Topic. The paper is devoted to the analysis of the dynamics of a complex system, i.e. a hinge mechanism plus a compound pendulum, in which where a differential equation is found, describing its nonlinear behavior. Aim. The paper is in the analysis of nonlinear oscillations of a complex dynamical system, which is a hinge, a rod and a ball, setting together in the one way. It is assumed to obtain differential equation of motion of the pendulum with regard to the gimbal friction and the resistance of the continuum. Method.