bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fundamental Dynamics of Reaction-Powered Space Vehicles
Authors: Thompson L. N. 
Published: October 2007

This paper is an attempt to place in correct perspective the current considerable speculation regarding the problem of interplanetary travel. The concept and importance of “escape velocity” is dealt with first, and then the elementary mass-ratio equations for the motion of a space vehicle under various conditions are derived. Available energy sources are considered next, the operational parameter being jet velocity. It is indicated that the maximum jet velocity conceivably attainable with chemical fuels is of the order of 20,000 ft. per sec. Nuclear fuels are dealt with and it is shown that, while energy potentials are very high, the problem of practical utilization is formidable. A thermodynamic type of atomic rocket motor employing an inert reaction mass to absorb the fission energy is postulated, and it is demonstrated that the heat transfer and materials requirements present a problem of the first magnitude. The influence of propellent density on the performance characteristics of both chemical and atomic rockets is discussed, and it is shown that propellents giving high jet velocities may not necessarily be the best to use. Orders of magnitude for the mass ratios required for various interplanetary flights are established, and it is indicated that only an atomic drive will render them small enough to be attainable in practice. It is concluded that, unless nuclear energy can be suitably harnessed, economical space-travel will not be feasible.
The Fundamental Geometry of Cutting Tools
Authors: Stabler G. V. 
Published: October 2007

A full geometrical analysis of a cutting tool edge is made, in which an effective rake of universal application is defined in terms of the primary rake and the angle of obliquity of the edge. The fundamental angles are related in an easy manner to the traditional workshop terms, and may readily be applied to any cutting tool. A law of chip flow is given and its effects on the resulting chip shape are analysed. The effect of unit cube passing through the shear plane is also analysed and a method is given of finding the direction cosines of the axes of the ellipsoid of stress. The flow law is used to find the directions ofthe cutting force between chip and tool and its various components. An examination of velocity and force diagrams for oblique cutting in Merchant's shear theory leads to a debatable result at variance with his fundamental machining equation. Although predominantly theoretical, the paper has a practical background.
Water Hammer in a Pumping Main and its Prevention
Authors: Binnie A. M. , Thackrah D. G. 
Published: October 2007

An earlier investigation has been continued on the protection of a rising water main against the consequences of a sudden interruption in the supply. In place of the air bottle previously tried, an automatic air-inlet valve was placed at the lower end of the pipe-line. Experiments on a laboratory scale showed that the cushion of air thus introduced brought the returning water column to rest without sound or shock. Theoretical calculations of maximum pressure and of air drawn in were verified. The lift of the pipe-line being small compared with its length, it was found that, over the range of velocity usually employed, the maximum pressure set up by the returning column diminished as the initial velocity of the interrupted supply was increased. With no protective device in use, a series of violent impacts took place owing to the column striking and rebounding from the closed valve at the lower end of the pipe-line. An electronic gauge, having a very high natural frequency, was used to measure the magnitude and duration of the shock pressures. Its indications were generally in accord with an analysis based on the usual theory of pressure waves, but the maximum pressures actually recorded somewhat exceeded the theoretical estimates, owing to the existence of additional pressure fluctuations caused by reflections from bends, sockets, and other discontinuities in the pipe-line. The insertion of a spring-loaded relief valve only slightly reduced the shock pressures.
Design Stresses in Fillet Weld Connexions
Authors: Koenigsberger F. 
Published: October 2007

Intuition and personal opinion, rather than theoretical investigation, have often been the main guides in the determination of design stresses for fillet weld connexions. Excessive safety at the expense of accuracy and economy have resulted in weld connexions which, although they did not fail under working conditions, were not always economical. In the case of eccentrically loaded joints the stress ftorsion under a torque T has been determined by using the polar moment of inertia J of the weld throats: ftorsion = Tr/J, where r is the distance of the extreme fibre from the centroid of the weld throat. This method, though accurate enough for closed weld arrangements, resulted in uneconomical sizes for other arrangements. This paper suggests a means of determining the working loads of eccentrically loaded fillet welded joints by working out the stresses in the plastic state prevailing immediately before failure occurs. From this calculation the value of the failing load is obtained, which is divided by a certain load factor, the result being taken as the permissible load. If the results are represented in the form of graphs the time spent on calculation is considerably reduced. Practical experiments gave results which were in close agreement with the result of these calculations. In the second part of the paper, the two differing opinions on the best arrangement of fillet weld connexions joining rolled angle sections to gusset plates are investigated, so far as their effect upon the strength of the assembly is concerned, and no difference is found with regard to the static strength of the assembly, while stress peaks at the end of the welds may indicate a weakness of one arrangement under fatigue loading conditions. Further research in this direction is suggested.
Effect of Shear in Transverse Impact on Beams
Authors: Christopherson D. G. 
Published: October 2007

In this paper the problem of transverse impact on a uniform beam is considered theoretically. Two examples which can be taken as representing a wide range of impacts which occur in practice are referred to particularly: (1) the beam struck transversely by a uniform square-ended rod travelling perpendicularly to it; (2) the same problem for the striker having a spherical end. In these examples it is shown that the ability of the beam to deflect in shear as well as in bending plays a dominant part in what takes place, and that, as far as the force between striker and beam is concerned, the length of the beam is usually without importance, as there is not time during the impact for an elastic wave to travel to the ends of the beam and return. It is shown that in regard to example (2) the theory presented is in good agreement with Arnold's experimental results obtained some years previously, and curves are given from which the maximum force between beam and striker can be obtained in terms of three parameters, representing respectively the velocity, the mass, and the radius of the striker, each dependent on the ratio of shear stiffness to bending stiffness for the beam.
Control of Boilers Fired by Solid Fuels in Suspension
Authors: Young Llewellyn 
Published: October 2007

In this paper are discussed those characteristics of boiler design and performance which have favoured the parallel development of automatic control of boiler auxiliaries. Consideration is given to those temporary conditions which arise during periods of load change, and which, if not accurately estimated and followed by the necessary corrective action, may lead to over-regulation of firing rate or feed-water supply. Instruments are provided to determine and inform the operator of the necessary action to be taken, and manual remote-control eliminates the laborious duties of routine readjustments necessary to maintain efficiency. In this field automatic control has many advantages and is quicker and more accurate in response than the human operator. The theory of elementary forms of automatic control devices is dealt with simply, and the mechanical means, employing pneumatically operated devices, by which these theoretical requirements are met are described. Examples are given of the use of standard apparatus in building up a composite control system, and the more complicated installations of boilers fired by spreader stokers, pulverized fuel and cyclone furnaces are dealt with.
Characteristics of a Spinning-disk Liquid Sprayer
Authors: Boshoff W. H. 
Published: October 2007

In this paper is described an attempt to increase the output of a spinning-disk sprayer without sacrificing the homogeneous drop-size characteristics found by previous investigators. A disk sprayer inches in diameter was designed, and the characteristics were determined by feeding various quantities of water centrally on to the disk, and noting the resulting drop sizes and their distribution over a range of disk speeds from 600 to 2,000 r.p.m. The critical flow rate for the production of uniform-size drops is in the range 6–22 cu. cm. per sec., and the size of drops produced is inversely proportional to the speed of the disk. The product of drop diameter and peripheral velocity of the disk is approximately constant and varies with the smoothness of the surface of the disk rather than with the rate of liquid flow. Above the critical flow rate the homogeneity of the drops disappears and a wider range of sizes is observed. The distribution and sizes of the drops are independent of the rate of liquid feed over a range of from 22 to 110 cu. cm. per sec, the size of the majority of drops being dependent on the peripheral speed of the disk. Above that range the liquid comes off the disk in a sheet, in which little or no break-up of the liquid takes place. It is concluded that spinning disks of large diameter will produce drops of uniform size even at relatively low rotational speeds.
Part II. Research on the Performance of a Type of Internally Air-cooled Turbine Blade
Authors: Ainley D. G. 
Published: October 2007

A comprehensive series of tests have been made on an experimental single-stage turbine to determine the cooling characteristics and the overall stage performance of a set of air-cooled turbine blades. These blades, which are described fully in Part I of this paper had, internally, a multiplicity of passages of small diameter along which cool air was passed through the whole length of the blade. Analysis of the, test data indicated that, when a quantity of cooling air amounting to 2 per cent, by weight, of the total gas-flow through the turbine is fed to the row of rotor blades, an increase in gas temperature of about 270 deg. C. (518 deg. F.) should be permissible above the maximum allowable value for a row of uncooled blades made from the same material. The degree of cooling achieved throughout each blade was far from uniform and large thermal stresses must result. It appears, however, that the consequences of this are not highly detrimental to the performance of the present type of blading, it being demonstrated that the main effect of the induced thermal stress is apparently to transfer the major tensile stresses to the cooler (and hence stronger) regions of the blade. The results obtained from the present investigations do not represent a limit to the potentialities of internal air-cooling, but form merely a first exploratory step. At the same time the practical feasibility of air cooling is made apparent, and advances up to the present are undoubtedly encouraging.
Main Propulsion Gas-turbine Set for the Oil Tanker Auris
Authors: Forsling B. E. G. 
Published: October 2007

In order to obtain operating experience with a main propulsion gas turbine under service conditions at sea, the Diesel electric oil tanker Auris has been equipped with a gas-turbine set which replaces one of the four Diesel engines originally installed. A description is given of the set which operates on the simple open cycle with a heat exchanger and independent (low pressure) power turbine. The set thus has one compressor and two turbines in series, the high-pressure turbine driving the compressor and the low-pressure turbine driving the alternator which supplies power to the propeller motor. In the design the emphasis was laid on high component efficiencies which necessitated the use of multi-stage uncooled turbines. A moderately high initial gas-temperature was adopted in order to ensure adequate length of life. The experience during test operation, which covered a running time of 680 hours, is fully recorded, and complete performance figures for all conditions are given. The set was operated with some success on heavy (residual) fuel oil. The total running time on heavy fuel oil was 363 hours, which included a continuous run of 270 hours, mainly at full load.
On the Graphical Solution of Transient Vibration Problems
Authors: Bishop R. E. D. 
Published: October 2007

Phase-plane methods have been used with great success in the theory of non-linear mechanics. They have also been applied to a different class of problems; viz. to dynamical systems with transient loading. The paper concerns this second use of the plane and some recent extensions of it. A survey is made of the literature covering the twenty years since these constructions were introduced. This relates to: (1) the transient disturbance of single-degree-of-freedom systems (which may include damping, non-linearity, hysteresis, etc.) and of multi-degree-of-freedom systems; (2) the deflexions of beam columns in the theory of elastic stability; and (3) Jacobsen's general method of graphical integration. Some new additions to the theory are given. These are: (1) a method of graphical differentiation; (2) a simplified approach to multi-degree-of-freedom systems leading to the treatment of transient loading of beams by moving and moving-and-varying loads (damping may be contemplated in these beam problems and the method that is devised easily carries over to certain plate problems); and (3) a demonstration that the graphical method can be used for deflexions—as well as bending moments —in the theory of beam columns. It is suggested that these constructions are of real importance, not only for practical engineering problems, but also for teaching purposes.
The Vibration of Rectangular Plates
Authors: Warburton G. B. 
Published: October 2007

In this paper are considered the free transverse vibrations of rectangular plates with all possible boundary conditions obtained by combining free, freely-supported, and fixed edges. The Rayleigh method, assuming waveforms similar to those of beams, is used to derive a simple approximate frequency expression for all modes of vibration. The terms in this expression depend on the nodal pattern and the boundary conditions; they are tabulated for fifteen boundary conditions—all four edges free, freely-supported, or fixed and the twelve cases in which some of the edges have one condition and the rest another. The expression can also be used to obtain frequencies for a plate which has a combination of all three boundary conditions. The effect on frequency of an edge being supported and partially restrained is discussed. For some boundary conditions it is possible to compare derived frequencies with those obtained by various methods of accurate analysis and by experiment; except for a few cases, the results from the approximate expression and accurate analysis agree closely. For rectangular plates and for most boundary conditions and modes of square plates, the nodal pattern consists of lines approximately parallel to the sides of the plate. The exceptions are discussed and the gradual transition from these non-parallel patterns characteristic of a square plate to those of a rectangular plate is traced. The frequencies of extensional vibrations of rectangular plates are derived for two boundary conditions.
The New British Standard for Engineering Drawing Practice
Authors: Abbott W. 
Published: October 2007

The new British Standard No. 308 is a comprehensive work which should go far to bring unity to drawing procedure. The standard has been long in preparation and at various stages in its compilation has been presented to British industry for comments. It has been discussed internationally, and particularly in American and Canadian committees, which have been giving considerable study to the same subject; the object has been that of reaching a common international understanding of the fundamental principles involved. In preparing the standard, reference has been made to the ‘Dimensional Analysis of Engineering Designs’, an important contribution to the subject published by H.M. Stationery Office in 1948. Recommendations of the standard fall into two main groups: those which relate to general practice, and those which deal with dimensioning and tolerancing.
Air Flow in a Naturally Aspirated Two-stroke Engine
Authors: Wallace F. J. , Nassif M. H. 
Published: October 2007

The problem of scavenging of naturally aspirated, two-stroke cycle engines by utilization of wave effects in the exhaust and induction system is treated theoretically and investigated experimentally by systematic variation of the exhaust and induction system, as well as engine speed. In the theoretical treatment accuracy is achieved with a minimum of numerical computation by the adoption of the theory of waves of finite amplitude and the use of charts, wherever possible. These two features constitute the most significant departure from List's very thorough analysis (List 1949/50)‡, which is based throughout on the small-wave theory and in which little attention appears to have been paid to the simplification of numerical work. The theoretical section is divided into two parts dealing with (1) the analysis of cyclical pressure fluctuations in the engine cylinder and pipe system, and (2) the treatment of the gas-exchange process in the cylinder on the basis of ‘perfect mixing’ and the derivation of the conditions for dynamic similarity. A novel experimental technique is used, air from an external compressor being admitted to the cylinder of the motored engine through a rotary valve. In this manner release pressures comparable with those obtaining in the firing engine are attained, while the effects of high temperatures, which are of secondary importance in relation to wave phenomena, are eliminated. The experimental work is divided into two parts: (1) tests corroborating the wave theory; and (2) systematic air-consumption trials with variable induction-pipe lengths and exhaust systems, incorporating ( a) plain pipes, ( b) an exhaust ejector similar to that described in the Kadenacy patent specifications, ( c) an expansion chamber, and ( d) a diffuser. The general conclusions are: (1) good agreement between observations and analytical results is obtained, (2) high air-consumption is possible with natural aspiration provided that effective use is made of wave action by correctly designed exhaust and inlet systems; and (3) satisfactory scavenging is only achieved if not only the external pipe system but also the engine speed and geometry conform to certain requirements conveniently expressed in the form of dimensionless groups.
Nodular Cast Iron—its Present Position and Future Prospects as an Engineering Material, with Special Reference to its Suitability for Crankshafts
Authors: Bailey S. B. 
Published: October 2007

The historical development of iron having graphite present in the nodular form as cast, is traced from the patent application by Morrogh and the British Cast Iron Research Association (1946)† to its selection as a crankshaft material by the Ford Motor Co. in 1952. The economics of the production of nodular iron by various methods is discussed and it is concluded that material produced by the magnesium-nickel process now in use cannot compete in price with established materials such as carbon steel and malleable iron. Methods for direct addition of magnesium to molten iron are described, and it is concluded that application of these methods to low-sulphur irons from basic cupolas may completely alter the situation. The engineering properties of nodular cast iron are compared with those of other ferrous metals. It is concluded that nodular irons in the as-cast condition may be used instead of high grade flake-graphite irons for components not subject to shock loading, and instead of malleable irons in applications where 2–4 per cent elongation at fracture is adequate. The annealed nodular cast irons may be used, where their extra ductility and impact resistance are considered essential, to replace malleable irons and cast or forged carbon-steels. Their chief advantage over malleable irons lies in the shorter heat-treatment they require, which becomes economically more important as the size of a casting increases and as its selling price per lb. falls. As a replacement for carbon steel, nodular cast iron will be attractive for components which are difficult to cast or which require high surface-hardness with medium strength and impact resistance. However, the extent to which nodular cast iron replaces any of these materials will be determined largely by the price at which it can be produced; this will have to be decreased very considerably before it becomes competitive. Ultimate output of nodular cast iron in Britain in peace time is likely to be limited by the high cost of the low-phosphorus ore which is necessary for its production; in war time, its output might be severely restricted by the difficulty in importing this ore. The particular application of nodular cast iron to crankshafts is discussed in detail. It can replace alloy flake-graphite irons with a gain in ductility and impact resistance, and is already replacing graphitic cast steel, chiefly because of its better founding properties, and because its lower pouring-temperature facilitates the use of mass-produced shell moulds. It seems doubtful whether its fatigue properties will permit of its replacing the forged low-alloy steel which is used for most British automobile crankshafts, unless some reduction in engine specific-power output is accepted.
Wave-Action in Gases: The Attenuation and Reflection of Compression Waves Propagated in Pipes
Authors: Mucklow G. F. , Wilson A. J. 
Published: October 2007

The investigation supplements a previous examination (Bannister and Mucklow 1948)‡ of the wave-action following sudden discharge of compressed gas into pipes. The paper consists of two parts, Part I dealing with the relation between the frictional attenuation of compression waves propagated in pipes and the effects of friction under conditions of steady flow. The object of the work covered in Part II was to compare experimentally the pressure amplitude of compression waves before and after closed-end and open-end reflection, with a view to verifying considerations based on theoretical argument. The apparatus consisted of a series of cylinders of 1.5, 2.0, and 4.285 inches bore, from which compressed air was discharged suddenly into pipes of varying length and of the same bore as the cylinder in use. Indicator diagrams were recorded at suitable intervals along the pipes. Theoretical considerations show that, with the same particle velocity, a simple relation exists between the rate of decay of small-amplitude waves and the steady-flow pressure-drop along a pipe. Experiment suggests that this relation applies approximately to finite-amplitude waves and, on this basis, a simple expression is devised to relate wave-head decay with initial amplitude, pipe diameter, and distance propagated, within the range considered. By use of this expression, the mean velocity of propagation may also be determined. The processes of open- and closed-end reflection of compression waves are examined and considerations outlined in an appendix to the previous paper are amplified. The resulting conclusions are supported by experimental evidence. The effects of discharge through a constriction are considered in the Appendix.