In 2006, the ss Great Britain Trust finished the project to recreate the ship’s 1845 engine. The engine is a full scale, turning, complex model that has been authentically recreated in its original context. It has been constructed using modern, lightweight materials so that the 160-year-old fragile ship is not overloaded with heavy materials, moving loads and live steam.
At her launch in 1845, the ss Great Britain was the largest and fastest ship in the world due to Isambard Kingdom Brunel’s innovative combination of the leading technologies of the day. Her 12-knot engine was an engineering wonder of the age and the viewing public were inspired in awe at the achievement which Brunel’s ship represented.
The original engine was designed by Thomas Guppy, in collaboration with Brunel, and was a development of the triangle engine (the first ‘Vee’ engine) that was invented by Brunel’s father Marc.
Engine Facts
The Engine Room is dominated by the three storey high steam engine of 340 tons whose components are moving and turning. It produced 1,000 horsepower, and the four 88 inch diameter cylinders were set low in the hull and arranged in a V-formation, two on either side, at 33 degrees to the vertical.
They drove a crankshaft (then the largest forged object in the world) which was set high up in the engine space. The crankshaft carried a wooden toothed chain wheel, 18’3” in diameter, between the two sets of cylinders. This chain wheel used four chains weighing seven tons to turn the smaller (6’ diameter) lower chain wheel attached to the propeller shaft.
As the engine turned the crankshaft at 18 rpm, the propeller shaft turned at 53 rpm (a gear ratio of 2.95:1), propelling the ship at 12 knots (around 22 kmph). The 1,000 horse power (745kw) engine is the equivalent today of the 70,000 horse power (52,000kw) Rolls-Royce Olympus engine.
The steam used by the engine was produced from sea water in the world’s largest boiler at the time, holding 200 tons of water. The furnaces under the boiler were fuelled by coal (the ship could carry 1,200 tons) which was shovelled by a gang of stokers into 24 stoke holes. The stokers worked in shifts to ensure a constant supply of heat. The engine room would have been an awe-inspiring sight - loud, filthy and monstrous.
The Working Engine
The furnace heated salt water in the boiler, turning it into steam, which then pushed through the ‘steam pipe’ into the ‘slide case’, which controlled the inlet and exhaust of steam from the cylinders. By adjusting the ‘expansion gear’ in the slide case, the crew could regulate the amount of steam entering the cylinders, to allow for greater economy of fuel.
The steam was fed into the cylinders, pushing the pistons up. At the same time, water was injected into the steam in the ‘condenser’ which then cooled, shrank and formed a vacuum. This vacuum worked in opposition to the steam pressure on the other side of the piston, and helped to draw the pistons up and down.
Although the engine does not run at full speed today and turns at a lower rate than the original, it helps visitors to understand some key technological and engineering principles. In particular, how a steamship is actually driven, the expansion working of steam engines, the significance of steam pressure and boiler efficiency and the transfer of linear motion to rotary motion.
The 1843 engine used a boiler with a low steam pressure of 5 lbs/sq inch. Boiler design developed fast during the 1840s, so that engines were able to operate at much higher pressures.
Consequently the original engine quickly became obsolete and was replaced with a smaller more efficient one in 1852. The 1843 engine therefore provides a snapshot of the state of marine engineering at an important time during a period of rapid development.
The project to recreate the ss Great Britain’s first engine was made possible by enthusiasm and time from volunteers over the years, funding from the Millennium Commission and expertise and additional funding from Rolls-Royce.
Fittingly the project brought together two pioneers of transatlantic travel – Rolls-Royce engines powered the first transatlantic flight in 1919, while the ss Great Britain powered across the Atlantic over 70 years earlier, using the most advanced engineering technologies of the day.
The ss Great Britain Trust thanks The Millennium Commission and Rolls-Royce plc for their support in making this project possible.
Footage of the Engine Room
Watch footage of the engine room
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