Physical knowledge on bicycles
Bicycle frame, tires, pedals, brakes, chains and other 25 components, the basic components 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 and braking system:
1. Guidance 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, sprocket, crank, chain, flywheel, rear axle and rear wheel. 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.
Here are some bicycle parts related to mechanical knowledge:
1. The frame component is the basic structure, skeleton and main body of a bicycle, and other components are directly or indirectly installed on the frame.
There are many structural forms of frame parts, but they can be roughly divided into two categories: men's frames and women's frames.
The frame is generally composed of ordinary carbon and copper pipes welded together. In order to reduce the weight of steel pipes and improve the strength, low alloy steel pipes are used in high-grade bicycles. In order to reduce the resistance of fast driving, some bicycles also use streamlined steel pipes.
Because the bicycle runs by the driving force and riding skills of the human body, the frame becomes an important structure to bear the impact load generated by the bicycle during running and whether it can carry the human body comfortably and safely. The manufacturing accuracy of frame components will directly affect the safety, stability and lightweight of vehicles. Generally, spokes have the same diameter. In order to reduce gravity, some spokes are made into variable diameter spokes with two big ends and a small middle, and some spokes are made into flat streamline to reduce air resistance.
2. Outer tires: There are two kinds of soft side tires and hard side tires. The cross section of the soft sidewall tire is wide, which can completely wrap the inner tube, and the landing area is relatively large, so it is suitable for driving on various roads. Hard-edged tires have the advantages of light weight, small landing area, small resistance and light driving.
The pattern on the tire is to increase the friction with the ground. Mountain bikes are especially wide in tire width and deep in pattern, and are also suitable for cross-country mountains.
3. Pedal assembly: The pedal assembly is assembled on the left and right cranks of the middle axle assembly, and is a device that converts horizontal force into rotational force. When a bicycle is riding, the pedal force is first transmitted to the pedal assembly, and then the pedal shaft drives the crank, the central shaft and the chain flywheel to rotate, so that the rear wheel rotates, thus making the bicycle move forward. Therefore, whether the structure and specifications of the pedal assembly are appropriate will directly affect whether the rider's foot position is appropriate and whether the bicycle can run smoothly.
Pedal: It can be divided into integral pedal and combined pedal. No matter what style of pedal, it must have a pedal surface, which is safe and reliable, has certain anti-skid performance, and can be made of rubber, plastic or metal materials. The pedal must turn flexibly.
4. Front fork assembly: The front fork assembly is located at the front of the bicycle structure, and its upper end is connected with the handlebar assembly, the frame assembly is matched with the front tube, and its lower end is matched with the front axle assembly to form the guiding system of the bicycle.
Turning the handlebar and the front fork can change the direction of the front wheel and play a guiding role in the bicycle. In addition, it can also play a role in controlling the operation of bicycles.
The front fork is a cantilever beam, so the front fork must have sufficient strength and other properties.
5. Chain: Chain, also known as cart chain and roller chain, is installed on the coupling wheel and flywheel. Its function is to transfer pedal force from crank and sprocket to flywheel and rear wheel to drive the bicycle forward.
Sprocket: made of high-strength steel to ensure the required tension.
6. Flywheel: The flywheel is fixed at the right end of the rear axle, has internal threads, keeps the same plane with the sprocket, and is connected with the sprocket through a chain to form the driving system of the bicycle. Structurally, it can be divided into two categories: single-stage flywheel and multi-stage flywheel.
Single-stage flywheel, also known as single sprocket flywheel, is mainly composed of jacket, flat block and core, jack, jack spring, washer, steel wire block and several steel balls.
The working principle of single-stage flywheel is that when the pedal steps forward, the chain drives the flywheel to rotate forward. At this time, the internal teeth of the flywheel and the jack are contained, and the rotating force of the flywheel is transmitted to the movement through the jack, and the movement drives the rear axle and the rear wheel to rotate, so that the bicycle can move forward.
When the pedal stops, the chain and the jacket do not rotate, but the rear wheel still drives the movement and the jack to rotate forward under the inertia. At this time, the internal teeth of the flywheel slide relatively, so that the movement is pressed into the notch of the movement, and the jack compresses the jack spring. When the tooth top of the jack slides to the inner tooth top of the flywheel, the compression of the jack spring is maximum. If it slides forward a little, the jack spring bounces to the tooth root and makes a "click" sound. The movement rotates faster, and the jack slides quickly on the inner teeth of each flywheel, making a "click" sound. Pedal in the opposite direction, and the jacket rotates in the opposite direction, which will accelerate the sliding of the jack and make the "click" sound more urgent. Multi-stage flywheel is an important part of bicycle transmission.
On the basis of single-stage flywheel, multi-stage flywheel adds several flywheel blades, which are combined with the sprocket on the central shaft to form various transmission ratios, thus changing the speed of bicycle.