McNaught, William

SUBJECT AREA: Steam and internal combustion engines

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b. 27 May 1813 Sneddon, Paisley, Scotland

d. 8 January 1881 Manchester, England

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Scottish patentee of a very successful form of compounding beam engine with a high-pressure cylinder between the fulcrum of the beam and the connecting rod.

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Although born in Paisley, McNaught was educated in Glasgow where his parents had moved in 1820. He followed in his father's footsteps and became an engineer through an apprenticeship with Robert Napier at the Vulcan Works, Washington Street, Glasgow. He also attended science classes at the Andersonian University in the evenings and showed such competence that at the age of 19 he was offered the position of being in charge of the Fort-Gloster Mills on the Hoogly river in India. He remained there for four years until 1836, when he returned to Scotland because the climate was affecting his health.

His father had added the revolving cylinder to the steam engine indicator, and this greatly simplified and extended its use. In 1838 William joined him in the business of manufacturing these indicators at Robertson Street, Glasgow. While advising textile manufacturers on the use of the indicator, he realized the need for more powerful, smoother-running and economical steam engines. He provided the answer by placing a high-pressure cylinder midway between the fulcrum of the beam and the connecting rod on an ordinary beam engine. The original cylinder was retained to act as the low-pressure cylinder of what became a compound engine. This layout not only reduced the pressures on the bearing surfaces and gave a smoother-running engine, which was one of McNaught's aims, but he probably did not anticipate just how much more economical his engines would be; they often gave a saving of fuel up to 40 per cent. This was because the steam pipe connecting the two cylinders acted as a receiver, something lacking in the Woolf compound, which enabled the steam to be expanded properly in both cylinders. McNaught took out his patent in 1845, and in 1849 he had to move to Manchester because his orders in Lancashire were so numerous and the scope was much greater there than in Glasgow. He took out further patents for equalizing the stress on the working parts, but none was as important as his original one, which was claimed to have been one of the greatest improvements since the steam engine left the hands of James Watt. He was one of the original promoters of the Boiler Insurance and Steam Power Company and was elected Chairman in 1865, a position he retained until a short time before his death.

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Bibliography

1845, British patent no. 11,001 (compounding beam engine).

Further Reading

Obituary, Engineer 51.

Obituary, Engineering 31.

R.L.Hills, 1989, Power from Steam. A History of the Stationary Steam Engine, Cambridge University Press (the fullest account of McNaught's proposals for compounding).

RLH