,illustration3 ,,interior ,,of #afj-,,ton ,b4 ,,and ,o4 ,,electric ,,locomotive4 ,general ,electric ,company4 ,electric ,railways ,a ,treatise on the ,,modern ,,development ,,of ,,electric ,,traction1 ,,including ,,practical ,,instruction ,,in ,,the ,,latest ,,approved ,,methods ,,of ,,electric ,,railroad ,,equipment ,,and ,,operation ,,electric ,,railways ,by ,james ,r4 ,cravath ,western ,editor 8,the ,street ,railway ,journal0 ,,the ,,single-,,phase ,,electric ,,railway ,by ,harris ,c4 ,trow1 ,s4,b4 ,american ,institute of ,electrical ,engineers4 ,editor ,textbook ,department1 ,american ,school of ,correspondence ,,illustrated ,,chicago ,,american ,,school ,,of ,,correspondence #aijh ,copyright #aijg by ,american ,school of ,correspondence ,entered at ,stationers' ,hall1 ,london ,all ,rights ,reserved ,foreword ,in recent years1 such marvelous advances have been made in the engineering and scientific fields1 and so rapid has been the evolution of mechanical and constructive processes and methods1 that a distinct need has been created for a series of practical working guides1 of convenient size and low cost1 embodying the accumulated results of experience and the most approved modern practice along a great variety of lines4 ,to fill this acknowledged need1 is the special purpose of the series of handbooks to which this volume belongs4 ,in the preparation of this series1 it has been the aim of the publishers to lay special stress on the practical side of each subject1 as distinguished from mere theoretical or academic discussion4 ,each volume is written by a well-known expert of acknowledged authority in his special line1 and is based on a most careful study of practical needs and up-to-date methods as developed under the conditions of actual practice in the field1 the shop1 the mill1 the power house1 the drafting room1 the engine room1 etc4 ,these volumes are especially adapted for purposes of self-instruction and home study4 ,the utmost care has been used to bring the treatment of each subject within the range of the common understanding1 so that the work will appeal not only to the technically trained expert1 but also to the beginner and the self-taught practical man who wishes to keep abreast of modern progress4 ,the language is simple and clear2 heavy technical terms and the formul of the higher mathematics have been avoided1 yet without sacrificing any of the requirements of practical instruction2 the arrangement of matter is such as to carry the reader along by easy steps to complete mastery of each subject2 frequent examples for practice are given1 to enable the reader to test his knowledge and make it a permanent possession2 and the illustrations are selected with the greatest care to supplement and make clear the references in the text4 ,the method adopted in the preparation of these volumes is that which the ,american ,school of ,correspondence has developed and employed so successfully for many years4 ,it is not an experiment1 but has stood the severest of all tests--that of practical use--which has demonstrated it to be the best method yet devised for the education of the busy working man4 ,for purposes of ready reference and timely information when needed1 it is believed that this series of handbooks will be found to meet every requirement4 ,illustration ,table of ,contents ,car ,equipment ,page #c ,classification of ,electric ,railways -- ,motors -- ,armature ,winding -- ,armature and ,field ,coils -- ,armature and ,motor ,leads -- ,brushes and ,brush-,holders -- ,gearing -- ,lubrication -- ,bearings -- ,motor ,suspension -- ,electric ,locomotive ,motors -- ,controllers -- ,rheostat and ,series-,parallel ,control -- ,controller ,construction -- ,multiple-,unit ,control 7,sprague1 ,general ,electric1 ,westinghouse ,electro-,pneumatic7 -- ,car-,heaters -- ,car ,wiring -- ,electric-,car ,accessories 7,canopy ,switches2 ,circuit-,breakers2 ,fuses2 ,lightning ,arresters2 ,lamp ,circuits2 ,trolley-,base2 ,trolley-,poles1 ,wheels1 and ,harp2 ,contact ,shoes2 ,sleet ,wheels7 -- ,single ,trucks -- ,swivel ,trucks -- ,maximum-,traction ,trucks -- ,car ,wheels -- ,brake ,rigging -- ,air-,brakes 7,compressor1 ,automatic ,governor1 ,storage ,tanks7 -- ,momentum ,brakes -- ,g4 ,e4 ,electric ,brake -- ,westinghouse ,electromagnetic ,brake -- ,track ,brakes -- ,motors as ,emergency ,brakes -- ,brake ,shoes -- ,track ,sanders -- ,drawbars and ,couplers4 ,car ,construction ,page #fg ,car ,bodies -- ,steel ,car ,framing -- ,car ,weights -- ,car ,painting4 ,line ,construction ,page #gc ,overhead ,construction -- ,trolley-,wire -- ,clamps and ,ears -- ,span ,wires -- ,brackets -- ,feeders -- ,section ,insulators -- ,high-,tension ,lines -- ,third-,rail ,system -- ,conduit ,systems -- ,contact ,plow -- ,current ,leakage -- ,track ,construction -- ,girder ,rail -- ,trilby ,groove ,rail -- ,shanghai ,t-,rail -- ,common ,t-,rail -- ,track ,support -- ,ballast -- ,joints 7,welded1 ,cast-,welded1 ,electrically ,welded1 ,thermit-,welded7 -- ,bonding and ,return ,circuits -- ,feeder ,systems -- ,block ,signals -- ,electrolysis and ,its ,prevention4 ,power ,supply and ,distribution ,page #ih ,direct-,current ,feeding -- ,booster ,feeding -- ,alternating-,current ,transmission -- ,interurban ,distribution -- ,power-,house ,location -- ,alternating-,current ,generators -- ,double-,current ,generators -- ,general ,plan of ,power ,stations -- ,switchboards -- ,generator ,d4 ,c4 ,panels -- ,starting ,up a ,generator -- ,feeder ,panel -- ,alternating-,current ,switchboards -- ,high-,tension ,oil-,switches -- ,storage ,batteries in ,stations -- ,three-,phase ,motors -- ,single-,phase ,motors4 ,operation of ,electric ,railways ,page #aae ,power ,taken by ,cars -- ,road ,tests of ,cars -- ,economy in ,power -- ,sliding and ,spinning ,wheels -- ,testing for ,faults -- ,bond ,testing -- ,motor-,coil ,testing -- ,grounds -- ,burn-,outs -- ,defects of ,armature ,windings -- ,sparking at ,commutator -- ,failure of ,car to ,start -- ,open-,circuit ,tests -- ,short-,circuit ,tests -- ,fuse-,blows -- ,armature and ,field ,tests for ,grounds -- ,reversed ,fields -- ,car ,repair ,shops4 ,the ,single-,phase ,electric ,railway ,page #acg ,commutator ,type ,single-,phase ,motor -- ,advantages and ,disadvantages of ,single-,phase ,system -- ,lines in ,operation4 ,index ,page #adi ,illustration3 ,,heavy-,,duty ,,cross-,,compound ,,condensing ,,engine1 ,,direct ,,connected ,,to #a1ejj ,k4,w4 ,,railway ,,generator4 ,st4 ,louis ,transit ,company's ,power ,house4 ,fulton ,iron ,works4 ,,electric ,,railways4 ,,part ,i4 ,the general name 8electric railway0 is applied to all railways employing electric motors to supply power for the propulsion of cars4 ,on all electric railways in commercial use to-day1 the electric motor is used to furnish power to the driving wheels of the car or locomotive1 the electric motor being the most efficient known means of transforming electrical into mechanical energy4 ,electric railways are usually classified according to the methods by which current is supplied to the moving car4 ,thus1 where an overhead trolley wire is used1 as on the great majority of electric railways1 the term trolley road is applied4 ,where an insulated steel rail is laid alongside the track rail for supplying current1 as on the 8elevated0 roads in ,america and on a few interurban roads1 the term third-rail road is used4 ,where1 as on the street railways of a few large cities1 the conductors are placed in a conduit underneath the surface of the street1 and current is taken by means of a plow or shoe running in the conduit1 the name electric-conduit railway is most commonly applied4 ,there are also a few systems using conductors buried beneath the pavement1 and having contact buttons or sections of conductor rail on the street surface1 which sections are supplied with current by automatic electromagnetic switching apparatus as the car passes1 but which are normally dead and harmless4 ,the overhead trolley and the third-rail systems are by far the most common4 ,a further general classification of electric railways has recently been made because of the introduction of alternating-current railway motors4 ,the great majority of electric railways employ direct-current motors4 ,where alternating-current motors are used1 the road is spoken of as one using single-phase alternating-current motors or three-phase alternating-current motors1 as the case may be4 ,all electric railway systems in commercial use are operated on an approximately constant potential or voltage1 and the various electric motor cars operating on the system are connected across the lines in parallel4 ,the most common practice is to utilize the rails and ground as one side of the circuit1 and the overhead trolley wire or 8third rail0 as the other side1 as in ,fig4 #a4 ,the trolley wire or third rail is1 of course1 thoroughly insulated from the ground4 ,the positive poles of the generators at the power house are usually connected to the trolley wire1 and the negative poles to the rails and ground4 ,the various electric motor cars1 being connected in parallel or multiple between the trolley wire and the ground1 draw whatever current is necessary for their operation4 ,where the conduit system is used1 both sides of the circuit are insulated from the ground1 and the contact shoe or plow collects current from two conducting rails in the conduit1 one of these conducting rails being positive and the other negative4 ,a double-trolley system is also in use to a limited extent4 ,in this system1 both the positive and the negative sides of the circuit are insulated from the ground1 one trolley wire being positive and the other negative4 ,illustration3 ,fig4 #a4 ,illustration3 ,fig4 #b4 ,railway ,motor4 ,further discussion of the matters just outlined will be taken up in the succeeding pages4 ,,car ,,equipment4 ,,motors4 ,the voltage most commonly employed by electric railways is #ejj to #fjj2 and the motors are #ejj-volt direct-current series-wound motors1 designed especially for railway service4 ,the electric railway motor must be dustproof and waterproof because of the position it occupies under the car4 ,for this reason electric railway motors are made in the form of a steel case 7,fig4 #b71 which entirely surrounds the field-magnet poles and takes the place of the yokes or frames that support the fields on stationary motors4 ,cast steel is the material now usually employed for railway motor cases and fields1 on account of its mechanical strength and its high magnetic permeability4 ,the four poles project inwardly from the case1 as seen in the open motor case1 ,fig4 #c1 which is that of a ,westinghouse ,no4 #fi motor4 ,illustration3 ,fig4 #c4 ,railway ,motor4 ,upper ,field ,raised4 ,railway motors have usually four poles because this permits of a symmetrical and economical arrangement of material around the armature1 and hence permits the motor to be placed in the small space available on the car truck4 ,two-pole motors have been used in the past1 but they were not as compact as the four-pole type4 ,characteristics of ,railway ,motors4 ,the curve sheet1 ,fig4 #d1 for the ,westinghouse ,no4 #fi motor represents in general the characteristics of all direct-current railway motors4 ,the figures for each curve are found with names corresponding to the curve to which they apply1 at each side represented by vertical distance on the sheet4 ,the amperes1 represented by the horizontal distance1 are marked at the bottom1 and apply in common to all the curves4 ,the tractive effort at different current consumption is represented by a line curving upwards somewhat4 ,this shows that the tractive effort increases1 in a proportion greater than directly1 as the current increases4 ,the torque required in starting may be many times greater than that necessary to maintain the car at full speed4 ,the series-wound motor1 therefore1 furnishes this great starting torque more economically than a shunt-wound motor the torque of which is proportioned to the current4 ,this feature of the series-wound motor makes it especially adapted to street railway work4 ,illustration3 ,,westinghouse ,no4 #fi ,,railway ,,motor #ejj ,,volts ,,gear ,,ratio1 #ad ,,to #fh4 ,,wheels1 #cc ,,continuous ,,capacity1 #be ,,amperes ,,at #cjj ,,volts1 ,,or #bc ,,amperes ,,at #djj ,,volts4 ,fig4 #d4 ,characteristic ,curves of ,railway ,motor4 ,the efficiency curve shows the motor to have an efficiency of about #hc per cent with gears4 ,much other information may be obtained by a proper study of the curves4 ,the fields are worked near the point of magnetic saturation4 ,this economizes metal and space and is also an advantage because of the fact that when so worked the armature reactions have very little effect on the fields4 ,the neutral points between fields are consequently shifted very little and it is therefore not necessary to shift the brushes when the motor is reversed4 ,illustration3 ,fig4 #e4 ,armature ,winding4 ,general ,data on ,street ,railway ,motors4 ,armature ,winding4 ,the armature winding is what is commonly known as the series or wave winding1 shown developed in the paper on ,direct-,current ,dynamos4 ,this winding is shown in ,fig4 #e1 which is an end view of an armature and commutator4 ,in the figure1 however1 the armature is shown with a much smaller number of slots than a railway armature should have in practice4 ,one reason for the employment of the wave or series winding on railway motor armatures1 is that with this winding no cross-connections are necessary when only two brushes are used1 and these two brushes may be placed #ij apart in a convenient and accessible position4 ,another reason is that the current1 in flowing from one brush on the commutator to another1 must always pass through the magnetic field of all four of the motor poles4 ,this makes it impossible for any unbalancing of the magnetic circuit to cause more current to flow through one portion of the armature than is flowing through another portion4 ,in a railway motor it has been found quite possible to have one pole or pair of poles exerting a greater magnetic attraction on the armature than another pair1 owing to differences in the iron and differences in the clearance between the armature and pole pieces1 which differences cause more magnetic lines of force to flow from some pole pieces than from others4 ,with the lap-armature or the ring-armature winding1 since the various portions of the armature under different poles are in parallel with one another1 any difference in the magnetic flux between different poles will cause a different amount of current to flow in the various paths through the armature4 ,type of ,horse ,amp- ,speed,total ,slots4,cond- ,commu- ,weight ,armature ,gears ,commutator ,pinion ,dia- ,length4 ,motor4 ,power4eres4,full ,field uctorstator complete,complete4 and ,bearing4 ,bearing4 meter ,load4,turns4 per ,bars4 with ,casing4 ,arma- slot ,gears4 ,inches4 ,inches4 ture4 ---------------------------------------- ---------------------------------------- --------------------- ,general ,electric #ea #hb #fdj #ef #cg #ab #aaa #chge #iec #cch #c #e #c #h #af #aj #eb #bg #fdj #aee4e #bi #bd #hg #agbe #ceg #bfe #b #f #b #g #aa #i #eg #eb #dgj #aaj #cc #ah #ii #bigb #gjd #cdj #b #f #c #h #ad #ab #ee #afj #dg #f #ada #edae #aeej #dij #c #g #c #aa #fg #dj #aaj #cg #ah #aaa #bche #eie #che #b #f #c #h #ed #be #aae #ahca #cie #bhe #b #f #b #g #gd #fe #aac #gj4e #cecd #hde #dae #c #f #c #h ---------------------------------------- ---------------------------------------- --------------------- ---------------------------------------- ---------------------------------------- --------------------- ,westing- house #fh #dj #ee #ab #aji #bbhj #eje #ccj #b #f #c #g #ad #h #fi #cj #ce #aje #aiej #che #ccj #b #f #b #g #ac #f #gf #ge #ci #aag #chdj #eje #hfj #c #h #c #i #af #ef #ee #ci #aag #cjjj #cae #gbj #c #g #c #h #ad #ab #ej;c #aej #add #ee #f #aae #eeej #aejj #di #ce #aad #ei #aag #aibe #dch #cbg #b #f #b #g #ac #f ---------------------------------------- ---------------------------------------- --------------------- ,by reference to the winding diagram given in ,fig4 #e1 it may be noted that a complete circuit through two coils ends at the segment adjacent to the one from which the start was made4 ,it may also be noted in the table of motor data that all of the armatures have an odd number of segments and an odd number of slots4 ,it is absolutely necessary in a wave winding to have an odd number of segments4 ,otherwise the winding could not be made symmetrical and the circuit through two coils be made to return to a segment adjacent to that from which the start was made4 ,with equal spacing between the top and bottom leads of the two coils1 an even number of segments would make the circuit return either on the segment from which the start was made or two segments from it4 ,the first drum-wound street railway motor armatures had as many slots in the armature as there were coils and segments4 ,the great number of slots necessarily made the teeth very thin and consequently weak4 ,this is very objectionable as sometimes the armature bearings wear away1 allowing the face of the armature to drag on the pole pieces and thin teeth are bent out of shape4 ,armatures are now almost entirely constructed with either two or three coils to a slot4 ,when two coils are used in each slot with an odd number of slots an even number of coils results4 ,if these were all connected to the commutator an even number of segments would be necessary4 ,as this is not possible with a wave winding1 one of the coils is 8cut out40 ,the ends are cut short and taped and it is termed a 8dead0 coil4 ,this makes the winding somewhat unsymmetrical1 all the coils not bearing the same angular relation to the commutator segments to which they are connected4 ,this difference is1 however1 not great enough to affect the operation of the machine4 ,the ,westinghouse #di motor is an example of an armature with a dead coil4 ,by reference to the table of motor data it will be seen that this armature has #ei slots4 ,two coils in each slot would make #aah coils4 ,one of these1 however1 is cut out1 giving #aag segments4 ,cutting out a coil can be avoided by putting three coils in each slot4 ,an odd number of coils results then no matter what the number of slots may be4 ,in the majority of examples given in the table there are three times as many segments as slots4 ,the sides of the slots of modern street railway armatures are straight4 ,the coils are prevented from flying out by bands of wire extending over the tops of the coils around the armature4 ,steel or silicon bronze wire of about ,no4 #ad gauge is used4 ,recesses are made in the armature teeth for the reception of these bands so that the wire when wound will come flush with the face of the armature4 ,the bands are usually to #a inches wide4 ,the wires are well soldered together to secure them in place4 ,one trouble experienced with armatures is the slipping off of these bands4 ,the heated armature expands and stretches them4 ,when the armature cools the bands are loose and then often slip off4 ,when they do so the coils fly out by centrifugal force1 strike the pole pieces and ground the motor4 ,illustration3 ,fig4 #f4 ,armature ,coil4 ,armature ,coils4 ,railway motor armatures are to-day universally constructed with form-wound coils1 which are wound on a form of proper shape and carefully insulated before being placed in the armature4 ,the coils of the smaller motors 7those up to #dj or #ej horsepower7 are usually wound with round wire4 ,the cotton covering of the wire is depended upon for insulation4 ,to strengthen this1 however1 the coils after being wound are immersed in an insulating compound and then baked in an oven4 ,the whole coil is usually wrapped with insulating tape 7,see ,fig4 #f74 ,the armatures of larger motors have coils made of copper bars4 ,mica is often placed between and around the bars for insulation1 though oiled linen cloth tape cut bias is also employed1 especially in repair work4 ,field ,coils4 ,field coils are so constructed that they may be readily removed should they become grounded or short-circuited4 ,some makers wind them on a brass shell or form which is slipped over the pole piece4 ,in some motors the field coils are composed of copper ribbon1 wound bare1 with ribbons of insulating material between the turns4 ,field coils of wire for the smaller motors1 if not wound on shells1 are wound on forms and before completion are taped in such a manner that they will hold their shape without being enclosed in a spool4 ,the terminals are brought out where they will be of easy access when the field is in place 7,see ,fig4 #g74 ,illustration3 ,fig4 #g4 ,field ,coil4 ,armature ,leads4 ,in ,fig4 #c is seen a completed armature in the motor casing of a ,westinghouse ,no4 #fi motor4 ,since the motors are four-pole1 the two sides of any one coil occupy slots #ij apart in the armature coil1 as indicated in ,fig4 #e4 ,the ends of the coils are connected to commutator bars #ahj apart4 ,the relative position of the commutator connections of any armature coil can1 of course1 be varied so as to bring the brushes in the most convenient position in the motor casing4 ,brushes are always of carbon1 and are placed where they can be easily reached from the opening in the motor casing over the commutator4 ,motor ,leads4 ,the reversing of the current through the armature1 independent of the field current1 to secure reversal of direction of rotation of the armature1 makes it necessary that four wires enter the motor4 ,the portions of these wires connected permanently to the motor are termed the motor leads because they 8lead out0 the current4 ,sometimes an ordinary two-way connector is used in connecting these leads to the wires of the cable1 but often a jack-knife connector is employed to facilitate connecting and disconnecting4 ,considerable difficulty has been experienced by the wearing away of the insulation of the leads where they rest on the motor shell4 ,to avoid this there has recently come into use a lead protected by a spiral metal covering4 ,brushes4 ,that the motor may operate in either direction equally well1 the carbon brushes are placed radially or nearly so4 ,no provision is made for shifting their position relative to the fields4 ,they usually occupy a position equidistant between pole tips4 ,the common types are either or -inch thick and from #b to #d inches wide4 ,illustration3 ,fig4 #h4 ,brush ,holder4 ,brush ,holders4 ,two methods of securing the brush holders are employed4 ,in ,fig4 #c1 the brush holders may be seen to be secured in position by being bolted through the end of the motor shell4 ,fig4 #h shows the brushes mounted on a yoke which is secured to the motor shell4 ,the yoke is of wood and provides the necessary insulation4 ,where the holders are fastened directly to the shell a block and washers of vulcabeston or other insulating material intervene to furnish the insulation between the shell and the holder4 ,in practice the greatest difficulty experienced with brush holders is preventing them from becoming grounded by dirt and carbon dust which collects on the insulation4 ,opening ,cases for ,inspection4 ,accessibility for inspection and repairs is essential in all railway motors4 ,a lid is always provided directly over the commutator to facilitate inspection of the commutator and brushes4 ,to open up the motor casing for more extensive inspection or repairs1 three general schemes are employed4 ,one is to have the lower half of the casing swing downward on a hinge as in ,fig4 #i1 which illustrates the ,westinghouse ,no4 #ch ,b motor4 ,the armature may be placed either in the lower half1 as shown in ,fig4 #i1 or in the upper half4 ,when a motor of this type is to be opened the car is run over a pit1 and the repair men work entirely from below4 ,often the hinge pins are removed and the lower shell containing the armature is dropped down by means of a jack placed underneath4 ,two handholes are usually provided in the bottom shell for observing the clearance between the armature and the pole pieces and also for removing dirt that may collect in the bottom of the shell4 ,another scheme is to have motors open from the top1 either by hinging the upper part of the motor casing1 as in ,fig4 #c1 or by having the top part of the casing lift off4 ,where this form of motor is used1 the car body is hoisted clear of the truck1 and the trucks are run out from under the car body before work is done on the motors4 ,in this case1 all the work can be done from above without the use of pits4 ,illustration3 ,fig4 #i4 ,railway ,motor4 ,lower ,half of ,casing ,swung ,down4 ,a third design is the box-frame motor casing1 from which the armature can be removed endwise only4 ,such an arrangement is shown in ,fig4 #aj1 which is a view of a ,no4 #ff motor of the ,general ,electric ,company4 ,in this motor a sufficiently large opening is provided in the ends of the motor casing to permit of the armature being removed endwise4 ,a plate or head1 which accurately fits into this opening1 carries the armature bearing4 ,in removing armatures from motors of this kind1 the usual method is to take the motor out of the trucks and stand it on end with the pinion up4 ,the bolts being removed from the end plate1 the armature can then be hoisted out of the case by means of a special hook attached to the pinion4 ,another plan that has been used in removing armatures from such motors1 is to place the motor in an apparatus where the armature shaft can be held between centers1 as in a large lathe4 ,the motor casing is then moved along in a direction parallel to the armature shaft1 until the armature is exposed4 ,this latter box-frame type of motor is very compact2 a stronger casing can be made for a given weight and space than if it were divided horizontally4 ,moreover1 the magnetic circuit cannot be disturbed by imperfect contact between two parts of the casing4 ,where this type of motor is used1 the bearings project inward under the commutator and armature1 thus getting long bearings with a short motor1 which is important where the room is limited1 as1 for example1 in the case of a large motor mounted on a standard-gauge truck4 ,illustration3 ,fig4 #aj4 ,box-,frame ,motor4 ,gearing4 ,in most cases1 spur gearing is used to transmit power from the armature shaft to the car axle1 although a few motors with armatures mounted directly on the car axle are in use4 ,various gearings other than the simple spur gear have been tried1 such as worm gears1 chain and bevel gears4 ,practically all have been abandoned in favor of the single-reduction spur gearing1 which is the most satisfactory from the standpoint of wear and efficiency4 ,this gearing is shown in ,figs4 #c and #i4 ,the gearing is covered with a gear case 7,fig4 #i71 which is usually of steel1 though gear cases of thin sheet metal and wood are sometimes used4 ,a solid gear is shown in ,fig4 #aa1 and a split gear in ,fig4 #ab4 ,the gear ratios in common use vary from #e to #a to #b to #a1 the larger ratio being common on the smaller motors4 ,a ratio often used on motors of #cj to #ej horsepower is #d4gh to #a1 the gear having #fg teeth1 the pinion #ad teeth4 ,street car wheels are usually #cc inches in diameter4 ,this makes necessary #fab revolutions per mile4 ,with a gear ratio of #d4gh the armature revolves #b1ibe times per mile4 ,at #ae miles per hour1 this gives #gca r4p4m4 ,illustration3 ,fig4 #aa4 ,solid ,gear4 ,illustration3 ,fig4 #ab4 ,split ,gear4 ,lubrication4 ,the lubrication of railway motors was for a number of years carried on almost exclusively with grease1 which it was customary to place in the gear casing and in grease boxes over the armature and car-axle bearings4 ,grease becomes most efficient as a lubricant only when the bearing is heated sufficiently to make the grease run like oil4 ,oil is now being used to a considerable extent1 especially for larger motors4 ,it is fed to the bearings by various devices that allow a very slow feed1 such as wicks and lubricators adjusted to pass a small amount of oil per hour4 ,bearings4 ,railway motor bearings are usually of ,babbitt metal1 which metal is cast into a steel shell4 ,this shell fits into receptacles in the motor casing1 which can be seen in ,figs4 #c and #i4 ,a steel shell is used so that the worn-out bearings can be easily renewed and the shells taken to a ,babbitt melting furnace to have new ,babbitt poured into them4 ,the motor has two sets of bearings1 those for the armature and those for the axle upon which the motor is mounted4 ,the axle bearings are always split diametrically to avoid removing a wheel when a bearing is replaced4 ,on the later designs of motors these are of brass1 no ,babbitt metal being used4 ,the armature bearings are distinguished by the terms 8gear end0 and 8commutator end0 bearings4 ,the gear end bearing is usually of larger diameter and of greater length because of the thrust of the gears it must take in addition to the weight of the armature4 ,this bearing is split so that it may be removed and replaced without the removal of the gear4 ,the commutator end bearing is in one piece4 ,armature bearings are shown in ,fig4 #ac4 ,illustration3 ,fig4 #ac4 ,armature ,bearings4 ,motor ,suspension4 ,two methods of suspending motors flexibly on trucks are in common use4 ,that end of the motor which has bearings on the car axle cannot1 of course1 be flexibly suspended with regard to the axle2 but the other end of the motor can be placed on springs1 or rest on a bar supported on springs1 as shown in ,fig4 #ad4 ,this suspension is commonly called nose suspension4 ,instead of having a special bar and special springs for the nose of the motor1 the nose may rest upon some part of the truck that is carried upon springs4 ,thus1 on the ,m4 ,c4 ,b4 type of swivel truck1 the nose usually rests on the truck bolster1 and thus gets the benefit both of the bolster springs and of the equalizer springs of the truck4 ,another general plan of suspension is that known in one form as cradle suspension1 and in another form as side-bar suspension4 ,a side-bar suspension is shown in ,fig4 #ae4 ,here a larger percentage of the weight of the motor is evidently taken by the springs than in the case of nose suspension4 ,it is desirable to relieve the car axle of as much dead weight as possible4 ,by dead weight is meant weight resting upon it without the intervention of springs4 ,illustration3 ,fig4 #ad4 ,nose ,suspension4 ,illustration3 ,fig4 #ae4 ,side-bar ,suspension4 ,motors of the ,new ,york ,central ,electric ,locomotive4 ,these motors are a radical departure from the usual type of railway motors4 ,the locomotive on which they are mounted has four driving axles1 upon each of which is mounted an armature1 direct1 no gears being used1 ,figs4 #af and #ag4 ,the motors are remarkable for three special features3 ,the method of mounting the armature1 the shape of the pole pieces1 and the path of the magnetic flux4 ,illustration3 ,fig4 #af4 ,longitudinal ,section of ,new ,york ,central ,locomotive4 ,illustration3 #ie ,,ton ,,electric ,,locomotive ,,for ,,new ,,york ,,central ,,railroad4 ,general ,electric ,company4 ,the mounting of the armature upon the driving axle and the motor fields on the truck frame makes it necessary to have flat pole pieces in order that the armature may play up and down as the journal box and axle slide in the guides of the truck frame4 ,the shape of the pole pieces may be observed in the drawing ,fig4 #af4 ,when in the central position there is a -inch air gap between the armature and pole pieces4 ,the magnetic flux is continuous through the fields of all four of the motors4 ,it returns through the cast steel side frames of the truck and two bars placed in the path4 ,the brush holders are so mounted that the brushes occupy a fixed position relative to the armature4 ,the armature is removed by lowering it with the wheels and axle upon which it is mounted4 ,this can be done without disturbing the fields of the motor4 ,,controllers4 ,in an ordinary electric car1 current is taken from the wire through the trolley wheel and pole1 and is first led from the trolley base through overhead switches or a circuit breaker1 and then to the controller1 from which it passes through the motors and thence through the motor frames1 car truck1 and wheels to the rails and ground4 ,if the car is designed to be operated from either end1 an overhead switch or circuit breaker is placed over each platform of the car so that current can instantly be cut off entirely from the controllers by throwing the switch or circuit breaker at either end of the car4 ,illustration3 ,fig4 #ag4 ,armature ,axle and ,wheels4 ,the lighting circuit is run from the trolley base independently of the motor circuit1 and has its own switch and fuse box4 ,current for the lights is taken from the trolley circuit before it reaches the main switches or circuit breakers4 ,current for electric heaters1 if such are used1 is likewise taken from a separate circuit4 ,on a #ejj-volt system five #ajj-volt lamps are usually connected in series for car lighting4 ,as many multiples of five can be employed as are necessary to light the car4 ,rheostat ,control4 ,the simplest form of controller is that employed where only one motor is used on a car4 ,a rheostat is placed in series with the motor when started1 just as on a stationary motor2 and the function of the controller is to short-circuit this resistance gradually until it is entirely cut out and the motor operates with the full voltage4 ,the controller also has a reversing switch by means of which the relative connections of the armature and fields are reversed1 which1 of course1 changes the direction of rotation of the motor armature4 ,such a simple equipment as this1 however1 is rarely to be found in practice4 ,series-,parallel ,control4 ,single-truck cars usually have two motors1 one on each axle2 and on such cars a series-parallel controller is the kind usually employed4 ,diagrams of connections on the various points of a series-parallel controller 7,type ,k#f7 of the ,general ,electric ,company1 are given in ,fig4 #ah4 ,illustration3 ,fig4 #ah4 ,diagram of ,k#f ,controller ,combinations4 ,from these diagrams it is seen that the motors are first operated in series until all the resistance is short-circuited by the controller4 ,when this has occurred1 the cars are running at about half speed4 ,the next point on the controller puts the two motors in multiple1 with some resistance in the circuit1 which resistance is cut out upon the following points1 until at full speed the two motors are in multiple1 without any resistance in the circuit4 ,four ,motors4 ,where four motors are used on a car1 as is frequently the case with double-truck cars1 the motors on each truck are usually controlled just as in case of the two-motor equipment that has been described2 but each pair of motors is operated in multiple4 ,that is1 on the first points of the controller1 the two motors of a pair are in series1 as in ,fig4 #ai1 and the two pairs are in parallel2 and on the last points of the controller1 all the motors are in parallel1 as in ,fig4 #bj4 ,illustration3 ,fig4 #ai4 ,motor in ,series4 ,illustration3 ,fig4 #bj4 ,motor in ,parallel4 ,controller ,construction4 ,the controller 7,type ,k7 shown open in ,fig4 #ba1 which in its various forms is the type most commonly used on street cars in the ,united ,states1 has a contact cylinder or drum mounted upon the main shaft of the controller4 ,this contact drum carries contact rings insulated from the drum1 and is suitably interconnected1 as indicated in ,fig4 #bb1 which shows the contact rings of the controller as they would appear if rolled out flat4 ,contact fingers are placed along the left side of the controller1 as seen in ,fig4 #ba1 one for each ring on the drum2 and as the controller handle is turned to revolve this drum1 the contact fingers make contact with the rings on the drum and give the various connections4 ,alongside the main controller drum is a reverse drum which simply reverses the armature connections of the two motors4 ,controller ,wiring4 ,the connection between motors1 controllers1 and resistances1 with two motors and a ,k#f controller is shown in ,fig4 #bb4 ,a careful study of this will show the combinations to be the same as indicated in the diagram1 ,fig4 #ah4 ,the wiring is rather complicated2 and in practice1 to avoid confusion1 the ends of each wire are labeled with tags showing the terminals to which they belong4 ,illustration3 ,fig4 #ba4 ,controller4 ,illustration3 ,car ,wiring for ,k-#f ,controllers with two ,motors ,fig4 #bb ,illustration3 ,fig4 #bc4 ,motors in ,series4 ,illustration3 ,fig4 #bd4 ,motors in ,parallel4 ,with the aid of ,figs4 #bb1 #bc and #bd1 the wiring of a type ,k#f controller with two motors may be followed4 ,figs4 #bc and #bd are for a different controller but can be used to assist in an understanding of the complicated diagram #bb4 ,the current leaves the choke or kicking coil of the lightning arrester and passes through the blow out coil of the controller4 ,it then goes to the top finger ,t of the controller4 ,on the first point the circuit is as shown in ,fig4 #bc4 ,the top segment ,a makes contact with the top or trolley finger4 ,all but the lower five segments of the cylinder are electrically connected together by means of the iron cylinder upon which they are mounted4 ,on the first point then the current passes from the cylinder over ,r1 and with straight series connections of the resistances1 it goes through all of the rheostats under the car1 and returns to the controller over the last resistance lead1 ,r4 ,behind the motor cut-out switches at the base of the controller this lead is tapped into a wire one end of which leads to finger #ai of the controller1 and the other end through the cut-out switch and reverse cylinder to ,no4 #a armature4 ,the current takes the latter path1 passes through the armature of the motor and returns by way of the reverse cylinder1 thence through the fields of ,no4 #a motor and then through the cut-out switch of ,no4 #a motor and to finger ,e1 of the controller4 ,segments ,o1 ,m1 ,n and ,l1 shown in ,fig4 #bc1 and corresponding segments of ,figs4 #bb and #bd1 are insulated from the remainder of the controller cylinder4 ,from finger ,e and segment ,o 7,fig4 #bc7 the current passes over finger #ae through ,no4 #b cut-out switch and the reverse cylinder to the armature of ,no4 #b motor4 ,returning it passes through the reverse cylinder1 then back through the fields of ,no4 #b motor and to the ground1 which is usually through a connection on the motor casing4 ,on points #b1 #c1 #d and #e1 the successive series points of the controller ,r1 ,r1 etc41 make contact with segments ,b1 ,c1 etc41 ,figs4 #bc and #bd1 until finally finger #ai rests on segments ,j1 the resistance is all cut out and the motors are connected in series directly across the line4 ,a further movement of the controller handle changes the motors from series to multiple connection and inserts in the circuit a portion of the external resistance4 ,there are four separate stages in making this change4 ,first1 the resistance fingers slide off their segments and the resistance is inserted in the line4 ,second1 fingers ,e and ,g make contact with segments ,p and ,q4 ,motor ,no4 #a is then across the line in series with the resistance2 the circuit being from ,e to ground over ,g4 ,when the lower finger ,e makes contact with ,p1 the upper one has not yet left segment ,o4 ,this short-circuits ,no4 #b motor1 the path being from the ground1 up wire ,g1 thence by way of segments ,p and ,q and through connecting clip ,v1 between the two ,e fingers back through finger #ae to the motor4 ,a further movement of the controller handle causes the fingers to leave segments ,m and ,o and ,no4 #b motor is open-circuited until finger #ae makes contact with segment ,n4 ,when this takes place the motors are in multiple4 ,on the successive points after this the external resistance is cut out in the same manner as previously described4 ,by reference to ,fig4 #bb1 it will be noticed that the leads to the motors and the resistances are tapped on wires of the cables connecting the two controllers on the ends of the car4 ,the two ends of these wires1 with the exception of the armature wires1 lead to similar binding posts on the two controllers4 ,the armature wires are interchanged connecting at one controller into binding post ,a ,a1 while the other end connects into binding post ,a4 ,this change of connection is necessary in order that the reverse handles be forward for forward direction of movement of the car4 ,illustration3 ,fig4 #be4 ,forward ,position of ,reverse4 ,to reverse a series motor it is simply necessary to reverse the direction of flow of the current in either the armature or field4 ,for several reasons1 it is advantageous in the case of the street railway motor to reverse the current in the armature rather than in the field4 ,figs4 #be and #bf show how this is accomplished4 ,the squares shown in the figures represent the lugs on the reverse cylinder as shown in ,fig4 #ba4 ,with the reverse handle in one position 7,fig4 #be71 the large lugs are under the reverse fingers1 and current passes from finger #ai to finger ,a1 and from finger #ae to finger ,a4 ,fig4 #bf shows the relative position of reverse fingers and lugs for the reverse position of the controller handle4 ,in this case the current passes from finger #ai to ,a ,a1 and from finger #ae to finger ,a ,a4 ,the effect is to change the direction of flow in the armatures while that in the fields remains the same as may be observed by the arrows4 ,illustration3 ,fig4 #bf4 ,reverse ,position of ,reverse4 ,wiring of ,type ,l ,controllers4 ,the type ,l controller1 shown in ,fig4 #bg1 while accomplishing the same results as the type ,k1 is wired in a radically different manner4 ,the circuit is opened in changing from series to multiple connections4 ,the controller handle makes two complete revolutions in moving from the series to the multiple position4 ,it is geared to the rheostatic cylinder in such a manner that the first half of both the first and second revolutions gives this cylinder one complete turn4 ,during the second half of the revolution the cylinder is returned to its original position4 ,the controller handle is so connected to the commutating arm that this stands in a central position for the off position of the handle4 ,at the beginning of the first revolution it is swung to the left1 throwing the motors in series4 ,at the beginning of the second revolution it is moved to the right1 putting the motors in multiple4 ,the rheostats instead of being wired in series are connected in multiple4 ,current passes from the blow-out coil to the bottom fingers of the controller ,s1 and thence to the rheostats4 ,on the first point the current returns over ,r to the controller cylinder4 ,it passes off through a collar at the base of the cylinder through ,no4 #a cut-out1 and the reverse1 which is shown in the central position1 to ,no4 #a motor4 ,on returning to the controller over ,e it passes to the upper section of the commutating arm4 ,in the diagram this is shown in the central position4 ,in series it is thrown to the left4 ,the current then passes from the commutating arm to ,no4 #b cut-out1 and to ,no4 #b motor4 ,movement of the controller handle further multiplies the paths through the rheostats and finally1 when fingers ,s rest on the cylinder1 the rheostats are short-circuited4 ,if the controller handle is moved still farther1 the rheostat cylinder is returned to the off position and the commutating arm is thrown to the left4 ,with the arm in this position the current divides1 one portion passing to ,no4 #a motor as before and to ground by way of the upper section of the commutating arm2 while the other branch goes by way of the lower section of the commutating arm to the cut-out switch for ,no4 #b motor and thence to the motor4 ,illustration3 ,diagram of ,connections for ,l#b ,controller ,fig4 #bg4 ,reversing is accomplished by one-quarter revolutions to the right and left of the segments shown4 ,it is evident that this will connect either ,a or ,a ,a1 to the trolley4 ,and likewise connect the other armature leads4 ,reversal4 ,the reversing handle and the main controller handle are made interlocking so that the motors cannot be reversed without first throwing the controller to off position4 ,this is to prevent damage to the motors through careless or inadvertent throwing of the reverse handle when the controller is on some of its higher points4 ,such a reversal would cause an enormous current to flow through the motors1 and would be likely to damage them and to open all the circuit breakers and fuses in that circuit4 ,the reason for the enormous flow of current is1 of course1 that the counter-electromotive force of the motors1 when reversed with the car going at some speed1 would materially add to the electromotive force of the trolley line1 instead of opposing it as when the cars are in operation4 ,the current flowing through the motor circuit would then be equal to 7electromotive force of line electromotive force of motors7 7resistance of motors71 which would result in a very large current4 ,magnetic ,blow-,out4 ,on the ,type ,k controller as well as on most other successful controllers1 the flashing or arcing between contact rings and fingers1 which occurs when the circuit is broken1 is materially reduced by a magnet that produces what is called the magnetic blow-out to extinguish the arc4 ,this magnet derives its current from the main circuit1 and is so arranged as to create a strong magnetic field in the neighborhood of the place where the arc is formed4 ,fig4 #ba shows a ,type ,k controller open with the magnetic blow-out magnet thrown back on a hinge4 ,the coil which produces this magnet is seen in the right side of the controller4 ,the main contact drum is in the middle1 and the reversing drum at the right hand4 ,there are in use a number of other controllers built upon these same general principles but differing in mechanical arrangement4 ,controller ,notches4 ,all controllers are provided with some device which prevents the motorman from stopping the controller handle between the various points or notches1 as the stopping between points might result in drawing an arc or an imperfect contact4 ,the most common arrangement to prevent this is a notched wheel on the controller shaft1 against which bears a small wheel of just the right size to enter the notches4 ,the small wheel is held against the notched wheel by a strong spring4 ,as the tendency of the small wheel is to seek the bottom of the notches1 it is difficult to stop the controller handle anywhere between notches1 and the motorman is thus given a guide which tells him without any effort on his part just where the notches are4 ,to prevent advancing the controller handle too rapidly and avoid the jerking of passengers1 excessive currents and slipping of wheels during acceleration1 several devices have been planned4 ,on the multiple unit control systems1 a limit switch is usually provided which prevents the controller advancing when the current exceeds a predetermined amount4 ,a device to accomplish the same results on the ,k type of controllers is termed the ,automotoneer4 ,a cam connected with a dash pot prevents movement of the controller handle to the successive notches faster than a previously prescribed rate4 ,a switch is usually provided in a controller1 for cutting out of service one motor or a pair of motors if defective1 and allowing the car to proceed with the good motor or motors4 ,illustration3 ,fig4 #bh;a4 ,car ,wiring for ,g4 ,e4 ,train ,control ,system4 ,illustration3 ,,westinghouse #cjj ,k4,w4 ,,direct ,,current ,,engine ,,type ,,three-,,wire ,,generators4 ,pittsburgh1 ,cincinnati1 ,chicago and ,st4 ,louis ,railroad1 ,columbus1 ,ohio4 ,,multiple-,,unit ,,control4 ,a system called 8multiple-unit control0 or 8train control0 has come into use where it is desired to operate motors under a number of different cars in a train2 all the motors being controlled from the head of the train or from any other point on the train where the motorman may be stationed4 ,there are several types of multiple-unit control4 ,in all of them there is on each car a controller of some kind which controls the current flowing to the motors on that car4 ,this controller is operated from a distance by means of electro-magnetic or electro-pneumatic devices controlled by circuits called pilot circuits1 which circuits are connected to the motorman's controller4 ,all the pilot circuits of a train are connected together by means of train plugs which make the connections between the cars4 ,the pilot circuits of each car are connected to a motorman's controller on that car and this makes it possible to operate the train from any controller4 ,sprague ,multiple-,unit ,system4 ,in the earliest form of multiple-unit control--which was that devised by ,f4 ,j4 ,sprague--the motors on each car were controlled by an ordinary ,type ,k controller1 which had geared to its shaft a small pilot motor4 ,the pilot motor was controlled by the pilot circuits connected with the motorman's controller4 ,in the more recent forms of multiple-unit control1 the use of main controllers having contact cylinders has been practically abandoned4 ,the contacts are made instead by a number of electro-magnetic or electro-pneumatic contact devices sometimes called contactors4 ,general ,electric ,train ,control4 ,in the ,general ,electric train-control system each contact for the motor circuits is made by a solenoid magnet which draws together two heavy copper contact fingers to establish the circuit4 ,a magnetic blow-out coil in series with the contact is also provided4 ,the contactors make contact only when energized by a small amount of current from the master or motorman's controller4 ,in ,fig4 #bh;a is a diagram of the car wiring for a motor car equipped with this system4 ,the motorman's controller is a drum controller1 but is comparatively small since it has to handle only the small amount of current necessary to operate the solenoid magnets of the contactors4 ,it is evident that by connecting together the pilot circuits1 which are connected to the motorman's controller1 so that the pilot circuits will be continuous for the entire length of the train1 any number of cars equipped with the train-control system can be operated2 and similar contacts will be made by the contactors under all the cars simultaneously1 by virtue of the circuits established by the master controller at any platform4 ,besides controlling the contactors1 the master or motorman's controller must control an electro-magnetic reversing switch1 or reverser1 to change the direction of car travel4 ,the handle of the motorman's controller is provided with a push button1 which must be depressed while the current is turned on4 ,should the motorman release this push1 the circuit through the controller will be opened and all the contactors will fall open4 ,this handle is called the dead man's handle because it is put there to provide for cutting off the current should the motorman fall dead or in a faint at his post4 ,the flow of the current in the control circuits1 which operates the reverser and picks up the contactors on the several points may be followed in the diagram ,fig4 #bh;a4 ,with the reverse handle in the forward position and the controller on the first point1 current passes from the main circuit through a single-pole fused switch called the control switch and through the auxiliary blow-out coil to a finger bearing on the upper section of the master controller cylinder by which connection is established to the adjacent finger and thence to the reverse cylinder4 ,it leaves this over wire ,no4 #h1 passing by way of the connection board and control cut-out switch to the forward operating coil of the reverser1 thence through the forward blow-out coil and over wire #ha1 through the switch underneath contactor ,no4 #b and to ground ,g1 by way of wire ,b #b after passing through the fuse shown4 ,the current through the operating coil of the reverser1 having thrown this1 the path is changed somewhat4 ,the current then instead of passing from the reverser over wire #ha1 is conducted through wire #ae1 through the operating coils of contactors ,no4 #a1 #b1 #c1 and #aa in series1 through the switch under contactor ,no4 #ab1 and to ground through finger #a of the controller4 ,contactors #a and #b are in multiple and when raised connect the trolley with the contactors controlling the resistance leads4 ,contactor #c connects ,r to the line while contactor #aa places the two motors in series4 ,the motors then operate with all of the resistance in circuit4 ,when contactor #b raises1 it opens the switch immediately below it1 making it impossible for the reverse to operate while current is flowing through the motors4 ,on the second notch of the controller an additional path is opened by way of finger #c of the controller4 ,this path leads from finger #c through four of the control circuit rheostat coils1 through contactor ,no4 #e and to ground over #cb4 ,on the #crd1 #dth and #eth points contactors #f1 #g and #i respectively are raised4 ,the motors are then in full series4 ,between the #eth and #fth points all the control circuits are broken preparatory to starting the multiple connections of motors4 ,on the #fth or the first multiple point the ground through finger #a of the master controller is opened while a ground through finger #c is established4 ,the current from the reverser then1 after raising contactors #a and #b as before1 instead of passing through contactors #c and #aa1 passes through the coils of #d1 #ab and #ac1 through the switch under contactor #aa and to ground over finger #b4 ,contactor #ab connects motor ,no4 #b to ,r1 while contactor #ac grounds ,no4 #a motor4 ,the motors now operate in parallel and on successive notches of the controller1 contactors #f1 #g1 #h1 and #i are raised1 cutting out all of the resistance4 ,the switches underneath contactors #aa and #ab make it impossible for #aa to raise with #ab and #ac or vice versa4 ,the reason for this arrangement is very evident1 as a direct ground for ,r would result4 ,the ,westinghouse ,electro-,pneumatic ,system of ,control4 ,in this system of multiple unit or train control1 the current to the motors is supplied through a set of unit switches or circuit breakers which are sometimes placed in a circular case or turret underneath the car and in other cases are ranged in a row under the car4 ,the opening and closing of these unit switches is done with compressed air acting on a piston in an air cylinder4 ,when the circuit is to be closed1 compressed air is admitted behind the piston and forces it down against the tension of a seventy-pound spring1 and the contacts are brought together4 ,when the switch is to be opened1 the air is let out of the cylinder and the spring forces the piston back4 ,the air supply is obtained from the storage tanks of the air brake system4 ,the valve controlling the air supply to the cylinder of each unit switch is operated by electromagnets which derive current from a seven cell1 fourteen-volt1 storage battery4 ,the small master controller operated by the motorman1 makes and breaks the battery connections to the magnets controlling the air valves4 ,illustration3 ,fig4 #bh;b4 ,car ,wiring for ,westinghouse ,control ,system4 ,an advantage of this over other multiple-unit systems is that by the use of battery current the control system is not disturbed by interruptions of the main supply of current4 ,the chief advantage of this is that it makes it possible to reverse the motors and operate them as brakes in emergencies at all times4 ,the battery is charged from the main line through lamps as resistance1 or may be charged by being connected in series with the air compressor motor4 ,in the accompanying diagram1 ,fig4 #bh;b1 there are two batteries shown which are charged in series with the compressor motor4 ,by means of two double-pole1 double-throw switches1 first one and then the other battery is connected for charging and for service4 ,the battery is charged in shunt with a resistance and a relay is connected in the circuit as shown1 so as to open the battery circuit whenever the current through the motor stops1 and thus prevent the battery discharging through the resistance4 ,the master controller has a double set of segments in order to decrease the length of the shaft4 ,the handle1 therefore1 is moved only one-sixth of a revolution from off to full speed4 ,the various circuits can be traced by the letters and numbers each wire bears1 so that the circuits will not be gone over in detail4 ,the first position of the master controller throws the reverser switch in the proper direction and also closes the main circuit breaker4 ,on the second point the motors are connected in series with all resistance in circuit1 and these resistances are automatically cut out one by one4 ,on the next point of the controller the motors are in multiple and the resistances are automatically cut out in a similar manner4 ,the automatic cutting out of resistances is accomplished by a limit switch in conjunction with operating and holding coils on the electro-pneumatic valves4 ,this limit switch is a kind of a relay which has the current from one of the motors flowing through its coil and which acts to open a certain battery circuit which operates the electro-pneumatic valves whenever the current in the motor circuit in question exceeds the amount for which the limit switch is set4 ,the automatic acceleration or cutting out of resistance is accomplished as follows3 ,each electro-pneumatic valve has two magnet coils1 one of which is an operating coil and the other a holding coil for holding the valve open after it is operated4 ,when first the current flows through a circuit to one of the electro-pneumatic valves1 it flows through the operating coil and operates the valve to close the corresponding switch or switches of the main circuit by turning the air into the cylinders4 ,as soon as the main switch is closed1 it cuts into circuit the holding coil of its corresponding electro-pneumatic valve and this coil will1 with the battery current1 hold the switch closed even though the circuit to the operating coil may be opened momentarily by the limit switch as each step of resistance is cut out4 ,this prevents the switches from opening when they are once closed and allows the operating coils to open an air valve each time the current through the limit switch coil falls below the amount for which it is set4 ,the contacts which close the holding coil circuit on each valve whenever a main switch is closed1 are called interlocks and are indicated on the diagram4 ,illustration3 ,fig4 #bi4 ,diagram of ,electric ,heaters4 ,the main line circuit breaker1 which is electro-pneumatically operated1 will open automatically on overload and can be reset by the motorman on all the cars of a train by closing a switch located beside each controller4 ,,car ,,heaters4 ,electric ,heaters for warming cars in winter1 consist of iron wire coils which are warmed by the passage of electric current through them4 ,the heat so evolved varies as the resistance multiplied by the square of the current4 ,the iron wire coils of the heater are mounted on non-combustible insulating supports1 and are arranged so that there is a free circulation of air through them4 ,the coils are surrounded with a perforated metal case1 the object of which is to prevent injury to the coils and to prevent persons or clothing coming in contact with the hot1 live wires of the coils4 ,heaters are sometimes arranged so that they can be connected in series or parallel to give different degrees of heat4 ,the diagram1 ,fig4 #bi1 shows the most common arrangement of electric heaters recently4 ,the tap from the trolley should be taken off on the trolley side of the circuit breaker4 ,after passing through a fuse the circuit goes to the switch4 ,each of the heaters contains two coils1 one of higher resistance than the other4 ,two independent circuits are run from the switch1 through the heaters and to the ground4 ,one circuit passes through the high resistance coils of the several heaters while the other goes through the low resistance coils4 ,the switch has three points4 ,on the first point a circuit is made through the high resistance coils4 ,the second point connects the low resistance coils while the third point puts both circuits in service4 ,with this arrangement three gradations of heat may be obtained4 ,to avoid complicated wiring sometimes but one circuit is employed4 ,in such a case the heat must either be all on or off1 no gradations being possible4 ,the chief difficulty encountered with electric heaters is the breaking of the wires because of the scale of oxide that forms gradually when they are run at a high temperature or because of water striking them from passengers' clothing on wet days1 which causes the wires to snap4 ,the ,consolidated ,car ,heating ,company gives the following data on the current required to heat cars3 ,length of ,car ,amperes4 ,body4 ----------------- ,switch ,positions4 ----------------- #a #b #c ---------------------------------------- -------------- #ad to #bj feet #c #d #g ,average conditions #bj to #bh 0 #c #f #i #bh to #cd 0 #d #g #aa ,severest conditions #ah to #bd feet #d #g #aa #bh to #cd 0 #f #h #ad ---------------------------------------- -------------- ,in his ,electrical ,engineers' ,hand ,book1 ,mr4 ,foster gives results of tests made on ,brooklyn cars as follows3 ,cars4 ,temperature ,f4 ,consumption4 ---------------------------------------- ------------------- ,doors4 ,windows4,contents,outside4,average,watt s4 ,amperes cu4 ft4 in car4 at #ejj volts4 ---------------------------------------- ----------------- #b #ab #hej #bh #ee #bbie #d4f #b #ab #hej #g #ci #bcbe #d4f #b #ab #hjh #bh #di #bahj #d4c #b #ab #iac #ce #eb #bgde #d4e #d #af #ajab #g #df #cjch #f4 #d #af #ajab #bh #ed #cafj #f4c ---------------------------------------- ----------------- ,when not watched carefully considerable current may be wasted by allowing the heaters to remain turned on when not needed4 ,many companies hang out signs where motormen may observe them1 indicating when the heaters shall be turned on and to what point4 ,illustration3 ,fig4 #cj4 ,electric ,heater4 ,the best practice in electric heating is to have plenty of heaters and run the wire at a low temperature1 rather than attempt to heat with a few at high temperature4 ,the greater the number of heaters the larger the radiating surface around which the air can circulate and a given amount of car heating can be accomplished with less current than with a few high temperature heaters4 ,the depreciation of the heater wires is less the lower the temperature at which they are operated4 ,an electric heater is shown in ,fig4 #cj4 ,hot-,water ,heaters are frequently used on large electric cars4 ,hot-water pipes are placed along the sides of the car1 and connected with a stove containing hot-water coils at one end of the car4 ,the water1 as it is heated in the stove or heater1 expands1 and consequently becomes lighter per cubic inch or other unit of volume2 it therefore tends to rise when balanced against the colder water in the car pipes4 ,hot water leaves the top of the heater1 flows up to an expansion tank and then down through the car piping1 and back to the bottom of the heater4 ,the car piping slopes continuously down from the top connection to the bottom connection of the heater4 ,at the top1 an opening to the atmosphere is provided through a small water tank1 called an expansion tank4 ,this prevents water pressure bursting the pipes as they become heated1 and allows any steam that may have formed to escape4 ,the most modern hot-water heaters for cars are completely closed except as to the ash pit at the bottom and a small feed door in the top4 ,the latter is locked so that the fire cannot come out even if the car is tipped over in a wreck4 ,fig4 #ca shows the pipes of a hot-water heating installation4 ,illustration3 ,fig4 #ca4 ,pipes for ,hot-,water ,heating4 ,,car ,,wiring4 ,the wires from motors to controllers1 when placed in exposed position under the car1 are bunched in cables or covered with hose4 ,in some cases special runways are provided in the bottom of the car to accommodate the car wiring4 ,all the wiring in a car should be heavily insulated with moisture-proof rubber-covered wire1 and further protected from mechanical abrasion by a tough outer covering4 ,stranded rubber insulated wire is used almost exclusively for wiring all parts of the car4 ,a general idea of the path of the motor circuit wiring may be obtained by reference to ,fig4 #bb4 ,the main lead after leaving the trolley stand is cleated to the trolley board on top of the car4 ,at the end of the car it passes through the roof and to the circuit breaker4 ,on leaving the breaker it is led down a post1 through the floor and to the choke coil and lightning arrester underneath the car4 ,it then passes to the trolley terminal of the controller4 ,the tap for the light wiring 7although shown otherwise in the drawing7 is usually taken off the main circuit before the circuit breaker is reached4 ,this arrangement allows the lamps to be burned when the circuit breaker is open4 ,after passing through fuses and switches in the motorman's cab the circuit for the lights is led through the car in moulding concealing it4 ,the wires running between the motors1 controllers and resistance frames underneath the car1 as has been stated1 are often carried in canvas hose4 ,usually two cables are made up1 for should all the wires necessary be placed in one cable this would become too bulky to be properly cleated up4 ,to make the canvas hose waterproof and to prolong its life it is usually given several coats of asphaltum paint4 ,the wiring of the new cars of the ,new ,york subway is an example of the most advanced practice4 ,all the wires under the cars are carried in 8loricated0 conduit1 which consists of a wrought-iron tube heavily enameled both inside and out4 ,the motor leads and the other larger wires are carried in separate conduits4 ,the conduits are usually hung to the steel beams of the floor framing by strap bolts4 ,this method of wiring gives a reasonable assurance that it will not become defective4 ,moreover1 it lessens fire risk4 ,the conduits are all grounded and should one of the wires come in contact with the conduit carrying it1 the dead ground resulting would cause the fuse to blow instantly1 and all danger would cease4 ,,resistances4 ,the type of resistance now most common for heavy motor equipment is in the form of cast-iron grids1 which are assembled together and connected in series4 ,these grids are sufficiently stiff to render unnecessary any solid insulation between them1 and hence they can radiate heat to the best advantage4 ,the only difficulty experienced with them is from the warping or cracking4 ,resistances for lighter equipment are composed of sheet-steel ribbons wound in coils4 ,each turn of a coil is insulated from the next by asbestos4 ,other forms of sheet-steel resistance with asbestos insulation between the turns1 have also been used4 ,in ,fig4 #cb is shown a ,westinghouse grid type diverter for street railway equipment4 ,,electric ,,car ,,accessories4 ,canopy ,switch4 ,an overhead switch1 sometimes called a 8canopy switch10 is commonly placed over each street-car platform where a controller is located1 usually in the deck or canopy above the motorman's head4 ,this is simply a single-point switch that may be used by the motorman to cut the trolley current off from the controller wiring so that the controllers will be absolutely dead4 ,when two such switches are used1 one on each end of the car1 they are connected in series4 ,illustration3 ,fig4 #cb4 ,grid ,type of ,resistance4 ,car ,circuit ,breaker4 ,frequently on large equipments an automatic circuit breaker is provided instead of this overhead switch4 ,this circuit breaker can be tripped by hand to open the circuit whenever desired2 and is also equipped with a solenoid magnet1 which can be adjusted so that it will trip or open the circuit breaker at approximately whatever current it is set for4 ,this circuit breaker protects the motor and car wiring from excessive current1 such as would occur in case of a short circuit in motors or car wiring1 or in case the motorman turned on current so rapidly as to endanger the windings of the motors4 ,circuit breakers1 however1 are most commonly used on cars having controllers located at only one end in a motorman's cab4 ,wiring of ,circuit ,breakers and ,canopy ,switches4 ,figs4 #cc1 #cd1 and #ce show the methods of wiring circuit breakers and canopy switches for double-end cars4 ,illustration3 ,fig4 #cc4 ,in the parallel connection as shown in ,fig4 #cc1 the trolley leads after passing through the choke coils go directly to the blow-out coil of the controllers4 ,aside from the fact that two lightning arresters and choke coils are required1 this method is preferable for automatic circuit breakers4 ,illustration3 ,fig4 #cd4 ,fig4 #cd shows the hand-operated circuit breakers connected in series4 ,this method is used where non-automatic breakers are employed1 but for automatic breakers it has the objection that an overload would throw the breaker set at the lowest point4 ,this might be the breaker on the opposite end to that occupied by the motorman and in such an event would necessitate a trip to the other end to set the breaker4 ,fig4 #ce shows a method of parallel connection requiring but one lightning arrester4 ,this method has the objection that the motorman on the front end would have no assurance that by throwing the breaker over him the power would be cut off4 ,the rear breaker might have been carelessly left set4 ,illustration3 ,fig4 #ce4 ,illustration3 ,fig4 #cf4 ,fuses4 ,a fuse is placed in series with the motor circuit before it enters the controller wiring1 but where circuit breakers are used instead of canopy switches1 the fuse box may sometimes be dispensed with4 ,the fuse box on street cars is usually located underneath one side of the car body where it is accessible for replacing fuses1 but where a motorman's cab is used1 the fuse may be placed in the cab4 ,the fuse may be of any of the types in common use1 either open or enclosed4 ,in the ,westinghouse fuse box it is necessary only to open the box and drop in a piece of straight copper wire of the right length and size4 ,the closing of the box clamps this wire to the terminals and establishes a circuit through the copper wire as a fuse4 ,of course this copper wire is of small enough size to be fused by a dangerously heavy current4 ,lightning ,arresters4 ,a lightning arrester is used on all cars taking current from overhead lines4 ,the lightning arrester is connected to the main circuit as it comes from the trolley base1 before it reaches any of the other electrical devices on the car1 so that it may afford them protection4 ,a common type of lightning arrester is shown in ,fig4 #cf4 ,one terminal of the lightning arrester is connected to the motor frame so as to ground it1 and the other is connected with the trolley4 ,in most forms of lightning arrester1 a small air gap is provided1 not such as to permit the #ejj-volt current to jump across1 but across which the lightning will jump on account of its high potential4 ,to prevent an arc being established across the air gap by the power house current after the lightning discharge has taken place and started the arc1 some means of extinguishing the arc is provided4 ,in the ,general ,electric ,company's lightning arrester1 the arc is extinguished by a magnetic blow-out1 which is energized by the current that flows through the lightning arrester4 ,the instant the discharge takes place the current flows across the air gap4 ,the magnetic blow-out extinguishes the arc1 and this opens the circuit1 leaving the arrester ready for another discharge4 ,in the ,garton-,daniels lightning arrester a plunger contact operated by a solenoid opens the circuit as soon as current begins to flow through the arrester4 ,this plunger operates in a magnetic field1 which extinguishes the arc4 ,a choke coil1 consisting of a few turns of wire around a wooden drum1 is placed in the circuit leading to the motors at a point just after it has passed the lightning arrester tap4 ,this choke coil is for the purpose of placing self-induction in the circuit1 so that the lightning will tend to branch off through the lightning arrester and to ground1 rather than to seek a path through the motor insulation to ground4 ,illustration3 ,fig #cg4 ,diagram of ,light ,circuit4 ,often1 however1 the choke coil is omitted1 the coils in the circuit breaker and the blow-out coil in the controller being depended upon to prevent the lightning charge from passing4 ,lamp ,circuits4 ,the lamp circuit of a car is protected by its separate fuse box1 and usually each lamp circuit has a switch4 ,as explained before1 five #ajj-volt or #aaj-volt lamps are placed in series between the trolley wire side of the circuit and ground4 ,if one lamp in the series burns out1 of course1 all five are extinguished until the defective lamp is replaced with a new one4 ,enclosed arc lamps are sometimes used for car lighting4 ,cars to be operated from either end are often wired so that by turning a switch the platform light on the front end1 a light for the sign and another for the headlight on the rear end will be extinguished and corresponding lights on the rear and front ends lighted4 ,this is accomplished by the method of wiring shown in ,fig4 #cg4 ,the interior of the car is lighted by six lights4 ,headlights of #cb candle power are used4 ,this method requires the use of two switches4 ,in all light wiring schemes a switch should be placed on the trolley side of the lights4 ,this permits the current to be cut off in the event of a ground occurring in the system4 ,on interurban cars arc headlights are almost invariably used4 ,the circuit for the headlight after passing through a switch in the motorman's cab goes through a resistance frame usually underneath the car and terminates in a socket near the car bumper4 ,the brackets on which the lamp is hung are grounded so that whenever the plug from the lamp is inserted in the socket and the switch in the cab is turned on1 the circuit is made4 ,usually there is a pressure of about #fj to #gj volts at the terminals of the lamp4 ,the remainder of the voltage drop1 from #ejj or #fjj volts 7or whatever the line may be71 is in the resistance under the car4 ,the current through the lamp is usually about four amperes4 ,with #fj volts at the arc and #ejj volts on the line1 this gives a consumption in the lamp of #bdj watts and a loss in the resistance under the car of #b1jjj watts1 or about #ij per cent4 ,the use of the headlight resistance to cut the voltage down is therefore a very inefficient method4 ,some schemes of wiring use the incandescent lamps used in lighting the car as resistance for the headlight4 ,another way is to light the interior of the car with arc lamps placed in series with the arc headlight4 ,trolley ,base4 ,the trolley base upon which the trolley pole swivels1 and which furnishes the tension that holds the trolley wheel against the wire1 is designed to maintain1 by means of springs1 an approximately even tension against the trolley wire1 whether the trolley wire is high above the track or near the car roof4 ,this is done by changing the relative leverage which the springs of the trolley base have on the trolley pole according to the height of the trolley pole4 ,illustration3 ,fig4 #ch4 ,trolley ,base4 ,illustration3 ,fig4 #ci4 ,trolley ,wheel4 ,fig4 #ch shows one form of trolley base4 ,the trolley base is bolted to a platform constructed for it on the roof of the car2 and the supply wire to the motors and other electrical devices on the car1 except in cases where a wooden trolley pole is used for certain special reasons1 is connected directly to the trolley base4 ,an insulated trolley wire is run down the wooden trolley pole1 and connected through a flexible lead to the car wiring4 ,trolley ,poles4 ,the trolley poles in general use are of tubular steel1 which gives the greatest strength for a given weight1 and which can usually be straightened if the pole has been bent by striking overhead work when the trolley wheel leaves the wire4 ,trolley ,wheels4 ,trolley wheels are from four to six inches in diameter over all1 the small wheels being used in the city service1 and the large wheels in high speed interurban service4 ,a typical trolley wheel is shown in ,fig4 #ci4 ,various companies use various forms of groove in the trolley wheels1 some adopting a groove approximately ,v-shaped4 ,the ,u-shaped groove1 however1 is the most common4 ,the trolley wheel is made of a brass composition selected for its toughness and wearing qualities4 ,illustration3 ,fig4 #dj4 ,trolley ,harp4 ,trolley ,harp4 ,the trolley harp1 which is placed on the end of the trolley pole and in which the trolley wheel revolves1 usually has some means for making electrical contact with the wheel in addition to the journal bearing4 ,in the harp illustrated in ,fig4 #dj1 which is a typical form1 this additional contact is secured by a spring bearing against the side of the hub of the wheel4 ,illustration3 ,fig4 #da4 ,third ,rail ,shoe4 ,since trolley wheels revolve at a very high speed1 some unusual means of lubrication must be provided1 since there is no opportunity for ordinary oil or grease lubrication4 ,graphite1 in the shape of what is called a 8graphite bushing10 is most commonly used4 ,this is a brass bushing1 which is pressed into the hub of the trolley wheel4 ,in this bushing is a spiral groove filled with graphite which is supposed to furnish sufficient lubrication as the bushing wears4 ,roller-bearing trolley wheels have been used to a limited extent1 with considerable success in some cases4 ,some companies have done away with the graphite bushing1 and have provided a very long journal for the trolley wheel instead of the usual short bushing4 ,contact ,shoes4 ,the contact shoe most commonly used on roads employing the third rail is shown in ,fig4 #da4 ,this is simply a shoe of cast iron hung loosely by links4 ,the weight of the shoe is sufficient to give contact4 ,the motion of the links permits the shoe to accommodate itself to unusual obstructions and variations in the height of the third rail4 ,the shoe is fastened to the truck frame by means of a wooden plank which furnishes the necessary insulation4 ,illustration3 ,fig4 #db4 ,sleet ,wheel4 ,the ,potter third-rail shoe which has been used to a limited extent1 employs a spring for giving the necessary tension to make electrical contact between the shoe and the third rail4 ,in some ways this is superior1 because a spring tension is quicker in its action than gravity1 and the shoe accommodates itself better to variations in the height of the third rail at very high speed4 ,the wear on the shoe1 however1 is likely to be greater4 ,sleet on ,trolleys and ,third ,rails4 ,the deposit of sleet on trolleys and third rails hinders greatly the operation of cars4 ,often sleet wheels of the type shown in ,fig4 #db are used as a trolley wheel4 ,these cut the sleet off instead of rolling over it4 ,on the third rail1 scrapers and brushes in advance of the contact shoe are usually effective where trains are frequent4 ,several roads are now melting the sleet on the rails by the use of a solution of calcium chloride4 ,the solution is stored in a tank on the car and is led through small pipes to the rail immediately in front of the collecting shoe4 ,about one gallon of solution is used per mile1 making the cost about #g cents per mile4 ,the effects of one treatment last for two or three hours during the continuance of a storm4 ,solutions of common salt have been used in the same manner1 but it is claimed that the corroding action on the iron of the calcium chloride is not as great as that of a salt solution4 ,,trucks4 ,electric railway cars are classified generally as double-truck and single-truck cars4 ,double-truck cars are those that have a truck that swivels at each end of the car4 ,a single-truck car is one having four wheels4 ,illustration3 ,fig4 #dc4 ,brill #ba-;,e ,car ,truck4 ,single ,trucks4 ,a great many types of single trucks have been designed4 ,it would be out of the question to discuss them all here4 ,in general1 however1 it may be said that truck builders have aimed to make a truck frame in itself a complete unit independently of the car body1 so that the car body will simply rest upon the trucks and there will be no strain on the car body in maintaining the alignment of the truck4 ,most single trucks1 therefore1 consist of a rectangular steel frame1 either cast or forged1 riveted or bolted together4 ,this frame holds the journal boxes in rigid alignment4 ,usually a spring is placed between each journal box and the truck frame4 ,this spring may be either spiral or elliptic4 ,the principal springs1 however1 are between the truck frame and the car body4 ,most truck builders have used a combination of spiral and elliptic springs between the car body and truck frame1 as this combination is considered to give better riding qualities and greater freedom from teetering or galloping than either spiral or elliptic springs alone4 ,fig4 #dc shows a ,brill single truck1 which illustrates all of the features enumerated4 ,swivel ,trucks4 ,swivel trucks1 commonly called double trucks1 are made in many forms1 but the most common is that known as the ,m4 ,c4 ,b4 type of truck4 ,this truck is similar to the standard truck which is in universal use on steam railroad passenger cars in the ,united ,states4 ,different truck builders have introduced many variations in this general type of truck1 in adapting it to electric service4 ,some modifications from the steam railroad standard truck were necessary to accommodate the electric motors and to permit in some cases a low-hung car body4 ,such trucks are made in a great variety of sizes4 ,illustration3 ,fig4 #dd4 ,st4 ,louis ,car ,company ,truck4 ,fig4 #dd shows one of these trucks built by the ,st4 ,louis ,car ,company4 ,in this type of truck the car body is fastened to the truck only by the kingbolt on which the truck swivels4 ,this kingbolt is placed in the center of the truck bolster4 ,there are also side bearings between the car body and the ends of the bolster1 to prevent tipping of the car body when it is unbalanced4 ,the arrangement of this part of the truck is shown in ,fig4 #de4 ,under this bolster are elliptic springs which rest on what is called the spring plank4 ,this spring plank is hung from the rectangular frame of the truck by links which allow a side motion4 ,this side motion gives easier riding1 especially upon entering and leaving curves4 ,all trucks having this feature are known as swing bolster trucks4 ,the weight1 being transmitted to the transom and truck frame through the swinging links just referred to1 is then taken by the equalizer springs that support the rectangular truck frame on equalizing bars1 which equalizing bars rest on the journal box at either end and are bent down to accommodate the springs located between them and the truck frame4 ,the truck frame holds the journal boxes in alignment by means of guides which permit an up-and-down movement without movement in any other direction1 just as on all other types of truck4 ,it is thus seen that there are two sets of springs between the car body and car journals2 one set of spiral springs between the equalizing bar and truck frame2 and one set of elliptic springs between the spring plank and the bolster4 ,all shocks must be transmitted first through the spiral springs and then through the elliptic springs4 ,the motors used on this type of truck usually have nose suspension1 the nose of the motor resting either on the bolster of the truck or on the truck frame4 ,illustration3 ,fig4 #de4 ,bolster1 ,links and ,spring ,plank4 ,illustration3 ,fig4 #df4 ,steel ,tire ,wheel4 ,there are a number of swivel trucks made which have departed considerably from ,m4 ,c4 ,b4 lines1 but nearly all retain the features of a bolster mounted by springs on a spring plank1 a spring plank hung from a transom1 a transom rigidly fastened to the rectangular truck frame of which it forms a part2 and a truck frame with one or more sets of spiral springs between it and the journal boxes4 ,maximum ,traction ,trucks4 ,a type of swivel truck that once was very popular but has largely been superseded by the type just described is the 8maximum traction truck40 ,this truck has two large wheels on an axle which carries #fj to #gj per cent of the weight on the truck1 and two small wheels carrying the balance of the weight4 ,the motors are on the large wheels4 ,car ,wheels4 ,the car wheels most commonly used are of cast iron4 ,in order to make a tread and flange upon which the wear comes1 hard enough to give a good mileage1 the tread and flange are chilled in the process of casting4 ,around the periphery of the mould in which the wheels are cast1 is a ring of iron instead of the usual sand4 ,when the molten cast iron comes in contact with this ring of iron1 which is called a 8chill10 the iron is cooled so suddenly that it becomes extremely hard4 ,the balance of the wheel1 cooling more slowly since it is surrounded by sand1 has the hardness of ordinary cast iron4 ,a steel tire wheel is shown in ,fig4 #df4 ,illustration3 ,fig4 #dg4 ,elevated ,car ,axle4 ,wheels with steel tires are coming into use for elevated and interurban cars because their flanges are not so brittle as those of cast-iron wheels4 ,in wheels of cast metal there is always a liability that the flanges and tread will chip and crack4 ,on high-speed cars the falling-out of pieces of flange may be a serious matter and result in a wreck4 ,steel-tired wheels have a hub and spokes either of cast or forged steel or iron4 ,on to this wheel a steel tire is shrunk4 ,the tire is heated in a furnace built for the purpose1 and is then slipped over the wheel4 ,it is made just such a size that it will slip over the wheel when hot1 and when it is cool it will shrink enough to make a very tight fit4 ,when the tire is to be removed after it is worn out1 it is heated until it has expanded sufficiently to drop off4 ,an axle for elevated car is shown in ,fig4 #dg4 ,when cast-iron wheels are worn to an improper shape or have flat spots upon them1 due to the sliding of the wheels with the brakes set1 an emery wheel grinder must be used to grind them down1 as nothing else is hard enough to have any effect on the iron4 ,illustration3 ,fig4 #dh4 ,standard ,m4 ,c4 ,b4 ,flange4 ,when steel-tired wheels are worn1 they can be put in a lathe and the surface of the tire turned off1 as this surface is of metal soft enough to be workable with ordinary tools4 ,illustration3 ,fig4 #di4 ,brake ,shoes and ,levers4 ,the types of wheel tread and wheel flange in use vary greatly among different electric railways4 ,there is a standard ,master ,car ,builders' wheel tread used on steam railroads1 which is shown in ,fig4 #dh4 ,electric railways1 however1 are usually obliged to use a smaller flange and narrower tread4 ,street railway special work1 such as switches and crossings1 usually has too shallow a flange way to permit a standard ,m4 ,c4 ,b4 flange to pass through4 ,some street railways use flanges as shallow as -inch1 although -inch is most common on city work4 ,the width of the tread on street railway cars1 that is1 the width of the wheel where it bears on the rail1 is usually from #a inches to #b inches4 ,there is a tendency1 however1 on electric railways1 on account of the increasing number of interurban cars which must use city tracks1 to build tracks that will accommodate wheels approaching the ,m4 ,c4 ,b4 standard of steam roads4 ,a few roads have adopted wheel treads and flanges very near to the ,m4 ,c4 ,b4 standard4 ,illustration3 ,,automatic ,,air ,,brake ,,cab ,,equipment4 ,westinghouse ,air ,brake ,co4 ,brake ,rigging4 ,the brake rigging on a single-truck car may be arranged in a variety of ways1 but should be such that a nearly equal pressure will be brought to bear on the brake shoes on all four wheels4 ,a typical arrangement of brake shoes and levers for single-truck cars is shown in ,fig4 #di4 ,the rods ,r terminate in chains winding around the brake staff upon which the motorman's handle or hand wheel is mounted4 ,illustration3 ,fig4 #ej4 ,brake ,levers and ,air ,brake4 ,for double-truck cars the brake rigging is necessarily more complicated1 as it must be arranged to give an equal pressure on all eight wheels of the car4 ,brake shoes are sometimes placed between the wheels of a truck and sometimes outside4 ,the arrangement of brake shoes between wheels is apparently finding most favor1 as when the shoes are applied in this position there is less tendency to tilt the truck frame when the brakes are applied1 and this adds to the comfort of passengers in riding4 ,fig4 #ej shows one form of arrangement of brake levers common on a double-truck car equipped with air brakes1 with inside-hung brake shoes4 ,brake ,leverages and ,shoe ,pressure4 ,the levers between the air cylinder and the brake shoes are usually so proportioned that with an air pressure of #gj lbs4 per sq4 in4 in the brake cylinders the total of the brake shoe pressures on the wheels will be equal to about #ij per cent of the weight of the car4 ,the diagram ,fig4 #ea has shoe pressures and strains in the several rods marked on shoes and rods4 ,the following example1 based on the diagram1 will explain the lever proportioning4 ,only round numbers are given on the diagram4 ,assume a four-motor car weighing #dj1jjj pounds4 ,a brake cylinder #g inches in diameter is used4 ,this gives #ch4e square inches and at #gj pounds air pressure a total force on the piston rod of #b1fie pounds4 ,the weight of the car is #dj1jjj pounds4 ,taking #ij per cent of this gives a total of #cf1jjj pounds to be exerted by the brake shoe when an emergency stop is made4 ,each of the eight shoes will press against the wheels with a force of #d1ejj pounds4 ,the dimensions of the truck are such that the 8dead levers10 those fixed at one end and which carry shoes1 cannot be over #ac inches long4 ,the shoe will be hung three inches from one end1 making the proportions #aj to #c1 and the pressure on the strut rod between shoes will be #d1ejj or #c1dfa pounds4 ,to clear the truck frame the live lever extends #ad inches above the point of application of the brake shoe4 ,to obtain #d1ejj pounds pressure on the shoe1 the distance between the brake shoe and the strut rod1 which we will call 8x10 will be found by regarding the upper end of the lever as fixed and the power applied at the lower end4 #ad x #dejj #cdfa ---------------- or #ad x #d4b inches4 ,now to obtain the force required in the rod to the truck quadrant1 the bottom end of the live lever must be regarded as the fulcrum4 ,the equation is #d4b x #dejj -------- #ajch pounds4 #ah4b ,as the pull rods from each side of the truck are attached to the truck quadrant1 the stresses in the brake rods are double this1 or #b1jgf pounds4 ,illustration3 ,fig4 #ea4 ,diagram of ,brake ,shoe ,pressures and ,strains4 ,the position of the brake cylinder under the car restricts the length of the 8live0 and 8dead0 cylinder levers to #af inches4 ,to obtain #b1jgf pounds pull on one end of the levers with the previously computed #b1fie #bjgf x pounds on the other1 the proportions must be -------- ------1 since #bjgf #dgga #af #bfie #dgga4 ,then x #g inches1 the distance from the brake piston to the pivotal point4 ,since #b1fie pounds pressure is exerted and #cf1jjj pounds results the proportion of the whole system of levers is #cf1jjj to #b1fie or #ac4c to #a4 ,in other words the travel of the piston in the cylinder will be #ac4c times that of the shoes if there were no lost motion to be taken up4 ,the piston travel should be from #d to #e inches4 ,this gives about -inch travel of the brake shoes4 ,increased travel of the brake shoes necessary to set them as they wear away causes increased travel of the piston of the air cylinder4 ,not only is more air used at each application of the brakes but the brakes are slower in acting4 ,it is therefore necessary to adjust the brakes frequently4 ,this is done in the system shown in the diagram by the use of a turnbuckle in the connecting rod between the live and dead levers of the truck4 ,when two motors are on one truck and none on the other1 allowance must be made in the levers for the increased weight of the motor truck and the inertia of the armature4 ,the leverage on the motor truck must be greater than on the other4 ,air ,brakes4 ,air brakes used on electric railway cars are usually of what is called the straight air brake type in distinction to the ,westinghouse automatic air brake4 ,a straight air brake is one in which the air is stored in a reservoir2 and1 when the brakes are to be applied1 air from this reservoir is turned directly into the brake cylinder1 in which works a piston operating the brake levers4 ,air admitted behind the piston forces it out with a pressure which applies the brakes4 ,when the air is let out of the brake cylinder1 a spiral spring forces the piston back to its original position and the brakes are released4 ,the motorman's valve by which he applies the brakes1 therefore1 provides1 first1 for turning air from the storage reservoir to the brake cylinder to apply the brakes1 and1 second1 for closing the opening to the storage reservoir and opening an exhaust passage from the brake cylinder so that the air can escape from the brake cylinder to release the brakes4 ,straight air brakes of this kind would not be suited to the operation of long trains1 because1 if the air-brake hose connection between cars should be broken1 the brakes would be useless2 but for trains of one or two cars1 such as are common in electric railway practice1 the simplicity of the straight air brake outweighs its disadvantages and this is the type of brake usually employed4 7,see ,fig4 #eb47 ,the ,westinghouse and other forms of automatic air brake are used on electric railways where cars are operated in long trains2 but it is out of the province of this paper to describe these brake systems fully1 as they are rather complicated4 ,it may be said in general1 however1 that the ,westinghouse automatic air brake is so arranged that1 should the hose connection between cars be broken1 should the train pull in two1 or should anything happen to reduce the pressure which is maintained in the train pipe that runs the length of the train1 the brakes would immediately be applied on the entire train4 ,illustration3 ,fig4 #eb4 ,diagram of ,straight ,air ,equipment4 ,compressors4 ,a small air compressor driven by an electric motor is frequently employed on electric cars to keep the storage reservoir of the car supplied with air4 ,these air compressors are carried under the car or in the motorman's cab4 ,they are generally arranged with an automatic device which closes the motor circuit and starts the motor as soon as the air pressure falls below a certain amount2 and the motor will continue in operation pumping air until the pressure rises to the amount for which the automatic device is set4 ,the pressure carried in the storage reservoir is usually from #fj to #ij pounds per square inch1 which1 as a general thing1 is considerably more than is required to apply the brakes hard enough to slide the wheels4 ,automatic ,governor for ,air ,compressors4 ,automatic governors are often installed in connection with air compressors in order that a fairly even air pressure may be maintained in the storage reservoir4 ,in these the fall and rise of the air pressure within certain limits closes and opens the circuits to the motor4 ,in some styles the air acting on a piston operates the circuit breaker4 ,the diagram shown in ,fig4 #ec shows the principle of the ,christensen governor1 in which the air pressure is employed to make and break a secondary circuit4 ,when the pressure in the storage reservoir falls below a predetermined value1 the hand of the air gauge makes contact with lug ,a4 ,this closes the circuit through solenoid ,no4 #a4 ,lug ,d1 mechanically connected to the armature of the solenoids is pulled in contact with lug ,c1 and this closes the circuit to the motor1 and shunts the winding of solenoid ,no4 #a4 ,when the air pressure rises to a predetermined value the hand of the air gauge is thrown in contact with lug ,b4 ,this energizes solenoid #b by connecting it across the motor terminals4 ,the armature is pulled to the right and the circuit to the motor is broken4 ,when this is done it is evident that the current through the energized solenoid is broken4 ,it is evident from the description that current passes through the solenoids only during the short periods that the armature is moving from one position to the other and the air gauge never has to break a circuit in which there is an appreciable voltage so that there is no arcing at lugs ,a and ,b4 ,illustration3 ,fig4 #ec4 ,a blow-out coil in series with the motor is provided immediately under lug ,c which extinguishes the arc at that point when the motor circuit is broken4 ,a ,westinghouse air compressor is shown in ,fig4 #ed4 ,storage ,air ,brakes4 ,the storage air-brake system does not have a small independent compressor on each car1 but is equipped with a large storage tank1 in which air is carried under high pressure--#bej to #cjj pounds per square inch4 ,this storage tank is filled at regular intervals when the car passes some point on its route at which a compressor is located4 ,in this case the car is obliged to stop long enough to make connection to the tank of the compressor plant1 and to allow the car storage tank to be filled4 ,this operation1 however1 does not take long4 ,the advantages of the system are a saving of the weight and a saving in the maintenance of a small compressor on each car4 ,from the main storage tank under the car1 air is led through a reducing valve to an auxiliary storage tank4 ,this reducing valve allows enough air to pass through to maintain a pressure of about #ej pounds per square inch in the auxiliary storage tank4 ,the auxiliary storage tank corresponds to the regular storage tank on a system employing compressors on each car4 ,the method of operation after the air has entered the auxiliary storage tank is the same as with any air-brake system4 ,illustration3 ,fig4 #ed4 ,westinghouse ,air ,compressor4 ,fig4 #ee shows the arrangement of the apparatus under the cars of the ,st4 ,louis ,transit ,company4 ,the two storage tanks are each #f feet long by #ah inches in diameter and are mounted one on each side of the car4 ,their combined capacity is equivalent to about #ajj cubic feet at #de lbs4 pressure4 ,the tanks are charged through an outlet near one side of the car4 ,this outlet contains a check valve and cock to prevent leakage4 ,the service or low pressure reservoir has a capacity of about #b cubic feet4 ,the position of the reducing valve between the high and low pressure valves may be noted in the illustration4 ,momentum ,brakes4 ,momentum or friction brakes have been used to some extent both on single-truck and on double-truck cars1 but particularly on single-truck cars4 ,they derive the power to operate the brakes from the momentum of the car by means of a friction clutch on the car axle4 ,the difference in various kinds of momentum brakes lies chiefly in the design of the clutch mechanism4 ,the clutch must evidently be arranged to act very smoothly1 and must be under very accurate control1 as the force with which the brakes are applied depends directly upon the pull exerted by the clutch4 ,illustration3 ,fig4 #ee4 ,arrangement of ,storage ,air ,brake ,apparatus4 ,in the ,price momentum brake a flat disc is cast on the car wheel1 which is turned off to a smooth surface4 ,against this disc a friction clutch acts1 which has a leather face4 ,the clutch is operated by a motorman's lever through a set of levers4 ,a small movement in the motorman's lever forces the clutch against the disc on the car axle4 ,the clutch winds up the brake chain1 and thus supplies power to apply the brakes4 ,other momentum or friction clutch brakes have been devised1 most of which also use an application of leather on iron for the clutch1 as this has been found to be most reliable1 and to be least affected by the grease and dirt that is liable to work in between the clutch surfaces4 ,g4 ,e4 ,electric ,brake4 ,the ,general ,electric ,company's electric brake makes use of current generated by the motors acting as dynamos1 to stop the car4 ,in order to accomplish this1 a brake controller is provided which reverses the armature connections of the motors1 and so connects them to operate as dynamos sending current through a resistance in the circuit2 the amount of current flowing and the braking effect depending on the car speed and the resistance4 ,in some forms of brake controller1 the two controllers are combined in one cylinder1 so that the motorman1 to apply the electric brake1 simply continues the movement of the handle past the 8off0 position4 ,in others1 the brake-controller drum is separate1 but is interlocked with the main controller so that it can be used only when the main controller is off4 ,however the controller may be arranged1 the principle involved is that when the motors are revolving by the motion of the car1 and the armature connections are reversed as they would be to reverse the direction of motion of the car1 the motors begin to generate current as series-wound dynamos4 ,the amount of current generated and the retarding effect will depend on two things--namely1 the speed of the car1 with the consequent electromotive force in the motors1 and the amount of resistance in the circuit4 ,the amount of resistance is regulated by the motorman by means of his electric brake controller4 ,the function of the electric brake controller is to reverse the motors and to insert enough resistance in the circuit to make a comfortable stop4 ,this current in the motors acting as dynamos1 in itself acts as a powerful brake to retard the motion of the car4 ,in the ,general ,electric type of electric brake1 the current generated in the motors1 in addition to having this retarding effect in the motors themselves1 is conducted to brake discs that act as magnetic clutches against one of the car wheels on each axle4 ,the car wheel has a disc cast upon it1 and against this the magnetic disc acts4 ,the magnetic disc contains a coil which is in series in the brake circuit4 ,in applying an electric brake of this kind the motorman first puts the controller on a point that inserts considerable resistance in the circuit4 ,when the motors have slowed down1 the electromotive force1 of course1 drops1 so that to maintain the same braking current there must be a reduction of the amount of resistance1 until1 when the car is almost at a standstill1 the resistance is nearly all cut out4 ,it might seem at first that the current would die down before the car came to a stop1 but it is found that there is enough induction in the motor fields to cause current to flow for a short time after the car has stopped4 ,the residual magnetism in the steel in the fields of the motor is sufficient to cause the motors to begin to generate current when the electric-brake controller is first turned on4 ,the greatest advantage of an electric brake using motors as generators is in the fact that the braking current instantly falls in value as soon as the wheels begin to slide1 and releases the brake until the wheels again revolve4 ,in fact1 it is almost impossible to skid the wheels as they are sometimes skidded by being locked by brake shoes4 ,this not only prevents flat wheels but insures a quick stop1 because when the wheels are locked and sliding1 the braking or retarding power is only about one-third what it was before the wheels began to slide4 ,the electric brake requires extra large motors because of the heating caused by the current generated while braking4 ,illustration3 ,fig4 #ef4 ,magnetic ,brake ,shoe4 ,westinghouse ,electromagnetic ,brake4 ,the ,westinghouse magnetic brake is in principle similar to the ,general ,electric brake as far as the use of motors as generators is concerned2 but1 instead of assisting the motors by means of a magnetic brake disc acting against the car wheel1 a magnetic brake shoe is used 7see ,fig4 #ef71 which acts against both car wheel and track4 ,this not only retards through the medium of the wheels but acts directly on the track4 ,it is not dependent upon the coefficient of friction between the wheels and track2 and it should1 therefore1 be possible to stop much more quickly than with any form of brake depending upon the coefficient of friction between the wheels and track4 ,illustration3 ,,magnetic ,,brake ,,showing ,,method ,,of ,,attaching ,,to ,,car ,,frame ,,and ,,trucks4 ,westinghouse ,air ,brake ,co4 ,track ,brakes4 ,track brakes have been used to some extent on very hilly electric roads4 ,these have a shoe fastened to the truck frame1 which acts directly on the track4 ,motors as ,emergency ,brakes4 ,the motors can of course be used to brake the car by simply reversing them if current is applied to them from the line4 ,but in case the trolley flies off or if the circuit breaker or the fuse opens the circuit1 or the supply of current is interrupted for any other reason1 they may be used as brakes by throwing the reverse lever and moving the controller handle to the multiple position of a two-motor equipment or by simply throwing the reverse lever of a four-motor equipment4 ,these movements throw the motors in multiple and connect the fields and armatures of the motor in such relation that they can generate current4 ,one of the motors then acts similarly to a generator in a power house1 deriving its power from the momentum of the moving car instead of from an engine1 and sends current through the other motor of the pair which acts like any auxiliary motor trying to revolve its wheels in the opposite direction from that in which they are revolving4 ,the motors of a four-motor equipment are permanently connected in two multiple groups as long as the reverse is not in the central position4 ,in the two motor equipment such connections are not made until the controller handle is turned to the multiple position4 ,as the external resistance is beyond the junction of the two motor circuits1 the braking effect is not increased by cutting out the resistance4 ,the difference in the residual magnetism of the fields or in the magnetic qualities of the fields of the two motors is primarily the cause of the generation of the current4 ,the motors at first act in opposition1 but one of them generates the higher voltage and forces a current through the other4 ,this current overcomes the residual magnetism of the second motor1 thereby changing its polarity and both motors then act in series to send the current through the low resistance path afforded by the windings4 ,any current passing increases the strength of the fields and consequently the voltages1 so that abnormal currents are generated and the braking action is consequently severe4 ,this generating action does not take place before the reverse lever is thrown because the connections of the armatures and fields are such that any current generated by reason of the residual magnetism of the fields1 flows in such a direction through these that this magnetism is destroyed4 ,the current then ceases to flow4 ,this explains why current is not generated in ,no4 #b motor with a ,k type of controller during the change-over period when it is short-circuited1 or in equipments when the trolley flies off and the controller is turned on4 ,illustration3 ,fig4 #eg4 ,pneumatic ,sander4 ,brake ,shoes4 ,the subject of brake shoes is of very little importance on the smaller cars traveling at slow speeds and controlled alone by hand brakes4 ,on the larger high speed interurban cars1 the brake shoe question becomes an important item because of the rapidity with which they are worn away4 ,on such cars shoes sometimes last but about one week4 ,this means eight shoes per week per car or an expense of about #d4jj per car per week4 ,brake shoes are usually of soft gray cast iron with inserts of steel1 although some companies use very hard iron4 ,they are usually fastened by means of a key to a brake shoe head permanently attached to the brake rigging4 ,the brake levers are so adjusted that the shoes clear the wheels about -inch when the brakes are released4 ,this distance increases as the shoes wear1 so that the brakes must be adjusted frequently to take up the slack and prevent waste of air4 ,track ,sanders4 ,a sprinkling of sand on the rail increases wonderfully the adhesion of the rail and wheel4 ,there is usually on cars some provision made for scattering sand on the rails immediately in front of the leading wheels4 ,from sand boxes placed under the seats in the smaller cars1 or on the truck of the larger ones1 flexible hose or pipes drop within an inch or two of the rail in front of the leading wheels4 ,a valve under the control of the motorman regulates the flow of sand to the rail4 ,sometimes air pressure is used to blow the sand out of the sand box into the hose4 ,in this case air pressure is obtained from the air brake system1 and an air valve leading to the sand box is placed in the motorman's cab4 ,a section through a pneumatic sander of this kind is shown in ,fig4 #eg4 ,illustration3 ,fig4 #eh4 ,curves of ,braking ,tests4 ,coefficient of ,friction4 ,it has been found by experiment that the coefficient of friction between the car wheel and rail is about #be per cent of the weight on the wheel when the rails are dry2 that is1 a car wheel having a weight of #b1jjj pounds upon it would not be able to exert either an accelerating or a retarding force exceeding #be per cent of this1 or #ejj pounds4 ,this is when the wheel is rolling4 ,there is apparently a kind of locking or inter-meshing of the rough surfaces of wheel and rail when the wheel is rolling1 because it is found that when a wheel begins to skid or slide1 the coefficient of friction falls off about two-thirds4 ,the maximum braking or retarding force that can be obtained1 therefore1 in a dry rail1 amounts to #be per cent of the weight of the car4 ,if the rail is slippery this is much reduced2 or if the wheels are allowed to slide it is also much reduced4 ,if more retarding force than can be obtained through the medium of a wheel rolling on the rail is desired1 it must be obtained either by the track brakes or by magnetism4 ,illustration3 ,fig4 #ei4 ,automatic ,coupler4 ,rate of ,retardation in ,braking4 ,the rate of retardation of cars in braking is usually #a to #b miles per hour per second4 ,in other words a car going at a speed of #dj miles an hour will usually be stopped in #dj to #bj seconds4 ,the plotted results of some braking tests 7,fig4 #eh7 show a higher rate of acceleration4 ,these tests were made on an interurban car weighing about #fc1jjj pounds1 equipped with straight air brakes4 ,of the six curves shown1 that giving the highest rate of retardation is ,no4 #d4 ,this shows a stop from a speed of #ch miles per hour in #i seconds or a rate of retardation of about #d miles per hour per second4 ,all of the curves shown are for emergency stops4 ,they show about the highest rate of retardation that could be made with the equipment4 ,drawbars and ,couplers4 ,for small surface cars a crude drawbar is usually provided consisting simply of a straight iron bar pivoted under the car and provided with a cast-iron pocket near the end4 ,a coupling pin passing through the pocket of one coupler and through a hole in the end of the bar of the other1 holds the two cars together4 ,the requirements of a coupler for heavier cars such as those used on interurban and elevated roads are more exacting4 ,the ends of the bars are usually pivoted under the car about five feet back from the bumper4 ,a spring cushion intervenes between the pivot point and the drawbar head4 ,the illustrations1 ,figs4 #ei and #fj1 show the action of the ,van ,dorn ,automatic coupler1 which is the one used by all the elevated lines in the ,united ,states4 ,the link is placed in one of the drawbar heads and the pin in the other4 ,as the cars come together the wedge-shaped end of the link forces its way between the pin and a spring4 ,when the faces of the drawbar heads meet1 the spring forces the link to engage the pin4 ,the mechanism is designed especially to prevent lost motion between coupler heads because1 unlike steam railroad drawbars1 electric car drawbars must swivel to round curves and a great amount of play at the point of coupling with swiveling drawbars would allow the couplers to bend under a pushing strain4 ,illustration3 ,fig4 #fj4 ,,car ,,construction4 ,car ,bodies4 ,in cities there are three general types in common use2 namely1 box cars1 suited for winter use only2 open cars1 suited for summer use only2 and semi-convertible cars1 which can be adapted to either summer or winter use4 ,the open and box cars are the older types4 ,the semi-convertible car is usually provided with a center aisle1 and cross seats on each side of this aisle4 ,illustration3 ,fig4 #fa4 ,side ,elevation and ,plan of ,car4 ,the windows are large1 so that they can be lowered or raised in summer to make something approaching the character of an open car4 ,the car bottom1 which forms the basis for the entire car structure1 is constructed with longitudinal sills either of steel or of wood combined with steel4 ,one form of construction employs as the main supports two steel channel bars extending the full length of the car4 ,steel ,i-beams are sometimes used4 ,where wood is used in combination with steel for longitudinal sills1 the steel is usually in the form of flat steel plates between the timbers4 ,most cars seat about one passenger per foot of length over all4 ,illustration3 ,fig4 #fb4 ,cross-,section of ,car ,body4 ,many more difficulties are met in the construction of passenger cars for electric railways than in steam coach construction4 ,the electric car must have low steps and platforms and turn short curves4 ,the difficulties are largely in the floor framing of the car4 ,the platforms at each end are usually eight to ten inches lower than the floor of the interior4 ,as the car must frequently be designed to pass around curves of small radius1 often of only thirty or forty feet1 sufficient clearance must be provided for the swing of the trucks4 ,this necessitates that the trucks of a double truck car be set far enough back towards the center of the car to clear the dropped platform timbers1 shown in ,fig4 #fc4 ,in the illustration shown1 ,fig4 #fa1 the truck centers are but #ba feet #h inches apart1 while the ends overhang the truck centers #aa feet #d inches4 ,it is difficult to support this overhanging weight properly4 ,the difficulty is increased by the fact that the rear platform is often crowded with passengers having an aggregate weight of one ton or more4 ,trusses manifestly cannot be employed to give rigidity to the long platform4 ,this is usually given in cars of wood construction by reinforcing the platform timbers with steel plates as shown in the figure4 ,in order that the dropping tendency of the platform shall not bow up the body of the car between the trucks this portion must be braced rigidly4 ,the space below the windows and above the side sill is utilized for this purpose4 ,the side sill is moreover strengthened by having steel plates bolted to it4 ,illustration3 ,fig4 #fc4 ,reinforcing ,plates4 ,the longitudinal members of the body framing are termed sills4 ,these are usually of long leaf yellow pine4 ,various combinations of wood and steel are employed for sills1 an example of which is seen in ,figs4 #fa and #fb4 ,the sills are kept the proper distance apart by 8bridgings0 or cross sills mortised into them at intervals and by 8end sills40 ,the whole framing is tied together by the rods running parallel to the bridging4 ,these tie rods are often provided with turn buckles for tightening when occasion may require4 ,the outer sills are termed side sills2 those nearest the center of the car1 the center sills or draft timbers2 while those between are called intermediate timbers4 ,the remaining portion of the car is constructed much after the manner of a steam coach4 ,the posts between the windows are mortised into the side sill at the bottom and into a top sill at their upper end4 ,they are laterally braced by a belt rail immediately under the window opening1 both the belt rail and the posts being gained out so that the rail fits flush with the posts4 ,a wide letter board gained into the post just below the side plate adds to the bracing of the side of the car1 as does also an iron truss usually one-fourth to one-half inch thick and two to three inches wide which is gained into the posts on the inside running just under the windows between the truck centers1 and then descends to pass through the side sills and fasten by a bolt underneath4 ,the roof consists of the upper and lower decks4 ,that portion over the platform or vestibule is termed the hood4 ,rigidity is given to the whole upper portion of the car by the end plates resting on the corner posts and extending between the side plates at either end of the car body proper1 and by steel carlins which conform to the peculiar shape of the roof and extend between the side plates4 ,the steel carlins are usually placed over alternate side posts4 ,bolted on either side of them and placed at intervals of about twelve inches between are wood carlins4 ,the wood carlins of the lower deck extend from the side plate1 to which they are fastened by screws1 to the top sill1 which is immediately below the windows of the upper deck4 ,above these windows is the top plate1 supporting the carlins of the upper deck1 which extend between and a few inches beyond the two top plates4 ,poplar sheathing three-eighths or one-half inch is nailed over carlins and on this heavy canvas usually of six or eight ounce duck is stretched tightly4 ,several coats of heavy paint on the canvas and a trolley board for supporting the trolley stand complete the roof4 ,on the underside of the carlins the headlining1 usually of birch or birdseye maple1 is secured4 ,this forms the interior finish of the ceiling of the car4 ,steel ,car ,framing4 ,as a result of the demands of the officials of the ,new ,york ,subway for cars of greater strength and less subject to danger from fire1 much progress has been made in the last few years in the construction of cars with steel framing4 ,steel construction is much more expensive than that in which the framing is of wood and is considerably heavier4 ,the advantages lie partly in the fact that it is more durable1 but the great reason for the interest with which the new style of construction has been received is that the danger of collapse and consequent injury to passengers1 in case of accident1 is greatly diminished4 ,car ,weights4 ,the total weight of a street car with a body #af feet long over corner posts mounted on a single truck with two motors is approximately #ad1jjj pounds4 ,of this the body weighs about #d1ejj pounds1 the truck #d1djj pounds1 and the motors and the electrical equipment the remaining #e1ajj pounds4 ,the weights of the separate parts of a certain interurban car measuring #eb feet #f inches over the bumpers mounted on double trucks1 one of which carried two motors1 is body #cd1jfe1 motor truck #i1efe1 trail truck #f1fgj1 electrical equipment #ab1hjj2 total #fc1ajj4 ,an interurban car of about the same size as the one just mentioned but equipped with four motors gave the following weights3 ,body with controller and resistance grids #ci1jjj pounds1 trucks #ai1acj pounds1 motors #ae1dbj pounds2 total #gc1eej pounds4 ,car ,painting4 ,a great deal of attention is given to the proper painting of cars4 ,a car painted with care and proper materials always presents an attractive appearance1 while one carelessly painted is readily noticeable4 ,new cars go through an elaborate painting process4 ,the time required is from two to three weeks4 ,the following scheme may be regarded as an example of a good process3 ,a coat of primer is given the car the first day4 ,on the third day all irregularities are puttied up smooth4 ,on the fourth and fifth days a heavy primer is applied1 one coat on each day4 ,a coat of filler is given on the sixth day and allowed to harden the following day4 ,the next paint applied is termed a guide coat4 ,this is of a color different from the preceding ones and serves as a guide for the rubbers1 who on the following day go over the car with mineral wool1 fine sandpaper1 or pumice stone1 and rub it until the guide coat is worn away4 ,this assures an even and smooth surface4 ,on the tenth day the car is allowed to stand4 ,a coat of the color desired is applied1 one on each of the following three days4 ,on the fourteenth and fifteenth days the car is striped with the desired ornaments and lettered4 ,this is usually done in aluminum or gold leaf4 ,the car is then given three coats of varnish on alternate days1 and the work is completed4 ,the best practice brings the cars in once each year to be revarnished4 ,illustration3 ,,typical ,,high ,,grade ,,track ,,construction ,j4 ,g4 ,white ,co4 ,,electric ,,railways4 ,,part ,,ii4 ,,overhead ,,construction4 ,illustration3 ,fig4 #fd4 ,trolley ,wire4 ,the trolley wire is suspended from the span wires or brackets in such a way as to permit of an uninterrupted passage of an upward pressing trolley wheel underneath it4 ,the trolley wire itself may be either round1 grooved1 or figure #h in section4 ,where a round wire is used1 ,no4 #jj ,b4 ,s4 gauge is the most common size4 ,figure #h wire1 so called from its section1 which is shown in ,fig4 #fd1 is designed to present a smooth under surface to the trolley wheel1 which will not be interrupted by the clamps or ears used to support it4 ,clamps are fastened to the upper part of the figure #h4 ,the grooved wire is rolled with grooves into which the supporting clamps fasten4 ,this wire also presents a smooth under surface to the trolley wheel4 ,illustration3 ,fig4 #fe4 ,trolley ,wire ,clamp and ,ear4 ,trolley-,wire ,clamps and ,ears4 ,the trolley is supported either by clamps or by soldered ears4 ,one type of clamp grasps the wire by virtue of screw pressure4 ,a soldered ear is shown at ,e1 ,fig4 #fe4 ,this ear has small projections at each end1 which are bent around the wire to assist the solder in holding the wire to the ear4 ,another form of ear1 used to some extent1 holds the wire by virtue of having the edges of the groove offset or riveted around the wire4 ,the ear or clamp screws to a bolt which is insulated from the metal ear through which passes the span wire4 ,a cross-section through a common type of trolley-wire hanger is shown in ,fig4 #ff4 ,here there is an outer shell of metal1 which is adapted to hook to the span wire4 ,in this shell is an insulating bolt1 that is1 a bolt surrounded with some form of insulating material which is very strong mechanically and not likely to be cracked by the hammering action of the passing trolley wheel4 ,most of the insulating compounds used in making trolley-wire insulators are trade secrets4 ,another kind of insulator called the 8cap and cone0 type is shown at ,c1 ,fig4 #fe4 ,in these insulators1 the metal part ,b which fastens to the span wire does not completely surround the insulation ,c4 ,wood has sometimes been used for the insulation of trolley-wire hangers4 ,illustration3 ,fig4 #ff4 ,cross-,section ,trolley ,wire ,hanger4 ,span ,wires4 ,in city streets1 the trolley wire is commonly suspended from span wires stretched between poles located on both sides of the street4 ,these span wires are of -inch or -inch galvanized stranded steel cable4 ,in order to add to the insulation between the trolley wire and the poles at the side of the street1 what is called a strain insulator is placed in the span wire4 ,this is an insulator adapted to withstand the great tension put upon it by the span wire4 ,one of these is shown in ,fig4 #fg4 ,means are usually provided for tightening the span wires as they stretch and as the poles give under the strain4 ,the insulator in ,fig4 #fg has a screw eye for that purpose4 ,illustration3 ,fig4 #fg4 ,strain ,insulator4 ,illustration3 ,fig4 #fh4 ,overhead ,construction4 ,brackets4 ,in the bracket type of overhead construction1 a trolley wire is fastened to brackets placed on poles near the track4 ,this construction is used on suburban and interurban lines where the presence of poles near the track is not objectionable4 ,it has been found that a rigid connection of the trolley wire to a bracket is likely to result in the breaking of the trolley-wire insulators4 ,for this reason the brackets now commonly used provide for a flexible suspension of the trolley-wire hanger from the bracket4 ,a bracket employing such flexible construction1 made by the ,ohio ,brass ,company1 is illustrated in ,fig4 #fh4 ,an example of standard straight-line bracket construction is shown in ,fig4 #fi4 ,feeders4 ,where additional conductivity is needed beyond that furnished by the trolley wire itself1 feeders are run on insulators along the poles at the side of the track4 ,such feeders are connected to the trolley wire at regular intervals4 ,where span-wire construction is used1 the feed wire may be substituted for the span wire at the pole where the connection between feed wire and trolley wire is made4 ,in such a case1 of course1 a trolley-wire hanger is used which has no insulator1 so that the current feeds directly through the hanger4 ,another method is to run the feed connection parallel with a span wire and a short distance from it4 ,illustration3 ,fig4 #fi4 ,standard ,straight ,line ,construction4 ,section ,insulators4 ,section insulators are usually placed in the trolley wire at regular intervals4 ,such a section insulator is shown in ,fig4 #gj4 ,its purpose is to insulate one section of trolley wire from the next1 so that in case the trolley wire of one section breaks1 or is grounded in any other manner1 that section can be disconnected and the other sections on either side kept in operation4 ,in large city street-railway systems1 each section of trolley wire usually has its own feeder or feeders1 independent of the other sections4 ,this feeder is supplied through an automatic circuit breaker at the power house4 ,in case a certain section of trolley wire is grounded the large current that immediately flows will open the circuit breaker supplying that section2 but1 unless the ground contact is of an extremely low resistance1 it will not affect the operation of the other feeders4 ,should it be of sufficiently low resistance to cause all the generator circuit breakers to open1 it would1 of course1 interrupt the entire service temporarily2 but usually the circuit breaker on any individual feeder will cut that feeder out before all the circuit breakers will open4 ,illustration3 ,fig4 #gj4 ,section ,insulator4 ,high-,tension ,lines4 ,where high-tension alternating-current wires are run1 as in the case where the road is of such length as to require the establishment of several substations1 these high-tension circuits are usually carried some distance above the #ejj-volt direct-current trolley and feeders4 ,an example of interurban overhead construction is shown in ,fig4 #fi4 ,here the high-tension wires are carried on large porcelain insulators of a size necessary for #bf1jjj volts4 ,these insulators are placed #ce inches apart4 ,high-tension wires are kept so far apart because of the danger that arcs will in some way be started between the lines1 as the high-tension current will maintain an extremely long arc4 ,the blowing of green twigs across the lines1 or birds of sufficient size flying into the lines1 is likely to establish arcs which will temporarily short-circuit the line4 ,the greater the distance apart of the wires1 the less danger that such things will occur4 ,both glass and porcelain insulators are successfully used on lines of very high tension4 ,glass is the cheaper and porcelain has the greater mechanical strength4 ,high-tension wires are usually of hard-drawn copper or of aluminum made up in the form of a cable of several strands4 ,aluminum is lighter for a given conductivity than copper2 and1 at the market price controlling at the present time1 is cheaper4 ,it is1 however1 more subject to unevenness of composition1 which leaves weak spots at certain points in the wire2 and that is the reason why aluminum is now always used in the form of a stranded cable rather than as a single conductor4 ,aluminum1 being considerably softer than copper and melting at a lower temperature1 is more likely to be worn through as a result of abrasions or to be melted off by a temporary arc4 ,these slight objections are balanced against its smaller first cost as compared with the cost of copper4 ,the calculation of the proper amount of feed wire for a given section of road is somewhat similar to the calculation of electric light and power wiring as already outlined4 ,it is first necessary to estimate approximately the amount of current required at different portions of the line4 ,the amount of drop to be allowed between the power house and cars must be decided arbitrarily by the engineer4 ,a drop of #aj per cent is probably the one most commonly figured upon in designing feeding systems4 ,the resistance in ohms of the copper feeders required to conduct a given current with a given loss in volts1 can be calculated by dividing the volts lost by the current1 according to ,ohm's law4 ,by the aid of a table which gives the conductivity of various sizes of wire according to the methods outlined in connection with 8,electric ,wiring10 the proper number and size of the feeders can be determined4 ,the most difficult thing to determine is the load that will be placed upon any section of the line4 ,of course1 there will be times when cars are bunched together owing to blockades4 ,it is out of the question to provide enough feeder copper to keep the loss in voltage within reasonable limits at such times4 ,the ordinary load upon any feeder is used as the basis of calculation in most cases4 ,the amount of current required per car depends on the weight of the car and the character of the service4 ,this will be taken up later under the head of 8,operation40 ,,third ,,rail4 ,illustration3 ,fig4 #ga4 ,third-,rail ,insulator4 ,location4 ,the third-rail system of conducting current to electric cars1 as most commonly employed in the ,united ,states1 follows the example set by the ,metropolitan ,west ,side ,elevated ,railway of ,chicago4 ,all the elevated roads in the ,united ,states are now operated by means of third rails located at one side of the track4 ,the third rail is an ordinary ,t-rail and is located with the center of its head #bj inches outside of the gauge line of the nearest track rail1 and #f inches above the top of the track rail4 ,on a few interurban roads this distance has been increased in order to accommodate certain steam railroad rolling stock which must at times be operated over the line4 ,insulators4 ,the third rail is supported every fifth tie on an insulator4 ,these insulators on first construction were made of wooden blocks boiled in paraffine1 but at the present time more substantial forms of insulation are being used4 ,one form of third-rail insulator1 known as the 8,gonzenbach10 has a base of cast iron resting on the tie4 ,over this is placed a cap of insulating material similar to that used in strain and trolley-wire insulators4 ,over this insulating material is another cast-iron cap upon which the third rail rests4 ,the weight of the third rail holds it in position1 and there is no clamping together of the various parts of the insulator4 ,another form of third-rail insulator is made of what is called 8reconstructed granite10 and another of vitrified clay4 ,fig4 #ga shows one of the latter4 ,switches4 ,where the third rail is used1 a contact shoe is placed on each side of both trucks of the motor car4 ,at switches it is necessary to omit the third rail for a short distance on one side of the track1 and place a short section of third rail on the other side of the track so that the current supply to the car will be uninterrupted4 ,at ,highway ,crossings4 ,where the third-rail system is employed on interurban surface lines1 it is necessary to omit a section of it at every highway crossing4 ,if the crossing is too wide to be bridged across by a car1 the car must have sufficient momentum to drift over such crossings when it comes to them4 ,to connect across the break in the third rail at such points1 an underground cable is generally used4 ,this cable must be thoroughly protected against leakage of moisture into the insulation where it comes to the surface for connection to the third rail4 ,another form of third rail1 laid several years ago on some of the lines of the ,new ,york1 ,new ,haven ,hartford ,railroad1 was of an inverted ,v-shape1 and was laid midway between the track rails with its top #a inch above them and its bottom only #a inches above the ties4 ,it was supported on wooden blocks4 ,this location of the third rail has never been popular1 because of the poor insulation with the rail located so close to the ties between the rails4 ,conductivity4 ,the conductivity of a steel rail varies considerably4 ,a rail of the ordinary composition used on steam railroads is too high in carbon to give the best conductivity4 ,such a rail has about one-tenth the conductivity of the same cross-section of copper4 ,steel can easily be obtained1 however1 which will have one-seventh the conductivity of copper1 and the additional cost of obtaining such special steel is quite low1 so that the majority of roads installing the third-rail system have seen fit to pay the extra cost and thereby secure a softer rail than that usually employed in track rails4 ,cost4 ,the cost of the third-rail system is less than an overhead trolley system1 provided enough copper is placed in the trolley feeders to make the conductivity of the trolley system equal to that of the third-rail system4 ,it is very seldom1 however1 that a trolley system is so constructed on an interurban road2 and hence the trolley system1 as usually constructed1 is cheaper than the third-rail system1 because it is not of equal conductivity to a third-rail system4 ,advantages in ,operation4 ,where very heavy cars or trains are to be operated1 the third-rail system is decidedly an advantage1 for two reasons4 ,in the first place1 it affords the cheaper method of conducting a given heavy volume of current2 and in the second place1 the contact shoes that conduct the current from the third rail to the moving car or train are built to carry a much larger volume of current than the trolley wheel1 which has only a small area of contact on the trolley wire4 ,ordinarily there are two of these contact shoes in multiple for every motor car4 ,another advantage of the third rail over the trolley is that the trolley may leave the wire at high speeds or in passing switches4 ,on well-constructed roads1 where the trolley wire is kept in good alignment and the track is smooth1 there is little trouble from this source2 but it is undoubtedly a convenience to be able to operate cars or trains without giving any attention to a trolley pole4 ,illustration3 ,fig4 #gb4 ,cross-,section of ,conduit4 ,,conduit ,,systems4 ,the underground conduit system1 in which the conductors conveying the current to the cars are located in a conduit under the tracks1 is in use in two cities of the ,united ,states--,new ,york ,city and ,washington1 ,d4 ,c4 ,the cost of this system1 and the danger of interruption of the service where the drainage is not excellent1 have prevented its more extensive adoption4 ,the ,new ,york type of conduit is a good example of this construction4 ,the conductors consist of ,t-bars 7,,cc7 of steel supported from porcelain cup insulators located #ae feet apart in the conduit4 ,a cross-section of the conduit is shown in ,fig4 #gb4 ,at each insulator a handhole is provided 7,fig4 #gc71 so that access may be had to the insulator from the street surface4 ,manholes are provided at intervals of about #aej feet1 so that the dirt which collects in the conduit can be scraped into these manholes and removed at intervals4 ,the manholes also serve as points of drainage to the sewer system4 ,illustration3 ,fig4 #gc4 ,handhole4 ,contact ,plow4 ,current is conducted to the car through a pair of contact shoes commonly called a plow 7,fig4 #gd74 ,this plow has the two shoes insulated from each other1 and from the frame of the plow4 ,they are provided with flat springs that hold the shoes against the conducting bars in the conduit4 ,the shank of the plow is thin enough 7 inch7 to enter the slot of the conduit4 ,the conductors pass up through the middle4 ,these plows can1 of course1 be removed only when the car is over an open pit4 ,cost4 ,a conduit system of this kind is very expensive to build because of the fact that a very deep excavation must be made in the street to accommodate the conduit4 ,the track rails1 slot rails1 and sheet-steel conduit lining are held in alignment by cast-iron yokes placed #e feet apart4 ,the entire space around and underneath these yokes is filled with concrete in order to give rigidity and a permanent track4 ,three expensive items1 therefore1 enter into the construction of a conduit road--namely1 the deep excavation1 which may call for the changing of other underground pipes or conduits in the street2 the large amount of iron and steel needed for the yokes and slot rails2 and the large amount of concrete needed4 ,on ,american conduit roads the slot and conduit are placed under the middle of the track4 ,some of these roads are simply reconstructed cable-conduit roads in which the old cable conduit has been used for electrical conductors4 ,in the conduit road at ,buda-,pest1 ,hungary1 the slot is placed alongside one of the track rails4 ,current ,leakage4 ,the leakage on an underground conduit road is considerable1 because the insulators are necessarily located in a damp1 dirty place1 which causes leakage over the surface of the insulators4 ,this leakage1 however1 is not prohibitive so long as the conductor rails are not under water4 ,if on account of poor drainage the conductor rails become submerged1 the leakage becomes so great that it is impossible to operate the road4 ,illustration3 ,fig4 #gd4 ,contact ,plow4 ,it will be noticed that the conduit system as illustrated here employs two conductor rails--one for the positive side of the circuit and the other for the negative4 ,the track rails1 therefore1 are not used as conductors1 and one side of the circuit is not grounded as in the ordinary trolley system1 although the leakage to ground may be considerable from one or both conductor rails4 ,,track ,,construction4 ,girder ,rail4 ,a great variety of track rails are used in electric railways4 ,the most common at one time was the girder1 a typical section of which1 with joint1 is illustrated in ,fig4 #ge4 ,this is an outgrowth of the old tram rail used on horse railways4 ,it has a tram alongside of the head1 on which vehicles may be driven4 ,its chief advantage from the standpoint of the railway company is that there is plenty of room for dirt and snow to be pushed away by the flanges of the cars4 ,if the company maintains the paving1 it may be to its advantage to have teams use the steel track rather than the paving1 although this advantage in maintenance is probably more than compensated for by the delay of cars through the regular use of the track by teams4 ,illustration3 ,fig4 #ge4 ,girder ,rail4 ,trilby ,groove ,rail4 ,a modification of the girder rail1 known as the ,trilby1 and sometimes as the grooved girder1 is shown in ,fig4 #gf4 ,a rail similar to this is used in several large cities of the ,united ,states4 ,it has a groove of such a shape that the flanges of the car wheels will force snow and dirt out of it instead of packing it into the bottom of the groove1 as in the case of the regular ,european narrow-grooved rail4 ,a narrow-grooved rail in which the grooves correspond closely to the shape of the car-wheel flanges is sure to make trouble in localities where there is snow and ice1 as the grooves become packed and derail the cars4 ,illustration3 ,fig4 #gf4 ,grooved ,rail4 ,shanghai ,t-,rail4 ,in some systems a ,t-rail is used4 ,where the ,t-rail is to be used with paving1 the popular form is the ,shanghai ,t1 shown in ,fig4 #gg4 ,this rail is high enough to permit the use of high paving blocks around it4 ,illustration3 ,fig4 #gg4 ,shanghai ,t-,rail and ,joint4 ,common ,t-,rail4 ,the ,t-rail used by steam railroads is known as the ,a4 ,s4 ,c4 ,e4 standard ,t-rail1 because it follows the standard dimensions recommended for ,t-rails by the ,american ,society of ,civil ,engineers4 ,a standard #fe-pound ,t-rail of this kind is shown in ,fig4 #gh4 ,other weights of this rail have the same relative proportions4 ,such a rail is used for interurban roads1 and for suburban lines in streets where there is no block paving4 ,the high rails are used to facilitate paving with high paving blocks4 ,illustration3 ,fig4 #gh4 ,standard ,a4 ,s4 ,c4 ,e4 ,rail and ,one ,joint ,plate4 ,track ,support4 ,the greater portion of track is laid on wooden ties4 ,these ties1 in the most substantial wooden tie construction1 are #f inches by #h inches in section1 and #h feet long4 ,they are spaced two feet between centers4 ,sometimes smaller ties1 spaced farther apart1 are used in cheaper forms of construction2 but the foregoing figures are those of the best construction known in ,american railway practice4 ,in paved streets1 ties are usually employed1 although sometimes what is known as 8concrete stringer0 construction is used instead of ties to support the rails4 ,a strip of concrete about #ab inches deep is laid under each rail1 and the rails are held to gauge by ties or tie rods placed at frequent intervals4 ,sometimes the concrete is made a continuous bed under the entire track4 ,in most large cities the concrete foundation is used under all paving2 and consequently1 when concrete is used instead of ties to support the rails1 this concrete is simply a continuation of the paving foundation4 ,where ties are used1 they are laid sometimes in gravel1 crushed stone1 or sand1 although frequently1 in the largest cities1 they are embedded in concrete4 ,sometimes this concrete is extended under the ties1 and sometimes it is simply put around the ties4 ,ballast4 ,a ballast of gravel1 broken stone1 cinders1 or other material which is self draining and which will pack to form a solid bed under the ties1 should be used to get the best results under all forms of tie construction1 whether in paved streets or on a private right of way1 as on an interurban road4 ,of course1 if concrete is placed under the ties1 the gravel or rock ballast is not necessary4 ,if ties are placed directly in soft earth1 which forms mud when wet1 they will work up and down under the weight of passing trains1 and an insecure foundation for the track will be the result4 ,joints4 ,the matter of securing a proper joint for fastening together the ends of rails so as to make a smooth riding track without appreciable jar or jolt when the wheels pass a joint1 has been given much study by electric railway engineers4 ,a section through an ordinary bolted angle-bar joint is shown in ,fig4 #ge4 ,this joint is formed by bolting a couple of bars1 one on each side of the rails4 ,the edges of these bars are made accurately to such an angle that they will wedge in between the head and base of the rail as the bolts are tightened2 hence the name angle bars4 ,this is the form of joint generally used on steam railroads and on electric roads in exposed track1 or in track where the joints are easily accessible1 as in dirt streets4 ,in paved streets1 the undesirability of tearing up the pavement frequently to tighten the bolts on such joints1 has led to the invention of several other types1 which will be described later4 ,nevertheless very good results have been obtained in recent years with bolted joints laid in paved streets where care has been given to details in laying the track1 and where the joints have been tightened several times before the paving is finally laid around them4 ,welded ,joints4 ,several forms of welded joints are in use4 ,all these welded joints fasten the ends of the rails together so that the rail is practically continuous--just as if there were no joints--so far as the running surface of the rail is concerned4 ,it was thought at one time that a continuous rail would be an impossibility because of the contraction and expansion of the rail under heat and cold1 which1 it was thought1 would tend to pull the rails apart in cold weather and to cause them to bend and buckle out of line in hot weather4 ,experience has conclusively shown1 however1 that contraction and expansion are not to be feared when the track is laid in a street where it is covered with paving material or dirt4 ,the paving tends to hold the track in line1 and to protect it from extremes of heat and cold4 ,the reason that contraction and expansion do not work havoc on track with welded joints1 is probably that the rails have enough elasticity to provide for the contraction and expansion without breaking4 ,it is found that the best results are secured by welding rail joints during cool weather1 so that the effect of contraction in the coldest weather will be minimum4 ,in this case1 of course1 there will be considerable expansion of the track in the hottest weather1 but this does not cause serious bending of the rails2 whereas occasionally1 if the track is welded in very hot weather1 the contraction in winter will cause the joint to break4 ,illustration3 ,,portable ,,cupola ,,for ,,cast-,,welding ,,joints ,,of ,,street ,,car ,,rails4 ,cast-,welded ,joints4 ,the process of cast-welding joints consists in pouring very hot cast iron into a mould placed around the ends of the rails4 ,these moulds are of iron2 and to prevent their sticking to the joint when it is cast1 they are painted inside with a mixture of linseed oil and graphite4 ,iron is usually poured so hot that1 before it cools1 the base of the rail in the center of the molten joint becomes partially melted1 thus causing a true union of the steel rail and cast-iron joint4 ,this makes the joint solid mechanically and a good electrical conductor4 ,to supply melted cast iron during the process of cast-welding joints on the street1 a small portable cupola on wheels is employed4 ,fig4 #gi gives an idea of the process of making cast-welded joints4 ,illustration3 ,fig4 #gi4 ,process of ,cast-,welding ,joint4 ,electrically ,welded ,joints4 ,an electrically welded joint is made by welding steel blocks to the rail ends4 ,a steel block is placed on each side of the joint1 and current of very large volume is passed through from one block to the other4 ,this current is so large that the electrical resistance between the rail and steel block causes that point to become molten4 ,current is then shut off1 and the joint allowed to cool4 ,there is in this case a true weld between the steel blocks and the rails and joint4 ,an electric welding outfit being expensive to maintain and operate1 this process is used only where a large amount of welding can be done at once4 ,current is taken from the trolley wire4 ,a rotary converter set takes #ejj-volt direct current from the trolley wire1 and converts it into alternating current4 ,this alternating current is taken to a static transformer which reduces the voltage and gives a current of great quantity at low voltage1 the latter current being passed through the blocks and rails in the welding process4 ,a massive pair of clamps is used to hold the blocks against the rails1 and to conduct the current to and from the joint while it is being welded4 ,these clamps are water-cooled by having water circulated through them so that they will not become overheated at the point of contact with the steel blocks4 ,thermit ,welding4 ,a process of welding rail joints which was developed after the cast-welding and electric-welding processes1 is known as the ,goldschmidt process1 which makes use of a material called 8thermit0 for supplying heat to make the weld4 ,a mould is placed around the joint and the thermit is put in this mould and ignited4 ,the heat produced by the thermit is so intense as to reduce the iron in the thermit mixture and make a welded joint4 ,the thermit consists of a mixture of finely powdered aluminum and iron oxide4 ,when this is ignited1 the aluminum oxidizes1 that is1 absorbs oxygen so rapidly that an intense heat is the result4 ,in the process of oxidation1 the aluminum takes the oxygen from the oxide of iron1 leaving molten metallic iron1 which metallic iron makes the weld by union with the molten rail ends4 ,this process has the advantage over other welding processes1 of not requiring an elaborate apparatus and a large crew of men to operate it2 and consequently it can be used where but a few joints are to be welded4 ,illustration3 ,fig4 #hj4 ,channel ,pin ,bond4 ,bonding and ,return ,circuits4 ,when the track rails are used as the conductors1 as is usually the case1 it is necessary to see that the electrical conductivity of the rail joints does not offer too high a resistance to the passage of the current4 ,for this reason1 when bolted or angle-bar joints are used1 the rails are bonded together by means of copper bonds4 ,it was soon found after electric roads were in use a short time1 that unless the rail ends were so bonded1 the resistance of the joints was so great as to cause great loss of power in the track4 ,first1 small iron bonds were used2 but these bonds were so insufficient that large copper-wire bonds soon began to be used2 and at the present time1 on large roads1 bonds of heavy copper cable are common4 ,the resistance of a steel rail1 such as used in city streets1 is about eleven times that of copper4 ,in order to secure as great carrying capacity at the rail joint as is afforded by the unbroken rail1 it is therefore necessary to install bonds having a total cross-section that of the rail4 ,where welded joints are used1 bonding is unnecessary1 except at crossings and switches where bolted joints are employed4 ,where track is welded1 however1 cross bonds should be put in at frequent intervals from one rail to another1 and1 if the track is double1 from one track to the other1 so that if one of the track rails breaks at a joint there will be a path around the break for the current4 ,illustration3 ,fig4 #ha4 ,chicago ,rail ,bond4 ,illustration3 ,fig4 #hb4 ,rail ,bond4 ,a great many schemes have been devised to insure good contact between the copper bond and the rail1 as the terminal is the weak point in any bond4 ,one of the earliest and most efficient of small bonds was made by the use of channel pins1 ,fig4 #hj4 ,this bond consisted of a piece of copper wire having its ends placed in the holes in the rail ends4 ,alongside this wire1 a channel pin was driven in4 ,the objection to the channel pin was the small area of contact between the copper bond and rail4 ,next after the channel pin came the ,chicago type of bond1 ,fig4 #ha1 which is a piece of heavy copper wire with thimbles forged on the ends4 ,these thimbles were placed in accurately fitted holes in the rail ends1 and a wedge-shaped steel pin was driven into the thimbles to expand them tightly into the hole in the rail4 ,several other bonds using modifications of this principle are in use4 ,a type of bond in very common use consists of solid copper rivet-shaped terminals1 ,fig4 #hb4 ,between these terminals is a piece of flexible stranded copper cable1 made flat to go under the angle bars4 ,in one type the terminal lugs are cast around the ends of the cables1 and in another type the cables are forged at their ends into solid rivet-like terminals4 ,these terminal rivets were first applied as any other rivets1 with the use of a riveting hammer4 ,because of the difficulty of thoroughly expanding such large rivets into the holes made for them in the rails1 it has become customary to compress these rivets either with a screw press or a portable hydraulic press1 which brings such great pressure to bear on the opposite ends of the rivet that it is forced to expand itself so as to fill the hole in the rail completely4 ,this expansion is made possible by the ductile character of the copper4 ,this great ductility characteristic of copper1 however1 has been the source of one of the difficulties in connection with rail bonding1 because the soft copper terminal has a tendency to work loose in the hole made for it in the rail4 ,it is practically impossible to maintain good bonding where the rail joints are so loose as to allow considerable motion between the rail ends4 ,several types of bonds have been introduced1 in which the contact between the rail and bond is made by an extra piece or thimble4 ,another method of expanding bond terminals into the holes made to receive them1 is that employed in the ,general ,electric ,company's bond4 ,in it a soft pin in the center of the terminal is expanded by compression of the terminal so that it forces the copper surrounding it outward4 ,the copper terminal1 in expanding to fill the hole1 is therefore backed by the steel center pin4 ,all types of bonds must be installed with great care if they are to be efficient4 ,unless the bond terminal thoroughly fills the hole and is tightly expanded into it1 moisture will creep into the space between the copper and the iron1 and the copper will become coated with a non-conducting scale which destroys the conductivity of the contact4 ,the plastic rail bond1 so called because it depends for the contact between the rail and the bond upon a plastic1 putty-like alloy of mercury and some other metal1 is applied in a number of different ways4 ,one form consists of a strip of copper held by a spring against the rail ends under the fish-plate4 ,the rail ends at the point of contact with this strip of copper are amalgamated and made bright by the use of a mercury compound similar to the plastic alloy4 ,these points of contact are then daubed with plastic alloy1 and the copper bond plate applied4 ,it is not necessary1 with any form of plastic bond1 that the mechanical contact be unyielding1 as the amalgamated surfaces with the aid of the plastic alloy between them1 maintain a good conductivity in spite of any slight motion4 ,the plastic alloy can be applied in a number of other ways1 one of which is to drill a hole forming a small cup in the rail base in adjacent rail ends1 fill these cups with plastic alloy1 and bridge the space between them with a short copper bond having its ends projecting down into the cups4 ,resistance of the ,track4 ,the resistance of the return circuit is usually much higher than it should be owing to the bad contact of the bonds4 ,the resistance of rails varies greatly with the proportions of carbon1 manganese and phosphorus4 ,the following figures1 however1 may be regarded as the average4 ,weight per ,yard4 ,resistance ,single ,rail per ,mile4 #ej 4#jbec ohms #fj 4#jbaa 0 #gj 4#jahj 0 #hj 4#jaei 0 #ij 4#jad 0 ,a track laid with continuous rails as in the case of welded joints1 would have one-half the resistance given since there are two rails to be considered4 ,tests of new unbonded track constructed with rails #fj feet long show that the joints cause an increase of 4#be ohms or more per mile4 ,several roads in testing bonds consider a bond good when the bond and one foot of the rail over it have a resistance equal to five feet of the solid rail4 ,supplementary ,return ,feeders4 ,on some large roads it is necessary to run additional return feeders from the power house to various points on the system1 to supplement the conductivity of the rails4 ,otherwise the track rails near the power house would have to carry all the current1 and in some cases there are not enough such lines of track passing the power house to do this properly4 ,sometimes these feeders are laid underground in troughs2 sometimes they are laid bare in the ground1 and sometimes on overhead pole lines4 ,when laid in the ground1 frequently old rails are used instead of copper or aluminum cables4 ,the old rails are1 of course1 thoroughly bonded together with bonds giving a conductivity nearly equal to that of the unbroken rail4 ,,feeder ,,systems4 ,illustration3 ,fig4 #hc4 ,there are two general schemes of direct current feeding in common use4 ,one of these is shown in ,fig4 #hc4 ,here the trolley wire is continuous and is fed into at different points4 ,the long feeders supplying the more distant portion of the road are larger than those supplying the trolley near by1 so as to maintain as nearly as is feasible the same potential the entire length of the line4 ,with such a system of feeding1 in order to maintain absolutely the same voltage at all points1 it would be necessary to have just one trolley feeder and that feeding into the extreme end of the line farthest from the power station and further to make the resistance per #a1jjj ft4 of trolley and feeder the same as the resistance per #a1jjj ft4 of the track return circuit4 ,the plan shown in ,fig4 #hc evidently does not fully carry out these rather impracticable requirements but is in the nature of a compromise1 giving a higher potential near the power station than at distant points but nevertheless much more even potential than if the heaviest feeders were feeding into the trolley near the power house4 ,the other plan1 shown in ,fig4 #hd1 divides the trolley wire into sections and feeds each section through a separate feeder which is calculated of such size as to maintain the same voltage on all the sections with the ordinary load4 ,in calculating a feeder system a certain probable load is assumed at certain points along the line4 ,this load will manifestly depend on the size and number of cars in operation1 grades and many local conditions4 ,illustration3 ,fig4 #hd4 ,drop in rail section #c4a ,volts #b4a ,volts #a4je ,volts ,total drop in rail #c4a 0 #e4b 0 #f4be 0 ,drop in trolley #bj4e 0 #bj4e 0 #bj4e 0 ,drop in feeder #cf4d 0 #cd4c 0 #cc4be 0 ,resistance feeder 4#gbh ,ohms 4#fhf ,ohms 4#ffe ,ohms ,feet per ohm #gbec #bcjjj #cigjj ,size of wire ,no4 #a #bej1jjj ,c4 ,m4 #dbj1jjj ,c4 ,m4 ,the following example will show the method pursued4 ,the figures resulting from the calculations are placed immediately below the sections to which they refer in ,fig4 #hd4 ,the rails are assumed to be #gj pound to the yard4 ,these have a resistance of about 4#jah ohms per mile4 ,adding one-sixth for additional resistance of bonds gives 4#jba and since the track is composed of two rails the resistance of the track will be one-half of this or 4#jaje ohms per mile4 ,the maximum drop in any section occurs when the car is farthest from the power house4 ,each car is assumed to take #ej amperes and the feeders are to be so designed as to allow a #aj per cent or #fj volts drop4 ,the current in the two miles of track nearest the power house is #aej amperes1 in the next section #ajj amperes1 and in the last section #ej amperes4 ,the drop in each section is as shown4 ,the drop in the trolley which is #jj wire is1 in each section1 #bj4e volts4 ,subtracting from #fj volts the drop in the return circuit and trolley1 gives the allowable drop in the feeder4 ,the resistance of each feeder can be calculated1 since the current in each one is #ej amperes4 ,the first feeder is one mile long1 the second #c miles and the third #e miles1 and with these figures the feet per ohm can be computed4 ,the size of wire may be obtained by reference to a table of copper wire resistances4 ,,block ,,signals ,,for ,,electric ,,railways4 ,the simplest block signal used by electric roads is a hand-operated one constructed on the principle shown in the diagram ,fig4 #he4 ,a double throw switch is placed at each terminal of the section of track that is to be protected4 ,illustration3 ,fig4 #he4 ,the switches have no central position1 the knife blade always making contact with one or the other of the terminals shown4 ,if the lamps are lighted1 throwing either one of the switches will put them out4 ,if they are not burning1 they will be lighted by throwing either one of the switches4 ,a motorman on reaching a section of track finding the lamps not burning throws the switch4 ,lamps now burn in each switch box and show that the section is in use4 ,on arriving at the other terminal of the block the switch is thrown1 extinguishing the lights and showing that the block is clear4 ,automatic signal systems have been devised on the same principle1 in which magnets1 operated by contacts made by the passage of the trolley wheel1 cause the lamps to be lighted and extinguished automatically4 ,,electrolysis4 ,much has been said about the possibilities of electrolysis of underground metal by the action of the return current of electric railways1 when such railways are operated with grounded circuits1 as they usually are4 ,if electric current is passed through a liquid from one metal electrode to another1 electrolysis will take place2 that is1 metal will be deposited on the negative pole1 and the positive pole or electrode will be dissolved by becoming oxidized from the action of the oxygen collecting at that pole4 ,illustration3 ,fig4 #hf4 ,showing ,electrolytic ,action4 ,in an electric-railway return circuit1 there is necessarily a difference of potential between the rails at outlying parts of the system and the rails and other buried pieces of metal located near the power house4 ,just what this total difference of potential is1 depends on the loss of voltage in the return circuit4 ,thus1 suppose there is #be volts drop in the return circuit between a certain point on the system and the power station4 ,there is1 therefore1 a pressure of #be volts tending to force the current through the moist earth from the rails at distant portions of the line1 to the rails1 water pipes1 and other connected metallic structures located in the earth near the power station4 ,the amount of current that will thus flow to earth in preference to remaining in the rails1 depends on the relative resistance of the rails1 the earth1 and the other paths offered to the current to return to the power house4 ,to take a very simple case1 let us suppose a single-track road1 ,fig4 #hf1 with a power house at one end1 and a parallel line of water pipe on the same street passing the power house4 ,if the positive terminals of the generators are connected to the trolley wire1 the current passes1 as indicated by the arrows1 out over the trolley wire through the cars and to the rails4 ,when it has reached the rails it has the choice of two paths back to the power house4 ,one is through the rails and bonding2 the other is through the moist earth to the line of water pipe and back to the power house1 leaving the pipe for the rails1 at the power house4 ,should the bonding of the rails be very defective1 considerable current might pass through the earth to the water pipe4 ,remembering now the principles of electrolysis1 we see that the oxidizing action of this flow of current from the rails to the water pipes at the distant portion of the road will tend to destroy the rails1 but will not harm the water pipe at that point1 as it will tend to deposit metal upon it4 ,when1 however1 the current arrives at the power house1 it must in some way leave this water pipe to get back to the rails1 and so to the negative terminals of the generators4 ,here we see that there is a chance for electrolysis of the water pipe1 because at this point the water pipe forms the positive electrode1 which is the one likely to be oxidized and destroyed4 ,this very simple case is taken merely for illustration4 ,in actual practice the conditions are never so simple as this1 for there are various pipes located in the ground running in various directions1 which complicate the case very much2 but we can see from this simple example that the principal place electrolysis of water pipe is to be feared is at points where a large volume of current is leaving the water pipe to take to some other conductor4 ,as an indication of how much current is likely to be leaving the water pipes at various points1 it is customary to measure the voltage between the water pipes and the electric railway track and rails4 ,when this voltage is high1 it does not necessarily mean that a large volume of current is leaving the water pipes at the point where these pipes are several volts positive with reference to the rails2 but such voltage readings indicate that1 if there is a path of sufficiently low resistance through the earth1 and if the moisture in the earth is sufficiently impregnated with salts or acids1 there will be trouble from an electrolytic action due to a large flow of current4 ,there is obviously no method of measuring exactly the amount of current leaving a water pipe at any given point1 since the pipe is buried in the earth4 ,voltmeter readings between pipes and rails simply serve to give an indication as to where there is likely to be trouble from electrolysis4 ,the danger to underground pipes and other metallic structures from electrolysis has been much overestimated by some people1 as the trouble can be overcome by proper care and attention to the return circuit4 ,trouble from electrolysis1 however1 is sure to occur unless such care is given4 ,prevention of ,electrolysis4 ,remedies for electrolysis may be classified under two heads--general and specific4 ,the general remedy is obviously to make the resistance of the circuit through the rails and supplementary return feeders so low that there will be but little tendency for the current to seek other conductors1 such as water and gas pipes and the lead covering of underground cables4 ,this remedy consists in heavy bonding1 in ample connections1 around switches and special work where the bonding is especially liable to injury1 and in additional return conductors at points near the power house to supplement the conductivity of the rails4 ,it is important that all rail bonds be tested at intervals of six months to one year in order that defective bonds may be located and renewed1 as a few defective bonds can greatly lower the efficiency of an otherwise low-resistance circuit4 ,the specific remedy for electrolysis which may be applied to reduce electrolytic action at certain specific points1 consists in connecting the water pipe at the point where electrolysis is taking place1 with the rail or other conductor to which the current is flowing4 ,thus1 for example1 if it is found that a large amount of current is leaving a water pipe and flowing to the rails or to the negative return feeders at the power house1 the electrolytic action at this point can obviously be stopped by connecting the water pipe with the rails by means of a low-resistance copper wire or cable1 thereby short-circuiting the points between which electrolytic action is taking place4 ,there are certain cases in which it is advisable to adopt such a specific remedy4 ,it should be remembered1 however1 that a low-resistance connection of this kind1 while it reduces electrolysis at points near the power house1 is an added inducement to the current to take to the water pipes at points distant from the power house1 because of the decrease in resistance of the water-pipe path to the power house resulting from the introduction of the connection between the water pipe and the negative return feeder at the power house4 ,with the water pipes connected to the return feeders in the vicinity of the power house1 the current which flows from the rails to the water pipes at points distant from the power house will obviously cause electrolysis of the rails but not of the water pipes1 since the current is passing from the earth to the pipe1 and the pipe is negative to the earth4 ,in this case the principal danger is that the high resistance of the joints between the lengths of water pipe will cause current to flow through the earth around each joint1 as indicated on some of the joints1 ,fig4 #hf1 and will cause electrolytic action at each joint4 ,it is evident1 however1 that the conditions of the track circuit and bonding must be very bad if current would flow over a line of water pipe1 with its high-resistance joints1 in sufficient volume to cause electrolysis1 in preference to the rail-return circuit1 especially since ordinarily the resistance offered to the flow of current over the water pipes back to the power house must include the resistance of the earth between the tracks and water pipes4 ,it is usually considered inadvisable to connect tracks and water pipes at points distant from the power house1 because of the danger of electrolysis at water-pipe joints1 as just explained4 ,methods of testing rail bonds in the track will be explained under the head of 8,tests40 ,,power ,,supply ,,and ,,distribution4 ,direct-,current ,feeding4 ,as already explained1 the majority of electric railways are operated on a #ejj-volt constant-potential direct-current system with a ground return4 ,a constant potential of #dej to #eej volts is maintained between the trolley wire and track4 ,where the trolley wire is not sufficient1 additional feeders are run from the power house and connected to the trolley wire1 the number of feeders depending on the distance from the power house and the traffic4 ,booster ,feeding4 ,boosters are sometimes used on long feeder lines where there is a heavy load only a small portion of the time4 ,these boosters are direct-current dynamos that are connected in series with the feeder upon which the voltage is to be raised above the regular power-house voltage4 ,the booster may be driven either by a small steam engine or by an electric motor4 ,the simplest form of booster is a series-wound dynamo4 ,a booster armature must1 of course1 be of sufficient current capacity to pass all the current that will be required on its feeder4 ,the voltage yielded by this dynamo1 plus the power-station voltage1 is the voltage of the boosted feeder as it leaves the power house4 ,supposing that a series-wound booster will give #abe volts at full load2 it is obvious that being series-wound it will give no voltage at no load4 ,the voltage will increase approximately as the load on the feeder increases2 and since the drop in voltage on the feeder for which the booster is to compensate also varies with the load1 the action of the booster is simply to add sufficient voltage to its feeder at any instant to compensate for the line loss upon that feeder and to maintain approximately constant potential at the far end of the feeder4 ,boosters raising the power-station voltage of a feeder more than #bej volts above the normal power-station voltage1 are not common1 though cases are on record where a feeder has been boosted as high as #a1ajj volts above the power-station voltage4 ,since all the power used in driving a booster is wasted in line loss1 this method of feeding is not economical2 but where used only a few days out of the year it is sometimes to be preferred to a heavy investment in feeders4 ,the investment in feeders might involve more interest charges than the cost of power wasted in booster feeding would amount to4 ,alternating-,current ,transmission4 ,high-tension alternating-current transmission to substations1 with direct-current distribution from substations1 is extensively used on long interurban roads1 and on large city street-railway systems where power is to be distributed over a wide area4 ,in such cases the power house is equipped with alternating-current dynamos supplying high-tension three-phase alternating current to high-tension transmission lines or feeders4 ,these high-tension feeders are taken to substations located at various points on the road1 where the voltage is reduced by step-down transformers2 and these transformers supply current to operate rotary converters1 which convert from alternating to direct current for use on the trolley4 ,the advantage of this system of high-tension distribution is that1 owing to the high transmission voltage1 there is but a small loss in the high-tension lines1 which lines can be made very small1 and will thus involve but little copper investment4 ,the substations can be located at frequent intervals1 so that the distance the #ejj-volt direct-current must be conducted to supply the cars is not great4 ,current from one power house can thus be distributed over a very large system in cases where1 if the #ejj-volt direct-current system of distribution were used1 the cost of feeders for distributing such a low-voltage current would be prohibitive4 ,were the alternating-current high-tension scheme of distribution not used1 it would be necessary to have a number of small power houses at various points on the system instead of one large power house4 ,the cost of operation of several small power plants per kilowatt output1 is likely to be much greater than that of one large power plant4 ,the first cost of the alternating-current distributing system1 including power house and substations1 is likely to be considerably higher than would be the cost of a number of small power houses2 but in cases where alternating-current distribution has been installed1 it has been figured that the cost of operation of the central power house with alternating-current distribution would be sufficiently low as compared with several small ones to pay more than the interest on this extra investment4 ,illustration3 ,fig4 #hg4 ,diagram of ,distributing ,system4 ,a ,system of ,distribution for an ,interurban ,railway4 ,the typical features of a high tension system of distribution for an extensive interurban railway system are shown in ,fig4 #hg1 which represents the electrical transmission and distribution system of the ,indiana ,union ,traction ,company4 ,the central power station at ,anderson feeds into thirteen rotary converter substations from #g to #fe miles distant from the power house4 ,the substations east of ,indianapolis are fed at #af1jjj volts and are placed about #aa miles apart4 ,the substations due north of ,indianapolis are located at intervals of about #ag miles and are fed at #cj1jjj volts4 ,the power station at ,anderson has a total capacity of #e1jjj ,k4 ,w4 ,the substations vary in capacity from #bej to #a1ejj ,k4 ,w4 ,efficiency of ,transmission ,systems4 ,the average efficiency of a high tension transmission system for a certain interurban electric railway system are given below4 ,current was generated at #chj volts4 ,the step-up transformers raised it to a potential of #af1jjj volts at which pressure it was transmitted to eight substations at distances from #aj to #dj miles from the power station4 ,it was then stepped down to #chj volts and converted to direct current by a rotary converter4 ,the tests extended over a period of three days4 ,the efficiency of the step-up transformers was #ie per cent2 of the high tension line #ib4i per cent2 of the step-down transformers #ie per cent2 and of the rotary converters #hh per cent2 giving a total efficiency of the transmission system of #gc4e per cent4 ,power ,house ,location4 ,a power house is usually located where coal and water supply can be cheaply obtained4 ,for this reason it is placed either on some line of railroad or where coal can be taken to it over the electric railway4 ,as it is always desirable to operate the engines in connection with condensers1 on account of the saving in fuel1 which is approximately #bj per cent with condensers1 power stations are located1 when possible1 near rivers and ponds from which a large supply of cold water for condensation of exhaust steam can be obtained4 ,where no such natural water supply is available1 it has become customary to provide means for artificially cooling a sufficiently large supply of water for condensation4 ,one method is to erect a number of towers1 so constructed that the water when pumped to the top will fall through a structure that breaks the water up into fine spray as it falls1 thus allowing it to cool by evaporation so that it can be used again for the condensers when it arrives at the bottom of the tower4 ,where more room is available1 ponds are sometimes excavated near the power house1 and the water is made to flow back and forth through a series of troughs located above the pond1 and it is thus cooled4 ,where a power station is of the direct-current type1 operating at #ejj to #fjj volts1 it is desirable to have it as near the center of electrical distribution as possible1 in order to keep down the amount of investment in the feed wire2 but it is more important to have it located near a cheap coal and water supply than exactly at the center of distribution4 ,it is also desirable to have the station located where there is room for coal storage1 on account of the chances for interruption of the coal supply by strikes1 railroad blockades1 and other causes beyond the company's control4 ,the continuity of the coal supply is also another argument against placing the station where dependence must be placed upon wagons or inadequate railroad facilities4 ,coal handling1 after the coal has reached the station1 is done by hand in the smaller power stations2 but in larger power stations it has come to be the general practice to do as much of the handling as possible by means of automatic coal conveyors4 ,the most elaborate power stations have means for dumping coal from cars into hoppers1 from which it is conveyed by an endless chain provided with buckets1 called a coal conveyor1 to storage bins4 ,coal conveyors also take the coal from the storage bins1 and deposit it in the hoppers of mechanical stokers in front of the boilers4 ,ashes are conveyed from under the boilers by the same kind of conveyors1 and are dumped into hoppers1 whence they are drawn into cars or wagons to be hauled away4 ,the coal1 having been deposited in hoppers at the boiler front1 is automatically fed into the furnaces by automatic stokers4 ,one type of automatic stoker in common use is of the chain-grate or link-belt type1 which is constructed like an endless sprocket chain1 with links composed of heavy cast-iron blocks that serve as grate bars4 ,this link belt or chain is kept in constant1 slow motion by a small stoker engine or motor which operates all the stokers of a line of boilers4 ,the coal is fed from the hopper on to the chain grate1 and the chain is slowly moved under the boilers4 ,as the coal on that part of the grate under the boilers is on fire1 the fresh coal as it enters the furnaces is soon ignited4 ,the grate is run at such a rate1 and the thickness of the coal is so adjusted1 that the coal is burned to an ash by the time it has traveled to the back of the furnace4 ,there the grate turns down over a sprocket wheel1 and the ashes are dumped into the ash pit as the grate revolves4 ,the boilers in most common use in large ,american electric-railway power houses are of the water-tube type1 in which water is contained inside of a bank of tubes1 the ends of these tubes being connected to drums or headers4 ,the horizontal return-tubular type of boiler is used in many of the smaller power stations1 and vertical boilers are also in use4 ,the engines in the larger and more economical stations are generally of the ,corliss compound-condensing type1 running at speeds of from #fj to #abj revolutions per minute1 according to the size of the unit4 ,the smaller the unit1 the higher the speed4 ,in the smaller and older stations1 simple ,corliss engines belted to generators are frequently found1 and high-speed engines also are used4 ,it is the almost universal custom now1 to place the generator directly on the engine shaft1 making a direct-connected unit4 ,steam turbines1 in which the steam acts in jets against the blades of a turbine wheel1 are beginning to come into use at the present time4 ,these turbines rotate at very high speed1 the largest and slowest speed-units running #fjj r4p4m41 and others at higher rates4 ,as the output of any generator varies directly according to its speed1 a very much smaller generator can be used when coupled to a high-speed steam turbine1 to obtain a given output1 than if the generator must be coupled to a ,corliss steam engine which revolves at very low speed4 ,the economy of the steam turbine at full load is about that of a compound-condensing ,corliss engine1 but is better on light loads than the engine4 ,the turbine requires less building space and a much less expensive foundation4 ,illustration3 ,fig4 #hh4 ,plan of ,power ,house4 ,railway generators or dynamos for direct current are usually built with compound-wound fields1 so that1 as the load increases1 they will automatically raise the voltage at their terminals to compensate for the drop in the feeders and to maintain a constant potential at the cars4 ,thus1 if the line loss on a system is #aj per cent1 or #ej volts at full load1 the generators will be provided with shunt fields of sufficient strength to give #ejj volts at no load1 and with series field coils which will add to the field strength enough to give #eej volts at full load4 ,the amount of 8compounding0--which is the term applied to this method of increasing voltage--may be any amount within reasonable limits4 ,the pressure maintained at different companies' electric-railway power houses varies1 but is usually between #ejj and #fjj volts4 ,alternating-,current ,generators4 ,alternating-current generators used for generating alternating current to be distributed at high tension1 are generally constructed to give a three-phase current at #be cycles per second4 ,the voltage of these alternating-current generators is sometimes the voltage at which the power is to be transmitted1 if the distances are not too great4 ,a number of stations have alternating-current generators giving #f1fjj volts at their terminals1 which is a voltage well adapted to high-tension distribution within the limits of a large city4 ,however1 generators giving #aa1jjj volts at their terminals are now becoming common4 ,for higher voltages than this1 it is considered necessary to use step-up transformers1 in order to raise the voltage to the proper pressure for transmission over long distances4 ,in such cases there is no object in having a high generator voltage4 ,at such stations the voltage of the generators adopted may be anything desired1 and it varies according to the ideas of the constructing engineer4 ,voltages of #djj1 #a1jjj1 and #b1cjj are among those in most common use4 ,double-,current ,generators4 ,double-current generators are sometimes used1 which generators will give direct current at a commutator at one end of the armature for use on a #ejj-volt direct-current distribution system supplying the trolley direct4 ,the other end of the armature has collector rings from which the three-phase alternating current is obtained1 which can be taken to step-up transformers and raised to a sufficient pressure1 for high-tension transmission to substations at distant parts of the road4 ,the same generator can therefore be used on both the direct-current and the high-tension alternating-current distribution4 ,general ,plan of ,power ,stations4 ,the general plan of an electric-railway power station is usually such that the building can be extended and more boilers1 engines and generators added without disturbing the symmetrical design of the station4 ,thus1 the boilers and engines are placed as in ,fig4 #hh1 in parallel rows1 although almost invariably in different rooms separated by a fire wall4 ,by adding to the row of engines and to the row of boilers1 the station capacity can be increased4 ,other arrangements are sometimes required by circumstances2 but this is the most common arrangement and gives the greatest capacity with the minimum amount of steam piping4 ,large stations are sometimes constructed with a boiler room of several floors and with boilers on each floor1 in order to save ground space and bring the boilers near to the large engine units so that there will not be an excessive amount of steam piping4 ,illustration3 ,fig4 #hi;a4 ,g4 ,e4 ,circuit ,breaker4 ,switchboards4 ,direct-current stations have switchboards1 which may be considered under two general classes--generator boards and feeder boards4 ,each board consists of panels4 ,generator ,d4 ,c4 ,panels4 ,the generator panel usually contains an automatic circuit breaker which will open the main circuit to the generator in case of an overload due to a short circuit4 ,these circuit breakers consist of a coil in the main circuit1 which acts upon a solenoid4 ,when the current in the coil exceeds a certain amount1 the solenoid is drawn in1 and a trigger is tripped which allows the circuit breaker to fly open under the pressure of a spring4 ,in the ,general ,electric circuit breaker1 the main contact is made by heavy copper jaws1 but the last breaking of the contact is made between points which are under the influence of a magnetic field4 ,this magnetic field blows out the heavy arc that would otherwise be established4 ,on the ,i-,t-,e1 the ,westinghouse and most other types of circuit breaker1 the breaking of the contact takes place between carbon points1 which are not so readily destroyed by an arc as are copper contacts1 and which are more cheaply renewed4 ,the main contact through the circuit breaker1 in either type1 is made between copper jaws of sufficient cross-section for carrying the current without heating4 ,these jaws open before the current is finally broken by the smaller contacts which take the final arc4 ,in ,fig4 #hi;a is seen a ,general ,electric circuit breaker with the magnetic blow-out coils at the top1 the solenoid at the left1 and the handle for resetting the circuit breaker at the bottom4 ,the small handle for tripping the circuit breaker1 when it is desired to open the circuit by hand1 is shown just under the solenoid4 ,an ,i-,t-,e circuit breaker is shown in ,fig4 #hi;b4 ,this is of the type previously mentioned1 in which the break occurs between carbon contacts and there is no magnetic blow-out4 ,illustration3 ,fig4 #hi;b4 ,i-,t-,e ,circuit ,breaker4 ,in addition to the circuit breaker there is usually an ammeter1 to indicate the current passing from the generator2 and a rheostat handle1 geared to a rheostat back of the board1 for cutting in and out more or less resistance in the shunt field coils of the generator so as to reduce or raise the voltage4 ,there is a small switch for opening and closing the circuit through the shunt field coils4 ,the main leads from the generator pass through two single-pole quick-break knife switches4 ,the most recent practice is to have the switches on the switchboard in only the positive and negative leads from the generator1 leaving connection to the equalizer to be made by a switch located on or near the generator4 ,however1 all three leads may be taken to the switchboard1 and a three-pole knife switch may be used instead of the positive and negative switches spoken of4 ,in ,fig4 #ij is given a simple diagram of the general relative connection of generators and feeders in a direct-current railway power station4 ,it is seen that the generators are connected in parallel across the positive and negative bus bar4 ,there is a third bus bar--called an 8equalizing bus0--which connects in parallel the series coils of all the generator fields4 ,the object of this equalizer is to prevent the weakening of the series field of any one generator1 so as to allow it to take current and to act as a motor instead of as a generator4 ,starting ,up a ,generator4 ,suppose that a new generator is to be started up and connected to the bus bars in addition to others already in operation4 ,the engine of that generator is first brought up to speed4 ,the switch controlling the shunt field circuit is then closed1 causing current to flow through the shunt fields2 and the generator begins to 8build up10 its voltage gradually rising until it approximates that upon the bus bars4 ,before the generator is thrown in parallel with the others by connecting it with the bus bars1 it is important that its voltage be nearly the same as that of the bus bars4 ,otherwise1 when connected to the bus bars1 it might take more than its share of the load2 while1 on the other hand1 if its voltage were too low1 it might act as a motor1 taking current from the bus bars4 ,the voltage of the bus bars in a railway station is constantly fluctuating1 owing to the varying load and to the fact that generators are often compounded1 as before mentioned1 in order to compensate for the line loss4 ,illustration3 ,fig4 #ij4 ,connection of ,generators and ,feeders4 ,in order that the voltage of the generator to be thrown in shall vary in accordance with the bus bar voltage1 the next step in the operation is to close the positive switch1 assuming that the equalizer switch on the generator has already been closed4 ,this throws the series field of the new generator in parallel with the series fields of the other generators4 ,the voltage of the new generator will therefore vary just as the voltage on the bus bars2 and1 by adjusting the resistance of the shunt field1 this voltage can be adjusted so as to be the same as that on the bus bars4 ,the voltages on the bus bars and on the new generator are measured usually by a large voltmeter on a bracket at the end of the generator switchboard4 ,by means of a voltmeter plug or of a push button on the generator panel1 the voltmeter can be connected either to the bus bars or to the new generator4 ,when the two voltages are the same1 the negative switch of the new generator can be closed1 and it will operate in parallel with the other generators1 taking its share of the load4 ,if the attendant sees that any generator is not taking its share1 he can raise its voltage by cutting out some of the resistance in series with its shunt field1 and this makes that generator take more load4 ,illustration3 ,fig4 #ia4 ,railway ,switchboard4 ,feeder ,panel4 ,the feeder panel is simpler than the generator panel1 since it usually handles only the positive side of the circuit4 ,frequently two feeders are run on a single panel side by side4 ,the feeder panel has an automatic circuit breaker1 an ammeter for indicating the current on that feeder1 and a single-pole switch for connecting the feeder to the bus bar4 ,all generators feed into a common set of bus bars2 and the positive bus bar continues back of the feeder panels so that all feeders can draw current from the bus bars4 ,fig4 #ia shows a railway switchboard with #g feeder panels at the right2 #d generator panels at the left2 and1 in the middle1 a panel with an ammeter and recording wattmeter for measuring total output4 ,in some stations two and even three sets of bus bars are used1 as it may be desired to operate different parts of the system at different voltages or to feed a higher voltage to the longer lines than to those near the station4 ,in such a case double-throw switches are provided for connecting feeders and generators to either set of bus bars4 ,alternating-,current ,switchboards4 ,in an alternating-current station1 generator switchboards are radically different from those in a direct-current station4 ,practice in alternating-current generator switchboards has not yet been so fully standardized and is not so uniform as in direct-current railway switchboards4 ,there is always1 however1 a three-pole main switch for opening and closing the main three wires from the three-phase generator4 ,automatic circuit breakers are usually provided1 as well as indicating ammeters and wattmeters to show the output4 ,indicating wattmeters1 recording the number of watt hours passing through them1 are frequently used both on alternating and direct-current generator panels4 ,a station usually has what is called a 8total load0 panel1 which has a recording wattmeter measuring the total output of the station in kilowatt hours4 ,this panel also has an ammeter indicating the total station load4 ,high-,tension ,oil ,switches4 ,alternating-current generators for high voltages usually have oil switches to interrupt the main circuit1 that is1 switches in which the contact is made and broken under oil4 ,these switches have been found very efficient in preventing the formation of a destructive arc upon the opening of a high-voltage circuit1 on circuits up to #fj1jjj volts4 ,some of the larger oil switches are operated by electric motors or solenoids4 ,the machine-type oil switch of the ,general ,electric ,company has the motive power for operating the switches1 stored up in a spring4 ,the spring is wound up by a small electric motor4 ,this motor operates every time the switch is opened or closed1 and winds up the spring enough to compensate for the amount it was unwound in operating the switch4 ,each circuit is broken under oil in a long tube1 and these tubes are mounted in individual cells1 each cell being separated from the next by a masonry wall so that there can be no flashing across from one leg of the circuit to another in case of any defect in the switch4 ,all the high-tension wiring to and from such switches1 is taken either in lead-covered cables1 or on bus bars separated from each other by masonry walls to prevent the spread of short circuits4 ,these precautions are necessary because of the great length of arc that may be established between adjacent high-tension conductors4 ,where alternating-current generators of low voltage are used in connection with step-up transformers1 one practice is to have the switches for each generator directly in the generator leads1 between the generators and the step-up transformers1 in the low-voltage circuit4 ,another practice which has recently been introduced1 is to consider each generator with its step-up transformers as a unit and to connect the generator permanently with its bank of transformers1 and to control this unit by a single three-pole machine-operated oil switch4 ,in this case there are no switchboard switches between generators and transformers1 and this simplifies the switchboard considerably4 ,there must be switches on the high-tension side of the transformers in any event4 ,the switchboard for rotary converters in the substations is1 of course1 a combination of alternating and direct-current apparatus4 ,the direct-current ends of the rotary converters are treated almost exactly like direct-current railway generators2 and their switchboard panels are similarly equipped1 except that usually there is a rheostat that can be connected in series with the armature whereby a rotary converter can be brought up to speed from a state of rest by connecting it with the direct-current bus bars of the substation4 ,the alternating-current end of the rotary converter is supplied through switches in the alternating-current leads from the step-down transformers4 ,a rotary converter can be started from a state of rest by connecting it to the alternating-current leads through the medium of compensating coils which reduce the voltage4 ,a very heavy current is required to do this1 as the motor thus starts as a very inefficient induction motor with a very low power factor4 ,illustration3 ,fig4 #ib4 ,connection of ,substations4 ,there are usually but two direct-current feeder panels in a substation of an interurban electric road4 ,one of these feeders is to supply the trolley or third rail extending in one direction from the substation1 and the other feeds that extending in the other direction from the substation4 ,the trolley or third rail has a section insulator directly at the substation4 ,when both feeders are connected to the bus bars1 it is evident that this section insulator is short-circuited through the medium of the substation bus bars1 every substation on the line being connected in this way1 as indicated in ,fig4 #ib4 ,it is seen that1 should a short circuit occur on any section1 it would open the circuit breakers at the substations at both ends1 and that section would not interfere with the balance of the road4 ,at the same time1 when the road is in normal operation and there is an unusually heavy load between any two substations1 the other substations along the line can help out those nearest to the load by feeding through the bus bars of the nearest substation4 ,the high-tension apparatus at a substation consists usually of a bank of high-tension lightning arresters2 high-tension switches1 for shutting off the high-tension current2 and step-down transformers1 for reducing from the high transmission voltage to the #cgj volts commonly fed to the alternating-current end of railway rotary converters4 ,storage ,batteries in ,stations4 ,storage batteries are frequently used both in substations and in direct-current power stations4 ,they may be connected directly across the line and allowed to 8float10 as it is termed2 or they may be used in connection with storage-battery boosters1 which will cause the storage battery to take the fluctuations in the load and to give a constant load on the rotary converters or power station4 ,the action of storage-battery boosters which cause the storage battery to be charged automatically at light loads and to discharge and assist the station at heavy loads1 is explained in the paper on 8,storage ,batteries40 ,,alternating-,,current ,,systems4 ,so far this paper has been devoted almost entirely to electric railway systems employing #ejj-volt direct-current motors on the cars1 since this is the system almost universally employed on electric railways at the present time4 ,there are1 however1 several systems employing alternating-current motors on cars1 which have already been used experimentally and to some extent commercially4 ,some of these give promise of coming into extensive use4 ,three-,phase ,motors4 ,on several roads in ,europe three-phase induction motors are employed4 ,these induction motors are operated by three-phase alternating current taken direct from the trolley wires4 ,as three conductors are necessary1 two trolley wires are used1 with the rails as the third conductor4 ,the two principal objections to the system are the necessity of two trolley wires1 and the fact that the induction motor operates very much like a direct-current shunt motor in that it is a constant-speed motor and not adapted to variable-speed work4 ,the power factor is low in starting2 that is1 a great volume of current is taken1 although1 owing to the voltage and the current not being in phase1 the actual energy consumed is small4 ,single-,phase ,motors4 ,the ,westinghouse ,electric ,manufacturing ,company has brought out a railway motor adapted to operate on single-phase alternating-current circuits4 ,this motor is very similar in construction to the ordinary series-wound #ejj-volt direct-current railway motor4 ,it has1 however1 more field poles than the ordinary direct-current motor2 and the pole pieces are laminated to avoid heating of the iron by eddy currents caused by the influence of the alternating current4 ,there are also other special features in the design that reduce the sparking at the commutator1 which sparking was for several years the greatest obstacle to the use of alternating-current motors of this kind4 ,in the ,westinghouse system the current is taken from the trolley wire at high potential1 and is reduced by an auto-transformer on the car4 ,this auto-transformer is connected with an induction regulator so arranged that a low voltage can be supplied to the motor in starting or for slow running1 and this voltage increased to increase the speed4 ,there is thus no need to reduce the trolley voltage by wasting part of it in a rheostat1 as is the case with direct-current motors2 and the efficiency during acceleration is1 therefore1 higher with this alternating system than with the direct current4 ,several other single-phase railway motors are also being worked out at the present time1 including that of the ,general ,electric ,company4 ,alternating-,current ,motor ,advantages4 ,there are two great advantages secured by the use of an alternating-current railway motor4 ,the first is a reduction in investment and operating expenses by doing away with substations containing rotary converters4 ,such substations are necessary on long lines of railway operating with direct-current motors4 ,the second advantage is that1 owing to the fact that a high tension current can be used on the trolley wire and reduced by a transformer on the car1 the difficulties of collecting a large amount of energy from a trolley wire are much reduced4 ,first1 in regard to the substations1 it will be seen that with the alternating-current motor system1 high-tension current can be conducted from the power house to substations along the line which contain nothing but static transformers4 ,since these transformers have no revolving parts they do not require the constant attendance that a rotary converter does4 ,furthermore1 the investment in rotary converters is entirely dispensed with1 and this makes a considerable reduction in the total cost of the distribution plant4 ,with the alternating-current system1 current is fed direct to the trolley wire from the secondary terminals of the transformers at the substations4 ,as regards the advantages of carrying a high voltage on the trolley wire1 it will readily be seen that1 since the amount of power1 or the watts required by a car1 is equal to the product of the voltage and current1 an increase in the voltage reduces the volume of current necessary4 ,by having high voltage on the trolley wire1 even a large car can be operated with a small volume of current1 and this current can be taken through an ordinary trolley wheel without difficulty4 ,where #ejj volts is the pressure used on the trolley wire1 there is considerable flashing and burning of trolley wheel and wire when large cars and locomotives are run1 owing to the heavy current conducted2 and this has been one of the principal reasons for the adoption of the third rail instead of the trolley on certain roads4 ,even with the third rail1 the volume of current that must be conducted to large electric locomotives involves some difficulties in the way of heated contact shoes and considerable loss of energy4 ,the use of high voltage on the trolley wire1 with transformers on the car to reduce the voltage to a safe pressure for use on the motors1 overcomes many of the difficulties that would otherwise be found in the use of electricity for heavy railroad work4 ,,operation4 ,power ,taken by ,cars4 ,the amount of power required in the practical operation of a car depends upon so many variable elements that many of the calculations sometimes given for determining the power required by a car are of little value4 ,the theoretical horsepower required to maintain a car at a certain speed on a level1 is evidently the tractive effort in pounds multiplied by the speed in feet per minute and divided by #cc1jjj4 ,what the tractive effort per ton of car will be1 depends on the condition of the rail and on several other uncertain factors4 ,for street-railway motor cars1 #bj pounds per ton is the usual tractive effort assumed as necessary4 ,a calculation of this kind1 however1 takes no account of the losses in the motors and gears1 nor of the fact that the greater part of the power required to propel a street car in practical service is used in accelerating the car from a state of rest to full speed4 ,in interurban service1 of course1 the power required in acceleration is not so great a proportion of the whole4 ,illustration3 ,fig4 #ic4 ,plotted ,data of ,road ,test4 ,the safest figures to use in engineering calculations as to the amount of power required1 are those taken from actual results obtained in everyday commercial service4 ,the power required by an eight-ton car in service in a large city like ,chicago1 is in the neighborhood of one kilowatt hour per car-mile run4 ,on outlying lines this figure may be reduced to 4#g kilowatt hour1 and in the down-town districts may run up to #a4e kilowatt hours per car mile4 ,double-truck cars in city service1 weighing from #bj to #be tons1 take from #b to #d kilowatt hours per car mile at the power station4 ,interurban cars around ,detroit1 weighing about #cb tons1 in interurban service1 making #be miles per hour1 including stops1 in level country1 and geared to #dc miles per hour1 take about #c kilowatt hours per car mile at the power station4 ,however1 interurban railway conditions are extremely variable4 ,the reports of several ,indiana electric railways show an average power consumption of #a4dh kilowatt hours per car mile for city cars and #e4ah kilowatt hours for interurban cars1 including line and distribution losses4 ,an interurban car weighing #ca tons and equipped with two #aej horsepower motors1 on a test run of #ej miles at an average speed of #ci miles per hour consumed #b4bj kilowatt hours per car mile4 ,this car made #ah stops4 ,a similar car under the same conditions made the same run at an average speed of #bf miles per hour with #dd stops1 consumed #b4dd kilowatt hours and a third car1 making #ab stops and at a speed of #cc miles per hour1 consumed #b4aj kilowatt hours per car mile4 ,these individual car test figures are from measurements taken at the car and do not include line losses4 ,road ,tests of ,electric ,cars4 ,of late considerable attention has been given to making road tests of electric cars4 ,the results of the tests are usually plotted in the form shown in ,fig4 #ic4 ,time is plotted horizontally in seconds1 while volts1 amperes1 speed and per cent grade are plotted vertically4 ,the diagram referred to is the result of a continuous run of #f minutes of a #cb4e ton car equipped with two motors4 ,the line voltage1 motor consumption and other readings may be obtained for any instant of time4 ,the acceleration in miles per hour per second may be obtained by noting the increase in height of the speed curve in one second4 ,in making such a test the necessary instruments1 voltmeters1 ammeters1 wattmeters and speed indicators are mounted direct on the car and are read at intervals of a few seconds4 ,the curve of motor consumption gives an idea of the abnormal current required to get the car under headway4 ,economy in ,power4 ,as already stated1 a large part of the energy taken by a car in city service is used in accelerating the car4 ,much of this energy must be destroyed or used up in the brake shoes at the next stop4 ,the energy stored up in a car by process of acceleration is represented by the formula3 ,mass in lbs4 7,velocity in ft4 per sec47 ,energy in ft4 lbs4 ---------------------------------------- ---------------------------------------- ----1 which #b is the formula for kinetic or live energy1 the derivation of which is found in any ,instruction ,paper on ,mechanics4 ,in performing any given schedule with frequent stops1 the more rapid the acceleration the lower the maximum speed required to make the schedule1 and the less the energy required in acceleration4 ,for city street and elevated service1 therefore1 rapid acceleration and low maximum speeds are desirable because not only more economical but safer4 ,for economical operation with any given equipment and schedule1 it is important to use as much of the energy stored up in the car as possible1 before wasting it by applying the brakes4 ,motors are built of a size to yield the large horsepower required in acceleration1 and consequently are lightly loaded when operating the car at maximum speed4 ,to economize in power1 current should be shut off as soon as possible after the car has attained full speed2 and the car should be allowed to drift without current as long as possible before the brakes are applied4 ,in this way the energy stored in the car will propel it at nearly maximum speed for a considerable distance between stops2 there will be the smallest possible waste of energy in the brake shoes2 and the losses of energy which take place when the current is in the motors will be prevented as far as possible4 ,practical tests as well as theoretical calculations show a possibility of very material saving in energy in the operation of an electric railway car or train1 by the observance of this simple rule of drifting as much as possible and using the brakes as little as possible4 ,whatever energy is used up in the brake shoes is necessarily wasted4 ,the smaller this waste can be kept while performing a given service1 the greater the economy secured4 ,cost of ,power4 ,the reports of #he per cent of the railway power generating stations in ,indiana show the average cost at the station per kilowatt hour to be 4#gee cent4 ,this was divided as follows3 ,fuel 4#ebf cents1 labor 4#aeh cents1 lubricants and miscellaneous supplies 4#jcb cents1 repairs 4#jci cents4 ,the lowest cost reported was 4#eje cents4 ,during #aija the average cost of power generated at the power house of the ,indiana ,union ,traction ,company was 4#ddc cents per kilowatt hour at the switchboard4 ,distributed from the substations it was 4#gfe cents per kilowatt hour4 ,natural gas was used for fuel4 ,on occasions when this failed1 coal at #a4ej per ton was burned4 ,sliding and ,spinning ,wheels4 ,in accelerating a car1 however1 there is no economy in turning on current so rapidly as to spin the wheels4 ,as mentioned in the section on 8,brakes10 the tractive effort between wheels and rails falls off about two-thirds when the wheels begin to slip2 and this slipping of wheels1 therefore1 reduces the chance of securing the acceleration which is possible4 ,for the same reason1 in making emergency stops either by the use of brakes or by reversing the motors1 care should be taken not to slide the wheels1 as by so doing the time required to stop the car is much increased4 ,in the ordinary straight air-brake equipment used on heavy electric cars1 there is much higher pressure carried in the storage reservoir than it is permissible to turn into the brake cylinder1 since1 if the full pressure were turned into the brake cylinder1 it would result in sliding of the wheels--which1 it has just been shown1 is something to be avoided1 not only on account of making flat spots on the wheels1 but also because of the reduction in the braking force as soon as the wheels begin to slide4 ,an experienced motorman can tell from the feeling of the car when the wheels are sliding1 and will instantly release the brake sufficiently to allow the wheels to begin to revolve as soon as he notices that this has taken place4 ,the friction between brake shoes and car wheels decreases as the speed increases4 ,a certain pressure applied to the brake shoes upon a car running #ej miles per hour1 therefore1 exerts much less retarding force than the same pressure at ten miles per hour4 ,in order to give the same braking or retarding force at higher speeds1 the brakes must be applied harder than at the lower speeds4 ,if they are applied at the maximum pressure possible without sliding the wheels at higher speeds1 it is evident that this pressure must be reduced as the speed of the car is reduced1 or the wheels will be 8skidded40 ,in the ,westinghouse high-speed automatic air brake used on steam roads1 this reduction of pressure is automatically accomplished4 ,,testing ,,for ,,faults4 ,illustration3 ,fig4 #id4 ,bond ,testing4 ,bond ,testing4 ,it is important to test the conductivity of rail bonds from time to time in order to determine if they have deteriorated so as to reduce their conductivity and introduce an unnecessary amount of resistance into the return circuits4 ,one way of doing this is to measure the drop in potential over a bonded joint as compared with the drop in potential of an equal length of unbroken rail4 ,to do this1 an apparatus is employed whereby simultaneous contact will be made bridging three or more feet of rail and an equal length of rail including the bonded joint1 as shown in ,fig4 #id1 which illustrates the connections of a common form of apparatus where two milli-voltmeters are employed that measure the drop in voltage of the bonded and unbonded rail simultaneously4 ,if the current flowing through the rail due to the operation of the cars were constant1 of course one milli-voltmeter might be used1 being connected first to one circuit and then to the other4 ,the current in the rail1 however1 fluctuates rapidly1 so that two instruments are necessary for rapid work4 ,the resistance of the bonded joint is usually considerably more than that of the unbroken rail1 and the milli-voltmeter used to bridge the joint consequently need not be so sensitive as that bridging the unbroken rail4 ,in another form of apparatus1 a telephone receiver is used instead of the milli-voltmeter1 the resistance of a long unbroken rail being balanced against that of the bonded joint1 as in a ,wheatstone bridge1 until1 upon closing the circuit1 these two resistances when balanced give no sound in the telephone receiver4 ,bond tests of this kind can be made with satisfaction only when a considerable volume of current is flowing through the rails at the time of the test1 because the drop in voltage is dependent on the current flowing1 and in any event is small4 ,it has sometimes been found necessary or advisable to fit up a testing car equipped with a rheostat which will itself use a considerable volume of current1 so as to give a current in the rail which will give an appreciable drop of potential across a bonded joint4 ,some of the latest forms of testing cars carry motor generators which will pass a large current of known value through a bonded joint1 and so cause a drop of potential across the joint large enough to be easily measured4 ,motor-,coil ,testing4 ,testing for faults in the motor armature and field coils is done in a great variety of ways4 ,the resistance of these coils can be measured by means of a ,wheatstone bridge employing a telephone receiver in place of the galvanometer used in such bridges in laboratory practice2 but other less delicate tests are also in use4 ,another method is to pass a known current through the coil to be tested and to measure the drop in the voltage between the terminals of the coil1 the voltage divided by the current equaling the resistance4 ,a simple method1 and one which involves no delicate instruments1 has lately been introduced into railway shop practice very successfully4 ,this is known as the transformer test for short-circuited coils4 ,it requires an alternating current which can easily be supplied either by a regular motor generator or by putting collecting rings onto an ordinary direct-current motor and connecting these rings to bars of opposite polarity on the commutator4 ,the method of testing for short-circuited armature coils employed in the shops of the ,st4 ,louis ,transit ,company is indicated in diagram in ,fig4 #ie4 ,a core built up of soft laminated iron is wound with #bh turns of ,no4 #f copper wire4 ,this coil is supplied with alternating current from a #aaj-volt circuit4 ,the core has pole pieces made to fit the surface of the armature4 ,when one side of a short-circuited coil in the armature is brought between the pole pieces of this testing transformer1 as in ,fig4 #ie1 the short-circuited armature coil becomes like the short-circuited secondary of a transformer1 and a large current will flow in it4 ,this current will in time manifest itself by heating the coil2 but it is not necessary to wait for this1 as a piece of iron held over that side of the coil not enclosed between the pole pieces1 as indicated in4 ,fig4 #ie1 will be attracted to the face of the armature if held directly over the coil1 but will be attracted at no other point4 ,illustration3 ,fig4 #ie4 ,method of ,testing for ,short-circuited ,armature ,coils4 ,this testing can be done very rapidly1 and does not require delicate instruments or skilled operators4 ,tests for short circuits in field coils can be made in a similar manner1 by placing the coils on a core which is magnetized by alternating current4 ,the presence of a short circuit1 even of one convolution of a field coil1 will be apparent from the increase in the alternating current required to magnetize the core upon which the field coil is being tested4 ,the insulation resistance of armatures and fields is frequently tested by means of alternating current1 about #b1jjj volts being the common testing voltage for #ejj-volt motor coils4 ,one terminal of the testing circuit is connected to the frame of the motor1 and the other to its windings4 ,any weakness in the insulation insufficient to withstand #b1jjj volts will1 of course1 be broken down by this test4 ,alternating current is generally used for such tests because it is usually more easily obtained at the proper voltage1 as it is a simple matter to put in an alternating transformer which will give any desired voltage and which can be controlled by a primary circuit of low voltage4 ,open circuits in the armature can be easily detected by placing the armature in a frame so that it can be rotated1 the frame being provided with brushes resting #ij apart on the commutator4 ,if either an alternating or direct current be passed through the armature by means of these brushes1 and the armature be rotated by hand1 a flash will occur when the open-circuited coils pass under the brushes4 ,a large current should be used4 ,the tests just mentioned are among the best of the methods used by electric-railway companies for systematic work in the location of certain classes of faults4 ,a large number of other methods of testing have also been evolved4 ,the following are some of the most common faults experienced with electric railway car equipments3 ,grounds4 ,as one side of the circuit is grounded1 any accidental leakage of current from the car wiring or the motors to ground will cause a partial short circuit4 ,such a ground on a motor will manifest itself by blowing the fuse or opening the circuit breaker whenever current is turned into the motor4 ,in case the fuse blows when the trolley is placed on the wire and the controller is off1 it is a sign that there is a ground somewhere in the car wiring outside of the motors4 ,moisture and the abrasion of wires are the most common causes of grounds in car wiring4 ,in motors1 defects are usually due to overheating and the charring of the insulation4 ,burn-,outs4 ,burning out of motors is due to two general causes3 ,first1 a ground on the motor1 which1 by causing a partial short circuit1 causes an excessive current to flow2 second1 overloading the motor1 which causes a gradual burning or carbonizing of the insulation until it finally breaks down4 ,short-circuited field coils having a few of their turns short-circuited1 if not promptly discovered1 are likely to result in burned-out armatures1 as the weakening of the field reduces the counter-electromotive force of the motor1 so that an abnormally large current flows through the armatures4 ,cars with partially short-circuited fields are likely to run above their proper speed1 though1 if only one motor on a four-motor equipment has defective fields1 the motor armature is likely to burn out before the defect is noticed from the increase in speed4 ,illustration3 ,fig4 #if4 ,defects of ,armature ,windings4 ,defects in armature windings probably cause one-third the maintenance expenses of electrical equipment of cars4 ,almost all repair shops have men continually employed in repairing them4 ,the most frequent trouble with armatures is through failure of the insulation of the coils and consequent 8grounding40 ,this term is used in connection with armatures and fields and other electrical apparatus where a direct path exists to ground4 ,as the armature core is electrically connected to the ground through its bearings and the motor casing1 a break down of the insulation of the coils in the slots permits the current to pass directly to ground4 ,this shunts the current around the fields and an abnormal current flows because of their weakness4 ,the circuit breaker or fuse is placed in circuit to protect the apparatus in such an emergency1 but usually before such devices break the circuit1 several of the coils of the armature are burned in such a manner as to make their removal necessary4 ,the coils are so wound on top of one another that in order to replace one coil alone1 one-fourth of the coils of the armature must be lifted4 ,illustration3 ,fig4 #ig4 ,with the armature of ,no4 #a motor grounded the car will not operate and if the resistance points be passed over1 the fuse will usually blow4 ,when ,no4 #b motor is grounded the action of ,no4 #a motor is not impaired and this latter motor will pull the car until the controller is thrown to the multiple position4 ,but if the motors are thrown in multiple1 the path through the ground of ,no4 #b motor shunts motor ,no4 #a4 ,a study of ,fig4 #ah will make this evident4 ,illustration3 ,fig4 #ih4 ,next to grounding1 open circuits are the most serious defects of armatures4 ,these are usually caused by burning in two of the wires in the slot1 or where they cross one another in passing to the commutator4 ,sometimes the connections where the leads are soldered to the commutator become loose4 ,the effect of an open circuit is shown in ,fig4 #if4 ,the circuit is open at n4 ,the brushes are on segments a and d4 ,by tracing out the winding it will be found that no current flows through the wires marked in heavy lines4 ,whenever segments c and d are under a brush the coil with the open circuit is bridged by the brush and current flows as in a normal armature4 ,as segment c passes out from under the brush the open circuit interrupts the current in half the armature and a long flaming arc is drawn out4 ,in ,fig4 #ig is shown the result of a short circuit between two coils4 ,the short circuit is at b1 c1 the two leads coming in contact with each other when they cross4 ,the effect is to short-circuit all of the winding indicated by the heavy lines4 ,illustration3 ,fig4 #ii4 ,mistakes in ,winding ,armatures4 ,the armature winder is given very simple rules as to how to wind the armature1 but the great number of leads each to be connected to their proper commutator segment sometimes so confuse him that misconnections are made4 ,the effect of getting two leads crossed is shown in ,fig4 #ih4 ,the leads to segments b and c from the right are shown interchanged4 ,this short-circuits the coils shown in heavy lines4 ,the abnormal current resulting in these would usually cause them to burn out4 ,fig4 #ii shows the results of placing all of the top leads1 or all of the bottom leads one segment beyond the proper position4 ,this causes the circuit starting from a and traveling counter clockwise around the armature to return on segment m instead of on segment b as is the case in ,fig4 #ig4 ,the only result of such connections is to change the direction of rotation of the armature4 ,it may be noticed by comparing the two figures that with the positive brush on segments a the arrows show the currents to be in opposite directions in coils similarly located with reference to the position of the brushes4 ,some armatures are intended to be wound as in the last case mentioned4 ,sparking at the ,commutator4 ,as railway motors are made to operate1 and usually do operate1 almost sparklessly1 sparking at the brushes may be taken as a sign that something is radically wrong4 ,the pressure exerted by the spring in the brush holder may not hold the brush firmly against the commutator4 ,if brushes are burned or broken so that they do not make good contact on the commutator1 they should be renewed or should be sandpapered to fit the commutator4 ,a dirty commutator will cause sparking4 ,a commutator having uneven surface will cause sparking1 and should be polished off or turned down4 ,illustration3 ,fig4 #ajj4 ,sometimes the mica segments between commutator bars do not wear as fast as the bars and when this is the case1 the brushes will be kept from making good contact when the commutator bars are slightly worn4 ,the remedy is to take the armature into the shop1 and groove out the mica between the commutator bars for a depth of about -inch below the commutator surface4 ,a greenish flash which appears to run around the commutator1 accompanied by scoring or burning of the commutator at two points1 indicates that there is an open-circuited coil at the points at which the scoring occurs as in ,fig4 #ajj4 ,the magnetic field may be weakened by a short circuit in the field coils1 as before explained1 and this may give rise to sparking4 ,short circuits in the armature may give rise to sparking1 but will also be made evident by the jerking motion of the car and the blowing out of the fuse4 ,failure of ,car to ,start4 ,the failure of the car to start when the controller is turned on may be due to any of the following causes3 ,opening of the circuit breaker at the power house4 ,poor contact between the wheels and the rails owing to dirt or to a breaking of the bond wire connections between the rail on which the car is standing and the adjacent track4 ,one controller may be defective in that one of the contact fingers may not make connection with the drum4 ,in this case try the other controller if there is another one on the car4 ,the fuse may be blown or the circuit breaker opened4 ,the occurrence of either of these1 however1 is usually accompanied by a report which leaves little doubt as to the cause of the interruption in current4 ,the lamp circuit is always at hand for testing the presence of current on the trolley wire or third rail4 ,if the lamps light when the lamp circuit is turned on1 it is a tolerably sure sign that any defect is somewhere in the controllers1 motors1 or fuse boxes1 although in case the cars are on a very dirty rail enough current might leak through the dirt to light the lamps1 but not sufficient to operate the cars4 ,in such a case1 the lamps will immediately go out as soon as the controller is turned on4 ,ice on the trolley wire or third rail will have the same effect as dirt on the tracks4 ,,locating ,,defects ,,in ,,motor ,,and ,,controller ,,wiring4 ,defects in the wirings are those due to 7#a7 open circuits1 7#b7 short circuits4 ,open circuits make themselves evident by no flow of current1 short circuits usually by a blowing of the fuse or opening of the breaker4 ,the point of the short circuit or 8ground0 can be located roughly by noting on what point the fuse is blown4 ,accurate location can be made by cutting out the motors1 disconnecting1 etc41 according to directions in the following pages4 ,the tests outlined apply particularly to the ,k type of controller with two-motor equipment4 ,,open-,,circuit ,,tests4 ,no current3 ,on #ast point1 ,open circuit but not located4 ,on #ast point multiple1 ,motors most probably ,o4 ,k4 ,on series-resistance points after trying #ast point multiple1 ,open circuit outside controller and equipment wiring4 ,with an open anywhere between trolley and ground no current will flow on the first point4 ,opens are most likely to occur in the motors and these may be tested first4 ,however1 as will be explained later1 one open in an armature will not stop the current4 ,to test the motors open the breaker and put the controller on the first point multiple4 ,then flash the breaker quickly4 ,current flowing indicates that one or the other of the motors has an open circuit4 ,in the series position this open prevented the flow but in multiple the current flows through the other motor4 ,which one is at fault can be quickly determined by returning the controller to the off position and cutting out one or the other of the motors by means of the cut-out switch and then trying for current4 ,the car can in any event be run on the remaining motor4 ,on returning to the shop the open can be determined definitely by the use of the lamp bank4 ,but should no current flow when the breaker is flashed on the #fth point it is reasonable to presume that the motors are ,o4 ,k4 and that the open is elsewhere4 ,the ground for such a supposition is that as there is a path through each motor normally1 there would necessarily be an open in each one to stop the current4 ,it is hardly probable that such a coincidence would occur4 ,after failure to find fault with the motors1 doubt as to the resistance may be removed4 ,the controller should be placed on progressive series-resistance points and the breaker flashed on each one4 ,if current is obtained on any point1 the open is in the resistance or the resistance lead just behind the one being used4 ,special care should be used to flash the breaker quickly for otherwise the fuse may be blown4 ,the tests indicated are sufficient for the motors1 controllers and resistance wiring4 ,if no current is obtained on either of them1 the trouble is evidently caused by a bad rail contact1 ground wire off if both motors are grounded through the same wire1 an open in the blow-out coil1 at the lightning arrester1 circuit breaker or on top of the car4 ,none of the tests applied locate the open definitely1 but this can easily be done in the shop or wherever a lamp bank is at hand4 ,connect one terminal of the lamp bank to the trolley just behind the circuit breaker and the controller on the #ast point series1 then with the other terminal begin at ground and trace backwards up the circuit until the lamps fail to light4 ,the path in a ,k type of controller is readily traced with the help of ,fig4 #bb4 ,,short-,,circuit ,,tests4 ,the location of short-circuits is much more tedious4 ,the blowing of the fuse or opening of the breaker will locate them as shown below4 ,the separate tests can then be followed until location is definite4 ,these tests it must be kept in mind are more especially adapted to cases on the road or where no facilities for testing are at hand4 ,rather than blow fuses as frequently as indicated it would in most cases be better to place a lamp bank across the open circuit breaker and note the flow of the current by the lights4 ,fuse ,blows3 ,i4 ,when overhead is thrown on may be due to3 #a4 ,grounded controller blow-out coil4 #b4 ,grounded trolley wire or cable4 #c4 ,grounded lightning arrester4 ,,ii4 ,on first point3 #a4 ,grounded resistance near ,r #a4 #b4 ,grounded controller cylinder4 #c4 ,bridging between the insulated sections of cylinder4 ,,iii4 ,near last point series3 #a4 ,grounded resistance near ,r #c1 ,r #d and ,r #e4 #b4 ,no4 #a motor grounded4 ,,iv4 ,near last point multiple3 #a4 ,no4 #b motor grounded4 #b4 ,bridging between lower sections of cylinder4 #c4 ,armature defective4 ,,case ,i4 ,fuse ,blows when overhead is thrown on3 #a4 ,grounded controller blow-out coil4 #b4 ,grounded trolley wire or cable4 #c4 ,grounded lightning arrester4 ,the blowing of the fuse immediately on closing the overhead switch or circuit breaker1 when the controller is on the off position1 indicates that the fault exists somewhere between the overhead and the upper or trolley finger of the controller4 ,should the defect occur during a thunderstorm1 it may be presumed at once that lightning has grounded the blow-out coil of the controller4 ,,case ,,ii4 ,fuse ,blows on first point3 #a4 ,grounded resistance near ,r #a4 #b4 ,grounded controller cylinder4 #c4 ,bridging between sections of cylinder4 ,when the controller is on the first point all of the wiring of the system with the exception of the ground wire for ,no4 #a motor is connected with trolley4 ,but a defect in the wiring beyond the resistance will not show itself on the first point by an abnormal rush of current because the resistance of the rheostats is sufficient to prevent any excessive flow of current4 ,illustration3 ,fig4 #aja4 ,illustration3 ,fig4 #ajb4 ,the resistance and leads and the controller cylinder are the only parts to be tested when the fuse blows on the #ast point4 ,,case ,,iii4 ,fuse ,blows on #crd or #dth point3 #a4 ,grounded resistance near ,r #d or ,r #e4 #b4 ,no4 #a motor grounded4 ,with either of the above defects the car will most probably refuse to move as the current is led to ground before passing through the motors4 ,illustration3 ,fig4 #ajc4 ,plan of ,car ,shop4 ,no4 #a motor may be tested by cutting it out of service by means of its cut-out switch4 ,if this removes the ground1 the motor is at fault4 ,,case ,,iv4 ,fuse ,blows near last point multiple3 #a4 ,no4 #b motor grounded4 #b4 ,either armature short-circuited4 ,the fact that the fuse did not blow on the series positions excludes the resistances and ,no4 #a motor from investigations for grounds4 ,cut out both motors4 ,if the ground still exists the controller is defective4 ,if not1 the fault may be located in either one of the motors by cutting out first one and then the other4 ,,armature ,,tests ,,for ,,grounds4 ,with a lamp bank at hand tests for grounded armature can be made as follows3 ,throw the reverse on center4 ,attach one terminal of the lamp bank to the trolley4 ,put the other terminal on the commutator of the armature to be tested4 ,no current shows the armature ,o4 ,k4 ,if current flows remove brushes and try again1 to be certain that the ground is not in the leads4 ,,field ,,tests ,,for ,,grounds4 ,disconnect field leads and put test point of the lamp bank on one side of the terminals4 ,no current indicates that the fields are ,o4 ,k4 ,,reversed ,,fields4 ,in placing new fields in the shell it often happens that one or more are wrongly connected4 ,reversed fields make themselves known by excessive sparking at the brushes in each case4 ,in ,fig4 #aja all of the fields are connected correctly4 ,the flow of magnetism is in one pole and out of the adjacent one4 ,some of the magnetism leaks out of the shell and affects a compass held near the outside4 ,the direction taken by the compass needle in the different positions is shown4 ,the needle should point in opposite directions over adjacent coils and should lie parallel to the shell in positions half way between two coils4 ,figure #ajb shows the flow of magnetism when one field is reversed4 ,in such a case the compass will take the position shown4 ,the field marked 8,x0 is the one reversed4 ,with one reversed field a machine will usually operate1 as the magnetism in three of the poles is in the normal direction4 ,but an excessive flow of current that has no effect in turning the armature will take place on that side of the armature next to the reversed field4 ,,car ,,repair ,,shops4 ,every electric railway system has a repair shop in which the cars are overhauled4 ,hardly two shops are built alike4 ,in those shops where only a few cars are cared for1 the work is sometimes all done in one room4 ,the shop plan shown in ,fig4 #ajc was presented to the ,american ,railway ,mechanical and ,electrical ,association by ,w4 ,d4 ,wright4 ,it contains the idea upon which the larger shops are now being constructed1 having a transfer table between the separate departments on either side4 ,in the general design of shops the blacksmith shop1 machine shop and truck shop or equipping shop should be close together as a great deal of heavy material is carried between these departments4 ,the paint shop should be separated as much as possible from the other departments in order that flying dust and dirt be avoided4 ,the wood shop may occupy a position at a considerable distance from the other departments as no heavy material is carried from this shop to them4 ,the tracks of the motor and truck repair shop are usually provided with pits so that trucks and electrical equipment may be repaired and inspected from below4 ,the tracks in shops are usually about #ae or #af feet between centers4 ,this gives a clearance of about #f or #h feet between cars when adjacent tracks are occupied4 ,a large portion of the work done in the average shop consists of the repairing of trucks and the motors mounted on them4 ,with the smaller car1 especially those with single trucks1 much of this work is done from the pit below while the trucks are in position under the cars4 ,in this case the armatures are either removed by letting them down with the lower half of the motor shell by means of a pit jack1 or the lower half of the armature shell is swung down by the use of a chain and block placed in the car and the armature rolled out on a board4 ,the trucks of double truck cars are usually taken out from under the car body when repairs are to be made4 ,in this case the motor leads1 the sand box connections and the brake rigging are disconnected and the car body either raised or the trucks lowered from it4 ,several methods of raising the car body are in use4 ,where no special apparatus is at hand1 this is done by means of jacks1 hydraulic or mechanical1 placed under the side sills of the car near the end to be raised4 ,sometimes an overhead crane is employed to lift the car body4 ,a special apparatus to raise the body is employed by the ,st4 ,louis ,transit ,company4 ,this consists of four screw jacks located below the floor of the shop4 ,an ,i-beam extends over the tops of the two located on the same side of the car4 ,the jacks are motor driven by means of one sprocket chain so that they rise at the same speed4 ,when a car is to be raised it is run on the track between the jacks1 bars are placed under the car resting across the ,i-beams and the jacks raise the car off the trucks4 ,the trucks are then rolled out from under the car and the repairs made4 ,sometimes1 as has been stated1 the trucks are dropped from the car body4 ,in this case the car is so placed that the truck rests on an elevator or section of track that drops to the floor below4 ,after the car is blocked up the trucks are dropped and the repairs made4 ,this method is also used in changing wheels in small shops4 ,the old pair of wheels is dropped by a hand-operated drop section of track4 ,a new pair is then elevated into position4 ,this saves jacking up one end of the car4 ,illustration3 ,,one ,,of ,,the ,,single-,,phase ,,locomotives ,,on ,,the ,,new ,,york1 ,,new ,,haven ,,hartford ,,railroad ,,co4 ,note the two pantograph bow trolleys for collecting the current4 ,,the ,,single-,,phase ,,electric ,,railway4 ,in no other line of electrical activity have developments during the last few years been so rapid as in that of electric railway work1 and from all indications the limit has not yet been reached4 ,until recent years all electric traction has been dependent upon direct current as a motive power4 ,this is due principally to the fact that the series direct-current motor is admirably adapted for such work1 and no alternating-current motor had been developed which could be substituted for it4 ,one of the great advantages possessed by the direct-current series motor is its large starting torque1 which may be several times greater than that required to propel a car at full speed4 ,this type of motor is also essentially a variable speed machine1 and lends itself very well to wide variations in speed control2 consequently1 for many years1 in this country at least1 all advance was made along direct-current lines4 ,the trolley voltage used at first was from #dej to #ejj volts1 this being supplied directly to the cars by means of a trolley wire1 the rails being used for the return circuit4 ,it is evident from the outset that the comparatively low voltage1 necessitating as it did a correspondingly large current for a given amount of power1 would place a definite limitation on the use of such a system for anything other than purely local distribution4 ,to overcome this difficulty as far as possible1 the trolley voltage was gradually raised to #fjj or #fej4 ,this of course decreased the required current1 thus increasing the scope of the system accordingly4 ,the limit of increase of direct-current voltage on the trolley was reached at about this point1 and the fact was recognized that some means must be devised for using a still higher voltage1 since there are difficulties to increasing the trolley voltage beyond #fjj or #gjj1 due to flashing of the motors1 which seems to increase directly with the voltage4 ,it may be mentioned in passing that one prominent electric traction expert has stated that a direct-current trolley voltage of #aejj can be used1 but it remains to be proven whether or not he is correct4 ,a very satisfactory solution of the problem for large city street railway systems and long interurban roads1 consists in the use of a combination alternating-current direct-current system in which three-phase high tension alternating current is generated and distributed on high tension lines to substations along the road4 ,it is here stepped down by means of transformers1 and then changed to direct current by rotary converters1 and supplied to the trolley wire as direct current at the usual voltage of say #fjj4 ,this system has many advantages1 as there is but small loss in the high-tension lines1 and these lines can be made comparatively small1 thus effecting a considerable saving in investment for copper4 ,the above mentioned system of distribution is very generally used1 and has been found quite satisfactory4 ,the substations can be located at frequent intervals1 and the distance that the #fjj-volt current must be conducted to supply the cars is not great4 ,by this means current can be distributed over wide areas with a small loss1 where it would be impossible to use the straight direct-current system of distribution4 ,while1 as stated1 this furnishes a fairly satisfactory solution of the problem1 it is far from perfect1 as it necessitates the intervention of the rotary converter substation1 in which the investment must be large2 and moreover the cost of operation is high1 as such a station requires skilled attendance on account of the somewhat intricate nature of the rotary converter4 ,the ideal system1 therefore1 is one which does away altogether with the use of direct current1 the power being generated1 distributed1 and utilized by the motors1 as alternating current4 ,three-phase induction motors have been used quite extensively and with considerable success in ,europe for many years past4 ,the three-phase motor1 however1 is not entirely adapted for railway work1 since it possesses the characteristics of the shunt rather than of the series motor1 being a constant speed1 not a variable speed machine4 ,moreover1 two trolley wires are necessary instead of one1 and still another disadvantage consists in the low power-factor of the three-phase induction motor at starting4 ,the recent application of the single-phase alternating current to railway work has opened up a new field1 which bids fair to supplant all other forms of distribution to a great extent at least1 and it is impossible to predict at the present time just what its limitations may or may not prove to be4 ,this has been made possible by the development of a practical commercial single-phase motor1 which permits of the use of alternating current on the trolley wire with all its advantages1 and yet sacrifices few1 if any1 of the advantages of the direct-current series motor on the car4 ,illustration3 ,,interior ,,of ,,sub-,,station ,,showing ,,rotary ,,converter ,,and ,,transformers4 ,the three-phase current is delivered to the transformers where it is stepped down to the voltage required for the rotary converter4 ,in this machine it is transformed to direct current and delivered to the trolley wire4 ,this motor1 which is the latest and most important development in the electric railway field1 is of the series commutator type1 and does not differ in principle from its direct-current contemporary4 ,it is called the commutator type single-phase motor1 and is the one type of alternating-current motor which has the same desirable characteristics for railway work as the direct-current series motor4 ,illustration3 ,compensating ,alternating-,current ,railway ,motor4 ,at first thought it may seem strange that a motor built fundamentally on the same lines as a direct-current machine would operate on an alternating current1 as it might appear that the motor would tend to turn first in one direction and then in the opposite direction with no resultant motion4 ,this1 however1 is not the case1 because the direction of rotation of a motor depends upon the relative direction of its field and armature currents4 ,if now the field were maintained in a constant direction and the armature supplied with alternating current1 then the tendency would be to rotate first in one direction and then in the other1 it is true1 but as a matter of fact the alternating current is supplied to the field in series with the armature1 so that when the direction of current in the armature changes it also reverses in the field4 ,the result is that the relative direction of current in the field and armature is constant and the motor has1 therefore1 a tendency to turn continuously in one direction as long as the alternating-current power is supplied4 ,this being true1 the question may arise as to why the single-phase motor was not brought to the front for railway work long ago4 ,the answer is that there were certain inherent difficulties to be overcome1 and the development of the single-phase motor has been simply the removal of these difficulties1 rather than the design of an entirely new type of machine4 ,the most serious obstacle to overcome is the sparking at the commutator1 due to the fact that when the terminals of a coil are bridged by a brush1 the coil acts like the short circuited secondary of a transformer of which the field winding constitutes the primary4 ,also there is an iron loss due to the alternating magnetic flux through the magnetic circuit2 while another objectionable feature is the counter ,e4,m4,f4 induced in the field coils4 ,illustration3 ,alternating-,current ,railway ,motor ,field4 ,in order that it may overcome these difficulties1 to some extent1 at least1 the single-phase motor presents certain modifications from the direct-current type1 in that it has more field poles1 and the entire magnetic circuit of field frame1 cores1 and pole pieces1 is carefully laminated4 ,the number of commutator segments is also increased1 thus reducing the number of armature turns per coil1 and there are special features introduced to prevent sparking1 such as compensating windings which neutralize the effect of armature distortion2 the use of narrow brushes2 a type of armature winding which gives a low reactance per coil2 the use of high resistance leads between the armature coils and commutator segments1 etc4 ,the single-phase motor is then a refined and highly perfected type of direct-current motor1 and this explains the fact that it will operate on either alternating- or direct-current circuits4 ,in fact some claim that it will operate even more efficiently on direct current than the regulation direct-current motor itself4 ,illustration3 ,single-,phase ,armature1 ,unmounted4 ,the field for which the single-phase motor seems particularly adapted is that of heavy service and interurban work1 where it has many distinct advantages1 among which may be mentioned the following3 ,the alternating current on the trolley allows the use of a high voltage and correspondingly smaller current1 which reduces the line loss and permits of the use of smaller wire1 which of course means a saving in the investment for copper4 ,moreover1 the difficulty of collecting a large current from the trolley wire is overcome4 ,rotary converter substations are eliminated1 being replaced by simple and cheap transformer substations1 which require no attendance4 ,the capacity can be easily increased by merely increasing the number of these transformer substations4 ,the efficiency of speed control is a point particularly worthy of mention4 ,in direct-current speed control1 the series-parallel method is used almost exclusively4 ,this consists of putting the motors in series for low speed and in parallel for high speed4 ,this permits of two1 and only two1 economical running points2 the one at full speed1 and the other at approximately half speed4 ,all intermediate points must be obtained by the insertion of dead resistance in which the voltage is simply wasted as heat1 thus causing a large loss particularly at starting4 ,with the single-phase motor the current is supplied to the car with a voltage of say #ccjj4 ,it is then stepped down by means of transformers on the car to the voltage of the motors1 which may be #bjj or #bej volts4 ,the speed is1 of course1 dependent upon the voltage applied to the motors1 and this voltage is cut down from the maximum1 to obtain various gradations1 by means of an induction controller1 or by taps from an auto-transformer4 ,thus the motor takes from the trolley only slightly more power than is actually required to operate it at any given speed1 instead of taking full voltage from the line and absorbing part of it in dead resistance4 ,illustration3 ,auto ,transformer4 ,the effect of electrolysis upon neighboring water pipes paralleling an electric road1 which is the cause of so much trouble with direct current1 is entirely eliminated1 as electrolysis evidently will not take place with alternating current4 ,in connection with this system a sliding contact device or bow trolley has in many cases been substituted with considerable success for the ordinary current collecting device1 or trolley wheel1 one advantage of this being that the car can be run in either direction without reversing the contact device4 ,another very satisfactory form of trolley is of the pantograph type with sliding shoe1 shown on the ,new ,york1 ,new ,haven and ,hartford locomotive4 ,a new form of trolley suspension known as the catenary has been developed to meet the demand for more substantial construction necessitated by the high trolley voltage4 ,this consists of a stranded galvanized steel messenger or supporting cable1 from which the trolley wire is suspended at intervals of about #aj feet1 thus keeping it at a uniform distance above the track4 ,illustration3 ,master ,controller ,used in ,connection with the ,multiple-,unit ,system as ,applied to ,single-,phase ,work4 ,the multiple-unit system of control can be used in connection with single-phase motors1 this being the scheme which has been in use for a long time on elevated and other roads using direct current1 whereby several cars can be operated in a train from a single point1 each car being equipped with its individual motor and controlling apparatus4 ,the entire system is then controlled as one unit by a single motorman stationed usually in the front of the first car4 ,this method of control has become of such tremendous importance that any system to which it cannot be applied would be seriously handicapped4 ,cars equipped with single-phase motors can be operated on either direct-current or alternating-current lines1 with high or low tension1 with trolley or third rail4 ,it must not be supposed1 however1 that with all the above mentioned advantages1 the single-phase system has no disadvantages1 as such is not the case4 ,the car equipment1 due to the transformers and the nature of the motors1 is considerably heavier4 ,the motors themselves are more expensive on account of their special construction4 ,the equipment is not always adapted for operation on existing lines4 ,there is a slight increased 8apparent0 resistance of the trolley line and a considerable increased 8apparent0 resistance of the rails1 due to reactance caused by the alternating nature of the current4 ,there is also an active electro-motive force between the field coils1 which is objectionable1 and there is a possibility of interference with neighboring telephone lines4 ,furthermore1 there is slight loss in power in the transformers on the car1 while the power-factor of the motors is less than unity4 ,summing the matter up as a whole1 however1 the advantages seem to overbalance the disadvantages1 at least for many kinds of work1 and it is safe to predict that this new system of operation will have a very wide and increasing application in the near future4 ,as to the operation of the system in general1 the current may be developed by single-phase1 two-phase1 or three-phase generators1 and supplied to the transformer substations just as it was formerly supplied to the rotary converter substations4 ,only a single phase is used on any section of the trolley line4 ,the voltage on this transmission line will depend upon the existing conditions1 and can be figured out like any other problem in power transmission4 ,illustration3 ,truck ,complete with ,single-,phase ,motors and ,contact ,shoes4 ,three-phase generators would ordinarily be used1 as less copper is required to supply a given amount of power4 ,the common frequency is #be cycles per second4 ,at the transformer stations1 the voltage is then stepped down to that required on the trolley1 which may be #b1jjj1 #c1cjj1 #f1fjj1 or even #aa1jjj volts4 ,while we cannot speak yet of a standard voltage1 #ccjj seems to be finding considerable favor4 ,the voltage for which the motors are wound is #bjj or #bej1 the ,general ,electric motors using the former voltage1 and the ,westinghouse the latter4 ,when operating on alternating current the motors are connected in parallel1 and when running on direct current they are connected in series4 ,motors have been constructed from #ej to #bbe horsepower1 and there is no apparent reason why larger ones could not be made to operate with equal satisfaction4 ,illustration3 ,magnetic ,speed ,indicator4 ,among the roads in this country which are either using1 or planning to use single-phase current1 may be mentioned the ,ballston-,schenectady line1 which was one of the first systems to be equipped and has been in successful operation for some time4 ,this road uses the alternating-current motor developed by the ,general ,electric ,co4 ,the motors are adapted for operation on the #b1jjj-volt alternating-current trolley between cities1 and on the standard #fjj-volt direct current in ,schenectady4 ,they are wound for #djj volts1 and are operated in series on the #fjj-volt direct current4 ,the frequency used is #be cycles4 ,current is supplied by an overhead trolley1 no feeders being used4 ,a second road of importance is one in ,georgia between ,atlanta and ,marietta1 which is #ae miles in length4 ,this uses the ,westinghouse equipment4 ,the current on the trolley is #b1bjj volts and #be cycles4 ,it is transmitted at a voltage of #bb1jjj4 ,another road of importance is the ,indiana and ,cincinnati interurban line1 #da miles in length1 which has been in operation on regular schedule since ,july #ast1 #aije4 ,for #cg miles the road is operated from alternating current1 and for #d miles1 from direct current4 ,four #ge-;horse power motors per car are used1 capable of a maximum speed of #fe miles per hour4 ,illustration3 ,armature ,quill4 ,the ,bloomington1 ,pontiac and ,joliet ,electric ,railway is a single-phase road equipped with ,general ,electric apparatus1 and has maintained a regular schedule over a distance of more than #aj miles since ,march1 #aije4 ,the plans are now being laid for a single-phase road1 which will run south from ,spokane1 ,washington1 a distance of #aej miles4 ,the current on the transmission line is #de1jjj volts1 which is stepped down to #f1fjj on the trolley4 ,the car will be capable of operating on current from a #f1fjj-volt alternating1 a #gjj-volt alternating1 or a #ege-volt direct-current supply4 ,perhaps the most important move which has been made in the direction of single-phase traction thus far is the decision of the ,new ,york1 ,new ,haven1 and ,hartford road to establish a long-distance passenger traffic on the single-phase system4 ,according to the latest plans this road will operate between the ,grand ,central ,depot and ,woodlawn1 ,n4 ,y41 over the terminal tracks of the ,new ,york ,central road1 on direct current taken from the trolley4 ,from ,woodlawn1 ,n4 ,y41 to ,stamford1 ,conn41 the road will be operated on the single-phase system4 ,illustration3 ,a ,pair of ,drivers with ,single-,phase ,motor ,mounted upon ,quill4 ,the equipment is being supplied by the ,westinghouse ,co4 ,the current is generated by revolving-field type turbine-driven alternators4 ,the armatures are designed for either three-phase or single-phase connection4 ,the current is generated at #be cycles and #aa1jjj volts1 being delivered directly to the trolley1 and thence to the cars1 without the intervention of any transformers4 ,the double catenary suspension from messenger wires is used to support the trolley4 ,the locomotives are each equipped with four #bjj-;,h4 ,p4 gearless motors1 designed to operate on #bce-volt alternating current and #bge- to #cjj-volt direct current4 ,the armature is not mounted on the shaft direct1 but is built upon a quill through which the axle passes with about -inch clearance all around4 ,there is a flange at each end of the quill from which seven pins project and fit into the hubs of the driving wheels4 ,on the direct-current part of the line1 current is delivered to the car through eight collecting shoes from a third rail4 ,on the alternating-current section1 current is delivered through two pantograph bow trolleys4 ,on the direct-current section the series-parallel method of speed control is used1 current being fed directly to the motors which are connected two in series permanently and the series-parallel control is applied to the motors in groups of two4 ,the alternating-current speed control is accomplished by six taps from an auto-transformer for the corresponding running points4 ,the cars weigh #gh tons and are capable of a speed of #fj to #fe miles per hour4 ,the electro-pneumatic unit-switch type of control is used4 ,at each end of the cab is a master controller from which the main controller is operated4 ,several locomotives can be operated together on the multiple-unit system1 if desired4 ,illustration3 ,six-,unit ,switch ,group1 ,single-,phase ,system4 ,the ,washington1 ,baltimore and ,indiana single-phase road is the latest in the field1 contracts having been placed very recently4 ,the current will be transmitted at #cc1jjj volts and #be cycles1 then being stepped down to #f1fjj volts on the trolley4 ,the road will be #fj miles long and will be equipped with ,general ,electric apparatus4 ,four #abe-;,h4 ,p4 motors capable of operating on either alternating current or direct current will be used1 and the cars will be capable of a speed of #fj miles per hour4 ,,index ,air brakes1 #ef ,air compressors1 #eg automatic governor for1 #eg ,westinghouse1 #eh ,alternating-current generators1 #aje ,alternating-current switchboards1 #aaj ,alternating-current systems1 #aac single-phase motors1 #aad three-phase motors1 #aac ,alternating-current transmission1 #ii ,armature coils1 #h ,armature leads1 #i ,armature tests for grounds1 #acc ,armature winding1 #e defects of1 #abd mistakes in1 #abf ,automatic governor for air compressors1 #eg ,ballast1 #he ,bearings of railway motors1 #ac ,block signals for electric railways1 #id ,bond testing1 #abj ,bonding and return circuits1 #hh ,booster feeder1 #ih ,brackets1 #ge ,brake leverages and shoe pressure1 #ed ,brake rigging1 #ec ,brake shoes1 #fd ,brush holders1 #aj ,brushes1 #aj ,burn-outs1 #abc ,canopy switch1 #ci ,car1 failure of to start1 #abg ,car bodies1 #fg ,car circuit breaker1 #ci ,car construction1 #fg ,car equipment1 #c ,car heaters1 #cd electric1 #cd hot-water1 #cf ,car painting1 #gb ,car repair shops1 #acd ,car weights1 #gb ,car wheels1 #ea ,car wiring1 #cg ,cast-welded joints1 #hg ,coefficient of friction1 #fe ,common ,t-rail1 #hd ,commutator type single-phase motor1 #aci ,compressors1 #eg ,conductivity of steel rail1 #hj ,conduit systems1 #ha contact plow1 #hb cost of1 #hb current leakage1 #hc ,contact plow1 #hb ,contact shoes1 #de ,controller construction1 #ai ,controller notches1 #bg ,controller wiring1 #bj ,controllers1 #af ,cost of power1 #aai ,couplers1 #ff ,current required to heat cars1 #ce ,current leakage1 #hc ,defects of armature windings1 #abd ,direct-current feeding1 #ih ,double-current generators1 #aje ,drawbars1 #ff ,economy in power1 #aah ,electric car accessories1 #ci canopy switch1 #ci car circuit breaker1 #ci contact shoes1 #de fuses1 #da lamp circuits1 #dc lightning arresters1 #da trolley base1 #dd trolley poles1 #dd trolley harp1 #de trolley wheels1 #dd ,electric cars1 road tests of1 #aag ,electric heaters for cars1 #cd ,electric railway1 #a ,electrically welded joints1 #hg ,electrolysis1 #ie prevention of1 #ig ,feeder panel1 #aaj ,feeder systems1 #ib ,feeders1 #ge ,field coils1 #h ,field tests for grounds1 #acc ,four motors1 #ai ,fuse blows1 #acj ,fuses1 #da ,gearing1 #ab ,g4 ,e4 electric brake1 #fa ,g4 ,e4 train control1 #bi ,generator1 starting up1 #ajh ,generator ,d4 ,c4 panels1 #ajf ,generators1 #aje ,girder rail1 #hc ,grounds1 #abc ,high-tension lines1 #gg ,high-tension oil switches1 #aaa ,highway crossings1 #hj ,hot-water heaters for cars1 #cf ,insulators1 third rail1 #gi ,interurban railway1 system of distribution for1 #aja ,joints for rails1 #hf ,lamp circuits1 #dc ,lightning arresters1 #da ,locating defects in motor and controller wiring1 #abh ,location of power houses1 #aja third rail1 #gi ,lubrication of railway motors1 #ac ,magnetic blow-out1 #bf ,maximum traction trucks1 #ea ,momentum brakes1 #ei ,motor leads1 #i ,motor suspension1 #ad ,motor-coil testing1 #aba ,motors1 #c as emergency brakes1 #fc of the ,new ,york ,central electric locomotive1 #ae ,multiple-unit control1 #bi ,oil switches1 high tension1 #aaa ,open-circuit tests1 #abh ,opening cases for inspection1 #aj ,overhead construction1 #gc brackets1 #ge feeders1 #ge high-tension lines1 #gg section insulators1 #gf span wires1 #gd trolley wire1 #gc trolley-wire clamps and ears1 #gc ,potter third-rail shoe1 #df ,power cost of1 #aai economy in1 #aah taken by cars1 #aae ,power house location1 #aja ,power stations1 general plan of1 #aje ,power supply and distribution1 #ih ,railway motors bearings1 #ac brushes1 #aj characteristics of1 #c gearing of1 #ab lubrication of1 #ac ,rate of retardation in braking1 #ff ,resistance of track1 #ia ,resistances1 #ch ,return feeders1 #ib ,reversal of motor1 #bf ,reversed fields1 #acc ,rheostat control1 #ag ,road tests of electric cars1 #aag ,sectional insulators1 #gf ,series-parallel control1 #ag ,shanghai ,t-rail1 #hd ,short-circuit tests1 #acj ,single trucks1 #dh ,single-phase electric railway1 #acf ,single-phase motors1 #aad1 #aci ,sleet on trolleys and third rails1 #df ,sliding and spinning wheels1 #aai ,span wires1 #gd ,sparking at the commutator1 #abg ,sprague multiple-unit system of control1 #bi ,steel car framing1 #ga ,storage air brakes1 #eh ,storage batteries in stations1 #aac ,street railway motors1 general data on1 #f ,supplementary return feeders1 #ib ,swing bolster trucks1 #di ,switchboards1 #ajf alternating-current1 #aaj ,switches1 third rail1 #gi ,swivel trucks1 #dh ,t-rail1 #hd ,thermit welding1 #hh ,third rail1 #gi advantages in operation1 #hj ,third rail conductivity of1 #hj cost of1 #hj highway crossings1 #hj insulators for1 #gi location1 #gi switches1 #gi ,three-phase motors1 #aac ,track brakes1 #fc ,track construction1 #hc ,track resistance1 #ia ,track sanders1 #fe ,track support1 #he ,transmission systems1 efficiency of1 #aja ,trilby groove rail1 #hd ,trolley base1 #dd ,trolley harp1 #de ,trolley poles1 #dd ,trolley wheels1 #dd ,trolley wire1 #gc ,trolley-wire clamps and cars1 #gc ,trucks1 #df maximum traction1 #ea single1 #dh swing bolster1 #di swivel1 #dh ,type ,l controllers1 wiring of1 #bd ,,announcement ,,of ,,coming ,,books ,,practical ,,and ,,scientific ,,carpentry4 ,by ,g4 ,townsend4 #aej pp41 #bbd illus4 ,a working manual for ,carpenters and ,woodworkers in general4 ,not a theoretical treatise1 but a practical working guide4 ,price1 #a4jj ,,gas ,,engines ,,and ,,producers4 ,by ,marks and ,wver4 #aej pp41 #ij illus4 ,latest information in this rapidly developing field4 ,for ,engineers1 ,machinists1 ,automobilists4 ,price #a4jj ,,masonry ,,construction4 ,by ,phillips and ,byrne4 #adj pp41 #dd illus4 ,latest and best ,american methods4 ,price #a4jj ,,water ,,supply4 ,by ,f4 ,e4 ,turneaure4 #aej pp41 #dj illus4 ,an exhaustive compendium for ,sanitary and ,waterworks ,engineers and all interested in matters affecting public health4 ,price #a4jj ,,highway ,,construction4 ,by ,phillips and ,byrne4 #adj pp41 #hj illus4 ,modern methods for ,road ,builders and all interested in better ways of communication4 ,price #a4jj ,,reinforced ,,concrete4 ,by ,webb and ,gibson4 #aej pp41 #adj illus4 ,a manual of practical methods for ,architects1 ,builders4 ,contractors1 ,civil and ,sanitary ,engineers4 ,information for the first time made known to the world4 ,based on recent construction work1 special tests1 etc4 ,price #a4jj ,,management ,,of ,,dynamo-,,electric ,,machinery4 ,by ,f4 ,b4 ,crocker4 #acj pp41 #fe illus4 ,for all who have to do with electric light or power plants4 ,price #a4jj ,,steam ,,engines4 ,by ,leland and ,snow4 #agj pp41 #fc illus4 ,a practical guide4 ,field covered in a way anyone can grasp4 ,price #a4jj ,,electric ,,railways4 ,by ,j4 ,r4 ,cravath4 #aej pp41 #ajc illus4 ,trolley and third-rail systems4 ,electric ,locomotive1 etc4 ,price #a4jj ,,estimating4 ,by ,edward ,nichols4 #adj pp41 #ce illus4 ,for all workers in ,building trades4 ,tells how to estimate intelligently4 ,price #a4jj ,,contracts ,,and ,,specifications4 ,by ,james ,c4 ,plant4 #acj pp41 fully illustrated4 ,forms of public and private contracts1 specifications1 bonds1 etc41 duties and responsibilities of ,architects1 ,contractors1 and ,owners4 ,price #a4jj ,,stair-,,building ,,and ,,steel ,,square4 ,by ,hodgson and ,williams4 #acj pp41 #ahj illus4 ,only up-to-date work on these subjects4 ,price #a4jj ,,valve ,,gears ,,and ,,indicators4 ,by ,leland and ,dow4 #aej pp41 #aje illus4 ,two books in one4 ,types of valves1 gears1 etc41 fully explained4 ,price #a4jj ,,strength ,,of ,,materials4 ,by ,e4 ,r4 ,maurer4 #adj pp41 #eh illus4 ,for ,architects1 ,builders1 ,steel and ,concrete ,workers4 ,enables one to avoid mistakes4 ,price #a4jj ,,the ,,electric ,,telegraph4 ,by ,thom and ,collins4 #aej pp41 #ha illus4 ,carries along by easy steps to complete mastery4 ,multiplex and ,wireless telegraph explained4 ,price #a4jj ,,mechanical ,,drawing4 ,by ,e4 ,kenison4 #afj pp41 #adj illus4 ,complete course in projections1 shade lines1 intersections and developments1 lettering1 with exercises and plates4 ,price #a4jj ,,power ,,stations ,,and ,,transmission4 ,by ,g4 ,c4 ,shaad4 #afj pp41 #dc illus4 ,for ,electrical ,workers4 ,up-to-date practice4 ,price #a4jj ,,pattern ,,making4 ,by ,james ,ritchey4 #aej pp41 #bej illus4 ,for ,wood and ,metal ,workers and ,molders4 ,methods of building up and finishing1 fully described4 ,price #a4jj ,,surveying4 ,by ,alfred ,e4 ,phillips4 #bjj pp41 #acc illus4 ,for ,civil ,engineers and ,students4 ,all details of field work explained4 ,price #a4ej ,,steel ,,construction4 ,by ,e4 ,a4 ,,tucker4 #cjj pp41 #bge illus4 ,covers every phase of the use of steel in structural work4 ,based on actual experience1 special tests1 etc4 ,for ,architects1 ,bridge ,builders1 ,contractors1 ,civil ,engineers4 ,price #a4ej ,,building ,,superintendence4 ,by ,e4 ,nichols4 #bjj pp41 #bej illus4 ,costly mistakes occur through lack of attention at proper time1 hurtful to ,owner and discreditable to ,architect and ,builder4 ,gives thorough knowledge of methods and materials4 ,price #a4ej ,,architectural ,,drawing ,,and ,,lettering4 ,by ,bourne1 von ,holst and ,brown4 #bjj pp41 #ee drawings4 ,complete course in making working drawings and artistic lettering for architectural purposes4 ,price #a4ej ,,machine ,,shop ,,work4 ,by ,f4 ,w4 ,turner4 #bjj pp41 #bjj illus4 ,meets every requirement of the shopman1 from the simplest tools to the most complex turning and milling machines4 ,price #a4ej ,,tool ,,making4 ,by ,e4 ,r4 ,markham4 #bjj pp41 #cbe illus4 ,how to make1 how to use tools4 ,profusely illustrated4 ,price #a4ej ,,machine ,,design4 ,by ,c4 ,l4 ,griffin4 #bjj pp41 #hb designs4 ,written by one of the foremost authorities of the day4 ,every illustration represents a new device in machine shop practice4 ,price #a4ej ,these volumes are handsomely bound in red art ,vellum de ,luxe1 size #f #i inches4 ,sent prepaid to any part of the world1 on receipt of price4 ,remit by ,draft1 ,postal ,order1 ,express ,order1 or ,registered ,letter4 ,,american ,,school ,,of ,,correspondence1 ,,chicago ,transcriber's ,notes3 ,text enclosed by underscores is in italics 7italics74 ,text enclosed by equals is in bold 7bold74 ,text enclosed by pluses is in small caps 7small caps74 ,obvious typographical errors have been silently corrected4