bluuebunny/crossref_metadata_2025 huggingface dataset:
The Linen Flax Industry and its Introduction to New Zealand
Authors: Barltrop S. B.
Published: October 2007

Although the possibilities of linen flax cultivation in New Zealand were first explored in 1936, it was the German invasion of France and the Low Countries—the flax-producing areas of Western Europe—which caused the British Government in June 1940 to make an urgent request for New Zealand to grow up to 15,000 acres of flax and to arrange for its processing. At that time there was not, in the whole of New Zealand, more seed than would suffice for sowing 2,000 acres; and some 500 tons of seed had to be imported from Great Britain. The paper describes how the difficulties of starting a new industry at such short notice were successfully overcome. The New Zealand Government secured the co-operation of the farmers in preparing the ground, and of the railway workshops in constructing the machinery. Essential materials were in exceedingly short supply, and the author recounts the way in which those responsible for the engineering side of the industry grappled with, and overcame, the difficulties which confronted them, and shows with what measure of success their efforts in conducting the new venture were rewarded.

The paper gives an account of the various processes in the production of linen flax for export, with descriptions of the machinery used, and concludes with a brief outline of the New Zealand Government's programme for 1941–2. Further statistical data relating to the industry are included in Appendixes I–IV, pp. 168–9.
The Measurement of Torsional Vibrations
Authors: Stansfield R.
Published: October 2007

An electromagnetic torsional vibration pick-up unit, developed at Sunbury in the Research Laboratories of the Anglo-Iranian Oil Company is described, the output being shown on the screen of a cathode ray oscillograph to which the unit is connected through an integrating amplifier.

Calibration curves are given to show the limits of accurate response, and methods for calibrating in service by simple checks are outlined. Torsiograms taken from a two-stroke and a four-stroke Diesel engine illustrate the type of diagram obtained for each cycle of operations.

The value of the unit is much increased by including an electrical filter system in the output. The resulting diagrams show any required harmonic component of the swings, and enable a sufficiently accurate analysis to be made on the test bed either of critical speed swings, forced swings on flanks, or major roll amplitudes. The technique for taking diagrams with this filter unit is described in detail.

Examples from actual test records are discussed in relation to points of particular interest in connexion with friction dampers, rubber absorber dampers, systems with two modes of vibration, etc.; and finally a brief reference is made to the measurement of linear vibrations.
Corrosion of Boiler Tubes
Authors: Turner T. Henry
Published: October 2007

The reduction of the number of boiler tube failures to a minimum is now a matter of national importance.

Revolutionary improvement is not expected in the nature of the tubes. Tubes fail rapidly by local, and less rapidly by general, corrosion.

The removal of scale by shot blasting before use will reduce the extent of losses due to pitting, and so will additions of 0·2–0·5 per cent of copper.

Metallurgical data regarding tubes, and chemical data regarding feed waters are summarized in the paper, from the author's extensive records. After discussing how corrosion occurs at cracks in oxide, scale, or paint, suggestions are made for preventing corrosion in locomotive, marine, and stationary boilers.

Recommendations include simplification and standardization of boiler water tests by a suitable British Standards Committee, and the suggested Specification is sketched in outline.

The paper is concluded by Appendixes comprising (i) a questionnaire (with answers) on the present-day practice as regards the manufacture of boiler tubes in Great Britain; (ii) a list of reports published by the American Railroad Engineering Association; and (iii) a bibliography of selected items on corrosion, for the index prepared and maintained at the Chemical Research Laboratory, Teddington.
The First Gas Turbine Locomotive
Authors: Meyer Adolf
Published: October 2007

The author traces the history of electrical transmission for locomotives in which steam or Diesel engines have been the prime movers, and refers to the important contributions made by his firm in this direction. Although there are over 1,000 exhaust and gas turbines in service, the locomotive forming the principal subject of the paper is the first example in which this form of power is applied. The author, after dealing with the design of the turbine in general, takes the reader for an imaginary trip with the driver of the gas turbine locomotive, and explains the principles of operation, and the method by which the system of governing enables the machine to adapt itself to various running conditions. The safety devices are described in detail, and some attention is given to the opportunity afforded by a locomotive of this type for the adoption of power braking, which the author has been quick to utilize. The paper concludes with an analysis of the economic prospects of gas turbine locomotives, which comprises some useful comparisons with other types of motive power, including valuable information in graphical and tabular form.
A New Rotary Compressor
Authors: Lysholm A. J. R.
Published: October 2007

The author shows how the helical lobe compressor originated during his development of the gas turbine, as he became convinced that a general solution of the gas turbine problem could be reached by means of the constant-pressure cycle with centrifugal compressors of the multistage type. Trouble with “pumping” in the compressor led to an examination of the possibilities of a displacement type running at high peripheral speed. After examination of a modified Roots type and of a conical screw compressor, the helical lobe compressor was developed. A comparison of the three types is given and various points of design are discussed. Various methods of increasing the efficiency are considered and the paper concludes with notes on compression ratios, methods of control, and the manufacture of the rotors.
Piston Crown Temperatures in a Compression-ignition Engine with “Comet” Head
Authors: Bride W. L.
Published: October 2007

The paper describes tests on a high-speed compression-ignition engine of 120 mm. bore fitted with a Ricardo “Comet” head in which the piston was of “Y” alloy. The temperatures were measured by thermocouples in the crown, the connexions to the temperature-measuring apparatus being intermittent, and made only when the piston approached bottom dead centre. Thermocouple voltages were measured on a potentiometer, using the “null deflexion” method. Piston crown temperatures were measured for various loads, speeds, and cylinder liner temperatures, and were found to be higher than those obtained in previous investigations because of the very high turbulence induced by the “Comet” type antechamber. Confirmatory tests were made by using temperature-indicating paints, but these were not as satisfactory as had been expected. The results are discussed in the light of knowledge gained in former work on this subject; and, in particular, comparison is made with temperatures obtained in tests on a Mirrlees-Ricardo sleeve valve engine of similar speed and using a piston of the same design and material.
Some Textile Finishing Machines
Authors: Laurie K. S.
Published: October 2007

Textile finishing comprises the processes undergone by cloth between leaving the loom and being made up for sale. Finishing works require large premises, situated by good water supplies.

Dyeing machinery to-day shows a greatly extended use of stainless steel construction. The problem of dye-jigger driving at constant speed is discussed by the author.

Moisture removal is an outstanding problem. Mechanical methods and heat methods are compared; and the machinery appropriate to each is described. In modern drying machines provision is made for tensionless drying, for working to controlled cloth dimensions, and for the handling of very delicate fabrics.

Methods of feeding cloth automatically by roller or by rail guiders are discussed, and attention is given to the recent development of pneumatic and hydraulic systems.

The use of calenders for finishing is long-established and has modern developments, which are described in the paper.
Surface Finish and the Function of Parts
Authors: Schlesinger Georg
Published: October 2007

The author begins by enunciating the principle that, given good design, a machine will work properly when the material, the fits and tolerances, and the quality of the surfaces are chosen to suit the working conditions, and then gives examples to show the improvement effected by proper attention to suitable fits, tolerances and working surfaces.

The use of pen records to provide data for surface finish is dealt with, and an account is given of comparative tests of British and German aero-engine parts. Fits for various functions are discussed and attention is paid to problems relating to lathe spindles, and the surfaces of fuel injectors. Ground and scraped surfaces are compared, and further sections are devoted to micro-finish by honing, the superfinishing process, and the dulling criterion for finishing tools.
Power District Heating at Brno, Czechoslovakia
Authors: Kulka W.
Published: October 2007

The most effective way to large-scale saving in industrial fuel is the pooling of power and steam consumption. This method, if spread over a wide area, say an industrial town or district, inevitably paves the way to district heating.

Ordinary district heating stations, distributing only low-pressure saturated steam or hot water from one central boiler house to consumers in the vicinity, are of but secondary importance when the aim is high overall thermal efficiency in the distribution and consumption of power and heat. Satisfactory economy can only be achieved by installing high-pressure stations and using the pressure drop down to the pipe line pressure for the generation and supply of electric power.

Not every community or district is, however, entirely suitable for the establishment of a power-heating plant. The difficulties arise from the geographical position of the industrial areas compared with the location of the mainly residential districts, from the customary times of use of heat and power, and, last but not least, from long-standing habits or traditions in the production and utilization of heat.

The power district heating plant built during 1928–30 at Brno, capital of Moravia, Czechoslovakia, is described as an example where considerable difficulties were overcome. Due to its absolute success, the plant subsequently served as a guide in the planning of far larger stations of this kind. The description in the paper embraces the general layout of the plant, followed by details of the boiler house, back-pressure and condensing turbines, piping inside the station, desuperheater, feed arrangement and make-up plant, heat accumulation, and finally the distribution of steam to the consumers. Further, the report gives some important features of the operation, difficulties arising and how they were mastered.
The Double-Beat Throttle Valve and its Relation to Governing
Authors: Chorlton F. O. L.
Published: October 2007

The paper contains details of the results of experiments made some time ago on the balancing of a particular form of double-beat throttle valve with the object of elucidating the troubles frequently encountered when using it for the speed control of steam engines. The experiments showed that although apparently in balance, as judged from the design, there was a force tending to close the moving valve of an unexpectedly large amount varying with the size of the valve, the inlet steam pressure, lift from the seating, and the outlet pressure.

The paper further gives the application of the results towards improvement in governing; a formula for obtaining an approximate figure of the out-of-balance force from given working conditions, and a design of valve giving almost perfect balance under all working conditions. Curves and tables in explanation are included.
The Impact Tube
Authors: Hodkinson B.
Published: October 2007

A simple impact tube having a hole facing upstream will give direct and accurate readings of the total pressure or energy of a moving fluid, except in special cases. It is not delicate in setting or design. If the static pressure is known, the kinetic energy or velocity head can be obtained by subtracting the static from the total pressure. If, further, the density is known, then the velocity can be derived. An application is given. The exceptional cases are velocity above acoustic and extremely low velocities.

At supersonic velocity there occurs, just in front of the mouth of the tube, a very steep pressure rise, often described as a standing wave or shock plane. The tube now reads less than the total pressure, but this can be calculated by a formula which Rayleigh derived from a study of intense waves. The author, not having seen a direct demonstration separate from wave theory, attempts in the paper to give this, and to sketch what occurs. Test experience confirms Rayleigh's formula.

For very low velocities, viscosity has influence; and the tube gives readings which exceed the static pressure by an amount approximately equal to the velocity head × [1 + (3/Reynolds number)].
Causes of High Dewpoint Temperatures in Boiler Flue Gases
Authors: Harlow W. F.
Published: October 2007

High dewpoint temperature in flue gases in boiler plants causes premature condensation in the cooler gas passages resulting in deposits and corrosion.

Evidence is submitted to show that high dewpoint can be caused by the increased temperature of the superheater tubes, the oxide film catalysing the conversion of the sulphur dioxide formed by combustion into sulphur trioxide, thereby increasing the sulphuric acid content of the gases.

The trouble is confined chiefly to plants fired by mechanical stokers, pulverized fuel plants generally being unaffected.

Coating the catalytic surfaces with lime or fine pulverized fuel ash prevents the action, and it is suggested that these materials sprayed on the tubes at intervals may prevent the formation of acid and its serious consequences.
Building-up and Hard Surfacing by Welding
Authors: Andrews William
Published: October 2007

The author describes the process of using fusion welding for renewing worn or corroded parts and points out that it can equally well form part of the original design for many structures. The characteristics of the various welding processes are considered from the point of view of the materials with which they may be concerned, and the features of the metallic arc process are considered in some detail, since it has by far the largest scope at the present time. Some illustrations of the type of weld deposit practicable are considered, and the more limited developments in the metals of non-ferrous metals and “super-hard” alloys are referred to. It is shown that a very wide variety of commercial products is available for the process, particularly in the direction of electrodes for metallic arc welding and that information as to alloy compositions used, and their response to fusion with different parent metals, is lacking.
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).
Statistical Control in Workshop Administration
Authors: O'Dea W. T.
Published: October 2007

Many publications on statistical methods applied to engineering problems have been devoted primarily to the control of physical properties. Others have indicated roughly the degree of applicability to machine shop problems without going into the actual methods of establishing the system as a method of production control. The present paper has been written with a view to simplifying the mathematical aspects as far as possible by reducing them to arithmetical or graphical processes. A section is devoted to the limitations as well as the advantages of the various statistical methods, together with some discussion of the relation between drawing limits, control limits, and the measuring devices available. Emphasis is laid on the aspects of statistical control as an instrument of works administration rather than some new method of inspection. It may be applied only to appropriate problems with success. The influence of sample size on the interpretation of control charts is discussed.
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.
The Modern Direct-Hydraulic System
Authors: Towler F. H.
Published: October 2007

The first hydraulic press invented by Joseph Bramah in 1795 employed the direct-hydraulic system; i.e. hydraulic pressure was directly supplied to the press cylinder by a hydraulic pump and, therefore, the pressure exerted by the press ram was directly proportional to the pressure supplied by the pump, and the speed of the press ram was directly proportional to the delivery of the pump. Later developments in the use of hydraulic power resulted in the invention of the hydraulic accumulator to store liquid under pressure. With the accumulator system the speed and pressure exerted by the press ram are not controlled by the pump, and in fact they cannot be controlled with any precision; also there is considerable wastage of power when the press ram is operating at less than full pressure. The advent of the high-speed reciprocating ram pump has produced the modern direct-hydraulic system in which the press and pump form one self-contained unit. The power to drive the pump is in direct proportion to the work done by the press, and the speed and pressure exerted by the press ram can be precisely controlled. The author considers that a saving of at least 75 per cent in electric power can be made by conversion from the accumulator system to the direct-hydraulic system. Indicator diagrams are reproduced in the paper to show the saving in power which can be achieved by the direct-hydraulic system, and a comparison is made between the power consumption, in kilowatt-hours, of a direct-hydraulic cartridge-drawing press and a mechanical double-rack press doing the same operation. The paper includes a number of illustrations of direct-hydraulic presses, ranging from those of Bramah to present-day types.
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.
The Tuned and Damped Gyrostatic Vibration Absorber
Authors: Arnold R. N.
Published: October 2007

The vibration absorber described in this paper consists of a gyrostat suspended symmetrically about an axis perpendicular to that of the torsional vibration which it is desired to suppress. The gyrostat is fitted with springs and a viscous damping mechanism which allow limited vibration about its axis. This device is a modification of that employed by Schlick (1904)†, in his attempt to stabilize the rolling of ships at sea. The new arrangement, however, is more efficient, is not restricted to very low frequencies, and is, in general, capable of application to vibration superposed on a mean velocity.

A theoretical study is made of the response of such an absorber to one- and two-mass vibratory systems under both forced and self-induced vibration, and design methods are derived by which the essential dimensions for any given application may be readily determined.

Experimental investigations with a gyrostatic absorber applied to a one-mass system under forced vibration are recorded, and the results compared with theoretical prediction. The design of a full-scale absorber built to suppress vibration of the table of a heavy planing machine is also given, together with the results obtained with the apparatus on trial.
Centrifugal Pumps—An Alternative Theory
Authors: Anderson H. H.
Published: October 2007

The hydraulic design of centrifugal pumps has in the past been almost entirely empirical, since there is a large discrepancy between conventional theory and actual tests. Several papers† have already considered this problem of providing a reconciliation of theory and practice. The author suggests that a possible solution may be obtained by considering the total head as being made up of ( a) head due to impact between impeller blade and water; and ( b) head due to centrifugal force.

It is assumed that the flow conditions may be such that the impeller blades shear the water without accelerating it. This is suggested as representing the maximum quantity-zero head state where the increase in velocity from branch to casing throat is obtained at the expense of suction pressure. Neglecting losses there will be no torque on the shaft and therefore no head generated. At less quantities the velocity differences between blade and water will cause impact and therefore generate a head.

It is also assumed that at less quantities the “pressure” existing between blade and water will transmit to the water the additional energy of the centrifugal head. This latter assumption is supported in some measure by the fact that in practice the head is affected by variation of the ratio of impeller diameter to eye diameter.

Head and quantity values are calculated for zero head quantity QF, maximum efficiency quantity Qf, half maximum efficiency quantity Qf/2, and zero quantity. These results compare very reasonably with actual test curves.
Discharge Tests on an Archimedean Screw
Authors: Donaldson A. C.
Published: October 2007

The paper records a series of tests carried out on an Archimedean Screw in use in a chemical plant. The main object of the tests was to increase, if possible, the overall throughput of the screw and to decide at what speed the screw should be run so as to give a maximum discharge under existing working conditions, thus increasing the production of the plant.

It was found that by a slight modification to the existing screw a much more uniform throughput could be obtained and the discharge increased considerably by increasing the speed.

The paper also includes some notes and formulae which, it is hoped, will be helpful in determining suitable proportions for similar screws.
The Flow of Metals under Various Stress Conditions
Authors: Nadai A. L.
Published: October 2007

The phenomena associated with the permanent deformations of the metals have attracted the attention of investigators during the last 100 to 150 years, and have inspired mathematically-minded observers in their endeavour to formulate mechanical rules or laws by which ductile metals flow under prescribed conditions. While the theory of elasticity is mostly concerned with very small strains, a theoretical treatment of the permanent or plastic deformations of metals must also frequently take account of strains of an order of ten to a hundred—and even more—times larger than the strains that can be sustained by them elastically.

The engineering means for dealing with finite strains of this order will be reviewed in the lecture, and certain new types of strains that seem to offer possibilities for expressing the stress-strain relations required for developing the theories of the flow of metals under various conditions will be introduced. Several ideal substances, representing behaviour of metals or of other materials under different conditions, may be considered. For a perfectly plastic substance a special solution is quoted for a plane problem and for plastic shells with rotational symmetry. A case of the creep of metals at eleyated temperatures will be mentioned.

Experiments made during the war years on the propagation of the plastic zone along mild-steel bars tested under tension, on the flow of copper and of medium carbon steel under combined stresses in the strain hardening range (including observations regarding the ensuing types of fractures which were observed), and experiments on the effect of the speed of deformation in these metals under normal and at elevated temperatures over a wide range of the rates of strain, will be reported.
A Theoretical Investigation into the Porting of a Two-Cycle High Mean Effective Pressure Internal Combustion Engine
Authors: Parker George
Published: October 2007

The paper is an attempt to determine on paper the sizes of ports and their timing to attain a high mean effective pressure—that is, a mean effective pressure of the order of 200 lb. per sq. in. as is usual in present day high-duty four-cycle engines—in a two-cycle engine of the half-stroke sleeve type. In the course of this attempt the various unknown factors influencing the accuracy of the results are pointed out and comments are made about these factors.