Why do trains shake?

Answered by Tom Adger

Trains shaking can be attributed to various factors, including the design of the train and the track, the speed at which the train is traveling, and the condition of the track itself. When a train moves along the track, it creates an oscillating force at each wheel/track contact point. This force is then transmitted to the ground at each sleeper/ground contact point, resulting in the shaking sensation.

One of the main reasons for the shaking is the interaction between the wheels of the train and the track. The wheels are not perfectly round; they have a slight conical shape known as the taper. This taper helps the train stay centered on the track and prevents it from derailing. However, it also leads to an oscillating force as the wheels rotate.

Another factor that contributes to the shaking is the irregularities in the track itself. Even though tracks are carefully laid and maintained, they are not completely smooth. Small imperfections such as bumps, dips, and unevenness can cause the train to vibrate as it moves over them. These irregularities can be caused by changes in temperature, wear and tear, or even the settling of the ground beneath the track.

The speed at which the train is traveling also plays a role in the shaking. As the train picks up speed, the oscillating force generated by the wheels becomes more pronounced, leading to a more noticeable shaking sensation. Similarly, when the train slows down or comes to a stop, the shaking may decrease.

Additionally, the type of train and its suspension system can affect the level of shaking. Different trains have different designs and suspension setups, which can either dampen or amplify the vibrations. Trains with better suspension systems are generally less prone to shaking.

Personal experiences can provide insights into the magnitude of train shaking. I have traveled on various types of trains, from high-speed trains to older, more traditional ones. The high-speed trains, with their advanced suspension systems and smoother tracks, generally provided a smoother and less shaky ride. On the other hand, the older trains, especially those running on poorly maintained tracks, often resulted in noticeable shaking and vibrations.

To summarize, trains shake primarily due to the oscillating force generated at the wheel/track contact points and transmitted to the ground at the sleeper/ground contact points. Factors such as the design of the train and track, the speed of the train, and the condition of the track all contribute to the shaking sensation. Personal experiences and observations further emphasize the impact of these factors on the level of train shaking.