THE FLYING MACHINE
It is now time we turn our attention from the airship to its important
rival, the flying machine.
At first sight it may perhaps appear that so far the flying machine has
accomplished less than the airship, and gives less promise of success,
since up to the present time no flying machine has taken a man any
distance into the air, or indeed done much more than just lift itself
off the ground. Nevertheless those who have made a study of the matter
are full of hope for the future. Many experts declare that already the
limits of what can be done with the airship, which depends upon the
lifting power of its gas to raise it and to sustain it in the air,
are being reached. It has indeed been proved that on a calm day, or
with only a light breeze, this form of sky vessel can be steered safely
about the heavens, and doubtless as engines are constructed yet lighter
and more powerful in proportion to their weight, more successful
voyages still will be accomplished. But it is extremely doubtful
whether an airship can ever be constructed which shall be able to stand
against a gale of wind.
So long as a balloon sails only with the breeze it offers no resistance
to the force of the wind, and can be made of the lightest and thinnest
material. But directly it has to face the wind, and fight its way
against it as an airship must do, then it has to be made of sufficient
strength and rigidity to withstand the wind’s power, or it will be
blown to pieces. To make so large a thing as an airship withstand
a rough wind, it must be built of very strong and rigid materials.
To do this means to add to the weight of the machine. To lift the
increased weight, a larger machine which can hold more gas is needed.
The larger the machine the more surface it offers to the wind, and
the stronger therefore must be its construction. It will now be seen
that we are arguing in a circle, and we can understand that a point
must be reached in the making of airships when, with our present
materials, the advantage gained by increase of strength will be more
than counterbalanced by increased weight. On this point Sir Hiram Maxim
says: “It is not possible to make a balloon, strong enough to be driven
through the air at any considerable speed, at the same time light
enough to rise in the air; therefore balloons must always be at the
mercy of a wind no greater than that which prevails at least 300 days
in the year;” adding, “Those who seek to navigate the air by machines
lighter than air have, I think, come practically to the end of their
tether.”
With the flying machine, on the contrary, the same difficulty does
not arise. Since it is at all times heavier than air, and is kept
aloft simply by its motive power and mechanism, its weight is of no
consequence, provided only its engine is sufficiently powerful. It may,
therefore, be built as rigidly as need be, while, from its size--which
is much smaller in proportion to its lifting power than in the case of
the airship--and also from its construction, it is much less liable to
be affected by the wind.
In constructing a flying machine which is heavier than air the inventor
has before him two examples of bodies which, though heavier than the
atmosphere, yet contrive to rise upwards into the sky; these are,
firstly, birds, and secondly, the familiar schoolboy toys, kites. To
imitate the flying powers of birds and kites, he must first understand
the means by which their flight is accomplished; and he will find,
on examination, that to a large extent the same principle underlies
each--the principle of what is termed the “aeroplane.”
[Illustration: KESTREL.]
As we watch birds--especially large birds, as hawks and gulls--winging
their way about the sky, we may notice that their flight is
accomplished in two ways; either they are moving through the air by
flapping their wings up and down, or else with wings wide outstretched
they are soaring or sailing in the air for long times together
without apparently moving their wings at all. Certain birds, such as
vultures and albatrosses, possess this power of soaring flight to an
extraordinary degree, and the exact way in which they keep themselves
poised aloft is indeed still a mystery. We cannot, however, as we
watch, say, a hawk, hovering in the air with motionless wing, help
being struck by its resemblance to the schoolboy’s kite, kept afloat
high in the sky by the action of the wind properly applied to its
surface, and we can at once see that the bird makes use of the same
principle as the kite in its soaring or hovering flight. Indeed, just
as a kite sinks to earth when the wind drops, so in a dead calm even an
albatross has to flap its wings to keep afloat.
It is to the principle of the kite, therefore, that the inventor of
the flying machine must turn. He must adapt the same principle to his
apparatus, and this he does in his aeroplane, which, as will be seen,
is an all-important part of his machine, and which, in its simplest
form, is nothing more or less than a kite.
We know that if a light flat body, such as a kite, is lying upon the
ground, and the wind gets under it so as to tilt it, it will be lifted
by the wind into the air. The string of a kite is so adjusted that as
the kite rises it is still held at an angle to the wind’s force, and so
long as the kite remains tilted at the necessary angle so long it will
continue to rise or poise itself in the air while the wind blows. When
schoolboys fly their kites they choose an exposed spot, and a day when
the wind is blowing freshly and steadily. One boy throws the kite into
the air, while another, holding the string to which it is fastened,
draws it tight by running with it against the wind. By this means the
kite, if rightly adjusted, is held at the proper angle to the wind, and
started without dragging along the ground to begin with. As soon as the
wind has fairly caught the kite and carried it up into the air, the boy
who holds the string need run no longer, but if the breeze suddenly
fails, and the kite begins to drop, he may still keep his toy aloft by
running quickly along and dragging the kite after him; the artificial
wind he thus creates making up for the lack of the other.
Now let us suppose that there is no string to hold the kite in proper
position, and no boy to run with it; but that their places are supplied
by a motor and propeller to drive it through the air; while at the same
time it is so balanced as to preserve a fitting angle against a wind of
its own making. We should then have a true flying machine, heavier than
air, and yet capable of sailing through the sky.
This is the kind of flying machine that inventors at the present moment
are trying to produce. They have, in their machines, to reproduce
artificially two essential conditions that cause a kite to fly. They
have to provide a substitute for the strength of the wind, and also a
substitute for the pull of the string which keeps the kite at the best
angle to profit by that strength. The first they achieve by using a
suitable engine or motor, and the second by supplying it with what are
called “aeroplanes”--large flat surfaces, light but rigid, inclined at
a suitable angle to the horizon. By the use of these the power of the
engine is employed to best advantage in causing the machine to sail
through the sky.
The great advantage of the aeroplane over any other mode of flying
is thus described by Major Baden-Powell, one of our greatest living
authorities on aeronautical matters: “When people realise that in the
case of the aeroplane a contrivance like the awning of a small steam
launch is capable of supporting the man and the engines, and that in
the case of the balloon a mass like a big ship is necessary to lift
the same weight, one can readily understand the advantages of the
aeroplane, especially when to the drawbacks of the bulky balloon are
added the great difficulties inherent in the retention of a large
volume of expensive, inflammable, and subtle gas, ever varying in its
density.”
The most successful inventors of flying machines at the present day
are all Americans, though one of them has made his experiments on this
side of the Atlantic. They are Sir Hiram Maxim, inventor of the famous
gun, and one of the greatest mechanicians living; Professor Langley,
Secretary of the Smithsonian Institute, Washington; and the brothers
Wright.
Mr. Maxim, as he then was, commenced his experiments in the early
nineties. As we have already shown, he went to Nature for his guide,
and in constructing his flying machine took as his analogy the flight
of birds. Birds urge their way onwards in the air by reason of the
strength of their wings. A flying machine must do the same by the power
of its engine; and as a bird’s wings must be strong in proportion to
the bird’s weight, so the strength or horse-power of the engine must
stand in a certain proportion to the number of pounds it weighs. Mr.
Maxim’s first task, therefore, was to discover what proportion this
must be, and by his experiments he arrived at a conclusion which
Professor Langley in America, working at the same task at the same
time, but quite independently, had also proved to be true, namely,
that the faster a machine travels through the air the greater weight
it may carry; or, in other words, the quicker a body moves through
the atmosphere the less tendency will it have to fall to the ground.
A quick-flying bird like an albatross, therefore, flies with less
exertion, and so could carry a greater weight, than a slow-moving bird
like a goose. It must therefore be to the advantage of the flying
machine that its engines should attain as great a speed as possible.
Maxim’s next task was to construct a suitable engine. Light but
powerful engines had not then reached the pitch of perfection they have
now, and his results proved at the time a perfect revelation of what
could be done in this direction, and led to great advances being made.
[Illustration: THE MAXIM AIRSHIP.]
Next came the designing of the great machine itself. It was an enormous
apparatus, weighing over three tons, capable of carrying three men, and
supported by no less than 4000 square feet of aeroplanes, placed one
above the other. Its steam-engine was of 363 horse-power, and worked
two screws of nearly 18 feet in diameter. Before such a machine could
rise from the ground it must first have attained a very great forward
impetus, and this it was to receive by running at a great speed on
wheels along a railway track specially laid down for it. To prevent the
apparatus rising unduly, a reversed rail was erected a short distance
above, on which the machine would begin to run as soon as it lifted
itself off the lower track. Along this railway the flying machine was
tested, and it was found that as soon as a speed of thirty-six miles
an hour was reached the wheels were lifted clear off the ground, and
were running only upon the upper rail. On the last occasion a speed of
forty-two miles an hour was attained, when the lifting power became so
great that the restraining rail broke away altogether, and the great
flying machine actually floated in the air for a few moments, “giving
those on board the sensation of being in a boat,” until, steam being
shut off, it fell to the ground and was broken.
The enormous expense of his experiments has not prevented Sir Hiram
Maxim from repeating them, and he hopes soon to have a much improved
machine. Nevertheless his experience and calculations have been of
great value to those who would follow in his footsteps, and have proved
the possibility of constructing a flying machine which shall fly by
virtue of its own motion.
Meanwhile in America Professor Langley was experimenting,
independently, almost on the same lines. He also was bent on producing
a flying machine, but instead of starting to work upon a large
apparatus like Maxim, he began by making models, and gradually worked
his way up to bigger things. For many months he studied to understand
the principle of those ingenious little toys sometimes seen, which, by
means of the tension of a twisted india-rubber band, will keep afloat
in the air for a few seconds. Next he constructed small models driven
by steam, in which he found his great difficulty was in keeping down
the weight. For years he persevered in his work without any great
success, until in 1896 he produced a model machine which he called
an “aerodrome.” It was quite small, weighing with its engine only 25
lbs., and measuring but 14 feet from tip to tip of its aeroplanes.
The experiments were made over water, and the necessary momentum was
given by dropping it from a platform 20 feet high. On more than one
occasion this little flying machine rose with great steadiness in the
face of the wind to a height of 100 feet, moving so smoothly that it
might have carried a glass of water without spilling a drop; and then,
the steam of its engine being exhausted, sank down gracefully upon the
water, having flown about half a mile in a minute and a half. This
success encouraged Professor Langley next to construct a full-sized
flying machine on the same lines; but this on its first voyage plunged
headlong into the water and was hopelessly damaged. The United States
Government have since granted him a sum of money to continue his
experiments.
Latest of all the airship inventors, and perhaps so far the most
successful, are the brothers Wright. Up to the date of writing this the
full details of their work are not yet made public, but it is known
that on the 17th of December 1903, their machine, which consists of two
large aeroplanes driven forward by an engine of sixteen horse-power,
after being started along a short track on level ground, rose into the
air and flew for about half a mile.
It remains for us now to make brief mention of how men have tried,
and are still trying, to imitate the soaring or gliding flight of
birds without the use of machinery to assist them. We have seen how an
albatross can, when the wind is blowing, convert itself, as it were,
into a kite, and keep aloft in the air for a while without moving its
wings. Similarly many people have attempted, by attaching themselves
to a large supporting surface or aeroplane, and casting themselves off
from a height, to glide with the wind across wide stretches of country.
In this mode of soaring flight some have made considerable progress.
Herr Lilienthal, a German, was perhaps for a time the most successful.
He started from small beginnings, jumping off a spring board a few feet
high, and gradually increasing the height as he became more accustomed
to his apparatus. Later he had a large artificial mound made specially
for him, and from the top of this he would throw himself into the
air, and with a favourable wind sail a distance of four hundred yards
at a considerable height above the ground. Lilienthal’s experiments,
however, came to a sad end. On August the 11th, 1896, after he had
glided along in the air for about two hundred yards, a sudden gust
of wind caught the wide-spread wings of his apparatus, and tilted it
upwards. This caused him to lose his balance, and he fell from a height
of sixty feet and broke his spine. A similar accident also caused the
death, a few years later, of a young Englishman, Mr. Percy S. Pilcher,
who had been following up Lilienthal’s experiments.
The greatest difficulty now to be overcome in solving the problem of
human flight, whether with soaring apparatus or flying machine, may be
summed up in one word--“balance.” Every schoolboy knows that the great
art of kite-flying consists in so adjusting the point of attachment
of the string and the length of the tail that his kite is properly
balanced, and is not liable to turn over or “dip” when in the air.
Every observer of birds, too, has noticed how largely the question of
balance enters into their flying. A bird in the air is continually and
instinctively adjusting its wings to its position, and to every puff of
wind, even as a man on a bicycle is continually, though unconsciously,
adjusting his handle-bar to the inequalities of the road; and as a
cyclist requires practice before he can ride his machine, or a skater
before he can keep his feet on the ice, so even a bird has to learn how
to balance itself before it can use its wings.
Dwellers in the country are familiar with the way in which the parent
birds teach their fledglings to fly, instructing them by example,
and encouraging them in their first short flights until they have
become familiar with their powers and can balance themselves aright
in the air. And if even birds, with whom flying is an instinct, have
to learn the art of balancing themselves in the air by practice, how
much more so must such a clumsy creature as a man, to whom flying is
entirely unnatural. Only by long and painful efforts can he ever hope
to succeed at all, and unfortunately all such efforts are necessarily
very dangerous. Many disastrous accidents have already occurred, and
although great progress has been made, and the time may not now be far
distant when, by means of improved machines, men will actually fly, it
will be at the cost of much labour, and, it is to be feared, at the
sacrifice of many more brave lives.