A contour formed by the rim and the tread on a radial section of the wheel forging. The choice of the rim and tread shape of the wheel forging not only affects the wear and service life of the wheel forging on the track, but also directly relates to the curve passing performance and running quality of the equipment. The rim allows the wheel forgings to reliably pass curves and turns without derailing.
The tread is conical and tapers 1:10 near the rolling circle. When passing the curve, the outer wheel rolls on the outer rail with a larger diameter close to the rim, and the inner wheel rolls on the inner rail with a smaller diameter, so that on the one hand, the wheel forging changes with the direction of the line, and the inner and outer wheels The difference in rolling distance also compensates for the effect of the difference between the length of the inner and outer rails.
When running on a straight line, if the wheel pair deviates from its center position on the line, the difference between the two rolling radius will cause the wheel to move in the direction of returning to its center position. The outer taper of the wheel is 1:5, which can increase the difference between the two wheels' rolling radius, making it easy to pass the small radius curve. Reducing the tread taper helps to suppress snake movement, but the rim wear is significantly increased, and the cycle and wheel life are greatly reduced. This method is only used on some high speed passenger trains.
On the other hand, the shape of the wheel forging rim surface wears faster in the initial stage of operation, and then gradually becomes stable and the wear is slowed down. The shape after the restoration is still not maintained for a long time, and the amount of metal cutting is large. Therefore, in some countries, the railway adopts a wheel-to-tread shape that is close to the wear and reaches a relatively stable state, called a concave tread, also known as a wear-shaped tread. This shape not only reduces wheel wear, but also prolongs the cycle period, and the contact stress can be reduced by improving the wheel-rail contact state.