library
ELECTRIC IGNITION
FOR
COMBUSTION MOTORS
BY
FORREST R. JONES, M.E.
Member of the A merican Society of Mechanical Engineers, and of the Society for
the Promotion of Engineering Education. Formerly Professor of Mechanic
Arts in the University of Tennessee, and of Machine Design successively
in the University of Wisconsin, the Worcester Polytechnic
Institute and Cornell University
FIRST EDITION
FIRST THOUSAND
NEW YORK
JOHN WILEY & SONS
LONDON: CHAPMAN & HALL, LIMITED
1912
COPYRIGHT, 1912,
BY
FORREST R. JONES
Stanhope ipms
F. H. GILSON COMPANY
BOSTON. U.S. A
/ ^'773
Engineering
Library
PREFACE.
THE plan of this work is based upon the supposition that
some of its readers may possibly be unfamiliar with electricity
and electrical devices. To meet this condition, the fundamen-
tal principles involved in each case are given before commercial
forms are described.
The range of the subject matter is from the small ignition
apparatus used on motor cycles to that used on the largest gas
engines.
More than half of the illustrations have been prepared espe-
cially for the book, largely from sketches, drawings, photographs,
and information kindly furnished by those making or dealing in
ignition appliances.
Electric connections, both internal and external, are shown,
by wiring diagrams and other means, for complete ignition sys-
tems and the parts of which they are composed.
Considerable attention is given to the operation, care, adjust-
ment, and testing of ignition systems and their various parts.
Lack of knowledge in this respect is the chief cause of ignition
troubles in connection with the excellent equipments now ob-
tainable.
FORREST R. JONES.
KNOXVILLE, TENNESSEE,
January, 1912.
257830
CONTENTS.
CHAPTER I.
INTRODUCTORY.
ART. PAGE
1. Electric ignition in general i
2. High-tension and low-tension electricity i
3. Sources of electricity 3
4. Permanent magnets. Forms and action 3
5. Poles of a magnet 5
6. Magnetic field 6
7. Magnet keeper and its effect 6
8. Magnetic and non-magnetic materials 7
9. Compound or composite magnets 8
10. Principle of electric generators &
11. Armature of electric generator 9
CHAPTER II.
LOW-TENSION ALTERNATING-CURRENT MAGNETOS WITH
SINGLE-WOUND SHUTTLE ARMATURES.
12. Field magnets of a magneto 10
13. Abutted magnets n
14. Armature of magneto n
15. Electric arc from a shuttle-wound armature 14
16. Effect of speed of armature on position for maximum arc 16
17. Positions of armature for strong electric arc 16
18. Laminated armature core 18
19. Magnetic flux in a rotating I-shaped armature core 19
20. Electromotive force and current induced in an armature 24
21. Armature lag 24
22. Alternating current generated 25
23. Graphical representation of current in a shuttle-wound armature 28
24. Cycle of current 29
25. Form of current curve as affected by shape of pole-pieces 29
26. Position of armature for maximum arc 30
27. Low-tension alternating-current magneto with shuttle- wound armature 31
28. Stationary armature and rotary magnetic sleeve 35
29. Action of the magnetic sleeve 37
30. Note regarding low- tension magnetos for high-tension ignition 37
CHAPTER III.
DIRECT-CURRENT MAGNETOS.
31. General 38
32. Elementary form of drum armature , 39
33. Generation of current 39
34. Commutation of current in a direct-current generator 41
35. Continuous-current electric generator 43
36. Laminated drum armature core 43
v
VI CONTENTS
ART. PAGE
37. Complete drum armature 44
38. Commutator for direct-current generator 44
39. Armature connections 45
40. Complete direct-current magneto 48
CHAPTER IV.
TESTING FOR DIRECTION OF CURRENT.
41. Water test. Bubbles at submerged wire-end 50
42. Color test 51
43. Magnetic compass test 52
44. Extemporized compass needle 53
45. Test with measuring instruments v 53
CHAPTER V.
ELECTRIC MEASURING INSTRUMENTS.
46. General 54
47. Ammeters 54
48. Voltmeters 56
49. Volt-ammeters 57
50. Dead-beat indicating needle 59
CHAPTER VI.
ELECTROMAGNETS.
51. Plain bar electromagnet 60
52. Plunger-core electromagnet 61
53. U-shaped electromagnet 62
54. Ring-shaped electromagnet with consequent poles 64
55. Bipolar ring-shaped electromagnet 64
56. Four-pole ring-shaped electromagnet 64
CHAPTER VII.
DIRECT-CURRENT GENERATORS WITH ELECTROMAGNETS.
57. General 65
58. Bipolar direct-current generator with U-shaped shunt-wound electro-
magnets 65
59. Bipolar direct-current generator with ring-shaped shunt-wound electro-
magnets 67
60. Four-pole direct-current generator with shunt- wound electromagnets. . . 71
61. Series-and-shunt field winding - 74
62. Field rheostat for regulating voltage 75
63. Reversing the rotation of the armature 76
CHAPTER VIII.
PRIMARY BATTERIES.
64. Carbon-zinc battery 78
65. Elementary Leclanche carbon-zinc wet cell 78
66. Polarization of primary electric cell 80
67. Dry cell with carbon and zinc electrodes 80
CONTENTS Vll
ART. * AGE
68. Deterioration of dry batteries while idle 82
69. New type of carbon-zinc dry cell 82
70. Exhaustion of dry batteries in service 83
71. Recuperation of dry cells 83
72. Lalande and Chaperon wet cell 84
73. BSCO wet cell 84
74. Edison primary battery 86
CHAPTER IX.
BATTERY CONNECTIONS.
75. General 88
76. Series-connected battery of four cells . . . 88
77. Reversed cell in a series battery 89
78. Parallel-connected battery of four cells 90
79. Reversed cell in a parallel-connected battery 91
80. Parallel-series batteries 92
81. Wrong arrangement of' a battery 93
82. Connection to external circuit 94
83. Screw-top battery cells . 95
CHAPTER X.
STORAGE BATTERIES, ALSO CALLED ACCUMULATORS
AND SECONDARY BATTERIES.
84. Storage battery defined 97
85. Electrodes, or plates, of a lead storage cell 98
86. Complete storage cell 99
87. Voltage of a storage cell having lead plates 101
88. Maximum rate of discharge of storage cell 102
89. General description of storage battery .^ 102
90. Exide storage battery 104
91. Charging the storage battery 107
92. Chemical action in a lead storage battery 108
93. Capacity of a storage cell 109
CHAPTER XI.
FLOATING THE STORAGE BATTERY ON THE LINE OF A
DIRECT-CURRENT GENERATOR.
94. Method of floating the battery on the line no
95. Automatic cut-out 113
96. Two- voltage system with two storage batteries floated on the line 117
97. Two-voltage system with lamps and ignition apparatus 118
98. Switchboard for two- voltage system with battery floated on the line . . 119
CHAPTER XII.
MECHANICALLY OPERATED MAKE-AND-BREAK IGNITERS
AND KICK-COILS FOR LOW-TENSION IGNITION.
99. Mechanically operated igniter : 123
100. Duration of contact between the electrodes 126
101. Bosch mechanically operated igniter 126
102. Truscott Boat Manufacturing Company's igniter 128
viii CONTENTS
ART. PAGE
103. Fay & Bowen low-tension igniter 131
104. Westinghouse make-and-break igniters 132
105. Snow Steam Pump Works mechanically operated igniter 133
106. Mechanical make-and-break operating mechanism of the Snow Steam
Pump Works igniter 133
107. Four-unit low-tension mechanism 137
108. Allis-Chalmers gas engine with mechanical make-and-break igniters.. . 138
109. Kick-coils 138
1 10. Screw-top kick-coil . 142
in. Tell-tale kick-coil 142
CHAPTER XIII.
MECHANICAL MAKE-AND-BREAK LOW-TENSION IGNITION
SYSTEMS.
112. Battery, reactance coil, and make-and-break igniter 144
113. Duration of contact 145
114. Magnet and make-and-break igniter 146
115. Direct-current generator, kick-coil, and mechanical make-and-break ig-
niter 148
116. System for four combustion chambers. Mechanical make-and-break
igniter, storage battery, primary battery, and direct-current generator 149
117. Alternating-current magneto, primary battery, and four make-and-
break igniters 150
118. Storage battery floated on the line of a shunt-wound generator, and
mechanical make-and-break igniters 151
119. no- volt generator and 6- volt primary battery mechanical make-and-
break system 152
1 20. Multiple system with switchboards, primary batteries, and no- volt
direct-current generator 155
121. Storage battery and no- volt generator mechanical make-and-break
system 159
122. Storage battery, primary battery, and no- volt generator make-and-
break system 160
123. Multiple system with storage batteries, no-volt generator, primary
battery, and switchboards 161
124. System using current from no-volt direct-current service without
ground connection 162
125. Multiple system using iio-volt to 125-volt direct current from general
service circuit 165
126. Triple low- tension ignition system for large engine with four double-
acting cylinders 165
CHAPTER XIV.
ELECTROMAGNETIC IGNITERS AND IGNITION SYSTEMS FOR
LOW-TENSION CURRENT.
127. Principle of operation 169
128. Elementary ignition system with a timer and an igniter having an elec-
tromagnet with a plunger core 169
129. Dual ignition system with plunger-core electromagnets in the igniter. . 171
130. Wisconsin Engine Company's electromagnetic igniter with plunger cores.
Details 175
131. Details of one-ring timer for large engine with four combustion cham-
bers 1 78
CONTENTS ix
ART. PAGE
132. Allis-Chalmers four-ring timer for large engine 181
133. Details of Allis-Chalmers electromagnetic igniter for a large engine 184
134. Wiring diagram for a four-ring timer and igniters actuated by a rotary
magnet armature 191
135. Bosch igniter with vibratory magnet armature 191
136. Magneto and wiring diagram for magnetic-plug ignition system 194
CHAPTER XV.
TRANSFORMER SPARK-COILS AND SYNCHRONIZER, OR MASTER,
TREMBLER-COILS.
137. General 200
138. Elementary transformer spark-coils 200
139. Operation of elementary transformer spark-coil without trembler 202
140. Trembler transformer spark-coil 204
141. Safety spark-gap 213
142. Lag of spark-coils 214
143. Tremblers, or vibrators: Bow-spring, hammer-break, and plain types. . . 214
144. Complete trembler transformer spark-coils 220
145. Synchronized spark-coils with master-trembler 222
146. Trembler spark-coil for use with high-tension distributor 223
147. Plain transformer spark-coils without a trembler 224
148. Connections to trembler spark-coils 225
CHAPTER XVI.
TIMERS AND SPARK-PLUGS FOR HIGH-TENSION IGNITION.
149. Elementary form of timer 227
150. Roller-contact timer 227
151. Sliding-contact timer 230
152. Timer with normal-pressure contacts 230
153. Spark-plugs. General description 231
154. Single-gap jump-spark plugs 231
155. Spark-plugs with two or more spark-gaps 234
156. Separable spark-plugs 236
157. Width of spark-gap 238
CHAPTER XVII.
IGNITION SYSTEMS WITH MAGNETIC TREMBLER INTERRUPTERS
AND INDIVIDUAL TRANSFORMERS.
158. Introductory 240
159. System with one spark-plug and trembler spark-coil 240
160. Auxiliary condenser in an ignition system 242
161. Grounded spark-coil condenser ; . 243
162. Individual trembler-coil systems 244
163. Synchronized system with master trembler-coil 245
164. Synchronized system with master trembler-coil and auxiliary condensers 247
165. Ammeter and voltmeter permanently in the circuit of a high-tension
ignition system 249
166. Speed of the timer 251
CONTENTS
CHAPTER XVIII.
HIGH-TENSION DISTRIBUTOR SYSTEMS WITH BATTERY CURRENT.
ART. PAGE
167. General 252
168. High-tension distributor system with trembler spark-coil 252
169. Mechanically operated contact-maker and high-tension distributor sys-
tem with battery current 254
1 70. Unisparker 255
171. Combined contact-maker, spark-coil, and distributor 258
172. Comparison of unisparker and ordinary timer 260
CHAPTER XIX.
SPARK-PLUGS IN SERIES AND IN SERIES-SHUNT.
173. Method of operating 261
174. Series-shunt connection of spark-plugs 262
175. Constructive form of series-shunt spark-plug ignition system 265
CHAPTER XX.
INTERRUPTER MAGNETOS AND JUMP-SPARK IGNITION SYSTEMS
WITH MAGNETO CURRENT ONLY.
176. Introductory 268
177. Interrupted primary-current magneto ignition system 268
178. Interrupted shunt-current magneto ignition system 271
179. Shunted-current magneto ignition system 272
180. High-tension magneto with single-wound armature 272
181. Double-wound high-tension magneto 273
182. Bosch high-tension magneto with double- wound rotary armature 275
183. U. & H. magneto with rotary double-wound shuttle armature 291
184. Remy magneto with stationary armature and rotary inductor 295
185. Effect of advance and retard on the strength of the ignition spark 301
186. Charged-and-discharged condenser ignition system 302
187. Shaft couplings for advancing and retarding the ignition 303
187.1 Eisemann high-tension magneto with automatic spark-advance
mechanism 305
188. Interrupted short-circuit magneto 307
189. Movable extensions of magnet poles for constant strength of spark. . . . 309
190. Pittsfield magneto with stationary armature and rocking pole-extensions 311
191. Mea magneto with rocking magnets 316
CHAPTER XXI.
HIGH-TENSION DUAL AND COMBINED IGNITION SYSTEMS.
192. Introductory 326
193. Remy ignition system with separate transformer 327
194. Splitdorf ignition system with separate transformer 330
195. Eisemann ignition system with separate transformer 334
196. Eisemann-Carpentier ignition system 337
197. Bosch dual ignition system 340
197. i Duplex high-tension ignition system having a battery in series with
the primary of the magneto 345
198. Magneto with two high-tension windings for dual ignition 352
CONTENTS XI
CHAPTER XXII.
HIGH-FREQUENCY ALTERNATING-CURRENT MAGNETOS.
ART. PAGE
199. Introductory 353
200. W. & S. magneto 353
201. K-W high-frequency magneto . 356
202. Ford high-frequency magneto 358
CHAPTER XXIII.
VARYING THE TIME OF IGNITION. MULTIPLE IGNITION.
203. Advancing the timer on account of lag in the ignition apparatus 361
204. Varying the time of ignition relative to the rate of combustion of the
charge in the motor 362
205. Varying the time of ignition with variable speed 364
206. Reduction of the variation of ignition by the use of two simultaneous
ignition sparks 365
207. Advancing and retarding the spark in a variable-speed motor 366
CHAPTER XXIV.
CARE AND ADJUSTMENT OF IGNITION SYSTEMS.
208. Introductory 368
209. Cleaning the spark-plug 369
210. Adjusting the width of spark-gap in jump-spark igniters 369
211. Repairing the spark-points of contact igniters 370
212. Adjusting the trembler 370
213. Lubricating and cleaning the timer 371
214. Care of the magneto or dynamo 372
215. Filing or dressing the contact-points 374
216. Care of batteries in general 374
217. Keeping electric connections tight 375
218. Testing a primary battery 376
CHAPTER XXV.
TESTING OF STORAGE BATTERIES.
219. Voltage-and-current test of a storage battery 378
220. Ammeter in series with resistance 379
221. Lamp for testing 381
222., Testing cells individually 381
223. Voltmeter test of a storage battery 381
224. Voltage-drop test 381
225. Lowest safe voltages of storage batteries while discharging 382
226. Curve of voltage drop while a storage battery is discharging 383
227. Testing the density of the electrolyte 384
CHAPTER XXVI.
CHARGING AND CARE OF STORAGE BATTERIES.
228. Precautions 387
229. Connections for charging a storage battery 387
230. Connections for charging two batteries at the same time 389
231. Rate of charging a storage battery 390
xii CONTENTS
ART. PAGE
232. Charging and care of lead-plate storage batteries 390
233. Removing the sediment from lead-plate cells 393
234. Taking a lead-plate cell out of commission 394
235. Charging and care of nickel-iron storage batteries 394
236. Taking a nickel-iron battery out of commission 396
CHAPTER XXVII.
TIMING THE IGNITION.
237. General features 397
238. Timing, or setting, the timer 398
239. Timing a rotary magneto of the interrupter type 400
240. Relative positions of the crank-shaft and piston of a motor 402
CHAPTER XXVIII.
IGNITION SYSTEM FAULTS AND REMEDIES.
241. Defects and conditions in the ignition system which cause faulty ignition 405
242. In the igniter 405
243. In the spark-coil 407
244. In the reactance coil, or kick-coil 408
245. In the timer 408
246. In the magneto 409
247. In the dynamo 413
248. In the battery 413
249. In the connections 415
CHAPTER XXIX.
OPERATING TROUBLES POSSIBLY DUE TO THE IGNITION SYSTEM.
250. Introductory 416
251. Motor will not start 416
252. Preignition 416
253. Back-firing into the intake of the motor 417
254. Overheating of the motor 418
255. Misfiring and exhaust explosions without other serious troubles 418
256. Knocking or pounding 419
257. Sudden stoppage of motor 419
258. Motor does not develop full power 419
259. Spark control must be advanced more than usual, and motor behaves
erratically 420
ELECTRIC IGNITION.
CHAPTER I.
INTRODUCTORY.
1. Electric ignition, as applied to motors, or engines, which
burn a combustible mixture of gas inside of the cylinder of the
motor, is accomplished, in modern practice, either by producing
an electric spark, or by drawing an electric arc, inside of the
cylinder in the inclosed space which is filled with the combustible
mixture. The spark, or arc, as the case may be, ignites the com-
bustible mixture and causes it to burn.
High-tension and Low-tension Electricity.
2. There are two classes of electric ignition as applied to
combustion motors. One class is known as high-tension, or
jump-spark, ignition; the other class as low-tension, make-and-
break, contact, or touch-spark ignition.
The terms " high-tension " and " low-tension " are used in
accordance with the intensity of the tension, also called pressure,
of the electricity that is used to produce the spark, or arc, for
igniting the combustible charge. An idea of the distinction
between high-tension and low-tension electricity as used for
ignition can be obtained from its action on the animal, or human,
body.
The high-tension electricity used for ignition is capable of
giving a very severe shock to one who touches the metal of a wire
or apparatus which is charged with the high-tension electricity.
The shock is not dangerous, however, unless continued for a
considerable time.
The low-tension electricity for ignition in motors used on
automobiles, traction engines, and other similar appliances is
2 ELECTRIC IGNITION
hardly capable of making its presence known by giving a shock
to one touching the bare portions of electric conductors charged
with it, when ordinary conditions exist. The same is in general
true qf the electricity used for low-tension ignition in stationary
engines when the electricity is supplied by apparatus especially
adapted to ignition usage. The pressure of the electricity sup-
plied by such means for low-tension ignition varies considerably
in different systems. Some systems operate on about 4 volts,
while others operate at about 50 volts. The latter pressure is
about the same as that used in some commercial lighting systems,
and gives only a slight shock under ordinary conditions. Some
stationary engines take electricity from commercial service mains
at a pressure of about no or even 220 volts. In such cases the
electric current is generally passed through incandescent lamps
which utilize a portion of the electric pressure and prevent, by
their electric resistance, too much current from passing through
the ignition apparatus.
The reason that the high-tension electricity used for ignition
is not dangerous, although its pressure is several thousand volts,
is that the apparatus used does not have capacity to furnish
enough electricity to do serious harm. The pressure is enor-
mously high, as compared with that in service wires for incan-
descent lighting, but the quantity of electricity is minutely small.
The condition of the skin where it comes into contact with
an electrically charged metal wire or piece of apparatus has much
to do with the extent of the shock that is received, especially
when the pressure is as low as that generally used for incan-
descent lighting and for low-tension ignition. When the skin
is dry or oily, the shock is very much less than when it is moist
or wet. If the skin is cut or deeply scratched so that the raw
flesh comes into contact with the charged metal, then the shock
is still more severe than when the skin is intact but wet. The
animal skin, or cuticle, offers more resistance to the passage of
electricity than the other parts of the body, at least the soft
parts. When the skin is removed, more electricity will pass
through the body than when the skin is intact, even though
moist or wet with water. In other words, a wet skin allows more
INTRODUCTORY 3
electric current to pass through it, on account of its lesser resist-
ance, than will pass through when the skin is dry or oily and
consequently offers greater resistance to the passage of electricity.
Sources of Electricity.
3. The electricity used for ignition is obtained either from a
power-driven machine, called an electric generator, or from an
electric battery in which the electricity is produced by chemical
action.
When an electric generator has permanent magnets, it is gen-
erally called a magneto. An electric generator which does not
have permanent magnets is ordinarily called either a dynamo
or an electromagnetic generator. Magnetos and electromag-
netic generators are both further classified according to the
nature of the electricity they produce. This will be taken up
in connection with the discussion of electric generators.
Electric batteries are of two distinctive kinds, known as
primary and secondary. A secondary battery is also called an
electric accumulator and a storage battery.
A primary battery is one which is ready to give out electric
current as soon as it is constructed.
A storage battery cannot give out electric current as soon as
it is mechanically constructed, but must have electricity charged
into it before it is ready to deliver electric current. It must
also be frequently recharged with electricity during its life.
Each unit of which an electric battery is made up is called
an electric cell. A primary electric cell is also called a galvanic
cell and a voltaic cell, after the names of its inventors. It is
quite common practice to call an electric cell a battery, or a
battery cell.
Permanent Magnets.
4. Forms and Action. Doubtless the most familiar forms of
permanent magnets are the horseshoe magnet and the magnetic
needle. The latter is part of the magnetic compass for deter-
mining the directions of north and south. Small horseshoe
magnets are sold in toy stores and hardware stores. The mag-
ELECTRIC IGNITION
netic compass is regularly used on board ocean-going vessels, in
surveying instruments, and in pocket compasses.
A common form of horseshoe magnet is shown in Fig. i . It
is made of a piece of bar steel bent to bring the ends of the bar
near together. After bending, the steel is first hardened and
then magnetized. The magnet will attract pieces of iron and
FIGS, i, 2, and 3.
Horseshoe Magnets. Permanent.
steel placed near the ends of the bent bar, and, if the pieces are
free to move, they will be drawn up against the magnet and
held there. It is immaterial what forms the pieces of iron and
steel to be attracted have. They may be in the form of wire
nails, tacks, balls such as used in ball bearings, rings, or any
other form. There is little or no magnetic attraction in the
region of the crown, or curve, of the bent bar.
Nails or tacks of comparatively mild steel or soft iron do not
remain magnetic to any great extent after they are removed
from the magnet. But hardened or tempered pieces of steel,
especially those of an elongated form, such as a knife blade,
sewing needle, and writing pen, retain considerable magnetism
for some time after removal from the magnet, and will pick up
INTRODUCTORY 5
tacks and other small pieces of steel. Still harder pieces of steel,
such as a file, will retain magnetism for a longer time than the
articles just mentioned.
6. Poles of a Magnet. The usefulness of the magnetic com-
pass depends on the fact that one end of the magnetic needle,
and that always the same end, points approximately in the direc-
tion of the north pole of the earth when the needle is allowed to
swing freely. The end of the needle which takes its position
toward the earth's north pole is called the north pole of the
needle; the opposite end, which points toward the south, is called
the south pole of the needle.
If a magnetic compass is placed near one of the ends of a
horseshoe magnet, the compass needle, if left free to swing, will
take a position with one end pointing more or less directly toward
the nearest end of the bent bar. For convenience, it will be
assumed that the north pole of the compass needle points toward
the nearest end of the bent bar. Then, if the compass is moved
to a new position so as to bring it near the other end of the bent
bar, the needle will swing on its pivot so that the south pole of
the needle will point more or less directly toward the nearest end
of the bent bar. If the compass is repeatedly moved away from
the bent-bar magnet and brought back near it as just described,
the north pole of the needle will always be attracted by and
point toward the same end of the bent bar, and the south pole
will always behave in the same manner relative to the other pole
of the bent bar.
In the horseshoe magnet, the bar-end which attracts the north
pole of the compass needle is called the south pole of the horseshoe
magnet ; and the bar-end which always attracts the south pole
of the needle is called the north pole of the horseshoe magnet.
The letters N and S are customarily used to designate the
north and south poles respectively of a magnet.
If the compass is placed immediately between the bar-ends of
the horseshoe magnet, the needle will take a position straight
across between the poles, with the north pole pointing toward
the south pole of the horseshoe magnet, and its south pole
pomting toward the north pole of the horseshoe magnet.
6 ELECTRIC IGNITION
6. Magnetic Field. The region throughout which a magnet
acts to attract pieces of iron and steel is called the " magnetic
field " of the magnet. The magnetic field has its greatest
strength near the ends, or poles, of the magnet, and is especially
strong in the space between the ends of the horseshoe magnet.
The magnetic field is said to be permeated with " magnetic lines
of force." The position which a very small compass needle
takes when placed in the magnetic field of a relatively large
magnet indicates with fair accuracy the direction of the lines
of force in the locality occupied by the compass needle. The
length of the needle approximately coincides with the direction
of the lines of force. The needle must of course be free to swing.
If the north pole of a long, thin magnetic needle is placed
between the poles of a horseshoe magnet, the magnetic force
tends to move the needle pole in the direction from the north
pole of the horseshoe magnet toward the south pole of the horse-
shoe magnet, which is the direction in which the lines of force
act in that locality. If the north pole of the needle is placed in
any other part of the magnetic field of the horseshoe magnet,
the magnetic force of the latter also tends to move the needle
pole in the direction of the lines of force at the needle pole, and
to carry it along the same lines of force in the direction from the
north pole to the south pole of the horseshoe magnet. The
path which the needle pole will follow may be a very indirect
one of a circuitous nature.
It is customary to assume that there is a flow of magnetism,
called magnetic flux, in the magnetic field from the north pole
to the south pole of a magnet, the flux at any point being in the
direction in which the magnetic force tends to move a magnetic
north pole. The complete magnetic circuit through which the
flux occurs includes the length of the steel bar from end to end.
7. Magnet Keeper and Its Effect. A magnet keeper of soft
iron or soft (mild) steel is generally provided with a horseshoe
magnet. In Fig. 2 such a keeper A is shown in place across the
ends of the magnet bar. The purpose of the keeper is to prevent
the magnet from losing its magnetism.
When the space between the poles of the magnet is bridged by
INTRODUCTORY 7
the keeper as shown in the figure, the magnet will not attract
pieces of iron and steel with nearly as much force as when the'
keeper is not in place. The keeper has a similar effect, and to
practically the same extent, if laid against the sides of the bent
bar so as to bridge the space between the poles of the magnet.
Or the keeper may be made so as to fit between the ends of the
bar as shown in Fig. 3, and will then also have the effect of weak-
ening the magnetic field in the manner described.
The weakening of the magnetic field by the keeper is more
complete when the keeper fits accurately against the magnet so
that there is a large area of metallic contact between them, than
when the surfaces that touch each other are rough and make but
imperfect contact.
The keeper offers an easier path for the magnetic flux than
is offered by air, therefore nearly all of the flux is through the
keeper, only a small proportion passing through the air.
The magnetic flux through the bent bar of the magnet is not
decreased by bridging the space between the poles with the
keeper, but, on the contrary, a large increase of flux through the
magnet bar is caused by putting the keeper in place. Proof of
the last statement will appear in connection with the method of
operating one of the various types of magnetos for generating
electricity.
8. Magnetic and Non-magnetic Materials. Iron and alloys
containing a large proportion of iron are the only materials that
are magnetic to an appreciable extent. Steel is a combination,
or an alloy, of chemically pure iron (ferrum) with other chemical
elements.
Except iron and steel, all of the materials ordinarily used in
machinery and electrical apparatus are either non-magnetic, or
magnetic to only such a slight extent, compared with commercial
iron and steel, that they can be considered non-magnetic for the
present purpose. These non-magnetic materials include brass,
bronze, aluminum, aluminum alloys generally, zinc, porcelain,
steatite (soapstone), glass, mica, rubber, pitch, dry wood, wood
fiber, cotton, silk, hemp, flax, and paper.
Strictly non-magnetic materials are not attracted by a magnet.
8
ELECTRIC IGNITION
The magnetic field is not affected by their presence. If a piece
of non-magnetic material is placed so as to bridge the air gap
between the poles of a magnet after the manner of using a magnet
keeper, no appreciable change will be produced in the magnetic
field.
9. Compound or Composite Magnets. The permanent mag-
nets used in magnetos for generating electricity for ignition pur-
poses are generally made up of several
bar magnets bent into the shape of the
letter U and grouped closely together.
Fig. 4 shows a method of grouping the
individual magnets together that is very
commonly used for forming a composite
magnet. The north poles of all the indi-
vidual magnets are placed together, and
likewise the south poles.
Rectangular bars bent flatwise as shown
are very generally used, but other forms
of steel bars, including round ones, are
also used to some extent. The reason for
using composite magnets is that it is dif-
ficult, in fact practically impossible, to
make magnets of one piece sufficiently
large for magnetos to be used for ignition purposes.
FIG. 4.
Compound or Composite
Magnet.
Principle of Electric Generators.
10. In all power-driven electric generators the generation of
electricity is due to directly and repeatedly varying the number
of lines of magnetic force that pass through the opening of a coil
of wire (not through the length of the wire itself). This varia-
tion generally includes reversing the direction of magnetic flux
through the coil opening, although in some unusual designs the
magnetic flux is not reversed in direction through the coil open-
ing. Varying the number of lines of magnetism through the
coil of wire induces an electromotive force in the wire, which
tends to cause a flow of electricity through the wire and also
INTRODUCTORY 9
through whatever apparatus may be suitably connected to the
wire.
The electromotive force is induced in the coil only during the
time of variation in the amount of magnetic flux through the coil.
A constant flux of magnetism through a coil, without change in
the number of lines of magnetic force passing through the coil
opening, does not induce an electromotive force in the coil.
The methods by which the number of lines of force passing
through a coil are made to vary are numerous. They come
under two general methods, however. In one of these general
methods the wires of the coil are caused to cut through the lines
of magnetic force in such a manner as to vary the number of
lines of force passing through the coil. In the other general
method the magnetic flux through a bar which the coil encircles
is caused to vary in intensity, also generally reverse, without the
wires of the coil cutting through any of the lines offeree. The
more important ways in which the variation of magnetic flux
through a coil is accomplished will appear in the descriptions
of various types of generators used in connection with electric
ignition.
11. The armature of an electric generator consists of a coil,
or coils, of wire over or around a core, or cores, of magnetic
material which is not a permanent magnet. In the more usual
forms of generators for electric purposes, the armature rotates
relative to the magnets. In less usual forms, the armature
remains stationary with regard to the magnets. In the latter
form there is a rotor (rotating part) of soft iron or mild steel,
called an inductor. In both cases the rotation, or oscillation, of
the rotor (armature or inductor) causes a variation in the num-
ber of the lines of force passing through the opening of the arm-
ature coil, and thus induces an electromotive force in the coil of
the armature, so that the coil will deliver current when the elec-
tric circuit is properly closed, as through the other apparatus of
an ignition system.
CHAPTER II.
LOW-TENSION ALTERNATING-CURRENT MAGNETOS WITH
SINGLE- WOUND SHUTTLE ARMATURES.
12. The field-magnets of a magneto are shown in Fig. 5. The
field magnet is composite, being made up of six individual magnets
in pairs, each pair consisting of a
large magnet fitted over a small
one.
Two pole-pieces, or pole-shoes,
of mild steel or cast-iron, are fast-
ened opposite each other and
against the inner surfaces of the
inside individual magnets by
means of screws which pass through
the magnets into threaded holes in
the pole -pieces.
The space between the extreme
ends of the magnets is bridged by
a piece of non-magnetic metal,
such as brass or aluminum alloy,
which forms a base for the mag-
netic field and is fastened to the
Field-Magnets and Pole-Pieces of a po le-pieces by screws, one of which
is shown partly removed beneath
the base. The opposite faces of the pole-pieces are bored out
cylindrical, so as to fit close to the armature, or. inductor,
which rotates, or oscillates, between them when the machine
is operating. The ends of the pole -pieces are slightly counter-
bored to receive an end-plate (not shown) and hold it con-
centric with the bore of the pole -pieces. The use of the
end-plate is to support the armature and other parts, as will
appear later.
FIG. 5.
10
ALTERNATING-CURRENT MAGNETOS
II
13. Abutted Magnets. Another arrangement of the field-
magnets is shown in Fig. 6. The magnets are placed on opposite
sides of the armature space with their ends against each other
so that the north poles are together and have one of the pole-
N | N
s I s
FIG. 6.
Abutted Field-Magnets of a Magneto.
pieces fastened to them. The south poles are also together and
have the other pole-piece fastened to them. Composite magnets
can be used in this arrangement as well as that shown in the
preceding figure.
Rotary Armature Types.
14. An armature suitable for rotating between the pole-pieces
of the magnets just described is shown in Fig. 7. The general
82-
FIG. 7.
Armature of an Alternating-current Electric Generator. Shuttle-wound Type.
nature of the construction of the armature can be seen by referring
to Figs. 8, 9, and 10.
The core of the armature has the general form shown in Fig. 8.
It is made of mild steel or very pure and soft iron machined so
that the crowned surfaces have a cylindrical form to fit between
the pole-pieces. The crowned surfaces should fit as close as
12
ELECTRIC IGNITION
possible to the pole-pieces without touching them, in order to
make the air-gap between the armature and pole-pieces as small
as possible.
The armature winding is a coil of wire wound around the neck
which lies between the crowned sides of the core. Fig. 9 shows
the core with part of one layer of winding in place. The neck
and sides of the space in which the coil is wound are first cov-
FIG. 8.
Core of Shuttle-wound Armature.
FIG. 9.
Partly Wound Armature of the Shuttle Type.
FIG. 10.
Elements of Shuttle-wound Armature.
ered with some insulating material, such as silk or paper that
has been oiled or varnished, mica, or wood fiber cut from sheets
or molded to form. The insulating material does not allow
electricity to flow through it in appreciable quantity. A side
piece of insulation is shown at i in Fig. 9. Copper wire, covered
with cotton or silk thread wound around it so as to form an
insulating covering, is used ordinarily. In the better class of
work, the wire is covered with two windings of silk or cotton,
one winding on top of the other. The wire used in magneto
ALTERNATING-CURRENT MAGNETOS 13
armatures is commercially known as armature wire or magnet
wire, single-covered or double-covered, as the case may be with
regard to whether there is one or two layers of thread wound
on it.
One end of the wire is bare and fastened to the metal of the
armature core at 2, so that the copper of the wire and the metal
of the core are in metallic (electric) connection. The rest of the
wire is carefully insulated from the core, and the different layers
of the coil are also carefully insulated from each other. The
wire-end 3 is intended to represent where the wire has been cut
off before the first layer of winding was completed, in order to
show the nature of the winding.
After the first layer of the winding is complete, the second
layer is wound over it, and so on, layer upon layer, till the wind-
ing is complete. There is one continuous winding throughout
all of the layers. Some insulating material, such as heavy paper
or cloth, is generally placed between the layers, especially at
the bends of the wire, as a protection to the silk or cotton wrap-
ping of the wire, and to make the insulation more perfect between
the layers.
The coil is then wrapped with insulating tape and bound
around circumferentially of the core with bare non-magnetic
wire, as shown in Fig. 7. The tape is generally of cotton or linen
web saturated with insulating varnish. Liquid varnish is also
generally applied to the tape while wrapping it over the coil.
The varnish is waterproof if the magneto is to be used where
there is any likelihood of water reaching it. It is better for it
to be waterproof so as to exclude atmospheric moisture even if
it is intended to be used only in places free from water. Brass
or bronze wire is generally used for the circumferential bands.
A disk-shaped head of non-magnetic material is fastened to
each end of the armature core after the winding is completed.
Brass, bronze, or aluminum alloy is generally used for these heads.
Each head carries a spindle which projects outward from the
winding. The spindles are usually made of steel. They run in
suitable bearings during the rotation, or oscillation, of the arma-
ture while the magneto is operating.
ELECTRIC IGNITION
One of the spindles shown in Fig. 10 is hollow. The outer end
of the armature wire passes through the hole so that its end
projects beyond the spindle at i . Carrying an end of the arma-
ture winding out through a hollow spindle is very commonly
used in magnetos intended for ignition purposes, although the
wire itself is not generally carried through the spindle. It is
more usual to connect the armature wire to a rod or screw which
extends through the hole and is insulated from the metal of the
spindle either by a tube of hard rubber or vulcanized fiber, a
wrapping of sheet mica, or some other suitable means of insulation.
An armature with a core of the shape shown in Fig. 8, and
wound as just described, is called either an I-armature, an H-
armature, or a shuttle- wound armature.
The latter name is on account of the
resemblance of the armature in general
appearance to the shuttle of a weaving
loom. The names I-armature and
H-armature come from the resemblance
of the core, when looked at endwise, to
either the letter I or the letter H, ac-
cording to whether the core is held, or
lies, with the crowned surfaces at the
top and bottom, or at the sides.
15. Electric Arc from a Shuttle-
wound Armature. Fig. u shows a
shuttle- wound armature in place be-
tween the pole -pieces of permanent
field-magnets. The armature is of the
Field-Magnets and Armature of general form of that shown in Figs. 7
Magneto with Device for an( j IO< T^ bare end i of the copper
Showing Positions of Arma- r ,-, -,.
ture for Maximum Electric Wlfe f the armature wmdln g P r J ects
Arc or Spark. from the end of the hollow spindle, part
of the insulation 2 being removed to
expose the wire. A cam-shaped projection 3 is shown on the
forward end of the front spindle. A cam of this particular form
is not usual in commercial magnetos, but is added here to facili-
tate the explanation of the principle of operation of the magneto.
FIG. ii.
ALTERNATING-CURRENT MAGNETOS 15
A bent wire 4 is shown in contact with the bare end i of the
armature wire and also in contact with the convex surface of
the cam or lug 3.
If the armature is rotated in the direction indicated by the
arrow on the armature head, and the bent wire 4 is held stationary
in the position shown, so as to have rubbing or slipping contact
with the wire-end i and cam 3, then when the bent wire snaps
off the edge of the cam as the latter rotates with the armature,
an electric arc will be drawn between the end of the wire and the
edge of the cam at the point of separation of the two, provided
the speed of rotation is sufficiently high. A rotative speed of 30
to 40 revolutions per minute is sufficient to draw quite a large
arc in some magnetos when the parts separate. A magneto of
the size commonly used on portable combustion motors will give
a large arc when the armature is twirled around through one or
two revolutions by grasping the spindle in the fingers ; half a rev-
olution caused in this manner will give a good-sized arc in some
low- tension magnetos for ignition.
If while the armature is rotating at a speed more or less uni-
form, the bent wire 4 is swung around to different positions but
held so that it is always in contact with both the wire-end i and
the cam 3 just before the edge of the latter breaks contact with
the end of the bent wire, it will be found that while a good-sized
arc will be drawn for some positions of the bent wire, at other
positions no arc whatever will appear when the contact is broken.
After one position of the bent wire for the largest electric arc
corresponding to the speed of rotation is determined, it can be
seen, by swinging the bent wire slowly around the axis of the
rotating spindle, that the other position of the bent wire for
maximum arc is diametrically opposite the position first deter-
mined. In other words, the largest arc is obtained at two
positions of the cam-edge diametrically opposite each other,
which may be expressed by saying that the two positions of the
cam-edge are half a revolution apart for maximum electric arcs.
The position of the cam at any instant corresponds of course
to definite positions of the armature, since the cam and armature
are rigidly fastened together.
1 6 ELECTRIC IGNITION
It can also be seen, by the same process as just described, that
the two positions of the bent wire at which no arc is obtained
lie midway, or approximately midway, between the positions for
maximum arcs. The two positions for no arc are also diametri-
cally opposite each other, and therefore half a revolution apart.
A larger, or hotter, arc is obtained at a high speed of rotation
than at slow speed.
16. Effect of Speed of Armature on Position for Maximum
Arc. If the positions of the armature for maximum arc and
no arc are first determined as above while the armature is rotat-
ing at slow speed, say 50 revolutions per minute, and then the
armature speed is increased to say 1 200 revolutions per minute,
and the experiment repeated, it will be found that the bent wire
must be held farther around in the direction of rotation of the
armature in the latter case in order to obtain the maximum arc
and no arc. This means that the maximum arc occurs later in
the revolution of the armature at high speed than at low speed,
each revolution being assumed to begin at the same position
of the armature, as when the neck of its core is in a vertical
position. The cause of this lag in the time of production of the
maximum arc will be explained later.
17. Positions of Armature for Strong Electric Arc. The posi-
tions of the armature at which the strongest arc can be obtained
vary with variation in the forms of the pole-pieces and armature
core, as well as with the speed of rotation, as has been mentioned.
Most magnetos that are to run at a variable speed when in
service are generally so constructed that a strong arc can be
produced throughout a considerable range of position of the bent
wire applied as stated above. This is done on account of the
advance and retard of ignition relative to the position of the
pistons of the motor, as well as on account of the lag in the mag-
neto with regard to the position of the armature at the instant
of maximum arc. The lag is not so great for the speed usual
for combustion motors but that the position of the armature for
maximum arc can be pointed out in a general way, as in the
following paragraphs.
Fig. 1 2 shows conventionally the pole-pieces and shuttle-wound
ALTERNATING-CURRENT MAGNETOS
armature of a magneto. A double, or two-lobed, cam is shown
fastened to the armature spindle. A bent wire for making electric
connection between the cam and the bare projecting end of the
armature wire is also shown in place. The two lobes of the cam
are diametrically opposite each other and are in such positions
relative to the core of the armature that if a line were drawn
FIG. 12.
Positions of Armature for Maximum Electric Arc or Spark. Approximate.
through the two cam-edges at which the contact with the bent
wire is broken as the armature rotates, the line would be parallel
to the neck which connects the two crowned parts of the core.
FIG. 13.
Positions of Armature for No Electric Arc or Spark. Approximate.
The bent wire is held so as to break connection with the cam-
edge which is uppermost just as the armature core passes through
its upright position in which its end view resembles the letter I.
The arrow indicating the direction of rotation of the armature
may be taken as cut into the metal of the core so that it rotates
with the core.
If the armature is rotating at a very slow speed, the maximum
electric arc for that speed will be obtained by breaking the cir-
cuit while the armature is passing through the vertical positions
i8
ELECTRIC IGNITION
shown in Fig. 12, or while it is passing through positions very
near the vertical. The maximum spark will occur twice during
each revolution.
The positions of no spark are shown in Fig. 13. The neck of
the armature core is horizontal, or nearly so, in these positions,
so that the end view of the core resembles the letter H.
FIG. 14.
Maximum-spark Positions of Armature.
If the armature is rotated at a speed as high as 1200 revolu-
tions per minute, then its positions of maximum arc will be some-
what as indicated in Fig. 14, which positions are somewhat later
FIG. 15.
Sparkless Positions of Armature.
in the revolution than for slow speed of rotation. The positions
of no spark at high speed will be somewhat as shown in Fig. 15.
18. Laminated Armature Core. The rotation of the arma-
ture in the magnetic field induces electric currents, called fou-
cault currents, in the armature, as well as current in the winding
of the armature. If the core is made of one solid piece of steel
or iron, the foucault currents in it cause it to heat and are other-
wise objectionable. In order to keep this objectionable action
as small as possible, it is common practice to build up the core
ALTERNATING-CURRENT MAGNETOS 19
from thin sheet steel cut into I-shaped pieces. The steel used
for these pieces is commercially known as armature steel. The
pieces are generally cut out by a stamping press.
Fig. 1 6 shows a laminated armature core built up in this
manner. The " disks," or laminations, are sometimes separated
from each other by some such material as silk fabric or thin sheet
paper properly prepared by oiling or varnishing; in other cases,
FIG. 16.
Laminated Core of Shuttle Armature.
varnish or the black scale on the surface of the steel is depended
on as sufficient insulation. The sheet steel from which the disks
are cut is of about the thickness of that used for stovepipes.
The armature disks are pressed together under heavy pressure,
as that of a hydraulic press, after they have been grouped to
form the core. They are then fastened together by rivets or
other suitable means.
19. Magnetic Flux in a Rotating I-shaped Armature Core.
It has been stated that the electromotive force and current in
the winding of an armature are induced by changing the amount
of magnetic flux through the space surrounded by the coil. In
the shuttle-wound armature the variation of magnetic flux
occurs in the steel neck of the core on which the insulated wire
is wound.
Fig. 17 shows the general nature of the magnetic flux through
an I-shaped magnetic core during the time it is rotating between
the pole-pieces of the magnets. Only the end views of the core
and pole -pieces are shown in the figure. The pole-pieces are
marked N and S to indicate the north and south poles respec-
tively. The letter and the feathered arrow indicating the direc-
20
ELECTRIC IGNITION
(a)
FIG. 17.
Magnetic Flux through Shuttle Armature Core in Different Positions.
ALTERNATING-CURRENT MAGNETOS
21
FIG. 17 (continued).
Magnetic Flux through Shuttle Armature Core in Different Positions.
tion of rotation of the core may be considered as cut into the
metal of the core.
In (a) the core is in the H position and the magnetic flux
through it is from N to 5, as indicated by the lines with arrow
heads along them. This is one of the positions of the core in
which the greatest amount of magnetic flux occurs through the
neck that connects the crowned ends of the core. When the core
has been rotated to the position (b) there is less flux through it,
because less of the crowned ends, or sides, is opposite the pole-
pieces. The direction of flux for this position is in general as in-
dicated by the arrow-headed lines. When the core is in position
(c) there is very little flux through it, because the crowned surfaces
have almost entirely moved away from opposite the pole-pieces.
In the vertical position of the core, as shown in (d), there is
no longer any magnetic flux through the core -neck around which
the coil is wound in the complete armature. In other words,
the magnetic flux through the coil is of zero value when the core
is in the I position. There is some flux through the crowned
22 ELECTRIC IGNITION
ends of the core, however, from pole to pole, as indicated by the
arrow-headed lines; but this has no effect to produce electro-
motive force and current in the armature winding.
In position (e) the magnetic flux through the core -neck is in
the opposite direction from that in the first three positions, but
the flux is from the N pole to the S pole, as it always is.
In the first three positions the flux is through the core from
the arrow-marked side toward the blank side, but in position
(e) the flux is from the blank side toward the arrow-marked side
of the core, as is also the case in positions (/) and (g). In the
latter position the flux is again a maximum of the same value
as for position (a), but in the opposite direction through the core.
In positions (g), (ti), (i), (&), and (/) the paths of flux are similar
respectively to those in (a), (>), (c), (e), and (/), but the flux is
in the opposite direction through the core -neck on account of
the core being half a revolution further around in the positions
(h) to (/) than in (b) to (/). In position (j) there is no flux through
the core-neck, but the flux through the crowned sides of the core
is in the opposite direction from what it was in (d), on account
of a difference of half a revolution between the two positions.
Fig. 1 8 is a diagram representing the relative amounts of
magnetic flux through the core -neck of an H-armature for all of
its positions during one-half a revolution. The distance from
O vertically up to the curve is the amount of flux when the core
is stationary in the position shown in Fig. 17 at (a). The vertical
distance B, Fig. 18, is the flux when the core has been rotated
45 degrees to the position in Fig. 17 at (&). At Z>, where the
curve crosses the zero line, there is no flux through the core -neck.
This corresponds to position (d) in Fig. 17. When the armature
is in position (/), three-quarters of a revolution from the starting
position, the flux is equal to that for position (b) but in the
opposite direction. This is indicated in the diagram by taking
the distance F below the zero line.
When the core is rotating at a very slow but uniform speed,
the rate of change in the magnetic flux through the core -neck is
more rapid while the core is passing from position (c) to position
(e), and from position (i) to position (&), than during the other
ALTERNATING-CURRENT MAGNETOS
portions of the revolution. (The reason for limiting this and
the following statement to slow speed will appear later.) While
the core is passing through positions at and near those shown in
(a) and (g), the rate of change in magnetic flux through the core
is very low compared with the rate for the movements just
mentioned. In one position at or near (a), and another at or
Zero Line
J Revolution-
FIG. i 8.
Graph Showing Magnetic Flux in
Shuttle Armature.
FIG. 19.
Graph Showing Rate of Variation of
Magnetic Flux in Shuttle Armature.
near (g), the rate of change falls to zero. This is when the flux
stops decreasing and just before it begins increasing.
As the armature core moves from position (c) to position (e),
the decrease first occurs in the flux through the core -neck, fol-
lowed by reversal and increase of flux in the opposite direction
through the core-neck. These are together equivalent to a
continuous decrease of magnetic flux. The same is true for
the movement from position (i) to position (&).*
* This may possibly be more readily understood by considering a somewhat
analogous case in the flow of water, as follows: If two pipes are delivering water
into a reservoir at the same time, a large pipe at the rate of 50 gallons per minute,
24 ELECTRIC IGNITION
Fig. 19 shows the rate of change of magnetic flux through the
core-neck for all positions of the core during one-half a revolu-
tion, starting from position (a), Fig. 17. The vertical distance
C, Fig. 19, represents the rate of change of flux while the arma-
ture is passing through the position shown at (c), Fig. 17. The
rate of change for position (e) in the latter figure is shown as
the vertical distance E, Fig. 19. If the curve were given for the
second half -re volution, it would be below the zero line, since the
increase and decrease take place in opposite directions through
the core-neck from what they do in the first half -revolution.
20. Electromotive Force and Current Induced. If a coil of
insulated wire is wound around the core-neck, as in Fig. 20, so
as to form an armature, an electromotive force is induced in the
coil while the armature is rotating in the magnetic field between
the pole-pieces of the magnets. This electromotive force is pro-
portional, or nearly so, to the rate of change of the magnetic flux
through the core-neck. (A steady flux of magnetism of constant
amount does not induce an electromotive force.)
If the electric circuit is closed, a current will flow through the
winding whenever there is an electromotive force. In the figure
a complete closed electric circuit is obtained by connecting both
ends of the insulated wire to the metal of the core. These con-
nections are indicated by black spots and are numbered i and 2.
21. Armature Lag. It has been stated that the maximum
arc is obtained later in the revolution of the armature when the
speed of rotation is high than when it is low, and that this is due
to armature lag.
The armature lag is due to both the magnetic lag of the core
and a small pipe at the rate of 10 gallons per minute, then the rate of increase in
the amount of water in the reservoir is 50 + 10 = 60 gallons per minute. If
the flow of the small pipe is stopped and another pipe opened to draw water from
the reservoir at the rate of 10 gallons per minute, the rate of increase of water in
the reservoir will be reduced to 50 10 = 40 gallons per minute. The difference
between the two rates of increase is 60 40 = 20 gallons per minute.
An analogous case is that of first flowing water into a tank at the rate of 10
gallons per minute, then stopping the inflow and drawing out water at the same
rate. Drawing out water may be considered as a negative filling of the tank.
The difference between the two rates of filling, one positive and the other negative,
is 10 + 10 = 20 gallons per minute.
ALTERNATING-CURRENT MAGNETOS 25
and the lag of the current behind the induced electromotive force.
It requires an appreciable amount of time, in comparison with
the speed at which the magneto rotates on a high-speed multi-
cylinder motor, to change the rate of magnetic flux in a piece of
steel or iron. And the electric current lags slightly behind the
electromotive force that is induced by the change of magnetic
flux. The current lag is due chiefly to the action of the current*
in each turn (or single wrap) of the coil winding upon the cur-
rent in the other turns of the winding, and to the reaction of
the current upon the magnetism of the core. These and other
causes together produce armature reactance and lag.
Referring to Fig. 17, if (a) is one of the two positions of the
core for maximum magnetic flux through the core -neck when the
core is standing still or rotating at very slow speed, then at high
speed of rotation the maximum flux will occur slightly later in
the revolution of the core; that is, after the core has passed
slightly beyond the position shown in (a). And if (d) is one of
the positions for no flux through the core-neck when the core is
not rotating, then the position of no flux through the core -neck
will be somewhat further around in the direction of rotation at
high speed. Thus, position (e) may be the position of no flux
through the core -neck at excessively high speed of rotation. The
same applies to positions (g), (/'), and (k).
The reactions in the armature cause the maximum current to
occur somewhat later than the maximum magnetic flux, as has
been stated.*
22. Alternating Current Generated. For convenience in dis-
cussing the nature of the current generated in an armature wind-
ing, it will first be assumed that there is no lag in the armature.
Referring to Fig. 20, (A) is one of the positions of maximum
magnetic flux through the core-neck when the armature is stand-
ing still, and also when it is rotating, the latter in accordance
with the assumed condition of no lag. As the armature rotates
* It is not thought desirable to give any further discussion of armature react-
ance and lag in a work of this nature, especially as it is very probable that the
largest, or hottest, arc is obtained by breaking the electric circuit slightly before
the armature reaches the position which would give maximum current if the circuit
were left closed.
26
ELECTRIC IGNITION
(A)
zzQn
/
CD)
FIG. 20.
Direction of Current Flow in Winding of Shuttle Armature.
ALTERNATING-CURRENT MAGNETOS
(K) (L)
FIG. 20 (continued).
Direction of Current Flow in Winding of Shuttle Armature.
through the first quarter-revolution from position (A), the mag-
netic flux through the core-neck decreases, slowly at first, and
at an increasing rate till the armature has reached position (D)
at the completion of the quarter-revolution, in which position
there is no magnetic flux through the core-neck. The decrease
of magnetic flux through the core-neck causes an electric current
to flow through the insulated wire of the winding. The direc-
tion of flow of the current is as indicated by the arrows on the
wire. The path of the current is from 2 through the length of
the wire to i, and thence through the metal of the core from
i to 2. The current, beginning at zero value, keeps increasing
during the first quarter-revolution and reaches its maximum
value in position (D). From position (D) to position (G) the
current decreases until it drops to zero at the completion of the
first half -re volution, corresponding to position (G).
During the second half -revolution, from (G) to (L), a similar
28 ELECTRIC IGNITION
action takes place; but, since the coil has been turned over, the
direction of current flow through the wire is opposite that during
the first half -revolution. The direction of current flow during
the second half-revolution is indicated by the arrows on the wire
in (H)j (7), (/), and (K). It flows through the wire from i to 2.
Briefly, under the assumed condition of no lag, starting from
position (A), the current increases from zero to its maximum
value during the first quarter-revolution, and decreases to zero dur-
ing the second quarter-revolution; then increases to a maximum
in the opposite direction during the third quarter-revolution,
and decreases to zero again during the last quarter-revolution.
This action is repeated during each revolution. The speed of
rotation has been assumed to be constant.
An electric current of the nature just described is called an
alternating current.
The lag causes the maximum current to occur later in the
rotation of the armature than just stated. At a high speed of
rotation positions (E) and (K) may be those for maximum cur-
rent. Although the lag is very small as measured in fractions
of a second of time, it may be very appreciable when measured
in parts of a revolution of the magneto. Thus, a shuttle-wound
magneto that is igniting a six-cylinder four-cycle motor runs at
1800 revolutions per minute when the speed of the motor is 1200
revolutions per minute. The current must rise from zero to its
maximum value and drop back to zero again 3600 times per min-
ute, which is 60 times per second. The current has ^o of a second
to rise to its maximum and drop back to zero again. A lag of
yAo of a second corresponds to 3*0 of a revolution, which is 9
degrees of angle.
23. Graphical Representation of Current in a Shuttle-wound
Armature. Fig. 21 shows graphically the general nature of the
current generated in a shuttle-wound armature. The revolu-
tions of the armature are measured horizontally, and the amount
of current is measured vertically. The rotation is measured
from the position in which the magnetic flux through the core-
neck is a maximum when the armature is not rotating; this is
position (a) in Fig. 17, and position (-4) in Fig, 20. In the dia-
ALTERNATING-CURRENT MAGNETOS
29
gram, Fig. 21, the point of zero rotation is indicated by O. It
is assumed that the armature rotates at a uniform speed. The
current flow is represented by the curved line ABODE.
The current has zero value at A after the armature has rotated
through a small angle. The current increases and reaches its
maximum value at B slightly after the completion of the first
quarter-revolution. The maximum value of the current at this
point is BF. Decrease of current begins at B and continues till
zero value is reached again at C, which is half a revolution from
A. The flow of current then begins in the opposite direction
-One Cycle of Current
B
1 Revolution
FIGS. 21 and 22.
Current in Armature Winding as Affected by Different Forms of Pole-pieces.
and increases till it reaches maximum value again at D, slightly
after three-quarters of a revolution. This may be called a
negative maximum. Its value is DG. Decrease then begins
and the current falls to zero again at E, just after the completion
of the revolution.
24. Cycle of Current. The series of changes through which
the current repeatedly passes is called the cycle of the current.
In this case the complete cycle is passed through during one
revolution of the armature.
25. Form of Current Curve is Affected by Shape of Pole-
Pieces. The shape of the pole-pieces, especially at the edges,
ELECTRIC IGNITION
or lips, determines to some extent the form of the current curve.
The lips of the pole-pieces are the edges i, 2, 3, and 4 in Fig. 17,
view (b).
If the current curve in Fig. 21 is obtained with the pole-piece
lips rounded as in Fig. 17, then for sharp-edged lips like those
in Fig. 20 the current curve will be flatter and broader at the
top and bottom, somewhat as shown in Fig. 22. The maximum
current is not so great in the latter figure, but the current remains
large during a greater part of a revolution than in Fig. 21.
Two forms of pole-pieces, which give broad peaks of the nature
of those at b and d in Fig. 22, are shown in Fig. 23. In (A) the
(A) (B)
FIG. 23.
Pole-pieces with Rounded Lips and with Tooth-shaped Lips.
middle portions of the lips extend out farther than the ends.
In (B) one lip of each pole-piece is in the form of teeth which
resemble, in a measure, those of a comb. The lips with teeth
extend out farther from the magnet poles than those which have
smooth edges. The pole-pieces in (B) are for an armature that
rotates clockwise, so that the surface of the core that is next to
the pole-pieces moves away from the pole-piece lips with teeth
toward the smooth-lipped pole-pieces. Pole-pieces of the forms
of those shown in Fig. 23 give a more gradual rate of change in
the magnetic flux as the armature, or inductor, rotates than
occurs when the lips are straight as in Fig. 17.
26. Position of Armature for Maximum Arc. In accordance
with what has been stated, it may be seen that in a magneto
with a shuttle-wound rotating armature, the largest, or hottest,
arc is obtained by breaking the electric circuit while the armature
is passing through a position near that in which the crowned
ALTERNATING-CURRENT MAGNETOS
3 1
sides of the core span the space between the lips of the pole-
pieces, as in Fig. 20 at () and (K).
27. A low-tension alternating-current magneto with shuttle-
wound armature is shown in Fig. 24. The illustration is partly
a longitudinal section and partly full view, the latter being mostly
of interior parts.
The beginning of the armature winding is connected to the
armature core by means of a screw so as to make metallic (elec-
FIG. 24.
Bosch Low-tension Alternating-current
Armature Mounted on Plain Journal
per Revolution.
1. Field magnets, composite.
2 . Armature plain on journal bearings.
3. Insulated bolt to which one end of
armature winding is connected.
4. Terminal with binding nut.
5. Metal mounting for carbon brush
which presses against end of 3.
6. Front bearing-plate with plain
journal-bearing and felt wick
lubricator.
Magneto with Rotary Shuttle-wound
Bearings. Sectional View. Two Sparks
7. Rear bearing-plate with plain
journal bearing and felt wick
lubricator.
8. Felt wick with coiled spring under it.
9. Leather washer.
10. Wick holder.
11. Carbon brush with coiled spring.
16. Dust cover over armature.
20. Steatite insulating washer on ter-
minal 4.
trie) connection. The end of the winding is metallically con-
nected to the insulated bolt 3 which passes through the hollow
rear spindle and projects beyond the end of the spindle. The
black around the bolt 3 indicates insulating material. A carbon
32 ELECTRIC IGNITION
brush* mounted in a metallic holder 5 is pressed against the end
of the insulated bolt 3 by a coiled compression spring. The
three latter parts are carried in an insulated terminal 4, which is
provided with a thumb-nut for holding the end of the wire
through which current can be carried to other apparatus. A
steatite washer 20, to which the terminal 4 is firmly attached,
holds the terminal in place and insulates it.
The spindles of the armature are of the plain cylindrical
journal type and rotate in corresponding bearings in the plates
6 and 7. The surface of each journal slides over the surface of
its supporting bearing.
The carbon brush n is pressed against the rear head of the
armature by a coiled compression spring so as to make electric
connection between the metal of the armature and the body of
the magneto.
The path of the current that is generated in the armature
winding, assuming a direction of flow, is from the insulated end
of the armature winding through the insulated rod 3, carbon
brush and mounting 5, terminal 4, wire leading to the external
apparatus and through the latter, then back to the body of the
magneto, through the brush 1 1 to the armature head, from which
it flows to and through the core to the end of the winding which
is connected to the core. The current also passes through the
armature winding, of course.
If means, such as brush n, were not provided for flow of
* In the earlier forms of electric generators, or dynamo-electric machines, a
"brush" was a brushlike bundle of copper wires used to make sliding contact
between electric conductors for the purpose of allowing current to flow from one to
the other. By common usage "brush" has come to mean any form of electric
conductor that has sliding contact with another part for the purpose just stated.
Ordinarily the brush slides continuously over the part against which it bears.
The latter may be either all electric conductor, or it may be part conductor and
part insulator. In some cases the electric contact is continuous; in others it is
broken by insulation, on which the brush rubs part of the time. Either the brush
or the part on which it rubs may be stationary, or both may move so as to have
motion relative to each other.
A carbon brush may be made of pulverized charcoal or graphite mixed with
suitable binding material and compressed to the desired shape. Frequently fine-
woven copper or brass wire (wire gauze) is embedded in the carbon to allow the
current to flow more freely through the brush.
ALTERNATING-CURRENT MAGNETOS
33
current between the armature core and the body of the magneto,
the current would have to flow through the journal bearings.
This is objectionable, since there is a thin film of oil between the
rubbing metal surfaces of the journal and its bearing when they
are properly lubricated with oil. Oil is an insulator, and there-
fore prevents to some extent the flow of current even when the
film is as thin as in bearings of this sort. The electric resistance
of the oil film also causes heating of the rubbing surfaces and
FIG.
Bosch Low-tension Alternating-current Magneto with
Armature Mounted on Ball Bearings. Sectional View.
lution.
i. Field magnets, composite. 21.
2a. Armature on ball bearing.
4. Terminal with binding nut. 22.
5. Metal mounting for carbon brush
which presses against end of 21. 23.
6a. Front end-plate for ball race.
ya. Rear end-plate for ball race. 24.
i6a. Dust cover over armature.
20. Steatite insulating washer on ter- 25.
minal 4.
tends to burn the oil, thus injuring the effectiveness of lubrica-
tion. All of this is objectionable.
The journal bearings are each lubricated by means of a pencil-
shaped felt wick, one of which is shown at 8. It is pressed up
Rotary Shuttle-wound
Two Sparks per Revo-
Insulated bolt to which one end of
armature winding is connected.
Inside steatite insulator on arma-
ture.
Outside steatite insulator on arma-
ture.
Carbon brush with mounting and
coiled spring.
Screw cover.
34 ELECTRIC IGNITION
against the bottom of the journal by a coiled spring. The felt
wick and coiled spring are held in place by a wick-holder 10,
which is a hollow screw. A leather washer 9 is placed between
the screw head and the end-plate into which the wick -holder
screws, in order to make an oil-tight joint. The wick-holder
has a small hole, or holes, through its sides to let oil in to the wick
from the oil reservoir which surrounds the body of the wick-
holder. One of these small holes is shown in the wick-holder
which is screwed into the rear bearing plate 7.
Fig. 25 shows a low-tension magneto with ball bearings upon
which the armature rotates. While this magneto is the same in
its general nature as the one just described, it differs in the form
and location of some of its parts. There are no oil reservoirs
FIG. 26. FIG. 27.
External View of Magneto shown Splitdorf Low-tension Magneto. Two
Sectionally in Fig. 24. Sparks per Revolution.
and no wick-oilers, since the ball bearings require only a few
drops of oil once a month or so. The brush 24 for making elec-
tric connection between the armature head and the body of the
magneto is at the head end of the armature instead of at the rear
end as in the other machine, and is perpendicular to the spindles
instead of parallel to them. The caption immediately beneath
the illustration describes the parts briefly.
Fig. 26 is a full view of the magneto shown in section in Fig. 24.
ALTERNATING-CURRENT MAGNETOS
35
The driving end of the armature spindle is shown projecting
forward from the front end of the machine.
Fig. 27 is a full view of a similar magneto showing the rear
end and the projecting terminal to which a wire leading to other
apparatus can be connected.
Stationary Shuttle-wound Armature Types.
28. Stationary Armature and Rotary Magnetic Sleeve. In-
stead of rotating the armature, it may be held stationary and
the required magnetic flux through the core-neck obtained by
rotating an inductor, having the form of a slotted soft steel
sleeve, between the armature and the pole-pieces, the latter being
bored considerably larger in diameter than the armature, so as to
leave space in which the sleeve can rotate.
Fig. 28 shows a magnetic sleeve for rotating between a sta-
tionary armature and the pole-pieces. The armature is shown
82
FIG. 28.
Rotary Magnetic Sleeve Inductor for a Magneto with a Stationary
Armature of the Shuttle Type.
FIG. 29.
Stationary Shuttle-wound Armature to go inside of the Magnetic Sleeve
shown in Fig. 28.
in Fig. 29. It is of the same general form as a rotary shuttle-
wound armature. When the parts are assembled the armature
lies inside the sleeve.
The two sides of the magnetic sleeve have the form of pieces
ELECTRIC IGNITION
cut from a tube by slotting it lengthwise. They are of mild steel
as already stated, and are held together by disk-shaped heads
(G) (H)
FIG. 30.
Magnetic Flux through Stationary Armature Core and Rotary Sleeve.
of non-magnetic material, such as brass, bronze, or aluminum
alloy, attached to them by suitable fastenings (screws in this
case). One of the heads has a driving spindle.
ALTERNATING-CURRENT MAGNETOS 37
29. The action of the magnetic sleeve in causing a variation
of magnetic flux through the core-neck of the armature can be
understood by reference to Fig. 30, in which the sleeve is shown
in all of its positions for maximum magnetic flux and for no flux
through the core-neck, no allowance being made for armature
lag. The direction of rotation of the sleeve is indicated by the
feathered arrow, which may be taken as stamped on the end of
the sleeve. The general direction of magnetic flux is indicated
by the lines with arrowheads along them.
In (A) there is no magnetic flux through the core-neck, but
a slight amount occurs through the crowned sides of the core.
In (B) the flux has a maximum value through the core-neck from
top to bottom; this position is about one-eighth of a revolution
later than (A). In (C) the sleeve bridges the gap between the
pole-pieces, and there is no flux through the core-neck. In (D)
the flux again has a maximum value through the core-neck, from
bottom to top, which is in the opposite direction from the flux
in (B). In (E) there is no flux through the core-neck. This
completes the first half -re volution, starting from position (A).
It may be noted that the flux, and consequently the current,
reaches maximum value twice during half a revolution, and since
the flux is in opposite directions in (B) and (D), the current
flows in opposite directions in these two cases. An alternating
current is therefore generated.
During the latter half of the revolution the variation of flux
through the core-neck is the same as that during the first half-
revolution. The current therefore passes through two complete
cycles during one revolution. An arc can be drawn four times
per revolution by breaking the circuit at or about the time maxi-
mum current occurs.
The field-magnets and pole-pieces for a magneto with a sta-
tionary shuttle-wound armature and rotary magnetic sleeve can
be of the same form as those for a rotary shuttle armature.
30. Note. There are several types of magnetos designed
especially to deliver low-tension alternating current for use in
high-tension ignition systems. The more important of these will
be described in connection with high-tension ignition.
CHAPTER III.
DIRECT-CURRENT MAGNETOS.
31. General. By the use of a suitable form of armature
between the pole-pieces of permanent magnets, a direct current
can be obtained. The same magnets and pole-pieces can be
used as for the shuttle-wound armature, but the armature core
FIG. 31.
Elementary Form of Drum Armature between Pole-Pieces of Magnets.
is different. Several forms of cores are used, among which one
in the form of a cylinder, and another having the form of a ring,
are most common. The cylinder generally has lengthwise slots
to receive the winding. An armature with a cylindrical core is
38
DIRECT-CURRENT MAGNETOS 39
generally known as a drum armature. This applies whether
the core has a smooth cylindrical surface or is slotted as just
stated.
32. Elementary Form of Drum Armature. A cylindrical core
A with one turn of insulated wire W around it is shown in Fig. 31
in the magnetic field between the pole-pieces of a set of permanent
magnets. The wire is continuous (without ends). The mag-
netic flux is from the N pole across the air-gap between the N
pole and the core to the core, through the core and across the
air-gap between the core and the S pole to the latter. The same
number of lines of magnetic force pass through the smooth cylin-
drical core whatever its position with regard to rotation about
its axis. This is also approximately true of a slotted cylindrical
core of the usual form.
33. Generation of Current. When this elementary armature
is standing in the position shown in Fig. 31, all of the magnetic
lines of force in the core pass through the space inclosed by the
wire. Other positions of the armature are shown in Fig. 32.
When in position (A) part of the magnetic flux through the core
passes through the space inclosed by the loop of wire, and part
passes outside of the loop. In (B) none of the flux is through
the space inclosed by the loop. In (C) part of the flux in the
core is through the coil space, and in (D), half a revolution from
the position in Fig. 31, all of the flux through the core passes
through the coil. The direction of the flux through the coil
space is in the opposite direction in (D) t relative to the coil,
from its direction in Fig. 31, where it enters the coil space from
the side next to the feathered arrow cut into the core. In (D)
the flux enters the coil space from the side opposite the feathered
arrow, which rotates with the core and coil.
When the armature is rotating, the positions at which all of
the flux in the core passes through the coil, and those at which
none of the flux- passes through the coil, occur later in the revo-
lution on account of magnetic lag and the reactions which occur
on account of the electric current generated in the coil and other
parts.
For convenience in discussing the manner in which a direct
ELECTRIC IGNITION
FIG. 32.
Current Flow in Winding of Elementary Drum Armature.
current is obtained, the effect of magnetic lag and armature
reactions will be neglected.*
As the armature passes through the position shown in Fig. 32
at (X) while rotating in the direction indicated by the feathered
arrow, electromotive force is generated in the wire of the coil
and current flows through the wire in the direction indicated by
* It is not thought necessary to discuss more fully the effect of cross-magnet-
ization and armature reactions.
DIRECT-CURRENT MAGNETOS 41
the arrow on the wire. The direction of current flow is similarly
indicated in (), (C), (), and (F). There is no current flow
in position (D) and in the position shown in Fig. 31. The elec-
tromotive force at any instant is proportional to the rate at
which the stretches of wire along the cylindrical surface of the
core are cutting through the lines of force. This rate corre-
sponds to the rate of change in the amount of magnetic flux
through the space inclosed by the coil. The current is approxi-
mately proportional to the electromotive force at any instant.
In the positions shown in Fig. 31, and at (D) in Fig. 32, the wire
is not cutting through lines of magnetic force, hence there is
neither electromotive force nor current.
In (E) and (F) the direction of current flow through the wire
is opposite that in (A), (B), and (C). In (E) and (F) the arrow
indicating the direction of flow through the stretch of wire
across the front end of the core points in the same direction as
the feathered arrow engraved in the end of the core, while in
positions (A), (B), and (C) the arrows point in opposite direc-
tions. The reason why the current changes its direction of flow
has been discussed in 22. It should be noted that the direction
of current flow through the portion of the wire that lies across
the end of the armature core is always from the S pole toward
the N pole when the armature is rotating clockwise. In other
words, the current flow through the wire next to the south pole
is always toward the observer when the rotation is clockwise.*
34. Commutation of Current in a Direct-current Generator.
In Fig. 33 the coil of wire is cut in two at the front end and the
ends fastened to two parts, i and 2, which are approximately
half-rings of metal. Brushes, 3 and 4, of metal, carbon, or some
other conductor of electricity, bear on the rings at points (really
areas) diametrically opposite each other. From these brushes
wires connect to an external circuit 5. While the armature is
rotating clockwise through the position shown, the current flows
from brush 3 (next to the S pole) to the external circuit 5, through
the external circuit and then to the brush 4. This continues as
* If the rotation were in the opposite direction, the current flow would also
always be in the opposite direction from that indicated.
ELECTRIC IGNITION
long as brush 3 is in contact with segment i and while current is
generated in the armature coil. When the armature reaches a
position similar to that in Fig. 31, which may be called the
" dead " position of the coil, the open spaces between the two
segments have come under the brushes. The brushes therefore
change from one segment to the other of the ring while no current
is flowing, and consequently there is no spark formed during this
VWWIAAJ
FIG. 33 .
Two-segment Commutator and Brushes of Elementary Drum Armature.
change from one segment to the other. When segment 2 is alone
in contact with brush 3 and current is again generated, the flow
is, as before, from brush 3 through the external circuit 5 to brush 4.
By the use of this two-segment commutator the flow of current
through the external circuit is caused to be always in the same
direction. The flow of current in the armature wire alternates
as before, however.
Since the flow of current is always from brush 3 to the external
circuit, this brush is called the positive brush and is usually indi-
cated by the sign +. The other brush, 4, toward which the
current flows, is indicated by the sign , and is called the
negative brush.
DIRECT-CURRENT MAGNETOS 43
A current which flows in one direction only is called a direct
current. As produced by the elementary generator shown in
Fig. 33, it is intermittent, or, more specifically, pulsating.
35. Continuous-current Electric Generator. In order to ob-
tain a continuous current it is necessary to use more than one
armature coil and more than two commutator segments. To
operate successfully for the usual requirements, the coils are
spaced uniformly around the core, and the commutator segments
are all of the same width circumferentially. In the more usual
constructions there is the same number of commutator segments
as there are coils, but not infrequently twice as many commutator
segments as coils are used. Each coil may have only one turn,
as in Fig. 33, or each may have several turns, or wraps. It is
probably that in all direct-current generators intended for igni-
tion purposes, each armature coil has several turns.
FIG. 34.
Thin Disk of a Laminated and Slotted Drum Armature.
36. Laminated Drum Armature Core. In the better genera-
tors for direct current the armature core is built up of a number
of thin disks cut from sheet metal and placed side by side in the
same manner as has been described for shuttle-wound armatures
and for the same reason. One of the disks for a direct-current
generator is shown in Fig. 34. The metal is cut out at regular
44
ELECTRIC IGNITION
intervals around the periphery to leave openings which, when
the disks are grouped together in the armature, form the slots
in which the wire is wound. The central opening is for the
armature spindle, which is usually all in one piece and passes
through the core. It is good practice to place a brass sleeve, or
quill, between the steel spindle and the core-disks.
37. A complete drum armature for direct current is shown in
Fig. 35. This armature has 12 coils, each of several turns of
FIG. 35.
Drum Armature of Direct-current Electric Generator.
wire wound in the slots of the core, and 12 segments in the
commutator.
38. A commutator similar in general form to that on the arma-
ture in the preceding figure is shown in Fig. 36, in which (A) is a
/- x .. ..
(A) (B)
FIG. 36.
Commutator for Direct-current Electric Generator. Twelve Segments.
view of the complete commutator, and (B) is a longitudinal sec-
tion. The segments are dove-tailed and held in place by the
DIRECT-CURRENT MAGNETOS 45
correspondingly dove-tailed inner sleeve and ring. Insulation i
is placed between the adjacent copper segments, and at 2, 3, 4,
and 5 between the segments and the metal sleeve. The annular
space 6 may or may not have insulation in it, according to the
will of the designer. There is a possibility of moisture collecting
in this space if it is not filled with insulation. The insulation
between adjacent segments must be of some material that will
withstand heat and is not readily burned by the sparks that
form as the brushes pass from one segment to the next, especially
when the brushes are not properly set. Mica or some composi-
tion composed chiefly of mica is used for this insulation.
Various methods of fastening the ends of the armature coils
to the segments are used. A common one is to notch or slit the
end of the segment and solder the wire into the notch. A hard
solder (one that does not melt at a low temperature) should be
used, so that it will not melt and fly out in case the commutator
becomes hot. It is well to swedge the segment down on the
wire to prevent the latter from flying out in case the solder melts.
Screws are sometimes used to fasten the wire to the segments,
but they are apt to become loose, unless soldered, on account of
the expansion and contraction due to heating while in service
and cooling while at rest.
39. Armature Connections. Fig. 37 is a diagram showing
conventionally how the ends of the armature coils are brought to
the segments of the commutator. This diagram is for an arma-
ture with 12 coils and the same number of commutator segments,
intended for use in a bipolar generator. Only one turn of wire
for each coil is represented, but each coil may have several turns.
Starting at segment i, connection is made to one side A of a
coil lying in a slot of the core. Side A is connected, across the
back end of the core, to the side A' of the same coil, and A' is
connected to the segment 2. Segment 2 is also connected to B,
which is connected across the back end of the core to B', and the
latter is connected to segment 3. The same method of connec-
tion is followed out for all of the coils, thus: 3, C, C', 4; 4, D, D',
5; and so on to 12, L, L', i.
The coils are not shown connected in the successive order in
46 ELECTRIC IGNITION
which they have to be wound on the core. The successive order
of winding is A, H, C, J, E, L, G, B, 7, D, K, F. If the coils
were connected to the commutator in the order of their winding,
as just given, the lengths of the different circuits through the
FIG. 37.
Winding Diagram of Direct-current Armature with Twelve Coils and Twelve
Commutator Segments.
armature would not be uniform, and the armature would not
operate as satisfactorily as when the connections are made as has
been shown.
The direction of current flow through the connections to the
commutator is indicated by the arrowheads on the lines repre-
senting the connections.
The brushes are shown in contact with the commutator, and
are indicated as positive and negative by the signs + and .
It can be seen that the -f brush electrically connects the seg-
ments i and 2, to which the ends of the coil A are attached, when
DIRECT-CURRENT MAGNETOS
47
the armature is in the position of its rotation shown in the dia-
gram. The brush bridges the insulation between i and 2. This
corresponds to the connection that occurs between the two half-
Direct-current Magneto.
1. Field magnets.
2. Pole-pieces.
3. Armature.
4. Brass tube enclosing armature.
5. Commutator.
6. Brush that bears on commutator.
7. Brush-holder. Insulated.
8. Insulation between brush-holder
and tube 4.
9. Insulation around screw that holds
brush-holder in place.
10. Coil-spring for pressing brush 6
against commutator.
FIG. 38.
Hercules Electric Co., Indianapolis, Ind.
11. Terminal for external wire.
12. Bearing for armature spindle.
13. Bell-shaped friction pulley.
14. Friction facing of pulley 13.
1 5 . Collar for speed governor.
16. Governor balls and arms.
17. Governor spring.
18. Setscrew.
19. Base of magneto.
20. Clamps for holding magnets against
pole-pieces.
21. Clamp bolt.
22. Name plate.
rings in Fig. 33 when the armature in the latter figure has rotated
one-quarter revolution from the position shown. But in Fig. 3 7
the coil A is in its dead position when thus short-circuited by
48 ELECTRIC IGNITION
the brush, just as the coil is in Fig. 33 when the ends of the half-
rings are under the brushes, therefore no electromotive force is
induced in the coil to cause current flow in that coil which would
cause sparking at the brush when segment 2 passes from contact
with the brush and thus breaks the short-circuit of coil A . The
same applies to coil G, which is shown short-circuited by the
negative ( ) brush. It also applies to all the other coils as
their segments pass successively under the brushes.
40. A complete direct-current magneto for giving a continuous
current is shown in Fig. 38. The armature is surrounded by a
brass tube 4 through which the pole-pieces project so as to come
FIG. 39.
Photographic View of Direct-current Magneto shown in Fig. 38.
close to the armature. This tube, together with the heads which
carry the spindle bearings, form a dust- and water-proof protec-
tion for the armature. The brushes are made of phosphor-bronze
wire gauze pressed in dies to a suitable form around a carbon
core. The carbon acts as a lubricator for the rubbing surfaces
of the brushes and commutator. A bell-shaped friction pulley
13 is carried on the driving end of the armature spindle. This
pulley is faced with a suitable friction material, such as leather,
paper composition, or rawhide, which is pressed by spring action
axially against a rotating part, such as a flywheel or pulley that
drives the friction pulley. The speed of rotation of the armature
is controlled by a shaft governor of the fly-ball type. The balls
DIRECT-CURRENT MAGNETOS
49
are drawn toward each other radially by a pair of coiled tension
springs, one of which, 17, is shown. As the speed increases the
balls move out radially and reduce the pressure between the
FIG. 40.
Direct-current Magneto with Friction Pulley and Speed Governor. Tritt Elec-
tric Company, Union City, Indiana.
facing of the friction pulley and the flywheel. This action allows
the friction pulley to slip enough on the flywheel to keep the
speed of the armature down to the required rate.
Fig. 39 is a photographic view of a direct-current magneto of
the general type shown in the preceding figure. Fig. 40 illus-
trates another machine that operates in a similar manner.
CHAPTER IV.
TESTING FOR DIRECTION OF CURRENT.
Chemical Tests.
41. Water Test. Bubbles Form at Submerged Wire-End. -
To about half a pint of water in a glass tumbler or other vessel
that is not a conductor of electricity add any one of the following :
Common salt (NaCl), one teaspoonful;
Common washing soda (sal soda, Na 2 CO3), one teaspoonful;
Sulphuric acid (H 2 SO 4 ), half teaspoonful of the strength sold
at drug stores;
Hydrochloric acid (HC1), half teaspoonful of the strength sold
at drug stores.
Connect a small wire with each of the two brushes of a direct-
current generator, or with the positive and negative terminals of
any source of direct-current supply, and dip the free bare-metal
ends of the wires into the impure water, first keeping the ends
as far apart as possible and then gradually bringing them toward
each other, without allowing them to touch.
Bubbles of gas will form on and rise from the submerged end
of the wire that is connected to the negative ( ) side of the
source of direct-current supply. (This test does not apply to
alternating current.) With the small currents and pressures
commonly used for ignition purposes, there is no appreciable
formation of bubbles at the positive wire-end.
There are numerous other substances that can be used for
adding to the water to make it impure for the direction-of -current
test. In fact, water from city mains often contains enough
matter in solution to make it impure enough (chemically speak-
ing) for this test.
The passage of the direct current through the impure water
decomposes it into its chemical elements, hydrogen and oxygen,
each of which is a gas. This action is more or less indirect so
50
TESTING FOR DIRECTION OF CURRENT $1
far as the water itself is concerned. The hydrogen is liberated
at the negative terminal. When water is decomposed it gives
two volumes of hydrogen for each volume of oxygen. The
oxygen tends to collect at the positive terminal, but at least
part of it is absorbed by the water and thus disappears so far as
its being a gas is concerned.
Each of the submerged ends of the wire is called an electrode.
The liquid, in this case impure water, is called the electrolyte.
The positive electrode (the one connected to the positive side of
current supply) is called the anode, and the negative electrode
is called the cathode.
The decomposition of the water sets up a counter-electromotive
force of about 1.48 volts. This is about the maximum electro-
motive force of one cell of ordinary dry electric batteries such
as are in common use for ignition. One cell of such a battery
will not therefore generally give bubbles at the electrode in this
test. At least two cells must be connected in series to make
certain of producing bubbles. Different methods of connecting
cells to form a battery are given later.
42. Color Test. If a tablespoonful of sal ammoniac (ammo-
nium chloride, NH 4 C1) is dissolved in half a pint of water, and
the bare ends of two wires placed in the liquid as described in
the preceding article, the liquid around the positive terminal,
or anode, will turn blue, and bubbles will form at the negative
terminal, when current flows.
There are several substances that will give color tests of this
nature. Different colors are obtained according to the sub-
stances used.
Convenient devices for making color tests are found on the
market. A small glass tube some two inches in length, set in a
mounting and having suitable terminals, is a convenient form.
The instrument should be marked so that there can be no mistake
in determining which of the two wires connected to it to test
them is positive or negative.
ELECTRIC IGNITION
Test with Magnetic Needle.
43. Magnetic-compass Test. Place the wire which carries
the current immediately above the case in which the magnetic
needle is mounted, as in Fig. 41, so that the direction of the wire
is the same in general as the length of the magnetic needle. If
the wire is not insulated it is best not to let it touch the metal
of the case. It is immaterial whether it touches the glass. The
Positive
Negative
Negative
(A)
FIG. 41.
Magnetic Compass Indicating Direction of Flow of Electric Current by the
Deflection of the Needle.
needle will be deflected from its north-and-south position during
the time a direct current flows through the wire placed in this
position.
If the current flows from the north toward the south above
the needle, it will be deflected in a clockwise direction as indicated
at (A). In other words, the needle will be turned through part
of a revolution in the same direction that the hands of a clock
rotate.
A current from the north above the needle turns it clockwise is a
convenient expression by which to remember the action of a
direct current on a magnetic needle.
TESTING FOR DIRECTION OF CURRENT 53
If the current flows in the opposite direction (toward the
north) above the needle, it will be rotated in the opposite direc-
tion as shown in (B). By placing the wire beneath the needle,
the action on the needle will be the reverse of that when the wire
is above the needle.
44. Extemporized Compass Needle. An ordinary sewing
needle magnetized and floated on water in a non-magnetic vessel
can be conveniently used in the absence of a compass. The
needle can be magnetized by bringing it in contact with a magnet,
or by means of an electric current. The latter method is ex-
plained in Chapter VI.
If the sewing needle is highly polished, as when new, it can
be floated on water by first drying it and then rubbing it with
a slightly oily cloth or one's fingers, slightly oily. If then laid,
or dropped lightly, on the water it will float and quickly assume
a north-and-south direction. A needle that is bright and prop-
erly oiled will float a day or more. The action of the electric
current upon this floating needle is the same as on the pivotally
supported needle in a compass.
Another method of floating the needle is to lay it on, or stick
it through, a flat piece of cork or paraffin.
A cup or saucer is convenient for holding the water. A brass,
copper, or aluminum vessel will answer, but the wire, if bare of
insulation, should not be allowed to touch the vessel in two
places at the same time. A steel or iron vessel is not so satis-
factory on account of the tendency of the needle to float up
against the side.
45. Test with Measuring Instruments. Many of the amme-
ters and voltmeters for measuring current and pressure are made
so that the direction of the current flowing through them can
be told. The terminals of the instrument are marked + and ,
or P-\- and N . The indicating needle, or pointer, of the
instrument moves so as to give a reading on the graduated scale
only when the wires are connected to the instrument terminals
in accordance with the signs; the positive wire to the terminal
with the + sign, and the negative wire to the terminal with
the sign.
CHAPTER V.
ELECTRIC MEASURING INSTRUMENTS.*
46. General. It is often desirable to test a battery to deter-
mine its condition by measuring its voltage and the amount of
current that it will give; also to measure the amount of current
that an ignition system is using. For this purpose numerous
types of small portable instruments have been developed, and a
lesser number of instruments intended to be fixed in place. The
smaller portable instruments frequently resemble a watch or
pocket compass in general appearance, and are about the size
of a large watch. These instruments ordinarily operate on the
principle that an electric current flowing through a coil of wire
attracts or repels a permanent magnet or a piece of magnetic
material and causes it to move when it is mounted so as to allow
movement, or upon the principle that
two coils of wire with current flowing
through them attract or repel each other
so that one coil is moved when mounted
for such movement.
The chief difference between the am-
meter, for measuring current, and the
voltmeter, for measuring pressure, is
that the ammeter has a coil, or coils,
of comparatively thick wire of short
length which has a very low resistance,
and the voltmeter has a coil, or coils,
Portable Ammeter for Measur- of very thin wire of great length and
ing Electric Current. Small verv frjgh resistance.
47. Ammeters. A small portable
ammeter for measuring current up to 30 amperes is illustrated in
* This chapter is intended to deal with only such measuring instruments as
are used in connection with ignition systems, and only to an extent sufficient to
give a general idea of their nature and use. It is not thought desirable to go into
details of measuring instruments in a work of this nature.
54
FIG. 42.
ELECTRIC MEASURING INSTRUMENTS
55
Fig. 42. The indicating needle (pointer, hand) which indicates
the amount of current flowing through the ammeter is pivoted
at the center of the instrument and shown pointing to zero of
the graduated scale. When current is flowing through the in-
strument, the needle is deflected and points to the reading that
FIG. 43.
Stationary Ammeter. Weston Electrical Instrument Company, Newark,
New Jersey.
corresponds to the number of amperes of current flowing. One
of the terminals is the projection at the bottom of the case, and
the other is at the free end of the attached wire.
When testing a primary battery, one terminal of the ammeter
is electrically connected to one terminal of the battery, and the
56 ELECTRIC IGNITION
other terminal of the ammeter is electrically connected to the
other terminal of the battery. Current from the battery then
flows through the ammeter. (The ammeter should not be used
in this manner for testing a storage battery, unless the instru-
ment is especially designed for such use, and current should not
be allowed to flow longer than necessary to obtain a reading
not longer than two or three seconds.)
TO measure the current flowing through any circuit, the am-
meter must be interposed in the circuit (cut into the circuit) so
that all of the current of the circuit will flow through the am-
meter. Thus, the ammeter may be cut into a circuit that has
a wire held by a binding screw, by disconnecting the wire from
the binding screw and connecting one terminal of the ammeter
to the binding screw, then connecting
the other terminal of the ammeter to the
disconnected end of the wire.
Fig. 43 is a high-grade ammeter in-
tended to be used in a fixed position, as
on a switchboard. Its range of current
is from zero to 50 amperes. Similar
instruments are made with ranges re-
spectively up to i, 5, 10, 15, 25, and 75
amperes.
48. Voltmeters. Fig. 44 is a small
TIG. 44. portable voltmeter reading up to 10
Portable Voltmeter for Measur- volts. It resembles, in general appear-
ing Electric Pressure. Small ance? ^ sma n ammeter just described.
One terminal is at the bottom of the
case, and the other at the free end of the attached wire.
For measuring voltage, the terminals of the voltmeter are
electrically connected to the two points between which the
pressure is to be measured, one terminal of the voltmeter to
each point. It is immaterial whether the circuit is otherwise
open or closed between the points of connection, so far as the
action of the voltmeter is concerned. Thus, the voltage of a
battery can be measured by connecting the terminals of the
voltmeter to the terminals of the battery, either while the battery
ELECTRIC MEASURING INSTRUMENTS 57
has no other connection to it (on open circuit), or while the
battery is connected in circuit and delivering current for its
regular service. The reading of the voltmeter will not generally
be the same under the two conditions, but this is because the
difference of pressure between the battery terminals is not the
same while it is delivering current as when it is on open circuit.
The amount of current that flows through the voltmeter while
measuring pressure is so small as to have no appreciable effect
on the action of the battery or the circuit to which the voltmeter
is connected.
49. Volt-ammeters. It is quite usual to combine a volt-
meter and an ammeter in one instrument, called a volt-ammeter.
In some of these only one indicating needle (hand, pointer) is
used, and the reading scale has two graduations, one for amperes
and the other for volts. Such an instrument cannot be used
for measuring both current and pressure at the same instant.
Other volt-ammeters are made up of two complete instruments,
a voltmeter and an ammeter, and can be used for measuring
both current and pressure at the same time.
Fig. 45 is a small portable volt-ammeter of the type having
only one indicating needle. The reading scale is graduated to
'10 volts and 30 amperes. The instrument has three terminals.
The one at the top is for both volts and amperes. The left-
hand one at the bottom is for volts, and the other for amperes.
For measuring purposes, the top terminal and the left-hand one
at the bottom are connected respective to the points between
which the pressure is to be measured. For measuring current,
the connections are made to the top terminal and the right-hand
lower terminal.
A comparatively small volt-ammeter for use in connection
with storage batteries (see Fig. 102) is shown in Fig. 46. Only
one indicator needle is used. The needle is shown in its zero
position, which is not at the end of the graduated scale. The
lower scale is for amperes, and is graduated in both directions
from its zero. When the instrument is used as an ammeter,
the needle is deflected either to the right or the left, according
to the direction in which the current is flowing through the
ELECTRIC IGNITION
instrument. To obtain a voltage reading, the push-button V
below the scale is pressed in and held while taking the reading.
FIG. 45.
Volt-ammeter for Measuring Both
Pressure and Current. Small
Pocket Form.
FIG. 46.
Stationary Volt-ammeter Which Indi-
cates the Direction of Current Flow.
Apple Electric Company, Dayton,
Ohio.
The voltage scale is graduated in only one direction from zero.
In Fig. 47 two complete instruments, a voltmeter and an
FIG. 47-
Ammeter and Voltmeter Mounted Together Permanently.
ammeter, are mounted on the same base. They can both be
used at the same time, and used continuously. The instrument
ELECTRIC MEASURING INSTRUMENTS 59
is so constructed that it can be used on vehicles. The upper
(middle) terminal is connected to both instruments. The right-
hand terminal is for the voltmeter only, and the left-hand terminal
is for the ammeter only.
50. " Dead-beat " Indicating Needle. Unless some means
is provided for quickly bringing to rest the indicating needle of
a voltmeter or an ammeter, the needle will continue vibrating
for a considerable time after the current is first sent through the
instrument. When the instrument is moved, as on a vehicle or in
one's hand, the needle may never come to rest. This vibration
of the needle makes it impossible to take an accurate reading.
The better class of instruments are constructed so that the
needle comes to rest quickly and stands almost without vibration
even when the entire instrument is subjected to a reasonable
amount of motion, yet is sensitive in its movement to indicate
variation in the current or pressure. Such an indicating needle
is said to be " dead-beat." This dead-beat effect is generally
obtained by constructing the instrument so that the movement
of the needle and its attached parts set up foucault currents that
in turn resist the movement of the parts to which the needle is
attached. This damping action is of much the same nature in
its effect as that which can be obtained in a stationary instru-
ment by attaching a vane, or wing, to the spindle on which the
needle is mounted, and submerging the vane in a liquid.
CHAPTER VI.
ELECTROMAGNETS.
51. Plain Bar Electromagnet. If an insulated wire is
wrapped around a bar of iron or steel as shown in Fig. 48, and
a direct current of electricity sent through the wire, the bar will
become a magnet and remain so as long as the electricity con-
tinues flowing. When the current stops, the bar will lose nearly
c
f
c
(B)
FIG. 48.
Electromagnets of Straight Bar Type.
all of its magnetism if it is of commercially pure soft iron or
steel. A small amount of magnetism will remain. This is called
residual magnetism. If the bar is hardened, or tempered like
a sewing needle, knitting needle, or a file for working steel, it
will retain a considerable amount of magnetism and be, for a
while at least, a permanent magnet. If of the quality and con-
dition of steel used for permanent magnets, it will remain a per-
manent magnet after the current stops and the bar is removed
from the coil.
If the current flows in the direction indicated by the arrow-
heads on the wire, then the upper, or top, end of the bar will be
60
ELECTROMAGNETS
61
a north pole, and the lower end, or bottom, of the bar a south
pole. This applies to both (A) and (B) in the figure. If the
current is made to flow in the opposite direction from that indi-
cated, then the lower end of the bar will be a north pole, and
upper end a south pole. The magnetic flux in the bar is from the
south pole to the north pole.
If the bar is held before the dial of a clock with one end point-
ing toward the dial, and current is flowing through the wire in
the direction of rotation of the hands of the clock, then the lines
of magnetic force will flow through the bar toward the clock.
The north pole will be next to the clock.
Another method of determining which is the north pole is as
follows: If the bar is vertical and the current in the portion of
the coil between the observer and the bar
flows east while the observer is looking
north, then the north pole is at the top.
If the bar is horizontal at the level of the
observer's eyes, and the current in the por-
tion of the wire between the observer and
the bar flows downward, then the north pole
is at the right-hand end.
52. Plunger-core Electromagnet. Fig.
49 shows a non-magnetic spool i with a
coil 2 of insulated wire wound around it. It
may be assumed that the coil is supported
in a vertical position. An iron or steel bar
3 is shown with its upper end projecting a
slight distance into the opening through
the spool. It may also be assumed that no
current is passing through the coil, and that the bar is resting
on some support, such as a table.
If an electric current, sufficiently large, is passed through the
coil, the core will be drawn up into the spool and will remain
suspended there as long as the current continues flowing through
the coil. The bar will remain in the central part of the spool
opening without touching any part. Its middle will be somewhat
below the middle of the coil, on account of the weight of the bar.
FIG. 49.
Electromagnet with
Plunger Core.
62
ELECTRIC IGNITION
As soon as the current is stopped the bar will fall. The current
must be direct (not alternating).
As indicating the force with which the bar is drawn upward, it
can be shot up completely through
and above the spool if the current
is stopped while the bar is still
moving rapidly upward just after
the circuit has been closed.
53. U-shaped Electromagnet. -
Fig. 50 shows an electromagnet
shaped like the letter U in an in-
verted position. When a direct
current flows through the winding
as indicated by the arrowheads,
the poles are N and S, according
F IG> 5a to the marking on the bar in
U-shaped Electromagnet. the % ure * If the current flows
in the opposite direction, the po-
larity of the poles is changed.
It can be seen that, when looking at the ends of the bar, the
FIG. 51.
Ring Electromagnet with Consequent Poles.
current flows clockwise around the south-pole leg of the bar,
and counter-clockwise around the north-pole leg of the bar. The
ELECTROMAGNETS
winding is as if the whole coil had been wound on a straight
bar, and the bar then bent to the U-form.
FIG. 52.
Ring Electromagnet with Two Projecting Poles.
FIG. 53-
Four-pole Ring-shaped Electromagnet.
By attaching suitably formed pole-pieces to the ends of the
bent bar, it can be used for furnishing the magnetic field of an
electric generator.
64 ELECTRIC IGNITION
54. Ring-shaped Electromagnet with Consequent Poles. A
plain ring of iron or steel can be magnetized electrically so as to
make a north pole and south pole as indicated in Fig. 51. The
manner of winding the coil and the direction of current are
indicated in the figure. Poles located in this manner are called
consequent poles.
By attaching suitable pole-pieces to the ring, one at N and
another at S, it can be used for the field-magnet of an electric
generator.
55. A bipolar ring-shaped electromagnet with winding on
pole-pieces is shown in Fig. 52. The pole-pieces may be either
an integral part of the ring, or separate parts attached to the
ring by bolts or other suitable fastenings.
56. A four-pole ring-shaped electromagnet is shown in Fig. 53.
A magnetizing coil is wound on each pole-piece. The direction
of the current through each coil is indicated by the arrowheads.
CHAPTER VII.
DIRECT-CURRENT GENERATORS WITH ELECTROMAGNETS.
57. General. Electromagnets can be used in conjunction
with either an armature that delivers an alternating current, one
that delivers a direct current, or one that delivers both direct
and alternating current. When the armature delivers only
alternating current, some auxiliary source of direct current must
be provided for supplying electricity to magnetize the field-
magnets; in other words, for exciting the field. But when the
armature delivers direct current, all or part of the current can
be used to excite the field-magnets, thus eliminating the necessity
of the auxiliary source of current supply.
It is believed that the only type of electromagnetic generators
that are used for ignition purposes is that in which the armature
delivers direct current, therefore only this type will be described.
Shunt-wound Direct-current Generators.
58. A bipolar direct-current generator with U-shaped shunt-
wound electromagnets is shown in elementary form in Fig. 54.
Two circuits are connected to the brushes, one through the
external circuit i, and the other through the field-coils 2 and 3.
The latter is called a shunt circuit, or simply a shunt. The
shunt is a comparatively small wire of considerable length and
a great number of turns around the magnet core, so that only
a small proportion of the current that the armature is able to
deliver passes through the field-coils.*
* The amount of direct continuous current that flows steadily through a wire
is inversely proportional to the length, and directly proportional to the sectional
area of the wire. A thin wire offers more resistance to the flow of current through
it than a thick wire of the same material. This is analogous to the greater resist-
ance offered to the flow of a liquid through a small pipe than through a large one.
The resistance offered to flow in both the wire and the pipe is proportional to the
length of the wire and the pipe.
65
66
ELECTRIC IGNITION
A generator of this nature must first have its field-magnets
magnetized by current from an exterior source, or by another
magnet. After being once magnetized, the field-magnets retain
enough residual magnetism to start the generation of a current
in the armature when it is rotated, unless the magnets are sub-
jected to some unusual demagnetizing influence.
When the armature is started to rotate, the slight electro-
motive force generated by the residual magnetism in the field-
FIG. 54.
Bipolar Direct-current Electric Generator with Shunt-wound U-shaped Electro-
magnets.
magnets sends a correspondingly small current through the field-
coils. This current strengthens the magnets, which in turn
induce a greater electromotive force in the armature, and more
current flows through the field-coils. By this progressive action,
the generator " picks up " or " builds up " its magnetism until a
condition is reached where the increase of magnetism becomes
slow in relation to the increase of current in the field-coils, and a
constant electromotive force is then maintained as long as the
external circuit remains the same.
DIRECT-CURRENT GENERATORS WITH ELECTROMAGNETS 67
An increase of current through the external circuit, such as
may be caused by removing a piece of apparatus from it, still
leaving the circuit closed, causes a reduction of voltage at the
brushes of the generator.
The generator is usually so constructed for ignition purposes
that the variation of pressure at the brushes is not excessive
for variations of current within the range through which the
machine is designed to operate. A method of preventing this
FIG. 55.
Shunt-wound Direct-current Electric Generator with Ring-shaped Bipolar Field-
magnets.
drop of pressure at the brushes, by using a " compound winding "
on the magnets, is given later.
59. A bipolar direct-current generator with ring-shaped
shunt- wound electromagnets is shown conventionally in Fig. 55.
The principle of operation is the same as for the generator shown
in the preceding figure. It may be noted, however, that the
brushes do not stand in the same position relative to the pole-
pieces as they do in the former figure. In Fig. 54 the position
of the brushes relative to the pole-pieces corresponds to that in
Fig. 37. In order to obtain the relative positions shown in
Fig. 55, the commutator in Fig. 37 may be twisted around a
quarter-turn counter-clockwise relative to the armature core
68
ELECTRIC IGNITION
without changing the connections of the wires to the commutator.
In any case, the brushes can be made to stand in any position
relative to the pole-pieces, by making the connections to the
commutator segments accordingly.
A complete commercial machine of the type shown conven-
tionally in Fig. 55 is illustrated in Fig. 56. The protective cap
FIG. 56.
(See also Figs. 57, 58, 59, and 60.)
Bipolar Direct-current Electromagnetic Generator. The Dayton Electric Manu-
facturing Co. Dimensions in inches: io| long; 5! wide; 5! high.
r 3 amperes continuously.
Capacity < 8 volts at 1000 r.p.m.
1 10 volts at 1 200 r.p.m.
1. Commutator.
2. Brush, insulated.
3. Brush spring, insulated at end that
presses against brush.
4. Terminal.
5. Connection between brush and
terminal 4.
6. Field Coil.
7. Steel tube around armature.
(Discarded in later designs.)
8. Oiler with felt wick.
9. Spider with bearing for armature
spindle and with brush-holders.
is opened out on a hinge at the commutator end to show the
working parts. The pole-pieces are above and below the arma-
ture. The brushes are perpendicular to the commutator, so
the armature can rotate in either direction. Each brush has
a short ribbon spring, somewhat like a short clock-spring, for
DIRECT-CURRENT GENERATORS WITH ELECTROMAGNETS 69
pressing it against the commutator. The magnetizing coil 6 of
the top pole-piece is partly visible. At 7 is a steel tube which
fits against the pole-pieces, and inside of
which the armature runs without touching
it. The use of this tube has been discon-
tinued in later designs.
The armature for this machine is shown
separately in Fig. 35. The oiling device is
shown in Fig. 57. It consists of an oil res-
ervoir into the top of which is fitted a
round felt wick that is pressed up against
the journal of the armature shaft by a coiled
compression spring. The capillary action of
FIG. 57.
., . , ,, ., ,, , Oiling Device with Felt
the wick carries the oil up to the bearing wkk? for Fig s6
gradually. The field-coils are shown in
Fig. 58. Each coil is made up of insulated wire which, after
being wound to form, has air and moisture removed by placing
it in a vacuum, and is then insulated by impregnating it with
FIG. 58.
Field-Coils, for Fig. 56.
liquid insulating compound that hardens like varnish upon dry-
ing. The coil is then wound with insulating tape. The brushes,
Fig. 59, are of graphite with a bronze-gauze core. The terminal
wires are soldered to the gauze core.
ELECTRIC IGNITION
Fig. 60 shows the spider 10 which supports the brushes and
the commutator end of the armature spindle.
The capacity of a machine like that in Fig. 56, having the
dimensions: i of inches long, 5! inches wide, and 5! inches high,
FIG. 59.
Commutator Brushes, for Fig. 56.
as rated by the makers, is 3 amperes of steady current at a pres-
sure of 8 volts when running at 1000 r.p.m., or a little more than
12 volts at 1200 r.p.m.
FIG. 60.
Bearing, Brushes, Oiler, etc., for Fig. 56.
The only means of regulating the pressure is by variation of
the speed. The current is also varied in practically the same
proportion as the pressure when the circuit remains unchanged.
A friction pulley or a belt pulley combined with a speed governor
is provided with the machine.
DIRECT-CURRENT GENERATORS WITH ELECTROMAGNETS 71
60. A four-pole direct-current generator with shunt-wound
electromagnets is shown diagrammatically in Fig. 61. Only two
brushes are used. They are placed at an angle of 90 degrees
with each other of necessity. The path and direction of mag-
netic flux is indicated by the broken lines with double arrow-
heads on them.
The connections for an armature of a four-pole machine with
two brushes are shown in Fig. 62. This armature has twenty-
FIG. 61.
Elementary Four-pole Direct-current Electric Generator with Shunt-wound
Magnets.
one coils and the same number of commutator segments, or
strips. The broken lines indicate the part of the winding that
is in the rear of the armature core. The core is not shown,
since it would detract from the clearness of the diagram. When
the direction of rotation is clockwise, as indicated by the feathered
arrow, the flow of current is as indicated by the arrowheads on
the lines.
Figs. 63 and 64 show a direct-current shunt-wound four-pole
generator with two brushes. The former figure is partly in sec-
tion. A governor spring bears against the commutator end of
the armature shaft and presses the friction pulley against the
flywheel that drives it. A speed governor is located on the
72 ELECTRIC IGNITION
shaft between the friction pulley and the armature. This gover-
nor moves the entire armature and the friction pulley endwise
as the speed increases, so as to reduce the pressure of the friction
pulley against the flywheel, thus allowing the friction pulley
FIG. 62.
Armature Connections for Drum Armature with Twenty-one Coils and the Same
Number of Commutator Segments. For Four-pole Field-Magnets.
to slip on the flywheel and limiting the speed to the desired
rate. An adjusting screw is provided for varying the pressure
of the governor spring against the end of the shaft so as to obtain
the desired speed limit.
There are two brushes set at 90 degrees with each other. They
are a combination of wire gauze and graphite. The armature
DIRECT-CURRENT GENERATORS WITH ELECTROMAGNETS 73
has twenty-one coils and the same number of segments in the
commutator. The frame of the generator, which is also the
GOVERNOR
FIBRE THRUSTWASHER
BEARING
FRICTION
PUUIY
COHMUTATOR
FIG. 63. (See also Fig. 64.)
Four-pole Direct-current Electric Generator. Sectional View. Apple Electric
Company, Dayton, Ohio.
magnet ring, is cast from semi-steel. This is a material between
soft steel and cast-iron in its physical and magnetic properties.
The generator is provided with an automatic cut-out for open-
ing and closing the circuit when used in connection with storage
COVERNORjSPRING
ADJUSTER
BRUSH SPRING
4KIU3TER
BRUSHES
GOVERNOR- SPRING
PRESSED STEEL LID
AUTOMATIC'CUTOUT ' OIL CL)P LINE.WlRt.f BINDING. POST
FIG. 64. (See also Fig. 63.)
Commutator End of Four-pole Direct-current Electric Generator.
batteries. This method of using is described later in connection
with a complete ignition system (see Fig. 95 and several follow-
ing figures). The machine is also equipped with a device for
keeping the current nearly constant when the speed of the
74
ELECTRIC IGNITION
armature is variable. This device automatically changes the
amount of resistance in the field circuit.
Compound-wound Direct-current Generators.
61. Series-and-shunt Field Winding. It is often desirable
to have a generator that will keep the voltage at the brushes
practically constant when the rotative speed of the generator is
constant, so that the pressure will be practically constant whether
FIG. 65.
Compound-wound Direct-current Electric Generator.
the amount of current delivered is variable or constant. This
is accomplished by means of a double winding on the field-mag-
nets. One of the windings is the regular shunt winding, and
the other winding carries the current that flows through the
external circuit. The latter is called the series winding. Fig. 65
shows diagrammatically a generator with compound field winding
of this nature.
The currents in both windings flow in the same direction
around the magnet cores. It has been explained that the voltage
at the brushes drops as the external current increases when only
DIRECT-CURRENT GENERATORS WITH ELECTROMAGNETS 75
a shunt winding is used. This tendency is counteracted by the
magnetizing effect of the current which flows through the series
coil. The magnetizing effect of the series coil increases as the
current through the series coil and external circuit increases.
By giving the series coil a suitable number of turns around the
magnet core, the voltage at the brushes can be kept almost
constant in a properly designed machine. By giving the series
FIG. 66.
Rheostat in Shunt-coil Circuit of Electric Generator.
coil more than this number of turns, the voltage can be made
to rise as the current in the external circuit increases. This
over-compounding is often desirable.
The voltage of a compound-wound machine such as shown in
Fig. 65 is approximately proportional to the speed of the arma-
ture, within the range of speed at which the machine is designed
to operate.
62. Field Rheostat for Regulating Voltage. When the rota-
tive speed of the armature of an electromagnetic generator is
constant, the voltage at the brushes can be regulated by varying
76 ELECTRIC IGNITION
the electrical resistance of the shunt-coil circuit. The usual
means of doing this is a rheostat.
Fig. 66 shows a compound-wound generator with an elemen-
tary form of rheostat in the shunt circuit. The principal parts
of the rheostat are shown at A and R. R is a series of coils of
wire. The ends of the wire are connected to metal contact-
points i, 2, 3, 4, and 5. These points are arranged in an arc
of a circle. A switch-arm A is pivoted at the center of the arc
and is of such a form that it can be moved into contact with any
of the contact-points just enumerated. This rheostat is inter-
posed in the shunt circuit by cutting the shunt wire at any con-
venient point and connecting the wire-ends thus obtained to the
rheostat as shown. One end is connected to the contact-point
i, and the other end to the pivot of the arm A.
When the rheostat arm A is set in contact with point 4 as
shown, the shunt current must pass through the rheostat coils
that lie between i and 4, and the resistance of these coils is
added to that of the field-coils. The current that flows through
the field-coils is therefore less than would flow if the rheostat
were not in the circuit, and the voltage at the brushes is in con-
sequence less than it would be without the rheostat. By moving
the arm into contact with either 3, 2, or i, the voltage can be
increased; or by moving it to 5, the voltage can be decreased.
The swinging end of the contact arm A is wide enough to
touch two of the contact-points at the same time when moving
from one to another. This is necessary in order to prevent
breaking the circuit while varying the resistance in the circuit.
The rheostat is generally a separate piece of apparatus. The
resistance wire used in it is ordinarily of a material that has high
electric resistance compared with that of copper.
A rheostat can be used in the field circuit of a plain shunt-
wound machine as well as in one that is compound- wound.
Reversing the Rotation of the Armature.
63. Most of the generators for ignition usage have the brushes
perpendicular to the commutator so that the armature can be
rotated in either direction without injury.
DIRECT-CURRENT GENERATORS WITH ELECTROMAGNETS 77
The field-coil connections to the brushes must be interchanged
when the direction of rotation of the armature is to be reversed.
If the armature is run in the new direction without making this
change of connections, it will not pick up its magnetism and
generate a current. This is because the different direction of
rotation changes the polarity of the brushes, so that the one
formerly positive becomes negative, and the former negative
one becomes positive. The current which is generated by the
residual magnetism therefore flows through the field-coils in
the direction to demagnetize them instead of strengthen their
magnetism. The result is that no appreciable pressure is gen-
erated, and of course no appreciable current can be obtained
without corresponding pressure.
CHAPTER VIII.
PRIMARY BATTERIES.
Carbon-zinc Battery.
64. When an electric battery is subject to considerable motion,
as in automobiles, railway motor cars, and motor boats, a " dry
battery " is almost exclusively used if ignition current is supplied
by a primary battery. The dry primary battery is also much
used for ignition in stationary motors.
Only one of almost innumerable types of dry batteries, as
distinguished by the substances used in them, is used to a
noticeable extent. In this commonly used battery the substances
_^ which designate it are carbon,
zinc, and sal ammoniac (also called
ammonium chloride, NH 4 C1) . Other
substances are used in connection
with these and are essential to its
operation for supplying current for
motor ignition. In order to make
clear the nature of this battery cell
and its operation, the elementary
form using only carbon, zinc, and
sal ammoniac will be first described.
65. Elementary Leclanche Car-
bon-zinc Wet Cell. A bar of zinc
and a slab of carbon immersed in a
FIG. 67.
Elementary Wet Electric Battery Solution f Sal ammoniac in a glass
Cell. vessel are shown in Fig. 67. The
solution is made by dissolving sal
ammoniac (a white salt) in water.* The carbon and zinc are
connected together by a wire.
* One-quarter pound of sal ammoniac to a quart of water is the proportion
generally used in a cell.
78
PRIMARY BATTERIES 79
A current of electricity begins to flow from the carbon to the
zinc through the wire as soon as the carbon and zinc are immersed
in the solution. The current also flows through the solution
from the zinc to the carbon inside of the cell. The amount of
current decreases very rapidly immediately, and then continues
to decrease at a slower rate till, after considerable time, there is
scarcely a perceptible flow. The cause of the decrease of current
is called polarization, and is described below.
Decrease of current on account of polarization also occurs
in this elementary form of cell when it is used in the manner
required for motor ignition. This action makes it unsuitable
for motor ignition purposes.
The electric current through the wire is generated by chemical
action between the zinc and the solution. The solution attacks
the zinc and combines with it. This action dissolves, corrodes,
or eats away the zinc.
The above combination is called a primary electric cell. In
earlier days it was commonly called a galvanic cell or a voltaic
cell. Two or more such cells properly connected together form a
battery of cells, called an electric battery. In commercial usage
a single cell is generally also called a battery.
The carbon and zinc are called the electrodes, and the solu-
tion is called the electrolyte. All three together are called the
active elements of the cell.
The point at which the wire is attached to the carbon is the
positive (+) terminal of the cell; and the point of attachment of
the wire to the zinc is the negative ( ) terminal of the cell.*
In commercial forms of cells, binding screws and nuts, or
other suitable fastenings, are usually provided for attaching
wires at the terminals.
If the wire is cut in two and the ends separated, the flow of
current through it is stopped. The chemical action in the cell
* On account of the confusion which arises when one of the elements of the
cell is referred to as the positive electrode, and the other as the negative electrode,
the terms positive electrode and negative electrode are not used herein in con-
nection with electric cells and batteries. The terms anode and cathode are omitted
in connection with batteries for the same reason.
8o ELECTRIC IGNITION
also stops with the stoppage of current through the wire, except
that there is generally some slight amount of local action on the
zinc. Impurities in the zinc, such as iron and copper, increase
this local action. But even if the zinc is very pure, local action
will still occur on account of a difference in the strength, or
quality, of the portion of the solution at the top and that at
the bottom. The local action due to this latter cause eats away
the zinc at and near the surface of the solution. Local currents
through the zinc are caused by this action.
The electromotive force of a primary cell with carbon and
zinc electrodes in sal-ammoniac solution is slightly less than
1.5 volts between the terminals after the cell has not been de-
livering current for some time. The voltage drops as soon as
the circuit is closed and current begins to flow. It slowly rises
again to its full value after the current is stopped by opening
the circuit.
66. Polarization of Primary Electric Cell. The decrease of
current that occurs while the circuit of a cell is kept closed, in
the case of a cell having only the elements carbon, zinc, and sal
ammoniac, is due to the formation of hydrogen gas by the
chemical action. The gas collects on the carbon and retards
chemical action. This retardation is apparently chiefly due to
a counter-electromotive force which the hydrogen sets up, and
also partly due, but to a less extent, to the formation of bubbles
on the carbon so as to prevent the electrolyte from having as
good contact with the carbon as it has before any bubbles are
formed. If the carbon is molded very dense and has a very
smooth surface, polarization can be at least largely prevented by
constantly brushing off the bubbles of hydrogen. This is not
practicable, however. The usual method is to prevent polariza-
tion by chemical means. This is ordinarily called depolariza-
tion. It is successfully applied to both wet cells and dry cells.
67. A dry cell with carbon and zinc electrodes and chemical
depolarizer is shown sectionally in Fig. 68. This is the type of
dry cell that is almost universally used for ignition where the
battery is subjected to much motion.
The containing vessel, cup, or can i is made of sheet zinc and
PRIMARY BATTERIES
8l
is one of the electrodes. The can is lined with absorbent paper 2
(blotting paper) that is saturated with water in which sal ammo-
niac and zinc chloride have been dissolved. In the center is a
molded bar of carbon 3 around which is packed a mixture 4 of
manganese dioxide (MnO 2 ) and car-
bon dust. The manganese dioxide
is in granular form (powder) . The
paper is turned in over the top of
the mixture so as to cover it nearly
or completely. On top of the paper
is a little sawdust or sand, and above
this a sealing compound 5, composed
chiefly of pitch, to make the cell
water-tight. The absorbent paper
and the mixture around the bar are
saturated with the electrolyte before
the cell is sealed. The carbon in
the mixture is generally coke-dust,
and the carbon bar is made of coke-
dust mixed with a binder such as
pitch. The plastic mixture for the
bar is molded to form and then
baked to give it strength and at the
same time convert the binder into
carbon. Carbon is a better con-
ductor of electricity than manganese
dioxide, hence mixing it with the manganese dioxide gives the
cell less resistance to the flow of electricity than if manganese
dioxide alone were used around the bar. A low resistance is
desirable in a dry cell, especially one that is to be used for
gas-engine ignition.
The carbon bar is capped with a tight-fitting brass piece which
has a binding screw and nut. Another binding screw is soldered
to the top of the zinc can. The cap on the carbon bar at the
center of the cell is the positive (+) terminal, and the binding
screw fastened to the zinc can is the negative ( ) terminal.
The manganese dioxide is a depolarizer. It gives up oxygen,
FIG. 68.
Dry Cell of an Electric Battery.
82 ELECTRIC IGNITION
which combines with the hydrogen gas that is liberated by the
action described in connection with the elementary carbon-zinc
cell. The hydrogen and oxygen combine in the proportion to
form water, which is a liquid and remains in the cell.
The electromotive force of a dry cell of the kind just described
is about 1.5 volts on open circuit when new and in good condition,
irrespective of the size of the cell. A large cell will give more
current than a small one.
The size of dry cell which has become standard is 2\ by 6
inches long. It is cylindrical in form. The cell is usually
covered with some insulating material, such as paper or straw-
board, except the terminals. This insulating covering prevents
the metal of one cell from coming into contact with that of
another when the cells are grouped together to form a battery.
A cell of this size will give from 15 to 20 amperes of current
through a low-resistance ammeter when the circuit is first closed.
The cell is practically short-circuited when its terminals are
connected through a low-resistance ammeter, the resistance of
the latter being about the same as that of a short, heavy copper
wire. The cell will deliver this maximum amount of current
during only a few seconds. The current rapidly decreases when
the cell is short-circuited, but continues with constantly de-
creasing value till the battery is exhausted.
The exhaustion of a dry cell of the usual construction is
due to weakening of the liquid electrolyte with which the
absorbent paper in the cell is saturated. This weakening is on
account of the chemical action necessary to produce electric
current.
68. Deterioration of new permanently sealed dry batteries
often occurs to a marked extent before they are put into use.
They sometimes deteriorate in a few months or less of storage so
as to become useless. Such rapid deterioration is not apt to
occur in well-made cells whose materials are suitably pure.
69. New Type of Carbon-zinc Dry Cell, not Sealed. A type
of dry cell which is actually and thoroughly dry until put into
use was first exhibited at the Atlanta automobile show in the
latter part of the year 1909. The cell resembles in general
PRIMARY BATTERIES 83
appearance and construction the one shown in Fig. 68, except
the carbon rod and the terminal on it.
The carbon rod of the new cell is made hollow and is provided
with a wooden stopper at the open end. The terminal is fastened
to one side of the top of the carbon. When the cell is manu-
factured it is left entirely dry, but all of the necessary chemical
elements are put in it. It is chemically inactive and does not
deteriorate in storage before putting into use.
To prepare the cell for use, it is only required to fill the hollow
carbon rod with water, after removing the stopper, which is
replaced after the water is poured in. The water dissolves the
chemical elements which with the water form the electrolyte.
After being thus put into operation, the cell is subject to ex-
haustion and deterioration the same as a permanently sealed cell
of the same quality.
70. Exhaustion and Running Down of Dry Batteries in Ser-
vice. The chemical action in the cell by which electric current
is generated of course consumes the active materials and pro-
duces new chemicals. The result is a dropping off of the activity
of the cell and finally its exhaustion to such an extent that it
becomes useless.
In a properly constructed cell, the chemical elements are so
proportioned that they become exhausted at about the same
time. The zinc cup is not much thicker than necessary to
furnish the requisite metal for the amount of chemicals present.
The fact that the zinc is sometimes eaten through before the
cell is nearly exhausted is an indication of local action in the zinc,
probably on account of impurities in the metal. Local action
is more apt to make itself known when the battery is allowed
to stand idle during a considerable portion of its life.
71. Recuperation of dry cells can generally be effected by
adding sal-ammoniac solution to the inside of the cell. The
solution can be added to a permanently sealed cell by making
an opening through the sealing compound at the top so as to
expose the blotting paper, and pouring the liquid into the open-
ing. The sealing compound can be readily dug out with a
pointed instrument. It is not necessary to replace it, since the
84 ELECTRIC IGNITION
cell will never be of much use after becoming exhausted the
first time. This expedient of recuperation is hardly worth
while except in case of emergency.
It is probable that the new type of unsealed cell described
above can be recuperated by pouring in a solution of sal ammoniac
after the cell has been run down in service.
The addition of water alone will sometimes recuperate a cell
slightly.
Copper Oxide and Zinc Wet Cell.
72. The Lalande and Chaperon wet cell, as brought out in
1881, has zinc amalgamated with mercury for one electrode,. and
either iron or copper for the other. The
electrolyte is a solution of either caustic
soda (concentrated lye, sodium hydrate,
NaOH) or caustic potash (potassium hy-
drate, KOH). A depolarizer of copper
oxide (cupric oxide, CuO) is used. Modi-
fied forms of this cell, one known as the
Edison-Lalande and more recently as the
Edison primary battery, and the latest one
, v . as the BSCO battery, are used to a consid-
FIG. 69. (See also Figs. . ...
70 and 71.) erable extent for gas-engine ignition, espe-
Copper Oxide and Zinc cially for stationary engines.
Wet Cell. Edison Man- 73. A BSCO wet cell is shown in Fig.
ufacturing Company, , Part of ^ cont aming vessel is broken
Orange, New Jersey. .
away to show the interior construction.
The electrodes, depolarizer, and the cover of the cell are shown
removed from the cell in Figs. 70 and 71.
The copper electrode has the form of an inverted U-shaped,
grooved, or channeled, frame A which hangs from the cover F
of the cell, the connection being made by a bolt which passes
through the cover and has thumbscrews above it. The depolar-
izer slab C is clamped between the legs of the copper frame,
which are drawn together against the beveled edges of the slab
by means of a copper cross-bar, or bridge, D, so as to make good
electric contact between the copper and the depolarizer slab.
PRIMARY BATTERIES
The lower ends of the copper frame are bent in under the slab
to support it. The zinc plates B are suspended from the cross-
bar by means of a steel bolt which passes through a porcelain
insulator E and holds the zincs firmly in place. The porcelain
insulates the zincs from the copper. An insulated wire is con-
nected to the zincs, and its outer free end is the negative ( )
FIGS. 70 and 71.
Elements and Top of Fig. 69.
terminal of the cell. The bolt from which the copper frame is
suspended is the positive (+) terminal.
The depolarizer slab is a mixture of copper oxide and magne-
sium chloride compressed to form in molds and then heated to
make it a firm mass. The magnesium chloride acts only as a
binder to hold the mass together.
The zinc plates are amalgamated by incorporating about two
per cent of mercury with them when they are cast.
The liquid electrolyte covers the zinc plates completely to
a depth of an inch or so above them. A layer of heavy mineral
oil is poured on the electrolyte and floats at the top to protect
the electrolyte from atmospheric action. If air is allowed to
come into contact with the electrolyte, it oxidizes it and de-
creases the length of life of the cell.
86 ELECTRIC IGNITION
Since the rigid parts of the cell are firmly fastened together,
the cell can be used where there is motion without danger of the
electrodes coming into contact with each other or with other
parts so as to short-circuit the cell. It can therefore be used on
vehicles if the top is sealed on, for which provision is made in
one type of the cell intended for ignition use. Cells for portable
use are made with enameled steel containing vessels, or jars.
The voltage of one of these cells on open circuit is slightly
less than one volt. The pressure does not drop much below one
volt during use until the battery is nearly exhausted.
The renewals for an exhausted battery consist of the parts
suspended from the cover, which are sent out as a unit fastened
together, and the electrolyte of dry caustic potash to be dissolved
in water. The oil for covering the electrolyte may also be in-
cluded as one of the renewal items. Renewal of the parts is made
by taking out the bolt which passes through the cover, discard-
ing the copper frame and parts attached to
it, and fastening the new frame and its
attached parts in place with the old cover-
bolt; also discarding the exhausted electro-
lyte and dissolving the new in water poured
into the jar.
The capacity of the portable cell intended
for ignition use is 200 ampere-hours.
74. The Edison primary battery, already
referred to as an earlier form of the one
FlG - 72. just described, differs from the newer form
Early form of Edison only in mec hanical construction. One of
Primary Battery shown . ... ., . . .
in Fig. 69. these earlier cells is shown in Fig. 72, with
part of the jar broken away to show the
interior. The zinc plates are suspended from the porcelain cover,
instead of from the copper frame, as in the later form, and the
copper frame is of different form, with a bolt connecting the two
sides under the depolarizer slab. The zincs are not so firmly and
accurately held in place as in the later type of cell. The cell is
therefore not so well adapted to portable use as the latter
type.
PRIMARY BATTERIES
The capacities and dimensions of some of these cells are given
in the following table according to the Manufacturer's rating:
Diameter and Height over All. Com-
plete Cell with
Capacity in
Ampere-Hours.
Porcelain Jar.
Enameled Steel Jar.
Inches.
4^X 7l
SIX 8f
7iXio|
Inches.
4*X 6f
5lX 8
7iXio
IOO
150
300
CHAPTER IX.
BATTERY CONNECTIONS.
75. General. In order to obtain suitable electromotive force
and current, cells are connected together to form a battery. The
best arrangement of the cell with regard to the order in which
their terminals are connected together depends on the nature of
the service to be performed and on the resistance of the external
circuit.
In the following discussion it is assumed that all of the cells
in a battery are alike. This assumption is in accordance with
the best practice. Moreover, the discussion relative to different
kinds and capacities of cells grouped together in a battery is
more complicated than is thought should be presented in a work
of this nature.
For convenience of discussion, it will be assumed that either
carbon-zinc cells or copper-zinc cells are used. The carbon ter-
minal, or the copper terminal, as the case may be, is the positive
one, and the zinc terminal is the negative one.
Series-connected Batteries.
76. A series-connected battery of four cells, all alike, is shown
in Fig. 73. -The carbon terminal of each cell is connected to the
Negative Terminal- ^.3^
of Battery. Zinc. (jg) \^6^ \ ^4^ \ ^-P \-PositiveTerminal
of Battery.
Carbon or Copper
FIG. 73.
Electric Battery of Series-connected Cells.
zinc terminal of another cell, except that the carbon terminal of
the right-hand cell and the zinc terminal of the left-hand cell
88
BATTERY CONNECTIONS
8 9
are left free. These two free terminals are the terminals of the
battery.
The voltage of a series-connected battery, measured between
its terminals, is equal to the sum of the voltages of all of the
cells. In this case the battery voltage is four times that of one
cell, since there are four cells, all assumed to be alike. If the
electromotive force of one cell is 1.5 volts on open circuit, then
the electromotive force of the battery of four cells is 4 X 1.5 = 6
volts. If the electromotive force of each cell drops to 1.25 volts
when the battery is delivering current in regular service, then
the working voltage of the battery is 4X1. 25 = 5 volts.
FIG. 74.
Reversed Cell in a Battery Intended to be Series-connected.
The current that the battery will give is greater than a single
cell will give. The increase of current obtainable by connecting
the cells together is not so great in proportion as the increase
in the number of cells in the battery. With the four cells, it is
not possible to get four times as much current as from one cell.
The current will be very nearly four times as great with the four
cells, however, if the resistance of the external circuit is very
great in comparison with the internal resistance of the battery.
The internal resistance of the series-connected battery is the
sum of the internal resistances of all of the cells. If the external
resistance is very low compared with the internal resistance of
the battery, the series-connected battery will give only very
little more current than one cell alone will give.
77. Reversed Cell in a Series Battery. If one of the cells is
90 ELECTRIC IGNITION
wrongly connected to its neighbors in a series battery, so that
its carbon is connected to the carbon of one adjacent cell, and
its zinc to the zinc of the other adjacent cell, the effect on the
voltage of the battery is equivalent to removing two cells from
the battery. It requires the electromotive force of one of the
properly connected cells to counteract that of the reversed cell.
The current that the battery will give is less than that of a
properly connected series battery with two less cells.
Fig. 74 is a six-cell battery intended to be series-connected,
but one cell A is reversed. The battery is therefore somewhat
less effective and efficient than a properly connected four-cell
series battery. While this error of making connections appears
plain on paper, it is one that frequently occurs and is not so easy
to notice in practice.
Multiple- or Parallel-connected Batteries.
78. A parallel-connected battery of four cells whose positive
(carbon) terminals are all connected together by one wire, or
other conductor, and whose negative (zinc) terminals are all
connected together by another conductor, is shown in Fig. 75.
FIG. 75-
Parallel or Multiple Connection of Cells in a Battery.
Any place on the wire connected to the carbons can be taken as
the positive terminal, and any place on the wire connected to the
zincs as the negative terminal.
The voltage of the battery is the same as that of one cell.
When connected to an external circuit of very high resistance,
the battery will deliver only slightly more than the amount of
current in amperes that one cell will deliver to the same circuit.
But when the positive and negative wires of the parallel-con-
nected battery are connected together by a conductor of very
BATTERY CONNECTIONS
low resistance, such as a thick, short copper rod, the four cells
will give nearly four times as much current as one cell with its
terminals similarly connected together.
In general, the current is but slightly increased by putting
cells in parallel if the resistance of the external circuit is high,
but if the external resistance is low compared with that of the
battery the current is materially increased.
79. Reversed Cell in a Parallel-connected Battery. In
Fig. 76 three cells, i, 2, and 3, are connected together. The
zinc of cell i is connected to the carbons
of cells 2 and 3, and the carbon of cell i
is connected to the zincs of 2 and 3.
When the cells are connected together in
this manner, current flows from the car-
bon of cell i to the zincs of 2 and 3, and
from the carbons of cells 2 and 3 to the
zinc. of i. The resistances of the circuits
are low, being only that of the connecting
wires and of the cells. The internal re-
sistance in circuit is one and one-half
times that of one cell when they are connected in this manner.
Unless the connecting wires are very unusually thin and long,
FIG. 76.
Wrong Connection of Cells
in a Battery.
FIG. 77-
Reversed Cell in a Battery Intended to be Parallel-connected.
the total resistance of the circuit, internal plus external, is not
more than that of two cells added together. The result is that
a large amount of current flows and the cells become exhausted
in a short time.
92 ELECTRIC IGNITION
Fig. 77 shows nine cells, eight of which are connected in parallel,
but the remaining one A is reversed from the position proper
for parallel connection with the others. The result is of the
same nature as that just stated for three cells. Current flows
as indicated by the arrowheads on the wires. The current is
not of the same amount in all parts of the wires, however. It
is greater in the wires which are between the cells near A than
in those between the cells more remote from A. All of the cells
will be rapidly exhausted.
Parallel-series Batteries.
80. Fig. 78 shows two sets of series-connected cells with four
cells in each set. One set is made up of cells i, 2, 3, and 4; the
FIG. 78.
Parallel-series Battery Connection of Two Sets of Series-connected Cells.
other set is made up of cells 5, 6, 7, and 8. The two sets are
connected together in multiple, or parallel. Any point on the
wire connecting the two carbons can be taken as the positive
(+) terminal of the battery, and any point on the wire connect-
ing the two zincs can be taken as the negative ( ) terminal.
The voltage of the parallel-series battery is the same as that
of each series of cells. In this case the voltage is four times
that of one cell, since there are four cells in each series.
More current will be sent through the external circuit by the
two sets of series-connected cells than by one series alone. The
increase of current will be greater when the external resistance
is low than when it is high. It is sometimes convenient to con-
sider each series as a unit whose terminals are those of the series.
BATTERY CONNECTIONS
93
When this is done the series can be dealt with as a single cell so
far as regards its relations to other units of a similar nature.
In Fig. 79 five sets, each of four series-connected cells, are
connected in parallel, or multiple, with each other. The cells
FIG. 79.
Parallel Connection of Five Sets of Series-connected Cells.
The
of each series are in a vertical row in the illustration,
voltage of the battery is four times that of one cell.
81. Wrong Arrangement of a Battery. In Fig. 80 five series-
connected cells are shown in the upper row, and four series-
FIG. 80.
Wrong Arrangement of a Battery.
connected cells in the lower row. The two series are connected
in parallel with each other. The result is that current flows
through the battery while the external circuit is open, on
account of the electromotive force of the upper row of five cells
94
ELECTRIC IGNITION
being greater than that of the lower row of four cells. The
direction of the current is indicated by the arrowheads on the
wires. The current will continue until the electromotive force
of the five cells in series drops to that of the four series-connected
cells. This action means exhaustion of the five cells. A battery
should not be made up in this manner.
82. Connection to External Circuit. The method of con-
necting two series batteries to the same external circuit is shown
in Fig. 81. The negative terminal of each series of cells is
connected to one of the contact-points, or poles, of a two-point
switch. The contact-points are insulated from each other and
from other parts of the system. The positive terminal of each
FIG. 81.
Correct Method of Connecting a Battery to the External Circuit.
set of series-connected cells is connected to the external circuit
R, from which connection is made to the switch-blade. When
the switch-blade is in the position shown, the upper row of cells
is the only one that delivers current. The other row of cells
is on open circuit. If the blade is moved into contact with the
lower switch-point, as indicated by the dotted lines, then the
lower row of cells is brought into operation alone. By placing
the switch-blade in mid-position, so that it has contact with
both switch-points, the complete battery is cut into circuit and
it all acts to furnish current to the external circuit. By throw-
ing the blade over so that it has no contact with either point,
the current is completely cut off from the external circuit and
there can be no local current in the battery of the nature of that
in Fig. 80, because there is no connection between the negative
BATTERY CONNECTIONS 95
terminals when the switch-blade has no contact with either point
of the switch.
It may be noted that, even when two series, both of the same
number of cells, are in parallel with each other, and one series
is run down or exhausted, while the other is in good condition,
there will be local current in the battery of the same nature as
that in Fig. 80.
83. Screw-top Battery Cells. An exceedingly convenient
way of connecting cells together in a battery is by means of a
FIG. 82.
Screw-top Cells and Battery Box. Stanley & Patterson, 23 Murray Street and
27 Warren Street, New York City.
screw top on each cell and a plate provided with suitable contact
pieces and connections. Such cells and a plate are shown in
Fig. 82. It is only necessary to screw the cells into the plate in
order to make the proper connections. The making of wrong
connections, which is not an unusual happening with the ordinary
cells, each having two terminal nuts, is thus entirely eliminated.
The cell is connected into the battery in a manner similar to
that in which an incandescent electric lamp is connected into
the circuit of the service wires. The carbon terminal of the
battery cell makes contact with a spring, and the zinc shell makes
contact with the threaded metallic ring into which it screws.
9 6
ELECTRIC IGNITION
\
The spring keeps the contacts pressed together and prevents
their jarring loose.
The cells are also made with combination screw-top and bind-
ing-post terminals. By means of the latter the cells can be
connected together with wires when
desired.
By the use of " emergency spring
clips " the ordinary type of cell with
two binding posts can be used in the
4L A m cap or plate.
Fig. 83 shows five dry cells and a
spark-coil (spark-coils are described
later) , each screwed into its receptacle
in the top-plate of the battery box.
The spark-coil occupies practically
the same amount of space as one of
the cells.
Battery boxes with this form of
connection are also made up with two
sets of cells and a switch which, when moved to its different
positions, connects the two sets of cells either in parallel or in
series, or connects either of the sets into the system, leaving the
other idle.
The boxes are made water-tight for marine use or for any
place where there is much water or moisture.
m
FIG. 83. (See also Fig. 82.)
Screw-top Spark-Coil and Cells
in Battery Box.
CHAPTER X,
STORAGE BATTERIES, ALSO CALLED ACCUMULATORS AND
SECONDARY BATTERIES.
84. A storage battery is one that must be charged by passing
an electric current from some exterior source through it in order
to bring it into a condition in which it can deliver an electric
current. Before charging by passing an electric current through
it, the storage battery is inert and cannot deliver current. After
it has been once charged and then discharged by delivering
current, it can be recharged and will again furnish current till
it is discharged a second time. Charging and discharging can
be repeated numerous times.
The charging current while passing through the battery effects
chemical changes in the elements of the battery. These chemical
changes take place in both of the electrodes and in the electro-
lyte. During discharge the reverse chemical actions occur and
bring the battery elements at least partly back to their condi-
tions before charging.
The name " storage battery " is a misnomer, strictly speaking.
Electricity is not actually stored in the battery. The charging
current passes through and out of the battery, effecting chemical
changes in the elements of the battery during its passage. The
distinction between this action and the actual storage of elec-
tricity will appear later in connection with electric condensers.
While a great variety of storage batteries have been constructed
and tried out, those in commercial use are limited almost exclu-
sively to two kinds as classified by the materials used in them.
Of these two types, the one which is used by far the more gener-
ally is known as a " lead accumulator " or " lead storage bat-
tery," on account of its electrodes being made of the metal lead
and oxides of lead. The other type is known as the " Edison
97
9 8
ELECTRIC IGNITION
storage battery." Its electrodes are composed chiefly of nickel
and iron.
85. The electrodes, or plates, of a lead storage cell are usually
made up of plate-shaped pieces of lead, or lead alloy, which have
perforations, pockets, or other forms of receptacles filled with
the electrically active material. This active material is usually
put into the pockets in the form of paste during the construction
of the cell. It is composed chiefly, when first put in, of an
FIG. 84.
Electrode, Plate, or Grid of a Lead Storage Battery.
oxide, or oxides, of lead. The plates are then treated chemically
and electrically so as to cause the paste to set firm and hard, and
to change its chemical composition. The plate, or plates, to
form the electrode to which the positive terminal of the cell is
connected are treated so that the final condition of the paste is
dioxide of lead (PbC^), and the plate has a brown color, including
the paste. The plate, or plates, to form the other electrode are
treated so as to remove the oxygen from the compound and leave
metallic lead in a porous, or spongy, condition with the charac-
teristic color of metallic lead.
STORAGE OR SECONDARY BATTERIES
99
One form of lead grid for a storage battery is shown in Fig. 84.
It has rectangular perforations for receiving and holding the
paste. The lug projecting upward is for making connection to
other plates or to the external circuit.
86. Complete Storage Cell. Fig. 85 shows several complete
plates grouped together to form the electrodes of one cell. Three
FIG. 85.
Group of Plates for a Lead Storage Cell.
of the plates are fastened together by a bar, or strap, which
carries one of the terminals of the cell at the top. The other
two plates are fastened together in a similar manner and have
the other terminal of the cell at the top. The pockets of the
plates, or grids, are shown filled with paste.
Separators are used between the plates to keep them from
coming into contact with each other. One of the separators
IOO
ELECTRIC IGNITION
FIG. 86.
Separator for Placing between the Plates of a Storage Cell.
FIG. 87.
Storage Cell Containing the Parts shown in Figs. 84, 85, 86 and 88.
Dayton Electrical Manufacturing Company, Dayton, Ohio.
STORAGE OR SECONDARY BATTERIES IOI
used with these particular plates is shown in Fig. 86. It is made
of hard rubber in one piece and has the general form of a number
of bars laid across each other at right angles.
The complete cell is made up of the plates and separators
immersed in an electrolyte of dilute acid solution contained in a
jar. The electrolyte should completely cover the main portion
of the plates, but the terminals and upper portion of the lugs
extend above the liquid.
The electrolyte is generally dilute sulphuric acid. The water
used with the acid should be very pure, as distilled water.
A complete storage cell having plates and separators like
those just described is shown in Fig. 87. The jar is of hard
rubber suitable for portable work. It is provided with a cover
which is sealed on to make the cell tight, except a small opening,
or vent, which is shown between the terminals.
The cover of the cell is shown in section in Fig. 88. The vent
is so made that the bubbles of gas, escaping during the charging
FIG. 88.
, Cover of Cell shown in Fig. 87.
of the cell and carrying the .liquid electrolyte up with them, can
escape through the upper part of the vent-plug without carrying
the liquid outside of the cell. The conical terminal of one set
of plates is shown in the opening through the left-hand end of
the cover. This cone is surrounded by a rubber washer and is
drawn up tight so as to make a liquid-proof joint.
87. The voltage of a storage cell having lead plates and dilute
sulphuric acid electrolyte is about 2.2 volts on open circuit. It
drops below the open-circuit value as soon as the external cir-
cuit is closed and current flows. The pressure drop is approxi-
102 ELECTRIC IGNITION
mately proportional to the amount of current flowing, for a
given cell, when the cell is in good condition. The pressure
decreases very slowly during discharge until the battery is almost
completely discharged, and then begins to drop very rapidly as
the discharge continues.
The voltage is independent of the number of plates in the cell.
It is the same when there is only one positive plate and one
negative plate, as when there are several of each. In one cell
the plates are generally all immersed in the same lot of electro-
lyte contained in one jar with no partitions to separate one
portion of the liquid from another. Exceptions to the last state-
ment are some unusual types of cells with porous jars.
88. The maximum rate of discharge of a storage cell, without
injury to the cell, is approximately proportional to the amount
of surface area of active material of the electrodes in contact
with the liquid electrolyte. If the same size and make of plates
are used to make up cells having different numbers of plates in
them, then the safe maximum amperage of the cells will be
approximately proportional to the number of plates in them.
The maximum safe rate of discharge of a cell having 15 plates
is about three times as great as that of one having only 5 plates,
the plates in both being of the same size and make, as already
stated. The rate of discharge is measured in amperes. An
excessive rate of discharge is injurious to the cell. It causes the
paste to swell and even to drop from the grids.
89. A storage battery is composed of storage cells connected
together. Any of the methods of connection that have been
given for primary cells can be used for storage cells.
The storage batteries used for ignition purposes are generally
made up of two or three cells connected together and inclosed in
a case. A battery of this nature does not differ much, in appear-
ance from a single cell.
The plates of three storage cells are shown connected together
in series in Fig. 89. The two positive plates of the right-hand
set are Connected by a lead strap to the three negative plates
of the middle set. The two positive plates of the middle set
are similarly connected to the three negative plates of the left-
STORAGE OR SECONDARY BATTERIES
103
FIG. 89.
Connected Plates of a Three-cell Storage Battery.
FIG. 90.
Three-cell Storage Battery with Cover Removed.
104 ELECTRIC IGNITION
hand set. The two threaded bolts at the opposite corners of
the entire group are the terminals of the battery.
In Fig. 90 a case containing the three sets of plates and their
corresponding jars is shown before the sealing compound is put
on the top. The complete battery is shown in Fig. 91. The
FIG. 91.
Complete Three-cell Storage Battery containing Plates shown in Fig. 89.
knurled nuts on the terminals are shown just above the marks
"P+" and " N-."
The voltage of the three cells connected in series is three times
that of one cell alone. While the three cells will send more
amperes of current through a given external resistance than one
cell will, the maximum allowable amperage is the same for the
three cells as for one cell alone.
90. " Exide " Storage Battery. Fig. 92 shows another form
of battery that used lead plates and dilute sulphuric acid electro-
lyte. It is commercially known as the " Exide " battery. One
side of both the case and the jar is removed in the illustration,
STORAGE OR SECONDARY BATTERIES 105
H
Exide Storage Battery.
A. Terminals of battery.
B. Inverted petticoat.
C. Pillar post.
D. Plate strap.
E. Lug on plate.
F. Positive plate.
G. Acid-resisting paint.
H. Handle.
I. Vent plugs.
J. Plastic asphaltum.
K. Beveled edge at top of wood case.
FIG. 92.
Electric Storage Battery Company, Philadelphia, Pa.
L. Connector.
M. Hard rubber cover, sealed in with
asphaltum J.
N. Apron. Part of plate strap.
O. Negative plate.
P. Wooden separator.
Q. Acid-resisting compound.
R. Hard rubber cell or jar.
S. Hard rubber ribs.
T. Expansion joint.
106 ELECTRIC IGNITION
and some of the interior members partly broken away to show
the construction.
'The separator between adjacent positive and negative plates
is made of wood chemically treated before using. The chemical
treatment of the wood is to remove any substance that might be
deleterious to the cell. There are deep vertical grooves in the
separator on the side that goes next to the positive plate. These
grooves are to allow free circulation of the electrolyte and escape
of gas while the cell is being charged. In some forms of this
battery a thin sheet of hard rubber with numerous perforations
is placed between the positive plate and the grooved side of the
separator. The plates rest on high rubber ribs at the bottom
of the jar, so that there is ample space left for the sediment which
collects at the bottom of the jar. This is important, since the
battery is short-circuited internally if the sediment rises high
enough to touch the electrodes. An apron N on each strap
which connects the plates prevents the wooden separators from
rising on account of the buoyant action of the liquid. Each
vent plug / is a hollow cone with a hole near the top to allow
the escape of gas from the cell while it is being charged, and a
drainage hole at the bottom through the apex of the cone to let
the electrolyte flow back into the cell, in case any of the liquid
is carried up with the escaping gas.
The binding posts are formed so as to prevent the acid electro-
lyte from creeping up and spreading over the top of the cell.
This prevention is accomplished by forming the lead alloy into
the shape of an " inverted petticoat " which is below the binding
screw far enough to be covered with the sealing compound of
" plastic asphaltum " that covers the top of the battery except
the terminals and vents. The edges of the wood case are beveled
at the top so that the sealing compound covers them and thus
prevents the acid from soaking down into the wood if any of
the electrolyte is spilled over the top. The acid is injurious to
the wood.
Each grid is cast in one piece and has the form of numerous
small horizontal bars held in place by several thin vertical strips.
A part section of the grid, made by cutting the plate in two
STORAGE OR SECONDARY BATTERIES
107
between two of the vertical strips, is shown in Fig. 93, in which
A is a side view of part of one of the vertical strips. The small
horizontal bars are shown in cross-section at A, B, C, D, E,
and F. There are of course a great many more horizontal bars
in the entire grid than shown in this section. The exposed sur-
face of each horizontal bar appears as a line, as shown in the
preceding figure. The object of making the grid in this form is
FIG. 93.
Section of Grid for Battery
shown in Fig. 92.
FIG. 94.
Phantom View of Exide
Storage Battery.
to expose as great a surface of the paste to the electrolyte as
possible, and at the same time provide a light-weight grid which
holds the paste securely in place.
A phantom view of an Exide battery intended for ignition
usage is shown in Fig. 94. This battery is of a slightly earlier
form than that shown in Fig. 92, but is the same in a general way,
lacking only some of the improvements in detail that appear in
the latter form. The battery, Fig. 94, is made up of three cells
connected in series. Each of the three cells has three positive
plates and four negative ones. Each cell is provided with its
own vent plug.
91. Charging the Storage Battery. A storage battery of the
ignition type is generally charged and ready for use when sent
108 ELECTRIC IGNITION
out from the factory. After it has been discharged it can be
charged again by connecting to some exterior direct-current
source of electric supply and sending current through it in the
reverse direction from that in which it discharges. The positive
side of the source of supply must be connected to the positive
terminal of the storage battery, and the negative of the supply
to the negative of the battery. An alternating current cannot
be used directly for charging a storage battery, but it can be
rectified by suitable apparatus for transforming it into a direct
current which can be sent through the battery to charge it.
In charging the battery, as in discharging it, the amount of
current must be kept within the maximum safe amperage of the
battery. This is ordinarily accomplished by the use of suitable
regulating apparatus inserted in the supply circuit. A rheostat
is generally used for regulating the amount of current.
Gas is formed in the battery while charging it, slowly at first,
and then more rapidly. The formation of gas is especially rapid
when the battery has become almost completely charged. (See
also Chapter XXVI.)
92. Chemical Action in a Lead Storage Battery. When a
storage cell is in a fully charged condition and ready for use,
the active material in the plates connected to the positive ter-
minal is in the chemical form of dioxide of lead (PbO 2 ) and has
a brown color. In the negative plates the active material is in
the form of porous, or spongy, metallic lead and has a gray color.
Although this has been stated before, it is repeated here to bring
it fresh in mind.
During the discharge of the cell, the dioxide of lead in the posi-
tive plate is partly changed to monoxide of lead (PbO) by the loss
of part of its oxygen. The metallic lead in the negative plate is
partly changed into monoxide of lead (PbO) also, by the addition
of oxygen to it. The amount of sulphuric acid in the electrolyte
is reduced by decomposition into sulphur and water, so that the
electrolyte becomes weaker and has a lower specific gravity.
During the charging of the cell the above reactions are reversed
and the elements of the cell are restored, more or less completely,
to their first-mentioned condition of the charged cell.
STORAGE OR SECONDARY BATTERIES
109
93. The capacity of a storage cell is measured in ampere-hours.
An ampere of current flowing for one hour is an ampere-hour.
So is half an ampere flowing for two hours, or four amperes flow-
ing for a quarter of an hour, etc. Four amperes flowing for one
hour are four ampere-hours, and the same amount, four amperes,
flowing for two hours are eight ampere-hours. In general, the
current in amperes, multiplied by the number of hours during
which it flows, equals the number of ampere-hours.
Amperes of current X hours of time = ampere-hours.
In order to fully specify a storage battery, its voltage, or the
number of cells in it, must be stated in connection with its capac-
ity in ampere-hours. The following table refers to lead storage
batteries for ignition use, as made by one manufacturer.
SIZE AND CAPACITY OF IGNITION STORAGE BATTERIES.
All of these batteries are 9 inches high and 6f inches wide over all.
Number of
Cells in Battery.
Volts Pressure.
(Approximate. )
Ampere-hours
Capacity at Ser-
vice Rate.
Length over All.
Weight.
Inches.
Pounds.
I
2
"I f
3 i
8|
2
4
i J
5ii
I 7
3
6
7^
25!
4
8
I
9&
34
i
2
i r
4tt
12
2
4
60 J
7&
24
3
6
f 1
9rl
351
4
8
J I
W*
47^
i
2
1 r
5if
151
2
3
4
6
80
lift
3t
46
4
8
J I
?sA
61
i
2
1 r
6^|
19
2
3
4
6
100
i4fl
37^
55^
4
8
J I
I9T*
74
CHAPTER XI.
FLOATING THE STORAGE BATTERY ON THE LINE OF A
DIRECT-CURRENT GENERATOR.
94. A storage battery can be kept in continuous service by
the method of operating known as " floating the battery on the
line." A direct-current generator which will give a voltage
somewhat higher than that of the battery is ordinarily used,
but modified forms of the system use generators giving a pressure
very much higher than that of the battery, sometimes several
times that of the battery.
It is assumed in the following discussion that the generator
maintains a constant, or nearly constant, voltage slightly higher
than that of the storage battery on open circuit when fully
charged.
One arrangement of the apparatus for the above method of
operation is shown diagrammatically in Fig. 95, in which A
FIG. 95.
Direct-current Generator and a Battery Floated on the Line, with a Light Load.
represents the commutator and brushes of a direct-current gen-
erator which maintains a constant voltage, or nearly so; B is
the storage battery, and C is any piece of electrical apparatus,
such as an incandescent lamp, through which current is sent.
The current flows from the positive (+) brush of the generator
to the junction D, where it divides, part flowing through the
no
FLOATING THE STORAGE BATTERY
III
lamp C and the remainder through the storage battery B in the
direction to charge it. These two currents come together again
at the junction E and flow through the same wire to the negative
( ) brush of the generator A. The direction of the current is
indicated by the arrowheads on the lines representing the cir-
cuits. This action continues as long as the conditions remain
unchanged.
Now suppose that several additional lamps are added to the
circuit, as shown in Fig. 96, which are the maximum number
that the system is intended to operate. The battery now dis-
~l
FIG. 96.
Battery Floated on the Line, with Heavy Load.
charges so as to furnish current to the lamps, thus aiding the
generator which still supplies current, all of which flows through
the lamps. The battery and generator now operate in conjunc-
tion, both sending current through the lamps. The generator
delivers more current when all of the lamps are in the circuit
than when only one is in the circuit. If all of the six lamps are
alike, they will take about six times as much current as any one
of them alone.
The greater number of lamps requiring more current than one,
lowers the voltage at the lamps and also the difference of pressure
at the junction points D and E. When the difference of pressure
between D and E drops to a lower value than the voltage of the
storage battery on open circuit, the battery begins to deliver
current instead of receiving it, as in the case where only one
lamp was in circuit. The lowering of the pressure between D
and , due to increasing the number of lamps, causes the genera-
tor to deliver more current.
112
ELECTRIC IGNITION
Another method of arranging the apparatus is shown in Fig. 97
for one lamp, and in Fig. 98 for several lamps. The operation
of this system is in a general way the same as that of the preced-
ing two figures. The direction of current is indicated by the
arrowheads on the circuits.
If the circuit is broken between the generator and other
apparatus, the generator will of course become inoperative so
FIG. 97.
Modified Form of Fig. 95.
FIG. 98.
Modification of Fig. 96.
far as the other parts of the system are concerned. The battery
will then furnish all of the current required for the lights. This
within the limits of the battery.
Still another method of arrangement is shown in Fig. 99. The
dynamo A is placed between the storage battery B and the load
C. When the load is small, as represented by one lamp C, and
the generator is at its proper voltage, it sends current through
both the storage battery to charge it and through the lamp. The
current from the generator divides at D, part going to the lamp
and part to the positive side of the storage battery, as indicated
FLOATING THE STORAGE BATTERY 113
by the arrowheads. These divided currents unite again at E
and flow together to the negative brush of the generator. If the
full load is put on, as represented by several lamps in Fig. 100,
then the storage battery discharges into the circuit, thus aiding
the generator. Both send current through the lamps. The
direction of the current is indicated by the arrowheads. The
two currents unite at D and flow together through the lamps.
FIG. 99.
Electric Generator between the Load and the Battery which is Floated on the
Line. Light Load.
m
I r4
.7*N -PF*
c
FIG. 100.
Electric Generator between Heavy Load and a Battery, which is Floated on the
Line.
They then separate at E, part going to the negative brush of
the generator and the remainder to the negative side of the
battery.
95. An automatic cut-out is used on some storage-battery and
generator systems in which the storage battery is floated on the
line. This has been mentioned in connections with Figs. 63
and 64. The purpose of this cut-out is to prevent the flow of a
large reverse current from the battery through the generator in
case the latter slows down so as not to give a sufficiently high
voltage, or in case of its complete stoppage. It is often desirable,
ELECTRIC IGNITION
and especially so for ignition service where the motor runs inter-
mittently, to have the cut-out also operate automatically to put
the generator into circuit when its speed is again sufficient to
give the necessary voltage.
An electric system with an automatic cut-out of the last-
mentioned type is shown diagrammatically in Fig. 101. The
cut-out consists of an electromagnet with a double winding and
an armature with a contact-point at one end. The cut-out
armature as shown consists of a blade spring to which is fastened
a contact point and a soft steel disk, the latter opposite the end
of the magnet core. One end of the blade spring is fastened to a
DTG7Generator>
la C
[
'
D
At
C
Core--:
Shunt ^
Coil
Seriesx^
Coil ^
itomatic
ut-Out
11
Storage
Battery
9~
~*
^T^
k ' F
_^ f
b
E
i
^kcot
^-kfJ tArmatuie Po
FIG. 101.
Complete Dynamo and Storage-battery System with an Automatic Cut-Out.
stationary block G in such a way that the elastic action of the
spring tends to draw the armature away from the core and sepa-
rate the contact-points. When the core is magnetized it attracts
the cut-out armature and holds it in the position shown with its
contact-point pressed against the mating contact-point to which
is connected one end of one of the magnetizing coils of the cut-out.
If the magnetism of the cut-out core becomes weak, the armature
then springs away from it so as to separate the contact-points.
One coil of the cut-out is permanently connected in series with
the field-magnet coils of the shunt-wound generator. This coil,
marked " shunt-coil " in the figure, has a comparatively great
number of turns of insulated wire large enough to continuously
carry the current that flows through the field-coils of the genera-
tor. The other coil of the cut-out, marked " series-coil," is in
series with the main circuit of the generator. This coil has com-
FLOATING THE STORAGE BATTERY 115
paratively few turns of insulated wire large enough to carry all
of the current from the generator.
When the system is operating in the regular manner, the cur-
rent flows through the circuits in the direction indicated by the
arrowheads on the lines representing the circuits. Since the
direction of flow in the two lines leading from the storage battery
to the points D and E may be first in one direction and then in
the other, it is indicated by a pair of opposed arrowheads on
each line. The currents in both coils of the cut-out flow in the
same direction around the core, and both magnetize the core in
the same direction so as to keep the contact-point of the cut-out
armature drawn up against its mate.
If the generator slows down so that its voltage drops below
that of the battery, then the battery sends current back to the
generator and through it and the cut-out coils. This back cur-
rent flows from the positive (+) terminal of the battery to D
and then to the positive (+) brush of the generator, where it
divides, part flowing through the field-coils of the generator and
the shunt-coil of the cut-out in the same direction as before to
the junction F. The remainder of the back current flows through
the armature of the generator to the negative ( ) brush and
thence to F. From F all of the back current flows through the
series-coil of the cut-out in the opposite direction from that
in which it flowed before. The direction of the back current
through the main circuit is indicated by the arrows alongside the
circuit.
The back current through the series-coil of the cut-out opposes
the magnetizing action of the current in the shunt-coil and demag-
netizes the core of the cut-out enough to allow the cut-out arma-
ture to spring back so as to separate the contact-points. The
current through the series-coil stops as soon as the circuit is
opened by the separation of the contact-points. A weak current
continues in the shunt-coil as long as the generator keeps running
at slow speed. This cur rent xeases as soon as the generator stops
running. There is then no current in any part of the system to the
right of the points D and E. The battery keeps sending current
continuously through the part of the system to the left of it.
n6
ELECTRIC IGNITION
If the generator is started again, the contact-points of the
cut-out still remaining apart, it will at first send current through
only its field-coils and the shunt-coil of the cut-out, including
of course the generator armature and the connections of this
circuit. When the voltage at the brushes of the generator be-
comes somewhat higher than that of the battery as the speed
increases, the current sent through the shunt-coil is great enough
to magnetize the core sufficiently to draw the cut-out armature
toward it and thus close the circuit at the contact-points. This
establishes the normal condition of operation.
The size of the cut-out as shown in the figure is much larger
in proportion to the other apparatus than it is in the constructed
apparatus. It is shown large in order to make its construction
appear plainly.
A compound-wound direct-current generator can also be used
with a cut-out of this nature.
In Fig. 102 a storage battery is floated on the line of a variable-
speed direct-current dynamo. A volt-ammeter is included in
VOLT AMMETER
U=-11CONNECT(-1)AND(+4)
WIRES THROUGH PROPER
SWITCHES FOR IGNITION
AND LIGHTING THE SAME.
^4JAS FROM A BATTERY
APLCO 10*
PATENTS DYNAMO WITH LOAD
APLCO LIGHTING STORAGE BATTERY PENDING REGULATOR & CUT-OUT
FIG. 102.
APLCO Electric System with Battery Floated on the Line. Apple Electric
Company, Dayton, Ohio.
the system, for measuring the voltage of the battery and the
amount of current flowing through the battery.
The hand, or pointer, of the volt-ammeter is shown pointing
to the zero of the scales on the dial. When the dynamo is send-
FLOATING THE STORAGE BATTERY
117
ing current through the storage battery to charge it, the indicator
hand moves to the left and points to the lower scale, which gives
the reading of the amount of charging current. When the
battery is discharging, the indicator hand moves to the right of
the zero and indicates the current rate of discharge. To obtain
the voltage of the battery, the push-button (" press-button ")
must be pressed in. The indicator hand then points to the
pressure on the upper scale. The current through the battery
is indicated continuously except during the time the button is
pressed in to obtain the reading of the voltage.
The dynamo is provided with an automatic cut-out and a load
regulator. The latter regulates the current delivered by the
dynamo within a limited range. It does this by automatically
varying the resistance in the field-coil circuit. The load regu-
lator makes it possible to drive the armature of the dynamo at
a rotative speed proportional to that of the crank-shaft of the
motor, even when the speed of the crank-shaft is extremely
variable, as in automobile and boat motors, and still keep the
current from the generator approximately constant as long as
the armature rotates fast enough to generate sufficient voltage.
The automatic cut-out opens the dynamo circuit when the speed
of the armature falls below the requisite amount.
FIG. 103.
Two-voltage System with Two Storage Batteries Floated on the Line.
96. A two-voltage system with two storage batteries floated
on the line is shown in Fig. 103. Two storage batteries of the
same voltage are connected in series between the positive and
negative sides of the circuit in the same manner as the one
Il8 ELECTRIC IGNITION
storage battery in Figs. 99 and 100. This system gives two
voltages, one double the other when the two storage batteries
are of the same voltage, as stated.
A two-point switch in the ignition circuit can be closed on
either of the two contact-points by placing the pivoted arm in
the corresponding position.
The flow of current through the system depends on the amount
of electrical resistance of the ignition apparatus relative to the
voltage of the storage batteries. The resistance of the ignition
apparatus is ordinarily low enough for the method of operation
to be as follows:
When the voltage of the dynamo brushes is higher than that
of the storage batteries in series, as measured between the points
T and U, and the switch is closed as shown, then while the cir-
cuit is closed in the ignition apparatus, the current from the
positive brush of the dynamo flows to O, then through the switch
and ignition apparatus to S, thence through battery 2 and to the
negative brush of the dynamo. At the same time current flows
from the positive terminal T of battery i to 0, then through the
switch and ignition apparatus to S, and thence to the negative
terminal of battery i. While the circuit is broken in the igni-
tion apparatus in the usual manner of operation, the dynamo
sends all of its current to T and through both storage batteries
in series so as to charge them. If the dynamo stops and is cut
out of circuit, then battery i supplies the current to the ignition
apparatus, and battery 2 is idle.
When the switch is closed as shown, and the voltage at the
dynamo brushes is higher than that of the two batteries in series,
then battery 2 continuously receives charging current, and
battery i is alternately discharged and charged in accordance
with the closed and open positions of the ignition apparatus.
When the switch is closed on its other contact-point, the bat-
tery 2 is alternately discharged and charged, and battery i is
continuously charged.
97. A two-voltage system with lamps and ignition apparatus
is shown in Fig. 104. The voltage at the lamps is approximately
twice that at the ignition-apparatus terminals. At the lamps
FLOATING THE STORAGE BATTERY
119
the voltage is approximately equal to that of both batteries in
series; at the ignition apparatus the voltage is approximately
equal to that of one battery. If there were no loss of voltage
Battery 1
1
+o
Ignition
Lar
&
ips
&
C
ND.C.
'Generator
T3
1 Apparatus
F -1 /
It ^
p2
1
1' -J Two-PointC
Switch
Battery 2
-
FIG. 104.
Two-voltage System with Lamps and Ignition Appliances.
in the connecting wires, the voltage at the lamps would be the
same as that of the two batteries in series; and that at the ignition
apparatus would be equal to that of one storage battery.
The manner of operation of this system is essentially the same
as that of Fig. 103.
98. A switchboard for a two-voltage system, a direct-current
dynamo, and two storage batteries are connected together in
Fig. 105. The switchboard has an ammeter for indicating the
amount of current, and a voltmeter for measuring the pressure
of the system. There is also a pilot lamp which glows while its
circuit is closed by pressing the push-button at the left-hand
side of the board. The voltmeter is made to register by pressing
the push-button at the right-hand side of the board. The opera-
tion of the system is essentially the same as that of Figs. 103
and 104.
The board has five switches, all of the blade, or knife, type,
whose handles are shown at i, 2, 3, 4, and 5.
When the double-pole double-throw switch i is closed on the
dynamo side of the switchboard, as shown, the dynamo sends
current through both storage batteries in series to charge them,
and at the same time supplies current to the 12 -volt lamp circuits.
Opening the switch breaks both the armature circuit of the
120
ELECTRIC IGNITION
FIG. 105. (See also Figs. 106 and 107.)
Switchboard Apparatus and Connections.
dynamo and its field-circuit, and also breaks the battery circuit
to the i2-volt lamps. When the switch is closed in its left-hand
position, the battery discharges through the i2-volt circuits if
the lamps are turned on. The connections to the ignition circuit
are not affected by opening or reversing the main switch i.
FLOATING THE STORAGE BATTERY
121
Q< Volt Meter ->Q_
^
^
1 "?
6 Volts for Ignition Coils a>| r f ^_ 12 Volts->
Lights
Indicates a Closed Switch
FIG. 106. (See also Figs. 105 and 107.)
Wiring Diagram showing Connections at the Back of the Switchboard.
The single-pole double-throw switch 2 is for cutting the am-
meter into or out of circuit. The ammeter is in circuit when
this switch is in the position shown. Opening this switch breaks
either the main circuit of the dynamo or the battery-discharge
circuit, according to the position of the main switch i.
The single-pole double-throw switch 3 is for reversing the
122
ELECTRIC IGNITION
direction of the 6- volt current through the ignition apparatus.
When the switch is in the right-hand position, as shown, the
ignition apparatus takes current from battery 2 if the main
switch is closed in the battery-discharge position. If the ignition
switch 3 is closed in its left-hand position, then battery i supplies
current to the ignition apparatus.
The single-throw switches 4 and 5 are for opening and closing
the lamp circuits.
The wiring diagram of the switchboard is shown in Fig. 106,
which also shows the automatic cut-out for protecting the dy-
FIG. 107. (See also Figs. 105 and 106.)
Dynamo, Storage Battery and Switchboard. Dayton Electrical Manufacturing
Company, Dayton, Ohio.
namo. The switch-blades are represented by broken lines. The
double-throw switches are represented as closed in the reverse
positions of the preceding figure. The diagram shows the igni-
tion apparatus connected to the positive side of battery i. The
ammeter is out of circuit, and both the main circuit and the field
circuit of the dynamo are open.
Fig. 107 is a photographic illustration of the dynamo, switch-
board, and two 6-volt storage batteries such as are used in a
system of the nature just described. It is suitable for ignition
and lights on a small boat.
CHAPTER XII.
MECHANICALLY OPERATED MAKE-AND-BREAK IGNITERS AND
KICK-COILS FOR LOW-TENSION IGNITION.
99. A mechanically operated igniter in the form of a low-
tension ignition plug is shown in Fig. 108 together with the
means of operating it. The illustration is elementary in its
FIG. 108.
Make-and-break Igniter or Spark-Plug.
Elementary Form.
nature. Part of the metal plug A is cut away to show the con-
struction. The front end of the igniter remains outside of the
cylinder of the motor when the igniter is in place, and the back
end either projects into the combustion chamber or forms part
of its wall.
123
124 ELECTRIC IGNITION
A metal rod B extends through the plug and is enlarged at
the inner end as shown at C. The hole through which this bar
passes is considerably larger than the bar and is coned at the
ends to fit correspondingly shaped insulators C and .D, which
hold the rod in place and insulate it from the plug A. When
the nut E is screwed down it draws the insulating cones C and D
into the taper ends of the hole in the plug so as to make a gas-
tight joint, and suitable packing around the rod next to the
enlarged inner end and under the nut makes tight joints at these
points.
A knurled nut F at the outer end of the insulated electrode B
affords a means to attach the wire or other form of electric con-
ductor which brings the current to the plug. The screw G can
be used for attaching the other wire when it is desired to bring
both sides of the electric circuit to the igniter in this manner.
The more general practice is to connect one side of the circuit
to the metal of the motor at the most convenient point. The
metallic contact between the plug and the motor metal gives
electric connection also between them.
A movable spindle H fits in another hole through the plug so
as to have metallic contact with the plug, and at the same time
be free to rotate, or rock, in the body of the plug. The inner
end of the spindle has a metal arm / rigidly attached to it. This
arm is sometimes called the movable electrode. Another rocker-
arm J is fastened rigidly to the outer end of the spindle H. A
blade-spring K is fastened to the rocker-arm J at the end next
the spindle H and is of such a form that its free end stands away
from the arm when the spring is not stressed. This completes
the igniter proper.
When the outer arm J is raised it rocks the inner arm / down
so that it makes contact with the inner end C of the insulated
electrode B and thus closes the electric circuit between the in-
sulated electrode and body A of the plug. Then when the arm
J is moved downward so as to separate the movable electrode
from contact with the insulated electrode, an electric arc is
drawn between the electrodes C and / at the point where the
contact is broken.
MAKE-AND-BREAK IGNITERS AND KICK-COILS 125
The means for operating the igniter consist, as shown, of a
cam L and a cam-follower M. The latter is in the form of a
push-rod with a collar N and an enlarged spherical upper end O.
The push-rod passes freely through suitable openings in the ends
of the arm / and spring K. The spring presses lightly down-
ward against the collar when the parts are in the position shown.
The guide P is for keeping the push -rod in position. The cam
is driven by the shaft on which it is mounted.
As the cam L rotates in the direction indicated by the arrow
on it, the projecting lobe of the cam lifts the push-rod M and
then allows it to drop when the edge of the lobe passes from under
the push-rod. This occurs when the cam has passed through
about three-quarters of a revolution from the position in which
it is shown.
The upper movement of the push-rod first lifts the rocker-arm
/ so as to bring the movable electrode I down against the station-
ary electrode. The movement of the rocker-arm is stopped as
soon as the movable electrode makes contact with the stationary
one. The continued upward movement of the push-rod bends
the spring K and the rod slips up through the arm so that the
enlarged end rises above the arm. When the edge of the cam
passes from under the push-rod, the reaction of the spring snaps the
push-rod down quickly so that the knob on the upper end strikes
the rocker-arm a sharp blow and drives its free end downward so
as to cause a rapid separation of the electrodes. This is known as
the hammer-break method of interrupting the electric current.
The rapid separation of the contact-points of the igniter is
very essential to the successful operation of the igniter. Com-
pared with slow separation of the contact-points, the rapid
separation produces a better arc for ignition and causes less
fusing, or burning, of the contact-points.
The insulation used in the igniter is generally either mica or
steatite (soapstone). The mica should be pure and especially
free from any metallic substance or metallic compounds. When
steatite is used, it is generally first machined to form and then
baked at a high temperature to bring it to the condition in which
it is commonly used for the tips of gas burners.
126 ELECTRIC IGNITION
The contact-pieces (points) of the igniter are generally made
of either platinum, an alloy of platinum and iridium (platino-
iridium), of steel alloy, especially a steel alloy containing a large
proportion of nickel together with less amounts of other elements.
While platinum and its alloys are excellent for the purpose, they
are extremely expensive. Only small pieces are set into the
electrodes, and are generally removable.
100. The duration of contact between the electrodes of a
mechanically operated igniter should be as short as possible to
establish current flow to the necessary amount when the source
of electricity supply is a battery. Long duration of contact is
wasteful of electricity and soon exhausts the battery. On the
other extreme, when an alternating-current generator supplies
the electricity in the usual manner, the electrodes may be kept
in contact continuously except during the time necessary to
separate them to form the arc and to close them again immedi-
ately, so far as current supply is concerned. When electricity
is supplied by a direct-current generator, it is generally advisable
to have a short period of contact, since imperfect contact main-
tained for some time may cause fusing of the electrodes.
Other conditions, such as the use of several igniters in the
different combustion chambers of a motor with several cylinders,
may make a short period of contact necessary. It is generally
undesirable to have the electric circuit closed through two or
more mechanically operated igniters in different combustion
chambers at the same instant. In some ignition systems it is
impossible to operate when two igniters in different combustion
chambers have their electrodes in contact at the same instant.
101. Bosch Mechanically Operated Igniter. Fig. 109 shows
two views of an igniter and operating mechanism as constructed
by the Bosch Magneto Company. The side of the igniter is
shown in (a), and the external end in (b).
A coiled tension-spring A acts on one end of the external
rocker-arm B so as to press the movable electrode C against the
stationary electrode D when the operating rod E is lifted by the
cam F. The operating rod E is pressed downward by a coiled
compression spring G, whose lower end bears against a collar on
MAKE-AND-BREAK IGNITERS AND KICK-COILS
127
the rod and whose upper end bears against the stationary sup-
port H.
As the cam F rotates it lifts the operating rod E against the
resistance of the compression spring so as to first allow the
coiled tension spring A to pull the contact-point of the movable
electrode against the stationary one, and then to push the rod
up still farther so that it slips through the hole in the external
rocker-arm. The enlarged upper end of the rod is thus lifted
FIG. 109.
Bosch Make-and-break Igniter. Bosch Magneto Company, New York City.
free from the rocker-arm. As the cam lobe passes from under
the cam follower, the operating rod E is forced downward by
the expansive action of the compression spring G, and the ball
at the top of the rod strikes the external rocker-arm and moves
it down so as to quickly separate the contact-points of the elec-
trodes. The compression spring G is made strong enough to
overcome the resistance of the tension spring A and keep the
128 ELECTRIC IGNITION
cam follower in continuous contact with the cam during the
highest speed at which the igniter is to be used in any particular
application.
The lower end of the operating rod E is pin-connected to one
end of each of a pair of links 7 whose opposite ends are similarly
connected to a short rocker-arm on the shaft J. These links
carry the roller K which bears against the cam and follows its
outline. The short rocker-arm just mentioned can be rocked by
a control lever L fastened to the same shaft. The shaft J of
the controller and the cam shaft are supported by bearings
which are maintained in fixed positions relative to the igniter
plug.
The control lever L is used to vary the instant of separation
of the contact-points of the electrodes relative to the rotative
position of the cam and to the position of the piston of the motor
in its movement; in other words, to advance the ignition by
causing it to occur earlier in the revolution of the cam, or to
retard it by causing it to occur later. The ignition is advanced
by moving the control lever to the right, and retarded by moving
it to the left. The dotted outline of the control lever to the
right is its position for early ignition, and the dotted outline at
the left is its position for late ignition.
102. Truscott Boat Manufacturing Company's Igniter. This
igniter is used especially in motor boats. It is shown in Fig. no.
The outer end of the stationary insulated electrode appears at
A . This electrode extends through the plug in the usual manner
and projects inward near the end of the movable electrode B,
which is fastened to a rotative spindle whose outer end is shown
at C. A hammer-break arm D fits freely rotatable on the spindle
C and is normally pressed against a stop on the spindle by a
coiled torsion spring E. One end of E is fastened to a taper pin
which passes through the rocker-shaft.
When ignition is to occur, the free end of the rocker-arm D
is raised by the lifter G, which is bored to fit freely rotatable
on the end of the push-rod H. As the arm D is lifted it rocks
the spindle C and contact arm B with it until the contact-point
in B strikes against the stationary electrode. This prevents
MECHANICAL MAKE-AND-BREAK IGNITERS 129
further movement of both the rocker-arm B and the spindle C,
but the hammer-break arm D is lifted still higher and turns on
the spindle C so as to separate itself from the stop on the spindle.
The lifting of D winds up the spring E to a slight extent more
than it is normally. The lifter-arm H continues rising till it
disengages from D. The spring E then snaps the hammer-break
H
FIG. no.
Make-and-break Igniter. Truscott Boat Manufacturing Company, St. Joseph,
Michigan.
arm D down quickly so that it strikes a sharp blow against the
stop on the spindle C and causes rapid separation of the ignition
points. The downward movement of D continues till it strikes
the arm F and is stopped in a horizontal position.
The lifter-rod H then descends, carrying with it the lifter G,
and the end of G strikes against the bevel / on D. The end of G
is also beveled where it strikes the bevel /. The action of the
bevel twists G around on H as they descend, so that G slips down
past D and is then snapped back under D by the coiled tension
spring / so that the lifter G is again brought into position to
lift D.
K and K are nuts on the stud-bolts L and M for fastening the
igniter to the motor. The lower stud-bolt M is extended outward
130
ELECTRIC IGNITION
and serves as a binding-post for holding one of the wires of the
external circuit.
Fig. in shows the mechanism for operating the push-rod.
This is accomplished by an eccentric N on the crank-shaft of
o
FIG. in.
Operating Mechanism of Fig. no.
the motor. The eccentric strap P is connected to the member
Q by the pin R. The member Q is fastened to the lower end of
the push-rod H and is limited to vertical movement by the
plunger S which fits in a suitable guide. The eccentric has a
free rotative fit on the crank-shaft and is connected to the arms
of a fly-ball governor (not shown) also mounted on the crank-
MECHANICAL MAKE-AND-BREAK IGNITERS 131
shaft. The eccentric is thus caused to rotate with the crank-
shaft so as to move the push-rod, but its angular position on the
crank-shaft is changed by the action of the governor as the speed
of rotation varies. This shifting of the eccentric varies the time
of ignition so that it occurs earlier at high speeds of rotation than
at slow speed. When the motor stops, the governor brings the
eccentric to a position such that ignition cannot occur before
the crank of the motor has passed its dead-center position just
after compression of the combustible charge. This prevents
ignition at such an instant as to drive the crank-shaft of the
motor backward when starting it.
103. The Fay & Bowen low-tension igniter, Fig. 112, has an
adjustable hammer-break device as part of the igniter. Both
FIG. 112.
Fay & Bowen Make-and-break Igniter.
the stationary electrode A and the movable electrode B are
provided with inserted contact-pieces, or points. The hammer
for breaking the circuit comprises a head C and a rod, or plunger,
D. The latter slides through holes in the outer end of the body
of the igniter, and is pressed against the cam E by a coiled com-
pression spring F which is wound around the plunger and bears
against a collar on it. The head of the hammer has an adjust-
able striking piece G which is pressed against the external arm
H of the movable electrode so that the contact-points of the
electrode are kept apart except while the plunger is pushed back.
When the plunger is pushed back by the rotating cam E, the
coiled tension spring 7 draws the contact-point of the movable
132 ELECTRIC IGNITION
electrode against the contact-point of the stationary electrode.
The tension spring / is connected to one end of the external arm
H of the movable electrode. The cam forces the hammer back
far enough to remove its striking piece to some distance from
the arm //. When the edge of the rotating cam passes out of
engagement with the plunger, the hammer, including the plunger,
is snapped down by the spring F and the striking piece hits the
arm H so as to drive it around and separate the contact-points
of the electrodes quickly.
104. Westinghouse make-and-break igniters are shown in
Fig. 113. One is right-hand and the other left-hand. The mica
FIG. 113.
Low-tension Igniter of the Westinghouse Machine Company, Pittsburg, Pa.
washers for insulating the stationary electrode at the outer end
are visible at A . The inner end of the plug is recessed to receive
similar insulation. The contact-points of the electrodes are
pressed together by a coiled torsion spring wound around the
rocker-spindle of the movable electrode and pressing against the
outer rocker-arm. These plugs have removable contact-points
in the electrodes.
MECHANICAL MAKE-AND-BREAK IGNITERS 133
105. The Snow Steam Pump Works mechanically operated
make-and-break igniter for low-tension current is shown in
Fig. 114. The cast-iron plug i has the metal cut away in the
middle portion to secure lightness and ease of construction. A
flange at the outer end serves as a means of supporting some
of the external parts and for fastening the plug to the engine.
The movable electrode 2 is of high-grade nickel steel and is
one piece with the inner rocker-arm 8 which carries the removable
contact-point 9. The inner end of the spindle rocks in a station-
ary bronze bushing 15, and the outer end is provided with a tight-
fitting bronze sleeve 17 which rocks in a steel bushing 16. The
external rocker-arm is fastened to the spindle by a bolt-and-nut
lock.
The stationary electrode 3 is insulated from the plug by mica
washers 4 and 5, and lava bushings 6 and 7. It is held in place
by nuts 12 and 13, which also hold the terminal n into whose
shank is soldered the wire for bringing electricity to the electrode.
A removable contact-point is set into its inner end.
Two oil pipes 20 connect the outer end of the plug with oil
passages leading to the inner bronze bushing 15. These oil
passages are shown most clearly in the " section on B-B."
A threaded hole 22 through the flange of the plug is for the-
insertion of a cap-screw, or a set-screw, which can be screwed
down to press its point against the metal of the engine and thus
forcibly withdraw the plug from the engine to a short distance
after the fastenings have been removed.
The outer ends of two of these igniters with all attached parts
are shown in Fig. 115. The reference numbers in this figure
are not the same as in the preceding one.
106. The mechanical make-and-break operating mechanism
of the Snow Steam Pump Works for a pair of igniters in the same
combustion chamber is shown in Fig. 115. The igniters are
like the one shown in the preceding figure.
The head of the upper igniter is shown at i, and that of the
lower one at 2. The ends of the insulated stationary electrodes
of the two igniters are at 3 and 4, and the wire terminals for the
electric conductors are shown in place fastened to these elec-
134 ELECTRIC IGNITION
FIG. 114. (See also Fig. 115.)
Low-tension Igniter. Mechanical Make-and-Break. For Large Engine. The
Snow Steam Pump Works, Buffalo, N. Y.
1. Body of plug; cast-iron.
2. Movable electrode; steel, not insulated.
3. Insulated stationary electrode, steel.
4. 5. Mica washers for insulating stationary electrode.
6, 7. Lava insulating bushings.
8. Inner rocker-arm; integral part of rocker-shaft 2.
9. Contact-point; movable and removable.
10. Contact-point; stationary, removable.
11. Terminal to which electric conductor (wire) is soldered.
12. 13. Nuts for fastening stationary electrode and terminal in place.
14. External rocker-arm end. Shown better in Fig. 115 as parts 5 and 6.
15. Bushing for rocker-arm bearing; stationary, bronze.
16. Bushing for rocker-arm bearings; stationary, steel.
17. Sleeve, tight on 2, loose in 14; bronze.
1 8. Oil hole.
19. Groove for oil pipe.
20. Oil pipe leading to inside bearing of rocker shaft.
21. Stud-bolt and nut for fastening igniter to engine. Two used.
22. Threaded hole in flange of plug. For bolt to start (loosen) the plug to remove
it from the engine.
MECHANICAL MAKE-AND-BREAK IGNITERS
22.
OUTER END OF PLUG
22
1
j
,1
ll
II
j
l!
|
i]
i
-i
i
i
i
i
?
-i
!' ''
l! !i ' i
ten <H
L_J
SIDE OF PLUG
15
LONGITUDINAL SECTION ON A-A
SECTION ON B-B SECTION ON C-C
FlG. 114.
INNER END
136 ELECTRIC IGNITION
trodes by nuts. The external rocker-arms, or tappet-arms, 5 <and
6 are in positions which they have when the contact-points of
the electrodes are touching each other. The contact-points and
inner rocker-arms are represented by broken lines. The coiled
tension springs, 7 for the upper igniter and 8 for the lower one,
connected to the external rocker-arms, are for bringing the con-
tact-points of the movable electrodes against the stationary
contact-points.
The cam-shaft 9 has fastened to it a cam-lobe 10, which pushes
back the cam-follower, or push-rod, n, as the cam rotates in the
direction of the arrow on the cam-shaft. The push-rod is con-
nected to the tappet-rod 13 by means of the pin 20. The tappet-
rod is pin-connected to the rocker-links 16 and 17, which swing
on stationary shafts 18 and 19 respectively. The pin 20 makes
the connection to 17, and a similar pin connects the tappet-rod
to the link 16.
As the push-rod n is forced back against the resistance of
the coiled compression spring 21 by the action of the cam, the
tappets 14 and 15 are moved away from the tappet-arms 5 and 6.
Then when the cam-lobe passes out of engagement with the push-
rod, the latter is forced quickly toward the left by the spring 2 1 .
The tappet-rod and tappets follow the same movement, and the
tappets strike the arms 5 and 6, thus causing rapid separation
of the contact-points of the electrodes. The push-rod and
attached parts continue their movement toward the left till the
buffer 25 strikes the stop-block 22. The push-rod is kept in
its position farthest toward the left by the action of the spring
21, with the buffer pressed against the stop-block, until the cam
again forces the push-rod back for another ignition. The con-
tact-points of the electrodes are thus kept separated and the
electric circuit broken at them except during the time the cam
pushes the rod back as far and farther than the position in which
the push-rod is shown.
The time of ignition can be adjusted by means of the parts
26 to 30 inclusive. The ignition is advanced by rotating the
hand-wheel 26 so as to run the screw farther into the nut 27.
This movement of the hand- wheel forces the block 29 against
Operating Mechanism for Make-and-break Igniter.
Outer end of upper igniter plug. 12.
Outer end of lower igniter plug. 13.
Insulated stationary electrode of upper igniter.
Insulated stationary electrode of lower igniter. 14,
External rocker-arm of upper igniter.
External rocker-arm of lower igniter. 16,
8. Coiled tension springs for drawing contact-points of elec- 18,
trodes together. 20.
Cam-shaft or lay-shaft. 21.
Cam-lobe for operating the pair of igniters. 22.
Cam follower, or push-rod; extends up to the yoke 12.
FIG. 115. (Se<
Two Igniters Arranged as a
Yoke on upper end of push-i
Tappet rod, pin-connected
16 and 17.
15. Flanged tappet nuts on i
5 and 6.
17. Upper and lower rocker-
19. Stationary shafts suppor
Pin for connecting 12, 13 an<
Coiled compression spring fo
Stop-block for stopping the
shaft.
SIDE VIEW
o Fig. 114.)
and Operated by One Push-Rod.
e yoke 12 and the rocker-links
striking the igniter rocker-links
on stationary shafts 18 and 19.
rocker-links 16 and 17.
:irig push-rod n toward cam 10.
on of push-rod n toward cam-
The Snow Steam Pump Works, Buffalo, N. Y.
23. Bracket for holding stop-block 22.
24. Guide, flanged at right-hand end.
25. Four leather washers between flange on guide 24 and steel wai
next to 22.
26. Hand-wheel and screw for adjusting time of ignition.
27. Adjusting nut and spring sleeve; held by stud 28.
28. Stud for supporting 27; stationary.
29. Block at end of adjusting screw.
30. Coiled compression spring for holding push-rod n against 29
MECHANICAL MAKE-AND-BREAK IGNITERS 137
the push-rod and moves the latter toward the coiled compression
spring 30, which is still further compressed by this action. Re-
tarding the ignition is accomplished by a reverse rotation of the
hand-wheel. The nut and spring- tube 27 is held in place by
the stationary stud-bolt 28.
The push-rod swings about the pin 20 as a hinge-joint when
the rod is moved sidewise to advance or retard the ignition. In
order to allow this motion of the push-rod, the stop-block 22
must move sidewise in its supporting bracket 23. The stop-
block has a sliding fit on the guide 24 which is fastened to the push-
rod. The bracket is cylindrically curved on the surfaces that
bear against the stop-block to prevent its moving in the direction
of the length of the rod, the center of curvature being coincident
with the axis of the pin 20 when the latter is in the position
shown. The corresponding bearing surfaces of the stop-block
are similarly curved to fit the bracket.
The portion of the mechanism consisting of the tappet-rod 13,
and the rocker-links 16 and 17, may be recognized as " Watt's
parallel motion," which causes the point at the middle of the axis
of the push-rod to move in almost exactly a straight line for a
short distance on either side of the position shown.
107. A four-unit low-tension mechanism with one make-and-
break igniter for each of four combustion chambers is shown in
outline in Fig. 116. The insulated stationary electrodes are i, 2,
3, and 4. The movable electrodes are A, B, C, and D. The
corresponding cams are #, , c, and d, all on the same shaft. The
full line GH with branches leading to each insulated electrode
represents the electric conductors for carrying current to the
insulated electrodes. The broken line with branches to each
rocker-spindle of the movable electrodes is to indicate that all
of these electrodes are electrically connected together by the
metal of the motor, or otherwise.
The cams are fixed on the cam-shaft at equal angles with each
other so as to operate the igniters at regular intervals relative
to the rotation of the cam-shaft. As shown, electrodes A and i
are in contact with each other. The order of action of the ig-
niters, given by the numbers of the insulated electrodes, is i, 3,
138
ELECTRIC IGNITION
4, 2 when the cams are fastened to the cam-shaft in the position
shown.
FIG. 116.
Make-and-break Igniters Arranged for Four Combustion Chambers.
108. An Allis-Chalmers gas engine with mechanical make-and-
break low-tension igniters is shown in Fig. 117, reproduced from
a photograph of the engine. The four igniters are at i, 2, 3, and
4. The cam-shaft 5 lies parallel to the stroke of the pistons and
carries four cams, one for each igniter. It is driven by screw-
gears and a cross-shaft in the casing 6. Advance and retard of
ignition is effected by moving one of the screw-gears along its
shaft so as to change the relative rotative positions of the driving
and driven shafts. The hand-wheel 7 is for shifting the screw-
gear to adjust the ignition as described.
Kick-Coils.
109. A single-wound kick-coil, also called reactance coil and
spark-coil in combustion-motor practice, is used in connection
KICK-COILS
139
W
140 ELECTRIC IGNITION
with low-tension mechanical make-and-break ignition systems
in order to obtain a good electric arc between the contact-points
of the igniter when current is supplied by a battery, also, under
some conditions, when current is supplied by a dynamo.
A kick-coil consists essentially of a coil of insulated copper wire
wound in several layers around a bundle, or sheaf, of small wires
of mild steel or soft iron. Fig. 118 shows one form of kick-coil.
FIG. 118. FIG. 119.
Kick-Coil with the Ends of the Kick-Coil with Protective Cap over
Core Exposed. Ends of Core.
A is the core of small wires of soft iron or mild steel, and B is
the coil of insulated copper wire. The core and wire are mounted
on a wooden frame C. The ends of the insulated copper wire
of the coil are connected to binding posts D and E, which are
the terminals of the coil. The kick-coil is neither more nor less
than an electromagnet, but it takes the names just given above
on account of the use to which it is applied.
Fig. 119 is another kick-coil in which the ends of the core are
covered with non-magnetic caps to prevent rusting.
Other forms of mountings for kick-coils are shown in Figs. 120
and 121. In the latter the coil is inclosed in a water-tight casing.
The sizes of the kick-coils found in use vary considerably,
those for very large engines being larger than those for small
ones. The average size is about 6 inches long over all, with a
core from ij to ij inches diameter, and with a coil from 3 to 3^
inches long containing from 5 to 6 pounds of insulated copper
wire, including the weight of the insulation on the wire. The
insulation on the wire is generally a double covering of cotton
KICK-COILS
141
thread such as is ordinarily used for insulating magnet wires.
The diameter of the copper wire is generally that corresponding
to No. 14 American wire gauge (.064 inch), or somewhat larger.
The electrical resistance of the coil is generally in the neighbor-
hood of one ohm. These dimensions apply to coils such as are
FIG. 1 20.
Kick-Coil. Ordinary Type.
FIG. 121.
Kick-Coil Inclosed in Waterproof Casing.
used with small stationary engines. Kick-coils longer in propor-
tion to the dimensions just given are sometimes used, but they
are not as efficient as the shorter ones of equal weight and elec-
tric resistance.
The kick-coils intended for use in damp places, as on open
boats, generally have the insulation on the wires saturated with
waterproof insulating varnish put on by a process which removes
moisture from the covering wrapped on the wires.
142
ELECTRIC IGNITION
110. Screw-top Kick-Coil. A kick-coil with a screw top is
shown in Fig. 122. The threaded top of the coil can be screwed
into a plate such as is sometimes used for
a battery (see Fig. 82). The size of the
coil, i\ by 6 T 3 g inches, is practically the
same as that of a standard dry cell. It
can therefore be put into the screw-plate
along with dry cells, occupying the same
amount of space as one of the cells. The
coil is also provided with the usual form
of terminals and nuts, so that wires
can be connected to it in the usual
manner.
111. Tell-tale Kick-Coil. A kick-coil
with a tell-tale for visibly indicating the
action of an igniter is shown in Fig. 123,
FlG I22 in both side and end views. The tell-tale
Screw-top Kkk-Coilto go in consists of a piece of mild steel A sus-
Battery Case with Dry pended by a short bar B which swings
Cells. Stanley & Patter- Qn the pin C that passeg through the
son, New York, N. Y. ^ , ,, , , , T 7^
upper end of the bar and a bracket D.
The latter is fastened rigidly to one of the caps of the kick-coil.
When no current is passing through the kick-coil, the tell-
tale hangs in the position shown in the figure. As soon as cur-
-,
I
1
u
^\J~B
FIG. 123.
Tell-tale Kick-Coil.
rent sufficiently large for contact ignition passes through the
coil, the part A is quickly drawn toward the core of the coil
by magnetic action. The tell-tale falls back again quickly when
the current is interrupted, as by the separation of the contact-
KICK-COILS 143
points of the igniter. The kick-coil is placed in series with the
igniter when used in a make-and-break ignition system.
If any trouble prevents the igniter from closing the circuit
so that the necessary amount of current flows for satisfactory
ignition, then the action of the indicator is sluggish as it is drawn
toward the coil core if some small amount of current flows.
If no current flows through the igniter, the tell-tale has no motion.
The indicator falls back sluggishly if the breaking of the circuit
is not accomplished quickly, as it should be at the igniter contact-
points.
The tell-tale is therefore an indicator of whether the igniter
is operating effectively, improperly, or not at all.
CHAPTER XIII.
MECHANICAL MAKE-AND-BREAK LOW-TENSION IGNITION
SYSTEMS.
112. A battery, a reactance coil, and a make-and-break igniter
of the mechanically operated type are electrically connected to-
gether in Fig. 124 so as to form a low-tension ignition system.
All of the parts are represented conventionally. Only the elec-
trodes of the igniter are shown. It is immaterial whether the
battery is considered a primary battery or a storage battery, so
far as the principle of operation of the system is concerned.
The positive (+) terminal of the battery is connected to one
of the terminals of the kick-coil, and the other terminal of the
coil is connected to the insulated electrode 6 1 of the igniter. The
negative ( ) terminal of the battery is electrically connected
ig-niter
*i
"QS I IJIJUJ//I Batter
"Ground" on Metal Structure
FIG. 124.
Elementary Low-tension Make-and-break Ignition System with Battery Current.
to the movable electrode M of the igniter. As shown in the
diagram, the negative wire from the battery is connected at F
to some part of the metal structure which forms part of the
engine or of the metal frame to which the metal of the engine
is metallically, and therefore electrically, connected. The metal
structure is customarily referred to as ground. The negative
side of the battery may, if desired, be connected by a wire direct
to the igniter. Diagrams in which the metal structure is used
as part of the electric circuit involve all of the features of those
in which the frame is not used as part of the electric circuit, and,
in many cases, several additional features.
144
MECHANICAL MAKE-AND-BREAK IGNITION SYSTEMS 145
As soon as the electrodes make contact with each other so as
to close the electric circuit, current begins to flow from the
positive (+) side of the battery through the kick-coil (reactance
coil), the igniter, and then through ground back to the negative
side of the battery. When the electrodes are separated to break
the electric circuit, an electric arc is formed between the contact-
points momentarily at the instant of separation. This arc will
ignite a combustible mixture of gases.
The reactance coil is placed in the circuit in order to secure
a sufficiently strong arc with a small current from a battery of
low voltage. The pressure at the battery terminals is generally
not more than six volts. The current seldom exceeds five am-
peres and is often less than two amperes. It is probably usually
between one and two amperes. With this pressure and current,
only a very minute arc, or spark, can be obtained without the
aid of a reactance coil.
The stronger arc obtained with the reactance coil in circuit
is due to the inductive action of the coil. Breaking the circuit
at the igniter causes an immediate decrease in the current. The
magnetic strength of the core of the reactance coil decreases in
consequence of the decrease of current in the winding of the coil.
This decrease of magnetism in the core reacts to prevent rapid
decrease of current in the winding. The decrease of current in
each turn of the coil also reacts inductively to prevent rapid
decrease of current in the other turns of the winding. The total
effect of the reactance coil is to cause the current to flow longer,
both in time and distance, across the gap formed between the
electrodes by separating them than when no reactance coil is used.
Although no switch for opening and closing the circuit by
hand is shown in the diagram, one can be put in at any convenient
point.
113. The duration of contact between the electrodes of the
igniter should be as short as possible with satisfactory operation
when a battery supplies the current. This in order to secure
economy of current and long life of the battery. The circuit
must be kept closed long enough, however, to allow the current
to become sufficiently strong to make a good arc when the elec-
146
ELECTRIC IGNITION
trodes are separated. The reactance coil prevents the current
from reaching its full strength as quickly as it would if there
were no reactance in the circuit. The coil prevents rapid in-
crease of current as well as rapid decrease.
114. A magneto and a make-and-break igniter are connected
together as parts of a low- tension ignition system in Fig. 125.
Cain
"Ground" on Metal Structure
A.C. Magneto
Armature/
FIG. 125.
Elementary Make-and-break Low-tension Alternating-current Magneto Ignition
System.
The magneto is of the shuttle-wound alternating-current type,
and the igniter is mechanically operated. The operating mechan-
ism is of the type shown in Fig. 108.
The insulated end of the armature winding of the magneto is
electrically connected to the insulated electrode S of the igniter
by a wire. This is the only connection necessary between them
if the frame or base-plate of the magneto is set on a metallic
structure which has metallic (electric) connection with the
igniter. If the magneto is mounted on a non-metallic base
which is not a conductor of electricity, then electric connection
between the magneto and the metal structure or the igniter
must be provided.
The magnets and pole-pieces of the magneto should not have
contact with or be very close to a piece of iron or steel, such as
part of the frame of the motor. It is generally best to have no
iron or steel connection whatever between the magnets and an
iron or steel part of the structure on which the magneto is
MECHANICAL MAKE-AND-BREAK IGNITION SYSTEMS 147
mounted. The base of the magneto, or the straps or other form
of fastening for attaching the magneto to a steel structure, can
be of any non-magnetic metal or alloy. Brass, bronze, and
aluminum alloy are commonly used for this purpose.
Low-tension alternating-current magnetos intended for igni-
tion usage generally have only one terminal for making external
connection. In case there are two terminals, one can be con-
nected to the metal structure (ground) or to the igniter direct,
and the other to the insulated electrode of the igniter in the usual
manner. The latter has been described.
The igniter must operate in synchronism with the production
of maximum electromotive force, or pressure, in the magneto,
since a suitable arc can be formed only when there is sufficient
pressure to cause a flow of current large enough to produce an
arc of the desired strength. If the magneto armature rotates,
and a one-lobe cam such as is shown in the figure is used to
operate the igniter, then the cam may rotate at twice the speed
of the armature, so as to draw an electric arc at each half -revo-
lution of the magneto armature, which is as frequently as an arc
can be drawn when the magneto is of the type shown. Or the
cam may rotate at the same speed as the armature, so that an
arc is drawn at every second production of maximum pressure in
the magneto.
It is customary to have a one-lobe cam make either two, one,
or one-half revolution for each revolution of the magneto arma-
ture when the magneto produces two impulses per revolution
of its armature. This applies to a magneto of the type shown
in the figure. If a magneto which gives four impulses per
revolution of its rotor is used, then the one-lobe cam may make
either four, two or one revolution per revolution of the magneto
rotor.
It is not necessary, on account of economy of current, to limit
the time during which the circuit is closed by keeping the elec-
trodes of the igniter in contact with each other when current
is supplied by an alternating-current magneto, since the magneto
does not supply current continuously and there is no need of
securing economy of current.
148 ELECTRIC IGNITION
No reactance coil is required in connection with an alternating-
current magneto. The armature of the magneto acts as a
reactance to produce a strong arc at the ignition points. A
switch can be placed at any convenient point in the circuit
for opening the circuit to stop ignition, or a switch between
ground and the wire leading to the igniter may be closed to stop
ignition.
115. A direct-current generator, a kick-coil, and a mechanical
make-and-break igniter are connected together for a low-tension
FIG. 126.
Elementary Make-and-break Ignition System with Direct-current Generator.
ignition system in Fig. 126. The generator is represented only
by its commutator and brushes.
The positive brush of the generator is connected to one ter-
minal of the reactance coil, and the other terminal of the coil
is connected to the insulated electrode S. The negative brush of
the generator is connected to the metallic ground of the structure.
This system is the same as that in Fig. 124 except the use of a
direct-current generator instead of a battery, and the same
statements apply regarding the manner in which connections
may be made.
A generator giving a pressure of five volts and having a capac-
ity of five amperes is suitable for this system. The current
capacity may be even less than five amperes. The field-magnets
of the generator may be either permanent magnets or electro-
magnets. If of the latter type, they may be either plain shunt-
wound or compound- wound. The shunt- wound type is less
expensive to construct and is entirely satisfactory. Either of
the electromagnetic types requires some time to pick up its
magnetism after starting, and is therefore not very convenient
to use in connection with an isolated motor which must be de-
MECHANICAL MAKE-AND-BREAK IGNITION SYSTEMS 149
pended on to drive the ignition generator, unless a battery is
provided for ignition while starting the motor.
Direct-current generators do not always have enough inductive
action to be used without a reactance in the circuit. A hand-
switch may be put in the circuit where desired.
116. System for Four Combustion Chambers. Mechanical
Make-and-break Igniter, Storage Battery, Primary Battery, and
Direct-current Generator. Fig. 127 shows connections for four
low-tension igniters, one for each of four combustion chambers,
to which current can be supplied either by a direct-current
generator, a primary battery, or a storage battery, using only
Primary Battery
FIG. 127.
Make-and-break Ignition System for Four Combustion Chambers and Having
Three Sources of Current Supply.
one at a time. This system is applicable to a four-cylinder
single-acting motor, or to a double-acting engine with two
cylinders.
The switch-arm F is pivoted at and its free end can be moved
into position to bear against either of the contact-points G, L,
or P of the switch. The arm is shown in the position to use
the generator. The switch-points G, P, and L should be far
enough apart to keep the arm from making contact with two
of them at the same time while shifting it from one point to
another.
It is immaterial whether the positive or the negative sides of
the generator and batteries are connected to the switch, but
it is advisable to have either all of the positive or all of the nega-
tive terminals connected to it, since there is then less chance of
150 ELECTRIC IGNITION
injury to the batteries in case electric connection is accidentally
made between the switch-points, or if the insulation of the switch
becomes poor so that leakage of current may occur. If G were
connected to the positive of the generator and L to the negative
of the storage battery, then if G and L were electrically connected
together an excessive current would flow through the generator
and storage battery in series. The path of this current would
be through the connections to the switch-points G and L, and
the ground connections of the generator and storage battery.
Little or no current would flow through the igniters, and there
would be no ignition in consequence. A similar, but less severe,
action would occur if the positive of the generator were connected
to the negative of the primary battery, or the positive of the
storage battery to the negative of the primary battery.
The storage battery is not floated on the line, and therefore
must be charged from some separate source of current supply.
The generator shown might be used to charge the storage battery
by connecting them together properly with a suitable rheostat
or other current-regulating device in the circuit.
An electric arc can be obtained at only one of the igniters at
a time. If two igniters are closed and then one opened, no arc
will be formed between the electrodes during their separation.
This system can be extended to any number of igniters, provided
only one igniter has its electrodes in contact at any instant.
117. An alternating-current magneto, a primary battery, and
four mechanical make-and-break igniters are used in the low-
tension system of Fig. 128. When the switch is closed on its
contact-point L as shown, current is furnished by the magneto
only. The battery and the reactance coil are both cut out of
circuit. By moving the switch-arm up to its contact-point P
the magneto is cut out of circuit, and the primary battery alone
furnishes current. When the battery is used, the current passes
through the reactance coil, but not when the magneto is fur-
nishing the current. This system can be used in the same
manner as that of Fig. 127, and is subject to the same restrictions
regarding two or more igniters being in the closed position at
the same time.
MECHANICAL MAKE-AND-BREAK IGNITION SYSTEMS 151
j Igniters
on_Metal__
Primary Battery
FIG. 128.
Four-igniter Low-tension Ignition System with Primary Battery and Alternating-
current Magneto.
118. A storage battery " floated on the line " of a shunt- wound
direct-current generator, and mechanical make-and-break igni-
ters, are used in the system of Fig. 129. The current to the ig-
"Ground'
Igniters
F
Reactance
o 2
Storage
Battery
O
*
t
\}\
J
IA
FIG. 129.
Ignition System with Four Low-tension Igniters and a Storage Battery Floated
on the Line.
niters always passes through the reactance coil. The use of a
storage battery in conjunction with a generator in this manner
has been discussed in earlier paragraphs.
No switches for opening the circuit are shown, but if one is
placed between A and the automatic cut-out, or between the
negative brush and the " ground " connection at B, it will cut
out the generator from the system but will not stop the current
through the field-coils of the generator. A switch between the
storage battery and either A or E will cut out the battery com-
pletely. One between A and F will cut off all the current from
152
ELECTRIC IGNITION
the igniters. When this last switch is open and the other two
closed, the generator will charge the battery if the pressure at
the brushes of the generator is higher than that of the battery.
119. no-volt Generator and 6-volt Primary Battery Mechani-
cal Make-and-break System.* Fig. 130 is a system in which
a no- volt direct-current generator is driven by the gas engine
FIG. 130.
Make-and-break Ignition System Using a 6-volt Primary Battery and a no- volt
D. C. Generator.
to which it furnishes ignition current. A primary battery is
provided for starting, since no current is available from the
generator till it is well up to normal speed.
The chief items of the system, as furnished by the Westing-
house Machine Company, are:
A. Combination switchboard.
BBB. Three no- volt i6-candle-power incandescent lamps
with carbon filament. f
* The diagrams shown in Figs. 130, 133, 135, 136, 137, and 139 are slightly
modified forms of those used by the Westinghouse Machine Company. They
have been modified only enough to make them conform with the conventions
used in this book. This modification does not change the ignition system.
t If incandescent lamps having filaments or " pencils " of other material than
carbon are used, the lamps should be of a size requiring the same amount of cur-
rent as the carbon-filament lamps specified. Any non-inductive resistance can
be used in place of the lamps, the only requirement being that the amount of
resistance shall be the same as that of the lamps specified.
MECHANICAL MAKE-AND-BREAK IGNITION SYSTEMS 153
C. 1 1 o- volt shunt- wound dynamo.
D. Edison primary battery, 6 cells.
The igniter M is part of the gas engine. Any number of
igniters can be used, provided only one has its electrodes in
contact with each other at any instant. In other words, not
more than one igniter should be in the closed position at any
instant.
The switchboard has two double-pole double-throw switches.
The one at the right is called the dynamo switch. It is shown
closed in its up-position with the handle at the top. The left-
hand one is the battery switch. It is standing open in a hori-
zontal position perpendicular to the vertical board. The handle
appears as a circle.
Double-throw switches are used in order to reverse the direc-
tion of current through the electrodes of the igniter. The object
in reversing the current is to secure equal rapidity of wear on
the contact-points of the igniter. There is a tendency for one
contact-point to wear more rapidly than its mate when the cur-
rent always flows in the same direction through the igniter. The
contact-point connected to the positive side of the circuit wears
more rapidly, other conditions being equal for the two points.
When the switches are positioned as in Fig. 130, the battery
is cut out of circuit and the generator is in circuit so that its
positive brush is connected to ground.
The switchboard connections back of the board are shown in
Fig. 131. The wiring is shown as if seen from the front through
a transparent board. The reference letters are the same as in
the preceding figure. A reactance coil is incorporated in the
switchboard. The switch-blades of the dynamo switch are
hinged to the middle terminals i and 2 of that switch.
When the dynamo switch is closed in the up-position as in
Fig. 130, the current from the positive brush of the dynamo
follows the path: Positive brush, 5, 4, through switch-blade to 2,
ground, igniter M, reactance coil, lamps BBB, then through the
connection to i, switch-blade to 3, negative brush of dynamo.
If the switch is thrown to its lower position with its handle
down, the path of the current is then: Positive brush, 5', i, lamps
154
ELECTRIC IGNITION
BBB, reactance coil, insulated electrode of igniter M, ground, 2,
6, 3, negative brush of dynamo.
When the battery switch is closed and that for the dynamo
open, the current does not flow through the lamps. If the
battery switch is closed in its up-position, the path of the current
FIG. 131.
Switchboard Connections for Fig. 130.
is: Positive of battery, 12, 9, 7, ground, igniter M, reactance coil,
8, 10, negative of battery.
The amount of current that flows through the igniter when
the dynamo alone is delivering current is regulated by the lamps.
The three lamps specified, no- volt, i6-candle-power, carbon-
filament, will allow a current of 1.5 to 2 amperes to flow through
the igniter, according to the efficiency of the lamps. This is
three times the current that flows through one lamp, since they
are in parallel with each other. The current flows through the
MECHANICAL MAKE-AND-BREAK IGNITION SYSTEMS 155
lamps only while one of the igniters is closed. The lamps flash
once for each ignition when using dynamo current.
When the battery alone is in use, the lamps remain dark.
If both switches are closed, the generator will send current
through the battery, at least during the time all of the igniters
are open. Although this is not noticeably injurious if continued
for only a short time, the primary battery will be injured if both
switches are left closed during a long period of running.
FIG. 132.
Switchboard Details for Fig. 130.
Fig. 132 shows front and side views of the switchboard as
constructed. The lamps are not shown, but the lamp sockets
appear.
120. Multiple System with Switchboards, Primary Batteries,
and no-volt Direct-current Generator. The system in Fig. 133
is for two engines. Two switchboards of the kind just described
are connected to one generator. Each switchboard has its
156
ELECTRIC IGNITION
own primary battery. Fuse-blocks E are placed between each
switchboard and the generator.
The system can be used either for two engines or for dual
ignition in one engine. In the latter case, two igniters are placed
in each combustion chamber. The two igniters in one com-
FIG. 133.
Two Switchboard Units for Distributing Current to Two Sets of Low-tension
Igniters.
bustion chamber are closed and opened simultaneously, so that
two ignition arcs are drawn in that combustion chamber at the
same instant.
The system can be extended to any number of switchboards
and the corresponding number of engines or of igniters in each
combustion chamber of one engine.
The wiring diagram is shown in Fig. 134, in which each switch-
board has four igniters. Two igniters, M and M, one connected
to each switchboard, are shown closed, which is allowable in
operation. Any igniter of one switchboard may be closed during
the same time as any igniter of the other switchboard.
The dynamo switches must both be closed either in the up-
position, as shown in Fig. 133, or both in the down-position,
when the igniters connected to both boards are put into operation
MECHANICAL MAKE-AND-BREAK IGNITION SYSTEMS 157
I
s
I
2 ,
158 ELECTRIC IGNITION
and while they are operating on current from the dynamo. If
one dynamo switch is closed in the up-position, then closing the
other dynamo switch in the down-position will short-circuit the
dynamo, and one of the fuses at the fuse-blocks E will be melted
or " blown," thus opening the dynamo circuit through one
switchboard. The blowing of the fuse will stop ignition by the
igniters connected to that board, unless the battery switch on
the board is closed.
If the dynamo switch on board i is closed in the up-position,
and the dynamo switch on board 2 is closed in the down-position,
then the positive brush of the generator is connected direct to
ground through board i, and the negative brush of the generator
is connected direct to ground through board 2, thus short-cir-
cuiting the generator as stated. A similar short circuit is made
by reversing both of the dynamo switches from the positions
just mentioned. The primary battery switch alone on one
board can be left closed any length of time commensurate with
the capacity of the battery, while either the dynamo switch or
the battery switch is closed on the other board, or boards.
Reversing the dynamo switches during the operation of the
system can be safely accomplished by first closing the battery
switch on any one of the boards and then opening the dynamo
switch on the same board. This should be done successively
for all of the switchboards. The dynamo switches can then
be closed in their reverse position, all of course being closed
either up or down.
The battery switch on each board can be opened as soon as
the dynamo switch on the same board is closed, or the battery
switches can all be left closed till all of the dynamo switches are
reversed, and then all of the battery switches can be opened.
Specifically, for two boards, the reversal of the dynamo
switches can be done as follows, referring to Fig. 133, in which
the battery switches are closed in the up-position and the battery
switches are open : Close battery switch on board i in either the
up- or down-position; open dynamo switch on board i; close
battery switch on board 2 in either the up- or down-position;
reverse the dynamo switch on board 2 to the down-position;
MECHANICAL MAKE-AND-BREAK IGNITION SYSTEMS 159
open the battery switch on 2; close the dynamo switch on i in
its down-position; open the battery switch on i.
When there are more than two switchboards, the reversal of
the dynamo switches can be carried out in a similar manner,
leaving all of the dynamo switches open till that of the last board
is reached, then reversing it and afterward closing the dynamo
switches of the other boards and opening the battery switches.
121. Storage Battery and no-volt Generator Mechanical
Make-and-break System. Referring again to the diagrams of
Figs. 130 and 131 for one switchboard, a 6-volt storage battery
may be substituted for the primary battery D. Then, if the
dynamo switch and the battery switch are both closed in either
the up-position or the down-position, the dynamo will send cur-
rent through the storage battery to charge it during the time
the igniters are all open. While an igniter is closed current will
flow through it, and the breaking of the circuit by separating
the contact-points of the igniter will draw an arc for ignition.
If the generator stops accidentally, as on account of the break-
age of a belt for driving it, the storage battery furnishes current
so that no interruption of ignition occurs. This when the
switches are both closed before the accident. No automatic
cut-out is necessary to protect the generator from excessive
current sent through it when the generator stops. The lamps
limit the current that the battery can send through the generator
in such a case, and keep it small enough to prevent injury to the
generator.
The path of the charging current, when the igniters are all
open and the switches are both closed in the up-position, is
(Fig. 131) from the positive brush of the generator to 5, 4, 2, 7,
9, 12, positive side of storage battery and through the battery,
10, 8, lamps BBB, 1,3, negative brush of generator. The amount
of this current is regulated by the resistance of the lamps, and
therefore is not greater than is safe for the battery. While both
switches are closed in the down-position, a similar battery-
charging action occurs. But if one switch is closed in the up-
position and the other closed in the down-position, then the
generator sends current through the battery in the direction to
i6o ELECTRIC IGNITION
discharge it. The switches should not be left closed long in these
opposite positions.
The amount and direction of current through the storage
battery while an igniter is closed are both variable in such a
system as usually made up. This refers to operation while the
generator is running and both switches are closed in their proper
positions. The inductive reaction of the reactance coil and the
length of time the contact-points of the igniter are kept together
both affect the action of the battery. The total result is that
the storage battery is gradually charged during the operation
of a properly designed system. The storage battery is thus
kept ready to supply current for starting the engine and to keep
it running for a considerable time.
The resistance (ohmic resistance) of the reactance coil is about
one ohm, not including the inductive resistance.
The direction of current through the igniters can be reversed
by reversing first one switch and then the other. The second
switch should be reversed immediately after the first. Either
switch can be reversed first.
122. Storage Battery, Primary Battery, and i lo-volt Generator
Make-and-break System. Fig. 135 is a diagram of a system in
which a storage battery is used in connection with a generator in
the manner just described. A primary battery is also included
in the system as a means of starting the engine when first installed
and before the storage battery has been charged. The primary
battery can also be used in an emergency.
The storage battery is shown at F and the primary battery at
D. An additional switch G is provided for throwing either the
storage battery or the primary battery into circuit. The switch
is of the double-pole double- throw type. The switches are
shown all three closed in the up-position so that the storage
battery and generator are in operation. The primary battery
is out of circuit.
To reverse the current through the igniters, the auxiliary
switch G should first be thrown to the down-position so as to
cut out the storage battery and put the primary battery into
circuit. The two switches on the main board can then be re-
MECHANICAL MAKE-AND-BREAK IGNITION SYSTEMS l6l
versed, one at a time. It is immaterial which of these two is
reversed first. The auxiliary switch G is then to be thrown into
its up-position again.
A 6- volt storage battery is suitable for use in this system. The
switchboard is the same as that of Fig. 130.
FIG. 135.
Low-tension Ignition System with Switchboard, Primary Battery, Secondary
Battery and no-volt D. C. Generator.
123. Multiple System with Storage Batteries, i lo-volt Genera-
tor, Primary Battery, and Switchboards. In Fig. 136 two units
of switches and storage batteries, both the same as in the pre-
ceding figure, are connected to one generator and one primary
battery. Fuse-blocks E are placed in the circuit in the same
manner and for the same purpose as has been stated in connection
with Fig. 133. Since the primary battery is intended only for
starting the engine, or engines, one is all that is needed for both
switchboards. The system can be extended to any number of
switchboards.
The same precautions must be observed with regard to not
having the dynamo switches closed in opposite positions as have
been pointed out in connection with Fig. 133. The dynamo
switches are those at the right-hand side of each of the switch-
boards i and 2. It is advisable to throw the auxiliary switches G
up to the primary battery position before reversing the dynamo
162
ELECTRIC IGNITION
FIG. 136.
Two Switchboard Units, Two Storage Batteries, One Primary Battery, and One
no-volt D. C. Generator, for Supplying Current to Two Sets of Low-tension
Igniters.
switches, and then throw them back to the storage-battery posi-
tion after the reversal has been made.
124. System Using Current from no-volt Direct-current Ser-
vice without Ground Connection. This system, Fig. 137,
operates by charging one storage battery while another supplies
current to the igniters. Neither side of the dynamo circuit is
grounded at any time, therefore the switchboard can be con-
nected to service wires such as supply no- volt direct current
for general use. C is the dynamo, and M one of the igniters on
the engine.
The apparatus, as supplied by the engine builder, consists of:
A. Switchboard.
BBB. Three no-volt 32-candle-power carbon-filament lamps.*
* If incandescent lamps having filaments or "pencils" of other material than
carbon are used, the lamps should be of a size requiring the same amount of cur-
rent as the carbon-filament lamps specified. Any non-inductive resistance can
be used, the only requirement being that the amount of resistance shall be the
same as that of the lamps specified.
MECHANICAL MAKE-AND-BREAK IGNITION SYSTEMS 163
FF. Two 6-volt storage batteries.
D. One 6-cell primary dry battery.
G. One double-pole double-throw 4-blade switch.
E. One i5-ampere fuse-block.
The connections in the switchboard A, Fig. 137, are shown in
Fig. 138. The switch-blades are hinged at i, 2, 3, and 4.
FIG. 137.
Switchboard and Low-tension Igniter Connections for Two Storage Batteries,
One Primary Battery, One no-volt Generator and One Set of Low-tension
Igniters.
When the switches are closed in the positions shown in Fig. 137,
the current to the igniters comes from the storage battery that
is connected to the right-hand side of the switchboard. The
path of this current is from the positive terminal of that storage
battery to n (see Fig. 138), and flows on to 7, 3, ground, igniter
M, reactance coil, 4, 8, 12, and the negative terminal of the bat-
tery. At the same time, the charging current for the other
storage battery comes from the service to 13 and flows on to
2, 6, 9, auxiliary switch G (Fig. 137), positive terminal of battery
164
ELECTRIC IGNITION
that is being charged, through the battery to its negative ter-
minal, switch G, 10 (Fig. 138), 5, i, lamps BBB, and the ter-
minal 14, to which the negative side of the service is connected.
The charging current is regulated by the resistance of the lamps,
which limit it to the amount that will pass through them.
When the 4-blade switch is thrown over to its right-hand
closed position, the storage battery connected to the left-hand
FIG. 138.
Switchboard Connections for Fig. 137.
side of the switchboard then furnishes current to the igniters,
and the other storage battery receives charging current from the
service. In this new position of the 4-blade switch, the cur-
rent flows through the igniters in the opposite direction from that
in which it did before.
MECHANICAL MAKE-AND-BREAK IGNITION SYSTEMS 165
The primary battery is for starting a new plant before either
of the storage batteries is charged. It can of course be used
temporarily in case of emergency.
While this system has been referred to as using no volts, it
is satisfactorily operative at any voltage from no to 125.
125. Multiple System Using no-volt to i25-volt Direct Cur-
rent from General-service Circuit. This system, Fig. 139, is a
FIG. 139.
Two Switchboard Storage-battery and Igniter Units like Fig. 137, together with
One Primary Battery and One no- volt D. C. Generator.
multiplication of the switchboard, switch, and storage-battery
units of the last-described system. Only one primary battery
is used. It is connected to both switchboards.
No precaution to avoid short-circuits of the nature mentioned
in connection with Fig. 133 is necessary in this system since each
storage battery connected to the service for charging it has its
own independent circuit that is without ground connection, and
each battery delivering current to the igniters has a circuit
through its own switchboard only.
126. A triple low-tension ignition system for a large engine
with four double-acting cylinders is shown in Fig. 140. Each
of the eight combustion chambers has three mechanically oper-
ated igniters. This is twenty-four igniters for one engine. The
complete system for one engine is shown, together with the
i66
ELECTRIC IGNITION
Rheostat
To No.4
Engine
Bus-Bar
To No. 3
Engine
Each Engine to have
Igniters, Kick-Coils and
Switches as shown for No.l.
24 Igniters for each
Engine with four
Double-Acting Cylinders.
FIG. 140.
Connections for Low-tension Ignition System with Three Igniters in Each of
Eight Combustion Chambers of One Engine, with Provision for Extending to
Any Number of Engines. Two Storage Batteries Operating on Direct Current
from a Generator.
MECHANICAL MAKE-AND-BREAK IGNITION SYSTEMS 167
bus-bar of a switchboard and the switches for circuits leading
out to the igniters of three other engines. The system can be
extended to any number of engines.
Electric current is furnished to the igniters by storage batteries
only. As shown, battery A is connected through the switch C
to the bus-bar on the positive (+) side, and to ground on the
negative ( ) side. The other battery, B, is connected by the
switch D to both sides of a charging circuit through a rheostat
for regulating the amount of charging current flowing through
the battery. C and D are both double-pole double-throw
switches. By reversing both of them, battery B will supply
current to the igniters while battery A receives a charge from
the service wires.
One side of each igniter is grounded to the metal of the engine.
The negative ( ) side of the battery which is supplying current
to the igniters is also grounded during the time its switch is in
the position for it to furnish current to the igniters. The
" ground " is represented by the broken line in the figures.
The three igniters in one combustion chamber operate simul-
taneously. The second group of three igniters from the top are
shown closed. These three igniters are all for one combustion
chamber. They all three break contact at the same instant so
as to form three ignition arcs simultaneously.
Each igniter is provided with its own individual switch, which
when open cuts the igniter and its kick-coil out of circuit without
interfering with the operation of any other part of the ignition
system. One igniter in each combustion chamber is fed current
through one of the three switches located at the bus-bar. The
three switches for engine No. i are at the right-hand end of the
bus-bar. The bottom igniter in each group of three is connected
to the switch at the extreme right-hand end of the bus-bar.
Opening this switch cuts out one igniter in each of the combus-
tion chambers. The middle igniter in each group of three is
similarly connected to the second switch from the right-hand
end of the bus-bar ; and the top igniter of each group is connected
to the remaining switch for engine No. i at the bus-bar. Safety
fuses should be put in at each switch.
1 68 ELECTRIC IGNITION
The above ignition system is essentially that designed for
twelve engines of 3200 horse power each. Tell-tale kick-coils of
the nature of that shown in Fig. 123 are used, and the ignition
apparatus at the engine is of the general nature of that in Figs.
114 and 115. Each storage battery has five cells so as to give
an average of about 10 volts while discharging.
CHAPTER XIV.
ELECTROMAGNETIC IGNITERS AND IGNITION SYSTEMS FOR
LOW-TENSION CURRENT.
127. Principle of Operation. In an electromagnetically
operated igniter of the simplest form, the contact-points at which
the arc is drawn for ignition are generally kept pressed together
by a spring without current flowing through them until the
instant at which ignition is to occur. An electromagnet forms
part of the igniter. As soon as the electric circuit is closed, as
by a timer which is a mechanically driven piece of apparatus
separate from the igniter, current begins to flow through the
magnet-coil and the contact-points of the igniter, and continues
until the contact-points are separated by the action of the electro-
magnet. The latter is energized by the current flowing through
it. The separation of the contact-points first draws an arc
suitable for ignition, and then breaks down the arc, thus stopping
the flow of current. The electromagnet also acts as a kick-coil
to produce a suitably hot arc. The electromagnet then loses
its magnetism and the contact-points of the igniter are drawn
together again by the action of the spring already mentioned.
The different pieces of apparatus are generally, and preferably,
so adjusted that the circuit is broken at the timer after the arc
is broken down at the ignition-points, and before the contact-
points of the igniter come together again after the arc is broken
down.
128. Elementary Ignition System with a Timer and an Igniter
having an Electromagnet with a Plunger Core. In Fig. 141,
A is the stationary contact-ring, and B the movable contact-
point, between which the ignition arc is drawn inside of the
combustion chamber of the engine. The stationary contact-ring
A is rigidly attached to the rod C which extends outside of the
engine cylinder. C and A are both insulated from the metal of
169
170
ELECTRIC IGNITION
the engine. The movable contact-point B is carried by the
rocker-arm D, which is fastened rigidly to the rod E that extends
outside of the engine cylinder and has an arm F rigidly attached
to its outer end. The tension spring G pulls on the arm F so as
to press the movable contact-point against the stationary con-
Battery
Timer
FlG. 141.
Elementary Low-tension Ignition System with Electrically Operated Igniter.
tact-ring. One end of the spring is fastened to some stationary
part of the igniter. As represented in the illustration, the mov-
able rod E makes metallic (electric) contact with the metal of
the engine, and the arm F is electrically connected to the engine
metal by the spring G. In addition to this, a copper wire H
connects F to the metal of the engine, the only purpose of this
wire being to insure a perfect " ground " connection for the
movable electrode.
The electromagnet which forms part of the igniter is repre-
sented by the solenoid coil M and the plunger-core P. The core
is shown held partly out of the coil by the tension spring 5,
whose right-hand end is fastened to some stationary part of the
igniter. One end of the magnet coil M is connected at K to the
outside end of the stationary insulated electrode; the other end
of the wire of the magnet winding is connected to one side of
the battery. The other side of the battery is connected to the
metallic contact-piece N of the timer for closing the electric
circuit when ignition is to occur. The contact-piece N is fast-
ened to a cylindrical piece of insulating material V which forms
the body of the timer. A metal arm R is connected to a shaft
ELECTROMAGNETIC IGNITERS AND IGNITION SYSTEMS 171
which rotates in a bearing at the center of the body of the
timer. R and 0, which together form the rotor of the timer,
are electrically connected to " ground." The broken line indi-
cates ground connection.
As the rotor R revolves, its outer end makes electric contact
with the stationary contact-piece N, thus closing the electric
circuit through the igniter once every revolution of the timer.
Electric current begins to flow through the igniter as soon as
the timer closes the electric circuit. The path of the current,
starting from the positive (+) side of the battery, is through the
coil M to the terminal K of the insulated electrode of the igniter,
thence through the contact-pieces A and B of the igniter, and
through " ground " to the rotor R of the timer; from R the
current goes to N, when the latter two parts are in contact with
each other, and thence to the negative ( ) side of the battery.
As soon as the current obtains sufficient strength, the con-
sequent energizing of the magnet-coil draws the plunger P
farther into the coil and causes the tappet U to strike the end
of the arm F so as to rotate the movable electrode slightly and
thus move the contact-point B away from A. This breaks the
circuit inside the combustion chamber and draws an electric arc
for ignition. The breaking down of the arc, which occurs imme-
diately after it is drawn, interrupts the current. The magnet
coil then becomes de-energized, and the spring S draws the
plunger P back again to the position shown. The spring G at
the same time pulls the contact-point B against the contact-
ring A inside the combustion chamber again. In the meantime
the rotor R of the timer should have moved out of contact with
^V. If R has not moved out of contact with ^V by the time the
ignition-points A and B are together again after drawing an arc,
then the action of the igniter will be immediately repeated, which
is undesirable.
129. Dual Ignition System with Plunger-core Electromagnets
in the Igniter. Fig. 142. The igniters used in this system are
of the plunger-core magnet type and operate in the same general
manner as the one shown in the preceding figure. Each igniter
has two electromagnets; also two pairs of contact-points inside
172
ELECTRIC IGNITION
"Ground"on Engine Metal
7T~ *^-^^ -TT - ' K ^~ '^~" "** "~ .K ~" *" ~^ -^ 7T -^.^ _ _
A
A m
2/T
u
1
l a
i
CQ
1
T
D.C.Generator
FiG. 142.
Connections for Low-tension Ignition System with Two Electromagnetic Igniters
for Each of Four Combustion Chambers of One Engine. The Details
of the Igniter and Timer are shown in Figs. 143 and 144.
ELECTROMAGNETIC IGNITERS AND IGNITION SYSTEMS 173
of the combustion chamber. Two igniters are used in each com-
bustion chamber; eight igniters for the four combustion chambers.
Only one igniter is shown. This system has been operated on
1 10- volt current from a direct-current generator.
The timer shown has four brushes, i, 2, 3, and 4, wEich bear
against a ring containing a long segment / of insulating material
(vulcanized fiber) and a short segment H of metal. The short
segment H is electrically connected to a complete metal ring F
against which a brush E bears. Current from the source of
supply is received at the brush E. As the rings of the timer
rotate, the short metal segment H successively makes contact
with the four brushes which bear against the ring J-H, thus
causing current to be delivered successively to these four brushes.
When the timer is in the position shown, current flows from
the positive (+) brush of the generator through the lower blade
of the double-pole main switch to the brush E, slip-ring F, seg-
ment H, brush i, and thence to A, where the current divides,
part going to switch Ai and part to switch Ai. These two
switches are for the two igniters which are in one combustion
chamber and operate simultaneously.
The current from switch A i passes through a safety fuse and
then divides, part going to ground through tell-tale lamp A i and
the remainder to igniter Ai. The current to igniter Ai divides
at K, part going through magnet-coil M to the insulated rod R;
the other portion flows through magnet-coil N to R. The cur-
rent flows through . the rod R to the movable contact-points
carried by the rocker- arm P attached to R, and thence to the
stationary contact-points 5 and T, both of which are grounded
on the metal of the engine. The current from ground flows
through the upper blade of the main switch to the negative ( )
brush of the generator.
Before current begins to flow through the igniter, the movable
contacts in the arm P are pressed against the stationary contacts
by action of the tension springs W and X. These springs pull
the plungers U and V partly out of the coils until the movement
of the plungers is stopped by the rings 7 and Z striking against
the arms e and / and moving them back till the movable contacts
174 ELECTRIC IGNITION
are pressed against the stationary ones in the combustion cham-
ber. As soon as the current flowing through the magnet coils
attains sufficient volume, after the closing of the circuit by the
timer, the plungers are magnetically drawn into the coils, thus
causing the rings g and h to strike the arms e and / and separate
the ignition contact-points in the combustion chamber. The
plungers move some distance into the coils and gain considerable
speed before the rings g and h strike the arms, thus causing rapid
separation of the ignition-points. The space between the rings
F and g is greater than the thickness of the arm e, and the con-
struction of the upper rings and arms is similar, in order to
obtain this hammer-blow action to separate the ignition contact
points. The double-arm member e-f is insulated from the elec-
trode rod R by the insulating ring, or bushing, Q.
The current from switch A 2 passes through a safety fuse and
then divides, part going to ground through tell-tale lamp A 2 and
the remainder to igniter A 2 (not shown). Igniter A 2 is in the
same combustion chamber as igniter Ai. Both of these igniters
operate at the same instant, thus drawing two arcs, one at each
igniter, to ignite the combustible charge in one cylinder.
The lamps Ai and A 2 both flash each time the timer closes
the circuit at the brush i as shown, during the rotation of the
rotor of the timer, provided the switches Ai and A 2 are both
closed and the system is operating properly. If one of the fuses
blows, the corresponding lamp remains dark. Each of these
lamps indicates whether current is going properly to the corre-
sponding igniter. The movement of the igniter indicates whether
it is operating as it should.
Each pair of igniters is connected into the system in the same
manner as just described for igniters Ai and A2. This is indi-
cated by the lettering on the diagram.
The lamp G is for indicating whether there is current in the
main circuit from the generator. This lamp glows continuously
while the pressure in the main circuit is correct.
Only one ignition arc is drawn when the two pairs of contact-
points of one igniter are separated. This arc sometimes occurs
at one pair of ignition-points, and sometimes at the other pair.
ELECTROMAGNETIC IGNITERS AND IGNITION SYSTEMS 175
The life of the contact-points is, therefore, practically doubled
by the use of two pairs of ignition-points, as compared with only
one pair for the same igniter.
The igniter and timer whose elements are shown in the accom-
panying illustrations are shown in detail in the following two
sections.
130. Wisconsin Engine Company's Electromagnetic Igniter
with Plunger Cores. Fig. 143, five views, (A), (B), (C), (Z>),
and (). This igniter has two pairs of contact-points, of which
both movable points, i and 2, are attached to the same double-
ended rocker-arm 3. The stationary contact-points, 4 and 5,
are inserted in lugs 6, 6, which project from the inside end of
the body of the igniter, and are part of the body casting. The
body of the igniter fits into a cylindrical hole which pierces the
cylinder wall of the engine; the body makes a tight joint near its
inside end. The material of the engine cylinder is represented
by the short herring-bone lines. The body of the igniter is in
metallic (electric) contact with the metal of the engine cylinder.
The rocker-arm 3 is carried on the live spindle 7 which passes
through the insulated metallic tube 8 from end to end of the
igniter body; the tube forms a bearing for the spindle. The
tube 8 is insulated from the body of the igniter at the inner
end by means of the mica washers 9, and at the outer end
by a wood-fiber bushing 10. A nut n fits on the outer end
of the tube 8 to hold the tube in place. A coiled compression
spring 12 and a pair of metallic washers 13 are placed between
the nut ii and the insulating bushing 10. The expansive force
of the coiled spring acts to keep the flange of the inner end of
the tube 8 tightly pressed against the mica insulating washers 9
so as to maintain a tight joint unaffected by different amounts
of expansion in contiguous parts on account of the heat of
combustion.
Two arms, 14 and 15, are rigidly attached to the outside end
of the spindle 7 for rocking the contact-points. These arms are
insulated from the spindle by the flanged bushing 16. The two
cap-screws, one on each side of the spindle, are tightened to grip
the arms on the spindle 7.
i 7 6
ELECTRIC IGNITION
ELECTROMAGNETIC IGNITERS AND IGNITION SYSTEMS 177
Two solenoid coils, 17 and 18, each with a soft-iron or mild-
steel plunger-core, are used for separating the contact-points at
which the arc is formed for ignition. The plunger-core of coil
17 is shown by dotted lines in view (5); the end inside of the
coil is tapered and bored to receive one end of a non-magnetic
rod 19, whose opposite end is fastened to a bar 20 that forms part
of a yoke. The end of the steel plunger-core that extends beyond
the end of the solenoid 17 is fastened to the yoke-bar 21 by
means of the nut 22. The end bars, 20 and 21, of the yoke are
also connected together outside of the solenoid by the rod 23,
which engages with the forked end of the arm 14 that is fastened
to the insulated spindle 7 of the rocker-arm, as already described.
A coiled compression spring 26 is placed between the yoke end-
bar 21 and the end of the solenoid coil 17. The expansive force
of this spring keeps the collar 24 pressed against the arm 14
when no current is flowing through the solenoid. The parts 19
to 26 are duplicated in connection with the solenoid 18. The
action of the two springs 26 is to keep the ignition contact-points
pressed together.
When the ignition timer (not shown) closes the electric circuit
so that current flows through the two magnet coils in parallel,
the steel plunger-core of each solenoid is drawn farther into the
coil than when no current is flowing. This drawing in of the
plunger brings the collar 25 against the side of the arm 14, and
likewise the duplicate of collar 25 against the side of arm 15.
This moves the arms 14 and 15 so as to rock the rocker-arm 3
and thus separate both pairs of contact-points, 1-4 and 2-5. The
plunger-cores move rapidly and gain considerable speed before
the collars 25 strike the arms 14 and 15. Consequently the
collars strike a hammer-blow against the arms so as to cause
rapid separation of the contact-points at which the ignition arc
is to be formed.
The terminal (binding post) to which the wire from the source
of electricity is connected is shown at 27. The current divides
at this terminal and flows through the two magnet-coils in parallel
and thence to the metallic washers 13 on the insulated electrode
rod 7.
178 ELECTRIC IGNITION
The ignition contact-points, i, 2, 4, and 5, can be driven out
for renewals by using a punch or piece of small rod inserted in
the slightly reduced extension of the hole into which each point
is fitted. The makers of this igniter find that the use of two
pairs of contact-points doubles the life of the points as compared
with an igniter using only one pair of contact-points.
The igniter is constructed for use on no- volt circuits. The
thickness and number of turns of wire in each magnet-coil of
course determine the voltage that is suitable.
131. One-ring Timer for Large Engine with Four Combustion
Chambers. The complete constructional form of a timer for
use with electromagnetic igniters is shown in Fig. 144. The
end view is shown at (yl), the side view at (J3), and one of the
brush-holders at (C). The mechanism for varying the time of
ignition is shown in Fig. 145 in connection with the ring, or
spider, which carries the brush-holders. This timer embodies
the slip-ring and segmental ring shown in elementary form in
Fig. 142.
In Fig. 144 the current is brought to the timer by the wire i
connected to the brush 2 which bears on the slip-ring 3. Part
of the slip-ring 3 is broken away at the top in view (A) in order
to expose the upper part of the long segment 4 of insulating
material and the side of the short metallic segment 5, which
together form the ring on which the four brushes 6, 7, 8, and 9
bear. The slip-ring 3 and the composite ring 4-5 are carried by
the heavy metal ring 10 which fits on the shaft n. The slip-
ring 3 is broken away under the brush 2 in view (A) so that the
brush apparently bears on the heavy ring 10, but this is not
actually so, since the brush is farther forward than the ring.
The segment 5 is metallically connected to the slip-ring 3, but is
electrically insulated from all of the other parts of the rotor.
The brush 6, of the four similar brushes, fits into the brush-
holder 12, which is hinged to the bracket 13. This bracket is
fastened to a piece of insulating fiber 14. A coiled compression
spring between the fiber and the brush end of the holder presses
the brush against the rotor of the timer. The fiber 14 is fastened
to a metal segment 15, which is flanged to fit into a circular
ELECTROMAGNETIC IGNITERS AND IGNITION SYSTEMS
179
<N bo
"t oj
H a
a
bO
o 5
i8o
ELECTRIC IGNITION
groove in the ring 16. The ring 16 carries all of the brush-holders
and is integral with four arms and a hub mounted coaxial with
the rotor of the timer. The segment 15 has worm-wheel teeth
into which the worm 17 meshes. This worm can be rotated by
means of the hand- wheel 18 on an extension of the worm. By
FIG. 145.
Ignition Advance-and-retard Mechanism for the Timer shown in Fig. 144.
rotating the hand-wheel, the brush is moved circumferentially
around in the supporting ring so as to vary the time of ignition
at the igniter, or igniters, connected to this brush. The wire
leading from the brush-holder to the timer, or timers, in one
combustion chamber is connected to the brush-holder by means
of the small screw at the left-hand end of the holder. Each of
the brushes, 7, 8, and 9 has its own brush-holder, which is carried
ELECTROMAGNETIC IGNITERS AND IGNITION SYSTEMS 181
by the ring 16 in the manner just described for brush 6, and is
individually adjustable in the same manner for varying the time
of ignition of its igniter, or its igniters.
In addition to the individual adjustment of the brushes as
just described, all of the brushes can be rocked collectively
around the rotor of the timer in order to simultaneously vary
the time of ignition in all of the combustion chambers of the
engine. The means for doing this are shown in Fig. 145. In
this figure, the left-hand end of rod 19 is hinged to the brush-
carrying ring 1 6 by the bolt 20. The right-hand end of the rod
19 is threaded into the corresponding end of a sleeve 2 1 . Another
rod, 22, is threaded into the right-hand end of sleeve 21, and the
right-hand end of this rod is hinged, by means of an end-piece,
to the rocker-arm 23 by the T-head bolt 24, whose head fits into
a slot in the rocker-arm. The rocker-arm is fastened to the
shaft 25, which is connected to the governor of the engine. The
governor rocks the shaft 25 as the speed of the engine varies,
and thus rocks the brush-carrying ring 16 so as to advance or
retard the time of ignition in each combustion chamber by the
same amount. The extent of the rocking motion given to the
brush-carrying ring can be decreased by moving the bolt 24
down nearer to the shaft 25, or increased by moving this bolt
farther away from the shaft 25.
Hand adjustment of the time of ignition is obtained in all of
the combustion chambers simultaneously by turning the threaded
sleeve 21 on the bolts 19 and 22. The sleeve has a right-hand
thread at one end and a left-hand thread at the other. A hand-
wheel 26 is provided for rotating this sleeve-nut. A lock-nut 27
prevents the sleeve-nut from rotating after the desired setting is
obtained.
132. Allis-Chalmers Four-ring Timer for Large Engine. In
the photograph, Fig. 146, the ring N near the front end of the
timer rotor, and the ring P at the back part, are both complete
metallic slip-rings. The segment E is electrically connected to
the adjacent front slip-ring N, and these two parts are insulated
from all of the other parts of the rotor. The segment E forms
part of a four-segment ring of which the other three metallic
182
ELECTRIC IGNITION
segments are two short segments, one at each end of E, and a
long segment, one end of which is visible at K. The long seg-
ment K and the two short segments are insulated from each
other and from all other parts of the rotor. The segment F in
the third ring from the front end of the rotor is electrically
connected to the adjacent slip-ring P. Segment F is like segment
FIG. 146. (See also Figs. 147, 148, 149, and 150.)
Four-ring Timers, Switches, and Lamps for Four Pairs of Electromagnetic Igniters.
Allis-Chalmers Company, Milwaukee, Wisconsin.
E, and is part of a four-piece ring like that of which E is a seg-
ment. F and P are together insulated from the remainder of
the rotor. In the ring of which E is a part, the other three
metallic segments are electrically insulated from each other and
from all other parts of the rotor. None of the parts which have
been mentioned has electric connection with the metal of the
engine. The timer is therefore without " ground " connection.*
* In the diagram, Fig. 150, the rings of the timer are shown separated from
each other, side by side, together with the brushes bearing on them. The reference
letter is the same for any one part in both the photograph and the diagram, when
the letter appears in both.
ELECTROMAGNETIC IGNITERS AND IGNITION SYSTEMS 183
The assumption of which is the positive, and which the negative
side of the supply circuit, as made below, is merely for conven-
ience of description.
The negative side of the main switch is connected to the
brushes / and F (shown at about the same level on opposite sides
of the timer), both of which bear on the slip-ring N. Segment
E is therefore negatively electrified, since it is electrically con-
nected to slip-ring N.
The positive side of the main switch is connected to the
brushes / and L (one at the top and the other at the bottom of
the timer), both of which bear on the slip-ring P. Segment F
is connected to slip-ring P, and is therefore positively electrified.
Brush G bears on segment , and brush H (next below G) bears
on segment F. These brushes are connected to the two double-
pole switches Ai and A 2 on the switchbox above the timer.
Each of these two brushes is connected to one blade of each of
these two switches. Switch Ai is connected to one igniter, and
switch A 2 to the other, of two igniters in the same combustion
chamber of the engine. These igniters operate simultaneously.
Four brushes bear on the ring of which is a segment. The
three of these brushes other than G, all bear on the long segment
K when the rotor is in the position shown. Segment K is
always electrically dead. The ring of which F is a segment also
has four brushes bearing on it, three of which are on the long,
dead segment as the rotor is shown. The pair of brushes, G and
H, are the only ones, of those on the segmental rings, that are
electrified while the rotor is in the position illustrated.
As the rotor revolves, the electrified segments E and F first
pass completely out of contact with the brushes G and H, then
make contact with the next similar pair of brushes, thus directing
the current to another pair of igniters in another combustion
chamber. The electrified segments E and F pass successively
under all four of the brushes that bear on the segmental rings,
thus successively directing current to the four pairs of igniters
in the four combustion chambers. There are four more switches
on the back part of the switchbox, which are not visible in the
illustration. Two safety fuses are located under each switch.
184 ELECTRIC IGNITION
The two short segments, one at each end of the electrified
segment E, are to prevent the long segment K from becoming
momentarily electrified each time the segment E passes either
out of or into contact with a brush. While the segment E is
passing from under brush G, the brush momentarily bridges the
insulation between G and the short segment. The latter is,
therefore, momentarily electrified, since the brush is in contact
with both the electrified segment E and the short segment. The
latter is long enough to allow E to pass completely out from
under the brush before segment K comes into contact with the
brush. The brush is thus left dead before segment K comes
into contact with it. The action is of the same general nature
while segment is moving into contact with a brush.
Each of the white lamps on the top of the switchbox is con-
nected to one circuit leading from the switch to an igniter. The
lamp is connected across the circuit so as to be in parallel with
the corresponding igniter. The lamp flashes each time the cir-
cuit to the corresponding igniter is electrified. The red lamp,
in the midst of the white ones, is connected to the wires between
the main switch and the slip-ring brushes of the timer. The red
lamp glows continuously while the wires going to the slip-ring
brushes of the timer are properly electrified; it remains dark
while the main switch is open.
133. Allis-Chalmers Electromagnetic Igniter for a Large
Engine. The photographs, Figs. 147 and 148, are from slightly
different viewpoints. The two views are shown in order to
present the constructive form as plainly as possible. Several
parts, which are completely hidden in the photographs, are
shown in the detail drawing, Fig. 149. The essential elements
of the igniter are shown in the skeleton drawing which is part
of the wiring diagram, Fig. 150.
The reference number is the same for any one part in each of
these figures where the part appears. All of the parts do not
appear in all of the figures.
The plug i has a flange at its outer end, by means of which
it is fastened to the engine cylinder. The casing 2 incloses
the electromagnets and the magnet-armature which actuate the
ELECTROMAGNETIC IGNITERS AND IGNITION SYSTEMS 185
FIGS. 147, 148, 149, and 150.
1. Igniter plug, flanged.
2. Housing, or casing, inclosing electromagnets and magnet-armature.
3. Shoulder which makes tight fit (with gasket) in wall of engine cylinder.
4. Contact-piece at ignition point of stationary electrode (insulated).
5. Rod of stationary electrode (insulated).
6. Arm carrying contact-point of movable electrode (insulated).
7. Outside end of insulated rod of movable electrode.
8. Arms rigidly fastened to outside end of insulated rod 7 of movable electrode.
9. Coiled tension spring for pressing the outer end of contact-arm 6 against the
stationary contact-piece 4.
10. Hammer rigidly mounted on rocker-spindle n, whose upper end extends
through the top of housing 2.
11. Rocker-spindle on which hammer 10 and magnet-armature 23 (the latter not
shown in Figs. 147 and 148) are rigidly mounted.
12. Fiber (insulating) button at the end of hammer-arm 10. This button strikes
the arm 8 to separate the contact-points in the combustion chamber.
13. Adjusting screw with fiber button on the end. For preventing hammer 10
from rotating back too far after current stops in the igniter.
14. Tubular bushing (insulated) around the rocker-arm 7.
15. Mica washers, or rings, for insulating stationary electrode 4-5.
16. Mica washers, or rings, for insulating tubular bushing 14 together with mov-
able electrode 6-7.
17. Collar clamped on rod 7 of movable electrode. A short coiled compression
spring between this collar and the adjacent end of the tubular bushing 14
holds the hub of the arm 6 against its seat on the inside end of 14 so as to
maintain a tight joint.
1 8. Bolts for fastening magnet-coils in place in housing 2.
The following parts are not visible in the photographic views.
19. 20. Coil winding of field-magnets.
21, 22. Cores and pole-pieces of the magnetic field.
23. Magnet-armature. Rigidly attached to rocker-spindle n.
i86
ELECTRIC IGNITION
igniter. This casing is bolted to the flange of the plug proper.
The shoulder 3, near the inside end of the plug, makes a gas-tight
joint, with the aid of a gasket, in the wall of the engine cylinder.
The stationary contact-piece 4 at the point of ignition is
, FIG. 147. (See also Figs. 148, 149, and 150.)
Electromagnetic Low-tension Igniter with Rocking Magnet-Armature.
Allis-Chalmers Company.
fastened to, or integral with, the rod 5, which together form the
insulated stationary electrode 4-5. The outside end of the rod 5
projects slightly beyond the nut which holds the terminal of the
wire through which current is brought to the stationary electrode.
The rocker-arm 6 which carries the movable contact-ignition
ELECTROMAGNETIC IGNITERS AND IGNITION SYSTEMS 187
point is fastened to a rod 7 which extends to the outside through
an insulated tubular bushing 14. Only a portion of the outer
end of 7 is visible in the photographs. To the outside end of 7
is clamped a two-armed piece 8, to the front arm of which is
FIG. 148.
Another view of Fig. 147.
attached a coiled tension spring 9 for keeping the ignition-contact
points pressed together when no current is flowing through the
igniter. The rear arm serves as an anvil against which hammer
10 strikes so as to slightly rotate the electrode 6-7, thus causing
separation of the contact-ignition points. The hammer 10 is
i88
ELECTRIC IGNITION
carried on a spindle which extends up through the housing 2.
A fiber button 12 on the hammer 10 strikes the arm 8. This
button prevents electric connection between 8 and 10. The eye-
bolt at the left-hand end of the coiled spring 9 is insulated from
the metal through which it passes. The two electrodes are
completely insulated from the main body of the igniter. The
adjusting screw 13 prevents the hammer 10 from swinging back
too far. This screw has a fiber end against which 10 strikes.
The mica washers 15 are for insulating the inner end of the
stationary electrode; and the mica washers 16 are for insulating
FIG. 149. (See also Figs. 147, 148, and 150.)
Detail of Electromagnets and Hammer of Igniter with Rocking Magnet- Armature.
the inner end of the tubular bushing 14. The collar 17 is clamped
on the movable electrode rod 7, and has a coiled compression
spring between it and the end of 14 for keeping the hub of the
igniter arm 6 pressed against the inner end of the tube 14 so as
to make a gas-tight joint.
The magnet-coils and their cores, which are all inside of the
casing 2, form, together with the iron casing, a magnetic field of
the same general nature as that of a bipolar electric generator
of the more usual form. These parts are shown in Fig. 149.
The coils 19 and 20, together with their cores and pole-pieces 21
and 22, are fastened to the casing 2 by the capscrews 18 which
ELECTROMAGNETIC IGNITERS AND IGNITION SYSTEMS 1 89
y
rs
^-4-^\
+T^j
+
1
i ^^+
E?
5
ir ll
1 />j
3 Switch Generator
Main Switch
JL
FIG. 150. (^ee <i^o Figs. 146, 147, 148, and 149.)
Connections for Four-ring Timer and Eight Electromagnetic Igniters, Two in
Each of Four Combustion Chambers of One Engine.
I QO ELECTRIC IGNITION
are threaded into the magnet-cores. A magnet-armature 23
of mild steel is rigidly mounted on the same spindle n that
has the hammer 10 rigidly fastened to it. The magnet-arma-
ture occupies part of the space between the pole-pieces of the
magnets.
The action of the igniter can be understood by referring to
its skeleton representation in Fig. 150. The positions of the
moving parts there correspond to those when no current is pass-
ing through the igniter. The movable ignition-point is shown
pressed against the stationary one by the effort of the coiled
tension spring 9. The hammer 10 is rotated back clear of the
anvil arm on 8. The magnet-armature has its length at a con-
siderable angle with the center line of the two magnet-cores.
The path of the current, when one is flowing through the
igniter from the positive (+) side of the connecting wire, is
through coil 19 to and through coil 20 to the outside terminal of
the stationary electrode 5-4, to the movable electrode 6-7 and
the arm 8, from which it leaves the igniter through the negative
( ) connection. As soon as a current starting through the
igniter gives the magnets sufficient strength, the armature 23 is
rotated by magnetic action, in the direction to bring its length
more nearly parallel with the axis of the magnet-cores. The
armature rotates the spindle n and the hammer 10 with it,
since they are all fastened rigidly together. The hammer strikes
the anvil arm which is the rear portion of 8 and moves it slightly
so as to rotate the movable electrode and separate the ignition
points between which an arc is drawn at the instant of their
separation. As soon as the arc breaks down and the current dis-
continues, the tension spring 9 draws the movable electrode back
against the stationary one again and at the same time rotates
the hammer 10 and magnet-armature 23 back to the positions
shown. The armature is shown rotated more out of line with
the magnet-cores than really occurs, this being done in order to
make the drawing clear. An examination of Fig. 149 will give
an idea of how far the armature and hammer rotate back.
Igniters of the form just described have been constructed in
large sizes for use on 8o-volt current.
ELECTROMAGNETIC IGNITERS AND IGNITION SYSTEMS IQI
134. Wiring Diagram for a Four-ring Timer and Igniters
Actuated by a Rotary Magnet- Armature. Fig. 150. This wir-
ing diagram is for a timer like that shown in Fig. 146, and for
eight igniters like that of Figs. 147, 148, and 149, two igniters
in each of four combustion chambers. The descriptions of the
timer and igniter cover practically all of the wiring diagram
except the source of electric supply.
A generator and a battery are represented for supplying cur-
rent to the system. Either may be thrown into circuit by the
double-pole double-throw switch near the generator. If a storage
battery is used, it must be charged from some source other than
the generator shown, unless additional connections are made for
this purpose. Most of the arrangements of generators and bat-
teries which have been shown in connection with mechanically
operated igniters can be used instead of the generator and
battery shown in the diagram. It should be remembered, how-
ever, that no kick-coil is required in connection with electrically
operated igniters.
135. Igniter with Vibratory Magnet- Armature. The small
magnetic plug shown in full view in Fig. 151 is of a size suitable
for use on automobile and small boat motors. The length over
all is slightly less than 4 inches, and the diameter of the cylin-
drical portion which incloses the magnet-coil is about I T \ inches.
The plug is shown in longitudinal section in Fig. 152. The
movable electrode, the magnet-core, and the U-shaped spring
which presses the movable electrode against the stationary one,
are shown in Fig. 153.
The movable contact-point 20 at which the ignition arc is
drawn is at the lower end of the movable electrode 1-20, whose
flattened upper end i is the armature of the magnet. The U--
shaped spring 3 presses the movable electrode against a blunt
knife-edge which is part of the magnet-core, or " pole-piece," 2,
and keeps the movable contact-point 20 pressed against the
stationary contact-point 21, except while these points are sepa-
rated to draw an ignition arc. The ends of the U-shaped spring
are slightly nearer the ignition-points than the knife-edge is.
The path of the current through the plug, assuming a direction
IQ2
ELECTRIC IGNITION
of flow for convenience, is from the terminal 9 through the plate
10, rivet 7, ring 6, magnet-coil 5, screw 26, body of the upper
portion of the plug, movable electrode 1-20 to the stationary
electrode 21, which makes electric connection with the metal of
the motor. The screw 26 is one of the terminals of the magnet-
coil, and has metallic contact with the upper body of the plug.
All of the upper body of the plug is insulated from the stationary
FIGS. 151 and 152. (See also Fig. 153.)
Small Electromagnetic Low-tension Igniter Plug. Bosch Magneto Company,
New York.
a = go millimeters. d = 37 millimeters.
b = 15 millimeters. e = 44.5 millimeters.
c = f-inch gas-pipe thread.
ignition-point 21 and the hexagon-head screw-plug 23 by means
of the steatite cone 22 and the mica rings, or " plates," 18.
As soon as the current through the plug attains sufficient
volume, the upper end i, of the movable electrode 1-20, is
attracted toward the magnet-core 2. This causes the movable
electrode to rock on the supporting knife-edge and thus separate
the ignition-points 20 and 21, so that an electric arc is drawn
between them. The electromagnet acts as a kick-coil to produce
an arc suitable for ignition. The brass piece 15 prevents the
ELECTROMAGNETIC IGNITERS AND IGNITION SYSTEMS 193
upper end i of the movable electrode from being drawn into
contact with the steel of the magnet-core, which action, if not
prevented, would probably cause the two parts to cling together
longer than allowable for the operation of the igniter at high
speed of the motor.
FIG. 153.
Details of Magnet-Core, Movable Electrode, and Spring of Figs. 151 and 152.
FIGS. 152 and 153.
1. Rocking electrode.
2. Magnet-core or pole-piece.
3. U-shaped spring.
4. Iron sleeve.
5. Magnet-coil.
6. Current conducting ring.
7. Current conducting rivet.
8. Mica disk.
9. Terminal nut.
10. Current conducting plate.
11. Insulating bush.
12. Mica ring.
13. Upper yoke of magnet.
14. Detachable brass piece.
15. Separating brass piece.
16. Internal ring-nut.
17. Centering ring.
18. Mica rings.
19. Packing ring.
20. Movable ignition-point.
21. Stationary ignition-point.
22. Steatite insulating cone.
23. Hexagon head with thread
plug.
24. Packing ring for coil body.
25. Lower yoke of magnet.
26. Connecting screw at end of magnet
winding.
of
This plug should be operated in a vertical position, with the
terminal 9 at the top. The motor cylinder should be well cooled
at the time of screwing the plug into it, and the air-current for
cooling the motor should strike the plug. The upper body of
the plug must not touch the metal of the motor, since it must be
electrically insulated from the motor and the metal of the car.
194
ELECTRIC IGNITION
The plug can be taken apart for examination and cleaning by
unscrewing the- coil body from the magnet-core, or " pole-piece."
The U-shaped spring can then be pressed upward by means of
some small tool such as a screwdriver or knife-blade, until the
crown projects far enough to be grasped for completely remov-
ing the spring. The brass piece 14 can then be removed, after
which the removable electrode can be taken out. If the coil
body does not unscrew readily, kerosene put into the groove at
the top of the screw-plug will loosen the threads.
136. Magneto and Wiring Diagram for Magnetic-plug Igni-
tion System. Fig. 1 54 shows the electric connections between
3 o *> 11
FIG. 154. (See also Figs. 151, 152, 153, 155, and 156.)
Magnetic-plug Ignition System for Small Motors with Four Combustion Cham
bers. Bosch Magneto Company, New York.
FIGS. 154, 155, and 156.
1. Permanent field-magnets. 12. Timing-lever.
2. Armature. 13. End cap over interrupter.
3. Flanged tube to which junction of 14. Spring for holding end cap.
main and auxiliary windings is
connected.
4. Fastening screw for contact-
breaker or interrupter.
5. Contact-piece on interrupter.
6. Interrupter-disk.
7. Long platinum contact-screw.
8. Spring acting on interrupter-lever.
9. Short platinum contact-screw.
10. Interrupter-lever.
11. Segments on timing-lever.
15. Conducting rods on distributer.
16. Carbon brush of distributer.
17. Distributer disk insulation.
18. Connection terminals.
19. Rotating arm of distributer.
20. Dust cover.
21. Fastening nuts for distributer disk.
22. Short-circuiting terminal.
23. Connecting piece for end of auxil-
iary winding.
ELECTROMAGNETIC IGNITERS AND IGNITION SYSTEMS 195
four magnetic plugs such as that described in the preceding
section, and a magneto especially adapted to supplying current
to such plugs. The plugs are lettered A, B, C, D. Only the
parts of the magneto essential to showing the electric connections
appear in the figure. They are illustrated in conventional form
to some extent. The armature is shown in part longitudinal sec-
tion at the middle lower portion of the figure. A mechanically
operated interrupter is shown at the right-hand lower part of
the illustration, and just above it is a distributer for directing
the current to each of the igniter plugs in succession. The
interrupter and distributer are shown as they appear when look-
ing toward the end of the armature spindle. The bent inter-
rupter-lever 10 and the contact-piece 5 rotate with the armature.
The distributer arm 19 rotates about a center which is concentric
with the center of the two large circles which surround it. As
the distributer arm rotates it makes contact successively with
the contact-pieces a, 6, c, d. The distributer arm is shown in
contact with a and the igniter A is operating. Each of the heavy
dot-and-dash lines is to show electric connection either between
the two views of the same part or between two parts which fit
together so as to have electric connection. The heavy broken
line with dashes all of the same length indicates ground connec-
tion between the magneto armature and the ignition plugs.
The magneto armature* is of the shuttle type and has two
windings, one of which is a continuation of the other. These
windings are illustrated diagrammatically by one coil of several
turns. The lower portion of the coil may be called the main
winding, and the upper portion the auxiliary winding. One end
of the main winding (the lower end as illustrated) is connected
to the core of the armature. The junction point of the two
windings, which is an end of each winding, is connected to the
flange 3 of an insulated tube which extends through the hollow
spindle of the armature and has the interrupter-disk 6 fastened
to its outer end. The interrupter-disk has a pin which carries
the interrupter-lever 10. The latter has electric connection
* The constructive form of the magneto is shown in Figs. 155 and 156. Exam-
ination of these illustrations may give a clearer understanding of the diagram.
196 ELECTRIC IGNITION
with the disk 6 and thence through the tube to the flange 3.
The upper end of the auxiliary winding is connected to a long
screw 4 which extends through the hollow armature spindle and
the contact-piece 5 on the disk 6. The screw 4 and contact-
piece 5 are electrically connected together, but are insulated
from all other parts of the magneto except a carbon button
(brush), mounted on a bow-spring, and pressed against the end
of the screw 4. Electric connection is made between the button
23 3 4
FIG. 155.
Bosch Magneto for Four Low-tension Magnetic Igniters. Longitudinal Section.
and the distributer rotor 19 by means of the clip-spring 14 and the
other parts shown in conjunction with 14 in Fig. 154. As the
contact-piece 5 and interrupter-lever 10, both mounted on the
disk 6, as stated above, rotate with the magneto armature, a
piece of insulating fiber in the end of one of the arms of the inter-
rupter-lever (the right-hand end as shown) strikes the stationary
segments u, thus rocking the lever and causing the contact-
point at the left-hand end of the lever to move away from
the contact-piece 5. The contact-points of the interrupter are
ELECTROMAGNETIC IGNITERS AND IGNITION SYSTEMS 197
pressed together by the spring during the time the fiber piece
is not in contact with one of the two segments n.
While the electric pressure and current are increasing in the
magneto armature on account of its rotation in the magnetic
field, the contact-points of the interrupter are kept pressed to-
gether by the spring 8. During this time the current divides
itself between two electric circuits exterior to the armature
windings. Part of the current flows through the closed inter-
rupter, and the remainder through one of the igniters. The
11
FIG. 156.
Interrupter End of Fig. 155. Interrupter Cover Removed.
amount of current through the igniter during this time is not
sufficient to cause separation of the ignition-points, however.
At, or about, the instant the current through the interrupter
attached to the armature spindle attains its maximum value,
the interrupter circuit is broken at the contact-points of the
interrupter. The interrupter is shown in its position just after
its circuit has been broken by the striking of the piece of fiber
against the upper stationary segment n, the rotation of the
interrupter being counter-clockwise (left-hand). The conse-
quent sudden stoppage of the current flowing through the inter-
198 ELECTRIC IGNITION
rupter and auxiliary winding of the magneto armature causes a
correspondingly sudden increase of voltage in the winding of
the armature and of current through the ignition plug. The
increased current through the igniter causes the ignition-points
to separate so that an arc is drawn for ignition. The igniter A
is shown operating, the distributer arm being in contact with
the corresponding contact-piece a of the distributer.
Two electric impulses per revolution of the armature are
generated in it, since the armature is of the shuttle-wound type
rotating in a bi-polar field. In order to deliver current once
to each of the four igniters, the armature must make two revo-
lutions and the distributer must make one revolution. The
distributer arm is driven by a pair of tooth-gears, one on the
armature spindle and the other on the distributer shaft. The
pitch circles of these gears are represented by the dash-and-dot
circles which touch each other. The gear on the igniter shaft
has twice as many teeth as the one on the armature spindle.
The rotative speed of the distributer gear is therefore half that
of the armature gear. The latter is the driver.
The timing-lever 12, to which are attached the segments n,
can be rocked about the armature spindle to vary the time of
ignition to advance or retard the spark.
The constructive form of the magneto with an interrupter for
operating four electromagnetic igniters is shown in Figs. 155 and
156. The former is a longitudinal section, and the latter is an
end view with the cover cap of the interrupter removed, the
spring which holds the cover cap being pushed to one side. The
following description is supplementary to that which has just
been given. The cover cap 13 has fastened to it a bow-shaped
spring (not numbered) which carries a carbon button (not num-
bered) that presses against the outer end of the screw 4. The
latter is connected to the end of the auxiliary winding of the
armature. By this means the cap 13 is placed in electric con-
nection with the auxiliary winding. The cap is insulated from
the contact-breaker. The spring 14, which holds the cap in
place, connects electrically with the central carbon 16 of the
distributer. This carbon is in contact with the distributer arm
ELECTROMAGNETIC IGNITERS AND IGNITION SYSTEMS 199
19 and also with the terminal 22. The four contact-pieces
(a, b, c, d in Fig. 154) are connected to the four terminals 18,
one to each terminal. From these terminals the wires lead to
the igniter plugs. The path of the current from the armature
winding of the magneto to the igniter plugs, when the interrupter
circuit is open, is through the screw 4, carbon button and bow-
spring to the cap 13, thence through the spring 14 and its fasten-
ings to the central carbon 16, distributer arm 19, thence to one
of the terminals 18 whose contact-piece the distributer touches
at the moment, to the igniter, and then back through ground to
the armature of the magneto, or in the opposite direction. The
current flows first in one direction and then in the opposite
through this path, since the magneto produces an alternating
current.
In order to have a convenient means to cut out the ignition
while the magneto is running, the short-circuiting terminal 2 2 is
provided. When this terminal is connected to ground, as through
a wire and switch, the closing of the switch diverts the current
from the igniters so that ignition ceases.
CHAPTER XV.
TRANSFORMER SPARK-COILS AND SYNCHRONIZER, OR
MASTER, TREMBLER-COILS.
137. General. The purpose of the transformer spark-coil
in connection with high-tension ignition is to transform elec-
tricity of low pressure into electricity having a pressure high
enough to cause it to jump across the space between metallic
parts when the space contains a mixture of air and fuel in the
state of gas or vapor. The low-pressure primary current which
the transformer receives rarely has a pressure greater than 10
volts. The secondary current which the transformer delivers
has a pressure of several thousand volts. The amount of elec-
tricity decreases during the transformation, to an extent some-
what greater proportionately than the pressure increases.
In order to cause the transformer spark-coil to operate, electric
current is first sent through it and then interrupted. The device
for interrupting the current is sometimes part of what is broadly
known as the transformer spark-coil. In other cases the inter-
rupter is separate from the spark-coil, so far as mechanical
connections are concerned. The separate interrupter may be
either mechanically operated, or it may be a coil similar in a
general way to a kick-coil (single winding) provided with an
electrically operated interrupter. The latter is generally called
a master trembler-coil, a' master vibrator-coil, or a synchronizer
coil.
138. Elementary Transformer Spark-Coils. In its more
usual form, the transformer spark-coil consists essentially of a
core in the form of a bundle or sheaf of small soft iron or mild
(soft) steel wires, a primary winding of insulated copper wire,
and a secondary winding, also of insulated copper wire. There
is generally a tube of some thin strong insulating material be-
tween the core and the windings. This tube, together with
200
TRANSFORMER SPARK-COILS AND SYNCHRONIZER 2OI
insulating washers, or rings, at its ends, forms a spool for retain-
ing the windings in place. Some thin insulating material is
generally placed between the two windings to keep them sepa-
rated from each other.
The primary winding, which is next the core, consists of some
200 to 300 turns of comparatively thick copper wire around
which is wrapped cotton or silk thread for insulating it. The
secondary winding consists of some 1500 to 2000 turns of thin
copper wire insulated in the same manner as the wire of the
primary winding. The secondary winding is practically always
wound outside of the primary winding.
In some transformer coils all four of the ends of the windings
are brought out separately; in others two of the wire-ends are
(a)
FIG. 157.
Four- terminal Winding of Transformer Spark- Coils. Conventional
Representations.
connected together, an end of the primary to an end of the sec-
ondary, and only one wire brought out from this junction of the
two windings. In the latter winding, the coil has only three
terminals, and the two windings are in one sense continuous.
Whether the two windings are kept separate and all four of the
wire-ends brought out as terminals, or the windings fastened
together end to end and only three terminals brought out, de-
pends chiefly on the nature of the ignition system in which the
coil is intended to be used, as will appear later.
It may be noted that a transformer coil can generally be
202
ELECTRIC IGNITION
readily distinguished from a kick-coil for low-tension ignition,
by the difference that the transformer coil has either three or
four terminals, while the kick-coil has only two terminals unless
it is of unusual design for some special purpose.
Some of the conventional methods of representing the core
and windings of transformer spark-coils are shown in Figs. 157
and 158. In Fig. 157 the primary and secondary windings are
not connected together, consequently four terminals appear in
both (a) and (ft), these being two conventional methods of repre-
senting this type of winding. In (a) the primary winding is
represented at the upper end of the core, and the secondary
(a) (b)
FIG. 158.
Three-terminal Winding of Transformer Spark-Coils. Conventional
Representations.
winding at the lower portion. In (b) the primary winding is
represented next to the core, and the secondary winding outside
of the primary. In Fig. 158 the primary and secondary wind-
ings are connected together, thus leaving only three terminals.
Otherwise these conventional representations are similar to those
of the preceding figure.
139. Operation of Elementary Transformer Spark-Coil without
Trembler. A plain transformer spark-coil is shown connected
to an electric battery in Fig. 159. Four different arrangements
of the connections are shown, including the different locations
of the break in the connecting wires. If in any of these arrange-
ments the ends of the wires are pressed together at the break
so as to close the primary circuit, a current will flow from the
TRANSFORMER SPARK-COILS AND SYNCHRONIZER 203
battery through the primary winding of the transformer. Then
by separating the wire-ends at the break so as to interrupt the
current suddenly, a spark will be caused to jump across the
spark-gap in the secondary circuit. If the wire-ends were sepa-
rated very slowly so as to draw an arc between them and thus
cause a gradual decrease of the primary current, no spark would
,Break
Battery
(A)
(D)
FIG. 159.
Various Connections of a Transformer Spark- Coil and a Battery.
appear at the spark-gap. Sudden interruption of the primary
current is requisite to the production of a jump-spark. No
spark appears at the spark-gap at the instant of closing the
primary circuit. This refers to such transformer coils as are
customarily used for ignition purposes, and when the primary
current is not greatly in excess of what it should be. If an
excessive current is sent through the primary of the transformer,
as by the use of too many cells in series in a battery, it is possible
204 .ELECTRIC IGNITION
to produce a spark sometimes at the instant of closing the primary
circuit.
The operation of the transformer more in detail is as follows:
The current in the primary winding magnetizes the iron or steel
core of the transformer. Then as the primary current ceases
suddenly, the core loses its magnetism rapidly. This rapid
decrease of magnetic flux through the core and also through the
secondary winding, since the core passes through the secondary,
induces electromotive force in the secondary. The secondary
circuit being open at the spark-gap, this induced electromotive
force builds up a pressure in the secondary until the difference
of potential between the two sides of the spark-gap causes a
spark to pass across the spark-gap.-
The circuit of the high-tension current embraces different
elements, or combinations of elements, in the four arrangements
of Fig. 159. The spark-gap is of course always included in the
high-tension circuit. The following refers to the high-tension
current that is induced by the interruption of the primary current,
and which flows while the primary circuit is open. In (A) the
high-tension current flows through the secondary winding only;
in (B) it flows through the secondary winding and the battery in
series; in (C) through the secondary and primary windings in
series; and in (D) the secondary current flows through the sec-
ondary and primary windings and the battery in series.
Any of the above arrangements of the spark-coil, battery,
and break in the primary circuit will operate satisfactorily for
ignition purposes, but it is probable that (A) and (B) are the
best.*
140. Trembler Transformer Spark-Coil. In Fig. 160 a
trembler, or vibrator, interrupter and a condenser are shown in
connection with a transformer spark-coil and an electric battery.
The trembler is a steel spring V rigidly fastened at one end to
the metal block A. The spring has fastened to it a contact-
piece M which is pressed against a mating contact-piece K by
* This last sentence does not apply to transformer coils in which there is not
such great difference in the number of turns in the two windings. Coils used for
medicinal purposes and physical treatment are generally of the latter class.
TRANSFORMER SPARK-COILS AND SYNCHRONIZER 205
the elastic action of the spring. K is shown in the form of an
adjusting screw held in place by the rigid metal part B.
The action of the trembler is as follows: Immediately upon
closing the primary circuit, as by pressing the wire-ends together
at the break in the battery circuit, current begins to flow through
the interrupter and the primary winding of the transformer in
series. The path of the primary current is from the positive
(+) side of the battery to and in series through B, K, M, V, A,
the primary winding and back to the negative ( ) side of the
Condenser
FlG. i 60.
Trembler Spark-Coil Connected to a Battery and a Spark-Plug. Requires both
Sides of Timer to be Insulated. Unbroken High-tension Circuit.
battery. As soon as the transformer core becomes sufficiently
magnetized by the action of the current, the core attracts the
free end of the trembler away from the stationary contact-piece
K, thus separating M and K. This breaks the circuit at the
trembler contacts and interrupts the flow of current through
the primary winding. As soon as the current stops flowing, the
magnet core loses magnetism to a sufficient extent to allow
the end of the spring to move away from it and again press the
contact-pieces together. This closes the primary circuit so that
206 ELECTRIC IGNITION
current begins to flow through it again, and the same operation
is repeated as long as the wire ends are kept pressed together
at the break. A spark passes at the spark-gap each time the
current is interrupted at the contacts of the trembler. The
trembler spring is not allowed to move far enough to touch the
end of the magnet-core, since it would tend to cling to the core.
The spring may be strong enough to keep it from being drawn
against the core, or a stop of some non-magnetic substance such as
wood, rubber, or brass may check its movement toward the core.
The adjustable contact-screw K affords a means of setting
the interrupter so as to secure the most satisfactory operation,
and of taking up wear at the contact-points on account of spark-
ing and burning. This is the only adjustment in numerous
makes of spark-coils. Others have a second means of adjust-
ment, as will appear later. Ordinarily the most desirable setting
of the adjustment means is that at which the least amount of
current is required in connection with sufficiently rapid vibration
of the trembler.
The condenser prevents excessive sparking and burning at
the contact-points of the trembler, and adds to the efficiency of
operation of the transformer. It consists of numerous sheets
of tin-foil laid together with thin sheets of insulating material,
such as mica or varnished paper, between them. Each second
sheet of foil projects beyond the insulation at one edge, and
the remaining (alternate) foil sheets all project in the same
manner at the opposite edge. The foil-sheet edges which pro-
ject next to each other are all pressed together so as to make
electric connection between them, this set of sheets forming
what is called one side of the condenser. The remaining foil
sheets, whose edges project in the opposite direction, have their
projecting edges pressed together in a similar manner, this second
set of sheets forming the other side of the condenser. This dis-
posal of the foil sheets is shown diagrammatically in the figure,
but the insulating sheets between the foil are not shown. The
condenser is connected to A and B, which are on opposite sides
of the contact-points K and M. The condenser is thus placed
in parallel with the interrupter.
TRANSFORMER SPARK-COILS AND SYNCHRONIZER 207
During at least the first part of the separating movement of
the trembler spring, the current tends to keep flowing across the
gap thus formed between the contact-points of the trembler.
If there is no condenser, or if it is inoperative, the arc drawn
between the contact-points soon burns and destroys the contact-
points at the trembler. But when the condenser is operative,
the current, instead of maintaining an arc at the contact-points,
is diverted into the condenser, thus charging the condenser.
The sparking and burning at the contact-points is thus kept
down to an amount so small that but little harm is done to the
points. The current ceases to flow into the condenser soon after
the trembler contacts begin to separate, and the condenser then
immediately discharges back through the primary circuit while
the circuit is still open at the contacts. On account of the
momentum of the discharge current, the condenser immediately
becomes again charged to a less extent with its polarity reversed,
then discharges in the opposite direction, and so on as the elec-
tricity continues oscillating. This oscillation of the electricity
through the primary winding produces a rapid series of sparks
at the spark-gap in the secondary circuit. This series of sparks,
occurring during one separation of the trembler contacts, is
ordinarily referred to as a single spark.
The current does not flow through the condenser.
There is always a complete metallic circuit, exclusive of the
spark-gap, for the high-tension current in Fig. 160. This is also
true of Fig. 161, which differs from the preceding figure in having
the trembler support connected to the junction of the two wind-
ings instead of to the end of the primary winding.
In Figs. 162, 163, 164, and 165, which show different arrange-
ments of the battery and connections, there is always a complete
circuit, exclusive of the spark-gap, for the secondary current.
This circuit includes the battery in each case. It is not objec-
tionable to have the high-tension current flow through the battery,
however.
All of the arrangements of the parts as shown in the last four
figures are commonly used in ignition systems. The arrange-
ments shown in Figs. 160 and 161, although entirely correct so
208
ELECTRIC IGNITION
FIG. 161.
Same as Fig. 160, Except the Connections to the Primary Winding of the Spark-Coil.
Condenser
.*. Spark
FIG. 162.
Trembler Transformer Connected to a Battery and a Spark-Plug so that One Side
of the Timer can be Grounded. Unbroken High-tension Circuit.
TRANSFORMER SPARK-COILS AND SYNCHRONIZER 209
p-n
II
FIG. 163.
Trembler Spark-Coil, Battery and Spark-Plug Connected so that One Side of Timer
can be Grounded and the Secondary Circuit is Unbroken.
FIG. 164.
Connections Giving Same Conditions as Stated under Figs. 162 and 163.
210
ELECTRIC IGNITION
far as the spark-coil and battery are concerned, are not so much
used on account of requiring a form of timer that is more expen-
sive to construct than that which can be used with the four
figures which follow these two.
At least some of the most prominent makers of spark-coils
think that a high-tension trembler spark-coil should not be
connected to the other parts of an ignition system in such a
manner that the high-tension current must pass through the
FIG. 165.
Connections Giving Same Conditions as Stated under Figs. 162 and 163.
trembler contacts of the spark-coil as a part of the only avail-
able high-tension circuit during part of the time. Arrangements
under which this condition may occur are shown in Figs. 166, 167,
1 68, and 169. Thus, in any of these arrangements, if the wire-
ends are suddenly separated at the break while the trembler is
operating, the breaking of the circuit may occur at the same
instant at both the break in the wire and at the trembler. This
leaves no metallic circuit for the high-tension current. The
tendency of the high-tension current is then to jump the gaps
at the trembler and at the break in the primary circuit. If the
resistance of these gaps is high at the instant, an excessive electric
pressure will be brought to bear on the condenser and may break
TRANSFORMER SPARK-COILS AND SYNCHRONIZER 211
Condenser
FIG. 166.
Trembler Spark-Coil, Battery and Spark-Plug Connected so that the High-tension
Circuit is Interrupted. One Side of the Timer can be Grounded.
FIG. 167.
Connections Giving Same Conditions as Stated under Fig. 166.
212
ELECTRIC IGNITION
FIG. 1 68.
Connections Giving Same Conditions as Stated under Fig. 166.
FIG. 169.
Connections Giving Same Conditions as Stated under Fig. 166.
TRANSFORMER SPARK-COILS AND SYNCHRONIZER 213
down its insulation. Such an injury to the condenser will of
course interfere with the operation of the spark-coil.
141. Safety Spark-Gap. In order to protect the windings
of the spark-coil against unduly high electric pressure, a safety
spark-gap is generally used in connection with the other parts
of the spark-coil. Such a safety gap is shown in Fig. 170. As
there shown, the safety gap is between the pointed edges of two
pieces of metal, each of which is connected respectively to an
Condenser
FIG. 170.
Shows Safety Spark-Gap for Protecting Winding of Spark-Coil.
end of the secondary winding. If the connections leading to
the ignition spark-gap are removed, thus destroying the regular
circuit for the high-tension current, sparks will jump across the
safety gap during the operation of the spark-coil. If there were
no safety gap, there would be danger of the pressure becoming
high enough to break down the insulation of the transformer
winding. The safety gap is made wide enough to prevent sparks
passing across it during the time the igniter is connected into
the circuit. Half an inch or somewhat less is the ordinary
width of the safety gap on a trembler spark-coil. Each side of
the gap may have either one or more points. It is sometimes
214 ELECTRIC IGNITION
placed inside the casing which contains the transformer and
condenser, sometimes outside of the casing so as to be plainly
visible.
142. Lag of Spark-Coils. Between the instant of the closing
of the primary circuit and the jumping of the spark in the second-
ary circuit (at the spark-plug) of a trembler spark-coil, an inter-
val of time elapses which is appreciable in comparison with the
length of time occupied by one revolution of a high-speed motor,
and decidedly more appreciable in comparison with the allow-
able variation in the time of ignition as related to the position
of the motor piston during its movement. A certain amount of
time is required for the primary current to attain its final strength
in the primary winding, and for the steel core of the coil to be-
come sufficiently magnetized to attract the trembler forcibly
enough to just begin to move it. This may be called the mag-
netic lag of the spark-coil. Then, after the magnetism has
become sufficiently strong, more time is required to move the
trembler far enough to interrupt the primary current. The
latter may be called the mechanical lag of the spark-coil. It
might be added that still more time is required to induce the
current in the secondary after the primary is interrupted, remem-
bering that the current is at first diverted into the condenser,
but this time is almost inappreciable in comparison with that
which has been mentioned.
143. Tremblers, or Vibrators: Bow-spring, Hammer-break,
and Plain Types. In order to have satisfactory operation of a
transformer spark-coil with a trembler interrupter, it is necessary
that the trembler respond promptly to the magnetic attraction
of the magnet-core, that the contact-points separate rapidly,
and that the contact-points make constant and firm contact
during the time they are intended to be pressed together between
each two successive vibrations of the trembler. The prompt-
ness of response to the magnetic attraction of the core is more
especially essential to satisfactory operation in connection with
motors which rotate at high speed. The above features are
generally secured by means of a compound trembler of either
the " bow-spring " type or the " hammer-break " type.
TRANSFORMER SPARK-COILS AND SYNCHRONIZER 215
A bow-spring trembler is shown in Fig. 171. The straight
spring V is rigidly held at one end by the metal block A to which
it is fastened by a screw. A thin bow-shaped spring W is fast-
ened at one end to the spring V by means of rivets near the
a
D
O-M 2
SIS
\
A
V
Thickness of Straight Spring- .022 Inch
" Bow " =.008 "
FlG. 171.
Bow-spring Trembler Blade for Spark-Coil. The Autocoil Company, 136 Seventh
Street, Jersey City, New Jersey.
supporting block A. The bow-spring carries the contact-piece
M at which the circuit is broken by the vibration of the trembler
during the operation of the interrupter.
In the standard size of this type of trembler, the dimensions
are:
Width of both springs J| inch.
Thickness of straight spring 022 "
Thickness of bow-spring 008 "
Free length of straight spring 2^ inches.
In a smaller size of this trembler, made to meet conditions
where the space is cramped, the free length of the flat spring is
if inches. This shorter blade is considered by the manufacturer
as inferior to the one of standard length.
A spark-coil whose interrupter has a bow-spring trembler of
the above form is shown in Figs. 172 and 173. (The safety
spark-gap appears plainly in the last figure.)
In the operation of the bow-spring trembler, the straight
spring is first drawn down a slight distance by the attraction
of the magnetized core of the spark-coil while the elastic action
2l6
ELECTRIC IGNITION
of the bow-spring still keeps its contact-point pressed against
the stationary contact-piece. The contacts then separate rapidly
as the straight spring continues moving toward the magnetized
core. When both blades spring back again after the core loses
its magnetism, the elasticity of the very thin bow-spring is effec-
tive in keeping the contacts together, which might not be true
if there were only one spring with the contact-point on it. In
FIG. 172.
Trembler Spark-Coil with In-
closing Case. Autocoil.
FIG. 173.
Top, or End, of Trembler Spark-Coil with
Switch. Autocoil.
the latter case the secondary vibrations of the spring while the
core is not magnetized between successive breaks in the circuit
have a tendency to cause slight (undesirable) separations of the
contact-points. The momentum gained by the straight spring
before the contact-points begin to separate provides sufficient
force to pull the contacts apart in case of any ordinary amount
of burning and fusing at these points. The bow-spring trembler
described above has been found satisfactory during extensive
use.
TRANSFORMER SPARK-COILS AND SYNCHRONIZER 217
A hammer-break trembler interrupter is shown in Fig. 174 in
connection with the adjacent end of the coil box. The flat steel
blade V is riveted to a short flat spring U which is rigidly sup-
ported at the opposite end by the stationary metal piece A so as
to stand opposite the end of the magnetic core E. A contact-
spring W carries the movable contact-piece M near one end and
is rigidly supported by A at the opposite end. The contact-
spring is very thin and flexible. It is sometimes made of copper.
The steel trembler carries a hammer H whose striking flange
FIG. 174.
Bogert Hammer-break Trembler for Spark-Coil, C. F. Splitdorf, New York City.
stands slightly away from the free end of the contact-spring
when rio current is passing through the spark-coil. This allows
a slight movement of the hammer and steel blade toward the
magnet without moving the contact-spring and the attached
contact-point M, further movement causes the flange of the
hammer to strike the free end of the contact-spring and carry
it, together with the contact-point M, along during the remainder
of the movement toward the magnet, thus separating the contact-
points. Since the steel blade and its hammer attain considerable
speed before the hammer strikes the contact-spring, a rapid
separation of the contact-points is effected. The hammer-blow
is also effective in breaking apart the contact-points in case they
become stuck together by fusing. The contact-spring, being
light and thin, maintains good contact between the contact-points
2l8
ELECTRIC IGNITION
while the hammer is not touching it. The movement of the
hammer-blade V is limited in both directions by the hammer-
stop D. The stationary contact-point K is in the end of an
adjusting screw with a knurled head and a ratchet R against
which a stop is pressed by a spring
so as to prevent the screw from turn-
ing of its own account. The stop is
carried by the stationary part B.
A spark-coil with a hammer-break
trembler interrupter similar to the
one just described is shown in Fig.
175. The box, or casing, inclosing
the transformer in this figure is of the
type generally used for ignition in
Laboratory Type of Spark-Coil, stationar motors Qr for laboratory
Sphtdorf. i i i
use. The high-tension terminals are
shown on the top of the box, and the two low-tension terminals
at the upper part of the front end.
Another type of hammer-break trembler interrupter is shown
in Fig. 176. The trembler spring W is rigidly fastened at its
FIG. 175.
FIG. 176.
Hammer-break Trembler for Spark-Coil. Pittsfield Spark Coil Company, Dalton,
Massachusetts.
right-hand end to the stationary metal block by means of a
screw. The movable contact-piece M is fastened to the free
TRANSFORMER SPARK-COILS AND SYNCHRONIZER 219
end of the spring W. A trembler blade V is riveted to the
spring W at SL point near the rigidly supported end of W. The
movable contact-point M stands up through a hole in the
trembler blade V so as to press against the stationary contact-
point K. An auxiliary spring G presses against the under side
of the trembler spring and is supported by a fulcrum F. An
adjusting screw Q for regulating the pressure of the auxiliary
spring against the trembler spring presses down against the
right-hand end of the auxiliary spring G. The stationary con-
tact-point K forms the point of an adjustable screw T which
passes through the stationary metal part B. A lock-nut D
serves to clamp T firmly in place. A similar lock-nut R answers
the same purpose for the screw Q.
When no current is flowing through the spark-coil, the trembler
spring W is pressed up so as to be slightly bent and thus cause
the free end of the trembler blade V to be separated from it by
a slight distance. When the trembler blade moves toward the
magnet-core E, the contact-points remain together during the
first part of the movement of V until V strikes the trembler
spring W. The contact-points are then rapidly separated on
account of the hammer-blow thus struck by V against W.
A plain single trembler interrupter is shown in Fig. 177. The
trembler spring V is fastened to the stationary metal block A
FIG. 177.
Trembler with a Single Blade. Splitdorf.
by small screws in such a way that the pressure of its contact-
point against the end of the contact-screw K can be regulated by
the adjusting screw D near the stationary end of the trembler
blade. The contact-screw K is adjustable, but it is intended
220 ELECTRIC IGNITION
that it shall be adjusted only to take up wear at the contact-
points. The trembler spring has a small piece of soft steel
fastened to its free end opposite the end E of the magnet-core.
This soft steel armature is to cause the end of the trembler to be
more strongly attracted toward the magnet-core than it would
be without the armature.
144. Complete Trembler Transformer Spark-Coils. A one-
unit spark-coil for stationary or marine use is shown in Fig. 178.
It has two low-tension terminals at the front end, and one high-
tension terminal at the side. Fig. 179 is a one-unit coil intended
FIG. 178. FIG. 179.
Marine Form of Trembler One-unit Trembler Spark-Coil with
Spark-Coil. Switch. Automobile Type.
for use on the dashboard of an automobile. The high-tension
terminal is at the bottom of the box. It appears large on account
of the insulating cap which covers it. There is a switch on the
front of the box by means of which either of two batteries can
be switched into circuit, or both cut out. This necessitates
three low- tension terminals. Two of these are at the bottom,
and the third at the top.
A two-unit dash coil of the same make as the last coil de-
scribed is shown in Fig. 180 with one of the units removed from
the outer casing. The two high-tension terminals are the large
ones at the bottom. The switch at the front is for cutting in
either of two batteries. There is a low- tension terminal at the
TRANSFORMER SPARK-COILS AND SYNCHRONIZER 221
top of each unit, and two low-tension terminals at the bottom
of the box. When a unit is placed in the outer casing, it auto-
FIG. 180.
Two-unit Trembler Spark-Coils with Switch. Automobile Type.
matically makes the electric connections necessary to complete
the circuit inside of the outer casing. Fig. 181 shows a two-unit
FIG. 181.
Marine Type of Trembler Spark-Coils. Two Units.
Company, Lowell, Massachusetts.
Heinze Electric
marine or stationary spark-coil with two high-tension terminals
at the top.
A four-unit dash coil is shown in Fig. 182. The switch at
the front of the casing is known as a " kick-switch/' since it can
be operated by kicking (sidewise) the switch handle at the lower
222 ELECTRIC IGNITION
part. When the small plug at the top of the switch is removed,
the circuit is broken so that it is impossible to operate the spark-
coils.
FIG. 182.
Four Spark-Coils Inclosed in a Case which has a Kick-Switch and a
Removable Plug.
145. Synchronized Spark-Coils with Master Trembler. It
is sometimes difficult to adjust all of the trembler interrupters
of a set of spark-coils so that the length of time which elapses
between the instant of closing the primary (low-tension) circuit
and the jumping of an ignition spark shall be the same for all
coils of the set. Expressed otherwise, it is difficult sometimes to
adjust the coils so that all of them shall have the same amount
of lag. When the lag of the coils is unequal (in length of time),
the ignition sparks do not jump at the right instant in all of
the cylinders of the motor. Thus, in most motors of the usual
types, the ignition should occur at regular time intervals. It
does not so occur, however, if the .spark-coils have different
amounts of lag.
In order to obviate such an irregularity of lag in the ignition,
only one interrupter is sometimes used for all of the transformer
spark-coils. This interrupter is caused to operate by a single-
wound electromagnet through which the low-tension current
for all of the transformer coils passes. This single- wound coil
TRANSFORMER SPARK-COILS AND SYNCHRONIZER 223
and its interrupter are together called a master trembler-coil,
a master vibrator-coil, or a synchronizer coil. The transformer
coils used in connection with a synchronizer coil either have no
interrupters, or their interrupters are rendered inoperative, as by
screwing down the contact-screw of each so that the contact-
points are pressed firmly together and the trembler cannot
vibrate, or by short-circuiting the tremblers with some electric
conductor such as a piece of wire.
A four-unit set of spark-coils and a synchronizer for them are
shown in Fig. 183, The synchronizer is in the left-hand end
FIG. 183.
Synchronizer Coil and Four Non-trembler Transformer Coils Inclosed in a Case
which has a Hand-Switch.
of the outer casing. It is of practically the same shape and size
externally as one of the transformer units. The connections are
shown later.
146. Trembler Spark-Coil for Use with High-tension Dis-
tributer. A top view of a transformer spark-coil showing the
beginning of the wires for connecting it to the other parts of the
ignition system is shown in Fig. 184. This coil can be used for
ignition in a single-cylinder motor with only one spark-plug,
just as any unit coil would be used for the same purpose. But
on account of its ability to do more work than is required for a
motor with only one combustion chamber, it can be used to
224
ELECTRIC IGNITION
transform current for ignition in several combustion chambers,
each chamber having its own spark-plug. This requires a dis-
tributer for directing the high-tension current to the different
spark-plugs, as is explained later. Any one-unit spark-coil can
be used for ignition in several combustion chambers with a suit-
able distributer, provided the spark-coil is able to stand up under
FIG. 184.
Trembler Spark-Coil for use with a High-tension Distributer to Direct Current to
Several Spark-Plugs Consecutively. Autocoil Company.
the work. Heating and burning at the trembler contacts is
one of the chief difficulties when a spark-coil is overloaded, as
may be the case when an ordinary coil is used for ignition in
several cylinders, as just mentioned.
147. Plain Transformer Spark-Coils without a Trembler. -
Coils of this nature are used in connection with an interrupter
which is entirely separate from them. The interrupter may
be mechanically operated, as when it is a separate piece of
apparatus or part of a magneto, or of a device for interrupting
the low-tension current and distributing the high-tension cur-
TRANSFORMER SPARK-COILS AND SYNCHRONIZER 225
rent, or it may be electrically operated, as when it is part of a
master trembler-coil. Plain transformer coils have long been
extensively used in motor-cycle ignition. Their use is becoming
rapidly extended in other fields, especially that of the automobile.
A plain transformer spark-coil in a cylindrical case is shown
in Fig. 185. It has two low-tension terminals and one high-
tension terminal.
A double transformer spark-coil is shown in Fig. 186. Two
separate coils are inclosed in the cylindrical case. There are
FIG. 185.
Non-trembler Transformer Spark- Coil in a Cylindrical Case.
five terminals, three low- tension and two high-tension ones.
One of the low-tension terminals is connected to both coils.
Fig. 187 is a single transformer coil inclosed in a wooden box,
which also contains a condenser. There are four terminals.
FIG. 186. FIG. 187.
Two Non-trembler Transformers Inclosed Non-trembler Transformer with
in Cylindrical Case. Condenser and Terminal Con-
nected to one side of the
Condenser.
Two of the terminals are low-tension, one is high-tension, and
the remaining one is for one side of the condenser. The other
side of the condenser is connected to one of the low-tension
terminals.
148. Connections to Trembler Spark-Coils. Some makers
of spark-coils mark the terminals of the coils to indicate which
terminal is to be connected to the positive side of the battery,
226 ELECTRIC IGNITION
etc., and recommend that the connections be made accordingly.
One reason for this recommendation is that, when the connections
are made as indicated, the wear on the contact-points of the
interrupter (trembler contacts) is greater at the contact-point
which is the easier to repair and the less expensive to replace
with another. A second and less common reason is that better
ignition is obtained when the ignition spark jumps in one direc-
tion than when it jumps in the opposite direction. When the
battery connections are made as indicated on the coil, the igni-
tion spark jumps in the direction which is the better for ignition.
CHAPTER XVI.
TIMERS AND SPARK-PLUGS FOR HIGH-TENSION IGNITION.
Timers.
149. Elementary Form of Timer. The device which periodi-
cally closes the primary (low-tension) circuit of a jump-spark
ignition system at the proper instant for ignition is called a
timer when it is a separate and distinct piece of apparatus. It
is not infrequently, but erroneously, called a commutator. A
commutator, as it appears in an electric ignition system, is a
part of a direct-current electric generator, or dynamo.
Probably the simplest form of timer is a shaft with a pro-
jecting lug or wire which strikes a stationary part as the shaft
rotates, thus closing the electric circuit once each revolution of
the timer shaft. A timer with only one stationary contact will
operate only one spark-coil when used in the ordinary manner.
The rotor of the timer is the part, or parts, which rotate with
the driving shaft. The casing, which is ordinarily referred to as
being stationary, can be rocked around the shaft a quarter-
revolution or less in order to advance or retard the spark; that
is, to vary the instant of ignition relative to the position of the
piston of the motor during the movement of the piston.
150. A roller-contact timer with four stationary contact-pieces,
for operating four spark-coils, is shown in Fig. 188. It has a
metal casing A into which fits an insulating ring B, generally of
wood fiber. Four terminals C, D, E, F, for wires leading to the
spark-coils, project radially from the casing. The terminal C
connects with a contact-piece G whose contact surface is flush, or
nearly so, with the inner surface of the insulating ring. The
contact-piece and terminal are insulated from the metal casing.
In the same manner, the terminal D has the contact-piece H,
and the other two terminals have similar contact-pieces. The
rotor K, with two arms, is rigidly fastened to a shaft which
227
228
ELECTRIC IGNITION
B A
FIG. 188.
Timer for Four Spark-Coils. Roller Contact.
! i
FIG. 189.
Rolling Contact Timer for Four Spark-Coils.
TIMERS AND SPARK-PLUGS
229
extends through and rotates in a hub that is part of the metal
casing. The bent lever L is connected to the short end of the
arm K by pin M. A contact roller N is pinned to the short
end of the bent lever. The contact roller is kept pressed against
the insulating ring and stationary contact-pieces by means of a
coiled tension spring P. This spring pulls the long end of the
bent lever toward the other rigid arm which projects to the left
FIG. 190.
Timer with Rubbing, or Sliding, Contact. Sectional View.
Spark Coil Company, Dalton, Massachusetts.
Pittsfield
from K. All of the parts inside of the insulating ring rotate
and together form the rotor of the timer. They are all electri-
cally connected together.
As the rotor revolves, the contact roller makes contact suc-
cessively with the contact-pieces of the terminals, thus com-
pleting the electric circuit between the shaft and each of the
230
ELECTRIC IGNITION
terminals in regular order. The casing is prevented from rotat-
ing by means of a link or rod connected to the arm R. The arm
R is frequently called the timing lever.
Another timer which has rolling contact is shown in Fig. 189.
The contact roller N in this timer has the form of a ring and is
mounted on a ball bearing whose balls run in a groove in the cir-
cular part of Q. The contact ring N is kept pressed against the
inside surface of the insulating ring by means of a coiled com-
pression spring inside of the part T.
151. A sliding-contact timer is illustrated in Fig. 190, which is
a sectional view. The rotor contact-piece is a forked spring
which passes between the fork-shaped ends of the stationary
contact-pieces, thus making a rubbing, or sliding, contact. The
stationary contact-pieces are insulated from the metal casing by
cylindrical pieces of insulating material, one insulator for each
contact-piece.
152. A timer with normal-pressure contact is shown in Fig. 191.
Two views are given. The rotor of this timer consists only of a
FIG. 191.
Timer with Plain Pressure Contact.
For Four Spark- Coils.
cam whose lobe (protuberance) presses against the four small
rollers successively and moves them outward as the rotor revolves.
Each of the four small rollers is carried in the end of its own
TIMERS AND SPARK-PLUGS 231
spring, whose opposite end is rigidly fastened to the casing. Each
roller spring carries a small contact-piece. When the roller
is moved outward by the action of the cam-lobe, the contact-
piece on the spring presses against the mating stationary contact-
piece opposite it. The stationary contact-piece is pressed inward
by a coiled compression spring which allows the contact-piece to
move outward when the contact-pieces are pressed together.
Spark-Plugs.
153. General Description. The ordinary form of high-
tension spark-plug has the following essential parts: A hollow
metal piece (bushing) threaded along part of its outside for
screwing into the cylinder of the motor, and usually having a
hexagonal head to be gripped by a wrench; an insulator of some
such material as porcelain, steatite, mica, or molded compound
which fits into the bush ; and a central wire, rod, or spindle which
passes through the insulation from end to end. One end of the
spindle, or a piece of metal fastened to its end, is either brought
near to the end of the threaded bushing or to a piece of metal
that projects from the bushing, thus forming the spark-gap which
goes inside of the combustion chamber of the motor. The outer
end of the spindle is provided with a terminal to which the high-
tension wire can be connected. Packing is used when necessary,
to make the plug gas-tight.
FIG. 192.
Spark-Plug with Insulation Molded into Place.
154. Single-gap Jump-spark Plugs. A simple form of plug
is shown in Fig. 192. The outer bushing i is insulated from the
central spindle 2 by the insulator 3, which is molded into place.
232
ELECTRIC IGNITION
A bent wire 4 projects from the bushing so that the end of the
wire is near the point of the insulated spindle. The space be-
tween the ends of the spindle and of the bent wire is the spark-
gap. The outer, threaded end of the central spindle has a
ring-nut 5 and a thumb-nut 6 between which the connecting
wire can be clamped. The spindle extends from end to end of the
insulation, although this is not clearly shown in the illustration.
FIG. 193.
Parts of Spark-Plug with Separately Molded Insulation.
The parts of another spark-plug are shown separately in
Fig. 193. The threaded outer bushing i has an interior shoulder
against which the packing gasket 2 rests when in place. The
porcelain insulator 3 enters the bushing from the top and is
clamped down by the threaded gland 4 so that the shoulder at
the under side of the ring on the porcelain presses against the
gasket, thus making a gas-tight joint. The hole through the
TIMERS AND SPARK-PLUGS 233
porcelain is large at the bottom, but the greater portion of its
length is small enough to fit the spindle 5 loosely. The spindle
enters the porcelain from the bottom, so that the shoulder on it
strikes the lower end of the small part of the hole in the porcelain.
Packing, such as fiber asbestos, is interposed between these two
shoulders. The spindle is drawn tightly into place by the ring-
nut 6, under which is the spring washer 7, whose elasticity allows
for variation in the expansion and contraction of the spindle
SPRING Oft SNAP
FIG. 194.
Spark-Plug with Sheet Mica Insulation and Porcelain Protector.
and the porcelain as they become heated and cool. The usual
terminal thumb-nut 8 is provided. The bent wire 9 projects
from the bushing so that its end comes within sparking distance
of the spindle when the latter is in place. The large hole in the
lower end of the porcelain, and the contracted outer diameter
of the same end of the porcelain, give a long stretch of insulating
surface between the spindle and bushing.
The spark-plug in Fig. 194 has mica insulation in the form of
a sheet wrapped around the central spindle. A protective por-
celain insulator is placed between the bushing and the terminal
to which the outside wire can be connected. The body of the
spindle is tapered where it comes into contact with the mica insu-
234 ELECTRIC IGNITION
lation, thus making the spindle easily removable. The nut which
holds the spindle in place clamps against the end of the porce-
lain protector.
155. Spark-Plugs with Two or More Spark-Gaps. When the
ignition current is supplied by a magneto, there is more apt to
be burning away of the sparking points of the spark-plug than
when an electric battery and a transformer spark-coil is used.
In order to overcome the burning of the spark-points as far as
possible, or at least to give the plug longer life, two or more pairs
FIG. 195.
Spark-Plug with Two Spark-Gaps. Full View and Part Sectional View.
of spark-points are used in one plug. The spark then passes
sometimes between one pair of points, and sometimes between
another pair, thus distributing the work and heat.
The spark-plug shown in Fig. 195 has two spark-gaps obtained
by bringing two bent wires from the outer bushing to within
sparking distance from the end of the central spindle. The ends
of the wires are bent up so that if oil or water collects on them
it will have a tendency to run down to the angle of the bend
when the plug is in a vertical position, as shown. The sectional
view shows how the plug is constructed. The insulation between
the insulated central spindle and the outer bush that screws into
the motor is of steatite coated with porcelain. The shoulder of
TIMERS AND SPARK-PLUGS
2 35
the insulator rests on a packing ring between it and the interior
shoulder of the threaded bush. The insulator is held in place
by a wedge-shaped ring which is forced into place and then held
there by bending the top of the outer bush inward over it.
FIG. 196.
Spark-Plug with Four Spark-Gaps. J. S. Bretz Company, Times Building,
New York City.
In the spark-plug shown in Fig. 196 the insulated central
spindle has four prongs each of which is within sparking distance
FIG. 197.
Eisemann Platinum Spiral Spark-Plug. Eisemann-Magneto Company, New York
and Detroit.
from the outer bush, thus forming four spark-gaps at which the
ignition spark may jump.
More than one spark-gap is obtained in a simple manner in
the plug shown in Fig. 197. The end of the outer bush is bridged
by a wire around which is wrapped a short piece of thin platinum
wire. The end of the insulated central spindle is flattened. The
236
ELECTRIC IGNITION
spark may jump between the end of the spindle and the nearest
part of any of the turns of the platinum wire.
156. Separable Spark-Plugs. Some spark-plugs are so con-
structed that they can readily be taken apart enough for clean-
ing without the use of any tool for taking them apart. The
plugs shown in the next two illustrations are of this nature.
FIG. 198.
"Breech Block" Separable Spark-Plug.
A separable spark-plug, Fig. 198, is shown " open " in view (a)
for cleaning or examination. In view (b) the plug is " closed "
ready for use. This plug differs from the ordinary type in having
the bushing threaded to the remainder of the plug by a screw
thread, part of which is cut away in the same manner as in the
breech-block of a cannon. The thread on each part is cut away
in three places, each extending about one-sixth of the way
around the circumference. This leaves three sections of thread
TIMERS AND SPARK-PLUGS
237
of equal length on each part, the sections being at equal distances
apart. The externally threaded part can be dropped into the
bushing to almost the full distance that it is to enter, then a
twist of less than one-sixth of a turn screws the parts firmly
together. When the bushing has been screwed into the motor,
FIG. 199. (See also next page.)
"Detachable" Spark-Plug with Knife-edge Spark-Gap. Knapp-Greenwood Com-
pany, 1000 Boylston Street, Boston, Mass.
the detachable part of the plug can be quickly removed by
twisting it through less than one-sixth of a turn (the flat
handle is provided for doing this), then lifting the detachable
part straight out. A wire is shown connected to the plug by
means of a spring clip.
Another separable plug, Fig. 199, is shown " open " in (a) and
" closed " at (b). The threaded bushing is slotted, a portion
238 ELECTRIC IGNITION
of the slot being cut at an angle like a screw thread, to receive
the smooth portion of the two screws that fasten the handle
to the inner removable part of the plug. In putting the parts
together, the detachable portion is dropped into the bushing
and then given part of a turn. A portion of the smooth body
of each of the two screws slides along the inclined edge of the
FIG. 199 Concluded.
corresponding slot, thus forcing the parts tightly together. The
parts can be separated by the reverse movement.
The spark-gap in this plug is the space between the edges of
two hollow cylindrical parts. The lower one of these is fastened
to the insulated central spindle by the nut at the lower end of
the spindle. The spark may jump anywhere across this gap.
The insulation is built up of mica disks.
157. The width of the spark-gap is ordinarily greater for an
ignition system having a trembler transformer to which low-
tension current is supplied by a battery, than in a system operat-
ing on current from a high-tension magneto. A satisfactory
distance between the spark-points of an igniter when the high-
TIMERS AND SPARK-PLUGS 239
tension current comes from a trembler spark-coil is % of an inch
or slightly more. Sometimes as much as ^ of an inch is recom-
mended by the makers of spark-coils, but this is unusual. For
current from a high-tension magneto, a distance from -^ to -fa of
an inch between the spark-points appears to give the best satis-
faction. It is of course possible to construct spark-coils and
magnetos each of which will operate most efficiently with a width
of spark-gap which is the same for all, but this condition has not
yet arrived in general practice.
CHAPTER XVII.
JUMP-SPARK IGNITION SYSTEMS WITH MAGNETIC TREMBLER
INTERRUPTERS AND INDIVIDUAL TRANSFORMERS.
158. Introductory. While the ignition systems in this chap-
ter are illustrated and described as operating on current from a
battery, they can all be operated with equal satisfaction on
current from a direct-current generator. They may also be
operated on high-frequency current such as is produced by
magnetos with more than two magnetic poles of the type in-
tended for ignition usage, provided the trembler blade of the
interrupter is light enough to vibrate at a very high rate.
FIG. 200.
High-tension Ignition System with One Spark-Plug.
159. System with One Spark-Plug and Trembler Spark-Coil.
In Fig. 200 the spark-coil is shown with the trembler and the
two low- tension terminals at the top, and the high-tension ter-
minal S at the side of the box. The timer is represented conven-
tionally by a ring F of insulating material. A metal contact-
piece E is set into the insulating ring, and a rotor R makes electric
240
JUMP-SPARK IGNITION SYSTEMS 241
contact with the contact-piece E once during each revolution.
The rotor of the timer is represented as electrically connected to
the metal of the motor by the broken line marked " ground."
Two batteries are shown, either of which can be thrown into
circuit by means of the switch whose blade H can be swung
around the pin K so as to make contact with either, or neither,
of the two contact-points (switch-points) L and M.
When the rotor R of the timer closes the battery circuit by
coming into contact with E during its rotation, current flows
from the positive side of the battery i (as the switch is shown
set) through the switch to the low-tension terminal P of the
spark-coil, through the primary winding of the spark-coil to the
low-tension terminal T 1 , thence to the contact-piece E of the timer
and on through the rotor R of the timer to ground, which takes
it to the grounded end of the wire connected to the negative side
of the battery. The current completes its circuit through this,
grounded wire and the battery in series.
The high-tension current flows from the high-tension terminal
S of the spark-coil to the insulated spindle (or firing pin) of the
spark-plug, jumps the spark-gap to ground, and then returns
to the spark-coil through the battery and switch in series. Some
of the high-tension current may return from ground to the battery
through the timer, but the portion following this return circuit
would be small under ordinary conditions.
The so-called ground connection through the metal of the
machinery has such slight electric resistance under proper con-
ditions that parts which are connected to ground can be con-
sidered as directly connected together.
The rotor of the timer is grounded more or less perfectly by
the contact of the rotor shaft with the metal of the bearing in
which the shaft rotates. Sometimes a brush which bears on the
shaft or some other part of the rotor, and is connected to ground,
is used to insure more perfect grounding of the rotor. If a timer
with an insulated rotor is used, a wire must be connected to the
rotor to carry the current to the proper point outside of the timer.
This wire replaces the ground connection of the rotor as shown
in the diagram.
242
ELECTRIC IGNITION
160. Auxiliary Condenser in an Ignition System. In order
to insure the occurrence of an ignition spark even though the
contacts of the trembler-interrupter should happen to stick to-
gether, as on account of burning and fusing, an auxiliary con-
denser is sometimes used. This auxiliary condenser also protects
the contact-points of the timer.
An auxiliary condenser used for the above purpose is shown
in the diagram, Fig. 201, which represents an ignition system
Timer
FIG. 201.
Auxiliary Condenser in Parallel with Timer is an Ignition System with
One Spark-Plug.
that is the same as that in the preceding figure with an auxiliary
condenser added to it. The condenser for protecting the contact-
points of the trembler V is shown at W connected in parallel
with the trembler contacts in the usual manner. The auxiliary
condenser Q is connected in parallel with the timer, one side of
the condenser being grounded. The action of the auxiliary con-
denser relative to the interruption of the current at the timer is
similar to that of the usual condenser W relative to interruption
of the current at the trembler contacts. The latter has been
described. If the contacts of the trembler stick together, the
interruption of the current, as the timer points separate from
each other, produces, with the aid of the condenser, an ignition
spark that is satisfactory for ignition. Without the auxiliary
JUMP-SPARK IGNITION SYSTEMS
243
condenser, the spark at the plug might be uncertain and weak.
The spark when the trembler does not operate will be somewhat
later than when it does, since the timer contacts naturally do not
separate as soon as the trembler contacts when the trembler is
operating properly. The auxiliary condenser may be either
inside of the spark-coil box, or it may be separate in a box of its
own.
It may be noted that if the auxiliary condenser is not con-
nected to ground, or is otherwise disconnected, as by the breaking
of the connecting wire or by error, the system will then be the
same as one which never had an auxiliary condenser. No harm
will be done, except very improbable injury to the timer contacts.
FIG. 202.
High-tension Ignition System with One Condenser in Parallel with Both the
Timer and the Trembler Interrupter. One Spark-Plug.
161. Grounded Spark-coil Condenser. A method of using
only one condenser for both the trembler of the spark-coil and
the timer is shown in Fig. 202. One side of the condenser is
connected to one side of the spark-coil interrupter, and the other
side of the condenser is grounded. This puts the condenser in
parallel with both the trembler and the timer, the latter two
being in series with each other. If the contact-points of the
trembler separate while the circuit is closed at the timer, the
condenser protects the trembler contacts and aids in the pro-
duction of a good ignition spark in the usual manner. If the
trembler contacts stick together, then the condenser operates in
244 ELECTRIC IGNITION
relation to the timer when the contact-points of the latter sepa-
rate, as it does relative to the trembler contacts when they
separate during the proper action of the system.
While the operation of this system is entirely correct when
all of the connections are properly made, there is a very serious
objection to it for general application by those not familiar with
it. This objection is due to the fact that most spark-coils for
ignition purposes have only three terminals, the condenser hav-
ing both of its connections to the other parts made inside of the
coil box. But when the condenser is grounded, there must be
a fourth terminal. The average operator will make connections
to only three of these, trying them till they are so made that the
trembler vibrates. This leaves the condenser out of action.
The result is heavy sparking and rapid burning at the trembler
contacts, together with unsatisfactory ignition sparks and corre-
spondingly bad ignition. The trembler contacts may be burned
away so as to stop operation, or stick together, in a few minutes.
The same effects are produced if the connections are properly
made at first, and the ground connection then becomes broken
or loose, which is a thing that often happens with unskilled
operators.
In the hands of a skilled and careful operator this system is
entirely satisfactory, however.
162. Individual Trembler-coil System. Fig. 203 represents
a system with four trembler spark-coils and the same number of
spark-plugs, a spark-coil for each igniter plug. This is applicable
to a four-cylinder motor of the single-acting type, or to a two-
cylinder motor of the double-acting type.
The timer in this case has four stationary contacts, a, b, c,
d, spaced at equal distances around the insulating ring. Each
of these contacts is connected to one of the low-tension terminals
of a corresponding spark-coil. The spark-coils are lettered A,
B, C, D, to correspond to the lettering of the stationary contacts,
or terminals, of the timer. The remaining low-tension terminals
of the spark-coils, one terminal on each coil, are connected to a
main wire which leads to the battery switch.
When the rotor revolves counter-clockwise, the spark-coils
JUMP-SPARK IGNITION SYSTEMS
245
are caused to operate in the consecutive order A, B, C, D. The
connections between the high-tension terminals of the spark-coils
and the spark-plugs are made so that the sparks jump at the plugs
in the consecutive order i, 3, 4, 2, this order being one that is
usual for four-cylinder motors of the automobile type. It is
customary in such motors to ignite first in the front cylinder,
second in one of the middle cylinders, third in the rear cylinder,
1
Spark
Plugs
L
'Ground'
Jl- A TEL A
V V 8 P V
I I I I
FIG. 203.
Multi-coil Ignition System with Four Spark-Plugs.
and fourth in the remaining middle cylinder. The numerical
order of ignition might also be i, 2, 4, 3, in accordance with this.
The timer has no condenser in parallel with its contact-points,
consequently, if the trembler contacts of one of the spark-coils
stick together, there will be no spark at the corresponding plug,
and one of the cylinders will misfire.
163. Synchronized System with Master Trembler-Coil. In
Fig. 204 four transformer spark-coils without interrupters, or
tremblers, are operated on battery current which passes through
a master trembler-coil. The trembler of the master coil vibrates
246
ELECTRIC IGNITION
so as to rapidly interrupt the current for each transformer during
the time the circuit for that transformer is closed by the timer.
The transformers have neither tremblers nor condensers. Each
transformer is connected to its own spark-plug.
While the battery circuit is closed for battery 2 as shown,
current flows from the positive side of the battery through the
switch and winding of the master trembler- coil to the trembler
FIG. 204.
Synchronized High-tension Ignition System with Four Spark-Plugs.
V, through the contacts of the trembler to the stationary metal
piece N, thence through the main wire F to the transformer A
and through its primary winding to the contact-piece a of the
timer, then through the rotor of the timer to ground, and from
ground through the ground wire of the batteries to the negative
side of the battery. The trembler of. the master coil vibrates
during this time, thus interrupting the current through the trans-
former so as to cause a series of sparks to jump between the
spark-points of the spark-plug i. The action is similar for each
JUMP-SPARK IGNITION SYSTEMS 247
of the other transformers as the rotor of the timer revolves and
closes the circuit at the stationary contacts of the timer in regular
order.
The condenser / is in parallel with the trembler of the master
coil and acts in the same manner as when used in connection
with a single transformer-coil. This elementary system has
only the one condenser.
If the trembler contacts stick together or fail to make electric
contact with each other, the whole ignition system fails to
operate, or becomes dead, as a result, and the motor stops. The
trembler contacts of a master coil used in this manner are more
apt to burn so as to fail to make electric contact with each other,
or to stick together on account of fusing, than the same trembler
used in connection with one coil only. This greater liability to
trouble is on account of the greater service the trembler is re-
quired to perform when used on a master coil. In this particular
system, the service of the trembler is four times as great as for
a single spark-coil, since there are four transformers for which
the trembler must interrupt the current.
164. Synchronized System with Master Trembler-coil and
Auxiliary Condensers. This system, shown in Figs. 205 and
206, is the same as that of the preceding figure with four con-
densers, one for each transformer, added to it. There is also a
key-switch E inserted in the circuit of each transformer four
key-switches in all, one for each transformer. Each switch is
shown just above its transformer. *Its blade is a flat spring,
something like that of the trembler. The elastic action of the
spring keeps the switch closed except when it is forced open by
the pressure of the hand or finger of the operator on the button
K. The purpose of these key-switches is to afford a means of
cutting out the ignition from any one of the combustion chambers
at will, as when testing to discover which cylinder is misfiring,
when this trouble occurs. The switches do not in any way
affect the operation of the system while the motor is running in
the ordinary manner.
Each of the auxiliary condensers has one side grounded, all of
them being grounded through one main wire. The condenser Q
248
ELECTRIC IGNITION
has the other side connected to the stationary block E of the key-
switch just above the transformer A. This is practically the
same, so far as the operation of the condenser is concerned, as
if the condenser were connected to the stationary contact a of
the timer, since there is no transformer winding, or other in-
ductive resistance, between the switch and timer. The con-
FIG. 205.
Synchronized Ignition System with a Grounded Condenser in Parallel with Each
Transformer Spark-Coil.
denser Q is therefore in parallel with the timer. The other three
auxiliary condensers are similarly connected relative to the
transformers B, C, and D respectively.
If the trembler contacts (of the master coil M) stick together
so that the trembler does not interrupt the current, then the
auxiliary condensers will act so that when the timer circuit is
broken by the separation of the timer rotor from any one of its
stationary contacts, a spark suitable for ignition will jump between
the points of the corresponding spark-plug. This would probably
not occur if there were no auxiliary condenser, or if a spark did
jump it would not be as strong as when there is a condenser in
JUMP-SPARK IGNITION SYSTEMS
249
parallel with the timer. The condenser also protects the con-
tact-points of the timer, which would suffer during the time the
Timer
Extra Ground Wire
Engine
FiG. 206.
Constructive Form of Fig. 205. C. F. Splitdorf, New York City.
trembler contacts are stuck together, if the auxiliary condensers
were not in the system.
165. Ammeter and Voltmeter Permanently in the Circuit of a
High-tension Ignition System. Fig. 207. The ammeter and
voltmeter are mounted on the same base, and the upper terminal
(marked ) is in connection with both instruments. The volt-
meter terminal (marked +) is at the right-hand side, and the
ammeter terminal at the left-hand side.
The upper terminal, common to both the ammeter and volt-
meter, is connected to the negative side of the battery. The
ammeter terminal is connected to the metal of the motor. The
path of the battery current is from the positive side of the battery
to and through the primary of the spark-coil which is operating
at the instant, then to the timer and through it to ground, which
brings the current to the engine metal, thence to and through
250
ELECTRIC IGNITION
the ammeter to the common terminal ( ) of the combined in-
struments, and then through the connecting wire to the negative
terminal of the battery.
Storage Battery
FlG. 207.
High-tension Ignition System with an Ammeter and a Voltmeter Permanently
in Circuit.
The connections between the voltmeter and the battery must
not, include the timer, an interrupter, or the winding of a coil.
The connection to the negative side of the battery shows plainly
that it meets this condition. The positive (+) terminal of the
voltmeter is shown connected by a wire to the contact-block of
one of the spark-coils. In order for this connection to be correct,
both of the contact-blocks of the spark-coils must be electrically
connected together by a non-inductive conductor of low resist-
ance. There must also be non-inductive, low-resistance connec-
tion between the contact-blocks and the terminals at the bottom
of the spark-coil when the switch is closed. The voltmeter will
not give the voltage of the battery if this connection includes
the winding of the spark-coil, as is true in many makes of coils.
JUMP-SPARK IGNITION SYSTEMS 251
If the connections of the coil are not known, a suitable place
for connecting the wire from the (+) terminal of the voltmeter
can generally be found in the following manner:
Disconnect one battery wire from the spark-coil;
Connect the wire from the (+) terminal of the voltmeter to
the spark-coil terminal to which the battery wire is still attached ;
Read the voltmeter while the motor is running;
Disconnect the voltmeter wire from the spark-coil and connect
it to other parts of the spark-coil (except the high-tension ter-
minal) till a place is found which gives the same voltage reading
as was obtained before, the motor still running;
Connect the other battery wire to the spark-coil, throw the
switch over to its other position, and test out for the second
battery as before, omitting the battery-wire terminal to which
the first battery wire is connected at the spark-coil.
If the same point on the spark-coil answers for reading the
voltage of both batteries, then it is a suitable place for connect-
ing the wire from the (+) terminal of the voltmeter.
166. Speed of the Timer. When a timer is of the general
nature of those described in this chapter, its speed of rotation is
as follows:
Half as fast as the crank-shaft of four-cycle motors, which is
the same speed as that of the cam-shaft.
The same as that of the crank-shaft of two-cycle motors.
CHAPTER XVIII.
HIGH-TENSION DISTRIBUTER SYSTEMS WITH BATTERY
CURRENT.
167. General. In systems of this nature only one trans-
former spark-coil is used, and the high-tension current from it
is distributed to the spark-plugs, generally to one plug at a time.
A spark-coil with a magnetic interrupter of the trembler type is
used in connection with a slightly modified form of the ordinary
timer in some systems. In other systems the spark-coil is of the
plain transformer type (without interrupter) used in connection
with a mechanically operated contact-maker which closes and
breaks the battery circuit at the proper instant for ignition.
High-tension Distributer Ignition System with Trembler Spark-Coil.
168. High-tension Distributer System with Trembler Spark-
Coil. In Fig. 208 one low-tension terminal of an ordinary
252
HIGH-TENSION DISTRIBUTER SYSTEMS 253
trembler spark-coil is connected to all of the four stationary
contact-pieces of an ordinary timer. This connection is made
by a wire leading from the transformer to one of the stationary
contacts of the timer, together with a wire C, shown as a circle,
which connects all of the stationary contacts of the timer to-
gether electrically. By this means the timer closes the battery
circuit four times through the same transformer (the only one
used) during one revolution of the rotor of the timer.
The distributer of the high-tension current is represented as
a circular piece of insulating material F inside of which an in-
sulated rotor R revolves and makes contact successively with
four insulated contact-pieces a, b, c, d. The high-tension ter-
minal of the spark-coil is connected to the rotor of the distributer.
Each of the contact-pieces a, b, c, d is connected to a corre-
sponding spark-plug. The high-tension current is thus distrib-
uted to the spark-plugs, one at a time, in regular order.
The timer and distributer rotors revolve at the same speed
when the timer has four stationary contact-pieces as shown.
Both rotors are generally mounted on the same shaft. The
rotor of the distributer is brought into contact with one of the
stationary contacts to which the spark-plugs are connected,
each time the circuit is closed by the timer. If the timer had
only two stationary contacts, located diametrically opposite each
other, then the timer would have to rotate
twice as fast as the distributer. And if
the timer had only one stationary contact-
piece, its rotor would have to revolve four
times as fast as that of the distributer. ^
rIG. 209.
^ A timer with only one stationary contact- Timer for H igh-tension
piece, but with four contact-points on the Distributer System
rotor, is shown in Fig. 209. The rotative with Four Spark-Plugs,
speed of this four-pointed rotor is the same as that of the dis-
tributer rotor when there are four spark-plugs.
The condenser A , Fig. 208, is in parallel with the magnetically
operated interrupter of the spark-coil in the usual manner. Con-
denser B is in parallel with the timer, so that ignition will con-
tinue even though the contact-points of the magnetic interrupter
254
ELECTRIC IGNITION
on the spark-coil stick together so as not to break the circuit.
This feature has been described in connection with other systems.
169. Mechanically Operated Contact-Maker and High-tension
Distributer System with Battery Current. Fig. 210. The
mechanical contact-maker which replaces the timer of the pre-
ceding system is represented by a stationary insulated piece H
which has a contact-point F, and by a rocker which is rocked
Switch
I Contact
| Maker j
-EE
L_ _!__ __L_ _J__
FIG. 210.
High-tension Distributer System with Mechanically Operated Contact-Maker.
on the pin by mechanical means. The movable contact-point
E of the rocker is thus brought into contact with and separated
from the stationary contact-point when an ignition spark is to
be produced. This form of contact-maker is fully described in
connection with the following illustrations.
The spark-coil is of the plain transformer type (without in-
terrupter). The condenser is part of the spark-coil and is in
parallel with the contact-maker. The distributer is of the usual
form that has been described in connection with other systems.
The contact-maker must close and break the battery circuit four
times during each revolution of the distributer for the four
spark-plugs shown. If the system were modified to operate six
spark-plugs, then the contact-maker would have to make and
HIGH-TENSION DISTRIBUTER SYSTEMS 255
break the battery circuit six times during one revolution of the
distributer, and similarly for whatever number of spark-plugs
are used. The distributer must have as many stationary con-
tacts as there are spark-plugs to be operated by it. The rotor
of the distributer may be mounted on the shaft that operates
the contact-maker, in order to obtain a compact form. This is
the more usual construction.
170. Unisparker. The constructive form of the contact-
maker, some of whose parts are shown in connection with the
preceding ignition system, is illustrated in Fig. 211. The driving
FIG. 211.
Contact-Maker of Unisparker.
shaft A- A rotates counter-clockwise, as indicated by the arrow.
It has four notches to correspond to the same number of spark-
plugs to be operated. As the shaft A- A rotates, each of its notches
in turn catches the hook at the end of the snapper A-D and draws
the snapper forward against the resistance of the coiled tension
spring A -E, until the pressure of the cylindrical surface of the shaft
against the snapper disengages the hook from the notch. The
position of these parts at the instant of disengagement is shown
in Fig. 212. The snapper then snaps back, and while doing so
the point of its hook rides on the cylindrical surface of the shaft.
This action presses the snapper against the lip L on the contact
arm A-F and causes the latter, together with the contact-point
Vj to rock on the pin so as to press the contact-point V
256 ELECTRIC IGNITION
against the point of the stationary contact screw A-H. Con-
tact-point V is mounted on a flat spring. When the snapper
has moved to the position shown in Fig. 213, it passes out of
contact with the lip L, and the contact-points are then rapidly
separated by the action of the coiled spring A-G, which acts
on the rocker arm A-F in such a manner as to rock it in the
direction to separate the contact-points. Pressing the contact-
FlG. 212. FlG. 213.
Unisparker Contact-Maker in Position Contact-Maker with Contact-Points
just before making Contact. Pressed Together.
points V and A-H together closes the battery circuit. The dura-
tion of the time of contact is regulated by adjusting the insulated
contact-screw A-H in the stationary part which holds it.
The snapper A-D is of very light weight, and the spring A-E is
of sufficient strength to draw the snapper back with great rapidity.
This movement is sufficiently rapid to give the same duration of
contact between the points V and A -H whatever the speed of ro-
tation of the shaft A- A up to speeds as high as are necessary for
ignition. The primary circuit must of course be kept closed
long enough to allow the battery current to reach a strength that
will produce a spark at the spark-plug when the circuit is broken
by the action of the contact-maker. If the adjustment is such
as to make the period of contact longer than this, a stronger,
or hotter, spark is produced at the igniter. The strength of the
ignition spark can therefore be regulated by adjusting the con-
HIGH-TENSION DISTRIBUTER SYSTEMS
2 57
tact screw A-H. Only one ignition
spark is produced for each ignition.
An external view of the unisparker is
shown in Fig. 214. The contact-maker
is in the lower part of the casing, and
the upper part contains the high-ten-
sion distributer. Five wires connect
to the latter at the top of the casing.
One of these is at the center of the top
for bringing high-tension current from
the transformer. The other four are
for carrying current to the spark-plugs.
The terminals for the latter four wires
are in a circle at equal distances from
each other. The arm projecting to-
ward the left just beneath the casing
is the timing lever for advancing and
retarding the spark. The rotating
FIG. 214. (See also Figs. 211.
212, 213 and 215.)
Unisparker. Atwater Kent
Manufacturing Works,
Philadelphia, Pa.
\
FIG. 215.
Parts of Fig. 214.
parts are driven by the shaft that projects from the bottom of
the casing.
The interior construction is shown in Fig. 215. The com-
258 ELECTRIC IGNITION
bined cover and distributer plate is at the right-hand side of
the illustration, and the distributer rotor in the center. The
contact-maker, at the left-hand side of the illustration, has a
condenser enclosed in the cylinder which can be seen to the right
of the driving shaft.
The coil box and switch to be used in connection with the
combined contact-maker and distributer shown in the last two
FIG. 216.
Non-trembler Transformer Spark- Coil and Switch for use with Unisparker.
illustrations is seen in Fig. 216. No condenser is required in the
coil box when there is one in the unisparker, as shown in the
preceding illustration.
171. Combined Contact-Maker, Spark-Coil, and Distributer.
Fig. 217. A contact-maker of the kind just described, a trans-
former spark-coil (without a trembler), a condenser, a high-
tension distributer, and a switch are all grouped together in this
device. The contact-maker is inside of the small cover A at
the top of the box. B is a starting button for starting the motor
on spark, provided the cylinder of the motor contain combustible
mixture. C is a wing-nut for holding the cover on the contact-
maker.
The distributer D is in the form of a shaft with four winglike
blades, of which one is lettered E. The high-tension current
is brought to the distributer through the brush-holder F, which
holds a brush (carbon pencil) that is forced outward by a spring
HIGH-TENSION DISTRIBUTER SYSTEMS
259
so as to make contact with the shaft of the distributer. G is
the distributer board which carries four high-tension binding
posts (terminals), each lettered H, for making connection to the
wires leading to the spark-plugs. Each of the distributer blades
E passes near to, or makes light contact with, the inner end of
the corresponding terminal H. Four push-buttons, each lettered
/, are provided for cutting off the ignition from the correspond-
FIG. 217.
Atwater Kent Combined Contact-Maker, Spark-Coil and High-tension Distributer
for Four Spark-Plugs.
ing cylinders of the motor. The housing / contains a spiral
sleeve which drives the rotors of the contact-maker and dis-
tributer. This sleeve is moved by the operator by means of the
spark-control lever at his hand, so as to advance or retard the
spark. M is the switch, N the switch plug, and O the switch
handle. The binding post for connecting to the positive (car-
bon) side of the battery is shown at P. The holes Q are for
260 ELECTRIC IGNITION
screws or bolts to fasten the device in place. R is an oil tube.
S is a clamping collar for setting the shaft D so as to have the
spark occur at the correct instant.
172. Comparison of Unisparker and Ordinary Timer. The
contact-maker described in this chapter is decidedly more eco-
nomical of electricity, and therefore of batteries, than a timer of
the ordinary type. The ordinary timer must keep the battery
circuit closed long enough, at the highest speed of the motor,
to allow the primary current to become strong enough to produce
a sufficiently large ignition spark when the current is interrupted ;
or, the timer must keep the circuit closed long enough for the
magnetic trembler of the spark-coil to interrupt the current. If
the motor is slowed down to half speed, then two or more igni-
tion sparks will be produced by a trembler interrupter for each
ignition, or if there is no trembler interrupter the current will
flow twice as long, and at least twice as much electricity will be
used for the corresponding one ignition as is necessary. A similar
statement is true relative to still slower speeds of the motor.
The electricity used for producing ignition sparks after the first
one for one ignition is wasted. The same is true of current that
flows after the current has become strong enough, when there
is no magnetic interrupter of the trembler type. This waste
represents the difference between the amount of electricity that
is used by the contact-maker that has been described, and the
ordinary form of timer.
CHAPTER XIX.
SPARK-PLUGS IN SERIES, AND IN SERIES-SHUNT.
173. Two jump-spark igniters can be operated in series with
each other on current from the same spark-coil. An ignition
system of this nature is shown in Fig. 218 with a trembler
spark-coil. The spark-coil of necessity has four terminals, two
high-tension and two low-tension. The primary and secondary
terminals of the coil are not connected together. The timer
FIG. 218.
Two Spark-Plugs in Series with Each Other in a High-tension Ignition System.
has two stationary contact-pieces, diametrically opposite each
other. These contact-points are connected together by a wire
so that the timer closes the battery circuit twice each revolution
at equal intervals. The spark-plugs are represented as in place
in a motor of the four-cycle two-cylinder opposed type. The
outer bushing of the spark-plug is grounded by its contact with
the metal of the motor in the ordinary manner, so that these
bushings are electrically connected together. The plugs are of
the ordinary jump-spark type.
261
262 ELECTRIC IGNITION
When the battery circuit is closed by the timer, the high-
tension current flows from one of the terminals of the spark-coil
to the insulated spindle of one of the spark-plugs, jumps the
spark-gap of the plug to the outer bushing of the plug and the
metal of the motor, then flows through the metal of the motor to
the outer bushing of the other spark-plug, jumps the spark-gap to
the insulated spindle of that plug, and then flows back to the
spark-coil. A spark jumps at the same instant at both plugs.
The sparks pass twice as often as necessary at each plug, since
the ignitions occur alternately in the two cylinders.
The timer with the two stationary contacts rotates at half
the speed of the crank-shaft (at the same speed as the cam-shaft)
for a four-cycle motor. A timer with only one stationary con-
tact-piece and one arm on the rotor can be used if it is rotated at
the same speed as the crank-shaft.
This system has a feature relative to backfiring into the intake
that does not appear in other systems. If the motor is rotated
at very slow speed, as when starting it, and the ignition is very
much retarded (set very late), then the mixture in both cylinders
may be ignited at the same instant. Thus, suppose the crank-
shaft and pistons are in the positions shown in the figure when
the sparks jump, and the speed of rotation is slow. One piston
is on its impulse stroke, and the other on its suction stroke. The
one on the suction stroke may have drawn in combustible mix-
ture enough to be ignited, and, since the inlet valve of that
cylinder is open to admit the mixture, the flame will run back
into the inlet passage, thus backfiring the incoming charge.
This action occurs frequently in small motors that are cranked
by hand when this system of ignition is used. Backfiring of
course occurs in motors that do not have this kind of an ignition
system, on account of entirely other causes. These other causes
will cause backfiring in the series-plug ignition system, as well as
in the other systems of ignition.
174. Series-shunt Connection of Spark-Plugs. A diagram-
matic representation of a high-tension ignition system in which
current is supplied by one transformer to the two spark-plugs
for two combustion chambers, one plug for each combustion
SPARK-PLUGS IN SERIES, AND IN SERIES-SHUNT
263
chamber, and which is provided with a short-circuiter for shunt-
ing the current from the spark-plug at which no spark is desired
at the moment of ignition in the combustion chamber that con-
tains a compressed charge, is shown in Fig. 219.
The transformer is of the non-trembler type with the primary
and secondary windings not connected to each other. Low-
FIG. 219. (See also Figs. 220 and 221.)
Series-shunt Connection of Two Spark-Plugs in a High-tension Ignition System.
tension current is supplied either by a battery or by a dynamo,
either of which can be thrown into the circuit by means of the
two-point switch whose blade is connected to the terminal A of
the primary winding of the transformer. The other low-tension
terminal B of the transformer is connected to one side of the
condenser C. The opposite side of the condenser is connected
to the battery and dynamo, and is also grounded by the wire
264 ELECTRIC IGNITION
DE which is connected to the metal of the engine at E. The
primary terminal B is also connected to the insulated stationary
contact F of the mechanically operated interrupter. The mov-
able contact G of the interrupter is attached to a spring-blade H
which is held in place by the grounded piece /. A piece of insu-
lating material J is fastened to the spring-blade so that the
lobes, or projections, of the rotor R f will strike it as the rotor
revolves. The spring is pressed down by the lobe of the rotor
so as to bring the contact-points together and close the primary
circuit. The circuit is immediately broken as the lobe passes
out of contact with the insulation /. It can be seen that the
connections are such that the primary circuit cannot be closed
by the interrupter unless the ground wire DE from the con-
denser is in place. It is therefore impossible to operate the
system while the condenser is not connected into it so as to pro-
tect the contact-points of the interrupter, as well as to add to
the effectiveness of the operation.
The novel feature of this system lies in the short-circuiting,
or shunting, device connected into the high-tension circuit. This
device resembles, in a general way, a high-tension distributer,
but acts in the reverse manner. The short-circuiter cuts off the
current from the spark-plug at which no spark is desired at the
instant of ignition at the other plug, instead of directing current
to the plug at which ignition is to occur, the latter being the
method of the ordinary high-tension distributer.
The spark-plugs M and N are connected in series with each
other to the secondary terminals S and T of the transformer.
The insulated contact-piece K of the short-circuiter is also con-
nected to the high-tension terminal 5 of the transformer. Like-
wise the other insulated contact-piece L of the short-circuiter is
connected to the high-tension terminal T of the transformer.
The grounded rotor R" of the short-circuiter makes contact
alternately with L and K during its rotation. The two rotors,
R' and R", of the interrupter and short-circuiter respectively,
rotate at the same speed. They are ordinarily mounted on the
same shaft as one piece of apparatus, although shown separately
for clearness in the diagram.
SPARK-PLUGS IN SERIES, AND IN SERIES-SHUNT 265
When the rotors have revolved somewhat less than a quarter-
revolution from the positions shown, the short-circuiter rotor
makes contact with the grounded contact-piece L. These two
parts remain in contact while, during further rotation of the
rotors, the primary circuit is made and broken at the interrupter.
The induced high-tension current passes, assuming a direction
of flow, from the terminal S to the insulated spindle of the spark-
plug M, jumps the spark-gap in M, thus reaching the metal of
the engine, through which it flows to the grounded rotor R" of
the short-circuiter, thence to the contact-piece L, since R" and
L are in contact with each other, and on to the other high-tension
terminal T of the transformer. No current flows through the
spark-plug N during this operation, since the resistance of its
spark-gap is enormous in comparison with that of the parallel
circuit through the short-circuiter. The action is similar for
producing a spark at the spark-plug N when the rotors have
revolved a half-revolution farther. An ignition spark is thus
produced first at one spark-plug and then the other, as required.
175. Constructive Form of Series-shunt Spark-plug Ignition
System. Fig. 220. This shows more clearly the nature of the
apparatus used in the system illustrated diagrammatically in
the preceding figure. Corresponding parts are designated by the
same letters in the two figures, as far as possible. In Fig. 220
the rotor R is a combination of the two rotors R' and R" of the
preceding figure. P and Q are merely suitable terminals by
means of which the high-tension wires are connected to the
insulated terminals K and L of the short-circuiter. The short-
circuiting pin which is a part of R corresponds to the rotor arm
R" of the diagram. The switch used is of the snap type, which
eliminates the possibility of drawing an injurious arc in the switch
when changing connections, as when switching from the dynamo
to the battery, and vice versa.
The stationary contact-piece F of the interrupter is cup-shaped,
and threaded on the inside so as to be adjustable. This piece,
together with the part into which it screws, is insulated. The
cup in the stationary contact-piece can be filled with oil, in which
the breaking of the circuit will occur for each ignition. The oil
266
ELECTRIC IGNITION
protects the contact-points against burning and fusing. The
short-circuiter contacts K and L are mounted on insulating
fiber pieces which are clamped into the stationary frame of the
FIG. 220. (See also Figs. 219 and 221.)
Constructive Form of Series-shunt Spark-plug Ignition System. The Bruce-
Macbeth Engine Company, Cleveland, Ohio.
combined interrupter and circuit-breaker. This frame is adjust-
able rotatively, and is clamped in position by means of the
thumbscrew shown at the top.
The combined interrupter and short-circuiter is shown more
in detail in Fig. 221.
The above apparatus is intended for use on a stationary engine.
The spark-coil used is much larger than those customarily used
for small motors, such as those of motor boats and automobiles.
SPARK-PLUGS IN SERIES, AND IN SERIES-SHUNT 267
CHAPTER XX.
INTERRUPTER MAGNETOS AND JUMP-SPARK IGNITION
SYSTEMS WITH MAGNETO CURRENT ONLY.
176. Introductory. This chapter is intended to describe the
more distinctive types of magnetos that are equipped with
interrupters for making and breaking the primary circuit, or
some part of it, at the instant a jump-spark is desired for ignition,
and with a high-tension distributer for directing the secondary
current to the spark-plugs in consecutive order. Some simple
jump-spark ignition systems using magneto current only are
presented in order to make clear the operation of the magneto.
A rotative armature of the shuttle-wound type is used most
frequently in the ignition-system diagrams, but this is merely
a matter of convenience. Alternating-current magnetos with
other types of armatures could be used equally well.
Magnetos which are especially designed to operate in connec-
tion with batteries in combination, or dual ignition systems, are
not described in this chapter, but are described later in connec-
tion with their ignition systems.
177. Interrupted Primary Current Magneto Ignition System.
Fig. 222. The magneto has a single-wound armature of the
shuttle type, which rotates between the pole-pieces of the mag-
nets in the usual manner. One end of the armature winding is
" grounded " by connection to the core of the armature. The
other end of this winding is connected to a transformer spark-
coil at the junction of the primary and secondary windings.
This connection is made through a suitable brush (not shown)
which has rubbing contact with the insulated part that rotates
with the armature and to which the insulated end of the arma-
ture winding is electrically connected. The low-tension ter-
minal of the primary winding P of the transformer spark-coil
is connected to an insulated contact block B of a mechanically
268
INTERRUPTER MAGNETOS AND JUMP-SPARK IGNITION 269
operated interrupter. The interrupter is part of the magneto,
although shown separate from it for convenience. The movable
contact-point of the interrupter is fastened to the interrupter
arm, or lever M , which keeps the contact-points pressed together
except when the arm is lifted by the two-lobed cam C as the cam
rotates. This cam is mounted on the armature shaft and
rotates with the armature. The left-hand end of the interrupter
FIG. 222.
Jump-spark Ignition System with a Low-tension Magneto, a High-tension
Distributer, a Separate Transformer and a Mechanical Interrupter for Breaking
the Magneto-Transformer Circuit.
arm is fastened to a block which has ground connection with
the body of the magneto. A condenser is in parallel with the
interrupter.
The cam C is set in such a position relative to the armature
of the magneto that the interrupter breaks the primary circuit
while the armature is passing through the position which corre-
sponds more or less nearly to the maximum flow of current
through the armature winding and the primary winding of the
spark-coil. The primary circuit is kept closed at the interrupter
during a quarter-revolution or so of the armature preceding the
270 ELECTRIC IGNITION
interruption of the current, during which quarter-revolution the
current gradually increases from nothing to its maximum value.
The maximum value of the current occurs when the armature
has rotated slightly past the position shown; also when it has
rotated slightly more than half a revolution past the position
shown.
The interruption of the current that flows through the armature
and the primary of the transformer spark-coil induces a high-
tension current momentarily in the secondary winding S of the
transformer. The high-tension terminal of the transformer is
connected to the insulated rotor R of a distributer which directs
the current to the spark-plugs in regular order as required. The
high-tension current, after jumping the spark-gap at the plug,
passes through ground to the metal of the magneto, thence to
and through the magneto winding to the junction end of the
secondary of the transformer. It is possible that at least some
of the high-tension current passes through the interrupter by
jumping across the opening between the contact-points while
they are separated to break the primary circuit. The distributer
is part of the magneto. The rotor of the distributer is generally
driven by gears, one on the armature shaft and the other on the
shaft that carries the rotor of the distributer. For four spark-
plugs, each in its own combustion chamber, the distributer rotor
revolves at half the speed of the magneto armature. The gear
on the distributer shaft therefore has twice as many teeth as its
mate on the armature shaft. The rotative speed of the armature
shaft must be the same as that of the crank-shaft of a four-cycle
motor that has four combustion chambers. For a four-cycle
motor that has six combustion chambers, the rotative speed of
the magneto armature must be one and a half times that of the
motor crank-shaft.
The ignition can be cut out by closing the switch, which is
shown open. Closing this switch short-circuits the armature of
the magneto and thus practically leaves the spark-coil out of
the circuit. Very little of the armature current then passes
through the spark-coil, since the resistance of its primary wind-
ing is much greater than that of the short circuit through the
INTERRUPTER MAGNETOS AND JUMP-SPARK IGNITION 271
closed switch. The resistance of the primary of the spark-coil
is both ohmic and inductive.
A safety spark-gap is generally provided in the secondary
circuit to prevent overstraining of the insulation of the high-
tension circuits in case one of the wires becomes disconnected
from its spark-plug. No safety spark-gap is shown in the dia-
gram, it being omitted in order to keep the diagram as simple as
possible. Safety spark-gaps will be shown in connection with
the constructive forms of magnetos.
FIG. 223.
Jump-spark Ignition System with a Low-tension Magneto, a High-tension Dis-
tributer, a Separate Transformer and a Mechanical Interrupter in a Shunt Circuit.
178. Interrupted Shunt-current Magneto Ignition System.
Fig. 223. The primary circuit is never broken in this system.
The interrupter is located in a shunt circuit which shunts the
major part of the primary current away from the spark-coil
during the time the interrupter contacts are closed.
During the rotation of the magneto armature from its zero-
current position to its position of maximum current the in-
terrupter is closed and most of the armature current is in
consequence shunted from the spark-coil and passes through the
272 ELECTRIC IGNITION
interrupter. When the magneto current is at or near its maxi-
mum value, the interrupter breaks the shunt circuit. This
interruption of the shunt current, together with the action of
the condenser, causes a sudden impulse of current through the
primary winding of the spark-coil. The inductive action of this
impulse current produces a momentary high-tension current in
the secondary of the transformer. The high-tension current is
distributed to the spark-plugs in the manner that has already
been described.
Closing the switch keeps the shunt circuit permanently closed,
thus cutting the spark-coil out of operation and stopping ignition.
179. Shunted-current Magneto Ignition System. If the cam
C in Fig. 223 is set forward on its shaft to the extent of about
a quarter-revolution relative to the armature of the magneto,
then one of the lobes on the cam would keep the interrupter
contacts separated during the time the armature is rotating from
its position of zero current to the position at or near maximum
current. The position of the armature at maximum current is a
little later than shown in the figure. The interrupter, or more
properly contact-maker in this application, would then close the
shunt circuit. The closing of the shunt circuit would divert the
armature current from the spark-coil, through whose winding
it flows while the contact-points of the interrupter are separated.
The shunting of the armature current through the interrupter
causes a sudden drop of current in the primary winding of the
transformer spark-coil, and a high-tension current is consequently
induced in the secondary of the spark-coil.
This system has the distinctive feature that the interrupter
contacts can be separated at the instant when little or no current
is flowing through the armature and interrupter. Burning and
fusing of the contact-points, therefore, do not occur. Other
features of the system seem to have prevented its coming into
extensive use, however.
180. High-tension Magneto with Single- wound Armature. -
If all of the apparatus except the spark-plugs and switch of the
preceding figures of this chapter are assembled in one piece of
apparatus, the combination is a high-tension magneto, since it
INTERRUPTER MAGNETOS AND JUMP-SPARK IGNITION 273
will deliver high-tension current suitable for jump-spark ignition
without the aid of any exterior apparatus for generating the
high-tension current. High-tension magnetos of this type (with
the transformer a part separate from the armature) are used to
a considerable extent. The transformer in such cases is gen-
erally located in the space between the armature and the crown
of the magnets.
181. Double-wound High-tension Magneto Ignition System.
Fig. 224. The magneto illustrated diagrammatically has an
Switch
"Ground 1
FlG. 224.
High-tension Magneto Connected to Spark-Plugs. A Complete Ignition System.
armature of the shuttle type with two windings, primary and
secondary. The beginning of the primary winding is grounded
by fastening the end of the wire to the core A of the armature,
and the wire is wound over the entire core-neck next to the core.
The end of the primary winding is connected to the beginning
of the secondary winding, and the latter is wound over the
primary. The high-tension terminal of the secondary winding
is connected to the high-tension distributer. The junction of
the two windings of the armature is connected to the stationary
274 ELECTRIC IGNITION
insulated contact-piece B of the mechanically operated inter-
rupter. The movable contact arm M of the interrupter is
grounded to the metal of the magneto. The interrupter arm is
actuated by the two-lobed cam C, which is mounted on the
armature shaft and rotates at the same speed as the armature.
The primary circuit is kept closed at the interrupter while
the armature of the magneto is rotating from a position about a
quarter-revolution earlier than that in which it is shown, to a
position slightly later than that shown. During this approxi-
mate quarter-revolution of the armature, the current in the
primary winding increases from zero to its maximum value, or
approximately so. During the same part revolution, electro-
motive force is also generated in the secondary winding of the
armature, but not sufficient to produce a pressure that will cause
a spark to jump across the spark-gap of the spark-plug. The
interrupter breaks the primary circuit while the primary current
is at or near its maximum value, and the consequent sudden
stoppage of current in the primary of the armature induces a
pressure in the secondary high enough to cause a spark at
the spark-plug.
The two-lobed cam of the interrupter causes the circuit to
be broken twice during each revolution of the armature, and
two ignition sparks are thus produced during one revolution of
the magneto armature.
The condenser is in parallel with the interrupter in the usual
manner.
Ignition can be cut out by closing the switch shown. This
short-circuits the primary winding of the armature and pre-
vents the sudden cessation of the primary current which occurs
when the switch is open as shown and the interrupter breaks
the circuit. The pulsating current which occurs in the primary
while the switch is closed will not produce a spark at the spark-
plug.
The distributer is of the usual type, driven at half the speed
of the armature for four ignition plugs. For six ignition plugs
the rotor of the distributer must be driven at one-third of the
speed of the armature. The distributer for six spark-plugs has
six contact-points equally spaced relative to each other. The
INTERRUPTER MAGNETOS AND JUMP-SPARK IGNITION 275
interrupter, distributer, and condenser are all component parts of
the magneto.
182. A Bosch High-tension Magneto with Double-wound
Rotary Armature is shown in Figs. 225, 226, and 227. Of the
latter two figures, one is a longitudinal section and the other a
view on the interrupter end. The
corresponding wiring diagram is
given in Fig. 228, and the parts are
shown separated in Plates I, II, and
III. Modified forms of some of these
parts are shown in Plate IV. The
system is the same as that shown in
Fig. 224. It may be noticed that
the interrupter (contact-breaker) le-
ver and the "stationary" contact-
piece of the interrupter rotate with
the armature.
Referring to Figs. 226, 227, and FIG
228, the beginning of the primary
winding is metallically connected
(grounded) to the metal of armature High-tension Magneto for Four
core. The end of the primary wind- Spark-Plugs. Bosch Magneto
ing is connected to the insulated brass Company, New York City,
plate i, which is also connected to one side of the condenser.
The other side of the condenser is grounded on the metal of the
magneto. The metal screw 2, which holds the interrupter in
place, carries the current from the junction of the armature
windings to the insulated block 3 which holds the platinum
contact-screw 5. The movable contact-screw 29 is in one end
of the interrupter lever 7. The interrupter lever is held in place
by a pin which passes through it at the angle which is at about
the middle of its length. This pin is hidden in Fig. 227 behind
a small flat spring that holds the lever on the pin. The inter-
rupter lever and the interrupter disk 4, on which the lever is
mounted by means of the pin mentioned, are grounded on the
metal of the frame of the magneto. The contact-points are
pressed together by the curved spring 6, one end of which is
fastened to the lever and the other end to the interrupter disk.
(See also Figs. 226,
227, 228, and Plates I, II, III,
and IV.)
276 ELECTRIC IGNITION
FIGS. 226 and 227.
1. Insulated brass plate connected to one side of condenser.
2. Screw for fastening the complete interrupter (contact-breaker) in place.
Insulated from the body of the armature and from the interrupter.
3. Insulated " stationary " contact-piece. Rotates with the armature.
4. Disk on which the interrupter parts are mounted. Not insulated.
5. Platinum contact-screw in 3.
6. Spring for pressing interrupter lever contact-point against the "stationary"
contact-point.
7. Interrupter (contact-breaker) lever. Not insulated..
8. Condenser.
9. Insulated slip-ring connected to the high-tension terminal of the armature
winding.
10. Carbon brush which presses against slip-ring 9.
11. Brush-holder for 10. Of insulating material.
12. Connecting bridge.
13. Carbon brush for carrying current to high-tension distributer.
14. Rotor of distributer.
15. Distributing brush for making contact with the stationary contact-pieces of
the distributer.
16. Stationary insulating piece of the distributer.
1 8. Ends of high-tension cables for making connection to the spark-plugs.
19. Fiber rollers against which the end of the interrupter lever strikes so as to
separate the contact points of the interrupter.
20. Arms to either of which the hand-control for regulating (advancing and re-
tarding) the ignition can be connected.
21. Dust-cover above armature.
22. Vulcanite cover for distributer.
23. Three-arm spider. Not insulated
24. Terminal for ground wire to hand-switch. Insulated.
25. Spring for holding cap 26 in place.
26. Brass cover cap for interrupter. Insulated.
27. Brass block for supporting 25.
29. Platinum contact-screw in interrupter lever 7.
30. Stop-screw to limit the rocking movement of the interrupter casing when
advancing or retarding the ignition.
INTERRUPTER MAGNETOS AND JUMP-SPARK IGNITION 277
,16
FIG. 226.
Longitudinal Section of Fig. 225.
FIG. 227.
Interrupter End of Fig. 225 with Covers removed.
2 7 8
ELECTRIC IGNITION
INTERRUPTER MAGNETOS AND JUMP-SPARK IGNITION 279
The beginning of the secondary winding of the armature is
connected to the end of the primary winding. The high-tension
terminal of the secondary winding is connected to the insulated
slip-ring 9 against which bears the carbon brush 10. This
brush is carried by the insulating brush-holder n. The carbon
brush 10 is connected to the insulated central spindle and
carbon brush 15 of the distributer by means of the metal con-
nector 12 and carbon brush 13. The brush 15 is carried by the
insulating material 14 of the distributer rotor. The distribu-
ter brush 15 makes contact successively with metal contact-
pieces set into the insulating piece 16. These contact-pieces
are connected to terminals into which fit terminals 18 for the
wires that go to the spark-plugs.
When the magneto armature is rotating, together with the
interrupter disk and the parts attached to it, the end of the
interrupter lever (right-hand end in Fig. 227) strikes first one and
then the other of two fiber rollers 19. The striking of the end
of the lever against the rollers causes the contact-points of the
interrupter to separate and thus break the primary circuit.
This causes a spark to jump at the spark-plug with whose
terminal the distributer is in contact at the instant.
The part carrying the fiber rollers 19 can be rocked slightly
relative to the frame of the magneto, in order to advance or
retard the ignition. Two arms 20 are provided for this purpose.
The rocking can be done by the hand-control, which is con-
nected to one of the arms 20.
For cutting out ignition, the terminal 24 is provided. This
terminal is insulated and connected to the insulated junction of
the primary and secondary windings by means of the spring
25 that presses against the insulated metal cap 26. The latter
carries a spring-mounted carbon button, or brush, which bears
against the outer end of the metal screw 2. The screw is con-
nected to the junction of the two windings, as has been stated.
If a wire is led from the terminal 24 to one side of a hand switch,
whose other side is grounded, then the closing of the switch
will keep the primary circuit of the magneto permanently closed
and thus prevent sparking at the spark-plugs. Under this
280 ELECTRIC IGNITION
PLATE I.
Magnets and End Plates.
30. Stop screw for timing-lever 20.
31. Magnet casing, pole-shoes, and base-plate (only 2 double magnets for "DR3,"
"D.R.4" and 2 single magnets for "DR6," not 3 as shown).
32. Long magnet-screws.
33. Short magnet-screws.
34. Holding down screws for pole-shoes to base-plate.
35. Front end-plate.
36. Long screws for front end-plate.
37. Short screws for front end-plate.
38a. Oil cover (with arrow <) for front end-plate.
38b. Oil cover (with arrow >) for front end-plate.
39. Oil cover screw for front end-plate.
40. Spiral spring for oil cover screws 39 and 50.
41. Ball-race collar for ball bearings.
42. Rear end-plate without screws.
43. Screw for rear end-plate.
44. Screw for bearing flange 53 and 56.
45. Rear end-plate cover.
46. Long screws for 45.
47. Short screws for 45.
48. Left-hand oil lid for 45.
49. Right-hand oil lid for 45.
50. Oil-lid screw for 45.
51. Paper strip for ball race in both end-plates.
52. Paper washer for ball race in both end-plates.
53. Flange with oil lid and ball-race collar for two ball bearings.
54. Ball-race collar for flange 53.
55. Paper for ball-race collar 54.
56. Flange with slide bearing, oil wick and oil cover.
57. Oil-wick screw for flange 56 with wick spring and packing washer.
58. Wick screw only without parts.
59. Felt wick and spiral spring.
60. Leather washer for wick screw.
61. Oil cover for flange 53 and 56 for type "DR4."
62. Oil-cover screw for flange 53 and 56 for type "DR4."
63. Spiral spring for oil-cover screw 62.
64a. Oil cover left upperside on rear end-plate for type " DR6."
64b. Oil cover right upperside on rear end plate for type "DR6."
65. Screw for oil cover 64a and 64b.
INTERRUPTER MAGNETOS AND JUMP-SPARK IGNITION 281
43
PLATE I. Parts of Fig. 225.
282 ELECTRIC IGNITION
PLATE II.
Armature and Contact Breaker.
1. Rear condenser-plate with insulator 78.
2. Contact-breaker screw.
3a. Platinum-screw block for anti-clockwise machines.
3b. Platinum-screw block for clockwise machines.
4a. Complete contact-breaker for anti-clockwise machines.
4_b. Complete contact-breaker for clockwise machines.
5. Long platinum screw.
6. Contact-breaker spring.
ya. Contact-breaker bell-crank lever for anti-clockwise machines,
yb. Contact-breaker bell-crank lever for clockwise machines.
8. Condenser with connections and paper insulation binding.
9. Slip-ring for armature.
29. Short platinum screw.
66. Complete armature with pinion, slip-ring, condenser, and two ball-race rings,
without ball-race collar.
67. Front armature-disk.
68. Fastening screw for 67.
69. Rear end insulation for slip-ring.
70. Front insulation for slip-ring.
71. Washer for shaft cone f".
72. Nut for shaft cone f ".
73. Rear armature-disk.
74. Fastening screw for rear armature-disk.
76. Ebonite insulating plate for the condenser.
78. Insulation button.
79. Insulation silk.
80. Front condenser-plate.
81. Condenser screw.
82. Small hexagon nut for the condenser.
83. Washer for 82.
84. Insulating strip for condenser.
85. Small gear wheel on armature disk.
86. Fastening screw for gear wheel 85.
87. Inside ball-race ring for the ball bearings.
88. Cage for balls suitable for both ball bearings.
89. Felt disk for packing the one end of the armature.
90. Screw for contact-breaker spring.
91. Washer for 90.
92. Nut for long platinum screw.
93. Insulation for contact-piece on contact-breaker.
94. Insulation bush for 93.
95. Screw for contact-piece on contact-breaker.
96. Insulation bush for center of contact-breaker disk.
97. Flat spring pressing on to bell-crank lever.
98. Washer for 97.
99. Carbon brush for the contact-breaker.
100. Spiral spring for 99.
INTERRUPTER MAGNETOS AND JUMP-SPARK IGNITION 283
85 73
78
O82
83
PLATE II. Parts of Fig. 225.
284 ELECTRIC IGNITION
PLATE III.
Current Collector, Distributer, and Timing Lever.
10. Carbon brush with spiral spring for carbon-holder n.
11. Carbon-holder without carbon and spiral spring,
na. Carbon-holder with carbon and spring.
12. Complete connecting bridge with carbon-holder (brass) together with in-
sulation piece and lock spring.
13. Carbon with spring for brass holder on connecting bridge 12.
14. Rotating distributer piece without carbon and spring.
i4a. Rotating distributer piece with carbon and spring.
15. Carbon with spiral spring for rotating distributer piece.
1 6. Distributer disk without screws.
18. High-tension cable 800 mm. long with terminal, brass plug and insulating
sleeve.
i8a. Brass plug with ebonite insulating sleeve only for cable 18.
19. Fiber rollers for advance and retard lever 20.
20. Complete timing lever with fiber rollers.
21. Dust-cover only with cap for safety gap.
22. Ebonite cover for distributing disk 16.
23. Complete triangular clamp for the distributer disk together with brass con-
necting piece and spring.
23a. Clamp only without parts.
24. Rundled nut for switch wire (short circuit).
25. Spring for brass cap 26.
26. Brass cap for timing lever 20 together with carbon and spring.
27. Brass block for spring 25.
28. Fixing or head bolt for fixing spring 25.
30. Stop screw for timing lever 20.
101. Bell-shaped insulation piece on the connecting bridge 12.
102. Spiral spring for carbon 13.
103. Steatite cover for safety-gap together with electrode 104.
104. Electrode of steatite cover for spark-gap.
105. Screw for fixing the dust-cover 21.
106. Spiral spring for carbon 10.
107. Insulating ring for brass cap 26.
108. Cover for fiber rollers in advance and retard lever 20 together with steel
stud 109.
109. Steel stud for fiber rollers in timing lever 20.
no. Fixing screw for cover 108.
in. Top screw for terminal block and clamp.
112. Bottom screw for terminal block and clamp.
113. Spiral spring for carbon 15.
114. Insulating plate for connecting piece 27.
115. Insulating bush for connecting piece 27.
116. Fixing screw for connecting piece 27.
117. Washer for spring 25.
1 1 8. Complete distributing gear wheel together with shaft and catch plate.
119. Fiber ring riveted on the distributing gear wheel (former execution).
120. Shaft for distributer gear wheel.
121. Fixing screw for shaft of distributer gear wheel.
122. Inside ball-race ring for the ball bearings fixed to shaft 120.
123. Cage with steel balls.
1 24. Spring ring at front end of the shaft 1 20.
125. Ebonite catch-plate.
126. Fastening screw for catch-plate 125.
INTERRUPTER MAGNETOS AND JUMP-SPARK IGNITION 285
101
PLATE III. Parts of Fig. 225.
286 ELECTRIC IGNITION
PLATE IV.
For Newer Designs.
1 a. Rear condenser-plate for condenser 8a.
2 a. Contact-breaker screw. (Only suitable for armature with rear shaft and
disk 73a.)
8a. Condenser with connection and connecting plate la. (Only suitable for
armature shaft and disk 73a.)
gc. Slip-ring in one piece, without thread. (Only suitable for armature shaft
and disk 67a.)
nb. Carbon-holder without thread, with spiral spring and carbon. (Only suitable
for dust-cover 21 a.)
nc. Carbon-holder without thread, minus spiral spring and carbon. (Only
suitable for dust cover 2ia,.)
2ia. Dust-cover with ball clip fastening, without any other parts. (Carbon-holder
minus thread No. nb is suitable for this cover.)
2ib. Dust-cover with ball clip fastening, without any other parts. (Carbon-holder
with thread 1 1 on illustration 1 1 1 is suitable for this cover.)
42a. Rear end-plate with center lubrication.
45b. Rear end-plate cover for center lubrication. (Only suitable for rear end-
plate 42a.)
47. Short screw for 4$b.
67a. Front armature shaft and disk minus thread on shaft (slip-ring gc is suitable
for this).
73a. Rear armature disk with protecting of condenser.
210. Bent steel washer for fastening slip-ring gc.
211. Brass nut on dust-cover 2ia for fastening carbon-holder nb.
212. Body carbon with cable for base plate of magnet casing.
213. Screw for fastening body washer to base plate of magnet casing.
214. Washer for screw 213.
215. Flat spring to keep body carbon 212 in position.
216. Fastening screw for flat spring 215.
217. Washer for screw 216.
218. Strengthening spring for bell-crank lever 7a and 7b.
219. Strengthening spring on projecting brass lug of the contact-breaker disk 4c.
220. Oil-paper strip to fix condenser 8a on rear armature shaft and disk 73a.
221. Felt strip to fix condenser 8a on rear armature shaft and disk 73a.
222. Linen strip to insulate condenser 8a.
223. Pressed linen insulation for condenser 8a.
224. Fastening screw for condenser 8a.
225. Insulating bush on connecting plate on condenser 8a.
INTERRUPTER MAGNETOS AND JUMP-SPARK IGNITION 287
PLATE IV. Parts of Fig. 225..
288
ELECTRIC IGNITION
INTERRUPTER MAGNETOS AND JUMP-SPARK IGNITION 289
Cf
FIG. 230.
Interrupter for Fig. 229.
FIGS. 229, 230, and 231.
A. Timing lever and cam lobes.
B. Clip-spring for holding timer cover in place.
C. Steel disk of interrupter.
C i. Slip-ring for the short-circuiting cut-out.
D. Interrupter arm.
d. Barrel of interrupter, bronze.
E. Spring on which the interrupter arm is mounted.
e. Centering disk, steel.
F. Socket for hinge pin of interrupter lever,
f. Contact-points of interrupter.
G. Nut for holding the interrupter in place.
H. Insulated stud.
h. Cover plate of condenser.
I. Brush-holder and terminal for the short-circuiting cut-out.
J, J. Cam lobes.
P. Distributer cover.
R. Clip- spring for holding distributer cover in place.
S. Distributer plate, of insulating material.
T. Distributer brush,
t. Distributer shaft.
2QO
ELECTRIC IGNITION
condition there can be no sudden interruption of the primary
current by the action of the interrupter. The variations of the
primary current in the permanently closed circuit will not pro-
duce a spark at the spark-plugs.
A safety spark-gap is provided in the secondary circuit. It
is shown in Fig. 226 between the insulated connecting strip 12
and the grounded dust-cover 21 which is just over the armature.
One spark-point of the safety-gap is connected to the insulated
FIG. 231.
Device for Setting the Interrupter of Fig. 229.
conductor 12; the other spark-point is connected to the dust-cap.
The safety-gap is enclosed by a short, tubular piece of metal
and a steatite cap on the top of the short tube, together with a
porton of the dust-cap. The tubular piece has several holes
leading to the atmosphere. These holes have fine-mesh wire
gauze over them to prevent the ignition of gasoline vapor out-
side of the safety-gap inclosure, in case such vapor should
happen to gather around the magneto to an amount that makes
a combustible mixture with air.
"Ground" connection between the body of the armature and
the frame of the magneto is made certain by a carbon brush
INTERRUPTER MAGNETOS AND JUMP-SPARK IGNITION 291
which presses against the metal of the armature. This brush
is shown just beneath the casing of the condenser in Fig. 226.
It is connected to the base-plate of the magneto by a short
electric cable that is fastened to the base-plate by a screw. A
flat spring presses against the outer end of the brush to keep the
latter in contact with the armature. The brush with the at-
tached cable is shown at 212 in Plate IV, together with the
other parts, 213, 214, 215, 216, and 217, for making the ground
connection. In some magnetos, the bearings in which the arma-
ture spindle rotates are depended upon to make the ground con-
nection of the armature to the frame of the magneto, but this
is not an entirely reliable means, for oil and dirt in the bearings
may at times cause imperfect contact between the spindle and
the supporting part of the bearing.
183. U. & H. (Unterberg & Helmle) Magneto with Rotary
Double-wound Shuttle Armature. In Fig. 229 this machine is
shown with some of the parts removed to make clear the con-
struction. The interrupter is also shown separately in Fig. 230.
The electric connections of this magneto are the same in effect
as those shown in Fig. 224.
The interrupter is of unusual design. Referring to Fig. 230,
the contact-points are shown at /. The stationary contact-
point is connected to the electrically insulated steel disk C,
upon which the slip-ring Ci is mounted and electrically con-
nected to it.
The movable contact-point is attached to an interrupter arm
D which is mounted on an elastic member E that is bent back
upon itself so as to form a spring of suitable form to carry the
interrupter arm. E is fastened between a steel centering disk e
and a cylindrical bronze part or barrel d. An insulated socket
F is provided for the rounded end of a hinge pin in the inter-
rupter lever D.
The interrupter lever D, the elastic member E, and the parts
e and d are electrically connected together. When the inter-
rupter is in place on the magneto these parts make connection
with the grounded side of the armature.
The curved portion of the interrupter arm which is shown
2Q2
ELECTRIC IGNITION
PLATE V. Parts of Fig. 229.
INTERRUPTER MAGNETOS AND JUMP-SPARK IGNITION 293
projecting at the upper part of the illustrations strikes against
the lobes of a cam as the armature rotates, so as to move the
lever back and separate the con tact- points. These lobes are
shown at / and / in Fig. 229. They are attached to the cam-
piece A, of which the timing lever for connecting to the spark
control is a part.
When the interrupter is in place the centering disk e bears
against one of the cover-plates h of the condenser which lies
between the interrupter and the winding of the armature.
The interrupter is held in place by a nut G which screws on
the insulated stud H, that is connected to the junction of the
primary and secondary windings of the armature. The insulated
disk C, bronze slip-ring Ci, and the stationary interrupter
point are thus connected to the junction of the two windings.
The beginning of the primary coil of the armature winding is
grounded to the armature core. The end of the secondary
winding is connected to a slip-ring at the end of the armature
next to the driving gear. This slip-ring is shown in Plate V.
The high-tension current is carried from this slip-ring through
a brush and suitable connections to the distributer brush T,
which is rotated in the usual manner by a pair of gears that
connect the shaft which drives / and its brush-holder for T to the
armature shaft. The brush and brush-holder are shown drawn
partly out from the recess in which they properly belong. The
distributer plate 5 is of insulating material and has four contact-
pieces against which the distributer brush T rubs successively
during its rotation.
When in proper position the interrupter rotor is protected by
the cover P which is held in place by the clip R.
The cam-piece A-J fits into the cylindrical housing on the
interrupter so as to bring the lobes / into the proper position for
the curved end of the interrupter arm D to strike them. The
rocking movement which can be given to the cam-lobes in order
to advance and retard the ignition, is limited by a small stop
shown in the inside of the cylindrical housing in the right-hand
lower part. The rocking part A-J is held in place by the
clip B.
2 94 ELECTRIC IGNITION
The brush-holder / fits into the threaded opening shown at
the left-hand upper part of the interrupter housing. The brush
in this holder bears against the slip-ring Ci. This brush-holder
forms the ground terminal which is to be connected to a switch
that remains open while the magneto is operating, but is closed
in order to stop the operation of the magneto. Connecting the
ground terminal to ground in the manner just stated short-
circuits the primary winding of the magneto.
A safety spark-gap is provided between one of the high-
tension connections and the grounded dust-plate which goes
just above the armature. The safety-gap is inclosed by porce-
lain and metal walls, the latter being perforated, so as to form
openings through which a spark passing between the points can
be seen. The openings of the metal are provided with mica
windows for the exclusion of vapor and dust.
A convenient manner of holding the interrupter in proper
position during the process of timing the magneto is by means
of the pin shown in Fig. 231. This pin passes through a small
hole in the cam-piece A and enters a hole Z in the interrupter.
The hole in the part A is closed by a screw during the operation
of the magneto.
This magneto, in some of its types, is provided with a start-
ing device which enables a motor to be started on magneto spark
without the necessity of cranking, or otherwise rotating the
motor, at a speed any higher than is necessary for battery
ignition with a trembler spark-coil. Briefly, the magneto is
driven by means of a device containing a stout spring and a
loose ball. When the driving mechanism is rotated slowly, the
ball locks the armature so that it cannot rotate until after the
spring has been wound up to some extent. The ball then strikes
a part which throws it out of its locking position, and the arma-
ture is rapidly rotated by the spring far enough to produce a
strong ignition spark. As soon as the motor starts on its own
power, the speed of the mechanism that drives the magneto is
high enough to prevent the ball from dropping into its locking
position, and the armature is then driven continuously at the
speed of the driving mechanism.
INTERRUPTER MAGNETOS AND JUMP-SPARK IGNITION 295
184. Remy Magneto with Stationary Armature and Rotary
Inductor. Fig. 232 is a full view of the magneto. Fig. 233 is a
photographic end view, and A of Fig. 236 is a line-drawing end
view; the covers of the interrupter and distributer are removed
FIG. 232. (See also Figs. 233, 234, 235, 236, and 256.)
Remy Magneto with Stationary Single-wound Armature and Rotary Inductor.
Remy Electric Company, Anderson, Indiana.
in both of these views. Sectional views are shown in Figs, 234
and 236. The armature winding and the inductor are shown in
Fig. 235.
The armature winding i is a single-wound circular coil. It has
296
ELECTRIC IGNITION
several turns of rather coarse insulated wire. The coil encircles
an enlargement of the inductor shaft 2, which has fastened to
it (by pins) two forged steel arms, or wings, 3 and 4. These
-
FIG. 233.
Interrupter End of Fig. 232 with Cover-Plates removed.
wings, together with the enlarged portion of the shaft, form the
rotary inductor of the magneto. The form and disposition of
the wings can be seen by examining Figs. 234, 235, and 236.
INTERRUPTER MAGNETOS AND JUMP-SPARK IGNITION 297
The wings extend in opposite directions from the shaft, and the
outer end of each wing is crowned cylindrically to conform to
the concave surfaces of the magnet-poles between which they
revolve. One of the magnet-poles is shown in section at 5,
Fig. 234. The armature coil is partly embedded in the magnet
2.0
FIG. 234.
Longitudinal Section of Fig. 232.
poles. The magnets 6 are of the ordinary U-shaped compound
type. One end of the armature coil is connected to the
grounded terminal 7 ; the other end is connected to the insulated
terminal 8, from which, in an ignition system, a wire leads to a
non-trembler spark-coil, or to a switch connected to the spark-
coil.
Each revolution of the inductor produces two impulses of
alternating current in the armature coil. The direction of mag-
netic flux through the inductor during each revolution is first
298 ELECTRIC IGNITION
from the north pole of the magnets to and through the inductor
wing 3, thence through the enlargement of the shaft and on
through the wing 4 to the south pole of the magnets. After
half a revolution of the inductor, the magnetic flux is from the
north pole of the magnets to the inductor wing 4, enlarged portion
of the shaft, wing 3, and the south pole of the magnets. The
FIG. 235.
Rotary Inductor and Stationary Armature Coil for Fig. 232.
magnetic flux is thus reversed in its direction of flow through the
armature coil twice each revolution.
The interrupter rocker-arm, or rocker-lever, 9, is kept pressed
against a two-lobed cam 10 by means of a coiled compression
spring ii. The cam is fastened to the inductor shaft and rotates
with it. The rocker-lever has two arms, to one of which is fas-
tened the blade-spring 12. The movable contact-point of the
INTERRUPTER MAGNETOS AND JUMP-SPARK IGNITION 299
FIGS. 232, 233, 234, 235, and 236.
1. Armature Coil.
2. Inductor shaft.
, 4. Wings of Inductor.
5. Magnet pole.
6. Magnets.
7. Grounded terminal of armature coil.
8. Insulated terminal of armature coil.
9. Interrupter rocker-lever.
10. Interrupter cam.
11. Compression spring.
12. Blade springs.
13. Insulated terminal of interrupter.
14. Metallic part of distributer rotor, insulated.
15. Central terminal of distributer.
16. Central contact carbon of distributer.
17. Distributer shaft.
18. Adjusting screw of interrupter contacts.
19. Hammer end of interrupter lever.
20. Arm for rocking the interrupter.
300
ELECTRIC IGNITION
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INTERRUPTER MAGNETOS AND JUMP-SPARK IGNITION 301
interrupter is fastened to the free end of the blade-spring. When
the cam is in the position shown in Fig. 236, the movable con-
tact-point is pressed against its mating stationary contact-point,
which is an extension of the insulated terminal 13. As the cam
rotates, it forces the rocker-lever back against the resistance of
the coiled compression spring and causes separation of the con-
tact-points so as to break the armature circuit. Quick separa-
tion of the contact-points is secured by means of the striking end
19 of the interrupter lever.
The stationary contact-point can be adjusted by turning the
screw in which it is mounted. A knurled piece of insulating
material 18 is provided for making this adjustment. The arm
20 is provided for rocking the entire interrupter by hand to ad-
vance and retard the time of ignition.
The distributer has high-tension current brought to its insu-
lated metallic rotor 14 from the spark-coil by means of a wire
connected to the terminal 15. The latter is connected to the
distributer rotor by the carbon contact brush 16. The rotor
of the distributer is rigidly mounted on the shaft 17, which is
driven by gears connecting it to the inductor shaft as shown.
The distributer rotor directs the high-tension current succes-
sively to the four terminals shown at the upper part of the illus-
trations. In a complete ignition system, these terminals are
connected to the spark-plugs that produce ignition in the
motor.
185. Effect of Advance and Retard on the Strength of the
Ignition Spark. One much-used method of varying the instant
of ignition (of advancing and retarding the spark) is to rock the
entire interrupter relative to the rotor (armature or inductor) of
the magneto. If the interrupter is rocked in the direction
opposite the rotation of the rotor, the ignition spark is thereby
advanced; or if the interrupter is rocked in the direction of
rotation of the rotor, the spark is thereby retarded.
It has already been pointed out that the alternating electric
current generated in the low-tension winding of a shuttle-wound
armature as it rotates between magnet-poles is at or near its
maximum value during only a very small portion of a revolution
302 ELECTRIC IGNITION
of the armature or inductor. The same is true relative to other
types of armatures in a bipolar alternating-current magneto.
Therefore if the interrupter is rocked relative to the magnet-
poles as well as relative to the armature, the primary current
will be smaller at the instant of its interruption, when the ignition
is either fully advanced or fully retarded, than when the inter-
rupter is in an intermediate position. The result is that a
weaker spark is obtained for ignition when the interrupter is
advanced or retarded than when it is at an intermediate posi-
tion. This weakening of spark strength is not so great, however,
but that numerous excellent magnetos are in operation in which
the advance and retard of the spark is obtained by rocking the
entire interrupter relative to both the rotor and the magnet-
poles, the latter remaining stationary relative to the frame on
which the magneto is mounted.
On the other hand, various methods have been adopted in
connection with interrupter magnetos, to secure an ignition
spark of the same length for all settings of the ignition, from full
advance to full retard. Of these methods, the chief ones are:
Rocking extensions of the magneto poles, to rock with the
interrupter;
Rocking magnets;
Shaft couplings in which one part can be rotated by the spark-
control mechanism, through a portion of a revolution relative
to the other part;
Alternately charged and discharged condenser.
These methods are described in the following part of this
chapter, either separately or in connection with a magneto.
186. Charged-and-Discharged Condenser Ignition System. -
The magneto for this system has a condenser of comparatively
large capacity. The armature has a low-tension winding only
and there is a non-trembler spark-coil separate from the arma-
ture. The magneto has two devices of the nature of an inter-
rupter, one of which will be called a circuit-closer, and the other
an interrupter. An alternating current is generated.
During the operation of the magneto, the condenser is first
INTERRUPTER MAGNETOS AND JUMP-SPARK IGNITION 303
connected to the armature of the magneto through the closed
interrupter until the condenser becomes charged. The inter-
rupter then breaks the connection between the armature and
condenser at about the instant of maximum voltage in the
armature, thus leaving the condenser charged on open circuit.
Then, at the instant of ignition, the circuit-closer closes the cir-
cuit between the spark-coil and the condenser. The condenser
discharges through the primary of the spark-coil as soon as the
condenser- transformer circuit is closed. The discharge current
from the condenser acts to produce an ignition spark at the
spark-plug. Two ignition sparks per revolution of the armature
are produced when the latter is of the ordinary shuttle-wound
type and rotates between bipolar magnets.
The breaking of the armature-condenser circuit always occurs
at the same instant with regard to the position of the armature
relative to the magnet-poles. The condenser, therefore, always
receives the same amount of charge, at a given speed of rotation
of the armature, regardless of the time of ignition relative to
advance and retard. Consequently, the condenser sends the
same amount of current through the transformer whatever the
time of ignition, at any given rotative speed of the armature.
The strength, or hotness, of the ignition spark is the same what-
ever the time of ignition. A hotter spark is produced at high
speeds of the armature than at low speeds, which is true of all
magnetos.
187. Shaft Couplings for Advancing and Retarding the Igni-
tion. A form of coupling that is quite commonly used for this
purpose consists of one or two pieces in which a helical slot or
groove is cut, and another part having a key or pin which fits
into the groove. By moving one part longitudinally relative to
the other, rotation of the one relative to the other is caused to a
limited extent. Thus, if the driving shaft is held from rotating,
then sliding one part of the coupling along the other will cause
the armature of the magneto to rotate through part of a revolu-
tion. If the interrupter is fixed in position (not constructed so
as to rock) the instant of ignition will be changed by this move-
ment of the armature. Moving the coupling so that the armature
34
ELECTRIC IGNITION
INTERRUPTER MAGNETOS AND JUMP-SPARK IGNITION 305
is thereby rotated through part of a revolution relative to the
driving shaft, in the direction that they run, advances the spark,
and vice versa. Since the interrupter is not rocked relative to
the magnet-poles, and is operated from the armature shaft, the
armature is always in the same position relative to the magnet-
poles at the instant that the interrupter breaks the primary
circuit to produce a spark. A spark of uniform strength is
therefore produced for all settings of the ignition from full advance
to full retard, at any given speed of the armature.
One form of helically slotted driving coupling is shown both
in detail and on the magneto in Fig. 237.
The smaller slotted tubular part is fastened rigidly to the
armature shaft, and the larger slotted tube fits loosely over the
smaller tube. The ring with two inward projecting pins fits
over the larger tube, and the pins project through the slots in
both tubes, thus preventing the rotation of one relative to the
other. The ring is held in place longitudinally by the collar
bearing shown in two parts at the upper portion of Fig. 237. The
collar bearing has two trunnion pins to which the timing lever
is connected for shifting the collar along the tubes.
Couplings of this nature are used for obtaining excessive ad-
vance of ignition, as on racing automobiles.
187.1. Eisemann High-tension Magneto with Automatic
Spark-advance Mechanism. The magneto has a double-wound
armature of the shuttle type which rotates between pole-pieces
in the usual manner, and a high-tension distributer for directing
the secondary current to the spark-plugs in consecutive order as
desired.
The device for advancing the ignition as the speed of rotation
of the armature increases is shown in the right-hand portion of
Fig. 238, which is a longitudinal section of the magneto. The
armature is driven through a coupling which has a groove or
grooves and a sleeve which, when moved longitudinally, causes
the armature to rotate through part of a revolution relative to
the driving shaft, which receives power from some external
source. The method of obtaining automatic advance is to
connect the weights of a centrifugal shaft-governor to the sleeve
306
ELECTRIC IGNITION
of the coupling so that when the weights are thrown outward
from the shaft by the centrifugal action due to the rotation of
the armature, the movement of the weights slides the sleeve
along the shaft so as to advance ignition. The safety spark-
INTERRUPTER MAGNETOS AND JUMP-SPARK IGNITION 507
gap A is shown distinctly in the illustration. The cylindrical
metal which forms part of the inclosing wall of the space in
which the safety-gap is inclosed is perforated with round holes
as shown. These hotes should be covered with wire gauze to
prevent ignition of an inflammable mixture which may collect
about the safety-gap, or with some such material as mica, for
the same purpose and to exclude dust.
188. A magneto with a separately-wound induction coil that
is embodied in the magneto is shown in Fig. 239. The end
FIG. 239. (See also Figs. 240, 241, and 242.)
High-tension Magneto with Separately-wound Transformer.
cover and several of the other parts are removed, including the
interrupter lever and the distributer rotor. Fig. 240 is a sec-
tional view of the magneto, and Fig. 241 shows most of the
parts separately. The wiring diagram is given in Fig. 242.
This magneto operates on the interrupted short-circuit system
that is shown in Fig. 223.
The armature is of the shuttle type with one winding. The
condenser 18 is just above the armature, and a non-trembler
transformer spark-coil 10 is located between the condenser and
the crown n of the magnets. The interrupter-lever is operated
by a pair of rolls in the ends of the roll-carrier 25, which is rigidly
fastened to the armature shaft. The beginning of the armature
winding is grounded on the armature core. The end of the
308
ELECTRIC IGNITION
FIG. 240.
Longitudinal Section of Fig. 239.
1. Armature.
2. Insulated fastening screw connected to armature winding.
3. Primary bridge for carrying 4.
4. Contact-carbon pressed against 2.
6. Hard rubber block.
8. Stirrup spring for holding interrupter lever in place.
10. Transformer.
11. Magnets, crown of.
13. High-tension terminal of transformer.
14. Blade-spring connector between 13 and 15.
15. Distributer rotor.
1 6. Carbon brush in distributer rotor.
17. Terminals for wire cables.
18. Condenser.
20. Coupling for driving the armature.
21. Fastening nut for coupling.
23. Cover.
25. Roll-carrier of interrupter.
INTERRUPTER MAGNETOS AND JUMP-SPARK IGNITION 309
armature winding is connected to the insulated stationary con-
tact of the interrupter, also to the primary of the spark-coil and
one side of the condenser, so that the armature, interrupter,
spark-coil, and condenser are all four in parallel with each other.
The high-tension current from the spark-coil is carried to the
distributer rotor which directs it to the different spark-plugs in
the usual manner. A terminal is provided which connects to
ground through a hand-switch. When the latter is closed, the
armature circuit is permanently closed so as to cut out ignition.
FIG. 241.
Parts of Fig. 239.
The armature is driven by means of a coupling which rotates
the armature through part of a revolution relative to the shaft
which drives it, when the spark-control is operated to advance
or retard the ignition. The interrupter is permanently fixed in
position relative to the magnet-poles. The magneto, therefore,
gives a spark of uniform strength at a given speed, whatever the
setting of the ignition relative to advance and retard.
189. Movable Extension of Magnet-Poles for Constant
Strength of Spark. This method of securing a nearly constant
strength of the ignition spark for positions of advance and retard
ELECTRIC IGNITION
of the ignition, at any given speed, has been applied to shuttle-
wound magnetos. The more usual method of applying it is to
make the bore of the magnet-poles considerably larger than the
diameter of the armature, and insert a movable piece of magnetic
material between each of the stationary poles and the armature.
Ordinarily a longitudinal portion of a soft steel or iron tube is
Primary Circuit
Secondary Circuit
Ground Circuit through.Frame
FIG. 242.
Connections of Fig. 239.
placed between each of the poles and the armature. The device
in one of its forms resembles, in a measure, the rotating shield
shown in Fig. 28 without the extension for a brush at one end.
Fig. 243 is a sectional view of the stationary magnet-poles,
movable extensions of the poles, and the core of a shuttle-wound
armature. The interrupter of the magneto and the movable
extensions of the poles are fastened together so that they move
as one piece when the interrupter is rocked to advance or retard
the spark. The interrupter is set to break the circuit while the
INTERRUPTER MAGNETOS AND JUMP-SPARK IGNITION 311
armature is passing through the position, relative to the movable
extensions of the poles, that is shown in the figure. In this
position, the edges of the crowned surfaces of the armature core
have passed a short distance beyond a position opposite the
movable extensions i and 2 of the poles. This short distance is
(A) (B)
FIG. 243.
Movable Magnetic Shield between Pole-pieces and Rotary Armature.
about the same in amount in both (A) and (B), in which (A)
represents the position of the pole extensions for advanced igni-
tion, and (B) their position for retarded ignition.
The rocking of the pole extensions together with the inter-
rupter has the effect, in a way, of carrying the magnetic field
around with the interrupter when it is rocked. The armature is
thus, in effect, in essentially the same position relative to the
magnetic field when the interrupter breaks the circuit, whether
the ignition is set early or late. The ignition spark is, therefore,
of about the same strength for all positions of the interrupter
from that for earliest ignition to that for latest ignition.
190. Pittsfield Magneto with Stationary Armature and Rock-
ing Pole-Extensions. Fig. 244 is an exterior view of the mag-
neto. Fig. 245 is a longitudinal section. Fig. 246 shows the
interrupter, and Fig. 247 is a cross-section on A-B of Fig. 245.
The construction of this magneto is unusual, in that the sta-
tionary coils 6 of the armature are not between the pole -pieces
of the permanent magnets, but are wound around a soft iron or
steel core 5 which is connected to two laminated soft iron or
steel bars 4 that extend in between the poles of the permanent
magnets 3. The laminated bars 4 are held rigidly in place by
312 ELECTRIC IGNITION
non-magnetic parts 2 and the non-magnetic base of the magneto.
These and the pole -pieces of the permanent magnets are bored
cylindrical to fit a longitudinally slotted iron sleeve which has
four slots so as to leave four bars 28. The inductor i rotates
inside of the slotted sleeve. The inductor has the form of a
thick tube slotted through from side to side, the width of the
FIG. 244. (See also Figs. 245, 246, and 247.)
High-tension Magneto with Stationary Double- wound Armature, Rotary Inductor,
and a Rocking Magnetic Shield between the Pole-pieces and the Inductor.
Pittsfield Spark Coil Company, Dalton, Massachusetts.
slot being somewhat less than the inside diameter of the tube.
The metal of the inductor is shown shaded in Fig. 247.
As the inductor revolves, it alternately directs the magnetic
flux from the permanent magnets through the bars 4 and core
of the armature windings and cuts off the flux through the arma-
ture core. While the inductor is in the position shown, the
magnetism flows from the north pole -piece of the permanent
magnets directly through the two sides of the inductor to the
south pole -piece of the permanent magnets. When the inductor
has rotated one -eighth of a revolution from the position shown,
the magnetic flux is then from the north pole -pieces of the per-
manent magnets through the upper side of the inductor to the
INTERRUPTER MAGNETOS AND JUMP-SPARK IGNITION 313
upper bar 4, then through the upper bar to the armature core 5,
down through the armature core to the lower bar 4, and through
this bar to the lower side of the inductor, and on through this
side of the inductor to the south pole -piece of the permanent
magnets. The magnetic flux is of course through the slotted
tube, or magnetic shield, 28, when going from the inductor to or
from the pole -pieces and bars 4. When the indicator has rotated
27-
19' A 1 28 21 2
FIG. 245.
Longitudinal Section of Fig. 244.
a quarter-revolution from the position shown, there is no mag-
netic flux through the armature core. At three-eighths of a
revolution (from the position shown) the magnetic flux through
the armature core is again at or near its maximum value, but in
the opposite direction from that at one-eighth of a revolution.
At half a revolution there is no flux through the armature core.
The same conditions exist again during the remaining half-
revolution. There are, therefore, four electric impulses induced
in the armature coils during each revolution of the inductor.
ELECTRIC IGNITION
The beginning of the primary winding of the armature is con-
nected to the frame of the magneto by the screw 7. The end of
the primary winding is connected to the beginning of the second-
ary winding, and the junction of the two windings is connected
to the insulated plate 8, which has electric connection to the
insulated stationary contact-piece 9 of the interrupter. The
stationary (insulated) contact-screw 10 of the interrupter is
FIG. 246.
Interrupter End of Fig. 244 with some
of the Parts Removed.
FIG. 247.
Cross-section of Fig. 244 on Plane A
of Fig. 245.
-B
carried by 9. The movable contact-screw 13 is in the end of the
interrupter-lever 12. The flat spring 14 acts on lever 12 to press
the contact -points together. The interrupter-lever is operated
by a four-lobed cam 15 that is fastened to the inductor shaft
and rotates with the inductor. The interrupter-lever is elec-
trically connected to the frame of the magneto, so that when
the contact-points of the interrupter are pressed together the
primary circuit is closed. The cam forces the contacts apart
four times each revolution of the inductor, thus interrupting the
INTERRUPTER MAGNETOS AND JUMP-SPARK IGNITION 315
primary current at each insjant that it reaches its maximum
value.
The interrupter is rigidly connected to the slotted tube, or
shield, 28, and both are rocked together by means of the timing
lever 35 to vary the instant of ignition.' Rocking the tubular
shield has the effect of moving the magnet-poles so as to always
have the current at or near its maximum value at the instant of
its interruption, as has been explained in the preceding section.
The high-tension terminal of the secondary winding of the
armature is connected to the contact-piece 18, against which the
insulated carbon brush 20 is pressed by a spring. The high-
tension current flows from the brush 20 through the conductor
21 to the metal rotor 23 of the distributer. Conductor 21 is
covered with insulation 19, and the metal rotor of the distributer
is carried by the insulation 22. The stationary contact-pieces
25 of the distributer are connected by conductors 26 to the
terminal block 27, from which wires lead to the spark-plugs.
Condenser 16 has one side connected to the junction of the
primary and secondary windings, and the other side grounded
to the body of the magneto. Terminal 29 is also connected to
the junction of the primary and secondary windings. When
this terminal is connected to ground, ignition is cut off on account
of the primary circuit being thus permanently closed through
a low-resistance path in parallel with the interrupter.
The rotative speed of the inductor, for a four-cycle motor with
four combustion chambers, must be half that of the crank-shaft,
which is the same as that of the cam-shaft, since there are four
sparks produced during each revolution of the inductor.
A modified form of this magneto interrupts the current only
twice during each revolution of the inductor, and therefore pro-
duces only two sparks per revolution of the magneto inductor.
This modified form must rotate twice as fast as the one just
described.
Of the numbered parts not mentioned, 17 is the condenser
case, 24 the front plate of the magneto, 30 the rear housing, 31
the latch for holding the rear housing in place, and 32, 33, and
34 are screws for holding the removable parts in place.
ELECTRIC IGNITION
191. Mea Magneto with Rocking Magnets. This magneto
has several distinctive features that are not found in those of
FIG. 248. (See also Figs. 249, 250, 251, 252, 253, 254, and Plates VI and VII.)
Mea High-tension Magneto Mounted on Trunnions. Marburg Bros., Broadway
& 58th Street, New York City.
FIG. 249.
Bell-shaped Field-Magnets of Mea Magneto, Fig. 248.
earlier design. The principal unique feature is the use of parts
of such a form that they can be assembled compactly so that the
entire magneto can be rocked on a supporting frame, or base,
INTERRUPTER MAGNETOS AND JUMP-SPARK IGNITION 317
for advancing and retarding the ignition. The advance and
retard can be carried to any extent ever required without
affecting the strength of the ignition spark. The magnets and
interrupter are of distinctive form, and there is a window
through which the position of the distributer rotor can be
observed.
Fig. 248 is a full view of the entire magneto resting on its
supporting frame. The magnets are shown in Fig. 249 with the
pole -pieces fastened to them. Fig. 250 is a longitudinal section
of the magneto, and Fig. 251 is a full view of the interrupter end
with the cover of the interrupter removed. Fig. 252 shows the
working parts of the interrupter.
The magnets are called " bell-shaped " by the manufacturer.
The armature is of the shuttle type with double winding. The
armature shaft lies parallel with the length of the magnets, and
one end of the shaft passes through a hole in the crown of the
magnets. The armature does not differ essentially from those
of the shuttle type ordinarily used.
The parts of the magneto are shown in detail in Plates VI
and VII.
The wiring diagram is essentially the same as in Fig. 224.
The beginning of the low-tension winding is grounded on the
armature core. The end of the low- tension winding is connected
to the beginning of the secondary winding of the armature, and
the high-tension end of the secondary winding is connected to the
insulated slip-ring, or collector-ring 4, against which the insulated
carbon brush 77 bears. Current from the high-tension end of the
winding passes through the brush 7 7, metal bridge 84, and brush 69
to the two brushes 68 of the distributer rotor. Each of these two
distributer brushes distributes current to its own two of the
four contact-pieces to which the terminals of the spark-plug wires
are connected. The use of two brushes in the distributer rotor,
as stated, makes it possible to have a rotor of small diameter
without bringing the stationary contact-pieces of the distributer
unduly close together.
The junction of the primary and secondary windings is con-
nected to the insulated plate of the condenser 12. This plate
318 ELECTRIC IGNITION
FIGS. 250, 251 and 252.
i. Armature.
4. Collector-ring, or slip-ring.
7. Pinion gear for driving the distributer rotor.
12. Condenser.
17, 1 8. Ball bearings.
24. Fastening and conducting screw.
27. Interrupter disk.
28. Insulated plate of interrupter.
30. Interrupter spring.
31. Fiber roller of interrupter.
33. Contact-point of interrupter.
34. Contact-point.
40. Cam-disk of interrupter.
46. Carbon brush.
47. Brush-holder.
50. Ground terminal.
53. Base of magneto.
66. Distributer rotor.
68. Brushes of distributer rotor.
69. Carbon brush bearing against distributer rotor.
70. Stationary plate of distributer, with contact-pieces.
72. Gear on distributer rotor.
74. Cover of interrupter housing.
76. Brush-holder.
77. Carbon brush on collector ring.
78. Brush making ground connection for armature.
84. Connecting bridge between 77 and the distributer rotor.
88. Arm for controlling the time of ignition.
91. Metal plate for supporting the brushes 77 and 78.
100. Magnets.
108. High-tension terminals.
INTERRUPTER MAGNETOS AND JUMP-SPARK IGNITION 319
66 70
69 78 89 84 76 91 77
5S 1 12 4:
FIG. 250.
Longitudinal Section of Fig. 248.
18 100 X 24
FIG. 251.
Interrupter End of Fig. 248 with In-
terrupter Cover removed.
27,
FIG. 252.
Interrupter of Fig. 248.
320 ELECTRIC IGNITION
is threaded to receive the fastening screw 24 that holds the inter-
rupter in place and conducts the primary current to its insulated
block 28.
The interrupter spring 30, which carries the movable contact-
point, is fastened to the insulated block 28. The interrupter
spring has the general form of a thin washer that has been
cut through on one side. The block 28 is fastened to the disk
27 but is insulated from it. The stationary contact-point of
the interrupter is mounted on the disk 27, and both are elec-
trically connected (grounded) to the frame of the magneto.
The interrupter spring is forced back, in a direction approx-
imately parallel to the length of the armature shaft, by the fiber
roller 31 at the instant the primary circuit is to be broken.
The roller is carried in a pocket in the disk 27. As the disk 27
and interrupter spring rotate with the armature, the roller strikes
successively against two projecting lobes on the stationary
cam-disk 40, and the roller is thus forced against the inter-
rupter spring so as to push the latter back and separate the
contact-points. The two lobes are half a revolution apart, so
that the circuit is broken twice during each revolution. The
parts of the interrupter are shown in Plate VI, Nos. 26 to 42
inclusive.
The numbers i, 2, 3, 4 are marked on the gear-wheel which is
attached to the distributer rotor of a magneto for four combus-
tion chambers. This numbering is shown in Fig. 253. When
the armature is in the position at which the interrupter contacts
should just begin to separate, one of these numbers should register
with a circular window in the upper part of the distributer casing.
In Fig. 253 the numeral i registers with the window, and the
armature is in the position, during its clockwise rotation, at
which the interrupter contacts should begin to separate. When
the armature has made half a revolution from this position, the
numeral 2 will register with the window. The numbers can be
seen, in the actual magneto, only when they register with the
window. In the illustration, the lower part of the casing is
broken away to show the numbers not at the window. The
distance between the edge of the armature core and the edge of
INTERRUPTER MAGNETOS AND JUMP-SPARK IGNITION 321
the magnet-pole is given as 1.5 millimeters (about yy or .06
of an inch) in the figure. In Fig. 254 the corresponding positions
of the armature and distributer are shown for counter-clockwise
rotation of the armature.
FlGS. 253 and 254.
Relative Rotative Positions of Armature and Distributer in Fig. 248 for Right-
hand and Left-hand Rotation.
There is a safety spark-gap for protecting the insulation of
the magneto against excessive electric pressure in case one of the
wires becomes disconnected from its spark-plug. The safety-
gap cannot be seen in the illustration, however.
322 ELECTRIC IGNITION
PLATE VI.
1. Complete armature with condenser, small gear-wheel, slip-ring, and two ball-
bearings without outer race collar.
2. Front armature-disk with spindle without other parts.
3. Rear armature-disk with spindle without other parts.
4. Slip-ring.
5. Front ball-bearing without race collar.
6. Rear ball-bearing without race collar.
7. Small gear-wheel.
8. Washer for slip-ring.
9. Fastening ring for 8.
10. Washer for spindle cone.
11. Nut for 10.
12. Complete condenser with brass furniture.
13. Silk strip for the circumference of the condenser.
14. Fastening screw of the condenser.
15. Silk insulating strip for the condenser.
16. Mica insulating plate for the condenser.
17. Complete front ball-bearing.
1 8. Complete rear ball-bearing.
19. Fastening screw for the small gear-wheel.
20. Fastening screw for the front armature-disk.
21. Fastening screw for the rear armature-disk.
22. Felt disk for the front ball-bearing.
23. Felt disk for the rear ball-bearing.
24. Fastening screw for contact-breaker.
25. Insulating piece for 24.
26. Complete contact-breaker.
27. Contact-breaker disk.
28. Contact-piece for contact-breaker spring.
29. Insulation for contact-piece.
30. Contact-breaker spring.
31. Contact-breaker roller.
32. Safety screw for 31.
33. Short platinum screw for contact-breaker.
34. Long platinum screw for contact-breaker.
35. Fastening screw for contact-piece 28.
36. Vulcanite insulation for 35.
37. Fastening screw for contact-breaker spring.
38. Washer for 37.
39. Insulation bush for contact-breaker disk.
40. Stud ring.
41. Fastening screw for stud ring.
42. Safety pin for stud ring.
43. Case for rear ball-bearing complete with race collar and fastening screw.
44. Race collar of rear ball-bearing.
45. Fastening screw for ball-bearing case.
46. Carbon brush for cover of contact-breaker case.
47. Complete fastening for 46 with nut.
48. Body for 47.
49. Fastening screw for 48.
50. Nut for switch wire (short circuit).
51. Mica disks for 48.
INTERRUPTER MAGNETOS AND JUMP-SPARK IGNITION 323
2 1
13
18
19 20 21
23 23
i k
26 (
-
25
O
24
35 37
38 .33
39 36
O O
31
27
29 |f9| ZB ^ ( 3(
itCQ ''*
i 32
46
^1 **f
L_O I Ci
PLATE VI.
Parts of Fig. 248.
324 ELECTRIC IGNITION
PLATE VII.
52. High-tension cable with terminal and cable sleeve.
53. Complete base for magneto.
54. Hinged link for closure of the base bearing.
55. Tension screw for 54.
56. Joint nut for 55.
57. Counter nut for 56.
58. Cover of the rear base bearing.
59. Cover of the front base bearing.
60. Oil cover for 58 or 59.
61. Side bearing cover.
62. Mica cover for inspection opening.
63. Ring around opening.
64. Fastening screw for 63.
65. Fastening screw of side bearing-cover.
66. Distributer finger.
67. Fastening screw for distributer finger.
68. Radial distributer carbon with spring.
69. Axial distributer carbon with spring.
70. Distributer case.
71. Fastening screw with nut for distributer case.
72. Large gear-wheel.
73. Case for contact-breaker.
74. Cover for 73.
75. Screw for 74.
76. Carbon holder.
77. Carbon with spring for 76.
78. Carbon with spring for body contact-screw.
79. Shaft of the distributer complete.
80. Spindle for distributer gear-wheel.
8 1. Fastening screw for 80.
82. Disk with safety pin.
83. Fastening screw for 82.
84. Connection piece between carbon holder and distributer.
85. Magneto casing complete without cover.
86. Spring of the closure.
87. Fastening screw for 86.
88. Timing lever.
89. Cover for magneto casing complete.
90. Spring for oil-hole.
91. Fastening screw for 90.
92. Catch-bolt with nut for cover of the magneto casing.
INTERRUPTER MAGNETOS AND JUMP-SPARK IGNITION 325
87 86 88
PLATE VII.
Parts of Fig. 248,
CHAPTER XXI.
HIGH-TENSION DUAL AND COMBINED IGNITION SYSTEMS.
192. Introductory. Of the ignition diagrams in this chapter
those which give the electric connections in detail are either in
accordance with blue prints and drawings kindly furnished by
the manufacturers or their agents, or are diagrams made by the
Author and approved by the manufacturers or their agents.
The illustrations showing the general external appearance of the
ignition systems are generally taken from the trade literature
of those who make and sell ignition apparatus or put it into use.
Most of the detail dia-
grams from manufacturers
and agents have been modi-
fied slightly in unimportant
details in order to make
them conform more nearly
with the conventions used
throughout this book.
Some of the systems repre-
sented are early ones that
were much used at one time,
but have been improved
upon by the manufacturers,
and in some cases almost or
quite discarded by them so
far as new installations are
concerned. It is believed,
however, that these earlier
systems deserve description
on account of the importance
they once had and because
many of them are still in use where they were installed in earlier
constructions.
326
Switch
Fig. 255. (See also Fig. 256.)
Remy High-tension Ignition System.
HIGH-TENSION DUAL AND COMBINED IGNITION SYSTEMS 327
193. Remy Ignition System with Separate Transformer.
The Remy magneto has been described in another chapter. The
general outside appearance of the ignition system used with
this magneto is shown in Fig. 255. A non- trembler transformer
spark-coil with its own condenser is used in connection with both
the magneto and a battery. A turn-switch and a push-button
are mounted on the box which contains the transformer and the
FIG. 256. (See also Fig. 255.)
Internal and External Connections for Remy High-tension Ignition System.
condenser. The battery is for starting the motor on " spark "
by pushing and releasing the push-button when the switch is
set in the battery position.
The wiring connections are shown in detail in Fig. 256. The
insulated terminal 8 of the stationary armature of the magneto
is connected to the contact-point, or pole, M (represented by a
dotted circle), of the switch. The other terminal of the armature
winding is connected to the ground-screw 7 of the magneto. The
ground-screw is connected by a wire to one side each of the
328 ELECTRIC IGNITION
battery, the push-button, and the condenser. The insulated
terminal 13 of the magneto interrupter is connected to the low-
tension terminal F of the transformer, which is also connected
to one side of the condenser. The insulated terminal 13 is also
connected to a crescent-shaped piece of metal C-C in the switch.
C-C is not connected to any of the contact-points, or poles, of
the switch, but is connected to one of the contacts of the push-
button. One side of the battery is connected to the pole B of
the switch. The junction K of the two windings of the trans-
former is connected to both of the poles D and E of the switch.
The high-tension terminal S of the transformer is connected to
the rotor 14 of the distributer. The cross-bar of the switch is
not shown in its position corresponding to that in which the
diamond-shaped switch -handle is represented. It is shown by
broken lines in two positions. In one of these positions, when
connecting M and D, the magneto is cut into circuit so that its
current is used and the battery is out of circuit. In the other
position of the switch-bar, when connecting the poles B and E,
the battery is in circuit and the armature of the magneto is cut
out. The interrupter of the magneto is always kept in circuit,
since it must interrupt the current whether it comes from the
battery or the armature of the magneto. The condenser is in
parallel with both the interrupter of the magneto and the push-
button.
When the switch is set to use magneto current, the path of
the primary current, assuming a direction of flow, is from the
insulated terminal 8 of the armature winding to switch-pole M
through the switch-bar from M to D, thence to H and on to
the junction terminal K of the transformer, through the trans-
former primary to F and on to the insulated terminal 13, which
carries it to the contact-points of the interrupter, from which it
goes through the interrupter lever 9 to the ground-screw 7 to
which the other end of the armature winding is connected.
Since the primary current is an alternating one, it of course
flows in this direction at one impulse and in the opposite direction
at the next impulse.
The secondary current flows from the high-tension terminal 5
HIGH-TENSION DUAL AND COMBINED IGNITION SYSTEMS 329
of the transformer to the rotor 14 of the distributer, and the
rotor directs it to the spark-plugs. From the spark-plugs the
high-tension current goes through ground to the ground-screw 7,
then through the armature winding to 8 and on through the
connecting wire to the switch -pole M, through the switch -bar
to D, thence to H and the junction terminal K of the trans-
former. It is probable that some of the high-tension current
does not go through the armature winding as just stated, but goes
from the ground-screw 7 through the interrupter, jumping the
space which exists at the instant between the contact-points of
the interrupter, so as to reach the insulated terminal 13, then
flows through the connecting wire to F and on through the
primary of the transformer to the junction point K, thus com-
pleting the circuit when the secondary of the transformer is
included. The high-tension current of course also alternates
in its direction of flow in the same manner that the primary
current does while the system is operating on magneto current.
The battery circuit is open at the switch when the magneto is
cut into circuit, since under this condition the pole B of the
switch has no connection with anything but one side of the
battery.
When the switch is set to the battery position, the poles B
and E are connected, and the magneto circuit is left open at the
pole M. The path of the battery current is then from B, through
the switch -bar to E, thence to H and on to the junction terminal
K of the transformer, through the transformer primary to F and
on through the connecting wire to the insulated interrupter
terminal 13, then through the interrupter to the ground-screw 7
and on through the connecting wire to P and the battery. The
path of the high-tension current is from the secondary high-
tension terminal 5 to the distributer, the spark-plugs and ground
in series as before to the ground-screw 7, but from 7 it goes
through the connecting wire to P, thence through the battery
and switch to B and E, then to H and the junction terminal K
of the transformer. Just as in the case of using magneto cur-
rent, part of the secondary current may go from 7 through the
interrupter to the primary terminal of the transformer.
330
ELECTRIC IGNITION
If the push-button contacts are pressed together while the
switch is set in battery position and the contacts of the magneto
interrupter are separated, then current will flow from the battery
to the switch-pole B, switch-bar to E, then to H and on to the
junction terminal K, through the primary winding of the trans-
former to Fj thence to G and on to the crescent-shaped bar
C-C, to and through the push-button and on to P and the
battery. If the push-button contacts are then allowed to spring
apart quickly, the interruption of the batteiy current will cause
a spark to jump at one of the spark-plugs. In this manner a
motor can be started on spark
when there is a combustible
charge in the combustion cham-
ber at whose spark-plug the
spark jumps. The condenser,
being in parallel with the push-
button, aids in the production of
a jump-spark in the same manner
that it aids the interrupter when
the latter is operating.
The push-button can also be
used to cut out ignition when
the motor is running on either
battery current or magneto cur-
rent. This is done by keeping
the contacts of the push-button
pressed together. As long as the contacts of the push-button
are kept pressed together there is a permanently closed circuit,
through which either the battery current or the magneto current,
according to the setting of the switch, can flow without going
through the interrupter. The latter cannot, therefore, interrupt
the current so as to produce an ignition spark as long as the
push-button circuit is kept closed.
194. Splitdorf Ignition System with Separate Transformer.
The magneto used in this system is shown in Fig. 257. It has a
rotary armature of the shuttle type with one winding, and is
provided with a mechanically operated interrupter and a high-
FIG. 257.
Single-wound Magneto with High-
tension Distributer. C. F. Split-
dorf, New York City.
HIGH-TENSION DUAL AND COMBINED IGNITION SYSTEMS 331
tension distributer. The interrupter and distributer end of an
earlier type of the magneto is shown in Fig. 258. This earlier type
is shown because it conforms to the wiring diagram of Fig. 259,
which gives the external appearance of the connections. This
wiring diagram is essentially the same as that for the later form
of the magneto.
10
5 4. 6
FIG. 258.
Interrupter End of Early Form of Splitdorf Magneto. Cover Removed.
Insulated outside terminal of armature winding. Connected to brushes 5,5.
Insulated terminal connected to contact-screw 10.
Ground terminal for connecting to outside wires.
Insulated central rod or screw connected to insulated end of armature coil.
Brushes pressing against 4.
Insulated brush-holder for 5, 5. Connected to A.
Interrupter arm, or lever. Grounded.
Cam for lifting interrupter arm. Grounded.
Tension spring for holding interrupter arm against cam and contact-screw.
Contact-screw. Insulated and stationary.
Bracket for holding contact-screw.
Insulation.
Distributer rotor. High-tension.
Contact-points of terminals for wires leading to spark-plugs.
The electrical connections are shown in detail in Fig. 260.
The magneto operates on the interrupted short-circuit prin-
ciple while using its own current. An elementary system of this
A.
2.
3-
4-
5. 5-
6.
7-
332
ELECTRIC IGNITION
nature has been shown in Fig. 223. When the battery is in use,
the interrupter of the magneto breaks the battery circuit com-
pletely at the instant of ignition.
In the magneto, one end of the armature winding is grounded
to the armature core and consequently to the frame of the
machine. A ground terminal 3 is provided for making connection
to an external wire. The insulated end of the armature winding
is connected to an insulated rod, or long screw, 4, which passes
through the hollow spindle of the armature and projects beyond
the end of the spindle. Two insulated brushes, 5, 5, (which
FIG. 259. (See also Fig. 260.)
Splitdorf High-tension Ignition System.
are replaced by a single brush that bears against the end of
screw 4 in the more recent design) press against the cylindrical
surface of 4 near its outer end. These brushes are carried in
the brush-holder 6 which is electrically connected to the terminal
A. The stationary contact-screw 10 is carried by the insulated
bracket n which has the terminal 2. The interrupter-lever 7
is pivoted at its right-hand end and held against the cam 8 by
the tension spring 9. The cam is mounted on the tubular portion
of the armature shaft. The interrupter-lever is grounded to
the frame of the magneto.
HIGH-TENSION DUAL AND COMBINED IGNITION SYSTEMS 333
When the switch-blade is set in the magneto position, as in
Fig. 260, the battery is cut out of circuit. The primary current
flows from the insulated terminal A of the magneto to the point
B of the switch. When the contact-points of the interrupter
7-10 are separated, as shown, all of the armature current flows
from B on through the switch-blade to its pivot E and then
through the permanent connection from E to F. From F the
current flows to and through the primary winding of the trans-
former spark-coil, then from the junction of the two windings of
FIG. 260. (See also Fig. 259.)
Internal and External Connections for Splitdorf High-tension Ignition System. -
the latter back to the ground terminal 3 of the magneto, which
brings it to the armature winding again. But while the contact-
points of the interrupter are together so as to close the circuit
through the interrupter, the current divides at the switch -blade,
most of it going to the switch-point C and then by the path 2-2
to the insulated contact-point 10 of the interrupter, and thence
through the interrupter-lever to ground and the grounded end
of the armature winding. The resistance of the shunt-circuit
C-2-2-io~7 through the closed interrupter is very much less than
that of the circuit through the spark-coil, therefore most of the
334 ELECTRIC IGNITION
armature current flows through the shunt circuit while the
interrupter is closed. When the interrupter breaks the shunt
circuit, at the instant the armature current is at or near its
maximum value, sufficient current is sent through the spark-
coil primary to cause a spark to pass at the spark-plugs.
The high-tension current, after flowing from the secondary
terminal D to the distributer and one of the spark-plugs in the
usual manner, can return to the spark-coil through the per-
manently closed circuit 3-3. Part of it may go back by way of
the armature and part through the interrupter, however.
When the switch is set in battery position, with the finger
on the blade pointing to " BAT" the armature circuit of the
magneto is left open at B. Battery current then flows to the
switch-point G, on through the switch-blade to F, and thence
through the primary of the spark-coil and the connections to
the ground terminal 3 of the magneto. This brings it to the
grounded interrupter lever 7, from which it flows through the con-
tact-points of the interrupter to 10, and thence through the con-
nections 2-2- H to the battery. The battery circuit is broken
by the interrupter at the instant ignition is to occur, as has been
stated.
The push-button can be used for starting the motor on spark
with battery current, or for cutting out the ignition when the
motor is running on either battery current or magneto current.
Closing the push-button and then allowing its contacts to sepa-
rate quickly, when the switch is in battery position and the
interrupter contacts open, produces an ignition spark at one of
the plugs. Keeping the push-button closed makes a permanent
circuit in parallel with the interrupter, such that the action of the
latter when the motor is running will not cause an ignition spark.
195. Eisemann Ignition System with Separate Transformer.
The external connections of this system are shown in Fig. 261,
and the complete wiring system is shown conventionally in
Fig. 262. The magneto has an armature of the shuttle type
with a single winding and operates on the interrupted shunt-
circuit system. The spark-coil is of the non- trembler trans-
former type. A battery is provided.
HIGH-TENSION DUAL AND COMBINED IGNITION SYSTEMS 335
The switch-handle i is shown in its position for cutting off
ignition, and the switch-plug which goes in the hole 2 is removed.
In order to throw in either the battery or the magneto, the plug
must be inserted at 2 and the switch-handle thrown either to the
left or right, according to whether the magneto or the battery is
FIG. 261. (See also Fig. 262.)
Eisemann High-tension Ignition System, Early Form. Eisemann-Magneto
Company, New York, N. Y., and Detroit, Michigan.
to be put into operation. The handle of the switch is hinged at
the center of the large circle. The arm which extends from the
center of the large circle up to 2 does not swing with the handle,
but remains permanently in the position shown.
When the magneto is cut into circuit by putting the plug into
the hole at 2 and throwing the switch to the left so as to make
336
ELECTRIC IGNITION
connection between the contact-pieces 3 and 4, referring more
particularly to Fig. 262, the current from the magneto terminal
Ma flows through the connecting wire to the switch-point 4 and
switch-blade i. The current divides at the switch-blade when
the interrupter 7-8 of the magneto has its contact-points together
FIG. 262. (See also Fig. 261.)
Internal and External Connections of Early Form of Eisemann High-tension
Ignition System.
so as to close its circuit. Most of the current then flows through
the low-resistance shunt circuit from i to the plug in 2, then to 6
and on through the connecting wire to the stationary contact-
point 7 of the interrupter and to the interrupter-lever 8, which
brings it to the grounded end of the armature winding 10. A
small portion of the current flows from i to the switch-point 3
and on to 12 and the primary winding of the spark-coil 1 1 , then
HIGH-TENSION DUAL AND COMBINED IGNITION SYSTEMS 337
from the junction of the two windings of the coil to the terminal
MB and on to ground at 13, thus returning to the ground end
of the armature winding of the magneto. At the instant that
the interrupter breaks the shunt circuit by separating the con-
tact-points 7 and 8, a comparatively large current is sent through
the primary of the spark-coil and a jump-spark passes between
the points of one of the spark-plugs. The high-tension terminal
H of the spark-coil is connected to the rotor 14 of the distributer,
which is of the usual form.
When the battery is in circuit, the switch-blade being thrown
to the right to make contact with the switch- point 5, and the
plug in at 2, the magneto armature is on open circuit. Current
flows from the positive (+) side of the battery through the
connection B-I2 to the primary winding of the spark-coil and
thence through MB to ground at 13. This brings it to the
interrupter lever 8, from which it passes through the closed con-
tact-points to the stationary contact-piece 7 and thence through
R to the switch terminal 6, then through the plug in 2 and on
through the switch-blade i, which is in contact with 5, and on
to the negative ( ) side of the battery. Interruption of the
current by the separation of the contact-points of the interrupter
produces a spark at one of the spark-plugs.
The condenser 9 is in parallel with the interrupter in the usual
manner. A safety spark-gap is shown at 15.
196. Eisemann-Carpentier Ignition System. Figs. 263 and
264. In this system the battery has its own timer and trembler
spark-coil, and the magneto has its own mechanically operated
interrupter and a non-trembler spark-coil. The same distributer
is always used for directing the high-tension current to the spark-
plugs. The two spark-coils are inclosed in the same box, which
has a hand-switch for throwing in either the battery or the
magneto, or for cutting both out of circuit.
The movable part of the switch is represented conventionally,
in Fig. 264, as a piece of insulating material i to whose ends are
fastened two metal contact-pieces 2 and 3. The stationary
contact-points of the switch are 4 and 5 for the battery circuit,
6 and 7 for the magneto circuit, and 8, 9, and 10 for the high-
ELECTRIC IGNITION
tension circuits. The timer is of the form common to battery
ignition systems with individual spark-coils of the trembler type,
but is modified by connecting all of the stationary contact-points
together with a wire 16.
The switch is shown set for using battery current. The path
of the current is from the positive (-h) side of the battery to
the terminal P and switch -pole 4, through 2 to 5, thence to the
trembler interrupter n and primary winding of transformer 17,
from which it flows to ground by the path 12-13-14. This
brings it to the rotor 15 of the timer, from which it goes to the
Timer
Magneto
FIG. 263. (See also Fig. 264.)
Eisemann-Carpentier High-tension Ignition System.
negative ( ) side of the battery. The high-tension current
follows the path from the secondary terminal 19 to the switch-
pole 8, then through 3 to switch-pole 9, thence to terminal H
and on to the rotor 21 of the distributer, which directs it to the
spark-plugs. From the ground side of the spark-plug the high-
tension current has the permanent circuit 14-13-12 back to the
spark-coil 17.
When the switch is set to the position for magneto current,
the part 2 connects the poles 6 and 7, and the part 3 connects
poles 9 and 10. The magneto is of the interrupted shunt-circuit
type. During the time the interrupter parts 23 and 24 are in
HIGH-TENSION DUAL AND COMBINED IGNITION SYSTEMS 339
contact with each other (interrupter closed) most of the armature
current flows from 23 through the interrupter lever 24 to ground
and thence to the grounded end of the armature winding 25. A
small portion of the armature current flows at the same time
from 23 through the path 22-MG to the switch -pole 7, then
FIG. 264. (See also Fig. 263.)
Internal and External Connections of Eisemann-Carpentier High-tension Ignition
System.
through 2 to 6 and on to the non- trembler transformer 18,
through whose primary winding it flows, and then to ground by
the path 12-13-14. This brings it to the grounded end of the
armature winding. At the instant the shunt circuit is broken
by the interrupter of the magneto, a comparatively large current
is sent through the transformer circuit just followed out, and
340 ELECTRIC IGNITION
a spark is caused to jump at one of the spark-plugs. The high-
tension current goes from the secondary terminal 20 to switch-
pole 10, then through the metal 3 on the switch-bar to pole 9
and on to the rotor 21 of the distributer.
The push-button 26 is for starting the motor on spark. The
switch must be set in battery position, as shown, when doing
this, and the timer rotor must not be in contact with any of the
stationary contacts of the timer. Pressing the push-button
then closes the battery circuit through the trembler coil 17. If
the rotor of the timer is in contact with one of the stationary
contact-pieces of the timer while the motor is standing still, the
battery circuit is then closed through the trembler coil when the
switch is in the position shown.
The safety spark-gap 27 is for protecting the trembler coil 17,
and the safety -gap 28 answers the same purpose for coil 18.
The condenser 29 is in parallel with the trembler interrupter
n, and condenser 30 is in parallel with the interrupter 23-24 of
the magneto.
The rotor of the timer and the interrupter of the magneto
must be set so that the instant of ignition will not be greatly
changed by switching from one source of primary current to the
other.
197. Bosch Dual Ignition System. Fig. 265. This system
operates on magneto current or on battery current, according
to the position of the switch. It comprises a high-tension mag-
neto having two interrupters and a double-wound armature of
the rotary shuttle type, a transformer spark-coil in conjunction
with a switch, a battery, and jump-spark igniters as its chief
elements. Of the two mechanically operated interrupters in
the magneto, one is for the battery current and the other for
magneto primary current. The transformer coil is not in action
while the system is operating on magneto current.
The transformer is of the non-trembler type, so far as its
operation while the motor is running is concerned, but it has a
trembler interrupter to be used for starting the motor on spark.
When the switch is in battery position, pressing the push-
button lightly closes the battery circuit at the trembler inter-
HIGH-TENSION DUAL AND COMBINED IGNITION SYSTEMS
341
rupter, and the trembler then begins to vibrate so as to inter-
rupt the battery current through the spark-coil, provided the
magneto has not stopped in such a position as to keep the
battery circuit closed on account of its interrupter contacts
being pressed together. But if the battery circuit is closed in
the magneto, as just stated, then a harder pressure on the push-
button, followed immediately by release of pressure, produces a
spark at the igniter at the instant of release of pressure.
Spark-coil Side view
and Switch of coil
Battery
Sec.to Dist.
Mg.Sec.to Switch
Mg.Grounding Wire
FIG. 265. (See also Figs. 266, 267, and 268.)
Bosch Dual High-tension Ignition System.
The interrupter end of the magneto is shown in Fig. 266. In
this figure, the interrupter for the current generated in the pri-
mary winding of the magneto is called the " magneto inter-
rupter," and that for interrupting the battery current is called
the " battery timer." Both of these are of the rocking-lever
type.
The magneto interrupter rotates with the magneto armature.
A piece of fiber in one end of the lever strikes against cam-
lobes so that a rocking movement of the lever is produced twice
342
ELECTRIC IGNITION
during each revolution of the armature. The upper end of the
lever, as shown in the illustration, is in contact with one of the
cam-lobes. The part to which these cam-lobes are attached does
not rotate, but can be rocked by the spark control to vary the
time of ignition. The contact-piece which carries the "inter-
rupter adjustment " is connected to the junction of the primary
OH TENSION CONNECTION
FIG. 266.
High-tension Magneto with Two Interrupters for Fig. 265.
and secondary windings of the armature and to the insulated
" short-circuiting terminal," but is insulated from the other parts
of the magneto. The interrupter-lever of the magneto inter-
rupter is electrically connected to the frame of the magneto.
The battery timer does not rotate. Its interrupter-lever is
operated by a two-lobed steel cam which revolves with the
armature of the magneto. This cam is in the form of a. steel
ring with outwardly projecting lobes. The interrupter-lever of
HIGH-TENSION DUAL AND COMBINED IGNITION SYSTEMS 343
the battery timer is electrically connected to the frame of the
magneto. The " timer adjustment " and the " battery con-
nection " are electrically connected together and are insulated
from the other parts of the magneto. The battery timer moves
with the " timing control arm " when the latter is rocked to
vary the time of ignition.
The " high-tension connection " is in permanent electric con-
nection with the distributer brush.
The beginning of the primary winding of the armature is
electrically connected to the armature core and thence to the
FIG. 267. (See also Fig. 268.)
Transformer Spark-Coil and Switch for Fig. 265.
frame of the magneto; the high-tension end of the secondary
winding is connected to a slip-ring against which bears a brush
that is carried by the insulated brush-holder 3, Fig. 265. There
is no connection, in the magneto, between the high-tension
winding of the armature and the distributer. It has been
stated that the junction of the two armature windings is con-
nected to the insulated part of the magneto interrupter.
The combined spark-coil, switch, and push-button starter are
shown assembled in Fig. 267. The coil body, the connecting
plate of the switch, and the protecting cover for it are shown
344
ELECTRIC IGNITION
separately in Fig. 268. The switch is provided with a lock and
removable key, by means of which it can be locked so that the
ignition system cannot be used.
When the switch is in battery position, the battery circuit is
closed at the coil, and the high-tension terminal of the trans-
former coil is connected to the central terminal 4 of the distrib-
uter of the magneto. The short-circuiting terminal 2 of the
magneto is also connected to ground through the switch so as
FIG. 268.
Parts of Fig. 267.
to prevent the induction of high pressure in the magneto arma-
ture, and the high-tension terminal 3 of the magneto is on open
circuit at the switch. Under this condition the magneto is elec-
trically inactive, although its parts move mechanically in the
usual manner. The battery timer interrupts the battery cur-
rent, which flows through the primary winding of the spark-
coil, thus inducing high-tension current in the secondary of the
spark-coil, which current flows to the distributer brush of the
magneto and is distributed to the spark-plugs.
When the switch is in magneto position, the battery circuit
and the high-tension circuit of the spark-coil are both open at
HIGH-TENSION DUAL AND COMBINED IGNITION SYSTEMS 345
the switch, thus making the battery circuit inoperative. The
short-circuiting circuit is open at the switch, and the high-
tension terminal 3 of the magneto is connected, through the
switch, to the distributer terminal 4 of the magneto. The
magneto then generates and delivers high-tension current to the
spark-plugs. The battery timer is electrically inoperative under
this condition, but moves mechanically in the usual manner.
197.1. Duplex High-tension Ignition System Having a Bat-
tery in Series with the Primary Winding of the Magneto. -
The complete system is shown in Fig. 269. Its essential parts
.Kick Coil
and Switch
L Keylock
K Kick lever
O Off position
B Battery operating
M Magneto operating
P Press button
FIG. 269. (See also Figs. 270, 271, and 272.)
Bosch Duplex High-tension Ignition System.
are the spark-plugs; a battery; a combined kick-coil, switch, and
push-button; and a magneto of the double- wound shuttle-arm-
ature type provided with a two-segment commutator and com-
mutator brushes in addition to the mechanically operated inter-
rupter. The connections between the magneto, the battery, and
the kick-coil are shown more distinctly in Fig. 270. The kick-
coil, Fig. 271, has only one winding, and is provided with a key
lock for preventing the use of the ignition system while the
coil is locked. The interrupter end of the magneto is shown in
Fig. 272.
The switch can be set for operating the magneto system on
both battery and magneto current, at the same instant, and for
346
ELECTRIC IGNITION
operating on magneto current only. The real purpose of the
battery is to supply current for starting the motor, either on
spark by using the push-button, or when cranking the motor
or otherwise driving it by power from some external source.
Referring to the magneto, Fig. 272, the beginning of the
primary winding of the shuttle-wound armature is grounded to
the armature core. The junction of the two windings is con-
nected to the insulated side of the interrupter. This side of the
6 Volt Battery
+
Switeh.Plate of J
Coil 1
If Engine starts but will not continue to run
reverse the battery connections
FIG. 270.
Low-tension Connections for Bosch Duplex Ignition System.
interrupter has the means of adjustment for one of the plat-
inum contact-points. The high-tension end of the secondary
winding is connected to the distributer brush by means of a
slip-ring, brushes, and other suitable connectors, or other corre-
sponding devices. The interrupter-lever is grounded to the frame
of the magneto.
The characteristic feature of this magneto consists of a two-seg-
ment commutator whose insulated segments are fastened to the
inner side of the interrupter cover, and a pair of carbon brushes,
A and B, which make sliding contact with the commutator.
HIGH-TENSION DUAL AND COMBINED IGNITION SYSTEMS 347
Brush A is carried by and electrically connected to the insulated
side of the interrupter, and brush B is electrically connected to
the grounded lever of the interrupter. Each commutator seg-
ment has an insulated terminal connected to it. These two
terminals are on the outer side of the interrupter cover. They
are numbered i and 2 in Figs. 269 and 270.
When the switch is set in its battery-magneto position, one
side of the battery is connected to terminal i of the commutator,
and the other side of the battery is connected to terminal 2 of
FIG. 271.
Single-wound Kick-Coil for Fig. 269.
the commutator. As shown in Fig. 270, the positive (+) side
of the battery is permanently connected to terminal i of the com-
mutator, and, when the switch is in battery-magneto position,
the negative ( ) side of the battery is connected to terminal 2
of the commutator. Then, while the armature is standing still
with brush A in contact with the commutator segment to
which terminal i is connected, and carbon brush B in contact
with the commutator segment connected to terminal 2, current
flows from the positive side of the battery to brush A , thence in
parallel through the interrupter contacts and the primary of the
348 ELECTRIC IGNITION
armature in parallel while the interrupter contacts are together,
or through the primary of the armature alone while the inter-
rupter contacts are separated, to brush B and the commutator
segment connected to terminal 2, and on back through the
switch to the negative side of the battery. The current thus
flows into the insulated end of the primary of the armature and
out of the grounded end of the primary, while the conditions
are as just described. The ohmic resistance of the kick-coil
limits the battery current to a safe amount. When the arma-
ture and the interrupter have been rotated to a position to
bring the brush B into contact with the segment connected to
terminal i, and brush A into contact with the segment con-
nected to terminal 2, then, while the armature is at rest, the
battery current flows through the armature primary in the
opposite direction. By quickly separating the closed contacts
of the interrupter while battery current is flowing through them,
the consequent interruption of the battery current sends a
sudden impulse of battery current through the primary of the
armature so as to induce an electromotive force in the secondary
high enough to produce a spark at the igniter. The reaction
of the kick-coil helps to make the impulse current sufficiently
large. The direction of flow of this impulse current is the same
as that of the small amount of battery current that flows through
the primary before the contact-points are separated.
If the battery current is now cut off, either by disconnecting
one of the battery wires, or by moving the switch to its magneto
position, both of which have the same effect, then rotating the
magneto armature induces an alternating current in its primary
winding. The direction of flow of this generated primary cur-
rent at any instant is opposite that which the battery current
had, as just described. The interruption of the generated cur-
rent produces a spark at the igniter when the speed of rotation
of the armature is sufficiently high.
While the switch is in its battery-magneto position, so that
the battery is connected to the magneto as has been described,
then the electromotive force generated in the armature primary
by the rotation of the armature opposes the tendency of the
HIGH-TENSION DUAL AND COMBINED IGNITION SYSTEMS 349
battery to send current through the armature primary. While
the rotative speed of the armature is extremely slow, the battery
current predominates in the armature winding. The ignition
spark under this condition is due to the interruption of the
portion of the battery current that flows through the contact-
points.
At some speed of the armature slightly higher than that just
mentioned, and at the instant the contact-points just begin to
separate, the generated electromotive force in the armature
primary just balances the tendency of the battery to send
current through the armature primary. There is consequently
no flow of current in the armature primary at the instant of
interruption of the battery current, all of which flows through
the contact-points just before its interruption. Under this
condition the ignition spark is due to the interrupted battery
current.
At high speeds of rotation, the electromotive force generated
in the armature primary sends a current through the primary
in the direction opposite that in which the battery current
flows through it while the armature is not rotating, or is rotat-
ing at extremely slow speed. This generated current and the
battery current flow together in the same direction through the
contact-points of the interrupter just before the contact-points
are separated. The separation of the contact-points then stops
the flow of the generated current through the armature primary
and sends an impulse of battery current through the primary
in the direction opposite that in which the generated current
was flowing. This sudden decrease of generated current and
increase of battery impulse current is in effect a reversal of
current in the primary, and it induces pressure in the secondary
of the armature sufficient to make an ignition spark at the
igniter.
At ordinary operating speeds of the magneto the electro-
motive force induced in the armature primary reduces the bat-
tery current to an amount less than that which flows while the
armature is at rest or rotating at slow speed. Therefore, even
though the switch is left in battery-magneto position while
350
ELECTRIC IGNITION
COMMUTATOR SEGMENTS
FIG. 272.
Bosch Duplex Magneto for Fig. 269.
HIGH-TENSION DUAL AND COMBINED IGNITION SYSTEMS 351
running, the battery does not deliver much current, and the
operation of the system is chiefly on magneto current.
When the switch is set in its magneto position, the battery is
cut out of circuit completely.
In the off position of the switch the battery is cut out and
the wires between the magneto and the switch are connected
together at the switch, thus short-circuiting the magneto pri-
mary so as to prevent the interruption of the primary current
and the generation of pressure in the magneto high enough to
cause an ignition spark.
Pressing the push-button while the switch is in its battery-
magneto position breaks the battery circuit provided the arma-
ture of the magneto is in such a position that the contacts of
the interrupter are separated. The sudden stoppage of cur-
rent thus caused in the magneto primary induces a pressure in
the secondary that forces a spark across the spark-gap of the
igniter. But if the interrupter contacts are together so as to
close the circuit through them, then, although pressing the
button breaks the battery circuit and stops the flow of current,
no ignition spark is produced. This is because the amount of
battery current that flows through the magneto primary while
the interrupter contacts are together is so small that it will not
produce an ignition spark when it is interrupted.
If the battery is connected to the magneto in the reverse
manner from that shown, so that the positive (+) side of the
battery is connected to terminal 2 of the magneto, and the
battery negative ( ) to terminal i, then, although the motor
can be started by pressing the push-button or by slow rotation
of the motor and the magneto, ignition will cease as soon as the
motor gains some speed, the switch still remaining in battery-
magneto position. This is because the battery current and the
current generated in the magneto primary flow in the same
direction through the primary. Under this condition the
amount of current flowing through the interrupter contacts at
the instant their separation begins is not sufficient to produce an
ignition spark when the current through the contact-points is
interrupted.
352 ELECTRIC IGNITION
198. Magneto with Two High-tension Windings for Dual
Ignition. In this system, one of the two high-tension windings
of the magneto is used in connection with its own set of spark-
plugs, and the other high-tension winding with its own set of
spark-plugs. Two ignition plugs are put in each combustion
chamber and are caused to spark at the same instant on high-
tension current from the magneto. One of these plugs is con-
nected to one of the high-tension windings of the magneto, and
the other plug to the other high-tension winding. The two
plugs thus receive current from different windings. The inter-
ruption of the current in the primary winding of the magneto
armature induces the sparks at the two plugk in the same com-
bustion chamber at the same instant, as stated.
CHAPTER XXII.
HIGH-FREQUENCY ALTERNATING-CURRENT MAGNETOS.
199. Introductory. The high-frequency magnetos described
in this chapter can be substituted for the battery in battery
ignition systems which have a trembler spark-coil and a timer
for closing the low-tension circuit at, or slightly before, the
instant of ignition, provided the trembler of the spark-coil is
one that has a high rate of vibration. The trembler must be
sensitive. In some such ignition systems a battery is used for
starting, and the magneto is then switched on to supply the
low-tension current. The battery is cut out when the magneto
is switched on. The magneto does not of necessity rotate in
synchronism with the motor, and can therefore be driven by a
belt or other form of friction drive. The magneto is run at a
speed high enough to generate a low-tension current whose
alternations are rapid enough to cause only a slight variation
in the instant of ignition so far as affected by lack of synchronism
between the rotation of the magneto and motor. The rapidity
of alternation of the current is limited by the degree of prompt-
ness with which the trembler responds to the magnetic attraction
caused by the flow of current through the spark-coil. The
inductive resistance of the spark-coil is also a factor to be con-
sidered in determining how rapidly the current can alternate.
Magnetos of this type have the advantage of being extremely
simple in form and inexpensive.
200. The W. & S. magneto is shown in Fig. 273 in complete
form. Figs. 274, 275, and 276 show groups of different parts
of the magneto. Fig. 277 gives the positions of the inductor
arms relative to each other; also the path of magnetic flux.
The armature winding C is a single spiral coil of insulated
copper wire with terminals at D and Di. This stationary coil
encircles the neck between the two rotary inductor spiders A
353
354
ELECTRIC IGNITION
and B, each of which has three arms. These spiders are pinned
to a shaft K which runs on two ball bearings and is driven by a
belt on the pulley E. One of the ball bearings is indicated by
FIG. 273. (See also Figs. 274, 275, 276,
and 277.)
High-frequency Low-tension Magneto with
Stationary Armature and Rotary In-
ductor. Wheeler & Schebler, Indianap-
olis, Indiana.
FIG. 274.
Parts Remaining after Magnets are
Removed from Fig. 273.
the letter M. The bearing farthest from the pulley is supported
by the end-piece P. The pole -pieces F and Fi are separated by
FIG. 275.
Inductor, Pulley and Spirally-wound Armature of Fig. 273.
the aluminum piece G (non-magnetic) and are fastened to the
non-magnetic base H. The only moving part of the magneto
is the rigidly connected group made up of the inductor spiders,
the pulley, and the shaft upon which they are mounted.
HIGH-FREQUENCY ALTERNATING-CURRENT MAGNETOS 355
FIG. 270.
End View of Fig. 274.
In Fig. 277 the spider with the arms Ai, A2, and A$ is in
front of the armature coil C, and the spider with the arms Bi,
B2, and 3 is in the rear of
the coil. It can be seen that
the arms of one spider lie
opposite the angles between
the arms of the other. While
the inductor is in the position
shown in Fig. 277, the path of
magnetic flux is from N along
the broken line L, through the
arm Ai, then back through
the neck of the inductor (and
the opening of the coil) to the
rear spider and out through
the arm Bi to S. When the
inductor has rotated one-
twelfth of a revolution there
is no magnetic flux through the neck between the two spiders.
One of the spiders is then in the position shown in Fig. 276,
neglecting the lettering of this
figure. When the inductor has
revolved clockwise one-sixth
of a revolution from the posi-
tion shown in Fig. 277, so as
to bring the arm B2 opposite
the pole-piece Fi, and A\
opposite Fj then the magnetic
flux is from Nmto the inductor
arm B2 and forward through
the inductor neck to the spider
A , then out through arm A i
to S. Similar changes of flux
occur twice more during the
FIG. 277. remainder of the revolution.
Outline of Fig. 273. xhe result is that six impulses
of current are generated during one revolution of the inductor.
356
ELECTRIC IGNITION
The rotative speed of the inductor should be about three
times that of the motor crank-shaft for high-speed motors, and
at a higher relative speed for slow-speed motors.
201. K-W High-frequency Magneto. This magneto has a
stationary spiral-wound armature coil and a rotary inductor
with four arms. Fig. 278 is an exterior view of the type that
FIGS. 278 and 279. (See also Figs. 280 and 281.)
Two Forms of K-W High-frequency Magneto with Stationary Armature and
Rotary Inductor. The K-W Ignition Company, Cleveland, Ohio.
has the armature and inductor at the bottom when the machine
is set in the position that is in accordance with its design. Fig.
279 is designed to operate with the armature and inductor at
the top. The internal construction is shown in Fig. 280. One
of the straight bars, each of which forms two arms of the rotary
inductor, is shown with its crowned end A nearest to the observer.
The other bar of the inductor has its end B nearest to the ob-
server. These bars are laminated. They are mounted on a shaft
HIGH-FREQUENCY ALTERNATING-CURRENT MAGNETOS 357
FIG. 280.
View showing Armature and Inductor of Figs, 278 and 279.
and joined together by a large neck that
is encircled by the armature coil C.
The two arms, A and B, of the inductor
are at right angles to each other, as
shown in Fig. 281. This figure also
shows the position of the armature and
inductor relative to the pole-pieces N
and S of the magnets.
The action of this machine in generat-
ing a current is similar to that of the
W. & S. magneto that has been described,
except that the K-W machine produces
four impulses per revolution of the in-
ductor, instead of six.
The armature and the inductor are
inclosed in a cylindrical case which is
practically water-tight.
The makers recommend a speed from
two and a half to three times that of
the crank-shaft of a high-speed motor.
For low-speed motors the magneto
should have a higher speed as compared
with that of the motor crank-shaft. It should not run much
slower than for the high-speed motor.
FIG. 281.
Outline of Field-magnets,
Armature and Inductor
of Figs. 278 and 279.
358
ELECTRIC IGNITION
FIG. 282.
(See also Figs. 283, 284, and 285.)
Armature of Ford High-frequency
Magneto.
202. The Ford high-frequency magneto has several spool-
shaped armature coils spaced at equal distances in a circle, with
the axes of the spools all parallel
to each other and to the axis of
rotation of the inductor. Fig. 282
shows sixteen spools mounted in
this manner with their windings
connected so that the coils are in
series with each other. One pair
of coils are not connected to each
other, but the ends of the windings,
one end for each coil, are left free
for terminals. The inductor has
several V-shaped magnets such as
shown in Fig. 283. Sixteen of these
magnets are bolted to the flywheel
of the motor, with the angle of the
V next to the center of the flywheel, as shown in Fig. 284. The
north poles of the magnets are placed next to each other,
and the south poles likewise next to each other. The
magnets rest on a non-magnetic ring at about one-third
of the length of the magnets in
from their outer ends. The
complete assembly is shown in -pic. 283.
Fig. 285, together with some Oneofthe
of the transmission mechanism V-shaped
of an automobile. The spools Magnets
, ,, ,. used in
are mounted on the stationary Fi 2g
casing that incloses the fly-
wheel and plane tary change-speed gears .
Sixteen electric impulses are pro-
duced during each revolution of the
flywheel (inductor) when that number
of coils and of magnets are used. The
FIG.
Rotary Magnet Inductor
for Fig. 285.
current is passed through a trembler spark-coil in the usual man-
ner, a timer being used to close the low-tension (magneto) circuit
just before the instant that ignition is to occur in the motor.
HIGH-FREQUENCY ALTERNATING-CURRENT MAGNETOS 359
While the rotor of the magneto is in such a position that the
magnet-poles are opposite the ends of the coils, as shown in
Fig. 285, then, taking any three consecutive coils, A, B, C, of
which the middle coil B is opposite the north poles of two adja-
cent magnets, i and 2, the S pole of i opposite A, and the S
pole of 2 opposite C, the magnetic flux is as follows: From the
FIG. 285. (See also Figs. 282, 283, and 284.)
Ford High-frequency Low-tension Magneto Embodied with Other Parts.
two N poles through the coil B to the casing which carries the
coils. The flux then divides and goes in opposite directions
through the casing to the cores of A and C. The portion which
goes to A then goes through the core of that coil to the S pole
of magnet i and on through the bar of magnet i back to its N
pole. In a similar manner, the portion that goes to coil C goes
through the core of C to the 5 pole of magnet 2 and thence
through the bar of 2 back to the N pole.
When the inductor has rotated half the distance between the
centers of two adjacent coils, so as to bring the magnet poles
opposite the spaces between the coils, then there is no magnetic
flux through the cores of the coils. When the inductor has
360 ELECTRIC IGNITION
rotated from its first-mentioned position through a distance
equal to that between the centers of two adjacent coils, so as to
bring the magnet-poles opposite the coils again, the magnetic
flux through the cores of the coils will be in the opposite direction
from that for the first position mentioned.
CHAPTER XXIII.
VARYING THE TIME OF IGNITION. MULTIPLE IGNITION.
203. Advancing the Timer on Account of Lag in the Ignition
Apparatus. It has been stated, in connection with ignition
systems which comprise a trembler interrupter, that, in vari-
able-speed motors, the timer must be moved so as to interrupt
the primary current earlier in the stroke of the piston when the
speed of rotation of the motor crank-shaft is high than when it
is low. The reason that was given for the necessity of thus
advancing the timer was that there is a certain amount of lag
in the operation of the ignition apparatus after the timer has
closed the primary circuit, which lag covers the time interval
between the instant of closing the primary circuit by the timer
and the jumping of a spark between the ignition points of the
igniter.
Since the time interval of lag, measured as a fraction of a
second, is constant whatever the rotative speed of the motor,
the rotative movement of the crank-shaft of the motor during
the period of lag is greater when the motor is running fast than
when it is running slowly. If the timer is set so that the spark
jumps while the crank-shaft is in its dead-center position when
the motor is rotated very slowly, as when turning it by exterior
power for starting it, then the spark will not jump till after the
crank-shaft has passed its dead-center position when the motor
begins to run on its own power. The angular movement of the
crank-shaft from its dead-center position to its position when the
spark jumps will be greater when the rotative speed is high than
when it is low. Thus, at 1000 revolutions per minute, the crank-
shaft will move twice as far beyond its dead-center position
before the spark jumps as it will when rotating at 500 revolu-
tions per minute. The lag of the spark is proportional to the
rotative speed of the motor when the timer remains at the same
361
362 ELECTRIC IGNITION
position. In order to have the ignition spark jump at the in-
stant the crank-shaft is passing through its dead-center position,
the timer must be advanced as the speed of the motor increases.
The amount of this advance is proportional to the speed of the
motor, if the initial position of the timer is that which gives a
spark at dead-center position of the crank-shaft when the latter is
rotated at a very slow speed by exterior power, as has been stated.
In ignition systems whose interrupter is mechanically oper-
ated, the lag is much less than in one operating with a trembler
interrupter. Mechanical interrupters of the types ordinarily
used on magnetos entirely eliminate mechanical lag. This is
also substantially true of other forms of mechanical interrupters
in which the moving part which causes the interruption of the
current is moved by a spring to cause the interruption, pro-
vided the spring-actuated part is of light weight and moved by
a spring powerful enough to produce a very rapid movement.
In ignition systems operating with a trembler interrupter,
the movement of the spark-control lever to advance the timer,
ordinarily called " advancing the spark/' does not actually ad-
vance the time at which the ignition spark jumps relative to
the movement of the piston when the rotative speed of the
motor is increasing, unless the advance of the timer is sufficient
to more than counterbalance the effect of the increasing speed.
The advance of the timer in trembler-interrupter ignition
systems must be greater than in those with mechanically oper-
ated interrupters. This is in accordance with the facts that
have just been stated.
204. Variation of the Time of Ignition Relative to the Rate
of Combustion of the Charge in the Motor. This can be most
conveniently discussed first in connection with motors which
run at a constant speed.
The rate of burning (combustion, explosion) of the charge in
the motor cylinder varies in accordance with the composition of
the combustible mixture and the intensity of compression.
There is a certain proportion of air and fuel, for each kind of
fuel, that burns more rapidly than a mixture containing either
a greater or less proportion of fuel. The mixture which has
VARYING THE TIME OF IGNITION 363
the highest rate of combustion may be called the normal mix-
ture for that particular fuel. The proportions of air and fuel
in the normal mixture are different for the different kinds of
fuel, and the rate of burning is in general different for the nor-
mal mixture of each kind 'of fuel. In general, a normal mixture
which has a high heating value has a higher rate of burning
than a normal mixture which has a lower heating value. There
are apparently exceptions to this statement, however, since
some of the permanent gases used in combustion motors have a
higher rate of combustion than others.
If a stationary engine operating on producer gas has its
ignition properly timed for a normal mixture while the producer
is delivering rich gas (of high heating capacity for that kind of
gas), and the gas then becomes lean (of less heating capacity)
after the manner of operation of producers, the combustible
mixture going into the engine will then become lean if the setting
of the proportioning device remains unchanged. The ignition
will then have to be advanced to secure the most efficient re-
sults for the kind of mixture then received. This is because the
lean mixture is slower burning than the normal mixture, and
unless it is ignited earlier than the normal mixture, combustion
will be completed too late in the stroke of the piston to secure
the maximum impulse effect against the piston to drive it. In
the same manner, if the ignition is properly timed for normal
mixture when the producer is delivering lean gas, the ignition
will have to be advanced if the gas coming from the producer
becomes very much richer and the setting of the gas-propor-
tioning device is not changed. In this case the over-rich mix-
ture is slower burning than the leaner normal mixture. The
variation of the timing is not so great in the latter case, however,
as when the change is from a normal mixture using rich gas to lean
gas. Upon setting the proportioning device so as to obtain a
normal mixture with the rich gas, the ignition should be retarded.
Relative to variation in the intensity of compression of the
combustible charge, ignition must be advanced when the com-
pression is reduced, in order to secure the maximum amount
of power from the charge ignited. Some engines, while operat-
364 ELECTRIC IGNITION
ing on a normal mixture made from gas of a constant com-
position, are regulated to meet the varying demand for power
by admitting to the cylinder an amount of mixture approxi-
mately proportional to the power which the engine is called
upon to deliver. If an engine, governed to approximately con-
stant speed in this manner, is operating on full load with its
ignition properly timed, then if the load falls off so as to be-
come light, the ignition must be advanced on account of the
reduced compression and consequent lower rate of combustion.
When the full load comes on again, the ignition must be re-
tarded to its initial position. This refers to the time of igni-
tion for obtaining the maximum efficiency in the use of the fuel.
The above statements, modified to suit the conditions, are
applicable to motors using liquid fuel.
205. Varying the Time of Ignition with Variation of Speed. -
Since the combustible mixture takes an appreciable amount of
time to burn, or explode, in the motor cylinder, it must be
ignited earlier in the movement of the piston when the motor
is running at high speed than at low speed, in order to obtain
the maximum amount of power from the fuel consumed.
The extent of the variation of the time of ignition in accord-
ance with the variation of speed depends on the kind of ignition
cystem used and the location of the igniter, or igniters, in the
combustion chamber. An ignition system which gives a spark
of constant strength regardless of the speed of rotation of the
motor must have the time of ignition varied more with varia-
tion of speed than is the case for a system which gives a stronger,
or hotter, spark as the speed of rotation of the motor increases.
If the igniter is located away from the body of the mixture in
the combustion chamber, as in the pocket over the valve, or
between the valves, of some types of motors, then the ignition
must be more advanced than when the ignition spark is made
nearer to the center of the volume of the charge.
Most ignition systems operating on battery current give a
spark whose strength is the same whatever the speed of the motor.
On the other hand, most magneto ignition systems using cur-
rent direct from the magneto give a stronger spark as the speed
VARYING THE TIME OF IGNITION 365
of the motor, and consequently that of the magneto, increases.
Less advance of the spark is, therefore, required in magneto
systems of this nature than in battery systems. This state-
ment applies to the actual occurrence of the ignition spark, or
arc, and is not intended to include the lag which occurs in a
system operating with a trembler interrupter. The lag due to
the trembler makes additional advance of the timer necessary.
206. Reduction of Variation of Ignition by the Use of Two
Simultaneous Ignition Sparks. It is common practice in gas
engines of large size to have two or more simultaneously oper-
ated igniters in each combustion chamber. These are generally
located some distance apart and in such positions as to have at
least one of them in the part of the combustion chamber where
the mixture is such as to be easily ignited when there is a re-
duction in the amount of gas admitted on account of light
demand for power. Aside from the greater certainty of pro-
ducing ignition of the charge, the use of igniters at more than
one place decreases the time required for combustion when
ignition occurs at more than one locality. This is due to the
fact that each of the propagating flames emanating from the
points of ignition has a less distance to travel when ignition is
at more than one point than when it is at only one point. The
whole charge becomes inflamed quicker when ignited at two
widely separated points than when ignited at one point only.
Since combustion is completed more rapidly with ignition at
two or more points, there is less movement of the piston and
crank-shaft during combustion, and consequently less advance
of ignition is required. This means that there is less variation of
the time of ignition under different conditions of the composition
of the combustible mixture and of compression of the charge.
The decrease in the time occupied by combustion, as this de-
crease is effected by the use of two simultaneous ignition sparks
at widely separated positions, when compared with single
ignition, is more decided when the single igniter is located at
one side of the main volume of the charge. The results that
have been obtained in a motor of the automobile type by trial
in the laboratories of the Association of Automobile Engineers
366 ELECTRIC IGNITION
are striking examples of this. The motor tested had its inlet
and exhaust valves on opposite sides of the cylinders. During
the trials with single ignition the spark-plug was located in one
of the pockets in which the valves are located, and in the trials
with double ignition, a spark-plug was located in each of the
valve pockets. The use of the two plugs reduced the distance
through which the propagating flame had to travel to slightly
more than half of its necessary travel when one plug was used.
The electricity was supplied by a high-tension magneto. The
results showed not only a decided decrease in the advance of
ignition required with increased speed when the two plugs were
operated, but also a very decided increase of power, especially at
high speeds. The two plugs also made it possible to run the motor
at much higher speed while obtaining a large amount of torque.
207. Advancing and Retarding the Spark in a Variable-speed
Motor. On account of the extremely wide range of conditions
under which an automobile motor operates, the proper manipu-
lation of the spark control to obtain the most effective results
affords a complete example of variation in the time of ignition.
When the motor is to be started by cranking, the spark con-
trol should be set so that ignition will not occur before dead-
center position of the crank-shaft if the ignition is by battery
current. When battery current is used, the motor can be
started by extremely slow cranking. If the ignition were to
occur before dead center while cranking very slowly, the first
explosion in the cylinder would drive the crank-shaft of the
motor backward, which is not only undesirable but dangerous
to the operator. With magneto ignition the speed of cranking
must generally be fast enough to carry the crank-shaft beyond
dead-center position before the force of the explosion is great
enough to stop the rotation, even if ignition does occur slightly
before dead center. The latter statement is not intended to
apply to magnetos which are provided with a spring device
for snapping the rotor of the magneto over so as to produce an
ignition spark when the motor is cranked at slow speed. Some
such magnetos are so constructed as to make it impossible to
obtain a spark before dead center when starting the motor by
VARYING THE TIME OF IGNITION 367
external power. Those without such a retarding device must
have the control set for late spark in the same manner as a
battery system.
After the motor is started and while it is running light, as
before the car is started, the throttle should be closed as far as
possible without stopping the motor, and the spark advanced
only far enough to keep the motor running at slow speed. This
will use the least amount of fuel and cause the smallest amount
of heating of the motor. When the car is to be started, the
spark should be well retarded before opening the throttle to
obtain the requisite amount of torque. While the car is running
on a good level road, the throttle should be closed as far as
possible and the spark advanced as far as possible without
reducing the speed of the car. If the motor is at all worn so as
to allow play in the working parts, too much advance of the
spark will generally be indicated by a characteristic knocking or
pounding in the motor, as well as decrease of power, as evidenced
by loss of speed of travel of the car. Upon starting up a hill, in
order to maintain the same speed of travel of the car, the spark
must first be retarded slightly and the throttle then opened as
much as is found necessary, or these two operations may be
performed simultaneously if it is possible to operate both the
spark and throttle controls simultaneously. The retard of the
spark is necessary on account of the higher rate of combustion
that accompanies the increased amount of the charge and the
consequent increased intensity of compression pressure. The
reverse manipulation of the spark and throttle are in order when
the car has reached the top of the hill and again starts on a
piece of good level road. If the speed of the car is to be in-
creased gradually on a level road, then the throttle can be opened
gradually without retarding the spark. The increasing speed of
the motor compensates the increasing rate of combustion due
to the larger charge and the consequent higher compression.
When the motor is pulling at slow speed of rotation on open
throttle along a heavy road or up a hill, the spark should be
well retarded, since otherwise there will be loss of power and,
in a worn motor, knocking or pounding.
CHAPTER XXIV.
CARE AND ADJUSTMENT OF IGNITION SYSTEMS.
Introductory. This chapter relates only to good igni-
tion apparatus which is kept in order by proper care. It does
not deal with the troubles that arise on account of neglect and
inferior or defective apparatus. The latter are reserved for later
discussion.
The ignition apparatus should be kept clean and properly
lubricated. The insulated wires should be kept free from oil
as far as possible. This is especially important relative to
wires that carry high-tension current for jump-spark ignition.
Oil destroys the insulating property of rubber insulation.
In case of unsatisfactory ignition suspected to be due to the
ignition system, it is generally advisable to first make sure that
the spark-plugs are clean and in order, and that the battery, if
one is used while ignition is unsatisfactory, is capable of deliver-
ing the requisite amount of current. The examination and
cleaning of a spark-plug, and the testing of a battery, can gener-
ally be readily accomplished.
It should always be remembered that there are other causes
of unsatisfactory ignition than the ignition system itself. Prom-
inent among these other causes is an improperly proportioned
combustible mixture. This fault can ordinarily be remedied by
adjusting the carbureter when one is used for liquid fuel, or the
proportioning device when gas is used as the fuel. Water in
liquid fuel is a cause of a lean combustible mixture, and leakage
of water into the combustion chamber of the motor may cause
ignition trouble on account of the water collecting on the
igniter.
All of the matter given below does not relate to any one
ignition system, but such parts as do relate to any particular
system can be applied to it.
368
CARE AND ADJUSTMENT OF IGNITION SYSTEMS 369
209. Cleaning the Spark-Plug. It not infrequently happens
that dirt collects on the insulation or between the spark-points
of the igniter. This may be in the form of dry carbon or of
carbon mixed with gummy residue of lubricating oil. The
gummy deposit generally indicates that the oil used to lubricate
the motor piston is unsuitable, but it may be due to an excess
of lubricating oil that would not give the gummy residue if
used in smaller quantity. Sometimes a flake of carbon from
some part of the walls of the combustion chamber lodges be-
tween the ignition points and prevents the formation of an
ignition spark or arc.
The plug can be cleaned, after removal from the motor, by
the use of a stiff bristle brush and gasoline. A toothbrush or
a small stiff brush such as is used for painting is suitable. A
piece of cloth may facilitate the cleaning of some parts of the
insulation. It is not generally advisable to take the plug apart
unless it is of the separable type. It is sometimes difficult
to get the parts of an ordinary plug together again so as to be
gas-tight, and there is danger of breaking porcelain insulation.
The insulation of a plug should not be scraped with any hard
tool, such as a knife or screw-driver, that will roughen it, since
the roughened surface would take on and retain dirt more
readily than the smooth one.
The plug should not be screwed very tightly into the motor
if it has a taper thread (gas-pipe thread), if it is replaced while
the motor is hot, for when the plug and motor come to the same
temperature the plug will bind more tightly in the motor.
210. Adjusting the Width of Spark-Gap in Jump-spark
Igniters. The width of the spark-gap in a battery ignition
system should ordinarily be about % of an inch, but a wider
gap is sometimes used. Magneto makers generally recommend
a spark-gap width, for magneto current, of 0.4 to 0.5 of a milli-
meter (approximately ^ to $ of an inch) for plugs and mag-
netos of the size commonly used on automobiles. In magneto
ignition systems for motors much larger than those used on
automobiles, and in which the spark-plug and magneto are
much larger than those for automobile use, the spark-gap
370 ELECTRIC IGNITION
is wider. About -fa f an i ncn * s suitable for these large
plugs.
The width of the spark-gap is often increased in a magneto
ignition system by the burning away of the points. When the
spark-gap becomes widened from this or other cause, it should
be adjusted to the proper width. This can be done by bend-
ing the wire which forms one side of the spark-gap, or by ad-
justing the insulated spindle or other part of the plug, according
to its design. It is convenient to have a gauge of the proper
thickness to which the adjustment can be made. A piece of
wire flattened at the end, or a piece of clockspring, is suitable.
A silver dime is approximately fa of an inch thick after the
raised edges are worn off.
If a bead of metal has formed at the spark-gap, or if the
points or edges have become rough and irregular, it is advisable
to file them to a more regular shape. The end of a wire may
be filed off square across the length of the wire, thus leaving
sharp edges from which a spark will jump more readily than
from a smoothly rounded point.
211. Repairing the Spark-Points of Contact Igniters. The
spark-points of contact (low-tension) igniters generally become
pitted and uneven where they make contact with each other.
They should then be dressed with a very smooth-cut file so as
to make good contact with each other. Care should also be
taken to see that the points separate at least as much as ^ f
an inch when operated to draw the ignition arc. A much
wider separation than this is customary in large plugs, and also
sometimes in small ones. There is no objection, so far as the
formation of the arc is concerned, to a wide separation of the
contact-points. A large movement involves increased mechan-
ical wear as compared with slight motion, however.
212. Adjusting the Trembler. The trembler should be ad-
justed so that the least amount of battery current that will
give a spark for satisfactory ignition is used. The amount of
battery current that passes through the trembler can be meas-
ured by means of an ammeter inserted in the battery circuit.
The amount of current required varies for different spark-coils.
CARE AND ADJUSTMENT OF IGNITION SYSTEMS 371
For the more usual sizes of coils, from one-half ampere to one
and a half amperes is required for operating a four-cylinder
high-speed motor with four combustion chambers. In the
absence of information as to the amount of current required for
any particular system, it can be determined by trial.
If there is more than one trembler and spark-coil, then the
current passing through each trembler should be measured
separately and the tremblers adjusted so that all take the same
amount of current. The current for one trembler is less than
that for all of them, in proportion to the number of tremblers.
The sound given out by the tremblers should be of the same
pitch for each when all are of the same size and design.
It has been stated that some tremblers have only one means
of adjusting them, while others have two.
In the absence of an ammeter for measuring the current, the
tremblers can all be adjusted to the same pitch of sound as
nearly as possible. In general, the rate of vibration of the
tremblers should be somewhere near midway between the high-
est and lowest rate that will give ignition. Ordinarily more
current flows when the rate of vibration is high than when it
is low.
213. Lubricating and Cleaning the Timer. When the timer
is of the sliding-contact type, the rubbing surfaces should be
kept well lubricated. This can be done by a copious supply of
oil, or by packing the timer with soft grease if it is of a form
that will retain grease in the casing. Some sliding-contact
timers are continuously lubricated by oil pumped to them.
For a timer with roller contact, it is generally better to use
oil for lubricating than grease. The grease is apt to prevent
good electric contact between the roller and the stationary
contact-pieces. If grease is used, it should be very thin.
A timer which makes only pressure contact (after the manner
of magneto interrupter and trembler contacts), and is not in-
tended to be submerged in oil, should not have any oil on the
contact-points at which the circuit is closed. The oil sometimes
prevents effective closing of the circuit when the contact-points
are covered with it.
372 ELECTRIC IGNITION
A timer should be cleaned whenever dirt has collected in it
to an appreciable amount The dirt may be only small par-
ticles and is generally mixed with the oil or grease. A moder-
ately soft bristle brush and kerosene are suitable for cleaning.
Oil should be applied to the rubbing surfaces after cleaning.
214. Care of the Magneto or Dynamo. A magneto or
dynamo whose armature shaft runs on ball bearings requires
only a very few drops of oil on each bearing, including the bear-
ings of the distributer shaft when there is such a shaft, about
once a month in ordinary service. Those which have plain
journal bearings and are equipped with oil reservoirs and wicks
for keeping the bearings continuously lubricated require a little
more oil about as frequently. Plain journal bearings without
oil reservoirs and wicks or corresponding devices require fre-
quent oiling, as two or three drops daily on each bearing when
in continuous use.
In some magnetos the interrupter-lever is bushed with wood
fiber where the lever rocks on the pin that supports it, and a
piece of wood fiber is fastened to the end of the lever where it
strikes the cam that operates the lever. The wood fiber works
on the metal satisfactorily without lubrication under the con-
ditions existing in interrupters of magnetos. When there are
no other rubbing parts in the interrupter, no lubrication of the
interrupter is necessary. There are other materials that can
be used without lubrication, as the wood fiber is used in this case.
If the interrupter (contact-maker) has metallic surfaces that
rub against each other, a slight amount of lubrication is gener-
ally necessary. Only a very small amount of oil should be
used, however, so that there will not be an excess to collect
between the contact-points and interfere with their operation
by preventing good electrical contact between them.
Care should be taken not to use an excess of oil on any part
of a magneto or dynamo. If too much oil is applied, some of
it may get on the winding of the armature and injure the insu-
lation. Oil is also undesirable on the commutator of a dynamo.
If much carbon dust or dirt collects in the neighborhood of a
carbon brush, the brush should be examined to see whether it
CARE AND ADJUSTMENT OF IGNITION SYSTEMS 373
has become much worn. If it is greatly worn, it should be re-
placed by a new one.
The magneto should be kept clean, especially the inter-
rupter and the distributer. Carbon dust and particles of metal
in the distributer are very apt to cause a short circuit and thus
interfere with the ignition. The same is true to a less extent of
the interrupter. A soft bristle brush or cloth may be used for
cleaning either. If there is any oil present, kerosene or gasoline
will facilitate the cleaning. Do not scrape the non-metallic
parts with a steel tool. After using gasoline, all of the metal
surfaces with which it came in contact should be coated with a
little oil or kerosene, except the contact-points of the inter-
rupter. The coating of oil can be put on with a piece of cloth
or a small brush. It is not necessary to coat with oil after using
kerosene for cleaning.
The contact-points of the interrupter of a magneto should be
adjusted so that they separate from ^ to ^ of an inch to
break the circuit. In very large magnetos the separation of the
contact-points may be somewhat greater than this amount.
The contact-pieces are generally threaded so that they can be
adjusted. The lock-nut or other locking device should be tight-
ened after adjustment, so as to hold the contact-pieces firmly
in place.
The commutator of a small dynamo for ignition use seldom
requires any attention, since the brushes are ordinarily of a
material that is self-lubricating. The self-lubricating property
is generally obtained by making the brushes partly of graphite.
In the dynamo for supplying ignition current to several large
engines, the brushes are not always of such material as lubri-
cates well. In such a case, the commutator should be lubricated
by applying a hard lubricant to the commutator while it is
running. Sticks or " candles " of commutator lubricant can be
found on the market.
If the commutator becomes very much roughened, it can be
smoothed by holding a piece of fine-grained sandpaper (not
emery paper or emery cloth) against it while it is running, first
lifting the brushes from contact with the commutator. In case
374 ELECTRIC IGNITION
of extreme roughness, the commutator can be filed smooth with
a fine-cut file. The brushes should always be lifted from the
commutator while doing this, and the armature run at as slow a
speed as possible.
Water should not be allowed to get on the electric generator
unless it is positively waterproof, as are some of those made
for use on boats. Water injures the insulation, and in the inter-
rupter it interferes with the breaking of the circuit if it gets
between the contact-points.
215. Filing or Dressing the Contact-Points. For filing the
platinum contact-points of the interrupter of a magneto or
trembler coil, only a very smooth (fine-cut, dead-smooth) file
should be used. A convenient method of holding the threaded
contact-pieces (contact-screws) of a magneto interrupter is to
drill and tap a hole through a flat piece of metal somewhat
thinner than the length of the contact-piece, and screw the latter
into the threaded hole so that its contact-point projects slightly
beyond the surface of the holder. The projecting end can then
be filed level with the surface of the holder. If the hole is per-
pendicular (square) with the surface of the holder, the end of
the contact-piece will then be square with its length, which is
the proper method of making it. If the screw fits loosely in the
holder so that it turns around while filing it, the holder should
be slotted so as to split it through the length of the tapped
hole. The screw can then be clamped tightly by gripping the
holder in a vise so as to press the sides of the slot toward each
other, or by putting a binding screw through the holder at right
angles to the hole for the contact-piece.
The contact-points of large igniters of the make-and-break
type can be filed down in a similar manner. A coarser-cut file
can be used than for the small points. A very fine-cut file does
not remove metal rapidly. It is advisable to finish with a
smooth-cut file.
216. Care of Batteries in General. A battery should be
kept clean and dry. No metallic tools or appliances should be
placed where they can come into contact with the terminals,
since they may make a short circuit, thus causing rapid exhaus-
CARE AND ADJUSTMENT OF IGNITION SYSTEMS 375
tion of the battery and unsatisfactory ignition. A storage bat-
tery is apt to be permanently injured by a short circuit made in
this manner. A collection of dirt around and between the ter-
minals, especially if moist, is enough of a conductor to allow the
battery to discharge slowly through it.
If the pasteboard covering commonly used on individual dry
cells becomes wet, it allows leakage of current through it when
the cells of a battery are grouped against each other or when
they are in a metal case without other insulation than that of the
pasteboard. If the battery must be used after the pasteboard
covering of the cells has become wet, they should be separated
so as not to touch each other and should not be allowed to
touch a metallic part so as to make metallic connection between
their coverings. It is also unadvisable to have two or more of
them in contact with the same piece, or connected pieces, of
wet wood, but this is not so important as keeping them away
from metal. In case of necessity of keeping them in use, the
cells with wet covering can be separated from each other by
pieces of insulating material, such as glass, porcelain, or rubber.
Corrosion of the terminals of a storage battery can be pre-
vented by coating the terminals with vaseline, paraffine, or
varnish after cleaning them thoroughly.
217. Keeping Electric Connections Tight. The connections,
or fastenings, between different parts of the ignition system
should be kept tight so as to make good electric contact. This
is more important in low-tension circuits than in high-tension
ones, such as those of the secondary circuit in jump-spark
systems.
The nuts of dry batteries of the ordinary form are especially
given to working loose. Such a nut should be tightened hard
against the wire which it holds, but not hard enough to break
the wire or cut it in two. It is not bad practice to use pliers for
tightening it. If the nut is loose on the thread it can generally
be made tight by removing it and pinching the thread of the
bolt part of the terminal between the jaws of a pair of pliers, or by
striking the nut with a hammer so as to slightly close the hole.
Or the nut may be secured in place with a drop of solder, after
376 ELECTRIC IGNITION
tightening. These practices are decidedly not recommended
for other parts of the ignition system, or for the terminals of
storage batteries. If the cells of the battery are securely held
in place so as not to shake about, there is very much less lia-
bility of the binding nuts working loose than when the cells can
shake about.
218. Testing a Primary Battery.* When an ammeter is per-
manently connected in the battery circuit, its reading while the
motor is running is an indication of the condition of the battery,
provided there are no unusual causes in other parts of the
ignition system which effect a decrease in the amount of bat-
tery current. If there is some cause of decrease of battery cur-
rent exterior to the battery, then a voltmeter connected to
the battery terminals will indicate to some extent the condition
of the battery. If the voltage of the battery shows normal while
the system is operating on a reduced amount of current, then
the trouble is outside of the battery, but if the voltage at the
battery terminals is low as well as the current, then the battery
is at fault. The fault may be loose connections between the
cells of the battery.
If a primary battery is not delivering the requisite amount
of current, it is advisable to test the cells separately with an
ammeter. This can be done without disconnecting the cells
from each other when they are of the type with exposed ter-
minals. The test is made by applying the terminals of the am-
meter to the terminals of each cell to be tested, after the manner
that has already been described, and noting the amount of
current as indicated by the ammeter. The terminals of both
the cell and the ammeter must be clean so as to make good
electric connection with each other. If the terminals are not
clean or not pressed together firmly, the reading of the ammeter
is apt to be misleading. If one of the cells is found to be very
much exhausted, as indicated by the small amount of current
that it sends through the ammeter, it is generally advisable to
take it out of the battery, even though there may not be a good
one at hand to replace it immediately.
* Testing storage batteries is discussed in the following chapter.
CARE AND ADJUSTMENT OF IGNITION SYSTEMS 377
Connecting the ammeter to one of the cells individually in
the manner just described may stop the motor. It is ordi-
narily sure to stop it if the ammeter is connected so as to test
two or more cells at once.
A wet primary battery (one in which there is no absorbent
material for retaining the liquid electrolyte) can be tested in
the same manner as a dry primary battery. The internal re-
sistance of a wet cell is greater than that of a dry one; there-
fore, the current that flows through an ammeter connected to the
terminals of a wet primary cell, or wet primary battery, will be
less than that from a dry primary cell or battery.
It is advisable to always use the same ammeter when testing
a battery. The current that flows through an ammeter con-
nected to a cell or battery terminals depends to some extent
upon the resistance of the ammeter. The use of ammeters of
different resistance at different times may therefore give mis-
leading information.
On account of the varieties of forms and sizes of batteries and
the different resistances of ammeters, it is not possible to state
with any degree of accuracy how much current a battery or cell
should give through an ammeter. It is advisable to compare
the current obtained while testing a used battery with that of
a like battery in good condition, the same ammeter being used in
both cases.
The more thorough methods of testing storage batteries can
be applied to primary batteries. These methods are given in
the following chapter.
It has been stated earlier that an ammeter should not be
applied to the terminals of a storage battery unless the am-
meter is especially constructed for such use. Ordinary ammeters
are not so constructed.
CHAPTER XXV.
TESTING OF STORAGE BATTERIES.
Caution. Do not connect an ammeter alone to the ter-
minals of a storage battery.
219. Voltage-and-current Test of a Storage Battery.
When an ammeter and a voltmeter are permanently connected
into the ignition system so that the ammeter shows the amount
of current that flows through the battery circuit while the
ignition system is operating, and the voltmeter shows the cor-
responding pressure at the terminals of the battery, the current
and voltage readings of the two instruments indicate fairly well
the condition of the battery relative to the proportion of a
full charge that is still in the battery, provided the battery is
in good order. The voltage reading during the discharge should
be compared with the voltage when the battery circuit is open,
except the voltmeter circuit. The open-circuit voltage of two
kinds of storage cells is given later in this chapter. These two
kinds are the lead-plate cell and the nickel-iron cell.
A portable ammeter can of course be inserted in the battery
circuit temporarily so as to obtain readings of the current de-
livered by the battery while the ignition system is operating,
and a portable voltmeter can be applied at the same time to
the battery terminals in order to measure the corresponding
voltage.
An ammeter can be connected into an ignition system while
it is operating without interfering with the ignition. This can
be done in the following manner, first assuming that one side of
the battery is grounded: Connect one terminal of the ammeter
to the grounded side of the battery without removing the ground
connection (ground wire) of the battery. Connect the other
side of the ammeter to ground. The ammeter and ground
wire of the battery are then in parallel with each other. Then
378
TESTING OF STORAGE BATTERIES 379
remove the ground wire of the battery. This leaves the ground
connection through the ammeter as the only one directly be-
tween the battery and ground. All of the battery current must
therefore flow through the ammeter, assuming that the battery
has no circuits which are not grounded leading out from it. In
a similar manner, an ammeter can be connected into any part of
the battery circuit. This can be done in case the battery is
not grounded. There must be no apparatus between the two
points to which the ammeter is connected, and the portion of
the regular circuit between the connecting points of the am-
meter must be of low electrical resistance. An extreme method
is to connect the ammeter to two near-together points of a wire
and then cut the wire between the places to which the ammeter
is connected. The wire must of course be bare and clean where
the ammeter is connected to it. Before removing the ammeter
the original connections must be made again.
A voltmeter can be connected to the terminals of a battery
at any time without interfering with the operation of the ignition
system.
220. Ammeter in Series with Resistance. Probably the
most satisfactory method of testing a storage battery while it
is not delivering current to operate an ignition system (or any
other apparatus) is by means of an ammeter in series with a
resistance. The resistance should be of such a value as to
allow the flow of a current approximately equal to that for
charging the battery at the beginning of the charge. (The
charging rate for some storage batteries is given later in this
chapter.) One terminal of the ammeter should be connected to
one terminal of the battery, and one terminal of the resistance
should be connected to the other terminal of the battery. The
current will then flow through the ammeter and resistance in
series. The amount of current that flows is an indication of the
condition of the battery when compared with the amount of
current that flows under the same conditions when the battery
is in good order and fully charged. A voltmeter used in con-
junction with the ammeter and its series resistance will give
additional information.
380 ELECTRIC IGNITION
The resistance to be used in series with an ammeter in the
manner just described can be determined approximately for
any particular battery by dividing the voltage of the battery
by the amount of current that is to flow. This is expressed by
the formula
K E
R,-,
in which
C = amperes of current;
E = volts pressure of battery;
R = ohms of resistance.
If the average voltage of the battery is 6 volts while dis-
charging at the rate to be used in the test, which will be taken
as 5 amperes, then, substituting in the formula the values
E = 6 and C = 5,
R = = 1.2 ohms.
5
It is on the safe side to first use a resistance larger than the
1.2 ohms thus obtained, and then decrease the resistance to
obtain the desired amount of current. After the resistance is
once determined in the latter manner it should not be changed,
since such a change would be contrary to the method of making
the test of the battery, especially when no voltmeter is used.
The resistance to be used in series with the ammeter may be
in the form of a bare wire exposed so as to radiate the heat
generated by the current passing through it, of a rheostat, or
of wire embedded in enamel. A sufficient number of low-
resistance incandescent lamps, in parallel with each other and the
group of lamps in series with the ammeter, are suitable. The
amount of current that will flow through the lamps in parallel
with each other is approximately proportional to the number of
lamps of equal resistance, under the conditions mentioned. The
wire embedded in enamel can be made up in a form convenient
for portable use. Special resistance, or rheostat, wire is gener-
ally used for such purposes as the above, but ordinary iron or
steel wire will answer for a time at least. The resistance of an
TESTING OF STORAGE BATTERIES 381
iron wire 25 feet long and No. 18 American wire gauge is about
1.2 ohms. As the wire becomes hot its resistance increases.
221. Lamp for Testing. An incandescent electric lamp
which glows at a voltage the same as that of the storage battery
to be tested is a convenient means of testing such a battery.
If the lamp requires only a small proportion of the amount of
current that the battery can deliver at its maximum safe rate of
output, then the lamp can be connected to the terminals of the
battery while the latter is delivering current for ignition. If the
lamp glows only dimly, it is an indication that the voltage of
the battery is lower than it should be. It should be remembered
that a lamp which glows brilliantly in the dark will appear dull
in daylight, and very dull in bright sunlight.
222. Testing Cells Individually. Each cell of the storage
battery should be tested separately when the battery is of the
open type such that the terminals of the cells can be readily
reached. Each cell of a battery should give the same readings
when tested with the same testing instruments. In the case of
portable storage batteries which are sealed so as to prevent
spilling of the liquid, the terminals of the individual cells are
generally so inclosed in the battery box that they cannot be
reached for testing without unsealing the cell. This is not gen-
erally advisable unless the battery is in a bad condition which
cannot be remedied without unsealing it. The trouble may be
due to the electrolyte not being of the proper strength, which
can be remedied without unsealing the cell.
223. A voltmeter test of a storage battery that is on open
circuit is of practically no value alone when the battery is in
good order, since the voltage of the battery on open circuit is
practically the same whether the battery contains a large or a
small proportion of its full charge. If the battery is in extremely
bad order, the voltage may be low.
224. Voltage-drop Test. Tests which show when a rapid
drop of voltage begins while the battery is discharging at a
constant rate are valuable for indicating the proportion of the
charge that still remains in the battery. Since there may also
be a rapid drop of pressure just at the beginning of a discharge
382 ELECTRIC IGNITION
after the battery has been fully charged, the actual voltage must
also be taken into consideration in the absence of knowledge as
to about how much electricity the battery has given out since it
was charged.
225. Lowest Safe Voltages of Storage Batteries While Dis-
charging. It has been stated that when a storage battery is
discharging, the drop of voltage between the terminals of the
battery is less while the battery is delivering a small current
than while it is delivering a large one. The current which a
storage battery is called upon to furnish an ignition system is
generally small in comparison with that which the battery is capa-
ble of furnishing continuously for a shorter period of time cover-
ing its complete discharge. The current supplied to the ignition
system is also generally small in comparison with the amount of
current sent through the battery while charging it at the nor-
mal rate. Since storage batteries especially intended for ignition
service are not generally rated with regard to the maximum
amount of current (amperes) they can deliver efficiently through-
out the entire period of discharge, and since the normal rate of
current flow while charging them is generally given and should
always be known, it is convenient to refer the rate of discharge
to the normal rate of charging.
While a lead-plate storage battery is discharging at a rate
which is about one-fifth to one-fourth of the normal rate of
charging the battery, the discharge should not be continued
after the voltage (while discharging) has dropped to 1.8 volts
for each cell of the battery, and the discharge should not gener-
ally be continued long after the voltage (measured while dis-
charging) has dropped to 1.9 volts. The safe minimum voltage
is not the same, however, when the battery is new as after it has
been charged and discharged several times, and it is somewhat
lower when the electrolyte is weak than while it is up to full
strength for the discharged condition of the battery. The
normal average voltage of a lead-plate storage battery, while
discharging at the rate common to ignition service, is 2.0 volts,
or slightly more, per cell.
In the nickel-iron storage battery the voltage should probably
TESTING OF STORAGE BATTERIES
383
not be allowed to drop below i.i volts per cell while the battery
is discharging at a rate as low as one-fourth of the charging rate
of the battery. The minimum allowable voltage may be
slightly lower, however, if the electrolyte is below its normal
strength. The normal average discharge voltage of a nickel-
iron storage battery, while delivering current at the low rate
mentioned above, is slightly more than 1.2 volts per cell.
The greatly increased rapidity of the drop of voltage, which
begins shortly before the battery is discharged as far as it should
be, is the surest indication of the nearly complete discharge of
the battery. After the rate of drop becomes rapid the bat-
tery discharge should be stopped. Discharge carried on after
this condition has arrived is very apt to be injurious to the
battery.
226. Curve of Voltage Drop While a Storage Battery is Dis-
charging. In Fig. 286 the curved line represents the voltage of
1.50
1.40
1 *30
\
^^^
1.20
1.10
,1.00
{
'^^
.
.,
" -
S^^M
" ~
*
*-
-^*>
-" ,
X
\
) 40 80 120 160 200 240 280 320 30
Minutes
FIG. 286.
Curve Showing Voltage Drop of Nickel-iron Storage Battery while Discharging
to Advisable Limit.
a nickel-iron storage battery discharging at its normal rate
(with other conditions also normal). The voltage drops rapidly
during the first five minutes or so, then the drop becomes more
gradual, and has a minimum rate at about the middle of the
discharge, then becomes more rapid again at the end. The
battery is practically discharged when the voltage has dropped
to i.o volt. If the rate of discharge were slower, the voltage at
the same stage of discharge would be higher.
384 ELECTRIC IGNITION
227. Testing the Density of the Electrolyte. Apparatus
suitable for testing the density of the electrolyte for a storage
cell is shown in Fig. 287. It consists of a tubular testing glass
for holding the portion of the electrolyte to be tested, a syringe
for withdrawing some of the electrolyte from the cell and putting
it into the testing glass, and a hydrometer which is to be immersed
in the electrolyte for determining its density. The stem of the
hydrometer is graduated so that a reading can be taken at the
surface of the liquid. The hydrometer does not sink so deep
FIG. 287.
Hydrometer, Testing Glass, and Syringe.
into a liquid of high density, or high specific gravity (a heavy
liquid), as into one of lower density. A strong electrolyte has
greater density than a weak one.
The stem of the hydrometer may be graduated to read in
density (specific gravity), but of those found on the market
some are graduated to a different scale. Of these other scales
the Baume is found most often. The following table gives the
densities corresponding to a portion of the graduations of a
Baume hydrometer sufficient for testing the electrolytes most
commonly used in storage batteries.
TESTING OF STORAGE BATTERIES 385
DENSITY COMPARED WITH BAUME HYDROMETER.
Baum6
Degrees.
Density.
Baume
Degrees.
Density.
Baume
Degrees.
Density.
2O
1.152
25
I.I97
30
1.246
21
1. 160
26
I. 206
31
1 .256
22
1. 169
27
1.216
32
I. 267
23
1.178
28
i. 226
33
1.277
24
1.188
29
i . 236
34
1.288
A more compact device for testing specific gravity is shown in
Fig. 288. The hydrometer is inclosed in the glass body of the
FIG. 288.
Combined Hydrometer and Syringe.
syringe, so that, by drawing a sufficient amount of the liquid
into the syringe to make the hydrometer float, a reading can be
obtained.
A thermometer is a necessary accessory to the hydrometer
testing set if the electrolyte is sometimes warm and sometimes
cool when it is tested. The electrolyte has less density when
warm than when cool, within the range of temperature that is
allowable during the operation of the battery. Within this
range the density decreases about .001 for 3 Fahrenheit degrees
rise of temperature. Accordingly, if the density is 1.280 at 80
Fahrenheit, a rise of temperature of 30 degrees (to 110 Fahren-
heit) will cause a density drop of -^- X .001 = .01, thus making
the density 1.270 at the higher temperature.
Ordinarily the temperature of the electrolyte is supposed to
be at about 80 Fahrenheit when speaking of its density.
The electrolyte should be returned to the same cell from
386 ELECTRIC IGNITION
which it was withdrawn, in order not to lower the level of the
liquid in the cell.
The density of the sulphuric-acid electrolyte for one prominent
make of storage cells of the lead-plate type is recommended by
the manufacturer to be between 1.275 an d 1-300 while the cell
is fully charged. The lower density just given drops to about
1.20 by the time the cell is fully discharged, and retains this
lower value during the time the cell remains discharged. It is
not injurious to use a slightly lower density down to 1.25 in the
fully charged cell for a while. The density in the discharged
cell is correspondingly lower with this weaker electrolyte.
The potassium-hydrate electrolyte for the nickel-iron Edison
storage battery is 1.200, as recommended by the manufacturers
of the battery. The specific gravity does not vary appreciably
during the charging and discharging of the battery under normal
conditions. It is stated by the manufacturer that the efficiency
and capacity of the battery is not affected materially by allow-
ing the density of the electrolyte to become as low as 1.16, but
that if it gets below this the output of the battery will be tem-
porarily affected.
CHAPTER XXVI.
CHARGING AND CARE OF STORAGE BATTERIES.
228. Precautions. When charging a storage battery the
following three important items, among others, should be re-
membered :
First Item. Only a direct current can be used. An alter-
nating current will not charge the battery and is apt to injure
it. But an alternating current can be transformed into a direct
current that is suitable to charge the battery.
Second Item. The positive (+) terminal of the charging
source must be connected to the positive (+) terminal of the
battery, and the negative ( ) terminal of the charging source to
the negative ( ) terminal of the battery, but suitable resistance
must generally be placed in the circuit to regulate the current
to the proper amount. Methods of determining which is the
positive side of a circuit and which the negative, have been
given earlier.
Third Item. An excessive current must not be allowed to
pass through the battery. It is injurious and will overheat the
battery if continued long.
229. Connections for charging a storage battery from a light-
ing circuit of fixed voltage are shown in Fig. 289. If the
charging is to be done at the rate of 6 amperes, then 12 lamps
of 1 6 candle-power each, or 6 lamps of 32 candle-power each, of
the ordinary carbon-filament type, can be used as the resistance.
The lamps are used in parallel with each other. If some other
kind of incandescent lamp of higher efficiency (requiring less
current per candle-power) is used for the resistance, then more
lamps will be required. Thus, if each lamp takes one- third of
an ampere, 18 lamps will be required.
If one side of the circuit from which current is to be taken
is grounded, as in the case of most electric railway circuits, then
the corresponding side of the battery should be connected to
387
388
ELECTRIC IGNITION
ground without any resistance of substantial value between the
battery and ground. If the main resistance is placed between
FIG. 289.
Lamp Resistance and Switch Connected to a Storage Battery for Charging the
Battery.
FIG. 290.
Rheostat and Switch Connected to a Storage Battery for Charging it.
the battery and ground, there is probability of the operator re-
ceiving a dangerous shock.
A fuse-block with two fuses is shown just above the switch
CHARGING AND CARE OF STORAGE BATTERIES 389
at the right-hand side of the illustration. The fuses are of the
type commonly used in lighting circuits.
In Fig. 290, a rheostat is used for the resistance in the charg-
ing circuit; also an ammeter for measuring the charging current.
The rheostat is used to vary the amount of resistance in the
circuit, so as to regulate the current to the desired amount at
any time.
The resistance required in the charging circuit can be deter-
mined by the formula
in which
C = amperes of charging current;
E = voltage of the charging circuit;
e = voltage of the storage battery;
R = ohms of resistance.
If the voltage of the charging circuit (line voltage) is no
volts, and that of the battery is 6 volts, then, if the charging
is to be done at the rate of 4 amperes,
-n no 6 104
R - - = - = 26 ohms.
4 4
It is advisable to make the resistance somewhat larger than
the value determined in this manner, to allow for variation in
the line voltage and to be able to get a smaller current if desired.
230. Connections for charging two batteries at the same
time are shown in Fig. 291. As illustrated, the two batteries
are supposed to be in one box. Each battery consists of three
cells connected in series. The two batteries are not electrically
connected together.
The positive terminal of the main battery is at A ; its negative
terminal is at B. The positive terminal of the reserve battery
is at P, and its negative terminal is at N. C is the charging
circuit; D is a double-pole double-throw switch; is a single-
pole single-throw switch for the reserve battery. At M are six
lamps for resistance in the main battery circuit, and at R is one
lamp for resistance in the reserve battery circuit.
390
ELECTRIC IGNITION
The purpose of having a large and a small battery in the
same box, as just shown, is that the large one can be used till it is
9
M
in Batte
A
E R
'^
FIG. 291.
Connections for Charging Two Storage Batteries at the Same Time.
fully discharged, and then the small one can be used to supply
current for a short time till recharging can be done.
231. The rate of charging a storage battery should always be
given in instructions accompanying it. In the absence of such
information the matter given in the following two sections will
serve as a guide. On account of the differences in the form and
construction of batteries, it is not possible to make accurate
statements to cover the different varieties.
232. Charging and Care of Lead-plate Storage Batteries. -
The following is extracted from the instruction book for " Exide "
batteries of the portable type sealed in a case and intended for
ignition use :
" When a battery is received, remove and discard the soft
rubber caps from the vent-plugs and see if the electrolyte (the
liquid in the jars) is at the proper height (about one-fourth inch,
but not more) above the top of the plates; if it is lower, add
electrolyte of 1.300 specific gravity.
" The battery should not be discharged below the point of
exhaustion, i.e., 1.80 volts per cell when the current is flowing;
thus, with a 3-cell battery, the voltage should not be allowed to
fall below 5.40 volts. Nor should it be allowed to stand com-
CHARGING AND CARE OF STORAGE BATTERIES 391
pletely discharged. Never attempt to test the condition of the
cells with an ammeter, as is the practice with dry cells.*
" Immediate recharging is necessary when the discharge limit
is reached. If it is not possible to fully charge at once, then a
partial charge must be given, and the charge completed as soon
as possible and before again discharging.
" Always charge the battery at least once every two months,
whether used or not; this rule also applies if the battery is to be
out of service for any length of time, say for the winter months.
">When the battery is to be charged, unscrew the vent-plugs,
observe the height of the electrolyte, and add pure fresh water
if low, bringing the height up to one-fourth inch above the
plates, but not higher.
" Charge at the rate given on the name-plate on the case,
until there is no further rise in the voltage of the battery and
each cell has been gassing or bubbling freely for at least five
hours, and there is also no further rise in the specific gravity of
the electrolyte over the same period. The voltage at the end
of the charge may be between 2.40 and 2.70 volts per cell, de-
pending on the temperature and age; the higher voltages are
obtained on new batteries with the temperature low; on old
batteries at high temperatures the low voltages are obtained.
It, therefore, must be understood that, in determining the com-
pletion of the charge a fixed or definite voltage is not to be con-
sidered, but rather a maximum voltage, as indicated by there
being no further rise in the voltage over a period of five hours.
It is of the utmost importance that the charge be complete.
" The temperature of the electrolyte during charge should
not be allowed to get above 100 Fahrenheit, unless this cannot
be prevented, due to high temperature of the atmosphere. If
it tends to do so, either reduce the charging rate or discontinue
charging until the temperature has fallen. Low temperatures
are in no way injurious, but they have the effect of temporarily
reducing its discharge capacity; a return to normal temperature
restores the capacity.
* AUTHOR'S NOTE. An ammeter can be used in series with a suitable re-
sistance, however, as described in the chapter on " Testing of Storage Batteries."
392 ELECTRIC IGNITION
" After charging, replace vent-plugs and wipe off top and
sides of case.
" Great care should be taken not to bring a naked flame near
the openings in the top of the battery during or immediately
following a charge.
" The proper specific gravity of the electrolyte at the end of
the charge is 1.300 * * * , but a variation of from 1.275 to
1.300 is allowable. Do not adjust the specific gravity except
when a battery is fully charged; after adjusting, charge for an
hour, in order to thoroughly mix the liquid just added with the
electrolyte. Do not add electrolyte until it is determined that
the specific gravity cannot be brought up to the proper point by
charging. To add water or electrolyte, use a rubber syringe
(see Figs. 287 and 288). Addition of electrolyte is but seldom
necessary.
" The electrolyte can be made by mixing especially pure
sulphuric acid (1.840 specific gravity) and distilled water in
proportion of two parts of acid to five parts of water, by vol-
ume. The acid must always be poured into the water, and not
the water into the acid. A glass, earthenware, or other acid-
proof vessel, thoroughly cleaned, should be used, and the elec-
trolyte allowed to cool before using.
" The height of the electrolyte in each cell should be observed,
not only at the time of charging, but frequently between
charges, and if it is low, either because of evaporation or spill-
ing, it should be brought to the proper height (one-fourth inch
above the top of the plates) by the addition of pure water. If
a considerable amount of the electrolyte has been spilled out of
the cells, then the battery should be given a special charge as
soon as the water has been added, and the specific gravity ad-
justed to the proper point by adding some new electrolyte as
soon as the charge is completed.
" The sediment, which gradually accumulates in the bottom
of the jars, should be removed before it reaches the bottom of
the plates, as, if it does, it is very harmful to them. The need
for cleaning is indicated by lack of capacity, excessive evapora-
tion of the electrolyte, and excessive heating when charging.
CHARGING AND CARE OF STORAGE BATTERIES 393
When a battery requires removal of the sediment, better re-
sults follow if the work is done at a place where they are ac-
customed to it.
" Keep the holes in the vent-plugs clear.
" Keep all connections tight and clean."
The charging rate for "Exide " batteries, of which other items
are tabulated on page 109, is as follows:
Ampere-hour capacity at service rate, 40 60 80 100
Charging rate in amperes .... 4 6 8 10
It may be seen that the charging rate can be obtained by
dividing the ampere-hour capacity by 10.
In order to maintain a constant charging rate, the resistance
in the charging circuit must be reduced as charging progresses,
if the voltage of the source of electric supply remains constant.
It is not objectionable, and often advisable, to charge at a slower
rate toward the completion of the charge than during the early
portion.
233. Removing Sediment from Lead-plate Cells. In order
to remove the sediment which collects at the bottom of a cell,
the plates and electrolyte must be taken out of the containing
vessel, which is usually called the " jar." It may be necessary
to cut some of the lead connectors between the plates or be-
tween cells.
The cell should first be fully charged so that the voltage
remains constant for an hour or so during the latter part of
charging.
As soon as the plates are removed from the jar, they should
be stood on edge, with one of the side edges at the bottom and
the other side edge at the top, and the separators withdrawn
from between the plates. The removal of the separators is facili-
tated by spreading the plates apart slightly. Then without
delay wash the plates with a gentle stream of water, as from a
hose without a nozzle. Such of the separators as are in a con-
dition to be used again after cleaning, should be washed clean.
If the electrolyte is to be used again, it can be put into another
jar, as by siphoning it out or pouring carefully so as not to stir
394 ELECTRIC IGNITION
up the sediment. As soon as the jar is cleaned, the plates can
be put back in place, and the cut lead connectors " burned "
(fused) together again. The burning process involves skill and
practice, and will not be described here. The electrolyte should
be put in the jar so as to cover the plates again as soon as they
are in place, for the plates should not be allowed to become dry.
If new wooden separators are put in the cell, the electrolyte
should be made about 3 per cent higher in specific gravity than
it was at the time of taking the cell apart. This is to allow for
the diluting effect of the water contained in wet wooden plates.
234. Taking a Lead-plate Cell out of Commission. If the
cell is not to be used for several months, and it is not con-
venient to charge it at intervals while not in use, then, after
being fully charged so that the voltage remains constant for an
hour or so, it should be taken apart, washed, and the plates
dried. The taking apart and washing can be done as just de-
scribed. As soon as the positive plates become dry, they are
ready for storage.
But if the negative plates become so hot as to steam while dry-
ing, they should be washed again, or wet with water, and allowed
to dry again. They are then ready for storage.
If the cell has wooden separators between the plates, and they
are thought worth keeping, they should be immediately put in
water or electrolyte of low specific gravity, and left there during
storage.
235. Charging and Care of Nickel-iron Storage Batteries.
The normal charging rate for an Edison nickel-iron battery can
be obtained by dividing the rated ampere-hour capacity by 5.
The normal length of time for charging is 7 hours, but continuing
the charge 3 hours longer will increase the output capacity of
the battery about 30 per cent. The charging current can be
continued at its normal rate till the end of the charge if the
temperature of the cell does not rise above ioo 6 Fahrenheit.
If the temperature tends to rise above this point, the charg-
ing rate should be decreased or the cell kept cool by some
artificial means, as blowing a current of air against it with
a fan.
CHARGING AND CARE OF STORAGE BATTERIES
395
The voltage rises rapidly at the beginning of the charge,
sometimes to a value within an hour or two that apparently
indicates that the battery is charged; but the voltage then
drops somewhat below this amount and gradually rises again to
a maximum value, which remains constant at the end of the
charge. This maximum value generally lies between 1.80 and
1.85 volts per cell. Charging should be continued for 30 or 40
^---^
-4-
l.oU
i
S
-^
^
i^ 1
^^ ^
fc^
^
r ^
fa. ^
==!
M '
K- ^
p-* -"
_
1.50 4
1 40
/
Minutes
FIG. 292.
Curve Showing Rise of Voltage while Charging a Nickel-iron Storage Battery
minutes after the voltage becomes constant and is as high as
i. 80 volts.
Fig. 292 shows the curve of voltage variation of a nickel-iron
cell while it is being charged.
Higher rates of charging can be used for a short time, as high
as double the normal rate for an hour, but the temperature
should not be allowed to exceed 100 Fahrenheit.
A lower rate of charging can be used, as when the charging
source will not supply the normal amount of current, but this
lower rate should not be less than two-thirds of the normal rate.
Very low rates of charging are injurious.
When a new nickel-iron battery is first assembled and put
into use, it should be charged at the normal rate for about 15
hours. The same applies to putting a battery into use again
after it has been out of commission.
There should always be enough electrolyte to keep the tops
of the plates covered. Overcharging causes loss of water from
the electrolyte by decomposing the water. This loss of water
should be replaced by pure distilled water which is newly dis-
396 ELECTRIC IGNITION
tilled, or has been kept in a tightly closed vessel to prevent
carbonation by contact with the atmosphere.
The specific gravity of the electrolyte does not change during
charging and discharging, except possibly on account of loss of
water as just stated. Its normal specific gravity is 1.200.
Density tests should be made at the end of a charge; the liquid
is then thoroughly mixed.
Before putting in new electrolyte it is better to throw away
all of the old.
Cleaning the cell is limited to the outside. The containing
vessel (can) is so constructed that it cannot be opened to re-
move the plates without injuring it.
236. Taking a Nickel-iron Battery out of Commission. It
is not necessary to charge the battery when it is left idle.
" A battery can be put out of commission indefinitely if care
is taken to see that the outside of the retaining cans is left clean
and dry, and that the cells are in a discharged condition. It
should be stored in a dry place, and will require no attention
other than an inspection once in two or three months to make
sure the solution is kept at its proper height/'
CHAPTER XXVII.
TIMING THE IGNITION.
237. General Features. In the more general cases the re-
quirements of the ignition system relative to the time of ignition
are that it shall cause ignition as early as desired during the
compression stroke of the motor while the motor is running, and
that, while the motor is being started, it shall not cause ignition
until after the piston of the motor has started on its impulse, or
combustion, stroke.
The following statements regarding the setting of the timer,
the contact maker, or the magneto rotor, are intended to point
out general methods of meeting these requirements. In view of
the numerous kinds of ignition systems and the varied nature
of the mechanical part of their operation, the method which
best meets the requirements of each specific case should be
selected and, if necessary, suitably modified.
The instructions of the manufacturer of the apparatus should
be followed in preference to the general instructions given herein.
When the connections to the ignition control are apt to have
considerable lost motion on account of wear or loose fitting, an
allowance should be made for this lost motion.
In a system which will give an ignition spark or arc, however
slow the rotation of the crank-shaft of the motor, such as a
system operating on current from some source which will supply
current whether the motor is rotating or not, a timer operating
in conjunction with a trembler spark-coil or with a magnetically
operated igniter must not close the circuit, when the spark con-
trol is in position for latest ignition, until after the crank-shaft
of the motor has passed its dead-center position; and an inter-
rupter must not break the circuit until after the crank-shaft
has passed its dead-center position when operating on current
similarly supplied.
397
ELECTRIC IGNITION
Precaution should be taken to prevent an impulse of the
motor while timing the ignition. The removal of the spark-plug
or disconnecting the wires from it, in a high-tension system, will
prevent ignition. In a low-tension system, the opening of a
petcock so as to connect the combustion chamber with the
atmosphere will prevent an impulse of the motor. In the
absence of the petcock, some part may be removed to make an
opening into the combustion chamber. If there is no com-
bustible mixture in the motor, there can of course be no ignition
without these precautions. But certainty in this respect is apt
to be like that regarding a gun which is not loaded.
238. Timing, or Setting, a Timer. This can be done by
either of the following two methods, according to which is the
more convenient:
First Method. Rotate the crank-shaft of the motor some-
what past one of its dead-center positions, say 10 to 20 degrees
of angle past, so that one of the pistons has moved a slight dis-
tance on its impulse, or combustion, stroke. Leave the crank-
shaft in this position.
In a jump-spark system, disconnect the wire from the spark-
plug for the cylinder whose piston is on the impulse stroke, and
place the disconnected end of the wire within an eighth-inch
from the metal of the motor; or remove the spark-plug from its
position and place it so that its outer bushing makes contact
with the metal of the motor, but its insulated spindle and the
end of the connection to it do not make electric connection with
the metal of the motor.
Loosen the timer rotor from the part (shaft) that drives it,
so that the timer rotor can be revolved without rotating its
driver with it. Move the spark control to its position for
latest spark. Moving the part of the timer to which the con-
trol is connected around in the direction of rotation of the timer
rotor retards ignition.
Revolve the timer rotor slowly in the direction that it rotates
while operating, until it closes its circuit, as indicated by a
spark at the plug mentioned, or by movement of the magnetic
igniter corresponding to the cylinder whose piston is on the com-
TIMING THE IGNITION 399
bustion stroke, as the case may be. Fasten the timer rotor to
its driver permanently in the position thus determined.
Judgment must be used in selecting the value of the angle of
the crank-shaft past dead center for timing in this manner.
If there is probability of much wear in the control connections,
the angle should generally be made more than 10 degrees when
the motor is to be started from rest or from extremely slow
speed of rotation, by the impulse of an ignited charge in its
cylinder.
The movement of the spark control must be sufficient to give
the greatest advance desired.
If the timer rotor is mounted on a shaft separate from the
cam-shaft or crank-shaft, and which is only for driving the timer
rotor, then the desired setting of the rotor can be obtained ap-
proximately by taking the driving gears out of mesh with each
other and then putting them into mesh again in the desired
position. The accuracy of adjustment by this method is limited
to half of the angular movement of the timer rotor due to mov-
ing the gear on its shaft one tooth forward or backward relative
to the gear which meshes with it. This method can be used,
under the restrictions mentioned, when the timer rotor and its
gear are keyed or otherwise fastened permanently in position on
the shaft. It is immaterial whether the timer shaft also drives
a pump for cooling water or lubricating oil.
Second Method. Bring the crank-shaft to one of its dead-
center positions so that one of the pistons is at the end of its
compression stroke and ready to begin its impulse stroke.
Loosen the timer rotor from the shaft or other part that
drives it, so that the timer rotor can be revolved without rotat-
ing its driver with it.
Move the spark control to the position thought to be correct
for ignition at dead center while the motor crank-shaft is rotated
at very slow speed, as when starting the motor. This position,
for a high-speed motor, would generally be not more in advance
of the position for latest ignition than one-fifth of the entire
movement of the control. It may be more in advance for a
slow-speed motor.
400
ELECTRIC IGNITION
The remainder of the timing is the same as that in the second,
third, and fourth paragraphs of the first method, just given.
239. Timing a Rotary Magneto of the Interrupter Type. It
should always first be made certain that the magneto itself is so
adjusted that its interrupter breaks the primary circuit in accord
with the proper corresponding position of the rotating armature
or inductor. The ordinary method of determining this in a
magneto with rotating armature is by measuring the distance
A in Fig. 293 between the lip of the pole-piece and the edge of
the armature core, after the core has passed beyond the position
in which its crowned parts bridge the space between the pole-
FIG. 293.
Position of Armature for Timing a Magneto by the Advanced Spark-control
Method.
pieces. The arrows indicate the direction of rotation of the
armature. The distance A is as small as one-sixteenth inch for
some magnetos, and as large as one-fourth inch or larger, in
others. This depends on the size of the magneto and form of
the pole-piece lips, among other things. Sometimes there is a
reference mark to indicate the position of the armature at the
instant that the interrupter contacts should begin to separate.
In the absence of such a mark, the instructions of the manu-
facturer should be consulted.
Either of the following two methods of timing the magneto
may be followed:
First Method. Set the crank-shaft of the motor in the posi-
tion through which it is to pass at the instant the interrupter
TIMING THE IGNITION 401
contact-points begin to separate when the spark control is set
for the most advanced ignition. This position of the crank-
shaft is somewhat before its dead-center position for the end of
the compression stroke of one of the pistons of the motor. It
may be 40 degrees or more before dead center for a small high-
speed motor, and 10 degrees or less for a motor which runs at a
very slow speed. (See later for determining the corresponding
position of the piston.)
Loosen the gear or coupling which drives the magneto rotor so
that the rotor can be revolved independently of its driving shaft
or gear.
Set the spark control for most advanced ignition, thus moving
the timing lever of the magneto as far in the direction opposite
the direction of rotation of the magneto rotor as it is intended
to be moved while operating.
Move the magneto rotor around in the direction it is to ro-
tate, until the contact-points of the interrupter just begin to
separate, and the high-tension distributer arm is in position to
direct the secondary current to the cylinder whose piston has
nearly completed its compression stroke. Fasten the rotor of
the magneto to its driver in the position thus determined.
For a motor which is started by hand cranking, it should be
determined whether the latest ignition, as obtained by moving
the control to its full retard position, is late enough not to
give a back-kick of the crank-shaft when starting the motor.
The interrupter contact-points can separate a very short time
before the crank-shaft has reached dead center, without causing
a back-kick, since the movement of the crank-shaft carries it
past dead center before combustion can progress far enough
to cause an appreciable increase of impulse pressure on the
piston.
The method of disengaging the teeth of the driving gear, as
described for timing a timer, can be used if necessary.
Second Method. Set the crank-shaft of the motor in dead-
center position, with one of the pistons at the end of its com-
pression stroke.
Loosen the timer rotor from its driver.
402
ELECTRIC IGNITION
Move the ignition control to its position for latest spark.
This moves the timer lever of the magneto to its extreme posi-
tion in the direction of rotation of the magneto.
Move the magneto rotor to one of the positions shown in
Fig. 294, according to the direction of rotation of the magneto,
and so that the high-tension distributer is in position to direct
secondary current to the cylinder whose piston is at the end of
its compression stroke. Fasten the rotor to its driver in the
position thus determined.
The distance E for any magneto depends on the speed and
other conditions of operation. In a small magneto it is some-
FIG. 294.
Position of Armature for Timing a Magneto by the Retarded Spark Method.
times less than one-fifth of an inch, while in a large one it may
be as much as three-fourths of an inch.
The value of E should be obtained from the manufacturer's
instruction book for the magneto that is to be timed. is, or
should be, always greater than A of Fig. 293 for a given speed
of rotation of any particular magneto.
240. Relative Positions of Crank-Shaft and Piston. The dis-
tance of the piston of a motor from the extreme end of a stroke
is frequently given in connection with the timing of ignition.
The following formulas can be used for determining this dis-
tance in a motor whose cylinder is not off-set to one side of its
crank-shaft.
TIMING THE IGNITION 403
Notation for formulas:
R = radius of crank,
= one-half the length of the stroke;
n = ratio of the length of the connecting rod to the radius of
the crank;
S = angle, not greater than 90 degrees, of the crank-shaft from
its nearest dead-center position;
x = distance of the piston from its extreme position farthest
from the crank-shaft, i.e., from its head dead-center
position in a single-acting motor of the usual type ;
y = distance of the piston from its extreme position nearest
to the crank-shaft.
For the distance from the head dead-center position,
x = R\ vers 9 + n X versed sine of the angle whose sine is
sin 0~\
n \
And for the distance from the crank dead-center position,
y = R\ vers 6 n X versed sine of the angle whose sine is
sin 01
n _
The only difference between these two formulas is in the plus
and minus signs.*
As a concrete case of application of the formulas, the length
of the connecting rod will be taken as four times the radius of
the crank. This makes n = 4. And the angle of the crank
from head dead-center position will be taken as 30 = 6. Then,
by substituting these values of n and 6 in the first formula:
x = R\ vers 30 + 4 X vers of the angle whose sine is
L 4 J
The versed sine of 30 is .134.
* Either of these two formulas could be used for any position of the crank and
the corresponding position of the piston (for any value of 6), but on account of
the liability to confusion when using values of 6 greater than 90 degrees, it is
simpler to limit to a maximum of 90 degrees and use both formulas.
404 ELECTRIC IGNITION
sin
The sine of 30 is .500; therefore
4
The versed sine of the angle (about 7) whose sine is .125
is .008.
The last expression, therefore, becomes
x = R [.134 + 4 X .008]
= R (.134 + -032)
= .166 R.
And since R = half the length of the stroke, 2 R = length of
stroke, and
x = .083 X 2 R
= .083 X length of stroke.
This shows that the piston is .083 =8.3 per cent of its full
stroke from the head end of the cylinder when the crank is
30 degrees from its head dead-center position, and the connect-
ing rod is four times as long as the crank radius, as assumed.
If the stroke of the piston is 6 inches, then the linear distance
of the piston from the head end of its stroke is
x = .083 X 6 = .498 inch,
which is almost half an inch.
For the distance of the piston from the crank end of its stroke
when the angle of the crank is 30 degrees from head dead-
center,
y =#(.134- .032)
= .102 R
= .051 X length of stroke.
And the distance of the piston from the crank end of its
stroke is
y = .051 X 6 = .306 inch
for the assumed 6-inch stroke.
The positions of the piston for any crank angle up to 90
degrees can be found by substituting the assumed value of the
crank angle in the equations and solving in a similar manner.
CHAPTER XXVIII.
IGNITION-SYSTEM FAULTS AND REMEDIES.
241. Defects and Conditions in the Ignition System Which
Cause Faulty Ignition. In some cases a remedy is given for
the trouble mentioned, but in others the remedy is so obvious
that it is not mentioned.
In the Igniter.
242. Spark-gap too wide or too small. The spark-points
sometimes burn off in magneto ignition systems.
Carbon and oil deposit in the spark-gap or on the insulation.
Caused by too much lubricating oil or a poor quality of oil, or
by too rich a mixture.
Water on the spark-points. Generally due to a cracked or
porous cylinder. The water may be due to some other source
when the engine has been standing idle for a considerable
time.
Loose contact-points in a make-and-break igniter.
Porcelain insulation cracked or chipped. Steatite insulation
seldom cracks or chips. An igniter in this condition may give
a good spark or arc while the igniter is removed from the motor,
but when in place the defect may cause a short circuit so as to
prevent the formation of an ignition arc or spark. This is be-
cause the electric resistance of the spark-gap is greater in the
compressed charge in the motor than in the open air. Porce-
lain insulation that is chipped at the portion outside of the
motor will generally not cause a short circuit while the chipped
surface is still clean, but if it is touched by one's hafld while
working around the motor, so as to leave dirt on the chipped
surface, the dirt is apt to cause a short circuit sufficient to pre-
vent ignition, especially when the motor is working on full
405
406 , ELECTRIC IGNITION
charges, although the igniter may give a good spark while re-
moved from the motor. This short circuit is most apt to occur
when the chipped surface extends from the insulated spindle to
some of the other metallic parts of the igniter.
Mica insulation loose so that dirt can collect between the
layers, or laminations, of the mica. The behavior of an igniter
in this condition is much the same as that of one with solid
insulation that is cracked or chipped. It is generally not pos-
sible to clean mica that has become fouled in this manner. It
is generally advisable to discard an ordinary jump-spark plug
that has this defect, but in the case of a large make-and-break
igniter the better plan is to put in new insulation.
Mica insulation rough from scraping or crumbling. Crumbled
mica is worthless. It has somewhat the appearance of worm-
eaten wood. But when the surface of the mica is only roughened
it may be polished in some cases. The rough surface collects
dirt and the final result is a short circuit in the igniter.
Burned and pitted contact-points. This prevents the contact-
points of a make-and-break igniter from making good metallic
contact with each other. Consequently the full strength of cur-
rent does not flow and the arc is therefore weak. This condi-
tion causes sluggish action of a magnetically operated igniter.
Loose packing. This allows some of the compressed charge
to escape. A hissing sound can sometimes be heard. Lubri-
cating oil put around the igniter will sometimes indicate the
leak by bubbles or by being blown off at the leak. Put new
packing in a high-tension plug. A string of asbestos fiber
wrapped around a fine copper wire (a commercial product) is
suitable in the absence of the regular form of packing for small
plugs. A gasket made of sheet copper bent over so as to form a
deeply grooved ring with asbestos in the groove (copper-asbestos
gasket or washer) is convenient when there is no rubbing action
against the gasket. In a make-and-break igniter it may be only
necessary to tighten the movable electrode against its bearing,
in order to take up end wear.
Operating parts worn so as not to separate the contact-points
wide enough to draw a good arc.
IGNITION-SYSTEM FAULTS AND REMEDIES 407
In the Spark-Coil.
243. Contact-points at the trembler burned or pitted so as
not to make good electric contact. The most usual indication
of this condition is irregular ignition, sometimes followed by
complete stopping of ignition. A contact-point is pitted when
it has small depressions, or pits, burned into it.
Water or dirt on contacts at trembler. Water generally stops
ignition completely. Dirt has much the same effect as badly
pitted contact-points.
Contact-points stuck together by fusing. This sometimes
happens when one coil acts for several cylinders. It also
sometimes happens when there is excessive sparking at the
contact-points of a trembler coil that is used for only one
cylinder.
Excessive sparking at trembler contacts. May be due to too
high voltage in the primary circuit, as when there are too many
cells in the battery. Cut out one or two cells unless the number
is known to be correct. All spark-coils do not operate properly
at the same voltage. If reducing the number of cells does not
stop excessive sparking, then the trouble is probably due to the
condenser not performing its function correctly, as on account of
its insulation being broken down or one of its connecting wires
broken or loose. If there is, or should be, a separate ground
wire for the condenser, see that the wire is in place. Excessive
sparking as stated, may also be due to defective insulation in
either the primary or secondary winding of the coil.
Insulation broken down in transformer coil or condenser.
Indicated by excessive sparking at trembler contacts. May be
caused by too high a voltage in the primary circuit. Also by
allowing the trembler to operate while the secondary circuit is
disconnected, especially where there is no safety spark-gap as
part of the coil. Repair should be made by an expert, or the
defective coil replaced by a new one.
Loose contact-point on trembler. Unusual. Causes irregular
ignition. Rivet or solder with hard solder (one which does not
melt easily), such as that used for silver. .
408 ELECTRIC IGNITION
Trembler spring bent. May change rate of vibration or en-
tirely prevent it. Straighten or put in a new spring.
Difference of lag in producing ignition sparks when two or
more spark-coils are used on one motor. Adjust the tremblers
to vibrate at the same rate, as indicated by the pitch of the
sound.
In the Reactance Coil (Kick-Coil).
244. Defective insulation. May be caused by using too high
voltage. Causes a weak arc at the contact-points of the make-
and-break igniter, or entirely prevents arcing. Dirt between the
terminals may have the same effect. A kick-coil seldom gives
trouble, however.
In the Timer.
245. Dirt or grit between contact-pieces prevents closing the
circuit and causes rapid wear.
Hard grease between roller contact-points prevents closing
the circuit. Some grease that is very soft while warm becomes
quite hard when cooled, as when the motor stands over night in
a garage that is not warmed. Use oil or semifluid grease.
Oil between contact-points which close the circuit by pressure
only (without rubbing or rolling) may prevent good electric
contact.
Keep oil from contact-points.
Circuit closed at wrong time on account of worn or loose
parts.
Stationary timing part worn loose so as to wabble and shake
about. This is apt to cause irregularity in the time of closing
the circuit.
Stationary rollers loose on pins which support them. In
some designs where the rotor strikes stationary rollers to close
the circuit, the rollers, when worn loose, move about so as to
vary the time of closing the circuit.
Failure to close the circuit on account of worn or binding
parts.
Spring weak or broken.
Brush binding or sticking in its holder.
IGNITION-SYSTEM FAULTS AND REMEDIES 409
Rotor shaft does not have good electric connection with the
metal of the motor. Causes imperfect closing of the circuit,
and sometimes there may be complete failure to close it. Con-
sequently the ignition spark or arc is weak at times or fails
entirely.
Circuit not closed at the same instant relative to the position
of each piston in its stroke. May be due to faulty construction
or to worn parts.
Insulated contact-piece of the rotor not in continuous contact
with the part (shaft) on which it is mounted. Generally due to
a loose screw or other fastening. Causes weak spark and missing
of the spark.
Rotor very loose on its shaft. In some designs the rotor is
fastened to its shaft by a set-screw in such a manner that when
the set-screw works loose the rotor can gradually move around
on the shaft. Such a condition varies the time of ignition to
an extreme amount. If this moving around occurs slowly, it is
necessary to keep advancing the spark at the corresponding rate
to keep the motor running. After that the continued moving
of the rotor on its shaft will prevent ignition generally.
In the Magneto.
246. Dirt (carbon dust, particles of metal) in the distributer.
Due to wear of rubbing parts. Clean with a bristle brush and
piece of cloth without using any liquid if possible. Use kerosene
if found necessary to remove the dirt. Do not oil if a carbon
brush is used. Put a small amount of oil on the rubbing sur-
faces with a cloth if a metal brush is used to rub against metal.
Dirt in the interrupter. Clean with a bristle brush and a
cloth. It is better not to use gasoline, for although it is excellent
for cleaning, it leaves the rubbing surfaces in poor condition. If
the gasoline is used, care should be taken to see that the rubbing
surfaces are coated with a small amount of lubricating oil. Oil
the rubbing surfaces very sparingly, if at all. The interrupters
of some magnetos are self -oiling. Others do not require any
lubricant. This is the case when one of each pair of rubbing
surfaces is of wood fiber or some similar material. The inter-
410 ELECTRIC IGNITION
rupter lever is sometimes bushed with fiber where it rocks on
its supporting pin.
Contact-points of interrupter burned or pitted. Dress smooth
and flat with dead-smooth file.
Oil, grease, or water between contact-points of interrupter.
Grease prevents the points from making good contact with each
other. Oil is very apt to do the same. Water prevents the
interruption of the current.
Weak spring on interrupter lever. Does not press the con-
tact-points together firmly. Put in a new spring or bend the
old one so that it will press the contacts together harder. If a
steel spring is very soft it may be retempered. The retemper-
ing can be quickly done by one familiar with heat treatment of
high-grade steel.
> Interrupter lever binds on its pin. Refit. This should be
done by a skilled mechanic. A reamer of the proper size will
enlarge the hole slightly and leave it in good condition. A
twist drill may be used, but is not so good. In an emergency a
fine-cut round file may be used to enlarge the hole in a fiber
bushing. For hardened metal, a piece of fine-grained emery
cloth, or of crocus cloth, wrapped around a wire, can be used.
The part should be very carefully cleaned afterward. The pin
which supports the lever generally cannot be removed conven-
iently for reducing its diameter.
Interrupter contacts do not separate to the proper distance.
Adjust them.
Interrupter contacts do not separate at the proper time
relative to the position of the armature or inductor, according
to which is the rotor. This cannot occur in a magneto whose
interrupter is fitted to a definite position, and which was properly
determined when the machine was made. Otherwise adjust the
interrupter to its proper position.
Distributer not in proper position relative to the interrupter.
This can be corrected by shifting the gears which drive the dis-
tributer relative to each other when there are such gears and
when the interrupter and distributer are on separate shafts.
Take the gears out of mesh and advance or retard one relative
IGNITION-SYSTEM FAULTS AND REMEDIES 411
to the other by the amount of one tooth, or several teeth, as
seems necessary.
Roller or rollers of interrupter worn flat on one side. If the
roller can rotate, it will cause the contact-points to separate
farther at one time than at another.
Too much lubricating oil. If the oil reaches the insulation of
the armature, it is apt to destroy its insulating property to some
extent, and a short circuit may result.
Brush (carbon) worn out or binding in its holder so as not to
make good contact. File the brush a little smaller if it binds.
Brush spring weak. Stretch it if it is a coiled compression
spring. Cut off some of it if it is a coiled tension spring. Bend
a flat spring so that it will press harder against the brush or its
holder, as the case may be. Retemper a steel spring if thought
necessary.
Condenser insulation defective, or the condenser has loose
connection. Excessive sparking at the interrupter is the result
of either of these defects. The connection can sometimes be
easily tightened or repaired, but the defective insulation re-
quires the attention of an expert.
Armature insulation damp or wet. Remove the armature
and bake it in a moderately warm place for a day or more.
Then varnish the insulation with waterproof insulating varnish
if it appears necessary. A magnet keeper should be placed
across the pole-pieces when the armature is removed, and left
there till the armature is replaced. A flat piece of soft steel a
quarter-inch or so thick will answer. Several pieces of small,
flat bar steel or iron can be used in the absence of a larger piece.
Armature insulation defective. Requires the attention of an
expert.
Poor ground connection between armature and frame of
motor. This of course does not include machines in which the
armature winding is intended to be entirely insulated from the
frame. Is apt to occur in a machine which has no ground brush
for a rotating armature. May be due to the ground brush be-
coming worn out, or to* a loose connection between the brush
and ground.
412 ELECTRIC IGNITION
Bearings worn so that rotor strikes the pole-pieces.
Loose driving gear or coupling. Tighten and fit new pin or
key if the old one is worn.
Defective switch. May make a partial ground connection
when the switch is open and there should be no such circuit.
The switch may be only in need of cleaning.
Magnets have become weak. Sometimes caused by removing
the rotor (armature or inductor) without putting a keeper across
the pole-pieces or the ends of the magnets. The magnets can be
remagnetized by wrapping insulated wire around them in the
manner indicated in Fig. 50. It may be necessary to take a
compound magnet apart and deal with the magnets individually.
The wire can be wound from end to end of the magnet if de-
sired, or it may be put on only one leg. A coil wound on a non-
magnetic spool of a shape to fit fairly closely to the bar of the
magnet is convenient. If a spool is put over each leg, the con-
nection between the spools must be made so that the current
will flow through them in the directions indicated in Fig. 50. A
piece of iron or soft steel should be placed across the ends of the
magnet legs in the manner of a keeper. The electric current
needs to flow only a second or so, and should then be decreased
gradually. A gradual decrease of current can be obtained by
slowly separating two wire-ends so as to draw an arc that grad-
ually decreases in volume as the ends are moved farther apart;
or by separating the wire-ends gradually under impure water,
such as that containing salt or acid. Several applications of
current may be advantageous. The strength of the magnet can
be tested by its lifting power, as by placing a heavy piece of steel
or iron on weighing scales, and noting the decrease of scale
reading when the magnet is applied to lift the piece, after the
current has been stopped.
The current used is large enough when an increase of it pro-
duces no further increase in the strength of the magnet, as
measured after the current is discontinued. Care should be
taken to put the individual magnets together so that all of the
north poles are next to the same pole-piece.
IGNITION-SYSTEM FAULTS AND REMEDIES 413
In the Dynamo.
247. Excessive sparking at the brushes. Brush does not
make good contact with the commutator. Brush worn crooked.
Roughened commutator. May also be due to some of the
causes mentioned below.
Armature coil burned out or its insulation defective. Causes
excessive sparking at the brushes and at one or two segments of
the commutator. The commutator segments connected to the
defective coil appear burned at the edges.
Commutator burned along edges of all segments. Brushes not
set in proper position, thus causing sparking and burning at all
of the segments. Adjust the brush-holder rotatively so as to
bring the brushes in proper position if possible. Some dynamos
have no means of adjusting the brush-holder in this manner.
Commutator worn out of round. Causes sparking. If very
bad, turn true in a lathe. Can be trued somewhat, and smoothed,
by sandpapering with fine-grained sandpaper, after removing the
brushes from contact with the commutator.
Grease and dirt on commutator. Causes sparking and burning.
Brush-holder dirty. Causes a partial short circuit and some-
times heating of the armature by the excessive amount of current
that flows on account of the partial short circuit. Sparking and
burning of the commutator may accompany this action.
Field-coil connection broken. This may be inside of the in-
sulation, but only in unusual cases. Prevents the generation of
current completely if the ends are separated at the break. But
if the ends touch each other, there may be indifferent generation
of current.
Other troubles may be of the same general nature as some of
those in a magneto. (See "In the Magneto" immediately pre-
ceding.)
In the Battery.
248. Exhausted dry cells. If there are two dry batteries and
both are exhausted so that neither will supply sufficient current,
put the two batteries in series with each other. As a last resort,
dig some of the sealing compound from the top of each cell so
414 ELECTRIC IGNITION
as to expose the blotting paper, and put water in each cell, or
sal ammoniac and water solution such as is used for the elec-
trolyte. Keep the paper covering of the cells dry.
Wet coverings on dry cells. If the paper covers become wet,
keep the cells separated so that the covers cannot touch each
other. Do not let the cells rest against metal or water-soaked
wood.
Storage battery discharged. Indicated by low voltage of
battery while discharging. Recharge the battery. Do not put
storage batteries in series with each other to secure a higher
voltage after the battery voltage has become low, as just stated,
except in extreme emergency.
Wrong connections between cells or batteries. A reversed
cell reduces both the voltage and current of the battery. Some
wrong connections cause the battery to run down rapidly.
Cells loose so that they can shake about. Is apt to loosen the
connections or break them.
Loose connections between cells. Causes erratic ignition.
Tighten the nuts of dry cells with pliers, or flatten the nut
slightly with a hammer so that it binds on the thread. The
nut may be secured with a drop of solder. These methods are
suggested for dry cells only.
Corroded terminals. These are apt to make the connection
poor on account of high resistance. Clean and brighten the
metal. Cover with vaseline or varnish.
Dirt on insulation between terminals. Causes leakage and
waste of current, especially if the dirt is moist.
Metal of adjacent cells in contact. This may occur between
the terminals or metal cans of dry cells. Wastes current and
reduces voltage.
Metal tools or other metallic appliances on and against the
battery is apt to cause a short circuit.
Electrolyte low in cells, or not of proper strength (specific
gravity, density).
Sediment in bottom of the cells of a storage battery. The
battery runs down rapidly. Causes excessive heating of the
battery in extreme cases.
IGNITION-SYSTEM FAULTS AND REMEDIES 415
In the Connections.
249. Loose strand of wire cable. Is apt to touch some metal-
lic part so as to make a ground connection or a short circuit.
The strands of the cable should be twisted together where it is
bared to fasten to a binding post. It is sometimes advisable to
solder the strands together where they are bared.
Swinging or vibrating wire. If the wire strikes or rubs against
anything, the insulation will generally be worn off. Contact
with a metal part and intermittent short-circuiting may result,
thus causing irregular ignition.
Oil on insulation destroys it.
Loose binding screws and joints.
CHAPTER XXIX.
OPERATING TROUBLES POSSIBLY DUE TO THE IGNITION
SYSTEM.
250. Introductory. While any of the following troubles may
be due to a faulty ignition system, there are also other causes of
faulty ignition to which the trouble may be due, some of which
are mentioned in each case. The ignition system is referred to
only in a general way when the trouble may lie in it on account
of any or several of the causes mentioned in the preceding
chapter.
Motor Will Not Start.
251. Ignition switch not closed, or trouble in the ignition
system.
Fuel valve closed, or no fuel.
Compression valve open sometimes prevents starting.
Mixture not properly proportioned. Generally too lean when
this occurs. Partly close the air inlet when there is a carbureter.
This can be done safely with one's hand for small motors.
Prime the motor cylinders when liquid fuel is used.
Cold motor. If the starting methods just given fail, warm
the motor. Put hot water in the jacket space or blow steam
into it. A torch may be used, with care not to burn insulation
or injure other parts, in case of urgent emergency.
Water or moisture in cylinder. Remove the igniters and dry
the ignition points. Warm the motor cylinder. It may be
more convenient to blow air through a large engine.
Valve mechanism broken or valve timing wrong.
Preignition.
252. This is generally indicated by a sharp snapping sound or
heavy pounding in the motor. It is accompanied by the loss of
power. There may be very little sound to indicate preignition
in a very closely fitted motor, however.
416
OPERATING TROUBLES DUE TO IGNITION SYSTEM 417
Ignition control advanced too far.
Compression too high for the kind of fuel used. The normal
combustible mixture for some fuels ignites by the heat of com-
pression at a much lower compression pressure than others.
Carbon deposit on the walls of the combustion chamber, in-
cluding the head of the piston. A projecting point or partly
loose flake of hard dry carbon becomes incandescent and ignites
the charge early in the compression stroke.
Overheating of the cylinder, piston head, exhaust valve, igni-
tion-points or other projecting piece of metal in the combus-
tion chamber.
In the last two cases there will generally be at least a few
ignitions in the motor after the ignition system is cut out of
action. Sometimes the motor will continue running after cut-
ting off the regular system of ignition.
Back-firing into the Intake of the Motor.
253. Ignition timing entirely wrong.
Worn or loose part (as of the timer) causes the ignition circuit
to close at the wrong time.
A condition under which back-firing is due directly to the
ignition system is that in which two high-tension spark-plugs
are in series with each other for both cylinders of a two-
cylinder four-cycle motor. Then, when the ignition is very
much retarded while starting the motor, the incoming charge
for one cylinder is ignited at the same instant as the com-
pressed charge in the other. This action stops as soon as the
motor has gained speed.
Carbon deposit on the walls of the combustion chamber, in-
cluding the head of the piston. Preignition generally occurs
also in this case.
Overheating of the cylinder, piston, ignition points, or exhaust
valve, or of a projecting piece of metal in the combustion cham-
ber. Preignition generally occurs also.
Inlet valve stem binding or sticking.
Valve timing wrong. Weak spring on the inlet valve.
418 ELECTRIC IGNITION
Lean mixture. A lean mixture may be due to leaks at the
joints of the inlet pipe or manifold. The fuel valve may be
adjusted to admit too little gas fuel, or the carburetor adjusted
similarly. Water in gasoline will cause a lean mixture temporarily.
A lean mixture burns slowly, so that the flame may continue
from one charge to the next, thus igniting the incoming charge.
Rarefaction of the charge by throttling or cutting off the com-
bustible mixture early in the intake stroke. Back-firing under
this condition is especially apt to occur in a motor using liquid
fuel and a float-feed carbureter in such service as that on an
automobile or a motor boat, when the throttle is suddenly nearly
closed from full open position with the motor pulling hard.
The back-firing under this condition is probably due to both
the rarefaction of the charge and leanness of the mixture. The
fuel level in the float chamber of the carbureter is lowered some-
what when the motor is working at full torque and high speed.
The reduced suction of the carbureter, together with the low
level of the fuel in it, gives a lean mixture temporarily.
Overheating of the Motor.
254. Ignition too late. The exhaust connections generally be-
come very hot under this condition, sometimes red hot.
Mixture too rich. May be indicated by black (not white or
blue-white) smoke. Exhaust heats as just mentioned.
Cooling medium (water, oil, air) does not circulate freely.
May be due to stoppage of passages or faulty action of pump or
fan. When a motor car without a fan climbs a long grade with
the wind in hot weather, and with the sun shining full on the
radiator, overheating is very apt to occur.
Exhaust connections clogged. This causes back pressure and
necessitates the burning of more fuel than when the passages
are free.
Misfiring and Exhaust Explosions without Other Serious troubles.
255. When there is no back-firing, and the motor pulls well
during the intervals of no misfiring, the cause may be :
Any defect or improper condition of the ignition system.
OPERATING TROUBLES DUE TO IGNITION SYSTEM 419
Mixture too rich. When there is a carbureter for liquid fuel,
this may be caused by flooding of the carbureter on account of a
sticking or binding float or a leaky valve in the carbureter.
Lubrication of the motor excessive, or wrong kind of oil.
Exhaust valve binding or sticking.
Broken exhaust valve.
Knocking or Pounding.
256. Ignition control set too early.
Preignition on account of carbon in the motor cylinder, over-
heating, or too high compression.
Loose bolts or other fastenings.
Flywheel loose on shaft, or cracked.
Sudden Stopping of Motor.
257. Trembler contacts stick together.
Dirt between contact-points of any part of the ignition sys-
tem prevents closing of the electric circuit.
Electric connections broken or loose.
Valve binds or sticks so as to remain open.
Valve gear broken.
Motor Does Not Develop Full Power.
258. Ignition too late or too early.
Compression leaks prevent full compression.
Particle of carbon under valve so as to prevent its complete
closing.
Valve stem too long. This may not cause a leak until the
motor has become hot from working at full load for some time,
and then may disappear as soon as the motor has cooled slightly,
so that a compression test does not show the leak unless the test
is made immediately after the motor has been working at full
load.
Cracked cylinder.
Leaks around or through the igniter, compression relief valve,
piston, etc.
420 ELECTRIC IGNITION
Mixture lean or too rich.
Lubrication insufficient or wrong kind of lubricating oil.
Valves do not open wide enough.
Valve timing wrong.
Clogged exhaust passages.
Spark Control Must be Advanced More Than Usual and Motor
Behaves Erratically.
259. This is characteristic of a loose timer rotor, which is so
loose as to drop back part of a rotation on the shaft or other
part that drives it. Irregularity in the time of ignition, which
is not helped by advancing the control excessively, may be due
to other loose parts of the timer or corresponding device.
INDEX.
PAGE
Accumulator battery defined 3
Advance and retard, effect on strength of ignition spark 302
mechanism for ignition spark 306
Alternating current in shuttle-wound armature 25
Ammeter, dead-beat needle for 59
direction of current determined with 53
permanent in jump-spark system 249
portable 54
stationary 55
in series with resistance for testing 379
using 56
Ampere-hour defined 109
Anode 51
APLCO electric system 116
Apparatus for measuring voltage and current 54
Arc, position of armature for maximum : 30
speed of armature for 15
from shuttle-wound armature 14
Armature, alternating -current type 1 1
alternating current in shuttle-wound 2$
coil, wire for 12
connections of direct-current 45
connections for four-pole generator 71
core, laminated 18, 43
core, magnetic flux in I-shaped 19
core, shuttle type 12
current induced in I-shaped 24
current represented graphically 28
direct-current type, complete 44
direction of current in 26
drum type, current generated 39
drum types 38, 44
effect cf speed on position of maximum spark or arc 16
electromotive force in I-shaped 24
end-piece 13
of generator 9
head 13
H-type 14
l-type 14
421
422 INDEX
PAGE
Armature, lag of current in 16, 24
magnetic flux through stationary shuttle-wound 36
magneto rotary 1 1
positions for maximum spark affected by lag 16
positions for no spark 16
position for timing a magneto 400, 402
position of shuttle-wound at instant of maximum arc or spark 15, 30
positions for strong arc or spark 16
reactions, effect of 25
regulating the speed of direct-current type 48
rotary shuttle-wound n
reversing the rotation of 76
shuttle-wound 10
sparks per revolution of shuttle-wound : 16
setting in position in a magneto 321
stationary shuttle-wound and rotary sleeve inductor 35
stationary, and inductor .,....,.,.. 298
shuttle-wound rotary r ... : n
speed for drawing an arc 15
spindle, hollow 14
winding of 12
winding of direct-current 45
Automatic spark-advance mechanism 113
Automatic cut-out for protecting a generator 113
Backfiring 417
Battery, see also Storage Battery.
accumulator type defined j
accumulator, see Storage Batteiy.
care of, in general 374
connections 88
connection to external circuit 94
connections kept tight 375
corrosion of terminals prevented 375
current capacity 89
decrease of current from primary 80, 82
defined 3
depolarization of 80
deterioration of dry 82
economy with timer and contact-maker 260
electrodes of ....... 79
electrolyte of 79
exhausted by a reversed cell 91
exhaustion by wrong connection 94
exhaustion of dry ...... .... . ... . 83
floated on the line no
floated, switchboard for two-voltage system with . 121
lamp for testing 381
INDEX 423
PAGE
Battery, leakage when wet 375
local action in 80
marine 96
multiple-connected 90
parallel-connected 90
parallel-series 92
polarization of 79
primary 78
primary, denned . 3
recuperation of dry 83
reversed cell in 89, 91
running down of dry 83
screw-top connected 95
secondary, see Storage Battery.
secondary, denned -3
series-connected 88
short-circuiting injurious 82
storage, secondary, or accumulator, see Storage Battery.
storage defined ^ 3
switch in connections to external circuit 94
terminals of 89
terminals of parallel-connected 90
testing the cells of 381
testing a primary 376
troubles 413
voltage of parallel-connected 90
voltage of series-connected 89
water-tight box for 96
without wire connections 95
wrong connections for 93
Battery cell . 3
action of carbon-zinc wet 79
BSCO wet 84
capacity and dimensions, table 87
carbon-zinc, new type 82
carbon-zinc primary wet 78
carbon-zinc primary dry 80
copper oxide and zinc wet 84
current capacity of dry 82
depolarizer for 81, 84
Edison primary wet 86
Lalande and Chaperon primary wet 84
Leclanche primary wet 78
polarization of 80
reversed in a battery 89
screw-top 95
terminals of 79
voltage of carbon-zinc 80
424 INDEX
PAGE
Battery cell, voltage of dry carbon-zinc 82
voltage of copper oxide and zinc 86
wet primaiy carbon-zinc 78
Battery cells, current increase by connecting 89, 90
Brush of electric machine denned 31
connecting rotary armature to frame of magneto 32
material for current-carrying 32
Brushes for dynamo 70
position in direct-current generator 67
Cam-shaft, speed of 147
Care and adjustment of ignition systems 368-377
Cathode 51
Cell of battery 3
Coil, induction, see Spark-coil.
Condenser, auxiliary in ignition system 242, 247
grounded in ignition system 243, 247
use of, in spark-coil 206
Combustion, varying time of ignition relative to rate of 362
Commutator, care of 373
of direct-current generator 41, 44
lubricating the 373
Compass needle, extemporized 53
Compass test for direction of current 52
Connections, keeping tight 375
trouble in the 415
Contact, duration of, in mechanically operated igniter 126
duration of, in make-and-break igniter 145, 147
Contact-maker, mechanically operated for jump-spark ignition 254
snap-spring type 254
Contact-points, filing or dressing 374
life increased by using two pairs of 175
magneto, adjusting 373
repairing 369, 374
Core-neck of armature 12
Crank-shaft and piston, relative positions of 402
Current, affected by form of pole-pieces 29
alternating, in shuttle-wound armature 25
ammeter test for direction of 53
automatic regulation of direct, in dynamo 73
color test for direction of 51
cycle of alternating 29
cycles of, in stationary shuttle armature with rotary sleeve inductor 37
direction tests 50
direction determined by compass needle 52
direction of, in armature 26
in drum armature 39
economy with timer and contact-maker compared 261
INDEX 425
PAGE
Current, graphical representation of, in shuttle armature 28
induced, in I-shaped armature 24
lag of, in armature 24
magnetic needle test for direction of 52
testing for direction of 50
voltmeter test for direction of 53
water test for direction of 50
Current capacity of a battery 89, 90
Current supply system, APLCO 1 16
apparatus for two- voltage, with floated battery 122
automatic cut-out for 114
battery floated on the line no
Dayton Electrical Manufacturing Company 122
dynamo and floated battery no, 122
dynamo, storage battery and switchboard for 122
generator and two floated batteries 117
switchboard for two-voltage 119
two-voltage, batteries floated 117
volt-ammeter included 1 16
Cut-out, automatic, for protecting dynamo 73, 113, 121
Cycle of current 29
Density and hydrometer scales compared, table 385
Distributor, high-tension 252, 253
spark-coil and contact-maker combined 259
Dual ignition system, low-tension electromagnetic 171
plunger-core electromagnets in 171
Dynamo, Apple Electric Company, four-pole 73
armature connections for four-pole 71
automatic cut-out for 73
bipolar shunt-wound 65
brushes for 70
brushes, position of 67
building up of pressure in 66
capacity of 70
care of 372
compound-wound 74
current automatically regulated 73
current in field-coils of 65
Dayton Electrical Company's bipolar 68
defined 3
direct-current shunt-wound 65
electromagnets for 62
field-coils for 69
four-pole 71
speed governor for 71
shunt-wound 65
troubles 413
426 INDEX
PAGE
Electricity, high-tension, defined - t
low-tension, defined ; I
sources of, for ignition 3
Electric cell 3
Electric measuring instruments 54
Electric generator 3
armature of 9
field-magnets, electromagnetic 62
field-magnets, permanent 8
inductor of 9
principle of 8
troubles 409, 413
Electric supply, see Current Supply Systems.
Electric system, battery floated on the line no
two-voltage batteries floated on the line 117
two- voltage, floated batteries, lamps and ignition apparatus 119
Electrode 51
Electrodes of a battery 79
Electrolyte 51
of a battery 79
density of 386
density of, testing 384
hydrometer for testing the 384
mixing of 392
Electromagnets, see also Magnets.
Electromagnets 60
Electromagnet, bar-shaped 60
compound-wound 74
consequent poles in 62
four-pole, ring-shaped 63
plunger-core type 61
polarity relative to current 60
residual magnetism in 60
ring-shaped 62
ring-shaped four-pole 63
U-shaped 62
Electromagnetic igniters, low-tension 169, 199
Electromotive force in a generator 8
induction of 9
induction of, in an I-shaped armature 24
of carbon-zinc wet battery cell ; 80
Explosions in the exhaust 418
Field, magnetic ' 6
Field-coils 69
current in 65
rheostat in series with , 75
Field-magnets. .,,,,.,,...., 10
INDEX 427
PAGE
Field-magnets, abutted 1 1
four-pole ring-shaped 63
ring-shaped 62
U-shaped 62
Flux, magnetic 6
magnetic, in I-shaped armature core 19
methods of varying magnetic 9
variation of, to induce electromotive force 9
Generator, Apple Electric Company's four-pole 73
armature connections of direct-current 45
armature connections for four-pole 71
armature for direct-current 44
armature of electric 9
automatic cut-out for 73
bipolar electromagnetic 65
building up of pressure in an electromagnetic 66
brushes for commutator of 70
brushes, position of, for direct-current 67
capacity of direct-current 70, 148
care of electric 372
commutation of current in 41
commutator of direct-current 41
compound-wound direct-current 74
current automatically regulated 73
Dayton Electric Company's direct-current 68
direct-current electromagnetic 65
direct-current elementary , 42
direct-current four-pole 71
direct-current shunt- wound 65
direct-current type 38
direct-current type, with permanent magnets 38
electric 3
electromagnetic, denned 3
electromagnetic, field-magnets of 65
electromagnetic, time required to build up voltage 148
electromagnets for 62
field-coil current 65
field-coils for 69
field-magnets, electromagnetic 62
field-magnets, permanent 8
floated storage battery, lamps and ignition apparatus 114
four-pole direct-current 71
inductor of electric 9
pressure regulation in electric, 75
principle of electric .. 8
reversing the rotation of 76
rheostat for regulating voltage of 75
428 INDEX
PAGE
Generator, shunt-wound direct-current 65
shunt- wound four-pole 71
speed governor for 71
storage battery and lamp no
troubles in electric 409, 413
Governor for regulating speed of armature 48
Ground brush in a magneto 32
Ground connection defined 144
H-armature 14
High-tension electricity defined I
Hydrometer scale compared with density, table 385
Hydrometer for testing electrolyte 384
I-armature 14
Igniters: Make-and-break igniters are indexed under Igniters; jump-spark
igniters are indexed under Spark-plugs.
Igniter, action of make-and-break 145
action indicated by tell-tale kick-coil 143
advance and retard control of mechanically operated make-and-break 123, 136
Allis-Chalmers for large engine 184
automatic control of mechanically operated 131
Bosch electromagnetic, small 192
Bosch mechanically operated 126
contact duration in mechanical make-and-break 126
contact-point material 126
contacts, repairing 370
control for mechanically operated 128, 136
electromagnetic double-contact, large 176
electromagnetic, large 184
electromagnetic low-tension, small 191
electromagnetic of Wisconsin Engine Company 175
electromagnetic, operation of 169
elements of low-tension mechanically operated 123
Fay & Bowen mechanically operated 131
hammer-break in 125
low-tension electromagnetic, small 191
low-tension mechanically operated, elements of 123
make-and-break, action of 145
make-and-break, duration of contact 145, 147
make-and-break, double contact 171
make-and-break mechanically operated, elements of 123
operation of electromagnetic 169
operating mechanism of Snow Steam Pump Works' mechanical make-and-
break 133
plunger-core electromagnetic 170
Snow Steam Pump Works' mechanically operated 133
Truscott Boat Manufacturing Company's mechanically operated 128
INDEX 429
PAGE
Igniter, Westinghouse mechanically operated 132
Igniters, advance and retard control for mechanically operated 138
electromagnetic, low-tension 169-199
engine showing mechanically operated igniters in place 138
low-tension mechanically operated 123-139
make-and-break mechanically operated 123-139
mechanically operated in place on engine 138
operating mechanism for mechanical make-and-break 137
successive order of action of 137
Ignition, advancing and retarding in a variable-speed motor 366
advancing on account of lag 361
automatic advance and retard mechanism 180
control, advance must be excessive 420
coupling for varying time of 303, 306
general methods of electric . I
high-tension, denned i
shaft coupling for varying time of 303, 306
low-tension, defined I
manipulation of, in an automobile motor 366
premature 416
three igniters per combustion chamber 166
timing 397-404
variation of, reduced by simultaneous sparks 365
varying the time of 361-367
varying the time on account of lag 361
varying the time of, relative to combustion rate 362
varying the time of, relative to speed 364
varying the time of, in a variable-speed motor 266
varying the time of, with shaft coupling 303, 306
Ignition spark, means of obtaining constant strength of 302
strength affected by advance and retard 301
Ignition sparks, simultaneous 365
Ignition systems, see also Current Supply Systems for source of electricity.
Ignition systems, high-tension dual and combined . . .- 326-352
low-tension, electromagnetic igniters 169-199
low-tension mechanical make-and-break 144-168
magneto current only 268-325
jump-spark with trembler interrupters and individual spark-coils . . 240-251
jump-spark, distributor and battery 252-260
Ignition system, action indicated by tell-tak kick-coil 143
Allis-Chalmers electromagnetic 189
battery in series with magneto primary 345
Bosch dual 340
cam-shaft speed 147
charged and discharged condenser for constant strength of spark 302
condenser auxiliary 242, 247
condenser grounded in jump-spark ... 243, 247
connections kept tight 375
430 INDEX
PAGE
Ignition system, dual Bosch high-tension 340
dual electromagnetic low-tension 171
dual electromagnetic for large engine, low- tension 189
duplex Bosch high-tension 345
electromagnetic dual 171
electromagnetic make-and-break, with magneto 194
Eisemann-Carpentier high-tension 337
Eisemann high-tension 334
faults and remedies 405-415
flash lamps in low-tension 174, 184
high-tension Eisemann 334
high-tension Eisemann-Carpentier 337
high-tension Remy 327
high-tension Splitdorf, separate transformer 330
24 igniters for one engine 166
interrupted magneto current 268
interrupted magneto shunt current 271
jump-spark, auxiliary- condenser 242, 247
jump-spark, distributor and battery 252
jump-spark with ammeter and voltmeter permanently connected 249
jump-spark with grounded condenser 243
jump-spark, synchronized 245
jump-spark, one-unit trembler spark-coil 240
jump-spark, trembler coil 252
jump-spark with individual trembler coils 244
low-tension dual electromagnetic 171, 189
low-tension four-ring timer 189
magnetic plug and magneto 194
magneto with double- wound high-tension armature 273
mechanical make-and-break, alternating magneto current, elementary. . 146
mechanical make-and-break, battery current, elementary 144
mechanical make-and-break, direct-current generator, elementary 148
mechanical make-and-break, four-cylinder, elementary 149
mechanical make-and-break, using no-volt current 152-165
mechanical make-and-break, with switchboard 152
shunted magneto current 272
Remy high-tension 327
series-shunt spark-plugs 261
spark-plugs in series 261
switchboard, one-unit 152
synchronism of magneto in 147
synchronized jump-spark 245
triple low-tension mechanical 166
i lo-volt not grounded 162
Ignition apparatus, adjustment and care of 368
Induction coil,- see Sparkrcoil.
Inductor of electric generator 9
rotary sleeve, type 35
INDEX 431
PAGE
Inductor, rotary and stationary armature 298
sparks per revolution of sleeve type 37
Instruments for measuring voltage and current 54
Interrupter, Mea type 319
mechanically operated for battery current 254
mechanically operated in magneto 319
setting device for 290
of spark-coil, see Trembler.
U. & H. magneto 289
Interrupters, two on one magneto 342
Keeper of magnet 6
Kick-coils 138
Kick-coil, action of 145
screw-top type 142
with switch and key lock 347
tell-tale for indicating action of igniter 142
troubles 408
waterproof 140, 141
Kick-switch for spark-coil 222
Knocking or pounding in the motor 419
Lag of armature current 24
of electric current in a magneto 16
of spark from a magneto 16
of spark-coils 214
Lalande and Chaperon wet-battery cell 84
Lamination of armature core 18
Lamps used as resistance 2, 152, 388
Low-tension electricity defined i
ignition system, flash lamps in 174
Magnets, see also Electromagnets.
Magnet, action on compass needle 5
determination of N and S poles 5
keeper 6
poles of , 5
poles, consequent 62
Magnets, abutted 1 1
bell-shaped in a magneto 316
composite 8
compound 8
horseshoe form 4
for magneto 8
method of making permanent 4
permanent 3
rocking, in a magneto 316
U-shaped 8
432 INDEX
PAGE
Magnetic compass test for direction of current 52
field 6
field not affected by non-magnetic materials 8
flux 6,
flux th'rough stationary shuttle armature and sleeve inductor 36
flux in I-shaped armature core 19
flux, rate of change in I-shaped armature core 22
flux, variation of g
flux, methods of varying gi
materials 7
needle test for direction of current 52
Magnetism, residual 60
residual in electromagnetic generator 66
shield pole extensions 311, 314
sleeve pole extensions 311, 314
sleeve inductor, magnetic flux through armature 36
sleeve rotary inductor 35
Magnetos, see also Dynamo.
high-frequency low-tension alternating-current 353~36o
Magneto, advance and retard of spark, automatic 306
alternating current in shuttle-wound 25
arc from shuttle-wound 14
armature, setting to correct position 321
armature core 12
armature, double-wound 273
armature, shuttle- wound 1 1
automatic. advance .and retard mechanism on 306
Bosch duplex 350
Bosch high-tension 275
Bosch low-tension alternating-current 31
care of ' 372
charged-and-discharged condenser type 302
defined 3
detail description of low-tension shuttle- wound 31
direct-current types 38, 47
Eisemann high-tension 305
elementary shuttle-wound 14
fastenings of magnetic material not suitable 146
field-magnets, abutted 1 1
Ford high-frequency low-tension 358
high-tension 330
high-tension Bosch duplex 350
high-tension, with stationary armature and rocking pole-pieces 311
high-tension, with commutator and interrupter 350
high-tension, with single-wound armature 272, 307, 310
high-tension, double- wound rotary armature 275
high-tension, with two high-tension windings 352
high-tension, with, magneto primary in series with battery circuit 345
INDEX 433
PAGE
Magneto, high-tension, with separate transformer 307, 310
high-tension, with two interrupters 342
internal connections of low-tension alternating-current 30
interrupter types 268-325
interrupter type, for electromagnetic igniters 196
K-W high-frequency low-tension 356
lag of current in 16
low-tension alternating 10
low-tension alternating, sectional view of 31
low-tension, for electromagnetic igniters 196
low-tension, with stationary armature 354, 356, 359
magnets for 8
magnets rocked in 316
Mea high-tension, with rocking magnets 316
Pittsfield high-tension 311
Remy 275
rotary armature types 1 1
with rotating magnet inductor 358
sectional view of low-tension alternating-current 31
shuttle armature types 10
shuttle- wound low-tension 30
spark from shuttle-wound 14
speed for drawing an arc 15
speed governor for direct-current 48
Splitdorf high-tension 330
Splitdorf low-tension alternating-current 34
starting device for 294
stationary armature, high-tension 295
synchronism of alternating-current , 147
timing of a , 400
troubles 409
U. & H. high-tension 288
W. & S. high-frequency low-tension 353
Make-and-break igniters, see Igniters.
Materials, magnetic 7
non-magnetic 7
Measuring instruments for voltage and current 54
Misfiring 418
Motor, crank-shaft and piston positions in 402
overheating of a 418
full power not developed 419
knocking or pounding in. \ 419
pulls weakly 419
stops suddenly 419
will not start 416
Multiple battery, see Battery.
Non-magnetic materials 7
434 INDEX
PAGE
Oiler, felt-wick 69
Overheating of the motor 418
Parallel battery, see Battery.
Piston and crank-shaft, relative positions of 402
Plunger-core electromagnet 61
Polarization of a battery 79, 80
Poles of a magnet 5
Pole-pieces, crowned 30
different forms of 29
form of, affects range of advance and retard of spark 30
form of, affects current curve 29
of magnets 10, 29
magnetic sleeve extensions of 311, 314
movable extensions of 311, 314
notched or tooth-shaped 30
rounded 30
Pole-shoes of magnets, see Pole-pieces.
Pounding or knocking in the motor 419
Power not fully developed 419
Preignition 416
Pressure, compound-wound generator for constant 74
Pressure, electric, denned i
in low-tension ignition 2
Primary battery denned 3
Reactance coils, see Kick-coils.
Reactions, effect of, in armature of generator 25
Resistance for charging storage battery, computed 389
for use in series with ammeter 379
lamps used for 2, 152, 388
Reversed cell in a battery 89, 91
Rheostat for regulating voltage of generator 75
Safety spark-gap 213
Secondary battery denned 3
Secondary battery, see Storage Battery.
Series battery, see Battery.
Shaft couplings for advancing and retarding ignition 303, 306
Shock, electric t-
as affected by condition of skin 4
Short-circuiter, high-tension 264, 266
Spark advance and retard affected by form of pole-pieces 30
advancing and retarding in a variable-speed motor 366
constant strength, means of obtaining 302
manipulation of, in an automobile motor 366
positions of armature for maximum 30
from shuttle-wound armature 14
INDEX 435
PAGE
Spark, speed of armature for drawing 15
strength affected by advance and retard of 301
timing of the ignition 397-404
Sparks per revolution of shuttle armature 16
per revolution of sleeve inductor 37
Spark-coil, adjusting trembler of 370
Autocoil Company 216
condenser of 206
connections of 203
elementary forms of 200
high-tension, with switch and key lock 343
kick-switch type 222
laboratory type 218
lag of 214
lag, obviation of unequal 222
master type for synchronizing. 222
non-trembler transformer types 224, 258
operation of non-trembler 202
screw-top type 96
transformer types 200-226
transformer, use of , 200
trembler of 204
trembler types, complete 220-224
trembler type, operation of 205
troubles 407
varying the time of ignition on account of lag in 361
synchronized , 222
Spark control, advance must be excessive 420
automatic 180
Spark-gap, safety 213
width of 238, 369
Spark-plugs: Jump-spark igniters are indexed under Spark-plugs; make-and-
break igniters are indexed under Igniters.
Spark-plugs, jump-spark 231-239
Spark-plug, adjusting the spark-gap 369
Bosch electromagnetic low-tension, small 192
cleaning 369
electromagnetic low-tension, small 191
multiple spark-gap types 234
screwing into place, precaution 369
separable or detachable 236
spark-gap width 238
troubles 405
Spark-plugs in series 261
in series-shunt 262
Spark-points, repairing, in contact igniters 370
Speed governor 48
Storage batteries, see also Batteries.
436 INDEX
PAGE
Storage batteries 97-1 10
connection for charging two at once 390
Storage battery, action of 97
action of lead-plate type 108
ampere-hours capacity 109
capacity and size, table 109
care of lead-plate type of 390
care of nickel-iron type of 394
complete lead-plate 99
cell, voltage of lead 101
charging 97,107
charging lead-plate type of 390
charging nickel-iron type of 394
charging and care of 387-396
charging rate 390, 393, 394
connections for charging 388
cover vented 101
defined 3
density of electrolyte 386
discharge rate 102
discharge at rapid rate injurious 102
electrodes 97, 98, 99, 102
electrolyte, density of 386
electrolyte for lead-plate 101
electrolyte, mixing for 392
Exide 104
floated on the line no, 151
floated, APLCO system 116
as formed while charging 108
generator and lamp combined in system no
generator, lamps and ignition apparatus 114
grids of . 98, 107
ignition types 102, 107
lead-plate type 98
lead plates, color of 98
plates for 98, 99, 102
rheostat resistance used while charging 389
sediment in 106
sediment, removing 393
separator for plates of 100, 106
taking out of commission 394, 396
terminals of 104
testing 378-380
testing density of electrolyte 384
test by voltage and current method 278
voltage of 104, 395
voltage, lowest safe 382
voltage while discharging 383
INDEX 437
PAGE
Storage battery, voltage-drop test 381
Switch, kick-switch 222
location of, in make-and-break system 151
Switches, reversing the , . . 156, 158
Switchboard, automatic cut-out included 121
combination multiple 156, 162, 165, 166
combination no-volt 152-165
combination two-voltage 119, 121
combination, for no volts 152
one-unit 152
operation of 156, 158
reversing the switches 158, 161
two units 156, 162, 165
two-voltage, batteries floated 119
Tell-tale kick-coil 142
Tension, electric, defined I
Terminals of battery 79, 89, 90
Testing a battery 376
density of electrolyte 384
for direction of current. . 50
lamp for battery 381
a storage battery 378
Timers 227-231
Timer, Allis-Chalmers 182
automatic control, mechanism for 180
care of 371
elementary form of 227
cleaning and lubricating 371
four-ring type for low-tension ignition 182
four-point rotor 253
for large engine 178
one-ring type for low-tension ignition 178
plain pressure -contact type 230
roller contact 227
setting in position 398
sliding-contact type 229
snap-spring type 254
speed of 251
troubles 408
Wisconsin Engine Company's 178
Timing the ignition 397-404
automatic mechanism for 180
Transformer spark-coils, see also Spark-coils.
Transformer spark-coils 200-226
Trembler of spark-coil 204, 215, 217, 218, 219
adjusting the 370
bow-spring type 215
438 INDEX
PAGE
Trembler, hammer-break types 217, 218
plain type 219
Tritt direct-current magneto 49
Troubles and remedies 405-420
Unisparker 255, 259
Voltage of a battery 89
of carbon-zinc diy-battery cell 82
of carbon-zinc wet-battery cell 80
of copper oxide and zinc battery cell 86
of parallel-connected battery 90
of parallel-series battery 92
of series-connected battery 89
of storage battery while discharging 383
compound-wound generator for constant 74
Volt-ammeter 57
in an electric system 116
Voltmeter, dead-beat needle for 59
direction of current determined with 53
permanent, in jump-spark ignition system 249
portable 56
using 56
Vibrator of spark-coil, see Trembler.
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Manual of Assaying 12mo, 1 00
Minet's Production of Aluminum and its Industrial Use. (Waldo.). . .12mo, 2 50
Ricketts and Miller's Notes on Assaying Svo, 3 00
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Wilson's Chlorination Process 12mo, 1 50
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ASTRONOMY.
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Craig's Azimuth 4to, 3 50
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CHEMISTRY.
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* Abegg's Theory of Electrolytic Dissociation, (von Ende.) 12mo, 1 25
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Allen's Tables for Iron Analysis 8vo, $3 00
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Association of State and National Food and Dairy Departments, Hartford
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Jamestown Meeting, 1907 8vo, 3 00
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Laboratory Methods of Inorganic Chemistry. (Hall and Blanchard.)
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Miller's Cyanide Process 12mo, 1 00
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Penfield's Tables of Minerals, Including the Use of Minerals and Statistics
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* Qualitative Chemical Analysis 8vo, 1 2ft
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5
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Treadwell's Qualitative Analysis. (Hall.) 8vo, 3 00
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Whipple's Microscopy of Drinking-water 8vo, 3 50
Wilson's Chlorination Process 12mo, 1 50
Cyanide Processes. 12mo, 1 50
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CIVIL ENGINEERING.
BRIDGES AND ROOFS. HYDRAULICS. MATERIALS OF ENGINEER-
ING. RAILWAY ENGINEERING.
* American Civil Engineers' Pocket Book. (Mansfield Merriman, Editor-
in-chief.) 16mo, mor. 5 00
Baker's Engineers' Surveying Instruments 12mo, 3 00
Bixby's Graphical Computing Table Paper 19 X 24i inches. 25
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* Burr's Ancient and Modern Engineering and the Isthmian Canal 8vo, 3 50
Comstock's Field Astronomy for Engineers 8vo, 2 50
* Corthell's Allowable Pressure on Deep Foundations 12mo, 1 25
Crandall's Text-book on Geodesy and Least Squares 8vo, 3 00
Davis's Elevation and Stadia Tables 8vo, 1 00
Elliott's Engineering for Land Drainage 12mo, 1 50
* Fiebeger's Treatise on Civil Engineering 8vo, 5 00
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Folwell's Sewerage. (Designing and Maintenance.) 8vo, 3 00
Freitag's Architectural Engineering 8vo, 3 50
French and Ives's -Stereo tomy 8vo, 2 50
Gilbert, Wightman, and Saunders's Subways and Tunnels of New York.
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* Hauch and Rice's Tables of Quantities for Preliminary Estimates. . . 12mo, 1 25
Hayford's Text-book of Geodetic Astronomy , 8vo, 3 00
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* Text-book on Practical Astronomy 8vo, 2 00
Howe's Retaining Walls for Earth 12mo, 1 25
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Ives and Hilts's Problems in Surveying, Railroad Surveying and Geod-
esy 16mo, mor. 1 50
* Johnson (J.B.) and Smith's Theory and Practice of Surveying . Large 12mo, 3 50
Johnson's (L. J.) Statics by Algebraic and Graphic Methods 8vo, 2 00
* Kinnicutt, Winslow and Pratt's Sewage Disposal 8vo, 3 00
* Mahan's Descriptive Geometry 8vo, 1 50
Merriman's Elements of Precise Surveying and Geodesy 8vo, 2 50
Merriman and Brooks's Handbook for Surveyors 16mo, mor. 2 00
Nugent's Plane Surveying 8vo, 3 50
Ogden's Sewer Construction 8vo, 3 00
Sewer Design 12mo, 2 00
Parsons's Disposal of Municipal Refuse 8vo, 2 00
Patton's Treatise on Civil Engineering , . . . .8vo, half leather, 7 50
6
Reed's Topographical Drawing and Sketching 4to, $5 00
Riemer's Shaft-sinking under Difficult Conditions. (Corning and Peele.)-8vo. 3 00
Siebert and Biggin's Modern Stone-cutting and Masonry 8vo, 1 50
Smith's Manual of Topographical Drawing. (McMillan.) 8vo, 2 50
Soper's Air and Ventilation of Subways 12mo, 2 50
* Tracy's Exercises in Surveying 12mo, mor. 1 00
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Venable's Garbage Crematories in America 8vo, 2 00
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Wait's Engineering and Architectural Jurisprudence 8vo, 6 00
Sheep, 6 50
Law of Contracts 8vo, 3 00
\,a.w of Operations Preliminary to Construction in Engineering and
Architecture 8vo, 5 00
Sheep, 5 50
Warren's Stereotomy Problems in Stone-cutting 8vo, 2 50
* Waterbury's Vest-Pocket Hand-book of Mathematics for Engineers.
2JX5I inches, mor. 1 00
* Enlarged Edition, Including Tables , . . .mor. 1 50
Webb's Problems in the Use and Adjustment of Engineering Instruments.
16mo, mor. 1 25
Wilson's Topographic Surveying ' 8vo, 3 50
BRIDGES AND ROOFS.
Boiler's Practical Treatise on the Construction of Iron Highway Bridges.. 8vo, 2 00
* Thames River Bridge Oblong paper, 5 00
Burr and Falk's Design and Construction of Metallic Bridges 8vo, 5 00
Influence Lines for Bridge and Roof Computations 8vo, 3 00
Du Bois's Mechanics of Engineering. Vol. II Sma 4to , 10 00
Foster's Treatise on Wooden Trestle Bridges 4to, 5 00
Fowler's Ordinary Foundations 8vo, 3 50
Greene's Arches in Wood, Iron, and Stone 8vo, 2 50
Bridge Trusses 8vo, 2 50
Roof Trusses 8vo, 1 25
Grimm's Secondary Stresses in Bridge Trusses 8vo, 2 50
Heller's Stresses in Structures and the Accompanying Deformations. . . . 8vo, 3 00
Howe's Design of Simple Roof- trusses in Wood and Steel 8vo. 2 00
Symmetrical Masonry Arches 8vo, 2 50
Treatise on Arches 8vo, 4 00
* Hudson's Deflections and Statically Indeterminate Stresses Small 4to, 3 50
* Plate Girder Design 8vo, 1 50
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Johnson, Bryan and Turneaure's Theory and Practice in the Designing of
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Modern Framed Structures. New Edition. Part 1 8vo, 3 00
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Merriman and Jacoby's Text-book on Roofs and Bridges:
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Part II. Graphic Statics 8vo, 2 50
Part III. Bridge Design 8vo, 2 50
Part IV. Higher Structures 8vo, 2 50
Sondericker's Graphic Statics, with Applications to Trusses, Beams, and
Arches 8vo, 2 00
Waddell's De Pontibus, Pocket-book for Bridge Engineers 16mo, mor. 2 00
* Specifications for Steel Bridges 12mo, 50
Waddell and Harrington's Bridge Engineering. (In Preparation.)
HYDRAULICS.
Barnes's Ice Formation 8vo, 3 00
Bazin's Experiments upon the Contraction of the Liquid Vein Issuing from
an Orifice. (Trautwine.) 8vo, 2 00
Bovey's Treatise on Hydraulics 8vo, 5 00
7
Church's Diagrams of Mean. Velocity of Water in Open Channels.
Oblong 4to, paper, $1 50
Hydraulic Motors . 8vo, 2 00
Mechanics of Fluids (Being Part IV of Mechanics of Engineering) . .8vo, 3 00
Coffin's Graphical Solution of Hydraulic Problems .16mo, mor. 2 50
Flather's Dynamometers, and the Measurement of Power 12mo, 3 00
Folwell's Water-supply Engineering 8vo, 4 00
Frizell's Water-power 8vo, 5 00
Fuertes's Water and Public Health 12mo, 1 50
Water-filtration Works 12mo, 2 50
Ganguillet and Kutter's General Formula for the Uniform Flow of Water in
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Hazen's Clean Water and How to Get It Large 12mo, 1 50
Filtration of Public Water-sapplies 8vo, 3 00
Hazelhurst's Towers and Tanks for Water-works 8vo, 2 50
Herschel's 115 Experiments on the Carrying Capacity of Large, Riveted, Metal
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Hoyt and Grover's River Discharge 8vo, 2 00
Hubbard and Kiersted's Water-works Management and Maintenance.
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Mason's Water-supply. (Considered Principally from a Sanitary Stand-
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Merriman's Treatise on Hydraulics 8vo, 5 00
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* Morrison and Brodie's High Masonry Dam Design .8vo, 1 50
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Schuyler's Reservoirs for Irrigation, Water-power, and Domestic Water-
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Whipple's Value of Pure Water Large 12mo, 1 00
Williams and Hazen's Hydraulic Tables 8vo, 1 50
Wilson's Irrigation Engineering 8vo, 4 00
Wood's Turbines 8vo, 2 50
MATERIALS OF ENGINEERING.
Baker's Roads and Pavements 8vo, 5 00
Treatise on Masonry Construction . . 8vo, 5 00
Black's United States Public Works Oblong 4to, 5 00
Blanchard and Drowne's Highway Engineering. (In Press.)
Bleininger's Manufacture of Hydraulic Cement. (In Preparation.)
Bottler's Varnish Making. (Sabin.) (In Press.)
Burr's Elasticity and Resistance of the Materials of Engineering 8vo, 7 50
Byrne's Highway Construction 8vo, 5 00
Inspection of the Materials and Workmanship Employed in Construction.
16mo, 3 00
Church's Mechanics of Engineering 8vo, 6 00
Mechanics of Solids (Being Parts I, II, III of Mechanics of Engineer-
ing 8vo, 4 50
Du Bois's Mechanics of Engineering.
Vol. I. Kinematics, Statics, Kinetics Small 4to, 7 50
Vol. II. The Stresses in Framed Structures, Strength of Materials and
Theory of Flexures Small 4to, 10 00
Eckel's Building Stones and Clays. (In Press.)
* Cements, Limes, and Plasters 8vo, 6 00
Fowler's Ordinary Foundations 8vo, 3 50
* Greene's Structural Mechanics 8vo, 2 50
Holley's Analysis of Paint and Varnish Products. (In Press.)
* Lead and Zinc Pigments Large 12mo, 3 00
* Hubbard's Dust Preventives and Road Binders 8vo, 3 00
Johnson's (C. M.) Rapid Methods for the Chemical Analysis of Special Steels.
Steel-making Alloys and Graphite Large 12mo, $3 00
Johnson's (J. B.) Materials of Construction Large 8vo, 6 00
Keep's Cast Iron 8vo, 2 50
Lanza's Applied Mechanics 8vo, 7 50
Lowe's Paints for Steel Structures 12mo, 1 00
Maire's Modern Pigments and their Vehicles 12mo, 2 00
Maurer's Technical Mechanics *. . 8vo, 4 00
Merrill's Stones for Building and Decoration 8vo, 5 00
Merriman's Mechanics of Materials 8vo, 5 00
* Strength of Materials 12mo, 1 00
Metcalf 's Steel. A Manual for Steel-users 12mo, 2 00
Morrison's Highway Engineering 8vo, 2 50.
* Murdock's Strength of Materials . . 12mo, 2 00
Patton's Practical Treatise on Foundations 8vo, 5 00
Rice's Concrete Block Manufacture 8vo, 2 00
Richardson's Modern Asphalt Pavement 8vo, 3 00
Richey's Building Foreman's Pocket Book and Ready Reference. 16mo, mor. 5 00
* Cement Workers' and Plasterers' Edition (Building Mechanics' Ready
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Handbook for Superintendents of Construction 16mo, mor. 4 00
* Stone and Brick Masons' Edition (Building Mechanics' Ready
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* Ries's Clays : Their Occurrence, Properties, and Uses 8vo, 5 00
* Ries and Leighton's History of the Clay-working Industry of the United
States ......... 8vo. 2 50
Sabin's Industrial and Artistic Technology of Paint and Varnish 8vo, 3 00
* Smith's Strength of Material 12mo, 1 25
Snow's Principal Species of Wood 8vo, 3 50
Spalding's Hydraulic Cdment 12mo, 2 00
Text-book on Roads and Pavements 12mo, 2 00
* Taylor and Thompson's Extracts on Reinforced Concrete Design 8vo, 2 00'
Treatise on Concrete, Plain and Reinforced 8vo, 5 00
Thurston's Materials of Engineering. In Three Parts 8vo, 8 00
Part I. Non-metallic Materials of Engineering and Metallurgy 8vo, 2 00
Part II. Iron and Steel 8vo, 3 50
Part III. A Treatise on Brasses, Bronzes, and Other Alloys and their
Constituents 8vo, 2 50
Tillson's Street Pavements and Paving Materials 8vo, 4 00
Turneaure and Maurer's Principles of Reinforced Concrete Construction.
Second Edition, Revised and Enlarged 8vo, 3 50
Waterbury's Cement Laboratory Manual 12mo, 1 00
Laboratory Manual for Testing Materials of Construction. (In Press.)'
Wood's (De V.) Treatise on the Resistance of Materials, and an Appendix on
the Preservation of Timber 8vo, 2 00
Wood's (M. P.) Rustless Coatings: Corrosion and Electrolysis of Iron and
Steel 8vo, 4 00
RAILWAY ENGINEERING.
Andrews's Handbook for Street Railway Engineers 3X5 inches, mor. 1 25
Berg's Buildings and Structures of American Railroads 4to, 5 00
Brooks's Handbook of Street Railroad Location 16mo, mor. 1 50
* Burt's Railway Station Service 12mo, 2 00
Butts's Civil Engineer's Field-book. 16mo, mor. 2 50
Crandall's Railway and Other Earthwork Tables. 8vo, 1 50
Crandall and Barnes's Railroad Surveying .-. 16mo, mor. 2 00
* Crockett's Methods for Earthwork Computations 8vo, 1 50
Dredge's History of the Pennsylvania Railroad. (1879) , Paper, 5 00
Fisher's Table of Cubic Yards. Cardboard, 25
Godwin's Railroad Engineers' Field-book and Explorers' Guide. . 16mo, mor. 2 50
Hudson's Tables for Calculating the Cubic Contents of Excavations and Em-
bankments .... ;8vo^ 1 00
Ives and Hilts's Problems in Surveying, Railroad Surveying and Geodesy
16mo, mor. 1 50
Molitor and Beard's Manual for Resident Engineers 16mo, 1 00
9
Nagle's Field Manual for Railroad Engineers 16mo, mor. $3 09
* Orrock's Railroad Structures and Estimates 8vo, 3 OO
Philbrick's Field Manual for Engineers 16mo, mor. 3 OO
Raymond's Railroad Field Geometry 16mo, mor. 2 OO
Elements of Railroad Engineering 8vo, 3 5O
Railroad Engineer's Field Book. (In Preparation.)
Roberts' Track Formulae and Tables 16mo. mor. 3 OO
Searles's Field Engineering 16mo, mor. 3 00
Railroad- Spiral 16mo, mor. 1 50'
Taylor's Prismoidal Formulae and Earthwork 8vo, 1 50
Webb's Economics of Railroad Construction Large 12mo, 2 50-
Railroad Construction 16mo, mor. 5 00
Wellington's Economic Theory of the Location of Railways Large 12mo, 5 OO
Wilson's Elements of Railroad-Track and Construction 12mo, 2 OO
DRAWING
Barr and Wood's Kinematics of Machinery ... 8vo, 2 50
* Eartlett's Mechanical Drawing 8vo, .?, 00'
* " Abridged Ed 8vo, 1 5O
* Bartlett and Johnson's Engineering Descriptive Geometry 8vo, 1 50
Blessing and Darling's Descriptive Geometry. (In Press.)
Elements of Drawing. (In Press.)
Coolidge's Manual of Drawing 8vo, paper, 1 00"
Coolidge and Freeman's Elements of General Drafting for Mechanical Engi-
neers Oblong 4to, 2 50'
Durley's Kinematics of Machines 8vo, 4 OO
Emch's Introduction to Projective Geometry and its Application 8vo, 2 50'
Hill's Text-book on Shades and Shadows, and Perspective 8vo, 2 OO
Jamison's Advanced Mechanical Drawing 8vo, 2 OO
Elements of Mechanical Drawing 8vo, 2 50'
Jones's Machine Design:
Part I. Kinematics of Machinery 8vo, 1 50
Part II. Form, Strength, and Proportions of Parts 8vo, 3 00-
* Kimball and Barr's Machine Design 8vo, 3 00
MacCord's Elements of Descriptive Geometry 8vo, 3 00'
Kinematics; or, Practical Mechanism 8vo, 5 00
Mechanical Drawing 4to, 4 00
Velocity Diagrams 8vo, 1 50
McLeod's Descriptive Geometry Large 12mo, 1 5O
* : Mahan's Descriptive Geometry and Stone-cutting 8vo, 1 5O
Industrial Drawing. (Thompson.) 8vo, 3 50
Meyer's Descriptive Geometry 8vo, 2 00
Reed's Topographical Drawing and Sketching 4to, 5 00
* Reid's Mechanical Drawing. (Elementary and Advanced.) 8vo, 2 00
Text-book of Mechanical Drawing and Elementary Machine Design.. 8vo, 3 00
Robinson's Principles of Mechanism . 8vo, 3 00
Schwamb and Merrill's Elements of Mechanism 8vo, 3 00
Smith (A. W.) and Marx's Machine Design 8vo, 3 00
Smith's (R. S.) Manual of Topographical Drawing. (McMillan.) 8vo, 2 50
* Titsworth's Elements of Mechanical Drawing Oblong 8vo, 1 25
Tracy and North's Descriptive Geometry. (In Press.)
Warren's Elements of Descriptive Geometry, Shadows, and Perspective. . 8vo, 3 50
Elements of Machine Construction and Drawing 8vo, 7 50-
Elements of Plane and Solid Free-hand Geometrical Drawing. . . . 12mo, 1 00
General Problems of Shades and Shadows 8vo, 3 OO
Manual of Elementary Problems in the Linear Perspective of Forms and
Shadow 12mo, 1 00-
Manual of Elementary Projection Drawing 12mo, 1 50
Plane Problems in Elementary Geometry 12mo, 1 25
Weisbach's Kinematics and Power of Transmission. (Hermann and
Klein.) 8vo, 5 OO
Wilson's (H. M.) Topographic Surveying 8vo, 3 50
* Wilson's (V. T.) Descriptive Geometry 8vo, 1 5O
Free-hand Lettering 8vo, 1 OO
Free-hand Perspective 8vo, 2 5O
Woolf's Elementary Course in Descriptive Geometry Large 8vo, 3 00>
10
ELECTRICITY AND PHYSICS.
* Abegg's Theory of Electrolytic Dissociation, (von Ende.") 12mo, $1 25
Andrews's Hand-book for Street Railwa y Engineers. 3X5 inches mor. 1 25
Anthony and Ball's Lecture-notes on the Theory of Electrical Measure-
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Anthony and Brackett's Text-book of Physics. (Magie.) ... .Large 12mo, 3 OO
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Wood's Turbines 8vo, 2 50'
MATERIALS OF ENGINEERING.
Burr's Elasticity and Resistance of the Materials of Engineering 8vo, 7 50
Church's Mechanics of Engineering , 8vo, 6 00 i
Mechanics of Solids (Being Parts I, II, III of Mechanics of Engineering).
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Thurston's Materials of Engineering 3 vols., 8vo, 8 00
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14
"Waterbury's Laboratory Manual for Testing Materials of Construction.
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Wood's (De V.) Elements of Analytical Mechanics 8vo, $3 00
Treatise on the Resistance of Materials and an Appendix on the
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Wood's (M. P.) Rustless Coatings: Corrosion and Electrolysis of Iron and
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STEAM-ENGINES AND BOILERS.
Berry's Temperature-entropy Diagram. Third Edition Revised and En-
larged 12mo, 2 50
Carnot's Reflections on the Motive Power of Heat. (Thurston.) 12mo, 1 50
hase's Art of Pattern Making 12mo, 2 50
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Dawson's "Engineering" and Electric Traction Pocket-book. .. . 16mo, mor. 5 00
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Hirshfeld and Barnard's Heat Power Engineering. (In Press.)
Hutton's Heat and Heat-engines 8vo, 5 00
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Kneass's Practice and Theory of the Injector 8vo, 1 50
MacCord's Slide-valves 8vo, 2 00
Meyer's Modern Locomotive Construction 4to, 10 00
Miller, Berry, and Riley's Problems in Thermodynamics 8vo, paper, 75
Moyer's Steam Turbine 8vo, 4 00
Peabody's Manual of the Steam-engine Indicator 12mo, 1 50
Tables of the Properties of Steam and Other Vapors and Temperature-
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Thermodynamics of the Steam-engine and Other Heat-engines. . . .8vo, 5 00
* Thermodynamics of the Steam Turbine 8vo, 3 00
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Peabody and Miller's Steam-boilers 8vo, 4 00
Pupin's Thermodynamics of Reversible Cycles in Gases and Saturated Vapors.
(Osterberg.). -. 12mo, 1 25
Reagan's Locomotives: Simple, Compound, and Electric. New Edition.
Large 12mo, 3 50
Sinclair's Locomotive Engine Running and Management 12mo, 2 00
Smart's Handbook of Engineering Laboratory Practice 12mo, 2 50
Snow's Steam-boiler Practice 8vo, 3 00
Spangler's Notes on Thermodynamics 12mo, 1 00
Valve-gears 8vo, 2 50
Spangler, Greene, and Marshall's Elements of Steam-engineering 8vo, 3 00
Thomas's Steam-turbines 8vo, 4 00
Thurston's Handbook of Engine and Boiler Trials, and the Use of the Indi-
cator and the Prony Brake 8vo, 5 00
Handy Tables 8vo, 1 50
Manual of Steam-boilers, their Designs, Construction, and Operation 8vo, 5 00
Manual of the Steam-engine 2 vols., 8vo, JO 00
Part I. History, Structure, and Theory 8vo, 6 00
Part II. Design, Construction, and Operation 8vo, 6 00
Wehrenfennig's Analysis and Softening of Boiler Peed-water. (Patterson.)
8vo, 4 00
Weisbach's Heat. Steam, and Steam-engines. (Du Bois.) 8vo, 5 00
Whitham's Steam-engine Design 8vo, 5 00
Wood's Thermodynamics, Heat Motors, and Refrigerating Machines. . ,8vo, 4 00
MECHANICS PURE AND APPLIED.
Church's Mechanics of Engineering 8vo, 6 00
Mechanics of Fluids (Being Part IV of Mechanics of Engineering). . 8vo, 3 00
* Mechanics of Internal Works 8vo, 1 50
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Notes and Examples in Mechanics 8vo, 2 00
15
Dana's Text-book of Elementary Mechanics for Colleges and Schools .12mo, $1 50
Du Bois's Elementary Principles of Mechanics:
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Mechanics of Engineering. Vol. I Small 4te, 7 50
Vcl. II Small 4to, 10 00
* Greene's Structural Mechanics 8vo, 2 50
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James's Kinematics of a Point and the Rational Mechanics of a Particle.
Large 12mo. 2 00
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* King's Elements of the Mechanics of Materials and of Power of Trans-
mission 8vo, 2 50
Lanza's Applied Mechanics 8vo, 7 50
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* Vol. II. Kinematics and Kinetics 12mo, 1 50
* Vol. III. Mechanics of Materials 12mo, 1 50
Maurer's Technical Mechanics 8vo, 4 00
* Merriman's Elements of Mechanics 12mo, 1 00
Mechanics of Materials 8vo, 5 00
* Michie's Elements of Analytical Mechanics 8vo, 4 00
Robinson's Principles of Mechanism 8vo, 3 00
Sanborn's Mechanics Problems Large 12mo, 1 50
Schwamb and Merrill's Elements of Mechanism 8vo, 3 00
Wood's Elements of Analytical Mechanics 8vo, 3 00
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MEDICAL.
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von Behring's Suppression of Tuberculosis. (Bolduan.) 12mo, 1 00
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Bordet's Studies in Immunity. (Gay.) 8vo, 6 00
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Davenport's Statistical Methods with Special Reference to Biological Varia-
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Ehrlich's Collected Studies on Immunity. (Bolduan.) Svo, 6 00
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* de Fursac's Manual of Psychiatry. (Rosanoff and Collins.) . . . Large 12mo, 2 50
* Hammarsten's Text-book on Physiological Chemistry. (Mandel.).. . .8vo, 4 00
Jackson's Directions for Laboratory Work in Physiological Chemistry. .8vo. 1 25
Lassar-Cohn's Praxis of Urinary Analysis. (Lorenz.) 12mo, 1 00
Mandel's Hand-book for the Bio-Chemical Laboratory 12mo. 1 50
* Nelson's Analysis of Drugs and Medicines 12mo, 3 00
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* Pozzi-Escot's Toxins and Venoms and their Antibodies. (Cohn.). . 12mo, 1 00
Rostoski's Serum Diagnosis. (Bolduan.) 12mo, 1 00
Ruddiman's Incompatibilities in Prescriptions Svo, 2 00
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Salkowski's Physiological and Pathological Chemistry. (Orndorff.) ....8vo, 2 50
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Smith's Lecture Notes on Chemistry for Dental Students Svo, 2 50
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METALLURGY.
Betts's Lead Refining by Electrolysis Svo, 4 00
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16
Iron Founder 12mo, $2 50
Supplement 12mo, 2 50
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Burgess and Le Chatelier's Measurement of High Temperatures. Third
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Douglas's Untechnical Addresses on Technical Subjects 12mo, 1 00
Goesel's Minerals and Metals: A Reference Book 16mo, mor. 3 00
* Iles's Lead-smelting 12mo, 2 50
Johnson's Rapid Methods for the Chemical Analysis of Special Steels,
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Keep's Cast Iron 8vo, 2 50
Metcalf's Steel. A Manual for Steel-users 12mo, 2 00
Minet's Production of Aluminum and its Industrial Use. (Waldo.). . 12mo, 2 50
Palmer's Foundry Practice. (In Press.)
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* Ruer's Elements of Metallography. (Mathewson.) 8vo, 3 00
Smith's Materials of Machines 12mo, 1 00
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Thurston's Materials of Engineering. In Three Parts 8vo, 8 00
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Ulke's Modern Electrolytic Copper Refining 8vo, 3 00
West's American Foundry Practice 12mo, 2 50
Moulders' Text Book. 12mo. 2 50
MINERALOGY.
Baskerville's Chemical Elements. (In Preparation.)
* Browning's Introduction to the Rarer Elements 8vo, 1 50
Brush's Manual of Determinative Mineralogy. (Penfield.) 8vo, 4 00
Butler's Pocket Hand-book of Minerals 16mo, mor. 3 00
Chester's Catalogue of Minerals 8vo, paper, 1 00
Cloth, 1 25
* Crane's'Gold and Silver 8vo, 5 00
Dana's First Appendix to Dana's New " System of Mineralogy" . . Large 8vo, 1 00
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Manual of Mineralogy and Petrography 12mo, 2 00
Minerals and How to Study Them 12mo, 1 50
System of Mineralogy Large 8vo, half leather, 12 50
Text-book of Mineralogy 8vo, 4 00
Douglas's Untechnical Addresses on Technical Subjects 12mo, 1 00
Eakle's Mineral Tables 8vo, 1 25
Eckel's Building Stones and Clays. (In Press.)
Goesel's Minerals and Metals: A Reference Book 16mo, mor. 3 00
* Groth's The Optical Properties of Crystals. (Jackson.) 8vo, 3 50
Groth's Introduction to Chemical Crystallography (Marshall) 12mo, 1 25
* Hayes's Handbook for Field Geologists , 16mo, mor. 1 50
Iddings's Igneous Rocks 8vo, 5 00
Rock Minerals 8vo, 5 00
Johannsen's Determination of Rock-forming Minerals in Thin Sections. 8vo,
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pipe e 12mo, 60
Merrill's Non-metallic Minerals: Their Occurrence and Uses 8vo, 4 00
Stones for Building and Decoration 8vo, 5 00
'* Penneld's Notes on Determinative Mineralogy and Record of Mineral Tests.
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Tables of Minerals, Including the Use of Minerals and Statistics of
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17
3)8 Ries and Leighton's History of the Clay-working industry of the United
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* Rowe's Practical Mineralogy Simplified 12mo, 1 25
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MINING.
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* Crane's Gold and Silver 8vo, 5 00
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* 8vo, mor. 5 00
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* Dana and Saunders's Rock Drilling 8vo, 4 00
Douglas's Untechnical Addresses on Technical Subjects 12mo, 1 00
Eissler's Modern High Explosives 8vo, 4 00
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Riemer's Shaft Sinking Under Difficult Conditions. (Corning and Peele.)8vo, 3 00
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Wilson's Hydraulic and Placer Mining. 2d edition, rewritten 12'mo, 2 50
Treatise on Practical and Theoretical Mine Ventilation 12mo, 1 25
SANITARY SCIENCE.
Association of State and National Food and Dairy Departments, Hartford
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Jamestown Meeting, 1907 8vo, 3 00
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* Chapin's The Sources and Modes of Infection '. Large 12mo, 3 00
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Fuertes's Water-filtration Works 12mo, 2 50
Water and Public Health 12mo, 1 50
Gerhard's Guide to Sanitary Inspections 12mo, 1 50
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Hazen's Clean Water and How to Get It Large 12mo, 1 50
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Leach's Inspection and Analysis of Food with Special Reference to State
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Mason's Examination of Water. (Chemical and Bacteriological) 12mo, 1 25
Water-supply. (Considered principally from a Sanitary Standpoint).
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* Mast's Light and the Behavior of Organisms Large 12mo, 2 50
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Ogden's Sewer Construction 8vo, 3 00
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Parsons's Disposal of Municipal Refuse 8vo, 2 00
Prescott and Winslow's Elements of Water Bacteriology, with Special Refer-
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Richards's Conservation by Sanitation 8vo,
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Richards and Woodman's Air, Water, and Food from a Sanitary Stand-
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* Fritz, Autobiography of John 8vo,
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Jacobs's Betterment Briefs. A Collection of Published Papers on Or-
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Metcalfe's Cost of Manufactures, and the Administration of Workshops. .8vo, 5 00
Putnam's Nautical Charts 8vo, 2 00
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Thome's Structural and Physiological Botany. (Bennett) 16mo, 2 25
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Gesenius's Hebrew and Chaldee Lexicon to the Old Testament Scriptures.
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