The wheelset of any railway transport consists of two metal wheels, which are connected into a monolithic structure using the same metal axle. It is quite obvious that such a system does not know how to rotate from the word "absolutely", because there is not a single pivot hinge in the design. This raises a logical question: how then do the trains turn, after all, the track is by no means always straight?
The fact that the wheels of railway transport cannot turn inside the structure of the wheelset does not in any way interfere with the turning of the entire train. In order to understand how exactly all this works, it is necessary to remember and understand the general structure of the railway. So, a railway track always consists of two parallel-lying rails, fixed on perpendicular sleepers. The rails allow you to guide the flange of the railroad wheel and maintain the direction of movement of the carriage or tractor without additional friction.
The wheelsets are only one of the elements of the car's undercarriage. Its most important unit is the wagon bogie, on which the rest of the body rests. It is he who is the main turning device of the train. This unit consists of a frame, wheelsets, springs, axle boxes and brake pads. The relatively small dimensions of the wagon bogie allow it to easily fit into curves of a small radius. Most carts have two axles, less often there is a variant with three, even less often with four.
So how exactly does the turn take place? In fact, everything is quite simple. The bottom line is that two carriages form a single system, where there are external and internal wheels. And then physics and geometry come into play. First, the outer radii of the wheels are not cylindrical, as it might seem, but conical. Secondly, when driving on a curve, the outer wheel always travels a longer distance. As a result of all this, inertia arises, which moves the wheels, the wheel pairs seem to "slide". This is prevented by the flange - a special ridge on the inner radius of the wheel.
If you want to know even more interesting things, then you should read about is it correct to call a railway train a train: what is the difference between the two concepts.