Shulou(Shulou.com)11/24 Report--

Original title: "Disc brake VS drum brake, one clamp and the other open, intuitively show its principle."

History of development

Drum brake

In 1916, Americans invented the drum brake, which relied on the brake shoes installed on the axle to cooperate with the wheel brake drum to complete the braking function. Compared with the early bicycle brakes (including tire type, flange type, pulley type, holding type, etc.), this kind of brake has greater braking force, and the braking is more stable and reliable. At that time, almost all American motorcycles used this kind of brake. The drum brake used in modern motorcycles is developed on this basis.

Disc brake

Although the drum brake was promoted and used earlier, the disc brake appeared 3 years earlier than the drum brake.

In 1913, a set of mechanically operated disc brakes was prominently installed on a British-made Douglas motorcycle participating in the French Grand Prix. This is the first motorcycle in the world to use disc brakes.

In 1969, Japan's Honda took the lead in using hydraulically operated disc brakes on Honda 750 motorcycles. Since then, all highway motorcycle manufacturers around the world have used this advanced hydraulic disc brake.

Braking principle

During the drum brake, the external force exerts a force on the two semilunar brake shoes to tighten the inner wall of the drum and rely on friction to prevent the brake drum from turning so as to achieve the braking effect.

The working principle can be vividly described by a cup. The brake drum is like a cup. When you put five fingers into a rotating cup, the fingers are the brake pads. As long as you put the five fingers outward and rub the inside of the cup, the cup will stop spinning.

The brake disc is made of cast iron or alloy steel and fixed to the wheel and rotates with the wheel. The caliper is fixed on the front shock absorber or the rear rocker arm, and the two friction plates on the brake clamp are installed on both sides of the brake disc, and the hydraulic pressure pushes the friction disc against the brake disc, which is like clamping the rotating plate with pliers to achieve the effect of slowing down the brake.

Comparison of advantages and disadvantages 01, braking strength in terms of braking strength, the braking strength of the drum type is much greater than that of the disc type, not because the drum brake technology is more advanced, but because of its inherent structural characteristics.

In the drum brake system, there is a metal object that looks like a drum, which is the core component of the drum brake, hence the name.

Two sets of brake shoes are set in the brake drum. When we press the brake pedal, the driver's force will be transferred to the brake shoe, and the semicircular arc U-shaped brake shoe on both sides will be jacked up to make it expand and squeeze outward. Press the brake shoe on the brake drum. At this time, there will be strong friction between the brake drum and the brake shoe, which will play a braking effect.

The disc brake is different from the drum brake, the brake parts of the disc brake can be seen visually from the appearance, it will move with the movement of the wheel and keep synchronized with the wheel, which is equivalent to the brake drum in the drum brake.

When we pinch the brake, the hydraulic device transfers this force to the brake caliper and makes the brake caliper grip the brake disc tightly to achieve the purpose of braking through the friction between the brake disc and the brake caliper.

This kind of braking device can not produce strong force by itself, so it is not enough to obtain effective braking force only by human strength. It must be assisted by hydraulic device in order to produce sufficient braking force.

02, heat dissipation performance, but the disc brake is better than the drum brake in many ways, otherwise it would not be used in a large number of new models, but these benefits are not reflected in the braking force, but in other aspects.

Because the drum brake is in an airtight space, its heat dissipation is not very good, and a large amount of heat will be accumulated in the braking process.

Brake shoes and wheel drum are prone to extremely complex deformation under the influence of high temperature, which is easy to produce brake decline and shaking phenomenon, resulting in the decline of braking efficiency.

03. Drainage performance is another characteristic that the disc brake is better than the drum brake. When water enters the braking system, the influence on the braking performance is obvious. If the water can not be discharged in time, the braking performance will decline greatly.

As can be seen from the structure, the closed design of drum brake is obviously not as good as disc brake in drainage.

04. Economic cost drum brake is first used in braking system, and its manufacturing technology is relatively more mature, so it is better than disc brake in terms of cost.

The brake disc quality of the disc brake needs to be improved, and the cost of brake calipers, pistons, brake leather and other components is not equal to that of the drum brake.

05. In other places where there are many muddy roads in rural areas, they do not often run at high speed, and the braking strength of the drum brake is more suitable. At the same time, the advantage of the drum brake system, which is better sealed to deal with the harsh environment, is reflected, and the muddy road is very destructive to the disc brakes.

Drum brake response speed is not linear and accurate, so it is difficult to be based on drum brake equipped with ABS system, disc brake can be equipped with ABS to achieve uniform, fast and effective ABS braking.

Conclusion vehicles on the market generally use disc brakes on the front wheels and drum brakes on the rear wheels, that is, the so-called "front disc and rear drum" configuration. The rear wheel does not use the disc brake because of the cost problem, there are many large rows of motorcycles are the front and rear disc brake.

In general, when braking, the center of gravity will shift forward, the weight on the rear wheel will be less and less, and the braking force of the vehicle comes more from the front wheel. Even if the front and rear wheel brakes, the disc brake of the front wheel is obviously stronger than the rear wheel, because it has to bear more braking force.

So there is nothing wrong with drum brakes on rear wheels in models with low quality, as long as you pay attention to braking techniques, control speed and excessive use of brakes.

Front and rear disc brakes are not omnipotent, and drum brakes are not useless. No matter how hard the brakes are, they are not safe enough to drive carefully.

This article comes from the official account of Wechat: manufacturing principles (ID:zhizaoyuanli), author:-

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