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Issue 6 - Industrial revolutionary: James Watt

History & Heritage

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Scotland Magazine Issue 6
February 2003

 

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Industrial revolutionary: James Watt

HIS MODIFICATIONS OF THE STEAM ENGINE WERE SO SUCCESSFUL THAT SCOT JAMES WATT TRANSFORMED INDUSTRY FOREVER

Born in 1736 in Greenock near Glasgow, James Watt was the son of a ship-chandler. With little formal education, he showed great aptitude for maths and engineering, and became an instrument-maker for the University of Glasgow at 19. In 1763 he was asked to repair the university’s model of a Newcomen engine. These engines were used to pump water from mines but were inefficient and expensive.

So, Watt was not the first to develop the idea of a steam-driven engine. It all began in 1675. A French scientist, Denis Papin, based in London, developed a primitive engine consisting of an open-ended cylinder, with a piston fixed inside. The cylinder was heated and the piston rose as steam was created. Then the cylinder was cooled, condensing the steam and creating a vacuum. The piston was then freed and made a fast downward stroke, forced by atmospheric pressure. The cylinder was then reheated.

An engineer, Thomas Savery of Plymouth, furthered Papin’s ideas by generating the steam in a separate vessel, and cooling the cylinder by pouring water over its exterior, forming a vacuum into which water could be drawn. This method was used to pump water from wells and mines. Thomas Newcomen, a blacksmith from Dartmouth, went a step further, spraying water inside the cylinder to condense the steam and using the piston to pull down a beam on a pivot, with a pump at the other end. The first Newcomen engine was used in 1712.

Watt calculated that around 75% of the energy was wasted in operating the Glasgow University Newcomen engine. The problem lay in the need to heat the cylinder when full of steam, and to cool it to condense the steam to form a vacuum. This lead to a slow, inefficient process.

One Sunday morning, walking on Glasgow Green, Watt struck upon the idea of using a separate condenser. Two vessels could be linked so that the cylinder was kept hot and the condenser cold. If both were filled with steam initially, the vapour in the condenser would turn to water, creating a vacuum, and the steam from the cylinder would rush in to fill it, causing the piston to fall.

Watt later made a further advance in closing the top of the cylinder and placing it in an airtight jacket filled with steam. In this way, Watt’s engine was definitively the first ‘steam engine’, as those before had relied on atmospheric pressure to force the piston down. By enclosing the cylinder and using extra valves, it was also possible for the piston to make upward and downward strokes instead of just downward ones. Watt patented the steam engine in 1769.

In 1774, he joined forces with Birmingham-based entrepreneur and owner of the Soho Factory, Matthew Boulton, to build the improved steam engines for use in industry. Watt also pioneered the conversion of vertical piston movement into rotary motion, allowing machines such as looms to be engine-driven. The most satisfying innovation for Watt was that of parallel motion: a piston now moved upwards and downwards on a rocking beam and powered gears which then turned a shaft. Newcomen engines were slowly replaced by Watt engines, although a few were still used as late as the 20th century. Watt’s engine revolutionised the iron foundries, corn mills, cotton mills and weaving factories, greatly increasing productivity and efficiency; the Industrial Revolution was in full swing.

Watt’s talents did not end there: he produced plans for canals and railways, experimented with different clay mixes for use in potteries and designed a steam pressure indicator and a basic letter copier. He also coined the term ‘horsepower’, based on what weight a mine pony could lift over a given distance in one minute (measured in foot-pounds). A surviving example of a Watt engine, (recently reconstructed), one of only eight pre-1800 engines in existence, can now be seen at the Royal Museum, Edinburgh.

James Watt retired in 1800 a rich man. In 1882, 63 years after his death, a unit of electrical power, the watt, was named in his honour which is now found on light bulbs the world over.