Rope tension in double drum traction winches

Double drum traction winches can develop high tension ratios between rope held on low tension storage reels and rope deployed at high tension. Such winches are used for a variety of applications. The tension profile applicable to the rope passing through such a winch is controlled by the Eytelwein equation and involves local slippage (or creep) at the coefficient of sliding friction. ln an attempt to reduce the magnitude of creep, winch designs have been developed in which successive wraps have different diameters, to approximate to the rope stretch. This changes the tension profile with potentially serious consequences especially when retrieving rope at low or moderate tension. Furthermore if the two drums on such a winch are not mechanically coupled but hydraulically driven at equal torques, further complications can arise. 

Author(s): Chaplin, C.R.