The Daimler-Knight Engine.
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The discussion that was commenced on the 15th instant, after the reading of a paper at the Royal Automobile Club, by Mr. Charles V. Knight, was resumed on Thursday last at the
a.A.C. There was no lack of speakers, and the points raised were chiefly in the nature of technical criticism of the interest.ng engine which has been adopted by the Daintier Motor Company (1904), Limited, of Coventry, for its 1909 models. It is to be regretted, however, that an unnecessary amount of heat was brought into the discussion by some of the speakers. After a few introductory remarks from the Chairman, Mr. Dugald Clerk, F.R.S., Mr. ALEXANDER CRAIG essayed at some :ength to disprove most of the claims which had been put forward by the inventor. On the question of silence, he entirely disagreed, and stated that there are a number of cars now that are conspicuous for extreme silence when throttled clown. With regard to the inventor's claim for the smooth running of his engine, and which he ascribed to the absence of cams, Mr. Craig thought that Mr. Knight was again wrong, and expressed the opinion that the tremor at high speeds, which is a well-known occurrence in a four-cylinder engine, was clue to a slight want of inertia balance of the main reciprocating parts. Mr. Knight had stated that he attributed the flexibility of his engine to the shape of the combustion chamber, but it was contended by the speaker that this particular engine was not unique in that respect ; the principle of a pocketless combustion chamber had been enunciated by the Chairman many years ago, and he did not think that the flexibility of the Daimler-Knight engine was due to any very special design of the engine so far as its combustion chamber was concerned. It was due, he thought, to the carburetter.
In the course of his paper, Mr. Knight had made a rather unfortunate statement, which read as follows: " We welcome enquiry on all points about the engine: the more expert the
enquirer, the more interested we are, but we deprecate criticism obviously made with a view to prejudicing the prospects of•this
engine commercially." Mr. Knight was reminded by Mr. Craig
that engineers in this country, when they met to discuss technical matters, went into them as thoroughly as possible, and that "it
was not fair to hold them up by an expression like that, arid to give an impression to the general public that there was an ulterior motive in the criticism of those taking part in the discussion."
Many minor details in the cnnstructon were also criticised hy Mr. Craig, and he next dealt rather fully with the claims for mechanical efficiency which had been put forward by the in ventor, but the speaker was rather sceptical of the accuracy of some of these claims. Mr. Knight had, at some length, ex plained how, in spite of the great pressure under which the valve sleeves were moving, they were really aided by the piston in their downward stroke when the pressere was greatest, thus helping to secure a very high mechanical efficiency. Mr. Craig reminded the Author of the paper that, if the valves. were helped by the piston, they undoubtedly took work out of the piston, and he failed to see how mechanical efficiency could in this way be assisted.
Mr. S. F. Foca was the second speaker, and he, as might be expected, championed the caus-e of the six-cylinder engine. Hssubmitted a host of figures to show that the petrol consumption claimed by Mr. Knight could not by any means be considered exceptionally good. He expressed the opinion that, if Mr. Knight had gone to that meeting with records officially obtained nnd certified by the Club, it would have been more impressive than a mere statement as to improvement in flexibility. On the questinn of lubrication, Mr. Edge suggested that an engine which required splash lubrication in the years 1908 and 1909was obsolete from the start.
Loinn MONTAGU OF BE AULIE1 gave the results of his observations when driving a Daimler-Knight car, in which he had recently toured in France, and, taken on the whole, his views were very favourable to the inventor. ITe concluded his remarks by stating that he thought it was the best four-cylinder engine he had ever handled.
Mr. F. R. S. Biachaar thought that, with all due respect to Mr. Knight, he could not accela statements about performances in works. For instance, he stated : " If the thermal efficiency were taken on a bench test, one knew that, with a good and regular speed running on a dynamo, one could set the car
buretter and everything else se that a very high thermal efficiency could be obtained." Another point he raised was,, supposing a piston should seize up in its valve sleeve, the engine would not stop ; the valve sleeve lug would be torn away from the cylinder containing the seized-up piston. 'This speaker stated that he did not think very much of the claim of having combustion chambers all of the same size. To start with, he stated, he had hardly ever seen an engine that had got the same mixture in all the four chambers, and the exhaust gas analyses from the four exhaust pipes would reveal this. He also did not agree with the claim for number of parts, and cited a case of an ordinary type of four-cylinder engine in which the number of parts compared favourably with those in an engine of the Daimler-Knight type. Mr. T. B. BROWNE was of opinions that the large size of the ports in the valve sleeves w.mld ultimately lead to knocking, due to the striking of the edges of the compression ring against the edges of the valve ports. He also took exeeption to the concave form which had been given to the piston, and suggested that it formed a convenient bowl for the collection of carbon deposit. Mr. Ar STIN'S remarks were chiefly confined to the questions or noise and the relative merits of valves of the mushroom and of the sleeve type. He gave it as his opinion that, "if de signers examined and criticised the engine fairly, they would probably arrive at a better result than they would if they imagined that everything they had done up to the present was perfect, and that, if they followed Mr. Knight's view, they might yet be doing very wrong. At the same time," he thought, " their practice and experience would lead them to know that
some parts of the engine and some of the design were against
the weight of evidence which they had accumulated in practical experience of engine design." He thought that the noise of the hammer of the tappet in a well-designed and carefully-made eugine was nothing to be cempared with the noise that was given out by the gears in the gearbox. The mushroom-type valve, he claimed, gave such a comparatively small amount of
trouble, that he could nut see arty reason for the elaborate design by Mr. Knight. Ile had known mushroom valves to
runt from 15,000 es 18,000 miles without even re-grinding. He agreed with the inventor ont the question of the uniformity in the size of all the combustion chambers, and he thought that a considerable amount of the smooth action of Mr. Knight's engine might be attributed to this cause. It was not the main thing, but he thought it was a very important point. Looking at the design from a purely theoretical point of view, Mr. Austin said he did not believe that Mr. Knight's engine would give greater power or efficiency than, say, an engine where each cylinder had valves in the head opening into the combustion space. He could not see how any system could be better, purely on -the score of efficiency. Mr. 0. J. F. Kxowras' remarks were brief, but decidedly pointed. He thought Mr. Knight suffered from a disease rather
common among designers who were working on a new line. "Mr. Knight," he said, " knew the state of things when he started on his experiments. but it v as not clear that he had kept entirely up-to-date since.
Mr. WORRY BRAT:MONT thought a was a case such as is frequently found where the amateur had dared to do what the
trained engineer would not have attempted. Mr. Knight had arrived at certain results, and, as far as they had gone, one must admit, said Mr. Berturnont, that those results were apparently practical and extremely instructive. What would happen as a result of long-continued working was a matter for experience. Mr. SIIRAPNELT. SMITH disagreed with MT. Bircham On the point of exhaust gas analyses, but gave it as his opinion that, if it could be proved in actual practice that absolute uniformity of the sizes of all the combustion chambers was an essential point, he did not see any reason why an engine with mushroomtype valves could not be made with an equal degree of accuracy. Mr. CHARLES V. KNIGHT then rose and delivered a very entertaining reply to his many critics. rack of space prevents us from dealing, with this at any length, but the fell text of his reply will be found in the current issue of the " Royal Automobile Club Journal," in which also appears a verbatim report of the entire discussion.