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James Rumsey |
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James Rumsey: Blacksmith-Inventor, by David G. Allen for the Appalachian Blacksmiths Association © 2008
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Making Steam Power Work The age of steam took many, many years to develop. Robert Boyle published Boyle’s Law in 1662 which was a fundamental step in explaining the behavior of gases and science of thermodynamics. His work was later expanded by other scientists such as Daniel Bernoulli who offered mathematical formulas to explain Boyle‘s Law. Blacksmiths are familiar with Bernoulli whether they know it or not because Bernoulli’s Principle (1738) explains why a chimney flue drafts smoke and hot gases away from the hearth. Another key in understanding steam was the discovery of the heat of evaporation. People knew that it took a great deal of energy to convert water at 212o F. into steam. Early measurements of that burst of energy were done by whiskey distillers in Scotland. The distillers did so because they needed to calculate their fuel requirements. About 1710, Thomas Newcomen developed a practical steam engine. As underground coal mining in England began to develop, the mines needed a mechanical way to pump water out of the mines. Newcomen’s engine, primitive as it was, served the purpose. Newcomen’s engine was very inefficient. Steam filled the cylinder pushing the piston down. Then cold water was turned into the cylinder to condense the steam. This resulted in a vacuum which gave the piston rod its power stroke. Because these engines were being used to pump water from coal mines, the cost of fuel (coal) was negligible. Newcomen’s engine remained pretty much unchanged until 1765 when James Watt, an instrument maker at the University of Glasgow (Scotland), realized that the method of condensing the steam robbed the engine of its heat. He calculated that 80% of the fuel was being used to simply re-heat the cylinder. Watt’s breakthrough, a separate condenser, meant that steam engines could be used at locations where fuel was expensive. Watt’s engine design also benefited from new technology such as the development of machines to bore the piston cylinder. Newcomen’s cylinder was a hand-finished casting and the piston seals were made of leather. Other improvements such as Watt’s planet and sun gears and Pickard’s offset crankshaft greatly improved work efficiency of these engines. Watt also built a double-action steam engine. Robert Fulton’s steamboat (the Clermont, 1807) was the result of nearly 300 years of learning the science of thermodynamics and developing the machines and technology to harness the power of steam.
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