Summary of Mr. Dugald Clerk's Address.
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Mr. Dugald Clerk, M,lnst.C.E., F.C.S., whose knowledge of all matters concerning internal-combustion motors is profound, had a difficult task, on Monday evening last, in endeavouring to read something of interest into the tests which were undertaken, between April and July last, at the Putney laboratory of this society. It is a matter for keen regret that pressure of engagements had prevented many of the lubrication corn mittee from giving that measure of attention to the subject which the original programme deserved, and we cannot help but think that the meagreness of the results to date reflect somewhat upon those who were responsible for the suggested undertaking in the first instance. We sincerely trust that Mr. Dugalcl Clerk's appeal for full and proper investigation of the many problems which remain to be solved, in the matter of the practical application of internal-combustion e gines to road vehicles, will receive that share of support, alt the hands of the Society of Road Traction Engineers, or of
e Society of Motor Manufacturers and Traders, which lat r body has the necessary funds at its disposal, before
other year is passed, and some little consolation may be fund in the fact that the records of last summer's tests will ai least serve a useful purpose in indicating the necessity for a careful planning of the scheme of the tests in advance. Whilst Mr. R. G. Roberts, who conducted the tests, has undoubtedly done his best under somewhat adverse circumstances: he has unquestionably suffered from the absence of sympathetic co-operation and a definite programme. We would specially mention Mr. Clerk's insistence upon carburetter adjustment for maximum economy, in preference to maximum power, as the more ideal course, because such a choice unquestionably tends to perfect combustion.
Lord Montagu, the Honorary President of the Society, who presided at the opening of the proceedings, drew attention to the wider influence which the Society as now organised ought to wield. With regard to the position of the heavy vehicles, with which the Society was more closely identified than with other forms of mechanically-propelled vehicles, the position in London presented special features and problems of its own. The altitude taken up by the public, the police, and road authorities lied made the position of the road engineer a difficult one, but he believed these difficulties would be surmounted, and that they would not prejudice, except for a short time, the progress of the mechanical road vehicle. One of the recent features of London traffic had been the success of the motorcab, and these had been in the hands of drivers of such experience that there had been a relative immunity from accident. If he might yenttere a suggestion in this connection, it would be that the public were always willing to sacrifice a little speed in return for the sense of security.
With regard to the future of the inotor-omaibus, it was iaevitable that there should be checks to progress from time to time, but, when one had regard to the inconvenience of tramcars, one could not but feel that the motor omnibus had a great sphere of usefulness before it. It was but little over three years since the motorbus first made its appearance in the Metropolis, and no one could fail to be struck with the progress which had been made. The motorbus of to-day was infinitely quieter than its predecessor : it was well driven, and it was comfortable, and, in his opinion, it was destined to equal, if not to surpass, the usefulness of rival forms of traction. (Applause.) The Address.
Following the remarks of the Honorary President, who here vacated the Chair in favour of the Chairman of the Society, Mr. George Pollard, Mr. Dugald Clerk laid before the meeting a summary of the results of the Society's lubrication experiments. He said that the experiments were carried out for the lubrication sub-committee of the Society by Mr. Reginald G. Roberts, in a laboratory at Putney. It was originally intended to make experiments on several engines, but the Society, which was a young one, had carried out the research entirely at its own expense, and it had been found necessary to confine the experiments to one engine. This was a Milnes-Daimler engine, of the 1907 type, with four cylinders, each 4 5-16 inches in diem., by 51. inches of stroke, and a standard speed of 850 r.p.m. Forced lubrication was employed. The maximum brake horse-power given by that engine, at rated speed, was 30h.p., but the average b.h.p. at the full load tests was 25.3. On Automobile Club rating the engine was 29.7h.p. Lubricating oil was obtained from two firms, each firm supplying a thick and a thin oil, so that four oils were tested, and also various mixtures of the thick and thin. A water-cooled brake was used to measure the brake power given out by the engine, speed was taken by a tachometer, and both petrol and lubricating oil was measured accurately. The temperature of the oil in the crank-chamber was taken, and that of the cooling water. The tests were made with five different brands of petrol. In all, nineteen tests were made, of which thirteen were at full load, three at three-quarter load, and three at half load. Each full-load trial lasted five hours ; each light-load trial two hours.
With oil "A," six, full-load, five-hour trials were made, and the results were as follow : With a mixture of thick and thin (25 per cent, thick, and 75 per cent. thin) a consumption of 17.8 oz. per hour, or 0.7 oz. per b.h.p hour. With thin oil only, 28 oz. were required, or 1.03 oz. per b.h.p. hour. Six, full-load trials were also made with " B " oil, with the following results : Thick oil, 15.4 oz. per hour, or 0.6 oz. per b.h.p. hour ; with a mixture of 50 per cent, each of thick and thin, the consurnprion was 15.6 oz., or 0.63 oz. per b.h.p. hour, and, with thin oil only, 24 oz. per hour were required as a minimum, the maximum being 33 oz.
The light-load tests were afterwards made, but the results were somewhat irregular, and, in most cases, with the same mixtures, more lubricating oil was consumed than at full load.
When the oils were examined, after use, it was found that the nature of the "B" oils, which appeared to be pure hydro-carbon, had changed very little in the crank-case, but that the "A" oils had undergone a considerable change during the five hours. In the case of the "B" oils, the following figures represented the specific gravity at the beginning and end of the tests of different samples :—At beginning of test, light oil, 0.875 s.g., and, at end, 0.874 s.g.; thick oil, beginning, 0.887 s.g., and end, 0.887 s.g. ; for the 50 per cent, mixture, beginning, 0.880 s.g., and end, 0.878 s.g. In the case of the " A " oils, the figures were as follow :—Beginning of test, 0.912 s.g., and end, 0.880 s.g.; beginning, 0.884 s.g., and end, 0.876 s.g. ; beginning, 0.935 s.g., and end, 0.880 s.g.
The tests showed that, although both oils lubricated very well indeed, there were advantages in using the " B " oil, if the oil had had to remain in the crank-case for further running.
Petrol Tests and Exhaust Gases.
Tri the case of the five samples of petrol used, the best consumption results were : for two of the five, 0.076 gallon per b.h.p. hour ; for another sample, 0.087 gallon per b.h.p. hour ; arid for the other two, 0.093 gallon per b.h.p. hour. Considerable differences were revealed, in the course of the experiments, between the light and heavy petrols, in relation to the Composition of the exhaust gases, and their physiological effect upon the experimenters. The prejudicial effect of certain of the exhaust gases upon the observers was not, perhaps, to be attributed to the petrol, but to the fact that the carburetter had not been specially adjusted for each fuel. The jet was maintained the same Ceiroughout the experiments, and all that was done was to open up the air supply as wide as possible when using the heavier petrols.
He wished, in this connection, to combat a very pernicious error, and one cherished by some members of the motor trade, that carbonic oxide was not a poison. As a matter of fact, four or five deaths had followed the inhaling of a comparatively small quantity of carbonic oxide. There was no necessity that a petrol engine should produce carbonic oxide in the exhaust, but it was very difficult to get a carburetter to take the proper proportion of air and petrol at all speeds. It might be interesting to give some figures on this subject. In the course of these experiments, during which the observers fainted several times from breathing the exhaust gases, it was found that a 0.760 s.g. petrol gave off noxious fumes, that another petrol, 0.721 s.g., was innocuous, a third petrol, 0.753 s.g., was noxious, and a fourth, 0.710 s.g., gave off an innocuous exhaust. The noxious gases did not affect the power of the engine; indeed, rather more power was obtained with the noxious gases than without, but not with the same economy.
(To be continued.)