As a unique means of transportation, the biggest difference between trains and other land vehicles is probably the part in contact with the ground. Cars mainly use rubber, a material with high friction and elasticity, to make tires, but trains cannot be made with wheels. They also need the cooperation of rails to operate normally.

But we can see that the wheels of the train press forward on the thin rails, but there are very few derailment accidents. Why is this?

The wheel of a train looks like a cylinder on the outside with a slightly larger "disc" on the inside. Many people think that the disc on the inside is what fixes the wheels and rails. In fact, this is not the case at all.

After all, if part of the disc contacts the rails for a long time, the friction will inevitably increase significantly and affect the speed of the train. Therefore, the existence of this disk can be said to be an "insurance", which can only play its role in critical moments. The key is that the "cylinder" on the outside is actually a cone, or a truncated cone to be precise.

A simple cylinder will obviously not be able to keep moving in parallel on a smooth rail surface, but if there is an inclined surface, it will be different. Even when turning, the balance of the tires on both sides can be maintained. So on the surface it seems that the connection between the train and the rails is not close, but in fact the train stays on the rails in a very stable manner.

Furthermore, the weight of the train itself has reached a certain level, so it will not be unstable because it is too light, and of course it will not be unable to speed up because it is too heavy. Therefore, the train track may seem to have a simple structure, but in fact it contains many mechanical principles to ensure that the train does not derail.

"Learning" on the Rails

In addition to the train itself, the rails of the train are obviously also an extremely important part of transportation. Without suitable rails, the train will be unable to move. We know that in addition to the two basic rails, sleepers and ballast are also indispensable parts of railway tracks.

The sleeper has many functions. It plays the role of connecting two rails, dispersing the huge pressure of the train pressing on the rails and transmitting it to the roadbed below. Because the sleepers will deform to a certain extent when the train passes by, the material of the sleepers needs to be both soft and tough.

As for the role of ballast, it is mainly to buffer the pressure received by the sleepers and increase the life of the track. In addition, the drainage function provided by the gravel is also very important, which can allow rainwater to be discharged in time without greatly reducing the friction between the wheels and the track, thus increasing the safety of train driving and ensuring that it can operate under various climatic conditions，safety.