Features

Power

Rudder with central and port wing propellers^[c] for scale note the man at bottom of the photo

Titanic was equipped with three main engines—two reciprocating four-cylinder, triple-expansion steam engines and one centrally placed low-pressure Parsons turbine—each driving a propeller. The two reciprocating engines had a combined output of 30,000 hp and a further 16,000 hp was contributed by the turbine.^[16] The White Star Line had used the same combination of engines on an earlier liner, the SS Laurentic, where it had been a great success.^[27] It provided a good combination of performance and speed; reciprocating engines by themselves were not powerful enough to propel an Olympic-class liner at the desired speeds, while turbines were sufficiently powerful but caused uncomfortable vibrations, a problem that affected the all-turbine Cunard liners Lusitania and Mauretania.^[28] By combining reciprocating engines with a turbine, fuel usage could be reduced and motive power increased, while using the same amount of steam.^[29]
The two reciprocating engines were each 63 feet (19 m) long and weighed 720 tons, with their bedplates contributing a further 195 tons.^[28] They were powered by steam produced in 29 boilers, 24 of which were double-ended and five single-ended, which contained a total of 159 furnaces.^[30] The boilers were 15 feet 9 inches (4.80 m) in diameter and 20 feet (6.1 m) long, each weighing 91.5 tons and capable of holding 48.5 tons of water.^[31]
They were heated by burning coal, 6,611 tons of which could be carried in Titanic's bunkers, with a further 1,092 tons in Hold 3. The furnaces required over 600 tons of coal a day to be shovelled into them by hand, requiring the services of 176 firemen working around the clock.^[32] 100 tons of ash a day had to be disposed of by ejecting it into the sea.^[33] The work was relentless, dirty and dangerous, and although firemen were paid relatively generously^[32] there was a high suicide rate among those who worked in that capacity.^[34]
Exhaust steam leaving the reciprocating engines was fed into the turbine, which was situated aft. From there it passed into a surface condenser, to increase the efficiency of the turbine and so that the steam could be condensed back into water and reused.^[35] The engines were attached directly to long shafts which drove the propellers. There were three, one for each engine; the outer (or wing) propellers were the largest, each carrying three blades of manganese-bronze alloy with a total diameter of 23.5 feet (7.2 m).^[31] The middle propeller was slightly smaller at 17 feet (5.2 m) in diameter,^[36] and could be stopped but not reversed.
Titanic's electrical plant was capable of producing more power than an average city power station of the time.^[37] Immediately aft of the turbine engine were four 400 kW steam-driven electric generators, used to provide electrical power to the ship, plus two 30 kW auxiliary generators for emergency use.^[38] Their location in the stern of the ship meant they remained operational until the last few minutes before the ship sank.^[39]