William McNaught

William McNaught (1813–1881) was a Scottish engineer, from Glasgow, who patented a compound steam engine in 1845. This was a technique of improving the efficiency of a standard simple Boulton & Watt beam engine. The engine was compounded by adding a high-pressure cylinder between the support column and the flywheel, on the side opposite the low-pressure cylinder. This improvement could be retrospectively fitted to existing engines.

Family William McNaught was born on 27 May 1813 at Paisley, Renfrewshire, Scotland, son of John McNaught, the inventor of the McNaught indicator.

Engine building McNaught patented his compound steam engine in 1845 (Patent no. 11001).

MacNaught died in Chorlton upon Medlock, Manchester, on 8 January 1881, leaving two sons who carried on the business. He was buried in Glasgow. but when McNaught'ed the new high-pressure cylinder could run at over , which the then-new Lancashire boiler could produce. In addition the stress on the centre of the beam was substantially reduced, and stress on the crank pin slightly reduced. This was important in preventing beam failure.

Bolton Steam Museum displays a McNaught'ed beam engine. The Cellars Clough mill engine was McNaught'ed by Woodhouse and Mitchell of Brighouse in 1909.