The Boulton and Watt engine on show at the National Museum of Scotland in Chambers Street in Edinburgh is one of the oldest surviving beam engines in the world.
The metal and wood structure – weighing 20 tonnes – was made in London by Scottish inventor James Watt and dates from 1786.
In this video, curator Ellie Swinbank tells you more about the exhibit, which is one of the key displays in the Science and Technology section of the museum.
Ellie said: “The engine was built for the Barclay and Perkins Brewery in London. It’s been in the museum collection since 1886.
“The engine was one of the first to include Watt’s sun and planet gear, which was used to obtain the rotary motion of the flywheel. It consisted of a pair of cog wheels linked together, one running around the other. The planet gear was attached to the lower end of the connecting rod and was guided around the sun by a freewheeling crank.
“There were other arrangements developed around this time that allowed for rotary motion. But Watt’s had the advantage of increasing the speed at the drive shaft and the flywheel. It converted the slow speed of the beam engine’s piston from about 20 strokes per minute to around 40 rotations per minute.”
Of course, Watt’s big innovation was to use a separate condenser to improve the output of steam engines.
Ellie added: “Watt made the steam engine three times more efficient than it had been previously. This was a huge step forward in Britain’s Industrial Revolution.
“This engine is just one of their star attractions at the science and technology galleries at National Museum Scotland. Do come and visit it. The museum is open all year round and entry is free.”
The Museum’s main hall (level one) also features a statue of James Watt, by Sir Francis Chantrey. Dating from the 1820s, it’s on loan from Heriot-Watt University in the city.