A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
B
B.A.: British Association old standard size of threads.
B.S. Kite Mark: British Standards Kite Mark. The symbol of the British Standards Institute consisting of a triangle on its point with a capital B on its side above the triangle and a capital S inside the triangle.
B.S.F.: British Standard Fine size of thread.
Babbitt Metal: An alloy of tin, copper, antimony and lead used as a coating for plain steel bearings.
Back EMF: A voltage produced that tends to oppose the voltage that created it.
Back Plate: (1) Non-rotating plate carrying the shoes of a drum brake. (2) Metal member carrying friction material of the disc brake pad.
Back Pressure: The pressure build-up in the exhaust caused by the resistance to exhaust flow by pipe diameters and muffler baffles. Used in design to balance an exhaust to an engine.
Backfire: Combustion of fuel in the intake or exhaust resulting in a loud explosive noise.
Backlash: The clearance between two components, usually used to measure the running clearance of gear teeth.
Baffle: A plate that restricts the flow of a gas (muffler) or fluid (fuel tank) in a container.
Balance Shaft: A rotating shaft geared to another shaft, usually the crankshaft that carries counterbalance weights to bring the shafts into harmonic balance.
Balance Valve: A hydraulic device that controls the pressure in different parts of a hydraulic circuit. Used to balance front and rear brake actuation.
Balance Weights: Small weights used to balance a shaft or a wheel.
Balk Ring: A component of a synchromesh gear hub that provides a cone clutch and guidance of the outer hub to the gear dog teeth.
Ball Bearing: A bearing consisting of inner and outer tracks with a series of ball bearings in between. A single surface hardened steel ball.
Ball Flange: Flexible exhaust connection.
Ball
Ball Pivot: A pivot that allows movement in several directions.
Ball Valve: A simple valve that is closed off as a ball moves.
Ballast Resistor: Electrical resistor used in low tension circuit to regulate ignition coil output when the engine is running and is by-passed during starting to give an increased spark voltage for cold starting.
Banjo
Bar: Measurement of pressure - one atmosphere.
BARO (Barometric Pressure): Air or gas pressure measured in a standard unit. (Pascal, psi, bar)
Barrier Cream: Used to help prevent skin damage when working, for example, with oils.
Base: Terminal of a transistor that becomes conductive to the emitter when energised. The trigger terminal of transistors and thyristors.
BDC: Bottom dead centre. The position of the crankshaft when the piston is at its lowest position in the cylinder. The crankshaft is at 180 degrees of rotation from the top dead centre 0 degrees position.
Bead: Part of the tyre.
Beam Axle: Type of non-independent suspension.
Beam Setter: Equipment used to check the alignment of vehicle headlights.
Bearing Cap: Half-round parts that holds the big end and main bearings into place either on the con rods or engine block.
Bearing Clearance: The freeplay between a bearing shell and journal.
Bearing Nip or Crush: Applies to the applied grip of a split shell bearing when the two halves are tightened together.
Bearings: Components used to support a shaft and allow rotation.
Benzole: Hydrocarbon fuel additive and octane improver.
Bevel Gears: Gears cut at an angle from the periphery so that they can transmit a drive through an angle. An example is the final drive crown wheel and pinion.
Bi-Metal Spring: A spring made of two metals that expand differently with temperature change. This changes the tension as temperature changes.
Bias: Towards one side or one polarity.
Big End: End of the con rod that fits to the crankshaft.
Big End Bearings: The journals and shell bearings on a crankshaft that carry the big ends of the connecting rods.
Bimetal Strip: Two metals bonded together so that when heated, the different rates of expansion cause the strip to bend. The amount of bend is proportional to the temperature.
Bimetal Thermostatic Spring: A spring that changes tension with temperature.
Bimetallic Valve: A valve that operates when a temperature change moves a bimetal strip.
Binary: A system of numbering using 0 and 1 and used in computer operating systems.
Binary Counter: An electronic device that counts in binary (1s and 0s) by using logic gates and basic memory devices.
Binding: Term used to describe one component sticking or rubbing against another.
Blade Connector: An electrical cable connector consisting of a blade and spring sided socket.
Blanking Plugs: Screwed plugs used to blank off or block off a test port or adjustment point.
Bleed: The act of removing air from a liquid system.
Bleed Nipple: A small nipple valve that allows connection of a pipe and is operated by loosening.
Blending Flaps: Flaps used to mix hot/cold and fresh/recirculated air in a heater system.
Blipped Throttle: Description of a 'quick press' of the throttle to make the engine rev up.
Blocker Bar: General term used to describe a bar that prevents an action of some kind.
Blow Back: Ignition of fuel in the inlet manifold causing a flame to rise out of the air intake through the carburettor.
Blower Motor: A motor that uses a fan to assist in moving air.
BlueVision: Trade name for 'blue' headlight bulbs produced by Philips.
Body: Main portion of motor car.
Bond: Attraction between two things such as to cause them to stick together.
Bonding Cables: Cables or wires used to connect different panels together.
Bonding Resin: Adhesive often used on friction linings.
BOO: Brake on/off switch
Boost Pressure: The amount of increase above atmospheric pressure provided by a supercharger.
Booster Fan: See blower motor.
Boot: Usually made of rubber, a cover for a moving component such as a track rod end.
Boots/Gaiters: A rubber (or similar) boot used to cover working components. It is used to keep dirt out and in some cases lubrication in place. Also slang for alligator...
Bore (cylinder): The internal part of a hollow cylinder in which a piston is located.
Boring Bar: Used to cut cylinder bores.
Boss: A reinforcing section around a cylindrical bore in a component.
Bottom Dead Centre: The position of the crankshaft when the piston is at its lowest position in the cylinder. The crankshaft is at 180 degrees of rotation from the top dead centre 0 degrees position.
Bounce: Vehicle body suspension movement when hitting bumps.
Bounce Test: A manual test of suspension dampers (shock absorbers) by pushing down on the supension and observing the oscillations when released.
Bounce-back: Movement of an electric window as it hits an obstruction - and bounces back (opens again).
Bourdon Tube: A U shaped tube used to measure vacuum.
Box Sections: Parts of the vehicle body - chassis and structural members.
Boxer Engine: A horizontally opposed engine.
BP Sensor: A barometric pressure sensor.
Brake: (1) Device to retard the motion of a vehicle or to prevent inadvertent movement when parked. (2) Dynamometer for measuring the power of an engine, originally a friction brake by which torque could be measured. Also brake dynamometer (informal).
Brake Accumulator: A pressure container fitted into pumped hydraulic systems to maintain a reserve of pressure if the pump fails. They also smooth out the pump pulses in the system.
Brake Adjuster: A mechanical device for taking up the free play in brake components. Can be either manually or automatically operated.
Brake Balance: The splitting of brake effort to each axle in relation to the optimum that the axle can provide.
Brake Band: A friction material lined strap around a epicyclic gear annulus. Operated by hydraulic pressure to hold the annulus for gear ratio selection.
Brake Booster: See brake servo.
Brake Caliper: The fixed component of a disc brake holding the pistons that apply an inward force to press the brake pads onto the rotor.
Brake Cylinder: The wheel cylinders of hydraulic brakes in the brake unit.
Brake Drum: Rotating drum inside which brake shoes operate.
Brake Fade: Reduction of braking effort resulting from overheating of friction surfaces, or other transient effect.
Brake Fluid: A special liquid used in hydraulic brake systems. Always check data because some types should not be mixed.
Brake Horsepower (bhp): A measure of the power output from an engine when measured with a dynamometer using a brake applied to the engine flywheel. The engine effort to overcome the braking force gives the bhp value.
Brake Lines: The hydraulic pipes and hoses of the brake system.
Brake Lining: The friction material attached to brake shoes and pads.
Brake Linkage: A general term to describe components that link different parts of the brake system together.
Brake Pad: A steel plate with a bonded friction lining used on disc brakes. Similar to the brake shoe of a drum brake.
Brake Rollers: Rollers used to drive the wheels of a vehicle for brake testing purposes.
Brake Servo: A mechanism (vacuum or hydraulic) that increases the braking effort applied by the driver.
Brake Shoes: Part of drum brake carrying linings.
Braking Effort: The force applied to the brakes.
Braking Thrust: Forces that are caused by braking.
Breakout Box: A terminal box for carrying out diagnostic tasks on electrical and electronic systems.
Bridge Rectifier: A type of rectifier using four or more diodes to give full wave rectification.
Brush End Plate: A plate used to hold brushes in contact with a commutator.
Brushes: Pieces of carbon or metal ending in wires or strips. Contacts onto rotating slip-rings or generator/motor commutator.
BTDC - Before Top Dead Centre: The position of the crankshaft before the piston has passed the top of the cylinder and is still on the way up.
Bulkhead: Substantial structural panel of vehicle body in front of passenger compartment. Also known as a firewall.
Bump Cap: A hard hat.
Bump Steering: Steering action that results from hitting a bump.
Bump Stop: A rubber spring that limits and dampens the movement of a spring to prevent excessive deflection and spring damage.
Buoyancy: The ability to float in liquid or in air.
Burrs: Term used to describe rough edges on metal components.
Bush: Cylindrical sleeve forming a bearing surface for a shaft or pin.
Bushes (rubber): A metal and rubber composite bearing that provide both a limited range of movement and insulation from road vibration.
Buss Bar: A conductor in a fuse box or other electrical distribution device.
Butyl: Synthetic rubber impervious to oxygen.
Bypass: A secondary route in a system that allows gas, liquid or electicity to flow outside of the main route.
Bypass Valve: In a lubrication system a valve that allows oil to bypass a filter.