Dictionary of Automotive:(for B)

 Dictionary of Automotive:(for B)

Babbitt metal

 An alloy of tin, copper, antimony and lead formerly used for engine bearings. Sometimes Babbitt's metal. 

back axle 

The rearmost axle (usually of a two wheeled vehicle). Also rear axle.

backbone chassis 

 Chassis in which a single structural spine carries all powertrain and running gear, the body shell generally forming a secondary structure. See also punt-chassis; spine-back.

backfire 

 An explosion of unburned or partially burned fuel in an exhaust or inlet system. See also antibackfire valve.

backlight

The rear window or screen of a vehicle.

backlight defogging system (UK: rear screen heater)

System for clearing moisture from the interior surface of a rear window of a vehicle, either by an electrical element within the glass or heated air from a blower.

back-plate

(1) Non-rotating plate carrying the shoes of a drum brake. (2) Metal member carrying friction material of pad of disc brake. 

 back pressure

Pressure resisting the flow of a gas in a pipe, as in an exhaust pipe.

 back-up alarm (UK: reversing bleeper)

Acoustic warning that automatically sounds when a vehicle, particularly a commercial or public service vehicle, engages reverse gear. 

backup lamp (UK: reversing lamp) 

 (1) Lamp used to provide illumination behind a vehicle, particularly when reversing. (2) Lamp to supplement a standard headlamp system.

baffle plate 

An internal transverse plate in a muffler or silencer.

 balance pipe

Pipe or tube joining the Venturis of twin carburetors. 

balance shaft 

 A rotating shaft incorporating a harmonic balancer or vibration damper.

balanced crankshaft

Engine crankshaft designed so that the disposition of  its mass counteracts the out-of-balance effects of the crank and sometimes the reciprocating components. Balance is usually achieved by extending the crank webs to form counter-balances.

balk ring 

 Rotating component of a synchromesh gearbox that prevents, or 'balks', premature engagement of gears. Sometimes balk ring or blocking ring.

 ball and socket

Mechanical joint in which a spherical end moves freely within a recessed socket. Used on suspension and steering linkages. Also ball joint.

 ball bearing

Rolling element bearing in which hardened balls run in tracks formed in inner and outer races. Various types exist, capable of carrying journal or thrust loads, or a combination of loads. 

balloon tire 

 Low pressure, bulbous sectioned tire used in the late 1920s and 1930s.

brake piston

The hydraulically operated piston assembly that forces apart the shoes of a drum brake, thereby instigating the braking friction that retards the vehicle. The piston of the wheel slave cylinder. 

banjo axle

Drive axle with a drum shaped final drive or differential case. 

barrel

Main air pipe through a carburetor. Also mixing chamber.

 barrel cranking motor

Starter or cranking motor for engines with small flywheels, the pinion being attached to a barrel to increase inertia. 

barrel tappet

A hollow cylindrical tappet, sometimes with facility for adjustment.

bath tub 

Combustion chamber shaped like an inverted bath tub in the base of which the valves are seated. 

battery

Direct current electrical storage unit which converts chemical or other forms of energy into electrical energy. Also accumulator (archaic).

battery charger

Static device for recharging an electrical storage battery.

battery shedding

Loss of material from a battery plate, as caused by age or repeated over-charging.

Baverey compound jet

Submerged carburetor compensating jet through which the flow is determined by the ratio of throat pressure to atmospheric pressure. 

bead filler

Solid rubber fillet that bonds the outer plies of a tire to the bead core.

bead flange

Fixed or removable lip on the outer periphery of a wheel that retains the tire. Also rim flange. 

 bead heel 

Part of the bead of a tire that fits into the angle formed by the rim and rim flange.

bead seat 

Part of a road wheel, below the bead lip, on which the tire bead is seated.

beaded edge

Any edge, as of a tire, upholstery, or body panel, in the form of a continuous lip or bead. beam axle Rigid transverse beam on which nearside and offside wheels are mounted. The term originally described a dead axle of forged I-beam section but sometimes describes any rigid live axle or dead axle. 

bell housing

Conical or bell-shaped extension of an engine crankcase, containing the flywheel and clutch.

belt

(1) Continuous reinforcing around the periphery of a radial ply tire, usually woven from steel or a man-made fiber. Also breaker. 

(2) Drive or power transmission belt such as a V belt or toothed belt. 

 (3) A driver or passenger seat belt.

belt drive 

System of power transmission in which a flexible endless belt transmits power between pulleys. See fan belt; toothed belt; Variomatic transmission.

 bench seat

Wide vehicle seat for more than one person.

Bendix drive 

 A drive comprising a pinion wheel carried on a helically grooved shaft. The sudden rotation of the shaft causes axial movement of the pinion. Widely used to transmit starter motor power, the pinion engaging the ring gear teeth on the engine flywheel periphery. The sudden rotational acceleration caused by the firing of the engine throws the pinion out of engagement. 

bevel differential 

Differential in which the principal gear elements are bevel gears, with input and output shafts mutually at right angles.

bias belted

Tire of bias ply or crossply construction but incorporating a peripheral reinforcing belt such as used in a radial ply tire. Also belted bias. See also bias ply tire. 

bias ply tire (UK: crossply tire) 

 Tire constructed on core or carcass of diagonally laid plies of fabric.

birfield universal joint

Proprietary constant velocity joint that allows plunging action of one shaft relative to the other.

bleed

(1) To empty a system of working fluid prior to maintenance or replenishment.

 (2) A valve or other means whereby a system can be drained of working fluid, or pressure reduced.

bleed screw

Form of threaded tap to facilitate draining of a hydraulic system, as for example a brake system.

block 

 cylinder block.

 blocking ring

 balk ring.

 blow-back 

Sudden reversal of air flow through a carburetor, often as a consequence of incorrect ignition timing or valve timing.

blow-by 

Unwanted leakage of gas under pressure, as past a piston or its sealing rings.

blow-out

Sudden bursting of a tire.

bluff body 

 Aerodynamic terminology for any body that is relatively wide in relation to its length, and particularly one with a blunt or squared front end.

bob tail 

Articulated vehicle tractor operating without a trailer.

body-number

Manufacturer's bodywork identification number, normally unique to each vehicle.

body shell 

(1) The assembled body paneling of a vehicle.

 (2) The body structure of a vehicle, particularly of a monocoque construction passenger car, minus running gear, and electrical and other ancillaries. bodywork The structural panel work of a vehicle.

bogie

Heavy vehicle undercarriage in which tandem axles are mechanically linked and suspended as a unit. Also bogey, particularly in US. 

bonnet (US: hood) 

 Hinged body panel that gives access to the engine compartment of a vehicle.

boost start

Starting an engine of which the battery is discharged or feeble by applying a higher than normal voltage and current to the electrical system from an external source.

booster brake 

 Brake used in addition to the service brakes of a vehicle to increase retardation under exceptional circumstances.

 

booster coil

Auxiliary coil that increases the voltage or duration of the spark in a spark ignition engine.

bore

(1) The internal diameter of the cylinder of an engine or pump.

 (2) The cylinder wall of an engine.

 (3) To make a cylindrical or circular aperture with a suitable cutting tool.

bore-stroke ratio 

Ratio of bore to stroke. A ratio of 1:1 is referred to informally as square. 

bottoming

(1) Deflection of a vehicle suspension to its maximum compressive travel due to road surface irregularity or excessive load.

 (2) Deflection of a pneumatic tire so that the carcass is momentarily flattened against the wheel rim.

 (3) Contact between the underside of a vehicle and raised ground. 

bottom dead center

The point of piston travel when the piston is nearest to the axis of the crankshaft. On a vertical engine, the lowest point of travel of the piston. Also BDC, lower dead center, LDC.

bottom end bearing 

 The connecting rod to crankshaft journal bearing.

 bottom gear

 

 (1) The gear in a change-speed gearbox or transmission that gives the lowest ratio of driven wheel rotational velocity to engine speed. 

(2) The gear that gives the highest ratio of engine speed to road speed, and consequently the highest torque at the driven wheels, as for starting, hill climbing. First gear. 

bounce test 

 Testing of the suspension, and particularly the shock absorbers, of a vehicle by manually depressing and then releasing each corner and observing the decay of vibrations. 

Bowden brake 

Mechanical drum brake operated by a sheathed cable.

 

boxer engine 

A horizontally opposed engine.

brake 

Brake is a  mechanical device.which resits the motion of vehicle.

 brake anti-roll 

 Device to ensure that brake pressure is maintained when a vehicle is stopped on an incline.

brake chamber

Chamber containing diaphragm and push rod to apply brakes in an air or hydraulic brake system. Also brake actuator.

brake fluid

Oil with which a hydraulic brake system is charged.

brake mean effective pressure

(1) Engine cylinder pressure, derived by calculation, that would give the measured brake power.

 (2) The product of indicated mean effective pressure and mechanical efficiency.

 brake power

Power developed by an engine as measured at the shaft by a brake or dynamometer. Specifically brake horsepower. See also indicated power; pumping losses.

breeches pipe

Y configuration exhaust pipe forming confluence of two exhaust manifolds to one exhaust pipe, and resembling a pair of breeches, inverted.

bucket seat

Deep and rigid seat with side restraints to provide occupant constraint in fast cornering.

bump steer

Change of steer angle resulting from sudden vertical deflection of the suspension. 

bump stop 

 Compression spring, usually of rubber, that limits the deflection of a vehicle suspension on striking a bump.

bumper 

 Horizontal bar mounted at front and rear of vehicle to prevent or reduce damage in low speed impacts.

 

bus

A vehicle for conveying passengers, usually by serving a regular route. An omnibus. 

bush (US: bushing) 

 Cylindrical sleeve forming a bearing surface for a shaft or pin. 

butterfly carburetor 

 Carburetor in which the flow of the air-fuel mixture is controlled by a disc valve or butterfly valve. A fixed choke carburetor.

butterfly valve 

 Disc valve pivoted about its diameter and acting as a throttle in a pipe or chamber. A mild misnomer as the true butterfly valve consists of two hinged half-discs, opening and closing like the wings of a butterfly. See also throttle valve. 

by-pass filter 

Liquid filter, such as an oil filter, that filters only part of the flow on the principle that, during repeated circulation, all fluid in circulation will be filtered.

by-pass valve

A valve for directing flow through a by-pass.