What were the ancient bamboo dragonflies used for?

Bamboo dragonfly is a great invention in ancient China. When playing, rub your hands together, then let go, and the bamboo dragonfly will fly to the sky. It will spin for a while before it falls. This simple and magical toy once amazed western missionaries and called it "China spiral". In 1930s, Germans invented the helicopter propeller according to the shape and principle of "China spiral".

Bamboo dragonfly consists of two parts. One is a bamboo handle. Cut a bamboo pole (handle) with a length of 20 cm and a diameter of 4 to 5 mm from a bamboo. The second is "wings". Use a piece of bamboo with a length of 18 to 20 cm, a width of 2 cm and a thickness of 0.3 cm, punch a small round hole with a diameter of 4 to 5 mm in the middle, and install the bamboo handle. Then symmetrically cut an inclined plane on both sides of the small hole to play the role of bamboo dragonfly rising with the air vortex. When the wings are finished, insert the bamboo handle into its small hole. When playing, hold the bamboo handle with both hands and rub it quickly. When the hand is loose, the bamboo dragonfly flies to the sky.

origin

Bamboo dragonfly is an ancient toy in China. Its shape is T-shaped, with a horizontal bar like a propeller and a small hole on it. When a straight bamboo stick is inserted into it, the bamboo dragonfly will fly into the sky and then fall to the ground when the lift is weakened. In the process of making and playing bamboo dragonflies, we can appreciate the fun of ancient children's toys in China and the mystery of science and technology.

Inspired by observing the flying dragonflies in nature, China people made flying bamboo dragonflies in 500 BC, which have been children's toys in China for more than 2,000 years. /kloc-spread to Europe in the 0/8th century, which inspired people's thinking. George Kelly?? The Englishman, known as the "father of aviation", has been fascinated by bamboo dragonflies all his life. His first aviation research was to imitate the "bamboo dragonfly" in 1796, and thus realized some working principles of the propeller. His research promoted the development of aircraft. And it has inspired western designers to develop helicopters.

/kloc-in the 7th century, Xu, a skilled craftsman in Suzhou, China, spent all day thinking about bamboo dragonflies played by children, trying to build a dragonfly-like helicopter and take people to heaven. After more than ten years of research, he built a helicopter. It has a propeller like a bamboo dragonfly and a driver's seat like an armchair. It relies on the pedal to drive the propeller to rotate through the rotating mechanism. During the test flight, it actually flew more than a foot off the ground, flew over a small river ditch and then fell.

affect

When the Wright brothers, the inventors of the world's first airplane, were young, their father bought them a flying bamboo dragonfly. They liked it very much and began to imitate bamboo dragonflies of different sizes. Since then, their lives have been inseparable from flying.

record

In the Jin Dynasty (AD 265-420) in China, Ge Hong wrote a book called Bao Puzi, in which he said, "Or take jujube heartwood as a flying car and make a sword with cowhide to attract its opportunity. Or keep five snakes and six dragon three cows, ride them horizontally, and rise 40 miles, which is called Taiqing. Too clear, it is very angry and can win people. " Among them, the "flying car" is regarded by some as the earliest record of bamboo dragonfly, and people think that this toy was introduced to Europe through trade. The image of bamboo dragonfly appeared in a statue of the Virgin Mary in Europe 1463.

In Japanese tradition, people think that the bamboo dragonfly was invented by Hiraga Kennai in the Edo period. However, in 1984, a bamboo dragonfly cultural relic made of wood and feathers in the 8th century was unearthed at the site of Heisei Palace in Nara.

principle

There is an inclination between the leaves of the bamboo dragonfly and the horizontal rotating surface (this inclination can be adjusted).

When the rotor rotates, the rotating blades push the air downward to form a strong wind, and the air also gives the bamboo dragonfly an upward reaction lift, which changes with the inclination angle of the blades. When the inclination angle is large, the lift is large, and when the inclination angle is small, the lift is small. When the lift is greater than the weight of the bamboo dragonfly, the bamboo dragonfly can fly upwards.

The blade and the rotating surface of the bamboo dragonfly also keep an inclination angle, so when we rotate the bamboo dragonfly by hand, it will get the reaction thrust of the air and fly upwards.

The larger the resistance area of the wing surface, the greater the acting force, so the greater the reaction force (buoyancy), and the higher the bamboo dragonfly flies. However, we also found that the larger the resistance area, the greater the required rotating force, so it is not practical in the actual operation of bamboo dragonflies. It may be necessary to find a balance between force and angular area in order to make the bamboo dragonfly easy to operate and fly high.

The bamboo dragonfly in Doraemon

Aircraft (bamboo dragonfly)

It is valid for four hours, after which the battery will run out. This is the helicopter principle. You can put it anywhere on your body. But it is customary to wear it on your head. It is one of the most commonly used magic weapons. Bamboo dragonfly controls the direction according to the user's psychological induction. In other words, if you want to move forward after flying, just think about moving forward. You don't need to focus on it very much. If you can't see clearly, you will instinctively move your neck, head and body parts forward There is nothing special about taking bamboo dragonflies. Anyway, we should be comfortable up and down, left and right. For example, if we want to turn our head to the right, we just have to turn our head directly, even though the brain has to generate signals first, then spread them to the neck, shoulders, face and other places, and finally drive muscles and the like. As long as the bamboo dragonfly is on the user, it can immediately detect the user's mental activity, and it is no problem through the clothes. However, it should be noted that if the user has something similar to a prosthetic leg, the bamboo dragonfly cannot perceive his mental activity. But if the users themselves are made of iron (robots and the like), then bamboo dragonflies can still be used. In other words, the bamboo dragonfly must be attached to the user's own skin. Another point is that bamboo dragonflies are controlled by telepathy. If users are in a confused mood, bamboo dragonflies will be difficult to control.

On the switch of bamboo dragonfly: head (or tail? There is a switch that will start when you press it.