Latest content added for UNT Digital Library Collection: Technical Report Archive and Image Libraryhttp://digital.library.unt.edu/explore/collections/TRAIL/browse/?fq=str_title_serial:NACA+Technical+Reports&start=40&fq=untl_institution:UNTGD2011-11-17T22:13:23-06:00UNT LibrariesThis is a custom feed for browsing UNT Digital Library Collection: Technical Report Archive and Image LibraryThe efficiency of small bearings in instruments of the type used in aircraft2011-11-17T22:13:23-06:00http://digital.library.unt.edu/ark:/67531/metadc65744/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc65744/"><img alt="The efficiency of small bearings in instruments of the type used in aircraft" title="The efficiency of small bearings in instruments of the type used in aircraft" src="http://digital.library.unt.edu/ark:/67531/metadc65744/thumbnail/"/></a></p><p>This report deals with the construction and properties of bearings and pivots for use in instruments. The static and running friction for both thrust and radial loads was determined for a number of conical pivots and cylindrical and ball bearings. The static rocking friction was also measured for several conical and ball bearings under a heavy load, especially to determine their suitability for use in N. P. L. (National Physical Laboratory) type wind tunnel balance. In constructing conical pivots and sockets it was found that the pivots should be hardened and highly polished, preferably with a revolving lap, and that the sockets should be made by punching with a hardened and polished punch. It was found that for a light load the conical pivots give less friction than any other type, and their wearing qualities when hardened are excellent. Very small ball bearings are unsatisfactory because the proportional accuracy of the balls and races is not high enough to insure smooth running. For rocking pivots under heavy loads it was found that a ball-and-socket bearing, consisting of a hemispherical socket and a sphere of smaller diameter concentric with it, with a row of small balls resting between the two, was superior to a pivot resting in a socket. It was found that vibration such as occurs in an airplane will greatly reduce the static friction of a pivot or bearing, in some cases to as little as one-twentieth of its static value.</p>On the theory of laminar boundary layers involving separation2011-11-17T22:13:23-06:00http://digital.library.unt.edu/ark:/67531/metadc65686/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc65686/"><img alt="On the theory of laminar boundary layers involving separation" title="On the theory of laminar boundary layers involving separation" src="http://digital.library.unt.edu/ark:/67531/metadc65686/thumbnail/"/></a></p><p>This paper presents a mathematical discussion of the laminar boundary layer, which was developed with a view of facilitating the investigation of those boundary layers in particular for which the phenomenon of separation occurs. The treatment starts with a slight modification of the form of the boundary layer equation first published by Von Mises. Two approximate solutions of this equation are found, one of which is exact at the outer edge of the boundary layer while the other is exact at the wall. The final solution is obtained by joining these two solutions at the inflection points of the velocity profiles. The final solution is given in terms of a series of universal functions for a fairly broad class of potential velocity distributions outside of the boundary layer. Detailed calculations of the boundary layer characteristics are worked out for the case in which the potential velocity is a linear function of the distance from the upstream stagnation point. Finally, the complete separation point characteristics are determined for the boundary layer associated with a potential velocity distribution made up of two linear functions of the distance from the stagnation point. It appears that extensions of the detailed calculations to more complex potential flows can be fairly easily carried out by using the explicit formulae given in the paper. (author).</p>Transonic flow past cone cylinders2011-11-17T22:13:23-06:00http://digital.library.unt.edu/ark:/67531/metadc65581/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc65581/"><img alt="Transonic flow past cone cylinders" title="Transonic flow past cone cylinders" src="http://digital.library.unt.edu/ark:/67531/metadc65581/thumbnail/"/></a></p><p>Experimental results are presented for transonic flow post cone-cylinder, axially symmetric bodies. The drag coefficient and surface Mach number are studied as the free-stream Mach number is varied and, wherever possible, the experimental results are compared with theoretical predictions. Interferometric results for several typical flow configurations are shown and an example of shock-free supersonic-to-subsonic compression is experimentally demonstrated. The theoretical problem of transonic flow past finite cones is discussed briefly and an approximate solution of the axially symmetric transonic equations, valid for a semi-infinite cone, is presented.</p>Moisture resistant finishes for airplane woods2011-11-17T22:13:23-06:00http://digital.library.unt.edu/ark:/67531/metadc65735/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc65735/"><img alt="Moisture resistant finishes for airplane woods" title="Moisture resistant finishes for airplane woods" src="http://digital.library.unt.edu/ark:/67531/metadc65735/thumbnail/"/></a></p><p>This report describes briefly a series of experiments made at the Forest Products Laboratory, Madison, Wisconsin, to determine the comparative moisture resistance of linseed oil, impregnation treatments, condensation varnishes, oil varnishes, enamels, cellulose varnishes, rubber, electroplated and sprayed metal coatings, and metal-leaf coatings when applied to wood. All coatings except rubber and electroplated metal coatings, which were not developed sufficiently to make them practical, admitted moisture in varying degrees. The most effective and most practical coating was found to be that of aluminum leaf.</p>The Design of Wind Tunnels and Wind Tunnel Propellers2011-11-17T22:13:23-06:00http://digital.library.unt.edu/ark:/67531/metadc65731/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc65731/"><img alt="The Design of Wind Tunnels and Wind Tunnel Propellers" title="The Design of Wind Tunnels and Wind Tunnel Propellers" src="http://digital.library.unt.edu/ark:/67531/metadc65731/thumbnail/"/></a></p><p>Report discusses the theory of energy losses in wind tunnels, the application of the Drzewiecki theory of propeller design to wind tunnel propellers, and the efficiency and steadiness of flow in model tunnels of various types.</p>Airplane Stress Analysis2011-11-17T22:13:23-06:00http://digital.library.unt.edu/ark:/67531/metadc65730/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc65730/"><img alt="Airplane Stress Analysis" title="Airplane Stress Analysis" src="http://digital.library.unt.edu/ark:/67531/metadc65730/thumbnail/"/></a></p><p>Report presents stress analysis of individual components of an airplane. Normal and abnormal loads, sudden loads, simple stresses, indirect simple stresses, resultant unit stress, repetitive and equivalent stress, maximum steady load and stress are considered.</p>Data on the design of plywood for aircraft2011-11-17T22:13:23-06:00http://digital.library.unt.edu/ark:/67531/metadc65734/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc65734/"><img alt="Data on the design of plywood for aircraft" title="Data on the design of plywood for aircraft" src="http://digital.library.unt.edu/ark:/67531/metadc65734/thumbnail/"/></a></p><p>This report makes available data which will aid the designer in determining the plywood that is best adapted to various aircraft parts. It gives the results of investigations made by the Forest Products Laboratory of the United States Forest Service at Madison, Wisconsin, for the Army and Navy Departments, and is one of a series of reports on the use of wood in aircraft prepared by the Forest Products Laboratory for publication by the National Advisory Committee for Aeronautics. The object of the study was to determine, through comprehensive tests, the mechanical and physical properties of plywood and how these properties vary with density, number, thickness, arrangement of the plies and direction of grain of the plies.</p>Wind tunnel studies in aerodynamic phenomena at high speed2011-11-17T22:13:23-06:00http://digital.library.unt.edu/ark:/67531/metadc65733/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc65733/"><img alt="Wind tunnel studies in aerodynamic phenomena at high speed" title="Wind tunnel studies in aerodynamic phenomena at high speed" src="http://digital.library.unt.edu/ark:/67531/metadc65733/thumbnail/"/></a></p><p>A great amount of research and experimental work has been done and fair success obtained in an effort to place airplane and propeller design upon an empirical basis. However, one can not fail to be impressed by the apparent lack of data available toward establishing flow phenomena upon a rational basis, such that they may be interpreted in terms of the laws of physics. With this end in view it was the object of the authors to design a wind tunnel differing from the usual type especially in regard to large power and speed of flow. This report describes the wind tunnel at Mccook Field and gives the results of experiments conducted in testing the efficiency of the wind tunnel.</p>High-resolution autoradiography2011-11-17T22:13:23-06:00http://digital.library.unt.edu/ark:/67531/metadc65583/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc65583/"><img alt="High-resolution autoradiography" title="High-resolution autoradiography" src="http://digital.library.unt.edu/ark:/67531/metadc65583/thumbnail/"/></a></p><p>This investigation was made to adapt wet-process autoradiography to metallurgical samples to obtain high resolution of segregated radioactive elements in microstructures. Results are confined to development of the technique, which was perfected to a resolution of less than 10 microns. The radioactive samples included carbon-14 carburized iron and steel, nickel-63 electroplated samples, a powder product containing nickel-63, and tungsten-185 in N-155 alloy.</p>Pressure distribution over the wings of an MB-3 airplane in flight2011-11-17T22:13:23-06:00http://digital.library.unt.edu/ark:/67531/metadc65844/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc65844/"><img alt="Pressure distribution over the wings of an MB-3 airplane in flight" title="Pressure distribution over the wings of an MB-3 airplane in flight" src="http://digital.library.unt.edu/ark:/67531/metadc65844/thumbnail/"/></a></p><p>This investigation was carried out to determine the distribution of load over the wings of a high speed airplane under all conditions of flight. In particular it was desired to find the pressure distribution during level flight, over the portions of the wings in the slipstream and, during violent maneuvers, over the entire wing surface. The method used consisted in connecting a number of holes in the surface of the wings to recording multiple manometers mounted in the fuselage of the airplane. In this way simultaneous records could be taken on all of the holes for any desired length of time. (author).</p>