CoA. Notes (1952-1969)
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Item Open Access Aerodynamic characteristics of two low aspect ratio rectangular wings at Mach 2(College of Aeronautics, 1956-04) Marson, G. B.This note summarises the important results of a detailed experimental investigation into the flow and pressure distribution over two rectangular single wedge wings. The experiments were carried out .in the 9" x 9" supersonic tunnel at the College of Aeronautics, 6 at a Mach number of 2.0 and a Reynolds number of 2.5 x 10 per foot. Both wings had a chord of 3 inches and a total wedge angle of 6°. They had no real trailing edge, but were faired into a cylindrical support which could be rolled and pitched in the tunnel. Wing A was of 2 inch1span, giving an aspect ratio of 0.67. `Ting B was of 1 1/4 inch span, 0.42 aspect ratio. 132 pressure tappings 4 were spaced regularly over half of one surface of each wing, and up to 19 pressure readings could be taken simultaneously on vertical mercury manometers. models were pressure plotted at pitch angles of 0°, 2 1/2°, 5°, 7 1/2°, 10°, 15°, 20°, 25°, and 30°, and at all roll angles at intervals of 30°. Since each wing was symmetrical about the centreline, the complete pressure distribution over all surfaces at any roll angle Ø could he obtained from the readings taken on the one surface at Ø, 180°- Ø, 180° + Ø, and 360°- Ø. The pressure readings were then integrated to give the forces and moments on the complete wing… [cont.].Item Open Access Relationship between the limits of fit determined from B.S. 1916 and the functional requirements for interference fits(College of Aeronautics, 1963-04) Scarr, A. J.Introduction When a designer wishes to choose a shaft and hole deviation and tolerances, as, for example, an interference fit, he may be led to assume, when reading B.S.1916, that a particular fit combination will give the same functional characteristics over the entire size range covered by the standard. It is the intention of this note to show that this assumption is not necessarily valid, and that the fit combination_ required to meet a particular functional requirement will vary with size, These comments are not intended as a criticsm of the standard as such but, rather, that a supplement to the standard is required, to give the designer guidance on the choice of fit for particular functional requirements.Item Open Access Large scale metrology(College of Aeronautics, 1963-04) Scarr, A. J.Introduction This interim note covers some of the problems encountered in the measurement of large sizes, up to 80 inches (200 mm), during investigations carried out at the College of Aeronautics. A description of a new design of stick micrometer for internal diameters and a micrometer frame for external diameters is included, together with experimental results obtained in using this equipment. Problems associated with measuring large sizes These may be classified under three broad headings:- a) The influence of temperature on the measurement b) Problems associated with the stiffness of the measuring equipment. (c) The elimination of operator feel. (a) The influence of temperature In practice, it may be extremely difficult to maintain both the component and measuring equipment at the internationally agreed standard of 20°C. Figure 1 shows the effect of variations in the temperature of steel components with respect to the Fundamental Tolerance value (B.S. 1916), expressed as a percentage of the tolerance grade. The particular case illustrated is for a 3°C. change in temperature on steel components, (coefficient of expansion assumed to be 11 parts in a million/°C), manufactured +o tolerance grade IT.6. It can be seen from this graph that in the smaller sizes up to say 10 inches (250 mm), the percentage of the tolerance taken up by the change in temperature remains relatively small, but with increase in size the effect of temperature becomes increasingly significant, until at 100 inches (2500 mm) 82% of the tolerance has been consumed.Item Open Access Characteristics of the high temperature mechanisms of creep and recovery in graphite(College of Aeronautics, 1963) College of Aeronautics, (Cranfield)The research reported in this document has been made possible through the support and sponsorship of the U.S. Department of the Army, through its European Research Office. This report, not necessarily in final form, is intended only for the internal management use of the Contractor and the 1.T.S. Department of the Army.Item Open Access Characteristics of the high temperature mechanisms of creep and recovery in graphite(College of Aeronautics, 1962) College of Aeronautics, (Cranfield)The research reported in this document has been made possible through the support and sponsorship of the U.S. Department of the Army, through its European Research Office. This report, not necessarily in final form, is intended only for the internal management use of the contractor and the U.S. Department of the Army.Item Open Access Ergonomics in machine tool design: second progress report on M.T.I.R.A. research project(College of Aeronautics, 1963-04) Easterby, R. S.This report is the second of a series of reports, to be issued every six months, describing the progress of a research project on ergonomics in relation to machine tool design. The report covers, in broad outline, the progress made, and some projects anticipated in the ensuing year. Separate detailed technical reports will be issued from time to time, as experimental and survey data become available. The progress reports are numbered in The College of Aeronautics Notes series. The first report, issued in October, 1962, is CoA Note 150, Part 1. The technical reports will also be numbered in the series.Item Open Access Ergonomics in machine tool design: first progress report on M.T.I.R.A. research project(College of Aeronautics, 1962-10) Easterby, R. S.This report is the first of a regular series of reports to be issued describing the progress of a research project on Ergonomics in relation to Machine Tool Design. The project is being carried out in the Ergonomics Laboratory of the Department of Production and Industrial Administration under the sponsorship of the Machine Tool Industry Research Association. The report is in two sections, the first of which outlines the scope of Ergonomics in relation to Machine Tool design and the existing state of this aspect of design in various firms representative of the industry in the United Kingdom. The second section details a project which was undertaken after consultation with one of the Research Association's members, into the problems of legend design. Here the design approach is probably applicable to similar problems on most machine tool types.Item Open Access The free-molecule flow characteristics of concave surfaces(College of Aeronautics, 1963-06) Pratt, M. J.The problem of free molecule flow over concave surfaces is investigated, and general equations formulated for the lift, drag, and heat transfer characteristics of such surfaces. The effect of multiple reflections is taken into account by use of the Clausing integral equation to determine the redistribution of molecular flux over the surface. It is assumed that emission of molecules from the surface is purely diffuse, and that the reflected molecules are perfectly accommodated to the surface conditions. The equations obtained are solved for the cases of (i) an infinitely long circular cylindrical arc and (ii) a section of a spherical surface, at hyperthermal velocities. It is found that under the above conditions the local heat transfer characteristics are the same as those of the corresponding convex surface, the total heat transfer being independent of the geometry of the surface. As drag devices, the concave surfaces examined prove only slightly more effective than a flat plate at similar incidence, and as a generator of lift the cylindrically cambered plate is significantly inferior to the flat plate at similar incidence.Item Open Access Teaching machines for teaching work study(College of Aeronautics, 1963-05) Wiltshire, H. C.Machines which have been used successfully for the teaching of work measurement practices are described. Although designed to shorten the period of instruction for beginners) they appear to be suitable for postgraduate students and also for management - consultant trainees.Item Open Access The effect of nitrogen in alpha-iron on ferromagnetic domain boundary movement examined by a mechanical damping method(College of Aeronautics, 1963-05) Steward, M. J.The effect of ageing below 200°C on the hysteresis loss in a-iron containing nitrogen has been investigated. The extent to which nitrogen is removed from solid solution during ageing, and the domain boundary hindrance developed, was assessed by mechanical damping, using a low-frequency inverted torsional pendulum. Nitrogen, both in solution and as the precipitated form Fe5N, was found to increase the resistance to domain boundary movement, the precipitated form being the more effective in this respect. Most of the damping changes due to ageing are developed in less than 2 hours at 150°C; a further investigation to cover this region would need to be undertaken to establish quantitative relationships.Item Open Access The design of a hydrostatic lubrication arrangement for the horizontal and transverse slides of a no. 3 archdale vertical milling machine(College of Aeronautics, 1963-05) Loxham, J.The Department of Production and Industrial Administration of The College of Aeronautics has made a detailed analysis into the performance of numerically controlled machine tools, and this shows that when these machines are operating under light cutting loads, the total envelope tolerance is about 0.003 ins. Further investigation into the source of the errors showed that about 80 per cent of this error was due to mechanical mechanisms in the machine tool. The electronic equipment operated inside a total band of 0.0004 ins. over small distances, and 0.0006 ins. over 10 inches. This situation appeared to justify a comprehensive survey into the methods which may be used to improve the mechanical performance of these machines. After due consideration had been given to a number of possible alternatives, it was decided to fit hydrostatic lubrication to the slides, nut and screw arrangement, and the thrust bearings used on the X and Y axes of an existing No. 3 Archdale Milling Machine. The Z axis was not included in the redesign, because analysis showed that a new head casting would have been necessary. It was thought that this additional expense was not justified and that the data obtained from an examination of the performance given by the X and Y axes would show whether the system could be used with advantage in the design of new machines. The paper gives details of the calculations used to establish the dimensions of the new features fitted to the machine to satisfy the target performance conditions which appeared to be possible and are given in the introduction. The authors would like to express their appreciation to James Archdale and Co. for making a machine available for this investigation, to the Staveley Research Department, and in particular to Mr. Graham, Mr. Harris, Mr. Huntley) M r. Cummings and Mr. Hayward.Item Open Access A measurement of the radiated noise on a subsonic jet aircraft in gliding flight(College of Aeronautics, 1963-06) Hyde, D.The noise radiated from a gliding subsonic jet aircraft was measured in flight by a probe microphone installed in a ‘laminarised’ boom projecting from the fin of the aircraft. As the signal associated with the windmilling turbines was predominant even at flight speeds near the aircraft's limiting Mach number, it was not possible to relate the noise radiated from the turbulent boundary layers to flight speed. The measured sound pressure levels in the frequency band 4o c/s to 15 kc/s, for Mach numbers between 0.24 and 0.66 at an altitude of 20,000 ft., were in the range from 110 to 115 decibels relative to 0.0002 ubar. A calculation of the radiated noise from the boundary layers gave overall levels of 85 to 120 db relative to 0.0002 bar at the microphone position on the aircraft for the same range of flight conditions.Item Open Access Non-newtonian flow in incompressible fluids. Part 3: some problems in transient flow(College of Aeronautics, 1963-06) Kaye, A.N/AItem Open Access The acquisition of high speed skills. First progress report on D.S.I.R. research project(College of Aeronautics, 1963-04) Whitfield, D.N/AItem Open Access Grinding theory(College of Aeronautics, 1962-09) Hillier, M. J.This report presents a review and extension of current grinding theory. Grinding operations are classified on the basis of (a) the cutting action of the grit, (b) the geometry of wheel and work, (c) the type of chip produced, (d) the existence or otherwise of a continuous lateral traverse of the wheel. The theory is developed using the above method of classification. Recent experimental work by Purcell(12) on the wear of the wheel in surface grinding is reinterpreted in the light of the theory. It is shown to be consistent with the postulate of a constant task per grit. A method of calculation is suggested by which a satisfactory surface grinding technique may be applied to the form grinding of gears, where the task per grit is not independent of the imposed grinding conditions.Item Open Access Some tests on a circular ground effect machine with forward speed(College of Aeronautics, 1962-10) Harris, T. M.Wind tunnel tests have been made on a circular-wing with 90° downward peripheral blowing both in and out of ground effect. Tests made with two slot widths, a range of blowing pressures and choked jets, indicate that Cu is a unifying parameter for this type of test. The windspeed was varied between 0 to 200 ft/sec. at zero incidence and the static pressure distribution on both top and bottom surfaces was measured. The sum of the integrated pressures on both upper and lower surfaces 3 agreed reasonably well with the measured overall lift. Flow visualisation on a streamwise plate beneath the model showed the vortex system and the eventual 4 collapse of the forward jet with increasing windspeed.Item Open Access The Cranfield Ergonomics Laboratory(College of Aeronautics, 1963-03) Singleton, W. T.Ergonomics is a cross discipline between the human sciences and engineering. It is concerned with the design of man/machine systems, using the characteristics of the operator as the frame of reference. The state of our technology is now such that almost any purposeful activity involves a man and a machine operating together. Thus the basic working or fighting unit is the man/machine system and the efficiency of the system is dependent on the weakest link. Until recently this has usually been within the machine, but we have reached the stage when it may now be in the man, or between the man and the machine. It thus becomes necessary for the engineering designer to build his "hardware" to suit the human operator as well as to meet the need which the system is required to fulfil. To achieve this objective the designer requires data and advice on human performance. The provision of this information is a difficult task because of the complexity and variability of human performance. There are, at present, few laws of human behaviour which can take quantitative forms, and to obtain numerical information it is often necessary to resort to direct manipulation of the relevant variables. Fortunately, there is a considerable body of knowledge and experience on the measurement of human performance which has been developed by psychologists, physiologists, anatomists and work study practitioners. Thus, ergonomics is based on statistically controlled experimentation and, in common with other experimental sciences, it can only be taught effectively by a combination of lectures and laboratory periods. The objective of the Cranfield Ergonomics Laboratory is to provide these facilities so that students can acquire a knowledge of experimental techniques and of the variables which they are manipulating. The students may be specialists in this field or may be engineers from other fields who wish to acquire some knowledge of the subject. The formal experiments require at least two students, one to act as a subject and the other as observer. Each experiment takes two or three hours to perform, and a similar period is required to read appropriate reference material and write a report.Item Open Access The development and evaluation of an ultrasonic fatigue unit(College of Aeronautics, 1963-03) Clifton, T. E.A fatigue test apparatus operating at 20 kc/s is described. The unit is based on a standard magnetostrictive drive system as used in high energy stresswave generators. An automatic counting device has been developed and incorporated in the final equipment, resulting in improvements in accuracy and reproducibility of results. Some typical results of tests on aluminium alloys are presented.Item Open Access Wall pressure fluctuations under turbulent boundary layers at subsonic and supersonic speeds(College of Aeronautics, 1963-03) Lilley, G. M.The problem of pressure fluctuations at a rigid wall under a turbulent boundary layer has attracted much attention in the past decade. At low Mach numbers the theory is well established from the work of Kraichnan and Lilley, and reasonable agreement is obtained with the experiments of Willmarth, Hodgson and others. At high Mach numbers, measurements exist due to the work of Kistler and Chen but so far no theory is available, apart from that due to Phillips, which is however related to the noise radiated from supersonic turbulent shear flows. The present paper reviews the theory of wall pressure fluctuations in incompressible flow, and shows how the character of the pressure fluctuations changes in passing from the flow to the wall. Attention is drawn to the more important interactions giving rise to the pressure fluctuations, as well as to the region of the boundary layer mainly responsible for the wall pressure fluctuations … [cont.].Item Open Access Crack formation in blanking and piercing(College of Aeronautics, 1963-02) Noble, C. F.In recent experiments on blanking and piercing, it was found that cracks occurred in the region of maximum hardness gradient and that cracking could be eliminated by radiusing the punch and die edges. In this paper, a simple stress analysis is made of the corresponding plane strain deformation, account being taken of the strain-hardening property of the work material. The above experimental observations are then shown to be compatible with the predicted stress distributions.