Imitating modelling electromechanical oscillatory system of bacr-rotary movement with dry and equivalent viscous frictions is considered, the quantitative estimation of replacement of dry friction equivalent viscous is given at work of system on own frequency.

The paper studies a dynamically-balanced electromechanical core drilling tool on a carrying cable, its purpose and the area of its application, construction and design diagrams, a mathematical model and a block scheme of the closed system with positive feedback.