aeroplanes-第13章
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feet of surface; which would make each 5' by 30'
in size; or; it may be decided to make the planes
narrower; and proportionally longer。 This is immaterial。
The shorter the planes transversely;
the greater will be the stability; and the wider the
planes the less will be the lift; comparatively。
RULE FOR PLACING THE PLANES。The rule for
placing the planes is to place them apart a distance
equal to the width of the planes themselves;
so that if we decide on making them five feet wide;
they should be placed at least five feet apart。
This rule; while it is an admirable one for slow
movements or when starting flight; is not of any
advantage while in rapid flight。
If the machine is made with front and rear
horizontally…disposed rudders; or elevators; they
also serve as sustaining surfaces; which; for the
present will be disregarded。
Lay off a square A; Fig。 49a; in which the vertical
lines B; B; and the horizontal lines C; C; are
5' long; and draw a cross D within this; the lines
running diagonally from the corners。
Now step off from the center cross line D; three
spaces; each five feet long; to a point E; and join
this point by means of upper and lower bars F;
G; with the upper and lower planes; so as to form
the tail frame。
_Fig。 49a。 Rule for spacing Planes。_
As shown in Fig。 50; the planes should now be
indicated; and placed at an angle of about 8 degrees
angle; which are illustrated; H being the
upper and I the lower plane。 Midway between the
forward edges of the two planes; is a horizontal
line J; extending forwardly; and by stepping off
the width of two planes; a point K is made; which
forms the apex of a frame L; the rear ends of the
bars being attached to the respective planes H; I;
at their forward edges。
_Fig。 50。 Frame of Control Planes。_
_Fig。 51。 and Fig。 52。_
ELEVATING PLANES。We must now have the general
side elevation of the frame; the planes; their
angles; the tail and the rudder support; and the
frame for the forward elevator。
To this may be added the forward elevating
plane L; the rear elevator; or tail M; and the vertical
steering rudder N。
The frame which supports the structure thus
described; may be made in a variety of ways; the
object being to provide a resilient connection for
the rear wheel O。
Fig。 52 shows a frame which is simple in construction
and easily attached。 The lower fore
and aft side bars P have the single front wheel
axle at the forward end; and the aft double wheels
at the rear end; a flexible bar Q; running from the
rear wheel axle to the forward end of the lower
plane。
A compression spring R is also mounted between
the bar and rear end of the lower plane to
take the shock of landing。 The forward end of
the bar P has a brace S extending up to the front
edge of the lower plane; and another brace T connects
the bars P; S; with the end of the forwardly…
projecting frame。
_Fig。 53。 Plan view。_
The full page view; Fig。 53; represents a plan
view; with one of the wings cut away; showing the
general arrangement of the frame; and the three
wheels required for support; together with the
brace bars referred to。
The necessity of the rear end elevation will
now be referred to。 The tail need not; necessarily;
be located at a point on a horizontal line
between the planes。 It may be higher; or lower
than the planes; but it should not be in a position
to touch the ground when the machine is about
to ascend。
_Fig。 54。 Alighting。_
The angle of ascension in the planes need not
exceed 25 degrees so the frame does not require
an angle of more than 17 degrees。 This is shown
in Fig。 54; where the machine is in a position
ready to take the air at that angle; leaving ample
room for the steering rudder。
ACTION IN ALIGHTING。Also; in alighting; the
machine is banked; practically in the same
position thus shown; so that it alights on the rear
wheels O。
The motor U is usually mounted so its shaft is
midway between the planes; the propeller V being
connected directly with the shaft; and being behind
the planes; is on a medial line with the
machine。
The control planes L; M; N; are all connected up
by means of flexible wires with the aviator at the
set W; the attachments being of such a character
that their arrangement will readily suggest themselves
to the novice。
THE MONOPLANE。From a spectacular standpoint
a monoplane is the ideal flying machine。 It
is graceful in outline; and from the fact that it
closely approaches the form of the natural flyer;
seems to be best adapted as a type; compared with
the biplane。
THE COMMON FLY。So many birds have been
cited in support of the various flying theories that
the house fly; as an example has been disregarded。
We are prone to overlook the small insect; but it
is; nevertheless; a sample which is just as potent
to show the efficiency of wing surface as the condor
or the vulture。
The fly has greater mobility than any other flying
creature。 By the combined action of its legs
and wings it can spring eighteen inches in the
tenth of a second; and when in flight can change
its course instantaneously。
If a sparrow had the same dexterity; proportionally;
it could make a flight of 800 feet in the
same time。 The posterior legs of the fly are the
same length as its body; which enable it to spring
from its perch with amazing facility。
_Fig。 55。 Common Fly。 Outstretched Wings。_
The wing surface; proportioned to its body and
weight; is no less a matter for wonder and consideration。
In Fig。 55 is shown the outlines of the fly with
outstretched wings。 Fig。 56 represents it with
the wing folded; and Fig。 57 is a view of a wing
with the relative size of the top of the body shown
in dotted lines。
_Fig。 56。 Common Fly。 Folded Wings。_
The first thing that must attract attention; after
a careful study is the relative size of the body
and wing surface。 Each wing is slightly smaller
than the upper surface of the body; and the thickness
of the body is equal to each wing spread。
_Fig。 57。 Relative size of wing and body。_
The weight; compared with sustaining surface;
if expressed in understandable terms; would be
equal to sixty pounds for every square foot of surface。
STREAM LINES。The next observation is; that
what are called stream lines do not exist in the fly。
Its head is as large in cross section as its body;
with the slightest suggestion only; of a pointed
end。 Its wings are perfectly flat; forming a true
plane; not dished; or provided with a cambre; even;
that upward curve; or bulge on the top of the aeroplane
surface; which seems to possess such a fascination
for many bird flight advocates。
It will also be observed that the wing connection
with the body is forward of the line A; which
represents the point at which the body will balance
itself; and this line passes through the wings
so that there is an equal amount of supporting
surface fore and aft of the line。
Again; the wing attachment is at the upper side
of the body; and the vertical dimension of the
body; or its thickness; is equal to four…fifths of the
length of he wing。
The wing socket permits a motion similar to a
universal joint; Fig。 55 showing how the inner
end of the wing has a downward bend where it
joins the back; as at B。
THE MONOPLANE FORM。For the purpose of
making comparisons the illustrations of the monoplane
show a machine of 300 square feet of surface;
which necessitates a wing spread of forty
feet from tip to tip; so that the general dimensions
of each should be 18 1/2 feet by 8 1/2 feet at its
widest point。
First draw a square forty feet each way; as in
Fig。 58; and through this make a horizontal line
1; and four intermediate vertical lines are then
drawn; as 2; 3; 4; 5; thus providing five divisions;
each eight feet wide。 In the first division the
planes A; B; are placed; and the tail; or elevator
C; is one…half the width of the last division。
_Fig。 58。 Plan of Monoplane。_
The frame is 3 1/2 feet wide at its forward end;
and tapers down to a point at its rear end; where
the vertical control plane D is hinged; and the
cross struts E; E; are placed at the division lines
3; 4; 5。
The angles of the planes; with relation to the
frame; are usually greater than in the biplane;
for the reason that the long tail plane requires
a greater angle to be given to the planes when
arising; or; instead of this; the planes A; B; are
mounted high enough to permit of sufficient angle
for initiating flight without injuring the tail D。
Some monoplanes are built so they have a support
on wheels placed fore and aft。 In others
the tail is supported by curved skids; as shown
at A; Fig。 59; in which case the forward
supporting wheels are located directly beneath the planes。
As the planes are at about eighteen degrees
angle; relative to the frame; and the tail plane
B is at a slight negative angle of incidence; as
shown at the time when the engine is started; the
air rushing back from the propeller; elevates the
tail; and as the machine moves forwardly over
the ground; the tail raises still higher; so as to
give a less angle of incidence to the planes while
skimming along the surface of the ground。
_Fig。 59。 Side Elevation; Monoplane。_
In order to mount; the tail is suddenly turned
to assume a sharp negative angle; thus swinging
the tail downwardly; and this increases the angle
of planes to such an extent that the machine leaves
the ground; after which the tail is brought to the
proper angle to assure horizontal flight。
The drawing shows a skid at the forward end;
attached to the frame which carries the wheels。
The wheels are mounted beneath springs so that
when the machine alights the springs yield sufficiently
to permit the skids to strike the ground;
and they; therefore; act as brakes; to prevent the
machine from traveling too far。
CHAPTER X
POWER AND ITS APPLICATION
THIS is a phase of the flying machine which has
the greatest interest to the boy。 He instinctively
sees the direction in which the machine has its
life;its moving principle。 Planes have their
fascination; and propellers their mysterious elements;
but power is the great and absorbing question
with him。
We shall try to make its application plain in
the following pages。 We have nothing to do here
with the construction and operation of the motor
itself; as; to do that justice; would require pages。
FEATURES IN POWER APPLICATION。It will be
more directly to the point to consider the following
features of the power and its application:
1。 The amount of power necessary。
2。 How to calculate the power applied。
3。 I