Either there is more force exerted in sailing than is at first sight apparent or else extra strength is called for in making sudden turns, or when it becomes necessary, as it does more or less frequently, to take a sudden wing stroke. As wings are levers of the third order the longer the wing the more force is required to move it and more strength is needed at the fulcrum or shoulder joint, and since sailing birds have long wings the need of strength is evident.
Neither birds nor any creatures that live or have lived afford us any criterion as to the limit of size that must be placed on an aeroplane. The largest of whales is weak and insignificant beside an ocean liner, and the condor and albatross, with their spread of ten or twelve feet and weight of ten to twenty pounds, tell us nothing of what may be the possibilities of size and weight.
Among the various problems confronting the would-be navigator of the air is that of at times making headway against a medium moving at the rate of ten, twenty, or thirty miles an hour, sometimes even more, a difficulty that neither locomotive nor steamer is called upon to meet. True, an aeroplane would, to use a technical term, probably lie within two and one-half points of the wind and could thus advantageously beat to windward, but any deviation from a straight course means loss of time, and nowadays time is everything.
The mode of propulsion may be, undoubtedly will be, as entirely different from a wing as the propeller is unlike the tail of a fish, and as the study of fish has thrown little or no light on the problems of the proper form or best motor for a ship, it is doubtful if the study of birds will do more for the aerodrome. Nor does it seem likely that a study of the bird will suggest any new devices in the way of joints, braces, or rudders, for what must be discouraging to those engaged in solving the problems of flight is the utter inadequacy of the bird’s wing, from a mechanical standpoint, for the work it is called upon to do, for in all its articulations there is a freedom of movement, an amount of play that would be inadmissible in any machine. The shoulder, elbow and wrist joints are but loose affairs, depending for their efficiency on the pull of the muscles; subtract the element of life from the wing of a bird and it becomes at once limp and useless. And herein is the key to the bird’s success as a flying machine; it has life, and while the wing may reveal certain principles of balancing, it cannot teach us all the art, for it is done instinctively. The bird has back of it untold ages of experience and its actions during flight demand no thought; the muscles respond instinctively to each change in the pressure and direction of the wind, and the bird need take no thought as to how it shall fly.
Mr. Chanute has taken the greatest step yet made towards overcoming the difficulty of responding to changes in the velocity of the fickle air, but whether or not it will be possible to construct apparatus that will not only adjust itself to changes in the force of the wind, but to eddies and changes in direction as well, remains to be seen, the more that it must act not on planes six feet in length, but on surfaces infinitely larger. The proper method of constructing the wings of an aeroplane so as to insure stability and utilize the power of the wind to the best advantage, and some hints as to balancing and steering are the main assistance that we seem likely to gain from a study of the structure and flight of birds.
ELECTRIC AUTOMOBILES.
By WM. BAXTER, Jr.
As electricity has been so successful in the street railway, where it has superseded all other forms of motive power, it might naturally be supposed that it would do equally well in the automobile; but when the difference in the conditions is taken into consideration it will be found that such a conclusion is not justified. In the street railway systems the cars run continuously over the same route, and on that account the electric current required to operate the motors can be conveyed to them from a central power station by means of wires. With the automobile the case is very different; the vehicle has no fixed course, but is required to go everywhere, and the current must be supplied from a source carried by it. If primary batteries could be made so as to furnish electric currents at a low cost, then the electric carriage would be in the same position as those operated by steam or gasoline, and it could go wherever the proper chemicals to renew the battery could be obtained. But as there are no such primary batteries, the only way in which the current can be supplied is by the use of storage batteries, and these cannot give out any more energy than is put into them, and in practice cannot give quite as much. Thus if the capacity of the battery is sufficient to run the vehicle forty miles when this distance has been traversed the propelling power will be exhausted, and the batteries will have to be recharged before the carriage can go any further. If the recharging could be done in a few minutes, the storage battery would be as good as a primary battery that would generate electricity economically; but as it requires three or more hours, the electrical vehicle cannot be used for long runs, unless the user is willing to make long stops each time the battery has to be recharged. Even then an electric vehicle could not go everywhere, for it would be compelled to follow routes along which facilities for recharging the batteries could be found. From this fact it can be seen that the electric automobile carriage cannot cover the same field as the steam or the gasoline (in the present state of electrical development). Within the limits to which it is applicable, however, it can perform its work in the most satisfactory manner, and, in fact, no possible objection can be raised against it. Its operation is noiseless and vibration of the vehicle is impossible. There is no heat to inconvenience the passengers, no disagreeable smell, no escaping steam. Any desired speed can be obtained, although, of course, a heavy delivery wagon cannot be used also as a racer. The power can be made sufficient to propel any desired load up any grade, including grades far steeper than any to be encountered on streets or highways.
The only point in which the electric vehicle suffers in comparison with the others is in the weight. The capacity of a storage battery is proportional to its weight, and if it is made light, the power derived from it will be small or the time during which it is furnished will be short. To furnish one horse power for one hour requires about one hundred pounds of battery, so that if the average consumption of energy is at the rate of two horse power, one thousand pounds of battery will keep the vehicle in motion for five hours. The weight of batteries used in automobiles ranges from four or five hundred to about two thousand pounds, and the distance traversed without recharging varies from twenty-five to ninety miles, so that the radius of action of electric vehicles can be said to vary from about twelve to forty-five miles from the charging station.