This is employed in all dynamical engineering. It covers the designs
of prime motors of all sorts, steam, gas, and gasoline reciprocating
engines; also steam and water turbines, wind-mills, and wave-motors.
It comprises all means of transmitting power, as by shafting, ropes,
pneumatic pressure, and compressed air, all of which seem likely to be
superseded by electricity.
It covers the construction of machine tools and machinery of all kinds.
It enters into all the processes of structural, hydraulic, electrical,
and industrial engineering. The special improvements are: The almost
universal use of rotary motion, and of the reduplication of parts.
The steam-engine is a machine of reciprocating, converted into rotary,
motion by the crank. The progress of mechanical engineering during the
nineteenth century is measured by the improvements of the steam-engine,
principally in the direction of saving fuel, by the invention of
internal combustion or gas-engines, the application of electrical
transmission, and, latest, the practical development of steam turbines
by Parsons, Westinghouse, Delaval, Curtis, and others. In these a jet
of steam impinges upon buckets set upon the circumference of a wheel.
It was clearly indicated by the Italian engineer Bronca, in 1629,
but he was too early. The time was not ripe, and there were then no
machine tools giving the perfection of workmanship required.
Their advantages are that their motion is rotary and not reciprocal.
They can develop speed of from 5000 to 30,000 revolutions per minute,
while the highest ever attained by a reciprocating engine is not over
1000. Their thermodynamic losses are less, hence they consume less
steam and less fuel.
It is a very interesting fact that the basic invention upon which not
only steam turbines and electric dynamos, but, indeed, all other parts
of mechanical engineering, depend, is of such remote antiquity that we
know nothing of its origin. This is the wheel which Gladstone said was
the greatest of man’s mechanical inventions, as there is nothing in
nature to suggest it.
Duplication of parts has lowered the cost of all products. Clothing is
one of these. The parts of ready-made garments and shoes are now cut
into shape in numbers at a time, by sharp-edged templates, and then
fastened together by sewing-machines.
Mechanical engineering is a good example of the survival of the
fittest. Millions of dollars are expended on machinery, when suddenly
a new discovery or invention casts them all into the scrap heap, to be
replaced by those of greater earning capacity.
Prime motors derive their energy either from coal or other combinations
of carbon, such as petroleum, or from gravity. This may come from
falling water, and the old-fashioned water-wheels of the eighteenth
century were superseded in the nineteenth by turbines, first invented
in France and since greatly perfected. These are used in the electrical
transmission of water-power at Niagara of 5000 horse-power, and form a
very important part of the plant.
The other gravity motors are wind-mills and wave-motors. Wind-mills are
an old invention, but have been greatly improved in the United States
by the use of the self-reefing wheel. The great plains of the West are
subject to sudden, violent gales of wind, and unless the wheel was
automatically self-reefing it would often be destroyed. Little has been
written about these wheels, but their use is very widely extended, and
they perform a most useful function in industrial engineering.
There have been vast numbers of patents taken out for wave-motors. One
was invented in Chili, South America, which furnished a constant power
for four months, and was utilized in sawing planks. The action of waves
is more constant on the Pacific coast of America than elsewhere, and
some auxiliary power, such as a gasoline engine, which can be quickly
started and stopped, must be provided for use during calm days. The
prime cost of such a machine need not exceed that of a steam plant,
and the cost of operating is much less than that of any fuel-burning
engine. The saving of coal is a very important problem. In a wider
sense, we may say that the saving of all the great stores which nature
has laid up for us during the past, and which have remained almost
untouched until the nineteenth century, is _the_ great problem of
to-day.
Petroleum and natural gas may disappear. The ores of gold, silver, and
platinum will not last forever. Trees will grow, and iron ores seem
to be practically inexhaustible. Chemistry has added a new metal in
aluminum, which replaces copper for many purposes. One of the greatest
problems of the twentieth century is to discover some chemical process
for treating iron, by which oxidation will not take place.
Coal, next to grain, is the most important of nature’s gifts; it can
be exhausted, or the cost of mining it become so great that it cannot
be obtained in the countries where it is most needed; water, wind, and
wave power may take its place to a limited extent, and greater use may
be made of the waste gases coming from blast or smelter furnaces, but
as nearly all energy comes from coal, its use must be economized, and
the greatest economy will come from pulverizing coal and using it in
the shape of a fine powder. Inventions have been made trying to deliver
this powder into the fire-box as fast as made, for it is as explosive
as gunpowder, and as dangerous to store or handle. If this can be done,
there will be a saving of coal due to perfect and smokeless combustion,
as the admission of air can be entirely regulated, the same blast
which throws in the powder furnishing oxygen. Some investigators have
estimated that the saving of coal will be as great as twenty per cent.
This means 100,000,000 tons of coal annually.
Bituminous coal will then be as smokeless as anthracite, and can
be burned in locomotives. Cities will be free from the nuisance of
wasted coal, which we call soot. This process will be the best kind
of mechanical stoking, and will prevent the necessity of opening the
doors of fire-boxes. The boiler-rooms of steamships will no longer be
“floating hells,” and the firing of large locomotives will become easy.
Another problem of mechanical engineering is to determine whether it
will be found more economical to transform the energy of coal, at the
mines, into electric current and send it by wire to cities and other
places where it is wanted, or to carry the coal by rail and water, as
we now do, to such places, and convert it there by the steam or gas
engine.
In favor of the first method it can be said that hills of refuse coal
now representing locked-up capital can be burned, and the cost of
transportation and handling be saved. Electric energy can now transport
power in high voltage economically between coal-mines and most large
cities.
The second method has the advantage of not depending on one single
source of supply, that may break down, but in having the energy stored
in coal-pockets near by the place of use, where it can be applied to
separate units of power with no fear of failure.
It seems probable that a combination of the two systems will produce
the best results. Where power can be sent electrically from the mines
for less cost than the coal can be transported, that method will be
used.
To prevent stoppage of works, the separate motors and a store of coal,
to be used in cases of emergency, will still be needed, just as has
been described as necessary to the commercial success of wave-motors.