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HOW IT WORKS

AUTHOR'S NOTE.

I beg to thank the following gentlemen and firms for the help they have given me in

connection with the letterpress and illustrations of "How It Works"—

Messrs. F.J.C. Pole and M.G. Tweedie (for revision of MS.); W. Lineham; J.F.

Kendall; E. Edser; A.D. Helps; J. Limb; The Edison Bell Phonograph Co.; Messrs.

Holmes and Co.; The Pelton Wheel Co.; Messrs. Babcock and Wilcox; Messrs. Siebe,

Gorman, and Co.; Messrs. Negretti and Zambra; Messrs. Chubb; The Yale Lock Co.;

The Micrometer Engineering Co.; Messrs. Marshall and Sons; The Maignen Filter

Co.; Messrs. Broadwood and Co.

ON THE FOOTPLATE OF A LOCOMOTIVE.

How It Works

Dealing in Simple Language with Steam, Electricity,

Light, Heat, Sound, Hydraulics, Optics, etc.

and with their applications to Apparatus

in Common Use

By

ARCHIBALD WILLIAMS

Author of "The Romance of Modern Invention,"

"The Romance of Mining," etc., etc.

THOMAS NELSON AND SONS

London, Edinburgh, Dublin, and New York

PREFACE.

How does it work? This question has been put to me so often by persons young and

old that I have at last decided to answer it in such a manner that a much larger public

than that with which I have personal acquaintance may be able to satisfy themselves

as to the principles underlying many of the mechanisms met with in everyday life.

In order to include steam, electricity, optics, hydraulics, thermics, light, and a variety

of detached mechanisms which cannot be classified under any one of these heads,

within the compass of about 450 pages, I have to be content with a comparatively

brief treatment of each subject. This brevity has in turn compelled me to deal with

principles rather than with detailed descriptions of individual devices—though in

several cases recognized types are examined. The reader will look in vain for accounts

of the Yerkes telescope, of the latest thing in motor cars, and of the largest

locomotive. But he will be put in the way of understanding the essential nature of all

telescopes, motors, and steam-engines so far as they are at present developed, which I

think may be of greater ultimate profit to the uninitiated.

While careful to avoid puzzling the reader by the use of mysterious phraseology I

consider that the parts of a machine should be given their technical names wherever

possible. To prevent misconception, many of the diagrams accompanying the

letterpress have words as well as letters written on them. This course also obviates the

wearisome reference from text to diagram necessitated by the use of solitary letters or

figures.

I may add, with regard to the diagrams of this book, that they are purposely somewhat

unconventional, not being drawn to scale nor conforming to the canons of professional

draughtsmanship. Where advisable, a part of a machine has been exaggerated to show

its details. As a rule solid black has been preferred to fine shading in sectional

drawings, and all unnecessary lines are omitted. I would here acknowledge my

indebtedness to my draughtsman, Mr. Frank Hodgson, for his care and industry in

preparing the two hundred or more diagrams for which he was responsible.

Four organs of the body—the eye, the ear, the larynx, and the heart—are noticed in

appropriate places. The eye is compared with the camera, the larynx with a reed pipe,

the heart with a pump, while the ear fitly opens the chapter on acoustics. The reader

who is unacquainted with physiology will thus be enabled to appreciate the better

these marvellous devices, far more marvellous, by reason of their absolutely automatic

action, than any creation of human hands.

A.W.

Uplands, Stoke Poges, Bucks.

CONTENTS.

Chapter I.—THE STEAM-ENGINE.

What is steam?—The mechanical energy of

steam—The boiler—The circulation of water in a

boiler—The enclosed furnace—The multitubular

boiler—Fire-tube boilers—Other types of

boilers—Aids to combustion—Boiler fittings—

The safety-valve—The water-gauge—The steam￾gauge—The water supply to a boiler

13

Chapter II.—THE CONVERSION OF HEAT

ENERGY

INTO MECHANICAL MOTION.

Reciprocating engines—Double-cylinder

engines—The function of the fly-wheel—The

cylinder—The slide-valve—The eccentric—"Lap"

of the valve: expansion of steam—How the cut-off

is managed—Limit of expansive working—

Compound engines—Arrangement of expansion

44

engines—Compound locomotives—Reversing

gears—"Linking-up"—Piston-valves—Speed

governors—Marine-speed governors—The

condenser

Chapter III.—THE STEAM TURBINE.

How a turbine works—The De Laval turbine—

The Parsons turbine—Description of the Parsons

turbine—The expansive action of steam in a

Parsons turbine—Balancing the thrust—

Advantages of the marine turbine

74

Chapter IV.—THE INTERNAL￾COMBUSTION ENGINE.

The meaning of the term—Action of the internal￾combustion engine—The motor car—The starting￾handle—The engine—The carburetter—Ignition

of the charge—Advancing the spark—Governing

the engine—The clutch—The gear-box—The

compensating gear—The silencer—The brakes—

Speed of cars

87

Chapter V.—ELECTRICAL APPARATUS.

What is electricity?—Forms of electricity—

Magnetism—The permanent magnet—Lines of

force—Electro-magnets—The electric bell—The

induction coil—The condenser—Transformation

of current—Uses of the induction coil

112

Chapter VI.—THE ELECTRIC

TELEGRAPH.

Needle instruments—Influence of current on the 127

magnetic needle—Method of reversing the

current—Sounding instruments—Telegraphic

relays—Recording telegraphs—High-speed

telegraphy

Chapter VII.—WIRELESS TELEGRAPHY.

The transmitting apparatus—The receiving

apparatus—Syntonic

transmission—The advance of wireless telegraphy

137

Chapter VIII.—THE TELEPHONE.

The Bell telephone—The Edison transmitter—The

granular carbon transmitter—General arrangement

of a telephone circuit—Double-line circuits—

Telephone exchanges—Submarine telephony

147

Chapter IX.—DYNAMOS AND ELECTRIC

MOTORS.

A simple dynamo--Continuous-current dynamos--

Multipolar dynamos--Exciting the field magnets--

Alternating current dynamos--The transmission of

power--The electric motor--Electric lighting--The

incandescent lamp--Arc lamps--"Series" and

"parallel" arrangement of lamps--Current for

electric lamps--Electroplating

159

Chapter X.—RAILWAY BRAKES.

The Vacuum Automatic brake—The

Westinghouse air-brake

187

Chapter XI.—RAILWAY SIGNALLING.

The block system—Position of signals—

Interlocking the signals—Locking gear—Points—

200

Points and signals in combination—Working the

block system—Series of signalling operations—

Single line signals—The train staff—Train staff

and ticket—Electric train staff system—

Interlocking—Signalling operations—Power

signalling—Pneumatic signalling—Automatic

signalling

Chapter XII.—OPTICS.

Lenses—The image cast by a convex lens—

Focus—Relative position of object and lens—

Correction of lenses for colour—Spherical

aberration—Distortion of image—The human

eye—The use of spectacles—The blind spot

230

Chapter XIII.—THE MICROSCOPE, THE

TELESCOPE,

AND THE MAGIC-LANTERN.

The simple microscope—Use of the simple

microscope in the telescope—The terrestrial

telescope—The Galilean telescope—The prismatic

telescope—The reflecting telescope—The

parabolic mirror—The compound microscope—

The magic-lantern—The bioscope—The plane

mirror

253

Chapter XIV.—SOUND AND MUSICAL

INSTRUMENTS.

Nature of sound—The ear—Musical

instruments—The vibration of strings—The

sounding-board and the frame of a piano—The

strings—The striking mechanism—The quality of

270

a note

Chapter XV.—WIND INSTRUMENTS.

Longitudinal vibration—Columns of air—

Resonance of columns of air—Length and tone—

The open pipe—The overtones of an open pipe—

Where overtones are used—The arrangement of

the pipes and pedals—Separate sound-boards—

Varieties of stops—Tuning pipes and reeds—The

bellows—Electric and pneumatic actions—The

largest organ in the world—Human reeds

287

Chapter XVI.—TALKING-MACHINES.

The phonograph—The recorder—The

reproducer—The gramophone—The making of

records—Cylinder records—Gramophone records

310

Chapter XVII.—WHY THE WIND BLOWS.

Why the wind blows—Land and sea breezes—

Light air and moisture—The barometer—The

column barometer—The wheel barometer—A

very simple barometer—The aneroid barometer—

Barometers and weather—The diving-bell—The

diving-dress—Air-pumps—Pneumatic tyres—The

air-gun—The self-closing door-stop—The action

of wind on oblique surfaces—The balloon—The

flying-machine

322

Chapter XVIII.—HYDRAULIC

MACHINERY.

The siphon—The bucket pump—The force￾pump—The most marvellous pump—The blood

350

channels—The course of the blood—The

hydraulic press—Household water-supply

fittings—The ball-cock—The water-meter—

Water-supply systems—The household filter—

Gas traps—Water engines—The cream

separator—The "hydro"

Chapter XIX.—HEATING AND LIGHTING.

The hot-water supply—The tank system—The

cylinder system—How a lamp works—Gas and

gasworks—Automatic stoking—A gas governor—

The gas meter—Incandescent gas lighting

386

Chapter XX.—VARIOUS MECHANISMS.

Clocks and Watches:—A short history of

timepieces—The construction of timepieces—The

driving power—The escapement—Compensating

pendulums—The spring balance—The cylinder

escapement—The lever escapement—

Compensated balance-wheels—Keyless winding

mechanism for watches—The hour hand train.

Locks:—The Chubb lock—The Yale lock. The

Cycle:—The gearing of a cycle—The free

wheel—The change-speed gear. Agricultural

Machines:—The threshing-machine—Mowing￾machines. Some Natural Phenomena:—Why sun￾heat varies in intensity—The tides—Why high tide

varies daily

410

[Pg 13]

HOW IT WORKS.

Chapter I.

THE STEAM-ENGINE.

What is steam?—The mechanical energy of steam—The boiler—The circulation of

water in a boiler—The enclosed furnace—The multitubular boiler—Fire-tube

boilers—Other types of boilers—Aids to combustion—Boiler fittings—The safety￾valve—The water-gauge—The steam-gauge—The water supply to a boiler.

WHAT IS STEAM?

If ice be heated above 32° Fahrenheit, its molecules lose their cohesion, and move

freely round one another—the ice is turned into water. Heat water above 212°

Fahrenheit, and the molecules exhibit a violent mutual repulsion, and, like dormant

bees revived by spring sunshine, separate and dart to and fro. If confined in an air￾tight vessel, the molecules have their flights curtailed, and beat more and more

violently against their prison walls, so that every square inch of the[Pg 14] vessel is

subjected to a rising pressure. We may compare the action of the steam molecules to

that of bullets fired from a machine-gun at a plate mounted on a spring. The faster the

bullets came, the greater would be the continuous compression of the spring.

THE MECHANICAL ENERGY OF STEAM.

If steam is let into one end of a cylinder behind an air-tight but freely-moving piston,

it will bombard the walls of the cylinder and the piston; and if the united push of the

molecules on the one side of the latter is greater than the resistance on the other side

opposing its motion, the piston must move. Having thus partly got their liberty, the

molecules become less active, and do not rush about so vigorously. The pressure on

the piston decreases as it moves. But if the piston were driven back to its original

position against the force of the steam, the molecular activity—that is, pressure—

would be restored. We are here assuming that no heat has passed through the cylinder

or piston and been radiated into the air; for any loss of heat means loss of energy,

since heat is energy.

THE BOILER.

The combustion of fuel in a furnace causes the[Pg 15] walls of the furnace to become

hot, which means that the molecules of the substance forming the walls are thrown

into violent agitation. If the walls are what are called "good conductors" of heat, they

will transmit the agitation through them to any surrounding substance. In the case of

the ordinary house stove this is the air, which itself is agitated, or grows warm. A

steam-boiler has the furnace walls surrounded by water, and its function is to transmit

molecular movement (heat, or energy) through the furnace plates to the water until the

point is reached when steam generates. At atmospheric pressure—that is, if not

confined in any way—steam would fill 1,610 times the space which its molecules

occupied in their watery formation. If we seal up the boiler so that no escape is

possible for the steam molecules, their motion becomes more and more rapid, and

pressure is developed by their beating on the walls of the boiler. There is theoretically

no limit to which the pressure may be raised, provided that sufficient fuel-combustion

energy is transmitted to the vaporizing water.

To raise steam in large quantities we must employ a fuel which develops great heat in

proportion to its weight, is readily procured, and cheap. Coal[Pg 16] fulfils all these

conditions. Of the 800 million tons mined annually throughout the world, 400 million

tons are burnt in the furnaces of steam-boilers.

A good boiler must be—(1) Strong enough to withstand much higher pressures than

that at which it is worked; (2) so designed as to burn its fuel to the greatest advantage.

Even in the best-designed boilers a large part of the combustion heat passes through

the chimney, while a further proportion is radiated from the boiler. Professor John

Perry[1] considers that this waste amounts, under the best conditions at present

obtainable, to eleven-twelfths of the whole. We have to burn a shillingsworth of coal

to capture the energy stored in a pennyworth. Yet the steam-engine of to-day is three

or four times as efficient as the engine of fifty years ago. This is due to radical

improvements in the design of boilers and of the machinery which converts the heat

energy of steam into mechanical motion.

CIRCULATION OF WATER IN A BOILER.

If you place a pot filled with water on an open fire, and watch it when it boils, you

will notice[Pg 17] that the water heaves up at the sides and plunges down at the

centre. This is due to the water being heated most at the sides, and therefore being

lightest there. The rising steam-bubbles also carry it up. On reaching the surface, the

bubbles burst, the steam escapes, and the water loses some of its heat, and rushes

down again to take the place of steam-laden water rising.

Fig. 1.

Fig. 2.

If the fire is very fierce, steam-bubbles may rise from all points at the bottom, and

impede downward currents (Fig. 1). The pot then "boils over."

Fig. 2 shows a method of preventing this trouble. We lower into our pot a vessel of

somewhat smaller diameter, with a hole in the bottom, arranged in such a[Pg 18]

manner as to leave a space between it and the pot all round. The upward currents are

then separated entirely from the downward, and the fire can be forced to a very much

greater extent than before without the water boiling over. This very simple

arrangement is the basis of many devices for producing free circulation of the water in

steam-boilers.

We can easily follow out the process of development. In Fig. 3 we see a simple U-tube

depending from a vessel of water. Heat is applied to the left leg, and a steady

circulation at once commences. In order to increase the heating surface we can extend

the heated leg into a long incline (Fig. 4), beneath which three lamps instead of only

one are placed. The direction of the circulation is the same, but its rate is increased.

Fig. 3.

A further improvement results from increasing the number of tubes (Fig. 5), keeping

them all on the slant, so that the heated water and steam may rise freely.

[Pg 19]

THE ENCLOSED FURNACE.

Fig. 4.

Fig. 5.

Still, a lot of the heat gets away. In a steam-boiler the burning fuel is enclosed either

by fire-brick or a "water-jacket," forming part of the boiler. A water-jacket signifies a

double coating of metal plates with a space between, which is filled with water (see

Fig. 6). The fire is now enclosed much as it is in a kitchen range. But our boiler must

not be so wasteful of the heat as is that useful household fixture. On their way to the

funnel the flames and hot gases should act on a very large metal or other surface in

contact with the water of the boiler, in order to give up a due proportion of their heat.

[Pg 20]

Fig. 6.—Diagrammatic sketch of a locomotive type of boiler. Water indicated by

dotted lines. The arrows show the direction taken by the air and hot gases from the air￾door to the funnel.

[Pg 21]

THE MULTITUBULAR BOILER.

Fig. 7.—The Babcock and

Wilcox water-tube boiler. One side of the brick seating has been removed to show the

arrangement of the water-tubes and furnace.

To save room, boilers which have to make steam very quickly and at high pressures

are largely composed of pipes. Such boilers we call multitubular. They are of two