Construction and Operation
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Unknown >> Construction and Operation
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Effect of Non-Uniformity.
"Now, as all of the portions of this type of screw
propeller must travel at some pitch speed, which must have
for its maximum a pitch speed in feet below the calculated
pitch speed of the largest diameter, it follows that
some portions of its blades would perform useful work
while the action of the other portions would be negative
--resisting the forward motion of the portions having a
greater pitch speed. The portions having a pitch speed
below that at which the screw is traveling cease to perform
useful work after their pitch speed has been exceeded
by the portions having a larger diameter and a
greater pitch speed.
"We might compare the larger and smaller diameter
portions of this form of screw propeller, to two power-
driven vessels connected with a line, one capable of traveling
20 miles per hour, the other 10 miles per hour. It
can be readily understood that the boat capable of traveling
10 miles per hour would have no useful effect to
help the one traveling 20 miles per hour, as its action
would be such as to impose a dead load upon the latter's
progress."
The term "slip," as applied to a screw propeller, is the
distance between its calculated pitch speed and the actual
distance it travels through under load, depending upon
the efficiency and proportion of its blades and the amount
of load it has to carry.
The action of a screw propeller while performing useful
work might be compared to a nut traveling on a
threaded bolt; little resistance is offered to its forward
motion while it spins freely without load, but give it a
load to carry; then it will take more power to keep up its
speed; if too great a load is applied the thread will strip,
and so it is with a screw propeller gliding spirally on the
air. A propeller traveling without load on to new air
might be compared to the nut traveling freely on the bolt.
It would consume but little power and it would travel at
nearly its calculated pitch speed, but give it work to do
and then it will take power to drive it.
There is a reaction caused from the propeller projecting
air backward when it slips, which, together with the supporting
effect of the blades, combine to produce useful
work or pull on the object to be carried.
A screw propeller working under load approaches more
closely to its maximum efficiency as it carries its load
with a minimum amount of slip, or nearing its calculated
pitch speed.
Why Blades Are Curved.
It has been pointed out by experiment that certain
forms of curved surfaces as applied to aeroplanes will lift
more per horse power, per unit of square foot, while on
the other hand it has been shown that a flat surface will
lift more per horse power, but requires more area of surface
to do it.
As a true pitch screw propeller is virtually a rotating
aeroplane, a curved surface may be advantageously employed
when the limit of size prevents using large plane
surfaces for the blades.
Care should be exercised in keeping the chord of any
curve to be used for the blades at the proper pitch angle,
and in all cases propeller blades should be made rigid so
as to preserve the true angle and not be distorted by
centrifugal force or from any other cause, as flexibility
will seriously affect their pitch speed and otherwise affect
their efficiency.
How to Determine Angle.
To find the angle for the proper pitch at any point in
the diameter of a propeller, determine the circumference
by multiplying the diameter by 3.1416, which represent
by drawing a line to scale in feet. At the end of this line
draw another line to represent the desired pitch in feet.
Then draw a line from the point representing the desired
pitch in feet to the beginning of the circumference line.
For example:
If the propeller to be laid out is 7 feet in diameter, and
is to have a 7-foot pitch, the circumference will be 21.99
feet. Draw a diagram representing the circumference
line and pitch in feet. If this diagram is wrapped around
a cylinder the angle line will represent a true thread 7
feet in diameter and 7 feet long, and the angle of the
thread will be 17 3/4 degrees.
Relation of Diameter to Circumference.
Since the areas of circles decrease as the diameter
lessens, it follows that if a propeller is to travel at a uniform
pitch speed, the volume of its blade displacement
should decrease as its diameter becomes less, so as to
occupy a corresponding relation to the circumferences of
larger diameters, and at the same time the projected
area of the blade must be parallel along its full length
and should represent a true sector of a circle.
Let us suppose a 7-foot circle to be divided into 20
sectors, one of which represents a propeller blade. If the
pitch is to be 7 feet, then the greatest depth of the angle
would be 1/20 part of the pitch, or 4 2/10 inch. If the
line representing the greatest depth of the angle is kept
the same width as it approaches the hub, the pitch will
be uniform. If the blade is set at an angle so its projected
area is 1/20 part of the pitch, and if it is moved
through 20 divisions for one revolution, it would have a
travel of 7 feet.
CHAPTER XXV.
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.
Marked gain in lightness and speed of the motor has enabled
aviators to get along, in some instances, with one-quarter of
the plane supporting area previously used. The first Wright
biplane, propelled by a motor of 25 h.p., productive of a fair
average speed of 30 miles an hour, had a plane surface of 538
square feet. Now, by using a specially designed motor of 65
h. p., capable of developing a speed of from 70 to 80 miles an
hour, the Wrights are enabled to successfully navigate a machine
the plane area of which is about 130 square feet. This
apparatus is intended to carry only one person (the operator).
At Belmont Park, N. Y., the Wrights demonstrated that the
small-surfaced biplane is much faster, easier to manage in the
hands of a skilled manipulator, and a better altitude climber
than the large and cumbersome machines with 538 square feet
of surface heretofore used by them.
In this may be found a practical illustration of the principle
that increased speed permits of a reduction in plane area in
mathematical ratio to the gain in speed. The faster any object
can be made to move through the air, the less will be the
supporting
surface required to sustain a given weight. But, there
is a limit beyond which the plane surface cannot be reduced
with safety. Regard must always be had to the securing of
an ample sustaining surface so that in case of motor stoppage
there will be sufficient buoyancy to enable the operator to
descend safely.
The baby Wright used at the Belmont Park (N. Y.) aviation
meet in the fall of 1910, had a plane length of 19 feet 6 inches,
and an extreme breadth of 21 feet 6 inches, with a total surface
area of 146 square feet. It was equipped with a new Wright
8-cylinder motor of 60 h. p., and two Wright propellers of 8
feet 6 inches diameter and 500 r. p. m. It was easily the fastest
machine at the meet. After the tests, Wilbur Wright said:
"It is our intention to put together a machine with specially
designed propellers, specially designed gears and a motor which
will give us 65 horsepower at least. We will then be able,
after some experimental work we are doing now, to send forth
a machine that will make a new speed record."
In the new Wright machines the front elevating planes for
up-and-down control have been eliminated, and the movements
of the apparatus are now regulated solely by the rear, or
"tail"
control.
A Powerful Light Motor.
Another successful American aviation motor is the aeromotor,
manufactured by the Detroit Aeronautic Construction.
Aeromotors are made in four models as follows:
Model 1.--4-cylinder, 30-40 h. p., weight 200 pounds.
Model 2.--4-cylinder, (larger stroke and bore) 40-50 h. p.,
weight 225 pounds.
Model 3.--6-cylinder. 50-60 h. p., weight 210 pounds.
Model 4.--6-cylinder, 60-75 h. p., weight 275 pounds.
This motor is of the 4-cycle, vertical, water-cooled type.
Roberts Aviation Motor.
One of the successful aviation motors of American make, is
that produced by the Roberts Motor Co., of Sandusky, Ohio.
It is designed by E. W. Roberts, M. E., who was formerly
chief assistant and designer for Sir Hiram Maxim, when the
latter was making his celebrated aeronautical experiments in
England in 1894-95. This motor is made in both the 4- and
6-cylinder forms. The 4-cylinder motor weighs complete with
Bosch magneto and carbureter 165 pounds, and will develop
40 actual brake h. p. at 1,000 r. p. m., 46 h. p. at 1,200 and 52
h. p. at 1,400. The 6-cylinder weighs 220 pounds and will
develop 60 actual brake h. p. at 1,000 r. p. m., 69 h. p. at
1,200 and 78 h. p. at 1,500.
Extreme lightness has been secured by doing away with all
superfluous parts, rather than by a shaving down of materials
to a dangerous thinness. For example, there is neither an intake
or exhaust manifold on the motor. The distributing valve
forms a part of the crankcase as does the water intake, and
the gear pump. Magnalium takes the place of aluminum in
the crankcase, because it is not only lighter but stronger and
can be cast very thin. The crankshaft is 2 1/2-inch diameter
with a 2 1/4-inch hole, and while it would be strong enough in
ordinary 40 per cent carbon steel it is made of steel twice the
strength of that customarily employed. Similar care has been
exercised on other parts and the result is a motor weighing 4
pounds per h. p.
The Rinek Motor.
The Rinek aviation motor, constructed by the Rinek Aero
Mfg. Co., of Easton, Pa., is another that is meeting with favor
among aviators. Type B-8 is an 8-cylinder motor, the cylinders
being set at right angles, on a V-shaped crank case. It is water
cooled, develops 50-60 h. p., the minimum at 1,220 r. p. m., and
weighs 280 pounds with all accessories. Type B-4, a 4-cylinder
motor, develops 30 h. p. at 1,800 r. p. m., and weighs 130 pounds
complete. The cylinders in both motors are made of cast iron
with copper water jackets.
The Overhead Camshaft Boulevard.
The overhead camshaft Boulevard is still another form of
aviation motor which has been favorably received. This is
the product of the Boulevard Engine Co., of St. Louis. It is
made with 4 and 8 cylinders. The former develops 30-35 h. p.
at 1,200 r. p. m., and weighs 130 pounds. The 8-cylinder motor
gives 60-70 h. p. at 1,200 r. p. m., and weighs 200 pounds.
Simplicity of construction is the main feature of this motor,
especially in the manipulation of the valves.
CHAPTER XXVI.
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 handled by Americans. Moissant and Drexel
navigated Bleriot machines, Harkness an Antoinette, and
Glenn Curtiss a single decker of his own construction. On
the other hand the various foreign aviators who took part in
the meet unhesitatingly gave preference to monoplanes.
Whatever may have been the cause of this seeming prejudice
against the monoplane on the part of American air sailors,
it is slowly being overcome. When a man like Curtiss, who
has attained great success with biplanes, gives serious attention
to the monoplane form of construction and goes so far as
to build and successfully operate a single surface machine,
it may be taken for granted that the monoplane is a fixture in
this country.
Dimensions of Monoplanes.
The makes, dimensions and equipment of the various monoplanes
used at Belmont Park are as follows:
Bleriot--(Moissant, operator)--plane length 23 feet, extreme
breadth 28 feet, surface area 160 square feet, 7-cylinder, 50 h.
p.
Gnome engine, Chauviere propeller, 7 feet 6 inches diameter,
1,200 r. p. m.
Bleriot--(Drexel, operator)--exactly the same as Moissant's
machine.
Antoinette--(Harkness, operator)--plane length 42 feet,
extreme breadth 46 feet, surface area 377 square feet, Emerson
6-cylinder, 50 h. p. motor, Antoinette propeller, 7 feet 6 inches
diameter, 1,200 r. p. m.
Curtiss--(Glenn H. Curtiss, operator)--plane length 25 feet,
extreme breadth 26 feet, surface area 130 square feet, Curtiss
8-cylinder, 60 h. p. motor, Paragon propeller, 7 feet in
diameter, 1,200 r. p. m.
With one exception Curtiss had the smallest machine of
any of those entering into competition. The smallest was La
Demoiselle, made by Santos-Dumont, the proportions of which
were: plane length 20 feet, extreme breadth 18 feet, surface
area 100 square feet, Clement-Bayard 2-cylinder, 30 h. p. motor,
Chauviere propeller, 6 feet 6 inches in diameter, 1,100 r. p. m.
Winnings Made with Monoplanes.
Operators of monoplanes won a fair share of the cash prizes.
They won $30,283 out of a total of $63,250, to say nothing about
Grahame-White's winnings. The latter won $13,600, but part
of his winning flights were made in a Bleriot monoplane, and
part in a Farman machine. Aside from Grahame-White the
winnings were divided as follows: Moissant (Bleriot) $13,350;
Latham (Antoinette) $8,183; Aubrun (Bleriot) $2,400;
De Lesseps (Bleriot) $2,300; Drexel (Bleriot) $1,700; Radley
(Bleriot) $1,300; Simon (Bleriot) $750; Andemars (Clement-
Bayard) $100; Barrier (Bleriot) $100.
Out of a total of $30,283, operators of Bleriot machines won
$21,900, again omitting Grahame-White's share. If the winnings
with monoplane and biplane could be divided so as to
show the amount won with each type of machine the credit
side of the Bleriot account would be materially enlarged.
The Most Popular Monoplanes.
While the number of successful monoplanes is increasing
rapidly, and there is some feature of advantage in nearly all
the new makes, interest centers chiefly in the Santos-Dumont,
Antoinette and Bleriot machines. This is because more has
been accomplished with them than with any of the others,
possibly because they have had greater opportunities.
For the guidance of those who may wish to build a machine
of the monoplane type after the Santos-Dumont or Bleriot
models, the following details will be found useful.
Santos-Dumont--The latest production of this maker is
called the "No. 20 Baby." It is of 18 feet spread, and 20 feet
over all in depth. It stands 4 feet 2 inches in height, not
counting the propeller. When this latter is in a vertical
position
the extreme height of the machine is 7 feet 5 inches. It
is strictly a one-man apparatus. The total surface area is 115
square feet. The total weight of the monoplane with engine
and propeller is 352 pounds. Santos-Dumont weighs 110
pounds, so the entire weight carried while in flight is 462
pounds, or about 3.6 pounds per square foot of surface.
Bamboo is used in the construction of the body frame, and
also for the frame of the tail. The body frame consists of
three bamboo poles about 2 inches in diameter at the forward
end and tapering to about 1 inch at the rear. These poles are
jointed with brass sockets near the rear of the main plane so
they may be taken apart easily for convenience in housing or
transportation. The main plane is built upon four transverse
spars of ash, set at a slight dihedral angle, two being placed on
each side of the central bamboo. These spars are about 2 inches
wide by 1 1/8-inch deep for a few feet each side of the center of
the machine, and from there taper down to an inch in depth
at the center bamboo, and at their outer ends, but the width
remains the same throughout their entire length. The planes
are double surfaced with silk and laced above and below the
bamboo ribs which run fore and aft under the main spars and
terminate in a forked clip through which a wire is strung for
lacing on the silk. The tail consists of a horizontal and
vertical
surface placed on a universal joint about 10 feet back of
the rear edge of the main plane. Both of these surfaces are
flat and consist of a silk covering stretched upon bamboo ribs.
The horizontal surface is 6 feet 5 inches across, and 4 feet 9
inches from front to back. The vertical surface is of the same
width (6 feet 5 inches) but is only 3 feet 7 inches from front
to back. All the details of construction are shown in the
accompanying illustration.
Power is furnished by a very light (110 pounds) Darracq
motor, of the double-opposed-cylinder type. It has a bore of
4.118 inches, and stroke of 4.724 inches, runs at 1,800 r. p. m.,
and with a 6 1/2-foot propeller develops a thrust of 242 1/2
pounds
when the monoplane is held steady.
Bleriot--No. XI, the latest of the Bleriot productions, and
the greatest record maker of the lot, is 28 feet in spread of
main
plane, and depth of 6 feet in largest part. This would give a
main surface of 168 square feet, but as the ends of the plane
are sharply tapered from the rear, the actual surface is reduced
to 150 square feet. Projecting from the main frame is an
elongated tail (shown in the illustration) which carries the
horizontal and vertical rudders. The former is made in three
sections. The center piece is 6 feet 1 inch in spread, and 2 feet
10 inches in depth, containing 17 square feet of surface. The
end sections, which are made movable for warping purposes,
are each 2 feet 10 inches square, the combined surface area in
the entire horizontal rudder being 33 square feet. The vertical
rudder contains 4 1/2 square feet of surface, making the entire
supporting area 187 1/2 square feet.
From the outer end of the propeller shaft in front to the extreme
rear edge of the vertical rudder, the machine is 25 feet
deep. Deducting the 6-foot depth of the main plane leaves 19
feet as the length of the rudder beam and rudders. The motor
equipment consists of a 3-cylinder, air-cooled engine of about
30 h. p. placed at the front end of the body frame, and carrying
on its crankshaft a two-bladed propeller 6 feet 8 inches in
diameter. The engine speed is about 1,250 r. p. m. at which
the propeller develops a thrust of over 200 pounds.
The Bleriot XI complete weighs 484 pounds, and with
operator and fuel supply ready for a 25- or 30-mile flight, 715
pounds. One peculiarity of the Bleriot construction is that,
while the ribs of the main plane are curved, there is no
preliminary
bending of the pieces as in other forms of construction.
Bleriot has his rib pieces cut a little longer than required
and, by springing them into place, secures the necessary
curvature. A good view of the Bleriot plane framework is
given on page 63.
Combined Triplane and Biplane.
At Norwich, Conn., the Stebbins-Geynet Co., after several
years of experiment, has begun the manufacture of a combination
triplane and biplane machine. The center plane, which is
located about midway between the upper and lower surfaces,
is made removable. The change from triplane to biplane, or
vice versa, may be readily made in a few minutes. The
constructors
claim for this type of air craft a large supporting
surface area with the minimum of dimensions in planes. Although
this machine has only 24-foot spread and is only 26
feet over all, its total amount of supporting area is 400 square
feet; weight, 600 pounds in flying order, and lifting capacity
approximately 700 pounds more.
The frame is made entirely of a selected grade of Oregon
spruce, finished down to a smooth surface and varnished. All
struts are fish-shaped and set in aluminum sockets, which are
bolted to top and lower beams with special strong bolts of
small diameter. The middle plane is set inside the six uprights
and held in place by aluminum castings. A flexible twisted
seven-strand wire cable and Stebbins-Geynet turnbuckles are
used for trussing.
The top plane is in three sections, laced together. It has a
24-foot spread and is 7 feet in depth. The middle plane is in
two sections each of 7 1/2 feet spread and 6 feet in depth. The
center ends of the middle plane sections do not come within
5 feet of joining, this open space being left for the engine.
The bottom plane is of 16 feet spread and 5 feet in depth. It
will thus be seen that the planes overhang one another in depth,
the bottom one being the smallest in this respect. The planes
are set at an angle of 9 degrees, and there is a clear space of 3
1/2 feet between each, making the total distance from the bottom
to the top plane a trifle over 7 feet. The total supporting
surface in the main planes is 350 square feet. By arranging the
three plane surfaces at an angle as described and varying their
size, the greatest amount of lifting area is secured above the
center of gravity, and the greatest weight carried below.
The ribs are made of laminated spruce, finished down to
1/2x3/4-inch cross section dimensions, with a curvature of about
1 in 20, and fastened to the beams with special aluminum
castings.
Number 2 Naiad aeroplane cloth is used in covering the
planes, with pockets sewn in for the ribs.
Two combination elevating rudders are set up well in front,
each having 18 square feet of supporting area. These rudders
are arranged to work in unison, independently, or in opposite
directions. In the Model B machine, there are also two small
rear elevating rudders, which work in unison with the front
rudders. One vertical rudder of 10 square feet is suspended
in the rear of a small stationary horizontal plane in Model A,
while the vertical rudder on Model B is only 6 square feet in
size. The elevating rudders are arranged so as to act as
stabilizing
planes when the machine is in flight. The wing tips are
held in place with a special two-piece casting which forms a
hinge, and makes a quick detachable joint. Wing tips are also
used in balancing.
Model A is equipped with a Cameron 25-30 h. p., 4-cylinder,
air-cooled motor. On Model B a Holmes rotary 7-cylinder
motor of 4x4-inch bore and stroke is used.
Positive control is secured by use of the Stebbins-Geynet
"auto-control" system. A pull or push movement operates the
elevating rudders, while the balancing is done by means of
side movements or slight turns. The rear vertical rudder is
manipulated by means of a foot lever.
New Cody Biplane.
Among the comparatively new biplanes is one constructed by
Willard F. Cody, of London, Eng., the principal distinctive
feature of which is an automaticcontrol which works independently
of the hand levers. For the other control a long lever
carrying a steering wheel furnishes all the necessary control
movements, there being no footwork at all. The lever is
universally jointed and when moved fore and aft operates the
two ailerons as if they were one; when the shaft is rotated it
moves the tail as a whole. The horizontal tail component is
immovable. When the lever is moved from side to side it works
not only the ailerons and the independent elevators, but also
through a peculiar arrangement, the vertical rear rudder as well.
The spread of the planes is 46 feet 6 inches and the width 6
feet 6 inches. The ailerons jut out 1 foot 6 inches on each
side of the machine and are 13 feet 6 inches long. The cross-
shaped tail is supported by an outrigger composed of two long
bamboos and of this the vertical plane is 9 feet by 4 feet, while
the horizontal plane is 8 feet by 4 feet. The over-all length
of the machine is 36 feet. The lifting surface is 857 square
feet. It will weigh, with a pilot, 1,450 pounds. The distance
between the main planes is 8 feet 6 inches, which is a rather
notable feature in this flyer.
The propeller has a diameter of 11 feet and 2 inches with a
13-foot 6-inch pitch; it is driven at 560 revolutions by a chain,
and the gear reduction between the chain and propeller shaft
is two to one.
The machine from elevator to tail plane bristles in original
points. The hump in the ribs has been cut away entirely, so
that although the plane is double surfaced, the surfaces are
closest together at a point which approximates the center of
pressure. The plane is practically of two stream-line forms,
of which one is the continuation of the other. This construction,
claims the inventor, will give increased lift, and decreased
head resistance. The trials substantiate this, as the angle of
incidence in flying is only about one in twenty-six.
The ribs in the main planes are made of strips of silver spruce
one-half by one-half inch, while those in the ailerons are solid
and one-fourth inch thick. In the main planes the fabric is
held down with thin wooden fillets. Cody's planes are noted
for their neatness, rigidity and smoothness. Pegamoid fabric
is used throughout.
Pressey Automatic Control.
Another ingenious system of automatic control has been
perfected by Dr. J. B. Pressey, of Newport News, Va. The
aeroplane is equipped with a manually operated, vertical rudder,
(3), at the stern, and a horizontal, manually operated,
front control, (4), in front. At the ends of the main plane, and
about midway between the upper and lower sections thereof,
there are supplemental planes, (5).
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