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Report No. 379. Rolling moments due to rolling and yaw for four wing models in rotation
806
BOOK REVIEWS.
[J. F. I.
authors have evolved a text on practical physical chemistry which for its size, would be difficult to surpass in its clarity and detail. In addition to the excellent directions on how to carry out these physical chemistry measurements, each unit of experimental procedure is prefaced by an appropriate theoretical exposition which will give the student a better insight into the laws characterizing the physical and chemical properties of substances as well as teach him the significance of his results and enable a correct evaluation of the data. The book is quite up to date and contains practically all the well established methods universally employed by chemists in their physical-chemistry researches. Among those procedures of more recent development we may list: (I) Coagulation of a Sol by Electrolytes of Different Valencies; (2) The Transformation of RadioElements; (3) Ultra-Violet Spectrography; (4) Preparation of Substances by Electrochemical Means. T. K. CLEVELAND. NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS. Report No. 374, The Automotive Ignition Coil, by T. H. Darnell, 28 pages, illustrations, quarto. Washington, Government Printing Office, 1931. Price twenty-five cents. This paper which was submitted by the Bureau of Standards for publication gives the results of an extensive series of measurements on the secondary voltage induced in an ignition coil of typical construction under a variety of operating conditions. These results show that the theoretical predictions hitherto made as to the behavior of this type of apparatus are in satisfactory agreement with the observed facts. The large mass of data obtained is here published both for the use of other investigators who may wish to compare them with other theoretical predictions and for the use of automotive engineers who will here find definite experimental results showing the effect of secondary capacity and resistance on the crest voltage produced by ignition apparatus. Report No. 379. Rolling Moments due to Rolling and Yaw for Four Wing Models in .Rotation, by Montgomery Knight and Carl J. Wenzinger, 27 pages, illustrations, quarto. Washington, Government Printing Office, 1931. Price fifteen cents. Tiais report presents the results of a series of auto-rotation and torque tests on four different rotating wing systems at various rates of roll and at several angles of yaw. The investigation covered an angle-of-attack range up to 9°0 and angles of yaw of o °, 5°, IO°, and 20 °. The tests were made in the 5-foot, closed-throat atmospheric wind tunnel of the National Advisory Committee for Aeronautics. The object of the tests was primarily to determine the effects of various angles of yaw on the rolling moments Of the rotating wings up to large angles of attack. It was found that at angles of attack above that of maximum lift the roiling moments on the wings due to yaw (or side slip) from 5 ° to 20 ° were roughly of the same magnitude as those due to rolling. There was a wide variation in magnitude of the rolling moment due to yaw angle with both angle of attack and with pb/2V. The rates and ranges of stable autorotation for the monoplane models were considerably increased by yaw, whereas for an unstaggered biplane
June, I93I. ]
BOOK REVIEWS.
80 7
they were little affected. The immediate cause of the rolling moment due to yaw is apparently the building up of large loads on the forward wing tip and the reduction of loads on the rearward wing tip. Report No. 384 . The Comparative Performance of Superchargers, by Oscar W. Schey, 15 pages, illustrations, quarto. Washington, Government Printing office, I93I. Price five cents. This report presents a comparison of superchargers on the basis of the power required to compress the air at a definite rate, and on the basis of the net engine power developed at altitudes from o to 4o,ooo feet. The investigation, which was conducted at the Langley Memorial Aeronautical Laboratory, included geared centrifugal, turbine-driven centrifugal, Roots, and vane-type superchargers. It also includes a brief discussion of the mechanical limitations of each supercharger and explains how the method of control affects the power requirements. The results of this investigation show that for critical altitudes below 20,000 feet there is a maximum difference of about 6 per cent between the amounts of net engine power developed by the various types of superchargers when ideal methods of control are employed, but for critical altitudes above 2o,ooo feet an engine develops considerably more power when equipped with a turbocentrifugal supercharger than with any other type. The Roots type gives the lowest net engine power of all at high critical altitudes, because it has the least efficient type of compression. The throttling method of control used on the geared-centrifugal type of supercharger is very unsatisfactory at low altitudes from a net engine power standpoint when compared with the method used on the Roots or turbocentrifugal. R. FLOW AND MEASUREMENTOF AIR AND GASES. By Alec B. Eason, M.A., of the Eng.ineer-in-Chief's Office, G.P.O., Assoc. M. I. C. E., M. I. E. E. M. I. Post Office Engineers. Second edition, thoroughly revised, xii-254 pages, 8vo, cloth, illustrations. Philadelphia, J. B. Lippincott Company, I93O. The analysis of the motion of fluids has always proved a most elusive study and the assumption of stream-line flow has governed the purely theoretic side of the subject. Since a formula so derived is only representative within a limited range of conditions, an immense amount of experimental work has been done in hydraulic projects, and more latterly on air and gas transmission systems, to determine coefficients which will give the theoretical formula applicable value. The transmission of air and gases being a development of less maturity than the flow of water, in gathering between the covers of a single volume a highly documented synopsis and critical review of a representative collection of investigations of air- and gas-flow, the author has provided a source of information from original sources which should be invaluable alike to the practicing engineer and the advanced student. The subject is discussed under three main divisions: (I) the friction of gases and the coefficient of friction in pipes; (II) the question of suitable meters for gas and air; (III) the working of pneumatic tubes. The specific problems investigated comprise pneumatic tubes, compressed-air systems, gaslighting systems and ventilating systems.
BOOK REVIEWS.
[J. F. I.
authors have evolved a text on practical physical chemistry which for its size, would be difficult to surpass in its clarity and detail. In addition to the excellent directions on how to carry out these physical chemistry measurements, each unit of experimental procedure is prefaced by an appropriate theoretical exposition which will give the student a better insight into the laws characterizing the physical and chemical properties of substances as well as teach him the significance of his results and enable a correct evaluation of the data. The book is quite up to date and contains practically all the well established methods universally employed by chemists in their physical-chemistry researches. Among those procedures of more recent development we may list: (I) Coagulation of a Sol by Electrolytes of Different Valencies; (2) The Transformation of RadioElements; (3) Ultra-Violet Spectrography; (4) Preparation of Substances by Electrochemical Means. T. K. CLEVELAND. NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS. Report No. 374, The Automotive Ignition Coil, by T. H. Darnell, 28 pages, illustrations, quarto. Washington, Government Printing Office, 1931. Price twenty-five cents. This paper which was submitted by the Bureau of Standards for publication gives the results of an extensive series of measurements on the secondary voltage induced in an ignition coil of typical construction under a variety of operating conditions. These results show that the theoretical predictions hitherto made as to the behavior of this type of apparatus are in satisfactory agreement with the observed facts. The large mass of data obtained is here published both for the use of other investigators who may wish to compare them with other theoretical predictions and for the use of automotive engineers who will here find definite experimental results showing the effect of secondary capacity and resistance on the crest voltage produced by ignition apparatus. Report No. 379. Rolling Moments due to Rolling and Yaw for Four Wing Models in .Rotation, by Montgomery Knight and Carl J. Wenzinger, 27 pages, illustrations, quarto. Washington, Government Printing Office, 1931. Price fifteen cents. Tiais report presents the results of a series of auto-rotation and torque tests on four different rotating wing systems at various rates of roll and at several angles of yaw. The investigation covered an angle-of-attack range up to 9°0 and angles of yaw of o °, 5°, IO°, and 20 °. The tests were made in the 5-foot, closed-throat atmospheric wind tunnel of the National Advisory Committee for Aeronautics. The object of the tests was primarily to determine the effects of various angles of yaw on the rolling moments Of the rotating wings up to large angles of attack. It was found that at angles of attack above that of maximum lift the roiling moments on the wings due to yaw (or side slip) from 5 ° to 20 ° were roughly of the same magnitude as those due to rolling. There was a wide variation in magnitude of the rolling moment due to yaw angle with both angle of attack and with pb/2V. The rates and ranges of stable autorotation for the monoplane models were considerably increased by yaw, whereas for an unstaggered biplane
June, I93I. ]
BOOK REVIEWS.
80 7
they were little affected. The immediate cause of the rolling moment due to yaw is apparently the building up of large loads on the forward wing tip and the reduction of loads on the rearward wing tip. Report No. 384 . The Comparative Performance of Superchargers, by Oscar W. Schey, 15 pages, illustrations, quarto. Washington, Government Printing office, I93I. Price five cents. This report presents a comparison of superchargers on the basis of the power required to compress the air at a definite rate, and on the basis of the net engine power developed at altitudes from o to 4o,ooo feet. The investigation, which was conducted at the Langley Memorial Aeronautical Laboratory, included geared centrifugal, turbine-driven centrifugal, Roots, and vane-type superchargers. It also includes a brief discussion of the mechanical limitations of each supercharger and explains how the method of control affects the power requirements. The results of this investigation show that for critical altitudes below 20,000 feet there is a maximum difference of about 6 per cent between the amounts of net engine power developed by the various types of superchargers when ideal methods of control are employed, but for critical altitudes above 2o,ooo feet an engine develops considerably more power when equipped with a turbocentrifugal supercharger than with any other type. The Roots type gives the lowest net engine power of all at high critical altitudes, because it has the least efficient type of compression. The throttling method of control used on the geared-centrifugal type of supercharger is very unsatisfactory at low altitudes from a net engine power standpoint when compared with the method used on the Roots or turbocentrifugal. R. FLOW AND MEASUREMENTOF AIR AND GASES. By Alec B. Eason, M.A., of the Eng.ineer-in-Chief's Office, G.P.O., Assoc. M. I. C. E., M. I. E. E. M. I. Post Office Engineers. Second edition, thoroughly revised, xii-254 pages, 8vo, cloth, illustrations. Philadelphia, J. B. Lippincott Company, I93O. The analysis of the motion of fluids has always proved a most elusive study and the assumption of stream-line flow has governed the purely theoretic side of the subject. Since a formula so derived is only representative within a limited range of conditions, an immense amount of experimental work has been done in hydraulic projects, and more latterly on air and gas transmission systems, to determine coefficients which will give the theoretical formula applicable value. The transmission of air and gases being a development of less maturity than the flow of water, in gathering between the covers of a single volume a highly documented synopsis and critical review of a representative collection of investigations of air- and gas-flow, the author has provided a source of information from original sources which should be invaluable alike to the practicing engineer and the advanced student. The subject is discussed under three main divisions: (I) the friction of gases and the coefficient of friction in pipes; (II) the question of suitable meters for gas and air; (III) the working of pneumatic tubes. The specific problems investigated comprise pneumatic tubes, compressed-air systems, gaslighting systems and ventilating systems.