INVESTIGATION OF DYNAMIC CHARACTERISTICS OF GONDOLA CARS ON PERSPECTIVE BOGIES

Dep. «Cars and Car Facilities», Dnipropetrovsk National University of Railway Transport named after Academician V. Lazaryan, Lazaryan St. 2, Dnіpropetrovsk, Ukraine, 49010, tel. +38 (056) 776 84 98, e-mail sergeymyamlin@gmail.com., ORCID 0000-0002-7383-9304 JSC «Main Specialized Design Bureau of Car Building named after Valerii Mykhailovych Bubnov», Mashynobudivnyky Sq., 1, Donetsk region, Mariupol, Ukraine, 87535, tel. +38 (0629) 56 08 67, e-mail bubnov@azovmash.com, ORCID 0000-0002-5896-801X Research Institute of the Rolling Stock, Track and Transport Constructions, Dnipropetrovsk National University of Railway Transport named after Academician V. Lazaryan, Lazaryan St. 2, Dnіpropetrovsk, Ukraine, 49010, tel. +38 (0562) 33 55 38, e-mail diit_ndi@ua.fm, ORCID 0000-0003-1957-0292


Introduction
The design of cars improvement and increase of train speeds requires solution of a question concerning safety in operating, reliability of rolling stock and a track.In seeking to resolve such matter the important factor is operations on modernization of existing ones and creation of new structures of a truck.Dynamic and strength qualities of cars in general depend on their workability.
These requirements were the basis for the development of a new freight bogie, model 18-1711 with increased axle load [3,7].
The bogie 18-1711 is a three-element structure consisting of two side frames and a bolster.In the bogie the central bilinear suspension and friction wedge-type shock absorbers of spatial actions were implemented.
One of the bogie 18-1711 features is the presence of elastic coupling between the side frames and wheel sets implementing through the herringbone absorber that works in all three planes.Therefore, the bogie 18-1711 can be considered as having two stages of suspension.

Purpose
The aim of this work is the dynamic properties research of the gondola car with bogies, model 18-1711 when it moves on straight and curved sections of a track and their comparison with the dynamic qualities of the gondola car with bogies, model 18-100.Results comparison of such calculations will determine the direction of scientific research in order to improve the dynamic qualities of gondola cars.

Methodology
A mathematical model of bogies, model 18-1711 was built in this study.The dynamic characteris- tics of the gondola car in empty and loaded state, when it is installed on these trucks were determined too [1,2].Dynamic properties determination of gondola cars with bogies 18-1711 was performed during its movement on straight and curved sections of a track.At the same time the dynamic characteristics evaluation of the gondola cars was carried out ac-cording to the following regulatory dynamic parameters: coefficient of vertical dynamics (C dv ), the coefficient of horizontal dynamics (C dh ), the safety factor against derailment (SF d ) [4,5].
For the calculations a typical gondola car with the following inertia characteristics was chosen (table 1).The calculations were performed using the object-oriented programming on the program "Dynamics of Rail Vehicles" ("DYNRAIL" Myamlin S. V. registered 20.03.2003).Mathematical models of a gondola car and bogies 18-100 and 18-711 were created for the calculations [6,8,9].
In order to compare the obtained results calculations were performed for gondola cars on bogies of the typical model 18-100 and new bogie 18-1711.
Track irregularities in vertical and horizontal transverse planes were assigned as perturbations.They should be so that the dynamic indexes, of the widely used in operation gondola cars on bogies, model 18-100 keep in admissible range of speeds up to 80 km/h for the empty gondola car and at speeds up to 90 km/h for the loaded gondola cars.
Next, movement simulation of empty and loaded cars on straight and curved section of a track with middle (600 m) and small (300 m) radii with the above mentioned irregularities of tracks was carried out.The results of these calculations will be used as reference values for comparison of them with the results for the gondola car on the bogies, model 18-1711 [10][11][12][13][14].

Findings
In all the figures the results for cars on bogies 18-100 are shown by the line with a triangular marker and for cars on bogies 18-1711 -by the line with rhomboid markers.
Analysis of the results obtained during the research let us make the following conclusions: 1.The use of the spring grouping bogie with a bilinear characteristic in the central stage of sus-pension has improved dynamic performances of described gondola cars.
2. To a large extent dynamic performances of empty gondola cars have improved in comparison with loaded.This explains the fact that the static deflection of spring grouping in the empty gondola car is on a section characteristic with less rigidity.Dynamic performances of loaded gondola cars on bogies, model 18-1711, were improved too, though to a lesser extent.
Improving the dynamic performances is more evident in the modeling of freight gondola cars motion on a straight section of the track than at motion on curve of medium and small radii.This is due to the fact that the dynamic performances of gondola cars during motion on curves are largely determined by the centrifugal forces that operate on cars.

Originality and practical value
Firstly calculations to determine the dynamic performances of gondola cars with bogies, model 18-1711 during its motion on straight and curved sections of the track were carried out.At the same time the assessment of dynamic characteristics of a gondola car was made and the following regulatory dynamic performances were identified: the coefficient of the vertical dynamics (C dv ), the coefficient of horizontal dynamics (C dh ), and the stability factor against derailment (SF d ).The use of bogies with bilinear characteristic of the central suspension will improve the dynamic performances of gondola cars, currently operating on bogies, model 18-100.And by improving the dynamic performances it may increase the permissible speed of these cars.

Conclusions
Analysis of the calculations results and comparison of dynamic parameters of the gondola car with bogies 18-1711 and the gondola car with bogies 18-100 shows that the bilinear characteristic of the central suspension of freight car bogie has a positive effect on its dynamic performances both during motion on a straight sector and in the curved sections of the track.Besides the dynamic performances improvements are more pronounced in the gondola car in empty state.Thus, the use of bogies 18-1711 with bilinear characteristic of the central suspension for gondola cars will enable to

Fig. 1 .Fig. 2 .Fig. 3 .Fig. 4 .Fig. 5 .Fig. 6 .
Fig. 1.Dependence graphs of the dynamic parameters of the empty gondola car on the speed movement (Direct): a -coefficients of the vertical dynamics; b -coefficients of the horizontal dynamics; c -the safety factor

Table 2 The maximum permissible values of the main dynamic parameters for gondola cars with the bogie, model 18-1711
Maximum permissible values of determined dynamic parameters for gondola cars with bogies having over axle box suspension are presented in the Table2.