Warnockhead Beam Engine

The remains of a water-powered beam engine at Wanlockhead


A Watt engine: showing entry of steam and water


The cast-iron beam of the 1812 Boulton & Watt engine at Crofton Pumping Station – the oldest working example in the world

A beam engine is a type of steam engine where a pivoted overhead beam is used to apply the force from a vertical piston to a vertical connecting rod. This configuration, with the engine directly driving a pump, was first used by Thomas Newcomen around 1705 to remove water from mines in Cornwall. The efficiency of the engines was improved by engineers including James Watt who added a condenser, Jonathan Hornblower and Arthur Woolf who compounded the cylinders, and William McNaught (Glasgow) who devised a method of compounding an existing engine. Beam engines were first used to pump water out of mines or into canals, but could be used to pump water to supplement the flow for a waterwheel powering a mill.

The rotative beam engine is a later design of beam engine where the connecting rod drives a flywheel, by means of a crank (or, historically, by means of a sun and planet gear). These beam engines could be used to directly power the line-shafting in a mill. They also could be used to power steam ships.


The first beam engines were water-powered, and used to pump water from mines. A 'preserved' example may be seen at Wanlockhead, in Scotland.

Beam engines were extensively used to power pumps on the English canal system when it was expanded by means of locks early in the Industrial Revolution, and also to drain water from mines in the same period, and as winding engines.

The first steam-powered beam engine was developed by Thomas Newcomen. The Newcomen steam engine was adopted by many mines in Cornwall and elsewhere, but it was relatively inefficient and consumed a large quantity of fuel. James Watt resolved the main inefficiencies of the Newcomen engine in his Watt steam engine, and these beam engines were used commercially in much larger numbers.

Watt held patents on key aspects of his engine's design, and it was not until these patents expired that others could develop modifications to improve it. The beam engine was considerably improved and enlarged in the tin- and copper-rich areas of south west England, which enabled the draining of the deep mines that existed there. Consequently the Cornish beam engines became world famous, as they remain the most massive beam engines ever constructed.

Rotative beam enginesEdit

Thomas Horn Beam Engine

A small rotative beam engine, built in 1870 by Thomas Horn to a design by James Watt. The crank is visible at the front, the flywheel part-hidden by the engine. (Originally installed in a waterworks in Ashford, now operational and preserved at the Bredgar and Wormshill Light Railway.)

In a rotative beam engine, the piston is mounted vertically, and the piston rod does not connect directly to the connecting rod, but instead to a rocker or beam above both the piston and flywheel. The beam is pivoted in the middle, with the cylinder on one side and the flywheel, which incorporates the crank, on the other. The connecting rod connects to the opposite end of the beam to the piston rod, and then to the flywheel.

Early Watt engines used Watt's patent sun and planet gear, rather than a simple crank, as use of the latter was protected by a patent owned by someone else. Once the patent had expired, the simple crank was employed universally.

The first steam-powered ships used variants of the beam engine. These marine steam engines – known as side-lever, grasshopper, crosshead, or 'walking beam', among others – all varied from the original land-based machines by locating the beam or beams in different positions to take up less room on board ship.


Compounding involves two or more cylinders; waste low-pressure steam from the first, high-pressure, cylinder is passed to the second cylinder where it expands further and provides more drive. This is the compound effect; the waste steam from this can produce further work if it is then passed into a condenser in the normal way. The first experiment with compounding was conducted by Jonathan Hornblower, who took out a patent in 1781. His first engine was installed at Tincroft Mine, Cornwall. It had two cylinders – one 21-inch (0.53 m) diameter with 6-foot (1.8 m) stroke and one 27-inch (0.69 m) diameter with 8-foot (2.4 m) stroke – placed alongside each other at one end of the beam. The early engines showed little performance gain: the steam pressure was too low, interconnecting pipes were of small diameter and the condenser ineffective.[1]

At this time the laws of thermodynamics were not adequately understood, particularly the concept of absolute zero. Engineers such as Arthur Woolf were trying to tackle an engineering problem with an imperfect understanding of the physics. In particular, their valve gear was cutting-in at the wrong position in the stroke, not allowing for expansive working in the cylinder. Successful Woolf compound engines were produced in 1814, for the Wheal Abraham copper mine and the Wheal Vor tin mine.[2]

McNaught enginesEdit

William McNaught of Glasgow, not to be confused with William McNaught of Rochdale (Petrie and McNaught), patented a compound beam engine in 1845. On a beam engine of the standard Boulton & Watt design he placed a high-pressure cylinder, on the opposite side of the beam to the existing single cylinder, where the water pump was normally fitted. This had two important effects: it massively reduced the pressure on the beam, and the connecting steam pipe, being long, acted as an expansive receiver – the element missing in the Woolf design.[3] This modification could be made retrospectively, and engines so modified were said to be "McNaughted". The advantages of a compound engine were not significant at pressures under 60psi, but showed at over 100psi.

See also Edit

Engineerium beam engine baseplate

Baseplate and mahogany lagging, beam engine, British Engineerium, Brighton

Preserved beam enginesEdit

Main article: List of Pumping Stations
  • Bolton Steam Museum (Bolton, England) – includes several rotative beam engines originally used to drive mills
  • Crofton Pumping Station (Great Bedwyn, England) – two engines, including the oldest working 'Cornish' engine, in its original location, in the world (1812)
  • Crossness Pumping Station (Abbey Wood, London, England) – set of four rotative beam engines: the largest surviving working examples
  • Museum De Cruquius (Cruquius, The Netherlands) – the eight-beamed engine at Cruquius is thought to be the largest steam engine ever built
  • Dogdyke Engine (Tattershall, Lincolnshire) – drainage engine and scoop wheel, steamed summer weekends.
  • Eastney Beam Engine House (Portsmouth, England) – contains two rotative beam engines for sewage-pumping, dating from 1887.
  • Elsecar (Elsecar, South Yorkshire, England) – the only surviving Newcomen engine (in the world) to have remained in its original location (1795)
  • Kew Bridge Steam Museum (Brentford, London, England) – four 'Cornish' engines (in original location) and several rotative engines (in museum), including the largest working 'Cornish' engine in the world
  • Levant Mine and Beam Engine (Trewellard, Pendeen, England) – a working beam engine on a National Trust property in West Cornwall, England
  • Markfield Beam Engine (Tottenham, London, England) – a compound, rotative engine
  • Pinchbeck Engine (Spalding, Lincolnshire) – statically preserved 'A'-frame engine.
  • Ryhope Engines Museum (Ryhope, England) – twin rotative beam engines; built 1868
  • Smethwick Engine (Smethwick, Birmingham, England) – oldest working steam engine in the world (1779)
  • Stretham Old Engine (Stretham, Cambridgeshire) – Statically preserved engine and scoop wheel.
  • The Western Springs Water Works (Auckland, New Zealand) – 1877 double Woolf compound engine. In original location, restored in working order with Transport and Technology Museum built around it. The restoration of the Pumphouse and original Engineers cottage was awarded with the 2009 Award of Merit from UNESCO's Asia-Pacific Heritage Awards for Culture Heritage Conservation programme.


  1. Hills 1989, p. 147
  2. Hills 1989, p. 153
  3. Hills 1989, p. 157


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