Physical knowledge in bicycles ① Why do bicycle tires have uneven patterns? Friction is related to two factors: pressure and roughness of contact surface. The greater the pressure, the greater the friction. The rougher the contact surface, the greater the friction. Bicycle tires have uneven patterns. By increasing the roughness between the bicycle and the ground, the friction can be increased to prevent the bicycle from slipping. ② Why can bicycles go forward? When we ride a bicycle, because people and bicycles have pressure on the ground, the tires are not smooth, and there is friction between the bicycle and the road. However, why can bicycles move forward? This is also caused by the friction between the rear wheel and the ground. The direction of friction is forward. What is the friction of the front wheel? Hinder the movement of the car! Its direction is opposite to that of the bicycle. It is these two forces that are equal in magnitude and opposite in direction, so the bicycle moves at a constant speed. When a person pushes a bicycle forward on the ground, the friction direction between the front wheel and the rear wheel is backward. Who will balance these two forces? The friction between the foot and the ground is forward! ③ Why can a bicycle stop after braking? When braking, the friction between the brake shoe and the rim will hinder the rotation of the rear wheel. The greater the hand pressure, the greater the pressure of the brake shoe on the rim, the greater the friction and the slower the rotation of the rear wheel. If the brakes stop completely, the friction between the rear wheel and the ground will become sliding friction (originally rolling friction, the direction is forward), which hinders the movement of the bicycle, so it will stop. Why Zhu Gang? There are steel balls in the front axle, middle axle, rear axle, handlebar rotation and pedal rotation of bicycles. People always want to ride a bike easily, flexibly and with less effort. Rolling instead of sliding can greatly reduce friction, so we should install steel balls where the bicycle rotates, and we can often add lubricating oil to keep the contact surface away. In this way, the friction can be reduced. 2. Knowledge of levers and shafts on bicycles. ① Lever A on the bicycle, the lever to control the steering of the front wheel: The handlebar of the bicycle is a labor-saving lever, and people can turn the front wheel of the bicycle with little force to control the movement direction and balance of the bicycle. B. Lever to control the brake: the handle on the handlebar is a labor-saving lever. People can press the brake on the rim with little force. ② The A-axis on the bicycle, the pedal on the middle axis and the roulette wheel: form a labor-saving axis (the pedal radius is greater than the roulette wheel radius). B handlebar and front fork shaft: form a labor-saving shaft (the turning radius of handlebar is larger than the front fork shaft). C, the gear on the rear axle and the rear wheel: form a labor-saving shaft (the radius of the gear is smaller than the radius of the rear wheel). Knowledge of bicycle air pressure. Inflating bicycle inner tube: In the early days, all kinds of wheels were wooden wheels and iron wheels, which were bumpy. Modern bicycles use inflatable inner tubes mainly to increase the pressure in tires, which can play a buffering role and reduce the resistance of bicycles. Function of valve core: The valve core on the inflatable inner tube acts as a one-way valve, allowing only gas to enter, preventing gas from leaking out and facilitating air intake. Ensure the sealing of the gas filling pipe. 4. Optical knowledge on bicycles. The red taillight on a bicycle can't glow by itself, but it can remind the driver at night, because the taillight of a bicycle is composed of many honeycomb-shaped "cells", and each "cell" is composed of three reflective surfaces with an angle of about 90 degrees. In this way, at night, the light of the car behind hits the taillight of the bicycle, which will reflect light, because red is very eye-catching. It can attract the driver's attention. 5. The reason why the bicycle fender is placed is the principle of centrifugal force. When the wheel rotates, every point on the wheel will produce centrifugal force, and the farther away from the center of the wheel, the greater the centrifugal force. When the wheel touches the ground, the sewage on the ground will be thrown out in the opposite direction of the wheel movement under the action of centrifugal force, which is why riding a bicycle without fenders will throw sewage on the back in rainy days, which is also the reason why the bicycle is equipped with fenders. 6. Variable speed bicycles. The angular velocity of the tire is the same as that of the axle; The tires are full of air. First of all, it reduces the contact area with the ground and reduces the rolling friction. Second, it can reduce vibration. The handlebar is an equal ratio lever, that is, the handlebar rotates at the same angle as the front wheel. Spokes: one is to reduce the weight of the wheel, and the other is to adjust the deflection. 7.5. Mechanical knowledge on bicycles is a very popular means of transportation in China. A lot of mechanical knowledge is applied to its "body". When measuring the length of the runway, you can use a bicycle. If the diameter of an ordinary wheel is 0.7 1 m or 0.66 m, then the length of a circle is the diameter multiplied by π, which is about 2.23 m or 2.07 m. Then, let the car roll along the runway and write down the number of laps n, so the length of the runway is n*2.23 m or n*2.07 m. 2. The application of force and motion (1) reduces and increases friction. The front axle, the intermediate axle and the rear axle of the car all roll to reduce friction. In order to further reduce friction, people often add lubricants to these parts. Many places are engraved with uneven patterns to increase friction. Such as automobile tires, plastic covers of handlebars, pedal covers, brake handle covers, etc. Changing rolling friction into sliding friction to increase friction. For example, when braking, the wheels stop rolling and slide on the ground, and the friction is greatly increased, so that the car can stop quickly. When braking, hold the brake handle tightly, increase the pressure of the brake pad on the steel ring, and stop the wheel from rolling. (2) The damping effect of the spring. There are many springs under the car seat cushion. Use its buffering function to reduce vibration. 3. Application of pressure knowledge (1) bicycle tires are engraved with loads. If the vehicle is too heavy, the tires will be crushed due to excessive pressure. (2) The seat cushion is saddle-shaped, which can increase the contact area between the seat cushion and the human body to reduce the pressure on the buttocks, so that people are not easy to feel tired when riding. 4. Application of simple mechanical knowledge The brake handle and connecting rod in the bicycle brake system are the same. Rear wheel and flywheel, faucet and rotating shaft, etc. 5. Knowledge application of work and mechanical energy (1).
2. Basic knowledge of bicycles
Bicycles, also known as bicycles or bicycles, are usually small land vehicles with two wheels.
After people get on the bus, they are green and environmentally friendly vehicles powered by pedaling. Bi means two in English bicycle or bike, while cycle means wheel.
In Japan, it is called "bicycle"; In Chinese mainland, Taiwan Province Province and Singapore, it is usually called "bicycle" or "bicycle"; In Hong Kong and Macau, it is usually called "bicycle". Principle Among the 25 parts of bicycle, such as frame, tire, pedal, brake and chain, its basic parts are indispensable.
Among them, the frame is the skeleton of the bicycle, which bears the largest weight of people and goods. According to the working characteristics of each component, it can be roughly divided into guiding system, driving system, braking system: 1, and guiding system: composed of handlebar, front fork, front axle and front wheel.
The rider can change the driving direction and keep his body balanced by manipulating the handlebar. 2. Drive (transmission or walking) system: It consists of pedal, central shaft, toothed plate, crank, chain, flywheel, rear axle, rear wheel and other parts.
The pedaling force of people's feet is driven by pedals through crank, sprocket, chain, flywheel, rear axle and other parts, thus making the bicycle move forward continuously. 3. Brake system: composed of brake parts, the cyclist can control the brake at any time to slow down and stop the running bicycle and ensure the driving safety.
In addition, for safety and beauty, as well as from a practical point of view, it is also equipped with lights, brackets and other components. The car body consists of frame, front fork, handlebar, seat and front fork. It is the main body of the bicycle.
The transmission part includes pedal, crank, sprocket, chain, central shaft and flywheel. The pedal is stepped by manpower, and the wheel is driven to rotate and drive forward through the transmission parts. The moving parts are front wheel and rear wheel, including front wheel and rear wheel axle parts, spokes, rims (rims), tires, etc.
Safety devices include brakes, lights, bells and reflectors. Some accessories can be added as needed, such as brackets, clothes hangers, safety forks, fenders, air pumps, etc.
In addition, sports cars, racing cars and mountain bikes equipped with speed change mechanisms are also equipped with speed change controllers and front and rear derailleurs. Classification of road vehicles used on smooth roads, due to the low resistance of smooth roads, the design of road vehicles should pay more attention to high speed. They often use downward-bent handlebars that can reduce wind resistance, narrow high-pressure and low-resistance tires, higher gears and larger wheel diameters than ordinary mountain-climbing off-road vehicles. Because the frame and accessories don't need to be strengthened like mountain bikes, they are often light in weight and efficient when riding on the road.
Because the frame does not need to be strengthened, it often adopts a simple and efficient diamond design, and the road bike is the most beautiful bicycle. Track bicycles are used for bicycles to be used on very smooth oval tracks indoors. This kind of bicycle has no brakes, no gearbox and no reversible flywheel.
Triathlon/ Time Trial Bike (Triathlon/Time Trial Bike) A road bike used for triathlon and time trial sports. The biggest feature of triathlon and time trial is that draught is not allowed, that is to say, riders must overcome air resistance by their own efforts and cannot ride behind other riders. Therefore, the design of triathlon/time trial bicycle pays great attention to keeping the rider in a riding posture to reduce air resistance. Triathlon bicycles also allow athletes to use similar muscle groups when riding, which makes it easier to switch from riding to running.
Mountain bike Mountain bike 1977 originated in San Francisco, USA. Vehicles designed to drive in mountainous areas usually have a transmission, which can shift gears easily or quickly. Some will install shock absorbers on the frame, and some tire treads are chocolate patterns, which is convenient for riding on unpaved roads.
The dimensions of mountain bike parts are generally in English units. The rim is 24/26/29 inches, and the tire size is generally 1.0-2.5 inches.
The frame size is also expressed in English units, such as 14 ",17" and 19 ". Downhill bike Downhill bike, also known as downhill bike.
English abbreviation DH. This is a very challenging activity.
Riders use special DH bicycles to slide on the hillside and even go down the mountain to beg for help. Activities are mostly carried out on ridges, mines and snow.
The Austrian set a world record of 2 10.4KM/H/h with DH. The frame angle of downhill bike is different from that of mountain bike, and the parts are in English units like mountain bike.
Please wear a helmet, armor and other equipment when doing this activity. The damping stroke of the front fork is longer than that of mountain bikes and XC bikes.
Tire width is generally more than 2 inches. Recumbent bicycles are very different from bicycles of traditional design.
There are usually large and comfortable seats with two or three wheels. Its advantages are comfort and low wind resistance.
Tourist bicycles are developed from road bicycles and are suitable for long-distance self-sufficient travel. It has a more comfortable and relaxed frame geometric design, can bear the load, has a very low minimum gear, uses wider tires, pursues reliability and durability in the selection of accessories, but pays little attention to weight reduction, and often uses mountain bike pedals. Advertising Bicycle Advertising Bicycle is a special bicycle made of thin-shell frame authorized by China National Patent Office (ZL2007 2 03 12 144.6), which uses the surface area of the frame to publish advertisements.
Cross-country bikes are developed from road bikes, which originated from riders' desire to conquer roads and mountains with one bike. Therefore, cyclists choose stronger road frames and wheels, install stronger brakes and wide tires, and use the pedals of mountain bikes. Off-road vehicles can not only achieve high speed on expressways, but also have certain off-road capabilities.
A tandem bike, also known as a tandem bike, is driven by more than two people, and the direction is controlled by the first person. Folding bicycle is a kind of vehicle designed for easy carrying and putting in the car. In some places, railways, aviation and other public transport vehicles allow passengers to carry foldable, foldable and bagged bicycles.
Electric bicycle (motorized).
3. 1. Knowledge of ordinary bicycles and variable-speed bicycles.
A variable speed system is added. The transmission ratio between the toothed disc and the flywheel of an ordinary bicycle is fixed (that is, the number of revolutions of the wheel is fixed after pedaling once). Variable-speed bicycles have adjustable gear ratio, which can be adjusted to make riding more labor-saving when encountering uphill or uneven road sections (for example, when applied to mountain bikes, adjust the current toothed disc to the minimum disc, and then adjust the flywheel tower to a larger toothed disc, so that you can climb steep slopes); If the road is flat or meets a downhill slope, and you want to have a fast speed, you can reverse the transmission ratio just mentioned and push it once to go a long way. But if ordinary cars want to achieve high speed, they can only achieve it by increasing the frequency of pedaling. At a certain high frequency, it is difficult for the legs to hold on, and it is easy to slip off (the feet slip off the pedals), which is very dangerous. Therefore, the general racing car is often equipped with a matching transmission system according to the specific terrain needs, so that riding can adapt to various road sections well.
4. What are the basic theoretical knowledge of cycling?
Cycling is a semi-mechanized sport. Coaches and athletes should master certain mechanics principles and knowledge, effectively use transmission ratio, reasonably master exercise intensity, skillfully save physical energy consumption, and carry out high-quality and efficient scientific training with abundant physical strength.
Bicycle is a kind of transmission machinery, and its transmission device includes: driving gear (commonly known as wheel), driven gear (commonly known as flywheel), chain and transmission. Gear ratio and transmission ratio are related to the use efficiency of bicycles, and coaches and athletes should know and master the calculation and application of these data.
Transmission ratio: the ratio of the number of teeth of the driving wheel and the driven wheel is the transmission ratio. If the two gears have the same number of teeth, step on it once. The gear and the rear wheel rotate once each. If the number of teeth of the driving gear is greater than that of the driven gear, then the number of revolutions of the driven gear will be more than one cycle and the speed will increase. Therefore, the transmission ratio is directly proportional to the number of teeth of the driving gear and inversely proportional to the number of teeth of the driven gear. G stands for transmission ratio, C stands for the number of teeth of driving gear, and F stands for the number of teeth of driven gear. The relationship between them is expressed by a formula, that is, g=c/f, for example, the racing wheel has 49 teeth and the flywheel has 14 teeth. The transmission ratio can be obtained by substituting into the formula: g=c/f=49/ 14=3.5. Transmission ratio (transmission coefficient): the transmission ratio multiplied by the diameter of the rear ring is the transmission ratio. D stands for transmission ratio and B stands for the diameter of rear ring. The relationship between them is expressed by a formula, that is, d=c/f*b=gb. It can be seen that after the transmission ratio is determined, the transmission ratio is proportional to the diameter of the rear ring. For example, when the wheel is 49 teeth, the flywheel is 14 teeth, and the diameter of the rear ring is 27 (usually in English time), the transmission ratio can be obtained by substituting the formula: d = c/f * b = 49/14 * 27 = 3.5 * 27 = 94.5 transmission stroke. It is calculated by multiplying the transmission ratio by pi. M represents the transmission stroke and π represents pi (this is a constant, π=3. 14), and the relationship between them is expressed by a formula. That is: M=Dπ=C/F*b*π The measurement of the diameter of the rear wheel of a bicycle is generally expressed in English, while the travel calculation is generally expressed in metric, so it is necessary to convert English into metric when calculating. One inch =2.54CM, represented by k, that is, K=2.54CM, and substituted into the formula, that is, M=G/F*B*π*k For example, the wheel of a racing car has 49 teeth, the flywheel has 14 teeth, and the real diameter of the rear wheel is Bishop Huangshi. When finding its travel distance, find its travel distance. The substitution formula is: m = c/f * b * π * k = 49/65438+.
The answer comes from the extreme outdoor network official website.
5. What do you know about bicycle mechanics?
Bicycle is a very popular means of transportation in China. Its "body", 1, applies a lot of mechanical knowledge. The application in measurement can be used in measuring the length of runway. For example, if the diameter of an ordinary wheel is 0. Write down the number of laps n, then the length of the runway is n*2.23 meters or n*2.07 meters. 2. The application of force and motion (1) reduces and increases friction. The front axle, the intermediate axle and the rear axle of the car all roll to reduce friction. In order to further reduce friction, people often add lubricants to these parts. Many places are engraved with uneven patterns to increase friction. For example, the plastic cover of automobile tires and handlebars increases the pressure of brake pads on the rim and prevents the wheels from rolling. (2) The spring has a damping effect. There are many springs under the car seat cushion, which can be used to reduce vibration. (3) Application of pressure knowledge (1) Bicycle tires are engraved with loads. If the vehicle is too heavy, the tires will be crushed due to excessive pressure. (2) The seat cushion is saddle-shaped, so that people will not feel tired when riding. Rear wheel and flywheel, faucet and rotating shaft, etc. 5. Knowledge application of work and mechanical energy (1) According to the principle of work, it takes a long distance to save energy. Therefore, when people go uphill, they often ride the "S-shaped" route. (2) The mutual transformation between kinetic energy and gravitational potential energy. For example, before riding uphill, people often have to pedal several times, so it is easier to get up, which converts potential energy into kinetic energy. If the front wheel brakes suddenly, why does the rear wheel jump? People and rear wheels should go straight ahead, so that the rear wheels will jump. Remember not to use the bicycle front brake alone when going downhill or at high speed, otherwise a rollover accident will occur! (1) Exercise and force application: The bicycle's outer tire, handlebar plastic sleeve and pedal sleeve enable the car to brake quickly. Rolling bearings are used to reduce friction in front axle, middle axle and rear axle of automobiles, and people often add lubricating oil to these parts to further reduce friction. Increase and decrease mechanical knowledge on bicycles. There is a thick coil spring under the car seat cushion. Use its buffering effect to reduce vibration. 2. The damping effect of the spring. Mechanical knowledge on bicycles. 2. Application of stress knowledge. Bicycle tires are engraved with load capacity, which clearly tells people not to overload. If the tire load is too large, the stress area of the tire will remain the same, and the tire will be crushed if it is stressed too much. 1. The physical cushion on the seat is saddle-shaped. It makes people feel more comfortable when riding a bike. (3) Application of simple mechanics knowledge. The brake lever and connecting rod in the bicycle brake system are labor-saving levers, and the faucet and the rotating shaft are wheel shafts, which can save labor. (4) The knowledge of mechanics, work and energy on bicycles is applied to 1. When riding a bike on a steep slope, people often take the "S" route to increase the slope. Therefore, we can go uphill smoothly. (4) Using the knowledge of work and energy. (2) The mutual transformation between kinetic energy and potential energy. Before riding a bicycle uphill, people often have to pedal a few times, so that the speed (kinetic energy) of the car, that is, potential energy, is converted into kinetic energy, and the kinetic energy is increasing, so the speed is also increasing. (5) Braking and inertia bicycles can't be braked only by the front brakes at high speed, especially when going downhill. Cause a rollover accident. Mechanical knowledge on bicycles (VI) Application in measurement When measuring the length of roads, bicycles can be used. For example, the diameter of type 24 wheel is 0. 1.95 m or n * 2.07 m. Mechanical knowledge on bicycle (VII) Application of thermal expansion knowledge. In hot summer, the air in the tire cannot be filled too much, let alone exposed to the scorching sun, because the air in the tire will expand rapidly when heated. A sudden increase in pressure will burst the tire. Mechanical knowledge on bicycles (8) Conversion between mechanical energy and internal energy Inflate tires with a pump. After a period of time, the cylinder wall will heat up, so that the internal energy in the cylinder wall will increase and the temperature will rise, so the cylinder wall will heat up.
6. What are the basic bicycle knowledge?
First, mountain biking.
Features: specially designed for conquering all kinds of terrain, the frame is firm; The rim is generally 26 inches; The tire is thicker; Generally, the handle or swallow handle will be balanced.
Second, the road car
Features: specially designed for the pursuit of speed, the rim is 700C specification; Thin tires with claw handlebars.
Three, BMX climbing car
Features: specially designed to show skills, the frame is stable, the tire is wide and toothless, the handlebar can rotate 360 degrees, the wheel diameter is small, and the maneuverability is extremely strong. It is suitable for young people to play, so I won't elaborate. The second tire
First, mountain tires.
Features: thick and stable tires, low tire pressure. Generally, there are several specifications, 1.5,1.95,2.1. Because of different uses, it is divided into mud tires and sand tires, which are characterized by wide tires and deep teeth. Dual-purpose tires are characterized in that when riding on roads, only a small part of the tires contact the ground, so the resistance is small, while when riding on dirt roads, the teeth on both sides of the tires can stabilize the vehicle; Bald tires are characterized by low resistance and are suitable for road riding.
Second, road tires.
Thin tires and high tire pressure; Generally, there are specifications such as 25C, 23C, 20C, 18C, among which 25C, 23C are suitable for training, no puncture is allowed, and 20C, 18C have low resistance and are suitable for competition.
The third handlebar
First, mountain biking.
Mountain bikes are generally equipped with flat handles or swallow handles. The advantage is that both hands are wide when grasping, which is beneficial to control; Among them, the swallow handle can raise the upper body and move the center of gravity backward, which is more suitable for downhill vehicles. The disadvantage is that driving is a big burden.
Second, the road car
Road vehicles are generally equipped with claw handles, which are 44CM and 42CM wide. The width suitable for them is shoulder width, which is characterized by reducing wind resistance and suitable for long-term riding. The fourth quarter shock absorption system
It can be divided into front shock absorber and rear shock absorber, which can make riding more comfortable, especially downhill bicycle is an essential component; However, riding on uphill and horizontal roads will have negative effects. If the damping system has locking function, the adaptability of the car will be stronger. For the road conditions in Shenzhen, it is recommended to equip only the front shock absorber. Section 5 Transmission System
The function of the transmission system is to generate different driving torques by using different transmission ratios between the toothed disc and the flywheel, so as to adapt to different road conditions and the physical condition of the rider.
First, mountain biking.
The toothed plate is generally three gears, namely 44(42), 34(32) and 28(24) teeth. After the flight, there are 7- 10 gears with 1 1-28 (34) teeth respectively.
Second, the road car
Generally, the toothed plate is two gears with 52(54) and 42(39) teeth respectively. After the flight, there are 8- 10 gears with 1 1-25 teeth respectively. ***3 pages: Previous page 123 Next page
The answer comes from the extreme outdoor network official website.