BOSS--An extension or strengthened section, such as
BEAD--The circular wire-reinforced section of a tire
the projections within a piston which supports the
that joins with the wheel rim.
piston pin.
BEARING--A part in which a journal pivot, or pin,
BOURDON TUBE--A hollow circular-shaped tube
turns or revolves. A part on or in which another
used as the pressure-sensing element in some
part slides.
gages.
BENDIX DRIVE--A type of drive used in a starter
BOYLE'S LAW--The absolute pressure of a fixed
that provides automatic coupling with the engine
mass of gas varies inversely as the volume,
flywheel for cranking and automatic uncoupling
provided the temperature remains constant.
when the engine starts.
BRAKE ANCHOR--A steel pin-shaped stud, rigidly
BERNOULLI'S PRINCIPLE--If a fluid flowing
mounted to the backing plate, upon which the brake
through a tube reaches a constriction, or narrowing
shoe either is attached or rests against.
of the tube, the velocity of the fluid flowing through
the constriction increases and the pressure de-
BRAKE BACKING PLATE--A rigid steel plate
creases.
upon which certain brake components are attached.
BEVEL GEAR--One of a pair of meshing gears
BRAKE BAND--A flexible band, usually made of
whose working surfaces are inclined to the
metal with an inner lining of brake fabric, that is
centerline of the driving and driven shafts.
tightened on a drum to slow or stop drum rotation.
BEZEL--A device used to attach a glass face to an
BRAKE, DISK TYPE--A braking network con-
instrument.
sisting of a rotating disk that is restrained during
application by stationary brake pads mounted on
BLACKOUT LIGHTS--A lamp installed on a
both sides of the disk.
vehicle for use during blackouts, which can be seen
from the air only at very close range.
BRAKE DRUM--A metal drum mounted on a car
wheel or other rotating members. Brake shoes or a
BLEEDER, AIR--A bleeder for the removal of air.
brake band is mechanically forced against the
BLOCK--See CYLINDER BLOCK.
brake drum, causing it to slow or stop.
BLOWBY--Leakage of the compressed fuel-air
BRAKE FADE--A reduction in the coefficient of
mixture or burned gases from combustion, passing
friction between retarding members as a result of
the piston and rings, and into the crankcase.
excessive heat buildup.
BLOWER--A mechanical device for compressing
BRAKE FLUID--A compounded fluid used in
and delivering air to the engine at higher than
hydraulic brake systems. It transmits hydraulic
atmospheric pressure.
force from the brake master cylinder to the wheel
BODY--The assembly of sheet metal sections,
cylinder.
framework, doors, windows, etc, which provides
BRAKE HORSEPOWER--The power actually
an enclosure for passengers or carriage space for
delivered by an engine that is available for driving
freight.
the vehicle.
BOGIE--A suspension unit consisting of tandem
BRAKE HOSE--A tubular hose used to transmit fluid
axles jointed by a single cross support (trunnion
pressure when a flexible joint is required.
axle) that also acts as a vertical pivot for the entire
BRAKE LINE--A rigid tube used to carry brake fluid.
unit.
BRAKE LINING--A special woven fabric material
BOILING POINT--The temperature at which a
with which brake shoes or brake bands are lined: it
liquid boils.
withstands high temperatures and pressures.
BOND--To bind together.
BRAKES--The mechanism that slows or stops a
BORE--The diameter of an engine cylinder hole.
vehicle or mechanism when a pedal or other control
Also, the diameter of any hole; for example, the
is operated. Also called the brake system.
hole into which a bushing is fitted.
AI-3
