The Brake System:
Air-Hydraulic System's Master Cylinder
Above Image: Example of a typical air-hydraulic system
An air-hydraulic brake system has all the components of a straight hydraulic system plus those of the compressed air system. Besides boosting the hydraulic pressure of the brakes on the truck, the compressed air system can also be used to apply the brakes of a trailer and operate accessories such as the wiper motor and horn.
The master cylinder used with air-hydraulic brakes is like the one described in the lesson on hydraulic brakes. In straight hydraulic brake systems, the master cylinder receives the initial mechanical force from the pedal linkage, changes it to hydraulic pressure, and sends the brake fluid under pressure directly to the wheel cylinders. In air-hydraulic brakes, the master cylinder sends brake fluid under pressure to an air-hydraulic cylinder before it goes to the wheel cylinders. |