Abstract: A friction gear for a separate accessory of a combustion engine equipped with belt-driven auxiliary units, including a frictional wheel guided by a swivel arm coupled to the engine, to which a protection device is assigned, with the swivel arm and the frictional wheel/protection device provided as a single assembly. The swivel arm provided in the form of a hollow profile includes, on the one hand, a housing which has a single part, flat-cylindrical design and which serves as an essentially closed frictional wheel/protection device with a frictional wheel that can be rotationally mounted between housing end walls and, on the other hand, a coupling location, such that the swivel arm forming a whole with the protective housing and with the coupling location is designed so that it can be assembled over at least one longitudinal partition.