There have been some references in these columns recently to that great automobile engineer, Sir Harry Ricardo, LLD, FRS, who is remembered by the motorsporting world as designer of the advanced engine of the three-litre twin-cam TT Vauxhall, the Ricardo-Triumph motorcycle and the Ricardo lightweight slipper piston. Also on account of his important book The HighSpeed Internal-Combustion Engine, first published in 1923 and running to at least five editions, in which Sir Harry crystalised all the work he had done on combustion-chamber form and engine design in general. Later this author was to write an entertaining autobiography.
Ricardo was born in January 1885 and educated at Rugby and Trinity College, Cambridge, after which, in 1906, he joined the staff of Rendel, Palmer & Tritton as a mechanical engineer, working on locomotives, steam-plant and diesel engines. When war came Ricardo was appointed a consulting engineer, at first with the Mechanical Warfare Department (where he designed the Ricardo tank engines), later transferring to the same position with the Air Ministry. When peace returned he formed the research organisation of Ricardo & Co Ltd, at Shorehamby-Sea, of which he was Chairman and Technical Director and which is still active in this field today.
Sir Harry Ricardo was elected President of the 1 Mech E for 1944/45. He lived in Petworth, enjoyed sailing and gardening and his London Club was the Athenaeum. That is the way in which most people remember this great engineer. Less well-known is the fact that Ricardo designed an engine for a French automobile company. His specialist firm in Sussex was doing research on fuels for Shell in 1921 but his engineering laboratory was engaged also on developing a special form of lever-valve gear for silent operation and investigating the reduction of oil consumption in the design of piston-rings. Another project was the design of a four cylinder side-valve 69 x 140mm (2094cc) engine so efficient that a power output of 38bhp at 2800 to 3000rpm, with the low fuel thirst of 0.56 of a pint per horse-power hour, or, say, some 35mpg from a 25cwt, car was claimed. Ricardo’s theory that it was highly desirable to have maximum gas turbulence at the point when the sparking-plug fired was obtained by the shape of the combustion spaces, the valves were operated by quickly detachable rocker-arms, and tensioning of the timing-chain was also a simple operation. Another feature of this engine was the absence of external oil-pipes. Oil was forced into the hollow camshaft via its bearings and thence to the three main bearings, through the drilled crankshaft, the big-ends also being pressure-fed, leakage of lubricant from these bearings supplying mist to the gudgeon-pins and cylinder walls.
Whether it was the publicity accorded to Ricardo’s TT Vauxhall engine that attracted the French manufacturer to his skills I do not know, but as only one of the three Vauxhalls that started in the 1922 TT race (won by Sunbeam, with a three-litre Bentley second) finished, one retiring with the embarrassment of a broken piston, this may well not have been so! The fact is that Ricardo got the job. The concern that had asked the British designer to make it an engine was Le Zebre, who had been making small-engined cars successfully at Suresnes on the Seine.
Good materials were used, the cooling-system was well-contrived, and so was engine lubrication, although one British user noted that because the car was high-geared for its 1100cc engine size the customery 40mph cruising pace of similar English cars was not possible. But as economy cars the Le Zebres were a good proposition. They had appeared in 1900 as single-cylinder confections but the makers soon saw the light, discarding the veteran-car aspect while eschewing the coming cyclecar boom, by going over to a four-cylinder engine for their shaft-drive chassis late in 1912. This 785cc light car maintained the popularity of the former Scv 600cc “one-lunger” Le Zebre. After the war had ended it was continued, with the luxury of a four-speed gearbox, and engine size increased to 998cc. So why did they call in Harry Ricardo? The answer is not far to seek.
M Salomon, their chief engineer, had been lured by Citroen to leave them and help, using his knowledge of small-cars, produce the 5cv (7.5hp in England) Citroen, and another Le Zebre technician, M Lamy, had gone off to work for the Amilcar people. At the same time Le Zebre had decided to introduce a two-litre car. Maybe they sensed that the economy-car scene was becoming overcrowded, with competition from 900cc Amilcar, 752cc Benjamin, 738cc two-stroke Bieriot, the aforesaid 855cc Citroen, 760cc Mathis, 668cc Peugeot Quad, the British 4WD 747cc Austin 7, 970cc Talbot-Darracq, 898cc Chapuis-Dornier-engined Derby, 893cc Ruby-powered EHP, 979cc Short-Ashby, 1088cc Bignan, 968cc Carteret, 900cc friction-drive Fournier, 1086cc GN, 988cc Griffon, 1100cc Hinstin-Sup, 1096cc Maie, 1088cc Salmson, 900cc Senechal and the 1088cc Sigma, etc.
Whatever the reason, the rather nice-looking Le Zebre light car gave way to the new two-litre model. Whether the engine Ricardo had laid down by early 1921 was an experimental project or intended for the new Le Zebre announced in 1922, has not been established. But the specification was similar, even to a bore and stroke of 60 x 132mm (1974cc). Perhaps the French company heard of it and found it was just what they wanted. Anyway, it was thought a great honour that such a long-established Continental concern should look to England for its next model. The engine, which had a three-bearing crankshaft threaded into a one-piece crankcase, a detachable head with Ricardo-patented combustion chambers, aluminium pistons, and a gear-driven dynamo, used a plunger-type oil-pump. The camshaft of this side-valve power-unit was spur-gear-driven, the centre gear on a spider so that the mesh of the teeth was easily adjustable to ensure quiet running. Ricardo’s engine was installed in a conventional chassis with half-elliptic springing and a foot-applied transmission brake, and it ran on 765 x 105 tyres. In times gone by the tiny 645cc “one-pot” Le Zebre was so popular here as to merit a race for them at Brooklancis in 1912, 10 of them, all with standard F B Goochild torpedo bodies, being entered.
But after the war the up-market shift proved to be a gamble which didn’t come off, in spite of the agent here being called Tattersalls… It was probably no fault of Harry Ricardo’s but the two-litre Le Zebre was almost unheard of here, although it apparently persisted in showing itself at the Paris Salon up to 1930. W B