As a result of reading the various communications to the SCIENTIFIC
AMERICAN and SUPPLEMENT, and _Van Nostrand's Engineering Magazine_,
including descriptions of proposed and tested machines, and the
reports of the British Aeronautical Society, the writer of the
following concludes:
That, as precedents for the construction of a successful flying
machine, the investigation of some species of birds as a base of the
principles of all is correct only in connection with the species and
habits of the bird; that the _general mechanical principles_ of flight
applicable to the _operation_ of the _same unit_ of wing in _all_
species are alone applicable to the flying machine.
That these principles of _operation_ do not demand the principles of
_construction_ of the bird.
That as the wing is in its stroke an arc of a screw propeller's
operation, and in its angle a screw propeller blade, its animal
operation compels its reciprocation instead of rotation.
That the swifter the wing beat, the more efficient its effect per unit
of surface, the greater the load carried, and the swifter the flight.
That the screw action being, in full flight, that of a screw propeller
whose axis of rotation forms a slight angle with the vertical, the
distance of flight per virtual "revolution" of "screw" wing far
exceeds the pitch distance of said "screw."
That consequently a bird's flight answers to an iceboat close hauled;
the wing _force_ answering to the _wind_, the wing _angle_ to the
_sail_, the bird's _weight_ to the leeway fulcrum of the _ice_, and
the passage across direction of the _wing_ flop to the fresh _moving_
"inertia" of the wind, both yielding a maximum of force to bird or
iceboat.
That the speed of _reciprocation_ of a fly's _wing_ being equivalent
to a _screw rotation_ of 9,000 per minute, proves that a _screw_ may
be run at this speed without losing efficiency by centrifugal vacuum.
That as the _object_ of wing or screw is to mount upon the inertia of
the particles of a mobile fluid, and as the rotation of steamship
propellers in water--a fluid of many times the inertia of air--is
_already_ in _excess_ of the highest speed heretofore tried in the
propellers of moderately successful flying machines, it is plain that
the speed employed in _water_ must be many times exceeded in _air_.
That with a _sufficient_ speed of rotation, the supporting power of
the inertia of air must _equal_ that of _water_.
That as mere speed of rotation of propeller _shaft_, minus blades,
must absorb but a small proportion of power of engine, the addition of
blades will not cause more resistance than that actually encountered
from inertia of air.
That this must be the measure of load lifted.
That without _slip_ of screw, the actual _power_ expended, will be
little in _excess_ of that required to support the machine in _water_,
with a slower rotation of screw.
That in case the same _power_ is expended in water or air, the only
difference will lie in the sizes and speed of engines or screws.
That the _greater_ the speed, the _less_ weight of engine, boiler, and
screw must be, and the stronger their construction.
That, in consequence, solid metal worked down, instead of bolts and
truss work, must be used.
That as the bird wing is a screw in action, and acts _directly_
between the inertias of the load and the air, the position and
operation of the screw, to the load, must imitate it.
That, in consequence, machines having wing planes, driven _against_
one inertia of air by screws acting in the line, of flight against
another inertia of air, lose fifty per cent. of useful effect, besides
exposing to a head wind the cross section of the stationary screw wing
planes and the rotating screw discs; and supporting the dead weight of
the wing planes, and having all the screw slip in the line of flight,
and carrying slow and heavy engines.
That as a result of these conclusions, the supporting and propelling
power should be expressed in the rotation of screws combining both
functions, the position of whose planes of rotation to a fixed
horizontal line of direction determines the progress and speed of
machine upon other lines.
That the whole weight carried by the screws should be at all times
exactly below the center of gravity of the plane of support, whether
it be horizontal or inclined.
That while the _permanently_ positioned weight, such as the engines,
frame, holding screws, etc., may be rigidly connected to or around the
screw plane of support, the variable positioned weight, such as the
passenger and the car, should be connected by a _flexible joint_ to
the said plane of support.
Consequently, the car may oscillate without altering its weight
position under center of supporting plane, thus avoiding an
involuntary alteration of speed or direction of flight.
That to steer a machine so constructed, it is merely necessary to move
the point of attachment of car to _machine_ proper, out of the center
of plane of support in the desired direction, and thus cause the plane
of support or rotation of propellers to incline in that direction.
That the reservoir of power, the boiler, etc., should be placed in the
_car_, and steam carried to engines through joint connecting car with
machine.
That at present material exists, and power also, of sufficient
lightness and strength to admit of a machine construction capable of a
limited successful flight in any fair wind and direction.
That such _machine_ once built, the finding of a _power_ for long
flights will be easy, if not already close at hand in _electricity_.
That the _easiest_ design for such _actual machine_ should be adopted,
leaving the adaptation of the principles involved to the making of
more perfect machines, to a time after the success of the _first_.
That such design may be a propeller, and its engine at each end of a
steel frame tube, supporting tube horizontally, a car to be supported
by a universal joint from center of said tube, and the joint apparatus
movable along the tube or a short distance transverse to it, to alter
position of center of gravity.
That the machine so built might traverse the water as well as air.
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