Steam Engines of the Eighteenth Century

The Smethwick Engine The Smethwick Engine was designed by James Watt for the Birmingham Canal Navigation Company and, went into service in May 1779. The engine was used to conserve water by pumping it back up a series of canal locks. The design principles used on the Smethwick Engine completely revolutionised steam engine design. By the late 1770s there were seventy five Newcomen engines working in the mineral mines in Cornwall and, within four years they had all been replaced by this new design of engine. The Watt engine was more powerful and also used much less coal. The Smethwick Engine is first engine in the world to use a principle which became synonymous with James Watt. It was a three-valve engine.
	The engines operating on the principles first developed by Thomas Newcomen in 1712, worked for the following sixty five years pumping the flood water from the coal and mineral mines. However, in 1769 James Watt made a great discovery, by creating the powering vacuum away from the operating cylinder of the engine he discovered that a great saving in coal would be the result.
He would eliminate the heating and then cooling of the cylinder on every working stroke of the engine. James Watt took out a patent for this idea which was applied to the Smethwick Engine.The engine at Smethwick became the first engine in the world to use both the expansive force of steam and a vacuum at the same time. The vacuum was created inside Watt’s separate condenser, low pressure steam was applied onto the pistons top and the vacuum was applied onto the underside of the piston. The engine pumped the water on the Birmingham canal system until 1891, often working twenty four hours per day only stopping for maintenance and repairs. On each stroke of the piston 170 gallons of water was lifted to refill the canal at the top of the flight of locks and, for each minute the engine made ten pumping strokes. The powering cylinder of this engine was 32 inches in diameter and the piston made a stroke of 8 feet.
	The model is the culmination of ten years research by the Birmingham Science Museum and a further three and a half years were needed to research the construction methods of the original engineers and to make this engine in miniature. The book "The Early Development of the Steam Engine" gives all the details of how this engine was made in 1778/9 and also how I researched it and made the miniature.
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