Author: Ma’anshan Tianjun Machinery Manufacturing Co., Ltd. Publish Time: 2024-04-22 Origin: train-wheels.com
The structure of a railway wheel consists of the wheel rim, wheel tread, wheel hub, wheel spokes, and wheel diameter, each part having its specific significance in shape.
The diameter of train wheels has a significant impact on both the wheels themselves and the entire vehicle. On one hand, as the wheel diameter increases, the vehicle's center of gravity rises, leading to poorer dynamic performance. On the other hand, increasing the wheel diameter can reduce the contact stress between the wheel and the rail, decrease the rate of wheel wear, increase the wheel's heat capacity, and enhance its ability to withstand braking thermal loads on the tread surface.
Therefore, the size of the rail wheel diameter should be determined comprehensively based on the vehicle's specific circumstances. Generally, as the axle load of the vehicle increases, the wheel diameter should also increase to enhance the wheel's heat capacity and increase the contact area with the rail, thereby reducing tread damage and wear. Additionally, attention should be paid to standardization series issues when selecting the wheel diameter value to facilitate wheel manufacturing and maintenance.
The width of the rail wheel rim primarily depends on the load capacity of the rail. When wheelsets are operating on curves, the outer rail wheel rim is closer to the rail while the inner wheel rim is farther away. Sufficient load capacity on the inner wheel tread is essential to prevent derailment.
The mass of the wheel rim constitutes a significant portion of the wheel's overall mass, with the quality of the wheel rim largely determining the quality of the wheel. This is particularly true for cast steel wheels, where a larger initial mass of the wheel rim necessitates thicker spokes, resulting in increased wheel mass. As the mass of the wheel increases, it exerts a greater vertical force on the rail, impacting vertical dynamics.
The railway wheel and axle are assembled together by interference fit. The main function of the wheel hub is to securely fix the wheel to the axle, and its dimensions are primarily determined by the tightening force required for the wheel-axle fit. The thickness of the wheel hub varies with different axle loads. With a certain amount of interference fit between the wheel hub length and the axle, the thicker the wheel hub, the greater the mass of the train wheel, and the greater the tightening force between the axles.
The optimal thickness of the wheel hub should be: as thin as possible while meeting the requirements for axle tightening force, in order to reduce the mass of the train wheel.
Hub flange distance refers to the axial distance between the inner side of the wheel flange and the inner side of the wheel hub. This value is related to the inner distance of the wheel pair and the distance between the two wheel seats of the axle. Therefore, when selecting the hub flange distance, it should not be considered solely from the perspective of the wheel, but should be considered in coordination with the inner distance of the wheel pair and the axle.
The strength of the spokes directly affects the safety of train operation, so the wheel spokes should have sufficient strength. The shape of the spokes has a significant impact on the structural strength and stiffness of the wheel. A smaller radial stiffness can give the wheel greater elasticity, which can improve the stress state of the wheel under braking heat load and reduce the dynamic forces on the wheel and rail.
Therefore, the radial stiffness of the spokes should be moderately small. The axial stiffness of the spokes should be as large as possible; otherwise, the wheel will experience significant axial deformation. Excessive axial deformation can alter the normal contact position between the wheel and rail and the angle of the wheel flange, affecting the vehicle's operational performance and increasing the risk of climbing rail. A well-designed spoke shape can significantly increase the structural stiffness of the wheel without adding weight, improving the overall stiffness of the wheel. Therefore, the spokes are a key area of focus in the design and optimization of wheel structures.
When designing the outer profile of the wheel tread, consideration should be given to its compatibility with the profile of the rail head. An ideal wheel-rail profile matching state can effectively reduce contact stress and wear, contributing to improved performance of trains negotiating curves and effectively increasing the critical speed at which trains become unstable. At the same time, newly designed treads should closely resemble the shape after wear to minimize the amount of metal removed during tread correction.
