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The Double-Acting Principle in East and West

1970; Johns Hopkins University Press; Volume: 11; Issue: 2 Linguagem: Inglês

10.1353/tech.1970.a894148

1097-3729

Ladislao Reti,

Historical and Literary Studies

The Cover Design THE DOUBLE-ACTING PRINCIPLE IN EAST AND WEST LADISLAO RETI Since 1757, when Sir William Chambers called attention to the “per­ petual bellows” of China,1 Western scholars, first among them that pioneer of the history of technology in America, Thomas Ewbank,2 joined with enthusiasm in praise of this unique piece of human ingenuity. Writing in 1937, Rudolf P. Hommel maintained that the Chinese boxbellows has the merit of surpassing in efficiency any other bellows made before the advent of modern machinery.3 Joseph Needham not only supported Hommel’s statement with his undisputed authority,4 he made the Chinese box-bellows the focal point of his thought-provoking study on the origin of the steam engine.5 Indeed, the steam engines of Newcomen were single acting as were the first engines of Watt. The double-acting principle, that is, the fluid acting on both strokes of the reciprocating piston, was first conceived by James Watt for his atmospheric rotative engines in 1775 and became a standard feature of all engines working by the expansive action of steam after 1782. Now we find this same principle, constituting the very essence of Watt’s revolutionary innovation, to be already embodied in the Chinese box-bellows. For the sake of clarity, I shall illustrate this well-known Dr. Reti, professor emeritus in the Department of Medical History at the Uni­ versity of California, Los Angeles, is the author of many articles on Renaissance science and technology. He is editor of the forthcoming facsimile edition of the Leonardo da Vinci codices in the Biblioteca Nacional of Madrid. 1 Sir William Chambers, Designs of Chinese Buildings, Furniture, Dresses, Ma­ chines, and Utensils . . . (London, 1757). 2 Thomas Ewbank, A Descriptive and Historical Account of Hydraulic and Other Machines for Raising Water, Ancient and Modern ... (New York, 1842), pp. 247-51. 3Rudolf P. Hommel, China at Work . . . (New York, 1937), pp. 18-20. 4 Joseph Needham, Science and Civilisation in China (Cambridge, 1965), 4, pt. 2: 135-50. 5 Joseph Needham, “The Pre-natal History of the Steam-Engine,” Transactions of the Newcomen Society 35 (1962-63): 3-58. 178 The Cover Design 179 instrument once more and point out its characteristics, using Aubrey F. Burstall’s reconstruction8 (fig. 1). While the cuneate bellows, still found beside our domestic fireplaces, is capable only of an intermittent blast, that is, on compression or on the downstroke, the Chinese box-bellows blows continuously, thanks to its ingenious construction. The central piston, moved back and forth by a handle, is equally active in either pushing or pulling. Each end wall of the box has an intake valve. The compressed air from both halves of the box finds its way to a single delivery outlet through a flapper valve placed at the point where the air ducts join. In short, the Chinese box-bellows is a double-acting force and suction pump. More Fig. 1.—Chinese box-bellows. Reproduced by permission from Aubrey F. Burstall, A History of Mechanical Engineering (London, 1963), p. 104. Flap valves can be seen at each side of the piston, but a single valve is at the central delivery outlet. Chicken feathers form the packing on the piston. detailed information on this instrument may be found in the publica­ tions of Ewbank, Hommel, and Needham cited earlier. The homology of both devices is immediately apparent, as the con­ structive principle of the Chinese box-blower, known at least since the 13th century (Needham has good reason to believe that the invention may go back as far as the 7th) is identical to the one that, applied to prime movers, appeared for the first time in Watt’s double-acting en­ gine in 1775.7 The difference is, using Needham’s precise terminology, that the Chinese bellows is an ad-fnstonian instrument, while a modern steam engine is ex-pistonian6 (fig. 2). 6 Aubrey F. Burstall, A History of Mechanical Engineering (London, 1963). 7 H. W. Dickinson, James Watt . . . (Cambridge, 1936), p. 134. 8 Needham introduced this expressive term to indicate the interchangeability of passive and active action in a machine working with the aid of pistons. Ad-pistonian 180 Ladislao Ret...