Spicer Drive Axles Application Guidelines - Manual (Page 100)

AXAG-0200 June 2009 100
Glossary
Multiplexing
- A means of sending discreet electrical
signals to multiple devices along a common pair of wires.
Neutral Engagement Valve
- A component of pneumatic
system that permits the service brake to be applied when
the transmission is in neutral and the driver is out of the
cab. Typically found on refuse trucks.
NoSPIN
- Speed sensitive automatic locking differential. It
powers both drive wheels while automatically permitting
differential action to compensate for wheel speed
differences from turning or driving on uneven surfaces.
OAW (Overall Width)
- Width across the widest portion
of the vehicle / axle / etc.
OEM (Original Equipment Manufacturer)
- Company
which first created the product.
Off Highway
- Refers to trucking usually performed on
private logging roads, construction sites, mining locations,
etc. Off-highway trucks are always constructed much more
ruggedly as they are subjected to severe stresses.
On Highway
- Refers to trucking performed on turnpike
quality roads, freeway or expressway.
On/Off Highway
- Refers to trucking operations that
involve traveling both on highways and on roads of lesser
standards; typically of this is in some timber haulage
wherein logs are hauled on forest tracks or roads, and then
on the highway to a mill or rail sliding. Also livestock
haulage when the loading point is some distance along a
rough road, and the load is then moved to abattoirs or
elsewhere on a highway or similar road.
Original Equipment Manufacturer
- See " OEM ".
Out of Round Drum
- Brake drum with variations in its
inner diameter, causing reduced braking efficiency. An
out-of-round drum often can be machined, within
manufacturer's limits, to restore concentricity.
Outset Wheel
- Wheel with a centerline of the tire
outboard of the wheel mounting surface.
Overall Width
- See " OAW ".
Overhang
- The distance from the center of the leaf spring
or air suspension bracket to the centerline of the tire/tires.
Oversized Drum
- Refers to a brake drum having an inner
diameter greater than the discard diameter marked on the
drum by its manufacturer.
Parallelogram Suspension
- A suspension with four
trailing arms that allow the axle to travel in a linear motion
without caster change.
Parking Brake
- See " Spring Brake ".
Parking Brake Priority
- A type of trailer brake control
valve that prioritizes delivery of air for quick release of a
trailer's parking brakes after being hooked to a tractor .
Charging a trailer's service reservoirs, to provide braking
ability, is a secondary concern.
Pawl
- A mechanical device allowing rotation in only one
direction. One type consists of a hinged tongue, the tip of
which engages the notches of a cogwheel, preventing
backward motion.
Payload
- Actual weight of useful cargo carried by the
vehicle.
Piston Type Chamber
- Incorporates a piston in place of
the diaphragm inside the spring chamber. This chamber
will provide approximately 30% to 40% higher pushrod
output for parking. The service chamber, however, still
utilizes a diaphragm. Piston type chambers are more
common in Europe and also for transit buses in North
America.
Pitman Arm
- Arm attached between the steering gear
sector shaft and the drag link which transmits the steering
force from the cross shaft to the steering linkage system.
This is how the rotary motion of the steering wheel is
turned into lateral movement of the arm.
Planetary Double Reduction Axle
- The double reduction
axle provides greater overall gear reduction and is ideal for
peak torque development and transmission. This feature
makes the axle desirable for starting heavy loads in adverse
terrain. The first reduction is through the primary gearing.
The second reduction is with adjacent planetary gearing.
Planetary Gears
- A gearing unit consisting of a ring gear
with internal teeth, a sun or central pinion gear with
external teeth, and a series of planet gears that mesh with
both the ring and the sun gear. Frequently used in
overdrives and automatic transmission. Also called
epicyclic gearbox.
PLC (Power Line Carrier)
- A form of multiplexing
wherein a discreet electrical signal is sent along a wire
already carrying power for another purpose. PLC
technology is used in tractor /trailer communications,
allowing more utility than the standard, J-56O, 7-pin
connector could otherwise afford.
Pneumatic Balance
- Achieved when individual air
chambers receive the air pressure required for each brake
in the system to do its fair share of the work. Lack of
pneumatic balance is most likely at low brake application
pressures, rarely during panic stops.