There are generally four principles of cycling: axle, lever, application of friction, and human force.
Wheel axle: The pedal and large gear on the center axle form a labor-saving wheel axle, with a pedal radius greater than the large gear radius; Bicycle handlebar and front fork shaft: forming a labor-saving axle, the rear axle teeth with an outer radius of the handlebar greater than the radius of the front fork shaft Wheels and rear wheels, The radius of the gears that make up the steering shaft is smaller than the radius of the rear wheels.
Levers: Control the steering of the front wheels. The steering wheel of a bicycle is a labor-saving lever that allows people to rotate the front wheels of the bicycle with small force, controlling the direction of motion and balance of the bicycle; The lever for controlling the brake: The lever on the steering wheel is a labor-saving lever. People can use less force to press the brake with greater pressure on the steel rims of the wheels.
The application of friction: Like other vehicles, bicycles also rely on the friction between the wheels and the ground to move forward. The bicycle itself has mass and self weight, so the wheels and the ground are not smooth. Pressing on the road surface will generate static friction. When a person gets on the bicycle and starts moving it with force, the rear wheels and the ground will generate static friction, which is in the same direction as the bicycle's travel, thus causing the bicycle to move forward.
Human force application: The principle of a bicycle is to apply force to the pedal with the human foot. The sprocket rotates through the crank, and the sprocket rotates through the chain flywheel. The flywheel further rotates the rear wheels, and the friction between the rear wheels and the ground prevents the rear wheels from sliding relative to the ground. The rear wheels roll on the ground, making the entire vehicle work.