The Thornycroft compound steam engine. Image courtesy of the Liverpool Daily Post and Echo
The technical side of engineering holds for me, Stephen Guy, many mysteries but I am fascinated by working steam engines which I find strangely soothing.
Steam power transformed the world of shipping as it did when land transport moved on to railways – pioneered by British innovators and inventors. When James Watt
gave the world its first efficient steam engine in 1769 he provided the means for ships to eventually carry cargo reliably to all corners of the world. Sailing ships had to make the best progress they could depending on the winds. Only with the advent of steam was it possible to introduce dependable timetable services.
Single cylinder engines between 1800 and 1850 worked at low pressures of less than 20 lbs per square inch (psi). More economical compound engines, introduced in 1854, extracted useful work from higher pressure steam (up to 60 psi) by passing it through two cylinders. Triple and quadruple expansion engines took this principle further in later decades.
Long after the introduction of steam, merchant sailing vessels remained profitable on longer routes. Early steamships had limited cargo space because they had to carry so much coal. Clipper ships such as the Liverpool-built Fiery Cross dominated the trades in China tea and Australian wool.
The 1869 opening of the Suez Canal was crucial because it shortened voyages and steamships became economically viable. Coaling stations were built at intervals, the colonies of the British Empire providing many suitable locations so that steamers could reach all parts of the globe.
A memorable Royal Naval tug o’ war was staged in 1845 to test the power of the propeller. The screw steamer Rattler beat the otherwise identical paddle steamer Alecto. Not only was the propeller shown to be more effective but it was also less vulnerable than paddles and therefore more suited to naval duties.
Continuing improvements to the efficiency and reliability of steam engines ensured that, by the end of the century, steamships no longer had to carry sails to bring them home in the event of an engine or boiler failure.
There is a fine set of real and model engines at Merseyside Maritime Museum to illustrate the power of steam. A Thornycroft compound steam engine is from the 63 ft-long torpedo boat No 71 of 1880. Model engines include: side lever engine (1836), an oscillating engine used on paddle steamers (1847), triple expansion engines (1887 and 1937) and a compound engine (1890). The largest oscillating engines ever built were those on Brunel’s legendary giant Great Eastern
(1858) with four cylinders of 74 inches in diameter.
A new Maritime Tale appears every Saturday in the Liverpool Echo