The class retained roughly 32.5-knot speed while extending cruising range to about 7,000 nautical miles at 16 knots. Four enhanced Admiralty three-drum boilers generated about 72,000 shaft horsepower in a hull slightly lighter than a completed Leander. Unlike the Leanders' concentrated machinery layout and single funnel, the Amphions alternated boiler and engine rooms and therefore used two funnels. The longer machinery space modestly increased the length requiring protection, but separated vital systems. Steam could be redirected through auxiliary connections, and a single torpedo was less likely to eliminate every engine at once. Hobart's later survival gives the design discussion a concrete wartime counterpart.
Notable Point · 21:06-23:51
Amphion machinery layout and torpedo resilience
The Amphions paired long range and high speed with a split boiler-and-engine arrangement intended to make a single torpedo less likely to disable all propulsion.