Glossary – Spicer Drive Axles Application Guidelines User Manual
Page 93
AXAG-0200 June 2009 93
Glossary
Blue Drum
- Brake drum with friction surface turned blue
from high temperature. High temperature may result from
dragging of brakes caused by weak return springs. Blue
drum also may result from lack of brake balance, i.e.
excessive brake torque at wheel with Blue drum and lack
of brake torque and other wheel ends.
Bogie
- A combination of two axles usually pivoting about
a common trunnion.
Brake Adjuster
- See "
".
Brake Balance
- Balance is achieved when all brakes on
all axles do their fair share of the work. The four types of
brake balance are: pneumatic, thermal, timing, and torque.
Brake Block
- Friction material, also known as brake
lining, attached to a brake shoe. Disc brakes use pads with
friction material.
Brake Chamber
- Device inside which a diaphragm
converts air pressure to mechanical force, via a push rod,
for brake actuation. Consists of service chamber or service
chamber/spring chamber. For example: A 30/36 chamber
consists of a Type 30 service chamber and a Type 36
spring chamber. See "
" and "
Spring Brake
".
Brake Chamber Diaphragm
- Compression molded
device within a brake chamber that converts air pressure to
mechanical force via a push rod. The size of the brake
chamber correlates with the effective area of the
diaphragm. A Type 30 chamber diaphragm has an
effective area of 30 in.
Brake Drag
- Failure of one or more brakes to release
immediately and/or completely after a driver removes his
foot from the brake treadle. Constant drag, unrelated to a
brake application, also can exist. See "
".
Brake Drum
- Attached to the hub. Converts kinetic
energy from the shoe and lining assembly to heat and
transfers that heat away from the brake surface to dissipate
into the atmosphere over time. The majority of drums are
entirely of cast iron. Generally these are divided into three
service-rating codes based on application. There is
standard duty, heavy duty, and extra heavy duty. In
addition, there are inboard mounted drums (with spoke
wheels) and outboard mounted drums (with hubs). The
other brake drum is the steel jacketed type. This consists
of a steel mounting face with a cast iron braking surface
insert.
Brake, Engine
- See "
Brake, Exhaust
- See "
Brake Fade
- There are many types and causes of braking
fade. Fade may result, for example, from a reduction in
friction between linings and drums caused by exposure to
water. Most typically, however, fade involves a reduction
in braking force experienced when dragging brakes on a
long grade. If brakes are maladjusted, an overheated drum
may expand to the degree that push rod travel is
insufficient to fully actuate the brakes. This is one
example of mechanical fade, which also may result from
various mechanical defects (e.g., scored drums) within the
foundation brake system. In contrast, heat fade occurs
when linings overheat and become less aggressive.
Gradual and predictable fade is desirable as a warning.
Brake Proportioning
- Optional safety-oriented system,
often called "bobtail proportioning," for limiting drive-
axle brakes while a
is operated without a trailer.
Also, system that varies individual axle braking effort in
response to weight or other variable.
Brake Treadle
- Functionally, the brake pedal - a
mechanical lever attached to the foot brake valve.
Breakaway Valve
- Upon accidental separation of
trailer(s), a
protection system that prevents air loss
from the power unit. See "
".
Breather
- A vent in the drive axle housing for relieving
internal pressure due to heating and cooling within the
housing.
Bridge Formula
- See "
Broached Bushing
- Bushing that is finished by a round
cutting tool that has multiple teeth each removing a small
portion of the bushing material to achieve desired finished
size.
B/S-B/S
- See "
Bearing Shoulder to Bearing Shoulder
Burnish
- The conditioning or "seasoning" of a brake
lining by wear and temperature via a test procedure or in-
service operation.
Caliper
- In an air disc brake system, the clamping device
containing friction material mounted to pads. When
actuated, the caliper applies braking force to both sides of
the rotor.
Camber
- The tilt of the wheel side to side while looking
from the front - places the road contact point closer to the
king pin axis thereby reducing road inputs to the steering
system and contributes to steering stability.
Camber, Negative
- Top of the wheel tilts inward.