The Romance of Modern Mechanism
by Archibald Williams · English · Gutenberg #46094 · 580,554 chars · public domain (US)
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Title: The Romance of Modern Mechanism
Author: Archibald Williams
Release date: June 25, 2014 [eBook #46094]
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Language: English
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Transcriber's Note:
In text, italic is denoted by _underscores_ around the word/phrase.
The italic markup for single italicised letters (such as pounds and
pence symbols and in numbered lists) are deleted for easier reading.
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More Transcriber's Notes may be found at the end of this text.
THE ROMANCE OF
MODERN MECHANISM
[Illustration: A MECHANICAL SCULPTOR
The lower illustration shows the Wenzel Sculpturing Machine at work on
two blocks of stone ranged one on each side of a model. This machine
can make four copies simultaneously from one original. The upper
illustration shows the quality of work done by the automatic sculptor.]
THE ROMANCE OF
MODERN MECHANISM
WITH INTERESTING DESCRIPTIONS IN NON-TECHNICAL LANGUAGE OF WONDERFUL
MACHINERY AND MECHANICAL DEVICES AND MARVELLOUSLY DELICATE SCIENTIFIC
INSTRUMENTS, &c., &c.
BY
ARCHIBALD WILLIAMS,
B.A., OXON., F.R.G.S.
AUTHOR OF
"THE ROMANCE OF MODERN INVENTION," "THE ROMANCE OF MODERN MINING,"
"THE ROMANCE OF MODERN ENGINEERING," "THE ROMANCE OF MODERN
EXPLORATION," &c. &c.
WITH THIRTY ILLUSTRATIONS
LONDON
SEELEY AND CO. LIMITED
38 GREAT RUSSELL STREET
1910
_UNIFORM WITH THIS VOLUME_
THE LIBRARY OF ROMANCE
_Extra Crown 8vo. With many illustrations. 5s. each_
"Splendid volumes."--_The Outlook._
"This series has now won a considerable and well deserved
reputation."--_The Guardian._
"Each volume treats its allotted theme with accuracy, but at the same
time with a charm that will commend itself to readers of all ages.
The root idea is excellent, and it is excellently carried out, with
full illustrations and very prettily designed covers."--_The Daily
Telegraph._
By Prof. G. F. SCOTT ELLIOT, M.A., B.Sc.
THE ROMANCE OF SAVAGE LIFE
THE ROMANCE OF PLANT LIFE
THE ROMANCE OF EARLY BRITISH LIFE
By EDWARD GILLIAT, M.A.
THE ROMANCE OF MODERN SIEGES
By JOHN LEA, M.A.
THE ROMANCE OF BIRD LIFE
By JOHN LEA, M.A., & H. COUPIN, D.Sc.
THE ROMANCE OF ANIMAL ARTS AND CRAFTS
By SIDNEY WRIGHT
THE ROMANCE OF THE WORLD'S FISHERIES
By the Rev. J. C. LAMBERT, M.A., D.D.
THE ROMANCE OF MISSIONARY HEROISM
By G. FIRTH SCOTT
THE ROMANCE OF POLAR EXPLORATION
By ARCHIBALD WILLIAMS, B.A. (Oxon.), F.R.G.S.
THE ROMANCE OF EARLY EXPLORATION
THE ROMANCE OF MODERN EXPLORATION
THE ROMANCE OF MODERN MECHANISM
THE ROMANCE OF MODERN INVENTION
THE ROMANCE OF MODERN ENGINEERING
THE ROMANCE OF MODERN LOCOMOTION
THE ROMANCE OF MODERN MINING
By CHARLES R. GIBSON, A.I.E.E.
THE ROMANCE OF MODERN PHOTOGRAPHY
THE ROMANCE OF MODERN ELECTRICITY
THE ROMANCE OF MODERN MANUFACTURE
By EDMUND SELOUS
THE ROMANCE OF THE ANIMAL WORLD
THE ROMANCE OF INSECT LIFE
By AGNES GIBERNE
THE ROMANCE OF THE MIGHTY DEEP
By E. S. GREW, M.A.
THE ROMANCE OF MODERN GEOLOGY
By J. C. PHILIP, D.Sc., Ph.D.
THE ROMANCE OF MODERN CHEMISTRY
SEELEY & CO., LIMITED
INTRODUCTION
In the beginning a man depended for his subsistence entirely upon his
own efforts, or upon those of his immediate relations and friends. Life
was very simple in those days: luxury being unknown, and necessity the
factor which guided man's actions at every turn. With infinite labour
he ground a flint till it assumed the shape of a rough arrow-head, to
be attached to a reed and shot into the heart of some wild beast as
soon as he had approached close enough to be certain of his quarry.
The meat thus obtained he seasoned with such roots and herbs as nature
provided--a poor and scanty choice. Presently he discovered that
certain grains supported life much better than roots, and he became an
agriculturist. But the grain must be ground; so he invented a simple
mill--a small stone worked by hand over a large one; and when this
method proved too tedious he so shaped the stones' surfaces that they
touched at all points, and added handles by which the upper stone could
be revolved.
With the discovery of bronze, and, many centuries later, of iron, his
workshop equipment rapidly improved. He became an expert boat- and
house-builder, and multiplied weapons of offence and defence. Gradually
separate crafts arose. One man no longer depended on his individual
efforts, but was content to barter his own work for the products of
another man's labour, because it became evident that specialisation
promoted excellence of manufacture.
A second great step in advance was the employment of machinery, which,
when once fashioned by hand, saved an enormous amount of time and
trouble--the pump, the blowing bellows, the spinning-wheel, the loom.
But all had to be operated by human effort, sometimes replaced by
animal power.
With the advent of the steam-engine all industry bounded forward again.
First harnessed by Watt, Giant Steam has become a commercial and
political power. Everywhere, in mill and factory, locomotive, ship,
it has increased the products which lend ease and comfort to modern
life; it is the great ally of invention, and the ultimate agent for
transporting men and material from one point on the earth's surface to
another.
Try as we may, we cannot escape from our environment of mechanism,
unless we are content to revert to the loincloth and spear of the
savage. Society has become so complicated that the utmost efforts of
an individual are, after all, confined to a very narrow groove. The
days of the Jack-of-all-trades are over. Success in life, even bare
subsistence, depends on the concentration of one's faculties upon a
very limited daily routine. "Let the cobbler stick to his last" is a
maxim which carries an ever-increasing force.
The better to realise how dependent we are on the mechanisms controlled
by the thousand and one classes of workmen, let us consider the
surroundings, possessions, and movements of the average, well-to-do
business man.
At seven o'clock he wakes, and instinctively feels beneath his pillow
for his watch, a most marvellous assemblage of delicate parts shaped
by wonderful machinery. Before stepping into his bath he must turn a
tap, itself a triumph of mechanical skill. The razor he shaves with,
the mirror which helps him in the operation, the very brush and soap,
all are machine-made. With his clothes he adds to the burden of his
indebtedness to mechanism. The power-loom span the linen for his
shirts, the cloth for his outer garments. Shirts and collars are glossy
from the treatment of the steam laundry, where machinery is rampant.
His boots, kept shapely by machine-made lasts, should remind him that
mechanical devices have played a large part in their manufacture, very
possibly the human hand has scarcely had a single duty to perform.
He goes downstairs, and presses an electric button. Mechanism again.
While waiting for his breakfast his eye roves carelessly over the
knives, spoons, forks, table, tablecloth, wall-paper, engravings,
carpet, cruet-stand--all machine-made in a larger or less degree. The
very coals blazing in the grate were won by machinery; the marble
of the mantelpiece was shaped and polished by machinery; also the
fire-irons, the chairs, the hissing kettle. Machinery stares at him
from the loaf on its machine-made board. Machines prepared the land,
sowed, harvested, threshed, ground, and probably otherwise prepared
the grain for baking. Machines ground his salt, his coffee. Machinery
aided the capture of the tempting sole; helped to cure the rasher of
bacon; shaped the dishes, the plates, the coffee-pot.
Whirr-r-r! The motor-car is at the door, throbbing with the impulses of
its concealed machinery. Our friend therefore puts on his machine-made
gloves and hat and sallies forth. That wonderful motor, the product of
the most up-to-date, scientific, and mechanical appliances, bears him
swiftly over roads paved with machine-crushed stone and flattened out
by a steam-roller. A book might be reserved to the motor alone; but
we must refrain, for a few minutes' travel has brought the horseless
carriage to the railway station. Mr. Smith, being the holder of a
season ticket, does not trouble the clerk who is stamping pasteboards
with a most ingenious contrivance for automatically impressing dates
and numbers on them. He strolls out on the platform and buys the
morning paper, which, a few hours before, was being battered about
by one of the most wonderful machines that ever was devised by the
brain of man. Mr. Smith doesn't bother his head with thoughts of the
printing-press. Its products are all round him, in timetables and
advertisements. Nor does he ponder upon the giant machinery which
crushed steel ingots into the gleaming rails that stretch into the
far distance; nor upon the marvellous interlocking mechanism of the
signal-box at the platform-end; nor upon the electric wires thrumming
overhead. No! he had seen all these things a thousand times before, and
probably feels little of the romance which lies so thickly upon them.
A whistle blows. The "local" is approaching, with its majestic
locomotive--a very orgy of mechanism--its automatic brakes, its
thousand parts all shaped by mechanical devices,--steam saws, planes,
lathes, drills, hammers, presses. In obedience to a little lever the
huge mass comes quickly to rest; the steam pump on the engine commences
to gasp; a minute later another lever moves, and Mr. Smith is fairly on
his way to business.
Arrived at the metropolis, he presses electricity into his service,
either on an electric tram or on a subterranean train. In the latter
case he uses an electric lift, which lowers him into the bowels of the
earth, to pass him on to the current-propelled cars, driven by power
generated in far-away stations.
His office is stamped all over with the seal of mechanism. In the
lobby are girls hammering on marvellous typewriters; on his desk rests
a telephone, connected through wires and most elaborately equipped
exchanges with all parts of the country. To get at his private and
valuable papers Mr. Smith must have recourse to his bunch of keys,
which, with their corresponding locks, represent ingenuity of a high
degree. All day long he is in the grasp of mechanism; not even at lunch
time can he escape it, for the food set before him at the restaurant
has been cooked by the aid of special kitchen machinery.
And when the evening draws on Mr. Smith touches a switch to turn his
darkness into light, wrung through many wonderful processes from the
stored illumination of coal.
Were we to trace the daily round of the clerk, artisan, scientist,
engineer, or manufacturer, we should be brought into contact with a
thousand other mechanical appliances. Space forbids such a tour of
inspection; but in the following pages we may rove here and there
through the workshops of the world, gleaning what seems to be of
special interest to the general public, and weaving round it, with a
machine-made pen, some of the romance which is apt to be lost sight of
by the most marvellous of all creations--Man.
AUTHOR'S NOTE
THE author desires to express his indebtedness to the following
gentlemen for the kind help they have afforded him in connection with
the gathering of materials for the letterpress and illustration of this
book:--
The proprietors of _Cassier's Magazine_, _The Magazine of Commence_,
_The World's Work_, _The Motor Boat_; The Rexer Automatic Machine Gun
Co.; The Diesel Oil Engine Co.; The Cambridge Scientific Instrument
Co.; The Marconi Wireless Telegraphy Co.; The Temperley Transporter
Co.; Messrs. de Dion, Bouton and Co.; Messrs. Merryweather and Sons;
Mr. A. Crosby Lockwood; Mr. Dan Albone; Mr. J. B. Diplock; Mr. W.
H. Oatway; The National Cash Register Co.; The Wenzel Sculpturing
Machine Co.; Mr. E. W. Gaz; Sir W. G. Armstrong, Whitworth and Co.; The
International Harvester Co. and Messrs. Gwynne and Co.
TABLE OF CONTENTS
PAGE
INTRODUCTION v
AUTHOR'S NOTE xi
CHAPTER I
DELICATE INSTRUMENTS--WATCHES AND CHRONOMETERS--THE
MICROTOME--THE DIVIDING ENGINE--MEASURING MACHINES 17
CHAPTER II
CALCULATING MACHINES 42
CHAPTER III
WORKSHOP MACHINERY--THE LATHE--PLANING MACHINES--THE
STEAM HAMMER--HYDRAULIC TOOLS--ELECTRICAL TOOLS IN THE
SHIPYARD 59
CHAPTER IV
PORTABLE TOOLS 90
CHAPTER V
THE PEDRAIL: A WALKING STEAM-ENGINE 97
CHAPTER VI
INTERNAL COMBUSTION ENGINES--OIL ENGINES--ENGINES WORKED
WITH PRODUCER GAS--BLAST FURNACE GAS ENGINES 112
CHAPTER VII
MOTOR-CARS--THE MOTOR OMNIBUS--RAILWAY MOTOR-CARS 130
CHAPTER VIII
THE MOTOR AFLOAT--PLEASURE BOATS--MOTOR LIFEBOATS--MOTOR
FISHING BOATS--A MOTOR FIRE FLOAT--THE MECHANISM OF
THE MOTOR BOAT--THE TWO-STROKE MOTOR--MOTOR BOATS FOR
THE NAVY 150
CHAPTER IX
THE MOTOR CYCLE 175
CHAPTER X
FIRE ENGINES 185
CHAPTER XI
FIRE-ALARMS AND AUTOMATIC FIRE EXTINGUISHERS 191
CHAPTER XII
THE MACHINERY OF A SHIP--THE REVERSING ENGINE--MARINE
ENGINE SPEED GOVERNORS--THE STEERING ENGINE--BLOWING
AND VENTILATING APPARATUS--PUMPS--FEED HEATERS--FEED-WATER
FILTERS--DISTILLERS--REFRIGERATORS--THE
SEARCH-LIGHT--WIRELESS TELEGRAPHY INSTRUMENTS--SAFETY
DEVICES--THE TRANSMISSION OF POWER ON A SHIP 203
CHAPTER XIII
"THE NURSE OF THE NAVY" 236
CHAPTER XIV
THE MECHANISM OF DIVING 240
CHAPTER XV
APPARATUS FOR RAISING SUNKEN SHIPS AND TREASURE 248
CHAPTER XVI
THE HANDLING OF GRAIN--THE ELEVATOR--THE SUCTION
PNEUMATIC GRAIN-LIFTER--THE PNEUMATIC BLAST
GRAIN-LIFTER--THE COMBINED SYSTEM 252
CHAPTER XVII
MECHANICAL TRANSPORTERS AND
CONVEYERS--ROPEWAYS--CABLEWAYS--TELPHERAGE--COALING
WARSHIPS AT SEA 258
CHAPTER XVIII
AUTOMATIC WEIGHERS 274
CHAPTER XIX
TRANSPORTER BRIDGES 277
CHAPTER XX
BOAT- AND SHIP-RAISING LIFTS 283
CHAPTER XXI
A SELF-MOVING STAIRCASE 295
CHAPTER XXII
PNEUMATIC MAIL TUBES 301
CHAPTER XXIII
AN ELECTRIC POSTAL SYSTEM 315
CHAPTER XXIV
AGRICULTURAL MACHINERY--PLOUGHS--DRILLS AND SEEDERS--REAPING
MACHINES--THRESHING MACHINES--PETROL-DRIVEN FIELD
MACHINERY--ELECTRICAL FARMING MACHINERY 318
CHAPTER XXV
DAIRY MACHINERY--MILKING MACHINES--CREAM SEPARATORS--A
MACHINE FOR DRYING MILK 330
CHAPTER XXVI
SCULPTURING MACHINES 335
CHAPTER XXVII
AN AUTOMATIC RIFLE--A BALL-BEARING RIFLE 345
LIST OF ILLUSTRATIONS
PAGE
A CARVING MACHINE _Frontispiece_
MEASURING MACHINES 34
A CASH REGISTER 45
LATHE TURNING A BIG GUN 59
LATHE FOR BORING 16-INCH GUN 65
A STEAM HAMMER 72
A HUGE HYDRAULIC PRESS 82
A PEDRAIL TRACTION ENGINE 108
GREAT GAS ENGINE FOR BLAST FURNACES 128
MOTOR-CAR AND MOTOR-BOAT 151
A MOTOGODILLE 156
A MOTOR LAWN MOWER 182
UP-TO-DATE FIRE BRIGADE ENGINES 186
HOISTING A HEAVY GUN ON BOARD MAN-OF-WAR 204
FIXING A RAM TO A BATTLESHIP 228
A TRIPOD CRANE 237
MODERN DIVING APPARATUS 245
COALING AT SEA 271
A TRANSPORTER BRIDGE AT BIZERTA 278
A CANAL LIFT 289
AN AMERICAN CUTTER AND BINDER 322
A MOTOR PLOUGH 327
GIRL CARVING BY MACHINERY 343
THE REXER GUN 352
THE ROMANCE OF MODERN MECHANISM
CHAPTER I
DELICATE INSTRUMENTS
WATCHES AND CHRONOMETERS--THE MICROTOME--THE DIVIDING ENGINE--MEASURING
MACHINES
Owing to the universal use of watches, resulting from their cheapness,
the possessor of a pocket timepiece soon ceases to take a pride in the
delicate mechanism which at first added an inch or two to his stature.
At night it is wound up mechanically, and thrust under the pillow, to
be safe from imaginary burglars and handy when the morning comes. The
awakened sleeper feels small gratitude to his faithful little servant,
which all night long has been beating out the seconds so that its
master may know just where he is with regard to "the enemy" on the
morrow. At last a hand is slipped under the feather-bag, and the watch
is dragged from its snug hiding-place. "Bother it," says the sleepy
owner, "half-past eight; ought to have been up an hour ago!" and out he
tumbles. Dressing concluded, the watch passes to its day quarters in a
darksome waistcoat pocket, to be hauled out many times for its opinion
to be taken.
The real usefulness of a watch is best learnt by being without one
for a day or two. There are plenty of clocks about, but not always in
sight; and one gradually experiences a mild irritation at having to
step round the corner to find out what the hands are doing.
A truly wonderful piece of machinery is a watch--even a cheap one.
An expensive, high-class article is worthy of our admiration and
respect. Here is one that has been in constant use for fifty years.
Twice a second its little balance-wheel revolves on its jewelled
bearings. Allowing a few days for repairs, we find by calculation that
the watch has made no less than three thousand million movements in
the half-century! And still it goes ticking on, ready to do another
fifty years' work. How beautifully tempered must be the springs and
the steel faces which are constantly rubbing against jewel or metal!
How perfectly cut the teeth which have engaged one another times
innumerable without showing appreciable wear!
The chief value of a good watch lies in its accuracy as a time-keeper.
It is, of course, easy to correct it by standard clocks in the railway
stations or public buildings; but one may forget to do this, and in a
week or two a loss of a few minutes may lead to one missing a train, or
being late for an important engagement. Happy, therefore, is the man
who, having set his watch to "London time," can rely on its not varying
from accuracy a minute in a week--a feat achieved by many watches.
The old-fashioned watch was a bulky affair, protected by an outer
case of ample proportions. From year to year the size has gradually
diminished, until we can now purchase a reliable article no thicker
than a five-shilling piece, which will not offend the most fastidious
dandy by disarranging the fit of his clothes. Into the space of a small
fraction of an inch is crowded all the usual mechanism, reduced to
the utmost fineness. Watches have even been constructed small enough
to form part of a ring or earring, without losing their time-keeping
properties.
For practical purposes, however, it is advantageous to have a timepiece
of as large a size as may be convenient, since the difficulties of
adjustment and repair increase with decreasing proportions. The ship's
chronometer, therefore, though of watch construction, is a big affair
as compared with the pocket timepiece; for above all things it must be
accurate.
The need for this arises from the fact that nautical reckonings made by
the observation of the heavenly bodies include an element of _time_. We
will suppose a vessel to be at sea out of sight of land. The captain,
by referring to the dial of the "mechanical log," towed astern, can
reckon pretty accurately how _far_ the vessel has travelled since it
left port; but owing to winds and currents he is not certain of the
position on the globe's surface at which his ship has arrived. To
locate this exactly he must learn (a) his longitude, _i.e._ distance
E. or W. of Greenwich, (b) his latitude, _i.e._ distance N. or S.
of the Equator. Therefore, when noon approaches, his chronometers
and sextant are got out, and at the moment when the sun crosses the
meridian the time is taken. If this moment happens to coincide with
four o'clock on the chronometers he is as far west of Greenwich as
is represented by four twenty-fourths of the 360° into which the
earth's circumference is divided; that is, he is in longitude 60° W.
The sextant gives him the angle made by a line drawn to the sun with
another drawn to the horizon, and from that he calculates his latitude.
Then he adjourns to the chart-room, where, by finding the point at
which the lines of longitude and latitude intersect, he establishes his
exact position also.
When the ship leaves England the chronometer is set by Greenwich time,
and is never touched afterwards except to be wound once a day. In order
that any error may be reduced to a minimum a merchant ship carries at
least two chronometers, a man-of-war at least three, and a surveying
vessel as many as a dozen. The average reading of the chronometers is
taken to work by.
Taking the case of a single chronometer, it has often to be relied on
for months at a time, and during that period has probably to encounter
many changes of temperature. If it gains or loses from day to day, and
that _consistently_, it may still be accounted reliable, as the amount
of error will be allowed for in all calculations. But should it gain
one day and lose another, the accumulated errors would, on a voyage
of several months, become so considerable as to imperil seriously the
safety of the vessel if navigating dangerous waters.
As long ago as 1714 the English Government recognised the importance of
a really reliable chronometer, and in that year passed an Act offering
rewards of £10,000, £15,000, and £20,000 to anybody who should produce
a chronometer that would fix longitude within sixty, forty, and thirty
miles respectively of accuracy. John Harrison, the son of a Yorkshire
carpenter, who had already invented the ingenious "gridiron pendulum"
for compensating clocks, took up the challenge. By 1761 he had made a
chronometer of so perfect a nature that during a voyage to Jamaica that
year, and back the next, it lost only 1 min. 54-1/2 sec. As this would
enable a captain to find his longitude within eighteen miles in the
latitude of Greenwich, Harrison claimed, and ultimately received, the
maximum reward.
It was not till nearly a century later that Thomas Earnshaw produced
the "compensation balance," now generally used on chronometers and
high-class watches. In cheap watches the balance is usually a little
three-spoked wheel, which at every tick revolves part of a turn and
then flies back again. This will not suffice for very accurate work,
because the "moment of inertia" varies at different temperatures. To
explain this term let us suppose that a man has a pound of metal to
make into a wheel. If the wheel be of small diameter, you will be able
to turn it first one way and then the other on its axle quite easily.
But should it be melted down and remade into a wheel of four times
the diameter, with the same amount of metal as before in the rim, the
difficulty of suddenly reversing its motion will be much increased.
The weight is the same, but the speed of the rim, and consequently
its momentum, is greater. It is evident from this that, if a wheel
of certain size be driven by a spring of constant strength, its
oscillations will be equal in time; but if a rise of temperature should
lengthen the spokes the speed would fall, because the spring would
have more work to do; and, conversely, with a fall of temperature the
speed would rise. Earnshaw's problem was to construct a balance wheel
that should be able to keep its "moment of inertia" constant under all
circumstances. He therefore used only two spokes to his wheel, and to
the outer extremity of each attached an almost complete semicircle of
rim, one end being attached to the spoke, the other all but meeting the
other spoke. The rim-pieces were built up of an outer strip of brass,
and an inner strip of steel welded together. Brass expands more rapidly
than steel, with the result that a bar compounded of these two metals
would, when heated, bend towards the hollow side. To the rim-pieces
were attached sliding weights, adjustable to the position found by
experiment to give the best results.
We can now follow the action of the balance wheel. It runs perfectly
correctly at, say, a temperature of 60°. Hold it over a candle. The
spokes lengthen, and carry the rim-pieces _outwards_ at their fixed
ends; but, as the pieces themselves bend inwards at their free ends,
the balance is restored. If the balance were placed in a refrigerating
machine, the spokes would shorten, but the rim-pieces would bend
outwards.
As a matter of fact, the "moment of inertia" cannot be kept quite
constant by this method, because the variation of expansion is more
rapid in cold than in heat; so that, though a balance might be quite
reliable between 60° and 100°, it would fail between 30° and 60°.
So the makers fit their balances with what is called a _secondary_
compensation, the effect of which is to act more quickly in high
than in low temperatures. This could not well be explained without
diagrams, so a mere mention must suffice.
Another detail of chronometer making which requires very careful
treatment is the method of transmitting power from the main spring
to the works. As the spring uncoils, its power must decrease, and
this loss must be counterbalanced somehow. This is managed by using
the "drum and fusee" action, which may be seen in some clocks and in
many old watches. The drum is cylindrical, and contains the spring.
The fusee is a tapering shaft, in which a spiral groove has been cut
from end to end. A very fine chain connects the two parts. The key is
applied to the fusee, and the chain is wound off the drum on to the
larger end of the fusee first. By the time that the spring has been
fully wound, the chain has reached the fusee's smaller extremity. If
the fusee has been turned to the correct taper, the driving power
of the spring will remain constant as it unwinds, for it gets least
leverage over the fusee when it is strongest, and most when it is
weakest, the intermediate stages being properly proportioned. To test
this, a weighted lever is attached to the key spindle, with the weight
so adjusted that the fully wound spring has just sufficient power to
lift it over the topmost point of a revolution. It is then allowed a
second turn, but if the weight now proves excessive something must be
wrong, and the fusee needs its diameter reducing at that point. So the
test goes on from turn to turn, and alterations are made until every
revolution is managed with exactly the same ease.
The complete chronometer is sent to Greenwich observatory to be tested
against the Standard Clock, which, at 10 a.m., flashes the hour to
other clocks all over Great Britain. In a special room set apart for
the purpose are hundreds of instruments, some hanging up, others
lying flat. Assistants make their rounds, noting the errors on each.
The temperature test is then applied in special ovens, and finally
the article goes back to the maker with a certificate setting forth
its performances under different conditions. If the error has been
consistent the instrument is sold, the buyer being informed exactly
what to allow for each day's error. At the end of the voyage he brings
his chronometer to be tested again, and, if necessary, put right.
Here are the actual variations of a chronometer during a nineteen-day
test, before being used:--
Gain in _tenths_
Day. of seconds.
1st 1/2
2nd 3
3rd 4
4th 4
5th 1/2
6th 3
7th 0
8th 0
9th 4-1/2
10th 3
11th 4
12th 3
13th 3
14th 4
15th 5
16th 2
17th 3
18th 5
19th 1
An average gain of just over one quarter of a second per diem! Quite
extraordinary feats of time-keeping have been recorded of chronometers
on long voyages. Thus a chronometer which had been to Australia _viâ_
the Cape and back _viâ_ the Red Sea was only fifteen seconds "out";
and the _Encyclopædia Britannica_ quotes the performance of the three
instruments of S.S. _Orellana_, which between them accumulated an error
of but 2·3 seconds during a sixty-three-day trip.
An instrument which will cut a blood corpuscle into several
parts--that's the MICROTOME, the "small-cutter," as the name implies.
For the examination of animal tissues it is necessary that they should
be sliced very fine before they are subjected to the microscope.
Perhaps a tiny muscle is being investigated and cross sections of it
are needed. Well, one cannot pick up the muscle and cut slices off it
as you would off a German sausage. To begin with, it is difficult even
to pick the object up; and even if pieces one-hundredth of an inch long
were detached they would still be far too large for examination.
So, as is usually the case when our unaided powers prove unequal to
a task, we have recourse to a machine. There are several types of
microtomes, each preferable for certain purposes. But as in ordinary
laboratory work the Cambridge Rocking Microtome is used, let us give
our special attention to this particular instrument. It is mounted
on a strong cast-iron bed, a foot or so in length and four to five
inches wide. Towards one end rise a couple of supports terminating in
knife-edges, which carry a cross-bar, itself provided with knife-edges
top and bottom, those on the top supporting a second transverse bar.
Both bars have a long leg at right angles, giving them the appearance
of two large T's superimposed one on the other; but the top T is
converted into a cross by a fourth member--a sliding tube which
projects forward towards a frame in which is clamped a razor, edge
upwards.
The tail of the lower T terminates in a circular disc, pierced with
a hole to accommodate the end of a vertical screw, which has a large
circular head with milled edges. The upper T is rocked up and down
by a cord and spring, the handle actuating the cord also shifting on
the milled screw-head a very small distance every time it is rocked
backwards and forwards. As the screw turns, it gradually raises the
tail of the lower member, and by giving its cross-bar a tilt brings the
tube of the upper member appreciably nearer the razor. The amount of
twist given to the screw at each stroke can be easily regulated by a
small catch.
When the microscopist wishes to cut sections he first mounts his object
in a lump of hard paraffin wax, coated with softer wax. The whole is
stuck on to the face of the tube, so as to be just clear of the razor.
The operator then seizes the handle and works it rapidly until the
first slice is detached by the razor. Successive slices are stuck
together by their soft edges so as to form a continuous ribbon of wax,
which can be picked up easily and laid on a glass slide. The slide is
then warmed to melt the paraffin, which is dissolved away by alcohol,
leaving the atoms of tissue untouched. These, after being stained with
some suitable medium, are ready for the microscope.
A skilful user can, under favourable conditions, cut slices _one
twenty-five thousandth_ of an inch thick. To gather some idea of what
this means we will imagine that a cucumber one foot long and one and
a-half inches in diameter is passed through this wonderful guillotine.
It would require no less than 700 dinner-plates nine inches across to
spread the pieces on! If the slices were one-eighth of an inch thick,
the cucumber, to keep a proportionate total size, would be 260 feet
long. After considering these figures we shall lose some of the respect
we hitherto felt for the men who cut the ham to put inside luncheon-bar
sandwiches.
In the preceding pages frequent reference has been made to index
screws, exactly graduated to a convenient number of divisions. When
such screws have to be manufactured in quantities it would be far too
expensive a matter to measure each one separately. Therefore machinery,
itself very carefully graduated, is used to enable a workman to
transfer measurements to a disc of metal.
If the index-circle of an astronomical telescope--to take an
instance--has to be divided, it is centred on a large horizontal disc,
the circumference of which has been indented with a large number of
teeth. A worm-screw engages these teeth tangentially (_i.e._ at right
angles to a line drawn from the centre of the plate to the point
of engagement). On the shaft of the screw is a ratchet pinion, in
principle the same as the bicycle free-wheel, which, when turned one
way, also twists the screw, but has no effect on it when turned the
other way. Stops are put on the screw, so that it shall rotate the
large disc only the distance required between any two graduations. The
divisions are scribed on the index-circle by a knife attached to a
carriage over and parallel to the disc. The DIVIDING ENGINE used for
the graduation of certain astronomical instruments probably constitutes
the most perfect machine ever made. In an address to the Institution
of Mechanical Engineers,[1] the President, Mr. William Henry Maw, used
the following words: "The most recently constructed machine of the kind
of which I am aware--namely, one made by Messrs. Warner and Swasey, of
Cleveland, U.S.A.--is capable of automatically cutting the graduations
of a circle with an error in position not exceeding one second of arc.
(A second of an arc is approximately the angle subtended by a halfpenny
at a distance of three miles.) This means that on a 20-inch circle the
error in position of any one graduation shall not exceed 1/20,000 inch.
Now, the finest line which would be of any service for reading purposes
on such a circle would probably have a width equal to quite ten seconds
of arc; and it follows that the minute V-shaped cut forming this line
must be so absolutely symmetrical with its centre line throughout its
length, that the position of this centre may be determined within the
limit of error just stated by observations of its edges, made by aid of
the reading micrometer and microscope. I may say that after the machine
just mentioned had been made, it took _over a year's hard work_ to
reduce the maximum error in its graduations from one and a-half to one
second of arc."
The same address contains a reference to the great Yerkes telescope,
which though irrelevant to our present chapter, affords so interesting
an example of modern mechanical perfection that it deserves parenthetic
mention.
The diameter of a star of the seventh magnitude as it appears in
the focus of this huge telescope is 1/2,500 inch. The spiders' webs
stretched across the object glass are about 1/6,000 inch in diameter.
"The problem thus is," says Mr. Maw, "to move this twenty-two ton mass
(the telescope) with such steadiness in opposition to the motion of the
earth, that a star disc 1/2,500 inch in diameter can be kept threaded,
as it were, upon a spider's web 1/6,000 inch in diameter, carried at a
radius of thirty-two feet from the centre of motion. I think that you
will agree that this is a problem in mechanical engineering demanding
no slight skill to solve; but it has been solved, and with the most
satisfactory results." The motions are controlled electrically; and
respecting them Professor Barnard, one of the chief observers with this
telescope, some time ago wrote as follows: "It is astonishing to see
with what perfect instantaneousness the clock takes up the tube. The
electric slow motions are controlled from the eye end. So exact are
they that a star can be brought from the edge of the field and stopped
instantaneously behind the micrometer wire."
Dividing engines are used for ruling parallel lines on glass and
metal, to aid in the measurements of microscopical objects or the
wave-lengths of light. A _diffraction grating_, used for measuring the
latter, has the lines so close together that they would be visible
only under a powerful microscope. Glass being too brittle, a special
alloy of so-called _speculum_ metal is fashioned into a highly polished
plate, and this is placed in the machine. A delicate screw arrangement
gradually feeds the plate forwards under the diamond point, which is
automatically drawn across the plate between every two movements.
Professor H. A. Rowlands has constructed a parallel dividing engine
which has ruled as many as 120,000 lines to the inch. To get a
conception of these figures we must once again resort to comparison.
Let us therefore take a furrow as a line, and imagine a ploughman going
up and down a field 120,000 times. If each furrow be eight inches
wide, the field would require a breadth of nearly _fourteen miles_ to
accommodate all the furrows! Again, supposing that a plate six inches
square were being ruled, the lines placed end to end would extend for
seventy miles!
Professor Rowlands' machine does the finest work of this kind. Another
very perfect instrument has been built by Lord Blythswood, and as some
particulars of it have been kindly supplied, they may fitly be appended.
If a first-class draughtsman were asked how many parallel straight
lines he would rule within the space of one inch, it is doubtful
whether he would undertake more than 150 to 200 lines. Lord
Blythswood's machine can rule fourteen parallel lines on a space
equivalent to the _edge_ of the finest tissue paper. So delicate are
the movements of the machine that it must be protected from variations
of temperature, which would contract or expand its parts; so the room
in which it stands is kept at an even heat by automatic apparatus, and
to make things doubly sure the engine is further sheltered in a large
case having double walls inter-packed with cotton wool.
In constructing the machine it was found impossible, with the most
scientific tools, to cut a toothed wheel sufficiently accurate to drive
the mechanism, but the errors discovered by microscopes were made good
by the invention of a small electro-plating brush, which added the
thinnest imaginable layer of metal to any tooth found deficient.
During the process of ruling a grating of only a few square inches
area, the machine must be left severely alone in its closed case. The
slightest jar would cause unparallelism of a few lines, and the ruin of
the whole grating. So for several days the diamond point has its own
way, moving backwards and forwards unceasingly over the hard metal, in
which it chases tiny grooves. At the end the plate has the appearance
of mother-of-pearl, which is, in fact, one of nature's diffraction
gratings, breaking up white light into the colours of the spectrum.
You will be able to understand that these mechanical gratings are
expensive articles. Sometimes the diamond point breaks half-way through
the ruling, and a week's work is spoilt. Also the creation of a
reliable machine is a very tedious business. Ten pounds per square inch
of grating is a low price to pay.
The greatest difficulty met with in the manufacture of the dividing
engine is that of obtaining a mathematically correct screw. Turning
on a lathe produces a very rough spiral, judged scientifically. Some
threads will be deeper than others, and differently spaced. The screw
must, therefore, be ground with emery and oil introduced between it
and a long nut which is made in four segments, and provided with
collars for tightening it up against the screw. Perhaps a fortnight
may be expended over the grinding. Then the screw must undergo rigid
tests, a nut must be made for it, and it has to be mounted in proper
bearings. The explanation of the method of eliminating errors being
very technical, it is omitted; but an idea of the care required may be
gleaned from Professor Rowlands' statement that an uncorrected error of
1/300,000 of an inch is quite sufficient to ruin a grating!
In the Houses of Parliament there is kept at an even temperature a
bronze rod, thirty-eight inches long and an inch square in section.
Near the ends are two wells, rather more than half an inch deep, and at
the bottom of the wells are gold studs, each engraved with a delicate
cross line on their polished surfaces. The distance between the lines
is the imperial yard of thirty-six inches.
The bar was made in 1844 to replace the Standard destroyed in 1834,
when both Houses of Parliament were burned. The original Standard was
the work of Bird, who produced it in 1760. In June, 1824, an Act had
been passed legalising this Standard. It says:--
"The same Straight Line or Distance between the Centers of the said Two
Points in the said Gold Studs in the said Brass Rod, the Brass being at
the temperature of Sixty-two Degrees by Fahrenheit's Thermometer, shall
be and is hereby denominated the 'Imperial Standard Yard.'"
To provide for accidents to the bar, the Act continues: "And whereas
it is expedient that the said Standard Yard, if lost, destroyed,
defaced, or otherwise injured, should be restored to the same Length by
reference to some invariable natural Standard: And whereas it has been
ascertained by the Commissioners appointed by His Majesty to inquire
into the subject of Weights and Measures, that the Yard hereby declared
to be the Imperial Standard Yard, when compared with a Pendulum
vibrating Seconds of Mean Time in the Latitude of London in a Vacuum
at the Level of the Sea, is in the proportion of Thirty-six Inches to
Thirty-nine Inches and one thousand three hundred and ninety-three
ten-thousandth Parts of an Inch."
The new bar was made, however, not by this method, but by comparing
several copies of the original and striking their average length. Four
accurate duplicates of the new standard were secured, one of which
is kept in the Mint, one in the charge of the Royal Society, one at
Westminster Palace, and the fourth at the Royal Observatory, Greenwich.
In addition, forty copies were distributed among the various foreign
governments, all of the same metal as the original.
The French metre has also been standardised, being equal to one
ten-millionth part of a quadrant of the earth's meridian (_i.e._ of
the distance from the Equator to either of the Poles), that is, to
39·370788 inches. Professor A. A. Michelson has shown that any standard
of length may be restored by reference to the measurement of wave
lengths of light, with an error not exceeding one ten-millionth part of
the whole.
It might be asked "Why should standards of such great accuracy be
required?" In rough work, such as carpentry, it does not, indeed,
matter if measurements are the hundredth of an inch or so out. But when
we have to deal with scientific instruments, telescopes, measuring
machines, engines for dividing distances on a scale, or even with
metal turning, the utmost accuracy becomes needful; and a number of
instruments will be much more alike in all dimensions if compared
individually with a common standard than if they were only compared
with one another. Supposing, for instance, a bar of exact diameter is
copied; the copy itself copied; and so on a dozen times; the last will
probably vary considerably from the correct measurements.
Hence it became necessary to standardise the foot and the inch by
accurate subdivisions of the yard. This was accomplished by Sir Joseph
Whitworth, who in 1834 obtained two standard yards in the form of
measure bars, and by the aid of microscopes transferred the distance
between the engraved lines to a rectangular _end_-measure bar, _i.e._
one of which the end faces are exactly a yard apart.
He next constructed his famous machine which is capable of detecting
length differences of _one millionth_ of an inch. Two bars are advanced
towards each other by screw gearing: one by a screw having twenty
threads to the inch, and carrying a graduated hand-wheel with 250
divisions on its rim; the other by a similar screw, itself driven by a
worm-screw, working on the rim, which carries 200 teeth. The worm-screw
has a hand-wheel with a micrometer graduation into 250 divisions of
its circumference. So that, if this be turned one division, the second
screw is turned only 1/250 × 1/200 of a division, and the bar it drives
advances only 1/20 × 1/200 × 1/250 = 1/1,000,000 of an inch. The screw
at the other end of the machine (which in appearance somewhat resembles
a metal lathe) is used for rapid adjustment only.
[Illustration: DELICATE MEASURING MACHINES
The upper illustration shows a Pratt-Whitney Measuring Machine in
operation to decide the thickness of a cigarette paper, which is
one-thousandth of an inch thick. This machine will measure variations
of length or thickness as minute as one hundredth-thousandth of an
inch. The lower illustration shows a Whitworth Measuring Machine which
is sensitive to variations of one-millionth of an inch.]
"He (Sir J. Whitworth) obtained the subdivision of the yard by making
three foot pieces as nearly alike as was possible, and working these
foot pieces down until each was equal to the others, and placing them
end to end in his millionth measuring machine; the total length of the
three foot pieces was then compared with a standard end-measure yard.
These three foot pieces were ground until they were exactly equal to
each other, and the three added together are equal to the standard
yard. The subdivision of the foot into inch pieces was made in the same
way."[2]
A doubt may have arisen in the reader's mind as to the possibility of
determining whether the measuring machine is screwed up to the exact
_tightness_. Would the measuring bars not compress a body a little
before it appeared tight? Workmen, when measuring a bar with callipers,
often judge by the sense of touch whether the jaws of the callipers
pass the bar with the proper amount of resistance; but when one has to
deal with millionths of an inch, such a method would not suffice. So
Sir Joseph Whitworth introduced a _feeling-piece_, or _gravity-piece_.
Mr. T. M. Goodeve thus describes it in _The Elements of Mechanism_:
The gravity-piece consists of a small plate of steel with parallel
plane sides, and having slender arms, one for its partial support, and
the other for resting on the finger of the observer. One arm of the
piece rests on a part of the bed of the machine, and the other arm is
tilted up by the forefinger of the operator. The plane surfaces are
then brought together, one on each side of the feeling-piece, until
the pressure of contact is sufficient to hold it supported just as it
remained when one end rested on the finger. This degree of tightness is
perfectly definite, and depends on the weight of the gravity-piece, but
not on the estimation of the observer.
In this way the expansion due to heat when a 36-inch bar has been
touched for an instant with the finger-nail may be detected.
One of the most beautiful measuring machines commercially used comes
from the factories of the Pratt-Whitney Co., Hartford, Connecticut,
the well-known makers of machine tools and gauges of all kinds. It
is made in different sizes, the largest admitting an 80-inch bar.
Variations of 1/100,000 of an inch are readily determined by the use of
this machine. It therefore serves for originating gauge sizes, or for
duplicating existing standards. The adjusting screw has fifty threads
to the inch, and its index-wheel is graduated to 400 divisions, giving
an advance of 1/20,000 inch for each division: while by estimation this
may be further subdivided to indicate one-half or even one-quarter of
this small amount. Delicacy of contact between the measuring faces is
obtained by the use of auxiliary jaws holding a small cylindrical gauge
by the pressure of a light helical spring which operates the sliding
spindle to which one of these auxiliary jaws is attached.
On one side of the "head" of the machine is a vertical microscope
directed downwards on to a bar on the bed-plate, in which are a number
of polished steel plugs graved with very fine central cross lines, each
exactly an inch distant from either of its neighbours. A cross wire in
the microscope tells when it is accurately abreast of the line below
it. Supposing, then, that a standard bar three inches in diameter has
to be tested. The "head" is slid along until the microscope is exactly
over the "zero" plug line, and the divided index-wheel is turned
until the two jaws press each other with the minimum force that will
hold up the feeling-piece. Then the head is moved back and centred
on the 3-inch line, and the bar to be tested is passed between the
jaws. If the feeling-piece drops out it is too large, and the wheel
is turned back until the jaws have been opened enough to let the bar
through without making the feeling-piece fall. An examination of the
index-wheel shows in hundred-thousandths of an inch what the excess
diameter is.
On the other hand, if the bar were too small, the jaws would need to be
closed a trifle: this amount being similarly reckoned.
We have now got into a region of very "practical politics," namely,
the subject of _gauges_. All large engineering works which turn out
machinery with interchangeable parts, _e.g._ screws and nuts, must keep
their dimensions very constant if purchasers are not to be disgusted
and disappointed. The small motor machinery so much in evidence to-day
demands that errors should be kept within the ten-thousandth of an
inch. An engineer therefore possesses a set of standard gauges to test
the diameter and pitch of his screw threads and nuts; the size of
tubes, wires; the circumference of wheels, etc.
Great inconvenience having been experienced by American railroad-car
builders on account of the varying sizes of the screws and bolts which
were used on the different tracks--though all were supposed to be of
standard dimensions--the masters determined to put things right; and
accordingly Professors Roger and Bond and the Pratt-Whitney Co. were
engaged to work in collaboration in connection with the manufacture of
tools for minute measurements, viz. to 1/50,000 inch. "To give an idea
of what is implied by this, let it be supposed that a person should
take a pair of dividing compasses and lay off 50,000 prick-marks 1/8
inch apart in a straight line. To do this the line would require to
be over 520 feet, or nearly a tenth of a mile long. Imagine that many
prick-marks compressed into the space of an inch, and you have an
imperfect idea of the minuteness of the measurements which can now be
made by the Pratt and Whitney Co."[3]
The standard taps and dies were supplied to tool-makers and engineers,
who could thus determine whether articles supplied to them were of the
proper dimensions. Nothing more was then heard of nuts being a "trifle
small" or bolts "a leetle large." And so beautifully tempered were the
dies made from the standards that one manufacturer claimed to have cut
18,800 cold-pressed nuts without any difference being perceptible in
their sizes.
To appreciate what the difference of a thousandth of an inch makes in a
true fit, you should handle a set of plug and ring gauges; the ring a
true half-inch internally, the plugs half-inch, half an inch less one
ten-thousandth of an inch, and half an inch less one-thousandth, in
diameter.
The true half-inch plug needs to be forcibly driven into the ring on
account of the friction between the surfaces. The next, if oiled, will
slide in quite easily, but if left stationary a moment will "seize,"
and have to be driven out. The third will wobble very perceptibly, and
would be at once discarded by a good workman as a bad fit.
For extremely accurate measurements of rods, calliper gauges, shaped
somewhat like the letter Y, are used, the horns terminating in polished
parallel jaws. Such a gauge will detect a difference of 1/20,000 inch
quite easily.
So accurately can plug gauges be made by reference to a measuring
machine, that a gold leaf 1/30,000 inch thick would be three times too
thick to insert between the gauge and the jaws of the machine!
You must remember that in high-class workmanship these gauges are
constantly being used. As time goes on, the "limit of error" allowed
in many classes of machine parts is gradually lessened, which shows
the simultaneous improvement of all machinery used in the handling
of metal. James Watt was terribly hampered, when developing his
steam-engine, by the difficulty of procuring a true cylinder for his
pistons to work in with any approach to steam-tightness. His first
cylinder was made by a smith of hammered iron soldered together. The
next was cast and bored, but stuffing it with paper, cork, putty,
pasteboard, and "old hat" proved useless to stem the leakage of steam.
No wonder, considering that the finished cylinder was one-eighth of
an inch larger in diameter at one end than at the other. Watt was in
advance of his time. Neither machinery nor workmanship had progressed
sufficiently to meet the requirements of the steam-engine. To-day
an engineer would confidently undertake to bore a cylinder five
feet in diameter with a variation from truth of not more than one
five-hundredth of an inch.
Before passing from the subject of measuring machines, which play
so important a part in modern mechanism, we may just glance at the
electrical method of Dr. P. E. Shaw. He discovered recently that two
clean metal surfaces can, by means of an electric current, feel one
another on touching with a delicacy that far transcends that of the
purely mechanical machine. The mechanism he employs is thus devised: A
finely cut vertical screw having fifty threads to the inch has a disc
graduated into 500 parts. The screw can be turned by means of a pulley
string from a distance, and it is thus possible to give the top end of
the screw a movement of 1/25,000 inch, when a movement corresponding to
one graduation is made.
This small movement is reduced by a train of six levers, the long arm
of each bearing on the short arm of the one before it. The movement of
the last lever of the train is thus reduced to 1/4,000 of that of the
screw point, so a movement of 1/4,000 × 1/25,000 inch = 1/100,000,000
inch is obtained!
How can such a movement be judged? A telephone and voltaic cell are
joined to the last lever of the train and to the object whose movement
is under examination. If they touch, the telephone sounds. An observer
listens in the telephone, and if the object moves for any reason he can
find out how much it moves by turning the screw until contact is made
again.
Out of the many applications of this apparatus three may be given.
(1) A short bar of iron when magnetised elongates about 1/1,000,000
of its length. If further magnetised it contracts. These changes can
readily be measured with the instrument.
(2) The smallest sound audible in the telephone is due to a movement
of the diaphragm of the telephone by about 1/50,000,000 of an inch.
This has been actually measured by Dr. Shaw and is by far the smallest
distance ever directly recorded. It is about twice the diameter of the
molecules of matter.
(3) Dispensing with levers, the screw alone is used for rougher work.
Dr. Shaw has shown that one hundred-thousandth of an inch is the
smallest dimension visible under a microscope. By fitting an electric
measuring apparatus to the microscope carriage it becomes quite easy
to measure minute distances. The microscope contains a cross wire
which, when the object has been laid on the microscope stage, is
centred on one side of the object. The electric contact screw is then
advanced till it makes contact with the stage and a sound arises in
the telephone. A reading of the screw disc having been taken, the
screw is drawn in and the microscope stage is traversed sufficiently
to bring the wire in line with the other side of the object. Once more
the operator makes electrical contact and gets a second reading, the
difference between the two being the diameter of the object. In this
manner the bacillus of tuberculosis has been proved to have an average
diameter of 31/250,000 of an inch.
The same method is employed to gauge the distance between the lines on
a diffraction grating.
FOOTNOTES:
[1] April 19th, 1901.
[2] G. M. Bond in a lecture delivered before the Franklin Institute,
February 29th, 1884.
[3] _Report on Standard Screw Threads_, Philadelphia, 1884.
CHAPTER II
CALCULATING MACHINES
The simplest form of calculating machine was the Abacus, on which the
schoolboys of ancient Greece did their sums. It consisted of a smooth
board with a narrow rim, on which were arranged rows of pebbles, bits
of bone or ivory, or silver coins. By replacing these little counters
by sand, strewn evenly all over its surface, the abacus was transformed
into a slate for writing or geometrical lessons. The Romans took the
abacus, along with many other spoils of conquest, from the Greeks and
improved it, dividing it by means of cross-lines, and assigning a
multiple value to each line with regard to its neighbours. From their
method of using the calculi, or pebbles, we derive our English verb, to
_calculate_.
During the Middle Ages the abacus still flourished, and it has left
a further mark on our language by giving its name to the Court of
Exchequer, in which was a table divided into chequered squares like
this simple school appliance.
Step by step further improvements were made, most important among
them being those of Napier of Merchiston, whose logarithms vex the
heads of our youth, and save many an hour's calculation to people
who understand how to handle them. Sir Samuel Morland, Gunter,
and Lamb invented other contrivances suitable for trigonometrical
problems. Gersten and Pascal harnessed trains of wheels to their
"ready-reckoners," somewhat similar to the well-known cyclometer.
All these devices faded into insignificance when Mr. Charles Babbage
came on the scene with his famous calculator, which is probably the
most ingenious piece of mechanism ever devised by the human brain. To
describe the "Difference Engine," as it is called, would be impossible,
so complicated is its character. Dr. Lardner, who had a wonderful
command of language, and could explain details in a manner so lucid
that his words could almost always be understood in the absence of
diagrams, occupied twenty-five pages of the _Edinburgh Review_ in the
endeavour to describe its working, but gave several features up as a
bad job. Another clever writer, Dr. Samuel Smiles, frankly shuns the
task, and satisfies himself with the following brief description:--
"Some parts of the apparatus and modes of action are indeed
extraordinary--and, perhaps, none more so than that for ensuring
accuracy in the calculated results--the machine actually correcting
itself, and rubbing itself back into accuracy, by the friction of the
adjacent machinery! When an error is made the wheels become locked and
refuse to proceed; thus the machine must go rightly or not at all--an
arrangement as nearly resembling volition as anything that brass and
steel are likely to accomplish."[4]
Mr. Babbage, in 1822, entered upon the task of superintending the
construction of a machine for calculating and printing mathematical
and astronomical tables. He began by building a model, which produced
forty-four figures per minute. The next year the Royal Society reported
upon the invention, which appeared so promising that the Lords of the
Treasury voted Mr. Babbage £1,500 to help him perfect his apparatus.
He looked about for a first-rate mechanician of high intelligence as
well as of extreme manual skill. The man he wanted appeared in Mr.
Joseph Clement, who had already made his name as the inventor of a
drawing instrument, a self-acting lathe, a self-centring chuck, and
fluted taps and dies. Mr. Clement soon produced special tools for
shaping the various parts of the machine. So elaborate was the latter,
that, according to Dr. Smiles, "the drawings for the calculating
machinery alone--not to mention the printing machinery, which was
almost equally elaborate--covered not less than four hundred square
feet of surface!"
You will easily imagine, especially if you have ever had a special
piece of apparatus made for you by a mechanic, that the bills mounted
up at an alarming rate; so fast, indeed, that the Government began to
ask, Why this great expense, and so little visible result? After seven
years' work the engineers' account had reached £7,200, and Mr. Babbage
had disbursed an additional £7,000 out of his own pocket. Mr. Clement
quarrelled with his employer--possibly because he harboured suspicions
that they were both off on a wild-goose chase--and withdrew, taking
all his valuable tools with him. The Government soon followed his
example, and poor Babbage was left with his half-finished invention,
"a beautiful fragment of a great work." It had been designed to
calculate as far as twenty figures, but was completed only sufficiently
to go to five figures. In 1862 it occupied a prominent place among the
mechanical exhibits at the Great Exhibition.
[Illustration: A MECHANICAL CASHIER
The printing apparatus of a National Cash Register. It impresses on
a paper strip the amount and nature of every money transaction; and
also prints a date, number, advertisement, money value, and nature of
business done on a ticket for the customer.]
We learn, with some satisfaction, that all this effort was not fated
to be fruitless. Two scientists of Stockholm--Scheutz by name--were so
impressed by Dr. Lardner's account of this calculating machine that
they carried Babbage's scheme through, and after twenty years of hard
work completed a machine which seemed to be almost capable of thinking.
The English Government spent £1,200 on a copy, which at Somerset House
entered upon the routine duty of working out annuity and other tables
for the Registrar-General.
From Babbage's wonderfully and fearfully made machine we pass to a
calculator which to-day may be seen at work in hundreds of thousands of
shops and offices.
It is the most modern substitute for the open till; and, by the aid of
marvellous interior works, acts as account-keeper and general detective
to the money transactions of the establishment in which it is employed.
There are very many types of Cash Register, and as it would be
impossible to enumerate them all, we will pass at once to the most
perfect type of all, known to the makers and vendors as "Number 95."
This register has at the top an oblong window. Dotted about the surface
confronting the operator are, in the particular machine under notice,
fifty-seven keys; six bearing the letters A, B, D, E, H, K; three the
words "Paid out," "Charge," "Received on Account"; and the others money
values ranging from £9 to 1/4d.
These are arranged in vertical rows. At the left end of the instrument
is a printing apparatus, kept locked by the proprietor; at the right
end a handle and a small lever. Below the register are six drawers,
each labelled with an initial.
A customer enters the shop, and buys goods to the value of 6s. 11d.
An assistant, to whom belongs the letter H, receives a sovereign in
payment. He goes to the register, and after making sure that his
drawer is pushed in till it is locked, first presses down the key H,
and then the keys labelled "6s." and "11d." Suddenly, like two
Jacks-in-the-box, up fly into the window two tablets, with "6s.
11d." on both their faces, so that customer and assistant can see
the figures. Simultaneously a bell of a certain tone rings, drawer H
flies open (so that he may place the money in it and give change, if
necessary), and a rotating arm in the window shows the word "cash."
The assistant now revolves the handle and presses the little lever.
From a slot on the left side out flies a ticket, on the front of which
is printed the date, a consecutive number, the assistant's letter,
and the amount of the sale. The back has also been covered with an
advertisement of some kind. The ticket and change are handed over to
the customer, the drawer is shut, and the transaction is at an end,
except for an entry in the shop's books of the article sold.
A carrier next comes in with a parcel on which five-pence must be
paid for transport. Mr. A. receives the goods, goes to the register,
presses his letter, the key with the words "paid out" on it, and the
key carrying "5d.," takes out the amount wanted, and gives it to the
carrier.
Again, a gentleman enters, and asks for change for half a sovereign.
Mr. B. obliges him, pressing down his letter, but no figures.
Fourthly, a debtor to the shop pays five shillings to meet an account
that has been against him for some time. Mr. K. receives the money and
plays with the keys K, "Received on account," and "5s.," giving a
ticket receipt.
Lastly, a customer buys a pair of boots on credit. Mr. D. attends to
him, and though no cash is handled, uses the register, pressing the
letter "Charge," and, say, "16s. 6d."
Now what has been going on inside the machine all this time? Let us
lift up the cover, take off the case of the printing apparatus, and see.
A strip of paper fed through the printing mechanism has on it five rows
of figures, letters, etc., thus--
s. d.
H 6 11
Pd. A 0 5
B 0 0
Rc. K 5 0
Ch. D 16 6
The proprietor is, therefore, enabled to see at a glance (1) who served
or attended to a customer, (2) what kind of business he did with him,
(3) the monetary value of the transaction. At the end of the day each
assistant sends in his separate account, which should tally exactly
with the record of the machine.
Simultaneously with the strip printing, special counting apparatus has
been (a) adding up the total of all money taken for goods, (b)
recording the number of times the drawer has been opened for each
purpose. Here, again, is a check upon the records.
This ingenious machine not only protects the proprietor against
carelessness or dishonesty on the part of his employés, but also
protects the latter against one another. If only one drawer and letter
were used in common, it would be impossible to trace an error to the
guilty party. The lettering system also serves to show which assistant
does the most business.
Where a cash register of this type is employed every transaction must
pass through its hands--or rather mechanism. It would be risky for
an assistant not to use the machine, as eyes may be watching him.
He cannot open his drawers without making a record; nor can he make
a record without first closing the drawers; so that he must _give
a reason_ for each use of the register. If he used somebody else's
letter, the ear of the rightful owner would at once be attracted by the
note of his particular gong. When going away for lunch, or on business,
a letter can be locked by means of a special key, which fits none of
the other five locks.
The printing mechanism is particularly ingenious. Every morning the
date is set by means of index-screws: and a consecutive numbering train
is put back to zero. A third division accommodates a circular "electro"
block for printing the advertisements, and a fourth division the figure
wheels.
The turn given to the handle passes a length of the ticket strip
through, a slot--prints the date, the number of the ticket, an
advertisement on the back, the assistant's letter, the nature of the
business done, and feeds the paper on to the figures which give the
finishing touch. A knife cuts off the ticket, and a special lever
shoots it out of the slot.
The National Cash Register Company, for prudential reasons, do not wish
the details of the internal machinery to be described; nor would it be
an easy task even were the permission granted. So we must imagine the
extreme intricacy of the levers and wheels which perform all the tasks
enumerated, and turn aside to consider the origin and manufacture of
the register, which are both of interest.
The origin of the cash register is rather nebulous, because twenty-five
years ago several men were working on the same idea. It first appeared
as a practical machine in the offices of John and James Ritty, who
owned stores and coalmines at Dayton, Ohio. James Ritty helped and
largely paid for the first experiments. He needed a mechanical cashier
for his own business, and says that, while on an ocean steamer _en
route_ to London the revolving machinery gave him the suggestion worked
out, on his return to Dayton, in the first dial-machine. This gave way
to the key-machine with its display tablet, or indicator, held up by a
supporting bar moved back by knuckles on the vertical tablet rod.
[Illustration: FIG. 1]
The cut (Fig. 1) shows the right side of this key register, the action
of which is thus described by the National Cash Register Company. The
key A, when pressed with the finger at its ordinary position--marked
1--went down to the point marked 2. Being a lever and pivoted to its
centre, pressing down a key elevated its extreme point B. This pushed
up the tablet-rod C, having on its upper part the knuckle D. This
knuckle D, pushed up, took the position at E; that is, the knuckle
pushed back the supporting-bar F, and was pushed past it and held above
it. If the same operation were performed on another key, the knuckle
on its vertical rod, going up, would again push the supporting bar
back, which would release the first knuckled rod, and leave the last
one in its place. This knuckled rod had on its upper end the display
tablet, or indicator G. James and John Ritty claimed and proved that
they invented this, but the attorney for the Dayton Company (formed by
them) in the Supreme Court was compelled to admit that this mechanism
was old. Yet if machines built like this were exhibited elsewhere, they
were at most only experimental models, and none of them had ever gone
into practical or commercial use. In fact, at this time nothing had
been really contributed which was useful to the public or used by the
public.
The trouble was that the knuckles, being necessarily oiled, held
dust and dirt which interfered with their free movement. And again,
a "five-cent" or "ten-cent" key would be used more than others, and
hence would become more worn. As a practical result the tablets
did not drop when wanted, and the whole operation was thrown into
confusion. When one tablet went up the other tablet stayed up, leaving
a false indication. The most valuable modification now made by these
Dayton inventors was to cease to rely on the knuckle to move back the
supporting bar, and to supply the place of this function by what became
known as "connecting mechanism," especially designed for this purpose.
This was placed at the other, or say the left, side of the machine as
you faced it. Cut No. 2 shows this new connecting mechanism. The keys,
when pressed, performed the functions as before, on the right side of
the machine, viz. to ring an alarm-bell, etc.; but on the other, or
left, side the key, when pressed, operated the connecting mechanism
marked M, N, O, P, and Q. The key pressed down by its leverage pushed
back a little lever (Q), the further end of which pressed back the
supporting bar F, and released the previously exposed indicator G,
without relying on the knuckle to perform this function.
The Supreme Court of the United States said that the suggestion or
idea to correct the old trouble and to drop the display tablet with
certainty, and to accomplish this _by dividing the force used_, and
applying a portion of it to the new connecting mechanism on the left
side of the machine, "was fine invention," and that "the results are so
important, and the ingenuity displayed to bring them about is such that
we are not disposed to deny the patentees the merit of invention. The
combination described in the first claim was clearly new."
To revert for a moment to the origin of the invention. Mr. John Ritty
gives an account differing from that of his brother; but the two can
probably be reconciled by supposing that the first ideas occurred
simultaneously and were worked out in common.
Late one summer night, before dispersing home, a group of men were in
his store. One of them said to the proprietor, "If you had a machine
there to register the cash received, you would get more of it," and
to the statement both owner and his clerks assented. This raised a
laugh. But Ritty who, in spite of a large business, which ranged over
everything from a needle to a haystack, did not make much profit by his
sales, took the suggestion seriously, and put on his thinking-cap, with
the result that the first machine was patented, and profits became very
greatly increased.
[Illustration: FIG. 2]
Before his machine had been perfected a rival was in the field. Mr.
Thomas Carney, a man who had seen much life as a lumber merchant,
captain during the Civil War, explorer, and railroad promoter, settled
down in 1884, at Chicago, to the manufacture of coin-changers. "When
in various businesses," he says, "we used gold and silver only, and it
seemed to be a sheer necessity to have something of a money-changer
to assist us in handling it and making change. The custom then was
to throw the different coins into a special receptacle marked for
each. I invented, and in my own shop built this coin-changer, the keys
of which, when touched, would, through the tube, drop the coin into
the hand as wanted. At Chicago we made five or six hundred of these
coin-changers, but by mistake placed the price too low, and after some
conference I became assured that there was not enough money in it. A
rich Chicago manufacturer had become familiar with the urgent need of
a cash register, and the losses which followed in business without
one. The National, at Dayton, had then been invented, but had not
then been perfected as it has been since. Parties at Chicago agreed
to put up the money if I would invent what would answer the purpose
of a cash register and make a marketable machine. I went home and
gave the matter some hard thinking, and talking with my son about the
matter one night, I looked up at the clock and said, 'Why, Harry,
there is the right thing. Sixty minutes make an hour; one hundred
cents make a dollar. All I have got to do is to change the wheels a
little, put some keys into it, and there will be a thing which will
register cents, dimes, and dollars, just as that clock will register
time in minutes and hours.' In clocks the minute wheel, when it has
revolved to its sixty point, throws its added result of sixty minutes
over on to another wheel, which takes up the story, with one hour in
place of the old sixty minutes. The first wheel then begins again
and goes its round. A second complete revolution of the minute wheel
throws another sixty minutes on to the hour, and gives one more hour
registered, making two hours, and so on. I took some wheels, and with
pasteboard made hands and a machine. It was very rough, but I took it
to my friends and explained it to them. We went on, but encountering
difficulties and obstacles, we merged our whole enterprise in the
National. I followed it, and have since invented, worked, and helped
along in the National Cash Register service. I developed the No. 35
machine which the company began on and uses yet. It is now in use in
every civilised country, for it can be made to register English money
and any decimal currency."
In 1883 Dayton contained five families. The following year Colonel
Robert Patterson bought a large property in the neighbourhood, and
helped to develop a small town, which has since grown into a thriving
manufacturing centre. His two sons, John H. Patterson and Frank J.
Patterson, bought out all the original proprietors of the National Cash
Register, greatly improved the machine's mechanism, and built the
huge factory which employs about 4,000 men, women, and girls, and is
one of the best-equipped establishments in the world to promote both
an economical output and the comfort of the employés. The Company's
buildings at Dayton cover 892,144 square feet of floor-space, and
utilise 140 acres of ground. In convenience and attractiveness, and for
light, heat, and ventilation, and all sanitary things, these structures
are designed to be models of any used for factory purposes. A machine
is made and sold every 2-1/2 minutes in the Dayton, Berlin, and Toronto
factories collectively. According to its destination, it records
dollars, shillings, marks, kronen, korona, francs, kroner, guildens,
pesetas, pesos, milreis, rupees, or roubles. Registers are also made to
meet the needs of the Celestials and the Japanese.
So necessary is it for these machines to be ever improving, that the
Company, with a wisdom that prevails more largely, perhaps, in the
United States than elsewhere, offer substantial rewards to the employé
who records in a book kept specially for the purpose any suggestion
which the committee, after due examination, consider likely to improve
some detail of mechanism or manufacture. Five departments are entirely
devoted to experiments carried out by a corps of inventors working with
a special body of skilled mechanics. New patents accrue so fast as a
result of this organised research that the National Company now owns
537 letters patent in the United States and 394 in foreign countries.
Many ideas come from outside. If they appear profitable they are bought
and turned over to the Patents Department, which hands them on to the
experimenters. These build an experimental model, which differs in many
respects from the types hitherto manufactured. A cash register must
be above all things strong, so that it can bear a heavy blow without
getting out of order, and must retain its accuracy under all conditions.
The model finished, it goes before the inspectors, who thump it,
hammer it, almost turn it inside out, and send it back to the Factory
Committee with reports on any defects that may have come to light. If
the inspectors can only knock the machine out of time they consider
that they have done their duty; for they argue that, if weaknesses thus
developed are put right, no purchaser will ever be able to dislocate
the machinery if he stops short of an actual "brutal assault with
violence."
Next comes the building of the commercial type, which will be sold
by the thousand. The machine goes down to the tool-makers, a select
board of seventy-five members, who list all the parts, and say how
many drill-jigs, mills, fixtures, gauges, etc., are necessary to make
every part. Then they draw out an approximate estimate of the cost
of producing the tools, and after they have listed the parts, they
turn them over to the various departments, such as the drafting-room,
blacksmiths' shop, pattern shop, foundry, etc., after which the
various parts are machined up. Then the tool-maker assembles together
the various tools, and makes a number of the parts that each tool is
designed for; so that when all the tools have done their preliminary
work, the makers possess about fifty machines "in bits." These are
assembled, to prove whether the tools do their business efficiently. If
any part shows an inclination "to jam," or otherwise misbehave itself,
the tool responsible is altered till its products are satisfactory.
Then, and only then--a period of perhaps two years may have elapsed
since the model was first put in hand--the Company begins to
entertain a prospect of getting back some of the money--any sum up
to £50,000--spent in preparations. But they know that if people will
only buy, they won't have much fault to find with their purchase.
"Preparations brings success" is the motto of the N.C.R. So the Company
spares no money, and is content to have £25,000 locked up in its
automatic screw-making machines alone!
Human as well as inanimate machinery is well tended under the roof of
the N.C.R. The committee believe that a healthy, comfortable employé
means good--and therefore profitable--work; and that to work well,
employés must eat and play well.
They therefore provide their boys with gardens, 10 feet wide by 170
feet in length; and pay an experienced gardener to direct their
efforts. To encourage a start, bulbs, seeds, slips, etc., are supplied
free; while prizes of considerable value help to stimulate competition.
One day, ten years or more ago, Mr. Patterson saw a factory girl
trying to warm her tin bucket of cold coffee at the steam heater in
the workshop. He is a humane man, and acting on the unintentional hint
he built a lunch-room which contains, besides accommodation for 455
people, a piano and sewing-machine which the women can use during their
noon recess of eighty minutes. A cooking school, dancing classes, and
literary club are all available to members. The Company encourages its
workers to own the houses they inhabit, and to make them as beautiful
as their leisure will permit. Mr. Mosely, who took over to America an
Industrial Commission of Experts in 1902, and an Educational Commission
in the following year, paid visits on both occasions to the National
Cash Register Works. In a speech to the Committee he said: "I do not
know of any institution in the world which offers so beautiful an
illustration of the proper working conditions as the National Cash
Register Company. Your President has asked me to criticise. I cannot
find anything to criticise in this factory. I have never seen such
conditions in any other factory in the world, nor have I ever seen so
many bright and intelligent faces as we have seen at luncheon in both
the men's and women's dining rooms. I believe this factory is as nearly
perfect as social conditions will permit."
NOTE.--The author desires to express his thanks to the National Cash
Register Company for the kind help given him in the shape of materials
for writing and illustrating this chapter.
[Illustration:
_By permission of The Sphere._
The jacket of a 12-inch gun being turned in a monster lathe at Messrs.
Vickers Maxim's works. Notice the long spiral strip coming off the edge
of the cutting tool.]
FOOTNOTE:
[4] _Industrial Biographies_, chap. xiii.
CHAPTER III
WORKSHOP MACHINERY
THE LATHE--PLANING MACHINES--THE STEAM HAMMER--HYDRAULIC
TOOLS--ELECTRICAL TOOLS IN THE SHIPYARD
"When I first entered this city," said Mr. William Fairbairn, in an
inaugural address to the British Association at Manchester in 1861,
"the whole of the machinery was executed by hand. There were neither
planing, slotting, nor shaping machines, and with the exception of
very imperfect lathes and a few drills, the preparatory operations of
construction were effected entirely by the hands of the workmen. Now,
everything is done by machine tools, with a degree of accuracy which
the unaided hand could never accomplish. The automaton, or self-acting,
machine tool has within itself an almost creative power; in fact, so
great are its powers of adaptation, that there is no operation of the
human hand that it does not imitate."
If such things could be said with justice forty-five years ago, what
would Mr. Fairbairn think could he see the wonderful machinery with
which the present-day workshop is equipped--machinery as relatively
superior to the devices he speaks of as they were superior to the
unaided efforts of the human hand? Invention never stands still.
The wonder of one year is on the scrap-heap of abandoned machines
almost before another twelve months have passed. Some important detail
has been improved, to secure ease or economy in working, and a more
efficient successor steps into its place. In his curious and original
_Erewhon_, Mr. Samuel Butler depicts a community which, from the fear
that machinery should become _too_ ingenious, and eventually drain away
man's capacity for muscular and mental action, has risen in revolt
against the automaton, broken up all machines which had been in use for
less than 270 years--with the exception of specimens reserved for the
national museums--and reverted to hand labour. His treatment of the
dangers attending the increased employment of lifeless mechanisms as a
substitute for physical effort does not, however, show sympathy with
the Erewhonians; since their abandonment of invention had obviously
placed them at the mercy of any other race retaining the devices so
laboriously perfected during the ages. And we, on our part, should be
extremely sorry to part with the inanimate helpers which in every path
of life render the act of living more comfortable and less toilsome.
So dependent are we on machinery, that we owe a double debt to the
machines which create machines. A big factory houses the parents
which send out their children to careers of usefulness throughout the
world. We often forget, in our admiration of the offspring, the source
from which they originated. Our bicycles, so admirably adapted to
easy locomotion, owe their existence to a hundred delicate machines.
The express engine, hurrying forward over the iron way, is but an
assemblage of parts which have been beaten, cut, twisted, planed,
and otherwise handled by mighty machines, each as wonderful as the
locomotive itself. But then, we don't see these.
This and following chapters will therefore be devoted to a few peeps at
the great tools employed in the world's workshops.
If you consider a moment, you will soon build up a formidable
list of objects in which circularity is a necessary or desirable
feature--wheels, shafts, plates, legs of tables, walking-sticks,
pillars, parts of instruments, wire, and so on. The Hindu turner, whose
assistant revolves with a string a wooden block centred between two
short spiked posts let into the ground, while he himself applies the
tool, is at one end of the scale of lathe users; at the other, we have
the workman who tends the giant machine slowly shaping the exterior of
a 12-inch gun, a propeller shaft, or a marble column. All aim at the
same object--perfect rotundity of surface.
The artisans of the Middle Ages have left us, in beautiful balusters
and cathedral screens, ample proofs that they were skilled workmen
with the TURNING-LATHE. At the time of the Huguenot persecutions large
numbers of French artificers crossed the Channel to England, bringing
with them lathes which could cut intricate figures by means of wheels,
eccentrics and other devices of a comparatively complicated kind. The
French had undoubtedly got far ahead of the English in this branch
of the mechanical arts, owing, no doubt, to the fact that the French
_noblesse_ had condescended to include turnery among their aristocratic
hobbies.
With the larger employment of metal in all industries the need for
handling it easily is increased. Much greater accuracy generally
distinguishes metal as compared with woodwork. "In turning a piece of
work on the old-fashioned lathe, the workman applied and guided his
tool by means of muscular strength. The work was made to revolve, and
the turner, holding the cutting tool firmly upon the long, straight,
guiding edge of the rest, along which he carried it, and pressing
its point firmly against the article to be turned, was thus enabled
to reduce its surface to the required size and shape. Some dexterous
turners were able, with practice and carefulness, to execute very
clever pieces of work by this simple means. But when the article to be
turned was of considerable size, and especially when it was of metal,
the expenditure of muscular strength was so great that the workman soon
became exhausted. The slightest variation in the pressure of the tool
led to an irregularity of surface; and with the utmost care on the
workman's part, he could not avoid occasionally cutting a little too
deep, in consequence of which he must necessarily go over the surface
again to reduce the whole to the level of that accidentally cut too
deep, and thus possibly the job would be altogether spoiled by the
diameter of the article under operation being made too small for its
intended purpose."[5]
Any modern worker is spared this labour and worry by the device known
as the SLIDE-REST. Its name implies that it at once affords a rigid
support for the tool, and also the means of traversing the tool in a
straight line parallel to the metal face on which work is being done.
The introduction of the slide-rest is due to the ingenuity of Mr.
Henry Maudslay, who, at the commencement of the nineteenth century, was
a foreman in the workshop of Mr. Joseph Bramah, inventor of the famous
hydraulic press and locks which bear his name. His rest could be moved
along the bed of the lathe by a screw, and clamped in any position
desired. Fellow-workmen at first spoke derisively of "Maudslay's
go-cart"; but men competent to judge its real value had more kindly
words to say concerning it, when it had been adapted to machines of
various types for planing as well as turning. Mr. James Nasmyth went so
far as to state that "its influence in improving and extending the use
of machinery has been as great as that produced by the improvement of
the steam-engine in respect to perfecting manufactures and extending
commerce, inasmuch as without the aid of the vast accession to our
power of producing perfect mechanism which it at once supplied, we
could never have worked out into practical and profitable forms the
conceptions of those master minds who, during the last half century,
have so successfully pioneered the way for mankind. The steam-engine
itself, which supplies us with such unbounded power, owes its present
perfection to this most admirable means of giving to metallic objects
the most precise and perfect geometrical forms. How could we, for
instance, have good steam-engines if we had not the means of boring out
a true cylinder, or turning a true piston-rod, or planing a valve face?
It is this alone which has furnished us with the means of carrying
into practice the accumulated results of scientific investigation on
mechanical subjects."
The screw-cutting lathe is so arranged that the slide-rest is moved
along with its tool at a uniform speed by gear wheels actuated by the
mechanism rotating the object to be turned. By changing the wheels the
rate of "feed" may be varied, so that at every revolution the tool
travels from 1/64 of an inch upwards along the surface of its work.
This regularity of action adds greatly to the value of the slide-rest;
and the screw device also enables the workman to chase a thread of
absolutely constant "pitch" on a metal bar; so that a screw-cutting
lathe is not only a shaping machine but also the equivalent of a whole
armoury of stocks and dies.
Some lathes have rests which carry several tools held at different
distances from its axis, the cuts following one another deeper and
deeper into the metal in a manner exactly similar to the harvesting
of a field of corn by a succession of reaping machines. The recent
improvements in tool-steel render it possible to get a much deeper cut
than formerly, without fear of injury to the tool from overheating.
This results in a huge saving of time.
For the boring of large cylinders an upright lathe is generally used,
as the weight of the metal might cause a dangerous "sag" were the
cylinder attached horizontally by one end to a facing-plate. Huge
wheels can also be turned in this type of machine up to 20 feet or
more in diameter; and where the cross-bar carrying the tools is fitted
with several tool-boxes, two or more operations may be conducted
simultaneously, such as the turning of the flange, the boring of the
axle hole, and the facing of the rim sides.
[Illustration: A Gun Lathe. 154 feet long between centres, for boring
and turning guns which, with their mountings, weigh 165 tons when
complete. The makers are the Niles-Bement-Pond Co. of New York.]
Perhaps the most imposing of all lathes are those which handle large
cannon and propeller shafts, such as may be seen in the works of Sir
W. G. Armstrong, Whitworth, and Company; of Messrs. Vickers, Sons and
Maxim; and of other armament and shipbuilding firms. The Midvale Steel
Company have in their shops at Hamilton, Ohio, a monster boring lathe
which will take in a shaft 60 feet long, 30 inches in diameter, and
bore a hole from one end to the other 14 inches in diameter. To do
this, the lathe must attack the shaft at both ends simultaneously, as a
single boring bar of 60 feet would not be stiff enough to keep the hole
cylindrical. The shaft is placed in a revolving chuck in the central
portion of the lathe--which has a total length of over 170 feet--and
supported further by two revolving ring rests on each side towards the
extremities. With work so heavy, the feeding up of the tool to its
surface cannot be done conveniently by hand control, and the boring
bars are therefore advanced by hydraulic pressure, a very ingenious
arrangement ensuring that the pressure shall never become excessive.
Perhaps the type of lathe most interesting to the layman is the
_turret_ lathe, generally used for the manufacture of articles turned
out in great numbers. The headstock--_i.e._ the revolving part which
grips the object to be turned--is hollow, so that a rod may be passed
right through it into the vicinity of the tools, which are held in a
hexagon "turret," one tool projecting from each of its sides. When one
tool has been finished with, the workman does not have the trouble
of taking it out of the rest and putting another in its place; he
merely turns the turret round, and brings another instrument opposite
the work. If the object--say a water-cock--requires five operations
performing on it in the lathe, the corresponding tools are arranged in
their proper order round the turret. Stops are arranged so that as soon
as any tool has advanced as far as is necessary a trip-action checks
the motion of the turret, which is pulled back and given a turn to make
it ready for the next attack.
One of the advantages of the turret lathe, particularly of the
automatic form which shifts round the tool-box without human
intervention, is its power of relieving the operator of the purely
mechanical part of his work. Those who are familiar with the inside of
some of our large workshops will have noticed men and boys who make the
same thing all day and every day, and are themselves not far removed
from machines. The articles they make are generally small and very
rapidly produced, and the endless repetition of the same movements
on the part of the operator is very tedious to watch, and must be
infinitely more so to perform. Such an occupation is not elevating,
and those engaged in it cannot take much interest in their work, or
become fitted for a better position. When this work is done by an
automatic lathe the machine performs the necessary operations, and the
man supplies the intelligence, and, by exercising his thinking powers,
becomes more valuable to his employers and himself. The introduction
of new machines and methods generally has a stimulating effect on the
whole shop, whatever the Erewhonians might say. The hubs and spindles
of bicycles are cut from the solid bar by these automata; the tender
has merely to feed them with metal, and they go on smoothing, shaping,
and cutting off until the material is all used up. The existence of
such lathes largely accounts for the low price of our useful metal
steeds at the present time.
A great amount of shaping is now done by milling cutters in preference
to firmly-fixed edged tools. The cutter is a rod or disc which has its
sides, end, or circumference serrated with deep teeth, shaped to the
section of the cut needed. Revolving at a tremendous speed, it quickly
bites its way into anything it meets just so far as a stop allows it to
go.
One of the most ingenious machines to which the milling tool has been
fitted is the well-known Blanchard lathe, which copies, generally in
wood, repetitive work, such as the stocks for guns and rifles. The
lathe has two sets of centres--one for the copy, the other for the
model--parallel on the same bed, and turned at equal speeds and in
the same direction by a train of gear wheels. The milling cutter is
attached to a frame, from which a disc projects, and is pressed by a
spring against the model. As the latter revolves, its irregular shape
causes the disc, frame, and cutter to move towards or away from its
centre, and therefore towards or away from the centre of the copy,
which has all superfluities whisked off by the cutter. The frame is
gradually moved along the model, reproducing in the rough block a
section similar to the part of the model which it has reached.
The self-centring chuck is an accessory which has proved invaluable
for saving time. It may most easily be described as a circular plate
which screws on to the inner end of the mandrel (the spindle imparting
motion to the object being machined) and has in its face three slots
radiating from the centre at angles of 120°. In each slot slides a
stepped jaw, the under side of which is scored with concentric grooves
engaging with a helical scroll turned by a key and worm gear acting
on its circumference. The jaws approach or recede from the centre
symmetrically, so that if a circular object is gripped, its centre will
be in line with the axis of the lathe. Whether for gripping a tiny
drill or a large wheel, the self-centring chuck is indispensable.
PLANING-MACHINES
Not less important in engineering than the truly curved surface is the
true plane, in which, as Euclid would say, any two points being taken,
the straight line between them lies wholly in that superficies. The
lathe depends for its efficiency on the perfect flatness of all areas
which should be flat--the guides, the surface plates, the bottom and
sides of the headstock, and, above all, of the slide rest. For making
plane metal superficies, a machine must first be constructed which
itself is above suspicion; but when once built it creates machines like
itself, capable of reproducing others _ad infinitum_.
Many amateur carpenters pride themselves on the beautiful smoothness of
the boards over which they have run their jack planes. Yet, as compared
with the bed of a lathe, their best work will appear very inaccurate.
The engineer's planing-machine in no way resembles its wooden relative.
In the place of a blade projecting just a little way through a surface
which prevents it from cutting too deep into the substance over which
it is moving, we have a steel chisel very similar to the cutting tools
of a lathe attached to a frame passing up and down over a bed to which
the member holding the chisel is perfectly parallel. The article to
be planed is rigidly attached to the bed and travels with it. Between
every two strokes the tool is automatically moved sideways, so that no
two cuts shall be in the same line. After the whole surface has been
"roughed," a finishing cutter is brought in action, and the process is
repeated with the business edge of the tool rather nearer to the bed.
Joseph Clement, a contemporary of Babbage, Maudslay, and Nasmyth,
is usually regarded as the inventor of the planing-machine. By 1825
he had finished a planer, in which the tool was stationary and the
work moving under it on a rolling bed. Two cutters were attached to
the overhead cross rail, so that travel in either direction might be
utilised. The bed of the machine, on which the work was laid, passed
under the cutters on perfectly true rollers or wheels, lodged and held
in their bearings as accurately as the best mandrel could be, and
having set screws acting against their ends, totally preventing all
end-motion. The machine was bedded on a massive and solid foundation
of masonry in heavy blocks, the support at all points being so
complete as effectually to destroy all tendency to vibration, with
the object of securing full, round, and quiet cuts. The rollers on
which the planing-machine travelled were so true, that Clement himself
used to say of them, "If you were to put a paper shaving under one
of the rollers it would at once stop the rest." Nor was this an
exaggeration--the entire mechanism, notwithstanding its great size,
being as true and accurate as a watch.[6] Mr. Clement next made a
revolving attachment for the bed, in which bodies could be revolved
under the cutter, on an axis parallel to the direction of travel.
According to the wish of the operator, the object was converted into
a cylinder, cone, or prism by its movements under the planing-tool.
So efficient was the machine that it earned its maker upwards of ten
pounds a day, at the rate of about eighteen shillings a square foot,
until rivals appeared in the field and finally reduced the cost of
planing to a few pence for the same area.
There are two main patterns of planes now in general use. The first
follows the original design of Clement; the second has a fixed bed
but a moving tool. Where the work is very heavy, as in the case of
armour-plates for battleships, the power required to suddenly reverse
the motion of a vast mass of metal is enormous, many times greater
than the energy expended on the actual planing. For this reason the
moving-bed machines have had to be greatly improved; and in some cases
replaced by fixed-bed planers.
It is an impressive sight to watch one of these huge mechanisms
reducing a rough plate, weighing twenty tons or more, to a smoothness
which would shame the best billiard table. The machine, which towers
thirty feet into the air and completely dwarfs the attendant, who has
it as thoroughly under control as if it were a small file, bites great
shining strips forty feet long, maybe, off the surface of the passive
metal, and leaves a series of grooves as truly parallel as the art of
man can make them. There is no fuss, no sticking, no stop, no noise;
the force of electricity or steam, transmitted through wonderfully
cut and arranged gear-wheels, is irresistible. The tool, so hard that
a journey through many miles of steel has no appreciable effect on its
edge, shears its way remorselessly over the surface which presently may
be tempered to a toughness resembling its own. If you want to resharpen
the tool, it will be no good to attack it with any known metal. But
somewhere in the works there is a machine whose buzzing emery-wheels
are more than a match for it, and rapidly grind the blunted edge into
its former shape, so that it is ready to flay another plate, one skin
at a time.
Planing-machines are of many shapes. Some have an upright on each side
of the bed limiting the width of the work they can take; others are
open-sided, one support of extra strength replacing the two, enabling
the introduction of a plate twice as broad as the bed. Others, again,
are built on the verge of a pit, so that they may cut the edges of an
up-ended plate, and make it fit against its fellows so truly that you
could not slip a sheet of paper edgeways between them. Thus has man,
so frail and delicate in himself, shaped metal till it can torture
its kind to suit his will, which he makes known to it by opening this
valve or pulling on that lever. Not only does he flay it, but pierces
it through and through; twists it into all manner of shapes; hacks
masses off as easily as he would cut slices from a loaf; squeezes it in
terrible presses to a fraction of its original thickness; and otherwise
so treats it that we are glad that our scientific observations have as
yet discovered no sentience in the substances reduced to our service.
THE STEAM HAMMER
The Scandinavian god Thor was a marvellous blacksmith. Thursday
should remind us weekly of Odin's son, from whose hammer flashed the
lightning; and, through him, of Vulcan, toiling at his smithy in the
crater of Vesuvius. In spite of the pictures drawn for us by pagan
mythologists of their god-smiths, we are left with the doubt whether
these beings, if materialised, might not themselves be somewhat alarmed
by the steam hammer which mere mortals wield so easily.
The forge is without dispute the "show-place" of a big factory, where
huge blocks of metal feel the heavy hand of steam. As children we
watched the blacksmith at his anvil, attracted and yet half-terrified
by the spark-showers flying from a white-hot horseshoe. And even
the adult, long used to startling sights, might well be fascinated
and dismayed by the terrific blows dealt on glowing ingots by the
mechanical sledge.
[Illustration: A steam hammer at work in Woolwich Arsenal, forging
a steel ingot for the inner tube of a big gun. It delivers a blow
equivalent to the momentum of a falling mass weighing 4000 tons. As
speech is inaudible, the foreman gives hand signals to direct his men,
who wear large canvas fingerless gloves to protect their hands from the
intense heat.]
James Nasmyth, the inventor of this useful machine, was the son of a
landscape painter, who from his earliest youth had taken great interest
in scientific and mechanical subjects of all kinds. At fifteen he made
a steam-engine to grind his father's paints, and five years later a
steam carriage "that ran many a mile with eight persons on it. After
keeping it in action two months," he says in an account of his early
life, "to the satisfaction of all who were interested in it, my friends
allowed me to dispose of it, and I sold it--a great bargain--after
which the engine was used in driving a small factory. I may mention
that in that engine I employed the waste steam to cause an increased
draught by its discharge up the chimney. This important use of waste
steam had been introduced by George Stephenson some years before,
though entirely unknown to me."
This interesting peep at the infancy of the motor carriage reveals
mechanical capabilities of no mean order in young James. He soon
entered the service of Mr. Joshua Field, Henry Maudslay's partner, and
in 1834 set up a business on his own account at Manchester.
At this date the nearest approach to the modern steam hammer was the
"tilt" hammer, operated by horse-, water-, or steam-power. It resembled
an ordinary hand hammer on a very large scale, but as it could be
raised only a small distance above its anvil, it became less effective
as the size of the work increased, owing to the fall being "gagged."
In 1837 Mr. Nasmyth interviewed the directors of the Great Western
Steamship Company with regard to the manufacture of some unusually
powerful tools which they needed for forging the paddle-shaft of the
_Great Britain_. As the invention of the steam-engine had demanded the
improvement of turning methods, so now the increase in the size of
steamboats showed the insufficiency of forging machinery.
Mr. Nasmyth put on his thinking-cap. Evidently the thing needed was a
method for raising a very heavy mass of metal easily to a good height,
so that its great weight might fall with crushing force on the object
between it and the anvil. How to raise it? Brilliant idea! Steam! In a
moment Nasmyth had mentally pictured an inverted steam cylinder rested
on a solid upright overhanging the anvil and a block of iron attached
to its piston-rod. All that would then be necessary was to admit steam
to the under side of the piston until the block had risen to its full
height, and to suddenly open a valve which would cut off the steam
supply and allow the vapour already in the cylinder to escape.
By the next post he sent a sketch to the company, who approved his
design heartily, but were unable to use it, since the need for the
paddle-shaft had already been nullified by the substitution of a screw
as the motive power of their ship. Poor Nasmyth knew that he had
discovered a "good thing," but British forge-masters, with a want of
originality that amounted to sheer blind stupidity, refused to look
at the innovation. "We have not orders enough to keep in work the
forge-hammers we have," they wrote, "and we don't want any new ones,
however improved they may be."
His invention, therefore, appeared doomed to failure. Help, however,
came from France in the person of Mr. Schneider, founder of the famous
Creusot Iron Works, notorious afterwards as the birthplace of the Boer
"Long Toms." Mr. Nasmyth happened to be away when Mr. Schneider and a
friend called at the Manchester works, but his partner, Mr. Gaskell,
showed the French visitors round the works, and also told them of
the proposed steam hammer. The designs were brought out, so that its
details might be clearly explained.
Years afterwards Nasmyth returned the visit, and saw in the Creusot
Works a crank-shaft so large that he asked how it had been forged. "By
means of your steam hammer," came the reply. You may imagine Nasmyth's
surprise on finding the very machine at work in France which his own
countrymen had so despised, and his delight over its obvious success.
On returning home he at once raised money enough to secure a patent,
protected his invention, and began to manufacture what has been
described as "one of the most perfect of artificial machines and
noblest triumphs of mind over matter that modern English engineers
have developed." A few weeks saw the first--a 30-cwt.--hammer at work.
People flocked to watch its precision, its beauty of action, and the
completeness of control which could arrest it at any point of its
descent so instantaneously as to crack without smashing a nut laid
on the anvil. "Its advantages were so obvious that its adoption soon
became general, and in the course of a few years Nasmyth steam hammers
were to be found in every well-appointed workshop both at home and
abroad."[7]
Nasmyth's invention was improved upon in 1853 by Mr. Robert Wilson, his
partner and successor. He added an automatic arrangement which raised
the "tup," or head, automatically from the metal it struck, so that
time was saved and loss of heat to the ingot was also avoided. The
beauty of the "balance valve," as it was called, will be more clearly
understood if we remember that the travel of the hammer is constantly
increasing as the piece on the anvil becomes thinner under successive
blows. Under the influence of this very ingenious valve every variety
of blow could be dealt. By simply altering the position of a tappet
lever by means of two screws, a blow of the exact force required could
be repeated an indefinite number of times. "It became a favourite
amusement to place a wine-glass containing an egg upon the anvil, and
let the block descend upon it with its quick motion; and so nice was
its adjustment, and so delicate its mechanism, that the great block,
weighing perhaps several tons, could be heard playing tap, tap upon the
egg without even cracking the shell, when, at a signal given to the man
in charge, down would come the great mass, and the egg and glass would
be apparently, as Walter Savage Landor has it, 'blasted into space.'"[8]
Later on Mr. Wilson added an equally important feature in the shape of
a double-action hand-gear, which caused the steam to act on the top as
well as the bottom of the piston, thus more than doubling the effect of
the hammer.
The largest hammer ever made was that erected by the Bethlehem Iron
Company of Pennsylvania. The "tup" weighed 125 tons. After being in use
for three years the owners consigned it to the scrap-heap, as inferior
to the hydraulic press for the manufacture of armour-plate, though it
had cost them £50,000. They then erected in its stead, for an equal sum
of money, a 14,000-ton pressure hydraulic press, which fitly succeeds
it as the most powerful of its kind in the world.
The change was made for three reasons. First, that the impact of so
huge a block of metal necessitates the anvil being many times as heavy,
and even then the shock to surrounding machinery may be very severe.
Secondly, the larger the forging to be hammered, the less is the
reaction of the anvil, so that all the force of the blow tends to be
absorbed by the side facing the hammer; whereas with a small bar the
anvil's inertia would have almost as much effect as the actual blow.
Thirdly, the blow of the hammer is so instantaneous that the metal has
not time to "flow" properly, and this leads to imperfect forgings, the
surface of which may have been cracked. For very large work, therefore,
the hammer is going out of fashion and the press coming in, though for
lighter jobs it is still widely used.
Before leaving the subject we may glance at the double-headed
horizontal hammer, such as is to be found in the forge-shop of the
Horwich Railway Works. Two hammers, carried on rails and rollers,
advance in unison from each side and pound work laid on a support
between them. Each acts as anvil to the other, while doing its full
share of the work. So that not only is a great deal of weight saved,
but shocks are almost entirely absorbed; while the fact that each
hammer need make a blow of only half the length of what would be
required from a single hammer, enables twice as many blows to be
delivered in a given time.
HYDRAULIC TOOLS
Before discussing these in detail we shall do well to trace the history
of the Bramah press, which may be said to be their parent, since the
principle employed in most hydraulic devices for the workshop, as
also the idea of using water as a means of transmitting power under
pressure, are justly attributed to Joseph Bramah.
If you take a dive into the sea and fall flat on the surface instead
of entering at the graceful angle you intended, you will feel for some
time afterwards as if an enemy had slapped you violently on the chest
and stomach. You have learnt by sad experience that water, which seems
to offer so little resistance to a body drawn slowly through it, is
remarkably hard if struck violently. In fact, if enclosed, it becomes
more incompressible than steel, without in any way losing its fluidity.
We possess in water, therefore, a very useful agent for transmitting
energy from one point to another. Shove one end of a column of water,
and it gives a push to anything at its other end; but then it must be
enclosed in a tube to guide its operation.
By a natural law all fluids press evenly on every unit of a surface
that confines them. You may put sand into a bucket with a bottom of
cardboard and beat hard upon the surface of the sand without knocking
out the bottom. The friction between the sand particles and the
bucket's sides entirely absorbs the blow. But if water were substituted
for sand and struck with an object that just fitted the bucket so as
to prevent the escape of liquid, the bottom, and sides, too, would be
ripped open. The writer of this book once fired a candle out of a gun
at a hermetically sealed tin of water to see what the effect would be.
(Another candle had already been fired through an iron plate 1/4 of an
inch thick.) The impact _slightly_ compressed the water in the tin,
which gave back all the energy in a recoil which split the sheet metal
open and flung portions of it many feet into the air. But the candle
never got through the side.
This affords a very good idea of the almost absolute incompressibility
of a liquid.
We may now return to history. Joseph Bramah was born in 1748 at
Barnsley, in Yorkshire. As the son of a farm labourer his lot in life
would probably have been to follow the plough had not an accident to
his right ankle compelled him to earn his living in some other way. He
therefore turned carpenter and developed such an aptitude for mechanics
that we find him, when forty years old, manufacturing the locks with
which his name is associated, and six years later experimenting with
the hydraulic press. This may be described simply as a large cylinder
in which works a solid piston of a diameter almost equal to that of
the bore, connected to a force pump. Every stroke of the pump drives a
little water into the cylinder, and as the water pressure is the same
throughout, the total stress on the piston end is equal to that on the
pump plunger multiplied by the number of times that the one exceeds the
other in area. Suppose, then, that the plunger is one inch in diameter
and the piston one foot, and that a man drives down the plunger with a
force of 1,000 lbs., then the total pressure on the piston end will be
144 × 1,000 lbs.; but for every inch that the plunger has travelled the
piston moves only 1/144 of an inch, thus illustrating the law that what
is gained in time is lost in power, and _vice versâ_.
The great difficulty encountered by Bramah was the prevention of
leakage between the piston and the cylinder walls. If he packed
it so tightly that no water could pass, then the piston jammed;
if the packing was eased, then the leak recommenced. Bramah tried
all manner of expedients without success. At last his foreman,
Henry Maudslay--already mentioned in connection with the lathe
slide-rest--conceived an idea which showed real genius by reason of
its very simplicity. Why not, he said, let the water itself give
sufficient tightness to the packing, which must be a collar of stout
leather with an inverted U-shaped section? This suggestion saved the
situation. A recess was turned in the neck of the cylinder at the point
formerly occupied by the stuffing-box, and into this the collar was
set, the edges pointing downwards. When water entered under pressure
it forced the edges in different directions, one against the piston,
the other against the wall of the recess, with a degree of tightness
proportioned to the pressure. As soon as the pressure was removed the
collar collapsed, and allowed the piston to pass back into the cylinder
without friction. A similar device, to turn to smaller things for a
moment, is employed in a cycle tyre inflater, a cup-shaped leather
being attached to the rear end of the piston to seal it during the
pressure stroke, though acting as an inlet valve for the suction stroke.
What we owe to Joseph Bramah and Henry Maudslay for their joint
invention--the honour must be divided, like that of designing the
steam hammer between Nasmyth and Wilson--it would indeed be hard to
estimate. Wherever steady but enormous effort is required for lifting
huge girders, houses, ships; for forcing wheels off their axles; for
elevators; for advancing the boring shield of a tunnel; for compressing
hay, wool, cotton, wood, even metal; for riveting, bending, drilling
steel plates--there you will find some modification of the hydraulic
press useful, if not indispensable.
However, as we are now prepared for a consideration of details, we may
return to our workshop, and see what water is doing there. Outside
stands a cylindrical object many feet broad and high, which can move up
and down in vertical guides. If you peep underneath, you notice the
shining steel shaft which supports the entire weight of this tank or
coffer filled with heavy articles--stones, scrap iron, etc. The shaft
is the piston-plunger of a very long cylinder connected by pipes to
pumping engines and hydraulic machines. It and the mass it bears up
serves as a reservoir of energy. If the pumping engines were coupled up
directly to the hydraulic tools, whenever a workman desired to use a
press, drill, or stamp, as the case might be, he would have to send a
signal to the engine-man to start the pumps, and another signal to tell
him when to stop. This would lead to great waste of time, and a danger
of injuring the tackle from over driving. But with an accumulator there
is always a supply of water under pressure at command, for as soon as
the ram is nearly down, the engines are automatically started to pump
it up again. In short, the accumulator is to hydraulic machinery what
their bag is to bagpipes, or the air reservoir to an organ.
In large towns high-pressure water is distributed through special mains
by companies who make a business of supplying factories, engineering
works, and other places where there is need for it, though not
sufficient need to justify the occupiers in laying down special pumping
plant. London can boast five central distributing stations, where
engines of 6,500 h.p. are engaged in keeping nine large accumulators
full to feed 120 miles of pipes varying in diameter from seven inches
downwards. The pressure is 700 lbs. to the square inch. Liverpool
has twenty-three miles of pipes under 850 lbs. pressure; Manchester
seventeen miles under 1,100 lbs. To these may be added Glasgow, Hull,
Birmingham, Geneva, Paris, Berlin, Antwerp, and many other large cities
in both Europe and the United States.
For very special purposes, such as making metal forgings, pressures
up to _twelve tons_ to the square inch may be required. To produce
this "intensifiers" are used, _i.e._ presses worked from the ordinary
hydraulic mains which pump water into a cylinder of larger diameter
connected with the forging press.
The largest English forging press is to be found in the Openshaw
Works of Sir W. G. Armstrong, Whitworth, and Company. Its duty is to
consolidate armour-plate ingots by squeezing, preparatory to their
passing through the rolling mills. It has one huge ram 78 inches in
diameter, into the cylinder of which water is pumped by engines of
4,000 h.p., under a pressure of 6,720 lbs. to the square inch, which
gives a total ram force of 12,000 tons. It has a total height of 33
feet, is 22 feet wide, and 175 feet long, and weighs 1,280 tons. On
each side of the anvil is a trench fitted with platforms and machinery
for moving the ingot across the ingot block. Two 100-ton electric
cranes with hydraulic lifting cylinders serve the press.
[Illustration: A HUGE HYDRAULIC PRESS
The 12,000-ton pressure Whitworth Hydraulic Press, used for
consolidating steel ingots for armour-plating. Water is forced into the
ram cylinder at a pressure of three tons to the square inch. Notice the
man to the left of the press.]
The Bethlehem Works "squeezer" has two rams, each of much smaller
diameter than the Armstrong-Whitworth, but operated by a 10-1/2 tons
pressure to the square inch. It handles ingots of over 120 tons weight
for armour-plating. In 1895 Mr. William Corey, of Pittsburg, took
out a patent for toughening nickel steel plates by subjecting them,
while heated to a temperature of 2,000° F., to great compression,
which elongates them only slightly, though reducing their thickness
considerably. The heating of a large plate takes from ten to twenty
hours; it is then ready to be placed between the jaws of the big press,
which are about a foot wide. The plate is moved forward between the
jaws after each stroke until the entire surface has been treated. At
one stroke a 17-inch plate is reduced to 16 inches, and subsequent
squeezings give it a final thickness of 14 inches. Its length has
meanwhile increased from 16 to 18-1/2 feet, or in that proportion,
while its breadth has remained practically unaltered. A simple sum
shows that metal which originally occupied 32-2/3 cubic inches has now
been compressed into 31 cubic inches. This alteration being effected
without any injury to the surface, a plate very tough inside and very
hard outside is made. The plate is next reheated to 1,350° F., and
allowed to cool very gradually to a low temperature to "anneal" it.
Then once again the furnaces are started to bring it back to 1,350°,
when cold water is squirted all over the surface to give it a proper
temper. If it bends and warps at all during this process, a slight
reheating and a second treatment in the press restores its shape.
The hydraulic press is also used for bending or stamping plates in all
manners of forms. You may see 8-inch steel slabs being quietly squeezed
in a pair of huge dies till they have attained a semicircular shape,
to fit them for the protection of a man-of-war's big-gun turret; or
thinner stuff having its ends turned over to make a flange; or still
slenderer metal stamped into the shape of a complete steel boat, as
easily as the tinsmith stamps tartlet moulds. In another workshop a
pair of massive jaws worked by water power are breaking up iron pigs
into pieces suitable for the melting furnace.
The manufacture of munitions of war also calls for the aid of this
powerful ally. Take the field-gun and its ammunition. "The gun itself
is a steel barrel, hydraulically forged, and afterwards wire-wound; the
carriage is built up of steel plates, flanged and shaped in hydraulic
presses; the wheels have their naves composed of hydraulically flanged
and corrugated steel discs, and even the tyres are forced on cold
by hydraulic tyre-setters, the rams of which are powerful enough to
reduce the diameter of the welded tyre until the latter tightly nips
the wheel. The shells for the gun are punched and drawn by powerful
hydraulic presses, and the copper driving-bands are fixed on the
projectiles in special hydraulic presses. Quick-firing cartridge-cases
are capped, drawn, and headed by an hydraulic press, whose huge mass
always impresses the uninitiated as absurdly out of proportion to the
small size of the finished case, and finally the cordite firing charge
is dependent on hydraulic presses for its density and shape."[9]
The press for placing the "driving-band" on a shell is particularly
interesting. After the shell has been shaped and its exterior turned
smooth and true, a groove is cut round it near the rear end. Into
this groove a band of copper is forced to prevent the leakage of gas
from the firing charge past the shell, and also to bite the rifling
which imparts a rotatory motion to the shell. The press for performing
the operation has six cylinders and rams arranged spoke-wise inside
a massive steel ring; the rams carrying concave heads which, when
the full stroke is made, meet at the centre so as to form a complete
circle. "Pressure is admitted," says Mr. Petch, "to the cylinders by
copper pipes connected up to a circular distributing pipe. The press
takes water from the 700-pounds main for the first 3/8-inch of the
stroke, and for the last 1/8-inch water pressure at 3 tons per square
inch is used. The total pressure on all the rams to band a 6-inch shell
is only 600 tons, but for a 12-inch shell no less than 2,800 tons is
necessary."
ELECTRIC TOOLS IN A SHIPYARD
Of late years electricity has taken a very prominent part in workshop
equipment, on account of the ease with which it can be applied to a
machine, the freedom from belting and overhead gear which it gives, and
its greater economy. In a lathe-shop, where only half the lathes may be
in motion at a time, the shafting and the belts for the total number is
constantly whirling, absorbing uselessly a lot of power. If, however,
a separate motor be fitted to each lathe, the workman can switch it on
and off at his pleasure.
The New York Shipbuilding Company, a very modern enterprise, depends
mainly on electrical power for driving its machinery, in preference to
belting, compressed air, or water. Let us stroll through the various
shops, and note the uses to which the current has been harnessed.
Before entering, our attention is arrested by a huge gantry crane,
borne by two columns which travel on rails. From the cross girder,
or bridge, 88 feet long, hang two lifting magnets, worked by 25 h.p.
motors, which raise the load at the rate of 20 feet per minute. Motors
of equal power move the whole gantry along its rails over the great
piles of steel plates and girders from which it selects victims to feed
the maw of the shops.
The main building is of enormous size, covering with its single roof no
less than eighteen acres! Just imagine four acres of skylights and two
acres of windows, and you may be able to calculate the little glazier's
bill that might result from a bad hailstorm. In this immense chamber
are included the machine, boiler, blacksmith, plate, frame, pipe, and
mould shops, the general storerooms, the building ways, and outfitting
slips. "The material which enters the plate and storage rooms at one
end, does not leave the building until it goes out as a part of the
completed ship for which it was intended, when the vessel is ready to
enter service; there are installed in one main building, and under one
roof, all the material and machinery necessary for the construction of
the largest ship known to commerce, and eight sets of ship-ways, built
upon masonry foundations, covered by roofs of steel and glass, and
spanned by cranes up to 100 tons lifting capacity, are practically as
much a part of the immense main building as the boiler shop or machine
shop."[10]
A huge 100-ton crane of 121-foot span dominates the machine-shop and
ship-ways at a height of 120 feet. It toys with a big engine or boiler,
picking it up when the riveters, caulkers, and fitters have done their
work, and dropping it gently into the bowels of a partly-finished
vessel. A number of smaller cranes run about with their loads. Those
which handle plates are, like the big gantry already referred to,
equipped with powerful electro-magnets which fix like leeches on the
metal, and will not let go their hold until the current is broken by
the pressing of a button somewhere on the bridge. Sometimes several
plates are picked up at once, and then it is pretty to see how the man
in charge drops them in succession, one here, another there, by merely
opening and closing the switch very quickly, so that the plate furthest
from the magnets falls before the magnetism has passed out of the
nearer plates.
Another interesting type is the extension-arm crane, which shoots out
an arm between two pillars, grips something, and pulls it back into the
main aisle, down which it travels without impediment.
On every side are fresh wonders. Here is an immense rolling machine,
fed with plates 27 feet wide, which bends the 1-1/8-inch thick metal
as if it were so much pastry; or turns over the edges neatly at the
command of a 50 h.p. motor. There we have an electric plate-planer
scraping the surface of a sheet half the length of a cricket pitch. As
soon as a stroke is finished the bed reverses automatically, while the
tool turns over to offer its edge to the metal approaching from the
other side. All so quietly, yet irresistibly done!
Now mark these punches as they bite 1-1/4-inch holes through steel
plates over an inch thick, one every two seconds. A man cutting wads
out of cardboard could hardly perform his work so quickly and well.
Almost as horribly resistless is the circular saw which eats its way
quite unconcernedly through bars six inches square, or snips lengths
off steel beams.
What is that strange-looking machine over there? It has three columns
which move on circular rails round a table in the centre. Up and down
each column passes a stage carrying with it a workman and an electric
drill working four spindles. Look! here comes a crane with a boiler
shell, the plates of which have been bolted in position. The crane lets
down its load, end-up, on to the table, and trots off, while the three
workmen move their columns round till the twelve drills are opposite
their work. Then whirr! a dozen twisted steel points, ranged in three
sets of four, one drill above the other, bite into the boiler plates,
opening out holes at mathematically correct intervals all down the
overlapping seam-plates. This job done, the columns move round the
boiler, and their drills pierce it first near the lower edge, then near
the upper. The crane returns, grips the cylinder, and bears it off to
the riveters, who are waiting with their hydraulic presses to squeeze
the rivets into the holes just made, and shape their heads into neat
hemispheres. As it swings through the air the size of the boiler is
dwarfed by its surroundings; but if you had put a rule to it on the
table you would have found that it measured 20 feet in diameter and as
many in length. A few months hence furnaces will rage in its stomach,
and cause it to force tons of steam into the mighty cylinders driving
some majestic vessel across the Atlantic.
We pass giant lathes busy on the propeller shafts, huge boring mills
which slowly smooth the interior of a cylinder, planers which face the
valve slides; and we arrive, eye-weary, at the launching-ways where
an ocean liner is being given her finishing touches. Then we begin
to moralise. That 600-foot floating palace is a concretion of parts,
shaped, punched, cut, planed, bored, fixed by electricity. Where does
man come in? Well, he harnessed the current, he guided it, he said "Do
this," and it did it. Does not that seem to be his fair share of the
work?
FOOTNOTES:
[5] _Industrial Biographies_, Dr. S. Smiles.
[6] _Industrial Biographies._
[7] _Industrial Biographies._
[8] _Chambers's Encyclopædia._
[9] Mr. A. F. Petch in _Cassier's Magazine_.
[10] _Cassier's Magazine._
CHAPTER IV
PORTABLE TOOLS
"If the mountain won't come to Mahomet," says the proverb, "Mahomet
must go to the mountain."
This is as true in the workshop as outside;--Mahomet being the tool,
the mountain the work on which it must be used. With the increase in
size of machinery and engineering material, methods half a century old
do not, in many cases, suffice; especially at a time when commercial
competition has greatly reduced the margin of profits formerly expected
by the manufacturer.
To take the case of a large shaft, which must have a slot cut along it
on one side to accommodate the key-wedge, which holds an eccentric for
moving the steam valves of a cylinder, or a screw-propeller, so that it
cannot slip. The mass weighs, perhaps, twenty tons. One way of doing
the job is to transport the shaft under a drill that will cut a hole at
each end of the slot area, and then to turn it over to the planer for
the intermediate metal to be scraped out. This is a very toilsome and
expensive business, entailing the use of costly machinery which might
be doing more useful work, and the sacrifice of much valuable time.
Inventors have therefore produced portable tools which can perform work
on big bodies just as efficiently as if it had been done by larger
machinery, in a fraction of the time and at a greatly reduced cost. To
quote an example, the cutting of a key-way of the kind just described
by big machines would consume perhaps a whole day, whereas the light,
portable, easily attached miller, now generally used, bites it out in
ninety minutes.
PNEUMATIC TOOLS
The best known of these is the pneumatic hammer. It consists of a
cylinder, inside which moves a solid piston having a stroke of from
half an inch to six inches. Air is supplied through flexible tubing
from a compressing pump worked by steam. The piston beats on a loose
block of metal carried in the end of the tool, which does the actual
striking. The piston suddenly decreases in diameter at about the centre
of its length, leaving a shoulder on which air can work to effect the
withdrawal stroke. By a very simple arrangement of air-ports the piston
is made to act as its own valve. As the plane side of the piston has
a greater area than that into which the piston-rod fits, the striking
movement is much more violent than the return. Under a pressure of
several hundreds of pounds to the square inch a pneumatic hammer
delivers upwards of 7,000 blows per minute; the quick succession of
comparatively gentle taps having the effect of a much smaller number of
heavier blows. For the flat hammer head can be substituted a curved die
for riveting, or a chipping chisel, or a caulking iron, to close the
seams of boilers.
The riveter is peculiarly useful for ship and bridge-building work
where it is impossible to apply an hydraulic tool. A skilled workman
will close the rivet heads as fast as his assistant can place them
in their holes; certainly in less than half the time needed for
swing-hammer closing.
Even more effective proportionately is the pneumatic chipper. The
writer has seen one cut a strip off the edge of a half-inch steel plate
at the rate of several inches a minute. To the uninitiated beholder it
would seem impossible that a tool weighing less than two stone could
thus force its way through solid metal. The speed of the piston is so
high that, though it scales but a few pounds, its momentum is great
enough to advance the chisel a fraction of an inch, and the individual
advances, following one another with inconceivable rapidity, soon total
up into a big cut.
Automatic chisels are very popular with ornamental masons, as they lend
themselves to the sculpturing of elaborate designs in stone and marble.
Their principle, modified to suit work of another character, is seen in
percussive rock drills, such as the Ingersoll Sergeant. In this case
the piston and tool are solid, and the air is let into the cylinder
by means of slide valves operated by tappets which the piston strikes
during its movements. Some types of the rock-drill are controllable
as to the length of their stroke, so that it can be shortened while
the "entry" of the hole is being made and gradually increased as the
hole deepens. For perpendicular boring the drill is mounted on a
heavily weighted tripod, the inertia of which effectively damps all
recoil from the shock of striking; for horizontal work, and sometimes
for vertical, the support is a pillar wedged between the walls of the
tunnel, or shaft. An ingenious detail is the rifled bar which causes
the drill to rotate slightly on its axis between every two strokes,
so that it may not jam. The drills are light enough to be easily
erected and dismantled, and compact, so that they can be used in
restricted and out-of-the way places, while their simplicity entails
little special training on the part of the workman. With pneumatic and
other power-drills the cost of piercing holes for explosive charges is
reduced to less than one-quarter of that of "jumping" with a crowbar
and sledgehammers. With the hand method two men are required, usually
more; one man to hold, guide, and turn the drill; and the other, or
others, to strike the blows with hammers. The machine, striking a
blow far more rapidly than can be done by hand, reduces the number
of operators to one man, and perhaps his helper. So durable is the
metal of these wonderful little mechanisms that the delivery of
360,000 blows daily for months, even though each is given with a force
of perhaps half a ton, fails to wear them out; or at the most only
necessitates the renewal of some minor and cheap part. The debt that
civilisation owes to the substitution of mechanical for hand labour
will be fully understood by anyone who is conversant with the history
of tunnel-driving and mining.
Another application of pneumatics is seen in the device for cutting
off the ends of stay bolts of locomotive boilers. It consists of a
cylinder about fifteen inches in diameter, the piston of which operates
a pair of large nippers capable of shearing half-inch bars. The whole
apparatus weighs but three-quarters of a hundredweight, yet its power
is such that it can trim bolts forty times as fast as a man working
with hammer and cold-chisel, and more thoroughly.
Then there is the machine for breaking the short bolts which hold
together the outer and inner shells of the water-jacket round a
locomotive furnace. A threaded bar, along which travels a nut, has a
hook on its end to catch the bolt. The nut is screwed up to make the
proper adjustment, and a pneumatic cylinder pulls on the hook with a
force of many tons, easily shearing through the bolt.
We must not forget the _pneumatic borer_ for cutting holes in wood
or metal, or enlarging holes already existing. The head of the borer
contains three little cylinders, set at an angle of 120°, to rotate
the drill, the valves opening automatically to admit air at very high
pressures behind the pistons. Any carpenter can imagine the advantage
of a drill which has merely to be forced against its work, the movement
of a small lever by the thumb doing the rest!
Next on the list comes the _pneumatic painter_, which acts on much the
same principle as the scent-spray. Mechanical painting first came to
the fore in 1893, when the huge Chicago Exposition provided many acres
of surfaces which had to be protected from the weather or hidden from
sight. The following description of one of the machines used to replace
hand-work is given in _Cassier's Magazine_: "The paint is atomized and
sprayed on to the work by a stream of compressed air. From a small
air-compressor the air is led, through flexible hose, to a paint-tank,
which is provided with an air-tight cover and clamping screws. The
paint is contained in a pot which can be readily removed and replaced
by another when a different colour is required. This arrangement of
interchangeable tins is also important as facilitating easy cleaning.
The container is furnished with a semi-rotary stirrer, the spindle
passing through a stuffing-box in the cover, and ending in a handle by
which the whole thing complete may be carried about. The compressor is
necessarily fixed or stationary, but the paint-tank, connected to it by
the single air-hose, can be moved close to the work, while the length
of hose from the tank to the nozzle gives the freedom of movement
necessary. Air-pressure is admitted to the tank by a bottom valve, and
forces the paint up an internal pipe and along a hose from the tank
to the spraying nozzle, to which air-pressure is also led by a second
hose. The nozzle is practically an injector of special form. The flow
of paint at the nozzle is controlled by a small plug valve and spring
lever, on which the operator keeps his thumb while working, and which,
on release, closes automatically. When it is required to change from
one colour to another, or to use a different material, such as varnish,
the can, previously in use, is removed, and air, or, if necessary,
paraffin oil, is blown through the length of hose which supplies the
paint until it is completely clean." The writer then mentions as an
instance of the machine's efficiency that it has covered a 30 feet by 8
feet boiler in less than an hour, and that at one large bridge yard a
70 feet by 6 feet girder with all its projecting parts was coated with
boiled oil in two hours--a job which would have occupied a man with
a brush a whole day to execute. Apart from saving time, the machine
produces a surface quite free from brush marks, and easily reaches
surfaces in intricate mouldings which are difficult to get at with a
brush.
The _pneumatic sand-jet_ is used for a variety of purposes: for
cleaning off old paint, or the weathered surface of stonework; for
polishing up castings and forgings after they have been brazed. At the
cycle factory you will find the sand-jet hard at work on the joints
of cycle frames, which must be cleared of all roughness before they
are fit for the enameller. The writer, a few days before penning these
lines, watched a jet removing London grime from the face of a large
hotel. Down a side street stood a steam-engine busily compressing
air, which was led by long pipes to the jet, situated on some lofty
scaffolding. The rapidity with which the flying grains scoured off
smoke deposits attracted the notice of a large crowd, which gazed with
upturned heads at the whitened stones. A peculiarity about the jet
is that it proves much more effective on hard material than on soft,
as the latter, by offering an elastic surface, robs the sand of its
cutting power.
After merely mentioning the _pneumatic rammer_ for forcing sand into
foundry moulds, we pass to the _pneumatic sand-papering_ machine,
which may be described briefly as a revolving disc carrying a circle
of sand-paper on its face revolved between guards which keep it flat
to its work. The disc flies round many hundreds of times per minute,
rapidly wearing down the fibrous surface of the wood it touches.
When the coarse paper has done its work a finely-grained cloth is
substituted to produce the finish needful for painting.
CHAPTER V
THE PEDRAIL: A WALKING STEAM-ENGINE
Have you ever watched carefully a steam-roller's action on the road
when it is working on newly laid stones? If you have, you noticed that
the stones, gravel, etc., in front of the roller moved with a wave-like
motion, so that the engine was practically climbing a never-ending
hill. No wonder then that the mechanism of such a machine needs to be
very strong, and its power multiplied by means of suitable gearing.
Again, suppose that an iron-tyred vehicle, travelling at a rapid pace,
meets a large stone, what happens? Either the stone is forced into the
ground or the wheel must rise over it. In either case there will be a
jar to the vehicle and a loss of propulsive power. Do not all cyclists
know the fatigue of riding over a bumpy road--fatigue to both muscles
and nerves?
As regards motors and cycles the vibration trouble has been largely
reduced by the employment of pneumatic tyres, which _lap over_ small
objects, and when they strike large ones minimise the shock by their
buffer-like nature. Yet there is still a great loss of power, and
if pneumatic-tyred vehicles suffer, what must happen to the solid,
snorting, inelastic traction-engine? On hard roads it rattles and
bumps along, pulverising stones, crushing the surface. When soft ground
is encountered, in sink the wheels, because their bearing surface must
be increased until it is sufficient to carry the engine's weight. But
by the time that they are six inches below the surface there will be a
continuous vertical belt of earth six inches deep to be crushed down
incessantly by their advance.
How much more favourably situated is the railway locomotive or truck.
_Their_ wheels touch metal at a point but a fraction of an inch in
length; consequently there is nothing to hamper their progression. So
great is the difference between the rail and the road that experiment
has shown that, whereas a pull of from 8 to 10 lbs. will move a ton on
rails, an equal weight requires a tractive force of 50 to 100 lbs. on
the ordinary turnpike.
In order to obviate this great wastage of power, various attempts
have been made to provide a road locomotive with means for laying
its own rail track as it proceeds. About forty years ago Mr. Boydell
constructed a wheel which took its own rail with it, the rails being
arranged about the wheel like a hexagon round a circle, so that as the
wheel moved it always rested on one of the hexagon's sides, itself flat
on the ground. This device had two serious drawbacks. In the first
place, the plates made a rattling noise which has been compared to the
reports of a Maxim gun; secondly, though the contrivance acted fairly
well on level ground, it failed when uneven surfaces were encountered.
Thus, if a brick lay across the path, one end of a plate rested on the
brick, the other on the ground behind, and the unsupported centre
had to carry a sudden, severe strain. Furthermore, the plates, being
connected at the angles of the hexagon, could not tilt sideways, with
the result that breakages were frequent.
Of late years another inventor, Mr. J. B. Diplock, has come forward
with an invention which bids fair to revolutionise heavy road traffic.
At present, though it has reached a practical stage and undergone many
tests satisfactorily, it has not been made absolutely perfect, for the
simple reason that no great invention jumps to finality all at once.
Are not engineers still improving the locomotive?
The Pedrail, as it has been named, signifies a rail moving on feet.
Mr. Diplock, observing that a horse has for its weight a tractive
force much in excess of the traction-engine, took a hint from nature,
and conceived the idea of copying the horse's foot action. The reader
must not imagine that here is a return to the abortive and rather
ludicrous attempts at a walking locomotive made many years ago, when
some engineers considered it proper that a railway engine should be
_propelled_ by legs. Mr. Diplock's device not merely propels, but
also steps, _i.e._ selects the spot on the ground which shall be the
momentary point at which propulsive force shall be exerted. To make
this clearer, consider the action of a wheel. First, we will suppose
that the spokes, any number you please, are connected at their outer
ends by flat plates. As each angle is passed the wheel falls flop on to
the next plate. The greater the number of the spokes, the less will be
each successive jar (or step); and consequently the perfect wheel is
theoretically one in which the sides have been so much multiplied as
to be infinitely short.
A horse has practically two wheels, its front legs one, its back legs
the other. The shoulder and hip joints form the axles, and the legs
the spokes. As the animal pulls, the leg on the ground advances at the
shoulder past the vertical position, and the horse would fall forwards
were it not for the other leg which has been advanced simultaneously.
Each step corresponds to our many-sided wheel falling on to a flat
side--and the "hammer, hammer, hammer on the hard high road" is the
horsey counterpart of the metallic rattle.
On rough ground a horse has a great advantage over a wheeled tractor,
because it can put its feet down _on the top_ of objects of different
elevations, and _still pull_. A wheel cannot do this, and, as we have
seen, a loss of power results. Our inventor, therefore, created in his
pedrail a compromise between the railway smoothness and ease of running
and the selective and accommodating powers of a quadruped.
We must now plunge into the mechanical details of the pedrail, which
is, strictly speaking, a term confined to the wheel alone. Our
illustration will aid the reader to follow the working of the various
parts.
In a railway we have (a) sleepers, on the ground, (b) rails
attached to the sleepers, (c) wheels rolling over the rails. In the
pedrail the order, reckoning upwards, is altered. On the ground is the
_ped_, or movable sleeper, carrying wheels, over which a rail attached
to the moving vehicle glides continuously. The _principle_ is used by
anyone who puts wooden rollers down to help him move heavy furniture
about.
Of course, the peds cannot be put on the ground and left behind; they
must accompany their rollers and rails. We will endeavour to explain in
simple words how this is effected.
To the axles of the locomotive is attached firmly a flat, vertical
plate, parallel to the sides of the fire-box. Pivoted to it, top and
bottom, at their centres, are two horizontal rocking arms; and these
have their extremities connected by two bow-shaped bars, or cams, their
convex edges pointing outwards, away from the axle. Powerful springs
also join the rocking arms, and tend to keep them in a horizontal
position. Thus we have a powerful frame, which can oscillate up and
down at either end. The bottom arm is the rail on which the whole
weight of the axle rests.
The rotating and moving parts consist of a large, flat, circular
case, the sides of which are a few inches apart. Its circumference is
pierced by fourteen openings, provided with guides, to accommodate as
many short sliding spokes, which are in no way attached to the main
axle. Each spoke is shaped somewhat like a tuning-fork. In the V is a
roller-wheel, and at the tip is a "ped," or foot. As the case revolves,
the tuning-fork spokes pass, as it were, with a leg on each side of
the framework referred to above; the wheel of each spoke being the
only part which comes into contact with the frame. Strong springs hold
the spokes and rollers normally at an equal distance from the wheel's
centre.
It must now be stated that the object of the framework is to thrust
the rollers outwards as they approach the ground, and slide them below
the rail. The side-pieces of the frame are, as will be noticed (see
Fig. 3), eccentric, _i.e._ points on their surfaces are at different
distances from the axle centre. This is to meet the fact that the
distance from the axle to the ground is greater in an oblique direction
than it is vertically, and therefore for three spokes to be carrying
the weight at once, two of them must be more extended than the third.
So then a spoke is moved outward by the frame till its roller gets
under the rail, and as it passes off it it gradually slides inwards
again.
It will be obvious to the reader that, if the "peds" were attached
inflexibly to the ends of their spokes they would strike the ground at
an angle, and, of course, be badly strained. Now, Mr. Diplock meant
his "peds" to be as like feet as possible, and come down _flat_. He
therefore furnished them with ankles, that is, ball-and-socket joints,
so that they could move loosely on their spokes in all directions;
and as such a contrivance must be protected from dust and dirt, the
inventor produced what has been called a "crustacean joint," on account
of the resemblance it bears to the overlapping armour-plates of a
lobster's tail. The plates, which suggest very thin quoits, are made of
copper, and can be renewed at small cost when badly worn. An elastic
spring collar at the top takes up all wear automatically, and renders
the plates noiseless. This detail cost its inventor much work. The
first joint made represented an expenditure of £6; but now, thanks to
automatic machinery, any number can be turned out at 3s. 6d. each.
A word about the feet. A wheel has fourteen of these. They are eleven
inches in diameter at the tread, and soled with rubber in eight
segments, with strips of wood between the segments to prevent suction
in clay soil. The segments are held together by a malleable cast-iron
ring around the periphery of the feet and a tightening core in the
centre. These wearing parts, being separate from the rest of the foot,
are easily and cheaply renewed, and repairs can be quickly effected,
if necessary, when on the road. The surface in contact with the ground
being composed of the three substances--metal, wood, and rubber, which
all take a bearing, provides a combination of materials adapted to the
best adhesion and wear on any class of road, or even on no road at all.
[Illustration: FIG. 3]
Motive power is transmitted by the machinery to the wheel axle, from
that to the casing, from the casing to the sliding spokes. As there
are alternately two and three feet simultaneously in contact with the
ground, the power of adhesion is very great--much greater than that
of an ordinary traction-engine. This is what Professor Hele-Shaw says
in a report on a pedrail tractor: "The weight of the engine is spread
over no less than twelve feet, each one of which presses upon the
ground with an area immensely greater--probably as much as ten times
greater--than that of all the wheels (of an ordinary traction-engine)
taken together on a hard road. Upon a soft road all comparison between
wheels and the action of these feet ceases. The contact of each of the
feet of the Pedrail is absolutely free from all slipping action, and
attains the absolute ideal of working, being merely placed in position
without sliding to take up the load, and then lifted up again without
any sliding to be carried to a new position on the road."
It is necessary that the feet should come down flat on the ground.
If they struck it at all edgeways they would "sprain their ankles";
otherwise, probably break off at the ball joint. Mechanism was,
therefore, introduced by which the feet would be turned over as they
approached the ground, and be held at the proper angle ready for the
"step." Without the aid of a special diagram it would be difficult to
explain in detail how this is managed; and it must suffice to say that
the chief feature is a friction-clutch worked by the roller of the
foot's spoke.
To the onlooker the manner in which the pedrail crawls over obstacles
is almost weird. The writer was shown a small working model of a
pedrail, propelled along a board covered with bits of cork, wood, etc.
The axle of the wheel scarcely moved upwards at all, and had he not
actually seen the obstacles he would have been inclined to doubt their
existence. An ordinary wheel of equal diameter took the obstructions
with a series of bumps and bounds that made the contrast very striking.
[Illustration: FIG. 4]
An extreme instance of the pedrail's capacity would be afforded by the
ascent of a flight of steps (see Fig. 4). In such a case the three
"peds" carrying the weight of an axle would not be on the same level.
That makes no difference, because the frame merely tilts on its top
and bottom pivots, the front of the rail rising to a higher level than
the back end, and the back spokes being projected by the rail much
further than those in front, so that the engine is simply levered over
its rollers up an inclined plane. Similarly, in descending, the front
spokes are thrust out the furthest, and the reverse action takes place.
With so many moving parts everything must be well lubricated, or the
wear would soon become serious. The feet are kept properly greased
by being filled with a mixture of blacklead and grease of suitable
quality, which requires renewal at long intervals only. The sliding
spokes, rollers, and friction-clutches are all lubricated from one
central oil-chamber, through a beautiful system of oil-tubes, which
provides a circulation of the oil throughout all the moving parts. The
central oil-chamber is filled from one orifice, and holds a sufficient
supply of oil for a long journey.
We may now turn for a moment from the pedrail itself to the vehicles
to which it is attached. Here, again, we are met by novelties, for in
his engines Mr. Diplock has so arranged matters, that not only can
both front and back pairs of wheels be used as drivers, but both also
take part in the steering. As may be imagined, many difficulties had
to be surmounted before this innovation was complete. But that it was
worth while is evident from the small space in which a double-steering
tractor can turn, thanks to both its axles being movable, and from the
increased power. Another important feature must also be noticed, viz.
that the axles can both tip vertically, so that when the front left
wheel is higher than its fellow, the left back wheel may be lower than
the right back wheel. In short, _flexibility_ and power are the ideals
which Mr. Diplock has striven to reach. How far he has been successful
may be gathered from the reports of experts. Professor Hele-Shaw,
F.R.S., says: "The Pedrail constitutes, in my belief, the successful
solution of a walking machine, which, whilst obviating the chief
objections to the ordinary wheel running upon the road, can be made
to travel anywhere where an ordinary wheel can go, and in many places
where it cannot. At the same time it has the mechanical advantages
which have made the railway system such a phenomenal success. It
constitutes, in my belief, the solution of one of the most difficult
mechanical problems, and deserves to be considered as an invention
quite apart from any particular means by which it is actuated, whether
it is placed upon a self-propelled carriage or a vehicle drawn by any
agency, mechanical or otherwise.... The way in which all four wheels
are driven simultaneously so as to give the maximum pulling effect
by means of elastic connection is in itself sufficient to mark the
engine as a most valuable departure from common practice. Hitherto this
driving of four wheels has never been successfully achieved, partly
because of the difficulty of turning the steering-wheels, and partly
because, until the present invention of Mr. Diplock, the front and hind
wheels would act against each other, a defect at first experienced and
overcome by the inventor in his first engine."
[Illustration: A PEDRAIL TRACTOR ENGAGED IN WAR OFFICE TRIALS
The inventor, Mr. J. B. Diplock, is standing on the left of the group.
Observe the manner in which the feet gradually assume a horizontal
position as they approach the ground.]
On January 8th, 1902, Mr. Diplock tried an engine fitted with two
ordinary wheels behind and two pedrails in front. The authority quoted
above was present at the trials, and his opinion will therefore be
interesting. "The points which struck me immediately were (1) the
marvellous ease with which it started into action, (2) the little
noise with which it worked.... Another thing which I noticed was the
difference in the behaviour of the feet and wheels. The feet did not
in any way seem to affect the surface of the road. Throwing down large
stones the size of the fist into their path, the feet simply set
themselves to an angle in passing over the stones, and did not crush
them; whereas, the wheel coming after invariably crushed the stones,
and, moreover, distorted the road surface.
"Coming to the top of the hill, I made the Pedrail walk first over
3-inch planks, then 6-inch, and finally over a 9-inch balk.... One
could scarcely believe, on witnessing these experiments, that the
whole structure was not permanently distorted and strained, whereas
it was evidently within the limits of play allowed by the mechanism.
As a proof of this the Diplock engine walked down to the works, and
I then witnessed its ascent of a lane, beside the engineering works,
which had ruts eight or ten inches deep, and was a steep slope. This
lane was composed in places of the softest mud, and whereas the
wheels squeezed out the ground in all directions, the feet of the
Pedrails set themselves at the angles of the rut where it was hard, or
walked through the soft and yielding mud without making the slightest
disturbance of the surrounding ground.... I came away from that
trial with the firm conviction that I had seen what I believe to be the
dawn of a new era in mechanical transport."
Mr. Diplock does not regard the pedrail as an end in itself so much as
a means to an end, viz. the development of road-borne traffic. For very
long distances which must be covered in a minimum of time the railway
will hold its own. But there is a growing feeling that unless the
railways can be fed by subsidiary methods of transport more effectively
than at present, and unless remote country districts, whither it
would not pay to carry even a light railway, are brought into closer
touch with the busier parts, our communications cannot be considered
satisfactory, and we are not getting the best value out of our roads.
For many classes of goods _cheapness_ of transportation is of more
importance than _speed_; witness the fact that coal is so often sent by
canal rather than by rail.
Here, then, is the chance for the pedrail tractor and its long train
of vehicles fitted with pedrail wheels, which will tend to improve the
road surfaces they travel over. Mr. Diplock sets out in his interesting
book, _A New System of Heavy Goods Transport on Common Roads_, a scheme
for collecting goods from "branch" routes on to "main" routes, where a
number of cars will be coupled up and towed by powerful tractors. With
ordinary four-wheeled trucks it is difficult to take a number round
a sharp corner, since each truck describes a more sudden circle than
its predecessor, the last often endeavouring to climb the pavement.
Four-wheeled would therefore be replaced by two-wheeled trucks,
provided with special couplings to prevent the cars tilting, while
allowing them to turn. Cars so connected would follow the same track
round a curve.
The body of the car would be removable, and of a standard size. It
could be attached to a simple horse frame for transport into the
fields. There the farmer would load his produce, and when the body was
full it would be returned to the road, picked up by a crane attached
to the tractor, swung on to its carriage and wheels, and taken away
to join other cars. By making the bodies of such dimensions as to fit
three into an ordinary railway truck, they could be entrained easily.
On reaching their destination another tractor would lift them out, fit
them to wheels, and trundle them off to the consumer. By this method
there would be no "breaking bulk" of goods required from the time it
was first loaded till it was exposed in the market for sale.
These things are, of course, in the future. Of more present importance
is the fact that the War Office has from the first taken great interest
in the new invention, which promises to be of value for military
transport over ground either rough or boggy. Trials have been made
by the authorities with encouraging results. That daring writer, Mr.
H. G. Wells, has in his _Land Ironclads_ pictured the pedrail taking
an offensive part in warfare. Huge steel-plated forts, mounted on
pedrails, and full of heavy artillery and machine guns, sweep slowly
across the country towards where the enemy has entrenched himself. The
forts are impervious alike to shell and bullet, but as they cross ditch
or hillock in their gigantic stride, their artillery works havoc among
their opponents, who are finally forced to an unconditional surrender.
Even if the pedrail is not made to carry weapons of destruction, we
can, after our experiences with horseflesh in the Boer War, understand
how important it may become for commissariat purposes. The feats which
it has already performed mark it as just the locomotive to tackle the
rough country in which baggage trains often find themselves.
To conclude with a more peaceful use for it. When fresh country is
opened up, years must often pass before a proper high road can be made,
yet there is great need of an organised system of transport. Whither
ordinary traction-engines, or carts, even horses, could scarcely
penetrate, the pedrail tractor, thanks to its big, flat feet, which
give it, as someone has remarked, the appearance of "a cross between a
traction-engine and an elephant," will be able to push its way at the
forefront of advancing civilisation.
At home we shall have good reason to welcome the pedrail if it frees us
from those terrible corrugated tracks so dreaded by the cyclist, and to
bless it if it actually beats our roads down into a greater smoothness
than they now can boast.
CHAPTER VI
INTERNAL COMBUSTION ENGINES
OIL ENGINES--ENGINES WORKED WITH PRODUCER GAS--BLAST FURNACE GAS ENGINES
If carbon and oxygen be made to combine chemically, the process is
accompanied by the phenomenon called _heat_. If heat be applied to a
liquid or gas in a confined space it causes a violent separation of its
molecules, and power is developed.
In the case of a steam-engine the fuel is coal (carbon in a more or
less pure form), the fluid, water. By burning the fuel under a boiler,
a gas is formed which, if confined, rapidly increases the pressure on
the walls of the confining vessel. If allowed to pass into a cylinder,
the molecules of steam, struggling to get as far as possible from
one another, will do useful work on a piston connected by rods to a
revolving crank.
We here see the combustion of fuel external to the cylinder, i.e. under
the boiler, and the fuel and fluid kept apart out of actual contact.
In the gas or oil-vapour engine the fuel is brought into contact with
the fluid which does the work, mixed with it, and burnt _inside_ the
cylinder. Therefore these engines are termed _internal combustion_
engines.
Supposing that a little gunpowder were placed in a cylinder, of which
the piston had been pushed almost as far in as it would go, and that
the powder were fired by electricity. The charcoal would unite with the
oxygen contained in the saltpetre and form a large volume of gas. This
gas, being heated by the ignition, would instantaneously expand and
drive out the piston violently.
A very similar thing happens at each explosion of an internal
combustion engine. Into the cylinder is drawn a charge of gas,
containing carbon, oxygen, and hydrogen, and also a proportion of air.
This charge is squeezed by the inward movement of the piston; its
temperature is raised by the compression, and at the proper moment it
is ignited. The oxygen and carbon seize on one another and burn (or
combine), the heat being increased by the combustion of the hydrogen.
The air atoms are expanded by the heat, and work is done on the piston.
But the explosion is much gentler than in the case of gunpowder.
During recent years the internal combustion engine has been making
rapid progress, ousting steam power from many positions in which it
once reigned supreme. We see it propelling vehicles along roads and
rails, driving boats through the water, and doing duty in generating
stations and smelting works to turn dynamos or drive air-pumps--not
to mention the thousand other forms of usefulness which, were they
enumerated here, would fill several pages.
A decade ago an internal combustion engine of 100 h.p. was a wonder;
to-day single engines are built to develop 3,000 h.p., and in a few
years even this enormous capacity will doubtless be increased.
It is interesting to note that the rival systems--gas and steam--were
being experimented with at the same time by Robert Street and James
Watt respectively. While Watt applied his genius to the useful
development of the power latent in boiling water, Street, in 1794, took
out letters patent for an engine to be worked by the explosions caused
by vaporising spirits of turpentine on a hot metal surface, mixing the
vapour with air in a cylinder, exploding the mixture, and using the
explosion to move a piston. In his, and subsequent designs, the mixture
was pumped in from a separate cylinder under slight pressure. Lenoir,
in 1860, conceived the idea of making the piston _suck_ in the charge,
so abolishing the need of a separate pump; and many engines built under
his patents were long in use, though, if judged by modern standards,
they were very wasteful of fuel. Two years later Alphonse Beau de
Rochas proposed the further improvement of utilising the cylinder, not
only as a suction pump, but also as a compressor; since he saw that a
compressed mixture would ignite very much more readily than one not
under pressure. Rochas held the secret of success in his grasp, but
failed to turn it to practical account. The "Otto cycle," invented by
Dr. Otto in 1876, is really only Rochas's suggestion materialised. The
large majority of internal combustion engines employ this "cycle" of
operations, so we may state its exact meaning:--
(1) A mixture of explosive gas and air is drawn into the cylinder by
the piston as it passes outwards (i.e. in the direction of the crank),
through the inlet valve.
(2) The valve closes, and the returning piston compresses the mixture.
(3) The mixture is fired as the piston commences its second journey
outwards, and gives the "power" stroke.
(4) The piston, returning again, ejects the exploded mixture through
the outlet or exhaust valve, which began to open towards the end of the
third stroke.
Briefly stated, the "cycle" is--suction, compression, explosion,
expulsion; one impulse being given during each cycle, which occupies
two complete revolutions of the fly-wheel. Since the first, second, and
third operations all absorb energy, the wheel must be heavy enough to
store sufficient momentum during the "power" stroke to carry the piston
through all its three other duties.
Year by year, the compression of the mixture has been increased, and
improvements have been made in the methods of governing the speed
of the engine, so that it may be suitable for work in which the
"load" is constantly varying. By doubling, trebling, and quadrupling
the cylinders the drive is rendered more and more steady, and the
elasticity of a steam-engine more nearly approached.
The internal combustion engine has "arrived" so late because in the
earlier part of last century conditions were not favourable to its
development. Illuminating gas had not come into general use, and such
coal gas as was made was expensive. The great oil-fields of America and
Russia had not been discovered. But while the proper fuels for this
type of motor were absent, coal, the food of the steam-engine, lay
ready to hand, and in forms which, though useless for many purposes,
could be advantageously burnt under a boiler.
Now the situation has altered. Gas is abundant; and oil of the right
sort costs only a few pence a gallon. Inventors and manufacturers
have grasped the opportunity. To-day over 3,000,000 h.p. is developed
continuously by the internal combustion engine.
Steam would not have met so formidable a rival had not that rival had
some great advantages to offer. What are these? Well, first enter a
factory driven by steam power, and carefully note what you see. Then
visit a large gas- or oil-engine plant. You will conclude that the
latter scores on many points. There are no stokers required. No boilers
threaten possible explosions. The heat is less. The dust and dirt are
less. The space occupied by the engines is less. There is no noisome
smoke to be led away through tall and expensive chimneys. If work
is stopped for an hour or a day, there are no fires to be banked or
drawn--involving waste in either case.
Above all, the gas engine is more efficient, or, if you like to express
the same thing in other words, more economical. If you use only one
horse-power for one hour a day, it doesn't much matter whether that
horse-power-hour costs 4d. or 5d. But in a factory where a thousand
horse-power is required all day long, the extra pence make a big
total. If, therefore, the proprietor finds that a shilling's-worth of
gas or oil does a quarter as much work again as a shilling's-worth of
coal, and that either form of fuel is easily obtained, you may be sure
that, so far as economy is concerned, he will make up his mind without
difficulty as to the class of engine to be employed. A pound of coal
burnt under the best type of steam-engine gives but 10 per cent. of its
heating value in useful work. A good oil-engine gives 20-25 per cent.,
and in special types the figures are said to rise to 35-40 per cent.
We may notice another point, viz. that, while a steam-engine must be
kept as hot as possible to be efficient, an internal combustion engine
must be cooled. In the former case no advantage, beyond increased
efficiency, results. But in the latter the water passed round the
cylinders to take up the surplus heat has a value for warming the
building or for manufacturing processes.
Putting one thing with another, experts agree that the explosion engine
is the prime mover of the future. Steam has apparently been developed
almost to its limit. Its rival is but half-grown, though already a
giant.
Some internal combustion engines use petroleum as their fuel,
converting it into gas before it is mixed with air to form the charge;
others use coal-gas drawn from the lighting mains; "poor gas" made in
special plants for power purposes; or natural gas issuing from the
ground. Natural gas occurs in very large quantities in the United
States, where it is conveyed through pipes under pressure for hundreds
of miles, and distributed among factories and houses for driving
machinery, heating, and cooking. In England and Europe the petroleum
engine and coal-gas engine have been most utilised; but of late the
employment of smelting-furnace gases--formerly blown into the air
and wasted--and of "producer" gas has come into great favour with
manufacturers. The latest development is the "suction" gas engine,
which makes its own gas by drawing steam and air through glowing fuel
during the suction stroke.
We will consider the various types under separate headings devoted
(1) To the oil-fuel engine,
(2) The producer-gas engine and the suction-gas engine,
(3) Blast-furnace gas engines, with reference to the installations used
in connection with the last two.
All explosion engines (excepting the very small types employed on motor
cycles) have a water-jacket round the cylinders to absorb some of the
heat of combustion, which would otherwise render the metal so hot as to
make proper lubrication impossible, and also would unduly expand the
incoming charge of gas and air before compression. The ideal engine
would take in a full charge of cold mixture, which would receive no
heat from the walls of the cylinder, and during the explosion would
pass no heat through the walls. In other words, the ideal metal for the
cylinders would be one absolutely non-receptive of heat. In the absence
of this, engineers are obliged to make a compromise, and to keep the
cylinder at such a temperature that it can be lubricated fittingly,
while not becoming so cold as to absorb _too much_ of the heat of
explosion.
OIL ENGINES
These fall into two main classes:--
(a) Those using light, volatile, mineral oils--such as petrol and
benzoline--and alcohol, a vegetable product.
(b) Those using heavy oils, such as paraffin oil (kerosene) and the
denser constituents of rock-oil left in the stills after the kerosene
has been driven off. American petroleum is rich in burning-oil and
petrol; Russian in the very heavy residue, called _astakti_. Given the
proper apparatus for vaporisation, mineral oils of any density can be
used in the explosion engine.
The first class is so well known as the mover of motor vehicles and
boats that we need not linger here on it. It may, however, be remarked
that engines using the easily-vaporised oils are not of large powers,
since the fuel is too expensive to make them valuable for installations
where large units of power are needed. They have been adopted for
locomotives on account of their lightness, and the ease with which they
can be started. Petrol vaporises at ordinary temperatures, so that air
merely passed over the spirit absorbs sufficient vapour to form an
explosive mixture. The "jet" carburetter, now generally employed, makes
the mixture more positive by atomising the spirit as it passes through
a very fine nozzle into the mixing chamber under the suction from the
cylinder. On account of their small size spirit engines work at very
high speeds as compared with the large oil or gas engine. Thus, while
a 2,000 h.p. Körting gas engine develops full power at eighty-five
revolutions a minute, the tiny cycle motor must be driven at 2,000 to
3,000 revolutions. Speaking generally, as the size increases the speed
decreases.
Of heavy oil engines there are some dozens of well-tried types. They
differ in their methods of effecting the following operations.
1. The feeding of the oil fuel to the engine.
2. The conversion of the oil into vapour.
3. The ignition of the charge.
4. The governing of speed.
All these engines have a vaporiser, or chamber wherein the oil is
converted into gas by the action of heat. When starting-up the engine,
this chamber must be heated by a specially designed lamp, similar in
principle to that used by house painters for burning old paint off wood
or metal.
Let us now consider the operations enumerated above in some detail.
1. _The oil supply._ Fuel is transferred from the storage tank to the
vaporiser either by the action of gravity through a regulating device
to prevent "flooding," or by means of a small pump, or by the suction
of the piston, which _lifts_ the liquid. In some engines the air and
gas enter the cylinder through a single valve; in others through
separate valves.
2. _Vaporisation._ As already remarked, the vaporising chamber must be
heated to start the engine. When work has begun the lamp may be removed
if the engine is so designed that the chamber stores up sufficient heat
in its walls from each explosion to vaporise the charge for the next
power stroke. The Crossley engine has a lamp continuously burning; the
Hornsby-Ackroyd depends upon the storage of heat from explosions in a
chamber opening into the cylinder. The best designs are fairly equally
divided between the two systems.
3. _Ignition_ of the compressed charge is effected in one of four ways:
by bringing the charge, at the end of the compression stroke, into
contact with a closed tube projecting from the cylinder and heated
outside by a continuously burning lamp; by the heat stored in some
part of the combustion chamber (_i.e._ that portion of the cylinder
not swept by the piston); by an electric spark; or by the mere heat of
compression. The second and third methods are confined to comparatively
few makes; and the Diesel Oil Engine (of which more presently) has a
monopoly of the fourth.
4. _Governing._ All engines which turn machinery doing intermittent
work--such as that of a sawmill, or electric generating plant
connected with a number of motors--must be very carefully guarded from
overrunning. Imagine the effect on an engine which is putting out its
whole strength and getting full charges of fuel, if the belt suddenly
slipped off and it were "allowed its head." A burst fly-wheel would be
only one of the results. The steam-engine is easily controlled by the
centrifugal action of a ball-governor, which, as the speed increases,
gradually spreads its balls and lifts a lever connected with a valve
in the steam supply pipe. Owing to its elastic nature, steam will do
useful work if admitted in small quantities to the cylinder. But a
difficulty arises with the internal combustion engine if the _supply_
of mixture is similarly throttled, because a loss of quantity means
loss of compression and bad ignition. Many oil engines are therefore
governed by apparatus which, when the speed exceeds a certain limit,
cuts off the supply altogether, either by throwing the oil-pump
temporarily out of action, or by lifting the exhaust valve so that the
movement of the piston causes no suction--the "hit-and-miss" method, as
it is called.
The means adopted depends on the design of the engine; and it must
be said that, though all the devices commonly used effect their
purpose, none are perfect; this being due rather to the nature of an
internal explosion engine than to any lack of ingenuity on the part of
inventors. The steadiest running is probably given with the throttle
control, which diminishes the supply. On motor cars this method has
practically ousted the "hit-and-miss" governed exhaust valve; but
in stationary engines we more commonly find the speed controlled by
robbing the mixture of the explosive gas in inverse proportion to the
amount of the work required from the engine.
THE DIESEL OIL ENGINE,
on account of some features peculiar to it, is treated separately.
In 1901 an expert wrote of it that "the engine has not attained any
commercial position." Herr Rudolph Diesel, the inventor, has, however,
won a high place for his prime-mover among those which consume liquid
fuel, on account of its extraordinary economy. The makers claim--as the
result of many tests--that with the crude rock-oil (costing in bulk
about 2d. a gallon) which it uses, a horse-power can be developed for
one hour by this engine for _one-tenth of a penny_. The daily fuel bill
for a 100 h.p. engine running ten hours per day would therefore be 8s.
4d. To compete with the Diesel engine a steam installation would have
to be of the very highest class of triple-expansion type, of not less
than 400 h.p., and using every hour per horse-power only 1-3/4 lbs. of
coal at 9s. per ton. Very few large steam-engines work under conditions
so favourable, and with small sizes 3-4 lbs. of coal would be burnt for
every "horse-power-hour."
The Diesel differs from other internal combustion engines in the
following respects:--
1. It works with very much higher compression.
2. The ignition is spontaneous, resulting from the high
compression of the charge alone.
3. The fuel is not admitted into the cylinder until the
power-stroke begins, and enters in the form of a
fine spray.
4. The combustion of the fuel is much slower, and therefore
gives a more continuous and elastic push to the
piston.
The engine works on the ordinary Otto cycle. To start it, air
compressed in a separate vessel is injected into the cylinder. The
piston flies out, and on its return squeezes the air to about 500 lbs.
to the square inch, thus rendering it incandescent.[11] Just as the
piston begins to move out again a valve in the cylinder-head opens, and
a jet of pulverised oil is squirted in by air compressed to 100 lbs.
per square inch more than the pressure in the cylinder. The vapour,
meeting the hot air, burns, but comparatively slowly: the pressure in
the cylinder during the stroke decreasing much more gradually than in
other engines. Governing is effected by regulation of the amount of oil
admitted into the cylinder.
In spite of its high compression this engine runs with very little
vibration. The writer saw a penny stand unmoved on its edge on the top
of a cylinder in which the piston was reciprocating 500 times a minute!
ENGINES WORKED BY PRODUCER-GAS
These engines are worked by a special gas generated in an apparatus
called a "producer." If air is forced through incandescent carbon in
a closed furnace its oxygen unites with the carbon and forms carbonic
acid gas, known chemically as CO_{2}, because every molecule of the
gas contains one atom of carbon and two of oxygen. This gas, being
the product of combustion, cannot burn (_i.e._ combine with more
oxygen), but as it passes up through the glowing coke, coal, or other
fuel, it absorbs another carbon atom into every molecule, and we have
C_{2}O_{2}, or 2 CO, which we know as _carbon monoxide_. This gas may
be seen burning on the top of an open fire with a very pale blue flame,
as it once more combines with oxygen to form carbonic acid gas.
The carbon monoxide is valuable as a heating agent, and when mixed with
air forms an explosive mixture.
If along with the air sent into our furnace there goes a proportion
of steam, further chemical action results. The oxygen of the steam
combines with carbon to form carbon monoxide, and sets free the
hydrogen. The latter gas, when it combines with oxygen in combustion,
causes intense heat; so that if from the furnace we can draw off carbon
monoxide and hydrogen, we shall be able to get a mixture which during
combustion will set up great heat in the cylinder of an engine.
In 1878 Mr. Emerson Dowson invented an apparatus for manufacturing
a gas suitable for power plant, the gas being known as Producer or
Poor Gas, the last term referring to its poorness in hydrogen as
compared with coal and other gases. While the hydrogen is a desirable
ingredient in an explosive charge, it must not form a large proportion,
since under compression it renders the mixture in which it takes part
dangerously combustible, and liable to spontaneous ignition before the
piston has finished the compression stroke. Water-gas, very rich in
hydrogen, and made by a very similar process, is therefore not suitable
for internal combustion engines.
There are many types of producers, but they fall under two main heads,
_i.e._ the _pressure_ and the _suction_.
The _pressure_ producer contains the following essential parts:--
The _generator_, a vertical furnace fed from the top through an
air-tight trap, and shut off below from the outside atmosphere by
having its foot immersed in water. Any fuel or ashes which fall through
the bars into the water can be abstracted without spoiling the draught.
Air and steam are forced into the generator, and pass up through the
fuel with the chemical results already described. The gases then flow
into a _cooler_, enclosed in a water-jacket, through which water
circulates, and on into a _scrubber_, where they must find their way
upwards through coke kept dripping with water from overhead jets. The
water collects impurities of all sorts, and the gas is then ready for
storage in the gas-holders or for immediate use in the engines.
A pound of anthracite coal thus burnt will yield enough gas to develop
1 h.p. for one hour.
_Suction Gas Plants._--With these gas is not stored in larger
quantities than are needed for the immediate work of the engine. In
fact, the engine itself during its suction strokes _draws_ air and
steam through a very small furnace, coolers, and scrubbers direct into
the cylinder. The furnace is therefore fed with air and water, not
by pressure from outside, but by suction from inside, hence the name
"suction producer." At the present time suction gas engines are being
built for use on ships, since a pound of fuel thus consumed will drive
a vessel further than if burnt under a steam boiler. Very possibly the
big ocean liners of twenty years hence may be fitted with such engines
in the place of the triple and quadruple expansion steam machinery now
doing the work.
BLAST-FURNACE GAS ENGINES
Every iron blast-furnace is very similar in construction and action
to the generator of a producer-gas plant. Into it are fed through
a hopper, situated in the top, layers of ore, coal or coke, and
limestone. At the bottom enters a blast of air heated by passing
through a stove of firebrick raised to a high temperature by the carbon
monoxide gas coming off from the furnace. When the stove has been
well heated the gas supply is shut off from it and switched to the
engine-house to create power for driving the huge blowers.
The gas contains practically no hydrogen, as the air sent through
the furnace is dry; but since it will stand high compression, it is
very suitable for use in large engines. Formerly all the gas from the
furnace was expelled into the open air and absolutely wasted; then
it was utilised to heat the forced draught to the furnace; next, to
burn under boilers; and last of all, at the suggestion of Mr. B. H.
Thwaite, to operate internal combustion engines for blowing purposes.
Thus, in the fitness of things, we now see the biggest gas engines in
the world installed where gas is created in the largest quantities, and
an interesting cycle of actions results. The engine pumps the air; the
air blows the furnace and melts the iron out of the ore; the furnace
creates the gas; the gas heats the air or works the engines to pump
more air. So engines and furnace mutually help each other, instead of
all the obligation being on the one side.
When, a few years ago, the method was first introduced, engines were
damaged by the presence of dust carried with the gas from the furnace.
Mr. B. H. Thwaite has, however, perfected means for the separation of
injurious matter, and blast-furnace gas is coming into general use in
England and on the Continent. Some idea of the power which has been
going to waste in ironworks for decades past may be gathered from a
report of Professor Hubert after experiments made in 1900. He says that
engines of large size do not use more than 100 cubic feet of average
blast-furnace gas per effective horse-power-hour, which is less than
one-fourth of the consumption of gas required to develop the same power
from boilers and good modern condensing steam-engines, so that there
is an immense surplus of power to be obtained from a blast-furnace
if the blowing engines are worked by the gas it generates, a surplus
which can be still further increased if the gas is properly cleaned.
It is estimated that for every 100 tons of coke used in an ordinary
Cleveland blast-furnace, after making ample allowance for gas for the
stoves and power for the lifts, pumps, etc., and for gas for working
the necessary blowing engines, there is a surplus of at least _1,500
h.p._; so that by economising gas by cleaning, and developing the
necessary power by gas engines, every furnace owner would have a very
large surplus of power for his steel or other works, or for selling in
the form of electricity or otherwise.
Yet all this gas had been formerly turned loose for the breezes to warm
their fingers at! Truly, as an observant writer has recorded, the sight
of a special plant being put up near a blast furnace to manufacture gas
for the blowing engines suggests the pumping of water uphill in order
to get water-power!
Messrs. Westgarth and Richardson, of Middlesbrough; the John Cockerill
Company, of Seraing, Belgium; and the De la Vergne Company, of New
York, are among the chief makers of the largest gas engines in the
world, ranging up to 3,750 h.p. each. These immense machines, some with
fly-wheels 30 feet in diameter, and cylinders spacious enough for a man
to stand erect in, work blowers for furnaces or drive dynamos. At the
works of the manufacturers mentioned the engines helped to make the
steel, and turn the machinery for the creation of brother monsters.
[Illustration: GIGANTIC GAS ENGINES
Five of sixteen 2,000 h.p. Körting Gas Engines built by the De la
Vergne Company of New York City for blowing the blast furnaces of the
Lackawanna Steel Company. The gas-engine plant at these works is the
largest in the world. Notice the man to the left.]
This use of a "bye-product" of industry is remarkable, but it can be
paralleled. Furnace slag, once cast away as useless, is now recognised
to be a valuable manure, or is converted into bricks, tiles, cement,
and other building materials. Again, the former waste from the coal-gas
purifier assumes importance as the origin of aniline dyes, creosote,
saccharine, ammonia, and oils. We really appear to be within sight of
the happy time when waste will be unknown. And it therefore is curious
that we still burn gas as an illuminant, when the same, if made to work
an engine, would give more lighting power in the shape of electric
current supplying incandescent lamps.
FOOTNOTE:
[11] The fact that air is heated to combustion point by compression has
long been known to the Chinese. In _The River of Golden Sand_, Captain
Gill writes: "The natives have an apparatus by which they strike a
light by compressed air. The apparatus consists of a wooden cylinder
2-1/2 inches long by 3/4 inch in diameter. This is closed at one end;
the bore being about the size of a stout quill pen, an air-tight piston
fits into this with a large flat knob at the top. The other end of the
piston is slightly hollowed out, and a very small piece of tinder is
placed on the top thus formed. The cylinder is held in one hand, the
piston inserted and pushed about half-way down; a very sharp blow is
then delivered with the palm of the hand on to the top of the knob; the
hand must at the same time close on the knob, and instantly withdraw
the piston, when the tinder will be found alight. The compression of
the air produces heat enough to light the tinder; but this will go out
again unless the piston is withdrawn very sharply. I tried a great many
times, but covered myself with confusion in fruitless efforts to get a
light, for the natives never miss it."
CHAPTER VII
MOTOR-CARS
THE MOTOR OMNIBUS--RAILWAY MOTOR-CARS
The development of the motor-car has been phenomenal. Early in 1896
the only mechanically moved vehicles to be seen on our roads were
the traction-engine, preceded by a man bearing a red flag, the
steam-roller, and, in the towns, a few trams. To-day the motor is
apparent everywhere, dodging through street traffic, or raising the
dust of the country roads and lanes, or lumbering along with its load
of merchandise at a steady gait.
As a purely speed machine the motor-car has practically reached its
limit. With 100 h.p. or more crowded into a vehicle scaling only a
ton, the record rate of travel has approached two miles in a minute on
specially prepared and peculiarly suitable tracks. Even up steep hills
such a monster will career at nearly eighty miles an hour.
Next to the racing car comes the touring car, engined to give sixty
miles an hour on the level in the more powerful types, or a much lower
speed in the car intended for quieter travel, and for people who are
not prepared to face a big bill for upkeep. The luxury of the age has
invaded the design of automobiles till the gorgeously decorated and
comfortably furnished Pullman of the railway has found a counterpart
in the motor caravan with its accommodation for sleeping and feeding.
While the town dweller rolls along in electric landaulet, screened
from wind and weather, the tourist may explore the roads of the world
well housed and lolling at ease behind the windows of his 2,000-guinea
machine, on which the engineer and carriage builder have lavished their
utmost skill.
The taunt of unreliability once levelled--and with justice--at the
motor-car, is fast losing its force, owing to the vast improvements in
design and details which manufacturers have been stimulated to make.
The motor-car industry has a great future before it, and the prizes
therein are such as to tempt both inventor and engineer. Every week
scores of patents are granted for devices which aim at the perfection
of some part of a car, its tyres, its wheels, or its engines. Until
standard types for all grades of motor vehicles have been established,
this restless flow of ideas will continue. Its volume is the most
striking proof of the vitality of the industry.
The uses to which the motor vehicle has been put are legion. On
railways the motor carriage is catering for local traffic. On the roads
the motor omnibus is steadily increasing its numbers. Tradesmen of all
sorts, and persons concerned with the distribution of commodities,
find that the petrol- or steam-moved car or lorry has very decided
advantages over horse traction. Our postal authorities have adopted the
motor mail van. The War Office looks to the motor to solve some of its
transportation difficulties. In short, the "motor age" has arrived,
which will, relatively to the "railway age," play much the same part
as that epoch did to the "horse age." At the ultimate effects of the
change we can only guess; but we see already, in the great acceleration
of travel wherever the motor is employed, that many
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