Basically, if the driver steps on the brake pedal, or the treadle valve, the air from the storage tanks will flow into the cylinder, and push the piston down the cylinder also known as the brake chamber. This is the service portion of the system.
The sequence by which this works is: the piston is attached to the push rod, which turns the slack adjuster which then connects the push rod to another rod, and then it rotates.
This rod is connected to the S-cam.
We have several types of Air brakes, including S-cam and wedge type brakes.
The S-cam
These types of brakes are the most popular among the drivers. After all it is the S-cam that turns and pushes the brake shoes against the lining of the drum brake!
The semi-trailer’s Air brakes are connecting to a tractor with two lines. The first line is the emergency line or the supply line. Normally, it is bigger than the other and its ether red ether with red fittings. This line provides air pressure to fill the semi-trailer’s reservoir tank and the pistons that activate the brakes.
