The paper deals with the numerical analysis of electromechanical systems. The system consists of a DC motor supplied from a half-wave, single phase, thyristor rectifier, and of a flexible rod fixed to the axis of armature. Discretization of rigid segments is used to model flexibility of the rod. The discrete structure is considered as a multibody system, i.e. as a single kinematical chain of rigid bodies connected by massless joints. Significant drift rotation is included in the rod model. Numerical integration is performed in order to predict behavior of the system. Two working conditions are tested: steady-state motion and transient braking of the system. The attention in the paper is concentrated on interactions between the mechanical and electrical systems.