Old Bess (beam engine)

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title: "Old Bess (beam engine)" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["preserved-beam-engines", "stationary-steam-engines", "steam-engines-in-the-science-museum,-london", "history-of-the-steam-engine", "industrial-revolution", "james-watt"] description: "1777 steam engine" topic_path: "history" source: "https://en.wikipedia.org/wiki/Old_Bess_(beam_engine)" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary 1777 steam engine ::

::data[format=table title="Infobox historic engine"]

Field	Value
name	Old Bess
image	Old bess beam engine may 2015.JPG
caption	Old Bess, as now preserved in the Science Museum, London
type	Watt beam engine
designer	James Watt
maker	Boulton and Watt
date
country_of_origin	England
cylinders	1
bore	33 in
stroke
former_operator	Soho Manufactory
purpose	Water-returning engine driving factory machinery
collection	Science Museum Group
location	Science Museum, London
working	No
::

|name = Old Bess |image = Old bess beam engine may 2015.JPG |image_size = |alt = |caption = Old Bess, as now preserved in the Science Museum, London |type = Watt beam engine |designer = James Watt |maker = Boulton and Watt |date = |country_of_origin = England |cylinders = 1 |bore = 33 in |stroke = |former_operator = Soho Manufactory |purpose = Water-returning engine driving factory machinery |collection = Science Museum Group |location = Science Museum, London |accession = |working = No Old Bess is an early beam engine built by the partnership of Boulton and Watt. The engine was constructed in 1777 and worked until 1848.{{cite book |last1=Dickinson |first1=H.W. |last2=Jenkins |first2=R. |title=James Watt and the Steam Engine |orig-year=1927 |year=1981 |publisher=Moorland Publishing |isbn=0-903485-92-3 |ref= |pages=120–126

The engine is most obviously known simply for being an early example of an engine built by Boulton and Watt. However it also played a far more important role in the development of steam engines for being the first engine designed to work with an early cutoff, and so to use the expansion of the steam for greater efficiency.

It is now preserved in the Power Gallery of the Science Museum, London.{{Cite web |title='Old Bess' engine by Boulton & Watt, 1777 |url=http://www.sciencemuseum.org.uk/on-line/energyhall/section5.asp |publisher=Science Museum |access-date=14 June 2011 |archive-date=5 June 2011 |archive-url=https://web.archive.org/web/20110605023254/http://www.sciencemuseum.org.uk/on-line/energyhall/section5.asp |url-status=dead |title='Old Bess' – general arrangement drawing |url=http://www.sciencemuseum.org.uk/images/NonSSPL/watt/1861-45-old-bess.aspx |year=1861 |publisher=Science Museum |access-date=14 June 2011 |archive-date=21 July 2011 |archive-url=https://web.archive.org/web/20110721142641/http://www.sciencemuseum.org.uk/images/NonSSPL/watt/1861-45-old-bess.aspx |url-status=dead |title="Old Bess" Science Museum – James Watt Exhibition |url=https://www.flickr.com/photos/quaerentia/5549433545/ |author=Mark Meynell |date=22 March 2011 |publisher=Flickr

Watt's previous Kinneil Engine

Watt's first engine at Kinneil in Scotland had been unsuccessful,{{Cite book |last=Crowley |first=T.E. |title=The Beam Engine |publisher=Senecio Publishing |year=1982 |isbn=0-906831-02-4 |pages=44–45

The Manufactory had been built to use a water wheel to drive its machinery, and the site had been chosen on that basis, but there were concerns over seasonal lack of water to power the wheel.{{Cite book |title=Engineering Heritage |last=Wilson |first=P.N. |publisher=Institution of Mechanical Engineers |volume=I |chapter=Water-Driven Prime Movers |year=1963 |pages=58–59

In 1777 Boulton and Watt decided to build a second engine for use at Soho, either to supplement the Kinneil Engine or primarily to experiment with Watt's new idea of expansive working of the steam. The new engine was also to be a water-returning engine Like the earlier Newcomen engines, it was only capable of pumping water rather than driving machinery directly.

Working life

Construction

As early as 1769, Watt was considering the possibility of working steam expansively, as recorded in a letter of 28 May to Dr. Small.{{Cite book |last=Arago |first=M. |title=Historical Eloge of James Watt |location=London |year=1838 |page=88 |quote=admit steam until one-fourth of the distance between it and the next valve is filled with steam, shut the valve and the steam will continue to expand and to press round the wheel with diminishing power

Construction began in 1777 with the ordering of a 33-inch cylinder (84 cm). The engine was erected and working at Soho by August, although still incomplete.

The engine always worked as a water pump and was equipped with two cast iron cylinders at opposite ends of the beam, one for the working cylinder and one for the pump. The pump cylinder was taller and thinner, of 24 in diameter and 8 ft tall, designed for a working stroke 7 ft within this, although only 6 ft was used in practice. The pumped water was delivered at a head of 24 ft. The engine was later described as being of 30 hp in power.

The beam was typical for early single-acting beam engines, pulling through wrought iron chains running over a curved arch-head at each end of the beam. At some later point, possibly when reconstructed after the fire, this beam was strengthened by being strutted and bridled with the additional timber and iron triangular trusses that are seen above the beam today.

''Beelzebub''

Initial operation of the engine was unsatisfactory. Watt was away in Cornwall and Boulton wrote to him, describing the engine's actions as "very fierce". His opinion was that the engine's cylinder was too large for the work expected of it. This led to it being worked at a pressure of around 5.7 psi, whereas if it were operating at 8 psi, it would be less jerky and violent. This action was so remarkable as to give the engine its initial nickname of Beelzebub.

Neither Watt nor Boulton had a solution to the engine's behaviour. Watt's experience with the Chacewater engine, a rebuilt Smeaton engine, at Wheal Busy, suggested that cutoff led to a violent action. In September he recommended throttling the steam supply to the engine. Boulton favoured further experimentation with cutoff (i.e. valve timing) and in 1779 suggested that a series of more scientific measurements be tried. With hindsight, Boulton's approach was the more thermodynamically efficient, although this lesson was not fully appreciated by locomotive drivers right to the end of steam power.

Fire and reconstruction

One morning in July 1778 the engine house was discovered to be on fire. The fire spread rapidly and within half an hour the roof was burned to the ground. The timberwork and soldered copper piping of the engine were also destroyed or damaged. Even the beam itself, a substantial timber construction, was "rendered unfit" by the fire. Fortunately the most important part of the engine, its cylinder, survived the fire relatively intact. Within three weeks the engine had been reconstructed and was expected to be working again shortly.

While the engine had been damaged, Watt, who was once again away in Cornwall, had advised that "no repair farther that the roof ought to be gone about at present", with his intention being to reconstruct the engine in some improved manner. The nature of these reconstructions, and their effectiveness, remains unclear.

By 1781, the engine had been working in its reconstructed form for some years. Whatever the improvements had been, they left Watt and Boulton still agreeing that this was, "one of the worst engines they had".

Closure of the Mint and preservation

The engine operated at the Soho Mint in Handsworth, West Midlands, until the mint's closure in 1848. It was sold for £48, then re-sold for £58 and placed on display on an island in Derrington Pool, outside the metal-rolling works of its new owner, a Mr. Walker. Although much of the Mint's coining machinery had been re-sold for further use at the new Birmingham Mint, this aged and thoroughly obsolete engine appears to have been one of the first artefacts of industrial archaeology to be deliberately preserved.

The engine was later re-sold and then presented to the Commissioners of Patents for their Patent Office Museum, which would in turn become the Science Museum in London. The engine is thus not only one of the museum's oldest exhibits, but also one of the first to enter its collection. When first displayed, the engine was erected in an open-fronted representation of a brick-built engine house. It is now displayed on free-standing timberwork, allowing a closer inspection of the cylinders.

For an engine that had been described as "one of the worst engines they had" when almost new, it had a relatively long working life of over 70 years. Its name had also shifted from the violent Beelzebub to the rather more friendly Old Bess, indicating a more satisfactory performance.{{Cite book |title=A Simple History of the Steam Engine |last=Storer |first=J.D. |year=1969 |publisher=John Baker |location=London |isbn=0-212-98356-3 |page=58

In 2009 it was awarded an Engineering Heritage Award by the IMechE.{{cite web |title=Engineering Heritage Award |publisher=IMechE |url=http://www.imeche.org/flipbook/marketing/engineeringheritageawards/#/12/zoomed |page=12

Confusion between engines

Several confusions exist about this engine, and have been widely repeated.

The first of these confusions is that this was Watt's second engine (after the Kinneil engine) and the first by the Boulton and Watt partnership. In fact several engines were built between 1773 (the return of the Kinneil engine to Birmingham) and the construction of Beelzebub in 1777. These include such well-known engines as the 1775 38-inch blowing engine for John Wilkinson's blast furnaces at New Willey, near Broseley in Shropshire, and the 50-inch pumping engine for Bloomfield Colliery near Tipton in the West Midlands.

The identity of Beelzebub is also confused. Some sources describe this as referring to the rebuilt Kinneil engine at Birmingham. There are two pieces of evidence to support the view that Old Bess and Beelzebub are the same engine. Firstly the name Beelzebub derives from its violent action when used experimentally for expansive working, an experiment applied to the engine built new in 1777. Secondly Beelzebub is described as a 33-inch engine, as is Old Bess on display today. There is no record of Boulton & Watt ever building another engine of this dimension.

References

References

1. "James Watt's Cottage". [[Gazetteer for Scotland]].
2. "Kinneil House". [[Historic Scotland]].
3. Letter to [[Gilbert Meason]], 24 April 1777, Boulton & Watt colln.
4. Letter to Watt, 18 August 1777, Boulton & Watt colln.
5. Letter to Boulton, 20 September 1777, Boulton & Watt colln.
6. Letter from Watt to Boulton, 1781, Boulton & Watt colln.
7. Crowley, Terence Eldon. (1986-01-01). "Beam Engines". Shire Publications.
8. Joseph Harrison, Science Museum collection
9. {{harvnb. Dickinson. Jenkins. 1927, Chap. IX, ''The Single Acting Pumping Engine'', pp. 111–119

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