bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Stresses in Hooks, and Their Determination by Relaxation Methods
Authors: Fox L. , Southwell R. V.
Published: October 2007

The “semi-inverse” method of Saint Venant has been applied to hooks by Golovin (1881)‡ and by Southwell (1942). The actual hook is replaced in calculation by a half-tore sustaining shear stresses appropriately distributed over its terminal sections, and having a cross-section identical with the principal section of the hook (shaded in Fig. 1). Golovin's solution was for a narrow rectangular hook; Southwell's is a formal solution applicable to any shape of section, and involves two stress-functions related by three conditions at the boundary.

In the present paper, stress distributions are determined on the basis of Southwell's solution for two B.S.I. standard hooks, the first of “trapezoidal” and the second of circular cross-section. The results are exhibited in Figs. 3–6.
An Exploratory Study of Oil Grooves in Plain Bearings
Authors: Clayton D.
Published: October 2007

A preliminary investigation has been made of the influence of oil holes and grooves on journal bearing performance to provide, in addition to fundamental information on fluid films in bearings, preliminary data for an ultimate analysis of the behaviour of internal combustion engine bearings. In the first part of the paper the effects of supplying oil to holes and grooves in the unloaded part of the bearing are investigated, the quantity of oil flowing through the bearing, the running temperature and the coefficient of friction being recorded. Amongst the results are shown the important part the clearance space at the point of supply plays in the quantity delivered; the surprising drop of feed as a 90 deg. circumferential groove is extended to 360 deg.; the marked effect of quantity of oil on bearing temperature for small flows and the rapid drop in efficiency of oil cooling as the quantity rises; and the absence of a groove arrangement giving more efficient cooling than the others. Change of supply temperature and pressure have a much less than proportionate effect on bearing temperature and flow. Increase of clearance leads to a disproportionate increase of oil flow.

In the second part of the paper the effect of holes and grooves in the pressure film is explored. In this case measurements were made of the pressure at the crown of the bush when the hole there was closed, and of the flow when open, in addition to the previous observations. Amongst the results may be noted the relatively small initial flow through the crown hole in spite of the high pressure there when it is closed; the increase of the crown hole flow at the expense of side flow as the groove is cut into the inlet film; and the relatively small changes in bearing temperature and coefficient of friction. Again changes of oil supply pressure and temperature had less than proportionate effects on flow and temperature of the bearing. A preliminary note is made of the decrease of load-line film pressure which was found as the temperature was increased. The temperature was also raised to cause incipient failure of the bush, and it was found that the final temperature was independent of whether the crown hole was open or closed, and yet there were indications of diminished film thickness for small grooves at natural running temperatures. The safety was decreased as grooves were cut in the loaded part of the bearing; some indications of the magnitudes of the changes are given.
The Calculation of the Stresses in a Turbine Wheel by the Method of Superposition
Authors: Kearton W. J.
Published: October 2007

The wheels of steam turbines are subjected to three separate forces, namely (1) the body forces due to the inertia of the wheel itself, (2) the force applied radially to the rim due to the inertia of such attached masses as blades, spacers, etc., and (3) the force applied to the bore of the wheel due to force fitting or shrinking the wheel on the shaft. The method of calculating the stresses in turbine wheels which is usually explained in textbooks and published papers takes account of these forces simultaneously. The calculations are tedious, and if it is desired to analyse the effects of changing the speed of rotation of the wheel, or of changing the magnitude of the attached masses, or of varying the degree of force fit on the shaft, then the calculations must be repeated for each combination of conditions.

In the method given in the paper, the stresses in the wheel are calculated (1) for a rotating wheel free from rim loading and radial stress in the bore due to force fitting, (2) for a stationary wheel subjected only to the rim load, and (3) for a stationary wheel subjected only to the force fit pressure. The resultant stress in the wheel is then simply the sum of the three stresses so obtained.

Since the wheel inertia stress varies directly as the square of the speed, and since the stresses in the stationary wheel are directly proportional to the boundary stresses, the effects of (1) varying the speed of rotation, (2) varying the magnitude of the attached masses, and (3) varying the degree of force fit may be analysed with very little effort.

The paper shows how the method of superposition may be employed in the calculation of (1) the stresses in a turbine wheel, (2) the amount of force fit necessary to satisfy specified conditions, (3) the effect of varying force fits on the maximum stress in the rotating wheel and in the stationary wheel, and (4) the distribution of stress in the stationary wheel.

The paper concludes with an estimation of the localized stresses in the neighbourhood of pressure-balancing holes.
The Thrust of a Marine Screw Propeller
Authors: Baker G. S.
Published: October 2007

Part 1 of the paper puts forward the proposition that since the phenomenon of development of thrust is much the same in all screws, there should be a common basis by which it can be represented.

The characteristics of aerofoils are considered, first in flight singly, and then the general effects which arise from the interference of adjacent blades. It is concluded from this work that for any blade there are two essentials to be fixed, the slip angle, and the slope of the lift curve as affected by aspect ratio and, or alternatively, cascade. This should afford a basis for plotting screw data.

Part 2 of the paper is an examination of the results obtained with over 100 model screws. The data are given in the form of the thrust constant kT/ sp to a base representing blade width. All the results plot reasonably well together, and mean curves for screws with various numbers of blades are given. These curves enable the designer of any screw of normal type to form an estimate of its thrust for any speed of advance and revolutions per minute. Methods are given in the paper for detecting eddymaking in the screw, and it is shown that a little roughness of blade surface, although having a material effect on efficiency, does not affect the thrust prediction.
The Variable-pitch Marine Propeller
Authors: Taylor J. Lockwood
Published: October 2007

The author first discusses propeller performance, dealing in turn with the order of the possible gain in efficiency to be expected by adopting the variable-pitch type for different classes of ships working within a range of operating speeds. The maintenance of speed in heavy weather and with a foul hull is then considered, and reference is made to the possibility of feathering for economical cruising, to the special application of variable-pitch propellers to tugs and trawlers, and to engine fuel consumption characteristics at part load and varying propeller r.p.m.

Details of manoeuvring and control are discussed, from the viewpoint of exploring the possibility of eliminating the engine reversing gear and the direct manipulation of the prime mover generally. Ship speed control from the bridge is considered, and an estimation is made of astern performance, followed by a comparison with the normal reversing of a fixed-pitch screw. Factors influencing blade design are then reviewed, e.g. type of root and size of boss, the effect of the type and number of blades on the efficiency; and reference is made to the calculation of pitch-changing moments and the possibility of balancing hydrodynamic and centrifugal components by suitable design and tilt of the blades.

Various types of operating mechanism are then examined—hydraulic, electric, mechanical, and combinations of these—and mention is made of the sealing of the hub against sea water. The author also refers to the need for indicating the pitch at the control station.

Lastly a comparison is made with aeronautical applications. The author shows that the range of operating conditions as affecting engine r.p.m., with a fixed pitch, is in general much less for marine screws; blade widths are much greater. In the author's conclusions it is suggested that full-scale determination of the optimum pitch setting may be valuable; consideration is also given to possible size and limitations of blade width, and to the effect of the costs involved.
Some Notes on the Mechanical Factors Affecting Ring Gumming in Petrol Engines with Particular Reference to the Rating of Lubricating Oils
Authors: Pugh B.
Published: October 2007

The phenomenon of piston ring gumming in petrol engines is well known. It is of importance not only because it is the cause of considerable trouble in service, but it has also formed the chief criterion in the majority of attempts to rate or classify lubricating oils according to their deterioration characteristics in an engine cylinder.

Existing standard chemical tests on lubricating oils form no guide to the behaviour of oils from the point of view of ring gumming in a petrol engine, and the only reliable method of grading oils at present is by tests in an actual engine. The next logical step is to develop a simple chemical test or series of tests which will give the same grading as that obtained in an actual engine. Before this can be done it is necessary to have a knowledge of the nature of ring groove deposits, the mechanism of ring gumming, and the relative effects of the various factors which affect the rate and degree of ring gumming. Mechanical factors can be of sufficient magnitude not only to affect, but possibly reverse, the relative rating of oils on a ring gumming basis. Various mechanical factors which affect the degree of ring gumming obtained are discussed in detail in the paper. Those mechanical variables which cannot be eliminated must either (1) be taken into account when sifting available engine data, or (2) must be a consideration when formulating a laboratory test or series of tests simulating engine conditions.

Correlation between engine tests and laboratory tests is best based on the time to give incipient gumming in the engine. To do this it is necessary to have a reliable indicator to show when ring gumming commences.

Preliminary experiments have indicated that piston-crown temperature is probably the best control temperature in oil rating tests; and the temperature at the back of the ring groove, taken in conjunction with the piston crown temperature, is probably the best indicator of incipient ring sticking capable of application to any engine.
The Flow of Gases at Sonic and Supersonic Speeds
Authors: Hankins G. A. , Cope W. F.
Published: October 2007

Problems involving the flow of gases at velocities near to or exceeding that of sound have been familiar to mechanical engineers for many years in connexion with the design of steam nozzles, and much valuable information has been accumulated from experience and from specific researches such as the classical work of Stodola (1927)‡ and of the Steam Nozzles Research Committee of the Institution (1923, etc.). The flow of steam through a converging-diverging nozzle, however, is only one instance of the flow of a gas in circumstances in which changes in density and pressure are produced or accompanied by changes in velocity. Behaviour of this kind is frequently referred to as compressible flow and arises in the design of gas turbines, in the jet propulsion of aircraft, in some high speed compressors, in diffusers, in flow through valves and measuring nozzles, in high speed aircraft and in the flight of projectiles.

The subject of compressible flow is thus of great importance in a wide range of problems of practical engineering and as it has not yet reached a stage at which the essential features are treated in textbooks readily available to engineers, the present paper has been written to cover as wide a field as practicable. The authors' main experience of the subject has been in the field of external ballistics and in the design, development, and use of supersonic wind tunnels; and the illustrations are taken largely from such work. The principles are of universal application, and it is hoped that the discussion will be on general lines and range over a wide field of applications from various branches of engineering practice.
Research and Development Applied to Bomb Disposal
Authors: Gough H. J.
Published: October 2007

An account of some of the principal lines of research and development pursued, during the late war, to solve the complex and changing problems presented by the designers of enemy bombs, which resulted in the devising of methods, apparatus, and equipment for use by the Unexploded Bomb Disposal Sections of the three Services. The three primary problems of bomb disposal are described: the location of the bomb; the rendering safe of fuzes, and anti-handling and booby-trap devices; and opening and emptying the bomb of its high-explosive filling. The considerable variety of fuzes—and their associated devices—fall into certain groups, and the technically important types of those encountered are described. As the result of intensive investigations, a large proportion of which could only be carried out on live bombs, satisfactory disposal techniques were developed, and suitable field equipment was designed and produced for use in this country and overseas theatres of war. The lecture deals primarily with German high-explosive general-bombardment bombs, but some mention is made of Italian and Japanese bombs, as well as the German flying-bomb and long-range rocket.
Airframe Production
Authors: Mensforth Eric
Published: October 2007

In reviewing some of the factors which have influenced the production development of aircraft during the recent war, the paper focuses the analytical attention of engineers on to the very large technical and manufacturing resources employed: over forty per cent of the whole munition effort of the country. Some comparison is made between the experience of the United Kingdom and that of the U.S.A., the broad conclusion being drawn that technically production methods have been similar, that peak production (having in mind the relative populations), has been comparable, although American outputs have been much higher per man-hour. In some British factories where sufficient concentration has been possible, man-hours have also been comparable with those of the U.S.A. The paper gives some general indications of cost for various elements of aircraft production—e.g. engineering design, provision of manufacturing facilities, tooling, materials, etc.—and it discusses the relationship between the quantity made and the continual reduction of man-hours commonly experienced during the production period. The general problems are examined of meeting the Services' changing demands, of co-ordination of manufacturing through groups, and of material standardization and supply.
Transfer Moulding
Authors: Freund M.
Published: October 2007

Since the early days of the commercial plastics moulding industry, injection moulding principles have been successfully applied. Compression moulding technique has achieved a high economic standard by the design of multiple-impression moulds, and when transfer moulding technique has been applied it has mainly been for technical reasons. Recent developments, however, make it possible to use transfer moulding on a large scale, and it can now compete with the orthodox compression moulding in economy and efficiency. Existing machines can be used for the transfer method, but special presses adapted or built for this purpose will give a better service.

Consideration of the engineering fundamentals of the transfer moulding process will contribute to the economy of tooling; the tooling is influenced by the presses used, and the plastics moulding engineer will have to co-ordinate all production items for successful competition with compression moulding. The strength of the finished mouldings, too, is influenced by the manufacturing method. Further developments in machines, tooling, and methods are necessary if conventional moulding methods are to be replaced entirely in mass-production applications.
Aircraft Wheel Brakes
Authors: Robson D. A. L.
Published: October 2007

In designing brakes for the landing run, account should be taken of aerodynamic forces acting on the aircraft that reduce the ground reaction in addition to helping to retard the aircraft. There are good grounds for designing brakes with a limiting torque, because most British tail-wheel type aircraft will nose over if the brake drag exceeds about 0·2–0·3 times the aircraft weight, and with tricycle landing gear the loads imposed on the nose-wheel structure during severe braking may be critical; furthermore, the danger from bursting a tyre, owing to locking the wheel, cannot be ignored. Calculations made for a hypothetical aircraft indicate that little is gained by designing for a brake drag in excess of about 0·3 times the aircraft weight.

Brakes are used both for steering and limiting the speed of the aircraft when taxi-ing, and in consequence, a very large amount of energy may have to be dissipated by them.

Shoe brakes are standard equipment on German aircraft, and are also widely used in America, but use on British aircraft is confined to the smallest types. British designers have used expander-tube brakes almost exclusively, but disk brakes—popular in America—are now receiving close attention in this country.

The British system of brake control is to use finger operation, with a differential mechanism coupled to the rudder control, but in most other countries foot pedals are employed. The British system necessitates power operation almost always, but direct operation is possible when foot pedals are used. Pneumatic power transmission for brake operation has been widely used on British aircraft, but most other countries have adopted hydraulic operation.
The Production of Small Worm Gears for Experimental Work
Authors: Gunner A. M.
Published: October 2007

Small worm gear drives are a common feature in the design of many types of apparatus, and the following description of the methods used for producing them in an experimental establishment may be of interest. Quantities are small, one or two to each pattern being the general rule, but there is certainly no lack of variety.

The worms and wheels most often called for range in size up to 1½ inches and 6 inches diameter respectively, while pitches vary from 10 to 60 d.p. (diametral pitch). Addendum and dedendum proportions of 1/ PN and 1·25/ PN have been standardized, and a pressure angle of 20 deg. is adopted throughout.

The gears are designed as hollow-faced helical (spiral) gears, and all calculations are based on the normal pitch. This is to enable standard hobs and cutters to be used for the worms. The shaft angle is usually 90 deg., but the angle of crossing may be varied up to 10 deg. either way on the particular machine employed for cutting the wheels.

For many applications, backlash must be reduced to the very minimum consistent with smooth running; and to avoid the extreme accuracy of workmanship which an exact centre distance would necessitate, provision is usually made for adjustment of the worm.

Although the Reinecker tangential feed method of worm wheel generation by a single-point tool —representing one tooth of a hob—is generally known, very little information on cutter forming is available. The method outlined was developed at the Admiralty Research Laboratory. Given the use of a modern worm grinder (not available), it should be possible to profile-relief grind these cutters after hardening.
An X-Ray Method of Measuring Poisson's Ratio
Authors: Hanstock R. F. , Lloyd E. H.
Published: October 2007

The paper describes the measurement of Poisson's ratio in metals by an X-ray diffraction method. The specimen, which is a small tensile test piece, is examined at various loads by a high-angle “back-reflection” X-ray technique. At any load (the value of which need not be known) X-ray patterns are obtained for various angular settings of the specimen relative to the incident X-ray beam, and, for each setting, the shift of the diffraction lines from their original position gives the strain in a direction normal to the reflecting crystallographic planes. The strains corresponding to various angular settings of the specimen, for any one load, give a linear graph when plotted against a simple function of the orientation of these crystallographic planes, and from this graph the value of Poisson's ratio is directly obtained.

Experimental results are quoted for the aluminium alloy known as “Hiduminium RR.56”. The results obtained for various elastic loads are consistent within the experimental error, the resulting value of Poisson's ratio being 0·36.

It is concluded that the method described is capable of an accuracy at least as good as that of the ordinary mechanical method, and that it has the additional advantage of providing values which apply to a single set of crystallographic planes in a polycrystalline metal.
Fuel Systems for the Aero-Gas Turbine
Authors: Watson E. A.
Published: October 2007

The purpose of the paper is to give an account of the problems associated with the development of the fuel systems of those aero-gas turbines with which the author has been principally associated. While, therefore, it cannot claim to cover all aero-gas turbines, the general problems involved are common to all the turbine units under development, so it is hoped that the paper will be of general, as well as specific, interest. Even so, the author has found very great difficulty in compressing some six years of very intensive work carried out by a large team of engineers into the space of one paper. Much important work has been omitted and other work compressed into small space, but it is hoped that it has been possible to give a fairly comprehensive treatment of certain particular developments while at the same time making clear the fundamental principles on which these have been based.

The paper is divided into two sections, the first dealing with the supply of the fuel in the appropriate quantity, and the second covering the atomization of the fuel preparatory to its evaporation and combustion.

As far as possible, the two sections will be treated as separate entities, although they are very closely interrelated, since the type of atomizer has an important bearing on the fuel system. In studying the paper, therefore, it may (for example) be necessary to refer to certain items in the second section before the first can be fully appreciated.
Some Recent Developments in the Technique of Radio Valve Manufacture
Authors: Davies J. W. , Gardiner H. W. B. , Gomm W. H.
Published: October 2007

There are many points in the construction of thermionic valves of general interest to the engineer, and the purpose of this paper is to bring some of these points to the knowledge of mechanical engineers in other fields than valve manufacture. It is not possible to cover all the aspects, but mention will be made to a few of the later developments that besides being of interest may find useful application in other spheres.

The principles of construction, the materials used, and the forms and types of various components—cathodes, grids, and anodes—are touched upon. The joining of glass and metal is dealt with, and notes on the machines used are given. The paper ends with particulars of the assembly processes, and tables showing the various types of join in common use and their application in valve manufacture.
The Tensile Yield Strength of Certain Steels under Suddenly Applied Loads
Authors: Warnock F. V. , Brennan J. B.
Published: October 2007

Dynamic tensile yield stresses are determined for eight steels, including one mild steel, two plain carbon steels, two carbon manganese steels, one heat-treated alloy, and two cast steels.

The dynamic loads are applied by means of an impact machine of the falling weight type. An attachment is fitted to this machine to enable the peak load to be reached in 3 milli-seconds (0·003 second). Supplementary tests, in which the time to reach the peak load is 1 milli-second, are carried out on three of the steels. Electrical resistance strain gauges mounted directly on the specimens are used to record the loads.

Comparison with static values reveals an increase in yield stress of from 21 to 36 per cent for the carbon steels under dynamic loading. This increase diminishes with increase in static yield strength. The annealed cast steels behave in a similar manner to the carbon steels, but the heat-treated alloy steel shows no appreciable increase in yield strength with increase in rate of loading.

Comparison is also effected with some results of other investigators. A theory is put forward to account for the variation in sensitivity of yield strength to load rate.

A division of tensile tests into three main types, on a basis of rate of loading, is suggested for future work.
The Mechanical Differential Analyser: Its Principles, Development, and Applications
Authors: Rose H. E.
Published: October 2007

In the physical sciences differential equations are encountered which are either extremely difficult or impossible to solve by formal methods. For the evaluations of such equations a number of numerical and graphical methods have been developed, together with electrical and other analogues for their direct assessment when the numerical or graphical methods are not practicable.

Each analogue will evaluate but one type of equation; the differential analyser—which is not an analogue in this sense but a machine for performing mathematical operations—will, however, evaluate any differential equation (within the capacity of the machine) and present the solution in graphical or tabular form.

In the paper the mechanization of integration and other algebraic operations are discussed, and a “non-linear” vibration problem is used as an example of the setting-up and operation of the machine for the solution of a differential equation.

Points of special interest in the design and construction of these machines are discussed together with an account of the existing machines.

A number of problems of special interest that have been solved by use of the machines are considered and possible lines of development are discussed.
The Calculation of Roll Force and Torque in Cold Strip Rolling with Tensions
Authors: Bland D. R. , Ford Hugh
Published: October 2007

From an approximate theory, equations are derived for roll force and torque with and without front and back tensions applied to the strip. Where tensions are applied the calculations for each pass take about an hour; without tensions, and with the use of curves given in this paper, they can be carried out in ten minutes. The accuracy of the calculations without tensions is within about 15 per cent.

At the end of the paper there is a discussion of the energy relationships in rolling. At present this should be considered as speculative in character.
The Calculation of Compressible Fluid Flow by the Use of a Generalized Entropy Chart
Authors: Kestin J. , Oppenheim A. K.
Published: October 2007

Calculations of the flow of gases in pipes or ducts of varying cross-sections are important in the design of turbines and compressors, nozzles for various applications, exhaust or radiator ducts, thrust augmenting devices, etc. Provided certain simplifying assumptions are made, there is no difficulty in writing down the basic equations, but when the velocities are comparable to that of sound and compressibility effects cannot therefore be neglected, the solution of the transcendental equations present difficulties which hinder a clear discussion of the physical phenomena. Here the problem is solved by the use of a generalized entropy chart, off which results may be directly read. For example, if the conditions in the reservoir from which the gas is assumed to be discharged are known, the complete conditions at any given cross-section may be read off when two parameters at the section considered are specified. The parameters may include the velocity, pressure, density, temperature, local Mach number, local velocity of sound, area of cross-section, mass flow per unit area, momentum per second, etc. The method is not confined to isentropic flows and may be applied to such problems as the flow in straight pipes or convergent and divergent nozzles including losses by either friction or condensation shocks.

The co-ordinates of the chart are: dimensionless entropy σ = ( s— s0) J/R and dimensionless enthalpy ι = h/h0 = T/T0 where the meaning of the symbols is given later. All other variables are expressed in terms of these two co-ordinates and tables for several values of the ratio of specific heats are included to facilitate the drawing of such charts.

The method does not aim at presenting new facts, but its usefulness lies in the provision of a comprehensive graphical means of calculating one-dimensional flow of compressible fluids. The charts lend themselves to the construction of a mechanical device for simplifying their use, such as a portable scale with sliding curves.
Chart for the Investigation of Thermodynamic Cycles in Internal Combustion Engines and Turbines
Authors: Gilchrist J. M.
Published: October 2007

The development of the internal combustion turbine engine has reawakened interest in the study of thermodynamic problems associated with internal combustion engines.

Graphical solutions find favour because ( a) widely varying mixtures of gases are used in modern engines, ( b) the specific heats of the gases vary with temperature and pressure, and ( c) the complete combustion of hydrogen, carbon, etc., cannot occur at high temperatures owing to dissociation.

In the paper it is shown by suitable selection of scales how the temperature-internal energy graph may be used to indicate enthalpy, and, for engine expansions, the work done and the energy supplied. In turbines and turbo-compressors the heat drop, velocity change, losses, etc., are given by readings from the temperature and internal energy graph.

The method is applied to a general cycle which embraces the Otto, Diesel, Atkinson, Humphrey, etc., cycles. To determine the work done and efficiency calculation is eliminated entirely. An indicator diagram taken from an oil engine is examined and the heat exchange for arbitrarily chosen parts of the cycle estimated.

Internal combustion turbine cycles are discussed and the advantages of stage reheating and inter-cooling demonstrated.

Energy-mixture strength tables, for temperature intervals of 200 deg. C. (360 deg. F.), are supplied for mixtures between 100 per cent weak and 20 per cent rich.
The Distribution of Load in Screw Threads
Authors: Sopwith D. G.
Published: October 2007

The distribution of load along the length of a nut is not uniform owing to the strains set up in the bolt and nut under load. These strains are analysed and the load distribution along the thread helix deduced. It is shown that the load may be taken as concentrated at mid-depth of the threads. In the normal bolt and nut case the maximum intensity of loading occurs at the bearing face of the nut, and may be from two to four or more times the mean, depending on the thread form, the proportions of the members, and the degree of lubrication; the maximum intensity is almost independent of the length of nut (unless yielding occurs). Possible methods of improving the load distribution are discussed—differential pitch, tapered threads, and the use of a softer material for the nut. The load distribution in the turnbuckle case is more favourable than in the bolt and nut case, and can theoretically be made uniform by suitably boring out the inner and shaping the outer member; this condition can be approached in practice by the use of “tension nuts”. The effect of yielding on the load distribution is discussed.

Experimental confirmation of some of the results is included.
District Heating
Authors: Stubbs A.
Published: October 2007

This paper regards district heating as a service intended to satisfy the space heating and domestic hot-water requirements of the public. It sets out a complete scheme for a large town of 250,000 people in such a manner as to show the values of the parts as well as the value of the whole.

The build-up of the district heating load is conveniently set out under the headings: ( a) industrial and commercial, ( b) community, and ( c) housing, whilst the engineering and economic features are related to the consumers, the sub- and main-distribution, and generation.

District heat is low-grade energy, and its generation is properly associated with the generation of electricity which is high-grade energy. In taking advantage of combined generation of heat and electricity, consideration is given to the already highly organized state of the electricity supply.

The conclusion deals with the costs and overall fuel economy and does not deal with improved amenities which, in the opening part of the paper, are taken for granted.
Modernization of a Coal-Discharging Depot
Authors: Shoosmith G. T.
Published: October 2007

The paper describes the modernization of a coal-discharging depot originally equipped with hydraulic transporters. The steps taken to enable the jetty to withstand a greatly increased loading are given, and the crane rail girders of special fabricated type are described.

The relative merits of various types of unloader are discussed, and the reasons given for adopting electric luffing cranes. The principal features of the special electric cranes installed are described, together with the reasons for adopting certain unusual features, and the provisions made for ease of maintenance and interchangeability of mechanical parts. The system of electrical control adopted is described. The design and operation of grabbing cranes is compared with that of normal cargo cranes.

The question of load balancing for cranes is considered and calculations given of speed, acceleration and power consumption for similar cranes without any balancing, and with varying degrees of balancing of the load. The effect of varying height of lift on power consumption is shown graphically. The importance of low inertia of the moving parts of high-speed cranes is emphasized, together with comments on the methods which can be adopted to achieve this end.

The design of crane ropes and sheaves and the effect of the reverse bending of crane ropes is discussed briefly, and figures are given of rope life with various designs of grabbing cranes. The importance of high rope-diameter/sheave-diameter ratio is stressed.

A brief description is given of a special form of crane weighgear used for the first time on the new cranes at the depot.

The question of grab design is discussed briefly, with particular reference to coal handling, and results are given of different designs of grabs dealing with various classes of coal under normal operating conditions.

An outline is given of the method of erecting the new cranes without interrupting the working of the depot.
Cinematography in Engineering
Authors: Bulleid H. A. V.
Published: October 2007

The cinematograph has become indispensable to the modern engineer, and is widely employed as an analytical, recording, and educational medium. Of these, the first only is dealt with in this paper; the others involving, in addition to an essential engineering precision, the artistic and technical resources of film construction.

The author deals with the analytical aspect in relation to apparatus, detailing minimum equipment and scope; straight records, with a standardized set-up; special records, with data on camera speed; complex images and multiple exposures; high-speed cinematography, and notes on special apparatus; low-speed cinematography, including animation; special methods for recording hidden transients; X-ray, infra-red, and micro-cinematography, and simpler alternatives.

The last section describes typical cases in which, for a variety of reasons, cinematography is not the best analytical tool to use.

The paper concludes with sections on the marking, developing, recording, and printing of film records, and describes suitable methods and apparatus for analysing the results.

Ten excerpts from 16 mm. films illustrate some of the more important applications described.
Invention and Sifting Out Engineering Facts
Authors: Bailey E. G.
Published: October 2007

The subject of invention is discussed with a view to increasing the number and value of inventions.

The relation between research and invention is explained with a plea that research should be so conducted that more valuable inventions will be forthcoming.

The various incentives to invent are listed, and the usual important steps actually required in making inventions are enumerated in a manner that will enable others to follow them.

The important steps in reducing an invention to practice are given for the guidance of those interested.

Some illustrations from the author's experience show how simple is the process of inventing when there is an incentive.

The present trends and future needs for invention in different fields are discussed under the headings of ( a) products and processes, ( b) communications, ( c) transportation, and ( d) power and heat.

The sifting out of facts in the engineering field results in only the good and useful surviving. The question is posed as to why facts within the area of human relations cannot be dealt with in a similar manner.
Investigations into Cyclone Dust Collectors
Authors: ter Linden A. J.
Published: October 2007

The paper describes experimental investigations made in the mechanical engineering laboratory at Delft, in the field of cyclone separators. These investigations aimed first at determining the most efficient shape of a cyclone, by measuring the effect of a variation of each of its principal dimensions on the efficiency; as a result, a very efficient cyclone shape was developed.

The influence of the position of a cyclone on the efficiency was examined, and a new type of cyclone with curved axis, horizontal gas exhaust, and vertical downward dust outlet was constructed.

The flow of gas and dust inside a cyclone was examined. The static pressure and the three components of the gas velocity at different points in a cyclone were measured with a globe-Pitot tube.

In a cyclone exhausting to atmosphere, a core of low pressure extends over the entire height of the cyclone. Inside this core the flow is very turbulent and unsteady, so that the gas velocities cannot be measured exactly; outside, the pressure is high throughout the remainder of the cyclone.

With the exception of the turbulent area in the centre, the total velocity of the gas deviates only slightly from the tangential component V t, which increases as the distance from the centre of the cyclone diminishes. The vertical component V h is directed downwards along the cyclone walls and carries the dust particles to the bunker, and the radial velocity V r is directed towards the centre in the greater part of the cyclone; but in the very turbulent centre, V r is directed outwards and V h upwards.

From these measurements a simple cyclone theory was developed, enabling the approximate calculation of the size of the largest dust particles that may escape a cyclone.

The effect of a variation in the quantity of gas on the efficiency was determined; this effect was small for a well-constructed cyclone.

Efficiencies are given for different sizes of similar shaped cyclones and for various sizes of dust particles. These data enable the selection of a cyclone collector suitable for a particular kind of dust, and the choice of cyclone dimensions for a given efficiency.

A method of measuring the dust content of a gas-flow, by means of a small cyclone, is described.
Some Current Types of Marine Diesel Engine
Authors: Pounder C. C.
Published: October 2007

The paper comprises brief descriptions of three distinctive types of marine Diesel engine, and some expressions of opinion upon a number of matters of current interest. The types considered are double-acting, two-stroke engines; single-acting, two-stroke, crosshead engines; and single-acting, two-stroke, trunk engines. The author restricts his remarks to some of the engine types with which, for many years past, his work has lain. Some matters of detail dealt with are the timing of cylinder lubricators, piston rings, pistons and liners, piston rod stuffing boxes, piston rod scraper boxes, feed pumps and valves, scavenge blowers and lubricating oil systems. Indicated horse-power and mechanical efficiency also find a place, together with crankcase safety precautions, vibration and noise, and materials of construction. The author also deals with surface finish, the effect of design changes upon maintenance, the use of lower-grade fuel oils, scavenging, and engine rating, and concludes with a reference to the comparison of Diesel and steam machinery and tables of typical sea-service results of a 6,000 s.h.p., double-acting, two-stroke engine.
Marine Boiler Deterioration
Authors: Slater I. G. , Parr N. L.
Published: October 2007

A survey is made of the several forms of boiler corrosion and deterioration encountered in marine practice. Problems of design, operation and maintenance at sea are discussed in relation to metallurgical and electro-chemical phenomena involved. As regards water-side corrosion, pitting is more frequently encountered; general wastage, corrosion fatigue, strain age embrittlement, and caustic embrittlement are in decreasing order of importance. Other forms of deterioration include high-temperature oxidation, bursts, high-temperature creep, and corrosion on the fire side. Several forms of each of the phenomena are illustrated and basic principles involved are discussed.
The Seizure of Metals
Authors: Bowden F. P. , Tabor D.
Published: October 2007

When metal surfaces are placed together, the area over which they touch is usually very small. As a result, the localized pressures at the points of real contact are sufficiently high to produce plastic flow of the metal. Even under static conditions, these high pressures may produce “cold-welding” between the surfaces, and the metallic junctions so formed may be very strong. These junctions are sheared during sliding, and if they are stronger than the parent metals, heavy damage may result which is not limited to the interface at which intimate contact occurs. The growth and extension of this localized damage constitutes seizure.

It follows that those factors which facilitate localized welding will, in general, increase the chances of large-scale seizure. Similarly, surface films which are capable of reducing localized adhesion will reduce the chances of seizure.
Hydraulic Seals
Authors: Beacham T. E. , Towler F. H.
Published: October 2007

Leakage is the most common source of complaint with regard to hydraulic machinery. During recent years considerable advances have been made in the prevention of leakage of liquid past moving surfaces. New materials and constructions have come into common use, and there has been a small but valuable amount of research into the action, wear and friction of packings and seals. The object of these papers is to initiate a comprehensive discussion of existing knowledge on the subject, which will perhaps indicate the fields to which future research and development might best be directed.

The authors' experience has been mainly in connexion with hydraulic machinery in which oil is the working medium; in this field particularly, the improvement of sealing methods has been very marked. It is hoped that contributors to the discussion will also deal with water, acids, and other liquids, and with the special problems encountered owing to high temperature, corrosion, dirty liquids, etc.

As the subject covers a wide field, it has been limited by excluding hydraulic joints. For the purpose of this paper, a hydraulic seal will be defined as one whose function it is to prevent the leakage of liquid between surfaces having relative movement.
Discharge of Exhaust Gases in Two-Stroke Engines
Authors: Weaving J. H.
Published: October 2007

The paper points out that the two-stroke engine still has a field of great importance, i.e. the compression-ignition engine, and that, although the two-stroke cycle has been known for so long, the theory of the discharge of exhaust gases from the cylinder is still in doubt, and some of the generally accepted assumptions have been challenged in recent years, in particular by Kadenacy.

A description is given of apparatus built at the Engineering Laboratories, University of Cambridge, to simulate the discharge portion of the cycle only. This apparatus utilizes the gases nitrogen and hydrogen under compression, these being respectively denser and less dense than exhaust gases. Experiments were made to ascertain whether the older theories were valid, and to investigate the claims of Kadenacy of supersonic discharge and resultant vacuum pressures in the cylinder. These tests demonstrated that the older theories, based on the assumption of steady flow and Bernoulli's theory, were substantiated, provided that modifications were made to the index of expansion and the coefficient of discharge.

Finally, a simplified system is derived for the calculation of the size of exhaust ports or valves, and this system is applied to a practical case.
The Engineering Implications and Economics of Surface Preparation of Mild Steel Prior to Fabrication
Authors: Johnson W. A.
Published: October 2007

Those steel structures which are subject to repainting during service are considered, particularly those subject to exposed atmospheric conditions. Since any major improvement in paint life is dependent on surface preparation, alternative methods are examined. Mechanical shot blasting is the cheapest method for structural steel, but it is only possible prior to fabrication. The choice of prime coats, which must satisfy several requirements, lies between paint, oil, and metallic coatings. It is believed that suitable paint could be developed. No suitable oil is yet available, and of the metallic coatings sprayed aluminium is the most suitable.

Fabrication difficulties, and in particular welding, require further investigation.

The cost of painting a structure during a life of fifty years shows that surface preparation prior to fabrication is economical.