lebus groove design advantage:

With the Lebus system, the continuous groove in the drum is parallel to the flange except for two crossover points on each revolution where the groove moves across the drum half a pitch to give a full pitch of movement for each revolution. With Lebus grooving it is possible to calculate exactly the direction of the forces that the rope imposes on the drum because the spooling is totally controlled. This is not possible with any other spooling system. it is widly used in crane ,mining,drilling ,marine ,offshore platform  and so on .