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MAKING THE MODERN WORLD
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story:Power

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Power for production
The adoption of higher steam pressures, as pioneered by Richard Trevithick in Cornwall, opened up a whole new range of possibilities for steam power.
James Watt's reliance on low steam pressures limited the steam engine's growth potential. Watt argued that the 'wagon' boilers used could not safely work at higher pressures. He may also have feared that high-pressure engines, being more efficient, could have operated without his cherished separate condenser.
Extracting more power from low-pressure steam was increasingly unsustainable as industry's power requirements increased. Low-pressure engines were increasingly more costly and bulky whereas high-pressure operation allowed engines to be reduced in size for comparable power output, or made larger and even more powerful.
Here we will discover the innovations that allowed the steam engine to grow to unparalleled size during the nineteenth century.
Images with this text:
Model double beam engine, 1840, scale 1:10. This model was shown at the Great Exhibition, 1851. It represents the double beam engine Benjamin Hick built for Marshall's Flax Mill, Leeds. Both mill and engine were built in the same Egyptian style. The engine was soon out of date, as the mills expanded and even larger engines using higher steam pressures were needed.
Sectioned model of Cornish boiler, 1840. Developed by Richard Trevithick, hot gases from the furnace passed through an internal flue and then beneath and around the boiler before exiting via a chimney, 'surrounding' the boiler water and heating it more efficiently. Later 'Lancashire' pattern boilers used two flues, and were correspondingly more fuel-efficient.
Model, scale 1:12, of a wagon boiler by Boulton & Watt. Older boiler designs remained widely used, limiting the spread of high pressure operation. In 1840, 75 per cent of boilers in Manchester cotton mills were still of the wagon type, and it was only after that date that the Cornish boiler developed by Trevithick began to be widely used.
The Cornish engine
In 1769, James Watt patented an engine worked by steam rather than atmospheric pressure but he never developed the idea. He opposed using steam at more than a few pounds per square inch (psi) because of the danger of boiler explosions. The wagon boiler used at the time was unable to withstand high steam pressures and new designs were required.
Cornishman Richard Trevithick (1771-1833) was the first British engineer to use high-pressure steam. In 1812 Trevithick implemented his ideas at Cornwall's Wheal Prosper mine. He used a new boiler design to supply steam at 40psi to a single-acting condensing engine.
The 'Cornish' engine acquired a reputation for excellent fuel economy, employing steam at high enough pressures for it to be used expansively. This allowed considerable fuel savings by reducing the amount of steam used. The steam supply to the cylinder was cut off only partway through the stroke, allowing the steam to exert force on the piston by expanding, albeit with diminishing force.
By 1830, comparisons showed the high-pressure Cornish engine to be more than twice as efficient as the best Boulton & Watt low-pressure engine. With the Cornish engine, expansion of steam in a single cylinder reached its practical limit. The way forward lay with the compound engine.
Images with this text:
Taylor's Cornish engine, 1840. This engine, built by the Perran Foundry, Cornwall, is representative of the pumping engines built for Cornish mines and exported around the world. It was a particularly well-designed and efficient engine.
Richard Trevithick, oil on canvas portrait attributed to John Linnell, 1816.
The compound engine
The compound engine was equipped with two or more cylinders of increasing volume with the steam passing through them in sequence at decreasing pressures. This 'recycling' of steam increased the amount of useful work done with it.
Jonathan Hornblower built a compound engine in 1781. The engine had two cylinders, making it more expensive to build than a Boulton & Watt engine. It was no more economical because it still used very low-pressure steam. Because Hornblower's engine used a separate condenser it infringed Watt's patent and few were built.
Arthur Woolf, a Cornishman who originally trained with Joseph Bramah in London, revived the idea in 1804. Initially, the highest-pressure cylinder was too small for it to work properly. Having resolved this problem his later engines used 50% less fuel than a Boulton & Watt low-pressure engine.
Despite these innovations many industrialists were uneasy about high-pressure steam. Their low-pressure engines were not robust enough to be converted to use it. William McNaught avoided this problem by installing a small high-pressure cylinder at the opposite end of the beam to the original low-pressure cylinder. This was cheaper than buying a completely new engine and avoided overstressing the beam.
The combination of high pressure steam and compound operation allowed the use of steam in industry to grow at an unparalleled rate during the nineteenth century.
Images with this text:
Jonathan Hornblower's (1753-1815) compound engine, 1781. Drawing from History of the Growth of the Steam engine by R H Thurston. Hornblower.
Woolf compound steam engine built by JE Hall, 1838. Hall's was particularly prominent in the early manufacture of Woolf compound engines.
Elevation of McNaught's 60 horsepower compound beam engine, 1848.
Smaller and smaller
Although high-pressure steam allowed the construction of the largest and most powerful engines, it also facilitated the construction of small, self-contained engines. These were increasingly sought after by small workshop-type businesses.
In 1799 William Murdock built his first bellcrank engine. This was the first 'independent' (ie: self-supporting) engine, of just two to three horsepower to be commercially available. It was followed by Freemantle's 'Grasshopper' engine in 1803 and Henry Maudslay's table engine in 1807. These provided the power for many small workshops and mills.
One other use for smaller engines was in powering sugar-cane mills on plantations in Mauritius and the Caribbean. The tough sugar canes were cut by hand by the enslaved Africans who had been forced into hard labour on the plantations. The mills then extracted the juice from the canes. Often waste cane was used to fuel their boilers. Smaller engines were easy to export overseas thus providing another way in which Britain could profit from its colonies.
Images with this text:
Model bellcrank engine, c.1799. The bellcrank engine was the first self-supporting engine. James Murdock, an employee of Boulton & Watt, designed it. This model appears to be contemporary and was probably made as a development model by the firm.
Steam table engine by Maudslay, Sons & Field, 1840. Maudslay developed this compact design of engine in 1807, and built it in a variety of sizes - from 1.5 to 40 horsepower - until around 1850.
Grasshopper engine, c.1855, probably made by Easton, Amos & Sons. The name is taken from the fancied resemblance of the links and beam, when in motion, to the rear legs of a grasshopper.
Perspective View of a Steam Engine and Horizontal Sugar Mill, 1827. Engraving by Wilson Lowry after a drawing by John Farey.
Impact
High-pressure steam paved the way for the rapid spread of steam power during the nineteenth century. Whether large or small, industry could now call upon steam to meet its energy needs reliably and economically.
Images with this text:
Inverted vertical engine, c.1848. This single-cylinder steam engine was probably made by James Nasmyth to drive a small machine tool in his private workshops. It bears a strong resemblance to the steam hammer which he invented in 1839.
Maudslay's table engine c.1815. Developed in 1807 as a compact, self-contained engine that required simple foundations, this model is half the size of the smallest that Maudslay made. It may have been made by Maudslay himself or built under his supervision as a development model.

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