HYDRAULICS.
The science of Hydraulics appears to be as old as the thirst of man.
When prehistoric men had only stone implements, with which to do their
work, they built aqueducts, reservoirs and deep wells which rival in
extent many great similar works that are the boast of their modern
descendants. Modern inventors have also produced with a flourish nice
instrumentalities for raising water, agencies which are covered with the
moss of untold centuries in China.
It was more than an ancient observation that came down to Pliny’s time
for record, that water would rise to a level with its source. The
observation, however, was put into practical use in his time and long
before without a knowledge of its philosophical cause.
Nothing in Egyptian sculpture portraying the arts in vogue around the
cradle of the human race is older than the long lever rocking upon a
cleft stick, one arm of the lever carrying a bracket and the other arm
used to raise a bucket from a well. Forty centuries and more have not
rendered this device obsolete.
Among other machines of the Egyptians, the Carthaginians, the Greeks,
and the Romans for raising water was the _tympanum_, a drum-shape wheel
divided into radial partitions, chambers, or pockets, which were open to
a short depth on the periphery of the wheel, and inclined toward the
axis, and which was driven by animal or manual power. These pockets
scooped up the water from the stream or pond in which the wheel was
located as the wheel revolved, and directed it toward the axis of the
wheel, where it ran out into troughs, pipes, or gutters. The _Noria_, a
chain of pots, and the screw of Archimedes were other forms of ancient
pumps. The bucket pumps with some modifications are known in modern
times as scoop wheels, and have been used extensively in the drainage of
lands, especially by the Dutch, who at first drove them by windmills and
later by steam.
The division of water-wheels into overshot, undershot and breast wheels
is not a modern system.
In the _Pneumatics of Hero_, which compilation of inventions appeared in
225 B. C., seventy-nine illustrations are given and described of simple
machines, between sixty and seventy of which are hydraulic devices.
Among these, are siphon pumps, the force pump of Ctesibius, a
“fire-pump,” having two cylinders, and two pistons, valves, and levers.
We have in a previous chapter referred to Hero’s steam engine. The fact
that a vacuum may be created in a pump into which water will rise by
atmospheric pressure appears to have been availed of but not explained
or understood.
The employment of the rope, pulley and windlass to raise water was known
to Hero and his countrymen as well as by the Chinese before them. The
chain pump and other pumps of simple form have only been improved since
Hero’s day in matters of detail. The screw of Archimedes has been
extended in application as a carrier of water, and converted into a
conveyor of many other materials.
Thus, aqueducts, reservoirs, water-wheels (used for grinding grain),
simple forms of pumps, fountains, hydraulic organs, and a few other
hydraulic devices, were known to ancient peoples, but their limited
knowledge of the laws of pneumatics and their little mechanical skill
prevented much general progress or extensive general use of such
inventions.
It is said that Frontinus, a Roman Consul, and inspector of public
fountains and aqueducts in the reigns of Nerva and Trajan, and who wrote
a book, _De Aquaeductibus Urbis Romae Commentarius_, describing the
great aqueducts of Rome, was the first and the last of the ancients to
attempt a scientific investigation of the motions of liquids.
In 1593 Serviere, a Frenchman, born in Lyons, invented the rotary pump.
In this the pistons consisted of two cog wheels, their leaves
intermeshing, and rotated in an elliptical shaped chamber. The water
entered the chamber from a lower pipe, and the action of the wheels was
such as to carry the water around the chamber and force it out through
an opposite upper pipe. Subsequent changes involved the rotating of the
cylinder instead of the wheels and many modifications in the form of the
wheels. The same principle was subsequently adopted in rotary steam
engines.
In 1586, a few years before this invention of Serviere, Stevinus, the
great engineer of the dikes of Holland, wrote learnedly on the
_Principles of Statics and Hydrostatics_, and Whewell states that his
treatment of the subject embraces most of the elementary science of
hydraulics and hydrostatics of the present day. This was followed by the
investigations and treatises of Galileo, his pupil Torricelli, who
discovered the law of air pressure, the great French genius, Pascal, and
Sir Isaac Newton, in the 17th century; and Daniel Bernoulli, d’Alembert,
Euler, the great German mathematician and inventor of the centrifugal
pump, the Abbé Bossut, Venturi, Eylewein, and others in the 18th
century.
It was not until the 17th and 18th centuries that mankind departed much
from the practice of supplying their towns and cities with water from
distant springs, rivers and lakes, by pipes and aqueducts, and resorted
to water distribution systems from towers and elevated reservoirs.
Certain cities in Germany and France were the first to do this, followed
in the 18th century by England. This seems strange, as to England, as in
1582 one Peter Maurice, a Dutch engineer, erected at London, on the old
arched bridge across the Thames, a series of forcing pumps worked by
undershot wheels placed in the current of the river, by which he forced
a supply of water to the uppermost rooms of lofty buildings adjacent to
the bridge. Before the inventions of Newcomen and Watt in the latter
part of the 18th century of steam pumps, the lift and force pumps were
operated by wheels in currents, by horses, and sometimes by the force of
currents of common sewers.
When the waters of rivers adjacent to towns and cities thus began to be
pumped for drinking purposes, _strainers_ and _filters_ of various kinds
were invented of necessity. The first ones of which there is any printed
record made their appearance in 1776.
After the principles of hydraulics had thus been reviewed and discussed
by the philosophers of the 17th and 18th centuries and applied, to the
extent indicated, further application of them was made, and especially
for the propelling of vessels. In 1718 La Hire revived and improved the
double-acting pump of Ctesibius, but to what extent he put it into use
does not appear. However, it was the double-acting pump having two
chambers and two valves, and in which the piston acted to throw the
water out at each stroke.
In 1730 Dr. John Allen of England designed a vessel having a tunnel or
pipe open at the stern thereof through which water was to be pumped into
the air or sea--the reaction thus occasioned driving the vessel forward.
He put such a vessel at work in a canal, working the pumps by manual
labor, and suggested the employment of a steam engine. A vessel of this
kind was patented by David Ramsey of England in 1738. Rumsey of America
in 1782 also invented a similar vessel, built one 50 feet long, and ran
it experimentally on the Potomac river. Dr. Franklin also planned a boat
of this kind in 1785 and illustrated the same by sketches. His plan has
since been tried on the Scheldt, but two turbines were substituted for
his simple force pump. Further mention will be made later on of a few
more elaborate inventions of this kind.
It also having been discovered that the fall of a column of water in a
tube would cause a portion of it to rise higher than its source by
reason of the force of momentum, a machine was devised by which
successive impulses of this force were used, in combination with
atmospheric pressure, to raise a portion of the water at each impulse.
This was the well-known _ram_, and the first inventor of such a machine
was John Whitehurst of Cheapside, England, who constructed one in 1772.
From a reservoir, spring, or cistern of water, the water was discharged
downward into a long pipe of small diameter, and from thence into a
shorter pipe governed by a stop-cock. On the opening of the stop-cock
the water was given a quick momentum, and on closing the cock water was
forced by the continuing momentum through another pipe into an air
chamber. A valve in the latter-mentioned pipe opened into the air
chamber. The air pressure served to overcome the momentum and to close
the chamber and at the same time forced the water received into the air
chamber up an adjacent pipe. Another impulse was obtained and another
injection of water into the chamber by again opening the stop-cock, and
thus by successive impulses water was forced into the chamber and
pressed by the air up through the discharge pipe and thence through a
building or other receptacle. But the fact that the stop-valve had to be
opened and closed by hand to obtain the desired number of lifts rendered
the machine ineffective.
In 1796 Montgolfier, a Frenchman and one of the inventors of the
balloon, substituted for the stop-cock of the Whitehurst machine a loose
impulse valve in the waste pipe, whereby the valve was raised by the
rush of the water, made to set itself, check the outflow and turn the
current into the air chamber. This simple alteration changed the
character of the machine entirely, rendered it automatic in action and
converted it into a highly successful water-raising machine. For this
invention Montgolfier obtained a Gold Medal from the French Exposition
of 1802. Where a head can be had from four to six feet, water can be
raised to the height of 30 feet. Bodies of water greater in amount than
is desired to be raised can thus be utilised, and this simple machine
has come into very extensive use during the present century.
Allusion was made in the last chapter to the powerful hydraulic press of
Joseph Bramah invented in 1795-1800, its practical introduction in this
century and improvements therein of others. After the great improvements
in the steam engine made by Watt, water, steam and air pressure joined
their forces on the threshold of this century to lift and move the
world, as it had never been moved before.
The strong hands of hydraulics are pumps. They are divided into classes
by names indicating their purpose and mode of operation, such as single,
double-acting, lift or force, reciprocating or rotary, etc.
Knight, in his celebrated _Mechanical Dictionary_, enumerates 100
differently constructed pumps connected with the various arts. In a
broader enumeration, under the head of _Hydraulic Engineering and
Engineering Devices_, he gives a list of over 600 species. The number
has since increased. About nine-tenths of these contrivances have been
invented during the 19th century, although the philosophical principles
of the operation of most of them had been previously discovered.
The important epochs in the invention of pumps, ending with the 18th
century, were thus the single-acting pump of Ctesibius, 225 B. C., the
double-acting of La Hire in 1718, the hydraulic ram of Whitehurst, 1772,
and the hydraulic press of Bramah of 1795-1802.
Bramah’s press illustrates how the theories of one age often lie
dormant, but if true become the practices of a succeeding age. Pascal,
150 years before Bramah’s time, had written this seeming hydraulic
paradox: “If a vessel closed on all sides has two openings, the one a
hundred times as large as the other, and if each be supplied with a
piston which fits it exactly, then a man pushing the small piston will
equilibrate that of 100 men pushing the piston which is 100 times as
large, and will overcome the other 99.” This is the law of the hydraulic
press, that intensity of pressure is everywhere the same.
The next important epoch was the invention of Forneyron in 1823, of the
water-wheel known as the Turbine and also as the Vortex Wheel. If we
will return a moment to the little steam engine of the ancient Hero of
Alexandria, called the Eolipile, it will be remembered that the steam
admitted into a pivoted vessel and out of it through little opposite
pipes, having bent exits turned in contrary directions, caused the
vessel to rotate by reason of the reaction of the steam against the
pipes. In what is called Barker’s mill, brought out in the 18th century,
substantially the same form of engine is seen with water substituted for
the steam.
A turbine is a wheel usually placed horizontally to the water. The wheel
is provided with curved internal buckets against which the water is led
by outer curved passages, the guides and the buckets both curved in such
manner that the water shall enter the wheel as nearly as possible
without shock, and leave it with the least possible velocity, thereby
utilising the greatest possible amount of energy.
In the chapter on Electrical inventions reference is made to the mighty
power of Niagara used to actuate a great number of electrical and other
machines of vast power. This utilisation had long been the dream of
engineers. Sir William Siemens had said that the power of all the coal
raised in the world would barely represent the power of Niagara. The
dream has been realised, and the turbine is the apparatus through which
the power of the harnessed giant is transmitted. A canal is dug from the
river a mile above the falls. It conducts water to a power house near
the falls. At the power house the canal is furnished with a gate, and
with cribs to keep back the obstructions, such as sticks. At the gate is
placed a vertical iron tube called a penstock, 7½ feet in diameter
and 160 feet deep. At the bottom of the penstock is placed a turbine
wheel fixed on a shaft, and to which shaft is connected an electric
generator or other power machine. On opening the gate a mass of water
7½ feet in diameter falls upon the turbine wheel 160 feet below. The
water rushing through the wheel turns it and its shaft many hundred
revolutions a minute. All the machinery is of enormous power and
dimensions. One electric generator there is 11 feet 7 inches in diameter
and spins around at the rate of 250 revolutions a minute. Means are
provided by which the speed of each wheel is regulated automatically.
Each turbine in a penstock represents the power of 5,000 horses, and
there are now ten or more employed.
After the water has done its work on the wheels it falls into a tunnel
and is carried back to the river below the falls. Not only are the
manufactures of various kinds of a large town at the falls thus supplied
with power, but electric power is transmitted to distant towns and
cities.
Turbine pumps of the Forneyron type have an outward flow; but another
form, invented also by a Frenchman, Jonval, has a downward discharge,
and others are oblique, double, combined turbine, rotary, and
centrifugal, embodying similar principles. The term _rotary_, broadly
speaking, includes turbine and centrifugal pumps. The centrifugal pump,
invented by Euler in 1754, was taken up in the nineteenth century and
greatly improved.
In the centrifugal pump of the ordinary form the water is received at
the centre of the wheel and diverted and carried out in an upward
direction, but in most of its modern forms derived from the turbine, the
principle is adopted of so shaping the vanes that the water, striking
them in the curved direction, shall not have its line of curvature
suddenly changed.
Among modern inventions of this class of pumps was the “Massachusetts”
of 1818 and McCarty’s, in 1830, of America, that of some contemporary
French engineers, and subsequently in France the Appold system, which
latter was brought into prominent notice at the London Exposition of
1851. Improvements of great value were also made by Prof. James Thompson
of England.
Centrifugal pumps have been used with great success in lifting large
bodies of water to a moderate height, and for draining marshes and other
low lands.
Holland, Germany, France, England and America have, through some of
their ablest hydraulic engineers and inventors, produced most remarkable
results in these various forms of pumps. We have noted what has been
done at Niagara with the turbines; and the drainage of the marshes of
Italy, the lowlands of Holland, the fens of England and the swamps of
Florida bear evidence of the value of kindred inventions.
That modern form of pump known as the _injector_, has many uses in the
arts and manufactures. One of its most useful functions is to
automatically supply steam boilers with water, and regulate the supply.
It was the invention of Giffard, patented in England in 1858, and
consists of a steam pipe leading from the boiler and having its nozzle
projecting into an annular space which communicates with a feed pipe
from a water supply. A jet of steam is discharged with force into this
space, producing a vacuum, into which the water from the feed pipe
rushes, and the condensed steam and water are driven by the momentum of
the jet into a pipe leading into the boiler. This exceedingly useful
apparatus has been improved and universally used wherever steam boilers
are found. This idea of injecting a stream of steam or water to create
or increase the flow of another stream has been applied in
_intensifiers_, to increase the pressure of water in hydraulic mains,
pipes, and machines, by additional pressure energy. Thus the water from
an ordinary main may be given such an increased pressure that a jet from
a hydrant may be carried to the tops of high houses.
In connection with pumping it may be said that a great deal has been
discovered and invented during this century concerning the force and
utilisation of jets of water and the force of water flowing through
orifices. In the art of mining, a new system called _hydraulicising_ has
been introduced, by which jets of water at high pressure have been
directed against banks and hills, which have crumbled, been washed away,
and made to reveal any precious ore they have concealed.
To assist this operation _flexible nozzles_ have been invented which
permit the stream to be easily turned in any desired direction.
Returning to the idea of raising weights by hydraulic pressure, mention
must be made of the recent invention of the _hydraulic jack_, a portable
machine for raising loads, and which has displaced the older and less
efficient screw jack. As an example of the practical utility of the
hydraulic jack, about a half century ago it required the aid of 480 men
working at capstans to raise the Luxor Obelisk in Paris, whilst within
30 years thereafter Cleopatra’s Needle, a heavier monument, was raised
to its present position on the Thames embankment by four men each
working one hydraulic jack.
By the high pressures, or stresses given by the hydraulic press it was
learned that cold metals have plasticity and can be moulded or stretched
like other plastic bodies. Thus in one modification a machine is had for
making lead pipes:--A “container” is filled with molten lead and then
allowed to cool. The container is then forced by the pump against an
elongated die of the size of the pipe required. A pressure from one to
two tons per square inch is exerted, the lead is forced up through the
die, and the pipe comes out completed. Wrought iron and cold steel can
be forced like wax into different forms, and a rod of steel may be drawn
through a die to form a piano wire.
By another modification of the hydraulic press pipes and cables are
covered with a coating of lead to prevent deterioration from rust and
other causes.
Not only are cotton and other bulky materials pressed into small compass
by hydraulic machines, but very valuable oils are pressed from cotton
seed and from other materials--the seed being first softened, then made
into cakes, and the cakes pressed.
If it is desired to line tunnels or other channels with a metal lining,
shield or casing, large segments of iron to compose the casing are put
in position, and as fast as the tunnel is excavated the casing is
pressed forward, and when the digging is done the cast-iron tunnel is
complete.
If the iron hoops on great casks are to be tightened the cask is set on
the plate of a hydraulic press, the hoops connected to a series of steel
arms projecting from an overhanging support, and the cask is pressed
upward until the proper degree of tightness is secured.
In the application of hydraulic power to machine tools great advances
have been made. It has become a system, in which Tweddle of England was
a pioneer. The great force of water pressure combined with comparatively
slow motion constitutes the basis of the system. Sir William Fairbairn
had done with steam what Tweddle and others accomplished with water.
Thus the enormous force of men and the fearful clatter formerly
displayed in these huge works where the riveting of boilers was carried
on can now be dispensed with, and in place of the noisy hammer with its
ceaseless blows has come the steam or the hydraulic riveting machine,
which noiselessly drives the rivet through any thickness of metal,
clinches the same, and smooths the jointed plate. The forging and the
rolling of the plates are performed by the same means.
William George Armstrong of England, afterward Sir William, first a
lawyer, but with the strongest bearing toward mechanical subjects,
performed a great work in the advancement of hydraulic engineering. It
is claimed that he did for hydraulic machinery, in the storage and
transmission of power thereby, what Watt did for the steam engine and
Bessemer did for steel. In 1838 he produced his first invention, an
important improvement in the hydraulic engine. In 1840, in a letter to
the _Mechanics’ Magazine_, he calls attention to the advantages of water
as a mechanical agent and a reservoir of power, and showed how water
pumped to an elevated reservoir by a steam engine might have the
potential energy thus stored utilised in many advantageous ways. How,
for instance, a small engine pumping continuously could thus supply many
large engines working intermittently. In illustration of this idea he
invented a crane, which was erected on Newcastle quay in 1846; another
was constructed on the Albert dock at Liverpool, and others at other
places. These cranes, adapted for the lifting and carrying of enormous
loads, were worked by hydraulic pressure obtained from elevated tanks or
reservoirs, as above indicated. But as a substitute for such tanks or
reservoirs he invented the _Accumulator_. This consists of a large
cast-iron cylinder fitted with a plunger, which is made to work
water-tight therein by means of suitable packing. To this plunger is
attached a weighted case filled with one or many tons of metal or other
coarse material. Water is pumped into the cylinder until the plunger is
raised to its full height within the cylinder, when the supply of water
is cut off by the automatic operation of a valve. When the cranes or
other apparatus to be worked thereby are in operation, water is passed
from the cylinder through a small pipe which actuates the crane through
hydraulic pressure. This pressure of course depends upon the weight of
the plunger. Thus a pressure of from 500 to 1,000 pounds per square inch
may be obtained. The descending plunger maintains a constant pressure
upon the water, and the water is only pumped into the cylinder when it
is required to be filled. With sensitive accumulators of this character
hydraulic machinery is much used on board ships for steering them, and
for loading, discharging and storing cargoes.
_Water Pressure Engines_ or _Water Motors_ of a great variety as to
useful details have been invented to take advantage of a natural head of
water from falls wherever it exists, or from artificial accumulators or
from street mains. They resemble steam engines, in that the water under
pressure drives a piston in a cylinder somewhat in the manner of steam.
The underlying principle of this class of machinery is the admission of
water under pressure to a cylinder which moves the piston and is allowed
to escape on the completion of the stroke. They are divided into two
great classes, single and double acting engines, accordingly as the
water is admitted to one side of the piston only, or to both sides
alternately. Both kinds are provided with a regulator in the form of a
turn-cock, weight, or spring valve to regulate and control the flow of
water and to make it continuous. They are used for furnishing a limited
amount of power for working small printing presses, dental engines,
organs, sewing machines, and for many other purposes where a light motor
is desired.
The nineteenth century has seen a revolution in _baths_ and accompanying
_closets_. However useful, luxurious, and magnificent may have been the
patrician baths of ancient Rome, that system, which modern investigators
have found to be so complete to a certain extent, was not nor ever has
been in the possession of the poor. It is within the memory of many now
living everywhere how wretched was the sanitary accommodations in every
populous place a generation or two ago. Now, with the modern water
distribution systems and cheap bathing apparatuses which can be brought
to the homes of all, with plunger, valved siphon and valved and washout
closets, air valve, liquid seal, pipe inlet, and valve seal traps, and
with the flushing and other hydraulic cleaning systems for drains and
cesspools, little excuse can be had for want of proper sanitary
regulations in any intelligent community. The result of the adoption of
these modern improvements in this direction on the health of the people
has been to banish plagues, curtail epidemics, and prolong for years the
average duration of human life.
How multiplied are the uses to which water is put, and how completely it
is being subjected to the use of man!
Rivers and pipes have their metres, so that now the velocity and volume
of rivers and streams are measured and controlled, and floods prevented.
The supplies for cities and for families are estimated, measured and
recorded as easily as are the supplies of illuminating gas, or the flow
of food from elevators.
Among the minor, but very useful inventions, are _water scoops_ for
picking up water for a train while in motion, consisting of a curved
open pipe on a car, the mouth of which strikes a current of water in an
open trough between the tracks and picks up and deposits in a minute a
car load of water for the engine. _Nozzles_ to emit jets of great
velocity, and ball nozzles terminating in a cup in which a ball is
loosely seated, and which has the effect, as it is lifted by the jet, to
spread it into an umbrella-shaped spray, are of great value at fires in
quenching flame and smoke.
Next to pure air to breathe we need pure water to drink, and modern
discoveries and inventions have done and are doing much to help us to
both. Pasteur and others have discovered and explained the germ theory
of disease and to what extent it is due to impure water. Inventors have
produced _filters_, and there is a large class of that character which
render the water pure as it enters the dwelling, and fit for all
domestic purposes. A specimen of the latter class is one which is
attached to the main service pipe as it enters from the street. The
water is first led into a cylinder stored with coarse filtering material
which clears the water of mud, sediment and coarser impurities, and then
is conducted into a second cylinder provided with a mass of fine grained
or powdered charcoal, or some other material which has the quality of
not only arresting all remaining injurious ingredients, but destroys
organisms, neutralises ammonia and other deleterious matter. From thence
the water is returned to the service pipe and distributed through the
house. The filter may be thoroughly cleansed by reversing the movement
of the water, and carrying it off through a drain pipe until it runs
clear and sweet, whereupon the water is turned in its normal course
through the filter and house.
In a very recent report of General J. M. Wilson, Chief of Engineers,
U.S.A., the subject of filtration of water, and especially of public
water supplies in England, the United States, and on the Continent, is
very thoroughly treated, and the conclusion arrived at there is that the
system termed “the American,” or mechanical system, is the most
successful one.
This consists, first, in leading the water into one or more reservoirs,
then coagulating suspended matter in the water by the use of the
sulphate of alumina, and then allowing the water to flow through a body
of coarse sand, by which the coagulated aluminated matter is caught and
held in the interstices of the sand, and the bacteria arrested. All
objectionable matter is thus arrested by the surface portion of the sand
body, which portion is from time to time scraped off, and the whole sand
mass occasionally washed out by upward currents of water forced through
the same.
By this system great rapidity of filtration is obtained, the rate being
120,000,000 gallons a day per acre.
The English system consists more in the use of extended and successive
reservoirs or beds of sand alone, or aided by the use of the sulphate.
This also is extensively used in many large cities.