Hi All,
Whenever Cornish tin mines are mentioned on the box or wherever, you always see a pickure that looks like a roodless house with a tall chimney.
Are there/were there lots of these scatterered around Cornwall, or is it just the same one they always show?
Also,
How big is it/they. I always assummed they are house sized, but it occurs to me they could equally be cathedral sized..
Also, what was there use when the mine was in production?
TIA
Chris
They originally housed the steam boilers and pump to keep the mine clear of water. One I visited was about 10m X 5m internally, walls around 1m thick and about 8m high. Chimney was a about 20m high. But they vary
There are lots of them about. They were too expensive to demolish after the mines closed.
It depends on how big the mine was. Mostly in the fifty to sixty foot square size range.
They are fairly chunky things that housed a boiler and a steam engine used to pump water out of the mines. There are quite a lot of derelict ones around the coast. They tend to always photograph the most scenics and picturesque ones for obvious reasons.
Stopping the mine from flooding. A bit of history:
There are many engine houses scattered around Cornwall, but also further afield, as the engines were highly efficient (for their day) and used for pumping, winding (hoisting) and driving crushing machinery, on mines all over the world, from Australia to Mexico and South America, and the USA. They are typically three stories high, with a sort of internal basement that housed the valve gear. Most of them are just empty shells, although they are now preserved as being part of Cornwall's cultural and engineering heritage. Some have been converted into private homes.
The engine houses contained a single-cylinder piston, connected to a rocking beam by a 'parallel motion' to allow the straight-up-and-down motion of the piston rod to connect onto the circular motion of the rocking beam. Cylinder diameters were measured in inches ID, and could range from say 20" to over 100", although the biggest ever built, the Cruquius engine for pumping Dutch polders and built by Harvey's of Hayle, had a cylinder of 144" ID. The majority of the pumping engines were single-acting (i.e. steam admitted to one side of the piston only), although winding and crushing engines were double-acting. They used steam at around 40 - 50 psi. See also
The boiler houses were external to the pumping engine houses. They were less substantially built and have seldom survived. They housed either Cornish, or later, Lancashire boilers. See
A number of actual engines have also been preserved, both in Cornwall and elsewhere, notably around Camborne and at St. Just (the National Trust owns or has responsibility for them), and the pumping engines at Kew Bridge.
The best book on the Cornish Beam Engine is that by D.B. Barton, available from several S/H booksellers through ABE Books, for around £20: see
I was just thinking of Kew Bridge Steam Museum, and you got there first. It's definitely worth a visit, as you can climb up inside the house-sized steam engine whilst it's operating.
Plenty of them left. They were stone-built, so hard to demolish.
has plenty of photos and drawings with scale. Here's a survivor, with a Mini alongside.
They're 4 stories high, although one of these was usually a semi-basement. = Size was fairly consistent, although the waterworks engines were bigger and= then there's Cruquius (one engine, multiple beams)
These engines were usually "Cornish engines" (which is a type, not a locati= on) and they went up and down as beam engines, rather than round and round = (many beam engines also drove a rotary crankshaft, but not these). They we= re primarily to drive a very long vertical wooden rod, with pumps at the bo= ttom of it for draining a mine shaft.
Another development was the "man engine"
There was a Grand Designs on one - maybe have a look for that if you are interested? They ended up with an impressive "balcony" that looked like it was not supported properly.
The boilers were usually outside the engine house, in a much lower side building that has usually disappeared by now.
Because the engines were "house built", the engine house itself supported the beam pivot and so had to be very substantially built (almost always stone). This made the engine house long-lasting, even when derelict.
The boiler house, in contrast, was little more than a shed. Many boilers were outdoors, covered by nothing more than a layer of bricks as some rudimentary insulation. Few boilerhouses thus survive.
I remember that one. The building inspector made the owner enclose the staircase in order to meet fire regulations, which completely ruined the interior layout. I bet he stripped it all back to the original open staircase after the BI's last visit!
Clotted cream extraction. The building was for storing barrels of the stuff.
The chimney is where they heated up their pasties at lunchtime.
Also used for pumping treacle at the Talskiddy treacle mines near Newquay (Google for them). On one occasion, the cream and treacle got mixed, and 'Thunder and Lightening' was invented (Google for that too)!
The valve gear is mostly on the ground floor, where the engine driver spent= most of their time. The basement was rarely visited and largely filled wit= h an open swamp of warm water and condensate. The main components down ther= e were the cataract (the engine's governor) and air or condensate pumps.
There were more differences than this. The Cornish cycle was surprisingly e= fficient, which is one reason why these arcane and ancient single-acting en= gines were still built new into the 20th century, even though their non-rot= ating nature was a limit for some tasks.
The construction of the tunnel used a great variety of engines, in a number= of different engine houses. For the operation of the tunnel though, the Gr= eat Spring (which is actually in Wales, inshore of the pump house and not u= nder the Channel, was pumped by a new pump house of six Cornish engines wor= king down the same shaft. These were removed in the 1960s, because the shaf= t was still required as the only location for pumping. It's in use to this = day.
One beam is preserved in Swansea (although it seems quite unloved and has b= ounced around between museums since). The engines couldn't be preserved be= cause there was nowhere to put them. They are some of the most house-built = engines I've ever seen, short of Cruquius, and it would have been astronomi= cally expensive to build any sort of house that could display them. Nor wer= e they terribly exciting engines, in comparison to many others being scrapp= ed around this time. Only as part of the overall tunnel and shaft were they= really that impressive.
Best books I know of for the Cornish engine in particular are these:
Woodall, Frank D. (1975). Steam Engines and Waterwheels.=20
Kelly, Maurice (2002). The Non-Rotative Beam Engine. Camden Miniature Steam= Services.
And I recall one building I went to as a lad down there having a substantial drop inside the 'door', presumably they needed more height than they actually built!
Brian
Chris Holmes formulated on Monday :
There are lots of them, all of a similar style.
most of their time. The basement was rarely visited and largely filled with an open swamp of warm water and condensate. The main components down there were the cataract (the engine's governor) and air or condensate pumps.
efficient, which is one reason why these arcane and ancient single-acting engines were still built new into the 20th century, even though their non-rotating nature was a limit for some tasks.
Supposedly where the expression going nineteen to a dozen originated,
19000 gallons of water pumped from a mine using 12 bushels of coal was used to describe an engine working well.G.Harman
Surely this would be entirely dependent on how high the water needed to be pumped.
Andy
Probably but I don't know any Cornish miners from the reign of King William the IV or Queen Victoria to ask which why I wrote supposedly. The expression is probably genuine enough but it's technical accuracy may not be. Not that it is alone in that,you hear people with a mike stuck near their nostrils by a reporter because they witnessed their neighbours results of some poor diy on the gas cooker say "it sounded like a bomb going off". There is quite a variety between Mills and Hydrogen.
G.Harman
I've seen this claimed before. I was sceptical then, and still am. One can get some idea of the numbers involved by doing some calculations, but because the amount of water raised by a pumping engine is critically dependent on the engine efficiency and the depth from which the water is being pumped, exact confirmation is not possible.
Consider an early and inefficient Newcomen engine operating at a duty of around 6 million. This means that the engine could raise 6,000,000 lbs. of water 1 foot by burning 1 bushel of coal (see below for the definition and calculation of engine duty). By burning 12 bushels,
72,000,000 lbs. of water, or 7,200,000 gallons, could be raised 1 foot, or 19,000 gallons could be raised about 380 ft. Newcomen engines were introduced to Cornwall in the 18th century, and Wheal Vor was among the first mines to have one. Hamilton Jenkin(1) says it pumped six lifts of 10 fathoms each, a total of 360 ft. For an engine of intermediate efficiency, doing a duty of say 25 million (a typical figure at the beginning of the 19th century), burning 12 bushels would raise 19,000 gallons by 1580 ft. (263 fm.). The mines of the time were around 1000 ft. (165 fm.) deep, not deep enough to be the origin of the phrase because such pumps operating from this depth would either burn less coal or pump more water.At the end of the 19th century, the most efficient Cornish engines performed duties of say 125 million (although this duty was also claimed for Austen's engine at Fowey Consols as early as 1835). The depth equivalent to requiring 12 bushels to pump 19,000 gallons would be 7,895 ft. But the deepest Cornish mine was Dolcoath at 550 fathoms or 3,300 ft., which means that these efficient engines are also not the origin of the phrase.
So if the claimed origin of the phrase is correct, it would have to have come from the 18th century, when the numbers agree reasonably well with the depths of the mines at that time and when inefficient Newcomen or possibly Savory engines were in use. Such a date would fit with the early use of the phrase, as for example in Sheridan's Journal of 1785: 'The Mother good humour'd and Civil, but talks nineteen to the dozen'.
On the other hand, even in the 18th century, engine duties were calculated in millions of pounds of water raised, not gallons, and always per bushel of coal, not per 12 bushels. 'Going nineteen to the dozen' is most likely to be just a turn of phrase and nothing to do with pumping engines, Cornish or otherwise. CALCULATION OF ENGINE DUTY:
The 'duty' of a pumping engine was a measure of its efficiency in converting heat from the burning of coal into useful work, i.e. the raising of water from a mine. It was defined as "the weight of water in lbs. raised 1 foot by burning 1 bushel of coal". One bushel is the unit quantity of coal normally used as the standard (a bushel is 8 gallons, but the weight in a bushel was not standard, seemingly, as both 84 and 94 lbs. are quoted (2,3)) but sometimes a hundredweight (112 lbs.) is used instead of a bushel(4,5). It is important to note which, because the calculated 'duty' differs accordingly.
Duty was measured by recording the amount of fuel burnt over a period of time and the number of strokes performed by the pump in that time. Knowing the size of the pumps, the height of the lifts (i.e. how high the water was raised by those pumps) and the amount of coal burned, the 'duty' can be calculated. The data supplied in the various tables recorded during the heyday of Cornish pumping engines are in various units, but all have to be reduced to pounds (lbs) and feet (ft). Pump piston diameters are usually given in inches, the pump stroke in feet and inches and the height of the 'lift' in fathoms. The calculation is as follows.
By definition, work is done when a force moves its point of application.
work done = force * distance
In a single pump stroke, the work done is the force on the pump piston multiplied by the distance traveled by that piston. The force on the pump piston (described as the 'load' in the old tables) is given by the pressure generated by the hydrostatic head in the 'lift' multiplied by the cross sectional area of the piston.
Thus l = (d/24) * (d/24) * pi *h * 6 *62.3
Where l = the 'load', or force on the piston d = pump diameter in inches h = height of the 'lift' in fathoms
The factor 24 converts the pump diameter in inches to pump radius in feet; the factor 6 converts 'lift' height in fathoms to feet, and the factor 62.3 is the density of water in lbs. per cu.ft.
The 'distance' moved by the piston is the length of the pump stroke.
So w = l * s
Where w = the work done in a single pump stroke l = the load calculated as above s = the length of the pump stroke in ft.
During the course of a trial, the pump would execute many strokes, so
total work done = force * distance * number of strokes
So w = l * s * n
Where n = the number of strokes performed by the engine and pump during the trial.
Thus, the 'duty', D is given by:
D = w / b
Where b = the number of bushels of coal burnt during the trial.
The first steam pumping engines, designed by Newcomen, were very inefficient and had duties of around 6 million. The most efficient and fully developed Cornish beam engines had duties of in excess of 100 million, but triple expansion compound steam engines in the 20th. century had duties of approaching 200 million.
(1) Hamilton Jenkin, A.K. 'The Cornish Miner',, George Allen & Unwin,
1927, p.99 (2) Dickinson, H.W., 'A Short History of the Steam Engine', Babcock & Wilcox and Cambridge University Press, 1938, pp.62, 87. (3) Barton, D.B., 'The Cornish Beam Engine', D. Bradford Barton Ltd., 1965, p. 52. (4) Dickinson H.W., loc.cit. , p. 101. (5) Barton D.B., loc.cit. , p. 82.
Lean's Engine Reporter is a whole book of this, with hard numbers. Printed editions in the last few decades too. "Engine duty" is the usual term for Cornwall.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.