William McNaught (Glasgow)

William McNaught (Glasgow)

For the engineer of the same name from Rochdale, see William McNaught (Rochdale).

William McNaught (1813–1881)[1] 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.[2]


William McNaught was born on 27 May 1813 at Paisley, Renfrewshire, Scotland. William was the son of John McNaught, the inventor of the McNaught indicator, a device that measured the cylinder pressure cycle in steam engines. John started producing the indicators in 1830, and for the period 1832–40 he lived at 24, then 26 Robinson Street, Glasgow. William is recorded at that address in 1840. William patented his compound steam engine in 1845 (Patent no. 11001).[1] He relocated to Manchester in 1849.

The Robertson Street workshop was operated by 'William McNaught & Son' as "Makers of Steam-Engine Indicators, Steam Gauges, etc" at 12 Hampden Terrace. Glasgow at least until 1895.[3]

MacNaught died in 34 Clarendon Rd, Chorlton upon Medlock, Manchester, on 8 January 1881, leaving two sons who carried on the business. He was buried in Glasgow.[1]

McNaught'ed beam engines

A beam engine might run at 5psi, using one low-pressure cylinder steamed by an 1840 wagon boiler,[4] but when McNaught'ed the new high-pressure cylinder could run at over 60psi, a pressure that the then new Lancashire boiler was capable of producing. In addition the stress on the centre of the beam was massively reduced, and those on the crank pin slightly reduced. This was important in preventing beam failure.

Sample engine Beam Crank Pin
Before compounding 85,408 42,704
After compounding 656 40,893
Units lbs [5]

The thermodynamic benefits of high-pressure steam were beginning to be understood, as scientific opinion turned away from the ideas of caloric to the laws of thermodynamics proposed by Joule in 1849.[6]

Many engine makers McNaughted existing beam engines including that of William McNaught (Rochdale).


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