bluuebunny/crossref_metadata_2025 huggingface dataset:
Overdrives: Problems in Their Application and Design
Authors: Ashby S. H.
Published: June 2010

Overdrives are by no means new, having been extensively used in the United States of America, and to a lesser extent in continental Europe, for many years. Their widespread use in Great Britain is comparatively recent although the American type was fitted to a small number of British cars before the 1939–45 war.

In America the Borg-Warner unit appears to hold the field, whilst on the Continent, probably the most popular type is the extra pair of overspeed gears fitted into the syncromesh gearbox. British use of the device has consisted mainly of the Laycock-de Normanville unit, although there are other types, such as the Daimler method of changing one of the trains in the Wilson gearbox from a reduction gear to a step-up gear, for example, turning a four-speed into a three-speed and overdrive gearbox. The Handa overdrive is also a British invention using dog engagement for selection, necessitating the use of the clutch pedal, and operated by manifold depression. Another mechanism producing a similar effect is the Eaton two-speed axle for commercial vehicles. This latter is not an overdrive in the strict sense; it should technically be described as ‘underdrive’, being a means of varying the gear reduction between the propeller shaft and the rear axle half-shafts. ‘Overdrive’ is a means of driving the propeller shaft faster than the engine, and while this is perhaps not the most suitable term it is now universally accepted.
The Motor Industry Research Association's Proving Ground
Authors: Fogg A.
Published: June 2010

In this paper are discussed the reasons for, and some of the problems involved, in establishing a co-operative vehicle proving ground. It records details of the facilities which have been provided by the Motor Industry Research Association (M.I.R.A.) in recent years for the British motor industry. These facilities include roadways and tracks simulating, in permanent form, conditions existing in the overseas territories to which British vehicles are exported in very large quantities. There are also a number of features which, when used in conjunction with instruments and apparatus specially developed and built by M.I.R.A. and by various member firms of the Association, enable systematic studies to be made of performance characteristics in a more satisfactory manner than is otherwise possible.

Although the conception of a co-operative proving ground for a very competitive industry was viewed, initially, with apprehension by many firms, the establishment is now in continuous use by manufacturers of all types of vehicle and component. It is playing a vital part in the development of greatly improved vehicles, particularly for operation overseas.
Performance of Vehicle Engines on Heavily Leaded Fuels
Authors: Long R. W.
Published: June 2010

Production problems on exhaust valves for vehicle engines, created as a result of the introduction of heavily leaded fuels during the 1939–45 war, resulted in the Ministry of Supply commencing research in 1948 to ensure that existing engines in civil and military vehicles would operate satisfactorily on a fuel containing 3.6 cu. cm. tetraethyl lead per Imperial gal. (T.E.L./I.G.)

Road tests at the Fighting Vehicles Research and Development Establishment at Chertsey, Surrey, were planned to establish the form of initiation of valve failure, which, in almost every instance, was found to be due to the partial seizure of the valve in its guide through fouling by overheated products of combustion. All modifications were, therefore, directed towards reduction of exhaust valve and guide temperatures, and the dispersal of combustion products.

Although fuels containing tetraethyl lead possess lead scavenging agents, nevertheless lead compounds form a large percentage of the deposits which accumulate on the surfaces of the combustion chamber and valves, and it is this increase in bulk, rather than the nature of the deposits, which appears to have the major effect on engine deterioration.

Modifications on the various engines differed considerably. Coolant systems were modified wherever possible and valve design amended. Changes involving major components such as cylinder blocks and cylinder heads, although desirable, were inappropriate to the programme. Design features on new engines directed towards reducing operating temperatures where they were highest should ensure much longer exhaust valve life on heavily leaded fuels.
Aero-Engine Exhaust Valve Development
Authors: Morgan J. E.
Published: June 2010

The chief problem affecting the exhaust valve is cooling, and most causes of failure emerge from it. For best results, therefore, development must extend to associated components such as guide, insert, etc., and all are surveyed in this paper. Development can be divided into three main channels: (1) heat transfer, (2) maintenance of gas seal, and (3) corrosion resistance.

Improvements in heat transfer were obtained by the introduction of sodium cooling, firstly in the stem only and secondly in the stem and head. Further advantage was derived from improving the cooling of the seat insert of the exhaust port.

The gas seal was improved by modifications to the insert. This was changed from Silcrome steel to Silcrome faced with Stellite, and finally to Nimonic 80. The latter material has good corrosion resistance qualities and yet is sufficiently ductile to be reformed by the valve when temperature gradients in the cylinder head have forced the insert shape out of round.

The search for corrosion resistance led to the testing of a variety of hard-coating alloys and valves forged in Nimonic alloys. The latter were unsatisfactory when made up as solid-head valves but, more recently, a similar alloy has given good results with the hollow head and stem design. In this instance, however, a hard-coating alloy was used on the seat and combustion chamber face.

Cylinder block life between overhaul is largely controlled by the performance of the exhaust valves, and whereas in 1947 block life at 400 hours was half that of the engine carcase, service testing has now shown that a block life of 1,250 hours is possible.
Exhaust Valve Life: Some Metallurgical and Mechanical Considerations
Authors: Mogford R. D. , Ball F. A.
Published: June 2010

The factors controlling heat flow into and from the head of an exhaust valve are discussed for the purpose of indicating the means by which temperature, the overriding important factor in exhaust valve failure, can be reduced. This analysis suggests the lines along which the designer and the metallurgist must co-operate.

The causes of exhaust valve failure are reviewed, and the conclusion is reached that the majority of these are the result of corrosion fatigue. Even for resistance to burning the two properties inherent in resistance to corrosion fatigue, namely resistance to corrosion and good hot strength, are essential.

Laboratory tests for determining resistance to high temperature corrosion fatigue and hot hardness are described, and some results given for exhaust valve materials. Corrosion fatigue resistance is considered to be so significant a factor in exhaust valve failure that it is suggested that laboratory tests to determine this property should form the basis for the development of improved exhaust valve alloys.
Front Suspension and Tyre Wear
Authors: Gough V. E. , Shearer G. R.
Published: June 2010

Tyre wear depends very largely on the cornering orces which tyres are called upon to develop. A consideration of the effects of front suspensions on tyre wear involves a discussion of the effects of suspension and steering geometry on the slip angles developed at the two front wheels.

The paper explains why a tyre, developing a cornering force, wears, and shows that the rate of wear increases rapidly with increase of cornering force. It then proceeds to a brief history of types of suspension. The two types predominantly in use are examined for such effects as changes of alignment and of track, which can cause the tyres to operate under slip angle conditions.

The location of the track rod and the rigidity of the steering linkage are shown to be of importance. Such trends in vehicle construction which have improved stability have tended to increase front tyre wear in relation to that of rear tyres. The paper attempts to deal with matters of principle rather than of practical detail of design and construction, but it is shown that quite small changes of practical detail can at times have significant effects on tyre slip angles, and hence tread wear.
Rubber Springs for Vehicle Suspension
Authors: Moulton A. E. , Turner P. W.
Published: June 2010

The authors believe that rubber is especially suitable as a suspension medium because of its intrinsic properties, and also because of the variety of forms into which it can be made, and that it will therefore take its place alongside steel springs as an accepted vehicle suspension. A research programme of both field and laboratory testing has been carried out to confirm the suitability of rubber for suspension purposes, and to develop some modern forms of rubber springs.

Laboratory work included, in addition to the fatigue testing of a wide diversity of spring types, the development of a method of strain measurement for springs of irregular shape, and the determination of a basic parameter of fatigue applicable to any type of rubber spring. Service testing included the investigation of endurance characteristics, optimum values for the static deflexion, damping and low temperature properties, permanent set and noise isolation.

As a result the authors consider that their tests have demonstrated the practicability of rubber as an automotive suspension medium, and that it can afford a simplification of the design by providing wheel location, a measure of inherent damping, and so long as the design is studied from the beginning to include rubber suspension, competitive cost in volume production. Rising rate characteristics, a degree of noise isolation and satisfactory fatigue life are readily obtained.
A Review of Hydrokinetic Fluid Drives and Their Possibilities for the British Motor Industry
Authors: Giles J. G.
Published: June 2010

The history of the development of hydrokinetic fluid transmissions is traced from its origin by Föttinger to the present time, and the important early developments and types of device are recorded. Consideration is given to special design features and current practice for the use of these devices in transmissions for motor vehicles, and the theoretical basis of design is reviewed briefly. Four important aspects of a specification for an automatic transmission for motor vehicles are enumerated, and the hydrokinetic fluid drive is shown to have characteristics specially suited to the fulfilment of this specification.

The trend of development after the 1939–45 war of these drives in the United States of America is discussed, and appears to be reaching finality. The application of this American experience to European conditions is considered; some versions of the automatic fluid transmission show possibilities for achieving an acceptable operating performance for lower power/weight ratio applications. The wider range of torque conversion necessary for the more popular cars results in a more complicated and costly transmission, so that it does not yet appear likely that this form of automatic transmission will become universal in the British industry.
Transmission Developments for Public Service and Heavy Goods Vehicles
Authors: Wilson A. Gordon
Published: June 2010

The author has set out to review the use, development, and history of the transmission system as applied to commercial vehicles and to forecast the future trends. The point is made that the transmission system is to be considered in relation to the vehicle and the service to which the vehicle is put rather than as an end in itself. The characteristics of the various systems at present available are therefore examined from the aspect of their effect on vehicle performance.

Since engines of similar characteristics are fitted into an ever-increasing range of vehicles of divergent types, features of the various types of transmission are analysed to give a rough guide as to their suitability for differing service. For this purpose the modern types are grouped under a form of genealogical tree, in which an attempt is made to trace their ancestry.

Commercial vehicle usage is broken down into type of vehicle, and the main markets into which they are sold and the various contradictory features exhibited by the behaviour of the transmission system in the vehicles are listed with a suggestion of preference for the type of vehicle in that particular market.

Characteristics of different classes of vehicle are examined in relation to driver reaction, and the type of control which would be most likely to appeal to drivers accustomed to them.

The Appendix gives diagrammatic drawings of transmission systems developed over the last half-century.
Some Important Problems Concerning the Small Utility Car
Authors: Giacosa D.
Published: June 2010

This survey on the small utility car is based on the work performed under the supervision of the lecturer as Director of the Design and Engineering Division at S.p.A. Fiat in Italy. The lecture deals with the general principles relating to the design of a small utility car, mass-produced at the rate of at least 350 per day, particularly suitable for the Italian market, but also of technical and commercial interest to other European countries.

Taking as his example a four-seater car having a weight ranging from 500 to 600 kg. (1,100 to 1,320 lb.) and with a total piston displacement of from 400 to 600 cc. (24 to 37 cu. in.), the lecturer analyses the most important factors that influence weight and therefore cost, such as general car architecture, dimensions, performance and quality.

Some of the problems peculiar to rear-engine installation, which required a larger amount of studies and research during the design and layout work for the Fiat ‘600’ car are then examined.

According to the lecturer, the rear-engined car represents the best solution both in regard to smaller outer dimensions required for given passenger accommodation, and as to constructional simplicity. The lecture is concluded with a forecast of future developments in this type of car.
Sealing Rings for Wet Cylinder Liners
Authors: Hepworth J. L.
Published: June 2010

It is vital to the performance of an engine that sealing rings fitted to wet cylinder liners should effectively prevent the leakage of coolant into the crankcase, prevent lubricating oil entering the coolant circuit and at the same time avoid distortion of the cylinder liner.

The sealing effect of the ring is due entirely to the pressure it exerts against the cylinder liner by virtue of its own elasticity. The effect of rubber hardness and compression upon wall pressure is investigated and proposals made for suitable standards. Design recommendations are proposed and a specification is laid down for material which will give satisfactory performance under arduous conditions.
The Supercharging of High-Speed Diesel Engines by Mechanically Driven Compressors
Authors: Millington B. W.
Published: June 2010

The most useful application of the mechanically driven supercharger is in the field of the smaller Diesel engine which operates over a wide range of speed, and especially where the duty calls for a high torque to be developed at low speed. Road vehicles and earth-moving plant commonly require these characteristics. In the interest of fuel economy a high adiabatic efficiency is of first importance in a supercharger so used. It is also desirable to be able to control the rate of air delivery from the supercharger to match the load on the engine; methods are discussed and test figures from the Fell locomotive propulsion engines are quoted.

Where a simple fixed ratio drive to the supercharger is used a good volumetric efficiency at low speed and at the working pressure ratio is important in order that the boost at low engine speeds shall be high. The Ricardo wobble-plate compressor designed to meet these conditions is described and performance data are given. Overall performance figures of an engine when supercharged by this compressor are also included and the methods of applying the engine in vehicle service are discussed.
The Turbo-Charging of High-Speed Diesel Engines, Present Position and Future Prospects
Authors: Bradbury C. H.
Published: June 2010

Consideration is given to the basic principles of supercharging and the advantages and/or drawbacks of using surplus exhaust energy to drive the supercharger.

A review is given of the application of the exhaust turbo-charger to high-speed engines of the road vehicle type. It is shown that there are now in existence units which can be mounted without adding appreciably to the overall bulk and weight of the engine, and which enable the latter to develop brake mean effective pressures of up to 140 lb. per sq. in. without undue smoke. Torque and acceleration characteristics are considered and limitations vis-à-vis positive displacement blowers are briefly surveyed.

Lessons to be learnt from large engine practice are then reviewed, particularly from the standpoint of charge cooling. The Miller and Bone systems are briefly described.

The trend of development towards higher pressure ratio turbo-chargers is then considered, together with the possibilities of incorporating in the engine design improved pistons and fuel-injection systems.

The paper concludes with a brief reference to the present position and practice of turbo-charging two-cycle engines.
Theoretical Prediction and Experimental Substantiation of the Response of the Automobile to Steering Control
Authors: Segel Leonard
Published: June 2010

Classical mechanics is applied to the automobile in order to study the lateral rigid-body motions produced by steering control. This research in the field of automotive lateral dynamics has included (1) the development of a mathematical model for a pneumatic-tyred vehicle and (2) its subsequent substantiation by means of full-scale response tests made with an instrumented vehicle. A review of the theoretical work is presented together with a description of the methods used to measure the response of the test car. The resulting agreement between theory and experiment is examined, and is followed by an extensive discussion of the nature of the lateral response of the automobile to steering control.
Tyre Tests and Interpretation of Experimental Data
Authors: Fonda Albert G.
Published: June 2010

The test techniques and associated equipment developed for use of the Air Force-Cornell Tire Tester have permitted road tests yielding unique data on the cornering characteristics of pneumatic tyres. Account is given of tests performed for the Dunlop Tire and Rubber Corporation, involving variations of inflation pressure (18 to 45 lb. per sq. in.), camber (±30 deg.), and steer (±30 deg.); these angular ranges are unprecedented. The tyres were nominally 5.00, 6.00, and 7.00 by 16 section, of normal construction but smooth and round to eliminate effects deriving from tread pattern.

The ensuing data analysis was based upon familiarity with aircraft derivative notation, the advantages of which are described, and upon simple tyre theory, which is outlined in an appendix. The outstanding conclusions, from a practical standpoint, are (1) that camber thrust strongly affects the static stability of the typical automobile; (2) that the motor cycle operates with negligible slip angle below 35-deg. tilt, whereas above 35-deg. tilt appreciable slip angle must be developed; (3) that a plot of pneumatic trail against side force has great value because of its linearity and ready significance; and (4) that tyre theory should be utilized to permit rational, concise interpretations of empirical data.
Design Implications of a General Theory of Automobile Stability and Control
Authors: Whitcomb David W. , Milliken William F.
Published: June 2010

The lateral-directional motions of an automobile are studied by means of equations of motion derived for a vehicle assumed to have yawing and side-slip degrees of freedom only, and travelling at a constant forward speed.

The equations are presented in terms of the automobile stability derivatives. The stability-derivative concept has its counterpart in aeroplane stability and control research.

The automobile transient and steady-state motions following the application of steering control or externally applied side forces and yawing moments are determined from the equations of motion. The responses are discussed with emphasis placed upon their principal characteristics and the identification of the significant vehicle parameters that determine them. Approximate solutions for the steady-state response are also presented.

The transient response characteristics are studied, first in terms of ‘single-degree-of-freedom’ approximations, and then in terms of the ‘two-degree-of-freedom’ representation. The transient motion is discussed in terms of the characteristics of a second-order dynamic system, and relations for natural frequency, damping ratio, and response time are derived. Conditions for system stability and oscillatory or non-oscillatory motion are also determined.

The results of a series of sample calculations based on the equations of motion are in an appendix. These show the general character and magnitude of the responses of a representative passenger sedan and a high-performance sports car.

The general characteristics of the transient and steady-state responses are summarized in chart form, and the influences of static margin, speed, and tyre and vehicle parameters are pointed out. A brief discussion of the desirability of certain response characteristics is presented as a generalized design objective.
Petrol Injection: Some Further Developments
Authors: Downing E. W.
Published: June 2010

In this paper is described recent developments of a shuttle metering injection system, and details of the construction and operation of high-speed six- and eight-cylinder units are included.

Accuracy in mixture control performance is stressed as an essential requirement of any injection system, and a description of a control giving automatic operation from cold starting and through the warm-up stages is given.

An account is given of some aspects of the application of the system to a high performance six-cylinder engine, and includes details of air flow measuring technique, and manifold design and development for this class of engine.

A description is included of the effect of mixture strength on fuel consumption and power output, where economy in the engine of a racing car is required, and combustion chamber and exhaust temperature variations with mixture strength are shown on graphs. It is concluded that on the engine referred to, injection can offer the advantage of an improved torque curve, or if needed, a worth-while gain of up to 10 per cent in economy over the carburettor at the same output.
Fatigue Testing of Vehicle Components
Authors: Stott T. C. F.
Published: June 2010

By far the greater part of the vehicle manufacturer's testing programme is carried out on components or assemblies operating under similar conditions to those of specific requirements in service. Accelerated test procedures can produce in a few days results which would otherwise necessitate running many thousands of road miles. This method of testing has resulted in the development of specialized equipment together with the more versatile rigs which can be used for a multitude of purposes.

To ensure true comparison and reproducibility of results, test procedures must be concise and based on service experience. Considerable attention must be given to failures which might either be reported from the field or occur during the normal course of the vehicle development so that a service background can be built up thus enabling ‘road miles’ to be closely related to ‘test cycles’.

The fatigue testing of a number of components and assemblies is discussed together with the development of test procedures and testing methods. The parts covered are in the main those that are the more highly stressed and therefore more likely to be subject to fatigue failure.
Some Aspects of Valve Gear Design
Authors: Beard C. A.
Published: June 2010

After introducing the fundamental formulae relating cam velocity and acceleration with physical sizes the author reviews the principal types of acceleration curve to be found in use in modern automotive engines. This is followed by short sections dealing with valve spring design, contact stresses, and the effects of valve train flexibility on high-speed operation. Finally, a brief discussion is made on the effect of tolerances on cam acceleration.
Balancing of High-Speed Four-Stroke Engines
Authors: Clink R.
Published: June 2010

The problem of balancing the rotating and reciprocating components of high-speed engines has engaged the attention of engineers for many years with the result that a considerable literature is now available on this subject. Generally, the need to minimize external and internal force and couple unbalance is well recognized, since only in this way is it possible to avoid excessive vibration of the engine and its surroundings as well as undesirable fluctuating loads on the engine and its mounting structure. Furthermore, an engine which is dynamically ‘quiet’ is generally more silent and durable than one which is not.

Unbalanced rotating forces may be readily dealt with by the addition of counterweights to the crankshaft although extravagant use of these is to be avoided. Not only do they increase engine weight and cost, but the additional rotational inertia which they produce may lead to difficulties in dealing with the problem of torsional vibration. It is pointed out in the paper that where such weights are a necessity from the balance aspect, they may be designed as pendulum vibration absorbers so producing an engine which is smoother in a torsional sense.

Unbalanced inertia forces are normally dealt with by selecting an engine assembly which provides collective balance of the forces at the individual cylinders, and in presenting this paper, the author considers that one of the best methods of studying these effects is by means of reverse rotation vectors. This method enables a clear picture to be obtained of the resultant unbalance effect of different engine arrangements and provides a ready means of determining the best solution. The representation of reciprocating forces by means of reverse rotation vectors is not new and, indeed, was the basis of the Lanchester second-order balancer for four-cylinder in-line engines.

Some of the engine balancing arrangements in current use in the automobile industry are reviewed and discussed and mention is also made of some of the more important practical problems encountered when carrying out actual balancing operations on crankshafts and their associated components. Variations in the balance of identical engines may be traced to assembly tolerances and hence there is an increase in the practice of assembly balancing. As a logical conclusion it is to be expected that final balancing operations will eventually be made on the complete engine on the test bed.
Standards and Standardization in the Motor Industry
Authors: Woodbridge E.
Published: June 2010

Reference is made to the I.A.E. standards, S.M.M.T. data sheets, ‘Big Six’ and ‘Heavy Five’ standards, S.A.E. standards, B.S.I., ISO, D.E.F., Company standards and the handbook published by the S.M.M. & T., ‘Standards for the British Automobile Industry’.

Standards for purchasing, materials specifications, dimensional standards, production standards, and standard methods are also mentioned.

Standards in relation to restrictive trade practices and the relationship between National and International organizations and Government regulations are included.

It is stated that the adoption of standards should in most cases be voluntary and that use should be made of research in standards, for instance M.I.R.A. and R.R.L. and industrial research. Abbreviations used throughout are classified in an explanatory footnote†.
Performance of Vehicles under Trans-Antarctic Conditions
Authors: Pratt D. L.
Published: June 2010

A 2158-mile vehicle journey was made for the first time across the Antarctic Continent from the Weddell Sea to the Ross Sea in the summer of 1957-58. A historical review of Antarctic polar journeys using vehicles is made. The problem set is analysed, and an operational specification temperature of -60°F chosen with storage to -90°F, which met the field conditions adequately.

Light vehicles were chosen and the reasons are stated. The meaning of performance in relation to the project is analysed and an investigation of the main factors affecting performance is made under the headings of:

Terrain (Traction and friction). Engines (Startability; preheating; batteries). Lubrication. Materials.

Antarctic performance is examined under the headings of:

Climate. Terrain (Traction, friction and field recovery). Engines (Startability; preheating; batteries). Lubrication (Consumptions, effects and analysis of wear and carbon deposit). Materials (Field fractures). Human factor (Wind chill—effect on design).

The performance of the vehicles under these headings is stated and discussed and conclusions drawn in most sections.

It is finally concluded that long-range unsupported vehicle journeys are feasible within the heart of the Antarctic Continent during the summer season.
Influence of Atmospheric Pressure and Temperature upon the Performance of the Naturally Aspirated Four-Stroke C. I. Engine
Authors: Dicksee C. B.
Published: June 2010

The compression-ignition (C. I.) engine differs from other types of internal-combustion (I. C.) engine in that the fuel supply is entirely independent from the air supply and, further, that at all times a large excess of air is present. It is to be expected therefore that although the weight of air received will be influenced by atmospheric changes, the effect of these changes will be much less than in the case of an engine in which the fuel supply is dependent upon the air flow. Basically the effect is a change in air utilization, that is, air/fuel ratio. This is not universally realized as is shown by the fact that, quite frequently, a formula developed for correcting petrol-engine test results for atmospheric changes is applied to C. I. engine figures.

The experiments described were designed to show the absurdity of this procedure and, if possible, to provide information from which a method of correcting C. I. engine results could be derived. The first objective is very definitely achieved; for the second, it is shown that a change in air utilization has precisely the same effect upon the indicated horsepower no matter whether the change is caused by the fuel delivery being varied while the air supply remains the same or the fuel supply is kept constant and the air supply varied by a change in temperature or in pressure.
Some Investigations on Cold-Starting Phenomena in Diesel Engines
Authors: Austen A. E. W. , Lyn W.-T.
Published: June 2010

In this paper are recorded the findings on the more fundamental aspects of cold-starting work carried out in the laboratory at Acton during the past three years. It deals with both the criteria of an ignition under cold-starting conditions and how these criteria may be met by some practical forms of starting aid. From available ignition delay data and measured compression temperature it has been possible to correlate, in order of magnitude, the variation of starting time with both cranking speed and ambient temperature. The increase in compression temperature and pressure during continuous cranking with fuelling is found to be due partly to sealing action of the injected fuel and partly to the increased compression ratio. The effect of the slow oxidation of the fuel carried over from the previous cycle has been investigated and found to be insignificant. From these basic considerations, the effects of engine design and operating variables on cold starting have been discussed.

The principles and limitation of intake air heating as a starting aid (both by burner as well as by electrical heating), heater plug, and heating the injected fuel have been investigated. For the engine used, the lowering of minimum starting temperature is about 20°C (for a fixed cranking speed) when using a burner aid, while a further reduction of 2° to 3°C may be expected if electric heating is used. It is found that the main function of a heater plug is to provide a high-temperature ignition source rather than a heat source. The failure of the fuel heating system is due to excessive heat loss both before the fuel enters the chamber and to the chamber wall due to impingement when it enters the chamber.
Contribution to the Problem of Starting and Operating Diesel Vehicles at Low Temperatures
Authors: Brunner M. , Ruf H.
Published: June 2010

Using systematic cold starting trials with diesel (and also gasoline) vehicles in a large cold room, means of extending the serviceability of Swiss Army vehicles down to temperatures of about -13°F (-25°C) were studied.

The first requirement for a successful cold start is a sufficient cranking speed. After study of the relation between motor oil viscosity at low temperatures and cranking speed, the minimum speed limits for a successful cold start were determined. It was found that the design and working temperature of the battery also had a very great influence. In addition, special ‘cold-starting’ batteries, or conventional batteries protected from excessive cooling gave much higher cranking speeds than unprotected types. It is therefore possible to have successful starts either at lower temperatures or at the same temperature using an oil of higher viscosity, the latter giving better lubrication in the warmed-up engine.

When the minimum cranking speed has been ascertained, the properties of the fuel necessary for trouble-free operation must be considered. For starting diesel engines at temperatures down to -13°F (-25°C) starting aids such as the injection of a volatile auxiliary fuel, or the use of heating plugs becomes indispensable. In this case, the ignition quality (cetane number) of the fuel, so long as it stays within commercial limits, is of less importance. The greatest difficulty arises with the separation of paraffin wax which clogs lines and filters. With the aid of a rig test, consisting of all the main parts of a Saurer fuel system, the filterability of different fuels was studied in some detail. It has been found that different fuels behave quite differently. If the wax separates in large crystals, for instance, the coarse pre-filters may sometimes clog at temperatures very little below the cloud point of the fuel. More frequently, finely divided wax separates out and the fine filter proved to be the more critical in which case clogging only occurred at temperatures well below the cloud point of the fuel.

It therefore proves rather difficult to correlate the behaviour of a fuel in practice with any of the conventional laboratory yardsticks used to assess the cold properties of gas oils. It is also unlikely that a ‘single-point’ laboratory test can be devised that covers all practical cases. A certain relationship between the results of the rig-filterability-test on the one hand and cloud point, pour point, and ‘filterability’ (DIN 51770) on the other is undeniable.

The use of additives to improve filter-clogging tendencies of diesel-gas oil was not very promising. The best method appeared to be dilution with kerosine.
Fuel-Injection System Calculations
Authors: Knight B. E.
Published: June 2010

A simplified method of calculating injection system performance has been developed for the use of applications engineers. It is particularly relevant to the problem of avoiding secondary injection and dribble.

The calculation of the complete behaviour of injection systems has been programmed for a digital computer. Agreement with experiment is satisfactory and confirms that all important factors have been taken into account. These factors are quoted and the methods used for dealing with compression waves in the pipes are described in detail. Viscous friction and voids in the fuel are taken into account. As an example of the use of the programme, an approach to the problem of stroke to stroke variations of delivery in one line is described.

A longer term objective is the reduction of the time required to match injection equipment to engines by using this and other computer programmes instead of experimental methods, up to the final trial stage.
Calculations of the Effect of Rate of Heat Release on the Shape of Cylinder-Pressure Diagram and Cycle Efficiency
Authors: Lyn W.-T.
Published: June 2010

In these papers the gas pressure, temperature and cycle efficiency are calculated for various assumed simple heat-release diagrams using a digital computer. It is concluded from these calculations that for a given heat-release period, the cycle efficiency is essentially a single valued function of peak pressure and is independent of the actual shape of the diagram. There is an optimum peak pressure beyond which no gain in efficiency can be expected. The rate of pressure rise, however, depends on the initial slope of the heat release diagram. It is therefore both desirable and possible to have a slow rate of pressure rise for the same peak pressure with only slight loss in efficiency.

The effect of compression ratio and the period of heat release have also been investigated. The theoretical cycle is then compared with what is regarded as the practically attainable ideal cycle. Finally, the optimum peak pressure for a given compression ratio, or alternatively the optimum compression ratio for a given peak cylinder pressure is defined.
Relation between Fuel Injection and Heat Release in a Direct-Injection Engine and the Nature of the Combustion Processes
Authors: Austen A. E. W. , Lyn W.-T.
Published: June 2010

Fuel injection and heat-release analysis for a direct-injection (D.I.) engine have been carried out over a wide range of load, speed, and injection timings using a digital computer. From these results emerge the broad principles governing the combustion in a D.I. engine. A model is proposed for relating quantitatively the rate of fuel injection to rate of heat release and hence cylinder-pressure diagram. It is found that the same law for correlation holds over wide range of load and speed and injection timing. The predicted cylinder-pressure diagram agrees reasonably well with the measured diagram over all test conditions, thus establishing the validity of at least the main features of the model. Whilst it is perhaps too optimistic as yet to predict i.m.e.p. (10 per cent error), the agreement in the rate of pressure rise (almost exact) and peak pressure (about 5 per cent error) is such that practical applications (for example, resulting noise) are already possible.

Arising from the heat-release analysis and high-speed photography a consistent picture of the combustion processes in a diesel engine is presented. It is shown that in general, and particularly in the case of D.I. engines, the highest rate of burning occurs immediately after ignition and the flame is essentially premixed in nature with low luminosity. This period of high rate of heat release is, however, very short and is followed by the main period which is essentially diffusion in character with high luminosity and comparatively lower rate. The effect of combustion-chamber type on these processes are discussed and comparison is made with heat release in a petrol engine.
Relation between Form of Cylinder-Pressure Diagram and Noise in Diesel Engines
Authors: Priede T.
Published: June 2010

This paper is a sequel to an earlier paper and carries this aspect of the investigation on from that stage.

The frequency analysis of cylinder pressure has been shown to be a satisfactory criterion of the ‘noisiness’ of a cylinder-pressure diagram. In this paper the effect of the properties of the measuring equipment, such as band width, is considered so that the results may be interpreted quantitatively in terms of the pressure rises and hence the amount of combustion involved.

The effect of operating variables on the frequency analysis is investigated.

In some cases stroke-to-stroke variations are of importance and frequency analysis and emitted noise are compared in relation to background noise.

Over a limited range, the effect of type of combustion chamber has been explored and some observations with petrol as the fuel are included.
Cylinder Pressure Variations in Petrol Engines
Authors: Soltau J. P.
Published: June 2010

The paper deals with a detailed research programme which was carried out in an endeavour to find out the cause of the cylinder pressure fluctuations from cycle to cycle which occur in a petrol engine. Every working variable was altered in turn, and its effect on combustion observed on an electronic engine indicator.

The development of the cylinder pressure over a large number of cycles was recorded at each setting with the aid of an oscillograph camera. For more detailed observations, the photographed traces were replotted on a volume scale and individual P-V diagrams were studied and in some cases drawn as log P-log V graphs. The experiment showed that the fluctuations in peak pressures and i.m.e.p. were caused by differences in the heat-release rate from cycle to cycle. All hydrocarbon fuels exhibit similar variations, but town gas with its more rapid burning produces steadier pressure development. The air/fuel ratio of the mixture is the main factor which influences the magnitude of the maximum pressure variations from cycle to cycle. The steadier mixture ratio is in the order of 13 and on either side of this the fluctuations increase rapidly, especially on the weak end. Using several simultaneous ignition sources, it is possible to decrease the individual flame front path and therefore increase the resulting combustion speed, which reduces the fluctuations.
Theoretical Studies in Braking
Authors: Chandler K. N.
Published: June 2010

In Part I of this paper, after a simple description of the basic properties of a pneumatic tyre, a highly simplified vehicle consisting of a pneumatic-tyred wheel bearing a load is considered mathematically during braking and during the release of brakes. By inserting numerical estimates it is shown that, among other results, from 15 mile/h a wheel may lock within 18 ms.

It is also shown that under perfectly uniform conditions the stopping distance is appreciably less when the brake-shoe torque is approximately equal to the moment of the maximum frictional force that is possible between the tyre and the road, than for both greater and lesser brake-shoe torques.

In Part II of the paper a commercial device—the Maxaret—designed originally to release the brakes of an aeroplane before the wheels lock on landing and then later to reimpose the brakes is briefly described and the mathematical equations of its operation, both in itself and in application to a highly simplified road vehicle, are set up. A numerical investigation, making use of the results given in Part I of this paper, was executed and the results are given. These show in detail the mode of operation of the device. These highly simplified calculations suggest that in its present form a much longer braking distance will result from using the device than would be obtained with locked-wheel braking. This is in conflict with experimental results and may be due to both the simplifications that had to be made for the numerical work and some of the empirical data used. Some of the former could be avoided if an electronic computer were available. Further investigation is desirable and this should enable the device to be adjusted to give the shortest stopping distance consistent with the avoidance of locked wheels.
A Test Schedule for Passenger-Car Brakes
Authors: Livsey A. E. , Prestidge A. F. , Woor D. F.
Published: June 2010

Various forms of brake-fade test are used in the motor industry, and it is suggested that a standardized test schedule is required, the latter being based on contemporary operating conditions. A study of brake usage of a number of passenger cars with different drivers operating over four selected routes had been carried out previously, and the results of this investigation are used to formulate two tests which it is proposed should replace the existing fade test. The proposed tests simulate as closely as possible maximum braking conditions recorded on the four routes, and the test specification for any particular car may be arrived at by substituting known car characteristics into formulae.

A test schedule is derived for a typical modern car, and the results obtained from the tests on this car are presented and interpreted.
Measurement of Piston-Ring and Cylinder-Liner Wear Using Radioactive Tracers
Authors: Pywell R. F. , Walker S. T.
Published: June 2010

In the paper the methods for measuring cylinder-liner wear using radioactive tracer techniques are discussed, and the manufacture and installation of a liner made of aluminium and cast iron are described. Also a method for measuring piston-ring and cylinder-liner wear simultaneously is described. In addition in the paper the selection of the electronic instruments and the factors affecting the design of the mechanical equipment associated with these techniques are considered.
Brake Usage in a Heavy Vehicle
Authors: Frood A. D. M. , Mackenzie D. K. , Newcomb T. P.
Published: June 2010

This paper summarizes measurements made of the duties imposed on the brakes of a heavy vehicle when driven over a continental route which included the Susten and other passes in Switzerland and in Austria. On the Susten Pass an investigation was made of the effect of driving in various gears.

The following data were determined for each brake application: vehicle deceleration, rate of energy dissipation and total energy dissipated at the brakes, the energy lost by drag losses, the energy absorbed by engine braking, and the temperatures attained in all drums and linings. Measurements were also made of the amount of energy imparted to the vehicle when it was accelerated by the engine between brake applications.

Analysis of the results shows that a heavy vehicle travels at a fairly uniform speed down the mountain passes and consequently only a small percentage of the total energy dissipated is given to the vehicle by the engine in between braking. The work done at the brakes varied between 15 and 62 per cent of the total energy dissipated, the proportion depending on the steepness of the gradient and the driver's choice of gear for the descent. The maximum amount of work done at the brakes (5·66 times 107 ft.lb) was on the Susten Pass when the vehicle was driven in third gear. During such a journey the drums attained an average temperature varying between 350–400°C while the linings reached an average temperature in the range 275–350°C.

A theoretical analysis is outlined which permits calculation of the temperatures attained at any stage of the descent. This analysis requires a knowledge of the work done in each brake application, together with cooling rates, and gives results in good agreement with the observed temperatures on the Susten Pass.

Little difference was observed between the driving behaviour of the two drivers on the various passes; one driver made more brake applications per mile than the other but the duration of each application was less. Consequently, both applied their brakes for approximately the same total time and dissipated similar amounts of energy at the brakes when both used the same gear over the same descents.
A Theory of Brake Squeal
Authors: Spurr R. T.
Published: June 2010

It is shown that frictional vibrations can be excited in small-scale apparatus; theories to account for such vibrations are given, and experiments on brake assemblies are described to show that the theories developed apply to brake squeal generally.