Proceedings of the Institution of Mechanical Engineers

Gas manufacture is generally carried out in either horizontal, continuous vertical, or intermittent vertical retorts supplemented by carburetted water-gas plant. At the present time a certain amount of gas from coke oven plants is purchased, but only one such installation is at present in use on a gas works primarily for the production of gas.

All four types of carbonizing plant, together with the carburetted water-gas plant, are described briefly, and a table is put forward to show the results obtainable from them. Four thermal balance diagrams demonstrate the possibility of heat recovery from the waste flue gases, hot coke, and the hot coal gas by the generation of steam. A brief description of the various ancillary plant employed is given, whilst the production and use of steam is discussed more fully. The use of back-pressure steam is advocated and a table shows the variation of power requirements in six works, two each of the three main types of carbonizing plant.

A brief description of the recently reconstructed Brentford works of the Gas Light and Coke Company shows the extent to which mechanical handling of material has been adopted.

Liverpool shipowners have played prominent parts in the long struggles for supremacy on the North Atlantic between the more notable steamship companies, such as the Cunard, White Star, Collins, Inman, Guion, Hamburg-Amerika, and Norddeutscher Lloyd Lines, and associated with their names are those of the celebrated engineers and shipbuilders who were responsible for building the transatlantic mail steamers. An historical account is given of the evolution of the mail service from its commencement in the year 1710 to the present day, and includes the British Government Post Office Packet service commenced in 1710 by the sailing packet brig Royal Anne, the inauguration in 1816 by the Black Ball Company of the first regular sailing packet line, the commencement of the Atlantic Ferry in 1840 by the Cunard Line, and the evolution of the mail steamer to its present size, as represented by the liner No. 534 now building. This period covers the development from wood to iron, and iron to steel, for the construction of hulls, the change from sail to steam, from paddles to single, twin, triple, and quadruple screw propellers, from simple to compound, triple-, and quadruple-expansion reciprocating engines, the development of the Parsons direct and single- and double-reduction geared turbines, the change from tank boilers to low- and high-pressure water-tube boilers, and the evolution of passenger accommodation to its present standard.

A few observations are made on the navigation and propulsion of modern liners. Tables show the record passages of Atlantic liners and dimensions of the present-day big ships. The state-rooms, lounges, ballrooms, cinema theatres, swimming baths, sports decks, and dining saloons in the modern liner are briefly described.

The author thinks it is improbable that the Atlantic steam ferry will be supplanted by an air ferry, and he gives an account of the competition with foreign lines which receive subsidies for shipbuilding and operation, and explains the reasons for building No. 534, and the part which Liverpool and the Atlantic Ferry might play in the future development of the United States of America and the Dominion of Canada.

The engine used for these tests is of the single-cylinder vertical Diesel type, having a 12-inch bore and 18¼-inch stroke and running at 250 r.p.m. Temperatures have been measured at nineteen points on a ribbed “jam pot” cast iron piston, at twenty-three points on a “mushroom” type aluminium piston, and at fourteen points on a cast iron piston with a conical head support. Temperatures have also been measured at eight points on the cylinder liner. A description is given of the pistons and special testing apparatus. The influence of subsidiary junctions in the thermocouple leads, which led to some discussion following Dr. Mucklow's recent paper on piston temperatures,† has been studied. Errors, varying with engine output and amounting to as much as 29 deg. C., have been measured where no compensator was used.

The effects of the temperature of the liner and of the jacket water outlet on the pistons have been measured, and are discussed. The conclusions are in general agreement with those of Dr. Mucklow except such as apply to the central portions of the heads, where the great differences of area exposed to flame lead to remarkably divergent results.

The temperature distributions throughout the pistons are considered, and a quantitative estimate is made of the value of the neck, ribs, etc., when these are considered as heat channels. The radial temperature differences recorded for the aluminium and cast iron pistons and for the piston tested by Dr. Mucklow, are roughly in the ratio of 1/5½/19. The effect of varying the engine output has been studied, also the time required to warm up the pistons, the light alloy reaching its maximum temperature in approximately half the time required by the cast iron.

A decrease in the number of rings from five to three is shown to have very little effect except in reducing the fuel consumption, while rings of forged “Y” metal slightly reduce the temperature of the piston. The effect of totally enclosing the piston shows that only some 2 per cent of the heat received is normally lost to the air circulating within it.

This experimental investigation relates to a general method of measuring stress distribution when force fits and shrinkage fits of the plane stress type are employed in engineering practice. Important cases occur in the webs of built-up crankshafts for locomotives and Diesel engines. When the latter are of high power and short stroke, so that crankshaft and crankpins are large and relatively close together, the initial constructional stresses are shown to attain high values.

More complicated cases, from an experimental point of view, occur in the driving wheels of locomotives with a tyre shrunk over a wheel centre having a crank and balance weight integral therewith, while the main axle and crankpin are forced or shrunk in. Such a case is examined with reference to a driving wheel of the London Midland and Scottish Railway locomotive Royal Scot, and the stress distributions measured in various parts of a model of it are described in detail.

The Alloys Research Committee of The Institution of Mechanical Engineers began its work in 1890, and from 1902 onwards the investigations were conducted in the National Physical Laboratory. The Eleventh Report, published in 1921, dealt very fully with the light alloys of aluminium. At that stage it was decided that further research should be devoted to the alloys of iron with the object of determining the fundamental nature of the alloys of iron with various metals and non-metals to serve as a basis for a more systematic knowledge of the steels used in practice. The investigation has comprised the construction of equilibrium diagrams using thermal, microscopical, X-ray, and other physical methods. Iron being more sensitive to the influence of minute quantities of impurities than most other metals, it was necessary to prepare very pure iron as the basic material. Since 1921, the alloys of iron with oxygen, phosphorus, silicon, chromium, and manganese have been studied. As all the alloys are of high melting point, many new laboratory methods have had to be developed, the technique of experiments at high temperatures becoming more difficult the higher the upper limit is raised. In the course of the research, therefore, it has been necessary to prepare new refractories and to design special forms of apparatus in order to avoid contamination. The paper contains a summary of the results obtained in the course of the work, and it is shown how these bear upon the improvement of steels for structural and engineering purposes. The investigation is being extended to other elements, and ultimately to the influence of more than one solid element when present simultaneously in the alloy.

The paper deals with those changes in the mechanical properties of steel having a low carbon content, which occur as a result of quenching from temperatures up to 900 deg. C. Attention is directed mainly to brittleness, especially to that resulting from ageing at atmospheric temperature, which the authors term “age embrittlement.” The range of temperature in which this occurs appears to include those temperatures used in the carburizing treatment of steel as well as lower temperatures. It is suggested that case-hardened steels should be subjected to a final tempering treatment after quenching to avoid the possibility of core brittleness.

Theories are briefly discussed, but at present no direct explanation of the phenomenon is forthcoming, as X-ray and microscopic examination reveal no abnormalities in the age-embrittled steel. Ageing at 100 deg. C., after quenching, shows distinct age hardening, but this is found to be dissociated from age embrittlement.

It is generally recognized that the sale and purchase of coal for steam generation on the basis of its calorific value would be more rational than the present methods. In the paper the advantages of the calorific value basis are briefly discussed, and reasons given for its relatively slow development. The non-uniformity of industrial coals makes it difficult to assess their value except in relatively large quantities. This has an important bearing on the selection of coal by the short boiler-trial method. Apart from the technical difficulties of attaining a reasonable degree of accuracy in a short boiler-trial, there must always be a doubt as to whether the sample tested was really representative.

An alternative method of evaluation is described which enables larger and more representative quantities of coal to be examined. This method is based on accurate sampling and analysis, and is claimed to be less liable to error. At the same time it permits a greater number of types of coals to be investigated, thus giving the purchaser a wider choice, and increasing his knowledge of coals. In addition, the author provides a basis of control for subsequent deliveries. It is, in any case, strongly recommended as a check on any other method.

In 1927–8 two cargo ships of roughly 11,000 tons displacement were built by Messrs. R. and W. Hawthorn, Leslie and Company for the Booth Steamship Company of Liverpool. Originally of identical design, the plans of S.S. Boniface were altered during construction to include a Bauer-Wach exhaust steam turbine, whilst S.S. Basil was built as originally designed with a triple-expansion engine only. Builders' trials on S.S. Boniface proved the turbine to give a reduction in coal consumption of 24·5 per cent.

The paper adds to the facts already known about this type of installation some information regarding reliability and economy in actual service. Following a general description of the propelling machinery and auxiliaries of the two ships, and a more detailed description of the exhaust steam turbine, gearing, hydraulic coupling, and control system of S.S. Boniface, notes are made regarding the general running and the troubles experienced with the extra equipment. Particulars of two trials at sea under normal conditions on S.S. Boniface are given, and finally, a coal consumption comparison on a yearly basis between the two ships is shown to give a saving of 15·9 per cent in favour of S.S. Boniface at the age of four years.