Fourteen boilers fed four funnels in an uneven four-four-four-two grouping and supplied three triple-expansion engines. The plant was rated at 23,000 indicated horsepower, 24 knots, and a range of about 7,500 nautical miles. A nominal top speed mattered less than the ability to maintain it, since a 21-knot battleship could eventually catch a raider unable to sustain her advantage. During a 20-hour run at 21 knots, severe vibration began breaking up brass bearings and forced their replacement with steel. The repair delayed completion by five months. Châteaurenault later reached 24.15 knots, but the trials exposed the reliability cost behind that headline speed.
Chapter · 24:49-28:19
Fourteen boilers, continuous speed, and vibration trials
The four-funnel plant delivered impressive trial figures, but destructive vibration showed the difference between reaching a speed and sustaining it reliably at sea.