Kurama retained vertical triple-expansion engines. Ibuki had also been designed around reciprocating machinery, but ultimately received Curtis steam turbines and Miyabara boilers after the intended Japanese turbine set failed to work as planned. The two related ships therefore ended up with different propulsion systems. Ibuki belongs directly to the uncertain transition from reciprocating engines to turbines, rather than fitting one simple class-wide label.
Notable Point · 36:26-37:17
Ibuki crossed the transition to steam turbines
A correction distinguishes Ibuki's adopted Curtis turbines from Kurama's triple-expansion machinery and places the class across a propulsion transition.