this magnet when 
 the armature or keeper is entirely removed. Fig. 
 14 shows the lines as they were when the arma- 
 ture was removed about one-third of an inch from 
 the poles, and Fig. 15 shows the lines as they ap- 
 peared when the polar ends of the magnet alone 
 were presented to the under side of the glass 
 plate. 
 
 We may look upon these lines of force as so 
 many elastic bands or strings by which the 
 magnet attaches itself to other pieces of iron. 
 
 67 
 
68 ELECTRIC RAILWAY MOTORS. 
 
 When the iron is in actual contact with the poles 
 of the magnet, it is bound to the latter by a great 
 number of these strings. When we endeavor to 
 pull the iron away, we have to pull against the 
 
 FIG. 
 
 combined elasticity of all these strings. The mo- 
 ment we succeed in pulling it the slightest distance 
 from the magnet a great many of these strings 
 snap or pull out of the iron and disappear in the 
 magnet just as india-rubber strings would if they 
 came out of a hollow tube and were attached to 
 the piece of iron we were trying to pull away. As 
 we remove the iron still farther more arid more of 
 
POLAEITY, MAGNETISM AND CURRENT. 69 
 
 these elastic strings or bands snap, until the iron 
 is removed beyond the attraction of the magnet, 
 when it may be said that all of the bands have 
 been snapped. 
 
 Reversing the operation by gradually approach - 
 
 FIG. 14. 
 
 ing a piece of iron to the poles, we will have to 
 draw upon our imagination somewhat for an 
 equally good illustration. As it comes within the 
 attraction of the magnet first one or two elastic 
 bands jump out of the north pole, thread their 
 way through the iron and attach themselves to 
 the south pole. With a nearer approach a great 
 
70 ELECTRIC RAILWAY MOTORS. 
 
 many more do the same thing and pull the iron to 
 the poles with all the force of their elasticity, and 
 finally as the iron comes nearer they come out 
 with a rush, and with their combined pull hold 
 
 FIG. 15. 
 
 the iron to the poles with the greatest force of 
 which that particular magnet is capable. 
 
 Now a clear conception of the behavior of these 
 lines of force is indispensable to an intelligent 
 understanding of the theory of the dynamo and 
 the motor, and it is for this reason that so 
 much space has been devoted to the subject. 
 Do not be deceived with the idea that these 
 
POLARITY. 71 
 
 lines of force are solely of theoretical interest. 
 We discussed them at first as though their exist- 
 ence was purely imaginary. Then we showed by 
 means of the iron filings and the photographs that 
 they really do exist. Next we discussed their 
 behavior in a somewhat theoretical manner, and 
 
 FIG. 16. 
 
 shortly we will show how upon this behavior 
 depends entirely the action of both the dynamo 
 electric machine and the electric motor. But 
 before taking up this latter task, which, to make 
 easily intelligible, so much has been said by way 
 of preparation, a few words must be added as to 
 the effect which the direction of flow of the cur- 
 rent in the solenoid has upon the polarity of the 
 resulting magnet. 
 
 POLAEITT. 
 
 It may be stated at once that the way in which 
 the wire of a solenoid is wound has absolute^ 
 nothing to do with which end of the inclosed iron 
 bar will be the north pole and which the south, 
 but all depends upon the direction in which the 
 current flows around it. 
 
 If in looking at the end of a coil the current 
 flows around it in the direction of the hands of a 
 clock, that end will be a south pole (Fig. 16). If 
 the current is flowing in the opposite direction to 
 that pursued by the hands of a clock, or from 
 
 OF THE 
 
 UNIVERSITY 
 
 XS 
 
 Y! 
 
 ^r 
 
72 ELECTEIC RAILWAY MOTORS. 
 
 right over the magnet to left, that end will be a 
 north pole (Fig. 17). It is therefore merely a matter 
 of convenience whether we wind a magnet right- 
 handed or left-handed ; we can make either end a 
 north pole and the other a south pole by simply 
 connecting the ends of the coil with our circuit so 
 that the current will flow around the magnet in 
 the proper direction, and if at any time we wish 
 
 FIG. 17. 
 
 to reverse the poles of the magnet we simply have 
 to reverse our connections. It is well to bear this 
 in mind, for there is a popular fallacy that the 
 direction of winding the magnet, right-handed or 
 left-handed, determines which end will be north 
 and which south, but as a matter of fact it has 
 nothing to do with it. 
 
 MAGNETISM AND CURRENT. 
 
 For the purpose of illustrating the part which 
 the lines of force (magnetism) play in the genera- 
 tion of current I went to a blacksmith's shop and 
 cut off a piece of |-inch round iron 5 inches 
 long. This I heated and bent into the shape of a 
 hairpin (A, Fig. 18), bringing the ends to within 1^ 
 inch of each other. I then cut off another piece 
 from the same rod and bent its two ends upward 
 at right angles (B, Fig. 18), so that the distance 
 between these two ends was the same- as between 
 the ends of A. The ends of both A and B were 
 
MAGNETISM AND CIHRRENT. 
 
 then filed smooth, so that when placed together 
 the surfaces rested flatly against each other. Any 
 blacksmith would probably have done this job for 
 me for twenty-five cents. 
 
 I next made two paper spools, each an inch long, 
 by wrapping several thicknesses of manilla paper 
 around a stick whittled to about the same diame- 
 ter as my iron, and forcing 
 onto this paper cylinder two 
 washers made of heavy card- 
 board, and pasting the up- 
 turned ends of the paper 
 cylinder to the outside sur- 
 faces of these washers, so as 
 to hold them in place. Then, 
 while the spools were still on 
 the stick, I wound on them 
 tightly and as evenly as possi- 
 ble layer after layer of insu- 
 lated wire until the spools 
 were full. I counted the num- 
 ber of turns on the first spool, and it happened to 
 be 382 turns. I wished both coils to be as nearly 
 alike as possible, so in winding the second spool 
 I put on just the same number of turns. Then, 
 slipping the spools off of the stick, I slipped one 
 on each leg of my bent iron rod A until about 
 a quarter of an inch or less of the ends protruded ; 
 one end of each of the coils, having been cleaned of 
 its insulation, were twisted together and the other 
 ends were connected to the battery. The connec- 
 tions of the coils with each other were such that, 
 in whichever way the current passed, when we 
 looked at the two poles it would be clockwise 
 around one and counter clockwise around the other. 
 Immediately the current began to flow in the coils 
 
74 ELECTEIC RAILWAY MOTORS. 
 
 the hairpin, or bent iron A, became a most power- 
 ful magnet, and upon bringing the ends of B in 
 contact with its poles it attracted it with great 
 force. Although the iron A weighed less than a 
 quarter of a pound, it sustained a weight of about 
 ten pounds attached to the armature B. That 
 such a small amount of iron could support such a 
 weight would seem almost incredible to one who 
 had not witnessed it, and, in fact, would have been 
 utterly impossible with a permanent magnet of the 
 same weight. On breaking the current the mag- 
 netism disappeared at once, as has already been 
 explained. It was found, however, that it would 
 still hold up a steel penpoint or two, showing that 
 its magnetism was not entirely lost. This residual 
 magnetism, as it is called, was probably due to the 
 fact that the iron had become somewhat hardened 
 either by the hammering it was subjected to on 
 the anvil or by too rapid cooling after it came 
 from the forge. After it had been left for twenty- 
 four hours without current, however, the residual 
 magnetism had become so small that it would no 
 longer support even the smallest piece of iron 
 accessible, although slight traces of polarity were 
 detectable on presenting the two ends successively 
 to one end of the floating needle. These tests, 
 therefore, showed that it fairly answered all the 
 requirements of a good electromagnet. 
 
CHAPTER IX. 
 
 ELECTROMAGNETIC INDUCTION. 
 
 I NEXT constructed a paper spool on the arma- 
 ture -Z?, similar to those placed on the legs of A, 
 and wound it as full as I could get it of insulated 
 wire. I counted the number of turns and found 
 it to be* 421. I may say here that all of these 
 dimensions were accidental, and are only given to 
 show what actual results were obtainable from 
 them. 
 
 The object of placing the coil on the short piece 
 -Z?, which we will hereafter designate as the arma- 
 ture, was to show what effect the snapping of the 
 lines of force which thread a solenoid, or their 
 sudden appearance in the same, would have upon 
 the solenoid. It is evident that if no current be 
 traversing the coils on A there will be no lines of 
 force traveling around them. If, however, we 
 place B in contact with A, we have practically a 
 closed magnetic circuit, and if, after having de- 
 tached one of the wires from the battery, we touch 
 it to its binding post, the full strength of the 
 magnet will be instantaneously developed, all of 
 the lines of force of which our apparatus is capable 
 will be instantaneously developed in A, and will 
 rush out of the north pole, thread their way 
 through the armature -B, which is the core of our 
 solenoid, and enter the magnet again at the south 
 pole. 
 
76 ELECTRIC RAILWAY MOTORS. 
 
 If we now break our electric current again, the 
 lines of force traversing the magnet and the arma- 
 ture coil will be as suddenly snapped and disappear, 
 the result being the same, though more effective, 
 perhaps, as if the armature B were suddenly jerked 
 away from the magnet while the latter retained its 
 full magnetic properties. To discover the effect 
 of the sudden introduction within or withdrawal 
 from the armature coil of these lines of force let 
 us connect its two ends with our solenoid (Fig. 2, 
 
 FIG. 19. 
 
 page 35). Next take a very small needle that has 
 been previously magnetized and suspend it at its 
 center, so that it will hang horizontally. Use a 
 coarse spider-web for suspension if possible, as even 
 the finest thread is a little stiff and has a twist which 
 will interfere more or less with the action we are 
 looking for. Hold the solenoid up to the needle so 
 that the latter projects for about one-third of its 
 length into the solenoid. If one of the battery 
 wires is disconnected from the battery, make the 
 connection by touching it to its binding post. 
 This, as we have seen, will cause a rush of lines of 
 force through the armature core. Note the be- 
 
ELECTROMAGNETIC INDUCTION, 77 
 
 havior of the needle as this rush occurs. It will 
 give a sudden kick, either outwardly or inwardly, 
 showing that the solenoid has momentarily exerted 
 upon it either a force of attraction or one of repul- 
 sion. But it is only momentarily, for if the condi- 
 tions remain the same, the needle, after swaying 
 back and forth a few times, will come to rest again 
 in exactly the same position that it assumed before 
 the lines of force traversed the armature core. 
 The lines of force are still there, but there is 
 neither attraction nor repulsion of the solenoid. 
 Now break the battery circuit so as to suddenly 
 withdraw the lines of force. Another kick will be 
 noticed in the needle, but in the opposite direction. 
 If the solenoid exerted an impulse of attraction 
 when the lines of force passed into the armature 
 core, it will exert an impulse of repulsion when they 
 are suddenly withdrawn. Next reverse the ends of 
 the armature 1 and repeat the experiment without 
 changing the position of the solenoid or its con- 
 nections. In the reversed position of the arma- 
 ture the end that was before in contact with the 
 north pole of the magnet will be in contact with 
 its south pole, and that which was in contact with 
 the south pole will be against the north pole, so 
 that the lines of force as they enter and withdraw 
 in the same directions with regard to the magnet 
 have opposite directions with respect to the coil. 
 As they enter, the solenoid will be found to repel 
 and to attract where they withdraw. 
 
 Now modify the experiment a little. While the 
 magnet remains excited jerk off the armature and 
 then replace it. Exactly the same effect will be 
 produced upon the needle by the solenoid as before 
 when the current was alternately broken and 
 closed. Next disconnect the solenoid, and connect 
 
78 ELECTRIC RAILWAY MOTORS. 
 
 in its place in the armature circuit the flat coil (Fig. 
 6, see page 41), which we employed in our galvan- 
 ometer. Hold this directly beneath the needle 
 with its wires parallel with the latter. Upon break- 
 ing and making the battery circuit or pulling off 
 or putting on the armature we will find that the 
 needle receives momentary impulses which cause 
 it to deviate alternately to the east and to the 
 
 FIG. 20. 
 
 west. As with the solenoid, the effect is only 
 momentary and not sufficient in the present in- 
 stance to cause the needle to swing far, but by tim- 
 ing the makes and breaks, remembering that they 
 give impulses in opposite directions, the needle may- 
 be caused to swing through gradually increasing 
 arcs, and finally to rotate completely around on its 
 support. 
 
 We will have recognized before this that the 
 action of both the solenoid and flat coil upon the 
 needle was due to an electric current caused by 
 the sudden introduction and withdrawal of the 
 lines of force through the armature coil, and that 
 the direction of the resulting current changed as 
 
ELECTROMAGNETIC INDUCTION. 79 
 
 the number of the lines of force threading the 
 coil is increasing or decreasing. In fact, had. we 
 a machine by which the armature could be rapidly 
 approached to or removed from the magnet poles 
 we would have an alternating current generator 
 producing currents in the armature circuit exactly 
 similar to those employed in lighting by alternat- 
 ing currents, and if, further, we had a device by 
 which the reverse currents after they are generated 
 could be changed in direction to correspond with 
 those which both precede and follow them, we 
 would have in all respects a direct current genera- 
 tor. In fact, almost before we have been aware of 
 it, we have actually developed experimentally an 
 electrical generator. It now only remains to 
 develop the details by which the current generated 
 is rendered continuous in one direction instead of 
 alternating, and practically steady instead of pulsa- 
 tory, as it would be were the currents we have just 
 generated all sent in the same direction. We have 
 also discovered that the electromotive force is not 
 due to the actual number of lines threading the 
 coil, for the same effect was produced when there 
 were no lines when the magnet was not excited 
 as when there was the greatest number that is 
 to say, there was no effect in either case, but the 
 current flowed only when the number of lines was 
 changing. The rule is that the potential difference, 
 which gives rise to the current, is proportional not 
 to the number of lines included by the coil, but to 
 the rate of change of the number of lines. In 
 our experiments it was an almost instantaneous 
 change from no lines to the full number we were 
 able to generate, and from that number to none 
 again. 
 
80 ELECTRIC RAILWAY MOTORS. 
 
 THE CONTINUOUS CURRENT DYNAMO. 
 
 Iii the dynamo of to-day a much more conven- 
 ient method of varying the number of lines in- 
 cluded in the coil is obtained by revolving that 
 coil around an axis in a uniform magnet field. 
 
 In Fig. 20 we have a representation of a single 
 turn of wire revolving around one of its sides, as 
 an axis in a uniform magnetic field. In the posi- 
 tion shown none of the arrows will be embraced 
 by the coil, but as we revolve it in either direction 
 it gradually will allow more and more lines 
 of force to pass through it, until it arrives at 
 a position at right angles to the one shown, when 
 it will embrace the maximum number, but in 
 this position its motion will be for a moment 
 parallel with the lines of force, so that for a very 
 small portion of its revolution near this position 
 it will cut no more and no fewer lines. Its rate 
 of cutting lines at this point being zero, no electro- 
 motive force, and consequently no current, will 
 be generated. As it proceeds around through 
 another right angle the number of lines which 
 the loop will include diminishes, gradually at 
 first, but more and more rapidly, until the position 
 of the loop is directly opposite that shown in the 
 cut, when it again becomes parallel with the lines 
 and for a moment includes no lines, but as it passes 
 this position the loop turns its other side to the 
 north pole, and commences to take in lines from 
 the opposite side that is to say that with respect 
 to the loop the direction of the lines is reversed. 
 At this point the rate of change of the number 
 of lines embraced by the coil is a maximum, 
 because at one instant there were a few lines 
 going through the coil in one direction, and at the 
 
THE CONTINUOUS CURRENT DYNAMO. 81 
 
 next there was the same number going through 
 in the opposite direction, or there were just that 
 many less than nothing going through in the 
 original direction the second moment. The 
 greatest rate of change in the number of lines 
 embraced by the coil that can possibly occur 
 takes place at this part of the revolution, and 
 therefore at this point in its path the greatest 
 electromotive force is generated. From this 
 point to the vertical position of the loop, at right 
 angles to the lines of force, the rate of change be- 
 comes slower and slower, and the electromotive 
 
 force less, until the loop arrives at the latter posi- 
 tion, when for a moment there is no change, since 
 its motion is for the time again parallel with the 
 lines of force. No electromotive force is, therefore, 
 developed at this point in the revolution, but 
 from here to the original position, shown in Fig. 20, 
 the rate of change gradually increases again, until 
 it becomes a maximum once more in the position 
 shown. It will be observed, therefore, that, as 
 the coil is revolved between the two poles of the 
 magnet, the electromotive force generated twice 
 reaches a maximum, once when the coil is in the 
 position shown, and again when 180 from this 
 position, and twice becomes zero, viz., when it 
 
82 ELECTEIC RAILWAY MOTORS. 
 
 is in the two positions at right angles to this 
 plane. In each case, as the electromotive force 
 passes through zero, the current resulting 
 changes its direction, so that in each revolution 
 of the coil the current will flow half the time 
 through the outside circuit from A to J5, and dur- 
 ing the other half in the contrary direction, from 
 JSto A. 
 
 The more usual way of explaining this genera- 
 tion of electromotive force is to speak of the rate 
 at which a wire represented in section by the dot 
 C y Fig. 21, cuts the lines of force when revolved 
 in a circular path A E D G in a uniform mag- 
 netic field represented by the parallel lines. Re- 
 ferring to the figure, when the wire is at (7, it is 
 traveling for the moment parallel with the lines of 
 force, and therefore cutting none and generating 
 no electromotive force. As it proceeds around 
 from left to right it cuts these lines more and more 
 rapidly, until at E it is moving at right angles to 
 them, where it cuts them at the maximum rate of 
 its course. At this part of its path the highest 
 electromotive force is generated. From E to D 
 it cuts them less and less rapidly, until it arrives at 
 D, where its motion is again parallel to the lines 
 and no electromotive force is generated. From D 
 to 6r the rate again increases and from G to C 
 decreases, but the direction of the current during 
 this half of its excursion is in the opposite direc- 
 tion to that resulting from its course in the first 
 half the changes of direction of the electro- 
 motive force or pressure upon which the current 
 and its direction depend taking place as the wire 
 passes through the positions where it cuts no 
 lines, called the neutral positions, A and D. 
 
 While the same results are reached by explain- 
 
THE CONTINUOUS CURRENT DYNAMO. 83 
 
 ing the action of a moving wire in a magnetic 
 field in this way as in the other, it is not strictly a 
 correct explanation, for according to it the gener- 
 ation of electromotive force is made to depend 
 upon the actual cutting of the lines of force by the 
 moving wire. We have seen that this is not a 
 fact, for in our experiment with the electromagnet 
 (Fig. 19) we found that with our coil on B per- 
 fectly stationary we generated an electromotive 
 
 FIG. 22. 
 
 force simply by making and breaking the battery 
 connection with .the magnet coils, thereby rapidly 
 changing the number of lines that threaded through 
 the armature core, from zero to a maximum, and 
 vice versa. In this case there was absolutely no 
 cutting of lines. But, as before stated, the same 
 results follow both methods of explanation, and the 
 latter, although strictly speaking not correct, is 
 simpler, and for that 'reason will be used here- 
 after. 
 
 Fig. 20 represents an electromagnetic generator 
 in its simplest form. 
 
 It is more usual, however, instead of having a 
 
84 ELECTRIC RAILWAY MOTORS. 
 
 narrow coil revolving around one of its sides as an 
 axis, to employ a larger coil and revolve it around 
 an imaginary axis in its center, as shown in Fig. 
 22. In this case when the coil revolves in the 
 direction indicated, while the side A J3 cuts the 
 lines in one direction, the other side, A D, cuts 
 them in the opposite direction. In the cut the 
 end J9 is represented as terminating in the hollow 
 cylinder JB, through the axis of which passes the 
 other end of the coil, also terminating in a cylin- 
 
 FIG. 23. 
 
 der. Upon these two cylinders copper brushes 
 are pressed, to which are attached the two ends of 
 the external circuit D G E. 
 
 With the coil in the position shown the maxi- 
 mum electromotive force is being generated for 
 the reasons already explained, and the direction of 
 the resulting current will be as indicated by the 
 arrows. When the coil has arrived at the position 
 shown in Fig. 23, it is cutting no lines of force 
 and generating no electromotive force, but imme- 
 diately after passing this position it commences to 
 cut the lines again, the two sides cutting the lines 
 
THE CONTINUOUS CURRENT DYNAMO. 85 
 
 in opposite directions, however, viz., A B has 
 exchanged places with A D, the former cutting 
 them from west to east, if in looking toward the 
 north pole we be supposed to be looking north, 
 and the latter now cutting them from east to west, 
 using the same points of the compass. The cur- 
 rent will, therefore, be reversed, and will reach its 
 maximum strength when in the position shown in 
 
 Fig. 24. It will again become zero and reverse 
 its direction when the coil has reached a position 
 at right angles to this ; and so the changes will 
 follow each other as the coil revolves, repeating 
 the changes with each revolution, becoming zero 
 and reversing its direction each time the coil takes 
 up a position at right angles to the lines of force, 
 and reaching a maximum each time it becomes 
 parallel with them. 
 
 We have here what may be termed a typical 
 
86 ELECTRIC RAILWAY MOTORS. 
 
 machine generating alternating currents, viz., 
 those which are periodically reversing their direc- 
 tion. What is wanted, however, is to generate a 
 current that shall flow always in the same direc- 
 tion in the outer circuit. It is evident that if at 
 the moment the coil arrived in its neutral position 
 (Fig. 23), when for one moment it is generating no 
 current and the next commences to generate one 
 
 FIG. 25. 
 
 in the opposite direction, we should exchange the 
 places of the two brushes D and E, placing E 
 upon the cylinder which terminates the end of the 
 wire B, and D upon the cylinder (7, and replace 
 them again in their original positions when the 
 coil arrives at its next neutral position, the current 
 in the external circuit would no longer be reversed, 
 but would continue to flow in the same direction 
 throughout the complete revolution of the coil. 
 A simpler way of accomplishing the same thing, 
 however, is at hand. 
 
 Suppose the hollow cylinder D, in Figs. 20, 22, 
 23, 24 (see pages 78-85), be slit longitudinally into 
 two equal parts, and let one part be connected to 
 each of the two ends of the turn of the wire, as 
 
THE CONTINUOUS CUBBENT DYNAMO. 87 
 
 shown in perspective in Figs. 25 and 26, and in 
 section to a larger scale in Figs. 27 and 28. 
 
 Calling these two halves m and ra, if we place 
 the slits at right angles to the coil, as shown in 
 the figures, and place the brushes D E in the 
 positions shown, the direction of the current in 
 the outer circuit will be automatically changed 
 at the proper time. In Fig. 28 the coil is in one 
 of its neutral positions. Just before this D has 
 been in contact with m and E with n; the current 
 
 FIG. 26. 
 
 at that time was flowing from n through E G- D to 
 m. When the coil has arrived at the vertical posi- 
 tion shown in Fig. 28, there is no electromotive 
 force generated, but just after it has passed this 
 position section n passes from under brush E and 
 section m passes from under brush D. There- 
 fore brush E rests upon section m and brush D 
 upon section n (Fig. 29), just as the direction of 
 the electromotive force in the coil changes, so that 
 the current will continue to flow in the same direc- 
 tion in the circuit E Gr D as before. 
 
88 ELECTRIC RAILWAY MOTORS. 
 
 This arrangement, by which the alternating 
 current is changed to one always flowing in the 
 same direction, is termed a commutator, and the 
 line joining the positions of the brushes where the 
 change of direction or commutation takes place 
 is called the " axis of commutation." 
 
 We have already accomplished part of our pur- 
 pose, but not all, for while the current now always 
 flows in the same direction, it is an exceedingly 
 unsteady one, having at one time no electromotive 
 force at all and at another a maximum. We must 
 
 FIG. 27. 
 
 have a more uniform current, and to this end let 
 us add another coil at right angles to the first 
 (Fig. 30). 
 
 If this second coil is added and the commutator 
 split into four sections, the currents in both coils 
 will be rectified, and as the coil b is in its neutral 
 position while coil c is generating its maximum 
 electromotive force, and vice versa, there will be 
 no time when the circuit is without current, for 
 while coil b is contributing nothing, the other 
 coil, c, is doing its best. Referring to the cut it 
 will be seen that each coil will come into action 
 when it comes within 45 of its position of maxi- 
 
THE CONTINUOUS CURRENT DYNAMO. 89 
 
 mum effect, and will go out of action when it has 
 passed 45 beyond that point. 
 
 While in the position shown the coil c is in a 
 maximum position, and section o is positive and p 
 negative. The current will therefore flow from 
 brush E through the circuit to B. The potential 
 will diminish until the coil has passed through 45. 
 Then the sections o and p of the commutator and 
 the coil will no longer be in connection with the 
 brushes and the outer circuit, and may be neglected 
 
 FIG. 28. 
 
 for the next quarter of a revolution. When the 
 segments o and p pass from under the brushes, 
 segments m and n immediately succeed them and 
 coil b is connected to circuit. This coil is approach- 
 ing its position of maximum effect, and therefore 
 its potential difference is increasing, and will con- 
 tinue to increase as it passes through an angle of 
 45, when it reaches its maximum, and will then 
 decrease as did coil c for 45 more, until like the 
 other coil it is cut out of circuit by its commutator 
 segments passing from beneath the brushes. Thus 
 a decreasing electromotive force of a strength due 
 to a position of one coil 45 beyond its position of 
 
90 ELECTEIC RAILWAY MOTORS. 
 
 maximum effect is succeeded by an increasing 
 electromotive force from another coil due to its 
 position of 45 in front of its position of maximum 
 effect, and we have a current still varying in 
 strength, but only between that which would re- 
 sult from a position of the coils of maximum 
 effect and that which would result from a position 
 45 removed from it instead of one varying be- 
 tween a maximum and zero. 
 
 If we double the number of coils again and 
 divide each of our commutator segments into two, 
 the fluctuations will become still less, and so, by 
 multiplication of coils each terminating at both 
 ends in commutator segments which come under 
 the brushes and leave them at a less angle from 
 jihe L position of maximum^ effect, th e re suTfing^ cur- 
 rent will vary between narrower and narrower 
 limits and gradually approach uniformity of 
 strength. 
 
 INCREASE OF ELECTROMOTIVE FORCE. 
 
 We observed from our experiments with the 
 solenoids that two turns affected the needle more 
 than one turn did, and it has been stated that the 
 magnetizing effect of a coil or the magnetomotive 
 force of an electromagnet was proportional to the 
 product of the current flowing, into the number of 
 turns in the coil, or the ampere turns, as we have 
 called this product. The converse of this is also 
 true. If a coil of one turn of wire such as has 
 been discussed heretofore revolving in a given 
 magnetic field at a certain speed generates an 
 electromotive force of say one volt, a coil of two 
 turns or a coil of three turns revolving at the same 
 speed in the same field will generate an electro- 
 
INCREASE OF ELECTROMOTIVE FORCE. 91 
 
 motive force of double or treble as much. That 
 is to say that since a given current passing two 
 and three times around a bar of iron or space will 
 generate two and three times as many lines of 
 force as it will if it passes around but once, so if 
 a coil of one turn cutting the lines of force at -a 
 given rate generates a certain electromotive force, 
 the same wire bent into a coil of two and three 
 turns will under like conditions generate two and 
 
 FIG. 29. 
 
 three times as many volts. Thus if a coil such as is 
 represented in Fig. 31 (seepage 93) be substituted 
 for the coils of a single turn represented in the 
 previous illustrations, it will at the same speed of 
 revolution generate twice as much electromotive 
 force, because in doubling the wire it is equivalent 
 to doubling the rate at which that wire cuts the lines 
 of force which alone determines the electromo- 
 tive force that will result. This being the law, 
 many other means of increasing the electromotive 
 force at once suggest themselves. If we revolve 
 our coil faster, its rate of cutting will be greater, 
 or if we increase the number of the lines, the rate 
 of cutting will still be faster, even though the 
 
92 
 
 ELECTRIC RAILWAY MOTORS. 
 
 speed of revolution be not increased. This latter 
 statement suggests two other means of increasing 
 the electromotive force, for we can increase the 
 number of lines of force in our field in two ways 
 either by increasing the magnetomotive force of 
 our magnet by increasing the number of ampere 
 turns, or by decreasing the magnetic resistance of 
 the air space in which our coils revolve. Since 
 
 FIG. 30. 
 
 our coils are of a certain size, we cannot bring the 
 poles of the magnet closer together, as we did in 
 Fig. 12 (see page 62), and still leave room for our 
 coils to revolve, but we can wind our coils on a 
 cylinder of iron, which is the best conductor of 
 the magnetic lines that is known, and thus by 
 greatly reducing the resistance in this gap greatly 
 increase the number of lines that our coils will 
 cut at a given speed, and thus increase enormously 
 our electromotive force. And this method is 
 always employed in dynamo construction, because 
 it results in an enormous saving in copper, since 
 with one turn of the wire on an iron core a greater 
 number of volts will be generated than with very 
 
OF THE 
 
 UNIVERSITT 
 
 EDDY CURRENTS 
 
 many turns of wire without the iron revolved at 
 the same speed. Nor is any expense spared to 
 have this core of the softest and best iron for the 
 purpose, for the saving in other directions where 
 the best iron is employed in the armature core 
 more than counterbalances the additional cost of 
 the extra quality. 
 
 EDDY CURRENTS IN ARMATURE. 
 
 Those who have seen generator or motor arma- 
 tures in process of construction will have noticed 
 also that they are not made of one solid piece, but 
 are built up of a great number of disks of thin 
 
 FIG. 31 AND 32. 
 
 sheet iron, each of these disks being insulated 
 from its neighbors usually by thin sheets of paper. 
 This lamination, as it is called, is not for the 
 purpose of increasing the capacity of the iron to 
 carry lines of force, but is for the purpose of per- 
 mitting the core to rapidly change the direction 
 of its magnetization. As will be seen later on the 
 armature becomes a magnet whose poles always 
 have a constant position with regard to the field 
 
94 ELECTEIC RAILWAY MOTORS. 
 
 magnet poles that is, they are stationary with 
 regard to the latter but since the armature is re- 
 volving, they are constantly changing with regard 
 to a fixed point on the armature. Thj^J^minaiipn 
 greatly facilitates the rapid shifting of these-poles, 
 which if retarded, as would be the case even with 
 the best iron if it were solid, would give rise to 
 eddy, or Foucault currents, as they are called, in 
 the iron itself, which would be at the expense 
 
 FIG. 33. 
 
 of the engine which drives the armature, would 
 contribute nothing in return to the output of the 
 dynamo, would cause the armature to heat up to 
 an abnormal degree so as to perhaps destroy the 
 insulation on the armature wires, and cause irreg- 
 ularities of working too numerous to mention at 
 tliis point. 
 
 Figs. 32 and 33 represent an armature con- 
 sisting of two coils of two turns wound on an 
 iron core at right angles to each other. It 
 will be seen that in Fig. 33 when the armature is 
 inserted between the pole pieces N S the distance 
 which the lines of force have to pass through air 
 is reduced to the two narrow spaces which need 
 
EDDY CURRENTS IN ARMATURE. 95 
 
 only be wide enough to permit the armature to 
 
 revolve rapidly without allowing the coils to strike 
 
 against the faces of the field magnets. Of course 
 
 as the armature revolves the wires on its surface 
 
 tend to fly outward, and sufficient room must be 
 
 allowed to provide for this. Other precautions are 
 
 taken to prevent these wires, E JF] 
 
 Fig. 32, from flying outward or 
 
 from moving in any way from 
 
 their position. In small motors 
 
 and dynamos the most common 
 
 way to prevent this is to bind them 
 
 down tightly to the core with p IG 34 
 
 a number of windings of wire. 
 
 In larger machines it is now becoming very 
 common practice, instead of winding the wires on 
 the outside of the cylindrical surface of the core, 
 to carry them through slots cut in the iron itself, 
 each coil, whatever the number of turns, occupy- 
 ing a slot by itself. 
 
 Fig. 34 represents an armature thus wound. 
 This method where the size of the machine per- 
 mits has several advantages, some of which are 
 mechanical, while others are purely electrical. One 
 of the chief advantages is that it is impossible for 
 the wires to move, and another is that the air space 
 between the armature and the pole pieces of the 
 field magnet may be made considerably smaller, 
 for it is evident that the space taken up by the 
 windings of the wire on the outside of the arma- 
 ture offers quite as high resistance to the magnetic 
 flow as does that additional space which must 
 necessarily be left for clearance. 
 
CHAPTER X. 
 
 SHIFTING OF THE ABMATUEE WIBES. 
 
 WE have laid some stress upon the injunction 
 that the windings of the armature must not be 
 allowed to move. It is evident that if they are 
 free to move ever so little it will be almost sure 
 to result in the breaking of the insulation with 
 which they are protected, and this being destroyed, 
 even over spaces the size of a pin head, the cur- 
 rent will pass from wire to wire of the coils, or 
 from wire to armature core, instead of passing 
 out through the commutator and outer circuit, 
 and this new path being short and of low resist- 
 ance, the flow will be large, or if not large at first 
 rapidly become larger, and the armature burns 
 out. In fact, this slight movement of the coils is 
 one of the most fruitful causes of burning out of 
 armatures. 
 
 There are three agencies constantly at work 
 when either the dynamo or motor is in operation 
 which tend to cause movement of the coils and 
 hence their ultimate destruction. One has 
 already been referred to the tendency of the 
 wires to fly off from the core when the latter is 
 revolving rapidly, which is counteracted by bind- 
 ing them down tightly to the core by bands or 
 coils of fine wire. Another is that when a 
 dynamo is doing work, and the coils are passing 
 
SHIFTING OF THE ARMATURE WIRES. 97 
 
 rapidly through the lines of force, the latter act 
 like material obstructions to their motion with 
 the core and tend to push them off sideways. It 
 is very much as though we were revolving the 
 armature rapidly in a tank of water ; considerable 
 friction would result between the water and the 
 wires on the surface of the cylinder, which would 
 tend to strip the former from the latter, and this 
 tendency would increase with the speed. One 
 can form an estimate of how great this stripping 
 force is when he realizes that practically all of the 
 force exerted by the engine in driving the arma- 
 ture is required to overcome it. That is to say, 
 that when an engine is exerting say 100 H. P. in 
 driving an armature there is practically 100 H. P. 
 being exerted upon the windings of that armature 
 tending to push them off sideways or to strip 
 them from their position. This stripping force is 
 divided among the coils, and increases for each 
 coil with the number of turns in the coil. In the 
 case of the dynamo this friction acts as a drag 
 upon the coils, tending to prevent them from pass- 
 ing from under the pole pieces of the magnets. 
 In the case of a motor the action is reversed, and 
 it manifests itself as a pull upon the wires as they 
 approach the pole pieces. 
 
 It is bad enough when this tendency to strip is 
 always in one direction, for, as the force exerted is 
 constantly varying with the load on the machine, 
 there is a tendency for the coils to move accord- 
 ingly, which if allowed to occur must inevitably 
 result in friction between the wires themselves, or 
 between the wires and the core, which will wear 
 away the insulation in places and cause a short 
 circuit and a burn out, but it is still worse where 
 the strain comes first in one direction and then in 
 
 / 
 
 (UNIVER 
 
 V OP 
 
 UNIVERSITY 
 
98 ELECTRIC RAILWAY MOTORS. 
 
 the opposite, as is the case with motors which are 
 constantly reversed, as are street car motors. One 
 of the trials to which street car motors are pecul- 
 iarly subject is the tugging in one direction at the 
 wires on the armature on starting up, and the tug- 
 ging at them again in the opposite direction when- 
 ever the car is reversed, and it is much aggravated 
 if these operations are performed too suddenly. 
 This is one of the reasons why motormen are always 
 instructed not to turn on the current too rapidly 
 in either direction, and why provision is made in 
 the controlling switch so that the current cannot 
 be turned on or off or reversed at full strength. 
 The deterioration of reversing motors (street car 
 motors) due to this cause, even with the best of 
 care on the part of the motorman, is slow but sure. 
 
 There are several methods of obviating this tend- 
 ency of the wires to shift, with which, however, 
 the motorman has nothing to do. One is that 
 which is resorted to to prevent the wires from flying 
 off tangentially, previously described, of tightly 
 binding the coils to the armature by metal bands 
 or wrappings of wire, and the other is by imbed- 
 ding the coils in channels or slots in the armature 
 core as shown in Fig. 34 (see page 95). This latter 
 method, however, is seldom practicable in small 
 motors such as are used on street cars, because of 
 lack of room for the required number of coils, but 
 in large generators and motors of many hundred 
 horse power it is becoming a favorite method, not 
 only on account of its efficiency for the purpose, 
 but because this method of building the armature 
 has other advantages to recommend it. 
 
 In street car motors, however, where of all cases 
 there should be the best possible provision against 
 these strains, we have to rely upon the least efficient 
 
SHIFTING OF THE ARMATURE WIRES. 99 
 
 method, viz., of holding the wires in place by the 
 binding wires referred to. The motorman who 
 has the best interests of his employers at heart will 
 therefore refrain from jerking his car, for he will 
 remember that these jerks all come upon the arma- 
 ture wires and will hasten the destruction of his 
 machine. 
 
 The third agency which tends to cause the wires 
 to move from their position upon the armature is 
 heat. As everyone knows, 
 metal expands with in- 
 crease of temperature. Now 
 the coils of an armature are 
 wound as tightly as possi- 
 ble, but if the temperature 
 of the wire be raised far ;p IG 
 
 above that at which it was 
 
 wound the wire will become appreciably longer, 
 and the coils, which were tight when cool, be- 
 come loose when hot. Upon cooling again they 
 contract, but this very expansion and contrac- 
 tion has caused a motion of the various con- 
 volutions of the wire relative to each other and to 
 the core which may be more or less harmful by 
 causing abrasion ; but the heating is still more 
 harmful for the reason that it aggravates the other 
 tendencies toward movement of the coils already 
 mentioned, for if these strains are brought to bear 
 upon a coil that is already loose it will be readily 
 seen how much more harmful they may become. 
 The only remedy for this is to avoid overworking 
 your machine. Over this remedy the motorman 
 has almost complete control. Starting up or 
 reversing too suddenly, or taking a heavy load too 
 rapidly up a grade, are all examples of practices 
 that should be prohibited, because in all of them 
 
100 ELECTRIC RAILWAY MOTORS. 
 
 the wires are overworked and likely to heat even 
 to burning out. Running at a high speed on a level 
 track is not overworking the motor, however, and 
 may be indulged in with impunity, almost, so far 
 as the heating of the motor is concerned, so that 
 it is much better to lose time on grades and make 
 it up on the level stretches than to save time at the 
 expense of the motor where the hardest work is 
 being done, viz., in starting and in ascending grades 
 and going round curves. 
 
 OPEN AND CLOSED COIL ARMATURES. 
 
 In all of the preceding cuts where the armature 
 is represented as having two coils and four com- 
 mutator segments it will be observed that, after 
 the coil has passed 45 from its position of 
 maximum activity, its commutator segments pass 
 from under the brushes, and the outside circuit 
 remains disconnected from the coil until the latter 
 has revolved through 90 and again approaches 
 within 45 of its next position of maximum 
 activity. This occurs twice during each revolu- 
 tion of every coil. That is to say, twice during 
 every revolution of the coil it is open and con- 
 tributes nothing to the outside circuit. An arma- 
 ture wound in this way is called an open coil 
 armature. Such construction is now never found 
 upon street railway apparatus of any kind, either 
 motors or generators, but is thought to have some 
 advantages for arc lighting dynamos, and is the 
 method employed on both the Brush and Thom- 
 son-Houston arc dynamos. 
 
 If, instead of having connected the coil so that 
 it was out of circuit except when generating a 
 certain potential, we had connected it so that it 
 
OPEN AND CLOSED COIL ARMATUBES. 101 
 
 would be always in circuit except when generating 
 no potential at all (the moment of reversal, when 
 it would be short-circuited by the brush), we 
 would have taken advantage of the small electro- 
 motive forces which we threw away in the other 
 arrangement by cutting out the coils before they 
 had reached and after they had passed 45* of 
 their positions of maximum activity. 
 
 Fig. 35 shows an armature wound in this way. By 
 comparing it with Figs. 32 and 33 (see pages 93-4), 
 it will be seen that the only difference between the 
 two is that the two coils are really the one a con- 
 tinuation of the other, but each has separate con- 
 nections with its own commutator segment. Each 
 coil is therefore always connected with the out- 
 side circuit directly through its commutator 
 segments when the latter are under the brushes, 
 and indirectly through the other coil and its com- 
 mutator blocks when its own have passed from 
 beneath the brushes. Armatures thus wound are 
 called closed coil armatures, and are the kind now 
 universally employed both for generators and 
 motors in street railway equipments and for 
 generators in incandescent lighting stations. 
 
CHAPTER XI. 
 
 DRUM AND RING ARMATURES. 
 
 BESIDES the two classes of armatures, open and 
 closed coil, above outlined, there are also two other 
 classes of importance, each of which may be either 
 open or closed coil. Reference is here made to 
 what are termed " drum " and " ring " armatures. 
 Those heretofore have represented the wire wound 
 lengthwise over a cylindrical or drum-shaped core. 
 They are therefore for this reason termed " drum " 
 armatures, and, as before stated, may be either open 
 or closed coils. 
 
 Instead of winding our wire on a cylinder we 
 may wind it on an iron ring. Fig. 36 represents 
 an elementary open coil armature of this kind cor- 
 responding to the open coil drum armature repre- 
 sented in Fig. 20 (see page 78). Another form, 
 with two coils, is shown in Fig. 37, which corre- 
 sponds very closely with the drum winding in Fig. 
 31 (see page 93). Fig. 38 is the counterpart in the 
 ring type of armature of Fig. 32 (see page 93), in 
 the drum winding. 
 
 Fig. 39 (see page 107) shows a four-part ring 
 armature of the closed coil type. In this can be 
 shown more clearly than was possible in the drum 
 armature drawing (Fig. 35, see page 99), how the 
 various coils are connected together and to the 
 commutator in the closed coil type of armature. 
 
 Of course in order to have the greatest output 
 102 
 
DRUM AND RING ARMATURES. 103 
 
 possible, whether the armature be drum or ring 
 winding, open or closed coil type, the whole of the 
 surface of the core is overwound with wire, and 
 this winding is divided up into as many coils as 
 the designer desires, the two ends of each coil 
 being connected to appropriate commutator seg- 
 ments, and if of the closed coil type also to the ends 
 of the adjacent coils. In the closed coil ring arma- 
 
 FIG. 36. 
 
 ture. Fig. 40 (see page 107), shows how the wind- 
 ing is really one continuous coil all the way around 
 the ring, its two ends finally being joined together. 
 Then the number of turns of wire that shall consti- 
 tute a coil having been determined on, the con- 
 tinuous coil is tapped at those intervals and con- 
 nected by means of a short piece of insulated 
 copper wire with a commutator bar or segment, 
 as is also shown in Fig. 40. 
 
 Now since the core of a ring armature may be 
 regarded as a cylinder, just like that used in the 
 drum armature, with its center cut out, it is evi- 
 dent that the former must be given a larger diam- 
 eter in order to give it the same capacity for carry- 
 
104 ELECTKIC KAIL WAY MOTORS. 
 
 ing lines of force, and the latter, instead of cutting 
 directly across from pole to pole of the magnet as 
 they do in the drum armature, in the ring armature 
 follow the iron in preference to the shorter path 
 through the air space in the center (Fig. 41). 
 
 The fact that the ring armature must be of 
 larger diameter than the drum armature for the 
 same capacity prohibits its use where the greatest 
 power is required in the smallest possible space, 
 and since in the street car motor this is a first 
 requisite, we seldom see the ring armature em- 
 ployed. On the other hand, in machines of great 
 size, such as street railway generators, it is more 
 frequently employed than the drum armature, 
 chiefly for structural reasons. 
 
 CONSEQUENT POLES AND MULTIPOLAB FIELD 
 MAGNETS. 
 
 Heretofore in considering magnets we have 
 dealt only with those of a straight bar or horse- 
 shoe shape, having two poles, or the closed iron 
 ring, with the closed magnetic circuit, having no 
 poles at all. Before proceeding further it may be 
 well to speak of two other forms frequently used 
 both in dynamos and motors. Suppose we have a 
 closed magnetic circuit, as in Fig. 42, and place 
 upon it on one side a coil with a current passing 
 around it so as to make its upper portion a north 
 pole and its lower portion a south pole. If noth- 
 ing more were done, the lines of force would flow 
 around part of them through the armature, and 
 perhaps a greater portion would flow around 
 through the other leg on the right. All these 
 latter would be lost, so far as our armature is con- 
 cerned. But if we place a second coil on the leg 
 
CONSEQUENT POLES. 
 
 105 
 
 so as to make the upper part of the magnet a north 
 pole also, it will drive these lines back and send 
 additional lines of its own in the same direction. 
 In fact, the effect of the two coils working in 
 opposition is to make two north poles adjoining 
 each other above and two south poles adjoining 
 each other below, as shown in Fig. 42. As like 
 poles repel each other their lines cannot pass each 
 other, but are forced to take the path indicated. 
 
 FIG. 37. 
 
 When the direction of the current in two legs of a 
 magnet is such as to bring two poles of the same 
 kind together, the latter are called consequent 
 poles. 
 
 It is possible, therefore, in any piece of soft iron, 
 such as a closed ring, for instance, by dividing the 
 winding up into any number of coils, and passing 
 the current through adjacent coils in opposite 
 directions, to make a magnet of as many poles as 
 is desired. In a closed ring, or equivalent shape, 
 with a single coil, if there be no leakage of lines 
 
106 ELECTRIC RAILWAY MOTORS. 
 
 across from one side to the other, there will be 
 no poles at all. If there be two coils upon this 
 ring through which the current passes, so as to 
 compel the. lines of force to pass around in oppo- 
 site directions, since the lines induced by one coil 
 cannot pass through the other coil, the lines due 
 to both coils will have to seek another path, and 
 will emerge from the ring somewhere between the 
 two coils, and jumping across to the other side 
 along the path offering the least resistance, re-enter 
 
 FIG. 38. 
 
 the ring again, producing consequent poles, as 
 already described and illustrated in Fig. 42. 
 
 If we take an iron ring and wind it, as in Fig. 43, 
 with four coils, A B G D, connecting them up so 
 that the current will travel around the ring in the 
 directions indicated by the arrows, we find that 
 the directions of the currents in coils JB and (7, if 
 looked at from a point in the ring midway between 
 the two, will be in the opposite direction to the 
 
CONSEQUENT POLES. 
 
 107 
 
 travel of the hands of a clock. Therefore both 
 currents tend to make the space between them a 
 north pole. Moving along now and placing our- 
 selves in the ring again between coils A and J?, 
 
 FIG. 39. 
 
 FIG. 40. 
 
 and looking towarcl J?, the current is found to be 
 flowing around the ring in the same direction as 
 the hands of a clock. That end of the coil JB at 
 which we are looking is therefore a south pole. 
 
 FIG. 41. 
 
 Turning around and looking at the end of coil A 
 nearest to us, we find that the current as we see it 
 from this point of view is also circling around in 
 the direction of the hands of a clock, so that this 
 
108 
 
 ELECTRIC RAILWAY MOTORS. 
 
 end of J5 must also be a south pole. We might 
 have known this without looking at it, for if the 
 other end of B was a north pole this end must be 
 a south pole. We find that the two adjacent ends 
 of the coils A and J3 are south poles, so the space 
 between them will be consequent south poles. In 
 like manner we will find consequent north poles 
 between B and G and consequent south poles 
 
 FIG. 42. 
 
 between C and D as lettered in the diagram. 
 Thus we have a magnet with four poles two 
 south poles and two north poles. A magnet hav- 
 ing but two poles, such as described in the earlier 
 chapters and also in Fig. 42 (for the two conse- 
 quent poles are counted as one), is called a "bi- 
 polar" magnet, and a magnet having more than 
 two poles, as shown in Fig. 43, is called a " multi- 
 polar " magnet. 
 
CHAPTER XII. 
 
 MULTIPLE ABC AND SERIES ARRANGEMENT. 
 
 As observed in Fig. 43 the current, before it 
 comes to the magnet coils, divides part of it going 
 through coils B and (7, and part of it going through 
 A and D, and then the two parts unite again after 
 having passed through their respective coils. It 
 is evident that instead of dividing the current into 
 two circuits, each half going through two coils in 
 succession, we might have divided it into four cir- 
 cuits, and have placed each coil in a separate circuit, 
 or we need not have divided the current at all, 
 but have compelled the whole of our current to 
 pass through first A, then D y then C and finally 
 through IB. Fig. 44 represents the latter arrange- 
 ment. When current is supplied to several coils 
 or lamps or other electrical devices or groups of 
 the same, so that each device or group receives a 
 certain fraction of the whole current independently 
 of all the others, viz., so that the current which 
 passes through one device or group does not pass 
 through any of the others, as would be the case 
 were we to divide our circuit into four in one of 
 which each of the four coils are placed, these four 
 coils would be said to be in " multiple arc" or " in 
 multiple" with each other, or "in parallel." In 
 Fig. 43 the current divides between two circuits, 
 the current of one of these circuits passing through 
 the group of coils A and D, and the current of the 
 
110 
 
 ELECTRIC RAILWAY MOTORS. 
 
 other passing through the group -B and (7. 1 These 
 two subordinate circuits are therefore in multiple 
 arc with each other, and the groups of coils supplied 
 by each circuit are said to be " in multiple arc " or 
 " in parallel " with each other, because none of the 
 current which passes through the coils A and D 
 subsequently passes through the coils B and C. 
 
 If, however, the current reaches its translating 
 devices (the term " translating device " is used to 
 
 FIG. 43. 
 
 designate anything through which the current 
 passes or which is operated by the current either 
 directly or indirectly) not at the same time or 
 independently as in previous example, but passes 
 through them in succession, so that the same cur- 
 
MULTIPLE ABC. Ill 
 
 rent which passes through the first one also passes 
 through the second and the third and so on until 
 all are thus supplied, the various devices are said 
 to be " in series " with one another. Thus in Fig. 
 43, while coils A and Z>, considered as a group, are 
 on a separate circuit from B and (7, and the cur- 
 rent which goes through A and D does not after- 
 ward pass through B and 6 T , and the two groups 
 are in multiple arc with each, still, if we regard the 
 coils separately, the same current which passes 
 through A subsequently passes through D, and 
 that which first passes through B also passes 
 through C. 
 
 A and D are therefore in series with each other, 
 and B and G are likewise in series with each other, 
 but if we arrange our coils as in Fig. 44, so that 
 the same current which passes first through A 
 and then through D also passes through C and B 
 in the order named, the four coils are then said 
 to be in series with one another. If the circuit 
 divides before it comes to A, one branch going 
 around the four coils, as just described, and the 
 other branch supplying in similar manner the 
 coils of another field magnet, then the two groups 
 of field magnets will be in parallel with each 
 other, while the various coils in each group are 
 in series with the others of the same group. This 
 is exactly a similar case to that represented in 
 Fig. 43, where the group of coils A and -D, while 
 its constituents, A and D, are in series with each 
 other, is in multiple arc or in parallel with the 
 other group of coils, B and C, whose constituents, 
 B and C, are in series with each other. 
 
 Such an arrangement as this, where the trans- 
 lating devices are divided up into groups, the 
 members of each group forming a series, but the 
 
112 
 
 ELECTRIC RAILWAY MOTORS. 
 
 various groups being in multiple arc with each 
 other, is called a " multiple series " arrangement. 
 
 If in Fig. 44* the current, after having passed 
 through all four coils, is carried to another group 
 of magnets or coils, these two larger groups will 
 be in series with one another. 
 
 Figs. 45, 46 and 47 represent respectively the 
 series, the multiple arc and multiple series ar- 
 rangement for translating devices. There is also 
 
 FIG 
 
 a fourth arrangement, represented in Fig. 48, 
 which is sometimes called the " series multiple " 
 arrangement. 
 
 It is well to fix thoroughly in mind the charac- 
 teristics of the series, multiple arc and multiple 
 series arrangements, as they will be frequently re- 
 ferred to hereafter, and a thorough understanding 
 of them is essential to an intelligent reading of 
 what follows. To facilitate this understanding it 
 
GENERATORS. 113 
 
 may assist us if we remember that the incandes- 
 cent lamps in a street car are arranged five in 
 series. The street cars themselves are in multiple 
 arc with each other, as are also the generators at 
 the power house if there be more than one con- 
 nected to the same feeder. Most of the incandes- 
 cent lamps except those in street cars are arranged 
 in multiple arc, whereas almost all the arc lamps 
 used for street lighting are arranged in series. 
 
 FIG. 45. 
 
 The motors under the cars are connected up in 
 various ways according to the position of the con- 
 trolling switch and the system of equipment em- 
 ployed ; sometimes the two motors are in multiple 
 arc with each other, and sometimes they are in 
 series, and the coils of their field magnets are 
 thrown into various combinations of series, mul- 
 tiple series and multiple arc, each arrangement 
 being employed for some specific purpose. 
 
 CURRENT CHARACTERISTICS OF MULTIPLE AND 
 SERIES ARRANGEMENTS IN GENERATORS. 
 
 If two pumps standing side by side pump water 
 into the same main, they will not increase the 
 pressure of the water, but will increase the amount 
 of water only. So if two dynamos are connected 
 in parallel or multiple arc with the same trolley 
 or feeder wire, the potential of the resulting cur- 
 rent will not be increased, but the number of 
 
114 ELECTRIC RAILWAY MOTORS. 
 
 amperes which may be drawn from that circuit, 
 or the number of car's or lights or other translat- 
 ing devices that may be supplied, will be equal to 
 the sum of those that could be supplied by both 
 separately. 
 
 If, however, one of two pumps delivers to the 
 other so many gallons of water per minute at a 
 pressure of say 100 pounds per square inch, and 
 
 FIG. 46. 
 
 the second pump receives that water into its 
 cylinders at that pressure and passes it on to the 
 main with an additional pressure of say 50 pounds 
 per square inch, the amount of water pumped 
 into the main will not be increased by reason of 
 the second pump, but its pressure will have been 
 
 FIG. 47. 
 
 increased so as to equal the sum of the pressures 
 imparted by both pumps, in this case equal to 150 
 pounds per square inch. 
 
 So if one dynamo pumps current into another 
 which passes it on to the line wire, or, in other 
 words, if two dynamos are connected in. series, 
 the number of amperes that can be drawn from 
 that circuit will not be greater than if but one 
 machine were working, but it will be at a pressure 
 
GENERATORS. 115 
 
 equal to the sum of the pressures impressed upon 
 the current by both. 
 
 If in our power house we have a 500-volt 
 dynamo capable of furnishing sufficient current 
 to operate ten cars, and it becomes necessary to 
 double our equipment of cars, we would put in 
 another 500-volt dynamo of the same capacity and 
 connect it up in multiple with the first one, and 
 the question is solved. 
 
 If, on the other hand, we had a 100-volt incan- 
 descent lighting dynamo, and wished to supply a 
 500-volt circuit for street car purposes, we would 
 have to connect up others in series with it whose 
 potentials were such that when added together 
 and to that of the machine already installed they 
 
 FIG. 48. 
 
 would equal 500. Thus we might add 4 more 
 machines of 100 volts each, making 5 machines 
 in series whose combined electromotive forces 
 would be 500, or 2 machines of 200 volts each, 
 or 1 machine of 100 volts and another of 300 
 volts. But if the original machine only had a 
 capacity of say 100 amperes, the 5 connected in 
 series would have no greater output. 
 
 The rule, therefore, may be laid down that a 
 combination of generators in multiple arc gives 
 an output in amperes equal to the combined out- 
 put of the several machines, but with no increase 
 in pressure, while a combination of generators in 
 series gives a pressure equal to the combined 
 pressures of the several machines, but with no in- 
 crease in amperes. 
 
CHAPTER XIII. 
 
 CURRENT CHARACTERISTICS IN TRANSLATING 
 DEVICES. 
 
 WHEN there are no cars on the line, or the 
 trolley wire is not otherwise connected with the 
 rails or the ground, the resistance between the two 
 is infinitely great, and no current will pass from 
 one to the other. If one car be now put into 
 operation, one path will be opened to the current 
 from the trolley wire to the rails. If now a 
 second car and a third be placed in operation, a 
 second and a third path will be opened, and if the 
 resistances of all three of these paths be the same 
 the resistance between the trolley wire and the 
 rail when two cars are in operation will only be 
 one-half, and when three cars are going one-third 
 what it was when but one car was receiving cur- 
 rent ; the pressure will remain the same with the 
 addition of cars in multiple ; but as each car put 
 into service opens a new path for the current 
 between the trolley wire and the rail, the number 
 of amperes of current that will flow will increase 
 with the number of cars will be twice as much 
 for two and three times as much for three cars as 
 for one. 
 
 A parallel" case is found in the consumption of 
 water. Supposing we have a line of water mains 
 connected with a reservoir 500 feet high. The 
 pressure of water in the mains at their lowest 
 
 116 
 
TRANSLATING DEVICES. 11 7 
 
 point would be that due to 500 feet of head. 
 Now suppose we have a number of small faucets 
 tapped into the main at its lowest point. When 
 they are all turned off, the strength of the main, 
 or its resistance, while not infinitely great, as 
 in the illustration of the trolley wire, is still suffi- 
 ciently great so that no water can flow out at any 
 point. Open one faucet and a single path of, we 
 will say, unknown resistance is opened, and a 
 stream of so many quarts or gallons per minute 
 will flow out onto the ground. Open a second 
 faucet and another path of equal resistance will be 
 opened, and double the quantity of water will flow. 
 The same quantity would flow if, instead of open- 
 ing a second faucet of the same resistance as the 
 other, the first one were closed and another one of 
 double the capacity or offering half the resist- 
 ance were turned on in its stead. Therefore, 
 while by opening one small faucet we have 
 decreased the resistance of the pipe from some- 
 thing more than sufficient to keep back water 
 under 500 feet pressure to some definite quantity 
 which is less than that, by opening two of the 
 same size we have divided the resistance remain- 
 ing by two, and by turning on a third it will be 
 reduced to one-third what it was when but one 
 was turned on. But no matter how many faucets 
 we open, nor how much water runs out (provided, 
 of course, it does not exceed the capacity of the 
 main or the reservoir is not emptied), our reservoir 
 remains 500 feet above us, and the pressure will 
 remain the same at the faucets. 
 
 We;may make the resemblance between the 
 electric flow and the flow of water still more 
 striking by supposing that each faucet connects 
 with a little water motor which, when working to 
 
118 ELECTEIC BAIL WAY MOTORS. 
 
 its fullest capacity, requires a stream of water as 
 large as that which can run out of the faucet when 
 turned on full under 500 feet head. 
 
 13y turning on the faucet part way, with 500 
 feet head of water behind it, enough water will 
 flow to enable the motor to do a fraction of its 
 maximum work, turn it further it will do more, 
 and finally turn it on full and it will do the most 
 that it is capable of doing. A second and a 
 third water motor may be attached to other similar 
 faucets and be caused to do varying amounts of 
 work by turning on more and more water, but 
 whether the motors are doing little or much work, 
 using little or much water, the pressure in the 
 main will not decrease until so many motors are 
 attached as to require for their operation more 
 water than the main can carry. If the capacity 
 of the main be exceeded, it will be necessary to 
 lay a larger main, and if this be fed by two pipes 
 of the same size the original pipe from the same 
 reservoir and another one from another reservoir 
 at the same height the pressure on the main will 
 not be increased, but its capacity for running 
 water motors will be doubled. 
 
 While there will have been no water consumed 
 by the water motors, for the reason that just as 
 many gallons will flow away from the motor as 
 was delivered to it, that which flows away has 
 lost its pressure. If, for example, it required just 
 10 gallons per minute under 450 feet of pressure 
 to drive each vinotor at its fullest capacity, and 
 the motor received that amount of water at 500 
 feet pressure, it may be said to absorb the pressure 
 due to 450 feet, and the water will flow away 
 from the wheel at the rate of 10 gallons per 
 minute, but having a head of but 50 feet. That 
 
TRANSLATING DEVICES. 119 
 
 is to say, a pressure equivalent to that exerted 
 by a column of water 450 feet high will have dis- 
 appeared in operating the water wheel. A second 
 wheel requiring a pressure of 450 feet head placed 
 below the first wheel could not be operated, be- 
 cause the remaining head would not be sufficient, 
 and if the two were placed together in this man- 
 ner i n series neither of them could be operated 
 to their full capacity, because when thus placed 
 their combined resistances would be opposed to the 
 wa ter that is to say, the resistance of both would 
 be double that of one, and the amount of water 
 that would pass through either would be only half 
 as much as when there was but one. If we increase 
 our pressure, however, more water will flow through 
 our faucet and from one motor to the other, until 
 when we have doubled our pressure, or connected 
 our main to a reservoir 900 feet high, both motors 
 will be operated at their maximum capacity. 
 The water running away from our last motor will 
 then have no pressure, each motor having ab- 
 sorbed a head of 450 feet ; the same amount of 
 water, 10 gallons per minute, will, however, be 
 found to have passed through, but it is no longer 
 capable of doing any work. 
 
 Thus we see that by operating translating de- 
 vices in series we consume pressure (volts), and 
 not current (amperes), which is just the reverse of 
 what takes place in the generating station where 
 we connect generators in series, thereby increas- 
 ing the volts with the number of machines, but 
 gaining nothing in the way of amperes. 
 
 Take the case of an incandescent dynamo giving 
 current at about 100 volts. Each 16 C. P. lamp 
 requires when working at its normal rate about 
 J ampere of current at 100 volts. That is to 
 
120 ELECTEIC RAILWAY MOTOES. 
 
 say, its resistance is such that it requires a pres- 
 sure of about 100 volts to force sufficient current 
 through the filament to heat the latter to a 
 white heat. If our dynamo had a maximum ca- 
 pacity of 100 amperes at 100 volts, and our lamps 
 required ampere each, 200 lamps could be fully 
 supplied by the circuit if placed in multiple arc with 
 one another, because there would be enough cur- 
 rent to go round and it would be delivered to each 
 lamp under the same pressure. Its capacity, how- 
 ever, would then be exhausted. If we connect up a 
 second dynamo of equal capacity to the same cir- 
 cuit in multiple arc with the other, 200 additional 
 lamps could be supplied in the same way. But 
 supposing we place 2 lamps in series across the 
 circuit : their resistances would be added, and at 100 
 volts pressure but half as much current could flow, 
 viz., j- ampere. The lamps, we have stated, re- 
 quired J- ampere each, hence if 2 were placed in 
 series neither would be heated sufficiently to give 
 much light. If, however, we connect our dynamos 
 in series so as to double the electromotive force or 
 pressure of the circuit, the required quantity, % 
 ampere, would be forced through the combined 
 resistance of the 2 lamps, and both would burn at 
 their normal candle power. A single lamp, unless 
 of double the resistance of those heretofore used, 
 could not be used on this 200-volt circuit, as the 
 pressure would be so great as to immediately 
 break it. For the same reason we cannot put 
 100-volt lamps in our cars in multiple arc arrange- 
 ment, for they would all be destroyed by the 500- 
 volt pressure, as fast as they could be placed in 
 their sockets. But if each lamp absorbs 100 volt 
 of pressure, and each added to a series consumes 
 the same number of volts, if we place 5 lamps 
 
MULTIPOLAR 
 
 OF THE 
 
 UNIVERSITY 
 
 OF 
 
 121 
 
 in series on the usual 500-volt circuit, there will 
 be just enougli pressure to give each of them what 
 is required to operate it at normal candle power. 
 We are thus limited on street cars operating on 
 the usual 500-volt circuits to 5 lamps placed in 
 series. If we want more, we must arrange another 
 series of 5, for if we placed 6 or 7 on the 
 first series each would only receive -fa or \ of 500 
 volts, which would not be sufficient to illuminate 
 them to full candle power, and if we placed but 1 
 or 2 on the second circuit, in the case of the 
 single lamp it would receive the full pressure of 
 500 volts, and in the case of 2 lamps, each would 
 receive 250 volts, which in both cases would be 
 entirely too much. We might, of course, make up 
 the second series of 1 or 2 lamps and dead 
 resistances equivalent to the resistance that would 
 be offered by the additional lamps required to 
 make up the series of 5, but these dead resist- 
 ances would consume as much energy as the lamps 
 they replaced and give no useful return, so that it 
 would be much better to complete the second series 
 with lamps than with dead resistances. If we had 
 a second series of 5 lamps, this second series would 
 be in multiple with the first. 
 
 The same reason which compels us when using 
 100-volt lamps on a 500-volt circuit to place 5 of 
 them in series would compel us in case our circuit 
 was at 1000 volts to use 10 lamps in series. 
 
 MTJLTIPOLAE FIELDS. 
 
 Referring to Fig. 43 we see how an unbroken 
 iron ring may be wound so as to have four distinct 
 poles. In practice it is desirable to have as lit- 
 tle air space, bet ween these polar surfaces and the 
 armature as possible, and for this purpose the ring 
 
122 ELECTRIC RAILWAY MOTORS. 
 
 which is to become our multipolar magnet is cast 
 with extensions, called pole pieces, extending in- 
 wardly, and the magnetizing coils are wound upon 
 these extensions. Fig. 49 (see page 124) shows this 
 arrangement for a four-pole field, also the direc- 
 tions taken by the lines of force. It is clear that in 
 a four-pole magnet we have tile exact equivalent 
 of two simple magnets, and a wire on the surface 
 of an armature revolving in this field will pass 
 four poles in one revolution. As it sweeps by the 
 first north pole it will generate a maximum elec- 
 tromotive force in a given direction. This will 
 decrease until it gets halfway between the 
 north and south poles, where it will become zero 
 and change its direction. That is, it will come to 
 the point where the currents must be commu- 
 tated in order to maintain them in the same di- 
 rection. From this point until it passes the adja- 
 cent south pole the generated electromotive force 
 will be increasing. It then decreases until it is 
 zero at a position halfway be ween the south pole 
 and the next north pole, where it must be commu- 
 tated again, and so on until the armature has made 
 a complete revolution. Thus in a four-pole field 
 the currents in the armature wires in every revo- 
 lution reach a maximum four times instead of 
 twice, as in the two-pole field once every time 
 they pass a polar surface; they also become zero 
 and change their direction four times midway 
 between the poles ; and, if the currents are to be 
 maintained continuous^ in the same directions, 
 they must be commutated whenever these changes 
 of direction occur. There will, therefore, be 
 required four brushes in this case instead of two. 
 In a six-pole field there will be six reversals and 
 there must be six brushes, and so on; two additional 
 
MULTIPOLAR FIELDS. 123 
 
 brushes must be added for every additional pair 
 of poles introduced into our field. In Fig. 50 is 
 shown the arrangement of the brushes in a four- 
 pole machine, the ring winding being used for 
 illustration as being simpler for the purpose. In 
 the bipolar (two pole) field it will be remembered 
 that the positive brush was placed diametrically 
 opposite the negative brush. In the four-pole 
 field this is not so, because the north pole of the 
 magnet is not opposite the south pole. They are 
 at right angles to each other, and therefore in 
 order that the brushes may have the same posi- 
 tion relative to the field that they had before, viz., 
 at right angles to them, they are in the four-pole 
 field at right angles to each other also. It will be 
 seen from Fig. 50 tfyat the positive and negative 
 brushes alternate, #nd by connecting two circuits 
 in the proper way to these brushes we would have 
 two independent currents. In fact, while in the 
 four-pole field we have practically two separate 
 bipolar magnets, we also have, when a single 
 armature is added, practically two distinct gener- 
 ators or motors. Or, as is more usually the case, 
 these two independent circuits are united into one, 
 and we have, if everything is properly arranged 
 and proportioned, a single machine equivalent 
 to the output of the two considered separately. 
 It is evident-that this can be accomplished by con- 
 necting the two positive brushes (those marked -|-) 
 together and to one end of the circuit, and the two 
 negative brushes (those marked ) to the other end 
 of the circuit, and in large multipolar generators 
 this is usually the method employed, all of the 
 brushes from which the current is coming (the posi- 
 tive brushes), being connected together and all of 
 those into which the current is passing (the nega- 
 
124 
 
 ELECTRIC RAILWAY MOTORS. 
 
 tive brushes) being connected together, and these 
 are attached to the positive and negative terminals 
 of the line circuit. 
 
 When the brushes of the same kind are thus 
 connected together, the electromotive force of the 
 whole armature is simply that of any of the sets 
 of coils from one positive brush to the adjacent 
 negative brush. In the diagram (Fig. 50), see page 
 126, the coils of the four quarters of the armature 
 are in multiple arc with each other, and since there 
 
 FIG. 49. 
 
 are therefore four paths of the same size for the 
 current, the resistance oifered to the passage of the 
 current is only one-fourth what it would be if the 
 coils of all four were in series, or if the coils on 
 one-half the armature were in parallel with those 
 on the other half, as would be the case were this a 
 bipolar field and there were but two brushes. 
 
 Referring again to Fig. 50, since in a four- pole 
 field the opposite poles are alike, the coils on the 
 armature, diametrically opposite to each other as 
 they sweep by these poles, will always have elec- 
 
MULTIPOLAK FIELDS. 125 
 
 tromotive forces generated in them in the same 
 direction. This being the case, we can connect 
 the diametrically opposite coils with each other, 
 either in series or in multiple, so that they prac- 
 tically form but one coil, and by bringing the 
 ends of this coil to the proper commutator blocks, 
 again reduce the number of brushes to two. In 
 this case the brushes will be most conveniently 
 located at right angles to each other, about half- 
 way between a north pole and its two adjacent 
 south poles, or between a south pole and its two 
 adjacent north poles. It is evident that if oppo- 
 site coils be connected in series the electro- 
 motive force generated will be doubled, while the 
 resistance is also doubled, and if they are con- 
 nected in parallel the electromotive force will be 
 that of either coil alone, while the current will be 
 doubled and the resistance halved. This method 
 of connecting together the opposite coils of an 
 armature in a multipolar field is the usual one in 
 multipolar street car motors, for the reason that 
 it reduces the number of brushes, which is a very 
 desirable accomplishment, and also enables the 
 brashes to be more conveniently located for in- 
 spection than would otherwise be possible. 
 
 We will have noticed another advantage in mul- 
 tipolar machines. In discussing bipolar machines 
 it was stated that in any given case the electro- 
 motive force generated by a coil revolving in a 
 magnetic field depended upon the number of revo- 
 lutions it made per minute in that field, or, in other 
 words, upon the rapidity with which it cut the 
 lines of force. We have just seen that in a four- 
 pole field the coil cuts the lines of force twice as 
 often in each revolution as it does in a bipolar field. 
 The armature, therefore, need revolve only half 
 
126 
 
 ELECTEIC RAILWAY MOTOBS. 
 
 as fast in a four-pole field as in one of two poles 
 to produce the same output, and thus we are 
 enabled to make slow-speed generators. The 
 same may be said of motors, and it will have been 
 observed that all slow-speed motors, such as the 
 gearless motors, are provided with multipolar 
 fields. The philosophy of this, simply stated, is 
 that if a given current fed to a motor having two 
 
 FIG. 50. 
 
 poles will give it at any specified speed a given 
 power, the same current acting upon a motor with 
 four poles would produce a motor practically 
 equivalent to two machines of the bipolar type, 
 and as the power of a motor is also dependent 
 upon its speed, a four-pole motor will produce the 
 
MULTIPOLAR FIELDS. 127 
 
 same power at half the speed of a similar motor 
 with only two poles. 
 
 Thus far we have said nothing as to how we get 
 the magnetism in our field magnets. We have 
 assumed, however, that they are electromagnets, 
 viz., that the field magnets are made of soft iron 
 and have no magnetism of their own, but are con- 
 verted into magnets by passing electric currents 
 through coils of insulated wire properly wound 
 around them, and this is now the universal prac- 
 tice in all but very small generators. Permanent 
 magnets made of very hard tempered steel might 
 be used, however, but as a. permanent magnet can 
 never be made so strong as an electromagnet of 
 the same size, and for other equally good reasons 
 which need not be mentioned here, the latter are 
 preferred. The earlier dynamos were, however, 
 frequently constructed with permanent magnets. 
 Such machines are properly called magnetoelectric 
 machines. Examples of magnetoelectric ma- 
 chines are found in the apparatus employed in the 
 telephone fixtures for" ringing up the exchange. 
 In the call box will be found a strong permanent 
 magnet between whose poles there revolves a small 
 iron bobbin (armature) wound with fine wire. As 
 this is rotated by turning the crank it generates 
 alternating currents which pass over the line and 
 ring the bells. It would be a simple thing to attach 
 a commutator to the armature which would con- 
 vert the alternating currents into direct currents, 
 as already described, but the telephone call bell has 
 been adapted to alternating currents, so that the 
 complication of commutators is not necessary. 
 
 Another method of obtaining our magnetism is 
 to construct our fields of soft iron and wind them 
 with coils, and connect these coils with some inde- 
 
128 ELECTRIC RAILWAY MOTORS. 
 
 pendent source of electricity, such as a large bat- 
 tery or another dynamo. When the current flows 
 through the coils, of course the fields become 
 highly magnetized, as we have seen. A machine 
 whose fields are thus excited is called a separately 
 excited dynamo. This method has some advantages, 
 chief of which is that the exciting current, coming 
 from a separate source, is entirely independent of 
 the fluctuations of current in the trolley circuit, 
 which would, if current from the latter were 
 added, produce similar variations in the magnet- 
 ism of the fields, which would in turn still further 
 complicate matters. It has the disadvantage, how- 
 ever, of requiring a separate machine for this pur- 
 pose, which in. very small plants would be scarcely 
 warranted by the attendant advantages. In large 
 electric power stations it is quite customary to find 
 a small machine used solely for this purpose, its 
 current being employed to excite the fields of all 
 generators in the plant. 
 
CHAPTER XIV. 
 
 THE DYNAMO-ELECTRIC PRINCIPLE. 
 
 THERE is still a third method, and this is the 
 most usual one, viz., to make the dynamo excite 
 its own fields by causing either all or a portion of 
 the current generated by the armature to pass 
 around the field magnet coils. But the question 
 naturally arises, how are we to start such a ma- 
 chine into action ? When the armature stops, the 
 current stops, and the magnetism of the fields 
 disappears. If we start the machine from rest, 
 there being no magnetism in the fields, there will 
 be no lines of force for the armature wires to cut; 
 the armature will therefore generate no current, 
 and our provision for utilizing that current to 
 excite our field will be useless. So reasoned the 
 early builders of electrical machines, and it was 
 thought necessary for a long time to separately 
 excite the fields, at least until the machine got into 
 action. It was therefore a very important dis- 
 covery that such was not necessary. It seems that 
 all iron, however soft, has a little magnetism, which 
 it either derives from the earth's magnetism 
 or retains from previous magnetization (residual 
 magnetism). 
 
 This may be very slight, but it is suflicient so 
 that when the armature is revolved before the 
 pole pieces it generates a very slight current. No 
 matter how insignificant this current may be, as it 
 
130 ELECTRIC RAILWAY MOTORS. 
 
 passes around the field magnets it adds somewhat 
 to their magnetism. This increased magnetism 
 of the fields enables the armature to generate a 
 little stronger current than before, and this pro- 
 duces more magnetism and that more current, so 
 that by the continued reaction between the field 
 and armature the machine "builds itself up," as 
 the phrase is, until the magnets have arrived at 
 full strength, and the armature is putting out 
 current to its maximum capacity. 
 
 This " building up " of the machine from prac- 
 tically nothing to its maximum output without 
 outside help except from the power necessary to 
 drive the armature, seeming at first sight to be very 
 much like the attempt to lift one's self over the 
 fence by one's boot straps, is known as the " dy- 
 namo-electric" principle. These " self -exciting " 
 machines, which are by far the most numerous of 
 those emploj^ed to-day, are the true " dynamo- 
 electric " machines. 
 
 SERIES, SHUNT AND COMPOUND WINDING. 
 
 The dynamo-electric principle gives rise to three 
 distinct types of machines. In the first type all of 
 the current from the armature passes around the 
 field coils, as in Fig. 51, before it goes out to the 
 exterior circuit. Since the field coils are in series 
 with the armature, a machine so wound is called a 
 series dynamo or motor, as the case may be. It is 
 evident that if resistances are placed in the outer 
 circuit the amount of current that will flow around 
 the coils will be lessened. This will lessen the 
 strength of the field magnets, and this will still 
 further lessen the amount of current that the 
 armature can give ; and if the exterior circuit 
 
SERIES, SHUNT AND COMPOUND WINDING. 131 
 
 becomes broken so that no current can flow, of 
 course the field magnets, no longer having any 
 current in their coils, lose their magnetism, and the 
 armature ceases entirely to generate current. If 
 the break in the outer circuit be now closed again, 
 the dynamo will gradually build itself up, as before 
 described under the heading "Dynamo-Electric 
 Principle," until it again attains its full strength, 
 but this will take an appreciable time. A series 
 dynamo, of course, could not be used on a multiple 
 
 arc street railway or on the usual incandescent 
 circuit, for on either of these circuits we want to 
 have at our command the full strength of the cur- 
 rent the moment we start the first car or turn on 
 the first light. We cannot wait for the dynamos 
 to build themselves up. There are other objec- 
 tions also to series dynamos for these purposes, but 
 for other purposes they have their use. 
 
 In the second type (Fig. 52) we only use a por- 
 tion of the current generated by the dynamos to 
 
132 
 
 ELECTRIC RAILWAY MOTORS. 
 
 excite the fields. From the brushes there are two 
 circuits, between which the current divides ; one 
 of these is the line circuit, which is of heavy wire 
 sufficient to carry all the current required in the 
 exterior circuit, and the other is a thin wire of 
 great length, and therefore of high resistance, 
 which is wound in many turns around the field 
 magnet cores. Since this latter wire is of high 
 resistance, but little current passes through it ; but 
 as it passes many times around the magnet there 
 
 FIG. 52. 
 
 are sufficient ampere turns with the small current 
 for our purpose. This latter wire, which forms in 
 this case the magnet coils, is in multiple arc, or in 
 parallel, or " in shunt" with the exterior circuit. 
 This type is therefore called the " shunt dynamo." 
 There is a law in the flow of electric currents to 
 which we have before referred, that when several 
 paths are open to the current the latter will di- 
 vide itself among them according to the relative 
 conductivities of those paths. In Fig. 52 the cur- 
 
SEBIES, SHUNT AND COMPOUND WINDING. 133 
 
 rent has two paths open to it one through the 
 fine wire of high resistance, which forms the 
 magnet coils, and the other through the large wire, 
 which forms the external circuit. The shunt cir- 
 cuit, as will be observed, is always closed, so that 
 no matter whether the external circuit be closed 
 or not a current will always be passing through 
 the field coils, and the full magnetism which they 
 are capable of imparting to the magnet is always 
 maintained. The shunt dynamo is therefore 
 
 FIG. 53. 
 
 peculiarly fitted for multiple arc circuits (street 
 railway and incandescent lamp circuits), because, as 
 we know, multiple arc circuits are always open 
 when there are no translating devices (lamps, 
 cars, etc.) operating. But if the magnetism of 
 the fields be maintained, the full current is always 
 available the moment it is wanted. But the 
 exterior circuit is one of variable conductivity. 
 The resistance between the trolley wire and the 
 ground is only half as great when two cars are 
 running as when only one is in operation. The 
 
134 
 
 ELECTEIC RAILWAY MOTOES. 
 
 relative conductivity of the two paths therefore 
 changes with the number of cars operated, being 
 greatest in the outside circuit when there are 
 many cars. 
 
 Now supposing that with the speed at which 
 our armature is driven, and the magnetism which 
 the ampere turns of our shunt coils is capable of 
 producing, our dynamo is capable of generating 
 an electromotive force of just five hundred volts 
 when but one car is in operation. If a second car 
 be started up, the conductivity of the exterior cir- 
 
 FIG. 
 
 cuit will have been increased, and it will take a 
 relatively larger portion of the total current gen- 
 erated by the armature. This will leave less to 
 go around the magnet coils, and the magnets 
 become weaker. With weaker fields the electro- 
 motive force generated by the same speed of 
 armature becomes less, and we will no longer have 
 a current of five hundred volts, but something 
 less than that. This loss of electromotive force 
 is what is technically termed " drop," and while 
 
THE REVERSIBILITY OF THE DYNAMO. 135 
 
 in very short lines with but a car or two operat- 
 ing it may* not amount to much, it becomes very 
 serious in long lines with many cars or lights 
 to feed. To correct this fault we sometimes have 
 recourse to the third method of winding, which is 
 known as compound winding, and the machines 
 so wound are known as compound dynamos. The 
 compound winding (Fig. 53) is a combination of 
 the series and shunt windings. As shown in the 
 diagram the winding consists of two coils, one 
 consisting of a few turns of coarse wire in series 
 with the armature, through which all the current 
 which goes to the exterior circuit passes, and the 
 other consisting of the fine wire coils in parallel 
 or in shunt to the latter. Now if we reduce the 
 resistance of the exterior circuit by putting on 
 additional cars, while we weaken the magnetizing 
 effect of the fine shunt coils, as in the last case, 
 the additional current which is diverted to the 
 exterior circuit, which has to pass through the series 
 coils, compensates for the other loss. By putting 
 on fewer or more turns of the series coils we may 
 exactly compensate for any loss of electromotive 
 force that might be occasioned in a shunt machine 
 by the addition of cars or length of line, or by 
 putting on more turns than is needed, for exact 
 compensation may even cause the electromotive 
 force to rise as the load on the dynamo increases. 
 A machine wound to produce the latter effect is 
 said to be " over compounded" 
 
 THE REVERSIBILITY OF THE DYNAMO. 
 
 It will have been observed that heretofore we 
 have referred to the dynamo and to the motor as 
 though they were synonymous terms. We have 
 
136 ELECTRIC RAILWAY MOTORS. 
 
 done this not indiscriminately, but as the one or 
 the other served the purpose of illustration the 
 better. But as a matter of fact the dynamo and 
 the motor are one and the same machine. 
 
 Supposing we have in a pipe, (7, two fans exactly 
 alike (Fig. 54), each furnished with a pullejr by 
 which it may be belted to a line shaft or to other 
 machinery. If we drive A rapidly, it will force a 
 current of air through the pipe C from A to J5, 
 and this current of air will cause JB to revolve like 
 a windmill. If, on the other hand, we drive B by 
 its pulley, the current of air which it will produce 
 will drive A, and if the current be strong enough 
 the latter, acting as a motor, may drive other 
 machinery to which it may be belted. In the first 
 case we have driven the fan A by belting it to a 
 driving pulley, and it has become a generator of a 
 current of air which, upon being conducted by the 
 pipe C to the similar fan jB, has caused the latter 
 to revolve as a motor, rendering it capable of 
 driving other machinery through its pulley and 
 belt. In the second case IB as a generator drives 
 A as a motor. 
 
 It is evident that these two fans are perfectly 
 reversible as regards their functions. By driving 
 either one it becomes a generator of air current 
 capable of driving the other one as a motor. That 
 is to say, if we apply mechanical energy to either, 
 it gives out wind energy, if we may use such an 
 expression, and if we apply to it wincj energy, it 
 will give out mechanical energy. 
 
 So it is exactly with the dynamo-electric ma- 
 chine. If we drive the armature by steam or 
 other power, the machine will generate an electro- 
 motive force electrical energy; and if we apply 
 electrical energy to its armature, the latter will 
 
THE BEVEBSIBILITY OF THE DYNAMO. 137 
 
 revolve and give out mechanical energy. If 
 two exactly similar machines have their Jbrnshes 
 connected by electrical conductors, they will 
 behave toward each other exactly as do the fans. 
 Since they are exactly alike, it is immaterial 
 which we shall employ as a generator and which 
 as a motor. If the armature of one is driven, it 
 will give rise to an electric pressure corresponding 
 to the pressure of air in C, which by giving rise to 
 a current will cause the other to revolve as a 
 motor, the general rule being that any machine 
 that will make a good generator will also make 
 a good motor, and vice versa. 
 
 It will be seen from the above that the electric 
 motor bears the same relation to the generator as 
 the driven pulley on one shaft does to the driving 
 pulley on another, and that the electric current 
 by which the energy is conveyed from the genera- 
 tor to the motor performs the same office exactly 
 as the belt does which connects the driving pulley 
 with the driven pulley. It is perfectly clear that 
 either of two lines of shafting may be used as the 
 driving shaft by connecting it with the steam en- 
 gine, and if the pulleys which are belted together 
 on the two shafts are of the same size, it will make 
 no difference in the operation of the machinery 
 to which shaft it is belted, but in mechanical 
 operations it is often desirable to give the driven 
 shaft a different speed from that of the line shaft, 
 and for that reason the pulleys on the two shafts 
 would be given different diameters to adapt them 
 to the required conditions. So in electrical 
 machinery the motor may differ radically in 
 appearance, and also differ somewhat in minor 
 details, from the generator, to better adapt it to 
 the particular work it has in hand. Thus in 
 
138 ELECTRIC RAILWAY MOTORS. 
 
 the street car motor compactness is a prime 
 requisite, and it is allowable to sacrifice some 
 of the requisites of a good machine in order 
 that this one feature may predominate. But 
 motors will not differ more ' in appearance from 
 generators than they do from each other. While 
 the construction of the two machines the dynamo 
 and motor may be and frequently is the same, the 
 theory upon which they operate is entirely differ- 
 ent, the one being the reverse of the other. The 
 same drawings are, however, entirely applicable to 
 the explanation of the motor. 
 
CHAPTER XV, 
 
 THE ELECTRIC MOTOR* 
 
 WE have seen (Fig. 10, see page 60) that if an 
 electric current is passed through a coil of wire 
 it sets up lines of force which have a definite direc- 
 tion within the coil and give the coil a distinct 
 polarity. Now if this coil while traversed by a 
 current of electricity be brought into a magnetic 
 field, viz., be placed between the poles of a magnet, 
 it will tend to take up such a position that the 
 lines of force generated within its own coils shall 
 have the same direction as those of the magnetic 
 field in which it is placed. That is, it will tend to 
 place its own axis directly on the line joining the 
 north and south poles of the field magnet, with the 
 south pole of the coil facing the north pole of 
 the magnet, and the north pole of the coil facing 
 the south pole of the magnet. In this position 
 the coil presents the least obstruction to the pas- 
 sage of the lines of force between the two poles of 
 the magnet, because it presents the greatest area 
 for their passage, and in fact assists the passage of 
 these lines by the magnetomotive force which its 
 own current adds to that of the magnet between 
 whose poles it is placed. When the coil is in the 
 position shown in Fig. 23 (see page 84), with a cur- 
 rent traversing it in such a direction as to assist 
 the lines of force across from ^to , we have this 
 condition fulfilled, and this is the position which 
 
 139 
 
140 ELECTEIC RAILWAY MOTOES. 
 
 any coil traversed by a current will take up, if free 
 to move, when placed- between the poles of a mag- 
 net. The usual way of expressing this fact is to 
 say that a closed electric circuit when placed in a 
 magnetic field tends to take up such a position as 
 to enable it to embrace the greatest possible num- 
 ber of lines of force. Clearly this condition is best 
 fulfilled when the plane, of the coil is at right angles 
 to the lines of force, as in Fig. 23, and least fulfilled 
 when it is in the position shown in Fig. 22 (see page 
 83), because in the latter the plane of the coil is 
 parallel to the lines of force passing from JVto S, 
 and it can embrace no lines of force unless by some 
 means they may be diverted from a direct line so 
 as to thread themselves through the loop in curved 
 lines. This they are induced to do by the current 
 in the coil, which sucks them in, as it were, either 
 from the upper side or the lower side of the coil, 
 according to the direction of the current in the 
 coil. With the current flowing as indicated by 
 the arrows in Fig. 22 in the direction of the 
 hands of a clock as we look down upon the coil, 
 the upper surface will have a south polarity that 
 is, its own lines of force will enter the coil from 
 that side and emerge from the lower side, which 
 will have north polarity. In like manner some of 
 the lines of force which extend in straight lines 
 from JV"to S will be bent out of the direct line so 
 as to thread themselves through the loop in the 
 same way. Other lines will crowd through, and 
 in doing so, and in trying at the same time to 
 straighten themselves out again, will pry the loop 
 around from its present position in a direction con- 
 trary to that indicated by the arrow. As the 
 angle through which the loop is thus turned 
 increases it permits still more lines to thread it, 
 
THE ELECTRIC MOTOR. 141 
 
 and these add their prying effort, until the plane 
 of the loop is at right angles to the lines, which 
 permits the lines to pass through without bending, 
 and therefore without further tendency to rotate 
 the coil. 
 
 We may note right here one peculiar fact: We 
 found that when we revolved the coil between the 
 poles N~ S from left to right in the direction indi- 
 cated by the arrow it produced a current in the 
 direction A B G C D A. Now, if we pass a 
 current through the coil in the same direction as 
 it took when the coil was mechanically revolved, 
 viz., DAB Gr C JB, it tends to cause the coil to 
 revolve in the opposite direction. That is to say, 
 the current which is generated by revolving a 
 coil in a magnetic field is in such a direction as 
 would cause the same coil to revolve in the oppo- 
 site direction : the action of the electrical current 
 generated in a coil is to directly oppose that of the 
 motion which produced it. This is a fundamental 
 law of electrics, and explains why, as the current 
 increases in a circuit, it requires more force to 
 drive the armature of the dynamo. It is because 
 the larger the current traversing the coils of the 
 armature, the greater the effort on the part of that 
 current to revolve the armature in the opposite 
 direction, and it is the energy that is absorbed in 
 overcoming this tendency that reappears in the 
 armature coils as electricity. 
 
 But to go back a little ways. If with the coil 
 in the position shown in Fig. 22 we should pass 
 the current in the opposite direction to that indi- 
 cated by the arrows, the lines would thread 
 through the loops from the under side and come 
 out on the upper side, thus prying the loop over in 
 the opposite direction. If at the same time that 
 
142 ELECTBIC BAIL WAY MOTORS. 
 
 we change the direction of the current in the loop 
 we also change the direction of the lines of force 
 in our field by making the right-hand field north 
 and the left-hand field south, we see that the lines 
 will enter the coil on the right hand from below 
 and emerge on the left hand from above, and 
 in the effort to straighten themselves out will 
 again tend to pry the loop in the same direction 
 as in the first case. We therefore see that revers- 
 ing both the magnetism of our fields and the 
 direction of the current in the armature has no 
 effect upon the direction of rotation of the arma- 
 ture. The direction of rotation will be changed, 
 however, if either of them alone be changed. 
 
 If we place a single coil of wire traversed by a 
 current in a magnetic field it will tend to revolve 
 about its axis until the plane of the coil is at 
 right angles to the lines of force of the field in 
 which it is placed, and the direction of its rotation 
 will be determined by the direction of the current 
 which flows through the coil. No matter how 
 strong the current or how powerful the field, the 
 coil will not tend to revolve further than 90 from 
 the direction of the lines of force. This is entirely 
 similar to the action of the compass needle when 
 a current-carrying wire is placed over it. We 
 remember that under these conditions the needle 
 was deviated in one direction or the other accord- 
 ing to the direction of the current in the wire, and 
 tended to take up a position at right angles to the 
 wire. It would be a more general statement, but 
 equally true, that the wire had an equal tendenc\^ 
 to place itself at right angles to the needle. The 
 action was more apparent in the needle, however, 
 because that was readily movable, while the coil 
 was not. 
 
THE ELECTRIC MOTOK. 143 
 
 Bat suppose we have two coils of wire with 
 their planes say at right angles to each other, as 
 in Figs. 30, 32 and 33. If the current be diverted 
 from that coil which has already been revolved to 
 * a position at right angles to the lines of force of 
 the field, to the other coil, which is now parallel 
 to those lines, as may be automatically accom- 
 plished by a commutator of four parts, the rotation 
 will be continued in the same direction, and we 
 have at once an elementary electric motor. Or if 
 we have but a single coil, as in the first case, 
 whose ends terminate in a two-part commutator, 
 and the direction of the current in the coil be re- 
 versed when it has reached a position at right 
 angles to the field, its own lines of force will be 
 reversed in direction and cause the field lines to 
 seek a passage by a circuitous route from the op- 
 posite side of the coil, and these, as before stated, 
 in their endeavor to straighten themselves out, 
 will pry the coil over still further and cause it to 
 make another half revolution. 
 
 In an electric motor advantage is taken of both 
 of these actions where there are many coils at 
 various angles to each other, and as each coil 
 comes to the position where the threading of the 
 lines of force through it in one direction exerts no 
 further tendency to cause it to rotate, the current 
 in that coil is reversed in direction so as to cause 
 the lines to enter from the opposite side and con- 
 tinue to exert an effort at rotation. Thus by 
 changing the direction of the current in the coil 
 at the proper time twice in each revolution a 
 single coil may be kept in continuous rotation. 
 But the effort which will be exerted will vary 
 widely with different positions of the coil with 
 respect to the field. Twice in every revolution, 
 
144 ELECTRIC RAILWAY MOTORS. 
 
 viz., when the coil is at right angles to the field 
 the effort will be nothing, and twice, viz., when 
 the coil is parallel to the field, it will be a maxi- 
 mum. We find that these positions correspond 
 with the positions of minimum and maximum 
 activities of the coil when used to generate current. 
 We remember that in describing the dj^namo with 
 two coils at right angles to each other it was 
 stated that the current would be more uniform, 
 for in that case when one coil was in its neutral 
 position and cutting no lines of force, the other 
 one would be in the position where it would 
 be cutting the lines of force at a maximum 
 rate. So with the motor. If we have two 
 coils at right angles to each other, one of these 
 will be exerting its greatest effort at rotation, 
 while the other one is exerting none. Thus by 
 increasing the number of coils at small angles with 
 each other the effort to turn the armature will not 
 only be increased, but become more uniform. The 
 effort exerted by the armature to revolve is 
 termed its " torque," and is dependent upon 
 the number of lines of force that can be induced 
 to thread themselves through the coil, and this is 
 dependent, as we know, upon the current. The 
 " torque " of a motor, or the effort which it exerts 
 to turn against a resistance, is therefore said to be 
 dependent upon the amount of current passing 
 through the armature coils. It is also, of course, 
 dependent upon the strength of the field, but if 
 that be constant it is proportional always to the 
 current. 
 
CHAPTER XVI. 
 
 THE ELECTRIC MOTOR. (Continued.) 
 
 ANOTHER way of explaining the action of an 
 electric motor, which is simpler, but in most cases 
 not so correct, is the following : Let us suppose 
 for the moment that there is but a single coil on our 
 armature (Figs. 55 and 56). If in looking at the 
 commutator end of the armature the current 
 passes through the coil as it passes over the end of 
 the armature coil in the direction of the arrow 
 (Fig. 55), which would be clockwise in the coil if 
 we look at the coil from the north pole of the 
 magnet, and anti-clockwise if viewed from the 
 south pole, it will make of the armature core an 
 electromagnet whose south pole is near the north 
 pole and whose north pole is near the south pole of 
 the field magnets. Since unlike poles attract each 
 other, the armature will tend to revolve until these 
 unlike poles are as near together as they can get, 
 or until the axis joining the two poles of the arma- 
 ture is in a straight line with or parallel to the 
 axis joining the field magnet poles. If nothing 
 more were done, the armature would simply os- 
 cillate back and forth a few times on either side of 
 this line, and finally come to rest in the position 
 stated, just as a compass needle does when a mag- 
 netic pole is brought near it, and the attractive 
 action of the unlike poles upon each other would 
 oppose any effort to move the armature in either 
 
 145 
 
146 
 
 ELECTEIC RAILWAY MOTOES. 
 
 direction. But we have seen that when these four 
 poles are in line the coil on the armature is in its 
 neutral position, viz., in that position where in the 
 dynamo the electromotive force generated in the 
 coils changes direction, and where by means of 
 the commutator it is rectified for the exterior 
 circuit. If, therefore, a direct current enter the 
 armature coil through the branches and commu- 
 tator, its direction in the coil will be reversed^ 
 at this point. Figs. 55 and 56 represent the coil 
 just before and after it has occupied this neutral 
 position, and the arrows show the directions of 
 the currents under these conditions. It will be 
 
 FIG. 55. 
 
 FIG. 56. 
 
 noted that just at the moment when the south 
 and north poles of the armature have reached 
 the point beyond which the mutual attractions 
 between them and the north and south poles of the 
 field magnets would no longer tend to cause the 
 armature to revolve, the direction of the current 
 is reversed by the commutator, and what were 
 the south and north poles of the armature become 
 the north and south poles, and like poles of the 
 machine are brought into proximity and repulsion 
 occurs and rotation is continued. Thus by prop- 
 erly arranging the coils and commutating the direc- 
 tions of their currents a continuous effort, first 
 
TORQUE. 147 
 
 of attraction and then of repulsion, is exerted upon 
 the armature, which causes it to keep in continuous 
 rotation and enables it to do more or less work as 
 this pull and push is large or small. 
 
 TOBQUE. 
 
 Now we know that the strength of a magnet- 
 viz., the ability which it evinces either to attract an 
 unlike pole or to repel a like pole depends, other 
 things being equal, upon the number of ampere 
 turns upon the magnet. In the case of the motor 
 or dynamo the number of turns on both the field 
 magnet and the armature is fixed, so that the only 
 way in which we can vary the strength of these 
 magnets is by increasing the current (remember- 
 ing that the ampere turns=number of turns of the 
 wire X current in amperes). We can therefore 
 increase the turning effort of the armature by 
 increasing the current and thus increasing the 
 strength of the poles. This effort to revolve which 
 the armature is able to- exert is technically termed 
 its " torque." The torque, therefore, is dependent, 
 among other things, upon the current, being 
 greater or less as the current in the armature is 
 greater or less. 
 
 But everyone knows that in turning a capstan, 
 or in winding up a heavy weight attached to a 
 rope on a windlass, it can be moved much more 
 easily if the crank arm or lever is long than if it is 
 short. In fact, to give a concrete example, if our 
 windlass drum have a diameter of 1 foot and the 
 load on the rope be 100 pounds, this can be exactly 
 balanced by hanging on the end of the crank arm a 
 weight of 10 pounds if that crank arm be 10 feet 
 long, and 11 pounds so placed would draw the 
 
148 ELECTEIC RAILWAY MOTORS. 
 
 heavier weight of 100 pounds up. In this case the 
 torque due to the force of 10 pounds acting on the 
 end of a lever arm 10 feet long is exactly equal to the 
 torque due to a weight of 100 pounds acting at the 
 end of a lever arm but 1 foot long. Thus we see 
 that while we can increase the pull and push on 
 the armature by increasing the current, we can 
 increase the effect of this pull or push, or, in other 
 words, make a machine which will have still 
 greater torque, by increasing the length of the 
 lever arm upon which the torque due to current 
 acts. As an example parallel to the one cited of 
 the windlass, an armature ten feet in diameter 
 would, with the same current, have ten times the 
 torque that one but a foot in diameter would have. 
 But in street car motors our space is limited and 
 we cannot far increase the torque of our motor in 
 this way. Our armature must necessarily be of 
 small diameter, so that our leverage is small. Nor 
 can we increase our current indefinitely, so other 
 means must be resorted to to give the motor suffi- 
 cient torque to start a loaded car from rest or 
 propel it up a steep grade. 
 
 It is a law of mechanics that what is termed 
 " work " is equal to the product of the force 
 (torque) into the space described by it in its 
 direction while overcoming the resistance, and 
 "horse power" is the rate at which this work is 
 done. Thus if we have an armature of small 
 diameter and small torque, it may be able to do 
 considerable work at a rapid rate if with this 
 small torque it be caused to revolve very fast. If 
 this were attached directly to the axle of a car, its 
 torque would not be sufficient to start it, but if we 
 geared it down through one or more gears so that 
 for every revolution of the axle the motor would 
 
TORQUE. 149 
 
 in the same time have made say fifty revolu- 
 tions, the torque on the car axle would be magni- 
 fied fifty times, and the car would easily start or 
 go up hill. It must not be imagined that by 
 gearing down a motor is enabled to do more work 
 in a given time, or that its horse power is in any 
 way increased thereby, for by the definition of 
 work it is the product "of the force into the space 
 through which it acts. If we exert a small force 
 through a very long distance in a given time, as is 
 
 FIG. 57. 
 
 the case with the rapidly running armature, the 
 same horse power is expended as if we exerted 
 fifty times as much force through a space one- 
 fiftieth as long. 
 
 Thus in street car motors with the small arma- 
 tures and bipolar fields the necessary torque on 
 the car axle is gained at the expense of speed by 
 gearing down. At first all street car motors were 
 double geared, but the wear of these gears and 
 the loss of power occasioned by them indicated 
 
150 ELECTRIC RAILWAY MOTORS. 
 
 the desirability of doing away with them either 
 partially or wholly. This could only be done by 
 increasing in some way the torque on the arma- 
 ture. Neither the diameter of the armature nor 
 the current used could be much increased, so re- 
 sort was had to the multipolar fields. It is very 
 clear that with a four-pole field each of the fields 
 may be made to exert the same pulling or pushing 
 force on the armature with the same current as 
 is exerted by each of the bipolar fields before 
 referred to. With four poles, therefore, the arma- 
 ture will have double the torque, and may there- 
 fore run at half the speed with the same mechan- 
 ical advantage. This would enable us to do away 
 with one of the two reduction gears of which we 
 have spoken, and if we had six poles and could 
 slightly increase the diameter of our armature, or 
 slightly increase the amount of current, or both, 
 we could put the armature directly on the axle 
 and do away with both gears and have the same 
 axle torque as we originally had with our double 
 gears. We would have then a single reduction 
 and gearless motor respectively. It was argued 
 that whatever excess of current might be required 
 for the gearless motor, for instance, would be 
 more than compensated for by the saving of the 
 loss in the gears. As an illustration of the gear- 
 less motor reference is made to the subjoined cut 
 of the Short gearless motor. It will be observed 
 that its field frame is triangular in section and 
 has but three pole pieces. It is, however, a six- 
 pole machine, since the fields are so wound as to 
 produce consequent poles in the centers of each of 
 the three parts of the frame connecting the three 
 pole pieces together. 
 
CHAPTER XVII. 
 
 THE LINE OF COMMUTATION. 
 
 HERETOFORE in describing the action of the 
 dynamo we have represented the two neutral 
 positions of the wire as being on a line at right 
 angles to the axis of the pole pieces (see Figs. 26 and 
 28, see pages 87 and 89). This would only be the 
 case, however, when there was no current in the 
 armature. Let us examine what would happen in 
 a motor armature, when a current is passing in its 
 coils. If it be a closed coil armature, such as is now 
 almost universally used on street cars, the current 
 passing through the armature coils will tend to make 
 north and south poles on the armature, which will 
 be at the ends of a diameter at right angles to 
 that which joins the north and south poles in- 
 duced in the armature by the magnetism of the 
 fields. Since under the circumstances there can- 
 not be more than two poles in the armature, there 
 will be a compromise between the north and south 
 poles produced by the armature coils and the cor- 
 responding north and south poles induced by the 
 field magnets. Should these two sets of poles be 
 of exactly equal strength, the compromise poles 
 will be halfway between the two, and the line of 
 commutation (the line which joins the positions 
 where the individual coil is generating no electro- 
 motive force) will be at right angles to the line 
 joining the compromise poles, and the brushes 
 
 151 
 
152 ELECTRIC RAILWAY MOTORS. 
 
 must be moved to this new position, else they will 
 pass from one commutator segment to the next 
 while there is a difference of potential between 
 them, which will cause sparking. 
 
 If the induced poles are relatively stronger than 
 the poles produced by the armature current, 
 which would be the case if the armature current 
 is weak compared with the field strength, the com- 
 promise poles would approach more nearly to the 
 induced poles, and if the field magnets were very 
 overpowering in their strength, the compromise 
 poles would nearly coincide with the induced 
 poles, and the line of commutation would nearly 
 coincide with that which we have provisionally 
 
 fiven it, viz., at right angles to a line joining the 
 eld magnet poles. But as a motor is called upon 
 to do more or less work, the current admitted to 
 its coils must be increased or decreased. This 
 results, of course, in strengthening or weakening 
 the resulting poles. The position of the com- 
 promise poles will therefore be constantly chang- 
 ing, which means, of course, that the line of com- 
 mutation is constantly shifting. It has already 
 been explained that to prevent sparking the 
 brushes must bear on the armature on the line 
 of commutation, so the brushes must be shifted 
 as that changes. By making the armature poles 
 weak relative to the field, considerable change of 
 current in the armature may occur without much 
 shifting of the neutral line, and under these cir- 
 cumstances it may operate through quite a range 
 of work with fixed brushes without sparking. It 
 is because of an abnormal rush of current through 
 the armature on starting up a car, resulting in an 
 abnormal shifting of the neutral line, that the 
 sparking in street car motors occurs. Since the 
 
COUNTER ELECTROMOTIVE FORCE. 153 
 
 street car motor is called upon to operate through 
 an exceedingly wide range of work, the field 
 magnets are made the dominating ffig o as to 
 Keep tlie neutral line very 'nearly stationary 
 throughout this range. In series motors, however, 
 if neither armature nor field is near saturation, the 
 neutral line will not change its position. 
 
 COUNTER ELECTROMOTIVE FORCE. 
 
 Considerable space was devoted to explaining 
 and emphasizing the fact that if a closed loop of 
 wire be revolved around its axis between the poles 
 of a magnet, or, in other words, is revolved in a 
 magnetic field, so that its rate of cutting the lines 
 of force is constantly changing, it will generate an 
 electromotive forces 
 
 It is perfectly apparent that when we operate 
 a motor by passing current through it from one 
 brush to the other we are fulfilling all of these 
 conditions, and the coils of the motor armature 
 must also develop an electromotive force. It 
 makes no difference whether an armature is 
 driven by electricity or by steam power, if its 
 coils revolve in a magnetic field, there will be gen- 
 erated in them an electromotive force. In the 
 case of the motor, however, this electromotive 
 force is in the opposite direction to that of the 
 current which operates the motor, and is there- 
 fore called the " counter " electromotive force. It 
 follows exactly the same laws as govern the gen- 
 eration of electromotive forces in dynamos, and 
 will be the higher the greater the speed of the 
 armature. A motor running at high speed, as it 
 will if allowed to when it is running without load, 
 will generate a counter electromotive force almost 
 
 > 
 
 (UNIVERSITY 
 
 V 
 
154 ELECTKIC RAILWAY MOTORS. 
 
 equal to that of the current by which it is operated, 
 and will therefore take but very little current. 
 The current that a motor will take under any 
 conditions is that which is due to the difference 
 between the direct electromotive force of the 
 current and the counter electromotive force of the 
 motor itself. The counter electromotive force of 
 a motor at any speed is exactly equal to that which 
 the same, motor would generate if driven as a 
 dynamo at the same speed. If, therefore, a motor 
 is starting from rest, it has, at first, no counter 
 electromotive force. The only obstacle to the flow 
 of current through the armature would be the 
 resistance within the machine itself, which, being 
 exceedingly small, would, according to Ohm's law, 
 permit an enormous current to flow through its 
 coils, which would inevitably result in a burn out 
 if it were not checked. This is the reason why a 
 rheostat is almost universally used in starting. 
 It opposes at first a great artificial resistance, and 
 this is decreased as speed is gained and counter 
 electromotive force is generated, when all artificial 
 resistances may be removed w r ith impunity. 
 
 This back electromotive force of a motor has 
 its exact counterpart in the resistance which the 
 armature of a dynamo offers to the driving engine. 
 We all know, or can find out for ourselves, that 
 when a dynamo is generating no current, as, for 
 instance, when the armature is not irr motion, 
 we can readily turn the armature with the hand, 
 and yet when it is working to its utmost capacity 
 it may take hundreds of horse power to keep it 
 in rotation. This resistance to the mechanical 
 effort of the steam engine is really the measure of 
 the work the dynamo is performing ; so the elec- 
 trical resistance opposed by the counter electro- 
 
COUNTER ELECTROMOTIVE FORCE. 
 
 155 
 
 motive force of the motor is a measure of the 
 work the motor is doing. 
 
 Professor Silvauus Thompson, in his great work 
 on " Dynamo-Electric Machinery," cites an ex- 
 ample which very well shows how the current that 
 a motor will take decreases with the speed of its 
 armature. He used a small Immisch motor with 
 separately excited fields, and connected it up with 
 a primary battery and amperemeter. At different 
 speeds the following figures were obtained : 
 
 Speed Revs, 
 per Minute. 
 
 o 
 
 Current 
 Amperes. 
 20 
 
 Speed Revs, 
 per Minute. 
 160 
 
 Current 
 Amperes. 
 
 78 
 
 50 
 
 . 162 
 
 180 
 
 . . . 61 
 
 100.. 
 
 ..12.2 
 
 195.. 
 
 ..5.1 
 
 Thus at its maximum speed it took only about 
 one-fourth of the current that it took when the 
 armature was held at rest. In this case 5.1 am- 
 peres were required to overcome the friction of 
 the armature. Had the friction been less the 
 armature would have revolved still faster and 
 finally come to constant speed with less current 
 than 5.1 amperes. 
 
 In the earlier days of the electric motor this 
 counter electromotive force was a bugbear and 
 thought to be an objectionable feature, and at- 
 tempts were made to construct motors from which 
 it would be eliminated. But we now know that 
 the_(xistence^ of this counter electromotive force 
 is of the utmost importance, and that upon it de- 
 pen ds the degree to which any given motor 
 enables us to utilize electric energy that is sup- 
 plied to it in the form of an electric current. "In 
 fact," says Professor Thompson, " this countei 
 electromotive force is an absolute and necessary 
 factor in the power of the motor, just as much as 
 
156 ELECTRIC BAIL WAY MOTORS. 
 
 the velocity to which (other things being equal) it 
 is proportional." 
 
 As will be seen from the figures given by Pro- 
 fessor Thompson and the subsequent remarks, the 
 amount of current that a motor will take is only 
 that which is absolutely necessary to do the work 
 which it is called upon to do. That is to say, if 
 it has no other work to do than to overcome its 
 own friction, its armature will automatically 
 attain such a speed as to generate a counter 
 electromotive force, or " back " pressure, such that 
 only sufficient effective electromotive force remains 
 to force through the motor sufficient current to 
 move the armature against this resistance. If 
 now an additional load is thrown on the motor, 
 the speed of its armature will be at once retarded, 
 less counter electromotive force will be generated, 
 and consequently more current will pass, and the 
 motor at once adjusts itself to this new load. 
 
CHAPTER XVIII. 
 
 COUNTER ELECTROMOTIVE FORCE AND SPEED 
 REGULATION. 
 
 BUT this counter electromotive force must not 
 be confounded with dead resistance. It has in 
 some respects the same effect as resistance, but 
 differs from the latter in very important particu- 
 lars. It has been stated that counter electro- 
 motive force cuts down the current. Resistances 
 placed in circuit will do the same thing exactly," 
 but the cutting down of current by means of the 
 counter electromotive force, which tends to pro- 
 duce a current in the opposite direction, is merely 
 a problem in subtraction the taking of a lesser 
 quantity from a greater, and the utilization of the 
 remainder. No energy whatever is consumed 
 when the current is reduced in this way, but 
 when it is reduced by the use of resistances the 
 electromotive force which disappears is employed 
 in overcoming these resistances, and the energy 
 thus expended appears as heat. In electric light- 
 ing, welding, etc., this energy is usefully expended, 
 for by designedly localizing the resistance we 
 localize the heat to such an extent as to produce 
 the desired results of high temperatures. But in 
 most other applications of electricity it is not heat 
 that we want, but mechanical energy. Every bit 
 of heat that is generated in our circuit or in our 
 translating devices, therefore, represents so much 
 
 157 
 
158 ELECTEIC RAILWAY MOTORS. 
 
 energy uselessly employed, and constitutes a drain 
 upon our source of energy for which we have to 
 pay as much as we pay for the energy which serves 
 a useful purpose. The heat produced in an 
 electric circuit corresponds very closely to the 
 water lost in a leaky water main along the route. 
 If the pipe be very leaky, half the water that is 
 pumped into it at the pumping station may leak 
 out, and while it does the consumer at the other 
 end of the line no good, costs at the pumping 
 station just as much as the other half does which 
 he can make use of. Where an electric motor 
 heats up badly, or resistances are introduced into 
 the circuit near the motor in order to cut down 
 the current to the required amount, they consti- 
 tute large leaks which, in the water analogy, would 
 correspond to the diversion of a portion of a 
 waterfall from a water wheel so as to let that por- 
 tion diverted run to waste, or where the water is 
 conveyed to a water motor in a pipe, to the open- 
 ing of a large faucet just above the water motor, 
 so that a portion only of the water that was de- 
 livered at that point would go to the motor, the 
 remainder being allowed to run out upon the 
 ground. 
 
 But it is often necessary with electric motors 
 to resort to these wasteful methods of regulation. 
 As everyone knows, it requires the expenditure 
 of considerable energy to set in motion any body 
 which is at rest, and it also requires the expendi- 
 ture of this energy for a considerable time before 
 that body especially if it be a heavy body can 
 be set into very rapid motion. Everyone also 
 knows that when the moving body has once at- 
 tained a certain speed this same speed can be 
 maintained with the expenditure of but a very 
 
COUNTER ELECTROMOTIVE FORCE. 5 
 
 small fraction of the energy required to bring it 
 up to that speed. The same is true, in a reverse 
 order, of bringing a moving body to rest. This 
 property, which is characteristic of all matter, by 
 which it resists any change as regards motion or 
 rest, is termed inertia, and the heavier the body 
 is the longer must a given force act upon it to 
 start it from a state of rest and bring it to a given 
 speed, or to check it from a given speed and bring 
 it to rest. We therefore see why in electric 
 motors it is necessary in starting them to reduce 
 the current by what have been termed dead or 
 hurtful resistances, for when the armature is at 
 rest there is of course no counter electromotive 
 force to oppose the current. The only resistance 
 opposed to its flow at this instant is that which 
 is offered by the coils on the armature (and fields 
 in the case of series winding), and this has been 
 made by the builder as small as possible purposely 
 to prevent the loss of energy which resistances 
 necessarily involve. If, therefore, the current 
 were turned on full from a five hundred volt cir- 
 cuit, the momentaiy rush would be so great as to 
 burn the motor up at once. 
 
 To realize how quickly the heating effects in- 
 crease with the current we need only to remember 
 the law that the heat thus produced is propor- 
 tional to the square of the current. It would be 
 bad enough under these circumstances if double 
 and treble the current produced only double and 
 treble the heat, for a motor in starting may take 
 ten times the amount of current that it would 
 require when doing the full work for which it was 
 designed, but when we remember that the heat 
 will be increased to four times and nine times for 
 double and treble the current, and one hundred 
 
160 
 
 ELECTKIC RAILWAY MOTORS. 
 
 times for ten times the current, the seriousness of 
 such a situation will be realized at once. 
 
 Some means must therefore be resorted to to 
 prevent this enormous rush at starting, and the 
 one usually employed is dead resistance. A large 
 resistance, sufficient to cut the current down to 
 the safe amount, is first introduced. As the 
 armature starts to revolve it immediately begins 
 to generate a slight counter electromotive force. 
 By reason of this the full amount of the original 
 resistance is no longer required to maintain the 
 same current, and a smaller resistance may be 
 substituted. As the speed of the armature in- 
 
 FIG. 58. 
 
 creases so does the counter electromotive force, 
 and in like manner does the necessity for dead 
 resistance decrease. In fact, with the speed of the 
 armature the counter electromotive force gradually 
 usurps the functions of the resistance until the 
 speed has reached that at which the motor was 
 designed to run, when it will have supplanted it 
 entirely. 
 
 To facilitate the introduction into the motor 
 circuit of resistances of various values as re- 
 quired, such resistances are usually grouped to- 
 gether and their terminals so connected that any 
 one or more of them may be thrown into circuit 
 
REQUIREMENTS OF SPEED REGULATION. 161 
 
 by the movement of a lever. Such an arrange- 
 ment is called a rheostat, and such, in fact, is the 
 arrangement on the platforms of electric cars to 
 which the controlling lever is attached by which 
 the motorman controls his car. 
 
 The desire to avoid as much as possible the 
 losses necessarily involved in the " rheostat regu- 
 lation " of current as well as the requirements for 
 speed regulation, so essential in street cars, has 
 resulted in numerous other arrangements, which 
 will be referred to after we have considered what 
 the requirements of speed regulation involve. 
 
 THE REQUIREMENTS OF SPEED REGULATION. 
 
 In discussing this question it will be under- 
 stood, of coursje, that we are not speaking of how 
 to build motors suitable for various speeds, but 
 how to regulate the speed of motors already built 
 or in use. We must, therefore, take the motor 
 as we find it, viz., with certain elements, such as 
 the number of turns of wire on the armature, 
 which, if changed, would modify the speed, fixed. 
 We cannot do better on this subject than to quote 
 from Crosby and Bell's most excellent treatise on 
 " The Electric Railway," which those wishing to 
 go more deeply into the subject of electric rail- 
 ways than it is intended to do in this volume 
 should certainly read : 
 
 " The other quantities, changes in which are con- 
 nected with changes in speed, are (1) strength of 
 field, (2) the rate of work, i. e., the quantity of 
 work done in a given time. As has been already 
 shown, the rate of work is measured by the prod- 
 uct of (3) the current and (4) the counter elec- 
 tromotive force. The current, however, is readily 
 
162 ELECTEIC RAILWAY MOTORS. 
 
 expressed in terms of the counter electromotive 
 force, the resistance of the machine and the 
 applied electromotive force, since it is always such 
 a current as will flow over the given resistance 
 under a pressure equal to the difference between 
 the two opposing pressures that applied or im- 
 pressed by the dynamo through the line, and that 
 generated by the motor armature itself. (5) As 
 seen from the above, change in the applied E. M. F. 
 is also connected with change in the speed. The 
 quantities (1), (2), (3), (4), (5) are interdependent, 
 but are separately mentioned, since convenience 
 requires reference first to one, then to another. 
 
 " Of these five quantities perhaps that which in 
 practice is most constant is strength of field. As 
 has been shown, the efficiency of a motor depends 
 upon the relation of the counter E. M. F. to the 
 applied E. M. F. High efficiency or^jnelajrixelj 
 high counter E. M. F. is desirable at any and all 
 speeds. But BTgK^counter E. M. F. goes wltli~a 
 large product of the three factors : (a) number 
 of armature loops, (b) speed of rotation and (c) 
 strength of field. As noted (), the number of 
 loops is fixed, (b) the speed is limited by practical 
 requirements, hence (c) great strength of field is 
 constantly desirable. It is therefore good prac- 
 tice so to wind a street railway motor by putting 
 a relatively large number of turns around its 
 magnet that a maximum strength of field is at- 
 tained, even when the current flowing is small as 
 compared with the maximum current. 
 
 " This is equivalent to saying that the magneti- 
 zation given by a relatively small current is yet 
 sufficient to saturate or nearly saturate the iron .of 
 the magnetic circuit. If, however, the field be 
 kept below saturation and be varied in strength, 
 
REQUIREMENTS OF SPEED REGULATION. 163 
 
 this variation may be used to accomplish a cer- 
 tain degree of speed regulation. Let us suppose 
 a car moving on a level (or on a uniform grade) 
 and at such a speed as to produce a counter E. 
 M. F. of 400, the applied E. M. F. being 500. 
 For convenience assume the internal resistance 
 of the armature circuit to be 10 ohms. Then the 
 current flowing will be 
 500400 impressed E. M. F. counter E. M. F. 
 
 10 resistance 
 
 100 
 
 = 10 amperes. 
 
 10 
 
 The mechanical work done would be 400X10=E. 
 XC.= impressed E. M. F.X current =4000 watts. 
 
 " Now suppose x it is desired to run more slowly. 
 Increase the field strength by ten per cent. The 
 counter E. M. F. at the same speed would be 44*0 
 volts. 
 
 500440 
 
 The current = =6 amperes, 
 
 10 
 
 and the work, 440X6=2640 watts. But since the 
 car requires 4000 watts to maintain the previous 
 speed, it is now evident that it must now decrease 
 its speed until there shall be an equality between 
 the work required to maintain the lower speed 
 and the work done by the motor at the lower speed 
 due to the greater field strength. Let us learn 
 what this speed is. 
 
 " It was seen above that work at the rate of 
 4000 watts 
 4000 
 
 (= =5.36 H. P. = 176,880 foot pounds per min.) 
 
 746 
 
164 ELECTEIC RAILWAY MOTORS. 
 
 must be performed in order to maintain the speed 
 existing before the change of field strength. Sup- 
 pose the car to weigh 8 tons, and suppose that on 
 the particular track in question a horizontal effort 
 of 25 pounds per ton is required to overcome all 
 resistances, including those of gears or other 
 mechanism between the armature and the axles ; 
 then a total horizontal effort of 8 X 25 = 200 pounds 
 must have been exerted. This quantity multiplied 
 by the number of feet traveled per minute must 
 be equal to the number 176,880, representing the 
 total foot pounds of energy utilized per minute. 
 Hence the travel per minute 
 176,880 
 
 == _ =884.4 feet == 10.05 
 
 200 
 
 miles per hour. At the new speed we must have 
 a similar relation, viz., 
 
 work done in foot pounds 
 
 200 
 
 feet traveled per minute ; or since 1 watt minute 
 =44.24 foot pounds. 
 
 work in watts 
 
 ; 200-7-44.24} "-Hi 
 feet traveled per minute ; hence the work in watts 
 =4.52 X feet traveled per minute." - *fS57 fj^ 
 It'will be observed from the above that a reduc- 
 tion in speed results from increasing the strength 
 of the field. The converse is also true, viz., that 
 a weakening of the field results in increased speed. 
 This latter can be readily proved by placing an 
 iron bar across the pole pieces of a stationary 
 motor, thus diverting some of the lines of force 
 from the armature. A very noticeable increase of 
 
 it i/o = WAX 
 
 'vy" 
 
REQUIREMENTS OF SPEED REGULATION. 165 
 
 speed of armature will at once occur due to the 
 weakening in this way of the field in which the 
 armature is working. 
 
 Thus far we have assumed that the car is run- 
 ning upon a level track or up a uniform grade, or, 
 in other words, that the work the motors are 
 called upon to perform remains constant. 
 
 Of course if the load be increased, more energy 
 is required to move it at the same speed a greater 
 torque will be required in the armature, and this 
 may be accomplished by increasing the current in 
 the latter, as already stated. The conditions for 
 maintaining uniform speed under increased load, 
 therefore, are obtained by a relatively large increase 
 of armature magnetism over field strength. Thus 
 in a shunt motor operating under constant E. M. 
 F. the strength of the field remains constant under 
 all conditions of work, while the armature current 
 may vary within wide limits, and does vary directly 
 as the load. But in a series wound motor, such as 
 is usually employed on street cars, since all the 
 current passing through the armature also passes 
 around the field, the magnetism of both will con- 
 tinue to increase in about the same ratio until 
 either one or the other becomes saturated, after 
 which its magnetism cannot increase further and 
 remains stationary, while the other increases with 
 additional current. It has already been stated 
 that in street railway motors it is customary to 
 make the fields relatively stronger than the arma- 
 ture. ' This is done by making so many turns in 
 the field magnet coils that with the currents usu- 
 ally employed the field magnets are nearer a state 
 of saturation than the armature. If this be the 
 case in a series motor, and sufficient load be thrown 
 on to slacken the speed of the motor and thereby 
 
166 ELECTEIC EAILWAY MOTOES. 
 
 lower the counter E. M. F., sufficient additional 
 
 current will pass to saturate the field. Should the 
 
 speed become still slower, more current would pass, 
 
 but the field, being already saturated, would not be 
 
 further increased in strength, while the__arm_ature 
 
 strength would be still furtheF increased, thus 
 
 I fulfilling the conditions of relative increase of 
 
 I 'armature ovg*' field required for greater speed, 
 
 \ and~tFe motor would run faster until the in- 
 
 \ crease of counter E. M. F. resulting f ronPlts 
 
 /Increased speect "restores a balance and the speed 
 
 remains constant. 
 
 Thus far we have considered all the windings 
 on the field magnet to constitute one integral coil. 
 Much greater elasticity or flexibility of control 
 may be obtained by winding the field magnet with 
 a number of separate coils which may be connected 
 up in various ways so as to be used separately, in 
 series or in multiple arc, thus enabling the motor- 
 man to change the relative strengths of field and 
 armature through a much wider range. This will 
 be made clear by reference to Fig. 59 (see page 
 160) and the following explanation. 
 
 Suppose three coils of wire to be wound around 
 the magnet cores of a motor, as shown in Fig. 59. 
 Let the resistance of each be 1 ohm. Connect 
 D to B and 12 to C (so that the three coils are in 
 series). Suppose a difference of potential of 100 
 volts be maintained between the terminals A and 
 F then the total resistance of this field circuit 
 would be 3 ohms. The current flowing would be 
 100 
 
 =33.3 amperes. 
 
 3 
 
 The number of turns in each coil is two one on 
 each leg. There will therefore be six coils in all, 
 
REQUIREMENTS OP SPEED REGULATION. 167 
 
 and the magnetizing effect expressed in ampere 
 turns would be 33.3X6 = 199.8. 
 
 If, however, we connect the three coils up in 
 parallel by connecting A, B and C together and 
 D, E and F together, the resistance of the field 
 circuit would be one-third of an ohm instead of 
 three ohms as before, and the current flowing 
 would be 100-i-^=300 amperes instead of 33.3, 
 and the number of turns around which this whole 
 current would flow would be but two, and the 
 resulting magnetizing effect expressed in ampere 
 turns would be 300X2=600, or three times the 
 former value. 
 
 If sufficient current passed through the coils 
 when arranged in series to saturate the field, no 
 further magnetism would be added to the field by 
 the second arrangement, but the strength of the 
 armature, if that were far from saturation, would 
 be proportionately increased, as well as relatively 
 
 fiving the latter a greater torque as well as a ten- 
 ency by reason of a relatively weaker field to 
 greater speed ; but even if the field also be far 
 from saturation with the first arrangement, and its 
 strength increases proportionately with the addi- 
 tional ampere turns of from 199.8 to 600, which 
 would result from the second arrangement, the 
 drop of potential required to force a given current 
 through the field windings would be much less in 
 the second arrangement than in the first because 
 of the lessened resistance (in this case 3 =2f 
 ohms), and the electromotive force in the armature, 
 if the latter be placed in series with the field coils, 
 would be greater in the second arrangement than 
 in the first, again fulfilling the conditions neces- 
 sary to greater speed. It is evident that other 
 combinations of these coils may be employed to 
 
168 ELECTRIC RAILWAY MOTORS. 
 
 produce different results. Thus in starting all 
 three coils may be put in series, then one may be 
 cut out and the other two connected in series, and 
 next the two in multiple with each other and in 
 series with the third, then two in multiple with 
 the third cut out, and finally the second arrange- 
 ment above described all three in multiple. The 
 various changes above enumerated changes of 
 connections from first to last are progressively 
 toward the attainment of higher speeds. This 
 method of regulation is known as that by " corn- 
 mutated field circuits." 
 
 On most street cars there are two motors. It is 
 evident that with two motors the commutation 
 method of control can be still further extended by 
 throwing the coils of the two motors not only into 
 the above combinations with the other coils on the 
 same motors, but by throwing the coils of one 
 motor into various combinations with the coils on 
 the other. Thus in starting all the coils on both 
 motors would be throw r n into series, and these in 
 series with the armature coils of both motors, 
 themselves in series with each other, and so by 
 various changes gradually decreasing the resistance 
 of the field circuits until all the field coils in each 
 motor are in multiple with each other, and the two 
 motors are in multiple with each other, which 
 would be the condition for maximum speed. 
 
CHAPTER XIX. 
 
 THE SPERBY AND JOHXSON-LUNDELL SYSTEMS. 
 
 THERE has existed quite a difference of opinion 
 among electricians as to the relative merits of 
 rheostat and commutated field control, but the 
 discussions which have taken place in the Ameri- 
 can Institute of Electrical Engineers and in the 
 technical periodicals on the merits of the two 
 systems have apparently resulted in no conver- 
 sions on either side. They have resulted, how- 
 ever, in making us better acquainted with the 
 demerits of each, many of which both sides are 
 willing to admit ; but while it would seem that it 
 makes no difference in the efficiency of a device 
 whether the resistances be external to it, as in the 
 rheostat control, or internal, as in the commutated 
 field, it is impossible to get sufficient resistance 
 into the field coils for starting purposes without 
 sacrificing other elements of efficiency. Cars 
 equipped on the commutated field principle are 
 therefore liable to start with a violent jerk, 
 because even with all the field and armature 
 coils in series the initial rush of current is too 
 great. 
 
 This disadvantage and the advantage possessed 
 by the rheostat control of permitting a perfectly 
 gradual admission of current, together with the 
 economy of current permitted by the commutated 
 field method, have led to a combination of the two 
 
170 ELECTEIC RAILWAY MOTOES. 
 
 being employed to great advantage. This com- 
 bination method, known as the series-parallel 
 method of control, is applicable where more than 
 one motor is employed, and consists usually not in 
 commutating separate coils on each field, but in 
 throwing the field coils and the armature coils of 
 the separate motors and various external resist- 
 ances into various combinations with each other. 
 It is apparent that the greater the number of 
 motors upon the car the greater the flexibility of 
 the system. It therefore seemed particularly 
 applicable on the Intramural Railroad at the 
 World's Fair, where the motor car carried four 
 motors, and the experience on that road with the 
 system is reported to have been entirely satisfac- 
 tory from every point of view. 
 
 As before stated, it has usually been customary 
 to equip each car with two motors. With this 
 arrangement it is often the practice to cut one 
 motor out of circuit entirely when the work re- 
 quired is small. This enables the remaining 
 motor to be operated at about its most efficient 
 output on loads which would be so small as to 
 render the operation of both motors inefficient. 
 
 There are many engineers who object on theo- 
 retical grounds to the use of two motors under 
 any conditions, on account of the tendency of any 
 two armatures to work out of unison if there 
 happens to be any disparity between them, either 
 in the armatures themselves or in the strengths of 
 the fields in which they revolve. It is very evi- 
 dent that if the two motors fail to work in the 
 most perfect unison the resultant effect will be 
 less than it should. That the perfect unison of 
 action between two separate motors, so essential to 
 the highest efficiency of operation, is practically 
 
THE SPERRY 
 
 unattainable is, I believe, now admitted by all, 
 bat it is approached so closely in modern con- 
 struction that this method of equipment, on ac- 
 count of the greater facility of gearing to the 
 axles and the greater facility of control by 
 coupling up armature and field coils by the 
 series-parallel method, is still almost universally 
 employed. 
 
 There are two systems now on the market, 
 however, which employ a single large motor 
 flexibly geared to both axles, and the promoters 
 of these systems claim a largely increased tract- 
 ive efficiency for their methods over that possible 
 with two independent motors. The best known 
 of these is the Sperry system, for which the claim 
 is made that " the motor being coupled to both, 
 axles, a tractive effort is available, which is 
 entirely impossible with separate motors. A per- 
 fectly uniform velocity of all the wheel peripheries 
 is obtained for adhesive effect. The great gain in 
 drawbar pull under conditions of coupled axles as 
 compared with the same torque applied to each 
 axle individually is a matter not of conjecture, but 
 of fact, the difference being more than eleven per 
 cent. The fact is that the tendency of one wheel 
 to slip is held back by all the others instead of by 
 its mate only. With separately driven axles one 
 pair may be in slipping frictional contact with the 
 rail while the other pair is doing the work of 
 adhesive contact." It is also claimed for the 
 single motor system that by substituting a large 
 single motor for two small ones the number of 
 wearing parts and consequent loss in friction is 
 greatly diminished, the cost of repairs, inspection 
 and general care of apparatus materially lessened, 
 and the commercial and electrical efficiency of the 
 
172 ELECTEIC BAIL WAY MOTOES. 
 
 system placed far above that of any double motor 
 equipment. 
 
 While most of these claims are theoretically 
 true, the mechanical difficulties of gearing both 
 axles to the same motor have been such that the 
 theoretical advantages of the single motor have 
 not appealed to practical men with sufficient 
 force to cause their general adoption. On the 
 contrary, we find to-day but one constructor build- 
 ing motors with this idea in view, whereas several 
 types of single motor equipment, once advertised 
 and pushed with considerable vigor, have dis- 
 appeared entirety from public view. Vandepoele, 
 Daft, Eickemeyer, Rae, are names that are all 
 connected with the single motor equipment 
 method, and there are now two more new names 
 that must be added to this list, viz., E. H. John- 
 son and Robt. Lundell. These latter two gentle- 
 men are now before the public with a single motor 
 car equipment which seems to possess a number of 
 features of real merit not hitherto employed. In 
 the Johnson-Lundell system a single motor is 
 employed, but the armature of this is wound with 
 two independent sets of coils, each of which has 
 its own separate commutator. There are thus 
 practically two armatures, but since they are both 
 revolving in the same field, they are bound to 
 work in harmony if the coils of the two are 
 exactly similar. This system also permits of con- 
 trol by the series-parallel method by the handling 
 of the two windings as though they were separate 
 armatures an advantage not possessed by any 
 other single motor system. The successive steps 
 for increasing speeds in the Johnson-Lundell sys- 
 tem as given to the author by the inventors them- 
 selves are as follows : 
 
THE JOHNSON-LUNDELL SYSTEM. 173 
 
 1. Starting, external resistance, l obms, all 
 field coils and both armature coils in series. 
 
 2. Same as 1 with resistance cut out. 
 
 3. Field coils in series, armature coils in parallel. 
 
 4. All coils in parallel. 
 
 To give greater facility in starting, and to take 
 up all instantaneous strains, the armature in the 
 Johnson-Lundell system is flexibly attached to its 
 shaft by means of springs which permit a con- 
 siderable angular motion of the armature in case 
 of suddenly applied strains before the cushioning 
 is suificient to cause the revolution of the shaft. 
 Besides permitting of a more gradual start of the 
 car, which is effected without jar, it is claimed 
 for this arrangement that it results in economy 
 of current in that it permits of the generation of 
 some counter electromotive force at the moment 
 of starting, when of all times it is most needed 
 and when in other arrangements it is totally 
 absent. 
 
 Another novel feature of this equipment is the 
 friction clutch arrangement on the armature shaft. 
 Keyed to the latter is an iron disk and pressing 
 against this are two other similar disks, which are 
 forced against the keyed disc by means of a nut 
 and spring under compression. To these latter 
 discs are rigidly attached the two driving gears, 
 which in this case are sprocket wheels. By 
 tightening or loosening this nut a greater or less 
 friction is maintained between the three disks. If 
 the strain upon the motor exceeds this friction 
 limit, the keyed disk will slip, allowing the arma- 
 ture to continue to revolve instead of stopping it 
 suddenly, as would otherwise be the case. In 
 practice this friction is determined by the maxi- 
 mum current it is deemed wise to permit the 
 
174 ELECTRIC RAILWAY MOTORS. 
 
 armature to take. This having been decided, the 
 compression of the spring is adjusted by the nut 
 so that the friction is just sufficient to permit the 
 inner disk to slip when the dangerous current is 
 passing through the armature. 
 
 As before indicated, the car axles are driven 
 from the motor shaft by means of chain and 
 sprocket gears. Whether this will prove entirely 
 satisfactory or not in practice remains to be seen. 
 The chain and sprocket have been repeatedly tried 
 before on s-treet cars, and have been abandoned as 
 not suitable the chief difficulty having been the 
 rapid wear and breakage occasioned by the sudden 
 strains to which they were necessarily subjected. 
 When in good order, however, this method of 
 gear is fairly satisfactory on the score of efficiency, 
 and with the improvements introduced in the 
 Johnson-Lundell equipment for obviating these 
 sudden strains and shocks, and with the improve- 
 ment in the chain gearing itself, the chain and 
 sprocket may again come into favor. It is certainly 
 the most convenient method for gearing to both 
 axles from a single motor. 
 
 The Johnson-Lundell system calls for special at- 
 tention for another reason, viz., that it is the latest 
 attempt to do away with the overhead trolley. It 
 is not, however, a conduit system, but rather a 
 surface contact system, the current supply for the 
 motor being taken from a surface conductor lying 
 midway between the rails and flush with the street 
 paving. This conductor is not electrically con- 
 tinuous, however, but broken up into lengths not 
 exceeding eight or ten feet, which are successively 
 thrown into electrical connection with the feeder 
 system as the car passes over them, and discon- 
 nected again after the car passes off of them. The 
 
THE JOHNSON-LUNDELL SYSTEM. 175 
 
 switching is automatically accomplished by elec- 
 tromagnetic devices, one of which is provided for 
 each separate section of the trolley rail. These 
 switches are contained in hermetically sealed boxes, 
 usually three in a box, buried in the street beside 
 the tracks. On board the car is placed a storage 
 battery which is kept continually charged by the 
 line current. The function of this battery is two- 
 fold : first, to furnish the current on starting the 
 car nedessary to actuate the electromagnetic switch 
 by which the feeder current is diverted into the 
 trolley rail section immediately below the car, and 
 second, to render the car independent of the power 
 station should occasion require, as in case it should 
 run off the track, or where it is required to run the 
 car over insulated portions of the track too long 
 to be conveniently passed by the car's momentum. 
 Since for either use but little drain is made upon 
 the battery, the cells are not required to be of large 
 capacity, and only a sufficient number is required 
 so that when coupled in series their combined 
 electromotive force will equal that of the feeder 
 circuit. On the experimental track now in opera- 
 tion in New York the electromotive force of the 
 feeder current is about. 250 volts ; 100 cells of the 
 chloride battery are therefore used. These are 
 arranged in series under the car seats, the whole 
 being in parallel with the motor circuit. When- 
 ever their electromotive force falls below that of 
 the trolley circuit, a portion of current from the 
 latter goes to recharge them. On the other hand, 
 should the trolley circuit electromotive force 
 drop they would come temporarily to the latter's 
 assistance. 
 
 There is still another new system for electric 
 railways that is destined to come into prominence 
 
176 ELECTRIC RAILWAY MOTORS. 
 
 in the near future, viz., that devised by Mr. H. 
 Ward Leonard. This system is already in success- 
 ful use both on electric cranes and on elevators, 
 and in these applications has demonstrated its 
 great economy over all other systems of control. 
 It has been seriously objected to for street car 
 application on account of the multiplicity of 
 machines required, and has been unjustly con- 
 demned because it has been supposed that it would 
 involve excessive sparking, with sudden changes of 
 load or speed. As a matter of fact, however, the 
 machines do not spark at all, and the efficiency of 
 control is far greater than is possible even with 
 the series-parallel method. 
 
CHAPTER XX. 
 
 THE LEONARD, PERRY AND OTHER SYSTEMS. 
 
 As before outlined, in speed regulation it is 
 necessary to vary the electromotive force as the 
 speed, and the current as the torque or effort. In 
 the previous methods of control this is attempted, 
 and imperfectly accomplished by various methods 
 of commutation of field coils and external resist- 
 ances. In fact, some such method as this is all that 
 is available where a current of constant potential, 
 such as that now universally employed on electric 
 railroads, is used. Mr. H. Ward Leonard, however, 
 has taken a very bold step in his system, which 
 consists in placing on each car a separate generator 
 from which the car motor is directly operated 
 the generator itself being directly driven from the 
 trolley current by a motor. By reference to Fig. 
 60 the following explanation of the system will be 
 readily understood. We quote from a paper read 
 by Mr. Leonard before the American Institute of 
 Electrical Engineers, June 8, 1892: 
 
 " Each axle is driven by a gearless motor, either 
 directly or by means of a connecting rod. The 
 fields of these motors are excited directly from the 
 constant E. M. F. of the line and independently of 
 the armature circuit. Beneath the car and between 
 the axles there is suspended a motor generator, 
 each armature winding being in a separate field. 
 The motor portion of the motor generator is shunt 
 
 177 
 
178 
 
 ELECTRIC RAILWAY MOTOES. 
 
 wound and connected just as a shunt motor is for 
 use upon ordinary constant potential circuits. The 
 field of the generator portion has its field connected 
 across the line, and has inserted in it a regulating 
 and reversing field rheostat. This field circuit is 
 independent of the armature circuit. The gener- 
 ating armature of the motor generator is in metallic 
 connection with the armatures of the gearless pro- 
 pelling motors. It will be noticed that this circuit, 
 
 FIG. 
 
 LEONARD SYSTEM. 
 
 T, trolley. M, motor portion of power converter. G, generator 
 portion of power converter. P, the propelling motor for the car. R, 
 the regulation and reversing rheostat in field of G. E, the connection 
 to ground. W, the car wheel. 
 
 including the armature, is a distinct and separate 
 metallic circuit having no connection with the line 
 in any way. 
 
 " Suppose now that our shunt motor is running 
 at full speed, and that our controlling rheostat in 
 the generator field circuit is at its central position, 
 so that the generator field circuit is broken. 
 Although the generator armature is being driven 
 at full speed, it is revolving in a field having no 
 magnetism except the residual magnetism, and 
 
THE LEONABD SYSTEM. 179 
 
 hence produces practically no volts. Let us now 
 move our controlling switch so as to place the 
 generator field across the line, but with a resistance 
 in series with the field of ten times the resistance 
 of the field coils. We now give a slight excitation 
 of the field and a development of volts at the brushes 
 of perhaps forty volts. This voltage will produce 
 a current through the armatures of the driving 
 motors dependent upon the ohmic resistance of this 
 circuit only ; and hence, even at this low voltage, 
 a large current will be produced, which, being in a 
 field of full strength, will cause a torque sufficient 
 to start the armature. The speed of the armature 
 will, of course, be governed by the counter E. M. F. 
 which its revolution produces in its strong field; 
 and hence, just as in the case of a shunt wound 
 motor, its speed will be practically constant so long 
 as the E. M. F. supplied is constant. 
 
 "If we now gradually increase the magnetic field 
 of the generator by cutting out resistance'by moving 
 the controlling switch, we will gradually raise the 
 E. M. F. of the armature circuit, and with it the 
 speed of the driving motors. Since these armatures 
 are revolving in a constant field, the torque they 
 produce will be exactly proportional to the current 
 in them, and the current will automatically flow 
 exactly as is required to produce the necessary 
 torque to maintain a speed such that the counter 
 E. M. F. will approximately equal the E. M. F. sup- 
 plied by the power converter. Thus it will be seen 
 that the speed of the car will be dependent upon, 
 and proportional to, the E. M. F. supplied by the 
 power converter, and the torque or tractive effort 
 will be dependent upon, and proportional to, the 
 current supplied by the power converter." 
 
 While this method has not as yet been actually 
 
180 ELECTEIC RAILWAY MOTORS. 
 
 introduced on electric street railroads, its feasi- 
 bility and economy and the facility of control 
 afforded have been amply demonstrated on numer- 
 ous electric cranes, elevators and hoists, and in 
 connection with machinery of various kinds requir- 
 ing the greatest nicety of speed control under 
 widely varying loads. In such applications econ- 
 omy of space has not been the prime requisite that 
 it is in street car traction, and the fact that the 
 arrangement seems necessarily bulky, with the 
 three machines involved, and the erroneous idea 
 which has been general that the sparking would be 
 excessive under working conditions, has militated 
 greatly against its introduction in street railway 
 work. As before stated, those who have examined 
 into the workings of the system, among whom 
 may be included the author, aver that there is 
 practically no sparking even under the most favor- 
 able conditions for the same, and the author is 
 advised that changes in detail (though not in 
 principle) have already been partially perfected 
 which will obviate the real difficulty that now 
 exists, viz., bulkiness. 
 
 Mr. Leonard has also adapted this same system 
 to the operation of cars from alternating current 
 .circuits. In this application a synchronous motor 
 generator is substituted for the direct current 
 motor generator employed in the direct current 
 method. Those who wish to read a full descrip- 
 tion of this system are referred to vol. xi. of the 
 Transactions of the American Institute of Elec- 
 trical Engineers under the title " How shall 
 we Operate an Electric Railway extending One 
 Hundred Miles from the Power Station?" by 
 H. Ward Leonard. 
 
THE PERKY SYSTEM. 181 
 
 THE PERRY SYSTEM OF SERIES ELECTRIC 
 TRACTION. 
 
 Thus far the method of distributing current for 
 electric traction has been that by constant poten- 
 tial. That is to say, the pressure at the dynamo 
 terminals has remained constant, and the current in 
 amperes delivered to the moving cars has varied 
 as the requirements. This method as a whole has 
 thus far proved the most flexible, but with the in- 
 creasing distances to which our electric roads are 
 constantly reaching it is becoming less and less 
 satisfactory. We have already adverted to the 
 drop in potential at the further end of the line 
 where the current is used by the present methods. 
 This drop can be obviated in either of two wa} r s, 
 either by placing sufficient copper in the feeders to 
 reduce it to a bearable amount, or by increasing 
 the potential. If the potential be raised sufficiently 
 to operate a car properly at the further end of a 
 long line, it will be too high for the same car when 
 nearer the power station, so recourse is had to 
 additional copper. But the amount of copper that 
 can be thus used with an initial pressure of five 
 hundred volts is soon limited by commercial con- 
 siderations, beyond which it becomes more expen- 
 sive than to erect and operate another power station 
 at a distant point. Just how far it is profitable to 
 operate a road from a single station must be 
 decided for each particular case, but it is probably 
 within the truth to say that where the distance to 
 be reached exceeds six or seven miles it will be 
 cheaper to build a second power house than to put 
 sufficient copper in the feeders to render those 
 greater distances practicable. In the constant 
 potential method of distribution the varying 
 
182 ELECTRIC RAILWAY MOTORS. 
 
 demands for energy are met by a varying quantity 
 of current, yet our conductors, which are fixed in 
 size, are properly proportioned only for a given 
 current. For that particular current they are of 
 exactly the proper size ; but for any other current, 
 be it larger or smaller, the conductor used is not 
 the most economical ; it will contain either more 
 copper or less than that which can most econom- 
 ically carry it. If, however, we should use a con- 
 stant current, and vary the energy transmitted by 
 varying the electromotive force, we could propor- 
 tion our copper to that current once for all, and 
 since by the conditions imposed the current does 
 not vary in quantity, the size of our conductors 
 need not vary whatever the amount of energy they 
 are required to carry or whatever the distances to 
 be reached. Illustrations of this method of distri- 
 bution are seen in our arc light circuits. Many of 
 these already extend upward of 20 miles and carry 
 from 60 to 100 or more 2000 C. P. lamps, yet the 
 conductors on such circuits are no heavier than 
 would be necessary for a circuit 1 mile or 5 miles in 
 length carrying but a single lamp or 4 or 5. To 
 render the same sized conductor equally econom- 
 ical for the transmission of large amounts of energy 
 to long distances, it is only necessary to raise 
 the electromotive force correspondingly. Large 
 amounts of energy can thus be much more econom- 
 ically transmitted to long distances by the constant 
 current method than by the constant potential 
 method, the economy becoming particularly con- 
 spicuous where the demands are variable and where 
 the distances are also variable, as is pre-eminently 
 the case in electric traction. 
 
 On account of these and other advantages of 
 the constant current method of distribution many 
 
THE PERKY SYSTEM. 183 
 
 attempts have been made to adapt it to street rail- 
 way purposes. But there have been difficulties in 
 the way of its adaptation to this use which until 
 they were removed introduced greater objections 
 than were the benefits sought to introduce. The 
 writer, however, has invented a system which he 
 believes obviates all the difficulties (see Trans. Am. 
 Inst. Elect. Engineers for 1892) hitherto thought 
 to be inherent in the constant current method, and 
 which at the same time sacrifices none of the 
 advantages sought to be gained. His improve- 
 ment over previous methods consists simply in 
 supplying to the railway circuit the same device 
 by which the series arc light system was con- 
 verted from a failure to a commercial success, 
 viz., an automatic cut-out by which on the failure 
 of an operating device it is automatically cut out 
 of circuit. Without this invention the practica- 
 bility of even two or three arc lamps in series was 
 uncertain ; with it any number may be practically 
 operated. 
 
 Professor S. H. Short experimented quite exten- 
 sively a few years ago with the constant current 
 method of distribution for street cars, and had for 
 a time two roads in more or less successful opera- 
 tion one, about three miles in length, between 
 Huntingtou, W. Va., and Guyandotte, and the 
 other, of about the same length, in the city of St. 
 Louis. He had not conceived the idea of the 
 automatic cut-out, and found it impracticable to 
 operate more than three cars simultaneously on 
 his lines. He, however, demonstrated the econ- 
 omy and efficiency of the system up to its practi- 
 cal limit. With the addition of the cut-outs and 
 the other radical changes introduced by the writer 
 it is believe^ that the new system possesses all the 
 
 XJHIVERSITY 
 
184 ELECTRIC RAILWAY MOTORS. 
 
 flexibility of the multiple arc method with the 
 additional advantages of the series method, and 
 in recognition of these claims the Franklin Insti- 
 tute of Philadelphia recently awarded him the 
 John Scott legacy premium and medal. 
 
 This system may be briefly described as a 
 double trolley system, divided up into sections of 
 greater or less length, according to the headway of 
 the cars provided for. Each of these sections is 
 fed independently from a common feeder wire by 
 means of electromagnetic devices inclosed in 
 hermetically sealed boxes along the side of the 
 track very similar in design to those employed in 
 the Johnson-Lundell system described above. 
 They are not nearly so numerous, however, as in 
 the suburban districts, where the distances between 
 cars is great, not more than one or two to the 
 mile are required. In the cities, however, where 
 the headway of cars is much less, their number 
 must be increased proportionately. 
 
 But one car can operate on a section. If a car 
 runs onto a section already occupied, both cars 
 will become inoperative until one of the two pulls 
 down its trolley thus constituting this a perfect 
 automatic block system. All cars on the system 
 are in series with each other, and since the current 
 strength by which they are operated is invariable, 
 their speed may be checked on descending a grade 
 or in bringing them to rest by reversing the con- 
 nections. This reversal of the brushes converts 
 the motor into a dynamo, which, being in series 
 with the one at the power house, contributes energy 
 to the line to the last turn of the wheels. In this 
 way the energy absorbed in ascending grades or 
 in starting from rest is thrown back on the line 
 for use elsewhere, instead of being frittered away 
 
STORAGE BATTERY TRACTION. 185 
 
 in heat on the brake shoe, as in present methods. 
 The method of control of cars operated by this 
 system is ideally simple. There are neither corn- 
 mutated fields nor external resistances to be con- 
 sidered, so that with this system the advocates of 
 both methods of control join hands, since the 
 method involves the disadvantages of neither. In 
 the series system the car is started, speeded up, 
 slowed down and reversed by simply shifting the 
 position of the brushes on the commutator. The 
 equipment of the generating or power station is 
 also extremely simple, requiring for each unit 
 nothing more than a voltmeter, an ammeter and a 
 line switch by which the circuit can be closed or 
 opened, no rheostats, bus bars or complicated 
 switchboard systems being required. This system 
 is thought to be peculiarly applicable to long lines, 
 such as suburban and interurban lines, and it is 
 believed that the time is not far distant when its 
 advantages on such lines will be fully appreciated. 
 
 STORAGE BATTERY TRACTION. 
 
 A self-contained car or one that is self-propel- 
 ling would be an ideal were there not attendant 
 disadvantages of such a serious nature as to over- 
 shadow the advantages possessed. The storage 
 battery seemed to hold out such bright prospects 
 of success that many earnest efforts have been 
 made almost from the first invention of the stor- 
 age battery by Plante and its improvement by 
 Faure down to the present day. It, however, has 
 been a disappointment in every case, in this coun- 
 try at least, where it has been tried, notwithstand- 
 ing the fact that neither engineering skill of the 
 highest character nor expense has been spared to 
 
186 ELECTRIC RAILWAY MOTORS. 
 
 make it a success. The causes of these failures 
 are many and seem to be inherent in the battery 
 itself as at present constructed. We know of no 
 more efficient method of storing electricity * than 
 by means of lead plates. These are so heavy that 
 a street car equipped with sufficient battery capac- 
 ity for its successful propulsion must carry in this 
 form alone more weight than it is possible to put 
 upon it in the shape of passengers. The empty 
 car is therefore handicapped on starting out with 
 a non-paying load greater than that from which 
 it can expect to derive revenue. This means not 
 only additional expense for haulage, but is destruc- 
 tive to track and cars alike. Since at least two 
 sets of battery equipments must be provided for 
 each car, which will greatly exceed the cost of 
 motor equipment, the fixed capital investment 
 upon which interest must be earned is excessive. 
 Another disadvantage of the battery is that not 
 more than about seventy per cent, of the energy 
 put into it can be drawn out of it again for 
 use, and even this amount is available only when 
 the batteries are new and in good condition. 
 When they are old, the percentage of energy used 
 for charging that is available for use is very much 
 less than this, running down to fifty, forty, thirty 
 per cent., and even less. The deterioration of the 
 plates, too, is very rapid in street car work owing 
 to the jarring of the cars and the swash of the 
 liquid, causing a loosening of the active material, 
 its falling out and causing short circuits, resulting 
 
 * It is not electrical energy that is stored in the storage 
 battery, as is popularly assumed, but chemical energy. The 
 term " electrical storage " has come into such general use, 
 however, and it is so convenient, that with this explanation 
 I may use it without creating confusion. 
 
CONDUIT SYSTEMS. 187 
 
 in the destruction of the plates. The wear and 
 tear or depreciation account is, therefore, excessive, 
 and, taken altogether, experience has almost con- 
 clusively pointed to the inadaptability of the stor- 
 age battery to traction purposes. 
 
 The storage battery, however, permits of the 
 most economical speed control of any known, as by 
 commutating the cells into groups in series and in 
 parallel, by using some for separately exciting the 
 fields, while various other combinations are used 
 for feeding the armature, an ideally economical 
 speed regulation is obtained, somewhat similar to 
 that advocated by Mr. Leonard, but without the 
 multiplicity of apparatus or external resistances 
 used by him. 
 
 Should a lighter and more durable storage bat- 
 tery than the present type ever be invented it is 
 not unlikely that it would come into general use 
 for traction purposes, but with our present types 
 it seems exceedingly unlikely that it can make 
 much progress in this direction. 
 
 CONDUIT SYSTEMS. 
 
 The unsightliness of the overhead trolley and 
 its obtrusiveness in the streets are its chief objec- 
 tionable features. To overcome these many at- 
 tempts have been made to carry the wire under- 
 ground in a conduit similar to that used in cable 
 railways. It would seem, at first blush, a very 
 simple thing to place the trolley wire in such a 
 conduit and have it work at least as well as it does 
 overhead, for that is all that is asked of any con- 
 duit system, but difficulties have arisen that have 
 militated against the success of the conduit sys- 
 tem thus far that have brought it into disfavor. 
 
188 ELECTRIC RAILWAY MOTORS. 
 
 The chief difficulty, to my own mind, is the greater 
 expense involved in such a plant. It is but nat- 
 ural that parties having railway franchises should 
 desire to avail themselves of them by the least 
 expensive and most efficient means where those 
 two qualities are not incompatible. It so happens 
 that the overhead trolley does possess both of these 
 qualities, hence since there is no advantage to the 
 investor in putting the trolley wire below the sur- 
 face of the street, but, on the contrary, a disadvan- 
 tage in the way of greater expense, capital has 
 not had the incentive to investment in conduit 
 systems that have been offered by the overhead 
 trolley. In our larger cities, however, the public 
 is already clamoring for the burial of the wires, 
 and with this incentive many inventors are at 
 work endeavoring to devise a practicable conduit 
 system which shall not at the same time be too 
 expensive either in installation or in operation. 
 
 The chief difficulties to be overcome in conduit 
 work are to maintain an efficient insulation of the 
 trolley wires from the ground or conduit itself ; to 
 prevent the insulation of the trolley wire from 
 the trolley contact by dirt entering through the 
 slot ; from mechanical and electrical difficulties, 
 switches, etc. ; and to provide an efficient contact 
 between trolley and wire under conditions which 
 prevent the entrance of dirt into the slot. 
 
 The two best known examples of successful 
 conduit construction are the Siemens and Halske 
 and the Love systems, in both of which the prin- 
 ciple of the overhead trolley is followed closely. 
 The conductors, however, are not placed directly 
 beneath the slot, but off to one side, where they are 
 protected by the roof of the conduit from in-fall- 
 ing dirt, water or snow. The traveling contacts 
 
CONDUIT SYSTEMS. 189 
 
 are made of proper shape to reach around to the 
 conductors, with which they are brought into con- 
 tact when desired. In the Siemens and Halske 
 system, which has now been in successful opera- 
 tion for several years abroad, the conduit and slot 
 are at the side of the track. In the Love system, 
 which has been tried in Chicago and is now in 
 successful operation in Washington, the conduit is 
 in the center of the track. While these two sys- 
 tems differ considerably in details, they are the 
 same in principle, whicli is exactly that of the 
 overhead trolley, special attention being given to 
 the insulation of the trolley wire from its sur- 
 roundings, to the adequate drainage of the conduit 
 itself and to adapting the trolley to its new 
 requirements. 
 
 Other inventors liave endeavored to solve the 
 insulation problem somewhat on the same lines 
 as those adopted in the surface contact system of 
 Johnson and Lundell, namely, by dividing the 
 trolley wire up into short sections which are nor- 
 mally dead, but which are successively thrown 
 into electrical connection with the live feeder wires 
 as the trolley passes onto them, and thrown out of 
 connection with them as the trolley passes off 
 from them. By thus having only that portion of 
 the trolley wire actually in use active, the tendency 
 to leakage of current is of course greatly lessened, 
 but there is introduced in its stead a multiplic- 
 ity of switches upon whose proper working the 
 success of the system depends, which is of 
 course a source of weakness, or possible weak- 
 ness, scarcely less desirable of avoidance than 
 leakage itself. Great ingenuity has been dis- 
 played in designing systems on this plan, but none 
 of them has been in practical use long enough 
 
190 ELECTRIC BAIL WAT MOTORS. 
 
 to demonstrate beyond question its absolute practi- 
 cability. 
 
 Still another type of conduit known as the 
 closed conduit has been devised in which by vari- 
 ous means, usually by electromagnetic devices, 
 the passing car maintains a supply of current by 
 attracting to short surface conductors the live 
 conductors buried beneath the surface of the 
 street. Sometimes this contact is made by the 
 pressure of the car wheels or their flanges upon 
 spring contacts over which they pass, but in all 
 cases the methods of speed control are identical 
 with those employed on the overhead trolley 
 systems. 
 
CHAPTER XXL 
 
 THE MANAGEMENT OF STEEET RAILWAY MOTORS. 
 
 AT the outset of this chapter the author might 
 as well confess his inability to teach a novice, either 
 by letterpress or pen, how to actually manage an 
 electric street car in its various moods and whims, 
 if so they may be called. If he can impress upon 
 his readers at the outset that motors do not have 
 whims at all, and that the seeming irregularities 
 of their behavior are all due to definite causes 
 which are in most cases within the control of the 
 motor man, he will have made a good start. No 
 one from book reading alone can expect to step 
 full-fledged a motorman upon his car. There is 
 much, after all is told, that must be learned by 
 actual experience. For instance, the sound of the 
 motors often tells one much, and not only indicates 
 either that everything is all right and permits him 
 to continue on with confidence, or that something 
 is wrong, and, moreover, frequently indicates just 
 what is wrong, or so nearly so that the experienced 
 motorman need not look far to find the trouble, 
 whereas the novice might spend an hour or two 
 fruitlessly hunting for the fault. And this was 
 the moral intended to be taught by the little 
 anecdote at the beginning of this book. 
 
 We believe, however, that if one thoroughly 
 understands the construction of his apparatus and 
 the principles upon which it operates, the instruc- 
 
 191 
 
192 ELECTEIC RAILWAY MOTOBS. 
 
 tions which follow will well supplement a grow- 
 ing experience, and enable the conscientious 
 operator to avoid many difficulties, and to correct 
 them, when they do occur, the more readily. It 
 was with the object of leading up to the manage- 
 ment of the motor rather than of teaching it that 
 this work has been undertaken. It only remains for 
 us to give a little kindly advice, which it is hoped 
 the reader will by this time have been prepared to 
 understand. The remaining pages will therefore 
 partake more of the nature of those medical works 
 intended for family use than of the nature of a 
 technical medical treatise. 
 
 The first thing to keep in mind is to keep your 
 motor dry, for if it get wet the whole structure is 
 liable to give way burn out. The second word of 
 advice is to keep it clean, for thereby most of its 
 ills will be avoided. Water and dirt are the two 
 greatest enemies of the electric motor. The third 
 is, study the wiring of your car, so that you have 
 clearly mapped out in your mind the various con- 
 nections and their functions. This will enable 
 you to test out a fault which could not easily be 
 detected by the eye, and to locate it, at any rate, 
 within a given circuit. In giving this last advice 
 to the motorman the author is not unmindful of 
 the difficulty, nay, even the impossibility, of the 
 motorman's being able to trace out the wiring of 
 his car unassisted. To do this he must have the 
 full co-operation of those in authority ; and here 
 we have a word of advice to give to those in charge 
 of the rolling stock. 
 
 If a motorman or other employee of yours, hav- 
 ing in the performance of his duty to do with 
 your motors, wishes any information in regard to 
 the same which it is in your power to supply, 
 
MANAGEMENT OF RAILWAY MOTORS. 193 
 
 supply it fully and freely. In fact, it is your duty, 
 if you would have good service, to educate your 
 employee to the highest degree possible in his 
 duties. Do not be content to let him do things 
 with your machinery simply because you tell him 
 to, thereby making of him a machine which is 
 even more likely to get- out of order than the 
 inanimate machinery he has to handle ; but after 
 telling him what to do and what not to do try to 
 explain to him the reasons therefor, and the penalty 
 not to him, but to the machinery in his charge 
 of disobedience. Encourage him to ask proper 
 questions and all questions in regard to his 
 motors are proper ones and help him to become 
 an intelligent man ; for by so doing alone can you 
 get the best service, the most for your money. 
 
 The next advice to the motorman is that he 
 study the " habit " of his motors. Let him keep 
 his ears open to every sound until any variation 
 from the same would awaken him even if he were 
 asleep, for the sounds given out by the motor are 
 as surely an indication of its condition as is the 
 pulse of a human being of his state of health. A 
 variation from the normal sound is often the first 
 indication the operator may have of trouble with 
 his machines. If heeded at once, disaster ma} r be 
 entirely averted where it might otherwise almost 
 surely follow. 
 
 If the ear detects anything unusual, the car 
 should be stopped at once and a careful examina- 
 tion made to detect if possible the cause. If it 
 cannot be located at once, it may be well to cut out 
 first one motor and then the other, running the 
 car carefully for a short distance with each sepa- 
 rately, if the grades are such as to make this safe. 
 In this way the trouble may be located by sound 
 
194 ELECTRIC RAILWAY MOTORS. 
 
 in the motor in which it exists, and thus its specific 
 nature and exact location be more easily traced. 
 
 The most common diseases of electric motors of 
 any kind, street car motors included, their symp- 
 toms and remedies, are the following : 
 
 First of all comes 
 
 SPARKING AT THE COMMUTATOR. 
 
 A properly constructed motor in normal work- 
 ing condition should not spark at all, or at least 
 not noticeably. Sparking may therefore be re- 
 garded more as a symptom of a disease than as 
 a disease. The sparking of the commutator is 
 often the first indication that the operator has that 
 everything is not as it should be. When sparking 
 is observed, therefore, an investigation should be 
 made at once to determine its cause and to rectify 
 it on the spot, if possible, or, in case it is not pos- 
 sible to do this, to run the car into the shop for 
 repairs. Sparking should be stopped for its own 
 sake, however, for if allowed to continue it will 
 corrode the commutator blocks, and in this way 
 increase itself until the commutator is so far gone 
 as to require renewal. 
 
 Crocker and Wheeler, in their most excellent 
 little work on "The Practical Management of 
 Dynamos and Motors," assign fourteen different 
 causes for sparking, not all of which, however, 
 need concern us here. The following, however, 
 are those which especially concern the motorman : 
 
 First Cause. Armature carrying too much cur- 
 rent. This means that the motor is being over- 
 worked. The motorman need not be alarmed if 
 his motor sparks some on ascending a heavy grade, 
 for that is rather to be expected, especially if the 
 
SPARKING AT THE COMMUTATOR. 195 
 
 load be at the same time heavy. The remedy for 
 this, of course, is to save your motor as much as 
 possible by gaining momentum before reaching a 
 grade, and then maintaining a uniform slow speed 
 until the grade is passed. A motor that sparks on 
 ascending a grade should never be stopped on the 
 grade, if it can by any possibility be avoided, as 
 on starting again the work it will be called upon 
 to do will be many times that which it ought to 
 do, and disastrous results may follow. 
 
 But the sparking from overload may not always 
 be due to the excessive useful work the motor is 
 performing. It may be due to the striking of the 
 armature against the pole pieces, to the binding of 
 the armature shaft in its bearings, to a bad short 
 circuit or to the grounding of the motor on the 
 frame. Any of these latter causes, if active, are 
 likely to cause sparking when the motor is not 
 doing much apparent work, and this fact will help 
 to distinguish which of the two classes of troubles 
 causes the overloading. The general indication 
 that the sparking is due to overload is the over- 
 heating of the whole armature. If this overload 
 is due to frictional causes, they may be detected 
 by examination first of the bearings, which will be 
 unusually hot if the trouble lies there, and second 
 by an examination of the armature. If friction is 
 indicated there, the trouble is extremely serious, 
 as in overwound armatures (viz., those on which 
 the coils are wound on the surf ace as distinguished 
 from the iron-clad armatures, in which the coils 
 are placed in slots on the surface, and therefore 
 beneath the surface) continued friction is sure to 
 wear off the insulation and cause a burn-out of the 
 armature. In this case the motor man should 
 exercise his mechanical ingenuity, and so center 
 
196 ELECTRIC RAILWAY MOTORS. 
 
 his armature that it will not strike the fields at 
 all. 
 
 Second Cause. Brushes not set at the neutral 
 point. We have seen that there are two positions 
 in every revolution of a coil in which it generates 
 no electromotive force. In a two-pole machine 
 these two positions are diametrically opposite each 
 other, and in a four-pole machine they are 90 from 
 each other. These points are called the neutral 
 points. If the brushes bear at exactly these points, 
 there should be no sparking, but if they bear at any 
 other points on the commutator the brushes will 
 pass off from bars that have an electromotive force 
 which is greater the further the brushes are re- 
 moved from the neutral points, and it is this electro- 
 motive force that causes the sparking. We have 
 seen that as the current supplied to the motor 
 changes, so do the positions of these neutral points 
 in some machines, so that it is necessary in such 
 to move the brushes back and forth as the load 
 varies. It is this change of the positions of the 
 neutral points that causes the sparking due to over- 
 load, just described. But the ampere turns on 
 street railway motors on the armatures and fields 
 are so disposed, the one predominating over the 
 other to such an extent that the load may vary 
 within wide limits without perceptible change of 
 the neutral points. The brushes are therefore 
 usually fixed once for all at the proper places, so 
 that the sparking, if due to the brushes, is probably 
 due to one or more of the following causes rather 
 than to wrong position : 
 
 a. Commutator rough, eccentric or has one or 
 more high bars, or what are termed fiats. To de- 
 tect these the commutator should be examined 
 while at rest for roughness and also for eccen- 
 
SPARKING AT THE COMMUTATOR. 197 
 
 tricity. This latter can be detected better, how- 
 ever, by watching the motor carefully when slowly 
 in motion. If the brushes alternately rise and fall, 
 the commutator is not centered properly on the 
 axle. When running fast, the whole armature 
 may chatter. High bars or flats the latter being 
 flat surfaces on the commutator are best detected 
 while the motor is running by resting the finger 
 nail against the commutator. Any irregularity of 
 surface will thus be readily detected. These are 
 all difficulties with which the motorman would 
 better not fool, for fear of increasing the trouble. 
 His duty will have been done if he cuts out this 
 motor a'nd proceeds to the car barns at once with 
 the other motor. 
 
 b. Brushes make poor contact with the com- 
 mutator. Close examination will show that the 
 brushes touch only, at one corner or only in front 
 or behind, or there is dirt on the surface of contact. 
 The remedy for this trouble readily suggests itself. 
 Clean the commutator and replace the brushes, 
 being careful that they have ample bearing on the 
 commutator. Occasionally the fault lies in the 
 brush itself : it may be extremely hard, or have 
 extremely hard spots in it which wear away less 
 readily than the remainder of the carbon. The 
 remedy for this is to throw away such brushes and 
 replace them by new ones. 
 
 Sometimes a good brush has worn unevenly 
 through grit on the commutator, and only needs 
 dressing down to give good service. This is best 
 done by drawing a strip of sandpaper back and 
 forth between it and the commutator while the 
 brushes are pressed down. This will dress their 
 bearing surfaces to fit the commutator properly. 
 
 Third Cause. Short-circuited coil in armature. 
 
198 ELECTRIC RAILWAY MOTORS. 
 
 This may be caused by a little carbon dust or 
 other conducting material getting in between two 
 of the commutator bars or between the connections 
 leading to the bars. Perhaps the best indication 
 of a short-circuited coil is the increase of heat in 
 that particular coil or coils on the armature. If 
 in feeling around the surface of the armature one 
 or more coils appear much hotter than the rest, a 
 short-circuited coil is to be suspected, and a care- 
 ful examination of the commutator and its connec- 
 tions should be made to discover the cause, and if 
 found it should, of course, be removed. If the 
 cause be removed early in the trouble it may have 
 done no harm, but a short circuit is very likely to 
 cause a burn out of the armature. If the trouble 
 is in the commutator or its connections, its remedy, 
 if taken in time, is exceedingly simple, but the 
 short circuit may be in the armature itself, and if 
 so cannot be corrected by the motorman. If he 
 have reason to suspect that it exists in the arma- 
 ture, his only recourse is to cut that motor out and 
 proceed to the stables with the other motor. The 
 short-circuited coils will there have to be replaced 
 by new ones. 
 
 The same effect may be produced exactly by a 
 "ground" on the armature, which together with 
 the intentional ground forms a short circuit. The 
 indication, aside from the unduly heated coil, is 
 very bad sparking occurring at intervals. 
 
 Fourth Cause. Broken circuit in armature. 
 This is usually indicated by violent flashes like 
 the preceding, but unaccompanied by the heating 
 of the coil, the flashing, as before, occurring at 
 intervals when the commutator segment belonging 
 to the broken coil passes under the brushes. The 
 flashing in this case will be very much worse than 
 
MOTOR STOPS OR FAILS TO START. 199 
 
 in the preceding case, even when the motor is run- 
 ning slowly. Examination should be made to see 
 that the flash is not due to a high bar or dirt or 
 other insulating material on one of the bars. If 
 not due to either of these, the break is most likely 
 to be found in the connections between the arma- 
 ture coils and the commutator bars. If it be due 
 to a broken commutator connection, a temporary 
 remedy is found in connecting the disconnected 
 bar with its neighbors by driving in between the 
 bars a piece of copper wire so as to short-circuit 
 the broken coil. If the break be in the coil itself, 
 rewinding is probably necessary, and the motor 
 should be cut out of circuit at once. 
 
 Fifth Cause. Chatter of brushes. The com- 
 mutator sometimes becomes sticky when carbon 
 brushes are used, causing friction, which throws 
 the brushes into rapid vibration. When this is 
 the case, it is readily detected by the tingling or 
 jarring sensation produced on the hand when 
 lightly placed on the brushes. At the first oppor- 
 tunity the commutator should be cleaned with a 
 rag or waste and oiled slightly. This will stop the 
 trouble at once. 
 
 Sixth Cause. Flashing all around the commuta- 
 tor. This may be due either to particles of car- 
 bon between the bars or to broken coils, or both, 
 and the remedy is that recommended before for 
 such troubles. If, after cleaning the commutator 
 and no breaks are found, the flashing continues, 
 the motor should be disconnected and the car run 
 into the shops for overhauling. 
 
 MOTOR STOPS OR FAILS TO START. 
 
 First Cause. Great overload. 
 
 Second Cause. Very excessive friction due to 
 
200 ELECTRIC RAILWAY MOTORS. 
 
 shaft, bearings or other parts being jammed, or 
 armature touching pole pieces. In either of these 
 cases the armature would most certainly burn up 
 were it not for the fuses, which are intended to 
 melt and break the circuit before sufficient heat 
 can be generated in the armature coils to do dam- 
 age. A careful examination should be made to 
 see what the trouble is, and it should be rectified, 
 if possible, at once. 
 
 Third Cause. Circuit open, due to : (a) Safety 
 fuse melted, (b) connection to motor broken or 
 slipped out of binding post, (c) brushes not in con- 
 tact with commutator, (d) hood or canopy switch 
 open, (e) broken or imperfect contact in control- 
 ling rheostat, (/') failure at generating station. 
 Trouble due to any of these causes is indicated if 
 the car fails to move when load is removed or 
 when load is light. In such cases the current 
 should be turned off immediately at the hood 
 switch, and the break looked for as indicated. 
 The lamp circuit should be turned on. If lamps 
 burn or other cars are found to be moving, the 
 trouble does not lie with the generating station. 
 
CHAPTER XXII. 
 
 SPECIFIC DIRECTIONS TO MOTORMEN. 
 
 SOME of the electrical companies furnish, and 
 all of them should furnish, a list of empirical rules 
 for the management of their motors. It is too often 
 that the motormen never see these rules at all, but 
 receive them by word of mouth from the foremen 
 or whomever they look to for instructions. It is 
 very desirable that each motorman should have 
 these rules in convenient form for reference, and 
 they are herewith reproduced. They are essen- 
 tially the same for all makes of motors, and are as 
 follows : 
 
 1. In taking a car out of the barn where it has 
 been standing with trolley off put on the trolley, 
 place handles on controlling stand and see that 
 the current is off ; then throw in the hood switch. 
 
 2. On most modern equipments there are two 
 levers one for reversing, the other for controlling 
 the current and speed of car. In starting move 
 the controller Quickly from right to left until you 
 feel the contact touch the first point, and then 
 slowly move it farther until the car moves. 
 Allow the car to gain a little headway, and then 
 move on as the car gains headway till the lever is 
 as far as it will go. Usually the controller switch 
 should be allowed to rest on each successive notch 
 long enough for the car to gain the headway due 
 to that combination before it is moved to the next 
 
 901 
 
202 ELECTRIC RAILWAY MOTOES. 
 
 notch. In the Westinghouse control the first 
 notch throws the whole resistance and the two 
 motors in series. The second notch cuts out half 
 the resistance, and the third notch the whole 
 resistance. The' fourth notch throws both motors 
 in parallel with one another and each in series 
 with half the resistance. The fifth notch cuts out 
 the resistance of one motor, and the sixth or last 
 notch cuts out the resistance of the other motor, 
 leaving them in parallel, which gives the greatest 
 speed and highest efficiency. In this arrangement, 
 which is a series-parallel arrangement, the first 
 two notches are merely starting points, and the 
 handle should only be allowed to rest momentarily 
 on each. The third is a good slow speed running 
 notch. To obtain greater speed or more pressure 
 the handle should be moved slowly, but con- 
 tinuously, from the third to the fourth notch. 
 This and the next notch should be used only 
 momentarily, not steadily. In this, as with all 
 other arrangements, the last notch should be used 
 for heavy work or fast running. 
 
 3. Before leaving the car barns, however, the 
 motorman should examine carefully the grease 
 cups and see that they are filled. Examine brushes 
 and motors, making sure they are in fit condition 
 to begin the day's work. 
 
 4. With hood switches open, try the reversing 
 lever and controller lever to make sure they are in 
 good working order. Then, with controller lever 
 off, close hood switches ; note that trolley is on 
 the line and that you have a current by lamps 
 being lighted. Now move controlling lever around 
 slowly. If car moves off, all is probably right. 
 If car refuses to move after controlling lever is 
 moved to last notch, turn lever back to "off" 
 
UNIVERSITY 
 
 SPECIFIC DIRECTIONS T 
 
 point, get down from car and note that rail is 
 clean, that the fuse plug is in place, that the ground 
 wire from motors is attached to truck frame and 
 that the cut-out switches for both motors are 
 closed. If the above conditions are fulfilled, then 
 examine car wiring for a broken wire or a loose 
 connection. Failing to find the trouble, report to 
 the car starter or person in charge. 
 
 5. If the General Electric Company's series-par- 
 allel controller, form K, is used, the motorman's 
 attention is directed chiefly to noting that every- 
 thing about the switches and contact points and 
 cable connections in the controller are in good 
 order. Two switches are located in the lower part 
 of these controllers. The one to the right when 
 thrown up as far as it will go cuts out motor No. 
 1, or the motor nearest the fuse box ; the switch 
 to the left when thrown up cuts out motor No. 2, 
 or the one farthest from the fuse box. A small 
 quantity enough only to form a very thin film 
 of vaseline should be used on the contact strip in 
 all controllers to prevent any cutting or wearing. 
 
 In both controllers of this type the upper cut- 
 cut plug cuts out the same motor, which is desig- 
 nated as No 1. The motorman should find out 
 which is motor No. 1, so that he will be able to 
 remove the proper cut-out in case of trouble with- 
 out experimenting. It is recommended that the 
 number of each motor be painted on it where the 
 motorman can see it. These cut-outs are designed 
 to be used only in case of trouble. When either 
 plug is removed, the starting of the car is delayed 
 until after the controlling handle has passed the 
 third notch. Hence, in starting with one cut-out 
 plug removed) throw the handle directly to the fourth 
 notch. 
 
204 ELECTRIC RAILWAY MOTORS. 
 
 6. The reversing switch determines the direction 
 in which the current shall flow through the motor 
 fields when it is turned on by the controlling 
 handle. In the Westinghouse apparatus, for in- 
 stance, the reversing switch has three notches. 
 The central one, at which the handle is placed, 
 cuts off all current from the motor fields, so that 
 in this position operating the controlling handle 
 has no effect. When it is desired to start the car, 
 first see that the controlling and reversing handles 
 are at the " off" position ; second, close canopy or 
 hood switch ; third, throw the reversing switch 
 forward or backward, according as it is desired to 
 go in one direction or the other; fourth, throw the 
 controlling handle, and the car will start. 
 
 Throwing the reversing switch entirely over re- 
 verses the direction of the current in the fields, 
 but this should never be done unless the control- 
 ling handle is at " off," otherwise the rush of cur- 
 rent through the coils which will be due to the 
 counter electromotive force of the motor added to 
 that of the line and that due to the discharge of 
 the magnetism of the fields will be so great as to 
 endanger the coils. 
 
 7. When throwing the controller arm to "off," 
 the movement should be rapid, especially in pass- 
 ing the first point, so as to avoid drawing an arc. 
 
 8. If the controlling arm should go hard or 
 stick, do not force it, as this would only make 
 matters worse. Pull down the trolley or open the 
 canopy switch, or, better, do both, then remove 
 cover of controller. An inspection will probably 
 show that the trouble is due to want of oil, rough- 
 ness of contacts, or something of this kind, which 
 can easily be corrected. 
 
 9. Never run with trolley in wrong direction 
 
SPECIFIC DIRECTIONS TO MOTORMEN. 205 
 
 except in cases of extreme necessity, and then 
 very slowly. 
 
 10. Never stop car so that the trolley wheel will 
 be directly under a circuit breaker in the line. 
 
 11. Always have current shut off when trolley 
 wheel is passing over a circuit breaker in the line, 
 else the wheel in passing off will draw an arc, 
 which tends to damage both line and wheel. 
 
 12. Never leave car without removing the con- 
 troller handles and opening canopy switches. 
 
 13. Never reverse the motors when the car is 
 running except in cases of extreme necessity, such 
 as avoiding a collision or to save a life. In these 
 cases reverse the current in the controller, keeping 
 the handle on the first or second notch until the 
 car begins to move backward. Remember that 
 if reversal takes place with controller at too high 
 a notch the wheels will lose their adhesion to the 
 rails and spin around backward, and the car will 
 not stop so quickly as if they kept revolving in a 
 forward direction. 
 
 14. Go around curves slowly, using third notch. 
 
 15. When entering a turn-out or curve, the 
 conductor should be on the rear platform and 
 should have the trolley rope in hand. 
 
 16. Slow up at all street and railway crossings, 
 at all rough places in the track, and pass overhead 
 switches with the current thrown off. 
 
 17. It is better not to stop on very heavy grades, 
 or on or just before entering curves, if it can be 
 avoided, on account of the extra current required 
 for starting up again under such conditions. 
 
 18. Ordinarily in stopping the car always release 
 the brake somewhat, just before the car comes to 
 a dead stop. Do not let the brake fly, or kick the 
 brake dog off, for if you do the armature will take 
 
206 ELECTRIC RAILWAY MOTORS. 
 
 up the lost motion in the gears, and when starting 
 again it will necessarily be with a jerk. This is 
 unpleasant to the passengers and hard on both 
 motors and gears. 
 
 19. Do not keep brakes on in rounding curves. 
 This has been advocated, but is wrong and involves 
 a useless waste of power at the worst possible time. 
 It is one of the commonest and worst mistakes 
 motormen make. It is well to have the brake in 
 hand so that it can be instantly applied if neces- 
 sary, but it should be entirely " off." 
 
 20. Motormen should never run the car when 
 the trolley is off, especially down grade, for if the 
 brake should fail he could not reverse. 
 
 21. In descending a grade it is best to run 
 slowly, for should it be necessary to stop suddenly 
 it would be impossible to do so if the speed were 
 high. 
 
 22. If, in wet weather, when climbing a grade 
 the wheels slip, gradually work the controller arm 
 toward the first point, throwing it to the position 
 of " off" if necessary, until the wheels get a grip, 
 then work the arm gradually over toward " full 
 power" again. 
 
 23. In applying brakes on down grade be sure 
 not to allow the wheels to get to slipping, for 
 when they once commence to slip or " skid " they 
 are of veiy little use in stopping the car. Many 
 accidents have occurred in this way. This pre- 
 caution is especially necessary where stops are 
 made on a descending grade. Should the wheels 
 begin slipping, however, better let the car run 
 faster for a few moments until they get hold 
 again, and then apply the brakes gradually until 
 the car is under control. 
 
 24. Run slowly through flooded places, if possi- 
 
SPECIFIC DIRECTIONS TO MOTORMEN. 207 
 
 ble, with current cut off. When examining motors, 
 never allow water to drip from clothing or hat 
 into the motors. 
 
 25. If car won't start on dry or dirty rail, put 
 controller arm on first or second point and rock 
 the car. If this fails to accomplish the purpose, 
 have conductor take a piece of wire or switch 
 stick and rub one end of it against the rear tread 
 of the wheel while the other end is pressed against 
 the rail. In case an uninsulated wire is used, 
 break contact at the wheel first, keeping the other 
 end against the track, else a shock will be received. 
 
 26. Never attempt to put in a new fuse unless 
 canopy switch is open or the trolley is off ; other- 
 wise you may get a shock and damage the fuse 
 connections also. 
 
 27. Should it be found impossible at any time 
 to start the car, try the following until the trouble 
 is located : 
 
 a. If there is no evidence of current, notice 
 other cars. If they are all right, the trouble is in 
 your own car. 
 
 b. Throw on lamp circuit. If the lamps light 
 up, the trolley and ground wires are all right. 
 Now work controller, and if the lights go down or 
 out the trouble is probably due to poor contact 
 between the wheels and the rails (try 25), or the 
 section of track on which the car is standing may 
 be " dead." Use a longer wire and connect wheel 
 with another rail, as in 25. 
 
 If lamps do not light, examine lamp fuse box to 
 see that fuse is not blown, and make sure that 
 ground connection is not broken. Make sure that 
 lamps have good connection in the socket. If 
 they still fail to light, you may be reasonably sure 
 the power is off. 
 
208 ELECTRIC RAILWAY MOTORS. 
 
 c. Ascertain whether the fuse has been blown. 
 If so, throw canopy switch and put in new 
 fuse (26). 
 
 d. See that both motor cut-outs are in place. 
 
 e. Try both controllers, and if one works the 
 trouble is probably due to poor contact in the 
 other. In this case throw canopy switch, remove 
 the cover of the controller and examine the con- 
 tact blocks to see that they all make proper 
 contact. 
 
 /. Examine the brushes of the motors to see 
 that they are not broken, and that they make good 
 contact. 
 
 28. In case current is shut off at station for any 
 reason while the car is running, bring controller to 
 " off " position immediately. Then turn on light 
 circuit, and wait until the lamps light up ; when 
 they have reached their usual brilliancy, but not 
 before, start the car. The reason for this precau- 
 tion is that, should you turn the controller far 
 enough to start the car before the full current was 
 on, there would be little or no counter electro- 
 motive force generated to keep back the rush of 
 current when it did come, and your armature 
 might be injured either by heat or by the sudden 
 jerk that would result. 
 
 29. In case the brakes of a car fail to operate 
 there are two methods of stopping the car by the 
 use of the motors. The first consists in reversing 
 the direction of the current in the motor fields as 
 follows : 
 
 a. See that the controlling handle is at " off." 
 
 b. Reverse the reversing switch. 
 
 c. Throw the controlling handle around to the 
 first or second notch never beyond the third 
 notch, unless the fuse blows. In that case (West- 
 
SPECIFIC DIRECTIONS TO MOTOEMEN. 209 
 
 inghouse) move the handle around to the last 
 notch and leave it there. This converts the motor 
 into a generator and it will come -to a stop if on 
 level, or if on a grade will slacken up. In other 
 makes (Short) the simple pulling over of the 
 reversing lever after the controlling lever is 
 turned to " off " will accomplish the same thing. 
 
 The second method will operate successfully 
 whether the trolley is off or on the wire. It is as 
 follows : 
 
 a. Place controlling handle at " off." 
 
 b. Throw canopy switch to " off." 
 
 c. Reverse the reversing switch. 
 
 d. (Westinghouse.) Throw controller handle 
 around to last notch and leave it there until the 
 car stops. The step c converts Short motors into 
 generators. The additional step, d, is required in 
 Westinghouse motors. 
 
 When cars are running away downhill, the 
 method of short-circuiting the motors on them- 
 selves and thereby converting them into generators 
 is recommended as a last resort. 
 
 30. In case a motor bucks or flashes, examine 
 brush holders, and if they are covered with dirt 
 or mud, open canopy switch and clean them. A 
 loose joint in the circuit between the brushes and 
 the field will almost invariably produce flashing ; 
 trace circuit carefully and find it. See that the 
 spring is tight and that there is no dirt coating on 
 the bearing surface of the brush. 
 
 31. If the trouble is not found with the brush 
 holder, and motor has a peculiar smell like burned 
 rubber or shellac, wait for the next car to push 
 her in. 
 
 32. Motormen should always have a wrench 
 on car to tighten up a loose nut, and should be 
 
210 ELECTRIC RAILWAY MOTORS. 
 
 constantly on the lookout for troubles of this 
 kind. 
 
 33. Always report to inspector any trouble with 
 track, such as " dead " rail, or of trolley wire, such 
 as break of line or insulator, etc., and any unusual 
 noises of motors, having first, however, endeavored 
 to account for these latter yourself. 
 
 34. When you desire to run at slower speed and 
 controller is full on, it is usually considered better 
 to first pull it clear back to starting point and then 
 back to position you think will give the desired 
 speed. 
 
 35. Never pull reversing lever over while con- 
 troller is on. If you do, you are likely to blow the 
 fuse or burn up the motor, in either case losing 
 control of your car. 
 
 36. If in running along you feel the car sud- 
 denly let up, throw controller off and ascertain the 
 cause if you can. It may be the trolley is off, 
 passing a trolley break, a fuse blown or current 
 cut off at the power house. 
 
 37. If you do not find any trouble, try to start 
 again. If the car does not move, proceed as 
 directed under such circumstances. 
 
 38. Do not run over sticks, wire or other ob- 
 structions on the track, as they are liable to get 
 entangled in the motor. Get down and remove 
 them. 
 
 39. If paving blocks or other projections stick 
 out above the pavement, slow up and be sure the 
 motor will pass over without touching before 
 attempting to pass. Of course you will remove 
 the obstruction, if possible. 
 
 40. In case of the repeated blowing of the fuse 
 without apparent cause, pull down your trolley 
 and wait to be pushed in. 
 
SPECIFIC DIRECTIONS TO MOTORMEN. 211 
 
 41. The proper handling of a car on a curve is 
 perhaps the most difficult task that the new 
 motorman has to learn. A good rule is the follow- 
 ing: In approaching a curve cut off your con- 
 troller, and bring the car down to a slow walk be- 
 fore entering, and have your brake in hand, but 
 free, unless it be down grade. This will let the 
 car run into the curve easily and without shock. 
 As soon as you feel that the car is fairly on the 
 curve apply sufficient current to carry the car 
 around the curve at about the same rate of speed, 
 cutting it off again just before leaving the curve. 
 This will allow the car to take the tangent with 
 the least possible shock. 
 
 Always bear in mind that anything that causes 
 the car to jerk is wrong. 
 
 42. If your car leaves the track, do not attempt 
 to run her back with the current until you are 
 sure she can roll freely without jamming. Move- 
 ment of the switch when the wheels cannot turn, 
 or are not turning freely, is likely to cause trouble 
 both with the motor and with the switch. 
 
 43. Avoid carelessness. Do not allow any metal, 
 viz., your oil can, etc., to touch brass screws on 
 motor boards unless the trolley is off the wire. 
 Do not handle the screws unless the trolley is off 
 or your person touches nothing but dry wood. 
 
 44. When examining the motor while the car is 
 in motion, face the rear of the car, or so place 
 yourself that any jerk as in sudden stopping will 
 not pitch you into the machinery. 
 
 45. Whenever the trolley leaves the wire the 
 conductor should signal the motorman to stop, 
 and then, after replacing the trolley, he should 
 signal to go ahead. The motorman should bring 
 controller to " off" position as soon as the trolley 
 
212 ELECTRIC RAILWAY MOTORS. 
 
 jumps and keep it there until the conductor sig- 
 nals to proceed. 
 
 46. If you notice any loose motion about the 
 trolley, or if it leaves the line frequently, or if, 
 when running fast on a straight track, there is any 
 flashing between the trolley and the wire, report 
 the same at once. 
 
 47. Remember that the trolley wheels need oil- 
 ing. This should be done as often as necessary. 
 The oil, especially in cold weather, should be of a 
 quality that will not become gummy or sticky. 
 
 48. Watch your track joints when going toward 
 a station. If there is sparking ahead of you at 
 the joints, the rail, connections are broken. If the 
 car suddenly gathers speed after passing any point, 
 or if when the lights are on they become very dim 
 and then suddenly brighten up, a broken or loose 
 track connection is also indicated. Report the 
 fact and place promptly. 
 
 49. Observe carefully whether the car takes her 
 natural speed for all positions of the switch, and 
 if not report trouble, or, better still, find it your- 
 self and correct, if possible. 
 
 50. If motor or car seems to work hard, feel of 
 bearings ; if one or more are hot, apply oil and 
 watch frequently; if heat increases, the car should 
 be run in and inspected. 
 
 51. If journals squeak, it means that they are 
 running dry and require oil. 
 
 52. When storing your car in the house for the 
 night, remove the trolley from the wire, cut out 
 the safety switch, turn the reverse lever so that 
 the car will be ready to run out. Take off the 
 levers and place them on the hook in the office 
 provided for them and marked by the number of 
 the car. 
 
CHAPTER XXIII. 
 
 INSTBUCTIONS TO INSPECTORS AND SUPERINTEND- 
 ENTS. 
 
 UPON you depends, more than upon anyone else, 
 the success or failure of any electrical system that 
 is placed in your hands, provided, of course, the 
 system in question is a fairly good one. Cases are 
 not unknown where a given electric system has 
 proved a failure under one superintendent and 
 made to work satisfactorily in every way by his 
 successor. The reverse is also often the case :*that 
 a success has been changed to failure by the trans- 
 fer of the management from the hands of a com- 
 petent man to those of one unqualified for this 
 most important position. The first requisite in an 
 inspector or superintendent is that he shall be 
 familiar with every detail of the system with 
 which his cars are equipped. If it is important 
 that the motormati shall be familiar with his appa- 
 ratus, it is much more important that his superiors, 
 from whom he receives instruction, should know it 
 also and in a broader sense. You must remember 
 that the motorman is largely what you make him. 
 He comes to you, perhaps, an untrained hand ; 
 perhaps, what is still worse, he has had instruction 
 on another line by a superintendent who was incom- 
 petent or careless, and has thereby acquired habits 
 which he must first unlearn. 
 
 You must realize that as you are responsible to 
 
 213 
 
214 ELECTRIC RAILWAY MOTORS. 
 
 your company for the proper working of the road, 
 so you must hold those under you responsible to 
 yourself. Your reputation and success are there- 
 fore largely dependent upon the fidelity and ability 
 of those whose training is in your care. Appre- 
 ciating this, you will first train yourself. Procure 
 from the company w r hose apparatus you are using 
 full instructions as to the handling of their ma- 
 chinery, together with blue prints showing the 
 wiring and connections of each individual circuit 
 connected with the electrical equipment of your 
 system. If not an electrician yourself, you should 
 call in someone who is, and who can and will go over 
 with you every detail of your system, and explain 
 the whys and wherefores of everything connected 
 with your plant. Try to understand everything 
 intelligently, and then try your hand at imparting 
 this knowledge to the mptormen, in w r hose hands 
 your reputation and success so largely lie. It is 
 the experience of those who have tried it that the 
 best way to learri a thing accurately one's self is by 
 trying to teach others what you partly know your- 
 self. This is true in mathematics, it is true in 
 science in general and it is true in the car stables, 
 and ,the superintendent who tries most to impart 
 knowledge to those under him will in a short while 
 outstrip in knowledge him who perhaps at first 
 knew more, but who through a mistaken idea of 
 the dignity or importance of his position has kept 
 his knowledge to himself. 
 
 The various means by which he himself has 
 gained his knowledge should as far as possible be 
 placed at the disposal of his employees, and they 
 should be encouraged in every way to avail them- 
 selves of them to the fullest extent. In fact, a 
 motorman who will not avail himself of such 
 
TO INSPECTORS AND SUPERINTENDENTS. 215 
 
 opportunities when offered is an unsafe man to 
 trust with a car. On some roads the plan has been 
 successfully adopted of furnishing each motorman 
 a diagram of the connections that are being made 
 as the handle of the controlling lever is moved from 
 point to point. On this diagram are also given a 
 few of the most important instructions, and these 
 instructions are supplemented by verbal ones from 
 time to time as occasion requires. Some roads 
 also provide a reading room for their employees, 
 where a few standard works of reference on elec- 
 trical subjects, and the street railway and electrical 
 papers, are kept on file. This is an excellent plan, 
 and another one is to hang upon the wall of the 
 car house or other convenient place large diagrams 
 of the motor connections and wiring circuits of 
 the car. If equipments of more than one system 
 of control or make are used on the line, each should 
 be similarly represented, so that the differences 
 will be apparent to those who are to manage them. 
 These diagrams might with profit be drawn to half 
 size, or even larger, and in order that the different 
 circuits may be the more readily distinguishable, 
 they should be designated by different colors and 
 the various parts of the equipment lettered for 
 ready reference. These should be hung where the 
 motormen are most apt to congregate when not on 
 duty on their cars, so that they may discuss them 
 at their leisure. 
 
 A spirit of emulation among the motormen as 
 to the best care of the equipment of their cars and 
 fulfillment of schedule time should be fostered, 
 and to this end a motorman should be kept on the 
 same car as much as possible. That car should, 
 as far as possible, be considered his own, and he 
 should be held responsible for its record. Nothing 
 
216 ELECTRIC RAILWAY MOTORS. 
 
 is so subversive of effective service as the frequent 
 change of assignment of cars. No motorman can 
 be held responsible for the monthly record of a 
 car which has been handled by a dozen others 
 beside himself, nor can he take a personal pride in 
 its condition at the end of the month under such 
 conditions. 
 
 Mr. P. P. Sullivan of the Lowell and Suburban 
 Street Railway Company, in speaking on this sub- 
 ject at a monthly meeting of the Massachusetts 
 Street Railway Association, said : " In addition to 
 creating an interest among the men, and in fact 
 to help create such interest, we have prizes for the 
 motormen whose cars have had the best records in 
 point of expense, delays, etc., and in this manner 
 we are also enabled to find out from the regular 
 men who the best relief men are. Motormen are 
 given printed forms which enable them to call the 
 attention of the night foreman to certain things 
 which may appear wrong, and such form is coun- 
 tersigned by such foreman and forwarded to the 
 superintendent. All loss of mileage or taking off 
 of cars is reported directly to the manager's desk, 
 who exacts an accounting for the cause from the 
 superintendent. By following the above methods 
 we have been enabled to adopt a standard of car 
 mile expenses, and the different foremen are given 
 to understand that if the expenses are kept below 
 such a figure they may expect a present at the end 
 of the fiscal year." 
 
 He further says : " We assume that a man be- 
 fore taking charge of a car is absolutely ignorant, 
 has no interest in the apparatus, and we aim to 
 teach him, we endeavor to excite his interest and 
 curiosity, so that he will look out for his motors, 
 inquire for certain motors, create a rivalry so that 
 
TO INSPECTORS AND SUPERINTENDENTS. 217 
 
 a man will boast of his record ; and we have such 
 instances. 
 
 "In the car house skilled mechanics are in 
 charge who are held responsible for results ; sub- 
 division of duties and labors in relation to parts of 
 machinery as far as practicable is practiced, so as 
 to more readily locate responsibility. The object 
 is that when a car leaves the shop newly equipped 
 such equipment shall be thoroughly done, through 
 the best material and workmanship, and after that 
 time a thorough inspection. Motors, trucks, and 
 cars are numbered, and an official record is then 
 begun, and date and description of any repairs 
 made are kept and comparisons formed and causes 
 sought." 
 
 The ideas above suggested will readily com- 
 mend themselves to- everyone who is not penny 
 wise and pound foolish, for experience has already 
 amply demonstrated that good system, good 
 material, good workmanship and skillful em- 
 ployees who feel a genuine interest in their work 
 are none too good for the best results. 
 
 But with all this there will be a failure if the 
 cars are turned over to the motorman in anything 
 but the best condition. It must be understood 
 that the motormau is usually not a mechanic and 
 he is not an electrician, and that if he were either 
 or both he would have but scant facilities for the 
 exercise of his talents while operating his car on 
 the road. He will have done his whole duty if 
 he handles intelligently what you give him and 
 reports all troubles as soon as they arise. 
 
 In the training of motormen it is the practice 
 on some roads to put them first in the machine 
 and repair shops, so that by this preliminary 
 experience they may get an insight into the 
 
218 ELECTRIC RAILWAY MOTORS. 
 
 anatomy of the car equipment and the adjustment 
 of parts to each other. This is certainly an 
 excellent plan where practicable, and another one 
 which is always feasible, but by far too seldom 
 practiced, is to hold what the doctors would call 
 " clinics " over disabled or diseased motors when- 
 ever such are brought in. For instance, if a 
 motor is sent to the repair shop for sparking on 
 account of any of the causes before mentioned, as 
 many of the employees as it is possible to gather 
 together should be called to witness the commu- 
 tator spark while in action and be told the specific 
 cause thereof, and then they should be shown in 
 the repair shop that the diagnosis is correct and 
 how the trouble is remedied. If a motorman has 
 once seen the sparking due to an open coil, he will 
 forever after recognize it. And so with the other 
 troubles an object lesson such as the one sug- 
 gested will be worth more than all the verbal 
 instruction you. can give. 
 
 Regular inspection should be made every day if 
 possible. It does not pay to allow cars to run 
 until they absolutely refuse to run any longer. 
 In no case does the old adage, "A stitch in time 
 saves nine," apply with more force than in this. 
 I cannot, therefore, insist too strongly that repairs 
 be made just as soon as it is discovered that they 
 are required. If the motorman discovers trouble, 
 he should fix it if he can if he can't fix it, he 
 should run the car into the stables at the first 
 opportunity and report. In no case should he 
 start out with a car that is not in condition, and it 
 is the especial business of the inspector to see that 
 he does not. 
 
 One of the leading manufacturers of street car 
 motors, in his instructions to inspectors, says : 
 
TO INSPECTORS AND SUPERINTENDENTS. 219 
 
 "Let us impress upon you the importance of keep- 
 ing a careful watch of all nuts, bolts, screws and 
 all wire connections to see that everything is 
 screwed up tight." 
 
 Daily examinations of connections of motors, 
 trolleys, lightning arresters, fuse blocks, etc., should 
 be made, and especial attention should be directed 
 to the connection between the wire from the in- 
 terior of the car and the trolley base to see that it 
 is in good condition. 
 
 In addition to the daily inspection at least once 
 a month the car should be run over the pit and the 
 equipment given a most thorough overhauling. 
 
 For testing out faults the magneto bell is an 
 instrument of great general utility, and the mana- 
 gers of electric roads will save their inspectors 
 much time and trouble by providing one or more 
 for their use. 
 
CHAPTER XXIV. 
 
 LOCATING FAULTS. 
 
 WHEN starting a new car, or one whose connec- 
 tions have been changed, or in fact any car that 
 has come from the repair shops, always try the 
 motors one at a time to see that the revolution of 
 the controller handle moves the car in the same 
 direction with each motor. 
 
 To find an open circuit in the car wiring try 
 both controller handles ; if one works, the trouble 
 is probably in the other. If neither works, the 
 trouble is probably not in the controllers. If in 
 one controller, throw the canopy switch to "off." 
 Now hold one of the wires from a magneto bell on 
 the iron work of the truck or motors, and touch 
 successively with the other wire, while the handle 
 of the magneto bell is being rapidly turned, the 
 different contact fingers on the controller ; if they 
 ring, the ground connection through that finger is 
 all right. If the bell fails to ring through any one of 
 the fingers, you have located the circuit on which 
 the trouble exists. Trace out that circuit and cor- 
 rect the trouble. If all points ring on one con- 
 troller, pursue the same method with the other. 
 If both are all right, look for a break or loose con- 
 nection in the wire running from the trolley base 
 to the fuse block, or to the canopy switch* 
 
 SWO 
 
COMMUTATORS. 221 
 
 The wearing parts and those requiring the most 
 careful attention are the following : 
 
 COMMUTATORS. 
 
 The color of the commutator is in itself a pretty 
 good guide as to its condition. As long as it 
 retains a good gloss and is of a chocolate color it 
 probably does not require attention. It should, 
 however, be carefully examined to see that it is 
 clean and true. 
 
 To clean it remove the brushes, and then, while 
 the car is running with that motor cut out, use 
 fine sandpaper applied on a block of wood which 
 exactly fits the curvature of the commutator. 
 Never use emery paper, as the emery itself is a 
 conductor of electricity, and particles detached 
 from the paper may find lodgment between the 
 commutator segments and cause future short 
 circuits. 
 
 In case of high bars on the commutator some- 
 times they may be hammered down by placing a 
 piece of wood or leather between the hammer and 
 the block. Never hammer a commutator block 
 directly with the hammer, however, as it is likely 
 to flatten out the surface so that it will extend 
 over the insulating mica between it and the next 
 block, causing a short circuit. Some authorities 
 say that a hammer should never be used at all, 
 and that the high block should be filed down. 
 But whatever the remedy, a commutator that 
 presents either high bars or flats must be abso- 
 lutely true after treatment, and this can only be 
 insured by turning it down on the lathe. 
 
 The lathe is the remedy also for a rough or 
 eccentric commutator or for mica projecting be- 
 
222 ELECTRIC RAILWAY MOTORS. 
 
 yond the surface, as well as for unevenly worn 
 commutators. The turning down of a commuta- 
 tor, however, is a nice piece of work, and should 
 only be intrusted to experienced hands. The 
 cutting should not go deeper than is absolutely 
 necessary to remove the difficulty, and should not 
 extend to the outer end of the commutator ; a 
 narrow ridge should always be left on the edge. 
 Crocker and Wheeler say: "In turning a commu- 
 tator in a lathe a diamond-pointed tool should be 
 used, this being better than either a round or 
 square end. The tool should have a very .sharp 
 and smooth edge, and only an exceedingly fine cut 
 should be taken off each time in order to avoid 
 catching in or tearing the copper, which is very 
 tough. The surface is then finished by applying 
 a 'dead smooth' file while the commutator re- 
 volves rapidly in the lathe." After turning down 
 or sandpapering the spaces between the commu- 
 tator blocks should be carefully examined for 
 copper dust or other conducting material. If 
 found, such should be removed. The commutator 
 should be carefully lubricated from time to time, 
 great care being taken, however, not to use an 
 excess. A little vaseline is perhaps as good a 
 lubricator as anything for either the commutator 
 or controlling switch. 
 
 The brushes should be examined frequently, 
 once a day is not too often, and the brush holders 
 should be cleaned whenever found to be dirty. 
 Brush holders should never be permitted to be- 
 come loose, and the brushes should not be allowed 
 to become too short, for in this case in the adjust- 
 ment of the holders the springs will not give suffi- 
 cient pressure for good contact. Brushes should 
 fit curve of commutator perfectly, and new ones 
 
DROP METHOD OF TESTING FOE FAULTS. 223 
 
 should be filed or sandpapered, if necessary, to 
 make a good fit. Brush tips should be kept clean, 
 and should not be allowed to become wedged in 
 the holders. 
 
 THE DROP METHOD OF TESTING FOR FAULTS. 
 
 While it is entirely beyond my province to dis- 
 cuss the methods of electrical testing at this time, 
 there are one or two simple methods that are so 
 generally available that it seems well to introduce 
 them here. 
 
 If a break or bad contact in a circuit is suspected, 
 it may be readily located by what is known as the 
 " drop method." This is founded on the principle 
 that if everything is normal in a circuit the resist- 
 ances between any two points equidistant on that 
 circuit should be about the same. If one terminal 
 of A galvanometer be fastened to one point of 
 a circuit, and the other be successively applied to 
 other points on the same circuit at equally increas- 
 ing distances, the needle will register in a circuit 
 which is intact a regular increase of deflection 
 with every successive point touched. The reason 
 for this is that the galvanometer, being con- 
 nected up in parallel with the conductor, registers 
 the relative resistance of the portion of the circuit 
 tested and that of its own circuit. The latter being 
 fixed, the indications will be greater as the resist- 
 ance of the circuit measured^is greater. If when 
 the galvanometer wire touches a new point on the 
 circuit the increase of deflection is much greater 
 than it should be, it indicates that there is trouble 
 between this point and the last one touched. A 
 common way of applying this method is to fix the 
 two terminals in a handle of some kind, so that 
 
224 ELECTRIC RAILWAY MOTORS. 
 
 their distance is not varied, and then move these 
 two terminals along the circuit. Since the length 
 of wire measured in this case is always the same, 
 the reading of the galvanometer will always re- 
 main the same if everything is right. If the deflec- 
 tion increases at any point, the trouble is at once 
 located between the two terminals of the galvanom- 
 eter. In testing for breaks in the armature coils 
 the two points are applied to adjacent commutator 
 blocks all around the commutator. The deflection 
 of the galvanometer should not vary between any 
 two successive segments, but if it does there is a 
 loose connection or a break somewhere in the coil 
 or connections between the two. 
 
 INSULATIOX TEST. 
 
 Another simple test that is not only of great use, 
 but also available to even the least technical if he 
 have but a magneto bell, is the test for insulation 
 resistance. It is very desirable to know that those 
 portions of your apparatus that should be insu- 
 lated from each other are so insulated, as, for in- 
 stance, the armature windings from the armature 
 core, or the brush holder from the brushes. The 
 ordinary magneto bell is rated to ring through 
 from 10,000 to 30,000 ohms resistance. If, there- 
 fore, one terminal of the bell be connected to each 
 of the parts that should be insulated from each 
 other, as, for instance, the armature shaft and 
 a commutator segment, or the brush and the brush 
 holder, and the bell can then be caused to ring, 
 it indicates either a very poor insulation between 
 the parts or else a bad short circuit. Its failure 
 to ring does not, however, indicate that the insula- 
 tion is perfect or sufficient, since it merely indi- 
 
INSULATION -TEST. 225 
 
 cates that the resistance is somewhat greater than 
 30,000 ohms (if that be the resistance through 
 which it is rated to ring), whereas the insulation 
 resistance between armature coil and core should 
 not be less than 100,000 ohms for every 100 volts 
 used on the circuit. This test should therefore 
 be considered only as a crude one and more as 
 a test for short circuit than as a test for insu- 
 lation. 
 
 A much more reliable test is that known as the 
 voltmeter test. This requires a sensitive high 
 resistance voltmeter, such as the Weston. The 
 Weston 150-volt instrument usually has a resist- 
 ance of its own of about 15,000 ohms. (Its exact 
 resistance is always stated on a certificate pasted 
 inside the case.) Apply the galvanometer first to 
 some circuit or battery having a high electro- 
 motive force say 100 volts and note the deflec- 
 tion of the needle. Then connect the parts whose 
 insulation resistance is to be tested with this 
 same circuit in series with the voltmeter. If the 
 armature resistance is to be tested, for instance, 
 connect one terminal of the circuit with the 
 armature shaft, and the other with one terminal or 
 binding post of the machine, and note the new 
 deflection. It will be less than before, because 
 an increased resistance (the insulation resistance) 
 has now been placed in series with the galvanom- 
 eter resistance. 'The insulation resistance will 
 then be found by the equation : 
 
 Insulation resistance = -- JR, 
 
 d 
 
 in which D is the deflection due to the galvanom- 
 eter alone : d = the deflection when the machine 
 is in series with the galvanometer, and M is the 
 
226 ELECTRIC RAILWAY MOTORS. 
 
 resistance of the galvanometer or voltmeter. Thus 
 if the circuit employed in testing is 100 volts, 
 then D=1QO. If the second deflection, viz., that 
 through the galvanometer (say 15,000 ohms), plus 
 the insulation of the machine is 1, our equation 
 becomes : Insulation resistance 
 100X15,000 
 
 = 15,000 = 1,485,000 ohms. 
 
 1 
 
 BEARINGS. 
 
 The importance of keeping the bearings in first- 
 class order will, of course, be apparent at once. 
 Be watchful at all times that they do not become 
 too much worn, else the armature is likely to strike 
 against the fields and become ruined. If, on in- 
 spection, you find that the clearance between ar- 
 mature and pole pieces is becoming small, put in 
 new bushings at once. Do not wait until the clear- 
 ance becomes dangerously small. Looseness of the 
 armature bearings can be detected by lifting on the 
 armature first at one end and then at the other. 
 Loose bearings on the main axle may cause gears 
 to break by reason of their being thrown out of 
 alignment. The grease boxes on the motor should 
 be given careful attention, and should be filled 
 every night or morning before the car is sent out. 
 There is no economy in using an inferior lubricant 
 rather the reverse ; but the best 'grease is liable to 
 thicken, and before adding fresh the old should be 
 stirred up with a little oil. In removing covers to 
 inspect grease boxes be careful that none of the 
 dirt or sand falls into the boxes. Occasionally all 
 the grease should be removed, the boxes thor- 
 oughly washed with gasoline, and a small quantity 
 allowed to run through the bearings to cut any 
 
OF THE 
 
 GEARS AND 
 
 grease which may have found lodgment there 
 and hardened. 
 
 GEARS AND PINIONS. 
 
 The life of the gears and pinions depends very 
 largely upon the intelligent care they receive. 
 Proper lubrication is one of the most largely con- 
 tributive agencies toward long life, but they should 
 be carefully examined every night to see that they 
 have not become loose on the shaft. Since they 
 usually have tapering seats, they may be tightened 
 by firmly tapping them with a hammer. With 
 this frequent examination there is no danger that 
 they will become unduly worn without your knowl- 
 edge. Tighten up all the bolts whenever exam- 
 ining them. Drive up the key or feather to insure 
 tightness of gears and pinions, and if these are 
 too much worn throw them away and substitute 
 new ones. The unusual " knocking " noises some- 
 times heard when the car is in operation are 
 usually due either to worn keys, worn-out gears or 
 to some hard object which has become lodged 
 between the teeth. This knocking sound is a 
 warning that must be heeded at once, and the 
 above causes are the first to be suspected. Investi- 
 gate, and if the pinion is worn out throw it away 
 and put on a new one with a new key. A new 
 pinion will not, however, go well with an old and 
 worn gear. If the gear be but slightly worn and 
 too good to throw away, keep it to go with some 
 slightly worn but equally good pinion, but don't 
 allow a new wheel to mesh into an old one. 
 
 On fitting new gears note carefully that the 
 teeth mesh properly before putting them into use. 
 This is best done by revolving the armature by 
 hand while the car is jacked up. The fitting of 
 
228 ELECTRIC RAILWAY MOTORS. 
 
 new gears is a nice operation, and should not be 
 intrusted to any but a responsible person. 
 
 CONTROLLERS. 
 
 The controllers should be thoroughly overhauled 
 every night ; the contact rings and fingers cleaned 
 and polished when found to be rough, and a little 
 vaseline rubbed on ; the screws that hold the con- 
 tact rings should be tightened if loose, and the 
 ratchet wheel and pawl at the top of the cylinder, 
 as well as the upper and lower bearings of the 
 cylinder, should be carefully lubricated, taking 
 care, however, that too much lubricant is not used 
 and that it does not run down upon the cylinder. 
 In equipments not emp^dng the usual platform 
 cylinder the equivalent parts beneath the car 
 should receive their appropriate attention. When- 
 ever a part becomes worn it should be replaced. 
 In fact, the directions in regard to the controlling 
 devices may all be summed up thus : See that they 
 are in perfect order every night or morning before 
 the car leaves the stables. 
 
CHAPTER XXV. 
 
 TROLLEY WHEELS. 
 
 THE life of the trolley wheel depends upon the 
 quality of the metal, the number of miles that it 
 travels and the care that it receives. Remember 
 that its speed is enormous. Take a trolley wheel 
 that is 6 inches in diameter, for instance. When 
 the car is running at 8 miles an hour, a 36-inch car 
 wheel will make 4482 revolutions, and we know 
 the necessity of lubrication for this. At the same 
 speed and in the same time a 4-inch trolley wheel 
 will make 126,720 revolutions, and yet we are liable 
 to overlook the necessity for lubrication here. In 
 fact, the trolley wheel is subject to something far 
 worse than frictional wear, viz., sparking. Every 
 time a spark occurs on a trolley it means the com- 
 bustion of so much copper. Oil the trolley wheel in 
 the J)arn, therefore, as often during the day as it 
 is practicable. Instruct your motorman to oil it 
 when he has an opportunity. See that the wheel 
 does not wobble or flash badly. If it does, it 
 requires attention. Sometimes a wheel may be 
 traced in the dark by its continuous sparking. It 
 requires attention then surely, for if it is not 
 attended to at once it will become so bad that it 
 will have to be thrown away. 
 
 The trolley wheel is a little thing, you may 
 think, and not very expensive to replace. The 
 sooner you get over excusing yourself for inatten- 
 
 229 
 
230 ELECTRIC RAILWAY MOTORS. 
 
 tion to little things the sooner you will be compe- 
 tent to fill your position. Be very careful of little 
 things, and there will be no big things to take care 
 of. This seems like a platitude, but if I can only 
 impress the truth of this statement upon every 
 superintendent I will have accomplished a very 
 great good to the cause of street railroad practice. 
 The matter of proper tension of the springs at 
 the base of the trolley is one that I am satisfied is 
 not usually given the proper attention. The trol- 
 ley wheel is, I believe, in nine cases out of ten 
 pushed too hard against the wire. It is better 
 to err on the other side, for if the tension be too 
 slight it will make itself manifest, but if it be too 
 
 freat it gives no evidence of the fact until the 
 amage is clone. Remember that the resistance of 
 the contact betw r een wheel and wire is not materi- 
 ally increased by increasing the tension of the 
 spring within the allowable limits. 
 
 It is a mistaken idea that an extremely high ten- 
 sion will cause the trolley to keep the wire better 
 than a moderate one. On the other hand, the pres- 
 sure must be sufficient to keep the wheel at its 
 enormous speed from "tapping" that is, from 
 jumping momentarily from the wire which.it is 
 apt to do if it happens to be a little eccentric or 
 otherwise runs a little unevenly. 
 
 In the earlier days, when we did not know so 
 much about these things as we do now, I remem- 
 ber seeing ai? electric road that was operated by a 
 superintendent who believed there was much to be 
 gained by a stiff pressure ; in fact, he carried the 
 idea to an extreme even for those days. The result 
 was that his trolley lifted the wire a couple of feet 
 as it passed along, and as the car jolted and rocked 
 it set the trolley wire into such violent vibration 
 
INCANDESCENT LAMPS. 231 
 
 that the motion imparted by one car to the wire 
 would often actually throw the wire off the trolley- 
 wheel of another car some distance either in the 
 rear or in advance. He had, in fact, commenced 
 running with too tight a spring, and had sought to 
 correct the difficulty by tightening it still more, 
 which, of course, only made matters worse. His 
 trolley wheels rapidly wore out, and, worse than 
 this, his hangers were knocked to pieces in a very 
 short time, and once when I was in the car, our 
 own trolley getting off, the pole struck a span wire, 
 not only snapping the trolley pole off, but bring- 
 ing down the whole overhead structure. This man, 
 finally learning his mistake, went to the other 
 extreme, perhaps, but he became a firm convert to 
 the loose spring. 
 
 INCANDESCENT LAMPS. 
 
 Remember that your lamps are in series, and 
 that any defect in one is visited upon all the others. 
 If one lamp breaks, the circuit is broken ; or if 
 one be not screwed in sufficiently tight to make 
 connection, none of them will burn. If, therefore, 
 your lamps refuse to burn, examine them individ- 
 ually to discover the fault before condemning your 
 lamp circuit. The situation of the car lamp is an 
 exceedingly trying one to fill. In the first place 
 there is the constant jar of the car, which tends to 
 break the filament, and in the second there is the 
 great variation in E. M. F. to which it is subjected. 
 The line current is apt to vary from 450 volts to 
 520 or more, which is, we will say, a variation of 
 fifteen per cent. 
 
 Now experience has proved that an increase 
 of three per cent, in the voltage above that for 
 
232 ELECTRIC RAILWAY MOTORS. 
 
 which the lamp was intended will divide its life 
 by two. For instance, if a 100-volt lamp has a 
 life of 1000 hours when used on a 100-volt cir- 
 cuit, it will only have a life of 500 hours if the 
 pressure is increased to 103 volts. 
 
 The illumination given by a lamp varies even 
 more widely with the pressure than does its life. 
 No definite law has as yet been discovered as to 
 this, but we know the temperature increases as 
 the square of the current, and as the current will 
 be proportional to the pressure, we may say that 
 the temperature will increase as the square of the 
 pressure ; the illumination will, however, vary 
 more widely than this, its variation being estimated 
 by some as being as the fifth power of the pressure. 
 These statements being true, or approximately 
 true, one sees at once the strain to which a street 
 car lamp is put. 
 
 If your lamps are already burning at a very 
 high pressure that is, at a pressure above that for 
 which they were intended, or, in other words, if 
 they are burning with high efficiency a compara- 
 tively small increase in pressure will break them 
 in a short time. The rule is, therefore, in street 
 cars not to use a high efficiency lamp ; first, because 
 under the conditions the light it will give will vary 
 too widely ; and second, because its life must 
 necessarily be a very short one. A low efficiency 
 lamp should always be chosen, for then, with the 
 wide variations of pressure to which it is subjected, 
 the variation in light will be less apparent and its 
 life be much longer. Then, again, be careful that 
 all the lamps on a car are of as nearly the same 
 resistance as possible exactly the same, if that 
 can be arranged, for it is not enough that the five 
 lamps shall in the aggregate absorb 500 volts ; 
 
CONCLUSION. 233 
 
 the} r must each absorb the same fraction of this 
 10cT volts. If one lamp absorbs 110 volts and 
 another but 90, the average is maintained, but the 
 one that absorbs 110 volts will burn out much the 
 quicker. Lamps have often been very unjustly con- 
 demned simply because, being of high resistance, 
 they have burned out first when put in the same 
 series with other lamps, either of the same make 
 or of another, that were of low resistance. 
 
 CONCLUSION. 
 
 I cannot better illustrate the part which a com- 
 petent superintendent can play in the general 
 efficiency of a road or a system than by recalling 
 an incident that occurred some years ago in a 
 Western city. Electric railroads were then com- 
 paratively new. In this city there were two street 
 railroad companies one a large corporation own- 
 ing nearly all the lines in the city, and the other 
 a small corporation owning but one line, and that 
 a short one not more than 3 miles long. The 
 large corporation equipped one of its lines with 
 the double trolley system, and the small corpora- 
 tion equipped its line with the single trolley. 
 Both lines were of about the same length, but that 
 of the small corporation abounded in long and 
 steep grades, one of which reached 13^ per cent, 
 at one point; while the other, although by no 
 means level, was a much easier line to operate. 
 
 A spirit of rivalry sprang up between the two 
 lines which was heightened by a lawsuit in which 
 the single trolley road was made the defendant (it 
 was one of the telephone cases), and in which the 
 double trolley, though not a party to the suit, fur- 
 nished much of the testimony for the plaintiff. 
 The double trolley people were called in to prove 
 
234 ELECTEIC RAILWAY MOTORS. 
 
 that the double trolley was better than the single 
 trolley ; and, among other arguments, showed 
 that with the double trolley the car was inde- 
 pendent of the condition of the track, and could 
 run under circumstances (such as heavy snow) 
 where the single trolley would be unable to get 
 current through its motors. That suit was decided 
 in favor of the parties for whom the double trolley 
 people testified. 
 
 Winter came on, and with it a heavy snowfall. 
 The double trolley road had every advantage as to 
 track and system to meet this emergency, but the 
 single trolley road had the more efficient superin- 
 tendent. There is not a street railroad man in the 
 country who would not know his name if I men- 
 tioned it. He kept the snow off his tracks and 
 weathered the storm without stoppage of cars. 
 The double trolley superintendent, less alive to the 
 situation, tried to run on top of the snow, and his 
 whole system was blocked for a day. The fact of 
 the blockade of the double trolley system and the 
 successful weathering of the storm by the single 
 trolley system was telegraphed all over the 
 country and taken by the masses as evidence of 
 the superiority of the single over the double trol- 
 ley. For that special emergency, at least, the facts 
 were exactly the reverse. The true significance 
 of the circumstance was that the single trolley 
 road had the better superintendent, but the public 
 did not understand it in that way. So you must 
 do much for which you will receive no credit from 
 the public at large ; but if you keep your cars 
 going and keep them from wearing out, and do 
 this at a minimum expense, your employers will 
 know it and give you full credit. 
 
INDEX. 
 
 Advice to Readers, 28 
 
 Air Gap, 59 
 
 Alternating Current Dynamo, 85 
 
 Alternating Currents, Rectification 
 
 of, 86, 146 
 
 Ammeter, 27, 48, 50, 51, 54 
 Ampere, 12, 13, 15, 81 
 Amperemeter (see Ammeter) 
 Ampere-Turn, 58, 90 
 Analogy between Electricity and 
 
 Magnetism, 60 
 
 Analogy between Water and Elec- 
 trical Distribution, 116 
 Analogy of Leaky Pipe and Mag- 
 netic Leakage, 65 
 Analogy of Lines of Force and 
 
 Elastic Strings, 67 
 Analogy of the Dog, 10 
 Analogy of the Pipe, 13, 15 
 Analogy of the Resistance of Rusty 
 Pipes and Poor Electrical Con- 
 dnctors, 14, 16, 29 
 Analogy of the Rotary Fan, 136 
 Analogy of the Waterfall, 12 
 Analogy of Waterwheel, 51 
 Armature Coll, Direction of Cur- 
 rent in, 85 
 
 Armature Coils, Shifting of, 96 
 Armature Coil, Reversal of Current 
 
 in, 80 
 
 Armature Coils, Stripping of, 97 
 Armature, Eddy Currents in, 93 
 Armature, Heating of, 94 
 Armatures, Closed Coil, 100, 151 
 Armatures, Drum, 102 
 Armatures, Open Coil, 100 
 Armatures, Ring, 102 
 Armature, Slotted , 95 
 Arrangement in Multiple, 109, 112 
 Arrangement in Parallel, 109. 112 
 Arrangement in Series, 109, 112 
 Automatic Block System, 184 
 Automatic Cut-out, 183 
 Axis of Commutation, 88, 151 
 
 Battery, Cost of Making, 32 
 
 Battery, Directions for Making, 32 
 
 Battery, Direction of Current in, 34 
 
 Battery, Dry, 33 
 
 Battery, Sal-Ammoniac, 32 
 
 Battery, Salt Water, 32 
 
 Battery, Zinc-Carbon, 30 
 
 Bearings, 226 
 
 Bell, Magneto, 224 
 
 Binding Wires, 95 
 
 Block System, Automatic, 184 
 
 Braking, Electrical, 184 
 
 Brass, Zinc, Iron. Rusty Pipes, 
 Resistance offered by, 14, 16 
 
 Building up of Dynamo, 130 
 
 Circuit, Derived (see Shunt Circuit) 
 
 Circuit, Shunt, 53 
 
 Clearance, 95 
 
 Clinics, Motor, 218 
 
 Closed Coil Armatures, 100, 151 
 
 Closed Conduit System, 190 
 
 Commutated Field Control, 169 
 
 Commutation, Axis of, 88, 151 
 
 Commutation, Line of, 151 
 
 Commutation of Currents, 86 
 
 Commutator, 88, 89, 221 
 
 Compass, 35, 37 
 
 Compound Dynamo, 130 
 
 Compromise Poles (see Resultant 
 Poles) 
 
 Conductors, Poor, 15 
 
 Conduit System, 187 
 
 Conduit System, Closed, 190 
 
 Conduit System, Love, 188 
 
 Conduit System, Siemens & 
 Halske, 188 
 
 Consequent Poles, 104 
 
 Controllers, 228 
 
 Conversion of Electrical into Me- 
 chanical Units, 27 
 
 Conversion of Motor into Dynamo, 
 184 
 
 Counter Electromotive Force, 153 
 
 Counter Electromotive Force, am 
 
 235 
 
236 
 
 INDEX. 
 
 Essential Factor in the Power of 
 
 a Motor, 155 
 Counter Electromotive Force and 
 
 Ohm's Law, 154 
 Counter Electromotive Force and 
 
 Resistance, 154, 157, 160 
 Counter Electromotive Force and 
 
 Speed regulation, 157 
 Counter Electromotive Force, for- 
 merly a Bugbear, 155 
 Counter Electromotive Force, the 
 
 Measure of Work, 155, 162 
 Crosby and Bell, 161 
 Cross Connection of Coils, 124 
 Current, Flow of, 13 
 Currents and Magnets, Mutual 
 
 Effects of, 38 
 
 Currents, Commutation of, 86 
 Currents, Deflection of Needle 
 
 by, 38 
 
 Cut-out, Automatic, 183 
 Deflection of Needle by Currents, 38 
 Demagnetization by Shock, 47 
 Derived Circuit, (see Shunt Circuit) 
 Direction of Current in Armature 
 
 Coil, 85 
 Direction of Rotation of Electric 
 
 Motor, 141 
 Directions to Motormen, Specific, 
 
 201 
 
 Dog, Analogy of the, 10 
 Drop, 134 
 Drop Method of Locating Faults, 
 
 Drum Armatures, 102 
 
 Dynamo, Alternating Current, 85 
 
 Dynamo, Building up of, 130 
 
 Dynamo Compound, 130 
 
 Dynamo, Continuous Current, 80 
 
 Dynamo-Electric Principle, 129 
 
 Dynamo Over Compounded, 135 
 
 Dynamo Series, 130 
 
 Dynamo, Shunt, 130 
 
 Dynamo, The Reversibility of, 135 
 
 Earth a Magnet, 46 
 
 Eddy Currents in Armature, 93 
 
 Effect of Change of Length and 
 
 Size of Conductor, 19 
 Electrical Braking, 184 
 Electrical Horse Power, 23, 148 
 Electrical into Mechanical Units, 
 
 Conversion of, 27 
 Electrical Pressure, 21, 90 
 Electric Current and its Properties, 
 
 28 
 
 Electric Motor, 139 
 Electric Motor, Direction of Rota- 
 tion of, 141 
 
 Electro and Permanent Magnets 
 
 Compared, 44 
 
 Electro-Magnet, 43, 44, 54, 55, 56 
 Electro-Magnet, Construction of, 72 
 Electro-Magnet, Tractive Power 
 
 of, 74 
 
 Electro-Magnetic Indnction,'75 
 Electromotive Force, 21, 23 90 
 Electromotive Force and Strength 
 
 of Field, 134 
 Energy, 22 
 
 Example, Test for Insulation, 225 
 Examples, Given C., L., and E. to 
 
 find R., 19 
 Examples, Given C., L., and R. to 
 
 find E., 20 
 Examples, Given C. and R. to find 
 
 H. P., 25 
 Examples, Given E. and R. to find 
 
 C., 18 
 Examples, Given E. and R. to find 
 
 H. P., 24 
 Examples, Given H. P. and E. to 
 
 find C., 26 
 Examples in Speed Regulation, 
 
 163,166, 
 Expenses, Standard of Car Mile, 
 
 216 
 
 Faults, Locating, 220, 223 
 Feeder Wire, 184 
 Flow of Current, 13 
 Flux, Resistance to, CO 
 Foot Pound per Second, 22, 23 
 Force, Electromotive, 21, 23, 90 
 Foucault Currents, 94 
 Friction, 13 
 
 Friction, Heat Caused by, 13 
 Fundamental Units of Electricity 
 
 15 
 
 Galvanic Battery, Principle of, 30 
 Galvanometer, 40, 78, 223 
 Galvanometer, Convenient Coil for, 
 
 41 
 
 Galvanometer, Directions for Mak- 
 ing, 40 
 
 Gearing, Double Reduction, 149 
 Gearing, Single Reduction, 150 
 Gearless Motor, 150 
 Gears and Pinions, 227 
 Heat Causf d by Friction, 13 
 Heating of Armature, 94 
 Horse Power, Electrical, 23, 24, 148 
 Horse Power, Mechanical, 22, 23, 
 
 148 
 
 Induced Poles, 152 
 Inertia, 159 
 
 Inspectors, Instructions to, 213 
 Instructions to Inspectors, 213 
 
INDEX. 
 
 237 
 
 Instructions to Superintendents, 213 
 
 Insulation Test, 224 
 
 Intra-Mnral Railroad, 170 
 
 Iron, Annealed, Magnetism of, 43, 
 
 Iron, Caet, Magnetism of, 45 
 
 John Scott Legacy and Medal, The, 
 184 
 
 Jobnston-Lundell System, 169 
 
 Kilowatt, 24 
 
 Lamination of Core, 93 
 
 Lamps, High Efficiency, 232 
 
 Lamps, Incandescent, 231 
 
 Lamp", Low Efficiency. 232 
 
 Law of Flow in Multiple Circuits, 
 132 
 
 Law of Heating Effects of Current, 
 159 
 
 Law of Magnetic Flux, 56 
 
 Law of Magnetizing Effect of Sole- 
 noid, 57 
 
 Leakage, Magnetic, 64, 65 
 
 Leonard System, 176, 177 
 
 Like and Unlike Poles, Mutual Ef- 
 fect of, 38 
 
 Line of Commutation (see Axis of 
 Commutation), 
 
 Lines of Force, 59, 60, 61, 62, 140 
 
 Locating Faults, 220, 223 
 
 Lowell & Suburban St. Ry. Co., 216 
 
 Magnetic Circuit Closed, 63, 75 
 
 Magnetic Curves, 67 
 
 Magnetic Leakage, 64, 65 
 
 Magnetic Poles, Definition of, 63 
 
 Magnetic Pressure, 57 
 
 Magnetic Saturation, 62 
 
 Magnetism and Current, 2 
 
 Magnetism, Change of Direction 
 of, 44 
 
 Magnetism, Conductors of , 59, 64 
 
 Magnetism, Electro, 43, 44. 54 
 
 Magnetism of Soft Annealed Iron, 
 43,44,54 
 
 Magnetism of Tempered Steel, 43, 
 44,54 
 
 Magnetism, Permanent, 43, 44, 54 
 
 Magnetism, Residual, 74 
 
 Magnets, Multipolar, 104, 121, 125, 
 127 
 
 Magneto-Electric Machine. 127 
 
 Magneto Bell, 224 
 
 Magnetization Assisted by Shock, 
 46 
 
 Magnetization by Contact, 45 
 
 Magnetization by Proximity, 45 
 
 Magnetization by the Earth, 46 
 
 Magnetization of Soft Iron Nearly 
 Instantaneous. 44, 75 
 
 Magnetization of Tempered Steel, 
 
 Time Required for, 44 
 Magneto-Motive Force, 57, 58 
 Magnet, Position of, when free to 
 
 Move in Horizontal Plane, 37 
 Magnet without Poles, 64 
 Management of Street Railway 
 
 Motors, 191 
 
 Measuring Instruments, 48 
 Mechanical Horse Power, 22, 23, 
 
 148 
 
 Motor Clinics, 218 
 Motor, Electric, 139 
 Motor, Electric, Consumes Volts, 
 
 51, 119 
 Motor, Electric, does not Consume 
 
 Current, 51, 119 
 Motor Fails to Start, 199 
 Motor, Gearless, 150 
 Motor, Slow Speed, 150 
 Motor Stops, 199 
 
 Multiple Arc Arrangement, 109, 112 
 Multiple Circuits,- Law of Flow in, 
 
 132 
 
 125, 
 
 Multiplying Effect of Coils, 40 
 Mnltipolar Magnets, 104, 121, 
 
 127 
 
 Mutual Effects of Currents and 
 
 Magnet*, 38 
 Mutual Effect of Like and Unlike 
 
 Poles, 38 
 
 North-seeking Pole, 46 
 North-seeking Pole in Reality a 
 
 South Pole, 46 
 Ohm, 14, 15, 18, 21 
 Ohm, George Simon, 16 
 Ohm's Law, 16, 17, 21 
 Ohmmeter, 53 
 Open Coil Armatures, 100 
 Overwork, What Constitutes, 99 
 Permanent and Electro Magnets 
 
 Compared, 44 
 
 Permanent Magnet, 43, 44, 54, 55 
 Perry System. 181 
 Pinions and Gears, 227 
 Pipe, Analogy of, 13, 15 
 Polarity Dependent on Direction 
 
 of flow of Current in Solenoid, 
 
 55 
 Polarity, Effect on, of Direction of 
 
 Flow of Current, 
 Polarity Independent of Direction 
 
 of Solenoid, 55 
 Polarity, Reversing by Reversing 
 
 Connections, 72 
 
 Polarity, Rule for Determining, 71 
 Poor Conductors, 15 
 Potential, Difference of, 52. 53 
 
238 
 
 INDEX. 
 
 Pressure, Electrical, 21, 90 
 Pressure, Magnetic, 57 
 Principle of Galvanic Battery, 30 
 Production of Steady Currents, 88 
 Rate of Flow, 21 (see Ampere) 
 Rate of Work, 22 
 Readers, Advice to, 28 
 Rectification of Alternating Cur- 
 rents. 86, 146 
 
 Remarks of P. P. Sullivan, 216 
 Residual Magnetism, 74 
 Resistance, 14, 21, 48, 53, 54, 56 
 Resistance, Measurement of, 53 
 Resistance offered by Iron, Brass, 
 
 Zinc, Rusty Pipes, 14, 16 
 Resistance to Magnetic Flux, 56 
 Resultant Poles, 151 
 Reversal of Current in Armature 
 
 Coil, 80 
 
 Reversibility of the Dynamo, 135 
 Rheostat, 161 
 Rheostat Control, 169 
 Rheostat Regulation, 161 
 Ring Armatures, 102 
 Saturation, Magnetic, 62 
 Separately Excited Machine, 128 
 Series Arrangement, 109, 112 
 Series Dynamo, 130 
 Series Parallel Control, 169 
 Series System, 181 
 Shifting of Armature Coils, 96 
 Shunt Circuit, 53 
 Shunt Dynamo, 130 
 Slotted Armature, 95 
 Solenoid, Directions for Making, 34 
 Solenoid, Magnetism and Property 
 
 of, 42 
 Solenoid, Magnetism Due Solely to 
 
 Current, 43 
 Solenoid, Magnetization by, 35, 48, 
 
 55,57 
 
 Solenoid of one Turn, 49 
 Solenoid of two Turns, 49 
 Solenoid of three Turns. 50 
 Solenoid of any Number of Turns, 
 
 50 
 
 Solenoid, Polarity Produced by, 
 
 36,55 
 
 Solenoid, Properties of, 42, 47, 57 
 Sparking at the Commutator, 194 
 Specific Directions to Motormen, 
 
 201 
 Speed Control, Johnston- Lundell, 
 
 173 
 
 Speed Control, Perry System, 185 
 Speed Regulation, Requirements of, 
 
 161 
 
 Standard of Car Mile Expenses, 216 
 Steady Currents, Production of, 
 
 88 
 Storage Battery, Disadvantages of, 
 
 186 
 
 Storage Battery, Inherent, 185 
 Storage Battery Traction, 185 
 Strength of Field and Electro- 
 motive Force, 134 
 Stripping of Armature Coils, 97 
 Sullivan, P. P., Remarks of, 216 
 Superintendents, Instructions to, 
 
 213 
 
 Surface Contact System, 174 
 Technical Terms, 9, 15 
 Tempered Steel, Magnetism of, 43, 
 
 Test for Insulation, 224 
 
 Torque, 144 
 
 Translating, Current Characteristics 
 
 in, 116 
 
 Translating Device, 110 
 Trolley Wheels, 229 
 Units of Electricity, Fundamental, 
 
 15 
 
 Volt, 12, 13, 15, 23 
 Voltage, 21 
 
 Voltmeter, 27, 48, 51, 53, 54 
 Voltmeter, Function of, 53 
 Waterfall, Analogy of the, 12 
 Watt, 23, 24 
 
 What Constitutes Overwork, 99 
 Whoatstone Bridge, 53 
 Work, 148 
 Work, Rate of, 22, 24, 148 
 
 .^^J&^S L 1 crn^/J ^^*v 
 j ^ OF THE \ 
 
 ftfNIVERSITT) 
 
 ^^CALJFORN^:.^^ 
 
Elementary 
 Electro -Technical Series. 
 
 EDWIN J. HOUSTON, Ph.D. and A. E. KENNELLY, D.Sc. 
 
 Alternating Electric Currents, Electric Incandescent Light- 
 Electric Heating, ing, 
 
 Electromagnetism, Electric Motors, 
 
 Electricity in Electro-Thera- Electric Street Railways, 
 
 peutics, Electric Telephony, 
 
 Electric Arc Lighting, Electric Telegraphy. 
 
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RECKNT PROORESS 
 
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REFERENCE BOOK OF 
 
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