What produces the braking action in a spring-loaded brake cylinder?

In a spring-loaded brake cylinder, the braking action is produced by the force of a strong spring inside the cylinder. When there is no compressed air pressure, the spring pushes the brake pads or shoes against the wheels, applying the brakes. This design is mainly used as a fail-safe system: if the air pressure fails, the spring automatically engages the brakes to stop the vehicle. Compressed air is used to compress the spring and release the brakes during normal driving, but the actual braking force comes from the spring itself. This ensures safety in case of air pressure loss.