What is the working principle of a car handbrake?
2 Answers
Car handbrake works as follows: Brake disc transmission tension: For small cars, some handbrakes are located behind the transmission, connected to the driveshaft with a brake disc, similar to a disc brake (though some use drum brakes). The tension is transmitted through steel cables to achieve parking braking. Hydraulic auxiliary cylinder drives air valve: When the handbrake is pulled, it uses a hydraulic auxiliary cylinder to push the main hydraulic cylinder beneath the car, which then drives the air valve. After the air valve moves, it brakes the driveshaft. Electronically controlled handbrake: High-end cars use electronic control. When the handbrake is engaged, an electric traction motor activates, tightening the steel cable and locking it after the air brake is completed.
The handbrake is essentially a braking device used to secure the car when parked, typically only acting on the rear wheels. When you pull the handbrake lever beside the driver's seat, it connects via a steel cable to the braking mechanism on the rear wheels. In disc brake systems, the handbrake activates a separate small caliper or brake shoe to clamp the brake disc; in drum brakes, it directly pushes the brake shoes against the drum surface, generating friction to prevent the wheels from rolling. This relies entirely on mechanical principles, unlike the main braking system which requires hydraulic assistance, so it can serve as an emergency backup even if the foot brake fails. Having driven for so many years, I've found that firmly engaging the handbrake is crucial when parking on slopes to prevent rollaway accidents. Regular maintenance is essential—for example, checking the cable every six months for rust or excessive looseness. Too tight, and it accelerates brake pad wear; too loose, and it becomes ineffective. Electronic handbrakes use a button to activate a small motor performing a similar action, saving effort but with higher repair costs. In short, understanding the principle makes operation more reassuring—never underestimate the safety value of this small device.
