(EN) Braking device comprising a rotor (3; 13) suitable for rotating around a main axis (X) in a substantially cylindrical seat (9; 19) suitable for containing a viscous fluid, wherein said seat (9; 19) is offset with respect to the main axis (X) and the rotor (3; 13) is provided with at least one rocking vane (4; 14) which is arranged substantially parallel to the main axis (X) for translating with an alternating motion with respect to the rotor (3; 13).