« PreviousContinue »
Birds Our Flying Models
By W. G. Fitz-Gerald
CIENTISTS of Euro- Therefore, some highly interesting ex
pean reputation, like periments have just been undertaken by Mr. C. G. Lamb, M. A., some members of the Aëronautical SociUniversity Lecturer in ety of Great Britain, including Mr. E. P. Electrical Engineering Frost, Mr. F. W. H. Hutchinson, and at Cambridge, consider Mr. C. R. D’Esterre, with an experiit to be of great impor- mental flying-machine model whose actance, in connection tion is scientifically based upon the move
with any serious at- ments of birds' wings. The experimenttempt to solve the problem of aërial loco- ers have collected a vast mass of data on motion, that investigation should first of the subject, including the studies of Mr. all be made by experiments as to whether Hargrave of New South Wales, and the lines of design should proceed on those of M. Marey, whose work Le Vol those seen in nature or on entirely dif- des Oiseaur is a standard authority. ferent lines.
The wing of a bird may be said to
FIG. 1. FIRST MODEL OF THE "BIRD.".
In regard to the problem of propulsion have two portions. First, we have the in water, the exigencies of mechanical section extending to the outer side of the construction have rendered it impossible wrist-joint. The principal feathers of to follow the method found in nature, this part usually number about ten, and since in that case the flexibility of the are known as "primary feathers." Then moving body is an essential. But in the there is the inner side of the wrist-joint, case of birds and insects, this confine- known as the “body” of the wing. If ment to an imitation of their methods of the primary feathers are examined, it progression does not arise.
will be seen that each differs from its
FIG. 2. MAKING ADJUSTMENTS FOR FLIGHT. The operator is about to start the wings of the weird, bird-like machine, which is made to roll along the ground
at the operator's will.
fellow in a graduated series, and the conducted some curious experiments with curves are more pronounced midway be- small birds, by liberating them in paper tween the wrist and the shoulder-joint. tubes the internal surfaces of which were
Mr. Frost, after years of observation coated with lamp black. of the structure of natural wings of all It was found that the wing as a whole kinds, and of their movement in fight, is essentially an elastic structure; and concluded more than twenty years ago, during flapping flight the primary feaththat, in the ordinary flight of a bird, the ers automatically exert a clawing, swimwing is merely beaten up and down, so ming action. It was obvious to observthat a lift and a drive are obtained. The ers, too, that a bird's wing, both as a wing is so shaped that the down stroke gliding and as a propelling surface, is a encounters much greater resistance than beautifully efficient instrument. the up stroke, apart from the question of To test these views, Messrs. Frost, energy; and Mr. Frost contended that Hutchinson, and D'Esterre arranged the the primary feathers are so arranged that apparatus shown in Fig. 1. on being struck downward in the air A pair of dried natural wings about their ends travel forward and upward. three square feet in area, were arranged For example, in flight, the wing-tips of with a small electric motor and a reduc
a the rook can be seen to be curled upward. tion gear so that they flapped up and
Marey obtained confirmation of this by down, the whole concern being susfixing a piece of white paper to the tip pended by a spring balance from the balof the first primary of a black crow, anced arm. With 24 volts, a maximum which was then caused to fly in front of lifting power of five pounds was devela dark screen, when the lens was exposed oped (350-400 flaps per minute). The during five beats of the wing. Major effect was most curious. The huge "bird" B. Baden-Powell, the well-known aëro- flapped itself round and round, although naut and inventor of military kites, also it sagged heavily between the down strokes. But it should be borne in mind The wings flap 100 times a minute ; that its speed was only four or five miles and when the machine has been susan hour, and the apparatus was crude. pended from a tree-bough, the whole apMoreover, the bird itself weighed twen- paratus apart from the carriage, weighty-one pounds; so it is little wonder that ing 232 pounds, is lifted up bodily into it drooped on the up strokes. The ratio the air and carried forward. It exactly of horse-power to lift was 1 horse-power resembles a giant bird trying to fly. At to 50 pounds. This agrees with the fig- the down stroke, it seems that if the rope ures given by various authorities as that were then cut the powerful sweep of the obtaining among larger birds. In what wings would lift and carry away the enwas called the "hovering lift," 1 horse- tire machine. With 100 flaps per minute, power gave a lift of 10 pounds.
the wings evoked a resistance of about The results were considered so encour- 100 pounds each, and each stroke raised aging that a much larger model was built the machine about 2 feet. Experiments (Fig. 2) and mounted on a special car- showed that a feathered wing made up riage. The new model has a total wing of a number of units exerts greater rearea twenty times the size of its prede- sistance than a simple wing such as that cessor's—that is, about 60 square feet. of an insect or a bat, or the mechanical The entire machine measures 20 feet wings hitherto made for wing-flapping across.
machines. The transmission is by a coned fric- It was clearly seen that the primary tion-clutch and chains in two stages to feathers act as a series of stepped aërothe connecting rod. The crank-throw is planes ;, and altogether a mass of data adjustable for altering the size of the was secured which is about to be emangle of the flap. "Pectoral cords" of bodied by the investigators in a far more elastic are attached to the brackets below ambitious machine than has yet been the wings. These are for storing up en- built. It is proposed to form a small ergy on the up stroke. A gasoline cycle syndicate of men with scientific tastes, to engine of about 3 horse-power is the mo- complete the work and produce a regular tor.
Line-unit on table at right; two correspondence-units on tables to left. This photograph serves to show trans
mitter and home recorder.
HE Rowland system of a perforated or printed tape at the other telegraphy was invented end of the line. The operations conby the late Prof. Henry nected with transmission by this method A. Rowland, of Johns offered too many loopholes for error and Hopkins University, one were too cumbersome to be practical.
of the world's greatest Professor Rowland, in devising his men of attainments in science. In this new system of telegraphy, aimed to acsystem, the alternating current was first complish two great results. First, realizsuccessfully applied to the uses of teleg- ing that the vast network of telegraph raphy.
wires spread over the world was working In their endeavors to improve upon the far below its possible capacity, he wished existing methods of communication and to increase this capacity by multiplexing. increase the capacity of wires, experi- Second, he wished to invent a machine menters have developed apparatus of two that would automatically and directly kinds: the Multiplex, which aimed to record, in page form, printed characters. send many messages simultaneously over In both these fields, little practical adone wire; and the Rapid, which increases vance had been made. As was remarked the speed of the, single transmitter. Of above, two messages each way was the the first kind, however, a Morse appara- limit of the multiplexing systems; and, tus sending two messages each way was although machines had been built to until recently the only one in practical record in printed characters, they were use. The rapid systems have been drop- found impracticable in America after ped, one after another, because their use trial. involved the preparation of a perforated Professor Rowland solved both these tape, which, being shot rapidly through problems with astonishing success. a transmitter, caused the reproduction of apparatus at its full capacity sends four