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Wheal Prosper Mine
Prosper Hill, Gwithian, Cornwall, UK
associated engineer
Richard Trevithick
date  1811 - 1837
era  Georgian  |  category  Mining/Quarrying  |  reference  SW587406
Wheal Prosper — sometimes known as Wheal Liverpool — was a rather unproductive copper mine. However, it is famous as the location for Richard Trevithick’s first plunger pole steam engine and the first Cornish engine. Nothing now remains of the surface mine buildings.
The mine’s sett (boundaries within which minerals could be extracted) was situated on land owned by Francis Basset, Lord de Dunstanville (1757–1835), south of Gwithian. Its name did not reflect the small quantity of copper ore that was mined here.
In 1810-12, Trevithick (1771-1833) was developing his ‘plunger pole’ pumping engine, which was in turn a refinement of the water-powered pole engine he invented in 1798. The pole, or piston, of the new engine was moved inside the pole case by high pressure steam rather than water, the steam cylinder being the pole case, which was supported on beams across the head of the mine shaft. The piston was connected by crossheads to the pump rods below, extending down the shaft. This meant there was no need for a rocking beam.
Work on the first plunger pole steam engine began at Wheal Prosper in 1811. Trevithick’s pupil Captain Samuel Grose (1791-1866) supervised its erection, and pumping started in spring 1812. It cost 750 guineas (£787.50).
Its piston was 410mm in diameter and worked a 2.44m stroke. It had two cylindrical wrought iron boilers, 910mm in diameter and 12.19m long, with an external fireplace at one end, and brick flues to convey heated air over the surface of the boilers. Each one was capable of working at 690kN per sq m over atmospheric pressure.
Steam entered the cylinder below the piston and was cut off before the end of the up stroke of the piston, at about one third distance, and the expanding steam completed the stroke. By this stage the pressure had dropped to138kN per square metre or less. The exhaust valve then opened and the steam escaped to the condenser and the air pump. This created a partial vacuum in the cylinder and the piston descended, aided by the weight of the pump rods. A balance bob regulated the movement and controlled the air pump, feed pump and plug rod to the valves.
Fellow engineer John Urpeth Rastrick (1780-1856), of Hazeldine Foundry, saw the engine and on 15th November 1812 wrote that it “works with less coal than any Engine I know of”. Trevithick calculated that the engine had a duty of 40 million and wrote to Rastrick on 26th January 1813 that this was “very nearly double the duty that is done by any other engine in the County”.
Trevithick went on to install other plunger pole engines in other mines, including his last at Herland Mine (SW590370) in 1816. He also took out a patent — number 3922 — for his engine in 1815.
Also at Wheal Prosper in 1812, Trevithick applied his Cornish boiler with internal fire tube, used first at Dolcoath Mine (SW661403), to create a prototype ‘Cornish engine’. This machine used high pressure steam in both expanding and condensing modes, and was manufactured with a second-hand 610mm diameter cylinder, reputedly from the tin mine of Relistian (SW601368) near Gwinear. Richard Hosking (1790-1866), of Perran Foundry, operated the engine for Trevithick.
This first Cornish engine was used for pumping water out of the mine. Its main rocking beam was fixed centrally beneath the cylinder, so the pumps had the same stroke length as the piston — 1.83m. It had a condenser near the bottom of the cylinder, and its piston worked between seven eighths and nine tenths of its stroke expansively. A beam above the cylinder worked the air pump and the feed pump to the boilers. The air pump had a 300mm diameter plunger and a 910mm stroke.
The tapering cylindrical boiler was 7.32m long and 1.68-1.83m in diameter, with flues along its sides and bottom. Steam pressure in the boiler exceeded 276kN per square metre over atmospheric pressure, and steam was let out of the boiler by a 180mm diameter valve. The cylinder was kept hot by an insulating layer of straw or reeds and lime plaster, rather than the steam cases that were used later.
The engine powered three pump lifts — 36.6m with a 150mm plunger, another 36.6m with a 250mm plunger and 18.3m with a 300mm diameter bucket.
The mine ceased operation in 1837 and the fate of Trevithick’s two famous engines is unknown.
Research: ECPK
bibliography
“Richard Trevithick: Giant of Steam” by Anthony Burton
Aurum Press Ltd, London, 2000
"Mines and Miners of Cornwall, Part V: Hayle, Gwinear and Gwithian” by A.K. Hamilton Jenkin, Truro Bookshop, Truro, 1963
“The Cornish Giant: The Story of Richard Trevithick, father of the steam locomotive” by L.T.C. Rolt, Lutterworth Press, London, 1960
“Richard Trevithick: the engineer and the man” by H.W. Dickinson and Arthur Titley, Cambridge University Press, London, 1934
“Life of Richard Trevithick, with an account of his inventions”
by Francis Trevithick, E. & F.N. Spon, London, 1872
“A Treatise on the Cornish Pumping Engine” by Dr William Pole
John Weale, London, 1844
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Location

Wheal Prosper Mine