The Purchase Department.
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Where to Buy your Supplies. t A Cleverly-designed Speedometer and its Drive.
Although many important firms arc manufacturing speedometers, there does not seem tf, be any accepted practice so far as design is concerned. Many types of speedometer, including magnetic, centrifugal, friction, and clockwork are in daily use, and are giving satisfactory results in service. We should imagine that the construction of a satisfactory speedometer embodying the magnetic principle, calls for a higher degree of skill than does the construction of other types. Recently we visited the premises of the A.T. Speedometer Co., Ltd., situated at 140, Long Acre, and were pleased to witness the care taken in the construction of these well-known recorders. A large sum of money has been spent on testing plant of many descriptions. Before leaving the company's works each appliance is tested for calibration, and, if not satisfactory, is returned for further adjustment before being sent out. The indicating body on the A.T. has no mechanical connection with the drive ; it is therefore unaffected by shocks. A satisfactory instrument, so far as calibration is concerned, does not mean, however, that it is ready for sale to the everyday user. The drive from the cardan shaft or wheel to the speedometer, forms a very important feature. We, personally, have experienced much annoyance from time to time, owing to the breakdown of the transmission from the road wheels or shafts to the speedometer. In an effort to overcome this trouble, the A.T. Speedometer Co., Ltd., has expended much money and Lime. We illustrate the clever metal protection for the driving shaft
now employed with the appliances. The outer covering consists of a length of flexible brass tubing, strengthened on the inside by a second tube composed of coiled steel. Inside this runs a link chain, which is strong enough to transmit the drive either on heavy racing motorcars or on 40 h.p. delivery vans without breaking. Judging by the recent great increase in the sales, users are appreciating the efforts made by this company to provide a reliable and efficient speed-registering appliance. A notable feature with these instruments is the fact that a guarantee for 12 months is given with both speedometers and transmission gear.
A Factor in the Problem of Silence.
The Editor of this journal remarked some two weeks ago, when giving evidence before the Committee appointed to deal with the traffic problem by the House of Commons, that the motorbus had now achieved such silent running that it had become a danger to the public. The saying was widely quoted in the Press both here and abroad.
It has not been without a tremendous amount of investigation, however, that tha exhaust silencing of internal-combustion engines has satisfactorily been secured. We are not overstating the case when we remark that, in our opinion, 75 per cent. of the silen,cers at present manufactured are wasteful and inefficient. A few years ago silence was effected by the deliberate wastage of power. Even then trouble was experienced from many unexpected sources. The choking of the outlets when running at slow speeds, the inefficiency of the device so far as silence was concerned when running at high speed, and several other points demanded careful investigation.
A satisfactory appliance designed to secure silence in the exhaust of motor engines is that known as the Dunlop. This is designed on the injector principle, and consists of three expansion chambers formed by conical diaphragms perforated at the top and bottom alternately. The simplicity of the appliance is one of its most advantageous and striking features. It is strongly constructed and unlikely in ordinary usage to get out of order. In service many favourable expressions of opinion have been given as to its good qualities, and we understand from the maker, the Dunlop Motor Co., Ltd., Kilmarnock, N.B., that the demand from all types of users is a continually increasing one.
White and Poppe Carburetters
Improvements in connection with the carburetteis associated -with this well-known Coventry maker, will at once command the interest of a very large number of users. White and Poppe, Ltd., Lockhurst Lane, Coventry, is in the enviable position of having, by now, completed a. series of exhaustive tests of carburetters, extending over many years, which has enabled a carburetter, embodying many improvements suggested by these experiments, to be placed on the market. Any modification in design, or improvement in manufacture of these fittings, will undoubtedly be for the benefit not only of the user of this maker's appliances, but also of those engine manufacturers who fit the White and Poppe to their products as standard practice. The latest improved form of this carburetter is known as type B. The chief improvement lies in the fact that the jet and throttle are now placed in a horizontal position. Many of our readers are familiar with the old type in which these fittings were vertically disposed. This modification has been brought about, we are informed, with the view to evolving a. more compact fitting, and also to provide that adjustable parts of the throttle will be more easily accessible. That this result has been satisfactorily achieved is evidenced by the fact that the latest model occupies something like 50 per cent, of the space taken up by the older type. Adjustments, necessary to ensure either a rich or weak mixture being supplied to the engine, can readily be made in a few moments. To ensure the satisfactory running of engines of either large or small bore, a correct mixture of gas and air is, of course, important, and so the cam-shaped disc for air regulation, which has been identified with the White and Poppe carburetter for so long, is still retained. The illustration gives an outside view of the latest model, on which the adjustable operating lever, and the disposition of the dirt-trap in the petrol-pipe lead, is clearly shown.
A New Lubricant.
Mr. B. W. Shilson, 28. Spencer Avenue, Coventry. informs us that he has taken up an agency for Oildag. a lubricant in which diffused graphite enters largely into the manufacture. Graphite has long been recog• nized as a suitable medium for lubrication, provided it be free from grit and other dangerous impurities. In the preparation of Oildag, it is claimed that the graphite, treated electrically, comes out of the furnace in so fine a state that, when placed in water, it, will run with the water through the finest filter paper.
Training the Driver by Correspondence.
'We were recently afforded an opportunity to inspect the headquarters of the International Correspondence School, which are situated in Kingsway, W. Many of our readers are acquainted with the clever advertise meats of this institute, which conducts a series of lessons dealing with many modern trades and businesses. The particular course in which we were greatly interested was that dealing with the internalcombustion engine. On our acquainting the secretary of the institution of our desire to inspect and report on the schools, we were at once afforded every facility for doing so. A unique organization has now been built up, and we are informed that many thousands of students are engaged in taking the course dealing with this subject. On first enrolling, the intending student submits himself to a preliminary examination for the purpose of showing how much knowledge on the subject of internal-combustion engines he has already in his possession. When his answers to the questions put to him have been examined by a duly qualified man, a course of lessons is arranged for him. All the text books supplied for this purpose are kept fully up-todate, and they have all been specially written for the International Correspondence School, by members of the staff, assisted by leading experts of all countries. Improvements taking place in the internal-combustion engine from time to time are noted and fully illustrated and described in a series of pamphlets which is issued as soon as possible, and which is later on incorporated in the new editions of the text books. The lessons given are progressive, and each carries with it an examination paper which the students are required to fill up and forward for correction and advice. Should the answers be fairly satisfactory, the learner is required to give attention to the particular questions in which his knowledge is not quite so complete. By this means he is firmly grounded in each subject before proceeding further with the course. This is where such individual tuition as this is scores over the extension-school system, with its class of students all working together. We have assured ourselves that every consideration and care is given to the studying and correcting of the papers sent in The difficulties experienced by each student are dealt with as they arise by competent and experienced teachers. It is, of course, impossible for a driver to be taught driving and practical work, or the repairing of motors and accessories. He can, however, by means of this correspondence course obtain a good theoretical idea of all descriptions of motors and transmission systems.