Every chain has rollers which are connected by side plates or Keepers. When counting the number of links in a length of chain, it is easiest to count the number of side plates on one side of the chain and multiplying the number by two. When a chain needs to be an odd number, a half link is included. The term half link is a misnomer. It should be called a single link. The side plate on a half link is not flat but has a step down shape. For this reason, it is called an offset link.
A driving key serving the same purpose as the regular key but it is shaped somewhat like a half circle. Also called a Woodruff key.
Half-moon slip joint pliers
A multiple-slip joint pliers with groove joint
Half-round body file
A body file with domed file surface for working reverse-crowned panels
A special file that’s flat on one side and convex on the other
A rotating shaft that transmits power from the final drive unit to one side of the drive wheels, but usually refers to the two shafts that connect the road wheels to the final drive with Independent rear suspension or Front-wheel drive as opposed to the axle shafts of a live rear axle. Also called an Axleshaft
A pulse generator that makes use of the Hall effect and consists of a rotor with vanes, a conductive element with a permanent magnet and the Hall IC. Also called Hall generator. When the air gap is unobstructed, a Hall voltage is generated; when a vane stands in the air gap, the magnetic flux cannot reach the Hall IC. Hall generators used as ignition pulse generators have as many vanes and Hall windows as the engine has cylinders, dwell being determined by the width of the vanes. Hall generators used in electronic-map ignition systems to provide the engine starting signal have only one Hall window
A pulse generator that makes use of the Hall effect and consists of a rotor with vanes, a conductive element with a permanent magnet and the Hall IC. Also called Hall element.
A switch that makes use of the Hall effect. When the air gap is free, a magnetic field acts on the Hall IC and the Hall voltage reaches its maximum (high). When a rotor vane obstructs the air gap, shielding the Hall IC from the magnetic flux, the Hall voltage reaches its minimum (low). The signal produced is a square wave
A volatile compound containing halogens, such as chlorine, fluorine or bromine.
A quartz light bulb with a tungsten filament surrounded by a trace of a halogen gas, such as iodine, bromine, fluorine, chlorine, astatine. A halogen bulb gives off a brighter light than conventional bulbs.
Tungsten-halogen bulb used in sealed beam unit or as separate bulb in composite headlamp
High intensity reflector with inner halogen bulb, precision lens, and 3-prong attachment. Don’t touch the glass of a halogen bulb with your fingers. The oil left on the glass will cause the glass to break or reduce the life of the bulb. If the glass is accidentally touched, it may be cleaned with methylated spirits or rubbing alcohol on a soft cloth
A type of Incandescent lamp that lasts much longer and is more efficient than the common incandescent lamp. The lamp uses a halogen gas, usually iodine or bromine, that causes the evaporating tungsten to be redeposited on the filament, thus prolonging its life.
Substance containing fluorine, chlorine, bromine, and iodine.
A suspended-mass-type sensor used in new air bag systems; avoids the ecological problems associated with the earlier mercury-type switches
To hit with a hammer.
To ride hard and fast.
Someone who rides hard and fast.
Trucker slang for the accelerator pedal as in ‘When we get past this parking lot we can really hit the hammer.’
A hand tool with a head (usually metal) and a handle. It is used to force one item against or through another. Several types of hammers are available
A brake operated by a hand lever. It may also refer to the Parking brake.
180° turn achieved by applying the handbrake (acting on the rear wheels) hard when the vehicle is starting to turn
Handbrake warning light
A light on the instrument panel that illuminates when the handbrake is applied; on most new cars it has been superseded by a multifunction brake warning light
An auxiliary set of components to allow disabled people to operate a vehicle.
Something that is built by hand rather than in an assembly line (i.e., mass produced).
Before Cadillac invented and first produced electric starters, engines were started by means of a handle which was inserted into the front of the engine and rotated manually. After 1930 it became obsolete.
A human powered cycle that is propelled by rotating the crank with your hands rather than your feet. Usually there is one wheel up front and two (often smaller) in the back. It is designed for people who are unable to use their legs.
A power-driven device for boring holes or (with the correct attachment) removing or securing screws and bolts
Something that is made for a specific side of a unit. For example, left hand arm rests are not interchangeable with right hand arm rests.
A flat File for shaping metal, with a rectangular cross section, constant blade width and one smooth edge
The relative ability of a vehicle to negotiate curves and respond to road conditions. It is a factor of the weight of the vehicle, the suspension, tires, air flow, etc.
The labor involved in moving product received from the trailer into the warehouse dock and then into the storage location on the ‘IN’ and moving the product out of the storage location and into a staging location to then be loaded onto a trailer on the ‘OUT’. The Warehouse Forklift / Clamp Operator moves product IN and OUT. If additional handling is involved such as opening on days off, pick packing etc., that are not the normal handling as defined in the warehouse contract, these would be defined as additional accessorial charges for handling.
A single pick-up, movement and set-down of a loaded or empty pallet.
A fastener where one end is gimlet pointed and has a wood screw thread. The other end consists of a coarse machine screw thread. The center section is unthreaded.
A modification of custom cars with separate chassis, e.g., pick-ups, which raises the floorpan and lowers the body, to give the impression that the body has been pulled down over the chassis right down to street level
A ship which has gone aground and is not able to move under her own power.
Hard anodic coating
Hard, wear-resistant, oxide layer produced in an anodic oxidation process
A special type of anodizing adapted to the production of thick, hard, abrasion-resistant films
A board-like building material made of compressed wood chip fibers and sawdust
Hard chromium plating
An electrolytic deposition of a hard, wear-resistant, chromium layer
A type of trouble code that causes the ECU to disengage the ABS and not re-engage it until the problem is repaired
The condition of paint when it is hard enough to polish
Specially treated pushrods designed for use with pushrod-guided rocker arms
Hardened Steel Nail
A heat treated and tempered steel pallet nail with a MIBANT angle between 8 and 28 degrees.
Chemical added to plastic filler to induce hardening as used in auto body repair.
The process of paint, epoxy, or glue becoming hard. The drying or hardening of paint film goes through several stages. The first stage is called dust-free; at this stage, the paint has hardened sufficiently to prevent dust from becoming embedded in the paint film. The second stage is called touch-dry; at this point, the paint film can actually be touched with light finger pressure. The third and final stage is referred to as hard-dry; at this point, the paint film is hard enough to polish.
A method of heat treating metals by heating to a temperature within, or above, the critical range, holding at that temperature for a given time, and then cooling rapidly, usually by quenching in oil or water.
A liquid into which steel is immersed in order to harden the steel. Usually involves cold water, brine, oil, and special polymers.
The toughness of the surface of a metal. Normally stated in terms of Rockwell or Brinell scale of measurement, hardness shows resistance of a fastener to rough marks and abrasions, can indicate yield strength and brittleness, and has a direct relationship to tensile strength in alloy steel fasteners. However, for stainless, brass, and silicon bronze, the correlation between hardness and tensile or yield is tenuous with no definite relationship. Case-hardening uses surface heat treatment on ferrous material to cause a harder outside surface than the center. Through-hardening hardens the entire fastener. Bright hardening calls for heat treatment without oxygen, so no oxides are formed on the material surface.
Resistance to plastic deformation by indentation, penetration, scratching or bending.
Chain hardness is typically measured in Vickers, Brinell or Rockwell.
A loss in braking efficiency so that an excessive amount of pressure is need to actuate brakes
Specific locations, usually called out on a full-sized body draft, of points that have to be adhered to when designing surfaces. Hard points include axle centerlines, seats, pedal locations, roof and sill heights, luggage-compartment dimensions, etc.
A part of the road that is divided by broken or continuous yellow lines from the rest of the road and should be used only by certain road users in certain situations
A British term for a trailer with foldable, hard wall panels
A trailer with foldable, hard wall panels
Uniting two pieces of metal with a material having a melting point higher than soft solder e.g., silver soldering
Shiny bluish/brown glazed areas on a brake drum or disc friction surface, caused by extreme heat. Excessive heat has changed their molecular structure. Hard spots can usually be removed by resurfacing
Hard braking, but not necessarily with locked wheels
A term for a bike (motorcycle or bicycle) which has no rear suspension
A two-door or four-door vehicle without a center door post, i.e., no B-post. It gives the impression of uninterrupted glass along the side of the car. The term is derived from hardtop convertible. Other generic names have included sports coupe, hardtop coupe, or pillarless coupe. In the face of proposed rollover standards, nearly all automakers turned away from the pillarless design to a pillared version by 1976-77.
A removable top made from fiberglass or steel that replaces the soft-top. It is usually painted the same color as the body of the car.
An automobile with a fixed roof that does not retract into the trunk, but gives the appearance of being a convertible because it does not have B-pillars
A type of convertible having a removable hard top. Such designs include tops that unfasten and lift off such as early Ford Thunderbirds, Mercedes Retractable hardtop, and the retractable Fords of the late 1950’s.
A foldable stand that holds a detached hardtop in a vertical position when stored
A vacation trailer with a hard top and (most often) canvas sides.
Instrument panel moldings, center consoles and similar plastic trim
A wood from broad-leaved species of trees (not necessarily hard or dense).
A disc-style flexible coupling
A type of universal joint commonly used with prop shafts
Hardy-Spicer universal joint
A type of universal joint commonly used with prop shafts
Also called Vibration damper. It usually is a solid crankshaftFan beltPulley that has a weight ring bonded by rubber to the inner crankshaft-mounted ring. The outer ring absorbs and cancels out crankshaft vibrations that otherwise might cause the crankshaft to break. Formerly, two gearwheels carrying an unbalanced weight, mounted in bearings below the middle main crankshaft bearing, driven at twice engine speed and rotating in opposite directions to counterbalance the secondary vibrations in a four-cylinder reciprocating engine.
A grooved wheel attached to the front end of the crankshaft which is connected by accessory belts to the fan, alternator, power steering pump, water pump, air conditioning compressor, and other devices so that the rotating crankshaft can drive these other parts as well. The crankshaft pulley usually has timing marks located on it, and these are necessary for checking and adjusting timing with a timing light.
A car design in which the rear trunk and lid are replaced by a rear hatch that includes the Backlight (i.e., rear window). Usually the rear seat folds down to accommodate more luggage. Originally a hatch was a small opening in the deck of a sailing ship. The term hatch was later applied to airplane doors and to passenger cars with rear liftgates. Various models appeared in the early 1950s, but weather-tightness was a problem. The concept emerged again in the early 1970s, when fuel economy factors began to signal the trend toward compact cars. Technology had remedied the sealing difficulties. By the 1980s, most manufacturers produced one or more hatchback models, though the question of whether to call them two-door or three-door never was resolved. Their main common feature was the lack of a separate trunk. Liftback coupes may have had a different rear-end shape, but the two terms often described essentially the same vehicle.
Originally a small opening in the deck of a sailing ship, the term hatch was later applied to airplane doors and to passenger cars with rear liftgates. Various models appeared in the early 1950s, but weather-tightness was a problem. The concept emerged again in the early 1970s, when fuel economy factors began to signal the trend toward compact cars. Technology had remedied the sealing difficulties. By the 1980s, most manufacturers produced one or more hatchback models, though the question of whether to call them two-door or three-door never was resolved. Their main common feature was the lack of a separate trunk. Liftback coupes may have had a different rear-end shape, but the two terms often described essentially the same vehicle.
A switch (usually located on the steering column below the steering wheel) which makes all the signal lights flash simultaneously, to warn other vehicles that your car is disabled or going very slowly down the road. Also called 4-way warning light switch.
Any area or space where combustible dust, ignitable fibers, or flammable, volatile liquids, gases, vapors or mixtures are or may be present in the air in quantities sufficient to produce explosive or ignitable mixtures.
Commodities classified by the Department of Transportation as hazardous, and which require special handling and documentation. Also known as hazmat.
Hazardous material tag
A red tag attached to delivery receipts and COSOs. The tag denotes the type and amount of hazardous material in the shipment.
Automotive wastes that are on the EPA’s list of hazardous materials or that have one or more hazardous characteristics
Hazard warning flasher
Actuates warning system of flashing front and rear turn signal lamps
Hazard warning switch
A switch (usually located on the steering column below the steering wheel) which makes all the signal lights flash simultaneously, to warn other vehicles that your car is disabled or going very slowly down the road. Also called 4-way warning light switch.
Abbreviation for Hazardous materials, as classified by the U.S. Environmental Protection Agency (EPA). Transport of hazardous materials is strictly regulated by the U.S. Department of Transportation. Also spelled HazMat
Abbreviation for unburned Hydrocarbons. They are at their worst with very rich or very lean mixtures. They combine with NOx in sunlight to form PhotochemicalSmog.
Abbreviation for High Clutch Drum Speed
A high-camshaft engine; the camshaft is located much higher than the crankshaft, (although not in the cylinder head), allowing for the use of shorter pushrods, thus improving the engine’s revving ability.
Abbreviation for Hydrochlorofluorocarbon. A gaseous compound that meet current environmental standards for minimizing stratospheric ozone depletion.
A chamfer at the end of a fastener formed at the time of heading but before threading.
A chamfer point, usually of 45 degrees included angle, forming by a die at the time of heading and prior to threading.
The down pipe connecting the exhaust manifold to the front of the muffler or to the connector pipe. The British term is headpipe.
A special exhaust manifold that replace the stock manifold. It is designed with smooth flowing lines to prevent back pressure caused by sharp bends, rough castings, etc. Headers are frequently used in performance engine applications and are generally less restrictive than the stock exhaust manifold, resulting in increased power.
Head required to overcome friction of the interior surface of a conductor and between fluid particles in motion.
The seal at the top of the cylinder which sits between the cylinder block and the head. It keeps the coolant out of the combustion chamber and retains compression in the cylinder. Also called cylinder head gasket. Because it is subject to tremendous pressures, it often fails if and when an engine overheats.
In Britain, headlamp refers to the actual unit, whereas headlight is used for the unit as well as for its function and where emphasis is on the actual light produced by the lamp. In North America the terms are interchangeable.
Automatically controls headlamp ON-OFF operation after ignition and main lighting switch are turned OFF
The uppermost piston Land, subject to the highest thermal load
The main light on the front of a vehicle. In Britain, headlamp refers to the actual unit, whereas headlight is used for the unit as well as for its function and where emphasis is on the actual light produced by the lamp. In North America the terms are interchangeable.
A sheet metal pot welded or screwed to the front fender that provides the housing for the headlight and its bulbs and wiring
The headlight housing of cars or motorcycles having separate headlights not integrated into the body line
A rigid or flexible protection against dirt or stone damage when lights are not being used. On some vehicles, when the lights are turned on, the covers are flipped up by an electric or vacuum operated device.
A clear protective cover which is permanently mounted in front of the headlights to protect the headlight itself from damage.
Headlight dimmer switch
A switch which changes the headlight from high beam to low beam or from low beam to high beam. In older vehicles, the switch was located on the floor to the far left and operated by the driver’s left foot. In newer vehicles, it is found on a stalk projecting from the steering column beneath the steering wheel. In Britain it is called the headlight dipper switch. Also called, dimmer switch.
On some vehicles, when you flick the direction indicator lever upwards against spring pressure, the headlights flash on and off quickly. It is used to remind on-coming traffic to dim their lights or to warn them about possible hazards on the road.
A system that compensates for a heavy load in the trunk which pushes the front of the car up and causes the headlights to project upward. The leveling system levels out the projection of the light. Some will do it automatically while others have a manual control.
Headlight leveling control
Usually a manual control with a vertical thumbwheel that adjusts the height of the headlight beam
Headlight mounting panel
A sheet metal panel for rectangular headlights that is spot-welded to the front section of modern cars where the radiator grille and the headlights are mounted adjacent to each other; provides the mounting points for the headlight
Headlight on/off delay system
A system with two functions when activated, it can automatically turn ON the headlights during darkness and OFF during daylight; it can also be set to keep the headlights ON for up to approximately three minutes after leaving the parked vehicle; useful in dark, high-risk areas. The system is controlled by a photovoltaic cell on the instrument panel
Headlight retractor indicator lamp
A light on the dash that illuminates when the headlight covers are opening or closing
The headlight housing of cars or motorcycles having separate headlights not integrated into the body line
A partial lid which encircles only the top part of the headlight.
An attachment between headlight rim and lens, used only on some classic cars
A system that cleans the headlights with a jet of water and a small wiper blade
Fabric or vinyl Upholstery on the interior of the roof of a vehicle and suspended by stiff, hidden wires. Late-model headliners are often molded from foam or cardboard and faced with fabric. The British term is headlining.
A British term for Headliner a soft lining on the inside of a car roof.
The bow plate on a vessel that is made of thick steel plate.
Raised or indented lines or dots on the top of a bolt or screw (or the side of a nut) to identify the type of material, its strength, and/or its thread type (e.g., a dot to indicate ISO metric).
An extension on the upper portion of the seatback. Some are permanently attached and other are adjustable. They are designed to reduce Whiplash injuries caused by sudden stopping or collisions. They limit the rearward motion of the head and neck. Some head restraints contain radio speakers or even TV sets.
On a bicycle or motorcycle, the component that secures the forks to the frame and consists of Cups, Cones, and Ball bearings that creates the bearing mechanism that allows the fork column to rotate inside the Head tube. It thus permits the fork to turn for steering and balancing. Headsets can be either threaded or threadless.
The nominal size of a headset is based on the outside diameter of the steerer. This is a source of confusion, because the steerer is not visible on an assembled bicycle. In the case of a bicycle with a traditional expander/wedge type stem, the stem shaft will be 1/8′ smaller than the steerer. Sometimes people measure the stem diameter and assume, incorrectly, that this is the size headset they have
Headset star fangled nut
A part of a threadless headset that is inserted into the fork steerer tube. The top cap bolt of a threadless headset is threaded into the star fangled nut.
Pressure of fluid expressed in terms of height of column of the fluid, such as water or mercury.
Heads up display
(HUD) A system of mounting gauges so that the read-out is shown on the windshield. In this way the driver does not have to take his eyes off the road to see how his vehicle is performing.
The vertical tube (visually identified as the shortest tube) in the main triangle of a bicycle frame, the one inside of which the fork column (fork steerer tube) is inserted and rotates. The Top tube and Down tube are attached to it. The fork steerer tube is inserted into the head tube.
Height of fluid equivalent to its velocity pressure in flowing fluid.
A brand of vehicle of which the 1949-50 Silverstone models are milestone cars.
That which increases the internal energy of a body by changing the motion of the molecules. This causes a change in temperature, volume, or state of the body.
Form of energy which acts on substances to raise their temperature; energy associated with random motion of molecules.
The energy associated with the motion of atoms or molecules in solids, which can be transmitted through solid and fluid media by Conduction, through fluid media by Convection, and through empty space by Radiation. All substances with temps above absolute zero contain heat
Small cracks on a brake disc or drum friction surface caused by heat. Heat check can usually be removed by resurfacing
Cracks in the clutch pressure plate
Speed and efficiency of heat energy movement through a substance.
The amount of heat energy available to be released by the transformation or use of a specified physical unit of an energy form (e.g., a ton of coal, a barrel of oil, a kilowatthour of electricity, a cubic foot of natural gas, or a pound of steam). The amount of heat energy is commonly expressed in Btu’s. Heat content of combustible energy forms can be expressed in terms of either gross heat content (higher or upper heating value) or net heat content (lower heating value), depending upon whether or not the available heat energy includes or excludes the energy used to vaporize water (contained in the original energy form or created during the combustion process). The Energy Information Administration typically uses gross heat content values.
A valve which is controlled by temperature changes. When the ambient temperature is cold or the engine has not warmed up, it is closed so that some of the hot exhaust gases passes by the intake manifold to pre-heat the fuel mixture going to the cylinders. As the engine warms up, the valve opens up and no exhaust gases pass by the intake manifold. If the valve does not operate properly, the engine has difficulty in start up or the fuel may cause Vapor locking.
A pattern of small, irregular cracks (e.g., on brake discs)
A passage from one exhaust manifold up, over, and under the carburetor and on to the other manifold. Usually found on V-8 or V-6 engines. This crossover provides heat to the carburetor during engine warmup.
Heat curing adhesives
Adhesives that require a definite period of time above room temperature to develop full bond strength. They can be of one or 2 part composition. The term is usually applied to those adhesives that require 82°C or above to effect a cure
A thin groove cut into the head of a piston between the top ring groove and the top of the piston. The heat, instead of passing through the aluminum of the piston to the ring, encounters the heat dam. This helps to minimize heat transfer.
The transfer of heat. In brake systems the heat produced by braking is transferred to the air.
Heated air inlet system
(HAI) a system that operates during cold weather and cold start. Brings warm, filtered air into the engine to control the volume of air entering the engine, vaporize the fuel better and reduce HC and CO emissions
Heated exhaust gas oxygen sensor
(HEGO) an EGO detection device with a heating element
An oxygen detection device (O2S) which is heated to improve sensor performance
Heated rear window
A rear window with a heating element that Defogs (Demists) inside and Defrosts (De-ices) the outside either by fine wires embedded or etched in the glass or by a heater and fan.
Heated tool welding
A welding process in which the parts to be welded are pressed against a heated plate and subsequently pressed together to produce a fusion weld
Windshield with a heating element to facilitate defrosting (de-icing)
A device which gives off heat. In automobiles, it heats the interior of the vehicle. In a water-cooled engine the coolant is channeled through the heater in the passenger compartment. Some cars used an electric or gasoline heater because they had no engine coolant (e.g., the Volkswagen Beetle).
A channel section incorporated into the side member or other structural sections that is designed to provide a flow of warm air into the interior of the vehicle, above all into the footwells (e.g., as used on the VW Beetle)
Electric fan to boost heating and ventilation. Also called heater fan
A finned unit located in the passenger compartment and through which coolant from the engine flows to heat the unit. A fan blows air over the unit to heat the passenger compartment
Electric fan to boost heating and ventilation. Also called heater blower
Heating element for preheating the intake air in small diesel engines
The system in a vehicle interior that provides heat or fresh air or both.
A device which transfers the heat of one substance to another (i.e., from a warm or hot surface to a cold or cooler one) such as evaporators, condensers, and radiators.
Temporary reduction of brake effectiveness due to a loss of friction between braking surfaces, resulting from heat
A number representing the effect of temperature and humidity on humans by combining the two variables into an apparent temperature. Introduced as a replacement for the temperature-humidity index. Later replaced by the Canadian introduced Humidex
Any equipment designed and/or specifically used for heating ambient air in an enclosed space. Common types of heating equipment include: central warm air furnace, heat pump, plug-in or built-in room heater, boiler for steam or hot water heating system, heating stove, and fireplace. Note: A cooking stove in a housing unit is sometimes reported as heating equipment, even though it was built for preparing food.
The path along which heat passes from the spark plug tip to the water jacket
Heat pipe, gas forced-air
High efficiency gas furnace that uses vertical liquid filled pipes. The pipes are heated by a burner at their base, and the liquid boils and vaporizes within the pipe. The furnace blower circulates air over the pipes for heating.
Refers to the operating temperature of a given style of spark plug. Plugs are made to operate at different temperatures depending upon the thickness and length of the Porcelaininsulator as measured from the sealing ring down to the tip. In this way it transfers heat from the combustion chamber to the cylinder head. The speed at which it transfers heat is considered in terms of hot and cold plugs. A hot plug transfers heat slowly, causing the plug to operate at a higher temperature. A cold plug transfers heat more quickly, thus operating at a lower temperature. If a plug is too cold, it will foul. If it is too hot, it will cause Preignition.
The distance to the start of pre-ignition under further increasing thermal loading of the spark plug. This reserve is expressed in degrees crankshaft, the amount by which the factory-set ignition timing can be further advanced without preignition occurring
To soften a dried thermoplastic adhesive film to a sticky state by application of heat. Used as a method of bond
To restore the tackiness of the adhesive with heat, and then to bond under pressure
Heat recovery system
Produces and stores hot water by transferring heat from condenser to cooler water.
The flapper in the exhaust manifold that is closed when the engine is cold, causing hot exhaust gases to heat the inlet manifold, thus providing better cold engine operation; a thermostatic spring opens the flapper when the engine warms up
The action of applying the brakes fast and hard especially during an emergency stop. Opposite to Light braking
Cable that is used for severe service where high strength is required. Opposite to Light cable
Having a stiff operation, e.g., requiring considerable effort to push down the pedal on cars and trucks; or squeeze the lever on motorcycles. Opposite to Light clutch
Crude oil with a high specific gravity and a low API gravity due to the presence of a high proportion of heavy hydrocarbon fractions and metallic content.
(HD) Something that is built for heavy loads or severe use. Opposite to Light-duty
Heavy-duty diagonal cutting pliers
Diagonal cutting pliers with a special joint and handle design for extra cutting power
Heavy-duty end cutting pliers
End cutting pliers with a special joint and handle design for extra cutting power
Heavy-duty ring wrench
A strong single end box wrench for use with a tubular handle. It can be used without the handle for quickly spinning on nuts or, with the handle slipped on, for final tightening or reaching otherwise inaccessible nuts
Vehicle weighing from 26,001 to 33,001 lbs. Also included off-highway trucks.
A tool which can withstand severe use (and abuse) before breaking
Heavy film build
Excessive thickness of paint coating
To drive at full throttle or high speeds as though the driver’s foot were very heavy so that the natural pressure of the foot against the throttle pedal caused high speeds
Heavy gas oil
Petroleum distillates with an approximate boiling range from 343.9°C to 537.8°C.
Heavy goods vehicle
(HGV) A British term expressing a vehicle capable of carrying heavy loads and requiring a special license to drive HGV.
Heavy machinery cargo
This category of cargo will tend to be on flatbed trucks and trailers. Examples: Off road-vehicles, like bulldozers and backhoes, forklifts, construction machinery, large lathes, and farm tractors.
Metallic elements, including those required for plant and animal nutrition, in trace concentration but which become toxic at higher concentrations. Examples are mercury, chromium, cadmium, and lead.
The fuel oils remaining after the lighter oils have been distilled off during the refining process. Except for start-up and flame stabilization, virtually all petroleum used in steam plants is heavy oil. Includes fuel oil numbers 4, 5, and 6; crude; and topped crude.
An electric railway with the capacity for a heavy volume of traffic and characterized by exclusive rights-of-way, multi-car trains, high speed and rapid acceleration, sophisticated signaling, and high platform loading. Also known as subway, elevated (railway), metropolitan railway (metro).
An oval spray pattern that is thicker toward the left or right hand side, i.e., it takes the shape of a crescent oriented towards the right or left. This is often caused by a clogged horn hole at the air cap of the spray gun
Having a stiff operation, e.g., requiring considerable effort to turn the steering wheel. Opposite of Light steering
Water containing a significantly greater proportion of heavy hydrogen (deuterium) atoms to ordinary hydrogen atoms than is found in ordinary (light) water. Heavy water is used as a moderator in some reactors because it slows neutrons effectively and also has a low cross section for absorption of neutrons.
A driving technique where the driver places the left side or the toes of his right foot on the brake pedal and the right side or the heel of his right foot on the throttle pedal so that he can simultaneously brake and blip the throttle for a downshift. This is done to lessen the strain on the Gearbox and Drivetrain and makes for smoother driving.
Heel and toe wear
Uneven wear of tread blocks on a tire. The trailing edge of the block often tends to wear at a faster rate that the leading edge.
The vertical transverse sheet metal panel running across the width of the car interior at the front edge of the rear seat well; this panel links the rear seat well to the floorpan and provides rigidity for both panels. Also called heel plate. Compare Toeboard
A Dolly in the form of a heel of a foot or shoe to shape and straighten dented panels, usually by holding the dolly behind the metal to be shaped and hammering the metal.
The inclination of a vessel to one side.
The vertical transverse sheet metal panel running across the width of the car interior at the front edge of the rear seat well; this panel links the rear seat well to the floorpan and provides rigidity for both panels. Also called heelboard. Compare Toeboard
The distance, measured perpendicular to the axis, between the major and minor cylinders or cones, respectively.
An automatic leveling control in hydropneumatic suspension systems
An extremely rigid articulating Joint, commonly known as a spherical rod-end, used in any precision linkage. Heim joints are often used in the suspension links of race cars because they locate wheels very precisely.
A spiraling shape such as that made by a Coil spring. In the shape of a helix.
Virtually all gears in modern cars are cut with a spiral helix angle rather than straight meshing. Straight gears are simpler to manufacture, but are extremely noisy.
A gear that has the teeth cut at an angle to the center line of the gear. This kind of gear is useful because there is no chance of intermittent tooth-to-tooth operation because there are at least two teeth engaged at any time. Also helical gears tend to operate quieter than straight-cut gears, but they do absorb a slight amount of power due to side thrust.
A helically (continuous spiral) threaded pallet nail, see also drive screw nail.
Helical spring lock washer
A locking device for threaded fasteners
Curved gear teeth on the edge of a gearwheel, cut at an angle to its axis
A trade name for a coil-type thread insert, commonly used to replace a stripped spark plug thread.
Coil of wire used as an insert to accept a screw or bolt and adding holding power by forcing itself between the fastener and the walls of the recess when the fastener is driven in.
A mirror that reflects solar rays onto a central receiver. A heliostat automatically adjusts its position to track daily or seasonal changes in the sun’s position. The arrangement of heliostats around a central receiver is also called a solar collector field.
Helium leak test
A pressure test using helium
A spiral, like the thread on a screw or a coil spring in a suspension system
Steering wheel installed on the bridge or wheelhouse of a ship to turn the rudder during maneuvering and navigation
A protective device for the head of bicycle and motorcycle riders as well as race car drivers.
A protecting hood which fits over the arc welder’s head, provided with a lens of safety glass through which the operator may safely observe the electric arc.
A special type of lug for connecting a battery with tapered terminal posts. Also called helmet lug.
The condition of a person’s hair after wearing a helmet for a period of time. Short hair tends to stand on end while long hair tangles and/or becomes flat.
A special type of lug for connecting a battery with tapered terminal posts. Also called helmet connector.
Helmhotz free energy
(A or F in US) Similar to Gibbs free energy but with internal energy substituted for enthalpy. A negative change in A is indicative of a spontaneous change in a closed system at constant volume.
An additional spring device (usually another Leaf spring) which permits a greater load on the axle. Also called helper leaf.
An additional spring device (usually another Leaf spring) which permits a greater load on the axle. Also called helper leaf.
Engine using Hemispherical-shaped (half of a globe or sphere) combustion chambers. The valves are cocked at 45 degrees from the piston top. Mopars, despite their fame, are not the only cars with hemi heads.
A round, dome-shaped combustion chamber. This shape permits larger valves and straighter Intake and exhaust ports for improved Breathing. Its small surface area in comparison to volume reduces the amount of heat loss. It is used in high performance cars and racing engines.
(H) A unit of inductance, equal to the inductance of a circuit in which the variation of current at the rate of one ampere per second induces an electromotive force of one volt. The term was named after US physicist, J. Henry (1797-1878)
A wiper system with a parking position below the normal visibility range
The ability of a paint to obscure the surface to which it is applied.
Type of SU carburetor with a horizontal integral float chamber
High and tight
Loading freight high in a trailer uses the full cube of the trailer and allows more freight to be loaded. Loading freight tight in a trailer eliminates the possibility of damage while en route.
A term used in car sales, the practice of stating a very high trade-in price to a customer who is known or expected to be shopping around, comparing prices. When the customer finds that other dealers cannot match the trade-in price, he will return to the original dealer, only to be told that the inflated figure was a mistake (e.g., based on wrong assumptions as to the trade-in’s clutch condition, etc.). Many customers will then accept a new, lower price because they are tired of shopping around.
All cars have at least two levels of lighting for night driving. The Low beam is used when there are other vehicles approaching or when you are following another vehicle. The high beam is used when driving on poorly lit roads where there is no visible traffic. The high beam light may be an integral part of the headlight assembly or is the inboard light when there are two Lamps on each side of the vehicle. When the lamps are stacked vertically, the high beam is the upper one. When the high beam switch is activated, the low beam lights may or may not be switched off. In a system with factory installed day-time running lights, the high beam light is illuminated at a lower intensity. The British term for high beam is main beam.
High beam indicator
A blue light on the instrument panel which comes on when the high beams are activated. Also called beam indicator. The British term is main beam indicator.
Status of the transmission when the two-speed transfer gearbox lever is in the high ratio position –for normal, on-road, day-to-day use.
A spray primer that leaves a relatively thick coat on the panel surface to cover up minor imperfections that would otherwise show up very prominently in the final color coat
A galvanizing process in which extremely heavy zinc coatings are applied
A very hard steel, as opposed to plain carbon steel. Hypereutectoid steels containing more than 0.8% carbon. Such steels consist of iron carbide (cementite) and pearlite when slow cooled. They are capable of being heat treated to high hardness, but tend to be brittle. Used for metal working formers and fine edge cutting tools (e.g., files)
Vehicle is stationary because the driving wheels are no longer touching the ground.
A curved block of cast iron for shaping high crown radius panels with a bumping hammer. It has a rounded corner which is useful for bringing up low spots as is done with a pick hammer
High crown panel
A panel shape that curves rapidly in all directions, e.g., around the headlights of older cars. The opposite is Low crown panel
High crown spoon
A spoon with a broad working surface and a heavily rounded tip that is ideal for using as a Dolly or a lever in confined areas, such as headlight housings or rounded body sections above the waistline
(HDPE) A very tough, chemically resistant thermoplastic, with a soapy touch; e.g., used for blow-molded parts such as fuel tanks or other moldings, such as bumpers
High efficiency gas furnace
Furnace which uses recycling of combustion gases or pulse combustion to obtain operating efficiencies from 85 to 95 percent.
High efficiency lighting
Lighting provided by HID lamps and/or fluorescent lamps.
High energy battery
An innovative battery type developed for electric cars
High energy coil
A coil which generates higher ignition voltage and/or offers increased spark efficiency; ballasted
High energy ignition
(HEI) an electronic ignition system used by GM
High energy ignition system
(HEI) An ignition system which provides more ignition power (higher voltage at higher amperage) than normal systems; a typical HEI includes an electronic control unit and magnetic pick-up in combination with mechanical ignition timing
High energy ignition system with electronic spark timing
(HEI-EST) A system consists of an electronic distributor, with the ignition coil mounted on the distributor cap on 6- and 8-cylinder models or externally on 4-cylinder models; the ignition timing is performed electronically by the electronic control module. (Used on several GM models since 1983.)
Higher Heating value
(HHV) The value of the heat of combustion of a fuel as measured by reducing all of the products of combustion back to their original temperature and condensing all water vapor formed by combustion. This value takes into account the heat of vaporization of water.
A transmission (even like the chain system on a bicycle) where a large gear drives a small one. The larger the drive gear and the smaller the driven gear the higher the gear ratio. It will result in high speed, but is poor for getting started from a stop.
A vehicle’s transmission system which has a higher than usual gearing, to improve fuel economy.
High gear pinion
Top gear on the mainshaft in a direct drive transmission. All gear ratios drive through the high gear pinion, which also holds the output sprocket.
Very shiny, bright appearance
High Impedance Injectors
Fuel injectors designed to work with a simple switch in a 12 volt circuit, no special signal conditioning is required to drive them. The resistance of a high impedance injector is about 10-15 ohms. Also called hi-Z
High impedance voltmeter
A voltmeter with high opposition to the flow of electrical current. Good for reading circuits with low current flow, such as found in the CCC system
(HID) A lamp that produces light by passing electricity through gas, which causes the gas to glow. Examples of HID lamps are mercury vapor lamps, metal halide lamps, and high-pressure sodium lamps. HID lamps have extremely long life and emit far more lumens per fixture than do fluorescent lights.
High-intensity discharge lamp
A lamp that produces light by passing electricity through gas, which causes the gas to glow. Examples of HID lamps are mercury vapor lamps, metal halide lamps, and high-pressure sodium lamps. HID lamps have extremely long life and emit far more lumens per fixture than do fluorescent lights.
High lead screw
A screw with a low pitch so that an engaged nut would move an appreciable distance with a partial revolution.
High leverage diagonal cutting pliers
Diagonal cutting pliers with special joint and handle design for extra cutting power
High leverage end cutting pliers
End cutting pliers with special joint and handle design for extra cutting power
A vehicle that exceeds 12,500 miles (20,000 km) per year. For example, a four-year old car has high miles if the odometer reads more than (12,500 x 4) 50,000 miles (80,000 km).
Households with estimated aggregate annual vehicle mileage that exceeds 12,500 miles (20,000 km).
High-mounted brake light
Third brake light mounted in the middle of the rear window or on some cars integrated in the trailing edge of the rear deck spoiler
High Occupancy Vehicle
(HOV) Vehicles having more than one occupant. Examples include carpools, vanpools, buses, and mini-buses. Transportation systems may encourage HOV use by having designated HOV lanes.
High Occupancy Vehicle Lane
(HOV Lane) Exclusive road or traffic lane limited to buses, vanpools, carpools, emergency vehicles, and in some cases, single occupant motorcycles. HOV lanes typically have higher operating speeds and lower traffic volumes than adjacent general purpose lanes. HOV lanes have proven to be successful in major metropolitan areas across the US; however, their full effectiveness is usually not realized until about one to two years after implementation.
Producing better than average results
A special exhaust manifold, which is not made of cast iron as usual, but of specially designed, curved and welded steel tubes, to produce a smooth flow path for the exhaust gases, avoiding any sharp bends; less heavy, less sturdy and more expensive than an ordinary manifold; usually replaces the down pipe
High Platform Bus
Depicting heavy-duty, OTR coaches and tour buses designed for long-distance or intercity travel. Passenger platform higher than driver’s seat, with large cargo holds under floor. May have a washroom. Some are two axle vehicles but most are found with three axles: One steering, one four-wheeled drive and one two-wheeled tag axle.
Operating under a lot of pressure e.g., braking systems or diesel fuel injection
Boiler furnishing steam at pressures of 205 kPa gauge or higher.
Electrical control switch operated by the high-side pressure which automatically opens electrical circuit if too high pressure is reached.
An intake manifold designed to mount the carburetor or carburetors, considerably higher above the engine than is done in the standard manifold. This is done to improve the angle at which the fuel is delivered.
In air conditioning systems, the high side (i.e., high pressure side or discharge side) is located between the compressor and expansion valve or orifice tube and includes the condenser. The opposite is Low side
Parts of a refrigerating system which are under condensing or high-side pressure.
Another term for discharge side. The part of the air conditioning system under high pressure, extending from the compressor outlet to the thermostatic expansion valve/tube inlet
Refrigerant control mechanism which controls the level of the liquid refrigerant in the high-pressure side of mechanism.
High-side float flooded system
Refrigeration system which has a float operated by the level of the high-side liquid refrigerant.
High-side service valve
A device, located on the discharge or high side of the compressor, at which high side pressure can be checked and other service operations can be performed
High side service valve
A device, located on the discharge or high side of the compressor, at which high side pressure can be checked and other service operations can be performed
Pitching a bike over away from the direction you are turning. The most dangerous kind of crash
Main air bleeds; located in the air horn
Main metering system
High speed direct injection
(HSDI) A system for rapid injection of fuel into a diesel engine
A raised area on a panel surface
A solar thermal collector designed to operate at a temperature of 82°C or higher.
High temperature superconductivity
A phenomenon discovered by Karl Alex MÃ¼ller and Johannes Georg Bednorz of IBM-Zurich in 1987 in which a compound containing copper, oxygen, barium, and lanthanum exhibited superconductivity at temperatures as high as 35°K. Subsequently in 1987, C. W. Paul Chu and Maw-Kuen Wu at the Universities of Houston and of Alabama-Huntsville respectively, developed a compound which was superconducting at temperatures as high as 90°K, a temperature above that of liquid nitrogen, a low cost substance. Several other compounds have been found to yield similar results. A number of theories have been proposed to explain this phenomenon. See Meissner effect.
(HT) capable of operating at a relatively high voltage
A circuit operating at more than 600 volts nominal.
The difference between the available ignition voltage and the ignition voltage required at a given moment
Any public road outside the cities with a foundation and a hard surface. Originally, the highway was a way higher than the ground, e.g., as opposed to stage coach tracks. Since similar speed limits exist in the USA and Canada for all types of highways, both single or multilane (usually between 50 and 70 mph or 80 and 110 kph), the terms highway driving speeds and highway driving should not be associated with speeds higher than 70 mph (110 kph).
An auxiliary lateral piece of metal (usually chromed for good appearance) fitted to the front down tubes or frame. Folding Pegs may be found at each end. The bar allows the rider to position his feet straight ahead for variety in leg position when riding long distances. Also called hi-way bar.
Official British code of conduct for all road users
Highway marker shield
A road sign which indicates the type and road number of a highway. In some cases the direction of travel (nearly always North, South, East or West) is also indicated.
A folding footrest which is mounted on the ends of a Highway bar
An old disc brake design formerly used on motor cycles; superseded by sliding-caliper disc brakes
Hinged quarter window
A rear side window between the B-post and the C-post and/or in the case of station wagons, between the C-post and the D-post. It is provided with hinges to allow it to be opened
A part of the door frame that includes the bracing and threaded plate for mounting the hinge to the door. It is not to be confused with the Hinge panel that is part of the hinge pillar of the body shell.
Sheet metal panel spot-welded to the A-post or rear of the front fender that accommodates the hinges for the front door
The vertical structural post to which the vehicle doors are attached. In most instances, the front doors are attached to the A-pillar while the rear doors are attached to the B-pillar. In a vehicle with suicide doors, the front doors are attached to the B-pillar while the rear doors (if suicide type) is attached to the C-pillar.
Hinge pillar reinforcement
The vertical section behind the visible A-pillar
The reinforcing plate between the hinge and the door panel which distributes the forces acting on the hinge bolts over a larger area of the panel
The threaded plate housed in a sheet metal cage spot-welded to the hinge pillar or, in some cases, to the door frame; the door is bolted to this plate and may be adjusted within certain limits, as the plate can be moved about in its sheet metal cage
A trailer hitch rated at 3500 lb gross trailer weight and 350 lb tongue weight.
A metal ball with a bolt attached to it. It is secured to a bracket on a vehicle in order to mount a trailer hitch. British term is towball
A heat-treated, hi-strength steel pin ranging from a diameter of 7/16′ to 1-1/4′ and a length from 3-1/2′ to 7′. A flange is at one end and a hole (through which a Hair pin cotter or Hitch pin clip can be inserted) at the other end. The hitch pin secures the hitch to the receiver.
A Hair pin cotter with one straight leg. Insert the straight leg into the hole of a rod so that the bent leg will encircle the rod.
A bicycle rack mounted to the hitch on the rear of a car or truck. Available in ball mount, 1.25′ receiver, and 2′ receiver versions.
Premium gasoline with the highest octane rating
An auxiliary lateral piece of metal (usually chromed for good appearance) fitted to the front down tubes or frame. Folding pegs may be found at each end. The bar allows the rider to position his feet straight ahead for variety in leg position when riding long distances. Also called highway bar.
The most common method of retaining a brake shoe to the backing plate. The pin passes through the backing plate and brake shoe. The spring and retainer are fastened to the pin, which holds the shoe against the backing plate
A separate relay coil, such as the hold-in winding in a starter solenoid, which is energized by contacts that close when the relay pulls in, to hold the relay in its energized position after the original operating circuit has been broken. Also called holding coil.
A separate relay coil, such as the hold-in winding in a starter solenoid, which is energized by contacts that close when the relay pulls in, to hold the relay in its energized position after the original operating circuit has been broken. Also called hold-in coil.
A part of a relay designed to hold it in the on-position. Compare Pull-in winding. Also called hold-in winding.
A part of a relay designed to hold it in the on-position. Compare Pull-in winding. Also called holding winding.
A unit which permits free fluid flow in either direction when the brakes are not applied, but prevents pressure buildup in one part of the brake system until pressure in the other part reaches a predetermined value.
A tool used for the final smoothing operation, e.g., when repairing a cylinder wall
The opening part of the vehicle body which covers the top of the engine in front engine vehicles. It may be hinged at the front, rear or sides. The British term is bonnet. In mid-engine cars the panel which conceals the engine is called the engine cover or access panel. In rear-engine cars the panel which conceals the engine is called a deck lid.
A British term for the soft-top roof of a convertible.
The panel on which the hood is lowered. It also houses the hood locking mechanism
A material secured to the underside of the hood to provide sound insulation. It is usually made of polyethylene, polypropylene, polyurethane, or a fabric of polyester
A mechanism which is made of a peg on the front end of the underside of the hood and a sliding latch on the panel above the radiator. The sliding latch is released by a lever under the hood or by a lever under the instrument panel in the passenger compartment.
A device which releases the Hood lock. The trigger, located under the instrument panel in the passenger compartment, is attached to a cable which controls the hood lock.
A bar or rod which keeps the hood in an open position. The rod is located under the hood. Once the hood is raised, the rod is swung upright and the free end is placed in a notch or hole in the hood to keep it in place
Increasing engine performance through various modifications.
On 14 November 1899, August Horch (1868-1951) established the A. Horch & Cie. company in the Ehrenfeld district of Cologne, Germany where he developed his first car, which was completed at the beginning of 1901. The company moved to Reichenbach in Saxony in March 1902 and converted to a share-issuing company two years later. On May 10, 1904, A. Horch & Cie. Motorwagen-Werke AG was established in Zwickau. In 1932 Horch joined Audi. Models built between 1925 and 1932 models are classic cars.
Lying flat, not upright
A screw for adjusting the lateral aim of the headlight beam
Horizontal axis wind turbine
The most common type of wind turbine where the axis of rotation is oriented horizontally.
A Keiretsu system where the keiretsu member companies have shareholdings in each other. The opposite is Vertical keiretsu. The member companies own relatively small chunks of shares in one another and are each centered on a core bank; the keiretsu system helps insulate company managements from stock market fluctuations and take-over attempts, allowing long-term planning and engagement in innovative projects; it is a key element of the automotive industry in Japan
Horizontally opposed engine
An engine possessing two banks of cylinders that are placed flat or 180 degrees apart. This configuration gives a lower center of gravity which improves handling. As well it has a lower hood height to improve aerodynamics. Also called a boxer engine.
A weld performed on a horizontal seam at least partially on a vertical surface.
Horizontal Zero Line
A locating line at the top of the chassis frame as seen in side view. Also called waterline and datum line.
Any opening chamber to intake air such as the entrance to a carburetor.
A part of a cleat
To line or square up
A device for sounding an alarm. On some entry level vehicles, a single horn makes a high pitch beep. On more expensive vehicles, the sound is made with two or more horns. The sound is made by an electrical charge which activates and deactivates a coil. The sound is then magnified by the shape of the horn. Large truck horns make a very loud noise because the sound is made by passing compressed air through the sounding device. A Claxton horn makes a sound that resembles the word A-hoo-gah. See blowing horn
a term defined by the Horseless Carriage Club of America applying to cars built before 1915. (See also Antique).
(HP) A measurement of the engine’s ability to perform work. One horsepower is defined as the ability to lift 33,000 pounds one foot in one minute. To find horsepower, the total rate of work in foot pounds accomplished is divided by 33,000. If a machine was lifting 100 pounds 660 feet per minute, its total rate of work would be 66,000 foot pounds per minute. Divide this by 33,000 foot pounds per minute to arrive at 2 horsepower. In metric terms, it is the ability to raise 250 kilograms a distance of 30 centimetres in one second. It is also equal to 745.7 watts.
The relationship between the total weight of the vehicle and the horsepower available. By dividing the weight by the horsepower, the number of pounds to be moved by one horsepower is determined. This factor has a great effect on acceleration, fuel consumption, and all around performance.
A wire spring retainer used to secure an inside door handle in place.
An adjustable metal ring, wire, or band placed around a hose where it connects to a metal pipe, to prevent leaks and to keep the hose in place. Hose clamps are tightened in one of three ways. In single wire clamps, it is tightened by spring tension of the clamp. In worm-gear clamps, by a worm screw. In strap-and-bolt clamps, by a screw. The British term is hose clip.
Hose clamp installer
A special tool for the installation of ear-type clamps, used e.g., on some types of CV joint boots, filters, cooling systems, and vacuum lines
Hose clamp pliers
A special tool used to remove and install hose clamps
Tractor used for moving trailers to and from the dock and around the yard.
Connected to the battery positive terminal, energized
The conventional method of retreading in which uncured rubber is added to a buffed Casing and cured in the mold at temperatures of approximately 143°–149°C. This temperature allows uncured rubber to flow in the matrix forming the tread design during vulcanization.
To coat metal parts by immersion in molten metal, such as tin or zinc
The deposition of aluminum coatings by hot dipping
To apply a zinc coating by hot dipping
Hot dry rock
Heat energy residing in impermeable, crystalline rock. Hydraulic fracturing may be used to create permeability to enable circulation of water and removal of the heat.
Heating metal to red-hot temperatures or temperatures above the recrystallization point to soften it before shaping a fastener. Hot forging is primarily used when the diameter of the metal is too large for cold forming or the quantity required is too small to economically set up a cold-forming machine.
Working operation such as bending and drawing sheet and plate, forging, pressing, and heading, performed on metal heated to temperatures above room temperature.
Expanded diesel fuel or gasoline that is sold at retail pumps at temperatures higher than the century-old government standard of 15.5°C. At the 15.5°C standard, a gallon of fuel delivers a certain amount of measurable energy, or BTU. But when expanded by higher temperatures, that same amount of fuel actually delivers less energy. The warmer the fuel, the less BTU and fewer miles to the gallons a vehicle will receive.
The state of the refrigerant between the compressor and the condenser
Hot gas bypass
Piping system in refrigerating unit which moves hot refrigerant gas from condenser into low-pressure side.
Hot gas defrost
Defrosting system in which hot refrigerant gas from the high side is directed through evaporator for short period of time and at predetermined intervals, in order to remove frost from evaporator.
A small air valve that allows fresh air to enter the manifold and lean the mixture when the engine is hot
Hot in-place recycling
Crews heat up and grind off the top few inches of pavement, which is thoroughly mixed with new material and put back down. This process, chiefly used on high-volume roads, creates a road bed that closely resembles a new road in consistency and strength.
That part of thermoelectric circuit which releases heat.
Abbreviation for High Occupancy Toll lanes, which are special lanes on a multi-lane road which can be used free of charge by vehicles with enough occupants to constitute a car pool, but which are subject to a toll for other vehicles. In some cases these lanes can be used only by vehicles that have special electronic tags and there are no facilities to pay tolls by means of cash. HOT lanes are a relatively new development.
The valve adjustment on a engine equipped with solid lifters
A spark plug which has a long insulator nose which absorbs more heat and dissipates heat slowly. A colder plug is used in a hot engine while a hot plug is used in a cold engine. Thus if the plugs are fouling too much, try a hotter plug. If the plugs are coming out white, try a colder plug. The ideal color of the center insulator nose should be a light chocolate brown.
A production car that has been modified by the owner in the attempt to increase acceleration and top end speed. Although the term can be applied to any modified car, it is usually reserved for vehicles produced from 1930 to 1940’s. Typically the engine is modified, and some body panels removed. Many were painted with a design of flames behind the front wheels to give the appearance that this vehicle was hot — thus the name.
Colloquial term for a local freight hauler
Colloquial term for a one ton truck equipped with a fifth wheel for pulling light weight trailers.
Occurs when the engine is topped during hot weather or after it has been run long enough to be fully warmed up; also the period during which the phenomenon known as percolation occurs
Refers to a comparatively thin section or area of the wall between the intake and exhaust manifold of an engine, the purpose being to allow the hot exhaust gases to heat the comparatively cool incoming mixture.
Also used to designate local areas of the cooling system which have above average temperature.
A spray process in which paint is preheated in a paint container so that its viscosity is reduced and it can be atomized without being diluted with a solvent
The starting of a hot engine may be difficult if it has been stopped for a few minutes; the accumulation of gasoline vapor in the air filter and inlet manifold, caused by the rise in engine temperature when left standing when hot, can be dissipated by slowly pressing the accelerator right down and turning the engine over until it fires
Hot start enrichment
A fuel mixture enrichment when starting a hot engine
A special cavity-sealing process developed by Volkswagen, which uses a solvent-free wax injected into the cavities of bodies preheated to 60°C
Hot-wax flooding unit
A device for Hot-wax flooding consisting of a preheating zone, a flooding zone and a drip-off zone
The positive wire coming from the battery or generating system.
Resistance wire in an electrical relay which expands when heated and contracts when cooled.
Electrical lead which has a voltage difference between it and the ground.
As a verb, it indicates the starting procedure when by-passing the ignition key and normal starting procedure.
Hot-wire airflow meter
A constant-temperature hot-wire sensing device, used in electronic fuel injection systems, which measures the rate of a mass airflow into the engine by measuring the current needed to keep the hot wire at the same temperature
An element in a hot-wire air-flow meter
hot wire relay
Heat-operated electrical control used to open or close a refrigeration system electrical circuit. This system uses a resistance wire to convent electrical energy into heat energy.
The outer sleeve through which a brake or gear cable is pulled. The housing transmits an equal push to counter the pull on the inner cable. Traditional housing consists of a tight spiral of steel wire, usually coated with plastic. Newer versions have synthetic liners to reduce friction.
A container or casing for mechanical components such as bearings, gears, etc.
Abbreviation for high-occupancy vehicle — A vehicle carrying two or more passengers used on marked commuter lanes. Examples include car pools, vanpools, buses, and mini-buses. Transportation systems may encourage HOV use by having designated HOV lanes.
A ground vehicle that is supported by a cushion of air to reduce friction. As well as traveling on the land, hovercraft can travel on the sea or swampy terrain.
Abbreviation for High Occupancy Vehicle Lane which is an exclusive road or traffic lane limited to buses, vanpools, carpools, emergency vehicles, and in some cases, single occupant motorcycles. HOV lanes typically have higher operating speeds and lower traffic volumes than adjacent general purpose lanes. HOV lanes have proven to be successful in major metropolitan areas across the US ; however, their full effectiveness is usually not realized until about one to two years after implementation.
On a bicycle, the center of a wheel consisting of a shell to which spokes attach and contains an axle along with two sets of bearings, bearing Cones, Lockwasher, Locknuts, and parts for attaching the wheel to the frame.
The base of a wheel (e.g., steering wheel, drive or driven wheels) with studs protruding from its face upon which the wheel itself is mounted to an automotive vehicle.
A rotating component at the center of a wheel that contains the wheel bearings to which the rest of the wheel are attached. It is connected to, or integral with, the brake drum or rotor.
Any type of brake (disc, drum, or Coaster) that operates through the wheel hub rather than the rim.
The covering that fits over the end of the wheel spindle to keep dust and water away from the wheel bearings and brakes. It is often a styling feature, but it also acts as a good container for keeping the Lug nuts from being lost when changing tires. When a vehicle becomes stuck in the snow, it can also be used as a temporary shovel. Also called wheel cover.
In a horizontal-axis wind turbine, the distance from the turbine platform to the rotor shaft.
In 4-wheel-drive vehicles, it is inefficient to have the front wheels connected when not needed. Most older vehicles required a person to get out and manually switch each front hub. Now these hubs can be changed remotely with a switch inside the vehicle.
A register mounted on the axle hub which shows the distance the vehicle traveled. It is popular to record mileage for leasing of vehicles or tires particularly on trailers, since there is no other odometer present.
The instrument on the wheel of a tractor used to record mileage.
The central element of a clutch driven plate which carries the splined hub
A special tool, of both jaw and slide hammer design, used to remove wheel hubs on vehicles by a pulling action
The distance from one outer cone to the other along the axle. Front bicycle hubs have a standard width of 100mm. Rear hubs on older road bikes which are set up for freewheels generally have a width of 126mm. More recent rear hubs set up for cassettes have a width of 130mm.
An abbreviation for Heads up display which is a system of mounting gauges so that the read-out is shown on the windshield. In this way the driver does not have to take his eyes off the road to see how his vehicle is performing.
A test chamber for simulating tropical and subtropical conditions
(short for humidity index) is a number which combines the air temperature in Celsius and the amount of humidity in order to give a single number to represent the perceived discomfort of weather that is hot and humid. It was devised by Canadian meteorologists and first used in 1965. The humidex is widely used in Canada and has been accepted in a number of other countries.
Range of humidex
Degree of comfort
Less than 29
30 to 39
40 to 45
Great discomfort; avoid exertion
Heat stroke imminent
The humidex is calculated with the following formula
Humidex = (air temperature) + h
h = (0.5555)*(e – 10.0);
e = 6.11 * exp(5417.7530 * ((1/273.16) – (1/dewpoint)))
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A large SUV produced by General Motors which is based on the military High Mobility Multipurpose Wheeled Vehicle (HMMWV or Humvee). Models included are
H3 Alpha (2008)
A raised portion on the rim bead seat of passenger car wheels, retaining the beads of an insufficiently inflated tubeless tire on the bead seats, thereby preventing the tire beads from jumping into the rim well.
An operating condition where the transmitted torque in a viscous coupling rises to a value several times higher than the value produced in the so-called Viscous mode, due to internal clamping, i.e., metal friction of the coupling discs
Designation for a rim featuring a safety contour (Round hump, Flat hump, combination hump) either on the outer or on both bead seats. This protection is particularly important with tubeless tires, where sudden deflation can occur if the tire beads leave the bead seats and drop into the well. Compare Hump and Safety bead seat
(cwt) An obsolete unit of weight measurement, used in some classic-car manuals. 1 British cwt = 5080 grams; 1 US cwt = 4535 grams
The uneven running of an engine, due to air/fuel mixture being too rich.
The action of some automatic transmissions when a vehicle is climbing a hill. The transmission constantly shifts between fifth gear and fourth gear
Erratic variation of the speed of the governor when it overcompensates for speed changes.
An extra, odd tooth on a gearwheel, designed to ensure the same teeth do not always mesh together, thus reducing wear
Hurst six-speed shifter
Upgraded shifter for manual transmissions which make the distance between gears shorter. The power band is more continuous from the bottom of first gear to the top of sixth. This means that when you shift, the amount of acceleration you experience will be more even throughout all the levels of the transmission. The result is that you can make the car accelerate faster and gain more control (through enhanced consistency) in turns or any application of power. Hurst also manufactures many other shifters with 2 to 6 gears for a variety of cars. Linda Vaughn has been their spokeswoman for many years.
(HEV) A vehicle that is powered by two or more energy sources, one of which is electricity. HEVs may combine the engine and fuel system of a conventional vehicle with the batteries and electric motor of an electric vehicle in a single drivetrain.
Hybrid pad sets
Brake pad sets that contain an organic pad for one side of the rotor, and a semi-metallic pad for the other
Two distinct but interdependent forms of propulsion, such as an electric motor and an internal combustion engine, or an electric motor with battery and fuel cells for energy storage, or pedal power and an electric motor.
Film circuits combined with integrated circuits, used especially for trigger boxes or electronic control units
Hybrid transmission line
A double-circuit line that has one alternating current and one direct circuit. The AC circuit usually serves local loads along the line.
A vehicle that uses two or more forms of Propulsion. Some examples are the following
A water filled back pack for cyclists and hikers. It has a tube placed within reach for supplying water for the user. Trade names are Camelbak® and Hydrapak®
When a quantity of water, oil, or other fluid is forced along one end of a line, it also forces against the other end of the line. Because these fluids (unlike a gas) cannot be compressed, when they are forced into a smaller cylinder they multiply the amount of force. Thus a driver can apply a small amount of force on the pedal or lever and a great amount of force is applied to the brake. Used in Power steering, clutches, and brake systems.
When used as a verb, it means that oil or excessive gasoline has entered the combustion chamber so that when compression takes place, the fluid cannot be compressed. Something has to give and it is usually the Connecting rod that bends. It is found in the expression, the engine hydrauliced.
A part of the hydraulic system which is charged by the fluid pump, absorbs fluctuating fluid delivery, stores fluid at pressure, and can provide a rapid flow of fluid under pressure.
Unit in an anti-lock brake system that can increase brake pressure, decrease brake pressure, or hold brake pressure steady based on signals it receives from the control module
The hydraulically operated struts which control the movement of the wheels in an active ride suspension system
A motorcycle system where the brakes use hydraulic fluid instead of a cable. When the lever/pedal is squeezed/pressed, hydraulic fluid forces the pistons to put pressure on the brake pads which rub against the brake disc and cause enough friction to stop the bike. A master cylinder that contains the hydraulic fluid sits on the handlebar near the brake lever.
Found in a motorcycle, the clutch is engaged/disengaged via hydraulic fluid instead of a cable. When the lever is squeezed, hydraulic fluid forces the pushrod to disengage the clutch. A master cylinder that contains the hydraulic fluid sits on the handlebar near the clutch lever.
A clutch operated by hydraulic pressure.
Hydraulically operated power booster
A power booster that uses hydraulic pressure to assist the driver in the application of the brakes. This hydraulic pressure usually comes from the power steering pump or an electro-hydraulic pump
The portion of an anti-lock brake system that houses the solenoid valves and electro-hydraulic pump
Hydraulic-Electronic Unit Injector
(HEUI) A type of unit injector actuated by engine oil pressure rather than the camshaft. A very high oil pressure (up to 3,000 psi) is created by a separate oil pump. This high pressure is routed to every injector through a gallery. The engine’s Electronic Control Module varies the pressure in response to engine speed and other parameters.
A special oil used in hydraulic systems, such as power steering, self-leveling suspension, to operate the system of master and slave cylinders. Also compare brake fluid and Automatic transmission fluid
Fracturing of rock at depth with fluid pressure. Hydraulic fracturing at depth may be accomplished by pumping water into a well at very high pressures. Under natural conditions, vapor pressure may rise high enough to cause fracturing in a process known as hydrothermal brecciation.
A device for lifting a vehicle from the ground. Usually found in service bays to facilitate inspection of the running gear and exhaust system or for removing fluids.
(HC) A Compound made up of hydrogen and carbon (e.g., gasoline, Petroleum products, etc.). Hydrocarbons are also found when gasoline is burned in an engine and thus produce visible Smog even though hydrocarbons make up only 0.1% of emissions.
(HFC) A group of man-made chemicals composed of one or two carbon atoms and varying numbers of hydrogen and fluorine atoms. Most HFCs have 100-year Global Warming Potentials in the thousands.
A vessel which skims the surface of the water and the shaped pieces on the bottom of the vessel which act like water wings to give it lift.
(H) A gas formed of the single element hydrogen. It is considered one of the most active gases. When combined with oxygen, it forms a very clean flame which, however, does not produce a very high temperature or very much heat.
A process which results in a decrease of the toughness or ductility of a metal due to absorption of hydrogen
A proprietary suspension system incorporating a conical rubber spring compressed by hydraulic pressure; this system also provides a hydraulic interconnection between front and rear wheels on one side of the vehicle.
Heating system which circulates a heated fluid. usually water, through baseboard coils by means of a circulating pump which is controlled by a thermostat.
When your tires start to float on top of water, causing them to lose contact with the road’s surface
When a tire rolls upon a layer of water instead of staying in contact with the pavement. Hydroplaning occurs when all of the water on the pavement cannot be displaced from under the tire tread.
A phenomenon of driving when water builds up under the Tire tread, causing it to lose contact with the road. Caused by speed, water depth, tread depth, and inflation pressure. Slowing down will usually restore normal tire contact with the road. Also called Aquaplaning.
A Suspension system which uses a gas and a liquid which are separated by a flexible Bladder. The setup causes the suspension to maintain a preset height. Used in Citroën cars.
A hydraulically operated system that can excite vibrations of various frequencies in a car; serves to find and eliminate noise sources
(OH) An important chemical scavenger of many trace gases in the atmosphere that are greenhouse gases. Atmospheric concentrations of OH affect the atmospheric lifetimes of greenhouse gases, their abundance, and, ultimately, the effect they have on climate.
Instrument used to measure degree of moisture in the atmosphere.
The energy lost and not returned, when tire materials are subjected to stress in any direction. Lost energy is converted to heat through molecular interaction, and since rubber has poor thermal conductivity, internal temperatures of a tire can build up rapidly under repeated flexing.
An oscillator effect wherein a given value of an operating parameter may result in multiple values of output power or frequency.
The pattern that is formed or described by the magnetic flux intensity as a magnet approaches a magnetic object.
The resistance offered by materials to becoming magnetized, reduced by using silicon steel laminations
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An automobile manufactured in South Korea which includes Accent (1995-2008), Azera (2006-07), Elantra (1992-2008), Entourage (2007), Excel (1985-94), Santa Fe (2001-07), Scoupe (1991-95), Sonata (1989-08), Tiburon (1997-2007), Tucson (2005-07), Veracruz (2007), XG300 (2001), and XG350 (2002-05)
A very strong chain made up of toothed plates positioned side by side and held together by pins.
Abbreviation for Hertz. A unit of frequency equal to one cycle per second.