On March 5, 1872, an American inventor, entrepreneur, and engineer patented a device that would revolutionize railway systems all over the world. After some time, his original designs were reworked and modified so that they could be applied by manufacturers of trucks and heavy road vehicles. Today, no matter how hard one may try, it’s almost impossible to find a road-safe truck without Westinghouse’s ubiquitous invention: the air brake.
How Do Air Brakes Work, or: Why Aren’t Hydraulic Brakes Used in Trucks?
In a typical car, the brakes are of the disc and shoe types. In the case of hydraulic brakes, calipers are used to squeeze brake pads that are stationary against a rotating disc (the rotor) to slowly and steadily bring the car to a complete stop. This process works incredibly well for small vehicles, like cars, because the amount of force required to stop the vehicle is relatively low, in comparison to larger, heavier vehicles like trucks. Simply put, it takes more force to stop a larger vehicle, and hydraulic brakes don’t cut it when needing to stop an 18-wheeler carrying all of its cargo.
Compare to hydraulic brakes, with some differences. Instead of using hydraulic fluid to force the brake pads to stop the rotating rotor, air brakes use highly compressed air to get the job done.
- First, compressed air is forced and stored into reservoirs (tanks), readily available for the driver to use.
- When the driver pushes the foot valve (called brake pedal), a signal is sent for the compressed air to be delivered and apply the brakes.
- Once the driver releases the foot valve (brake pedal), compressed air that is at the brake chamber will be exhausted into the atmosphere through a quick release valve, causing the brake shoes to release from the brake drum, enabling the vehicle to return to motion.
The Right Stuff: Operating Air Brakes and How a Driving School Can Help
Air brakes obviously work differently than hydraulic brakes, even if certain components and mechanisms are comparable. We, at North Shore Driving School, offer a host of truck driving lessons to ensure that all drivers know the ins and outs of driving a truck, before they sit behind the wheel.