Aviation.

Progress, Volume VI, Issue 9, 1 July 1911, Page 721

Aviation.

Ingenious Ornithopter Design Professor H. La V. Twining, president of the Aero Club of California, and head of the department of physics and electrical engineering at the poly technical High School, of Los Angeles, California, has completed an ornithopter in which he has embodied a knowledge of the principles of bird flight, gained during a close study of bird habits for twenty years. The ramework of this machine is made of bicycle tubing. It has a total weight of 100 pounds. The wings . measure 27 feet from tip to tip. They are four feet wide near the body of the machine, being triangular in shape, narrowing to a point at the tip. They are operated by hand and foot levers. The levers connect by links to the front rib of the machim

within three inches of the main bearing, the hand levers being on the inner and the foot levers being on the outer side of the main bearing. The bearings are ball throughout. The weight of the aviator is thus thrown upon the front edge of the wing both to raise and to lower it, the aviator at the same time being able to exert a pull between the hands and feet, the hands moving up while the feet move down to lower the wing. To raise the wing, the weight is thrown upon the hands, and at the same time the feet and the hands are made to approach one another by pulling up with the feet and pushing down with the hands. The levers give a mechanical advantage of two to one. By this means a pull of 250 pounds can be brought to bear upon the wings on both the up and down stroke. Professor Twining states that he can beat the wings fifty-two times per minute, a beat being designated as one movement of the wing down or up. The machine was suspended from a spring balance, in recent experiments, and the following data was obtained: Weight, 240 pounds with operator; speed of stroke, fifty-two bears per minute area of wing surface, fifty

square feet; sweep of tip of wing, ten and one-half feet; hands moved through 13 inches; feet moved through sixteen inches. With hands and feet moVed up the levers so as to get a leverage of two to one, a lift of 120 pounds whs obtained on the down stroke, the machine at the same time rising two inches. On the up stroke of the wing the machine moved forward and showed a slight lift. Owing to the difficulty of suspending the machine from its centre of gravity the whole leverage, four to one, could not be tested. The Professor says in his machine the weight of the wings will be borne by springs, which will relieve the operator of having to bear their weight in handling the levers. The wings, when flapping, displace air and force : it away at the rear tips and more air moves i,towards them at all other points, so that

pressure is developed under the wings. The up stroke of the wings in bird flight is very important, and has been ignored by those who have previously built bird-like machines, but he thoroughly believes that he will be able to use this force to excellent advantage. While the theory is correct, he believes that practice may develop unknown factors. In case of a failure in this he intends to continue his experiments until he solves the problem. Prof. H. L. Twining is at work on two machines of this type; the result is that he has continued his experiments and expects to soon build another. He is also engaged with Warren Eaton and P. S. Eaton, of Los Angeles, in the construction of a monoplane similar to the Bleriot. An important change in the control has been introduced since, instead of warping the wings or changing the angle of incidence of the fore and aft planes, auxiliary sliding planes are to be used. The sliding planes at the ends of the main planes, slip simultaneously to the right or left- thus decreasing the surface on one side and increasing it on the other. The tips of the rear planes slide in the same way, and the whole rear plane slides fore and aft, thus

increasing or decreasing, the leverage exercised by the elevator.” This secures fore and aft stability. The machine otherwise has the exact dimensions of the ‘••Bleriot XII/’ Fourteen machines are being constructed in or near ..Los, Angeles.