housings 20 22 when they are disconnected from their respective shafts 32 36 so as to ensure that the drums 4 8 do not rotate unintentionally other types of brakes such as band brakes may also be used it should be noted that it will normally make no sense to disconnect both drums 4 8 from the shafts 32 36 at the same time possible modes of operation with a draw works according to the description above may be summarized as follows dual mode both drums 4 8 are connected locked to their respective shafts 32 36 and the two shafts 32 36 are connected locked to each other the torque from the ac motors 30 34 from both sides is combined to rotate both drums 4 8 which are run synchronously this mode of operation will substantially double the hoisting speed as seen from the travelling block 16 compared to a single draw works with the same maximum rotation speed of the drum as described above this dual mode may be particularly beneficial to use during tripping due to reduced operation time single mode one of the drums 4 8 is disconnected unlocked from its respective shaft 32 36 the other one of the drums 4 8 is connected locked to its.