Browsing by Author "Scarr, A. J."

Now showing 1 - 6 of 6
  • Thumbnail Image
    ItemOpen Access
    An autocode programme to determine the flatness of a surface table using the least square mean plane criteria
    (College of Aeronautics, 1964-06) Scarr, A. J.
    Introduction The calculations involved in determining the flatness of a surface table from measurements made with instruments such as a block level or auto collimator can be lengthy, particularly where a large number of ordinates are taken. A solution to this problem is presented in this note in the form of an Autocode programme which will cater for up to 100 ordinates. The datum from which the variations in the flatness of the surface table are determined is the least squares mean plane. This may be defined as being that plane which makes the sum of the squares of the errors relative to it a minimum … [cont.].
  • Thumbnail Image
    ItemOpen Access
    Automatic assembly design project 1968/9: Report of component supply and separation committee
    (College of Aeronautics, 1969) Gray, A. F.; Hayes, D. A.; Jones, P. V.; Scarr, A. J.
    This report outlines the techniques for automatically feeding the components of an electrical contact block and describes the design of a feeding system for each component. All components of the contact block were initially analysed for automatic feeding and redesigned where necessary. Existing feeding methods were examined and consideration was given to their versatility. Decisions were then made as to the feeding system for each component.
  • Thumbnail Image
    ItemOpen Access
    Large scale metrology
    (College of Aeronautics, 1964) Scarr, A. J.
    INTRODUCTION It has been recognised in industry that the measurement of large components to high orders of accuracy presents a particularly difficult problem. This fact has been emphasised by a survey carried out by the N.P.L. (Ref. 1) in which a number of engineering firms in Great Britain were asked to declare the size of several prepared test pieces ranging in diameter from 15 inches to 80 inches. In general terms the result of this investigation showed that, under industrial conditions using conventional equipment, it was not possible V declare the size of large components to an accuracy of better than - 30 parts in a million under workshop conditions and - 15 parts in a million under inspection conditions. The survey also showed that above 20 inches the accuracy of determination of internal diameters was somewhat higher than for external diameters. The purpose of this paper is to indicate the main problems associated with measuring large sizes and to describe the experimental work undertaken at the College of Aeronautics in the design and testing of a new type of stick micrometer for internal diameters and micrometer frame for external diameters.
  • Thumbnail Image
    ItemOpen 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.
  • Thumbnail Image
    ItemOpen 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.
  • Thumbnail Image
    ItemOpen Access
    Thrust and stiffness nomograms for hydrostatic bearing calculations
    (College of Aeronautics, 1966-08) Cooke, P.; Scarr, A. J.
    The application of hydrostatic lubrication to slideways is now becoming common practice in the machine tool industry. The theoretical basis for determining design parameters for hydrostatic lubrication is well established (Refs. 1 and 2) but one of the practical problems facing the machine tool designer wishing to use this technique is the tedious computation involved in arriving at suitable design parameters ... [cont.].