non servo drum brake diagram

Understanding Non-Servo Drum Brake Systems A Comprehensive Overview

Drum brakes are an integral component of many automotive braking systems, providing reliable stopping power through a simple yet effective design. Among the various types of drum brakes, non-servo drum brakes present a unique operational mechanism that differs from servo drum brakes. Understanding the structure and functioning of non-servo drum brakes can enhance our knowledge of automotive engineering and improve maintenance practices.

What are Non-Servo Drum Brakes?

Non-servo drum brakes are a type of braking system that utilizes a drum, brake shoes, and hydraulic components to generate friction and slow down or stop a vehicle. Unlike servo drum brakes, where the action of the brake shoes is amplified by the motion of the drum, non-servo drum brakes operate without this added advantage. Instead, they rely purely on the friction created when the brake shoes press against the inner surface of the drum.

Key Components and Design

A typical non-servo drum brake system comprises several key components

1. Brake Drum Mounted on the wheel hub, the brake drum rotates with the wheel. When braking is applied, the brake shoes press against the inner surface of the drum, creating friction and slowing down the vehicle.

2. Brake Shoes These are curved metal plates lined with friction material. When the brakes are engaged, the shoes expand outward against the drum. In non-servo systems, this expansion does not create a self-energizing effect.

3. Wheel Cylinder This hydraulic device is responsible for actuating the brake shoes. When the brake pedal is pressed, brake fluid flows into the wheel cylinder, pushing the pistons outward and forcing the brake shoes against the drum.

4. Return Springs After the brake pedal is released, return springs pull the brake shoes back into their neutral position, ensuring they do not continuously contact the drum, which would cause unnecessary wear.

Mechanism of Action

When the driver presses the brake pedal, hydraulic pressure is generated within the brake lines. This pressure travels to the wheel cylinder, causing its pistons to move outward. In a non-servo drum brake, both brake shoes are pushed simultaneously against the inner side of the drum.

As the brake shoes contact the drum, friction is produced, which slows down the rotation of the wheel. However, unlike servo drum brakes, non-servo brakes lack a self-energizing mechanism that would help increase the force applied to the shoes. This means that the braking efficiency is somewhat lower in non-servo systems compared to their servo counterparts.

Advantages and Disadvantages

Non-servo drum brakes present both advantages and drawbacks. One of the primary advantages is their simplicity. With fewer components involved in the braking operation, non-servo drum brakes can be easier to maintain and repair. Additionally, they are typically less expensive to manufacture, making them a cost-effective choice for many vehicle manufacturers.

However, there are also notable disadvantages. The lack of self-energizing action means that non-servo drum brakes may not provide the same level of stopping power as servo systems, particularly under heavy loads or during rapid deceleration. This can make them less suitable for larger vehicles or those requiring high-performance braking.

Applications

Non-servo drum brakes are commonly found in older vehicles and some low to mid-range vehicles today. Their simplicity and cost-effectiveness make them ideal for applications where high performance is not critical. Often seen in rear brake configurations of smaller cars, these systems perform reliably under normal driving conditions.

Conclusion

Understanding non-servo drum brakes enhances our appreciation of automotive technology. While they may indeed lack some of the advanced features of other braking systems, their straightforward design and cost-effectiveness ensure that they remain a relevant choice in various applications. By gaining insights into how these systems work, drivers and automotive enthusiasts can make more informed decisions about vehicle maintenance and performance. As we continue to innovate in automotive design, the principles governing non-servo drum brakes remind us of the importance of foundational technologies in modern engineering.