bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Practical Application of Frequency Response Analysis to Automatic Process Control
Authors: Rutherford C. I. 
Published: October 2007

The paper shows how the basic principles of frequency response analysis may be applied to automatic process control without the introduction of any of the mathematics which are used in the servomechanism field of study, and which have in the past discouraged its use in the process field. It is shown how the frequency response of any part of an automatic control system may be represented graphically, how the response of any simple element of a system may be calculated, and how the response of the individual elements thus obtained may easily be combined to give the characteristics of the whole plant. Alternatively, the frequency response of the plant may be plotted experimentally without interrupting its operation. By reference to a typical example, it is shown that all proprietary “three-term” controllers do not necessarily function as simple theoretical controllers, but that their performance may often be represented as that of an effective theoretical controller, and may, in any case, be shown as a frequency response diagram from which the necessary information is available to match the controller to any particular process. The method introduced is shown to give a convenient measure of plant controllability, and by means of plant analysis on this basis, it is suggested how automatic control may often be improved by better design of the process rather than of the controller. The design of automatic controllers is also treated, and it is shown how various design features may be compared in the light of their frequency response characteristics. It is suggested that future controllers should be designed to give a specified frequency response.
The Particle Size Analysis of Crushed Products
Authors: Ratcliffe A. 
Published: October 2007

An examination is made of two particle size analyses which are typical of two categories of crushed products. One example represents material reduced in a hammer mill; subjected to indiscriminate reduction, it contains a preponderance of smaller sizes, and this is characteristic also of ball mill products and the small particles in the products of jaw, gyratory, and roll crushers. The second example illustrates the influence of the sizing action which occurs in the latter machines and results in a closer grading of the coarse particle fraction. These characteristic features are illustrated by graphs, and a mathematical basis is given for Gaudin's law of particle size distribution.
An Experimental Crank Press
Authors: Seed E. C. , Swift H. W. 
Published: October 2007

An account is given of the technical problems which arose in the design of an experimental single-action, double-sided crank press of tie-rod construction which has been built for use in the deep-drawing researches carried out in the University of Sheffield. This press was required to have a specified capacity of 20 tons during the second half of the down-stroke and 50 tons during the last inch of the down-stroke. To cover the drawing speeds of industrial practice, a variable speed of 5–60 strokes per min. and a variable stroke of 3–10 inches were specified, and to maintain a close control over the speed, the slowdown at any speed over the whole range was limited to 10 per cent. An air cushion and also an automatic means for stopping the press at top dead centre after each stroke and for interrupting the stroke at any prescribed point in order to obtain partially drawn pressings for examination and measurement were incorporated. Speed variations are obtained through a transmission system consisting of a substantially fixed speed electric motor with a fixed gear to the flywheel, and a variable gearbox between the flywheel and the main gears of the press. It is shown that, from the functional points of view this is the most satisfactory system of power supply and transmission for a variable speed press. Two safety devices are embodied in the press: a shear plate in the ram to protect the crankshaft and a shearing pin in the first reduction gear wheel to protect the gearing. The design of these devices is described in an Appendix.
Relations between Roll-force, Torque, and the Applied Tensions in Strip-rolling
Authors: Hill Rodney 
Published: October 2007

Expressions are derived for the roll-force P, and torque G, in strip-rolling under tension, as functions of the pressure distribution on the rolls and of the radius of the deformed arc of contact. By consideration of various artificial distributions of pressure the ratio G/P is shown to depend only slightly on the precise shape of the friction hill, and a linear relation is deduced between G/P and T/P, where T is the difference of the front and back tensions. This is confirmed by experiments on annealed mild-steel strip and it is found also that T/P is approximately equal to the angular arc-of-contact when the torque is zero (Steckel rolling). A more detailed investigation of the effects of tension, based on the simplest possible hypothesis, indicates that a back tension, Tb, increases the torque per roll by , while a front tension, T f, decreases it by , where r is the fractional reduction in strip thickness and R is the undeformed roll-radius. The theory indicates also that the roll-force decreases linearly with both front and back tensions. Experimental data confirm the theoretical predictions of linearity, and show that the formula for the effect on torque is accurate over a wide range of tensions.
Standardization of Steam Turbo-Generating Plant
Authors: Robinson I. V. 
Published: October 2007

“Standardization” is taken to cover (1) simplification of a range of components ; (2) standardization of capacities and of operating conditions; and (3) standardization of station arrangement. The paper deals with aspects of (2) and (3), and notes on auxiliary plant, including condensers, are added. A warning note is sounded, lest standardization should lead to stagnation. Reference is made to the possibilities of hydrogen-cooling as a means of reducing windage losses and the maximum indivisible weight of stator to be handled.
Industrial Design and its Relation to Machine Design
Authors: Conway H. G. 
Published: October 2007

The paper deals with improvement in “machine” design in relation to function (specification, durability, and performance), manufacturing cost (processing, redesign, and collaboration with suppliers), and styling. Conscious attempts at improvement in appearance should, in the author's opinion, be the last stage in the general process of improved machine design. In regard to styling the author stresses the importance of appearance, the functions of the specialist “industrial” designer dealing with appearance and utility in co-operation with the “mechanical” designer, and the need for training of engineering designers in “composition” (by which is meant “what not to do” rather than creative artistry, which springs perhaps from an intuitive rather than an instructed apprehension). Incidentally, the need to consider the buyers' tastes of the moment is the greater for products that do not outlast contemporary fashions. Improvement in product design may be brought about by the employment of specialist consultants (who are in continual contact with new materials and ideas); by managements' readiness to improve, and to encourage, rather than frustrate, the creative instinct in designers and engineers; by team concentration upon redesign of particular machines; by training young engineers to be product-conscious; and by the introduction of non-specialist technical literature dealing with design in the broadest sense and with the exploitation of new materials and processes.
Electronic Engine Indicators with Special Reference to Some Recent American Designs
Authors: Vinycomb R. K. 
Published: October 2007

For internal combustion engines, the mechanical indicator has been largely superseded by “single-point” systems or by electro-mechanical transducers in conjunction with electronic instruments. After dealing briefly with the history of engine indication and some early electronic devices for this purpose, the paper outlines the characteristics of an ideal indicator. Most commercially-available indicators now use a variable-capacitance “pick-up”. Three contemporary systems (two American and one British) of this type are described, with details of the pick-ups, basic circuits, and performance under practical operating conditions. This is followed by a description of a radically different type of pick-up developed in the United States. It uses a catenary-shaped diaphragm and a variable-resistance sensitive element. The improved performance realized by this pick-up is explained by reference to its unique design. In conclusion, the characteristics of all four of the systems described are examined with respect to the ideal indicator.
The Heat Unit
Authors: Griffiths Ezer 
Published: October 2007

This paper gives the history of various calories and British thermal units which have been in use. International agreement has now been reached that the joule (107 ergs) should be the fundamental unit of heat. The advantages of this unit are that it is (1) independent of the intrinsic properties of any particular substance, (2) independent of the temperature scale, and (3) easily realizable in terms of the electrical units. Calorimetric apparatus nowadays is calibrated by electrical heating and the electrical units are known with high precision. Since the international system of electrical units has now been superseded by the absolute system, it is necessary to express in absolute units the various heat units formerly defined in terms of international electrical units. The international steam table calorie defined as 1/860 of an international watt hour, when expressed in absolute joules, becomes 4.1868. The other calorie which is defined in terms of the international electrical units is the thermochemical calorie. This, in absolute joules, becomes 4.1840. Table 1 shows conversion factors to joules.
The Design and Development of the Twin Centaurus Power Plant for the Bristol “Brabazon”
Authors: Norton J. L. 
Published: October 2007

The adaptation of eight “Centaurus” engines, grouped in pairs, to drive airscrews presenting only four disks to the air stream in the Bristol “Brabazon”, is described, including their submersion within the wing thickness, and special cooling arrangements. The reasons chosen for the layout of the power plant are given. Description of the design of the dual-reduction gear includes the primary and auxiliary drives, free wheels, and propeller shafts. The operating system of the propellers is briefly reviewed. The plant used and programme for testing, including fire precautions and detection and an actual engine fire test, are described.
The New Factory
Authors: Bulger J. G. 
Published: October 2007

The building of a new factory is a major project, and the co-ordination of all interests, mechanical, civil, electrical, and administrative, connected therewith forms the subject of the paper. Special attention is drawn to the appointment of the project manager, his terms of reference, his authority, and his responsibility, upon which is based the organization for co-ordination. Stress is laid on the personal attitude of all concerned, who must sink personal feelings, jealousies, or bias, in favour of the satisfactory conclusion of the project. A broad plan, prepared by the permanent staff of the company should give as much information as possible to the project manager, who preferably will not be a permanent member of the staff himself. The project manager and his committee will formulate the final plan, and carry the project through to conclusion, but not finality. Time spent on the site selection is time well spent, since the site is permanent. Attention must be paid to position, labour, foundations, process water disposal, fuel and water, power, housing, and amenities. Considerations of plant, plant layout, buildings, site layout, and services are of considerable importance, many points common to all industries being covered by the paper. Planned progress is essential. There is no finality to the building of a new factory. The development is handed over by the project manager to the production staff.
The Effect of Speed and Feed on the Mechanics of Metal Cutting
Authors: Chao B. T. , Bisacre G. H. 
Published: October 2007

When the cutting speed or feed of a metal cutting tool is increased, the most striking effect is on the rate of tool wear, but there are other changes which take place at the same time. These are changes in the geometry of the chip, tool forces, and tool build-up and surface finish. An attempt is made in this paper to form a logical theory to explain these variations in the mechanics of the process. The problem of tool wear is not attempted. A series of tests has been conducted on mild steel and copper, over a wide range of speed, feed, and tool angle; and a theory has been developed. The results arrived at are:— (1) That local temperature in the chip plays an important part in affecting the friction at the chip tool interface. (2) For many purposes effects due to speed and feed can be treated as functions of the product of speed and feed. (3) Temperature does not affect the shear strength of the metal directly. (4) The extent of built-up edge prevailing can be put as a function of the product of speed and feed.
Some Fatigue Tests on Aluminium-alloy and Mild-steel Sheet, with and without Drilled Holes
Authors: Phillips C. E. , Fenner A. J. 
Published: October 2007

This paper describes fatigue tests, under pulsating direct stress, of aluminium-alloy and mild-steel panels, with and without central holes, approximately 0·1 inch in thickness and up to 12 inches in maximum width. Comparison of the results of tests on panels of similar shapes but of different sizes shows that larger panels are relatively weaker. The influence on the fatigue strength of varying the size of a drilled hole in a wide panel has been explored over a range of hole-diameters from to of the net width. While, in general, the presence of a hole causes a marked reduction in fatigue strength, the smallest holes result in only a slight reduction.
The Design of Flexible Disk Misalignment Couplings
Authors: Wolff P. H. W. 
Published: October 2007

This paper gives the results of calculations which were undertaken, in the first instance, to determine the increase in operating range of a disk coupling with skew misalignment which would be obtained by tapering the disks. The results of later investigations concerning the stresses due to “umbrella” deflexions, the vibration frequencies of tapered disks, and the torque buckling of disks of constant thickness, are also presented. All the results have been obtained by integration of the general differential equation for disk bending.
Extension of the Simple Plastic Theory to Take Account of the Strain-hardening Range
Authors: Roderick J. W. , Heyman J. 
Published: October 2007

In the simple plastic theory commonly used for mild steel it is assumed that after yielding has occurred in either tension or compression, straining can continue indefinitely at constant stress. Such an assumption has been found satisfactory for low carbon steels having a plastic range corresponding to eight to ten times the strain at yield, but for steels of greater strength this range is often considerably shorter, and it becomes necessary to take into account the strain-hardening range beyond. To obtain experimental data, four steels were selected, varying in carbon content from 0·28 to 0·89 per cent, and having widely different stress-strain relations. For each steel a number of simply supported beams of square section were subjected to a symmetrical two-point loading; tension specimens were prepared from the unyielded ends of these beams and tested in a spring-loaded autographic testing machine to determine upper and lower yield stresses. In addition, two tension specimens from each steel were tested in a lever type of machine, and the stress-strain relations through the plastic range and the initial stages of the strain-hardening range were obtained with the aid of a “Gerard” extensometer***. This information gave good support to the theoretical work, whereby the behaviour of these steels in flexure can be correlated with the tensile properties.
The Design of Large Pumping Installations for Low and Medium Heads
Authors: Wauchope G. A. , Humphreys H. P. 
Published: October 2007

This paper is concerned with the factors involved in the selection of the most suitable designs of pumping installations, particularly of the larger sizes, and, in the first place, discusses the effects of the different types of pump on the construction of the pumping station. It goes on to demonstrate the relative advantages of different designs over the wide range of specific speeds available. Methods of determining the most suitable hydraulic characteristics in three typical cases are examined and the effects of these factors on the first cost and running and maintenance costs are considered. As most selections are usually a compromise between the ideal hydraulic characteristics and those available from the pump and prime mover, the relative merits of constant-speed, variable-speed, and variable-pitch impellers are discussed. Certain aspects of the methods in use for priming pumps are considered and the chief causes of pressure surges in pipe-lines are briefly outlined. The paper concludes with a discussion of the various factors which may decide whether it is desirable that the plant shall be automatically operated, centrally controlled, or individually controlled.
Some Problems of Fluids for Hydraulic Power Transmission
Authors: Bingham A. E. 
Published: October 2007

The connexion between aircraft, land, and marine hydraulics is emphasized, especially in regard to the working fluid and the sealing problems. The ideal fluid which would suit all cases does not, as yet, exist. The properties, advantages, and disadvantages of a number of well known, and a few lesser known, fluids are discussed. The fluids include those based on petroleum, castor, water-glycol, halogenated, and synthetic compounds. The properties covered include viscosity and density, and their variation with temperature and pressure; chemical and toxic effects; bulk modulus or compressibility; water miscibility, and the significance of cloud, pour, and boiling points. The fire hazard, and its difficulties of assessment in relation to the usual recorded properties and conditions, is noted. Thermal conductivity, dielectric strength and storage conditions are also considered. Some of the information, of which much hitherto has been widely scattered, has been derived from recent research, and an attempt has been made to arrange the data in rational form.
High-temperature Alloys in Relation to Gas-turbine Design
Authors: Buckle K. L. 
Published: October 2007

In order to achieve a thermal efficiency in the gas turbine comparable with that realized in steam practice, a higher turbine-entry temperature is necessary. Limiting discussion to the combustion and expansion sections of the gas turbine, the paper first indicates that the use of metals in high temperature and stress conditions necessitates a new approach to component design. The phenomena of creep and fatigue assume major importance whilst pure temperature effects, such as expansion and thermal shock, are additional problems. These properties are defined and an indication is given of their significance in the design of combustion chambers, turbine wheels, and blades. Susceptibility to heat treatment, intended to induce the desired high-temperature properties, is another important factor to be considered in material selection, as are fabrication characteristics. Since the latter govern both detail and general design, the merits of forging, casting, and welding are outlined when applied to high-temperature alloys. The paper concludes with a survey of the problems likely to be encountered with future materials, particularly ceramics, whilst suggesting that increased efficiency may be obtained by further research on established alloys or by design innovations such as cooling.
Basic Engineering Standards and Their Place in Design
Authors: Adams G. C. 
Published: October 2007

In this paper standardization in design is considered. The argument is developed tat the detailed design of the parts of a mechanism demands a logical approach. The designer should state on the drawing, in the simplest possible terms, what he really wants. The necessary range of basic (or abstract) engineering standards, both for him to achieve this aim and to provide for economic production, are given. The basic standards cover definitions, geometric analysis, ultimate standards of size, basic sizes, limits and fits, measurement, surface texture, drawing practice, standard forms (for example, screw threads), and standards of design. Their nature and scope are examined in general terms and some of the main compromises necessary are discussed. The necessity is shown for a sound framework, wide enough to cover the normal needs of all engineers. The dangers of a parochial outlook are stressed and the needs of both small and large producers are emphasized. These standards are shown to be the essential preliminary to sound standardization of articles, which should be a natural by-product of sound design. Their main economic value, however, is that they affect every article which the engineer designs. At the present time there is only a partial framework and much disagreement on details. To standardize articles before agreement has been reached on the approach to detailed design of the articles, leads to difficulties in standardization and sometimes to bad standards. Several good solutions can be propounded for most problems, and many different ones are in local use. A single, wide, and all-embracing plan which can be used by everyone is needed. Education and explanation can then lead to general use, to the lasting advantage of the engineering industry.
Leakage of Air through Labyrinth Glands of Staggered Type
Authors: Kearton W. J. , Keh T. H. 
Published: October 2007

A simplified theory is presented for the flow of air through a single orifice or constriction. This theory is then extended to cover the flow of air through a labyrinth gland having several constrictions of equal area. Experiments are made over a wide range of pressure ratios to determine the coefficient of discharge for a single annular constriction having a small clearance. It is found that the curve has the same general characteristics as that for a circular sharp-edged orifice. The discharge coefficients are then used to calculate the critical ratio of inlet pressure to outlet pressure for a labyrinth gland. The results obtained agree well with experiments on a stationary labyrinth gland of the staggered type in which the number of constrictions may be varied from one to fourteen. The theoretical pressure distribution is derived and compared with experimental values under conditions where the pressure drop across the last constriction is either less or greater than the critical value. Finally, the coefficients of discharge are obtained experimentally for the final constriction and for the preceding n-1 constrictions in a gland having n constrictions. It is concluded that the carry-over effect in a staggered gland is small.