In earlier article in this series it was recalled that, in October, 1910, when the Daimler Company had been making the Knight sleeve-valve engine for about two years, and when this engine was attracting a considerable measure of popular approval, the Autocar published an article entitled “Some Criticisms of the Slide-Valve Engine,” by “A Manufacturer of Poppet-Valve Engines,” who claimed to base his criticisms on actual tests, evidently of a 38-h.p. Daimler, but, who insisted on remaining anonymous. The time has now come to re-deem the promise given on that occasion to pursue the further history of this affair and to reveal, in due course, the identity of the critic.
The Autocar had undertaken when the original article had been published that a champion of the “slide-valve engine” would be given an opportunity to reply, and, sure enough, the very next week no less a champion came forward than Mr. Charles Y. Knight himself. Nor could he complain that the journal unduly restricted his elbowroom in the matter: he took more than seven full pages in which to combat his unknown opponent – and I must be excused if I do not do full justice to his eloquence in about one seventh of the space. The anonymity of his critic, which to some might have seemed to place the respondent at a disadvantage, actually gave Mr. Knight free rein for his irony and allowed him to enjoy himself enormously. When, he explained, he first read the article, he exclaimed “An enemy hath done this !” Then he wondered who, among manufacturers of poppet-valve engines, could be so ill-informed, and could not think of anyone. (how he must have enjoyed imagining his adversary squirming at that one !) “Then,” he continued. “a sudden light dawned upon me and I said to myself, How stupid of me not to have thought of this before.’ There are tricks in all trades ” – it must be someone in the Daimler publicity department, determined to draw him out just at Show time; ” Then, I thought – ‘it’s just like Instone !’ and I must say that up to the time of writing Instone has not denied its inspiration !”
Having got off this quip, he promptly drew a red herring across the trail. “I positively know,” he wrote, “it isn’t my old and esteemed friend S. F. Edge. There is no mistaking his efforts. When he used to take up his pen to write upon the sleeve-valve question, he dipped it in vitriol instead of ink . . .” Besides, added Knight slyly, he knows too well the publicity value of adding “S. F. Edge” at the end. Edge, furious, no doubt, that for once he was not in the thick of a controversy, promptly deposited £250 with the R.A.C., accompanied by a challenge to any sleeve-valve engined car to emulate the recent performances of his Napier. A correspondent thereupon upbraided him for trying to make anyone do any such thing at a time of year when the weather was so bad, but nobody else seems to have paid much at attention.
“Efforts have been made,” continued Mr. Knight relentlessly, “to lead me to believe that the article emanated from the chief engineer of another leading company which produces six-cylinder cars exclusively. It is positively known that the Rolls-Royce Company did some time ago purchase a 38-h.p. Daimler chassis for the purpose of studying the motor ” – but he cannot believe that any firm of standing would publish the results of a test made of a rival’s product in secret, with no opportunity for the rival to be present and see that the tests were fair, and he is sure that Mr. Royce would not write anonymously to belittle the products of a competitor and boost his own. (Oh! whose pen is dipped in vitriol now ?) Besides he can exonerate Mr. Royce from holding the views of the anonymous critic, who declared that the sleeve-valve engine was inherently noisy on account of its large exhaust ports and that this could only be corrected by a silencing system which caused loss of power, because Mr. Royce “has spent valuable time and much money in an effort to perfect a motor possessing those exact qualities.” he then goes on to refer to the specification of a patent which Royce had taken out in 1909 for a piston-valve engine which from the drawing looks exceedingly interesting. The two piston valves, operated by push-rods and eccentrics from two camshafts in the crankcase, were placed at an included angle of 90 degrees in a hemispherical cylinder head, and the specification refers to the fact that the exhanst ports can be opened and closed rapidly and can stay open for a long time, while “the noise caused by the poppet valves dropping on their seats, which is present in the ordinary type of engine, is absent.” All of which, undoubtedly, could as well be said about the sleeve-valve.
So far Mr. Knight had had a great deal of fun but had not gone far towards answering the criticisms of his adversary. Now, however, he proceeded to take these seriatim, but not, for some reason, in the original order. He started with Fuel Efficiency, under which head his critic had declared that it was yet to be shown that a sleeve-valve engine could equal the performance of the four-cylinder Vauxhall or the six-cylinder Rolls-Royce in the 2,000 Miles Trial of 1908. This, he said, could not have been written by Mr. Royce because he would know how much better, in the 1909 Scottish Trials, the sleeve-valve Minerva had done than either – and he did not even have to mention Daimler for this thrust ! The figures, he said, in ton-miles per gallon, were : Minerva, 1909, 44.57; Napier, 1910, 42.57; 24-h.p. Vauxhall, 1909, 41.65; 20-h.p. Vauxhall, 1909, 41.16; Rolls-Royce, 1908, 40.98. The Rolls-Royce, in case it really was Mr. Royce, was at the bottom of the poll.
This seemed a pretty good point, but under the heading of Power, where his critic had talked about output in relation to engine size and weight, Mr. Knight was much less convincing, contenting himself with recording that, between Chartres and le Mans, Lord Montagu of Beaulieu in a 38-h.p. Daimler had done 32 miles in 45 minutes, and between Argentan and Bernay, 18 miles in 20 1/2 minutes. At the end of these scorching exploits, according to Lord Montagu, the tyres were very hot but the engine was quite cool. This, no doubt, was very satisfactory, but does not seem to get us much farther with regard to power in relation to engine size or weight.
On the subjects of Silence and “Foolproofedness,” the critic had suggested that the sleeve-valve engine was apt to he noisier unless it was given a restrictive silencing system, on account of the size of those exhaust ports and the time they stayed open, and that when chauffeurs with no mechanical perception raced their poppet-valve engines, they were warned to desist by the rattling of the valves (which I should have thought indicated some mechanical perception), while sleeve-valves gave them no such warning. On these points Mr. Knight replied that in Paris recently some enthusiasts had indulged in a game of guessing the identity of a number of invisible but very clearly audible engines, run without any silencers, and had easily recognised the relative softness and silence of the Daimler exhaust in these cacophonous circumstances: And as to the chauffeurs being warned by the rattling of their poppet valves, well, said Mr. Knight, in a phrase in which one can positively hear an American accent at forty-odd years’ distance, “If the sleeve-valve doesn’t give this warning, it’s because it doesn’t make the noise; isn’t it ?”
With regard to Engine Vibration, the critic had made a point which, when I read it, seemed to me to be a good one, namely that all valves were inherently out of balance but that with sleeve-valves this was a more serious matter because they were heavier. Mr. Knight, however, while agreeing that poppet valves were lighter, contended that on account of their springs they actually gave rise to more vibration, which at least seems plausible. With regard to Smokelessness, however, he was obviously on weaker ground, and contented himself with saying that it all depended on the design of the lubrication system.
On the score of Simplicity – or rather the lack of it – the critic had attacked the sleeve valve because it needs lubrication. Mr. Knight more or less conceded this point, but declared that if you were going to deny yourself nice things because they might give trouble, you might begin by dispensing with pneumatic tyres. Besides, he added, what is most likely to break in any type of engine is the piston, and if this happens it usually makes a pretty good mess whether the engine has sleeve valves or not. Of course he was convinced that his critic was not Mr. Royce, but still it just seemed worthwhile mentioning that in the 1908 Trial one of the Rolls-Royces had broken a piston. With regard to six-cylinder engines, he declared, these, whether they have poppet or sleeve valves, cannot be both efficient and silent. Of course he was convinced that his critic was not Mr. Royce, but still it just seemed worthwhile mentioning that in the 1908 Trial, when efficiency only was at a premium, Messrs. Rolls-Royce had themselves apologised for the noisiness of their cars. Today the main proposition seems decidedly surprising, but it remains it fact, in my experience, that right up to the time of the early Phantom II, Rolls-Royce had only got to put a bit of punch into an engine, and all the Rolls-Royce qualities were punched right out of it. That fact, if it is one, however, has nothing to do, as far as I know, with poppet or sleeve valves. Finally, said Mr. Knight, the makers of sleeve-valve engines have not yet had time to take all the records, but, in April, 1909, a Daimler sleeve-valve engine was run on the bench continuously at 1 1/2 times its rated power for 5 1/2 days; then put in a standard car to do 2,000 miles on Brooklands at over 40 miles an hour; and finally put back on the bench to run for another five hours, in the course of which it actually showed increased power. As an engine test that, he thought was a good enough record to be going on with; and with this sentiment the present-day commentator may be inclined to agree.
The Editor had undertaken that, when both sides had had their say, he would sum up, and this he proceeded to do on October 29th. I am sure that his successor will forgive me, however, if I say that in the course of this summing up he indulged in a fair measure of what would nowadays be called waffling. He obviously found it hard to believe the critic’s allegations about the inevitable loss of power in the sleeve-valve engine from the “choking of the carburetter,” and ventured the opinion that if they were true engines of this type must be basically even better than their sponsors claimed; on the other hand he came down quite firmly in favour of sleeve valves being smokier. He also discounted Mr. Knight’s table which showed the Minerva at the absolute winner on a fuel-consumption basis by pointing out that a Maudslay industrial chassis had achieved a figure of no less than 62 ton-miles per gallon. But, on the score of Power, and Noise, and “Foolproofedness,” and Engine Vibration, and Simplicity, and Durability, he really thought that there was nothing in it, and finally reached the conclusion that “perhaps the truest statement would he that there is no conclusion.” Cars, he added, must really be judged by the chassis as a whole, which, is, I suppose, equivalent to saying that a good chassis with a good engine is likely to be better than the same chassis with a worse engine, but which hardly gets one much nearer to deciding what is the best form of valve gear. The lot of those who sit upon the fence is always hard, however, and all the Editor got for his pains was a letter from a correspondent who described his summing-up as “so one-sided and unfair that you are liable to be credited with running down the slide valve simply to get popularity with the many makers of other engines.”
I should hardly have thought myself that this was a fair inference to draw from an almost excessively innocuous editorial, but it is true that the Editor showed some signs of failure to appreciate the breezy style of Mr. Knight’s article, into which, he complained, the author had introduced “an undue degree of personality and advertisement.” By November 5th, however, it was clear that at least one reader was far from appreciating the style of the original critic; and this reader was none other than F. W. Lanchester, who took it upon himself to deliver his own reply to the still anonymous “manufacturer of poppet-valve engines.” He was, he wrote, competent to do so, as a manufacturer of poppet-valve engines himself, as one who was associated with the development of the sleeve-valve engine, and as one who had been interested in internal combustion engines since the days of the old Otto engines with slide valves. He had, moreover, at least never been very conventional over poppet valves, for in his original engine he had used the same one as both inlet and exhaust, at the time of this controversy he provided a separate one for each function but arranged them at right angles to the axis of the cylinder, and, as already mentioned, he had recently patented a single sleeve-valve engine. In this engine, according to the specification, the sleeves were operated not by a cam but by eccentrics through the medium of a rocking lever “by which the sleeve is caused to move rapidly, then dwell in mid-position during the working and compression strokes, then to move rapidly into the open valve positions.”
Apart from his record as a designer, it is immediately clear from Lanchester’s contribution to this controversy that his was a clear and incisive mind which abhorred vague criticisms and defences; and it was upon the criticisms that he let loose his invective. “I object to the article published in the Autocar of 15th ult.,” he wrote, “on the dual ground – firstly that it is a very unsound piece of argument from start to finish and as such appears to be a very much prejudiced attack on the sleeve-valve system; and, secondly, that as a defence and vindication of the poppet valve it is an unworthy and unconvincing piece of work . . . A greater conglomeration of trashy argument in a given space it has rarely been my lot to read … there is not a single legitimate criticism to be met or answered . . .”
The sleeve valve, he went on, has solved at a single stroke a problem that has been attacked again and again by designers of poppet-valve engines, namely how to get large valves and port areas in conjunction with a compact combustion space. If the valves are in a pocket, either they must be small or else the combustion space will not be compact. There had, he continued, been various attempted solutions: Thornycroft and Maudslay had used “inverted valves,” and Pipe had used valves at 45 degrees. The contemporary objection to all of these solutions, although Lanchester did not say so, was doubtless that they were considered noisy, for which reason their use was deprecated, during the next few years, even on racing cars. The critics of sleeve valves, who contended that their vaunted silence hardly improved on that of poppet valves, which were “pretty silent,” little dreamt, probably, that in forty years’, time they would hardly be able any longer to tuck these away in a pocket, but would have to keep them quiet as best they could even when overhead camshafts or push-rods and rockers were adding to the clangour.
“One of the most successful of these special valve arrangements,” added Lanchester complacently, “is the Lanchester, for which I am myself responsible” – in which the valves were horizontal and opposed, because the exhausts could be directly water-jacketed, whereas overhead valves involved removable valve seats.
He next produced an exceedingly interesting piece of statistical information. “The sleeve-valve engine,” he wrote, “is very much an established fact (approximately one quarter of the total output of Great Britain are (sic) sleeve-valve engines built by the Daimler Company)” – a fact which I for one would never have guessed. Nevertheless. he thought there was room for both systems, but “the manufacturers of the poppet-valve engines will need to compete with the sleeve-valve engines by maintaining a high degree of excellence of their own product and not by anonymously running down their competitors’ goods.”
In the course of his contribution, it seems, Lanchester indulged in some speculation as to the identity of the critic, but this, unfortunately for posterity, was suppressed by the Editor, because in the same number of the paper his identity was revealed by the critic himself. Suspicion, unjustly as it proved, had inevitably fallen upon Royce; and the critic in consequence felt obliged to disclose that the author of the original article was not Royce, but his co-director Claude Johnson, who, however, admitted that Royce had checked It. But “Mr. Royce entirely disapproved of any suggestion that the results of experiments and conclusions arrived at should be made public. The responsibility for the publication of the information is, therefore, mine and mine alone …”
Today the sleeve-valve engine, for use in motor cars, is, at least apparently, as dead as the dodo; but it was not killed by Claude Johnson’s article. If Royce concluded in 1910 that its devotees were following a blind alley, how right he was! And if he “entirely disapproved” of these conclusions being made& public, at any rate on the lines that his co-director chose, again, how right he was!