bluuebunny/crossref_metadata_2025_split huggingface dataset:
Moulding Plant for Plastics
Authors: Daniels J. Lionel 
Published: October 2007

Commencing with a general outline of the method of pressure moulding as it may be applied to moulding powders or laminated material, the author passes on to a description of the usual types of hydraulic presses, divided into upstroke, downstroke, angle presses, and sheeting presses. The hydraulic system as applied to moulding presses, is then discussed, with a description of hydraulic pumps, and both weight-loaded and air-loaded accumulators. The relative merits of water and oil as the hydraulic medium are also considered. Modern practice favours self-contained hydraulic pump units where only a few presses are installed in a factory, and also for very large units which would put an undue strain on the accumulator system. The preheating of material in gas- or steam-heated ovens is described, also preheating by high-frequency high-voltage electric currents. Moulds and platens are heated by steam, gas, or electricity. The injection moulding of materials both of the thermo-plastic and thermo-setting type is discussed, with particular reference to the injection of thermo-plastic materials such as cellulose acetate, and to the injection and transfer moulding of thermo-setting materials such as wood-flour “filled” phenol formaldehyde. Screw-type extruders are used for certain materials such as casein, and for many of the newer thermo-plastic materials, such as “P.V.C.” The author then considers the manufacture of tools and dies, and gives a typical layout of the mould and ejector pins. He also describes a 500-ton hobbing press, and the moulds which can be hobbed on this machine. Attention is also given to preforming machines for making the plastic moulding powder into “preforms”. In the manufacture of laminated sheet, paper or fabric material is impregnated with resin, dried in ovens, and then cut into sheets for pressing. A short description is given of the equipment required.
Torsional Vibration Amplitudes at Non-Resonant Speeds with Special Reference to the Interpretation of Torsiograph Records
Authors: Wilson W. Ker 
Published: October 2007

The seismic torsiograph is commonly used for recording torsional vibration because it can be applied to many different types of oscillating system without elaborate preparatory measures. This instrument is available in several types each suitable for a particular measuring range so that there is little difficulty in selecting equipment to record with reasonable accuracy, the vibratory motion at a chosen point in any present-day transmission system. The motion recorded by a seismic instrument may, however, be very complex; and this implies that care must be taken when attempting to interpret the records in terms of shaft stress, particularly at non-resonant speeds. This problem can be very difficult, and is discussed in the present paper with the help of typical examples. It is shown that the interpretation of records obtained at resonant speeds is comparatively straight-forward, provided that the system is reasonably linear and does not contain components having a complex distribution of mass and, or alternatively, elasticity. Methods for computing shaft stresses from measured amplitudes are discussed, and attention is drawn to the use which can be made of tabulation methods when dealing with records obtained at non-resonant speeds and with systems containing complex components or having a marked degree of non-linearity. Cases where shaft stresses at non-resonant as well as at resonant speeds must be taken into account are by no means unknown. It is shown that under certain conditions a seismic type torsiograph will show no appreciable response or will become very unreliable at some non-resonant speeds. Finally, attention is drawn to the use of torsional strain gauges as an alternative to seismic torsiographs. The strain gauge method enables measurements of total shaft stresses to be made even if the system is markedly non-linear or contains complex components. The development of compact and reliable torsional strain gauge equipment for general use appears to be desirable.
Meteorological History and the Space-Heating Machine
Authors: Grierson Ronald 
Published: October 2007

During the past forty years, the cost of heat energy and of labour has risen, accurate methods of automatic temperature control have been devised, the standard of thermal comfort demanded in dwellings, offices, factories, etc., has increased ( vide the Factories Act of 1937) and, for many purposes, electricity, gas, and oil are used in preference to coal and coke. The rate of consumption of these more modern forms of potential heat energy can be readily measured by means of meters, and these developments all tend to concentrate attention on the quantitative aspects of space-heating technique, including the capacity of the installation to carry relatively heavy overloads during periods of severe weather. Warmed buildings should no longer be regarded as receptacles for unknown quantities of valuable heat energy, even in its crudest form. Conversely, their space-heating installations should be considered as energy converters, possessing a thermal efficiency which can be accurately assessed, when the hour-to-hour and day-to-day thermal potential (expressed in terms of degree-days), and certain other factors are known. The Royal Meteorological Society recently published two important papers covering the October–May heating season back to 1881, and the three winter months (December–February) back to 1783 respectively. The statistical data, thus made conveniently available, suggested to the author that the time had arrived when an attempt should be made, not only to make a broad (eight-month) but also a long (160-year) review of the space-heating aspect of meteorological history, based not only on averages or means of the monthly or seasonal temperature (energy consumption), but also on the extreme maximum and minimum values of daily temperatures (heating power).
Some Considerations in the Design of Class 1 Pressure Vessels
Authors: Heeley E. J. 
Published: October 2007

The fusion-welded mild steel pressure vessels generally known in this country as “Class 1” welded pressure vessels are those of a sufficiently high standard of manufacture to comply with the requirements of certain recognized specifications, such as those referenced in the paper. Such vessels are constructed of good-quality mild steel plate joined together by a metallic arc fusion-welding process. A radiographical examination is made of the full length of all the main seams, which are machined or dressed so as to be level with the surfaces of the plate on either side of the joint, and specified mechanical tests are carried out to ensure that the quality of the welded joint is of the required standard. The vessels receive a stress-relieving heat treatment on completion of the welding operations. The magnitude of the stress in the material is a dominant factor in the design of a pressure vessel, but difficulties arise in connexion with the design of Class 1 fusion-welded pressure vessels on account of the different viewpoints of various authorities on the stress to be applied to the welded joint. The extent of these differences is shown in the paper by a comparison of vessels designed in accordance with the specification requirements of four leading authorities (two British and two American). An analysis is made of the factors involved in the formulae employed by these authorities for determining the wall thickness, and it is shown that the formulae have been based on the riveted form of construction despite the very different conditions of stress at Class 1 welded joints. The characteristic physical properties of such joints are discussed in conjunction with the results of recent investigations on their behaviour under fluctuating stress conditions. A recommendation is made for a much-needed simplification in design formulae to take into consideration the actual characteristics of the welded form of joint. Illustrations are given of typical welding groove preparations for the attachment of flanges, branches, etc., designed to provide adequate accessibility for manipulation of the welding rods.
The Value of Heat with Special Reference to the Heat Pump
Authors: Faber Oscar 
Published: October 2007

It is well known that when electricity is used for heating by radiators or otherwise, approximately 3,415 B.Th.U. are given out for each unit of electricity consumed, and as the efficiency of the apparatus is 100 per cent, this represents the limit of the heat available from electricity with present-day methods. If therefore, someone confronts us with a statement that in fact many times this amount of heat can be delivered per unit of electricity consumed, he is likely to be looked upon as one who has not heard of the principle of the conservation of energy. Nevertheless this statement is perfectly correct, and many practical examples on a large scale are now in successful operation. The mechanism by which this result is achieved is known as the heat pump. The possibility of running a heat engine in reverse and producing not only refrigeration but warming as well, was pointed out by Kelvin as long ago as 1852.† The object of this paper is to show ( a) that with a proper theoretical approach there is nothing revolutionary in the principle, ( b) to describe plants of this character and give examples, ( c) to show that while the British Thermal Unit is in one sense a measure of heat, it is in no sense a measure of the value of heat, since a British Thermal Unit of lower-temperature heat has little value while a British Thermal Unit of high-temperature heat has a great value, and ( d) to show that electricity may be looked upon as equivalent to heat of the highest temperature and value and capable of producing, with the heat pump, many times its direct equivalent of heat.
Stresses by Analysis and Experiment
Authors: Pippard A. J. Sutton 
Published: October 2007

This is an attempt to outline in a single paper the bases of structural analysis when stresses do not exceed the limit of proportionality. The fundamental theorems are stated and the general problems in the analysis of just-stiff and redundant frameworks are discussed. The solution of a just-stiff frame is obtained when a compatible system of stresses is determined, but this is insufficient if the structure be redundant; the strains must then also be compatible. Passing reference is made to the best known methods of stressing just-stiff frames; the stress diagram and method of sections, but the method of tension coefficients is described in rather more detail with reference to the elementary space frame. The classical methods of dealing with redundant frames are next outlined. After a reference to slope-deflexion analysis, of which an early example was Clapeyron's treatment of the continuous beam (the theorem of three moments), the work of Castigliano is considered and in illustration his second theorem is used to obtain the stresses in a flywheel due to the heating of the rim by a brake. A most important contribution to the treatment of redundant structures was made in 1930 when Professor Hardy Cross described his moment distribution method. This is illustrated by an example and reference is made to the powerful relaxation methods developed by Professor R. V. Southwell. The paper concludes with a short description of an experimental method for obtaining influence lines and of another for the solution of certain problems of plane stress analysis.
Experiments on the Reproducibility of Engine Conditions for Ring-Sticking Tests in a Single-Cylinder Petrol Engine
Authors: Cantle G. S. 
Published: October 2007

A great deal of difficulty has been experienced in the reproduction of results obtained with small-scale accelerated engine tests used in classification of lubricating oils in the laboratory. The erratic results obtained are due to difficulties of standardizing conditions under which the tests are made. A number of factors make their variations manifest in the lubricating oil consumption rate, and a method has been developed which enables the oil consumption to be standardized when other easily controlled factors are maintained constant. The rings are run-in with a base oil to which has been added approximately one per cent of tri-butyl phosphite, and efficient bedding of the rubbing surfaces is obtained within six hours. The oil consumption rate is accurately measured throughout the run-in period, and the test is stopped when a standard oil consumption rate has been attained. The engine is then dismantled, cleaned with tri-chlorethylene and re-assembled for running with the test oil. The oil consumption rate curve has been found, under these circumstances, to give an indication of the manner in which the rings are operating, that is, whether the oil and test conditions are such as to cause the rings to be working unsatisfactorily owing to incipient ring sticking, and also, the time at which a ring sticks completely in its groove. The effect of brake mean effective pressure upon the ring-sticking propensity of an oil has been demonstrated in the paper, by comparing the oil consumption rate curves; and other factors which have been found to lead to erratic results have also been discussed.
Mechanical Principles of the Screw Extrusion Machine
Authors: Rogowsky Z. M. 
Published: October 2007

The screw extrusion machine is briefly described and submitted to a dimensional analysis resulting in generalized relations between, on the one hand, pressure developed, rate of discharge, and drive-power and, on the other, viscosity of plastic extruded, speed of machine, and a characteristic dimension. The velocity distribution of an assumed ideally viscous so-called plastic material within a rectangular screw thread is determined, and expressions for discharge and pressure developed are derived in terms of its dimensions. These expressions are used to discuss the effect of increasing the number of “starts” on a screw and a method of rating extrusion machines is proposed so as to allow an adequate description of the capacities of such machines.
Nomenclature of the Cutting Edge
Authors: Kurrein Max , Lea F. C. 
Published: October 2007

This brief paper is put forward in an attempt to encourage a discussion on the nomenclature of cutting tools. Attention is drawn to various terms used to describe the angles of cutting tools, and a number of illustrations is given to show the nomenclature adopted in published work and by makers. It is suggested that for lathe tools, drills, milling cutters, etc., the most important cutting angle should be the same when the same material is being cut. The illustrations show that rake is used in a number of ways, but always has reference to the face of the tool over which the chip moves; in very few cases, however, has it clearly defined reference to the all-important angle measured on a plane at right-angles to the cutting edge. This is the angle that very largely determines the cutting effects of the tool and the authors suggest that it should be called the breast angle. Front rake, side rake, etc., may then reasonably be used, as at present, to define setting angles for grinding. The breast angle for any material to be cut having been settled or (in the case of researches) defined, other angles can readily be obtained. Formulae are given in Appendices from which the breast angles can be determined in certain cases.
Feed Distribution and Hunting in Marine Water-Tube Boilers
Authors: Hillier H. 
Published: October 2007

Data and experience are given concerning the phenomenon of hunting in naval water-tube boilers and its elimination by arranging the internal feed water distributing piping to spray the water in the steam space of the boiler drum. Various internal feed-distributing arrangements are described, and calibration tests are given of various designs of feed-distributing piping. The paper discusses the factors causing circulation in a water-tube boiler, the conditions essential to give the equilibrium necessary for steady boiler operation, and the variations which occur in the steam volume below the water level in a boiler with changes in boiler load. The characteristics of boiler hunting are discussed and an analysis is given of the various factors in the hunting cycle. It is shown that hunting is due to the existence of a continuing time-lag between the rate of feed supply and the rate of steam generation, and that the time-lag and hunting are eliminated if the feed supply is heated to boiling point before it enters the circulation circuit. A review is made of feed-distributing arrangements in service, and various points are suggested to which consideration should be given to obtain a feed-distributing arrangement which will obviate hunting with highly rated water-tube boilers. Features concerning the water level control in naval boilers fitted with augmentors are discussed.
Aircraft Propulsion
Authors: Green F. M. , Wallington J. E. 
Published: October 2007

Mechanical flight began just over 40 years ago, and the only system of propulsion in use until five years ago was the internal combustion piston engine driving a propeller. Quite suddenly, the internal combustion turbine has come very much to the fore, both with and without a propeller, giving an increase in speed from under 500 to over 600 m.p.h.—a result chiefly due to the great increase in thrust horse-power available from a given weight and bulk of power plant. In much the same way as Parsons's demonstration of the possibilities of the steam turbine in the launch Turbinia eventually established the steam turbine as the chief prime mover for large powers, so the record-making Meteor has begun a similar change-over in aircraft propulsion, and perhaps in power plant for locomotives, ships, and power stations. The piston engine, however, has taken 40 years to reach its present development from the rather crude early motor-car engine, and doubtless it will be a long time before it becomes obsolete. It seems a suitable time to put on record the progress in power to weight ratio, reliability, and thermal efficiency that has been made possible by intensive development and research.
Free-Piston Compressor-Engines
Authors: Farmer H. O. 
Published: October 2007

The Pescara free-piston engine has been developed in France during the last twenty years, and the paper gives a description of a portable air compressor which has been proved in commercial work, and is now in production. An explanation is given of those characteristics in which this engine differs from the orthodox engine-driven crankshaft compressor. The power unit is an opposed-piston two-stroke compression-ignition engine, the compressor piston being directly attached to one of the engine pistons, while the cushion piston is directly attached to the other. The cushion piston gives stability, ensures that the energy available for the return stroke is constant for any conditions of operation, and thus gives a constant compression pressure in the combustion cylinder. The velocity characteristics of the pistons during the inward and outward strokes are described with their effect on the compressor and other sections. The fuel injection gear and also an alternative scheme is described; and indicator diagrams show the results obtained. The output of the compressor is controlled by the governor; the governor controls the fuel injected and thus determines the stroke of the pistons and thereby the quantity of air delivered. The efficiency of the combustion section is given, with the specific fuel consumption loop of the compressor as a whole. Methods of starting, by use of a spring or compressed air, are given to illustrate the characteristics dealt with. The development of the free-piston compressor has led to the development of the power gas-generator, in which the combination of free-piston compressor and turbine forms a new type of prime mover.
The Aeroplane Undercarriage
Authors: Conway H. G. 
Published: October 2007

This paper deals with current design and production practice in regard to aeroplane undercarriages, in particular the shock absorber element. While there are numerous types of shock absorber (steel or rubber springs., compressed air, etc.), disposed on aircraft in numerous ways (twin-leg undercarriages, undercarriages with two or more wheels, articulated units, nose wheels, tail wheels, etc.), the paper deals specifically with the more or less “classic” solution—a single telescopic leg with a single wheel mounted in cantilever. The methods of determining the capacity of the shock absorber and the required stroke are given, as well as details of methods of calculating telescopic friction, and the determination of “overlap”. Sufficient information is given on methods of stressing to enable a competent engineer to produce a design of adequate strength. The various main known types of shock absorber are illustrated, and the relative advantages of each discussed from the points of view of length, rebound control, orifice control, and methods of mounting the shock absorber in the actual undercarriage. The paper also gives: load deflexion curves with details of good practice on compression ratios, etc.; curves of performance obtained on actual drop test, illustrating what can be achieved in the way of energy absorption efficiency; and methods of effecting orifice regulation and the calculation of the size of the various orifices by an approximate formula. Current practice in relation to glands or seals is discussed, and the paper concludes with a description of a modern undercarriage assembly, and its testing.
The Future of Pulverized-Coal Firing in Great Britain
Authors: Sparks C. H. 
Published: October 2007

The success attained in the burning of semi-bituminous and bituminous fuels has established pulverized-fuel firing in dry-ash bottom furnaces as the preferred method of combustion for power stations in Great Britain. The tendency to divert a high proportion of the poorest quality coal to these new power stations should be viewed with alarm. Owing to the variable quality of ash and the limitations imposed by the presence of this refuse in increasing quantity, boiler units must be moderately rated to maintain satisfactory availability. Combustion rates must be controlled to obviate slagging and bird-nesting with the most unfavourable fuel, and this involves the provision of comparatively large furnaces for the duty. For boiler units much in excess of 400,000 lb. per hour a strong case can be established for using specially selected fuel, or, alternatively, liquid ash-removal may be employed. In either case, the fine dust from the arresters must be disposed of, and this frequently proves both difficult and expensive. With a view to solving this serious problem, as well as offsetting the disadvantages of variable ash characteristics, the cyclone furnace has been evolved and is at present undergoing trials in the United States, whilst overfeed firing with moving grates has already been developed there for application to boiler units of suitable size for power-station work. Some considerable increase in the output of dust fuel appears probable as the result of increased mechanization in the mines, so that in these circumstances pulverized-coal-fired boilers will always be in demand to dispose of this, unless it is eventually found more profitable to upgrade it for other processes.