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Article
Publication date: 1 October 1938

W.W. Twelvetrees

THE problem of tuning and adjusting carburettors can well be remembered as a legacy from the earliest internal combustion engines and one which has hardly become…

Abstract

THE problem of tuning and adjusting carburettors can well be remembered as a legacy from the earliest internal combustion engines and one which has hardly become simplified with the rapid development and improvement that aero‐engines have undergone in recent years. Although, to‐day, it is necessary to make but few individual adjustments in carburettors to suit the characteristics of particular engines, it is still essential in many instances to check every detail of carburettor functioning during engine bench tests. This creates difficulties, particularly when it is required to replace a carburettor on an otherwise serviceable engine. To subject the engine to complicated tests is obviously undesirable if satisfactory alternative means are available for checking the functioning of the carburettor as an interchangeable unit.

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Aircraft Engineering and Aerospace Technology, vol. 10 no. 10
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 1 March 1939

W.N. Twelvetrees

FOR many years the basic design and construction of aircraft has been closely linked with the cooling system employed for the power plant which it is desired to utilise…

Abstract

FOR many years the basic design and construction of aircraft has been closely linked with the cooling system employed for the power plant which it is desired to utilise and as a general rule machines have been produced specifically for either liquid‐ or air‐cooled engines. Conversions of liquid‐cooled engined machines to suit an air‐cooled installation and vice versa have been successfully carried out in the past and to‐day there is a tendency for twin‐engined military aircraft to be constructed so that alternative installations may be employed, but the complications necessitated by such a practice provide good reason for producing the airframe to suit one particular engine. The general recognition of this policy has served to emphasise the importance of deciding the type of engine most suitable for the purpose for which the machine is required and has possibly lent weight to the claims submitted by various engine manufacturers. The merits of one variety of engine as opposed to the other is a subject which has from time to time received much attention, but, as the object of this article is to trace the development of liquid‐cooling systems, a brief outline of what is considered parallel advancement in air‐cooled practice may be of interest.

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Aircraft Engineering and Aerospace Technology, vol. 11 no. 3
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 1 October 1945

W.N. Twelvetrees

ALL machines, particularly modern machines, are constructed and operated with the general understanding that they will at some time wear out. Wear is combated in many ways…

Abstract

ALL machines, particularly modern machines, are constructed and operated with the general understanding that they will at some time wear out. Wear is combated in many ways but never more successfully from both scientific and economic points of view than when all the major parts of a machine wear out together. This state of affairs is obviously preferable to having a machine which will never wear out at all; for even if such an article could be made, the cost of its construction and operation would be uneconomical. As is well known, many machines do not wear out before they become obsolete, but again this is rarely either a sound economic or scientific proposition. Not only is loss of capital involved but an inaccurate estimation of operational life is a failure in the application of engineering knowledge. If this outlook can be sustained for machines generally it is certainly vital and of the highest importance for prime movers such as aero engines with which this paper is chiefly concerned. An aero engine today must give definite life for definite cost and in no other branch of engineering are quality and reliability so vital and cost, by reason of its very magnitude, so deeply considered. Hence no one has attempted to construct an aero engine which could be economically scrapped after its first overhaul life and not even the most optimistic manufacturers have devised a non‐wearing, everlasting product. As might be expected, a reasonable compromise is the general rule but it is however a noticeable fact that modern engines are becoming more and more resistant to wear and if anything there is a general tendency to the second alternative referred to above. The term “wear” in the general sense covers a multitude of physical changes and chemical reactions, some of which it is hoped to consider later, but if for a moment this expression is held to embrace the deterioration of highly stressed steel parts from prolonged fatigue, marked recent improvements can be reported. Some years ago it was common to replace certain aero engine parts for no other reason than that they were “time expired”. It was considered in such cases that the parts after a certain life had passed the safe limit of their fatigue resistance, although the parts themselves and the rest of the engine would be in what appeared a perfect condition. Developments over the past few years have made it possible to eliminate such precautions and in most modern engines all parts can be relied upon to maintain a safe margin of fatigue resistance for the useful life of the complete engine. This is an isolated example of how the wearing qualities, or more accurately, the endurance, of engines has been improved and it is of interest to note that these advances in the selection and better use of materials have nearly been equalled by improvements in actual surface wear resistance. It can be safely asserted that bearing combinations are available today which will resist surface wear indefinitely under the heaviest possible conditions of loading, providing the loading is not associated with other factors which cannot as yet be overcome. It is therefore an object of this paper, in addition to considering wear generally, to examine these factors as their interest lies in the obstacles they present to the production of a machine which will approach the ideal of being completely worn out after a given life.

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Aircraft Engineering and Aerospace Technology, vol. 17 no. 10
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 1 June 1942

W.N. Twelvetrees

WHEN man invented the wheel, bearings were introduced into civilization and every machine since devised incorporates, in some form, means of sustaining a loaded member in…

Abstract

WHEN man invented the wheel, bearings were introduced into civilization and every machine since devised incorporates, in some form, means of sustaining a loaded member in motion by another fixed member. It is not surprising, therefore, that examination of bearings forms a high proportion of all engineering inspection and the phrase “to look at the bedding of the bearing” is probably one of the oldest in engineering practice. During recent years, particularly in the aircraft industry, developments have taken place in bearing design and bearing metals which require an inspection technique differing from conventional methods that served well when loadings were comparatively low and factors of safety high. Desirable clearances and surface condition of the earlier alloys will not answer at all well for some new bearing materials; while on the other hand defects such as minor cracks, which were very dangerous in white metal, have been proved by experience to have little or no effect on some heavily loaded lead bronze bearings.

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Aircraft Engineering and Aerospace Technology, vol. 14 no. 6
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 1 July 1969

W.N. Twelvetrees

THE helicopter presents a classic case of a device for which there is an insatiable world demand that cannot be met because the current state of engineering development…

Abstract

THE helicopter presents a classic case of a device for which there is an insatiable world demand that cannot be met because the current state of engineering development prohibits an economic product. The overriding factor in any airborne vehicle is the necessity of achieving a viable payload and performance at an acceptable cost with dependable standards of safety and reliability. Sensible figures are difficult to quote but it would not be far wrong to indicate that existing helicopters carry an all in cost penalty of 5 to 1 compared with fixed wing aircraft of the same all up weight. It is not surprising therefore that, apart from prodigal military usage and small specialist operations as with offshore drilling rigs, progress over the last decade has been slow. Indeed it would be more realistic to say that in terms of basic design there has been what is more like stagnation, as at least three major projects in the U.K. alone have been dropped after many millions of pounds had been spent on them.

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Aircraft Engineering and Aerospace Technology, vol. 41 no. 7
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 1 September 1944

W.N. Twelvetrees and K.W. Walpole

FEW engineering products receive the abuse to which aero engines are subjected in wartime and few mechanical devices are produced in which the margin of safety and failure…

Abstract

FEW engineering products receive the abuse to which aero engines are subjected in wartime and few mechanical devices are produced in which the margin of safety and failure is so small and yet so vital. Failures on a large scale are, therefore, inevitable and their consideration in detail would present a task of prohibitive magnitude but what little is known with any completeness and certainty can offer some useful data. Consideration of a large number of different makes of engines overhauled during wartime has revealed an amazing complexity of facts; it has shown that failures have developed from almost every conceivable cause which, in turn, have produced every conceivable result. There are few tangible pronouncements which can be made on the subject but nevertheless distinct common tendency has been observed which is sufficiently consistent to be worth consideration. This concerns the general trend of failures and will be referred to later; but with regard to failures in detail, the only safe statement to make is that invariably different parts‐fail on different types of engines subjected to similar conditions of severity in operation. The reason for this is not hard to find, and complexity of design in modern aero engines prohibits the mechanical ideal of simultaneous failure of adjacent parts subjected to a given overload. Not only is the exact functional strength of each individual part hardly known but the loadings which it has to endure cannot be foreseen.

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Aircraft Engineering and Aerospace Technology, vol. 16 no. 9
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 1 April 1899

The Food and Drugs Bill introduced by the Government affords an excellent illustration of the fact that repressive legislative enactments in regard to adulteration must…

Abstract

The Food and Drugs Bill introduced by the Government affords an excellent illustration of the fact that repressive legislative enactments in regard to adulteration must always be of such a nature that, while they give a certain degree and a certain kind of protection to the public, they can never be expected to supply a sufficiently real and effective insurance against adulteration and against the palming off of inferior goods, nor an adequate and satisfactory protection to the producer and vendor of superior articles. In this country, at any rate, legislation on the adulteration question has always been, and probably will always be of a somewhat weak and patchy character, with the defects inevitably resulting from more or less futile attempts to conciliate a variety of conflicting interests. The Bill as it stands, for instance, fails to deal in any way satisfactorily with the subject of preservatives, and, if passed in its present form, will give the force of law to the standards of Somerset House—standards which must of necessity be low and the general acceptance of which must tend to reduce the quality of foods and drugs to the same dead‐level of extreme inferiority. The ludicrous laissez faire report of the Beer Materials Committee—whose authors see no reason to interfere with the unrestricted sale of the products of the “ free mash tun,” or, more properly speaking, of the free adulteration tun—affords a further instance of what is to be expected at present and for many years to come as the result of governmental travail and official meditations. Public feeling is developing in reference to these matters. There is a growing demand for some system of effective insurance, official or non‐official, based on common‐sense and common honesty ; and it is on account of the plain necessity that the quibbles and futilities attaching to repressive legislation shall by some means be brushed aside that we have come to believe in the power and the value of the system of Control, and that we advocate its general acceptance. The attitude and the policy of the INTERNATIONAL COMMISSION ON ADULTERATION, of the BRITISH FOOD JOURNAL, and of the BRITISH ANALYTICAL CONTROL, are in all respects identical with regard to adulteration questions; and in answer to the observations and suggestions which have been put forward since the introduction of the Control System in England, it may be well once more to state that nothing will meet with the approbation or support of the Control which is not pure, genuine, and good in the strictest sense of these terms. Those applicants and critics whom it may concern may with advantage take notice of the fact that under no circumstances will approval be given to such articles as substitute beers, separated milks, coppered vegetables, dyed sugars, foods treated with chemical preservatives, or, in fact, to any food or drug which cannot be regarded as in every respect free from any adulterant, and free from any suspicion of sophistication or inferiority. The supply of such articles as those referred to, which is left more or less unfettered by the cumbrous machinery of the law, as well as the sale of those adulterated goods with which the law can more easily deal, can only be adequately held in check by the application of a strong system of Control to justify approbation, providing, as this does, the only effective form of insurance which up to the present has been devised.

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British Food Journal, vol. 1 no. 4
Type: Research Article
ISSN: 0007-070X

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Article
Publication date: 1 December 1943

H.L. Price

SYMMETRIC AND ANTI‐SYMMETRIC WING LOADING DISTRIBUTIONS IT is proposed to work out the span loading distribution and lift and drag coefficients of an unstalled wing in…

Abstract

SYMMETRIC AND ANTI‐SYMMETRIC WING LOADING DISTRIBUTIONS IT is proposed to work out the span loading distribution and lift and drag coefficients of an unstalled wing in symmetric flight, together with the wing rolling and yawing derivatives for rolling and yawing flight. The only data assumed are a knowledge of the geometry of the wing and of the slope of the lift‐incidence curve of any section of the wing when referred to infinite aspect ratio.

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Aircraft Engineering and Aerospace Technology, vol. 15 no. 12
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 1 May 1946

The action of the Ministry of Food, which was designed to check the abuses that had developed with regard to the advertising of food stuffs and the labelling of packages…

Abstract

The action of the Ministry of Food, which was designed to check the abuses that had developed with regard to the advertising of food stuffs and the labelling of packages made up for the retail trade, is not only most welcome but very necessary in the public interest. The term “misleading” is applied by the Ministry to the proceedings that have led them to take action. It is accurate, but official reticence necessarily causes it to be somewhat lacking in vivacity. The fact is that the consumer, for a number of years past, has been misled by means of deceptive labels and advertisements, as to the real nature of an admittedly important part of his food supply. The wording of the suggested code is incidentally exposure and condemnation of this. The mislabelling of foods has for a very considerable time attracted the attention of Public Analysts and of others who are interested in the purity of our food supply and in public health. We need only refer to the periodical reports of the health authorities to obtain convincing proofs of the need that had arisen for official action. The cruder forms of this particular species of fraud were obvious and scandalous. Others were more subtle and less obvious. With regard to the former we have had “digestive teas” said to contain a lower proportion of tannin than ordinary blends, but found on examination to contain the normal quantity. “Diabetic foods ”containing unaltered starch though the label said otherwise. “Cream” made of nut oil, and so forth. Vitamins then appeared on the scene. Their discovery aroused great public interest, and certain types of food manufacturers took good care that this interest, however unenlightened it might be, should not be allowed to flag. On the contrary, it was recognised as a valuable trade asset and it was therefore encouraged by advertisements which were not characterised by pedantic adherence to accuracy. Accuracy of statement was in fact not demanded at that time by anyone, and it was not supplied by the advertisers who, in apparent confidence, proclaimed in many of these advertisements the superior vitamin content of the food advertised and the peculiar advantage to health that would accrue to the consumer of it. The campaign was entered on with a light heart and was for a time successful. The statements made proved to be very effective stumbling blocks for the blind, and sales, presumably, increased. Unfortunately everybody whose business it was to manufacture certain kinds of processed foods thus advertised began to be involved. The straightforward manufacturer found his interests threatened by the action of his less scrupulous competitors. The unscientific use of the commercial imagination in this respect threatened to bring about a chaotic state of affairs when it was used as a weapon in acute trade competition. The great complexity of the chemical and physiological problems which a study of the vitamins involves was, and is, recognised by all who have dealt with these matters. In 1936 the Medical Officer of Health for Kensington, in a report, dealing with the misleading and deceptive labelling of food, says “originally jam invariably consisted of fruit plus sugar, but keenness of competition amongst manufacturers to secure the ‘lion's share’ of the trade led to the substitution of such cheaper substances as apple pulp, pectin and fruit juices for a percentage of the named fruit, with a consequent lowering of the general standard of the jams placed on the market. The jam manufacturers apparently became alarmed at the chaotic condition which they themselves had created.” The result, as we all know, was the drawing up of unofficial standards for jam by the trade and primarily for the benefit of the trade. The interests of the consumer were by no means the main object of the transaction. We have referred to this episode of some ten years ago and more because the question of the vitamin and mineral content of certain foods both in kind and quantity seemed to be drifting into the same unsatisfactory condition. Some of these foods were made for the benefit of children or of persons in a weak state of health. It was therefore the more important that they should be what they claimed to be. It may be conceded that under certain conditions unofficial regulations are better than no regulations at all, but it is unquestionably better that if regulations are to be made they should be made by impartial official experts and receive ipso facto the support of law. This has now been done. The interests of the consumer as well as legitimate trade interests, which theoretically at least should be identical with those of the consumer, have been taken into account. Under the Labelling of Food (No. 2) Order, 1944, it will be remembered, the disclosure of the quantity of vitamins or of minerals is obligatory. This, however, is not sufficient. Not only must the quantity of vitamins or minerals be disclosed, but that quantity must be such as to justify the claims made in respect thereof, and further the amount of the food “which an average consumer may reasonably be expected to consume daily should contain not merely a significant quantity of the vitamin or mineral in question, but a quantity sufficient in the light of modern nutritional science to justify whatever reference is made to it in the advertisement or on the label.” These remarks are quoted from the preamble to the suggested code of practice in framing labels and advertisements. The code was drawn up in response to many requests from traders to the Ministry of Food, and the composition of this suggested code is the result of the consultation of the Ministry with the Medical Research Council. It is printed verbatim below:—

Details

British Food Journal, vol. 48 no. 5
Type: Research Article
ISSN: 0007-070X

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Article
Publication date: 1 February 1940

TO some, Annual Estimates this year may have a nightmarish quality. Not perhaps so much in the safe areas to which many who had the means to do so have gone with those…

Abstract

TO some, Annual Estimates this year may have a nightmarish quality. Not perhaps so much in the safe areas to which many who had the means to do so have gone with those means and no doubt are contributing part of them to the local exchequers; but in the so‐called “dangerous” areas which have lost them and their means and have, because of their liability to air raids, huge expenditure on A.R.P., the librarian may have a severe battle to get what he needs to maintain his work. Our own policy would be to concentrate, so far as is possible, upon the book fund and on salaries. If these can be retained at a fair amount much good will ensue.

Details

New Library World, vol. 42 no. 7
Type: Research Article
ISSN: 0307-4803

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