Already in New York there are a great number of lofty piles due to the
introduction of the lifts or elevators, by which an office on the tenth
floor is made as convenient as one on the second. These buildings
usually receive the name of the owners of the structure, who occupy,
perhaps, only one floor. To mention only a few. There is the American
Tract Society building, with its twenty-three stories, 285 feet high,
which is one of the latest and handsomest of these tall piles in the
city. See Plate IV. Still loftier is the St. Paul building, fronting the
New York Post-Office at the junction of Park Row and Broadway. This
structure is splayed at the angle between Ann Street and Broadway, where
its width is 39½ feet, while its _loftiest_ part has frontages of about
30 feet along each of these thoroughfares. The height is no less than
313 feet above the pavement, and the number of stories is twenty-five.
This building is faced with light yellow limestone, and although it was
commenced only in the summer of 1895, it was expected to be ready for
occupation by the autumn of 1896. Even this great height is overtopped
by the Manhattan Life Insurance Company’s building, rising 330 feet, and
remarkable as perhaps beyond previous record of quickness in building a
gigantic structure. Obviously, the foundations of such a building must
be most seriously considered, prepared and tested, before the great bulk
of the building is begun, and in the _New York Engineering Magazine_ one
of the architects has given a full account, with complete illustrations,
of all the works, from the rock foundation to the completed edifice. A
description of the foundation work, though most interesting for the
professional engineer, would probably have little attraction for the
general reader; but its importance may be inferred from the fact of its
having taken nearly six months for its completion, while the huge
superstructure required only eight months. The eighteenth tier of beams
was reached in “three months from the time the foundations were ready on
which to set the first piece of steel, composing the bolsters that
support the cantilever system.... The substructure, which starts in
bed-rock and continues to the cellar-floor, consists of fifteen piers,
varying in size from 9 feet in diameter, to 21 feet 6 inches by 25 feet
square.... The number of bricks used in the piers amounted to 1,500,000.
From this it may be seen that a good-sized building was sunk out of
sight before any part of the superstructure could be begun.” An open
court within the main structure, special framing for the arrangements of
the company’s offices on the sixth floor, the great height and weight of
the tower, and the requisite provision for wind-bracing, delayed in some
degree a regular advance of the stories; but within three months no less
than 5,800 tons were placed in position. There were girders weighing 40
tons, many columns of 10 and 12 tons, and cantilevers of 80 tons weight
and 67 feet long. Strange to say, that in a building of this magnitude,
where such masses had to be raised 300 feet into the air, there was not
a single accident involving loss of life. When four stories of the steel
framework had been put up, the bricklayers were set to work, and they
followed the frame-setters throughout. After the masons came the
pipe-layers, with their ten miles of pipes, followed by electricians,
fixing their thirty-five miles of communicating wires. Thirty thousand
cubic feet of stone was cut and set on the Broadway front in eighty
days. Then craftsmen of the different trades followed each other, or
worked in harmony together, story after story upwards: the engineers for
boilers, heating, and elevators, the plumbers, the decorators, the
carpenters and cabinet-makers, the plasterers, the marble and tile
workers, the gasmen, etc. In fine, every story was completely finished
and ready for occupation in eight months after the start from the
foundations.
[Illustration:
FIG. 26_f_.—_Manhattan Insurance Co.’s Buildings nearly completed._
]
The shortness of the time in which these lofty buildings were run up is
not less remarkable than the completeness of their fittings, which
comprise everything requisite for communication within the premises and
in connection with the outer world. The elevators or lifts are the
perfection of mechanism in their way, and act with wonderful smoothness
and regularity; of these are usually two at least, as well as an ample
staircase. Notwithstanding all these appliances, some disastrous and
fatal conflagrations have occurred at buildings erected on the “tall”
principle; and as “business premises” of even 380 feet high are
projected, the authorities have been considering the desirability of
restricting the heights. It has been proposed that offices should not
exceed in height 200 feet; hotels, 150 feet; and private houses, 75
feet.
_BIG WHEELS._
The Paris example of an engineering feat upon an unprecedented scale
having proved sufficiently captivating for the general public to ensure
for itself a great commercial success, even amid the attractions of an
International Exhibition, was not lost upon the enterprising people of
the States when the “World’s Fair” at Chicago was in preparation in
1893. It was then that Mr. G. W. G. Ferris, the head of a firm of bridge
constructors at Pittsburg, conceived the idea of applying his
engineering skill to the erection of a huge wheel, revolving in a
vertical plane, with cars for persons to sit in, constituting, in fact,
an enormous “merry-go-round,” as the machine once so common at country
fairs was called. The novelty of the Chicago erection was, therefore,
not the general idea, but the magnitude of the scale, which, for that
reason, involved the application of the highest engineering skill, and
the solution of hitherto unattempted practical problems. Several
thousand pounds were, in fact, expended on merely preliminary plans and
designs. The great wheel at Chicago was 250 feet in diameter, and to its
periphery were hung thirty-six carriages, each seating forty persons. At
each revolution, therefore, 1,440 people would be raised in the air to
the height of 250 feet, and from that elevation afforded a splendid
prospect, besides an experience of the peculiar sensation like that of
being in a balloon, when the spectator has no perception of his own
motion, but the objects beneath appear to have the contrary movement,
that is to say, they seem to be sinking when he is rising, and _vice
versâ_. The axle of the Chicago wheel was a solid cylinder, 32 inches in
diameter and 45 feet long; on this were two hubs, 16 feet in diameter,
to which were attached spoke rods, 2½ inches in diameter, passing in
pairs to an inner crown, which was concentric with the outer rim, but 40
feet within it. The inner and outer crowns were connected together, and
the former joined to the crown of the twin wheel by an elaborate system
of trusses and ties, which, however, left an open space between the rims
of 20 feet from the outside. These last were formed of curved riveted
hollow beams, in section 25½ inches by 19 inches, and between them,
slung upon iron axles through the roofs, were suspended, at equal
intervals, the thirty-six carriages, each 27 feet long, and weighing 13
tons without its passengers, who added 3 tons more to the weight. The
wheel with its passengers was calculated to weigh about 1,200 tons, and
it rested on two pyramidal skeleton towers of ironwork 140 feet high,
having bases 50 feet by 60 feet. The wheel was moved by power applied at
the lowest point, the peripheries of both the rims having great cogs 6
inches deep and 18 inches apart, which engaged a pair of large
cog-wheels, carried on a shaft 12 inches in diameter.
[Illustration:
FIG. 26_g_.—_Original Design for the Great Wheel._
]
This curious structure was not begun until March, 1893, yet it was set
in motion three months afterwards, having cost about £62,500. The
Company had to hand over to the Exhibition one half of the receipts
after the big wheel had paid for its construction, but even then they
realised a handsome profit, and at the close of the World’s Fair, they
sold the machine for four-thirds of its cost, in order that it might be
re-erected at Coney Island.
No sooner had the great Ferris wheel at Chicago proved a financial
success than an American gentleman, Lieutenant Graydon, secured a patent
for a like machine in the United Kingdom; and as it has now become
almost a matter of course that some iron or steel structure, surpassing
everything before attempted, should form a part of each great
exhibition, a Company was at once formed in London, under the title of
“The Gigantic Wheel and Recreation Towers Co., Limited,” to construct
and work at the Earl’s Court Oriental Exhibition of 1895, a great wheel,
similar in general form to that of Chicago. But the design of the London
wheel had some new features, as will be seen from the sketches, Fig.
26_c_ (from _The Engineer_ of 20th April, 1894), and, moreover, having
been planned of larger dimensions than its American prototype, presented
additional engineering problems of no small complexity. After due
deliberation the scheme of the work was entrusted to Mr. Walter B.
Basset, a talented young engineer, connected with the firm of Messrs.
Maudslay, Sons, & Field, and already experienced in designing iron
structures. Under this gentleman, with the assistance of Mr. J. J.
Webster in carrying out some of the details, the work has been so
successfully accomplished that the “Great Wheel” of 1895 may be cited as
one of the crowning mechanical triumphs of the nineteenth century. The
original design has not been followed so far as regards the lower
platforms for refreshment rooms, &c. Plate V., for which we are indebted
to Mr. Basset, is a photographic representation of the actual structure.
The wheel at Earl’s Court exceeds the Ferris wheel in diameter by 50
feet, being 300 feet across. It is supported on two towers, 175 feet
high, each formed by four columns 4 feet square, built of steel plates
with internal diaphragms, and surmounted by balconies that may be
ascended in elevators raised by a weight of water, which, after having
been discharged into a reservoir under the ground level, is again pumped
up to the top of the towers. Between the balconies on each tower there
is also a communication _through the axle_ of the wheel, which, instead
of being solid as at Chicago, is a tube of 7 feet diameter, and 35 feet
long, made in sections, riveted together, of steel 1 inch thick, and
weighing no less than 58 tons. The raising and fixing in its high place
of such a mass of metal required specially ingenious devices, which have
been greatly appreciated by professional engineers. But for these
devices, the erection of scaffolding in the ordinary way of proceeding
would have entailed an outlay simply enormous. The axle is stiffened by
projecting rings, and, between pairs of these, the spoke rods are
attached by pins 3 inches in diameter. The axle was the production of
Messrs. Maudslay, Field & Co.; all the rest of the metal work was made
at the Arrol Works at Glasgow, and the carriages were constructed by
Brown, Marshall & Co., of Birmingham. The Earl’s Court wheel is turned
by a mechanism different from that of the Chicago wheel, for whereas the
latter was provided with cogs, the former has two chains, each 1,000
feet long and 8 tons weight, surrounding the periphery of the wheel on
either side. The chains go over drums in the engine-shed, from which
they pass underground to guide-pulleys, and as they unwind from the
Great Wheel, they again go over guide-pulleys to lead them back to the
drums. These chains are firmly held throughout in the jaws of V-shaped
grooves, and there are arrangements for taking up the slack. The drums
are actuated by wheel gearing, connected with two horizontal Robey steam
engines, each of 50 horse-power, one on either side, capable of being
worked singly or together. It is, however, found sufficient to use the
engine of one side only, and even then to work it at but 16 horse-power,
and the operation can be controlled by one man, who has also the command
of a brake. Both starting and stopping are accomplished with the
greatest smoothness and absence of strain or jar. There are forty
carriages, each 25 feet long, 9 feet wide, and 10 feet high. Each will
accommodate forty passengers, and these enter at the ends from eight
platforms at different heights from the ground, so arranged as to be on
the level of the eight lowest carriages while the wheel is stationary.
The passengers who have had their ride leave at the other end of the
carriages by eight similar platforms on the other side of the wheel.
After the change of passengers in one set of eight carriages, the wheel
is turned through exactly one-fifth of a revolution, which has the
effect of bringing the next eight carriages to the level of the
platforms, and it is again brought to a standstill whilst the change of
passengers is taking place; and so on, until the whole freight of say
1,600 persons has been changed during the five stoppages in one
revolution, for which about thirty-five minutes are required, and the
process of emptying and filling eight carriages at once is repeated.
There are first and second class carriages, the charge for the former
being two shillings, and for the latter one shilling; so that, reckoning
800 passengers of each class, one turn would bring to the treasury the
handsome sum of £120.
The sensations experienced in a journey on the Great Wheel are, as
already mentioned, comparable to those enjoyed by the aërial voyagers in
a balloon, where all perception of proper motion is lost, and it is the
world beneath that seems to recede and float away, presenting the while
a strangely changing panorama. Many people who have never made a balloon
ascent yet know the calm delight of floating in a boat without effort
down some placid stream, unconscious of any motion beyond that vaguely
inferred from the silent apparent gliding by of the banks. Very similar
are, in part, the feelings of the passenger who is almost imperceptibly
carried up into the air in a carriage of the Great Wheel, but the
vertical direction of the movement, and the gradual expansion of the
horizon as the vertex is approached, lend an unwonted novelty to the
situation. From the Earl’s Court Wheel the view is both interesting and
extensive, for on a clear day the prospect stretches as far as the Royal
Castle of Windsor.
The “Gigantic Wheel” at Earl’s Court was inaugurated on the 11th July,
1895, in the presence of an assemblage of 5,000 people, including many
distinguished personages, who were all treated to a ride. Plate I. shows
a portion of the wheel and carriages as in motion.
[Illustration:
PLATE V.
GENERAL VIEW OF THE GREAT WHEEL AT EARL’S COURT.
]
[Illustration:
FIG. 27.—_Sir Joseph Whitworth._
]
TOOLS.
Of the immense variety of tools and mechanical contrivances employed in
modern times, by far the greatest number are designed to impart to
certain materials some definite shape. The brickmaker’s mould, the
joiner’s plane, the stonemason’s chisel, the potter’s wheel, are
examples of simple tools. More elaborate are the coining press, the
machine for planing iron, the drilling machine, the turning lathe, the
rolling mill, the Jacquard loom. But all such tools and machines have
one principle in common—a principle which casual observers may easily
overlook, but one which is of the highest importance, as its application
constitutes the very essence of the modern process of _manufacture_ as
distinguished from the slow and laborious mode of making things by hand.
The principle will be easily understood by a single example. Let it be
required to draw straight lines across a sheet of paper. Few persons can
take a pen or pencil, and do this with even an approach to accuracy, and
at best they can do it but slowly and imperfectly. But with the aid of a
ruler any number of straight lines may be drawn rapidly and surely. The
former case is an instance of _making_ by hand, the latter represents
_manufacturing_, the ruler being the tool or machine. Let it be observed
that the ruler has in itself the kind of form required—that is to say,
straightness—and that in using it we copy or transfer this straightness
to the mark made on the paper. This is a simple example of the _copying
principle_, which is so widely applied in machines for manufacturing;
for, in all of these, materials are shaped or moulded by various
contrivances, so as to reproduce certain definite forms, which are in
some way contained within the machine itself. This will be distinctly
seen in the tools which are about to be described.
[Illustration:
FIG. 28.—_Whitworth’s Screw Dies and Tap._
]
Probably no one mechanical contrivance is so much and so variously
applied as the _Screw_. The common screw-nail, which is so often used by
carpenters for fastening pieces of metal on wood, or one piece of wood
to another, is a specimen of the screw with which everybody is familiar.
The projection which winds spirally round the nail is termed the
_thread_ of the screw, and the distance that the thread advances
parallel to the axis in one turn is called the _pitch_. It is obvious
that for each turn the screw makes it is advanced into the wood a depth
equal to the pitch, and that there is formed in the wood a hollow screw
with corresponding grooves and projections. Screws are formed on the
ends of the bolts, by which various parts are fastened together, and the
hollow screws which turn on the ends of the bolts are termed _nuts_. The
screws on bolts and nuts, and other parts of machines, were formerly
made with so many different pitches that, when a machine constructed by
one maker had to be repaired by another, great inconvenience was found,
on account of the want of uniformity in the shape and pitch of the
threads. A uniform system was many years ago proposed by Sir Joseph
Whitworth, and adopted by the majority of mechanical engineers, who
agreed to use only a certain defined series of pitches. The same
engineer also contrived a hand tool for cutting screws with greater
accuracy than had formerly been attained in that process. A mechanic
often finds it necessary to form a screw-thread on a bolt, and also to
produce in metal a hollow screw. The reader may have observed
gas-fitters and other workmen performing the first operation by an
instrument having the same general appearance as Fig. 28. This contains
hard steel _dies_, which are made to press on the bolt or pipe, so that
when the _guide-stock_ is turned by the handles, the required grooves
are cut out. The arrangement of these dies in Sir Joseph Whitworth’s
instrument is shown in Fig. 28, which represents the central part of the
guide-stock; A, B, C are the steel dies retained in their places, when
the instrument is in use, by a plate which can be removed when it is
necessary to replace one set of dies by another, according to the pitch
of thread required. The figure also shows the set of dies, A, B, C,
removed from the guide-stock. D is the work, pressed up against the
fixed die, A, by B and C, the pressure being applied to these last as
required by turning the nut, thus drawing up the key, E, so that the
inclined planes, _f_, _g_, press against similar surfaces forming the
ends of the dies. For producing the hollow screws, _taps_ are provided,
which are merely well-formed screws, made of hard steel and having the
threads cut into detached pieces by several longitudinal grooves, as
represented in the lower part of Fig. 28.
[Illustration:
FIG. 29.—_Screw-cutting Lathe._
]
The method of forming screws by dies and taps is, however, applicable
only to those of small dimensions, and even for these it is not employed
where great accuracy is required. Perfect screws can only be cut with a
lathe, such as that represented in Fig. 29. In this we must first call
the reader’s attention to the portion of the apparatus marked A, which
receives the name of the _slide-rest_. The invention of this contrivance
by Maudsley had the effect of almost revolutionizing mechanical art, for
by its aid it became possible to _produce true surfaces in the lathe_.
Before the slide-rest was introduced, the instrument which cut the wood
or metal was held in the workman’s hand, and whatever might be his skill
and strength, the steadiness and precision thus obtainable were far
inferior to those which could be reached by the grip of an iron hand,
guided by unswerving bars. The slide-rest was contrived by Maudsley in
the first instance for cutting screws, but its principle has been
applied for other purposes. This principle consists in attaching the
cutting tool to a slide which is incapable of any motion, except in the
one direction required. Thus the slide, A, represented in Fig. 29, moves
along the _bed_ of the lathe, B, carrying the cutter with perfect
steadiness in a straight line parallel to the axis of the lathe. There
are also two other slides for adjusting the position of the cutter; the
handle, _a_, turns a screw, which imparts a transverse motion to the
piece, _b_, and the tool receives another longitudinal movement from the
handle, _c_. The pieces are so arranged that these movements take place
in straight lines in precisely the required direction, and without
permitting the tool to be unsteady, or capable of any rocking motion. In
Whitworth’s lathe, between the two sides of the bed, and therefore not
visible in the figure, is a shaft placed perfectly parallel to the axis
of the lathe. One end of this shaft is seen carrying the wheel, C, which
is connected with a train of wheels, D, and is thus made to revolve at a
speed which can be made to bear any required proportion to that of the
mandril, E, of the lathe, by properly arranging the numbers of the teeth
in the wheels; and the machine is provided with several sets of wheels,
which can be substituted for each other. The greater part of the length
of this shaft is formed with great care into an exceedingly accurate
screw, which works in a nut forming part of the slide-rest. The effect,
therefore, of the rotation of the screw is to cause the slide-rest to
travel along the bed of the lathe, advancing with each revolution of the
screw through a space equal to its pitch distance. There is an
arrangement for releasing the nut from the guiding-screw, by moving a
lever, and then by turning the winch the slide-rest is moved along by a
wheel engaging the teeth of a rack at the back of the lathe. Now, if the
train of wheels, C D, be so arranged that the screw makes one revolution
for each turn of the mandril, it follows that the cutting tool will move
longitudinally a distance equal to the pitch of the guiding-screw while
the bar placed in the lathe makes one turn. Thus the point of the cutter
will form on the bar a screw having the same pitch as the guiding-screw
of the lathe.
Here we have a striking illustration of the copying principle, for the
lathe thus produces an exact copy of the screw which it contains. The
screw-thread is traced out on the cylindrical bar, which is operated
upon by the combination of the circular motion of the mandril with the
longitudinal movement of the slide-rest. By modifying the relative
amounts of these movements, screw-threads of any desired pitch can be
made, and it is for this purpose that the _change wheels_ are provided.
If the thread of the guiding-screw makes two turns in one inch, one
revolution of the wheel C will advance the cutter half an inch along the
length of the bar. If the numbers of teeth in the wheels be such that
the wheel D makes ten revolutions while C is making one, then in the
length of half an inch the thread of the screw produced by the cutter
will go round the core ten times, or, in technical language, the screw
will be of 1/20 inch pitch.
[Illustration:
FIG. 30.—_Whitworth’s Measuring Machine._
]