 The Royal Sovereigns were powered by a pair of three @-@ cylinder , vertical triple @-@ expansion steam engines , each driving one shaft . Their Humphrys & Tennant engines were designed to produce a total of 11 @,@ 000 indicated horsepower ( 8 @,@ 200 kW ) and a maximum speed of 17 @.@ 5 knots ( 32 @.@ 4 km / h ; 20 @.@ 1 mph ) using steam provided by eight cylindrical boilers with forced draught . The ships carried a maximum of 1 @,@ 420 long tons ( 1 @,@ 443 t ) of coal which gave them a range of 4 @,@ 720 nautical miles ( 8 @,@ 740 km ; 5 @,@ 430 mi ) at a speed of 10 knots ( 19 km / h ; 12 mph ) . 
