 By the time construction work on Derfflinger began , it was determined that the diesel engine was not ready for use . Instead , the plan to use a three @-@ shaft system was abandoned and the ships reverted to the standard four @-@ shaft arrangement . Each of the three ships were equipped with two sets of marine @-@ type turbines ; each set drove a pair of 3 @-@ <unk> screws that were 3 @.@ 90 m ( 12 ft 10 in ) in diameter on Derfflinger and Lützow and 4 m ( 13 ft 1 in ) in diameter on Hindenburg . Each set consisted of a <unk> and low @-@ pressure turbine — the high @-@ pressure machines drove the outer shafts while the low @-@ pressure turbines turned the inner pair . Steam was supplied to the turbines from 14 coal @-@ fired marine @-@ type double boilers and eight oil @-@ fired marine @-@ type double @-@ ended boilers . Each ship was equipped with a pair of <unk> @-@ electric generators and a pair of diesel @-@ electric generators that provided a total of 1 @,@ 660 <unk> at 220 volts . Each ship was equipped with two rudders . 
