Construction and Operation
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Fig. 1 therefore represented the case in which the
air was still, and in this case the aeroplane represented
by _A_ had perfect liberty of movement in any direction
In Fig. 2 the velocity of the wind was half that of the
aeroplane, and the latter could still navigate in any
direction, but its speed against the wind was only one-
third of its speed with the wind.
In Fig. 3 the velocity of the wind was equal to that
of the aeroplane, and then motion against the wind was
impossible; but it could move to any point of the
circle, but not to any point lying to the left of the tangent
_A_ _B_. Finally, when the wind had a greater
speed than the aeroplane, as in Fig. 4, the machine could
move only in directions limited by the tangents _A_ _C_
and _A_ _D_.
Matter of Fuel Consumption.
Taking the case in which the wind had a speed equal
to half that of the aeroplane, Mr. Lanchester said that
for a given journey out and home, down wind and back,
the aeroplane would require 30 per cent more fuel than
if the trip were made in still air; while if the journey
was made at right angles to the direction of the wind
the fuel needed would be 15 per cent more than in a
calm. This 30 per cent extra was quite a heavy enough
addition to the fuel; and to secure even this figure it
was necessary that the aeroplane should have a speed of
twice that of the maximum wind in which it was desired
to operate the machine. Again, as stated in the last
lecture, to insure the automatic stability of the machine
it was necessary that the aeroplane speed should be
largely in excess of that of the gusts of wind liable to
be encountered.
Eccentricities of the Wind.
There was, Mr. Lanchester said, a loose connection
between the average velocity of the wind and the maximum
speed of the gusts. When the average speed of
the wind was 40 miles per hour, that of the gusts might
be equal or more. At one moment there might be a
calm or the direction of the wind even reversed, followed,
the next moment, by a violent gust. About the same
minimum speed was desirable for security against gusts
as was demanded by other considerations. Sixty miles
an hour was the least figure desirable in an aeroplane,
and this should be exceeded as much as possible. Actually,
the Wright machine had a speed of 38 miles per
hour, while Farman's Voisin machine flew at 45 miles
per hour.
Both machines were extremely sensitive to high winds,
and the speaker, in spite of newspaper reports to the
contrary, had never seen either flown in more than a
gentle breeze. The damping out of the oscillations of
the flight path, discussed in the last lecture, increased
with the fourth power of the natural velocity of flight,
and rapid damping formed the easiest, and sometimes
the only, defense against dangerous oscillations. A
machine just stable at 35 miles per hour would have
reasonably rapid damping if its speed were increased to
60 miles per hour.
Thinks Use Is Limited.
It was, the lecturer proceeded, inconceivable that any
very extended use should be made of the aeroplane unless
the speed was much greater than that of the motor car.
It might in special cases be of service, apart from this
increase of speed, as in the exploration of countries
destitute of roads, but it would have no general utility.
With an automobile averaging 25 to 35 miles per hour,
almost any part of Europe, Russia excepted, was attainable
in a day's journey. A flying machine of but
equal speed would have no advantages, but if the speed
could be raised to 90 or 100 miles per hour, the whole
continent of Europe would become a playground, every
part being within a daylight flight of Berlin. Further,
some marine craft now had speeds of 40 miles per hour,
and efficiently to follow up and report movements of
such vessels an aeroplane should travel at 60 miles per
hour at least. Hence from all points of view appeared
the imperative desirability of very high velocities of
flight. The difficulties of achievement were, however,
great.
Weight of Lightest Motors.
As shown in the first lecture of his course, the resistance
to motion was nearly independent of the velocity,
so that the total work done in transporting a given
weight was nearly constant. Hence the question of fuel
economy was not a bar to high velocities of flight, though
should these become excessive, the body resistance might
constitute a large proportion of the total. The horsepower
required varied as the velocity, so the factor governing
the maximum velocity of flight was the horsepower
that could be developed on a given weight. At
present the weight per horsepower of feather-weight
motors appeared to range from 2 1/4 pounds up to 7
pounds per brake horsepower, some actual figures being
as follows:
Antoinette........ 5 lbs.
Fiat.............. 3 lbs.
Gnome....... Under 3 lbs.
Metallurgic....... 8 lbs.
Renault........... 7 lbs.
Wright.............6 lbs.
Automobile engines, on the other hand, commonly
weighed 12 pounds to 13 pounds per brake horsepower.
For short flights fuel economy was of less importance
than a saving in the weight of the engine. For long
flights, however, the case was different. Thus, if the
gasolene consumption was 1/2 pound per horsepower hour,
and the engine weighed 3 pounds per brake horsepower,
the fuel needed for a six-hour flight would weigh as much
as the engine, but for half an hour's flight its weight
would be unimportant.
Best Means of Propulsion.
The best method of propulsion was by the screw,
which acting in air was subject to much the same conditions
as obtained in marine work. Its efficiency depended
on its diameter and pitch and on its position,
whether in front of or behind the body propelled. From
this theory of dynamic support, Mr. Lanchester proceeded,
the efficiency of each element of a screw propeller
could be represented by curves such as were given
in his first lecture before the society, and from these
curves the over-all efficiency of any proposed propeller
could be computed, by mere inspection, with a fair degree
of accuracy. These curves showed that the tips of
long-bladed propellers were inefficient, as was also the
portion of the blade near the root. In actual marine
practice the blade from boss to tip was commonly of
such a length that the over-all efficiency was 95 per cent
of that of the most efficient element of it.
Advocates Propellers in Rear.
From these curves the diameter and appropriate pitch
of a screw could be calculated, and the number of
revolutions was then fixed. Thus, for a speed of 80 feet
per second the pitch might come out as 8 feet, in which
case the revolutions would be 600 per minute, which
might, however, be too low for the motor. It was then
necessary either to gear down the propeller, as was done
in the Wright machine, or, if it was decided to drive it
direct, to sacrifice some of the efficiency of the propeller.
An analogous case arose in the application of the steam
turbine to the propulsion of cargo boats, a problem as
yet unsolved. The propeller should always be aft, so
that it could abstract energy from the wake current, and
also so that its wash was clear of the body propelled.
The best possible efficiency was about 70 per cent, and
it was safe to rely upon 66 per cent.
Benefits of Soaring Flight.
There was, Mr. Lanchester proceeded, some possibility
of the aeronaut reducing the power needed for transport
by his adopting the principle of soaring flight, as
exemplified by some birds. There were, he continued, two
different modes of soaring flight. In the one the bird
made use of the upward current of air often to be found
in the neighborhood of steep vertical cliffs. These cliffs
deflected the air upward long before it actually reached
the cliff, a whole region below being thus the seat of
an upward current. Darwin has noted that the condor
was only to be found in the neighborhood of such cliffs.
Along the south coast also the gulls made frequent use
of the up currents due to the nearly perpendicular chalk
cliffs along the shore.
In the tropics up currents were also caused by
temperature differences. Cumulus clouds, moreover, were
nearly always the terminations of such up currents of
heated air, which, on cooling by expansion in the upper
regions, deposited their moisture as fog. These clouds
might, perhaps, prove useful in the future in showing
the aeronaut where up currents were to he found. An-
other mode of soaring flight was that adopted by the
albatross, which took advantage of the fact that the air
moved in pulsations, into which the bird fitted itself,
being thus able to extract energy from the wind.
Whether it would be possible for the aeronaut to employ
a similar method must be left to the future to decide.
Main Difficulties in Aviation.
In practical flight difficulties arose in starting and in
alighting. There was a lower limit to the speed at
which the machine was stable, and it was inadvisable to
leave the ground till this limit was attained. Similarly,
in alighting it was inexpedient to reduce the speed below
the limit of stability. This fact constituted a difficulty
in the adoption of high speeds, since the length of run
needed increased in proportion to the square of the
velocity. This drawback could, however, be surmounted
by forming starting and alighting grounds of ample size.
He thought it quite likely in the future that such grounds
would be considered as essential to the flying machine
as a seaport was to an ocean-going steamer or as a road
was to the automobile.
Requisites of Flying Machine.
Flying machines were commonly divided into monoplanes
and biplanes, according as they had one or two
supporting surfaces. The distinction was not, however,
fundamental. To get the requisite strength some form
of girder framework was necessary, and it was a mere
question of convenience whether the supporting surface
was arranged along both the top and the bottom of this
girder, or along the bottom only. The framework adopted
universally was of wood braced by ties of pianoforte
wire, an arrangement giving the stiffness desired with
the least possible weight. Some kind of chassis was also
necessary.
CHAPTER XXIII.
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 apprehensive that it
might involve them in litigation. There is no danger
of this, as will be seen by the following statement made
by the Wrights:
What Wright Brothers Say.
"Any amateur, any professional who is not exhibiting
for money, is at liberty to use our patented devices.
We shall be glad to have them do so, and there will be
no interference on our part, by legal action, or otherwise.
The only men we proceed against are those who, without
our permission, without even asking our consent,
coolly appropriate the results of our labors and use them
for the purpose of making money. Curtiss, Delagrange,
Voisin, and all the rest of them who have used our
devices have done so in money-making exhibitions. So
long as there is any money to be made by the use of the
products of our brains, we propose to have it ourselves.
It is the only way in which we can get any return for
the years of patient work we have given to the problem
of aviation. On the other hand, any man who wants
to use these devices for the purpose of pleasure, or the
advancement of science, is welcome to do so, without
money and without price. This is fair enough, is it not?"
Basis of the Wright Patents.
In a flying machine a normally flat aeroplane having
lateral marginal portions capable of movement to different
positions above or below the normal plane of the
body of the aeroplane, such movement being about an
axis transverse to the line of flight, whereby said lateral
marginal portions may be moved to different angles relatively
to the normal plane of the body of the aeroplane,
so as to present to the atmosphere different angles
of incidence, and means for so moving said lateral marginal
portions, substantially as described.
Application of vertical struts near the ends having
flexible joints.
Means for simultaneously imparting such movement
to said lateral portions to different angles relatively to
each other.
Refers to the movement of the lateral portions on the
same side to the same angle.
Means for simultaneously moving vertical rudder so
as to present to the wind that side thereof nearest the
side of the aeroplane having the smallest angle of incidence.
Lateral stability is obtained by warping the end wings
by moving the lever at the right hand of the operator,
connection being made by wires from the lever to the
wing tips. The rudder may also be curved or warped in
similar manner by lever action.
Wrights Obtain an Injunction.
In January, 1910, Judge Hazel, of the United States
Circuit Court, granted a preliminary injunction restraining
the Herring-Curtiss Co., and Glenn H. Curtiss, from
manufacturing, selling, or using for exhibition purposes
the machine known as the Curtiss aeroplane. The injunction
was obtained on the ground that the Curtiss
machine is an infringement upon the Wright patents in
the matter of wing warping and rudder control.
It is not the purpose of the authors to discuss the
subject pro or con. Such discussion would have no proper
place in a volume of this kind. It is enough to say that
Curtiss stoutly insists that his machine is not an
infringement of the Wright patents, although Judge Hazel
evidently thinks differently.
What the Judge Said.
In granting the preliminary injunction the judge said:
"Defendants claim generally that the difference in
construction of their apparatus causes the equilibrium or
lateral balance to be maintained and its aerial movement
secured upon an entirely different principle from that
of complainant; the defendants' aeroplanes are curved,
firmly attached to the stanchions and hence are incapable
of twisting or turning in any direction; that the
supplementary planes or so-called rudders are secured to
the forward stanchion at the extreme lateral ends of
the planes and are adjusted midway between the upper
and lower planes with the margins extending beyond the
edges; that in moving the supplementary planes equal
and uniform angles of incidence are presented as
distinguished from fluctuating angles of incidence. Such
claimed functional effects, however, are strongly
contradicted by the expert witness for complainant.
Similar to Plan of Wrights.
"Upon this contention it is sufficient to say that the
affidavits for the complainant so clearly define the
principle of operation of the flying machines in question
that I am reasonably satisfied that there is a variableness
of the angle of incidence in the machine of defendants
which is produced when a supplementary plane on one
side is tilted or raised and the other stimultaneously
tilted or lowered. I am also satisfied that the rear
rudder is turned by the operator to the side having the
least angle of incidence and that such turning is done
at the time the supplementary planes are raised
or depressed to prevent tilting or upsetting the machine.
On the papers presented I incline to the view, as already
indicated, that the claims of the patent in suit should be
broadly construed; and when given such construction,
the elements of the Wright machine are found in defendants'
machine performing the same functional result.
There are dissimilarities in the defendants' structure--
changes of form and strengthening of parts--which may
be improvements, but such dissimilarities seem to me to
have no bearing upon the means adopted to preserve the
equilibrium, which means are the equivalent of the claims
in suit and attain an identical result.
Variance From Patent Immaterial.
"Defendants further contend that the curved or arched
surfaces of the Wright aeroplanes in commercial use are
departures from the patent, which describes 'substantially
flat surfaces,' and that such a construction would
be wholly impracticable. The drawing, Fig. 3, however,
attached to the specification, shows a curved line inward
of the aeroplane with straight lateral edges, and considering
such drawing with the terminology of the specification,
the slight arching of the surface is not thought
a material departure; at any rate, the patent in issue
does not belong to the class of patents which requires
narrowing to the details of construction."
"June Bug" First Infringement.
Referring to the matter of priority, the judge said:
"Indeed, no one interfered with the rights of the
patentees by constructing machines similar to theirs until
in July, 1908, when Curtiss exhibited a flying machine
which he called the 'June Bug.' He was immediately
notified by the patentees that such machine with its
movable surfaces at the tips of wings infringed the patent
in suit, and he replied that he did not intend to publicly
exhibit the machine for profit, but merely was engaged
in exhibiting it for scientific purposes as a member
of the Aerial Experiment Association. To this the patentees
did not object. Subsequently, however, the machine,
with supplementary planes placed midway between
the upper and lower aeroplanes, was publicly exhibited
by the defendant corporation and used by Curtiss in
aerial flights for prizes and emoluments. It further appears
that the defendants now threaten to continue such
use for gain and profit, and to engage in the manufacture
and sale of such infringing machines, thereby becoming
an active rival of complainant in the business of
constructing flying machines embodying the claims in suit,
but such use of the infringing machines it is the duty
of this court, on the papers presented, to enjoin.
"The requirements in patent causes for the issuance
of an injunction pendente lite--the validity of the patent,
general acquiescence by the public and infringement
by the defendants--are so reasonably clear that I believe
if not probable the complainant may succeed at final
hearing, and therefore, status quo should be preserved
and a preliminary injunction granted.
"So ordered."
Points Claimed By Curtiss.
That the Herring-Curtiss Co. will appeal is a certainty.
Mr. Emerson R. Newell, counsel for the company,
states its case as follows:
"The Curtiss machine has two main supporting surfaces,
both of which are curved * * * and are absolutely
rigid at all times and cannot be moved, warped or
distorted in any manner. The front horizontal rudder is
used for the steering up or down, and the rear vertical
rudder is used only for steering to the right or left, in
the same manner as a boat is steered by its rudder. The
machine is provided at the rear with a fixed horizontal
surface, which is not present in the machine of the patent,
and which has a distinct advantage in the operation
of defendants' machine, as will be hereafter discussed.
Does Not Warp Main Surface.
"Defendants' machine does not use the warping of the
main supporting surfaces in restoring the lateral equilibrium,
but has two comparatively small pivoted balancing
surfaces or rudders. When one end of the machine
is tipped up or down from the normal, these planes may
be thrown in opposite directions by the operator, and
so steer each end of the machine up or down to its
normal level, at which time tension upon them is released
and they are moved back by the pressure of the
wind to their normal position.
Rudder Used Only For Steering.
"When defendants' balancing surfaces are moved they
present equal angles of incidence to the normal rush
of air and equal resistances, at each side of the machine,
and there is therefore no tendency to turn around a
vertical axis as is the case of the machine of the patent,
consequently no reason or necessity for turning the vertical
rear rudder in defendants' machine to counteract any
such turning tendency. At any rate, whatever may be
the theories in regard to this matter, the fact is that
the operator of defendants' machine does not at any
time turn his vertical rudder to counteract any turning
tendency clue to the side balancing surfaces, but only
uses it to steer the machine the same as a boat is
steered."
Aero Club Recognizes Wrights.
The Aero Club of America has officially recognized
the Wright patents. This course was taken following a
conference held April 9th, 1910, participated in by William
Wright and Andrew Freedman, representing the
Wright Co., and the Aero Club's committee, of Philip
T. Dodge, W. W. Miller, L. L. Gillespie, Wm. H. Page
and Cortlandt F. Bishop.
At this meeting arrangements were made by which
the Aero Club recognizes the Wright patents and will
not give its section to any open meet where the promoters
thereof have not secured a license from the
Wright Company.
The substance of the agreement was that the Aero
Club of America recognizes the rights of the owners of
the Wright patents under the decisions of the Federal
courts and refuses to countenance the infringement of
those patents as long as these decisions remain in force.
In the meantime, in order to encourage aviation, both
at home and abroad, and in order to permit foreign
aviators to take part in aviation contests in this country
it was agreed that the Aero Club of America, as the
American representative of the International Aeronautic
Federation, should approve only such public contests
as may be licensed by the Wright Company and that
the Wright Company, on the other hand, should encourage
the holding of open meets or contests where ever approved as
aforesaid by the Aero Club of America
by granting licenses to promoters who make satisfactory
arrangements with the company for its compensation
for the use of its patents. At such licensed meet any
machine of any make may participate freely without
securing any further license or permit. The details and
terms of all meets will be arranged by the committee
having in charge the interests of both organizations.
CHAPTER XXIV.
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 inspection will develop the fact that
in nearly every case some individual idea of the designer
has been incorporated. Thus, two propellers of the two-
bladed variety, while of the same general size as to
length and width of blade, will vary greatly as to pitch
and "twist" or curvature.
What the Designers Seek.
Every designer is seeking for the same result--the
securing of the greatest possible thrust, or air displacement,
with the least possible energy.
The angles of any screw propeller blade having a
uniform or true pitch change gradually for every increased
diameter. In order to give a reasonably clear
explanation, it will be well to review in a primary way
some of the definitions or terms used in connection with
and applied to screw propellers.
Terms in General Use.
Pitch.--The term "pitch," as applied to a screw propeller,
is the theoretical distance through which it would
travel without slip in one revolution, and as applied to
a propeller blade it is the angle at which the blades are
set so as to enable them to travel in a spiral path through
a fixed distance theoretically without slip in one revolution.
Pitch speed.--The term "pitch speed" of a screw
propeller is the speed in feet multiplied by the number of
revolutions it is caused to make in one minute of time.
If a screw propeller is revolved 600 times per minute,
and if its pitch is 7 ft., then the pitch speed of such a
propeller would be 7x600 revolutions, or 4200 ft. per
minute.
Uniform pitch.--A true pitch screw propeller is one
having its blades formed in such a manner as to enable
all of its useful portions, from the portion nearest the
hub to its outer portion, to travel at a uniform pitch
speed. Or, in other words, the pitch is uniform when the
projected area of the blade is parallel along its full
length and at the same time representing a true sector
of a circle.
All screw propellers having a pitch equal to their
diameters have the same angle for their blades at their
largest diameter.
When Pitch Is Not Uniform.
A screw propeller not having a uniform pitch, but
having the same angle for all portions of its blades, or
some arbitrary angle not a true pitch, is distinguished
from one having a true pitch in the variation of the pitch
speeds that the various portions of its blades are forced
to travel through while traveling at its maximum pitch
speed.
On this subject Mr. R. W. Jamieson says in Aeronautics:
"Take for example an 8-foot screw propeller having an
8-foot pitch at its largest diameter. If the angle is the
same throughout its entire blade length, then all the porions
of its blades approaching the hub from its outer portion would
have a gradually decreasing pitch. The 2-foot
portion would have a 2-foot pitch; the 3-foot portion a 3-
foot pitch, and so on to the 8-foot portion which would
have an 8-foot pitch. When this form of propeller is
caused to revolve, say 500 r.p.m., the 8-foot portion would
have a calculated pitch speed of 8 feet by 500 revolutions,
or 4,000 feet per min.; while the 2-foot portion would
have a calculated pitch speed of 500 revolutions by 2 feet,
or 1,000 feet per minute.
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