KISSING THE POPPETS GOODBYE
KISSING THE POPPETS GOODBYE
With the N.S.U.-Wankel Rotary Engine in the News, the Editor Considers the Many Endeavours Made to Abolish Pistons and Poppet Valves
I4AsT year I devoted myself in these columns of close-packed type as to whether Sunbeam or Peugeot was the first to produce an engine having the advantages of a hemispherical combustion chamber with the simplicity of push-rod valve gear. This article dismissed various derivatives on this theme and it aroused considerable interest, but it merely looked at a means of making an efficient engine. without recourse to twin overhead camshafts, an engineering instance of having the cake after eating it. My good friend Laurence Pomeroy, ALS.A.E., brought evidence that Sunbeam, with a lorry engine. may have led Peugeot to the. cross-push-rod valve gear, and front the ensuing discussion some interesting subsidiary evidence has come to light. For instance, it has been pointed out to me that the hemispherical head itself was probably introduced by Bucket, circa 1898, and that it was employed by Pfaender for the Pipe car engine of 1902. Push-pull actuation of inclined o.h, valves front a crankcase-located camshaft was seen on Fiat racing engines as early as 1904/5 and it has been suggested to me that Beechia, who went front Fiat to Sunbeam in 1922/3, may have evolved the cross-push-rod valve gear of " Pomeroy's " Sunbeam. Developing this theme, my correspondent goes on to consider who pioneered the twin overhead camshaft engine which the valve gears I referred to in MOTOR Settler last March twelvemonth sought " " to avoid. Ile reminds me that this valve gear figured in the 300-h.p. Delahaye Titan marine engine used in the motor-boat Dubonnet " which was so overwhelmingly successful at the 1905 Monaco Meeting, although the two upstairs " camshafts in this case actuated six valves in each cylinder, which were vertical, not inclined, in the heads. The same gentleman takes me to task for suggesting that the war by the Bristol engineers; he argues that Or. Porsche used B.M.W. led with the form of cross-push-rod valve gear, copied after
this layout for the P-Wagen or Auto Union Grand Prix engine he put-on the drawing-board in 1933. My defence is simply that 1 was concerned in the main with production engines. All this is very interesting-1 hope 1---but does merely concern one
problem confronting a limited number of designers, namely, how to keep the most efficient form of cylinder head ivhile simplifying the valve gear to obviate the use of twin o.h. camshafts or even a single o.h. camshaft with rockers reaching out to the inclined valves. Since 1 perpetrated this discussion, news and much technical dissecting of the revolutionary N.S.U.-Wankel rotary engine has come to hand, which is altogether a bigger step forward in internal combustion technology. Moreover. after I had spent a night tossing and turning in bed considering this new engine and whether it. will sound the deathknell of pistons and poppet valves. I arose to read
in a daily paper that the Rover engineers are aiming to put a massprodnetion paraffin-consuming gas-turbine car on the market in two years' time. On the face of it, these seem sure indications that soon we shall be kissing the poppets (and cranks and pistons) goodbye.
However. I have something of a reputation for being a cynic and I cannot help the observation that much of the discussion about the Wankel engine has been court-rued with whether it will prove a Practical proposition and that the journalist who foretold the people's " jet " Rover had the perception to conclude his announcement by remarking that the Rover terlinicians have two problems to solve, those of decreasing the average paraffin consumption from 14 to 20 m.p.g. and of speeding up while reducingthe cost of the handforged components which the gas-turbine demands in order to combat high internal temperatures.
I do not propose to give my views as to whether all motorcyclists and tome car owners will be. respectively, 'Wankel-propelled and turbine-projected a few years hence. The enormous resources of the great N.S.U. concern -may well make a Success of this newest rotary engine, which has the merits of being extremely compact. light, and very smooth, and certainly the Rover Company have had a great deal of experience of taming the turbine for motor-car installation.
The gas turbine, of course, runs on paraffin, which is an illegal fuel for road vehicles, while the power output of the Wankel engine, 27 b.h.p. at 17,000 r.p.m. front 125 c-c., is not particularly impressive when compared with a piston engine of equivalent size, which in the opinion of ninny critics represents a swept volume of 375 c.c., a theory which a jolly little " diagramatic " model of the Wankel engine.-whieh N.S.U. have sent to me seems to bear out. All I mutt setting out to do in this article is to sound a note of caution that may save the over-optimistic front disappointment, by reminding the rising generation that many experimental engines have
been built down the years, none of which, with the exception of the heavy oil engine, have been able to establish themselves on a commercial footing. Before we go on to look at some of these ingenious variants of the conventional i.e. engine, we can
emphasise this thesisby quoting the case of the sleeve-valve.---a definite Attempt to kiss the poppets goodbye.
Over fifty years ago the even then ancient and respected firm 01' Daimler, suppliers of motor carriages to the Royal Family, decided to discard the poppet valve by installing under the bonnets of their cars an American invention, in the form of the double sleeve-valve engine designed by Charles Y. Knight. To celebrate the revolutionary step a luncheon was held, attended by such" lions" as Percy Martin, Edward Manville, Ernest Instone and Eugene Stratton, and the menu was decorated by drawings depicting the flight of the vanquished poppets before the onslaught of the sleeves. Daimler's lead was copied in other countries by famous manufacturers--Panhard-Levassor and Peugeot in France, Minerva (wire) had foreshadowed Daimler) in Belgium, Mercedes in Germany, Willys-Knight and others in America. The Silent Knight abolished the clatter of conventional valve-gear but it did little to promote good performance and betrayed its presence by a pursuing haze of blue oil-smoke. Other famous manufacturers took up the Knight engine. notwithstanding--Siddeley-Deasy, Chlment-Bayard, Mors, and Voisin, amongst others; while the alternative of the Burt McCollum single sleeve valve was accepted by Argyll, Arrol-Aster, Piceard-Pietet, Vauxhall, etc. The Schmid culT-valve engine was prepared for racing by Rolland-Pilaih, and Argyll and Guyot built single sleeve-valve racing cars, Argyll taking a series of long-distance records with theirs:
Minerva was early in the field with a team of sleeve-valve racing ears and after the Armistice Peugeot used such engines in racing chassis to win the Coppa Florio, prior to habitually using sleeve-valve ears to secure honours in touring-car races. The sleeve-valve engine was not only well established before the First World War but by 1925 it had been considerably improved in efficiency. First Panhard-Levassor, then Daimler and Peugeot, east away heavy east-iron sleeves which had been Anything from three to five millimetres thick and used light steel sleeves. Panhard's new
sleeves were but l mns, thick, saving two-thirds the former weight, and both they, and Daimler in England, white-metalled the inner face of the outer sleeve, thus obviating steel rubbing steel, giving, in fact, a cast-ironfsteel/Ns II it e-tYle lalisteelf aluminium (of the piston) combinatien. Peugeot solved 1w diflieelty by using a special steel for the outer sleeve. V016irl retained east-iron sleeves, but drastically reduced the weight of other reciprocating parts and adopted as standard magnesium pistons on the 18-h.p. engine. Daimler later used an alloy cylinder block. These improved sleeve-valve power units achieved some notable successes. The Peugeot engine, for which the brilliant engineer Dufresne was responsible after having designed similar engines for Parthard and Voisin, developed 158 b.h.p. at 4,300 r.p.m. from 3.800 c.c. Panhard-Levassor were getting 130 b.h.p. at 4,800 r.p.m. from their 3-litre engine in 1925 and 200 b.h.p. at the same speed from the 4.8-litre engine which took the World's hour record. Voisin's standard 3.9-litre sleeve-valve engine gave 100 b.h.p. but this was increased to 145 h.p for competition purposes. In fact, from giving a smoky 5 b.h.p. per litre in 1909, the-sleeve,valve power unit Was producing 12/14 h.p. per litre at the same speed -of 1.000 r.p.m. and its top speed limit had been lifted to 4,000 r.p.m. in production, 6.000 r.p.m. in racing engines. This was progress
for the 191-1 Minerva T.T. double Sleeve-valve racing engines. ‘,Ilish were 31 -litre units, developed only 70 b.h.p. and could not ,xceed 2,800 r.p.m.; in attempting to obtain higher crankshaft !peed:, the experimental department had ruined no fewer than five engines due to breakage of the sleeve valves.
All three French manufacturers achieved notable racing and record-breaking successes with Knight-engined cars, PanhardLevassor. for instance, taking the World's hour record at 133.01 m.p.h. in 1934—this was with the 8-litre single-seater which G. E. T. Eyston drove in the eventful British Empire Trophy Race at Brooklands in 1932, when it averaged 128.35 m.p.h. for 100 miles. Re told me, when I met him in Castro! House the other day, that it is in honourable retirement at the Panhard works.
Yet what transpired ? One by one these manufacturers dropped sleeve valves; Daimler held out until 1935, Minerva continued with them up to 1939, but today not a single car can you buy with a moteur sans soupapes.
In Belgium the Imperia concern made a car with slide valves for some years, even listing a sports version of the normal 1.7-litre chassis, yet how many present-day enthusiasts have ever beard of slide valves being employed with internal combustion ? It is the same story when it comes to rotary valves. Darracq and t ala were making production rotary-valve engines before the 1914/18 %%at., and Data used such engines for their 1913 French G.P. ears,
one of which afterwards won many awards at Brooklands. That great rotary-valve advocate, the late Mr. Marcus Inman Hunter, M.I.Mech.E., M.I.A.E., covers a great number of these engines in his book, "Rotary Valve Engines" (Hutchinsons, 1946)—he. was endeavouring to convert a 900-cc. Austin engine to this valve system before the war. At Brooklancts an H.R.G. was raced with a Cross rotary-valve head and this engine in experimental motorcycle form gave an output equivalent to 70 b.h.p. per litre at 6,100 r.p.m. on 66-octant fuel. Only the war prevented the Norton Company from racing a rotary-valve engine. Yet how many rotary-valve ears can you buy today ?
I thought about the fate of one-off experimental engines when I was fifteen years old and wrote A letter which was published in The Autocar listing half a dozen such engines taken at random, inquiring why these had not been put on the market and why no more had been heard about them. As I expected, there were no replies to these queries.
The engines I listed were the four-cylinder 844-c.c. White-Wall two-stroke, built in 1924, which its inventor had Arranged to cool. condition and charge with a high-speed air stream; the 1,100-c.c. Coubert of 1925, which was a horizontally-opposed two-cylinder two-cycle engine with two pistons per cylinder; the variablecompression. Tobeeourt two-stroke of 1926, and the 1i-litre fourcylinder Etchtlgoin-Causan of the same year, which was another twostroke, with two crankshafts and eight pistons. I referred also to the rotary-valve Wolf Biehambre two-stroke of 1926 and the MinervaBournonville rotary-valve power unit of 1927. It will be seen that inventors of the period were convinced that some form of advanced two-stroke was the car engine of the future, yet today, with due deference to D.K.W. and Saab, where is this type of car engine ? Defunct : It may be argued that although it cost these inventors money to design, build and patent their engines, they were small fry financially. This, however, wasn't true of the Minerva-Bournonville rotary-valve engine. This engine; the invention of M. Bournonville, a Belgian engineer resident in New York, was taken up by the Minervi Company of Antwerp, who, after experimenting with it on bench and road for two years, pronounced it able " to challenge comparison with the best Knight engines,
while justifying claims to cheapness, simplicity and reliability not to be found in any other type of engine." Yet, two years after its announcement it had faded quietly away tind its sponsors did not bother to defend it when my letter referring to it appeared in The Autocar . . .
The experimental engines to which I have referred sought to get rid of the poppet valve and its operating gear but not the piston or crankshaft. Ilowever, there were plenty which did this—for example, the Northey rotary engine of 1934, the Mitchell swashplate unit of 1935, or, from an earlier era, the Statax seven-cylinder rotary engine of 1929 and the C.H.T. 65 X 252 mm. gas turbine and the Sanders pressure turbine that ran at 4,000 r.p.m. and received 40,000 power impulses per minute, of ten years earlier. These; and a host of others in between, were announced with great optimism, and some certainly got off tbe drawing-board and into metal. But where are they now? They have faded quietly away—not even the principles on which they functioned have found any place for earthbound transport.
In view of the foregoing, while wishing N.S.U. and Rover the very beat of luck with their revolutionary engine projects, I think I may be justified in suggesting that the time is not ripe for chucking on the serapheap your valve grinders and piston-ring clamps. The poppet valve hus had a very long innings and it may be expected to go on glowing cherry red in combustion chambers, preferably hemispherical, for many years to eome.—W. B.