ASME-Landmark:Boulton & Watt Rotative Steam Engine

James Watt (1736-1819) designed and built engines incorporating many of the mechanical innovations that became steam engine practice: separate condenser, parallel motion and centrifugal governor, the sun-and-planet crank motion, and the double-acting cylinder.

This oldest surviving rotative engine was built by Boulton and Watt in 1785 for the London Brewery of Samuel Whitbread to drive the malt crushing mill. It appears first on a drawing dated November 1784 as a single-acting engine displaying the parallel motion and sun-and-planet gear that enable shaft rotation. Conversion to double action in 1795 doubled the power output. The iron beam and flyball governor were also later modifications. The engine was high technology for its day, much more commanding than the other mechanical marvels of the time, the windmill and clock. King George III, a man of plain and practical tastes and amusements, partial to hunting and mechanical contrivances, brought Queen Charlotte and their four children to the brewery in May of 1797 to inspect the "wondrous works to be seen there," the moving and exciting engine being a key attraction.

The engine served the brewery for 102 years, until 1887, when Archibald Liversidge, a museum trustee visiting in London, was presented with the engine and had it sent to Sydney in 1888, where it has now been restored to working condition by the Power House Museum.

With a speed of 20 revolutions per minute and a mean effective pressure of 10 pounds per square inch, the 25-inch piston of 6-feet stroke would have produced about 35 horsepower in its prime. See ASME website for more information