AIRBRAKE SYSTEM - CONTINUED
GLADHANDS - coupling points for the towing vehicle air lines. They are marked, one emergency, the other service, to
ensure correct hookup.
AIR LINES - extend the length of the chassis to supply service and emergency air supply to the relay valve and air
RELAY VALVE- directs and controls the flow of air to and from the reservoir to the brake chambers. When no pressure
is in the reservoir, air from the towing vehicle flows through the emergency line into the relay valve which directs air into
the reservoir. At the same time, air is sent to the brake chamber which then applies the brakes. The brakes will remain on
until pressure in the reservoir reaches 60 psi (413.7 kPa). The relay valve will then release the brakes by venting the
brake chamber AIR RESERVOIR stores the system air pressure (normally 90 to 120 psi (620.55 to 827.4 kPa)) that
operates the airbrake system. Pressure to the reservoir Is initially supplied and then maintained through the emergency
supply line from the towing vehicle through the relay valve.
BRAKE CHAMBERS used to convert air pressure to mechanical motion. This movement, through the slack adjusters,
rotates the camshaft and applies the brakes When brake chamber air pressure is released spring action releases the
SLACK ADJUSTERS converts linear motion of the brake chamber to rotating motion of the camshaft. The slack
adjusters consist of a housing, two gears, and two gear covers Brake adjustments are made through the slack adjuster.
BRAKESHOES AND LINKAGE two brakeshoes on each wheel assembly are spread apart by the rotation of the camshaft
by the slack adjusters. The brakeshoes are pushed against the brakedrum causing friction to slow or stop the semitrailer.
ELECTRICAL SYSTEM- The Intervehicular receptacle on the front of the semitrailer receives the electrical current from
the towing vehicle. Electrical current is sent through a wiring harness to the marker lights, license plate light, and taillight.
Switches In the towing vehicle control the operation of the light assemblies. The light assemblies operate on 12 volts.
The semitrailer can be used with a commercial towing vehicle (12 volts) or a military vehicle (24 volts). When used with a
military vehicle, a resistor harness reduces the voltage from 24 volts to 12 volts.