Articles
The Science Museum in London has just opened a new permanent exhibition about James Watt and his impact on the modern world. The focus of the exhibition is Watt’s newly restored workshop. This used to be housed in the garret of Heathfield, the house he built near Birmingham, but was purchased by the Science Museum when the house was about to be demolished in the 1920s and moved wholesale to London. Watt is one of the key personalities of the Industrial Revolution. He made important improvements to the steam engine, making it far more efficient than Newcomen’s engine.
Watt was born in Greenock, Renfrewshire in 1736. He began to work in his father’s workshop after he left school, but due to the failure of his father’s business affairs both James and his brother had to seek employment elsewhere. He initially moved to Glasgow to learn the trade of mathematical instrument maker, but was advised to seek tuition in London. He went to John Morgan, an instrument maker, who, in return for 20 guineas and a year’s labour, taught him the trade. He returned to Scotland after his year was up, and a few months later opened a workshop in Glasgow University.
His interest in steam engines was sparked in 1763, when he was asked to repair a model Newcomen engine belonging to Glasgow University. As he mended it, he identified the main problems with the engine. He made a larger model and used it to conduct experiments. He is said to have conceived the idea for the separate condenser while walking in Glasgow in the spring of 1765. This was a critical development of the steam engine. Newcomen’s engines wasted a great deal of energy, 80% according to Watt’s calculations, by repeatedly cooling and reheating the cylinder, as the steam was condensed in the cylinder by injection of cold water. By having a separate condenser, the cylinder could be maintained at a constant temperature.
Watt also worked as a civil engineer during this time, and this delayed the development of his ideas, but in 1768 he went back to the experiments with his model steam engine. By the end of the year he was working on a colliery engine with a separate condenser, and he obtained a patent for the development in 1769. After early difficulties in accessing capital, Watt formed his famous partnership with Matthew Boulton in 1774.
They were relatively slow to convert the reciprocating motion of the engine to rotational power, which would widen the potential applications for the engine, and were therefore unable to use the more obvious solution of the crank, which had been patented by James Pickard. Instead, they developed the sun and planet gear in 1781, and continued to use this even after Pickard’s patent had expired. Other developments include the double-acting engine; compound engines, where two or more engines were connected together; and parallel motion, essential for double-acting engines, which was patented in 1784. In a letter to his son in 1808, Watt wrote that parallel motion was the invention of which he was most proud.
Initially Boulton and Watt worked as consulting engineers, and the engines were manufactured by subcontractors. They were paid a third of the cost of coal saved in comparison with a Newcomen engine doing the same amount of work; Watt developed an engine counter which sat on the beam of the engine and counted each stroke of the engine. The counter was in a sealed box, for which only their employees had the key. In 1794 they began to manufacture steam engines themselves. It has been estimated that during the period of Watt’s patent, Boulton and Watt manufactured 449 engines for the British market.
Watt retired in 1800, the same year that his main patent expired, but he continued to develop new inventions in his retirement. The wide spread of his interests is represented in the large collection of items to be found in his workshop.