Glossary – Spicer Drive Axles Application Guidelines User Manual
Page 91
AXAG-0200 June 2009 91
Glossary
ABA (Automatic Brake Adjuster)
- Also called an
Automatic Slack Adjuster (ASA), this is a lever
connecting the brake chamber push rod with the
foundation brake camshaft. It provides torque to rotate the
brake camshaft when the brake treadle is depressed. It also
provides a means of automatically adjusting clearance
between brake shoes and the drum to compensate for
lining wear. Some brake adjusters require manual
adjustment.
ABS (Antilock Brake System)
- Electronically monitors
wheel speed and prevents wheel lockup by rapidly cycling
the brakes during panic stops and when stopping on low-
friction surfaces.
ABS Control Valves
- Control valves that are actuated by
the ABS Electronic Control Unit (ECU) to ensure wheels
are optimally braked. On a
, they are called ABS
modulator valves. On a trailer, they're called ABS relay
valves.
A/C Centers
- The distance from the centerline of one
brake chamber to the other.
Ackermann Geometry
- The relative angular movements
of the front wheels while traveling along a curved path. A
double pivoting steering system where the outer tie rod
arms are bent slightly inward so that when a vehicle is
making a turn, the wheels toe out and the inside wheel will
turn more sharply than the outer wheel. This is done to
compensate for the greater distance the outside wheel
must travel. These angular movements relate to the length
of wheelbase and the width of track. True Ackermann
geometry includes the Jeantaud modification to Rudolph
Ackermann's original principle.
Active Suspension
- While conventional suspension uses
springs and shock absorbers to isolate the vehicle from the
bouncing movement of the wheels when it contacts rough
roads, active suspension uses power actuators that are
controlled by a computer. These actuators place the
wheels of the vehicle in the best position to accommodate
rough roads as well as compensate for different load
levels.
Actuate
- To initiate mechanical motion of a brake system
component.
Actuator
- A device that physically initiates mechanical
motion of a brake system component.
ADB
- See "
"
ADR 35 (Australian Design Rule 35)
- Specifies braking
requirements under normal and emergency conditions.
Aftercooler
- Optional device that condenses and
eliminates water from air pressurized by the compressor.
Air Build-up
- Process of compressor building pressure to
a predetermined maximum level, usually 100-120 psi,
within the brake system air tanks.
Air Compressor
- Engine-driven via a belt or direct gear,
the compressor pressurizes the air tank.
Air Compressor Cut-out
- Predetermined point at which
the air governor halts compression of air by the
compressor.
Air Disc Brakes
- Air-actuated brakes, which upon
application, employ a caliper to clamp two brake pads
against a rotor. Air discs, compared with drum-type
brakes, have superior ability to resist fade.
Air Dryer
- A filter, typically containing a desiccant,
which is installed between the compressor and service
reservoir to remove water and vapor plus oil blow-by from
the compressor.
Air Gauge
- Dash-mounted gauge indicating air pressure
in terms of pounds per square inch (psi).
Air Governor
- Controls the compressor unloader
mechanism and also maintains system air pressure
between predetermined minimum and maximum levels,
usually between 90-120 psi.
Air Over/Under
- In relation to suspensions.
Overslung
- Suspension arm goes above or over the
axle air bag.
Underslung
- Suspension arm goes below or under
the axle air bag.
Air System Balance
- Can be separated into two different
aspects, pressure level balance and timing balance. Air
system balance deals primarily with the vehicle air system
components that directly control the actuation of the
service brakes during normal stops, foot control valve,
check valves, relay valves and their arrangement or
system design. Their purpose is to balance the time it takes
air pressure to build uniformly at all wheel ends.
Air Tank
- A reservoir for compressed air. Typically, a
combination vehicle has several tanks: three in the
and one per trailer. The tractor's supply air tank (formerly
"wet tank") receives air from the compressor and delivers
it to the primary and secondary air tanks in the tractor. A
check valve on each tank prevents total air loss in the
event of a leak.
Alcohol Evaporator
- Optional device, installed in
compressor discharge line between the compressor and
supply air tank, which injects alcohol mist into the air flow
to reduce the risk of freeze up. It's not normally used in a
vehicle with an air dryer.