Dictionary of Automotive Terms Abbreviations

DICTIONARY OF AUTOMOTIVE TERMS-"Bu"

Bubble

A small blister in the finish of paint.
The bubble of air and spirit vapor within a Level tube loosely, the level tube itself.

Bubble car: A type of small car which was popular in the 1950s. It had a bulbous-shaped glass front to provide maximum interior room in spite of its small size. The door opened to the front of the driver. Examples are the BMW Isetta and Heinkel Trojan.

Bubble film: Duplex polymer film with regular array of bubbles thermoformed into one side, used for crush-proof packaging.

Bubble pack: See
Blister pack

Bubbles, pressure in: See
Pressure in bubbles

Bubble stabilization: Tendency of polymer bubble blown after extrusion in manufacture of film to maintain a constant shape without breaking or collapsing. Depends on tension stiffening behavior of molten polymer.

Also See
Troutonian fluid

Bubble trier: See
Level trier

Bubble tube: See
Level tube

Bucciali: A vehicle brand of which the 1925-1948 models with required application are Classic cars.

Buchholz relay: A protective relay for use with transformers or other oil-immersed apparatus; it embodies a float which becomes displaced and operates the relay contacts if gas bubbles are generated by a fault within the equipment being protected.

Buchmann-Meyer effect: The special type of reflection of light from the sound-track on a disk record whereby the lateral velocity of the track can be determined.

Bucket: See
Headlight bucket
Rust bucket
Shim under bucket

Bucket conveyor: A conveyor or elevator consisting of a pair of endless chains running over toothed wheels, and carrying a series of buckets which, on turning over, discharge their contents at the delivery end.

Bucket seat: Bucket Seat

An individual seat which is found in pairs in the front of a vehicle. Named because the curvature of the backrest and cushion resembles a cut-out bucket.

Bucket tappet: Bucket Tappet

Valve lifters that are hollow, cylindrical, and closed at one end and used with some overhead camshafts. The flat, closed end of the tappet (bottom of the bucket) rests against the Camshaft lobe with part of the Valve spring and Valve stem enclosed by the Cylinder. Called bucket tappets because they are shaped like upside-down buckets.

Bucket valve: A non-return (delivery) valve fitted in the bucket or piston of some types of reciprocating pump

Bucket coil: A winding on an electromagnet to oppose the magnetic field of the main winding. Such a device is sometimes used in electromagnetic loudspeakers to smooth out voltage pulsations in the power supply. Also called hum-bucking coil.

Buckland: See
AC Buckland Open Tourer

Buckle

A locking clasp usually found on seat belts and tie-down straps.
A metal strap
In foundry work, a swelling on the surface of a sand mold due to steam generated below the surface.
To crumple up, especially when metal bends in a vehicle accident. To twist or bend out of shape such as when plates of metal or a structural member deforms under compressive load.

Buckled plates: Battery plates that have been bent or warped out of a flat plane.

Buckler: A portable cover secured over the deck opening of the hawsepipes and the chain pipes to restrict the flow of water through the openings.

Buckle up: To put your seat belt on. British term is belt up

Buckley gauge: A sensitive ionization gauge for measuring very low gas pressures.

Buckling

A distortion of accumulator plates caused by uneven expansion, usually as a result of heavy discharges or other maltreatment.
Mode of deformation in which an elastic instability occurs in a plate or a structural member under compressive load, resulting in a twisting or bending out of shape. Usually leads to plastic deformation and eventual collapse.

Also See
Euler buckling limit
A term in reactor diffusion theory giving a measure of curvature of the deutron density distribution. The geometric buckling depends only on the shape and dimensions of the assembly while the material buckling provides a measure of the multiplying properties of an assembly as a function of the materials and their disposition.

Buck transformer: Transformer with secondary in mains circuit to regulate voltage according to a controlling circuit feeding the primary. Also called boost transformer

BUDC: Acronym for Before upper dead center". Same as BTDC.

Budd mounting: See
Double cap nut

Budd wheel: A ten-hole, stud-piloted disc truck wheel originally designed by the Budd Corporation.

Buff

To Polish.
A revolving disk composed of layers of cloth charged with abrasive powder; used for polishing metals.
An expert in a field or a person greatly interested in the field as in Jim is a car buff.

Also See
Nut

Buff contour: The specked shape of a buffed retread tire.

Buffed crumb: Flakes of rubber produced by abrading treads of worn tires for retreading; of limited use as recycled material for new tire compounds.

Buffer

A machine used to Rasp the old tread from the tire.
An electronic amplifier, often with unity gain, which is designed to decouple input from output. Normally designed to have high input impedance so that it does not load the driving stage and low output impedance such that it can provide current drive.
A spring-loaded pad attached to the framework of railway rolling-stock to minimize the shock of collision; any resilient pad used for a resilient purpose. May be hydraulically controlled or dampened.
A substance added to an electrolyte solution which prevents rapid changes in the concentration of a given ion. Also called buffer reagent

Also See
Jounce buffer

Buffer battery: A battery of accumulators arranged in parallel with a DC generator to equalize the load on the generator by supplying current at heavy-load periods and taking a charge during light-load periods

Buffer capacitor: See
Blocking capacitor

Buffer circuit: The resistance-capacitor unit which determines the rate of rise or fall of the envelope of the waveform of emitted sounds which has been generated in electrostatic circuits in electronic organs.

Buffered radius: A dimension that ensures the proper contour of the buffed surface according to tire size and type and matrix dimensions.

Buffer reagent: A substance added to an electrolyte solution which prevents rapid changes in the concentration of a given ion. Also called buffer.

Buffer resistance: See
Discharge resistance

Buffer spring: The part lending resiliency to railway buffing gear.

Also See
Buffer

Buffer tank: A closed tank that cushions the explosive expulsion of liquid from a system connected to it by controlling the gas pressure in the tank.

Buffet boundary: The limiting values of Mach number and altitude at which an aircraft can be flown without experiencing buffet in unaccelerated flight.

Buffeting

Severe, pulsating force of wind. When you drive in a convertible with the top down, you will often experience this buffeting action of the wind. It is also noticeable when a vehicle is driven quickly with the windows down.
An irregular oscillation of any part of an aircraft, caused and maintained by an eddying wake from some other part; commonly, tail buffeting in the downwash of the main plane, which gives warning of the approach of the Stall.

Buffing

Smoothing and polishing a surface by using a Buffing wheel and polishing paste or liquid.
Grinding or Rasping off remaining tread rubber to give the Casing proper texture to accept new retread stock and proper dimensions to fit the matrix.

Buffing template: A machined device of a specific shape used to obtain the required Buffed contour.

Buffing wheel: A disc which is covered in soft cloth or lambswool. It is powered by a tool like a drill which spins the disc to give a high gloss shine to the surface of a vehicle.

Buff line: The dividing line in the cross section of a tire between the buffed surface of the original tire and the new retread rubber.

Bug and tar remover: A solution which will dissolve bugs and tar residue. After application, it needs to be washed off or it will also remove the paint.

Bugatti: Click image for books on
Bugatti

A vehicle brand of which the 1925-1948 models are Classic cars. The 1951 Type 101 model is a Milestone car.

Bug deflector: Click image to supersize
Bug Deflector

A length of clear plastic which is attached to the front of the hood to prevent bugs from hitting the Windshield. Also called a bug shield.

Bug out: Trucker slang for leaving a CB radio channel as in "I better bug out and get some shut eye."

Bug shield: See
Bug deflector

Buick: Click logo for books on
Buick

A vehicle brand of which the Riviera for 1949 and 1963-70 are Milestone cars. The 1931-32 series 90 with required application are Classic cars. The 1953-54 Skylark are Milestone cars. Models include Allure (2005-08), Apollo (1973-75), Centurion (1971-73), Century (1936-42, 1954-58, 1973-2005), Electra (1959-90), Enclave (2008), Estate Wagon (1940, 1946- 1964, 1970-1996), Gran Sport (1965-1972), GSX (1970-1972), Invicta (1959-1963), LaCrosse (2005-08), LeSabre (1959-2005), Limited (1936-1942, 1958), Lucerne (2006-08), Park Avenue (1991-05), Rainier (2004-07), Reatta (1988-91), Regal (1988-04), Rendezvous (2002-07), Riviera (1963-1993, 1995-1999), Roadmaster (1936-1958, 1991-1996), Skyhawk (1975-1980, 1982-1989), Skylark (1953-1954, 1961-1972, 1975-1998), Somerset (1985-1987), Special (1936-1958, 1961-1969), Sport Wagon (1964-1972), Super (1940-1958), Terraza (2005-07), and Wildcat (1962-1970).

Build: The thickness of the paint film deposited on the body during spraying (measured in mils).

Also See
Heavy film build

Build date code: A code which tells you what day, month, and year the engine was made. Expressed alpha-numerically and stamped somewhere on the block.

Builder: In retreading a tire, a machine used to apply tread rubber to a Casing.

Also See
Body builder

Builders and Repairers Association: See
Vehicle Builders and Repairers Association

Building basin: A structure in which one or more ships may be built and floated by flooding the basin.

Build quality: The quality of workmanship and material composition in the construction of a vehicle.

Build up

To increase the surface level of metal by welding more material on it (and later grinding it to shape) or by adding filler to it.
To assemble or put something together.
To add material to something.

Also See
Carbon build-up
Pressure buildup

Buildup

The amount a weld face is extended above the surface of the metals being joined.
An excess of some material as in, "There was a buildup of carbon on the top of the piston."

Also See
Carbon build-up

Built-in voltage: The potential difference which arises across an unbiased Depletion layer in a semi-conductor device. The drift of charges in the electric field associated with it is exactly balanced by diffusion in the local charge concentration gradients. In effect the contact potential between regions of extrinsic semiconductor where there are abrupt changes in the doping.

Built-up crankshaft: A crankshaft which is not cast or forged as one piece, but made of several different parts.

Build-up sequence: The order in which successive welding runs or beads are applied in joining thick plates to achieve maximum strength with acceptable stress from heat distortion.

Bulb: An electronic device which gives off light by the heating of an element contained with a glass enclosure. The metal base which conducts the electricity may be a barrel with locating pins, or it may have small Filament wires protruding from the base. In some cases it is a tube with contacts at either end. When replacing bulbs, especially high intensity bulbs like halogen, be sure to avoid touching the glass. The oil from your fingers will cause the bulb to overheat and burn out quickly. If you do touch the glass, you need to clean it with Air dry it.

Also See
Alcohol
Bayonet bulb
Double filament bulb
Festoon bulb
Halogen bulb
Light bulb
Outer bulb
Quartz-halogen bulb
Quartz halogen bulb
Tungsten-halogen bulb

Bulb bar: A rolled, or extruded, bar of strip form in which the section is thickened along one edge.

Bulb, sensitive: See
Sensitive bulb

Bulk cargo: Cargo such as oil, coal, ore, woodchips, etc. not shipped in bags or containers.

Bulk carrier: Ship designed to carry cargo such as grain, woodchips, ore, coal, etc. in bulk.

Bulk charging: Using large containers of refrigerant to charge the system. Commonly employed with charging stations to perform complete system charges.

Bulk concrete: See
Mass concrete

Bulkhead

A structural partition that separates compartments. This is generally a metal wall that extends from one side of a vehicle to the other. In the engine compartment, you would find a Radiator bulkhead near the front and a Firewall near the back. Another bulkhead separates the passengers from the Trunk. The dashpanel is also a bulkhead.

Also See
Rear bulkhead.
On a public service vehicle (i.e., taxi, limo), partition at the front between the driver and passenger accommodation.
Vertical partition walls which separates the interior of a ship into compartments or rooms.
In fuselages, a major structural transverse dividing wall providing access between several internal sections, or a strengthened and sealed wall at the front and rear designed to withstand the differential pressure required for pressurization.
In power plant nacelles, a structure serving as a firewall.
A masonry or timber partition to retain earth, as in a tunnel or along a waterfront.

Also See
Afterpeak bulkhead
Collision bulkhead
Forepeak bulkhead
Screen bulkhead
Swash bulkhead

Bulkhead connector: An OEM device used to connect wiring inside the vehicle body with wiring outside the body. Usually located at the bulkhead or firewall.

Bulkhead deck: The uppermost deck to which the transverse watertight bulkheads are carried.

Bulking factor: Ratio between the volume of loosely placed material and the same weight of material when compacted to a given specification.

Bulk modulus: One of the four basic elastic constants for elastically isotropic materials, defined as the ratio of the applied, uniform triaxial stress (e.g., hydrostatic stress) to volumetric strain in a body. Symbol K. Related to Young's modulus (E), Poisson's ratio (v) and Shear modulus (G) by K = E/3(1-2v) = EG/3(3G-E)

Bulk refrigerant drum: A large (e.g., 10 lbs, 25 lbs, 30 lbs) container of refrigerant generally used in professional air conditioning service shops which employ charging stations to perform complete system charges.

Bulk sales: Wholesale sales of gasoline in individual transactions which exceed the size of a truckload.

Bulk station: A facility used primarily for the storage and/or marketing of petroleum products, which has a total bulk storage capacity of less than 50,000 barrels and receives its petroleum products by tank car or truck.

Bulk terminal: A facility used primarily for the storage and/or marketing of petroleum products, which has a total bulk storage capacity of 50,000 barrels or more and/or receives petroleum products by tanker, barge, or pipeline.

Bulk test: Test for materials having a high attenuation for use as a radiation shield.

Bull bar: The upward extension of a bumper to protect lights and the grille.

Also See
Nerf bar

Bulldog: Trucker slang for a Mack truck as in "Who we got in that eastbound bulldog."

Bulldozer: A power-operated machine, provided with a blade for spreading and levelling materials.

Also See
Angledozer

Bullet-point pick hammer: See
Pick hammer

Bull-headed rail: A rail section once used widely in the UK, having the shape roughly of a short dumb-bell in outline, but with unequal heads, the larger being the upper part in use.

Also See
Flanged rail

Bull horn: A warning horn that sounds like the bellow of a bull or the moo of a cow.

Bullion

Gold or silver in bulk, i.e., as produced at the refineries, not in the form of coin.
The gold-silver alloy produced before the metals are separated.

Bullion content: In parcel of metal of minerals being sold, where the main value is that of the base metal which forms the bulk of the parcel, the contained gold or other precious metal of minor value included in the sale.

Bull low: The lowest gear in a Transmission. Some older transmissions listed their gears as bull low (used for getting out of a stuck condition or climbing a very steep hill), low or first (used for starting out from a stop or for climbing a moderate hill), second (used for town driving or slight hills), third (used for highway cruising).

Bull-ring: A metal ring used in the construction of overhead contact wire systems for electric schemes; it forms the junction of three or more straining wires.

Bulwark

Fore-and-aft vertical plating immediately above the upper edge of the sheer strake.
A sea-wall built to withstand the force of the waves; in some cases the reinforcement of the natural Breakwater.

Bump

Bump Sign

A slight rising of the pavement possibly caused by a frost heave and if severe enough will be indicated by a sign
The upward movement of the wheels and Suspension. Also called Jounce.
The action of a vehicle dealer who increases the sale price of the vehicle, interest rate, monthly payments, etc.

Also See
Air pocket
Hood bump rubber

Bump and rebound: The two stages of suspension movement requiring damping.

Also See
Bump
Rebound

Bumper: Originally a bumper was a separate metal bar or blade at each end of a vehicle to prevent damaging the main part of the vehicle from damage occurred by a slight bump into an obstruction or another vehicle.

Also See
Bumper system
Bumper to bumper
Energy-absorbing bumper
Energy absorbing bumper
Front bumper
Hood bumper
Jounce bumper
Quarter bumper
Rear bumper skirt
Absorbing bumper
Bonnet bumper
Bumper to bumper
Wrapround bumper

Bumper bar: A tubular bar or series of bars which are designed to protect the front of a vehicle.

Bumper blade: A flat bar which is designed to protect the front or rear of a vehicle.

Bumper bracket: A device to which the bumper is attached to the frame, body, or chassis.

Bumper filler: A small panel usually made of plastic which fits between the bumper and the body of the vehicle.

Bumper horn: A short bumper extension which is mounted vertically (i.e., perpendicular to the main bumper), usually one on each side of the bumper. The British term is overrider

Bumper insert: A rubber or plastic strip fitted to the width of a bumper to prevent scoring of the bumper.

Bumper iron: A Bumper bracket

Bumper jack: Bumper jack

A device for lifting one corner of a vehicle to change a tire. Older cars used a long bar which fitted into a base. A device on the long bar had a hook which was placed in a strategic place on the vehicle. A Lug wrench was inserted into the other end of the device and used to move the moveable part up the long bar thus lifting the vehicle.

Bumper panels: See
Side bumper panels

Bumpers: See
Jounce bumpers

Bumper skirt: See
Rear bumper skirt

Bumper sticker

A piece of rectangular paper with a sticky back which can be attached to the back of a vehicle to promote something
Trucker slang for a car following too closely as in "Hey Charlie better watch out you got a bumper sticker on your backdoor."

Bumper system: An energy-absorbing system with some type of deformable material including Hydraulic Cylinders which enable the bumpers to protect the vehicle from damage in low- Speed impacts.

Bumper to bumper

A traffic condition in which a line of vehicles are stopped one after the other or are moving very slowly.
A way of expressing the entire vehicle from one bumper to the other.

Bumping: The action of correcting damaged panels by pounding out the dent.

Bumping blade: An autobody tool used for slapping out slight dents (sometimes without a supporting dolly). It has slight serrations which hold the metal to avoid stretching. Also called a bumping file.

Bumping file: An autobody tool used for slapping out slight dents (sometimes without a supporting dolly). It has slight serrations which hold the metal to avoid stretching. Also called a bumping blade.

Bumping hammer: An autobody hammer used with a dolly for restoring a panel's shape.

Also See
Fender bumping hammer

Bumping out: An autobody term in which a damaged panel is hit with a hammer until it is nearly the correct shape.

Bumping spoon: See
Spring beating spoon

Bump rubber: See
Bonnet bump rubber
Hood bump rubber

Bump start

A method of starting a manual transmission (not for automatics) vehicle by pushing it (especially down a hill) and letting in the clutch while in second gear and the ignition set to the on position.
To start a car using a bump start.

Bump steer: When an uneven road surface causes a vehicle to steer or lose Directional stability, this is called bump steer At the front, bump steer is associated with the tie-rod and linkage-arm relationship. It is caused by the method of locating the Rear suspension, the type of rear suspension, and the geometry of the various Linkages. In race cars, bump steer is designed out of the Suspension so that the handling is as precise as possible. In most cars it is present to some degree. In fact, it can be useful to allow engineers to design a small amount of Understeer or Oversteer into the Chassis.

Bump stop: Bump stop

A cushioning device, usually rubber, that limits the upward movement of the wheels and Suspension to prevent metal-to-metal contact that could lead to Suspension damage or failure. Also called Jounce bumpers.

Bunched conductors: See
Aerial bunched conductors

Buncher: Arrangement which velocity-modules and thereby forms bunches of electrons in the electron beam current passing through it. Bunching would be ideal if the bunches contained electrons all having the same beam velocity. Also called input gap.

Also See
Buncher gap
Catcher
Debunching
Rhumbatron

Buncher gap: See
Buncher

Bunching: The process of forming a steady electron beam into a succession of electron groups, or bunches. The result of interaction between an alternating electric field at the mouth of a cavity (see Rhumbatron) and an electron beam passing close by.

See
Velocity modulation.

Bunching angle: Transit delay or phase angle between modulation and extraction of energy in a bunched beam of electrons.

Bundle: See
Fuel assembly

Bundle conductor: Two or more overhead line conductors, suitably spaced to avoid Brush discharge loss, forming a phase, replaces a single large conductor.

Bundle divertor: See
Divertor

Bundled out: Trucker slang for Trailer is fully loaded as in "As bundled out as I am those hills will really slow me down."

Bungee cord: A rubber tie down strap of various lengths (usually 10 mm diameter) with a metal hook on each end. Most are covered with fabric. The hooks are often plastic coated to minimize scratching. Some have an extra hook attached in the middle. Others are linked with a second cord to produce an X-shape. They are used to secure objects to a luggage rack.

Also See
Bungee net

Bungee net: A specialized bungee cord shaped in the pattern of 25 squares with plastic covered hooks on two opposite sides of the net. It is used to secure objects to a luggage rack.

Also See
Bungee cord
Cargo net

Bunk

A Sleeper on a truck
A built-in bed on a ship.

Bunker

Space where ice or cooling element is placed in commercial installations.
A storage space for coal or oil fuel.

Bunker capacity: The capacity of a space in a ship used for carrying fuel. It is calculated at a fixed rate of stowage per unit volume, according to fuel, and allowances for obstructions are made in percentage.

Bunker Fuel Oil: Heavy, residual fuel oil used in ships.

Bunker fuels: Fuel supplied to ships and aircraft, both domestic and foreign, consisting primarily of residual and distillate fuel oil for ships and kerosene-based jet fuel for aircraft. The term international bunker fuels is used to denote the consumption of fuel for international transport activities. Note: For the purposes of greenhouse gas emissions inventories, data on emissions from combustion of international bunker fuels are subtracted from national emissions totals. Historically, bunker fuels have meant only ship fuel.

Bunkers: Fuel consumed by the engines of a ship.

Bunsen Burner: See
Injection burner

Bunsen photometer: See
Grease-spot photometer

Bunt: A maneuver in which an aircraft performs half an inverted loop, i.e., the pilot is on the outside where he experiences Negative g

Buoy: See
Buoy-to-buoy

Buoyancy: The apparent loss in weight of a body when wholly or partly immersed in a fluid, due to the upthrust exerted by the fluid.

Also See
Archimedes' principle
Center of buoyancy
Correction for buoyancy
Reserve buoyancy

Buoy-to-buoy: See
Block time

Buran: Soviet space shuttle which undertook a successful unmanned flight in November 1988, later missions were cancelled due to funding problems

Burden: The load on an instrument transformer. It is usually expressed as the normal rated load in volt-amperes, or as the impedance of the circuit fed by the secondary winding.

Also See
On-costs

Bureau: A credit report on a customer who is about to purchase a vehicle.

Bureau of land management: (BLM) The United States government agency within the U.S. Department of the Interior which has divided trails into four classes Type I is at least 7 feet (213 cm) wide (enough for a family vehicle), paved, easy to traverse. Type II is also at least 7 feet (213 cm) wide, not paved, but is usually improved. However it may be rough or rutted and contain Washboards. It is best travelled by high-clearance 4WD vehicles. Type III is a narrow unimproved dirt road, often with rocks, steep hills, and mud over which only 4WD should use. Type IV trails are for Mountain bikes, dirt bikes, and ATVs. 2WD or 4WD vehicles are not allowed.

Burglar: See
Car burglar

Burial site: Place for the deposition, usually in suitable containers, of radioisotopes after use, contaminated material or radioactive products of the operation of nuclear reactors. Also called graveyard.

Buried layer: A high-conductivity layer diffused into active regions of a semiconductor wafer before growth of the Epitaxial layer in which devices are defined. It is used to decrease the collector resistance of certain bipolar junction transistors.

Burned metal: A term occasionally applied to the metal which has been combined with oxygen to the end that some of the carbon has been changed into carbon dioxide and some of the iron into iron oxide.

Burn: Controlled firing of rocket engine for adjusting course and re-entry initiation.

Also See
Ion burn

Burnable poison: Neutron absorber introduced into a reactor system to reduce initial reactivity but becoming progressively less effective as burn-up proceeds. This helps to counteract the fall in reactivity as the fuel is used up. Boron-10, which is transmuted into helium by neutron capture, has been used in the form of borosilicate glass placed in empty control-rod guides.

Burned valves: Valves that have become pitted so that they do not close properly.

Burner

A device which tends to consume a lot of material.
Device in which burning of fuel takes place.
A device for the final conveyance of the gas, or a mixture of gas and air, to the combustion zone.

Also See
Argand burner
Fuel burner
Gas burner
Lead burning
Oil burner
Main burner
Automatically-lighted_burner

Burner firing block: Unit made from refractory material that fits into a furnace wall at the burner position, having a nozzle-protecting recess at back and a tunnel on the firing side. It is called quarl in oil-firing practice.

Burner head: That portion of a burner beyond the outlet end of the mixer tube that contains the ports.

Burner loading: Potential heat that can be liberated efficiently from a burner. Expressed in kilowatts or Btu h^-1

Burner turndown factor: Minimum gas rate at which a burner is capable of stable flame propagation without the flame flashing back to the air-gas mixing point or blowing off from the burner nozzle or head.

Burner valve: A manually or mechanically operated valve which permits control of the flow of fuel.

Burning

The violent combination of oxygen with any substance to produce heat.
The action of consuming something to produce heat, i.e., Combustion.
The heating of an alloy to too high a temperature, causing local fusion or excessive penetration of oxide, and rendering the alloy weak and brittle.

Also See
Lead burning.
The action of erosion or eating away. Electrical contacts are burning when they wear away; exhaust valves are burning when they pit and don't close properly.
Flame cutting.

Also See
Afterburning
Lead burning

Burnish

To bring a surface to a high shine by rubbing with a hard, smooth object.
The process of breaking-in new brake pads or shoes so the linings conform to the disc or drum friction surfaces.
The initial seating process in which the brake shoes or pads wear to conform to the exact contours of the brake drum or disc.

Burn mark: Molding defect found on polymer surfaces caused by adiabatic compression of gas trapped in mold cavity by advancing melt front

Burnout: Sudden failure of any device, caused by excessive current, leading in turn to overheating; may also be due to failure of artificial cooling in any electronic assembly or sub-assembly.

Burnout velocity: The maximum velocity achieved by a rocket when all the propellant has been consumed.

Burn rate: See
Cbr process
Controlled burn rate

Burn rubber: The action of rapid acceleration where the wheels make rapid rotation, but there is only very little Momentum. As a result, the driving wheels leave some rubber behind on the pavement.

Also See
Peel rubber.

Burnt metal: Metal which has become oxidized by overheating, and so is rendered useless for engineering purposes.

Burnt valves: See
Burned valves

Burn-up

In nuclear fuel, amount of fissile material burned up as a percentage of total fissile material originally present.
Of fuel element performance, the amount of heat released from a given amount of fuel, expressed as megawatt or gigawatt-days per tonne.

Burr

A roughness left on a cut or punched metal. A rough edge or Ridge.
A rotary tool with cutting teeth like a file.

Burred wheel: A wheel which has metal slivers or roughness around the edge of the rim.

Burr walnut: A wood veneer used for dashboards and door trim on some cars.

Also See
Zebrawood

Burst

To explode and suddenly lose all the air in a tire.
A defect, often very small, in fuel cladding or sheeting which allows fission products to escape.
Unusually large pulse arising in an ionization chamber caused by a cosmic ray shower.
Short period of intense activity on an otherwise quiet data channel.
Sudden increase in strength of received radio signals caused by sudden changes in the ionosphere.

Also See
Black burst

Burst-can detector: An instrument for the early detection of ruptures of the sheaths of fuel elements inside a reactor. Also called burst-cartridge detector or leak detector.

Burst cartridge: Fuel element with a small leak, emitting fission products. Also called burst slug.

Burst-cartridge detector: See
Burst-can detector

Burst slug: See
Burst cartridge

Bury the needle: Going beyond the displayed maximum speed. For example, a digital Speedometer may show speeds from zero to 137 kph (85 mph) on its display. When the needle goes beyond the maximum displayed point, it may go beyond the line of sight and is considered buried.

Bus

A large public or private passenger vehicle used for transporting many (at least 10) passengers.
Also See
Articulated bus
Single-decker bus
Double-decker bus.
The part of the payload of a space exploration vehicle which contains the atmospheric (re-)entry probes, or a universal platform for diverse space experiments and applications.
A Bus-bar which is a heavy electrical Conductor used to carry or make a mutual connection between several circuits.

Bus-bar

A heavy Conductor used to carry or make a mutual connection between several circuits. Also called a bus.
Length of constant-voltage conductor in a power circuit. Normally of rigid copper construction and located in a power station or substation.
Supply rail maintained in a constant potential (including zero or ground) in electronic equipment.

Bus-coupler switch: A switch or circuit breaker serving to connect two sets of duplicate bus-bars.

Bush

British term for Bushing.
A hardened cylindrical inset in a drilling jig to position a drill or reamer accurately.

Bush-hammering: The operation of dressing the surface of stone or concrete with a special hammer having rows of projecting points on its striking face for decoration or to improve bonding to the next placement of further concrete.

Bushing

A protective Liner or sleeve that cushions noise, Friction, or movement. Suspension bushings are often made from two pipes (one inside the other) with a sleeve of rubber in the space between the two pipes.
Rubber bushings on the Suspension system should be lubricated regularly.
A bearing for a shaft, spring Shackle, Piston pin, etc., of one piece construction which may be removed from the part.
An insulator which enables a live conductor to pass through a grounded wall or tank (e.g., the wall of a switch house or the tank of a transformer.)

Also See
Valve bushing

Bus-line: A cable, extending the whole length of an electric train, which connects all the collector shoes of like polarity. Also called power line

Bus-line couplers: Plug-and-socket connectors to join the bus-line of one coach of an electric train to that of the next.

BUS N: Acronym for Bus Negative -- the negative terminal.

BUS P: Acronym for Bus Positive -- the positive terminal.

Buster: See
Lock buster

Bustle pipe: Main air pipe surrounding blast furnace, which delivers low pressure compressed air to tuyères.

Bus-wire coupler: A flexible connection between the coaches of an electric train for maintaining the continuity of bus-wires which run throughout the train-length.

Busying: See
Backward busying

Busy intersection: A road junction where there is a lot of traffic and may be controlled by signal lights or not. Usually a place where accidents are more likely to occur.

Butane: A petroleum gas easily liquefied under pressure, recovered from natural gas. Used as a low-volatility component of motor gasoline, processed further for a high-octane gasoline component, used in LPG for domestic and industrial applications and used as a raw material for petrochemical synthesis. Often used as engine fuel in trucks.
Also See
LPG.

Butex: Trade name for diethylene glycol dibutyl ether, used for separating uranium and plutonium from fission products. Compare Purex

Buthocrome: Particular groups of atoms in organic compounds which have the effect of lowering frequency of the radiation absorbed by these compounds.

Butt

The end joint between two plates or other members which meet end to end.
The square ends of a piston ring.

Butt connector: A solderless wire connector used to permanently join two wire ends together.

Butted tubing: Tubing whose outside diameter remains constant but whose thickness is reduced in midsection where less strength is needed.

Butterfly: Term used in metal extrusion where an open U shape is first made and the sides then folded closer to make a vertically sided U. This enables the die to be much stronger because the narrow section to form the inside of the U can have a wider base.

Also See
Butterfly valve
Throttle butterfly

Butterfly curve: The strain versus applied field curve of ferroelectrics.

Butterfly valve: A nut with wings to be turned by thumb and finger. Sometimes called a Wing nut.

Butterfly tail: See
Vee-tail

Butterfly valve

A small metal Disc located in the Carburetor that controls the flow of air into the Carburetor. It is so named due to its resemblance to the insect of the same name.
A disk turning on a diametral axis inside a pipe; used as a throttle valve in a gasoline engine.
A valve consisting of a pair of semicircular plates hinged to a common diametral spindle in a pipe; by hinging axially, the plates permit flow in one direction only.

Buttermilk: Trucker slang for Any beer as in "When I get home I'm gonna get me some buttermilk."

Butt joint

A piston ring gap in which the two ends of the ring are squared off.
A weld where the two panels are not overlapped but fit against each other end to end.

Butt-jointed: See
Joint

Buttock planes: Longitudinal sectional planes drawn through a ship's form; used for laying-off in the molding loft, and for calculation of volumes, etc.

Button: A small disk or knob which activates something electrical when it is pressed such as a Starter button.

Also See
Abs override button
Eject button
Frequency scan button
Horn button
Memory button
Override button
Preset station button
Push button
Release button
Reset button
Scan button

Button head: A bolt with a Round head

Button-headed screws: Screws having hemispherical heads, slotted for a screwdriver. Also called half-round screws

Button microphone: Small microphone which can be fitted in the buttonhole.

Buttons: See
Button

Buttress

A thick rubber reinforcement in the shoulder of a tire. It provides support at the edge of the tread, limits shoulder area flexing, and protects the shoulder of off-road tires.

Also See
Fender strengthening buttress
A supporting pier built on the exterior of a wall to enable it to resist outward thrust.

Buttress screw-thread: A screw-thread designed to withstand heavy axial thrust in one direction. The back of the thread slopes at 45°, while the front or thrust face is perpendicular to the axis.

Buttressed thread: A screw thread with one vertical and one inclined flank.

Butt strap: A strap that overlaps the butt between two plates, serving as a connecting strength strap between the butted ends of the plating.

Butt-welded tube: Tube made by drawing mild steel strip through a bell-shaped die, so that the strip is coiled into a tube, the edges being then pressed together and welded.

Butt-welding: The joining of two plates or surfaces by placing them together, edge to edge, and welding along the seam thus formed.

Also See
Welding

Butyl: A non-porous synthetic rubber used in making inner tubes and tubeless tire liners.

Butyl Alcohol: Alcohol derived from Butane that is used in organic synthesis and as a solvent.

Butylene: (C₄H₈) An Olefinic hydrocarbon recovered from refinery processes.

Butyl rubber: A synthetic rubber used as a base for one type of adhesive. It has poor resistance to petroleum oils and gasoline but excellent resistance to vegetable and mineral oils; to such solvents as acetone, alcohol, phenol, and ethylene glycol; and excellent resistance to water and gas adsorption and sunlight.

Butyl tube: The typical material for tubes. Inexpensive, easy to repair.

Buxton certification: The certification of the suitability of electrical equipment for use in an atmosphere in which fire or explosion hazards are present.

Buy at end-of term interest rate: The effective net interest rate for the lease if, at the end of the lease, the car is purchased at the end-of-lease purchase price.

Buying decisions: The act of determining whether or not a product purchase or repair, will be made, and/or which product or service will be purchased.

Buy rate: The interest rate that banks or financing institutions will charge on all vehicle contracts being financed. It is a secret number between the bank and the dealer which is the real amount of the interest rate that the loan starts out at before the dealer increases it for its own extra profit.

Buzz

Severe vibration of a control surface in transonic or supersonic flight caused by separation of the airflow due to compressibility effects.
To interfere with an aircraft in flight by flying very close to it.