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The Characteristics of Two Model Six-Blade Counterrotating Pusher Propellers of Conventional and Improved Aerodynamic Design

Description: Two airfoil plans were used for propeller blades. One is modified Clark Y section designed for structural reliability and the second an NACA 16 airfoil section designed to produce minimum aerodynamic losses. At low air speeds, the propeller designed for aerodynamic effects showed a gain of from 1.5 to 4.0 percent in propulsive efficiency over the conventional type depending on the pitch. Because of the numerous variables involved, the effect of each one on the aerodynamic characteristics of the propellers could not be isolated.
Date: April 1, 1942
Creator: Pepper, Edward & McHugh, James G.

Chromite Deposits of Red Bluff Bay and Vicinity, Baranof Island, Alaska

Description: From introduction: The Red Bluff Bay area was examined briefly for the Geological Survey by John C. Reed and others in 1939. During the summer of 1941 the writers, with R. E. L. Rutledge, mapped this area on a scale of 1:12,000, and examined the serpentine masses in the interior during the course of reconnaissance trips into the surrounding region.
Date: 1942
Creator: Guild, Philip White & Balsley, James R., Jr.

Coal-Mine Accidents in the United States, 1939

Description: Report compiled by the U.S. Bureau of Mines including statistics on fatal and non-fatal accidents in coal mines located in the United States as well as data regarding the various operations (e.g., number of miners employed and average production). The information is organized into tables for comparison and the text draws some overall conclusions in the summary.
Date: 1942
Creator: Adams, William W.; Geyer, L. E. & Parry, M. G.

Coal-Mine Accidents in the United States, 1940

Description: Report compiled by the U.S. Bureau of Mines including statistics on fatal and non-fatal accidents in coal mines located in the United States as well as data regarding the various operations (e.g., number of miners employed and average production). The information is organized into tables for comparison and the text draws some overall conclusions in the summary.
Date: 1942
Creator: Adams, William W.; Geyer, L. E. & Parry, M. G.

Column strength of magnesium alloy AM-57S

Description: Tests were made to determine the column strength of extruded magnesium alloy AM-57S. Column specimens were tested with round ends and with flat ends. It was found that the compressive properties should be used in computations for column strengths rather than the tensile properties because the compressive yield strength was approximately one-half the tensile yield strength. A formula for the column strength of magnesium alloy AM-57S is given.
Date: July 1, 1942
Creator: Holt, M

A comparison of the results from general tank tests of 1/6- and 1/12-full-size models of the British Singapore IIC flying boat

Description: A 1/6-full-size model of the hull of the British Singapore IIC flying boat was tested in the NACA tank. The results are given in the form of charts and are compared with the results of previous tests made in the NACA tank of a 1/12-full-size model, published in NACA T.N. No. 580, and with the results of tests made in the British R.A.E. tank of another 1/6-full-size model of the same hull. When the data from the tests of the 1/6- and 1/12-full-size models were compared on the basis of Froude's law of comparison, differences were found. This fact supported the belief that the small scale of the model and the use of a model that was too small to suit the equipment of the NACA tank had caused the results of the tests of the 1/12-full-size model to be less reliable than the results of the tests of the 1/6-full-size model. The results of the tests of the two models agreed sufficiently well to show that test of a small model, if made meticulously and with suitable equipment, may give useable results, but that a larger model should be used whenever feasible. The results of the NACA tests of the 1/6-full-size model were found to be in good agreement with the R.A.E. tests of a model of the same size.
Date: August 1, 1942
Creator: Truscott, Starr & Dawson, John R

The Compressible Potential Flow Past Elliptic Symmetrical Cylinders at Zero Angle of Attack and with No Circulation

Description: For the tunnel corrections of compressible flows those profiles are of interest for which at least the second approximation of the Janzen-Rayleigh method can be applied in closed form. One such case is presented by certain elliptical symmetrical cylinders located in the center of a tunnel with fixed walls and whose maximum velocity, incompressible, is twice the velocity of flow. In the numerical solution the maximum velocity at the profile and the tunnel wall as well as the entry of sonic velocity is computed. The velocity distribution past the contour and in the minimum cross section at various Mach numbers is illustrated on a worked out-example.
Date: October 1, 1942
Creator: Hantzsche, W. & Wendt, H.

Contribution to the Design of Plywood Shells

Description: The writer sets out to prove by calculation and experiment that by extensive utilization of the skin to carry axial load (reduction of stringer spacing) the stringer sections can be made small enough to afford a substantial saving in structural weight. This saving ranges from 5 to about 40 percent.
Date: October 1, 1942
Creator: Blumrich, S.

Contribution to the ideal efficiency of screw propellers

Description: The stipulation of best thrust distribution is applied to the annular elements of the screw propeller with infinitely many blades in frictionless, incompressible flow and an ideal jet propulsion system derived possessing hyperbolic angular velocity distribution along the blade radius and combining the advantage of uniform thrust distribution over the section with minimum slipstream and rotation losses. This system is then compared with a propeller possessing the same angular velocity at all blade elements and the best possible thrust distribution secured by means of an induced efficiency varying uniformly over the radius. Lastly, the case of the lightly loaded propeller also is discussed.
Date: January 1, 1942
Creator: Hoff, Wilhelm

Control of Torsional Vibrations by Pendulum Masses

Description: Various versions of pendulum masses have been developed abroad within the past few years by means of which resonant vibrations of rotating shafts can be eliminated at a given tuning. They are already successfully employed on radial engines in the form of pendulous counterweights. Compared with the commonly known torsional vibration dampers, the pendulum masses have the advantage of being structurally very simple, requiring no internal damping and being capable of completely eliminating certain vibrations. Unexplained, so far, remains the problem of behavior of pendulum masses in other critical zones to which they are not tuned, their dynamic behavior at some tuning other than in resonance, and their effect within a compound vibration system and at simultaneous application of several differently tuned pendulous masses. These problems are analyzed in the present report. The results constitute an enlargement of the scope of application of pendulum masses, especially for in-line engines. Among other things it is found that the natural frequency of a system can be raised by means of a correspondingly tuned pendulum mass. The formulas necessary for the design of any practical version are developed, and a pendulum mass having two different natural frequencies simultaneously is described.
Date: November 1, 1942
Creator: Stieglitz, Albert

Correlation of data on the statistical theory of turbulence

Description: The statistical theory of turbulence affords an excellent medium for representing the kinematic conditions in turbulent flow and also serves as a valuable aid to exact experimental research. But it is still not developed enough for solving dynamic processes. Even in the simplest case of isotropic turbulence the calculation of the correlation curve or of the decrement of turbulence invariably reaches a point where clear-cut assumptions, such as omission of the inertia terms, or, earlier, mixing length assumptions or even merely general dimensional considerations, must be made.
Date: March 1, 1942
Creator: Wieghardt, K

The critical compression load for a universal testing machine when the specimen is loaded through knife edges

Description: The results of a theoretical and experimental investigation to determine the critical compression load for a universal testing machine are presented for specimens loaded through knife edges. The critical load for the testing machine is the load at which one of the loading heads becomes laterally instable in relation to the other. For very short specimens the critical load was found to be less than the rated capacity given by the manufacturer for the machine. A load-length diagram is proposed for defining the safe limits of the test region for the machine. Although this report is particularly concerned with a universal testing machine of a certain type, the basic theory which led to the derivation of the general equation for the critical load, P (sub cr) = alpha L can be applied to any testing machine operated in compression where the specimen is loaded through knife edges. In this equation, L is the length of the specimen between knife edges and alpha is the force necessary to displace the upper end of the specimen unit horizontal distance relative to the lower end of the specimen in a direction normal to the knife edges through which the specimen is loaded.
Date: September 1, 1942
Creator: Lundquist, Eugene E. & Schwartz, Edward B.

Critical Compressive Stress for Flat Rectangular Plates Supported Along All Edges and Elastically Restrained Against Rotation along the Unloaded Edges

Description: A chart is presented for the values of the coefficient in the formula for the critical compressive stress at which buckling may be expected to occur in flat rectangular plates supported along all edges and, in addition, elastically restrained against rotation along the unloaded edges. The mathematical derivations of the formulas required in the construction of the chart are given.
Date: January 1, 1942
Creator: Lundquist, Eugene E. & Stowell, Elbridge Z.

Critical Compressive Stress for Outstanding Flanges

Description: A chart is presented for the values of the coefficient in the formula for the critical compressive stress at which buckling may be expected to occur in outstanding flanges. These flanges are flat rectangular plates supported along the loaded edges, supported and elastically restrained along one unloaded edge, and free along the other unloaded edge. The mathematical derivations of the formulas required for construction of the chart are given.
Date: January 1, 1942
Creator: Lundquist, Eugene E. & Stowell, Elbridge Z.