Wheel Arrangement
The wheels of a railcar are typically fixed to the chassis at a fixed spacing, and the interaction between the wheels and the rails is coupled. This design prevents railcars from steering like ordinary cars by turning a steering wheel, as the wheel arrangement doesn't allow for overall wheel rotation. In fact, railcars can only steer the entire vehicle by rotating bearings, which is not easily achieved.
Suspension System
Besides the wheel arrangement, the suspension system of a railcar also limits its steering capability. Railcar suspension systems typically use rigid connections, meaning the vertical movement of each wheel is relatively independent. Therefore, when the wheels need to travel on a curve, they cannot adjust to the road curvature through suspension adjustments like in ordinary vehicles. This rigid connection design forces railcars to rotate the entire vehicle body to handle curved travel.
Traction System
Another reason limiting the steering capability of railcars is the design of the traction system. The motor of a railcar is usually mounted on the chassis, transmitting power to the wheels via a power transmission shaft. However, due to limitations in the traction system, the vehicle can only move forward or backward, and cannot move laterally.
In summary, the reasons why railcars cannot change direction include limitations in wheel arrangement, suspension system, and traction system. The design of these components dictates that the entire vehicle can only adapt to road conditions through as a whole-body steering mechanism.
