Introduction. The issue of ensuring the operable state of the DC traction motor is relevant due to its large-scale use on diesel locomotives, including modern powerful motors, operating on lines with increased train masses. At present, a rather difficult situation has developed in the locomotive industry with the failure of diesel locomotive traction electric motors due to a decrease in the insulation resistance of the armature windings of the electric motors and their subsequent breakdowns: up to 28 % of the total number of failures of electric motors are due to breakdown of the hull insulation and interturn short circuit of the armature and 13 % of cases are due to reduction in the resistance of the insulating material.Materials and methods. The paper considers the main directions of scientific research on the causes of insulation integrity failure, which lead to unscheduled repairs of traction motors. The theoretical substantiation of the root causes of insulation destruction is based on the importance of taking into account the coefficients of thermal linear expansion of copper and its insulating materials. In order to study thermodynamic processes in the winding of a traction motor, a computational finite element model of a winding coil laid in the groove of the armature core has been developed. The winding model is represented separately by a conductor and insulation, between which contact conditions are specified. The conductor of the calculation model heats up to 120 °C from the current flow. Mathematical apparatus embedded in the MSC calculation program, Patran – Nastran, made it possible to evaluate the deformation of the conductor relative to the insulation as a result of a linear increment due to thermal expansion.Results. With the help of mathematical modelling and based on the results of finite element analysis, the confirmation of the theoretical justification is clearly shown. The difference in elongation during heating of the motor armature conductor and insulation, obtained by mathematical modelling, is 0.6 mm and is significant for the winding (consisting of a conductor and insulation), which is usually considered as a single whole body.Discussion and conclusion. The obtained result shows the need for more detailed studies to select the technology for the insulation of the DC traction motor. The use of insulating materials for the armature winding with coefficients of thermal linear expansion equal to the coefficient of thermal expansion of the copper conductors of the winding will improve the reliability of traction electric motors of diesel locomotives in operation.

The article, based on the archives and other never published materials, discusses the history of design and construction of Krivandino–Ryazanovka and Sazonovo–Pilevo railway lines, which belonged to Moscow–Ryazan branch of Moscow railway. The objective of writing the article is to clarify the circumstances of design, construction and operation of these lines, as well as to identify the reasons that led to their decline and closure in the mid-2000s. To achieve this objective, well-known publications in the press and the Internet were analyzed. In addition to using data from these sources, work was carried out to search for written sources on the issue under study in archival institutions in Moscow. Some documents are published for the first time. he result of all the work carried out was establishment of the  following  previously  unknown  or  questioned  facts: Krivandino–Ryazanovka railway line was built in 1943–1944, Sazonovo–Ryazanovka section was built later than the rest of the line. The purpose of Krivandino–Ryazanovka line according to the project and in the first years of its existence was transportation of firewood for heating of Moscow. The date of acceptance of Sazonovo–Pilevo line in full for servicing Kurovskaya distance of the track is January 1, 1978. From the northern neck of Pilevo station, the access road went to the construction yard of Meshcherskoye peat enterprise. According to Kurovskaya distance of the track, the broad gauge transshipment station of Meshcherskoye peat enterprise was called Torfyanaya.The first part of the paper. The second part is scheduled for the next issue.

The final part of the article, the first part of which was published in the previous issue of the journal.The article, based on the archived and other never published materials, discusses the history of design and construction of Krivandino–Ryazanovka and Sazonovo–Pilevo railways which belonged to Moscow–Ryazan branch of Moscow railway. The objective of the article was to clarify the circumstances of design, construction and operation of these lines, as well as to identify the reasons that led to their decline and closure in the mid-2000s. To achieve this objective, well-known publications in the press and the Internet were analysed. In addition to using data from these sources, written sources on the issue under study were searched for in archival institutions in Moscow. Some documents are published for the first time.The work carried out resulted in revealing previously unknown or questioned facts: Krivandino–Ryazanovka railway line was built in 1943–1944, Sazonovo–Ryazanovka section was built later than the rest of the line. The purpose of Krivandino–Ryazanovka line according to the project and in the first years of its existence was transportation of firewood for heating of Moscow. The date of commissioning of the entire Sazonovo–Pilevo line for servicing Kurovskaya distance of the railway was January 1, 1978. From the northern neck of Pilevo station, the access railway went to the construction yard of Meshcherskoye peat enterprise. According to information of Kurovskaya distance of the railway, the broad-gauge transshipment station of Meshcherskoye peat enterprise was called Torfyanaya.