Proceedings of the Institution of Mechanical Engineers

In this lecture an analogy is described by means of which transmissions can be analysed and compared. Two important design parameters are the force density Δ and the effective volume V ^*, which can be used to analyse stationary and moving methods of transmission.

With this analogy a tool is given to the designer to compare transmissions with regard to performance, controllability, size and weight, intensity of loading, dynamic properties. A beginning has been made with formulating a relation between the intensity of loading and wear phenomena (II).

With this work we hope to have contributed to a sounder basis for the study and development of power transmissions and their use in machines. As mechanical, electrical, pneumatic, and hydraulic power transmissions can be compared by means of this analogy, the selection of transmissions can be made on a sounder basis.

Development of offshore oil and gas production from the continental shelf and in even deeper water will be dependent on engineers. It is of primary importance to understand the nature of the oil and gas production industry in order to follow more clearly the contribution that will be required from many of the professional branches of engineering, and a great deal of new technology must be developed in order that the problems of the future may be overcome. The difficulty may not be in defining the future engineering of oil and gas development but in finding engineers in sufficient numbers to meet the demand.

The effect of changes in atmospheric pressure and temperature on the performance of a compression-ignition engine without a turbocharger has been investigated. In addition, variations in exhaust smoke and temperature, cylinder peak pressure, coolant heat flow, engine friction and air flow rate were observed. A method has been devised for the prediction of the brake power and fuel consumption of an engine at any pressure and temperature using information obtained at normal atmospheric conditions only. This method has been checked using the results of several investigators. A prediction method for calculating the maximum permissible power output is also suggested in relation to various rating criteria.

Power and torque improvements of 30 per cent and 26 per cent respectively have been produced by turbocharging. A compression ratio of 7·6:1 is employed and petrol of 97 octane number RM is adequate.

An acceptable torque curve has been obtained by the use of a turbine outlet restrictor; the standard intake manifold is retained and the compressor delivers to the standard carburettor. A unique combination of vehicle performance and driveability has resulted and exhaust and intake noise is readily controlled.

Only minor engine component changes are necessary and mechanical reliability presents no problems. Specific fuel consumption is no higher than that of the normally-aspirated version of the engine, and emision of oxides of nitrogen is low.

This lecture sets out to review developments in numerical-control machine-tool technology with particular reference to the application of general-purpose digital computers to the control of individual machine tools or groups of machine tools, to meet the requirements of the end user.

The subject matter embraces very broad-based technology, ranging from factors which directly contribute to machine utilization to the application of advanced digital-control techniques which directly contribute to the versatility of modern numerical-control machine tools. Thus, the lecture begins with a review of worldwide growth in numerical-control machine business and a discussion on the technological evolution of numerical-control systems with particular reference to the fast growing utilization of mini-computers. The subject is illustrated by a practical case history in the United Kingdom based on a computer control system developed by the author's firm for turning, milling, and boring machines.

The lecture concludes with a review of operational benefits to be derived from the application of modern numerical-control machines to production processes and makes predictions concerning future developments in the application of general-purpose digital computers.

During the last 20 years, progressively smaller diesel engines have been turbocharged, so that units of 50-60 hp are produced today. Spark-ignition engines remain normally aspirated for most applications, although this picture may change.

Progress followed the adoption of radial flow turbines using lost-wax cast rotors. Other developments included:raising component efficiencies; dealing with bearing and seal design problems, and with vane vibration; and in devising manufacturing methods for quantities approaching 3000 weekly, in mixed and rapidly changing batch sizes.

Various control systems are available to match the turbocharger to the demands of variable speed engines.

Studies at the Royal Aircraft Establishment are aimed at the in-flight demonstration of improved control systems and policies in a fighter-attack and/or a transport aircraft. The systems being flight evaluated at the present time employ conventional linear-control policies, the design being based on a parameter-optimization technique. Two important modes are discussed briefly in the paper: a pitch-rate manoeuvre-demand system for the fighter-attack aircraft and an ILS glide path and flare system for the transport aircraft.

The design studies of these and other modes have yielded quantitative data on conflicts between different performance requirements which cannot be avoided when linear-control policies are used. Studies are being made therefore to replace linear control by variable-gain policies in selected parts of the control system in order to reduce the extent of these conflicts. The reasons for and principles of the variable-gain control policies are outlined in the paper; in addition certain system improvements are discussed (e.g. trim problems) which result from the application of these non-linear control policies.

Developments within the European Coal and Steel Community, since it was founded in 1952, are outlined. Particular attention is devoted both to the technical research that has been carried out under the E.C.S.C. cooperative research progamme and to the impact that technological change has had on the industry. An attempt is made to link the advances in technology and production with economic considerations. The lecture will discuss current trends in the availability of raw materials and energy and their influence on steel production. The future prospects of the iron and steel industry within the enlarged European Community are considered and the likely directions of technological advance are discussed.

This lecture reviews the significant developments in fatigue over the last twenty years as they pertain to the prediction of life in high-temperature service. Particular attention is given to the interpretation of fatigue test results for both low and high cycle fatigue at room and elevated temperatures. Emphasis is given to such effects as environment, frequency and strain rate, metallurgical factors, wave shape and thermal cycling, and some attempt is made to sort out their relative importance. Applicability of low cycle fatigue information to notch geometries is discussed. Lastly considered is the significance of these several factors to the current state of life prediction as well as to future directions for development of this important topic.

Unlike tyres, wheels and brakes for commercial vehicles which can be tested on the road as a major part of their development programme, such equipment for aircraft must be qualified to full service conditions in the laboratory before being fitted to an aircraft.

This paper covers the specification background, design features and construction of a large, high-speed dynamometer on which the development and qualification of aircraft tyres, wheels and brakes are carried out. Particular attention is given to several fundamental advances in design including the electrical stimulation of brake inertia, computer control and monitoring of the main systems and the real-time recording of tyre forces in three planes.

The paper covers a combination of the mechanical, electrical and instrumentation engineering content of the facility.

The main theme of this Address is the training of professional engineers, although it is apparent that training cannot be completely divorced from education. Primary education is dealt with briefly, but sufficiently to indicate its importance. A proposal is made for a system of mentor and tutorial guidance extending from the sixth form through the industrial student stage, and through University to Corporate Membership of C.E.I. and into management.

At each stage of development the responsibilities of the various participants are clearly outlined, and proposals are made for training and educational programmes. These are broad enough to be applicable to almost any discipline, and should be tailored to suit the individual requirements of any organization. The Address is concerned with the methods which should be adopted for manager development, not only for the graduate but right through, as a continuing process, for all grades of management.

The paper describes a practical method of calculating the aerodynamic effects of trains passing through interconnected tunnel systems so that these can be designed for acceptable pressure pulse levels, air velocities and train drag. The equations of unsteady compressible flow were developed into a form suitable for solving by the Method of Characteristics on a computer. Results obtained were compared with measurements taken on models and in real tunnels and some of the comparisons are shown and discussed.

The method of calculating the aerodynamic flows and pressure transients described in the first paper was used to make predictions for the Channel Tunnel. Results for single trains and for two-way working are shown. Some of the important parameters of the tunnels and trains were varied to show the effects of such changes so that the design could be checked and refined from the aerodynamic standpoint.

The object of this paper is to re-assess the existing principles used in the design of synchronized mechanical transmissions from the point of view of synchronizer duty. By a logical approach, when the main emphasis is given to synchronizer duty, a new transmission concept, known as the ‘M’ series, has been evolved, which brings with it some important advantages: saving of weight; faster synchronization, making for greater road safety; less space; lower manufacturing costs.

The theoretical study compares the expected performance with that of a conventional five-speed synchronized transmission under identical conditions. Laboratory and road tests have established the validity of the theoretical appraisal.

A method is given for calculating pressure transients in an axial piston hydraulic pump. Some theoretical predictions are given of the effect of port timing and the effect of introducing restricting grooves at the ends of the kidney ports in the valve plate and suggestions are made of the effects of these parameters on noise emission; comparative measurements of noise are then quoted that support the general arguments. A parallel shot is recommended as the best compromise for the restrictor groove geometry to give good results over the widest range of operating conditions, including reverse rotation. Finally, mention is made of the use of a relief valve in the port plate for noise reduction.

This paper is a subjective summary of nine conferences on quality and reliability organized by the Institution of Mechanical Engineers during the last decade. Starting from economic factors, optimum design is identified with minimum total life cost, which is, in turn, closely related to reliability. The paper examines reliability theory briefly for its practical implications, e.g. that reliability depends crucially on safety margin and loading roughness. The former is a design feature, but both are operator controlled. The matching of design to the requirements of the user in the intended environment is considered paramount. It is shown that reliability is so dependent on such factors that design for prescribed levels of reliability presents formidable difficulties. The design process is discussed, taking these and maintenance constraints into account. The necessity for proper development is underlined. It is noted how realistic theory supports everyday practical experience. Finally, the function of management is discussed.

The accuracy of the streamline-curvature method has hitherto not been evaluated for curved-axis convergent-divergent flow as found in transonic turbine cascades and for flow in cascades with flow divergence or flare. To provide the data for evaluation, two simple single-channel rectangular-section wind tunnels were built to simulate the flow between turbine blades. The supersonic channel was successfully and economically powered by a large steam ejector.

In transonic and supersonic flow, an examination of the sonic and M = 1·1 lines was used as a basis for evaluating the predictions. The correlation was found to be good near the convex surface, but showed a deterioration towards the concave surface. Both test and prediction revealed the unexpected fact that the sonic line contour is not smooth, but wavy. The correlation at the M = 1·1 line was positionally the same as the sonic line, but the experimental contour was considerably more wavy. The accuracy deteriorated further into the supersonic region. The discrepancies in the transonic region are thought to be caused by a very slow rate of change of area, which produces a complex boundary layer interaction in the throat region, affecting both the location of the throat and the area ratios in that zone.

The prediction method was shown to be extremely accurate for flared-cascade flow even up to the very exacting situation of a 40 per cent blade height increase, the only error being that due to boundary layers in the apparatus that effect the velocity distribution over the latter half of the suction surface in a highly staggered cascade.

In Part 1, optical interferometry is used to study an elastohydrodynamically lubricated line contact between a taper roller and a glass plate under pure rolling conditions. The results give detailed information on film profiles and show the effects of end blending, lubricant starvation, deep scratches and static oil entrapments. In Part 2, oil film thicknesses in an elastohydrodynamic line contact are measured using optical interferometry and compared with theory. Two empirical formulae are derived for film thickness in the central region and at the exit constriction. In addition to the optical measurements, electrical measurements (resistance and capacitance) are made simultaneously, enabling a direct comparison to be made.

Factors influencing the longitudinal variation of water level in the drums of circulating boilers are discussed with reference to the results of cold-circulation trials performed on a 500 MW assisted-circulation boiler. Numerical computation and small-scale model tests in support of the field trials are also presented. This information, together with evidence from further work on the operating boiler, has shown that small cold-water models provide an accurate analogue of drum operation at working pressures and temperatures.

A theory is given for calculating chip geometry, cutting forces, etc., from fundamental work material properties and cutting conditions. The flow stress properties of the work material (0·16 per cent carbon steel) used in the analysis are taken from high-speed compression test results. The theory predicts the main trends observed in machining experiments and a limited comparison with experimental results shows good quantitative agreement. A possible explanation for the occurrence of a built-up edge, involving the dynamic strain ageing (blue-brittleness) of the chip along the tool-chip interface, is considered and found to be consistent with the results.

A capacity gauge has been designed for operating in the conditions of a working engine. The method of using it for determining the oil-film thickness and piston-ring profile is described. Oil-film thicknesses in the range 0·4-2·5 μm between the piston rings and the cylinder liner have been observed. Their variation with speed, load and temperature has been measured and it is concluded that their behaviour is essentially hydrodynamic.

An iterative method of solving the hydrodynamic equations of lubrication of a piston ring is described. Some results of the calculations are compared with the measured values of the oil-film thickness in an actual engine. It is shown that there are disagreements of up to a factor of 8 between the theoretical and measured values. Further experiments were carried out on a single ring in a motored rig and here it was shown that although the film thickness is considerably greater, it is still not in complete agreement with the theory.

This paper presents the results of a study of the air motion in a motored four-stroke direct injection diesel engine using hot-wire anemometry.

The effects of engine speed, valve masking and supercharging on mean air swirl have been studied. A theoretical analysis is developed for the mean air swirl which in general shows good agreement with the experiments reported here and with the measurements of other workers on similarly sized engines.

The problem of ‘squish’ has been investigated and it is shown to be the radial component of the spiralling swirl flow entering the combustion chamber. Reasonable agreement has been found between measurement of the radial flow component at the edge of the combustion bowl and a theoretical analysis that considers the bulk radial flow of air to the combustion bowl during the last 30°-40° b.t.d.c. of the compression period.

A new family of high-efficiency, high-ratio reduction gears is described in which a counter-rotating epicyclic gear distributes power equally between two, three or four parallel drive paths. The mechanisms employ zero stiffness torque-balancing within and external to the epicyclic unit and work within a spectrum of operation bounded by designs having a fixed annulus or a fixed planet carrier.

A theory is developed to investigate the principal design problems associated with reduction ratios, bearing speed, centrifugal loading, bearing life and epicyclic efficiency. A primary application is to high-output torque transmission systems such as those used in helicopters.

This paper shows firstly how the choice of base stock reduces apex-seal wear. Results emphasize the influence of volatility, and particularly of the quantity and viscosity of the residue after heating.

The second part (section 3) concerns pre-ignition. Testing was difficult, but a connection was found between the ash content of the oil and severity of pre-ignition. Testing of anti-wear formulations for pre-ignition was found to be necessary.

The third part (section 4) is devoted to engine smoothness, which must not be confused with pre-ignition. Spark plugs and mixture strengths are the most important factors, fuel probably having only a secondary effect.

Rotary-engine lubrication studies have been conducted on four engines covering the two types of rotary engine now in production. Metallic or carbon-metallic apex seals were used.

Results presented have been obtained with 13 different oil formulations, including passenger-car-engine oils corresponding to API SC, SD or SE categories, automatic-transmission fluids of the Dexron II type, and oils for two-stroke engines. Seven different test procedures have been used in these investigations, employing either engine bench test stands or vehicles on chassis dynamometers.

Satisfactory rotary-engine performance has been obtained with oils containing from 0 to 1·2 per cent by weight of sulphated ash. The ability of the base stock to provide good film thickness has also been found of benefit in reducing rotary-engine wear. Passenger-car-engine oils can be excellent rotary-engine lubricants and those oils corresponding to the latest API SE classification exhibit better performance than previous API SC or SD oils. Automatic-transmission fluids have also given promising results.

A review has been made of the factors which may influence the development of lubricants suitable for the Wankel-type engines.

The lubricant requirements of the Audi-NSU Ro80 engine are discussed in comparison with the performance level of lubricants currently in use with conventional reciprocating piston engines.

In Europe, high-speed pre-ignition has been one of the main causes for concern, but at the other end of the performance scale, cold wear of cast-iron apex seals under ‘stop and go’ driving conditions, created conflicting performance requirements for the lubricant under development.

A compromise lubricant formulation has given complete freedom from pre-ignition and a marked decrease in the ‘cold wear’ rates, whilst maintaining the other desirable properties necessary for satisfactory Wankel-engine performance.

A general theory of pneumatically transporting industrial coals through pipework is proposed based on an adaptation of Hinkle's general equation for solids flow in pipework. The theory is suggested as an overall mathematical framework for designing systems for industrial and power station coal-fired plant and possibly for general transportation systems. Results are given for trials on a test rig based on three industrial coals—singles, dry/untreated and wet/washed smalls coal—and their fit with results predicted by the theory. In the design of the system, I propose the concept of dividing the system into three basic sections: (1) the clean-air section; (2) the coal-transportation section; and (3) the ash-transportation section. Equations are given for designing sections (1) and (2) and empirical data for section (3). Curves are given for the coal transportation section showing the effect of the coal concentration in the pipework, the pipework diameter and length and the verticality of the pipework on the dependent variables—pressure loss, coal quality, power requirements, energy consumption, flow rate and average pressure in the section. Important general conclusions are drawn from this work and practical information is given based on my experience. It is finally suggested that there is an urgent need for new concepts in the design of automatic systems for all types of coal-fired plant if coal is to assert its natural place in the current explosion in demand for world energy. I suggest that automatic systems are the best way of achieving this.

The low-cycle fatigue characteristics of an 11 per cent chromium steel, two nickel alloys and two titanium alloys have been studied in the range 20° to 500°C. For repeated-tension stress tests on all the materials, there was a sharp break in the stress-endurance curve between 10³ and 10⁴ cycles. The high stress failures were attributed to cyclic creep contributing to the development of internal cavities. At lower stresses, failures occurred through the growth of fatigue cracks initiated at the material surface. The whole fatigue curve could be represented by an expression developed from linear damage assumptions.

Data for different temperatures and types of stress concentration were correlated by expressing stress as a fraction of the static strength. Repeated-tensile strain cycling data were represented on a stress-endurance diagram and it was shown that they correlated with push-pull stress cycles at high stresses and repeated-tension at low stresses. In general, the compressive phase tended to accentuate cyclic creep so that ductile failures occurred at proportionally lower stresses. Changes in frequency from 1 to 100 cycle/min were shown to have no significant effect on low-cycle fatigue behaviour.

Hydrostatic thrust bearings are frequently designed for static operation with parallel surfaces although, in practice, they are required to operate under dynamic conditions and probably in a tilted state. Introducing tilt and dynamic action may result in the operating variables being quite different from those predicted for parallel static conditions.

Theoretical analyses of hydrostatic thrust bearings usually present the performance characteristics in a non-dimensional form. These describe the quasi-static operating conditions, but they do not give a direct indication of changes in individual operating variables because the parameters are interrelated.

This paper utilizes the non-dimensional parameters in a small perturbation analysis that allows the changes in individual operating variables to be evaluated directly. The analysis gives results that are in reasonable agreement with those observed during experimental tests, both for small and large variations in operating parameters.

Tests have been conducted on a 0·057 m³ (2 ft³) holder taken out of normal service and specially instrumented. The effects of water sealant temperature changes and evaporation on the volumetric readings of the holder have been measured. From these results, the mass transfer coefficient k, which is a measure of the rate of evaporation, has been evaluated.

It is concluded that well-maintained holders, whether used for pressure or vacuum testing, give rise to insignificant errors in volume measurement under normal test conditions, such as those specified in B.S. 4161, in a room with reasonable temperature control. Only when a holder is used to measure low flow rates do evaporative effects give rise to substantial errors.

The contents of this paper were originally prepared for a contribution to a conference on ‘Design of commercial vehicle cabs in relation to the driver's environment’, held on 26th April 1973. The information contained in the address by the author was considered of general interest and value to the commercial-vehicle industry. The paper is aimed at providing guidance in the derivation of commercial-vehicle cab design with particular reference to packaging, accessibility and visibility. Certain conflicting requirements, design problems and solutions are discussed and the author's observations on some of the possible future trends in cab design are included.

In designing control systems for parison shape in the blow moulding process it is necessary to take into account the forces that act upon the movable mandrel inside the convergent annular die.

These forces can be considered as consisting of two parts; firstly, a steady-state force acting along the axis of the mandrel whilst it is stationary and, secondly, an axial force Pertubation that arises as a consequence of controlled movements of the mandrel during the parison shape control process.

The present paper deals only with steady-state axial forces and its aim is to assist the design engineer by showing him how to calculate mandrel forces and die pressure drops, using a digital computer, for dies having a form composed of a series of tapered and parallel annular flow passages.

By careful design, under certain circumstances, an almost force-free arrangement can be obtained, so minimizing the power and strength requirements of the mandrel drive control system.

The theoretical analyses used assume that the polymer being processed is described by a power-law equation relating shear stress and shear rate. This is typical of polymers such as high-density and low-density polyethylene.

This feasibility study of hydrogen as a fuel for future vehicle propulsion considers fuel availability, economics and the storage system. The compatibility of a hydrogen-air engine with possible future requirements is assessed. The rate of formation of nitric oxide, based on the rate kinetics in a hydrogen-air mixture, indicates a higher nitric-oxide concentration in the exhaust gas of a hydrogen engine than in the exhaust gas of an equivalent petrol engine. Methods of reducing the emission levels and the design changes are discussed.

A design technique for coupler curve generating mechanisms is developed. The procedure is based on a multi-variable search using an objective function developed from topological properties of spatial curves in an arbitrary reference system. The method completely specifies the mechanism and its orientation relative to the chosen co-ordinate system, which generates the best approximation to the desired curve. The procedure always converges from any set of starting conditions. The technique is well suited to digital computer design of planar and spatial mechanisms, as it permits both the synthesis and the kinematic analysis of the mechanism. The 4R and the RGCR four-bar spatial linkages with coupler points are used to illustrate the synthesis procedure.

A new temperature sensor has been designed and tested, in which a change in ambient temperature changes its flow resistance. It may be constructed to give either a positive or negative change of resistance for an increase of temperature and may be capable of fluid shut-off. This paper gives the operating characteristics for three different configurations operating with air, which illustrate the high-pressure gain possible with this type of temperature sensor. Such a device may operate directly in the process pneumatic control pressure range without amplification.

An elasticity analysis to calculate the distribution of all bearing loads in a turbo-generator set is presented from first principles. It is shown that the movement of bearing pedestals caused by the thermal distortion of the foundation can cause considerable changes of load distribution between bearings with consequent problems of oil film instability and shaft whip. Acute misalignment encountered in practice can cause some bearings to take a negative load. The development of a computer programme is described, which can be used to investigate a range of possible cold re-alignments.

A separate analysis of the particular type of bearings used shows that the load capacity is completely adequate in the downwards direction, but greatly reduced in the upwards direction. Upwards loads of static or dynamic origin should be avoided with the type of journal bearing design considered here.

To predict the complete performance map of turbocharger centrifugal compressors, it has been found essential to include a procedure for estimating the slip factor at off-design flow rates. The many correlations available for the slip factor only concern themselves with design-point operation and consequently only provide a single value for the slip factor. The approach presented here attempts, within the confines of a one-dimensional procedure, to recognize the changing flow pattern at the impeller discharge in order to predict the variation of slip factor with flow rate. The procedure is based upon the well-established jet-wake flow model of Dean and the overall slip factor calculated from the jet slip factor.

Experimental and theoretical slip factors are presented for three impellers with 34, 30 and 12 radial blades, respectively. The complete performance map of the 12-bladed turbocharger compressor and the effect of using a constant and varying slip factor on the predicted performance are presented.

Previous investigations into cumulative damage fatigue under uniaxial stress are discussed in conjunction with the parameters relevant to the present experimental investigation. The results of two-level block programme tests on 2L65 aluminium alloy at four values of constant principal stress ratio and at several combinations of two different principal stress ratios are presented and discussed with reference to cumulative damage criteria developed for the case of uniaxial fatigue stress.

The amount of NO (nitric oxide) developed during the combustion and expansion phases of the spark-ignition engine cycle has been calculated using several different kinetic formulations, for a range of fuel-air ratios at each of two compression ratios. Comparing the results shows the effects of including or omitting certain reactions and of applying the quasi-stationary assumption to the concentrations of N and N₂O.

Kinetic models, incorporating elementary chemical reactions, are used to predict the concentrations of NO (nitric oxide) and CO (carbon monoxide) in spark-ignition engines during the expansion process. The kinetic equations are*** incorporated in a cycle synthesis computer programme, which can be used to calculate the thermodynamic state and the concentration of a number of species in the burnt gas.

The stability and accuracy of the programme is discussed and the validity of the results is confirmed by comparing the theoretical predictions with experimental results.

The coupled elasticity and hydrodynamic equations are solved for a plane externally-pressurized bearing consisting of an elastic layer bonded to a rigid substrate. Solutions for bearing load support, flow and minimum film thickness are presented for a wide range of bearing geometries and for both compressible and incompressible lubricants. For preloaded bearings, i.e. bearings with interference fits such that the compliant surface is initially indented by the mating surface, a criterion for incipient lift-off is postulated and formulae for calculating the lift-off pressure are derived.

Experimental results are presented for friction factor and surface finish measurements on eight graphite tubes machined to give a range of surface finishes from smooth up to the maximum roughness likely to occur in a reactor.

Correlations are given which allow estimation of friction factor from graphite surface finish measurements.

The results are compared with those obtained by Nikuradse in his sand-grain roughness tests. Except at low values of e_s ⁺, agreement is good, enabling the heat transfer similarity law of Dipprey and Sabersky to be used to predict any increases in Stanton number due to surface roughness.

Measurements of friction torque in a tapered roller bearing are made over a range of axial loads at low rotational speeds. Under these conditions considerable metallic contact between surface asperities occurs. Experimental and theoretical values of no-contact time are compared. The usually adopted ratio of calculated film thickness to gross surface r.m.s. value is shown to be a less meaningful measure of the quality of lubrication than one based on the r.m.s. after filtering out contributions due to asperities of wavelength greater than twice the Hertzian width. An analysis of the statistical properties of worn and unworn surfaces is made. Digital filtering of the power spectrum reveals differences that are not apparent in the unfiltered data. Asperities of long and very short wavelengths, compared with the Hertzian width, are shown to be little affected during running-in whilst those of intermediate size are removed.

Clamped aluminum circular blanks, having approximately planar isotropy, were bulge-formed by an oil pressure differential against hydrostatic back pressures of up to 69 MN/m². Both generalized strain-hardening and the onset of necking were found to be virtually independent of back pressure. Theoretical calculations of the maximum pressure differential agreed closely with experiment. Theory underestimates the critical generalized strain at necking.

A combustion model is presented to account for the nitric oxide formation in diesel engines at all operating conditions. The paper tries to introduce the concept of variable air-fuel ratio estimated to exist during diesel combustion. Analytical solutions are found to be in good agreement with experimental results. Further investigations will be directed to diesel engines having combustion systems other than the M.A.N.-FM system, and to possible remedies to reduce the formation of nitrogen oxides.

The accelerating rate of energy consumption and increasing environmental damage appear at present to be two unavoidable consequences of measures taken in the course of development planning.

One of the explanations for this is that the essential climatic function of a building development—that of modifying the natural climate so that it is favourable for man—is not borne in mind in all stages of the planning process. Hitherto, the effects of locating a polluting works on the regional climate have been disregarded. Little account has been taken of the way in which distributing green spaces and formulating town blocks affects the climate of urban areas. Insufficient attention is paid to the way in which the orientation and design of an individual building and the surrounding vegetation will influence the climate in the outdoor areas around the building. Sometimes, calculations are made of the changes between the outdoor and indoor heat climates that would occur as a result of the particular construction and material composition employed on the building, but these are used primarily as a means of defining the initial conditions for climatic control installations and not for determining the joint climatic properties of the building.

Another explanation of this uneconomic climatic planning is that the aim of climatic modification has been incorrectly formulated. Hitherto, endeavours have been made to create an indoor climate that keeps the physical environment of man in a static condition. This condition has been termed the ‘comfort climate’. This has been defined as those values of the elements of the physical environment that deliver neutral information to the sensory organs. If one wishes to be controversial, one can say that the aim of climatic planning has been to create a ‘comfort climate’, which effectively prevents man from receiving stimulating information from his surroundings. More economical climatic planning calls for a definition of the ideal climate to suit the way in which people function.

This paper discusses the need to define human environmental requirements as a basis for more conscious cooperation between planners, architects and engineers as well as a basis for developing products in the heating and ventilating industries.

Factual evidence is presented here which proves that the slip factor for a given impeller is not constant, but varies with the flow rate.

A schematic model is established that gives a possible explanation to the observed discrepancies between the existing theories and reality.

Without introducing novel technology, the advantages of the Cross cool-combustion chamber have been combined in a compact engine form. This has enabled a practical engine to be developed in a comparably smaller envelope than would be possible with a conventional arrangement. An eccentric crank mechanism is used, which eliminates swinging connecting rods and thus generates simple harmonic motion at the pistons.

The Cross rotary valve enables the bore-stroke ratio to be reduced significantly without combustion penalty and a bore-stroke ratio of 1:7 has been chosen for a prototype. The practical development of this engine is described, together with the rationale of its conception.

In the present climate of fuel shortage, it is anticipated that low fuel consumption and octane requirement, which have been well demonstrated for the Cross combustion chamber, will be of considerable importance, while the compactness of the complete engine should offer significant installational advantages.

Recently published work concerning the dynamic flow-rate through servo-valves is discussed. It is shown that there is some disagreement amongst workers concerning the effects that fluid inertia and valve discharge coefficients have on the dynamic performance of these devices.

The problem of measuring pulsating flow is discussed and the various commercially available transducers are shown to have shortcomings when used in conjunction with servo-valves. An alternative indirect dynamic flow measurement technique is described.

The technique is evaluated using an analogue model. It is concluded that the method is capable of determining the dynamic volumetric flow-rate. The difficulties involved in identifying the valve dynamics from these measurements are discussed.

The method is applied to determine the volumetric flow-rate in an experimental rig consisting of a servo-valve controlling a rectilinear motor used to position an inertial load.

The characteristics of externally pressurized journal bearings with four recesses and with membrane-type variable-flow restrictors as compensating elements are analytically investigated by using the bearing model of Raimondi and Boyd. The effects of the ratio of the recess pressure at zero eccentricity to the supply pressure (pressure ratio), the eccentricity ratio, the compliance of the membrane and the shaft rotation on the lubricant flow rate, the load capacity and the stiffness of these bearings are presented for a given aspect ratio and inter-recess*** land width-to-diameter ratio. For a non-rotating shaft, it is shown that when the bearing operates at zero eccentricity there is a pressure ratio that gives an optimum bearing stiffness. This pressure ratio is a function of the aspect ratio of the bearing only. Using this pressure ratio, data for the load capacity and stiffness of the bearing are presented for an eccentricity ratio that varies from 0 to 0·1. For these data, the membrane compliances used are those that would give an infinite bearing stiffness if the bearing were operating at zero eccentricity.

A study is made of steady and non-steady flow through a carburettor. A model is presented in which the carburettor is represented by an adiabatic pressure loss at a discontinuity in the intake system of an engine. It is shown that this simple model gives excellent predictions of the pressure-time development in the intake system except at small throttle openings where there is some error in the peak amplitude. Mass flow and trapped mass predictions are excellent.

The lecture gives a technical account of the Rolls-Royce RB 211 42 000 lb thrust turbofan engine now powering the Lockheed TriStar passenger transport.

This engine was the result of extensive preliminary design studies begun in 1960 to evolve a turbofan successor to the Conway bypass engine. The aim was to provide Rolls-Royce with a propulsion system that would give the United Kingdom the opportunity to share in the most important section of the air-transport market during the last quarter of this century. Low fuel consumption, low noise and low maintenance costs were the principal objectives. These studies led to the RB 211 three-shaft design which was specified for the Lockheed L1011 ordered in 1968 by a number of the larger U.S. airlines.

An idea of the large scale of the RB 211 project is given and some of the development problems and lessons are discussed. There is a brief outline of the supporting component, rig and high-temperature turbine development and a summary of the engine's performance is given which includes thrust, specific fuel consumption and noise, all of which have met or beaten the design targets.

A developed version of the RB 211, now being tested at over 50 000 lb thrust, is described, as well as the potential for further improvements in fuel consumption and for expected additional aircraft and industrial applications.

This paper describes calculation methods and the results obtained from a computer programme written for studying induction ramming in high-speed reciprocating engines. The calculation uses the method of characteristics for analysing the pressure fluctuations in the intake pipe. The calculated airflow figures are compared with results obtained experimentally from a motored air-cooled four-stroke motorcycle engine. Comparison shows a good correspondence between theoretical and experimental results of both the quantity of air flow and the engine speeds at which airflow peaks and troughs occur. The results also clearly illustrate how flow through the valve is affected by pressure variations at the inlet port.

The example of Boulton and Watt demonstrates the main factors in the creative process: recognition of a problem (thermal losses in the cylinder walls in a Newcomen engine), scientific knowledge (that steam would expand into an evacuated chamber), inspiration and understanding between inventor and administrator. These themes are traced through the more recent history of engineering in Britain, and the lecture discusses the importance of a favourable ambience and the interaction of individuals and organizations. In the education of engineers, institutions of higher education and post-market training arrangements both have parts to play; and although creativity cannot be taught to those who are devoid of it, and although some men will be highly creative irrespective of the way in which they have been educated, a suitable education will speed their progress to the front line of their activity—and it may tip the balance in the case of the much larger number who possess some innate creativity, but who may be discouraged from developing it by unimaginative training. The master/apprentice relation remains the most promising approach, and, more than anything else, a sense of purpose is needed on a national scale if creativity is to be encouraged.

Experimental results are presented which show vortex formations occurring within a model marine gas-turbine downtake. The basic phenomenon of vortex formation is discussed and the boundary-layer-potential-flow interaction identified as the cause. Further experiments on a model gas-turbine test stand are reported in which the vortex strength was assessed. On this basis, a simplified theory for the occurrence and strength of vortex formations is presented which agrees qualitatively with the principal experimental findings. The formation of air-entraining vortices in hydraulic installations is briefly examined in the light of the explanations previously advanced. Although a number of possible vortex formation mechanisms are identified, it is concluded that further research is required in this area.

Experimental results are presented for the variation of the static pressure rise coefficient C_p , the transformation efficiency η the total pressure loss coefficient C_L and the outlet kinetic energy coefficient ɛ₂ with the Mach number and the effective throat length for subsonic conical diffusers with total expansion angles of 5°, 12° and 20° and an overall area ratio of 10:1. The junction between the parallel entry pipe and the diffuser cone is sharp and the diffuser inlet conditions are evaluated from measurements on a plane 1°5 diameters upstream of the diffuser's sharp transition. The shock Mach number was varied from 1°05 to 1°25 whilst the diffuser inlet Reynolds number varied between 9°0 × 10⁵ and 1°22 × 10⁶. A comparison of the results with those of diffusers preceded by wholly subsonic flow in the entry pipe shows the beneficial effect of interaction, the most significant gains being with the lowest angle diffuser.

In this paper, the method of manufacturing the spiral spring is examined to develop a theory for this type of spring giving a closer agreement with practical tests than does the conventional theory. The theory makes use of Gardiner's (1***)^† equation for spring-back to develop the equation of the free spiral of the spring and then considers that, in operation, the process of winding up or running down can be considered as the difference between winding up from the free spiral to the run-down state and winding up from the free spiral to the wound-up state.

In the conventional theory for this type of spring, the active length is considered to be constant and equal to the strip length and the moment versus the rotation of the arbor plot (torque characteristic) is apparently always linear. In the theory presented below, the variation in active length is taken into account and non-linearities in the torque characteristic become evident. The theory assumes that the forming of the spring takes place under the action of pure bending without anticlastic curvature and the strip is assumed to behave as an ideal elastic-perfectly plastic material.

Temperature distributions for typical cases of orthogonal machining with a continuous chip were obtained numerically by solving the steady two-dimensional energy equation using the finite element method. The distribution of heat sources in both the primary and secondary zones was calculated from the strain-rate and flow stress distributions. Strain, strain-rate and velocity distributions were calculated from deformed grid patterns obtained from quick-stop experiments. Flow stress was considered as a function of strain, strain-rate and temperature. The chip, workpiece and tool (actual shape and size) were treated as one system and material properties such as density, specific heat and thermal conductivity were considered as functions of temperature.

The isostatic compaction and hydrostatic extrusion of two atomized powders, namely Alcoa grade 1202 aluminium and Atomet 28 iron, are described and it is shown that the extrusion pressures for these powders may be 50-100 per cent greater than for an equivalent wrought material.

Results of mechanical testing and metallographic and fractographic examinations of the extruded aluminium compacts are presented which show that good bonding can be developed by hydrostatic extrusion at ratios of 6·25 and that the resultant strengths can be higher than that of wrought material of a similar composition. This strength improvement is attributed to the strain hardening undergone by the materials during compaction. An interpretation of the bonding mechanism is also given.

Although it has been shown that isostatic compaction and hydrostatic extrusion can be combined to produce well-bonded bar material from metal powder at room temperature, it is suggested that the method is limited by the very high pressures that would be required to produce materials of commercial interest.

General equations are developed describing the kinematic behaviour of two rigid bodies in contact. The case of planar motion is then considered in more detail and the equations are developed in a form which is useful in synthesizing cam mechanisms.

Examples of the application of the general equations to synthesizing the profiles of rolling contact cams and of cam profiles for use with flat and circular followers are given. Use of the general equations in cases where the follower has a complex profile is also described.

The low-cycle fatigue behaviour of a ferritic and an austenitic steel have been studied under various conditions of reversed biaxial strain. These cyclically softened and hardened respectively. In all cases, relationships of the form

were found between total strain range Δε _t and life N_f for lives in the range 10²−10⁵ cycles, with an abrupt change of β at intermediate lives. Variation of state of strain affected both β and κ.

Various theories for the correlation of fatigue behaviour under multi-axial loading have been reviewed and compared with these results. None was found to account adequately for the effect of straining régime with the materials tested.

Pitting tests using 127 mm (5 in) centres distance gear rig under controlled conditions are described. These are compared with similar disc tests using the same materials and lubricants. Tests of both types confirm Dawson's conclusion that an important factor influencing pitting life is the ratio of surface roughness to the calculated lubricant film thickness. It has been shown that using a hunting tooth ratio, particularly when associated with a rough harder surface and a surface finish oriented normal to the motion, increases the likelihood of wear. Most importantly, the results show that using disc tests can greatly overestimate the pitting life of gears. These experiments and other evidence from the literature suggest that the most probable reason for these differences between gears and discs lies in dynamic gear loads.

The hydrodynamic entrance-region flow of pseudoplastic liquids is studied by solving both the differential and integral equations of the boundary-layer flow simultaneously by extending the procedure of Fargie and Martin. The results are strictly applicable in the high Reynolds number region only. Simple closed-form expressions for the velocity distribution, pressure distribution and loss coefficients in the entrance section result, which are presented in a form suitable for engineering design. Comparing the predictions of this work with the literature data shows agreement which is comparable to or sometimes even better than the more complicated analyses available in the literature.

The E-system of roughness measurement can be used either for a two-dimensional or a three-dimensional assessment of surface roughness. The procedure for computing the two- and three-dimensional envelopes from digitized profiles is briefly explained. This method will be useful for verifying the results obtained by practical instruments. The filtering characteristic of the E-system, when used for two- and three-dimensional roughness measurement, is analysed with reference to theoretical profiles. Various skid configurations are studied using a doubly curved skid simulated by a computer.

The dynamic characteristics of single-track vehicles are predominantly governed by forces and moments of tyre-pavement interaction. No experimental data are available in the literature on the rolling characteristics of the small size pneumatic tyres used on scooters. In the present investigations, a flat-type tyre testing machine was developed at Roorkee (India) and the free rolling characteristics of Dunlop 3·50-8, Inchek 3·50-8 and Kicorma 3·50-8 and 3·50-10 have been experimentally determined. Effects of tread wear and rim size have also been investigated and reported.

N.C.T. has dealt with virtually every industry. An analysis is presented of the use made of its consultancy and R&D services by equipment manufacturers and by plant users; and by large and small companies. Examples are given to illustrate the great diversity of problems encountered, both in application and scale. It is concluded that there is a need for tribological help to industry and that there is a demand for such a service on commercial terms.