Alexander Graham Bell’s bizarre tetrahedral kites, 1902-1912


In addition to developing the telephone, Scottish-born inventor Alexander Graham Bell conducted extensive research into aerodynamics. This series of photographs shows Bell and his colleagues demonstrating and testing various kite designs, all based on the tetrahedral structure, into whose pyramid-shaped cells Bell was drawn because they could share joints and Could reduce the weight-to-surface area. Ratio.

In his continuing research, Bell became obsessed with the idea of ​​building a kite large enough to carry a man. He actually created the box kite design in this quest to make the ultimate kite. This particular design joins several triangular kites together with a frame to form a box. Doing so increased the kite's surface area with a slight increase in weight - a good measure of improved flight capability.

Bell combined several box-like cells to form a large pyramidal structure with three triangular sides and a triangular base. This geometric form, known as a tetrahedral, is one of nature's most stable structures. Although it looks very complicated, tetrahedral kites are very manageable during flight.

His experiment with the tetrahedron was used in construction projects (a tower on his property in Bein Bhragh in Cape Breton, NS, and other structures) as well as in kite-making. Some of the sketches in his Notebook of Tetrahedral Design Ideas show how fascinated he was by the usefulness and strength of the tetrahedron as a three-dimensional structure.

Alexander Graham Bell and his wife Mabel Hubbard Gardiner Bell. 1903.

Other efforts in the development of early flight were achieved through his collaboration with a talented group of individuals known as The Aerial Experiment Association. Members of the AEA, in addition to Bell himself, were: Mabel Gardiner Hubbard Bell, Frederick Walker (KC) Baldwin, John Alexander Douglas McCurdy, Glenn Hammond Curtis and Lieutenant Thomas Atholn Selfridge.

In 1907, Bell built the largest tetrahedral kite, the Cygnet, which means "little swan" in French. It was composed of more than 3,393 cells, was 40 feet (12.2 m) long, and weighed 91 kilograms. When pulled behind a steamship, it successfully took off with a human passenger 168 feet above the water.

Unfortunately, it crashed and broke to pieces on landing. The man who was aboard the Thomas Atholan Selfridge actually survived the flight, but later became the first person to die in an airplane crash aboard a Wright military flyer in 1908.

A kite with four triangular cells in flight. 1902.

Although the signet was beyond repair, Bell felt it had "completed its function" and "demonstrated the important fact that tetrahedral systems can be used in structures for aerial locomotion."

During the same period Bell also experimented with a larger circular "tetrahedral truss" design. Tetrahedral kites are stable and easy to fly, but light-air kites are not. The large number of structural spars make it relatively heavy and require moderate to strong winds.

Despite a gradual distaste for kites and the increasing success of the Wright brothers' airplanes, Bell built two more giant quadrupedal kites, named the Cygnet II and III, but none were successful.

His Cygnet III with a 70-horsepower motor was reported to fly only a foot. Eventually, the famous scientist abandoned his experiments in 1912. Some of Bell's kites are on display at the Alexander Graham Bell National Historic Site.

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