Abstract: A rocker arm assembly (12), supporting the rope of an aerial tramway installation, comprises sheaves (14, 16), the spindles (18, 20) of which are fitted enabling their disassembly, cantilevered from an arm (22) fitted on the inward facing side of the sheaves. The arm (22), made of moulded material, has a rope catcher shoe (66), which protrudes on the outward facing side of the sheaves. A detector of excessive rocker arm (22) swing, due to the rope falling on the catcher shoe (66) or to a sheave being lost, is incorporated in the boss of the arm and protrudes into a shearing groove in the articulation spindle of the arm (22).