Both reciprocating engines in Harland And Wollf's factory
A cylinder casing for one of the reciprocating engines
The Titanic had 2 triple expansion reciprocating engines. The engines were located in the Reciprocating Engine Room on the orlop deck, aft of boiler room 1. The reciprocating engines drove(turned) the port, and starboard propellers. Aft of the reciprocating engines was the turbine engines which drove the central propeller. The reciprocating engines were 4 storeys tall, running on steam from the boiler rooms. The reciprocating room was vented through a slight shaft going up to the Boat Deck. The left over steam went aft to drive the turbine engine.
Kempton Park Big Triple Steam Engine Starting