bluuebunny/crossref_metadata_2025_split huggingface dataset:
Powder Metallurgy
Authors: Newson J. E. 
Published: October 2007

The term “powder metallurgy” covers the art of producing objects from metal powders, with or without the addition of non-metallic constituents. The powders may be pressed to a desired form in a suitable die and subsequently or simultaneously heated to produce a welded, alloyed, or coalesced mass. The material may then be suitable for immediate use or may be further worked by conventional methods, as, for example, by drawing down to fine wire. The chief advantages of this technique are that (1) it is possible to produce articles having unique properties unobtainable by other methods, e.g. controlled porosity; (2) it offers a method of producing parts in metals which cannot be melted commercially or only with considerable difficulty, and do not lend themselves to casting; (3) it is suitable for mixtures of metals and non-metals; (4) it can be used for metals which do not alloy; (5) it can be applied to metals of widely separated melting points or greatly different densities; (6) it offers a mass-production method of producing large quantities of parts identical in size and quality, perhaps of complex shape, without further operations; and is specially competitive where final machining constitutes a large proportion of the finishing costs by conventional methods. The limitations are: (1) restriction on the size of parts that can be produced on the presses available; (2) the restriction on the design of parts that lend themselves to pressing; (3) the fact that large quantities are required to justify the cost of dies and tools; (4) the cost of metal powders; and (5) the fact that the volume of the uncompressed powder is 2–3 times that of the finished piece. Future developments appear to lie in the direction of hot pressing, extended use of the process as the preferred technique for small parts in iron and other metals, and in combinations which retain desirable characteristics of the component metals, e.g. high wear resistance coupled with high electrical conductivity, which powder metallurgy makes possible in a way unobtainable by other means.
Elementary Principles of Plant Organization and Maintenance for Civil Engineering Contractors
Authors: Parrack H. O. 
Published: October 2007

The paper has been written as the result of evidence to the effect that the general standard of the application of plant to the requirements of the civil engineer in this country is in need of improvement. After brief reference to the position of the mechanical engineer in civil engineering industry, sections are devoted to repair depots, site maintenance, stores, mechanical plant organization, and personnel. The methods advocated have been tried in practice during some years' experience with a considerable volume of widely differing classes of plant, employed on contract sites of various types and sizes. No attempt is made to explain the actual work of operating and maintaining any particular type or make of machine—a matter which is related to the intention of the paper only to the extent by which the same principles of organization might apply.
Steam Flow in Nozzles: Velocity Coefficient at Low Steam Speeds
Authors: Giffen E. , Crang T. F. 
Published: October 2007

A considerable amount of controversy was raised by one aspect of the results reported by the Steam Nozzles Research Committee of the Institution over the years 1923–30. This was concerned with the variation of the velocity coefficient of a steam nozzle at low steam speeds, the Committee's results showing a tendency to higher values of coefficient at very low speeds. The work described in the present paper was undertaken to provide additional experimental evidence on this point and, in order to be comparable with that of the Committee, was carried out on apparatus employing the same general principles, but embodying certain improvements in detail. The impulse plate method was used in determining the steam velocity at the exit from the test nozzle. The apparatus was designed on a small scale for use with a small self-contained steam generating unit, and particular care was accordingly given to accuracy in all the necessary measurements. The design eliminated frictional effects in the determination of the force on the impulse plate, and tests could be carried out with wet steam as well as superheated. Two series of tests were made, one with steam superheated after expansion and the other with expansion into the supersaturated region. The exit velocity varied from about 500 to 1,200 ft. per sec., the final pressure being nominally atmospheric in all cases. The results showed that the velocity coefficient decreased continuously from the maximum to the minimum steam velocity, and that the values of the coefficient were substantially the same for the two series at corresponding speeds. This result is not in agreement with the Steam Nozzles Research Committee's work, but confirms the conclusions of other investigators in this field.
The Disk Spring or Belleville Washer
Authors: Ashworth Graham 
Published: October 2007

The conical disk spring, often known after the original patentee as the Belleville Washer, has considerable potentialities for cushioning purposes, but its use in this country has been restricted owing to the lack of published information regarding the load-deflexion and stress-deflexion relations obtaining. The circular conical disk of constant thickness, with a concentric hole and under central loading, is analysed in theory and design. Part I deals with theoretical aspects of the single disk, shows that a range of load-deflexion curves can be obtained (the shape of the curve depending on the ratio of the free camber to the thickness of the disk) and develops the relation between the distribution of internal stress and the ratio of the outside diameter of the disk to the inside diameter (showing that for economic utilization of space and material this ratio should not be more than two). Part II deals with the design of nests of disk springs, with particular reference to the use of these nests for buffering duties outside those for which helical springs can be easily employed. A figure for the maximum permissible calculated stress is suggested and a set of simple formulae which facilitate rapid design is developed from a consideration of the storage of energy under deflexion.
The Deflexion of a Thick Plain Ring under a Uniformly Distributed Couple
Authors: Johnson A. E. 
Published: October 2007

Several theoretical methods of estimating the deflexion of a thick plain ring under a uniformly distributed couple have been published, both in this country and in the U.S.A. Probably the best-known of these theories is that of Dr. R. W. Bailey.† In all cases the treatment has not been rigid from a mathematical point of view, the axial or shear forces in the ring notably being neglected, and the load being assumed concentrated on particular loading circles whereas in fact it is distributed over an appreciable area. The present paper attempts to treat the problem in a more rigid manner, with due consideration of the effect of load distribution. Expressions for the axial and radial deflexions, and the axial, shear, radial, and circumferential stresses in the ring are developed, and values of these functions are obtained for a wide range of ring dimensions, and are compared with the values of similar quantities obtained by the use of the theory of Dr. R. W. Bailey.
Considerations Affecting the Improvements in the Thermal Efficiencies of Non-Reheating Plants at High Steam Pressures
Authors: Finniecome J. R. 
Published: October 2007

This contribution is supplementary to the paper presented by Mr. K. Baumann entitled “Improvements in Thermal Efficiencies with High Steam Pressures and Temperatures in Non-Reheating Plant” (see p. 125).† It reviews the basic assumptions made in that paper. Particular attention is drawn to the condition line, to the corrections in the turbine efficiency due to higher pressures and temperatures relative to the basic conditions of 600 lb. per sq. in. gauge and 800 deg. F., and to the assessment of the decrease in the heat consumption due to feed heating. The method applied is demonstrated in detail by a typical calculation of a feed heating heat balance. Consideration is also given to the optimum decrease in heat consumption due to feed heating and also to the economic feed temperature for various operating factors. The factors affecting the improvement in thermal efficiency for the economic feed temperature and the power of the station auxiliaries for river and cooling tower conditions, at various pressures and temperatures at the stop valve, are presented by a series of graphs. The use of these graphs is clarified by a summary of comparative data on the improvement in thermal efficiency relative to 600 lb. per sq. in. gauge and 800 deg. F. The final results of the improvement in thermal efficiency for the economic feed temperature relative to 600 lb. per sq. in. gauge and for temperatures from 800 deg. F. to 950 deg. F. with five stage feed heating are indicated by a group of graphs for a range in pressure of 600 to 1,800 lb. per sq. in. gauge for a vacuum of 29 inches of mercury, both excluding and including power station auxiliaries. Finally, a graph indicates the percentage difference in the heat consumption per inch of mercury between 28 inches and 29 inches for temperatures from 800 to 950 deg. F. The results are summarized in seventeen figures and in two comprehensive tables.
An Analysis of the Lubrication between the Piston Rings and Cylinder Wall of a Running Engine
Authors: Courtney-Pratt J. S. , Tudor G. K. 
Published: October 2007

A method has been developed for the study of the lubrication in the cylinder of an engine under actual running conditions by an analysis of the electrical conductance between a piston ring and the cylinder wall. One of the compression rings was electrically insulated from the piston and a current passed from this ring to the cylinder wall: the potential drop between the moving surfaces was calibrated in terms of the resistance. With good conditions of lubrication, the electrical resistance is high, while low resistance values indicate breakdown of the lubricant film and consequent abrasive wear of the surfaces. A study of this resistance variation was made by means of a cathode ray oscillograph with the time base synchronized with the stroke of the engine. Results indicate that, with the oils used, the surfaces of the piston ring and the cylinder wall are not separated by a continuous oil film throughout the entire cycle. Intermittent breakdown of the oil film occurs to a varying degree under all circumstances, even using oils much heavier than are common in automobile practice. Also, in general, the resistance is lower; that is, more metallic contact occurs in the regions of top and bottom dead centres than during the remainder of the cycle. The method confirms the improvement in lubrication expected with increase of engine speed, or with increase of viscosity. The effects of gas pressure behind the rings are shown to be small, at least with the low brake mean effective pressure in the particular engine studied. A marked deterioration in the quality of the lubrication accompanies any increase in the temperature of the oil film on the cylinder wall—greater deterioration than can be accounted for simply by the decrease of viscosity due to the temperature rise. Finally, the results demonstrate the applicability of this method of analysis to problems of cylinder lubrication and abrasive wear, its chief value being the rapidity with which results may be obtained as compared with conventional wear tests.
The Development of the La Mont Boiler in Great Britain
Authors: Plummer G. A. 
Published: October 2007

The La Mont system of controlled forced-circulation was promoted in America in 1926, and developed in Europe by German interests from 1929. This development commenced with water walls added to existing natural-circulation boilers and proceeded to complete steam generators employing the La Mont principle. British engineers became interested, and in 1936 the La Mont boiler was introduced for manufacture in this country. Several visits of investigation were made to the Continent, which indicated that whilst much valuable experience was already available from the 150 or so installations then existing, a considerable amount of work would be required to adapt the La Mont boiler to British requirements. It was also realized that experience with larger units at higher pressures show the necessity for modifications in detailed design. The paper describes several difficulties encountered in the development of this type of boiler and how they have been overcome.
Operating Experience with La Mont Boilers, with Special Reference to Feed Water Problems
Authors: Begg G. A. J. , Hebblethwaite W. M. , Cooke G. 
Published: October 2007

The paper describes the chief troubles encountered in operating high-pressure La Mont forced circulation boilers with a difficult feed water consisting of 80 per cent chemically treated make-up. Attention is drawn to the thermodynamic and financial advantages gained by the use of the higher pressure system. The reasons for the choice of the La Mont boiler are given and also a summary of information obtained on the Continent in 1939 relating to feed water treatment with La Mont boilers working under nearly similar conditions of pressure and feed water. The initial feed water treatment and after-conditioning, together with details of the feed water treatment plant for the boilers actually installed, are described. The early troubles with feed water treatment and their effect on the availability of the boiler are dealt with in detail and the precautions found to be necessary to avoid accumulation of sludge in the headers and the formation of “Analcite” scale in the generating tubes are also described. Information is given of the troubles with secondary combustion as a result of insufficient turbulence in the combustion chamber and the fouling of the air heaters and the remedies employed. The general design of the boiler and power plant and of all auxiliary plant are described, and the reduction in power costs achieved, in spite of war time increases in the cost of coal and labour, are enumerated.
High-Pressure Gear Pumps
Authors: Beacham T. E. 
Published: October 2007

Gear pumps have been used in very large numbers for the various hydraulic services of war aircraft. For the higher pressures the main problems have been in connexion with the load on the journal bearings, with wear, and with the reduction in volumetric efficiency caused by internal leakage. The journal loads are affected by the number of teeth and by the ratio of width to diameter of the gears. With high pressures it is difficult to accommodate standard ball or roller races on account of their diameter: designs are illustrated using a combination of standard races and special needle roller bearings. Small amounts of wear cause comparatively large reductions in volumetric efficiency. Major causes of wear are rubbing on the gear end faces and solid matter in suspension in the liquid and methods of dealing with these are discussed. The percentage slip due to internal leakage varies inversely as the factor (r.p.m. × viscosity). At low speeds and with low-viscosity liquids, internal leakage often limits the pressure at which the pump can be used. Multistage pumps reduce the leakage and have been used extensively for undercarriage operation. Internal leakage becomes relatively less as the size of the pump is increased and the paper gives a graph, showing the relationship between the limit of pressure at which 80 per cent volumetric efficiency is possible, the capacity and rotational speed of the pump, and the viscosity of the liquid. Aircraft pumps generally use gears with involute teeth: ports in the end covers of the casing are used to prevent excessive pressure in the liquid trapped between the teeth. Low- and high-leakage conditions call for difficult arrangements of ports, and this involves differing displacements and variations in flow velocity.
Control and Planning of Maintenance with an Incentive Bonus Scheme
Authors: Talbot R. , Satow G. F. 
Published: October 2007

The paper describes the successful application at Royal Filling Factories of time study principles and techniques to the difficult problem of the control of the maintenance of production machinery. A considerable proportion of the work was analysed and reduced to a routine. Maintenance in this category could then be planned beforehand and the performance of the work controlled against predetermined schedules. The labour required was then found by a specialized form of time study and the paper gives a brief account of time study in general. Two methods are described: “work content” method, in which the labour is built up operation by operation, and “rating” method, in which the labour is found by an assessment of present efficiency. Finally, a standard team is determined, taking into account the varying degrees of skill required and the limited amount of time actually available for maintenance. An incentive to improved maintenance was devised and made the basis of a bonus scheme. This, together with the necessary records, both for the bonus and for the maintenance control, is fully described. The scheme, which has also been extended to the engineering shops in a modified form, has resulted in an increase in the quantity and quality of maintenance and in a reduction in the labour force.
The Development of Locomotive Power at Speed
Authors: Diamond E. L. 
Published: October 2007

The power developed per unit of cylinder volume of locomotives in the speed range from 250 to 400 r.p.m. has in recent years been doubled. Forty years ago it was often the case that the diminution of the mean effective pressure with increase of speed, rather than the evaporative capacity of the boiler, limited the power of the engine. The most advanced designs maintain the mean pressure at a high percentage of the calculated value to the highest speeds, and the effect of valve events and clearance volume on the calculated mean pressure thus becomes of practical importance, especially as designers are endeavouring to use considerably higher steam pressures in single-expansion cylinders. The first part of this paper sets out the effect of these factors over a wide range of steam pressures in the form of basic data graphs of mean pressure, relative efficiency, and steam consumption. It is shown that without the decrease of clearance volume and increase of expansion ratio which compound expansion affords, the improved thermal efficiency which higher steam pressure offers cannot be fully realized above about 250 lb. per sq. in. boiler pressure, though greater power can be obtained. The second part of the paper is devoted to an examination of the actual deviation of mean pressure with speed for a wide range of locomotives, including some of the most recent designs, and the reasons for the radical improvement are indicated. In 1905 the late Professor Dalby suggested a simple proportional relationship between mean pressure and speed. Such a relationship does not hold for modern locomotives, and at the end of the paper a simple exponential law is proposed with a single coefficient characteristic of the locomotive. This law may be used to estimate the power of a future design at any speed, or as a criterion for assessing the performance of an existing locomotive in respect of power developed, which is generally of more importance to railway companies than thermal efficiency.
The Use of Vibration as a Means of Industrial Drive
Authors: Thornton C. A. M. 
Published: October 2007

The application of vibration as a means of industrial drive has been considerably developed in the last twenty years. Starting from the obvious application of screening, it has been extended to conveying, heat interchanging, consolidation of material in packages to reduce shipping space, keeping material “fluid” in hoppers and chutes, hammering, etc. The paper discusses that part of the subject involved in the production and control of the vibration by mechanical or electrical means under all conditions of load. Formulae are developed for calculation of spring strength and for the calculation of the spring dimensions, and for the avoidance of spring fatigue. The various methods of electrical excitation are compared, and the relative advantages and disadvantages are discussed. The desirable instrument equipment is described, including the remote indication of vibration amplitude. A method is outlined by which it is claimed that vibration can be maintained constant at all loads and at any desired frequency. The testing of vibrating drives at the manufacturer's works and on site is discussed. In an Appendix to the paper the problem of transverse vibrations in long vibrating conveyors is treated mathematically, and a formula is developed for the natural frequency of transverse vibration of a conveyor of any uniform section and of any length.
Efficiency and Cavitation of Fluid Machines
Authors: Anderson H. H. 
Published: October 2007

In order to predict the performance of a fluid machine from scale-model tests, correction formulae are required. Professor Lewis F. Moody's formula is used for water turbine efficiencies but does not appear to be accepted for pumps; Pfleiderer† states that it is not practicable to use Reynolds number; and Wislicenus‡ does not give a formula for scale correction but states that efficiency increases slowly with size and speed. For cavitation, the only general formula is Thoma's parameter§ from which is developed suction specific speed. Wislicenus, Watson, and Karassik‖ rely entirely on suction specific speed and state that the influence of Reynolds number can be neglected. It is suggested that both the total head loss—given by (1 – η) where η denotes the efficiency—and suction side loss (cavitation) may be treated similarly and analysed according to the Reynolds number. Examples of centrifugal pump efficiencies and cavitation characteristics are analysed, and the resulting curves are found to have the same shape as corresponding portions of the original Reynolds curve for pipe friction. The losses in a fluid machine are thus represented by the friction loss of a certain length of pipe. Extrapolation for sizes and speeds beyond the known field of tests can then be made by analogy with the pipe friction curve. From the foregoing considerations, the author suggests that the Moody formula for the losses: (1– η)∝ 1/ D0·25 H0·1—where D and H refer to diameter and head respectively—should be replaced by (1 – η)∝ ( D✓ H)– x where x varies between 0·2 and 00·3, according to Reynolds number. A similar relation is derived for cavitation.