Clerk, Sir Dugald

SUBJECT AREA: Automotive engineering, Steam and internal combustion engines

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b. 31 March 1854 Glasgow, Scotland

d. 12 November 1932 Ewhurst, Surrey, England

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Scottish mechanical engineer, inventor of the two-stroke internal combustion engine.

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Clerk began his engineering training at about the age of 15 in the drawing office of H.O.Robinson \& Company, Glasgow, and in his father's works. Meanwhile, he studied at the West of Scotland Technical College and then, from 1871 to 1876, at Anderson's College, Glasgow, and at the Yorkshire College of Science, Leeds. Here he worked under and then became assistant to the distinguished chemist T.E.Thorpe, who set him to work on the fractional distillation of petroleum, which was to be useful to him in his later work. At that time he had intended to become a chemical engineer, but seeing a Lenoir gas engine at work, after his return to Glasgow, turned his main interest to gas and other internal combustion engines. He pursued his investigations first at Thomson, Sterne \& Company (1877–85) and then at Tangyes of Birmingham (1886–88. In 1888 he began a lifelong partnership in Marks and Clerk, consulting engineers and patent agents, in London.

Beginning his work on gas engines in 1876, he achieved two patents in the two following years. In 1878 he made his principal invention, patented in 1881, of an engine working on the two-stroke cycle, in which the piston is powered during each revolution of the crankshaft, instead of alternate revolutions as in the Otto four-stroke cycle. In this engine, Clerk introduced supercharging, or increasing the pressure of the air intake. Many engines of the Clerk type were made but their popularity waned after the patent for the Otto engine expired in 1890. Interest was later revived, particularly for application to large gas engines, but Clerk's engine eventually came into its own where simple, low-power motors are needed, such as in motor cycles or motor mowers.

Clerk's work on the theory and design of gas engines bore fruit in the book The Gas Engine (1886), republished with an extended text in 1909 as The Gas, Petrol and Oil Engine; these and a number of papers in scientific journals won him international renown. During and after the First World War, Clerk widened the scope of his interests and served, often as chairman, on many bodies in the field of science and industry.

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Principal Honours and Distinctions

Knighted 1917; FRS 1908; Royal Society Royal Medal 1924; Royal Society of Arts Alber Medal 1922.

Further Reading

Obituary Notices of Fellows of the Royal Society, no. 2, 1933.

LRD