This paper presents a simulation and experimental study on a passive “click” mechanism, which is designed to adapt the angle of incidence of a racing car flap along a circuit to have high down force when the car undertakes low speed corners and low drag force when the car sprints along the straights. The mechanism is composed by four rigid linkages connected via flexible pivot junctions. The paper first provides a parametric study that shows how the stiffness of the flexible pivot junctions, the length of the linkages and the rest angles of the linkages influence the typical N-shaped resistant moment–joint rotation function, which is at the basis of the clicking effect. The parametric study is then used to design a mechanism, which is characterised by a stable high pitch equilibrium configuration only and maintains the N-shaped moment-rotation feature such that the flap snaps from high-to-low pitch and vice versa at given critical speeds during acceleration and deceleration of the car. Finally, the dynamic response of a flap mounted on the proposed monostable clicking joint is analysed in detail and contrasted with that of a flap fixed on classical passive joints built with a stiff spring or a soft pre-loaded spring.
