 Charles Martel had two vertical triple expansion engines each driving a single screw , with steam supplied by twenty @-@ four Lagrafel d 'Allest water @-@ tube boilers . Her propulsion system was rated at 14 @,@ 900 indicated horsepower ( 11 @,@ 100 kW ) , which allowed the ship to steam at a speed of 18 knots ( 33 km / h ; 21 mph ) . As built , she could carry 650 t ( 640 long tons ; 720 short tons ) of coal , though additional space allowed for up to 980 t ( 960 long tons ; 1 @,@ 080 short tons ) in total . 
