PECULIARITIES OF AIRSHIP POWER.
As a general proposition it takes much more power to
propel an airship a given number of miles in a certain
time than it does an automobile carrying a far heavier
load. Automobiles with a gross load of 4,000 pounds,
and equipped with engines of 30 horsepower, have travelled
considerable distances at the rate of 50 miles an
hour. This is an equivalent of about 134 pounds per
horsepower. For an average moder
with a total load, machine and passengers, of 1,200
pounds, and equipped with a 50-horsepower engine, 50
miles an hour is the maximum. Here we have the equivalent
of exactly 24 pounds per horsepower. Why this
great difference?
No less an authority than Mr. Octave Chanute answers
the question in a plain, easily understood manner. He
says:
"In the case of an automobile the ground furnishes a
stable support; in the case of a flying machine the engine
must furnish the support and also velocity by which the
apparatus is sustained in the air."
Pressure of the Wind.
Air pressure is a big factor in the matter of aeroplane
horsepower. Allowing that a dead calm exists, a body
moving in the atmosphere creates more or less resistance.
The faster it moves, the greater is this resistance.
Moving at the rate of 60 miles an hour the resistance,
or wind pressure, is approximately 50 pounds to the
square foot of surface presented. If the moving object
is advancing at a right angle to the wind the following
table will give the horsepower effect of the resistance
per square foot of surface at various speeds.
Horse Power
Miles per Hour per sq. foot
10 0.013
15 0 044
20 0.105
25 0.205
30 0.354
40 0.84
50 1.64
60 2.83
80 6.72
100 13.12
While the pressure per square foot at 60 miles an hour,
is only 1.64 horsepower, at 100 miles, less than double
the speed, it has increased to 13.12 horsepower, or exactly
eight times as much. In other words the pressure
of the wind increases with the square of the velocity.
Wind at 10 miles an hour has four times more pressure
than wind at 5 miles an hour.
How to Determine Upon Power.
This element of air resistance must be taken into consideration
in determining the engine horsepower required.
When the machine is under headway sufficient
to raise it from the ground (about 20 miles an hour),
each square foot of surface resistance, will require nearly
nine-tenths of a horsepower to overcome the wind pressure,
and propel the machine through the air. As
shown in the table the ratio of power required increases
rapidly as the speed increases until at 60 miles an hour
approximately 3 horsepower is needed.
In a machine like the Curtiss the area of wind-exposed
surface is about 15 square feet. On the basis of this
resistance moving the machine at 40 miles an hour would
require 12 horsepower. This computation covers only
the machine's power to overcome resistance. It does
not cover the power exerted in propelling the machine
forward after the air pressure is overcome. To meet
this important requirement Mr. Curtiss finds it necessary
to use a 50-horsepower engine. Of this power, as
has been already stated, 12 horsepower is consumed
in meeting the wind pressure, leaving 38 horsepower
for the purpose of making progress.
The flying machine must move faster than the air to
which it is opposed. Unless it does this there can be no
direct progress. If the two forces are equal there is no
straight-ahead advancement. Take, for sake of illustration,
a case in which an aeroplane, which has developed a
speed of 30 miles an hour, meets a wind velocity of
equal force moving in an opposite direction. What is
the result? There can be no advance because it is a
contest between two evenly matched forces. The aeroplane
stands still. The only way to get out of the difficulty
is for the operator to wait for more favorable conditions,
or bring his machine to the ground in the usual
manner by manipulation of the control system.
Take another case. An aeroplane, capable of making
50 miles an hour in a calm, is met by a head wind of 25
miles an hour. How much progress does the aeroplane
make? Obviously it is 25 miles an hour over the ground.
Put the proposition in still another way. If the wind
is blowing harder than it is possible for the engine power
to overcome, the machine will be forced backward.
Wind Pressure a Necessity.
While all this is true, the fact remains that wind
pressure, up to a certain stage, is an absolute necessity
in aerial navigation. The atmosphere itself has very
little real supporting power, especially if inactive. If
a body heavier than air is to remain afloat it must move
rapidly while in suspension.
One of the best illustrations of this is to be found in
skating over thin ice. Every school boy knows that if
he moves with speed he may skate or glide in safety
across a thin sheet of ice that would not begin to bear
his weight if he were standing still. Exactly the same
proposition obtains in the case of the flying machine.
The non-technical reason why the support of the machine
becomes easier as the speed increases is that the
sustaining power of the atmosphere increases with the
resistance, and the speed with which the object is moving
increases this resistance. With a velocity of 12 miles
an hour the weight of the machine is practically reduced
by 230 pounds. Thus, if under a condition of absolute
calm it were possible to sustain a weight of 770 pounds,
the same atmosphere would sustain a weight of 1,000
pounds moving at a speed of 12 miles an hour. This
sustaining power increases rapidly as the speed increases.
While at 12 miles the sustaining power is figured at
230 pounds, at 24 miles it is four times as great, or 920
pounds.
Supporting Area of Birds.
One of the things which all producing aviators seek
to copy is the motive power of birds, particularly in their
relation to the area of support. Close investigation has
established the fact that the larger the bird the less is
the relative area of support required to secure a given
result. This is shown in the following table:
Supporting
Weight Surface Horse area
Bird in lbs. in sq. feet power per lb.
Pigeon 1.00 0.7 0.012 0.7
Wild Goose 9.00 2.65 0.026 0.2833
Buzzard 5.00 5.03 0.015 1.06
Condor 17.00 9.85 0.043 0.57
So far as known the condor is the largest of modern
birds. It has a wing stretch of 10 feet from tip to tip, a
supporting area of about 10 square feet, and weighs 17
pounds. It. is capable of exerting perhaps 1-30 horsepower.
(These figures are, of course, approximate.)
Comparing the condor with the buzzard with a wing
stretch of 6 feet, supporting area of 5 square feet, and a
little over 1-100 horsepower, it may be seen that, broadly
speaking, the larger the bird the less surface area (relatively)
is needed for its support in the air.
Comparison With Aeroplanes.
If we compare the bird figures with those made possible
by the development of the aeroplane it will be
readily seen that man has made a wonderful advance in
imitating the results produced by nature. Here are the
figures:
Supporting
Weight Surface Horse area
Machine in lbs. in sq. feet power per lb.
Santos-Dumont . . 350 110.00 30 0.314
Bleriot . . . . . 700 150.00 25 0.214
Antoinette. . . . 1,200 538.00 50 0.448
Curtiss . . . . . 700 258.00 60 0.368
Wright. . . . .[4]1,100 538.00 25 0.489
Farman. . . . . . 1,200 430.00 50 0.358
Voisin. . . . . . 1,200 538.00 50 0.448
[4] The Wrights' new machine weighs only 900 pounds.
While the average supporting surface is in favor of
the aeroplane, this is more than overbalanced by the
greater amount of horsepower required for the weight
lifted. The average supporting surface in birds is about
three-quarters of a square foot per pound. In the average
aeroplane it is about one-half square foot per pound.
On the other hand the average aeroplane has a lifting
capacity of 24 pounds per horsepower, while the buzzard,
for instance, lifts 5 pounds with 15-100 of a horsepower.
If the Wright machine--which has a lifting power of 50
pounds per horsepower--should be alone considered the
showing would be much more favorable to the aeroplane,
but it would not be a fair comparison.
More Surface, Less Power.
Broadly speaking, the larger the supporting area the
less will be the power required. Wright, by the use of
538 square feet of supporting surface, gets along with an
engine of 25 horsepower. Curtiss, who uses only 258
square feet of surface, finds an engine of 50 horsepower
is needed. Other things, such as frame, etc., being equal,
it stands to reason that a reduction in the area of
supporting surface will correspondingly reduce the weight
of the machine. Thus we have the Curtiss machine with
its 258 square feet of surface, weighing only 600 pounds
(without operator), but requiring double the horsepower
of the Wright machine with 538 square feet of surface
and weighing 1,100 pounds. This demonstrates in a
forceful way the proposition that the larger the surface
the less power will be needed.
But there is a limit, on account of its bulk and
awkwardness in handling, beyond which the surface area
cannot be enlarged. Otherwise it might be possible to
equip and operate aeroplanes satisfactorily with engines
of 15 horsepower, or even less.
The Fuel Consumption Problem.
Fuel consumption is a prime factor in the production
of engine power. The veriest mechanical tyro knows in
a general way that the more power is secured the more
fuel must be consumed, allowing that there is no difference
in the power-producing qualities of the material
used. But few of us understand just what the ratio of
increase is, or how it is caused. This proposition is one
of keen interest in connection with aviation.
Let us cite a problem which will illustrate the point
quoted: Allowing that it takes a given amount of gasolene
to propel a flying machine a given distance, half the
way with the wind, and half against it, the wind blowing
at one-half the speed of the machine, what will be
the increase in fuel consumption?
Increase of Thirty Per Cent.
On the face of it there would seem to be no call for
an increase as the resistance met when going against the
wind is apparently offset by the propulsive force of the
wind when the machine is travelling with it. This, however,
is called faulty reasoning. The increase in fuel
consumption, as figured by Mr. F. W. Lanchester, of the
Royal Society of Arts, will be fully 30 per cent over
the amount required for a similar operation of the machine
in still air. If the journey should be made at right
angles to the wind under the same conditions the increase
would be 15 per cent.
In other words Mr. Lanchester maintains that the work
done by the motor in making headway against the wind
for a certain distance calls for more engine energy, and
consequently more fuel by 30 per cent, than is saved by
the helping force of the wind on the return journey.
More
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ABOUT WIND CURRENTS
One of the first difficulties which the novice will encounter is the uncertainty of the wind currents. With a low velocity the wind, some distance away from the ground, is ordinarily steady. As the velocity increases, however, the wind generally be... AMATEURS MAY USE WRIGHT PATENTS.
Owing to the fact that the Wright brothers have enjoined a number of professional aviators from using their system of control, amateurs have been slow to adopt it. They recognize its merits, and would like to use the system, but have been apprehens... CONSTRUCTING A GLIDING MACHINE.
First decide upon the kind of a machine you want-- monoplane, biplane, or triplane. For a novice the biplane will, as a rule, be found the most satisfactory as it is more compact and therefore the more easily handled. This will be easily understood... DEMAND FOR FLYING MACHINES.
As a commercial proposition the manufacture and sale of motor-equipped aeroplanes is making much more rapid advance than at first obtained in the similar handling of the automobile. Great, and even phenomenal, as was the commercial development of t... EVOLUTION OF TWOSURFACE FLYING MACHINE.
By Octave Chanute. I am asked to set forth the development of the "two- surface" type of flying machine which is now used with modifications by Wright Brothers, Farman, [1]Delagrange, Herring and others. [1] Now dead. This type origin... FLYING MACHINES VS. BALLOONS.
While wonderful success has attended the development of the dirigible (steerable) balloon the most ardent advocates of this form of aerial navigation admit that it has serious drawbacks. Some of these may be described as follows: Expense and Oth... HINTS ON PROPELLER CONSTRUCTION.
Every professional aviator has his own ideas as to the design of the propeller, one of the most important features of flying-machine construction. While in many instances the propeller, at a casual glance, may appear to be identical, close inspecti... HOW TO USE THE MACHINE.
It is a mistaken idea that flying machines must be operated at extreme altitudes. True, under the impetus of handsome prizes, and the incentive to advance scientific knowledge, professional aviators have ascended to considerable heights, flights at... LAW OF THE AIRSHIP.
Successful aviation has evoked some peculiar things in the way of legal action and interpretation of the law. It is well understood that a man's property cannot be used without his consent. This is an old established principle in common law which... LEARNING TO FLY.
Don't be too ambitious at the start. Go slow, and avoid unnecessary risks. At its best there is an element of danger in aviation which cannot be entirely eliminated, but it may be greatly reduced and minimized by the use of common sense. Theoret... MECHANICAL BIRD ACTION
In order to understand the theory of the modern flying machine one must also understand bird action and wind action. In this connection the following simple experiment will be of interest: Take a circular-shaped bit of cardboard, like the lid of ... MONOPLANES, TRIPLANES, MULTIPLANES.
Until recently, American aviators had not given serious attention to any form of flying machines aside from biplanes. Of the twenty-one monoplanes competing at the International meet at Belmont Park, N. Y., in November, 1910, only three makes were ... NEW MOTORS AND DEVICES.
Since the first edition of this book was printed, early in 1910, there has been a remarkable advance in the construction of aeroplane motors, which has resulted in a wonderful decrease in the amount of surface area from that formerly required. Mark... PECULIARITIES OF AIRSHIP POWER.
As a general proposition it takes much more power to propel an airship a given number of miles in a certain time than it does an automobile carrying a far heavier load. Automobiles with a gross load of 4,000 pounds, and equipped with engines of 30 ... PLANE AND RUDDER CONTROL.
Having constructed and equipped your machine, the next thing is to decide upon the method of controlling the various rudders and auxiliary planes by which the direction and equilibrium and ascending and descending of the machine are governed. Th... PREFACE.
This book is written for the guidance of the novice in aviation--the man who seeks practical information as to the theory, construction and operation of the modern flying machine. With this object in view the wording is intentionally plain and non-... PROBLEMS OF AERIAL FLIGHT.
In a lecture before the Royal Society of Arts, reported in Engineering, F. W. Lanchester took the position that practical flight was not the abstract question which some apparently considered it to be, but a problem in locomotive engineering. The f... PROPER DIMENSIONS OF MACHINES.
In laying out plans for a flying machine the first thing to decide upon is the size of the plane surfaces. The proportions of these must be based upon the load to be carried. This includes the total weight of the machine and equipment, and also the... PUTTING ON THE RUDDER.
Gliders as a rule have only one rudder, and this is in the rear. It tends to keep the apparatus with its head to the wind. Unlike the rudder on a boat it is fixed and immovable. The real motor-propelled flying machine, generally has both front and ... RADICAL CHANGES BEING MADE.
Changes, many of them extremely radical in their nature, are continually being made by prominent aviators, and particularly those who have won the greatest amount of success. Wonderful as the results have been few of the aviators are really satisfi... SELECTION OF THE MOTOR.
Motors for flying machines must be light in weight, of great strength, productive of extreme speed, and positively dependable in action. It matters little as to the particular form, or whether air or water cooled, so long as the four features named... SOARING FLIGHT.
By Octave Chanute. [5]There is a wonderful performance daily exhibited in southern climes and occasionally seen in northerly latitudes in summer, which has never been thoroughly explained. It is the soaring or sailing flight of certain varieties... SOME OF THE NEW DESIGNS.
Spurred on by the success attained by the more experienced and better known aviators numerous inventors of lesser fame are almost daily producing practical flying machines varying radically in construction from those now in general use. One of t... THE ELEMENT OF DANGER.
That there is an element of danger in aviation is undeniable, but it is nowhere so great as the public imagines. Men are killed and injured in the operation of flying machines just as they are killed and injured in the operation of railways. Consid... THE REAL FLYING MACHINE.
We will now assume that you have become proficient enough to warrant an attempt at the construction of a real flying machine--one that will not only remain suspended in the air at the will of the operator, but make respectable progress in whatever ... THEORY, DEVELOPMENT, AND USE.
While every craft that navigates the air is an airship, all airships are not flying machines. The balloon, for instance, is an airship, but it is not what is known among aviators as a flying machine. This latter term is properly used only in refe... VARIOUS FORMS OF FLYING MACHINES.
There are three distinct and radically different forms of flying machines. These are: Aeroplanes, helicopters and ornithopers. Of these the aeroplane takes precedence and is used almost exclusively by successful aviators, the helicopters and o...