A Cornish engine is a type of
steam engine
A steam engine is a heat engine that performs mechanical work using steam as its working fluid. The steam engine uses the force produced by steam pressure to push a piston back and forth inside a cylinder. This pushing force can be trans ...
developed in
Cornwall
Cornwall (; kw, Kernow ) is a historic county and ceremonial county in South West England. It is recognised as one of the Celtic nations, and is the homeland of the Cornish people. Cornwall is bordered to the north and west by the Atlantic ...
, England, mainly for pumping water from a mine. It is a form of
beam engine
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 Newco ...
that uses steam at a higher pressure than the earlier
engines
An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy.
Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power ...
designed by
James Watt
James Watt (; 30 January 1736 (19 January 1736 OS) – 25 August 1819) was a Scottish inventor, mechanical engineer, and chemist who improved on Thomas Newcomen's 1712 Newcomen steam engine with his Watt steam engine in 1776, which was fun ...
. The engines were also used for powering
man engine
A man engine is a mechanism of reciprocating ladders and stationary platforms installed in mines to assist the miners' journeys to and from the working levels. It was invented in Germany in the 19th century and was a prominent feature of tin an ...
s to assist the underground miners' journeys to and from their working levels, for
winch
A winch is a mechanical device that is used to pull in (wind up) or let out (wind out) or otherwise adjust the tension of a rope or wire rope (also called "cable" or "wire cable").
In its simplest form, it consists of a spool (or drum) attache ...
ing materials into and out of the mine, and for powering on-site
ore stamping machinery.
Background: The steam engine in Cornwall
Cornwall
Cornwall (; kw, Kernow ) is a historic county and ceremonial county in South West England. It is recognised as one of the Celtic nations, and is the homeland of the Cornish people. Cornwall is bordered to the north and west by the Atlantic ...
has long had
tin
Tin is a chemical element with the symbol Sn (from la, stannum) and atomic number 50. Tin is a silvery-coloured metal.
Tin is soft enough to be cut with little force and a bar of tin can be bent by hand with little effort. When bent, t ...
, copper and other metal ore mines, but if mining is to take place at greater depths, a means to
dewater the mine must be found. Lifting the weight of water up from the depths requires great amounts of
work
Work may refer to:
* Work (human activity), intentional activity people perform to support themselves, others, or the community
** Manual labour, physical work done by humans
** House work, housework, or homemaking
** Working animal, an animal tr ...
input. This energy may be weakly supplied by horse power or a
waterwheel
A water wheel is a machine for converting the energy of flowing or falling water into useful forms of power, often in a watermill. A water wheel consists of a wheel (usually constructed from wood or metal), with a number of blades or buckets ...
to operate pumps, but horses have limited power and waterwheels need a suitable stream of water. Accordingly, the innovation of coal-fired steam power to work pumps was more versatile and effective to the mining industry than primitive means.
The mine ''
Wheal Vor
Wheal may refer to:
* Wheals, a type of skin lesion
* Brad Wheal (born 1996), British cricketer
* Donald James Wheal (1931–2008), British British television writer, novelist and non-fiction writer
* David John Wheal, Australian businessman
* " ...
'' had one of the earliest
Newcomen engine
The atmospheric engine was invented by Thomas Newcomen in 1712, and is often referred to as the Newcomen fire engine (see below) or simply as a Newcomen engine. The engine was operated by condensing steam drawn into the cylinder, thereby creati ...
s (in-cylinder condensing engines, utilising sub-atmospheric pressure) before 1714, but Cornwall has no coalfield and coal imported from south Wales was expensive. The cost of fuel for pumping was thus a significant part of mining costs. Later, many of the more efficient early
Watt engine
The Watt steam engine design became synonymous with steam engines, and it was many years before significantly new designs began to replace the basic Watt design.
The first steam engines, introduced by Thomas Newcomen in 1712, were of the "at ...
s (using an external condenser) were erected by
Boulton and Watt
Boulton & Watt was an early British engineering and manufacturing firm in the business of designing and making marine and stationary steam engines. Founded in the English West Midlands around Birmingham in 1775 as a partnership between the Engli ...
in Cornwall. They charged the mine owners a royalty based on a share of the fuel saving. The fuel efficiency of an engine was measured by its "duty", expressed in the work (in
foot-pounds
The foot-pound force (symbol: ft⋅lbf, ft⋅lbf, or ft⋅lb ) is a unit of work or energy in the engineering and gravitational systems in United States customary and imperial units of measure. It is the energy transferred upon applying a fo ...
) generated by a bushel () of coal. Early Watt engines had a duty of 20 million, and later ones over 30 million.
Cornish cycle
![PSM V12 D154 The cornish pumping engine 1877](https://upload.wikimedia.org/wikipedia/commons/f/f1/PSM_V12_D154_The_cornish_pumping_engine_1877.jpg)
The Cornish cycle operates as follows.
Starting from a condition during operation with the piston at the top of the cylinder, the cylinder below the piston full of steam from the previous stroke, the boiler at normal working pressure, and the condenser at normal working vacuum,
# The pressurized steam inlet valve and low-pressure steam exhaust valves are opened. Pressurized steam from the boiler enters the top part of the cylinder above the piston, pushing it down, and the steam below the piston is drawn into the condenser, creating a vacuum below the piston. The pressure difference between the steam at boiler pressure above the piston and the vacuum below it drives the piston down.
# Part way down the stroke, the pressurized steam inlet valve is closed. The steam above the piston then expands through the rest of the stroke, while the low-pressure steam on the other side (bottom) of the piston continues to be drawn into the condenser, thereby maintaining the partial vacuum in that part of the cylinder.
# At the bottom of the stroke, the exhaust valve to the condenser is closed and the equilibrium valve is opened. The weight of the pump gear draws the piston up, and as the piston comes up, steam is transferred through the equilibrium pipe from above the piston to the bottom of the cylinder below the piston.
# When the piston reaches the top of the cylinder, the cycle is ready to repeat.
The next stroke may occur immediately, or it may be delayed by a timing device such as a
cataract
A cataract is a cloudy area in the lens of the eye that leads to a decrease in vision. Cataracts often develop slowly and can affect one or both eyes. Symptoms may include faded colors, blurry or double vision, halos around light, trouble w ...
. If it was not necessary for the engine to work at its maximum rate, reducing the rate of operation saved fuel.
The engine is
single-acting, and the steam piston is pulled up by the weight of the pump piston and rodding. Steam may be supplied at a pressure of up to .
Real photos showing the components of the schematic design (
East Pool mine
East Pool mine (later known as East Pool and Agar mine), was a metalliferous mine in the Camborne and Redruth mining area, just east of the village of Pool in Cornwall, England. Worked from the early 18th century until 1945, first for copper and ...
Tailer's shaft Harvey's Engine):
File:East Pool Mine Taylor's Shaft boilers.jpg, Steam boilers
File:East Pool Mine Taylor's Shaft main steam cylinder.jpg, Main steam cylinder (A)
File:East Pool Mine Taylor Shaft control steam cylinders.jpg, Control steam
cylinders (G-H)
File:East Pool Mine Taylor Shaft pump lever.jpg, Pump lever (D)
File:East Pool Mine Taylor's Shaft pump piston.jpg, Engine house and pump piston (E)
File:Sacrifice block in the engine house of Taylor's Shaft East Pool mine.jpg, Sacrifice block in the engine house of Taylor's Shaft East Pool mine
East Pool mine (later known as East Pool and Agar mine), was a metalliferous mine in the Camborne and Redruth mining area, just east of the village of Pool in Cornwall, England. Worked from the early 18th century until 1945, first for copper and ...
Characteristics
The principal advantage of the Cornish engine was its increased efficiency, accomplished by making more economical use of higher-pressure steam. At the time, improvements in efficiency were important in Cornwall because of the high cost of coal; there are no coal fields in Cornwall and all the coal used had to be brought in from outside the county.
Increasing the boiler pressure above the very low, virtually atmospheric pressure steam used by James Watt was an essential element of the improvement in efficiency of the Cornish engine. However, simply increasing the boiler pressure would have made an engine more powerful without increasing its efficiency. The key advance was allowing the steam to expand in the cylinder. While James Watt had conceived of the idea of allowing expansive working of steam—and included it in his 1782 patent, he realized that the low steam pressure of his application made the improvement in efficiency negligible, and so did not pursue it.
In a Watt engine, steam is admitted throughout the piston's power stroke. At the end of the stroke, the steam is exhausted, and any remaining energy is wasted in the condenser, where the steam is cooled back to water.
In a Cornish engine, by contrast, the intake valve is shut off midway through the power stroke, allowing the steam already in that part of the cylinder to expand through the rest of the stroke to a lower pressure. This results in the capture of a greater proportion of its energy, and less heat being lost to the condenser, than in a Watt engine.
Other characteristics include insulation of steam lines and the cylinder, and steam jacketing the cylinder, both of which had previously been used by Watt.
Few Cornish engines remain in their original locations, the majority having been scrapped when their related industrial firm closed.
The Cornish engine developed irregular power throughout the cycle, completely pausing at one point while having rapid motion on the down stroke, making it unsuitable for rotary motion and most industrial applications.
This also requires some unusual
valve gear
The valve gear of a steam engine is the mechanism that operates the inlet and exhaust valves to admit steam into the cylinder and allow exhaust steam to escape, respectively, at the correct points in the cycle. It can also serve as a reversing g ...
, see
Cornish engine valve gear
Valve gear opens and closes valves in the correct order. In rotating engines valve timings can be driven by eccentrics or cranks, but in non-rotative beam engines these options are not available. In the Cornish engine valves are driven either man ...
.
Development of the Cornish engine
The Cornish engine depended on the use of steam pressure above atmospheric pressure, as devised by
Richard Trevithick
Richard Trevithick (13 April 1771 – 22 April 1833) was a British inventor and mining engineer. The son of a mining captain, and born in the mining heartland of Cornwall, Trevithick was immersed in mining and engineering from an early age. He w ...
in the 19th century. Trevithick's early "puffer" engines discharged steam into the atmosphere. This differed from the Watt steam engine, which moved the condensing steam from the cylinder to a condenser separate from the cylinder; hence Watt's engine depended on the creation of a vacuum when the steam was condensed. Trevithick's later engines (in the 1810s) combined the two principles, starting with high-pressure steam which was then passed to the other side of the piston, where it condensed and there it acted as a sub-atmospheric pressure engine. In a parallel development
Arthur Woolf
Arthur Woolf (1766, Camborne, Cornwall – 16 October 1837, Guernsey) was a Cornish engineer, most famous for inventing a high-pressure compound steam engine. As such he made an outstanding contribution to the development and perfection of the ...
developed the
compound steam engine
A compound steam engine unit is a type of steam engine where steam is expanded in two or more stages.
A typical arrangement for a compound engine is that the steam is first expanded in a high-pressure ''(HP)'' cylinder, then having given up he ...
, in which the steam expanded in two cylinders successively, each of which were at pressures above atmospheric.
When Trevithick left for South America in 1816 he passed his patent right of his latest invention to
William Sims
William Sowden Sims (October 15, 1858 – September 28, 1936) was an admiral in the United States Navy who fought during the late 19th and early 20th centuries to modernize the navy. During World War I, he commanded all United States naval force ...
, who built or adapted a number of engines, including one at Wheal Chance operating at above
atmospheric pressure
Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1013.25 millibars, 7 ...
, which achieved a duty of nearly 50 million, but its efficiency then fell back. A test was carried out between a Trevithick type single-cylinder engine and a
Woolf compound engine
Arthur Woolf (1766, Camborne, Cornwall – 16 October 1837, Guernsey) was a Cornish engineer, most famous for inventing a high-pressure compound steam engine. As such he made an outstanding contribution to the development and perfection of the ...
at Wheal Alfred in 1825, when both achieved a duty of slightly more than 40 million.
The next improvement was achieved in the late 1820s by
Samuel Grose, who decreased the heat loss by insulating the pipes, cylinders, and boilers of the engines, improving the duty to more than 60 million at Wheal Hope and later to almost 80 million at
Wheal Towan
Porthtowan ( kw, Porth Tewyn, meaning ''cove of sand dunes'') is a small village in Cornwall, England which is a popular summer tourist destination. Porthtowan is on Cornwall's north Atlantic coast about west of St Agnes, north of Redruth, ...
. Nevertheless, the best duty was usually a short-lived achievement due to general deterioration of machinery, leaks from boilers, and the deterioration of boiler plates (meaning that pressure had to be reduced).
Minor improvements increased the duty somewhat, but the engine seems to have reached its practical limits by the mid-1840s. With pressures of up to , the forces are likely to have caused machinery breakages. The same improvements in duty occurred in engines operating
Cornish stamps
Cornish is the adjective and demonym associated with Cornwall, the most southwesterly part of the United Kingdom. It may refer to:
* Cornish language, a Brittonic Southwestern Celtic language of the Indo-European language family, spoken in Cornw ...
and
whims, but generally came slightly later. In both cases the best duty was lower than for pumping engines, particularly so for whim engines, whose work was discontinuous.
The impetus for the improvement of the steam engine came from Cornwall due to the high price of coal there, but both capital and maintenance costs were higher than a Watt steam engine. This long delayed the installation of Cornish engines outside Cornwall. A secondhand Cornish engine was installed at
East London Waterworks
The East London Waterworks Company was one of eight private water companies in London absorbed by the Metropolitan Water Board in 1904.
The company was founded by Act of Parliament in 1806, and in 1845 the limits of supply were described as ''" ...
in 1838, and compared to a Watt engine with favourable results, because the price of coal in London was even higher than in Cornwall. However, in the main textile manufacturing areas, such as
Manchester
Manchester () is a city in Greater Manchester, England. It had a population of 552,000 in 2021. It is bordered by the Cheshire Plain to the south, the Pennines to the north and east, and the neighbouring city of Salford to the west. The t ...
and
Leeds
Leeds () is a city and the administrative centre of the City of Leeds district in West Yorkshire, England. It is built around the River Aire and is in the eastern foothills of the Pennines. It is also the third-largest settlement (by populati ...
, the coal price was too low to make replacement economic. Only in the late 1830s did textile manufacturers begin moving to high-pressure engines, usually by adding a high-pressure cylinder, forming a compound engine, rather than following the usual Cornish practice.
Preserved Cornish engines
![East Pool mine, Michells Shaft engine house](https://upload.wikimedia.org/wikipedia/commons/5/53/East_Pool_mine%2C_Michells_Shaft_engine_house.jpg)
Several Cornish engines are preserved in England. The
London Museum of Water & Steam
London Museum of Water & Steam is an independent museum founded in 1975 as the Kew Bridge Steam Museum. It was rebranded in early 2014 following a major investment project.
Situated on the site of the old Kew Bridge Pumping Station in Brentfo ...
has the largest collection of Cornish engines in the world. At
Crofton Pumping Station
Crofton Pumping Station, near the village of Great Bedwyn in Wiltshire, England, supplies the summit pound of the Kennet and Avon Canal with water.
The steam-powered pumping station is preserved and operates on selected weekends. It contains ...
, in
Wiltshire
Wiltshire (; abbreviated Wilts) is a historic and ceremonial county in South West England with an area of . It is landlocked and borders the counties of Dorset to the southwest, Somerset to the west, Hampshire to the southeast, Gloucestershire ...
are two Cornish engines, one of which (the 1812
Boulton and Watt
Boulton & Watt was an early British engineering and manufacturing firm in the business of designing and making marine and stationary steam engines. Founded in the English West Midlands around Birmingham in 1775 as a partnership between the Engli ...
) is the "oldest working beam engine in the world still in its original engine house and capable of actually doing the job for which it was installed", that of pumping water to the summit pound of the
Kennet and Avon Canal
The Kennet and Avon Canal is a waterway in southern England with an overall length of , made up of two lengths of navigable river linked by a canal. The name is used to refer to the entire length of the navigation rather than solely to the cent ...
. Two examples also survive at the
Cornish Mines and Engines museum on the site of
East Pool mine
East Pool mine (later known as East Pool and Agar mine), was a metalliferous mine in the Camborne and Redruth mining area, just east of the village of Pool in Cornwall, England. Worked from the early 18th century until 1945, first for copper and ...
near the town of
Pool, Cornwall
Pool ( kw, Poll) is a village in Carn Brea civil parish in west Cornwall, England. It is bypassed by the A30, on the A3047 between Camborne and Redruth, between Tuckingmill and Illogan Highway.
Facilities
Shops in the village include: a T ...
.
Another example is at
Poldark Mine
Poldark Mine is a tourist attraction near the town of Helston in Cornwall, England, UK. It lies within the Wendron Mining District of the Cornwall and West Devon Mining Landscape World Heritage Site. Its features include underground guided tour ...
at Trenear, Cornwall – a Harvey of Hayle Cornish Beam Engine from about 1840–1850, originally employed at Bunny Tin Mine and later at Greensplat China Clay Pit, both near St Austell. It no longer works as a steam engine but is instead moved by a hydraulic mechanism. In use at Greensplat until 1959, it is the last Cornish engine to have worked commercially in Cornwall. It was moved to Poldark in 1972.
The
Cruquius pumping station in the
Netherlands
)
, anthem = ( en, "William of Nassau")
, image_map =
, map_caption =
, subdivision_type = Sovereign state
, subdivision_name = Kingdom of the Netherlands
, established_title = Before independence
, established_date = Spanish Netherl ...
contains a Cornish engine with the largest
diameter
In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints lie on the circle. It can also be defined as the longest chord of the circle. Both definitions are also valid for ...
cylinder ever built for a Cornish engine, at diameter. The engine, which was built by
Harvey & Co in
Hayle
Hayle ( kw, Heyl, "estuary") is a port town and civil parish in west Cornwall, England. It is situated at the mouth of the Hayle River (which discharges into St Ives Bay) and is approximately seven miles (11 km) northeast of Penzance. ...
, Cornwall, has eight beams connected to the one
cylinder
A cylinder (from ) has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a prism with a circle as its base.
A cylinder may also be defined as an infin ...
, each beam driving a single pump. The engine was restored to working order between 1985 and 2000, although it is now operated by an oil-filled hydraulic system, since restoration to steam operation was not viable.
The
Cornish Engines Preservation Committee, an early
industrial archaeology
Industrial archaeology (IA) is the systematic study of material evidence associated with the industrial past. This evidence, collectively referred to as industrial heritage, includes buildings, machinery, artifacts, sites, infrastructure, docu ...
organisation, was formed in 1935 to preserve the
Levant winding engine. The Committee was later re-named for
Richard Trevithick
Richard Trevithick (13 April 1771 – 22 April 1833) was a British inventor and mining engineer. The son of a mining captain, and born in the mining heartland of Cornwall, Trevithick was immersed in mining and engineering from an early age. He w ...
. They acquired another winding engine and two pumping engines. They publish a newsletter, a journal and many books on Cornish engines, the mining industry, engineers, and other industrial archaeological topics.
''Trevithick Society.''
Cornish Miner - Books on Cornwall. Retrieved 22 September 2012.
See also
*Beam engine
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 Newco ...
*Mining in Devon and Cornwall
Mining in Cornwall and Devon, in the South West England, southwest of England, began in the early Bronze Age, around 2150 BC. Tin, and later copper, were the most commonly extracted metals. Some tin mining continued long after the mining of o ...
*Stationary steam engine
Stationary steam engines are fixed steam engines used for pumping or driving mills and factories, and for power generation. They are distinct from locomotive engines used on railways, traction engines for heavy steam haulage on roads, steam cars ...
*'' Lean's Engine Reporter''
*Cataract (beam engine)
A cataract was a speed governing device used for early single-acting beam engines, particularly atmospheric engines and Cornish engines. It was a kind of water clock.
The cataract is distinctly different from the centrifugal governor, in that i ...
References
External links
Cornish beam engine animation
(includes mechanical details, simulations, technical drawings, etc.)
Cornish engine history, context
*
{{DEFAULTSORT:Cornish Engine
Beam engines
Stationary steam engines
Steam engines
Mining in Cornwall
History of the steam engine