Propulsion
Almost all pre-dreadnoughts were powered by reciprocating steam engines. Most were capable of top speeds between 16 and 18 knots (21 mph; 33 km/h). The ironclads of the 1880s used compound engines, and by the end of the 1880s the even-more efficient triple expansion compound engine was in use. Some fleets, though not the British, adopted the quadruple-expansion steam engine.
The main improvement in engine performance during the pre-dreadnought period came from the adoption of increasingly higher pressure steam from the boiler. Scotch marine boilers were superseded by more compact water-tube boilers, allowing higher-pressure steam to be produced with less fuel consumption. Water-tube boilers were also safer, with less risk of explosion, and more flexible than fire-tube types. The Belleville-type water-tube boiler had been introduced in the French fleet as early as 1879, but it took until 1894 for the Royal Navy to adopt it for armoured cruisers and pre-dreadnoughts; other water-tube boilers followed in navies worldwide.
The engines drove either two or three screw propellers. France and Germany preferred the three-screw approach, which allowed the engines to be shorter and hence more easily protected; they were also more maneuverable and had better resistance to accidental damage. Triple screws were, however, generally larger and heavier than the twin-screw arrangements preferred by most other navies. The French also built the only class of turbine powered pre-dreadnought battleships, the Danton class of 1907.
Coal was the almost exclusive fuel for the pre-dreadnought period, though navies made the first experiments with oil propulsion in the late 1890s. An extra knot or two of speed could be gained by applying a 'forced draught' to the furnaces, where air was pumped into the furnaces, but this risked damage to the boilers.
Read more about this topic: Pre-dreadnought Battleship