FLYING MACHINE ACCESSORIES
THE ANEMOMETER.--It requires an expert to
judge the force or the speed of a wind, and even
they will go astray in their calculations. It is
an easy matter to make a little apparatus which
will accurately indicate the speed. A device of
this kind is called an Anemometer.
Two other instruments have grown out of this,
one to indicate the pressure, and the other the
direction of the moving air current.
THE ANEMOGRAPH.--While these instruments indicate,
they are also made so they will record the
speed, the pressure and the direction, and the device
for recording the speed and pressure is called
a Anemograph.
All these instruments may be attached to the
same case, and thus make a handy little device,
which will give all the information at a glance.
THE ANEMOMETROGRAPH.--This device for recording,
as well as indicating the speed, pressure
and direction, is called an Anemometrograph,
The two important parts of the combined
apparatus, for the speed and pressure, are illustrated,
to show the principle involved. While the speed
will give the pressure, it is necessary to make a
calculation to get the result while the machine does
this for you.
_Fig. 61. Speed Indicator._
THE SPEED INDICATOR.--Four hemispherical
cups A are mounted on four radiating arms B,
which are secured to a vertical stem C, and
adapted to rotate in suitable bearings in a
case, which, for convenience in explaining, is not
shown.
On the lower end of the stem C, is a small bevel
pinion, which meshes with a smaller bevel pinion
within the base. This latter is on a shaft which
carries a small gear on its other end, to mesh
with a larger gear on a shaft which carries a
pointer D that thus turns at a greatly reduced
speed, so that it can be easily timed.
_Fig. 62. Air Pressure Indicator._
AIR PRESSURE INDICATOR.--This little apparatus
is readily made of a base A which is provided
with two uprights B, C, through the upper ends of
which are holes to receive a horizontally-disposed
bar D. One end of the bar is a flat plane
surface E, which is disposed at right angles to the
bar, and firmly fixed thereto.
The other end of the bar has a lateral pin to
serve as a pivot for the end of a link F, its other
end being hinged to the upper end of a lever G,
which is pivoted to the post C, a short distance
below the hinged attachment of the link F, so
that the long end of the pointer which is constituted
by the lever G is below its pivot, and has,
therefore, a long range of movement.
A spring I between the upper end of the pointer
G and the other post B, serves to hold the pointer
at a zero position. A graduated scale plate J,
within range of the pointer will show at a glance
the pressure in pounds of the moving wind, and
for this purpose it would be convenient to make
the plane E exactly one foot square.
DETERMINING THE PRESSURE FROM THE SPEED.--
These two instruments can be made to check each
other and thus pretty accurately enable you to
determine the proper places to mark the pressure
indicator, as well as to make the wheels in the
anemometer the proper size to turn the pointer
in seconds when the wind is blowing at a certain
speed, say ten miles per hour.
Suppose the air pressure indicator has the scale
divided into quarter pound marks. This will
make it accurate enough for all purposes.
CALCULATING PRESSURES FROM SPEED.--The following
table will give the pressures from 5 to 100
miles per hour:
Velocity of wind in Pressure Velocity of wind in Pressure
miles per hour per sq. ft. miles per hour per sq ft
5 .112 55 15.125
10 .500 60 18.000
15 1.125 65 21.125
20 2.000 70 22.500
25 3.125 75 28.125
30 4.600 80 32.000
35 6.126 86 36.126
40 8.000 90 40.500
45 10.125 95 45.125
50 12.5 100 50.000
HOW THE FIGURES ARE DETERMINED.--The foregoing
figures are determined in the following manner:
As an example let us assume that the velocity
of the wind is forty-five miles per hour. If
this is squared, or 45 multiplied by 45, the product
is 2025. In many calculations the mathematician
employs what is called a constant, a figure that
never varies, and which is used to multiply or
divide certain factors.
In this case the constant is 5/1000, or, as usually
written, .005. This is the same as one two hundredths
of the squared figure. That would make
the problem as follows:
45 X 45 = 2025 / 200 = 10.125; or,
45 X 45 - 2025 X .005 = 10.125.
Again, twenty-five miles per hour would be
25 X 25 = 625; and this multiplied by .005 equals
2 pounds pressure.
CONVERTING HOURS INTO MINUTES.--It is sometimes
confusing to think of miles per hour, when
you wish to express it in minutes or seconds. A
simple rule, which is not absolutely accurate, but
is correct within a few feet, in order to express
the speed in feet per minute, is to multiply the
figure indicating the miles per hour, by 8 3/4.
To illustrate: If the wind is moving at the
rate of twenty miles an hour, it will travel in that
time 105,600 feet (5280 X 20). As there are sixty
minutes in an hour, 105,600 divided by 60, equals
1760 feet per minute. Instead of going through
all this process of calculating the speed per minute,
remember to multiply the speed in miles per
hour by 90, which will give 1800 feet.
This is a little more then two per cent. above
the correct figure. Again; 40 X 90 equals 3600.
As the correct figure is 3520, a little mental calculation
will enable you to correct the figures so
as to get it within a few feet.
CHANGING SPEED HOURS TO SECONDS.--As one-
sixtieth of the speed per minute will represent the
rate of movement per second, it is a comparatively
easy matter to convert the time from speed in
miles per hour to fraction of a mile traveled in
a second, by merely taking one-half of the speed
in miles, and adding it, which will very nearly express
the true number of feet.
As examples, take the following: If the wind
is traveling 20 miles an hour, it is easy to take
one-half of 20, which is 10, and add it to 20, making
30, as the number of feet per second. If the
wind travels 50 miles per hour, add 25, making
75, as the speed per second.
The correct speed per second of a wind traveling
20 miles an hour is a little over 29 feet. At
50 miles per hour, the correct figure is 73 1/3 feet,
which show that the figures under this rule are
within about one per cent. of being correct.
With the table before you it will be an easy
matter, by observing the air pressure indicator,
to determine the proper speed for the anemometer.
Suppose it shows a pressure of two pounds,
which will indicate a speed of twenty miles an
hour. You have thus a fixed point to start from.
PRESSURE AS THE SQUARE OF THE SPEED.--Now
it must not be assumed that if the pressure at
twenty miles an hour is two pounds, that forty
miles an hour it is four pounds. The pressure
is as the square of the speed. This may be explained
as follows: As the speed of the wind
increases, it has a more effective push against an
object than its rate of speed indicates, and this
is most simply expressed by saying that each time
the speed is doubled the pressure is four times
greater.
As an example of this, let us take a speed of ten
miles an hour, which means a pressure of one-
half pound. Double this speed, and we have 20
miles. Multiplying one-half pound by 4, the result
is 2 pounds. Again, double 20, which means
40 miles, and multiplying 2 by 4, the result is 8.
Doubling forty is eighty miles an hour, and again
multiplying 8 by 4, we have 32 as the pounds pressure
at a speed of 80 miles an hour.
The anemometer, however, is constant in its
speed. If the pointer should turn once a second
at 10 miles an hour, it would turn twice at 20 miles
an hour, and four times a second at 40 miles an
hour.
GYROSCOPIC BALANCE.--Some advance has been
made in the use of the gyroscope for the purpose
of giving lateral stability to an aeroplane. While
the best of such devices is at best a makeshift,
it is well to understand the principle on which they
operate, and to get an understanding how they are
applied.
THE PRINCIPLE INVOLVED.--The only thing
known about the gyroscope is, that it objects to
changing the plane of its rotation. This statement
must be taken with some allowance, however,
as, when left free to move, it will change in
one direction.
To explain this without being too technical, examine
Fig. 63, which shows a gyroscopic top, one
end of the rim A, which supports the rotating
wheel B, having a projecting finger C, that is
mounted on a pin-point on the upper end of the
pedestal D.
_Fig. 63. The Gyroscope._
When the wheel B is set in rotation it will maintain
itself so that its axis E is horizontal, or at
any other angle that the top is placed in when the
wheel is spun. If it is set so the axis is horizontal
the wheel B will rotate on a vertical plane,
and it forcibly objects to any attempt to make it
turn except in the direction indicated by the
curved arrows F.
The wheel B will cause the axis E to swing
around on a horizontal plane, and this turning
movement is always in a certain direction in relation
to the turn of the wheel B, and it is obvious,
therefore, that to make a gyroscope that
will not move, or swing around an axis, the placing
of two such wheels side by side, and rotated
in opposite directions, will maintain them in a
fixed position; this can also be accomplished by
so mounting the two that one rotates on a plane
at right angles to the other.
_Fig. 64. Application of the Gyroscope._
THE APPLICATION OF THE GYROSCOPE.--Without
in any manner showing the structural details of
the device, in its application to a flying machine,
except in so far as it may be necessary to explain
its operation, we refer to Fig. 64, which
assumes that A represents the frame of the aeroplane,
and B a frame for holding the gyroscopic
wheel C, the latter being mounted so it rotates on
a horizontal plane, and the frame B being hinged
fore and aft, so that it is free to swing to the right
or to the left.
For convenience in explaining the action, the
planes E are placed at right angles to their regular
positions, F being the forward margin of the
plane, and G the rear edge. Wires H connect
the ends of the frame B with the respective
planes, or ailerons, E, and another wire I joins
the downwardly-projecting arms of the two
ailerons, so that motion is transmitted to both at
the same time, and by a positive motion in either
direction.
_Fig. 65. Action of the Gyroscope._
In the second figure, 65, the frame of the aeroplane
is shown tilted at an angle, so that its right
side is elevated. As the gyroscopic wheel remains
level it causes the aileron on the right side to
change to a negative angle, while at the same
time giving a positive angle to the aileron on the
left side, which would, as a result, depress the
right side, and bring the frame of the machine
back to a horizontal position.
FORE AND AFT GYROSCOPIC CONTROL.--It is
obvious that the same application of this force may
be applied to control the ship fore and aft, although
it is doubtful whether such a plan would
have any advantages, since this should be wholly
within the control of the pilot.
Laterally the ship should not be out of balance;
fore and aft this is a necessity, and as the great
trouble with all aeroplanes is to control them
laterally, it may well be doubted whether it would
add anything of value to the machine by having
an automatic fore and aft control, which might,
in emergencies, counteract the personal control of
the operator.
ANGLE INDICATOR.--In flight it is an exceedingly
difficult matter for the pilot to give an accurate
idea of the angle of the planes. If the air is
calm and he is moving over a certain course, and
knows, from experience, what his speed is, he may
be able to judge of this factor, but he cannot tell
what changes take place under certain conditions
during the flight.
For this purpose a simple little indicator may
be provided, shown in Fig. 66, which is merely a
vertical board A, with a pendulum B, swinging
fore and aft from a pin a which projects out
from the board a short distance above its center.
The upper end of the pendulum has a heart-
shaped wire structure D, that carries a sliding
weight E. Normally, when the aeroplane is on
an even keel, or is even at an angle, the weight
E rests within the bottom of the loop D, but
should there be a sudden downward lurch or a
quick upward inclination, which would cause the
pendulum below to rapidly swing in either
direction, the sliding weight E would at once move
forward in the same direction that the pendulum
had moved, and thus counteract, for the instant
only, the swing, when it would again drop back
into its central position.
_Fig. 66. Angle Indicator._
With such an arrangement, the pendulum would
hang vertically at all times, and the pointer below,
being in range of a circle with degrees
indicated thereon, and the base attached to the
frame of the machine, can always be observed,
and the conditions noted at the time the changes
take place.
PENDULUM STABILIZER.--In many respects the
use of a pendulum has advantages over the gyroscope.
The latter requires power to keep it in
motion. The pendulum is always in condition
for service. While it may be more difficult to
adjust the pendulum, so that it does not affect
the planes by too rapid a swing, or an oscillation
which is beyond the true angle desired, still, these
are matters which, in time, will make the pendulum
a strong factor in lateral stability.
_Fig. 67. Simple Pendulum Stabilizer._
It is an exceedingly simple matter to attach the
lead wires from an aileron to the pendulum. In
Fig. 67 one plan is illustrated. The pendulum
A swings from the frame B of the machine, the
ailerons a being in this case also shown at right
angles to their true positions.
The other, Fig. 68, assumes that the machine is
exactly horizontal, and as the pendulum is in a
vertical position, the forward edges of both ailerons
are elevated, but when the pendulum swings
both ailerons will be swung with their forward
margins up or down in unison, and thus the proper
angles are made to right the machine.
STEERING AND CONTROLLING WHEEL.--For the
purpose of concentrating the control in a single
wheel, which has not alone a turning motion, but
is also mounted in such a manner that it will oscillate
to and fro, is very desirable, and is adapted
for any kind of machine.
_Fig. 68. Pendulum Stabilizers._
Fig. 69 shows such a structure, in which A
represents the frame of the machine, and B a
segment for the stem of the wheel, the segment
being made of two parts, so as to form a guideway
for the stem a to travel between, and the segment
is placed so that the stem will travel in a
fore and aft direction.
The lower end of the stem is mounted in a
socket, at D, so that while it may be turned, it
will also permit this oscillating motion. Near its
lower end is a cross bar E from which the wires
run to the vertical control plane, and also to the
ailerons, if the machine is equipped with them, or
to the warping ends of the planes.
_Fig. 69. Steering and Control Wheel._
Above the cross arms is a loose collar F to
which the fore and aft cords are attached that go
to the elevators, or horizontal planes. The upper
end of the stem has a wheel G, which may also be
equipped with the throttle and spark levers.
AUTOMATIC STABILIZING WINGS.--Unquestionably,
the best stabilizer is one which will act on
its own initiative. The difficulty with automatic
devices is, that they act too late, as a general
thing, to be effective. The device represented in
Fig. 70 is very simple, and in practice is found to
be most efficient.
In this Fig. 70 A and B represent the upper
and the lower planes, respectively. Near the end
vertical standards a, D, are narrow wings E E,
F F, hinged on a fore and aft line close below
each of the planes, the wings being at such distances
from the standards C D that when they
swing outwardly they will touch the standards,
and when in that position will be at an angle of
about 35 degrees from the planes A B.
_Fig. 70. Automatic Stabilizing Wings._
_Fig. 71. Action of Stabilizing Wings._
Inwardly they are permitted to swing up and
lie parallel with the planes, as shown in Fig. 71
where the planes are at an angle. In turning, all
machines skid,--that is they travel obliquely
across the field, and this is also true when the
ship is sailing at right angles to the course of the
wind.
This will be made clear by reference to Fig.
72, in which the dart A represents the direction
of the movement of the aeroplane, and B the
direction of the wind, the vertical rudder a being
almost at right angles to the course of the wind.
_Fig. 72. Into the Wind at an Angle._
In turning a circle the same thing takes place
as shown in Fig. 73, with the tail at a different
angle, so as to give a turning movement to the
plane. It will be seen that in the circling movement
the tendency of the aeroplane is to fly out
at a tangent, shown by the line D, so that the
planes of the machine are not radially-disposed
with reference to the center of the circle, the line
E showing the true radial line.
Referring now to Fig. 71, it will be seen that
this skidding motion of the machine swings the
wings E F inwardly, so that they offer no resistance
to the oblique movement, but the wings E
E, at the other end of the planes are swung outwardly,
to provide an angle, which tends to raise
up the inner end of the planes, and thereby seek
to keep the planes horizontal.
_Fig. 73. Turning a Circle._
BAROMETERS.--These instruments are used for
registering heights. A barometer is a device for
measuring the weight or pressure of the air.
The air is supposed to extend to a height of 40
miles from the surface of the sea. A column of
air one inch square, and forty miles high, weighs
the same as a column of mercury one inch square
and 30 inches high.
Such a column of air, or of mercury, weighs
14 3/4 pounds. If the air column should be
weighed at the top of the mountain, that part
above would weigh less than if measured at the
sea level, hence, as we ascend or descend the pressure
becomes less or more, dependent on the altitude.
Mercury is also used to indicate temperature,
but this is brought about by the expansive quality
of the mercury, and not by its weight.
_Fig. 74. Aneroid Barometer._
ANEROID BAROMETER.--The term Aneroid barometer
is frequently used in connection with air-
ship experiments. The word aneroid means not
wet, or not a fluid, like mercury, so that, while
aneroid barometers are being made which do use
mercury, they are generally made without.
One such form is illustrated in Fig. 74, which
represents a cylindrical shell A, which has at each
end a head of concentrically formed corrugations.
These heads are securely fixed to the ends of the
shell A. Within, one of the disk heads has a
short stem C, which is attached to the short end
of a lever D, this lever being pivoted at E. The
outer end of this lever is hinged to the short end
of another lever F, and so by compounding the
levers, it will be seen that a very slight movement
of the head B will cause a considerable movement
in the long end of the lever F.
This end of the lever F connects with one limb
of a bell-crank lever G, and its other limb has a
toothed rack connection with a gear H, which
turns the shaft to which the pointer I is attached.
Air is withdrawn from the interior of the shell,
so that any change in the pressure, or weight of
the atmosphere, is at once felt by the disk heads,
and the finger turns to indicate the amount of
pressure.
HYDROPLANES.--Hydro means water, hence the
term hydroplane has been given to machines
which have suitable pontoons or boats, so they
may alight or initiate flight from water.
There is no particular form which has been
adopted to attach to aeroplanes, the object generally
being to so make them that they will sustain
the greatest amount of weight with the least
submergence, and also offer the least resistance
while the motor is drawing the machine along the
surface of the water, preparatory to launching it.
SUSTAINING WEIGHT OF PONTOONS.--A pontoon
having within nothing but air, is merely a measuring
device which determines the difference between
the weight of water and the amount placed
on the pontoon. Water weighs 62 1/2 pounds per
cubic foot. Ordinary wood, an average of 32
pounds, and steel 500 pounds.
It is, therefore, an easy matter to determine
how much of solid matter will be sustained by a
pontoon of a given size, or what the dimensions
of a pontoon should be to hold up an aeroplane
which weighs, with the pilot, say, 1100 pounds.
As we must calculate for a sufficient excess to
prevent the pontoons from being too much immersed,
and also allow a sufficient difference in
weight so that they will keep on the surface when
the aeroplane strikes the surface in alighting, we
will take the figure of 1500 pounds to make the
calculations from.
If this figure is divided by 62 1/2 we shall find
the cubical contents of the pontoons, not considering,
of course, the weight of the material of which
they are composed. This calculation shows that
we must have 24 cubic feet in the pontoons.
As there should be two main pontoons, and a
smaller one for the rear, each of the main ones
might have ten cubic feet, and the smaller one
four cubic feet.
SHAPES OF THE PONTOONS.--We are now ready
to design the shapes. Fig. 75 shows three general
types, A being made rectangular in form,
with a tapering forward end, so constructed as to
ride up on the water.
The type B has a rounded under body, the forward
end being also skiff-shaped to decrease as
much as possible the resistance of the water impact.
_Fig. 75. Hydroplane Floats._
The third type C is made in the form of a
closed boat, with both ends pointed, and the bottom
rounded, or provided with a keel. Or, as in
some cases the body may be made triangular in
cross section so that as it is submerged its sustaining
weight will increase at a greater degree
as it is pressed down than its vertical measurement
indicates.
All this, however, is a matter left to the judgment
of the designer, and is, in a great degree,
dependent on the character of the craft to which
it is to be applied.