The purpose of this article was to find a solution to the problem of reducing the number of the electric multiple unit (EMU) trains traction drive unscheduled repairs due to the breakage of the M24 bolts of the rubber-cord coupling. For these purposes, it is proposed to develop a device that allows accumulating and transmitting data of the impact forces perceived by the bolts of th e rubber-cord coupling and whereby reduce the number of unplanned repairs, as well as the associated rolling stock maintenance financial costs for the JSC «Pasažieru vilciens» railway undertaking. The article presents the initial concept of the design development for a device based on the piezoelectric effect, which will make possible to determine the impact force acting on the M24 bolts of the rubber-cord coupling. The data on the minimum breaking force P were taken based on the results of determining the shear stress [τ] -on the shear acting on the M-24 bolts of the rubber-cord coupling fastening. Using the electronic modules included in the designed device, it is planned to provide storage and transmission of information with the further possibilit y of its processing by a developed PC software or mobile application. However, such devices have a significant drawback -a high development price. For this reason, in order to obtain economic viability, the challenge is creating a device, which cost is limited to 50 Euros. Putting this device into operation would reduce the number of unscheduled repairs therefore reducing the costs experienced by the JSC «Pasažieru vilciens».

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The article analyzes the statistics of rubber-cord coupling failures during 2015 till 2022. The analysis of failures shows that prevailing cases are rupture of the rubber-cord coupling side surface. It should be noted that the cost of eliminating the consequences of a rubber-cord coupling rupture is on average 575.21 EUR for one unscheduled repair. To study the possible reasons of the rubber-cord coupling rupture, the couplings removed from the motor cars after unscheduled repairs were taken. In the process of research, the warming temperature of the rubber-cord coupling, hardness at various temperatures and forces acting on the rubber-cord coupling during operation, i.e. the operational conditions of the rubber-cord coupling were determined. The purpose of these studies is to determine the possible causes of the rubber-cord coupling side surface. The research process of rubber-cord couplings consisted of four stages. 1. Determination of the geometric dimensions of the coupling and comparison of the obtained data with the data of ISO 14691:2008. 2. Theoretical determination (calculations) of: torque, centrifugal force, shear stress and radial load acting on the coupling. 3. Determination of hardness on the Shore A scale depending on the temperature of the rubber-cord coupling in three temperature ranges t = -20 °C; 0 °C; + 22 °C; + 60 °C in the RTU laboratory. Comparison of the obtained data with the data of ISO 14691:2008. 4. Drawing the main conclusions about the possible causes of rupture of the rubber-cord coupling. The purpose of these studies is to determine the possible causes of the rubber-cord coupling side surface. The forces and stresses acting in the zones of damage to rubber-cord couplings are determined. According to the results of calculations, the values of the forces Рс; Рс1 and stresses τk caused by the torque Ma acting on the rubber-cord coupling in the destruction zones and the values of forces and stresses capable of causing the destruction of rubber-cord couplings are determined. In the article hardness of the rubber-cord coupling was also studied at various temperature conditions.

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