Olympic Science

Excerpted from "The Light of Science and Technology in the Olympics", written by Zhao Zhizhen. Authorized by Mr. Zhao Zhizhen, published by the Scientific Squirrel Society on the Internet, reprinted from: Scientific Squirrel Society []

"As a highly efficient "energy converter", the bow can convert 70 to 80% of the elastic potential energy into the arrow's Kinetic energy, the "residual" energy becomes the damping vibration of the bow. "

The sound of archery

White, black, blue, red, and yellow, these five-color concentric circles. He is the "target" in the archery arena. The diameter of the archery target is 122 centimeters, and the diameter of the bullseye, known as the "bull's eye," is only 12.2 centimeters. Athletes have to shoot 10 rings from 90 meters away, which is equivalent to standing on a goal in a football field and shooting an apple in the opposite goal. In other words, the entire target looks like a thumbtack in front of you. It is indeed not an easy task to achieve the goal of "piercing a poplar with a hundred steps" and making perfect arrows.

It is difficult to find a nation in the world that has never used bows and arrows in history. Cupid's "golden arrows" and "lead arrows" govern love between heaven and earth, Robin Hood relies on his "magic arrows" to rob the rich and help the poor, and Hou Yi "shoots arrows for nine days" to transform the "ecological environment". How many myths and legends are there in the East and the West? All related to bows and arrows. In the long years before the advent of "hot weapons", bows and arrows have always been the most powerful military equipment. From hunting tools to weapons of war to sports, the role of bows and arrows in human civilization has fundamentally changed.

Women's Archery Competition at the 1908 London Olympics

At the 1900 Paris Olympics, archery was already an "old-qualified" sports competition. The old-style longbow was elegant and became the entry-level sport for women. The forerunner of the modern Olympic Games. Archery was disqualified from the 1920 Antwerp Olympics because the host countries did not have unified competition rules. We should be deeply grateful to Ms. Inge Brice. Under the leadership of the only female president of an international sports federation, the International Archery Federation finally returned archery to the Olympic family in 1972 through unremitting efforts. The U.S. men's team won individual and team championships at the Atlanta Olympics. Star shooter McKinney is known as the "evergreen tree" in the archery world; South Korea's "Dream Team", the "Oriental Archery Domination", also led the way at the Olympics. The coquettish Jin Shuining, known as the "Archery Machine", once became the world leader in women's archery. Chinese girl He Ying and her partners won the women's team championship for the first time at the 41st World Championships in 2001.

In shooting sports, the flight of bullets is propelled by gunpowder or compressed gas. All the power of archery comes entirely from human physical ability. The recurve bow used in the Olympic Games today is still the "direct descendant" of the traditional bow and arrow. It is connected by a rigid bow handle, elastic upper and lower limbs and a tough bow string. Under the action of the athlete's bow-holding arm and bow-drawing arm, the tension on the bowstring causes tensile deformation on the outside of the bow blade and compression deformation on the inside, resulting in bending of the bow blade and converting the force of muscle contraction into the elastic potential energy of the bow. It is stored and then suddenly released to propel the arrow's flight. The bow is actually an energy converter, converting human physiological energy into the kinetic energy of the arrow. During the bending process of the bow blade, each section bears different moments. The farther away from the bow handle, the smaller the stress. This is why the bow tip of the recurve bow is designed into a "recurve" shape.

The ancients were well versed in the principle of "holding the bow to hold back the strong". In an archery competition, the average strength of a male player's bow is about 50 pounds, and that of a female player is about 35 pounds. A regular world championship requires 288 shots with a bow in four days of double games. The male players use a cumulative force of nearly 8 tons, and the female players exceed 5 tons. A weightlifter can only lift a total of 1.5 tons in one competition. It can be seen how heavy "strength work" archery is. What’s even more difficult is that most of the time, archery athletes are in a state of “leaving without firing, jumping like a bird”. The horizontal support for the bow and arrow system and the vertical support for the body’s standing form a “cross-shaped” force structure. “The body is as straight as a stem, "Straight arms are like branches." This high level of "static balance" is really not something that can be achieved in a day.

The reason why archery aiming is more difficult than shooting aiming is that there is only a crosshair on the bow and no "sight", so it is impossible to find a ready-made "aiming baseline" like a gun.

Suppose we use the bull's-eye as the origin to draw the horizontal X-axis and the vertical Y-axis. When the bull's-eye, front sight, edge of the bow string and the eye are in the same straight line, the vertical plane in the arrow's flight direction should be consistent with the "bow plane", and It coincides with the Y-axis on the target, so that the shot arrows are concentrated towards the Y-axis. So, how to ensure that the shot arrow moves closer to the X-axis on the target?

Whenever an athlete draws a bow, he or she will place the finger on the string at a precise position on the right side of the mandible. Some archers place a small "kissing button" on the bow string and press it through their lips. "One kiss for each arrow" allows the bowstring to "lean" against the midpoint of the nose, philtrum, and chin. This "string leaning method" ensures a fixed "string leaning distance" from the arrow nock groove to the aiming eye. ", so the point where the aiming line passes through the bow string becomes the second "datum" on the bow. The height of the arrow shot is easy to control.

Ensuring the linearity of force is one of the key points of archery technique. The combined force point of pushing the bow, the hooking point of the string, and the center point of the elbow joint of the bow-drawing arm should be in a straight line. When holding the skill, athletes cannot "hold the bow" with their whole palm but use the tiger's mouth to "push the bow". This is to ensure as much as possible "point contact" between the hand and the bow instead of wide "surface contact".

Recurve Bow

A seemingly inconspicuous small part called a "signal piece" can be called a significant invention in the history of archery. This is a steel piece on the bow handle that is used to hold down the arrow shaft. When the archer draws the bow in place, the arrow slides out, and the steel piece hits the bow handle in the rebound, making a crisp "crackling" sound. The signal piece can accurately "monitor" the athlete's bow draw depth every time, ensuring that the bow arm maintains the same tension, which is equivalent to capturing the "best release time" with "voice-controlled operation". The most important thing in archery is the consistency of movements. The skills developed by each player through repeated training must be highly fixed and programmed, as accurate and repetitive as a machine, and must not be out of shape or deformed at any time.

People often use the term "arrow leaving the string" to describe the speed. The initial speed of the arrow shot by the recurve bow is about 240 kilometers per hour, exceeding the "bullet train". The speed of an arrow depends on the power and efficiency of the bow, the shape, weight and surface area of ??the arrow. Feathers glued together in different ways allow the arrow to rotate around its longitudinal axis and ensure stable flight. As a flying body with a large length-to-diameter ratio, the acceleration from the bowstring will cause the arrow shaft to produce flexible bending and elastic vibration, reducing flight stability. However, compared with shooting, the "action" of arrows is too slow. The speed is only one-tenth of that of bullets, and it takes about 1 second to reach a range of 70 meters. If the direction of the initial velocity is "flat throwing motion" towards the target, the arrow will fall nearly 5 meters when it reaches the target due to the gravity of the earth. Therefore, archery must have an "elevation angle" to allow the arrow to perform an "oblique throwing motion" and make the "trajectory" become an arched parabola. No wonder the archery targets are placed at an angle of 15 degrees to the vertical direction of the ground, facing the "thousands of arrows piercing the heart" with a "looking up" attitude. By the way, today's archery targets are made of coiled straw ropes sewn together and then covered with target paper. The materials used in Zhuge Liang's "straw boat borrowed arrows" are still used.

The archery target is at an angle of 15 degrees to the vertical direction

As a highly efficient "energy converter", the bow can convert 70 to 80% of the elastic potential energy into the kinetic energy of the arrow, leaving "the remaining "The energy becomes the damping vibration of the bow. According to research by experts in the history of science, the emergence of early human string instruments was inspired by the sound produced by the vibration of bowstrings. As for the cotton-playing bow, it is obvious at a glance that it has its origin. These complex sticks installed on the recurve bow are called "shock absorbers", which are designed to increase the static inertia and rotational inertia of the bow, thereby reducing the displacement and vibration of the bow during release. It also achieves a "counterweight" effect, bringing the center of mass of the bow system closer to the push point to maintain balance.

Compound Bow

At the 38th World Archery Championships held in Jakarta in 1995, the compound bow, which had gone through many hardships and ups and downs, was finally approved by the International Archery Federation as an official competition event. This is a truly "modern bow" invented by American Allen in 1969. Its "innovation" is precisely the combination of the wheel and the bow and arrow, the two most "old" inventions of mankind.

Compound bows are equipped with eccentric wheels at the ends of the upper and lower limbs. The lever principle of the movable pulley is used to maximize the bow force. As the draw length increases, it becomes more and more "effort-saving". When the bow is full, the force can be reduced by 70%. . This not only allows athletes to hold the bow and aim in a more relaxed and comfortable state, but also allows women to cross the physical gap and use "hard bows" like men.

Compare the tension curve of a recurve bow. Since it is proportional to the increase in draw distance, the force of the bow string acting on the arrow when released is sudden and decreasing. The acceleration force of the compound bow on the arrow increases from small to large, gradually approaching the peak value, and the effective working distance is correspondingly extended, thus making the arrow leave the string faster and the flight trajectory is flatter. In addition, the compound bow no longer uses three fingers to hook the string and release it, but "pulls the trigger" and lets the "releaser" do the work. The use of optical sights and bubble levels greatly improves the accuracy of arrow shooting. Compound bows embody scientific wisdom everywhere and have rapidly become popular all over the world in recent years. Sales have accounted for more than 90% of the world's bow and arrow market, becoming the most prosperous "mainstream" of the bow and arrow family. Although the Olympic Games have not yet accepted compound bows as an official event, the 13th Paralympic Games held in Beijing in 2008 gave the green light to compound bows for the first time.

More and more archery competitions are held all over the world every year. In the long-distance competition, each group shoots 6 arrows and the best result shall prevail. The world record for hand-held bows reaches 1220 meters; the ground target competition is based on A benchmark erected on the ground draws a 15-meter-diameter target in the center of the circle. Players shoot 36 arrows from a distance of 100 meters to determine the outcome. Horseback riding and archery are still favorite traditional competitions of many ethnic groups. It is a foregone conclusion that ski archery will officially enter the Winter Olympics. In the forest of modern sports that are competing for prosperity, the vitality of archery is increasing day by day.

From the skilled craftsmen of ancient workshops to the high-tech equipment of modern enterprises, from bamboo chips, horns, wooden poles to aluminum alloys, fiberglass and carbon fiber, humans have not stopped making bows and arrows for thousands of years. We may inevitably fall into nostalgia for the past and the pursuit of civilization. Bows and arrows come from our primitive ancestors and will be passed down to distant descendants.