Automobile ignition - Manly
AUTOMOBILE IGNITION
Operation, Upkeep, Care and Repair of Modern Forms of Storage Battery and Magneto Ignition Equipment for Automobiles.
BY HAROLD P. MANLY
CHICAGO, FREDERICK J. DRAKE & CO., 1919
DOWNLOAD FREE AUTOMOTIVE BOOK: Automobile ignition
PREFACE
Automobile Ignition is designed to meet a definite need for a reference and instruction book in which may be found complete information covering all phases of present day ignition, either battery or magneto.
While a non-technical explanation of theory and principle is always given, the greater part of the work is devoted to descriptions of, and instructions relating to, actual equipment in every-day use. This plan allows principles, as well as practice, to be given in a practical, rather than a theoretical way.
A great majority of the illustrations showing methods of construction and operation have been made to show the devices as built by the several manufacturers; and, whenever possible, the name of the maker has been given as an assistance to the practically inclined reader. Methods of adjustment and wiring, both external and internal, have been considered as: of first importance in all cases.
Although the subject of modem ignition has been treated in many of the newer works on electrical equipment, it has always been treated as of somewhat secondary importance; while the author has found in his experience that a majority of automobile workers regard ignition as highly important. For that reason, the entire volume has been devoted to this one subject, and each principle of operation and method of building has been considered only from the ignition point of view.
Automobile Ignition is designed to meet a definite need for a reference and instruction book in which may be found complete information covering all phases of present day ignition, either battery or magneto.
While a non-technical explanation of theory and principle is always given, the greater part of the work is devoted to descriptions of, and instructions relating to, actual equipment in every-day use. This plan allows principles, as well as practice, to be given in a practical, rather than a theoretical way.
A great majority of the illustrations showing methods of construction and operation have been made to show the devices as built by the several manufacturers; and, whenever possible, the name of the maker has been given as an assistance to the practically inclined reader. Methods of adjustment and wiring, both external and internal, have been considered as: of first importance in all cases.
Although the subject of modem ignition has been treated in many of the newer works on electrical equipment, it has always been treated as of somewhat secondary importance; while the author has found in his experience that a majority of automobile workers regard ignition as highly important. For that reason, the entire volume has been devoted to this one subject, and each principle of operation and method of building has been considered only from the ignition point of view.
TABLE OF CONTENTS
- ELECTRIC IGNITION
- ELECTRICITY AND MAGNETISM
- PRODUCTION OF ELECTRICITY
- PRODUCING THE SPARK
- THE IGNITION CIRCUIT
- IGNITION TIMING
- BATTERY IGNITION SYSTEMS
- FORD IGNITION
- MAGNETO IGNITION
- MAGNETO TIMING, WIRING AND DRIVE
- HIGH TENSION MAGNETOS
- TRANSFORMER COIL MAGNETOS
- INDUCTOR MAGNETOS
- LOCATION AND REMEDY OR IGNITION TROUBLES
CHAPTER I - ELECTRIC IGNITION
The object of the whole ignition system of an automobile is simply the production of a small spark about a fiftieth of an inch in length in the cylinder of the engine, yet the parts required for producing this spark are among the most interesting and highly developed of all the units that go to make up the completed car.
Many methods of ignition have been used, not all of them electric, but all except one, the jump spark system, have disappeared. This remaining system makes use of a current of electricity having such high pressure or voltage that it is capable of passing through the highly compressed gas in the cylinder and across the space between two metallic points as shown at C in Figure 1. This passage of current produces an electric spark of great heat and from this spark the inflammable mixture of gasoline vapor and air or the vapor of any other fuel is ignited and the resulting combustion produces the pressure and power that operates the car.
Early types of engines made use of fireproof tubes maintained at incandescence by an external flame and when the gas in the cylinder was allowed to come into contact with these tubes, ignition resulted. This type is shown at A in Figure 1, Certain forms of engines in use today ignite the combustible gases by the heat resulting from high compression, the Diesel engine being the best known example of this method.
Stationary engines now in use, and early types of automobile engines use the "make and break" system of ignition shown at B in the illustration. "With this method a current of low voltage and large volume or amperage normally passes from a stationary contact mounted within the combustion space of the engine cylinder to a movable contact likewise carried inside of the cylinder. At the proper instant these contacts are caused to separate by external mechanism and the result of this interruption of the flow of current is a hot spark at the contacts. While the study of these obsolete methods would be interesting, it would be of no practical usefulness because cars using them have long since passed out of use, therefore they are not considered in the following pages.
Modem forms of jump spark ignition may be divided into three classes. The oldest class, and at present the least used, is that known as the battery system. This form was popular from the inception of the present type of gasoline car and retained its position of importance until about the year 1907 or 1908. At that time the magneto was introduced on a large number of cars that had not previously carried it because of the high cost of this instruments From that time until about 1914 the magneto dominated the field almost to the exclusion of other forms. With the advent of electric starting and lighting came the new type of battery ignition that draws its current supply from the lighting and starting battery and from the lighting dynamo. At the present time, while the magneto has its strong supporters and is found on a great number of cars, the battery systems are found in greater numbers than are magnetos.
TIME OF IGNITION
Engine Cycle, - The instant at which ignition is effected is an important point in the cycle of operations through which the internal combustion engine passes. Those familiar with this class of work know that the type of engine usually employed makes use of the four cycle principle in which four strokes, as shown in Figure 2, are required to perform the necessary "operations. The first stroke is called the inlet, during which fresh gas is drawn into the cylinder and the second is the compression during which the gas is forced into the combustion space, and. at the end of which comes the ignition point or time at which the compressed gas is ignited. During the third stroke of the piston the burning gas expands And on the fourth and final stroke the spent charge is exhausted.
It is at some time during the compression stroke, or at the end of this stroke, that the gas must be ignited. The exact instant at which the spark occurs depends on several factors, but in all cases the object sought is that the entire charge will be fully aflame and at the point of greatest pressure when the piston has reached the top of its stroke and is ready to descend on the power stroke.
The space occupied by the gas when compressed is of considerable volume but in the usual design it is only at one small point in this space that the ignition spark takes place. Rapid though the travel of the flame may be, an appreciable time is required for the whole charge of gas to become fully ignited and to reach its point of greatest pressure. The ignition flame starts in the gas immediately surrounding the spark and finally reaches the farthest points of the combustion space in the cylinder.
During this time of flame travel, the piston of the engine is moving with greater or less rapidity up or down in the cylinder, the piston speed depending on the number of revolutions that the crank shaft is then making in a given length of time. In order that the engine may develop the greatest possible power from the amount, of fuel being used it is necessary that the gas be ignited at such time as will insure maximum pressure immediately after the piston starts on its down stroke.
Should the gas become fully ignited while the piston is still traveling upward on the compression stroke, a strong downward force would be exerted, tending to retard the speed of the engine and greatly reducing the power output
On the other hand, should ignition fail to take place until the piston had reached the top and again started on its downward stroke, the gas would have lost much of its power possibilities because of the reduced degree of compression. The power and pressure of the burning gas is in direct proportion to the compression pressure of the gas when ignited and the cylinder is so designed that the stroke of the piston causes the correct degree of compression. If ignition takes place too late, part of this compression pressure is lost with a resulting lowering of the power output and economy.
When the piston is traveling very slowly, as for instance, in the cranking operation, the gas will fully ignite before the piston has traveled more than a very little of its stroke and the spark can safely take place practically at the same instant that full ignition is desired, this being when the piston is at the top of its stroke.
If the time at which the spark passes is not changed according to the engine speed, and if the engine is then run very fast, full ignition will not take place until the piston has started on its down stroke with the results already outlined.
SPARK CONTROL
In order to cause the electric spark to pass through the inflammable mixture at such time as to produce complete ignition of the charge when required, a majority of systems provide means for altering this time to correspond with engine speed. All of the systems in which such means are provided are included in the class known as variable spark ignition systems. In some of these types the spark timing is controlled by the driver and this form is given the name of hand or manual control. In others the timing of the spark is changed mechanically by some form of governor and these are known as automatic advance systems.
Many magneto installations have been made without provision for altering the time at which the spark passes and this type goes by the name of set spark ignition. With set spark ignition the permanent advance is made sufficient to care for all average conditions of operation.
While the set spark method causes ignition to commence considerably before the piston reaches top center, no ill effects are encountered even while cranking the engine because of the fact that when the cranking is done at speed sufficiently high to cause the magneto to generate current enough for a spark, the flywheel is travelling fast enough to require such an advance and the power impulse takes place as usual. Set spark ignition has the advantage of simplicity because of the absence of control members and will give better average operation than will improper spark manipulation by a careless or ignorant driver. This method has the disadvantage of giving perfect operation only over a very limited range of engine speed.
DOWNLOAD FREE AUTOMOTIVE BOOK: Automobile ignition
Many methods of ignition have been used, not all of them electric, but all except one, the jump spark system, have disappeared. This remaining system makes use of a current of electricity having such high pressure or voltage that it is capable of passing through the highly compressed gas in the cylinder and across the space between two metallic points as shown at C in Figure 1. This passage of current produces an electric spark of great heat and from this spark the inflammable mixture of gasoline vapor and air or the vapor of any other fuel is ignited and the resulting combustion produces the pressure and power that operates the car.
Early types of engines made use of fireproof tubes maintained at incandescence by an external flame and when the gas in the cylinder was allowed to come into contact with these tubes, ignition resulted. This type is shown at A in Figure 1, Certain forms of engines in use today ignite the combustible gases by the heat resulting from high compression, the Diesel engine being the best known example of this method.
Stationary engines now in use, and early types of automobile engines use the "make and break" system of ignition shown at B in the illustration. "With this method a current of low voltage and large volume or amperage normally passes from a stationary contact mounted within the combustion space of the engine cylinder to a movable contact likewise carried inside of the cylinder. At the proper instant these contacts are caused to separate by external mechanism and the result of this interruption of the flow of current is a hot spark at the contacts. While the study of these obsolete methods would be interesting, it would be of no practical usefulness because cars using them have long since passed out of use, therefore they are not considered in the following pages.
Modem forms of jump spark ignition may be divided into three classes. The oldest class, and at present the least used, is that known as the battery system. This form was popular from the inception of the present type of gasoline car and retained its position of importance until about the year 1907 or 1908. At that time the magneto was introduced on a large number of cars that had not previously carried it because of the high cost of this instruments From that time until about 1914 the magneto dominated the field almost to the exclusion of other forms. With the advent of electric starting and lighting came the new type of battery ignition that draws its current supply from the lighting and starting battery and from the lighting dynamo. At the present time, while the magneto has its strong supporters and is found on a great number of cars, the battery systems are found in greater numbers than are magnetos.
TIME OF IGNITION
Engine Cycle, - The instant at which ignition is effected is an important point in the cycle of operations through which the internal combustion engine passes. Those familiar with this class of work know that the type of engine usually employed makes use of the four cycle principle in which four strokes, as shown in Figure 2, are required to perform the necessary "operations. The first stroke is called the inlet, during which fresh gas is drawn into the cylinder and the second is the compression during which the gas is forced into the combustion space, and. at the end of which comes the ignition point or time at which the compressed gas is ignited. During the third stroke of the piston the burning gas expands And on the fourth and final stroke the spent charge is exhausted.
It is at some time during the compression stroke, or at the end of this stroke, that the gas must be ignited. The exact instant at which the spark occurs depends on several factors, but in all cases the object sought is that the entire charge will be fully aflame and at the point of greatest pressure when the piston has reached the top of its stroke and is ready to descend on the power stroke.
The space occupied by the gas when compressed is of considerable volume but in the usual design it is only at one small point in this space that the ignition spark takes place. Rapid though the travel of the flame may be, an appreciable time is required for the whole charge of gas to become fully ignited and to reach its point of greatest pressure. The ignition flame starts in the gas immediately surrounding the spark and finally reaches the farthest points of the combustion space in the cylinder.
During this time of flame travel, the piston of the engine is moving with greater or less rapidity up or down in the cylinder, the piston speed depending on the number of revolutions that the crank shaft is then making in a given length of time. In order that the engine may develop the greatest possible power from the amount, of fuel being used it is necessary that the gas be ignited at such time as will insure maximum pressure immediately after the piston starts on its down stroke.
Should the gas become fully ignited while the piston is still traveling upward on the compression stroke, a strong downward force would be exerted, tending to retard the speed of the engine and greatly reducing the power output
On the other hand, should ignition fail to take place until the piston had reached the top and again started on its downward stroke, the gas would have lost much of its power possibilities because of the reduced degree of compression. The power and pressure of the burning gas is in direct proportion to the compression pressure of the gas when ignited and the cylinder is so designed that the stroke of the piston causes the correct degree of compression. If ignition takes place too late, part of this compression pressure is lost with a resulting lowering of the power output and economy.
When the piston is traveling very slowly, as for instance, in the cranking operation, the gas will fully ignite before the piston has traveled more than a very little of its stroke and the spark can safely take place practically at the same instant that full ignition is desired, this being when the piston is at the top of its stroke.
If the time at which the spark passes is not changed according to the engine speed, and if the engine is then run very fast, full ignition will not take place until the piston has started on its down stroke with the results already outlined.
SPARK CONTROL
In order to cause the electric spark to pass through the inflammable mixture at such time as to produce complete ignition of the charge when required, a majority of systems provide means for altering this time to correspond with engine speed. All of the systems in which such means are provided are included in the class known as variable spark ignition systems. In some of these types the spark timing is controlled by the driver and this form is given the name of hand or manual control. In others the timing of the spark is changed mechanically by some form of governor and these are known as automatic advance systems.
Many magneto installations have been made without provision for altering the time at which the spark passes and this type goes by the name of set spark ignition. With set spark ignition the permanent advance is made sufficient to care for all average conditions of operation.
While the set spark method causes ignition to commence considerably before the piston reaches top center, no ill effects are encountered even while cranking the engine because of the fact that when the cranking is done at speed sufficiently high to cause the magneto to generate current enough for a spark, the flywheel is travelling fast enough to require such an advance and the power impulse takes place as usual. Set spark ignition has the advantage of simplicity because of the absence of control members and will give better average operation than will improper spark manipulation by a careless or ignorant driver. This method has the disadvantage of giving perfect operation only over a very limited range of engine speed.
DOWNLOAD FREE AUTOMOTIVE BOOK: Automobile ignition
Free books category:
