Page:Aerial Flight - Volume 1 - Aerodynamics - Frederick Lanchester - 1906.djvu/370

§ 230 The following account of these experiments is condensed from Professor Langley's Memoir, “Experiments in Aerodynamics,” published by the Smithsonian Institute, Washington, 1891.

The site chosen for these experiments was situated in the grounds of the observatory at Allegheny, Pa., U.S.A., some 1,145 ft. above sea level.

The whirling table, erected in the open air, consisted of a trussed cantilever beam, arranged to rotate about a central vertical axis, being driven by an underground horizontal shaft from a separate power house through the medium of bevel gearing. The total length of the beam is given as 60 ft., that is to say, the extremities describe a circle of 30 ft. radius. In construction the beam itself is figured as resembling a light ladder, laid horizontally and stayed from a point about 9 ft. above its centre by a vertical strut, and a number of wire guys taken out to various points along its length. Lateral stiffness is given to the structure by a pair of guys on either side stretched from each extremity to a central outrigger. Provision is made for obtaining at will peripheral speeds from 15 to 100 ft. per second, and for chronographically recording each quarter-revolution by electrical means.

The mode of employment of the whirling table above described involves the use of a number of distinct apparatus, each specially schemed and designed by Prof. Langley for the particular purpose in view.

It is impossible to altogether detach the description of the apparatus from the discussion of its employment and results. In the Memoir a chapter is devoted to each instrument, and in the present précis and discussion the author has followed a similar arrangement, a separate section being devoted to each chapter of Professor Langley's work.

§ 231. Langley's Experiments, “The Suspended Plane.”—This instrument consists of a square plane of thin brass, mounted “slidably” on anti-friction rollers in a frame and suspended by a