During holidays, people will go to the supermarket to buy some daily necessities, go to the supermarket to push shopping carts, and walk around to see what they need. But, have you noticed that the wheels of the supermarket trolley can rotate freely, and the shopping cart can be easily changed in which direction we want to go.
How is this done?
We will share with you, let us first understand the development history of wheels. Throughout the history of human development, people have created many great inventions, and these inventions have greatly changed our lives. The wheel is one of them. The vehicles we use every day rely on wheels for transportation. It is now difficult to verify who invented the wheel, but one thing is certain, the invention of the wheel is a slow and long evolutionary process. It was initially found that rolling is much less labor intensive than sliding.
People put the logs under heavy loads and transported them by rolling, and later inspired the logs to invent the wheel. The wheels should appear at the same time as the car. Because a single wheel is useless, combining several wheels with axles can take full advantage of its effect. It is difficult to assume that humans did not invent the wheel, whether it is ancient or modern, what our society would be like. The advent of wheels enables humans not only to travel long distances, but also to transport heavier objects to farther places. Through commercial activities, large cities have been developed. During the development of the wheel, people found that the wheel can only run in a straight line, and it is difficult to change direction when carrying heavy objects.
Therefore, people invented a wheel and steering structure, namely casters. The invention of casters greatly improves the processing efficiency. With the development of industry, it has been more and more widely used, becoming one of the indispensable parts. Casters include casters, fixed casters and casters with brakes. Movable casters are what we call universal wheels, which can rotate 360°. Usually two casters are used together.
There are four casters in the airport under the supermarket shopping carts or trolleys for luggage. All four casters are casters. If you look closely, you will find that the axles and the universal casters of the body are not fixed, but are freely rotatable vertical axles. If the axle is fixed on the body, the casters can only go straight forward, and the car cannot turn. In addition, you can also find that when you push a cart, the wheels of the casters always follow the axis of rotation. If you move from front to back, the wheels of the casters will suddenly turn 180° around the vertical axis, or the wheels are still following the axis of rotation. Generally speaking, the rolling direction of the casters must be consistent with the forward direction in order to make the shopping cart move smoothly. Once the rolling direction of the casters is inconsistent with the front direction of the car body, ground friction will generate torque on the front vertical rotation axis and push the casters to a position that matches the direction of travel.
