Possibilities of improving the safety of rail vehicles with independently rotating wheels
Authors: Myhajlov Yevhen , Semenov Stanislav , Dizho Yan , Blatnitsky Miroslav 
Published: February 2024

One of the promising ways to achieve high speed and smooth running of rail vehicles during stable movement in straight sections of the track and to improve the characteristics of fitting the vehicles in a curve is the use of independently rotating wheels in their running parts. Such undercarriages are already becoming quite widespread, for example, in urban rail transport vehicles. But independently rotating wheels can rotate in a wheel pair around a common axis with different angular velocities. It follows that during their movement, longitudinal creep forces do not arise, which form the controlling moment and center the wheel pair in the rail track. This can lead to increased angles of attack of the wheels on the rails, increased lateral forces and accelerated wear of the wheels and rails.  In turn, this increases the tendency of vehicles with independently rotating wheels to derail by rolling the flange onto the head of the rail.

The accumulated global experience of operating similar vehicles confirms this. To overcome the mentioned disadvantages of independently rotating wheels, a number of various technical solutions have been proposed. Some of them relate to ensuring the given elastic-dissipative characteristic of the torsional articulation of the wheels in a wheel pair. A promising direction is the improvement of the characteristics of the connections of wheel pairs with the bogye and bogyes with the vehicle body, the use of mechatronic systems for controlling the position of the wheel pairs in the horizontal plane for their radial installation in curved sections of the track. In this work, attention is paid to the issue of the use in the design of independently rotating wheels of a perspective design scheme that allows independent rotation of the wheel's support surface and its guide surface (flange). The question of the effect of changing the design scheme of the wheel on the safety of movement due to the roll-in of the ridge on the rail head was considered.

The influence of a promising design scheme of a wheel in comparison with a traditional design scheme of a wheel on the safety of driving down a rails was investigated. The peculiarities of the distribution of frictional forces in the ridge contact during movement along the rails of the wheels of both design schemes are analyzed. For a wheel of a traditional design scheme, the module and the direction of the friction force vector in the ridge contact are uniquely determined by the geometric characteristics of the contact between the wheel and the rail and the angular speed of the wheel rotation. At the same time, when the wheel of the prospective design scheme moves, the direction and module of the friction force vector of the ridge on the rail also depend on the ratio of the angular velocities of rotation of the supporting surface of the wheel and its guiding surface (flange) around the common axis. The obtained results allow us to draw a conclusion about the expediency of using a promising design scheme in independently rotating wheels to increase the safety of movement of rail vehicles.