Page images
PDF
EPUB

wing strikes vertically downwards, for, as already explained, the body of a flying bird is a body in motion; but as a body in motion tends to fall downwards and forwards, the wing must strike downwards and forwards in order effectually to prevent its fall. Moreover, in point of fact, all natural wings and all artificial wings constructed on the natural type invariably strike downwards and forwards. With regard to the second point, viz., the supposed rigidity of the anterior margin of the wing, it is only necessary to examine the anterior margins of natural wings to be convinced that they are in every case flexible and elastic. Similar remarks apply to properly constructed artificial wings. If the anterior margins of natural and artificial wings were rigid, it would be impossible to make them vibrate smoothly and continuously. This is a matter of experiment. If a rigid rod, or a wing with a rigid anterior margin, be made to vibrate, the vibration is characterized by an unequal jerky motion, which contrasts strangely with the smooth, steady, fanning movement peculiar to natural wings.

As to the third point, viz., the upward bending of the posterior margin of the wing during the down stroke, it is necessary to remark that the statement is true if it means a slight upward bending, but that it is untrue if it means an extensive upward bending.

consisting of a rigid ribbing in front, and a flexible sail behind. A membrane so constructed will, according to him, be fit for flight. It will suffice if such a sail elevates and lowers itself successively. It will of its own accord dispose itself as an inclined plane, and receiving obliquely the reaction of the air, it transfers into tractile force a part of the vertical impulsion it has received. These two parts of the wing, moreover, are equally indispensable to each other. Marey repeats Borelli and Durckheim with very trifling modifications, so late as 1869.1 He describes two artificial wings, the one composed of a rigid rod and sail-the rod representing the stiff anterior margin of the wing; the sail, which is made of paper bordered with card board, the flexible posterior margin. The other wing consists of a rigid nervure in front and behind of thin parchment which supports fine rods of steel. He states that, if the wing only elevates and depresses itself, "the resistance of the air is sufficient to produce all the other movements. In effect (according to Marey) the wing of an insect has not the power of equal resistance in every part. On the anterior margin the extended nervures make it rigid, while behind it is fine and flexible. During the vigorous depression of the wing, the nervure has the power of remaining rigid, whereas the flexible portion, being pushed in an upward direction on account of the resistance it Borelli does not state the amount of upward bending, experiences from the air, assumes an oblique position which but one of his followers, Professor E. J. Marey, maintains causes the upper surface of the wing to look forwards." The that during the down stroke the wing yields until its under reverse of this, in Marey's opinion, takes place during the surface makes a backward angle with the horizon of 45°. | elevation of the wing-the resistance of the air from above Marey further states that during the up stroke the wing causing the upper surface of the wing to look backwards. yields to a corresponding extent in an opposite directionAt first," he says, "the plane of the wing is parallel the posterior margin of the wing, according to him, passing with the body of the animal. It lowers itself—the front through an angle of 90°, plus or minus, according to cir- part of the wing strongly resists, the sail which follows it cumstances, every time the wing rises and falls. being flexible yields. Carried by the ribbing (the anterior margin of the wing) which lowers itself, the sail or posterior margin of the wing being raised meanwhile by the air, which sets it straight again, the sail will take an intermediate position and incline itself about 45° plus or minus according to circumstances. The wing continues its movements of depression inclined to the horizon; but the impulse of the air, which continues its effect, and naturally acts upon the surface which it strikes, has the power of resolving itself into two forces, a vertical and a horizontal force; the first suffices to raise the animal, the second to move it along."2 Professor Marey, it will be observed, reproduces Borelli's artificial wing, and even his text, at a distance of nearly two centuries.

That the posterior margin of the wing yields to a slight extent during both the down and up strokes will readily be admitted, alike because of the very delicate and highly elastic properties of the posterior margins of wings, and because of the comparatively great force employed in their propulsion; but that they do not yield to the extent stated by Professor Marey is a matter of absolute certainty. This admits of direct proof. If any one watches the horizontal or upward flight of a large bird he will observe that the posterior or flexible margin of the wing never rises during the down stroke to a perceptible extent, so that the under surface of the wing never locks backwards. On the contrary, he will perceive that the under surface of the wing (during the down stroke) invariably looks forwards and forms a true kite with the horizon, the angles made by the kite varying at every part of the down stroke, as shown more particularly at c d e f g, i j k l m of fig. 30, p. 317. The authors who have adopted Borelli's plan of artificial wing, and who have endorsed his mechanical views of the wing's action most fully, are Chabrier, Straus-Durkheim, Girard, and Marey. Borelli's artificial wing, it will be remembered, consists of a rigid rod in front and a flexible sail behind. It is also made to strike vertically downwards. According to Chabrier, the wing has only one period of activity. He believes that if the wing be suddenly lowered by the depressor muscles, it is elevated solely by the reac tion of the air. There is one unanswerable objection to this theory: the bats and birds, and some if not all the insects, have distinct elevator muscles, and can elevate their wings at pleasure when not flying and when consequently the reaction of the air is not elicited. Straus-Durkheim agrees with Borelli both as to the natural and the artificial wing. Durkheim is of opinion that the insect abstracts from the air by means of the inclined plane a component force (composant) which it employs to support and direct itself. In his theology of nature he describes a schematic wing as

The artificial wing recommended by Professor Pettigrew is a more exact imitation of nature than either of the foregoing. It is of a more or less triangular form, thick at the root and anterior margin, and thin at the tip and posterior margin. No part of it is rigid. It is on the contrary highly elastic and flexible throughout. It is furnished with springs at its root to contribute to its continued play, and is applied to the air by a direct piston action in such a way that it descends in a downward and forward direction during the down stroke, and ascends in an upward and forward direction during the up stroke. It elevates and propels both when it rises and falls. It, moreover, twists and untwists during its action and describes figure-of-8 and waved tracks in space, precisely as the natural wing does. The twisting is most marked at the tip and posterior margin, particularly that half of the posterior margin next the tip. The wing when in actionmay be divided into two portions by a line running diagonally between the tip of the wing anteriorly and the

1 Revue des Cours Scientifiques de la France et de l'Étranger, 1869, par M. le Docteur Marey, professeur au Collège de France. 2 Professor E. J. Marey, op. cit., 1869,

root of the wing posteriorly. The tip and posterior parts | rotate, the blades, because of their elasticity, assume a of the wing are more active than the root and anterior great variety of angles, the angles being least where the parts, from the fact that the tip and posterior parts (the wing is an eccentric) always travel through greater spaces, in a given time, than the root and anterior parts.

The wing is so constructed that the posterior margin yields freely in a downward direction during the up stroke, while it yields comparatively little in an upward direction during the down stroke; and this is a distinguishing feature, as the wing is thus made to fold and elude the air more or less completely during the up stroke, whereas it is made to expand and seize the air with avidity during the down stroke. The oblique line referred to as running diagonally across the wing virtually divides the wing into an active and a passive part, the former elevating and propelling, the latter sustaining.

It is not possible to determine with exactitude the precise function discharged by each part of the wing, but experiment tends to show that the tip of the wing elevates, the posterior margin propels, and the root sustains.

b

a

[ocr errors]

g'

B

B

a

[blocks in formation]

FIG. 34.-Double elastic wing driven by direct piston action. During the up stroke of the piston the wing is very decidedly convex on its upper surface (abcd, A A'); its under surface (ef gh, A A') being deeply concave and inclined obliquely upwards and forwards. It thus evades, to a considerable extent, the air during the up stroke. During the down stroke of the piston the wing is flattened out in every direction, and its extremities twisted in such a manner as to form two screws, as seen at a' b'c' d', e'ƒ g' h', B, B'. The active area of the wing is by this arrangement considerably diminished during the up stroke, and considerably augmented during the down stroke; the wing seizing the air with greater avidity during the down than during the up stroke. i,j, k, elastic band to regulate the expansion of the wing; 7, piston;, m, piston head; n, cylinder. (Pettigrew, 1870.)

The wing-and this is important is driven by a direct piston action with an irregular hammer-like movement, the pinion having communicated to it a smart click at the beginning of every down stroke-the up stroke being more uniform. The following is the arrangement (fig. 32). If speed of the blades is greatest and vice versa. The pitch of the blades is thus regulated by the speed attained (fig. 35).

e

[merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small]

FIG. 32. Elastic spiral wing, which twists and untwists during its action, to form a mobile helix or screw. This wing is made to vibrate by a direct piston action, and by a slight adjustment can be propelled vertically, horizontally, or at any degree of obliquity.

a b, Anterior margin of wing, to which the neuræ or ribs are affixed. c d, Posterior margin of wing crossing anterior one. z, Ball-and-socket joint at root of wing, the wing being attached to the side of the cylinder by the socket. t, Cylinder. rr, Piston, with cross heads (w, w) and piston head (s). o o, Stuffing boxes. e, f, Driving chains. m, Superior elastic band, which assists in elevating the wing. n, Inferior elastic band, which antagonizes m. The alternate stretching of the superior and inferior elastic bands contributes to the continuous play of the wing, by preventing dead points at the end of the down and up strokes. The wing is free to move in a vertical and horizontal direction and at any degree of obliquity. (Pettigrew, 1870.)

the artificial wing here represented (fig. 32) be compared with the natural wing as depicted at fig. 33, it will be seen that there is nothing in the one which is not virtually reproduced in the other. In addition to the foregoing,

m

FIG. 83 shows the spiral elastic wings of the Gull. Each wing forms a mobile helix or screw. ab, Anterior margin of left wing; c d, posterior margin of ditto; dg, primary or rowing feathers of left wing; g a, secondary feathers ditto; z, root of right wing with ball and socket joint; 7, elbow joint; m, wrist joint; n, o, hand and finger joints. (Pettigrew, 1870.)

Professor Pettigrew recommends a double elastic wing to be applied to the air like a steam-hammer, by being fixed to the head of the piston. This wing, like the single wing described, twists and untwists as it rises and falls, and possesses all the characteristics of the natural wing (fig. 34).

FIG. 35.-Elastic aerial screw with twisted blades resembling wings (a b c d, efgh); x, end of driving shaft; v, w, sockets in which the roots of the blades of the screw rotate, the degree of rotation being limited by steel springs (z, s); a b, ef, tapering elastic rods forming anterior or thick margins of blades of The screw; dc, hg, posterior or thin elastic margins of blades of screw. arrows m, n, o, p, q, r indicate the direction of travel. (Pettigrew, 1870.)

The peculiarity of Professor Pettigrew's wings and screws consists in their elasticity, their twisting action, and their great comparative length and narrowness. They offer little resistance to the air when they are at rest, and when in motion the speed with which they are driven is such as to ensure that the comparatively large spaces through which they travel shall practically be converted into solid bases of support.

Since Professor Pettigrew enunciated his views (1867) as to the screw configuration and elastic properties of natural wings, and more especially since his introduction of spiral, elastic artificial wings, and elastic screws, a great revolution has taken place in the construction of flying models. Elastic aero-planes are now advocated by Mr Brown,1 elastic aerial screws by Mr Armour,2 and elastic aero-planes, wings, and screws by M. Pénaud.3

M. Pénaud's experiments are alike interesting and instructive. He constructed models to fly by three different methods:-(a) by means of screws acting vertically upwards; (b) by aero-planes propelled horizontally by screws; and (c) by wings which flapped in an upward and downward direction. An account of his helicoptère or screw model appears in the Aeronaut for January 1872, but before giving a description of it, it may be well to state very

1 "The Aero-bi-plane, or First Steps to Flight," Ninth Annual

of Report of the Aeronautical Society of Great Britain, 1874.

He also recommends an elastic aerial screw consisting two blades, which taper and become thinner towards the tips and posterior margins. When the screw is made to

"Resistance to Falling Planes on a Path of Translation," Ninth Annual Report of the Aeronautical Society of Great Britain, 1874. 3 The Aeronaut for January 1872 and February 1875.

[merged small][ocr errors]

vertical screws received a fresh impulse from the experiments of MM. Ponton d'Amécourt, De la Landelle, and Nadar, who exhibited models driven by clock-work springs, which ascended with graduated weights a distance of from 10 to 12 feet. These models were so fragile that they usually broke in coming in contact with the ground in their descent. Their flight, moreover, was unsatisfactory, from the fact that it only lasted a few seconds.

Stimulated by the success of his spring models, M. Ponton d'Amécourt had a small steam model constructed. This model, which was shown at the exhibition of the Aeronautical Society of Great Britain at the Crystal Palace in 1868, consisted of two superposed screws propelled by an engine, the steam for which was generated (for lightness) in an aluminium boiler. This steam model proved a failure, inasmuch as it only lifted a third of its own weight. Fig. 37 embodies M. de la Landelle's ideas.

[graphic]

b

[ocr errors]

FIG. 36.-Cayley's Flying Model (1796).

George Cayley gave a practical illustration of the efficacy of the screw as applied to the air by constructing a small machine, consisting of two screws made of quill feathers, a representation of which we annex (fig. 36). Sir George writes as under :

"As it may be an amusement to some of your readers to see a machine rise in the air by mechanical means, I will conclude my present communication by describing an instrument of this kind, which any one can construct at the expense of ten minutes' labour. "a and b, fig. 36, are two corks, into each of which are inserted four wing feathers from any bird, so as to be slightly inclined like the sails of a windmill, but in opposite directions in each set. A round shaft is fixed in the cork a, which ends in a sharp point. At the upper part of the cork b is fixed a whalebone bow, having a small pivot hole in its centre to receive the point of the shaft. The bow is then to be strung equally on each side to the upper portion of the shaft, and the little machine is completed. Wind up the string by turning the flyers different ways, so that the spring of the bow may unwind them with their anterior edges ascending; then place the cork with the bow attached to it upon a table, and with a finger on the upper cork press strong enough to prevent the string from unwinding, and, taking it away suddenly, the instrument will rise to the ceiling."

Cayley's screws were peculiar, inasmuch as they were superimposed and rotated in opposite directions. He estimated that if the area of the screws was increased to 200 square feet, and moved by a man, they would elevate him. His interesting experiment is described at length, and the apparatus figured, in Nicolson's Journal, 1809, p. 172.

Other experimenters followed Cayley at moderate intervals:-Deghen in 1816, Ottoris Sarti in 1823, and Dubochet in 1834. These inventors all constructed flying models on the vertical screw principle. In 1842 Mr Philips succeeded in elevating a steam model by the aid of revolving fans, which flew across two fields after having attained a great altitude; and in 1859 Mr Bright took out a patent for a machine to be sustained by vertical screws, the model of which is to be seen at the patent museum, Kensington, London. In 1863 the subject of aviation by

FIG. 37. m, n, o,p; q, r, s, t, screws arranged on vertical axes to act vertically upwards. The vertical axes are surmounted by two parachutes, and the body of the machine is furnished with an engine, propeller, rudders, and an extensive aero-plane. (M. de la Landelle, 1863.)

All the models referred to (Cayley's excepted1) were provided with rigid screws, which, for many reasons, we are disposed to regard as an error. In 1872 M. Pénaud discarded the rigid screws in favour of elastic ones, as Professor Pettigrew had done some years before.

M. Pénaud also substituted india-rubber under torsion for the whalebone and clock springs of the smaller models, and the steam of the larger ones. model is remarkable for its lightness, simplicity, and power. His helicoptère or screw The accompanying sketch will serve to illustrate its construction (fig. 38). It consists of two superposed elastic screws (a a, b b), the upper of which (a a) is fixed in a vertical frame (c), which is pivoted in the central part From the centre of the under (d) of the under screw. the part of a crank, projects in an upward direction. screw an axle provided with a hook (e), which performs Between the hook or crank (e) and the centre of the upper

1 Cayley's screws, as explained, were made of feathers, and consequently elastic. As, however, no allusion is made in his writings to the superior advantages possessed by elastic over rigid screws, it is to lightness. Professor Pettigrew, there is reason to believe, was the be presumed that feathers were employed simply for convenience and first to advocate the employment of elastic screws for aerial purposes

[blocks in formation]

15 to 30 seconds.

M. Pénaud next directed his attention to the construction of a model, to be propelled by a screw and sustained by an elastic aero-plane extending horizontally. Sir George Cayley, it should be stated, proposed such a machine in 1810, and Mr Henson (as will be shown subsequently) constructed and patented a similar machine in 1842.

Several other inventors succeeded in making models fly by the aid of aero-planes and screws, as, e.g., Mr Stringfellow in 1847,1 M. du Temple in 1857, and M. Jullien in 1858. As rigid aero-planes and screws were employed in the construction of these models they flew in a hap-hazard sort of a way, it being found exceedingly difficult to confer on them the necessary degree of stability fore and aft and laterally. M. Pénaud succeeded in overcoming the difficulty in question by the invention of what he designates his automatic rudder. This consists of a small elastic aero-plane placed aft or behind the principal aero-plane which is also elastic. The two elastic aero-planes extend horizontally and make a slight upward angle with the horizon, the angle made by the smaller aero-plane (the rudder) being slightly in excess of that made by the larger. The motive power is india-rubber in the condition of torsion; the propellor, a screw. The reader will understand the arrangement by a reference to the accompanying drawing (fig. 39).

a

a

directions; and in the event of only one screw being employed it may be placed in front of or behind the aeroplane.

FIG. 39.-Acro-plane model with automatic rudder. a a, elastic aero-plane; bb, automatic rudder; c c, aerial screw centred at f; d, frame supporting aero-plane, rudder, and screw; e, india-rubber, in a state of torsion, attached to hook or crank at f. By holding the aero-plane (a a) and turning the screw (cc) the necessary power is obtained by torsion. (M. Pénaud, 1872.)

When the model is wound up and let go it descends about two feet, after which, having acquired initial velocity, it rises and flies in a forward direction at a height of from 8 to 10 feet from the ground for a distance of from 120 to 130 feet. It flies this distance in from 10 to 11 seconds, its mean speed being something like 12 feet per second. From experiments made with this model, M. Pénaud calculates that one horse power would elevate and support 85 lb.

Models on the aero-plane screw type may be propelled by two screws, one fore and one aft, rotating in opposite

Mr Stringfellow constructed a second model, which was exhibited at the exhibition of the Aeronautical Society (Crystal Palace), in 1868. It is described and figured further on.

Mr Brown has also written (1874) in support of elastic aero-bi-planes. His experiments prove that two elastic aeroplanes united by a central shaft or shafts, and separated by a wide interval, always produce increased stability. The production of flight by the vertical flapping of wings is in some respects the most difficult, but this also has been attempted and achieved. M. Pénaud and M. de Villeneuve have each constructed winged models. Professor Marey was not so fortunate. He endeavoured to construct an artificial

insect on the plan advocated by Borelli, Straus-Durckheim, and Chabrier, but signally failed, his insect never having been able to lift more than a third of its own weight.

MM. de Villeneuve and Pénaud constructed their winged models on different types, the former selecting the bat, the latter the bird. M. Villeneuve made the wings of his artificial bat conical in shape and comparatively rigid. He

[blocks in formation]

FIG. 40.-Artificial flying bird. a b c d, a' b'c'd', elastic wings, which twist and untwist when made to vibrate; a b, a' b', anterior margins of wings; cd, cd', posterior margins of wings; c, c, inner portions of wings attached to central shaft of model by elastic bands at e; f, india-rubber in a state of torsion, which provides motive power, by causing the crank situated between the vertical wing supports (g) to rotate: as the crank revolves the wings are made to vibrate by means of two rods which extend between the crank and the roots of the wings; h, tail of artificial bird. (M. Pénaud, 1872.)

controlled the movements of the wings, and made them strike downwards and forwards in imitation of natural wings, as described by Professor Pettigrew. His model possessed great power of rising. It elevated itself from the ground with ease, and flew in a horizontal direction for a distance of 24 feet, and at a velocity of 20 miles an hour. M. Pénaud's model differed from M. de Villeneuve's in being provided with elastic wings, the posterior margins of which in addition to being elastic were free to move round the anterior margins as round axes (see p. 313, fig. 24). India-rubber springs were made to extend between the inner posterior parts of the wings and the frame, corresponding to the backbone of the bird.

A vertical movement having been communicated by means of india-rubber in a state of torsion to the roots of the wings, the wings themselves, in virtue of their elasticity, and because of the resistance experienced from the air, twisted and untwisted and formed reciprocating screws, precisely analogous to those originally described and figured by Professor Pettigrew in 1867. M. Pénaud's arrangement is shown in fig. 40.

If the left wing of M. Pénaud's model (a b, c d of fig. 40) be compared with the wing of the bat as drawn by IX.

4I

Professor Pettigrew (fig. 18, page 313), or with Professor Pettigrew's artificial wing (page 319, fig. 32), the identity of principle and application is at once apparent.

The twisting kite-like action of the wings, to which allusion has so frequently been made, and to which, as has been shown, Professor Pettigrew first strongly directed attention in 1867, justifies our introductory remarks as to the very intimate relation which subsists between natural and artificial flight. As already stated, it is not possible to understand artificial flight in the absence of a knowledge of natural flight.

In M. Pénaud's artificial bird the equilibrium is secured by the addition of a tail. The model cannot raise itself from the ground, but on being liberated from the hand it descends 2 feet or so, when, having acquired initial velocity, it flies horizontally for a distance of 50 or more feet, and rises as it flies from 7 to 9 feet. The following are the measurements of the model in question :-length of wing from tip to tip, 32 inches; weight of wing, tail, frame, india-rubber, &c., 73 grammes (about 2 ounces). We have referred to Mr Henson's flying machine, which was designed in 1843. As it was the earliest attempt at aerostation on a great scale it deserves a more than passing notice. Mr Henson was one of the first to combine aerial screws with extensive supporting structures occupying a nearly horizontal position. The accompanying illustration explains the combination (fig. 41).

The defect of Mr Henson's machine consists mainly in its rigidity, and in the vast amount of sustaining surface displayed by it, this approximating it in some measure to the balloon.

Mr Wenham, thinking to improve upon Mr Henson, invented in 1867 what he designated his aero-planes.1 The aero-planes are thin, light, long, narrow structures, arranged above each other in tiers like so many shelves. They are tied together at a slight upward angle, and combine strength and lightness. The idea is to obtain great sustaining area in comparatively small space. It was hoped that when the aero-planes were wedged forward in the air by vertical screws, or by the body to be flown, each aero-plane would rest or float upon a stratum of undisturbed air, and that practically the aero-planes would give the same support as if spread out horizontally. The aero-planes may be said to form a compound kite, and have only been partially successful. They are rigid, and present a large extent of dead surface, so that the same objections made to Mr Henson's arrangement apply to them. The great sustaining surface they present forms at once their strength and weakThey sustain and lift, but are very difficult to wedge forward, and if a breeze be blowing they become unmanageable, in the sense that a balloon is unmanageable. The accompanying figures illustrate Mr Wenham's views (figs. 42 and 43).

ness.

[merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small]
[graphic]

Fig. 42.

FIG. 41.-Henson's Acrostat (1843).

"The chief feature of the invention was the very great expanse of its sustaining planes, which were larger in proportion to the weight it had to carry than those of many birds. The machine advanced with its front edge a little raised, the effect of which was to present its under surface to the air over which it passed, the resistance of which, acting upon it like a strong wind on the sails of a windmill, prevented the descent of the machine and its burden. The sustaining of the whole, therefore, depended upon the speed at which it travelled through the air, and the angle at which its under surface impinged on the air in its front. The machine, fully prepared for flight, was started from the top of an inclined plane, in descending which it attained a velocity necessary to sustain it in its further progress. That velocity would be gradually destroyed by the resistance of the air to the forward flight; it was, therefore, the office of the steam-engine and the vanes it actuated simply to repair the loss of velocity; it was made, therefore, only of the power and weight necessary for that small effect." The editor of Newton's Journal of Arts and Sciences speaks of it thus:-"The apparatus consists of a car containing the goods, passengers, engines, fuel, &c., to which a rectangular frame, made of wood or bamboo cane, and covered with canvas or oiled silk, is attached. This frame extends

on either side of the car in a similar manner to the outstretched wings of a bird; but with this difference, that the frame is immovable. Behind the wings are two vertical fan wheels, furnished with oblique vanes, which are intended to propel the apparatus through the air. The rainbow-like circular wheels are the propellers, answering to the wheels of a steam-boat, and acting upon the air after the manner of a windmill. These wheels receive motions from bands and pulleys from a steam or other engine contained in the car. To an axis at the stern of the car a triangular frame is attached, resembling the tail of a bird, which is also covered with canvas or oiled silk. This may be expanded or contracted at pleasure, and is moved up and down for the purpose of causing the machine to ascend or descend. Beneath the tail is a rudder for directing the course of the machine to the right or to the left; and to facilitate the steering a sail is stretched between two masts which rise from the car. The amount of canvas or oiled silk necessary for buoying up the machine is stated to be equal to one square foot for each half pound of weight."

[ocr errors]

Fig. 43.

FIG. 42 represents a system of aero-planes designed to carry a man. α, a, thin planks, tapering at each end, and attached to a triangle; b, similar plank for supporting the aeronaut; c, c, thin bands of iron which truss planks a, a; d, d, vertical rods. Between these are stretched five bands of holland 15 inches broad and 16 feet long, the total length of the web being 80 feet. This apparatus, when caught by a gust of wind, actually lifted the aeronaut. (Wenham, 1867.)

α α,

FIG. 43.-A system of aero-planes similar to that represented at fig. 42. main spar 16 feet long; b, b, panels, with base board for aeronaut attached to main spar; e e, thin tie-band of steel with struts starting from main spar. This forms a strong light framework for the aero-planes, consisting of six webs of thin holland 15 inches broad. The acro-planes are kept in parallel plane by vertical divisions of holland 2 feet wide. c, c, wing propellers driven by the feet. (Wenham, 1867.)

Mr Stringfellow, who was originally associated with Mr Henson, and constructed a successful flying model in 1847, built a second model in 1868, in which Mr Wenham's aero-planes were combined with aerial screws. This model of Great Britain, held at the Crystal Palace, London, in was on view at the Exhibition of the Aeronautical Society 1868. It was remarkably compact, elegant, and light, and obtained the £100 prize of the exhibition for its engine, which was the lightest and most powerful ever constructed. The annexed woodcut (fig. 44), taken from a photograph of Mr Stringfellow's model, gives a very good idea of the arrangement, a, b, c representing the superimposed planes, d the tail, e, f the vertical screw propellers. imposed planes (a, b, c) in this machine contained a sustaining area of 28 square feet, in addition to the tail (d). Its engine represented a third of a horse power, and the weight of the whole (engine, boiler, water, fuel, superimposed planes, and propellers) was under 12 b. Its sustaining area, if that of the tail (d) be included, was something like 36 square feet, ie.,. 3 square feet for every 1 "On Aerial Locomotion," Aeronautical Society's Report for 1867.

The super

« EelmineJätka »