C – Terminologies

CENTRIFUGAL COMPRESSOR – A compressor designed to deliver large quantities of air or gas at low pressure, moved by centrifugal force generated by a fast revolving rotor.

CHARLE’S LAW – At constant pressure, the volume of a gas is proportional to its absolute temperature. At constant volume, the pressure is proportional to its absolute temperature.

CLEARANCE VOLUME EFFECT – Volumetric efficiency of the reciprocating compressor depends upon the clearance volume in the air cylinder. The greater the clearance volume, the greater the volume of the cylinder occupied by the clearance air which expands and prevents the entrance of free air during the early part of the admission stroke.

COMPRESSED AIR – Air forced into a smaller space than it originally occupied. When air is compressed both its pressure and temperature rise.

COMPRESSION CONSTANT – According to Boyle’s law, product of pressure and volume at any instant is constant, at constant temperature.

COMPRESSION EFFICIENCY – Ratio of the theoretical power required to compress the amount of air actually delivered to the actual power developed in the cylinder as shown by the indicator diagram.

COMPRESSOR OVERALL EFFICIENCY – Ratio of actual power developed in the air cylinder as shown by the indicator diagram to the power supplied to the compressor shaft.

CONSERVATION OF ENERGY – Energy can be transmitted from one body to another or transformed in its manifestations, but can neither be created nor destroyed.

CALIPER – A housing for the hydraulic components of a disc brake system.

CAMBER – Tilting of the top of wheels from the vertical, when the tilt is outward, camber is positive.

CAMBER ANGLE – The outward (positive) or inward (negative) angle of the wheel centre line to absolute vertical.

CARDAN UNIVERSAL JOINT – A universal joint of the ball and socket type.

CARLIFT – An air, electrical or hydraulically operated piece of shop equipment which can lift the entire vehicle, or in some cases, one end of the vehicle.

CARRIER BEARINGS – Bearings upon which differential case is mounted.

CASING OF TYRE – The tyre casing, made of fabric or cord to which rubber is vulcanized. It is the outer part of the tyre assembly.

CASTER – The tendency of a wheel to follow the direction of the pivot movement. Tilt of the top of the king pin forward or backward from the vertical. When tipped forward it is called negative caster. Backward tilt from the vertical is called positive caster.

CASTER ANGLE – The rearward (positive) or forward (negative) angle of the steering axis to absolute vertical.

CENTRE STEERING LINKAGE – Steering system utilizing two tie rods connected to steering arms and to central idler arm. Idler arm is operated by drag link that connects idler arm to pitman arm.

CENTRIFUGAL CLUTCH – Clutch that utilizes centrifugal force to expand a friction device on driving shaft until it is locked to a drum on driven shaft. The clutch comes into action as it spins faster.

CHANNELED – Car body lowered down around frame.

CHASSIS – Generally chassis refers to the unit that consists of frame, engine, front and rear axles, springs, steering and brake systems, controls, drive train and fuel tank. It is an assembly of mechanisms that make up the major operating part of the vehicle. In short, it is assumed to include everything except the vehicle body and fenders.

CLASSIC or NORMAL CONTROL TRUCK – has the engine located in front of the driver’s cabin.

CLUTCH – Device used to connect or disconnect flow of power from one unit to another. In a vehicle, the mechanism in the power train that connects the engine crankshaft to or disconnects it from the transmission and thus with the remainder of the power train.

CLUTCH CHATTER – A shaking or shuddering of the vehicle as the clutch is operated.

CLUTCH DIAPHRAGM SPRING – Round dish shaped piece of flat spring steel, used to force pressure plate against clutch disc in some clutches.

CLUTCH DISC – Part of the clutch assembly splined to transmission clutch or input shaft, faced with friction material. When clutch is engaged, disc is squeezed between flywheel and clutch pressure plate.

CLUTCH DRAG – A problem in which the clutch disc does not come to a complete stop after the clutch pedal is depressed.

CLUTCH EXPLOSION – Clutches have literally flown apart (exploded) when subjected to high rotational speed. Scatter shield is used on competition cars to protect driver and spectators from flying parts in event clutch explodes.

CLUTCH HOUSING – A metal housing that surrounds the flywheel and clutch assembly.

CLUTCH LINKAGE – The rods and levers that allow the driver to operate the clutch.

CLUTCH PEDAL – A pedal in the driver’s compartment that operates the clutch.

CLUTCH PEDAL FREE TRAVEL – Specified distance clutch pedal may be depressed before throw out bearing actually contacts clutch release fingers.

CLUTCH PILOT BEARING – A small bronze bushing or ball bearing positioned in the crankshaft end or centre of flywheel, used to support outboard end of transmission input shaft.

CLUTCH PRESSURE PLATE – Part of a clutch assembly, that through spring pressure, squeezes clutch disc against flywheel thereby transmitting driving force through the assembly. To disengage clutch, pressure plate is drawn away from the flywheel via linkages.

CLUTCH SEMI CENTRIFUGAL RELEASE FINGERS – Clutch release fingers that have a weight attached to them, so that at high rpm release fingers place additional pressure on clutch pressure plate.

CLUTCH SHAFT – The shaft on which the clutch is assembled, with the gear that drives the countershaft in the transmission on one end. It has external splines that can be used by a synchronizer drum to lock the clutch shaft to the main shaft for direct drive.

CLUTCH SLIPPAGE – A condition in which the engine over revs during shifting or acceleration.

CLUTCH THROWOUT FORK – In the clutch, a Y shaped member into which is assembled the throw out bearing.

CLUSTER or COUNTER GEAR – Cluster of gears that are all cut on one long gear blank. Cluster gears ride in the bottom of transmission. Cluster provides a connection between transmission input shaft and output shaft.

COEFFICIENT OF FRICTION – An index of the frictional characteristics of a material.

COEFFICIENT OF ROLLING RESISTANCE – is numerically equal to the ratio of the force causing uniform rolling of the wheel to the normal reaction of the road.

COIL SPRING CLUTCH – A clutch using coil springs to hold the pressure plate against the friction disc.

COLLAPSIBLE STEERING COLUMN – is the steering column which will collapse in its length due to the impact of the driver on to the steering wheel, on a front end crash. This safety device prevents the possibility of the driver getting injured.

CONE CLUTCH – Clutch utilizing cone shaped member that is forced into a cone shaped depression in the flywheel, or the other driving unit. Although no longer used in cars, cone clutch finds some applications in small riding tractors, heavy power movers etc.

CONSTANT VELOCITY JOINT – Two closely coupled universal joints arranged so that their acceleration and deceleration effects cancel out each other, resulting in an output driven shaft speed to be always identical with drive shaft speed.

CONTACT PATCH – The part of a tyre that is in contact with the road surface.

CONTROL ARM – A suspension member mounted horizontally with one end attached to the frame and the other end the knuckle or axle housing.

CORD – A string or thread that makes up the fabric used in tyre plays.

CORNERING WEAR – A type of tyre tread wear caused by taking turns at excessive speeds.

COUNTERSHAFT – Intermediate shaft that receives motion from one shaft and transmits it to another. It may be fixed (gears turn on it) or it may be free to rotate. In the transmission countershaft is driven by the clutch gear, gears on the countershaft drive gears on the main shaft when the latter are shifted into gear.

COWL – Part of car body between engine firewall and front of dashboard.

CROSS SHAFT (steering) – Shaft in steering box that engages steering shaft worm. Cross shaft is splined to pitman arm.

CURB WEIGHT – The weight of the complete vehicle with its normal load, less driver and passengers but with a full tank of fuel, engine and vehicle oil and coolant.

CUT OUT – operates as an automatic switch which connects and disconnects the battery with the generator, according to the speed of the latter.

CAVITATION – The formation of cavities in the fluid due to excessive speed of the activator resulting in loss of efficiency in the pump.

CHEMICAL DELAY PERIOD – The time that elapses between the beginning of chemical reaction and the begining of ignition.

CLOSED TYPE NOZZLE – A hydraulically operated, spring loaded needle valve, which opens inward under the pressure acting on the differential area of the needle valve (which is a cylinder lapped in with the body and seated by a spring when the fuel pressure is reduced sufficiently).

COLD SMOKE – The smoke that is made up of droplets of unburned or partly burned fuel or due to water vapour. Also called WHITE SMOKE.

COMBUSTION CHAMBER – The space wherein combustion of fuel with air takes place, more or less equal to the clearance volume.

COMBUSTION SWIRL – Air motion created by the ejection of the combustion products from the pre-combustion chamber into the clearance space above the piston.

COMMON RAIL SYSTEM – The fuel injection system which consists of a high pressure pump which distributes the fuel to a common rail or header to which injectors are connected.

COMPRESSIBILITY – The property of a substance by virtue of which its density increases with increase in pressure.

COMPRESSION IGNITION – Ignition of fuel due to the heat of compression.

COMPRESSION SWIRL – Rotary motion given to air, as the air is forced, during compression stroke, from the cylinder into the spherical or cylindrical combustion chamber through the throat which is located tangential to the combustion chamber.

CONSTANT PRESSURE COMBUSTION – Combustion which occurs without a change in pressure. In an engine, this is obtained by a slower rate of burning than with constant volume combustion.

CONTROLLED COMBUSTION – During uncontrolled combustion, high temperature and pressure prevail within the combustion chamber. After this combustion, fuel that is injected burns without any delay. By controlling the rate of injection, complete control is possible over the rate of burning.

CONTROL RACK – A toothed rack that runs along the upper end of the fuel pump and engages pinions (gear teeth) on each pump plunger to control the amount of fuel injected and thereby determines engine power output.

CRITICAL COMPRESSION RATIO – Lowest compression ratio at which any particular fuel will ignite by compression under prescribed test procedure. The lower the critical compression ratio the better ignition qualities the fuel has.

CALCIUM BORIDE – An alloy of calcium and boron corresponding (when pure) to the formula CaB6 containing about 61% boron and 39% calcium, and used in deoxidation and degasification of nonferrous metals and alloys.

CALCIUM MANGANESE SILICON – An alloy containing 17 to 19% calcium, 8 to 10% manganese, 55 to 60% silicon and 10 to 14% iron used as a scavenger for oxides, gases and non-metallic impurities in steel.

CALCIUM SILICON – An alloy of calcium, silicon and iron containing 28 to 30% calcium, 60-65% silicon and 6% max iron, used as a deoxidizer and degasifier for steel and cast iron.

CASTING – Metal poured into a mould to form an object. Act of pouring molten metal into a mould.

CASTING STRAINS – Strains resulting from internal stresses created during cooling of a casting.

CAVITY, MOULD or DIE – Impression or impressions in a mould or die that give the casting its shape.

CENTRIFUGAL CASTING – Process of filling moulds by pouring the metal into sand or metal mould revolving about either it’s horizontal or vertical axis and continues pouring the metal into the mould that is being revolved before solidification of metal is complete. Molten metal is moved from the center to the periphery by centrifugal action.

CERAMIC MOULD – Mould in which the refractory and binder are such that when fired at high temperature, a rigid structure is formed. The mould can be made in a flask or in the form of a shell.

CEREAL – Substance derived from corn flour, which is added to core and moulding sands to improve their properties for casting production.

CHALK TEST – Method of crack detection which consists of applying a penetrating liquid to the excess from the surface which is then coated with whiting or chalk. After a short time, the penetrant seeps out of the cracks into the whiting, causing an appreciable difference in whiteness.

CHAMOTTE – Coarsely graded refractory material prepared from calcined clay and ground firebrick mulled with raw clay, used in steel foundries.

CHAPLET – A metallic insert or support to hold the core in position in the mould.

CHEEK – Intermediate sections of a flask inserted between cope and drag.

CHILL – A metal object placed on the outside or inside a mould cavity to induce more rapid cooling at that point and thereby produce hard zone i.e., hard, unmachinable surface.

CHILL TEST – Method of determining the suitability of a gray iron for specific castings through its chilling tendency, as measured from the tip of a wedge shaped test bar.

CHILLED IRON – Cast iron poured against a chill to produce a hard unmachinable surface.

CHOKE – Restriction in a gating system to control the flow of metal beyond that point.

CHVORINOV’S RULE – Solidification time is proportional to the square of the volume of the metal and inversely proportional to the square of the surface area.

CLEANING – Process of removing sand, surface blemishes etc. from the exterior and interior surfaces of a casting. Includes degating, tumbling, or abrasive blasting, grinding off gate stubs.

COD – A sand projection left behind in the mould by some patterns. Strictly speaking it is a core.

COLD SHUT – Where two streams of metal do not unite thoroughly in a casting.

COMBINATION DIE – A die casting die having two or more cavities of dissimilar parts.

CONTRACTION – Act or process of a casting becoming smaller in volume and/or dimensions during the solidification of the metal or alloy which composes the casting.

COPE – The upper or top most section of a flask, mould or pattern.

COPE (false) – A temporary cope which is used only to establish the parting line.

CORE – Separable part of the mould, usually made of sand and generally baked, to create openings and various shaped cavities in the castings. Also used to designate the interior portion of an iron base alloy which after case hardening is substantially softer than the surface layer or case.

CORE BINDER – Any material used to hold the grains of core sand together.

CORE BOX – Box with an opening in which the core is formed.

CORE PRINT – An extension of the pattern for locating the core or an extension of the mould cavity for locating the core.

CORE (ram up) – Core attached to the pattern and rammed up in the mould, where it remains when the pattern is withdrawn.

CORE SHIFT – Defect resulting from movement of the core from its proper position in the mould cavity.

CORE VENTS – A wax product, round or oval in form, used to form the vent passage in the core.

CRUSH – Casting defect appearing as an indentation in the surface due to displacement of sand in the mould, usually at the joint surfaces.

CUTS – Defects in castings resulting from erosion of the sand by the molten metal pouring over the mould or core surface.

CADMIUM – White ductile metallic element used to plate steel and as an alloying element.

CALCIUM ALUMINIUM SILICON – An alloy composed of 10-14% calcium, 8-12% aluminium, and 50-53% silicon used for degasifying and deoxidizing steel.

CALCIUM BORIDE – An alloy of calcium and boron, containing about 61% boron and 39% calcium and used in de-oxidation and degasification of non-ferrous metals and alloys.

CALCIUM CARBIDE – A greyish black, hard crystalline substance made in the electric furnace by fusing lime and coke. Addition of water to calcium carbide forms acetylene and a residue of slaked lime.

CALCIUM MANGANESE SILICON – An alloy containing 17 to 19% calcium, 8 to 10% manganese, 55 to 60% silicon and 10 to 14% iron, used as a scavenger for oxides, gases and non-metallic impurities in steel.

CALCIUM MOLYBDATE – A crushed product containing 40-50% molybdenum, 23-25% lime, 3% iron (max) and 5-10% silica, used to add molybdenum to iron and steel produced in open hearth, air furnace or electric furnace.

CALCIUM SILICON – An alloy of calcium, silicon and iron containing

28-35% calcium, 60-65% silicon and 6% max iron used as a deoxidizer and degasifier for steel and cast iron. Sometimes called CALCIUM SILICIDE.

CAPPED STEEL – Semiskilled steel cast in a bottle top mould and covered with a cap fitting into the neck of the mould. The cap causes the top metal to solidify. Pressure is build up in the sealed in molten metal and results in a surface condition much like that of RIMMED STEEL.

CARBIDE – A compound of carbon with one or more metallic elements.

CARBOHYDRATES – Constitute a large group of molecules, widely distributed in nature, which contains only carbon, hydrogen and oxygen. The simplest carbohydrates are sugars.

CARBON – A non-metallic element found in all organic substances that is used as an alloying element in ferrous metals.

CARBON STEEL – Steel containing carbon up to about 2% and only residual quantities of other elements except those added for de-oxidation, with silicon usually limited to 0.60% and manganese to about 1.65%. Also termed PLAIN CARBON STEEL.

CARBORUNDUM – Artificially manufactured abrasive, trade name for a carbide of silicon (SiC) which is prepared by heating sand with coke in an electric furnace.

CARTRIDGE BRASS – Alloy containing about 70% copper and 30% zinc, in which impurities are kept to a minimum, and it possesses a high degree of strength, combined with good ductility.

CAST ALLOY TOOL – A cutting tool made by casting a cobalt base alloy and used at machining speeds between those for high speed steels and sintered carbides.

CAST IRON – Iron obtained by slightly purifying the pig iron in a cupola or other furnace. This has high carbon content, averaging between 2.5 and 4.5% and frequently alloyed with small percentage of other elements and primarily used for making castings. It is somewhat brittle.

CELLULOSE – A polysaccharide of glucose units that constitutes the chief part of the cell walls of plants. For example, cotton fibre is over 90% cellulose and is the raw material of many manufactured goods such as paper, rayon and cellophane. In many plant cells, the cellulose wall is strengthened by the addition of lignin, forming lignocelluloses.

CEMENT – Material used for uniting other materials so that they adhere permanently.

CEMENTED CARBIDE – A solid and coherent mass made by pressing and sintering a mixture of powders of one or more metallic carbides, and a much smaller amount of a metal, such as cobalt, to serve as a binder.

CEMENTITE – Hard, brittle, crystalline iron carbide (compound of iron and carbon Fe3C) found in steels having high carbon content. It is characterized by an orthorhombic crystal structure. When it occurs as a phase in steel, the chemical composition will be altered by the presence of manganese and other carbide forming elements.

CERAMIC – Metallic oxides of metals such as silicon and aluminium.

CERAMIC MATERIALS – The materials that demonstrate great hardness and resistance to heat and are used to make cutting tools, coatings on tools, parts subjected to very hot conditions, abrasives and mechanical parts.

CERMET (Ceramal) – A body consisting of ceramic particles bonded with a metal.

CESIUM 13T – A radioisotope, recovered as a fission product from nuclear reactors, with a half-life of 33 years and a dominant characteristic gamma radiation of 0.66 MeV. It is suitable as a gamma radiation source, especially in radiography and therapy.

CHILL – (1) A metal insert embedded in the surface of a sand mould or core or placed in a mould cavity to increase cooling rate at that point. (2) White iron occurring on a gray iron casting such as the chill in the wedge test.

CHINESE SCRIPT – An angular micro-structural form with the constituents’ alpha (AI-Fe-Si) and alpha (AI-Fe-Mn-Si) in cast aluminium alloys. A similar microstructure is found in cast magnesium alloys containing silicon as Mg2Si.

CHROMEL – (1) 90% Ni, 10% Cr alloy used in thermocouples. (2) A series of Nickel chromium alloys some with iron, used for heat resistant applications.

CHROMIUM – Greyish white metallic element obtained from chromites, chemical symbol is Cr and melting point 1830°C, used in alloying steels and corrosion resisting plating.

CLAD METAL – A composite material containing two or three layers that have been bonded together. The bonding may have been accomplished by rolling, welding, casting, heavy chemical deposition or heavy electroplating.

COAL TAR – Also called crude oil, when subjected to fractional distillation and purification, yields a variety of useful products-neutral, acidic, and base oils.

COBALT-60 – A radio isotope with a half-life of 5.2 years and dominant characteristic gamma radiation energies of 1.17 and 1.33 MeV. It is used as a gamma radiation source in industrial radiography and therapy.

COLD FINISHED STEEL – Steel bar which has been cold drawn/cold rolled, centerless ground or turned smooth to improve surface finish, accuracy or mechanical properties.

COLD ROLLED STEEL – Steel which has been passed through rollers at the steel mill to size it accurately and smoothly.

COLLOIDS – Finely divided material, less than 0.5 micron in size, gelatinous, highly absorbent and sticky when moistened.

COLUMNAR STRUCTURE – A coarse structure of parallel columns of grains having the long axis perpendicular to the casting surface.

COMBINED CARBON – The part of the total carbon in steel or cast iron that is present as other than FREE CARBON.

COMPOSITE FIBRES – The strands of material used as reinforcement extending through a resin or other matrix in a composite material. An example is carbon fibres in an epoxy matrix. Loads applied to the structure are carried by the fibres.

COMPOSITE MATERIAL – Materials exhibiting a much higher strength than the matrix or base material because of reinforcement fibres.

CONDUCTORS (electrical) – Materials in which an electromotive force causes appreciable drift of electrons, called CURRENT.

CONSTANTAN – A group of copper nickel alloys containing 45-60% copper with minor amounts of iron and manganese and characterized by relatively constant electrical resistivity irrespective of temperature used in resistors and thermocouples.

CONVERSION COATING – A coating consists of a compound of the surface metal produced by chemical or electro-chemical treatments of the metal.

COPPER – A reddish, soft, ductile metal with very good heat and electrical conductivity and is the basic element in brass and bronze.

CORE – (1) In a metal casting, the hollow parts (which cannot be shaped as easily by the pattern) that are made by using formed sand shapes that are strengthened by baking or by using epoxy. (2) In a ferrous alloy, the inner portion that is softer than the outer portion or case.

CORE SAND – Variety of silica sand. Rock sand, river bed and sea shore sand, commonly known as sharp sand, used for making of cores in the foundry because they are capable of withstanding high temperatures, and resisting the penetrating action of the molten metal.

CORUNDUM – Natural abrasive of the aluminium oxide type that has higher purity than emery.

ROCUS CLOTH – A very fine abrasive polishing cloth.

CHROMIUM BRONZE – It is a precipitation hardening alloy of copper with up to 1 per cent chromium. It has high electrical conductivity and high temperature resistance.

CRUCIBLE – A vessel or pot, made of refractory substance or of a metal with a high melting point, used for melting metals or other substances.

CRUCIBLE STEEL – A high grade steel made by melting iron in a crucible and adding charcoal, pig iron and some substance rich in carbon so that the resulting metal will contain from 0.75-1.5% carbon. This steel is used for tools, dies and better grades of cutlery.

CRYSTAL – A solid composed of atoms, ions or molecules arranged in a pattern which is repetitive in three dimensions.

CRYSTALLOID – A substance that forms a true solution and is capable of being crystallized.

CUNIFE – Cunife is a copper-nickel iron alloy that is malleable, ductile and machinable, even in an age-hardened form. Magnets are formed from wire stock in round, square, or rectangular form.

CUPRO NICKEL ALLOY – Alloy of nickel and copper (approximately 60% nickel and 30% copper), which combines the strength of steel with immunity from corrosion and resistance to high temperature.

CURIE – The quantity of a radioactive nuclide in which the number of disintegrations per second is 3. 700 × 10 to the power of ten.

CUTTING FLUID – A fluid, usually a liquid, used in metal cutting to improve finish, tool life or dimensional accuracy.

CARBON RESIDUE – Determined (canradson carbon test) by evaporating under specified test conditions, a known weight of oil and weighing the residue.

CENTIPOISE – A unit of viscosity of a fluid used in figuring pressure drop etc.

CENTRIFUGAL OIL SLINGER – Cup shaped centrifugal oil filter mounted to the end of the crankshaft. As the oil passes through the slingers, centrifugal force removes impurities that are heavier than oil.

COEFFICIENT OF FRICTION – Ratio between the resistance due to friction in the direction of motion and the load carried normal to the plane of motion.

COLLAR BEARING – The collar which may be at any part of the length of the shaft, takes up the thrust produced along the axis of the shaft.

CRANKCASE DILUTION – Dilution of lubricating oil in the oil pan by liquid gasoline seeping down the cylinder walls. Accumulation of unburned gasoline in the crankcase.

CRITICAL SPEED – The limiting or critical speed corresponding to a given pressure is that speed at which surface irregularities may intervene and so lead to seizure.

CALORIE – The amount of heat required to raise one gram of water through 1°C i.e., from 17 to 18°C. Calorie is unit of heat.

CALORIFIC INTENSITY – The maximum flame temperature attained when the fuel is burnt.

CALORIFIC VALVE – The heat value of a fuel, expressed in either BTU per pound or CHU per pound or kilocalories/kg. The amount of heat produced by burning unit weight of fuel.

CALORIEMETER – Measuring instrument used to determine the amount of heat produced when a substance is burned, also friction and chemical change produce heat.

CARBON – One of the non-metallic elements constituting fuel and lubricating oil.

CARBON DEPOSIT – A black, hard or soft deposit left on engine parts by the combustion of fuel. Carbon forms on pistons, rings, plugs, valve heads etc., inhibiting their action.

CARBONDIOXIDE – A colourless, odourless gas which results when hydrocarbon or carbon is burned completely.

CARBONIZE – Building up of carbon on objects such as spark plug, piston head etc., of an engine.

CARBON MONOXIDE – A colourless, odourless, tasteless, poisonous gas found in engine exhaust. Formed when carbon or hydrocarbons are burned incompletely.

CARBURETED WATER GAS – An artificial gas formed by passing steam through a bed of glowing coke and thereafter enriching the gas so formed with petroleum vapour.

CATALYTIC CONVERTER – A muffler like device for use in an exhaust system that converts harmful gases in the exhaust into harmless gases by promoting a chemical reaction between a catalyst and the pollutants.

CETANE NUMBER – Rating of ignition quality or performance characteristic of diesel fuel. A high cetane number fuel ignites more easily at lower temperature than a low cetane number fuel.

CHARCOAL – Product obtained by heating wood out of contact with air.

CHARCOAL CANISTER – A container filled with activated charcoal used to trap gasoline vapour from the fuel tank and carburettor while the engine is off.

CHEMICAL CHANGE – A change which alters the composition of the molecules of a substance producing new substances with new properties.

CLOUD POINT – The temperature of a liquid (fuel or lubricant) at which a haze or a cloud first appears in a sample of oil, when cooled in a prescribed manner.

COAL – A firm, brittle, sedimentary, combustible rock derived from vegetable debris which has undergone a complex series of chemical and physical changes during the course of many million years.

COAL GAS – A fuel formed by the distillation of coal, usually in a retort or a coke oven.

COEFFICIENT OF HAZE – A measurement of visibility interference in the atmosphere.

COKE – A fused cellular porous structure that remains after the free moisture and the major portion of the volatile matter have been distilled from coal.

CAKING COALS – Coals that become soft under the usual furnace temperatures and merge into undesirable masses of coke. The coal that becomes soft, melts and solidifies into a more or less solid mass which further hardens on heating out of contact with air.

COLLOIDAL FUEL – A mixture of fuel oil and powdered coal.

COMBUSTION – Process involved during quick burning. Release of chemical energy into heat energy occurs during combustion.

COMBUSTION EFFICIENCY – is the ratio of the (heat) energy liberated to that which could be liberated under ideal conditions. Quantity of CO2 and H2O in the exhaust indicate energy liberated, whereas the quantity of H2, CO and CH₄ indicate unliberated energy.

CRACKING – The process of breaking of heavy molecules into lighter hydrocarbons.

COMPRESSION IGNITION – Ignition of fuel through the heat of compression as in a diesel engine.

COMPRESSED NATURAL GAS – usually assumes the form of compressed methane, and is suitable for obtaining ultra low emissions from combustion engines. Soot production is virtually zero.

COMPOUND – A combination of two or more ingredients mixed together.

CONSTANT PRESSURE COMBUSTION – Combustion which occurs without a change in pressure. In an engine, this is obtained by the slower rate of burning than with constant volume combustion.

CRUDE OIL – Petroleum as it comes from the oil well (raw or refined state). It forms the basis of gasoline, engine oil, diesel oil, kerosene etc.

CAN TYPE COMBUSTION CHAMBER – Combustion chamber in which the air leaving the compressor is split into several streams and each stream is supplied to a separate cylindrical combustion chamber.

CARRY OVER LOSS – Kinetic energy discarded in the exhaust. Axial exit of the fluid from the turbine blades reduces this loss.

CASING – Turbine enclosure to which the nozzles and guides are fixed. Also called a SHELL or CYLINDER.

CENTRIFUGAL COMPRESSOR – A type of compressor in which air is sucked into the impeller eye, whirled around at high speed by the vanes on the impeller disc and flung out by centrifugal force.

CLOSED CYCLE TURBINE – Turbine in which the working fluid does not come in contact with the atmospheric air and the heat to the working fluid is provided in the heater by burning the fuel externally.

COMBINATION PLANT – A gas turbine plant that utilizes reheat, intercooling and regeneration.

COMBUSTION CHAMBER – The unit in which the chemical combination of oxygen in the air supplied by the compressor takes place with the carbon and hydrogen components of the fuel in such a manner that a steady stream of the gases at uniform temperature is produced and delivered to the turbine.

COMBUSTION EFFICIENCY – The ratio of the actual heat realised by the combustion of fuel to the ideal value i.e., calorific value.

COMBUSTION INTENSITY – Ratio of the rate of heat supply by fuel to the product of volume of combustion chamber and inlet pressure in atmospheres.

COMPRESSOR EFFICIENCY – Ratio of work required for isentropic compression to the actual work input. Also called ISENTROPIC COMPRESSION EFFICIENCY.

COMPRESSOR MECHANICAL EFFICIENCY – Ratio of rotor horse power to shaft horse power supplied to the compressor.

CONSTANT PRESSURE TURBINE – Turbine in which the fuel is burnt at constant pressure. Combustion is a continuous process.

CONSTANT VOLUME TURBINE – Turbine in which the combustion takes place at constant volume. Also called EXPLOSION TYPE TURBINE.

CONVERGENT DIVERGENT DIFFUSER – A type of diffuser which can build up pressure when velocities are reduced from supersonic to subsonic values.

COOLING OF TURBINE BLADES – Turbine blades are cooled by water or air. This enables the temperature of the blade metal to be several hundred degrees lower than the gas temperature and permits employment of correspondingly higher turbine inlet temperatures, with the metals available at present, resulting in higher turbine efficiency.

COUNTERFLOW HEAT EXCHANGER – A heat exchanger in which compressed air and hot gases let out by the turbine, flow in opposite directions.

CROSS COMPOUNDED UNIT – The system in which the low pressure compressor is driven by the high pressure turbine and the high pressure compressor by the low pressure turbine.

CROSS FLOW HEAT EXCHANGER – A heat exchanger in which the compressed air and the hot gases let out by the turbine flow normal to one another.

CYCLE PRESSURE RATIO – Ratio of the pressure at inlet to the gas turbine to that at inlet to the compressor.

CYCLE WITH INTERCOOLED COMPRESSION – Gas turbine cycle in which the compression of the working fluid is cut off at some intermediate pressure and the fluid is cooled by passing it through a heat exchanger supplied with coolant from some external source before being compressed in the second compressor to the required pressure ratio.

CADMIUM PLATING – Electroplating process for the application of cadmium to steel and iron parts to prevent rust.

CALORIZING – Rust proofing process for ferrous metals in which an aluminium film is formed on the surface of the metal. Means of protecting iron from oxidation at elevated temperatures.

CARBURIZING – A process that introduces carbon into a heated solid ferrous alloy by having it in contact with a carbonaceous material. The metal is held at a temperature above the transformation range for a period of time. This is generally followed by quenching to produce a hardened case.

CASE HARDENING – Heating a steel in the presence of a solid, liquid or gas, rich in carbon, in order to enable the surface to be hardened, while retaining a tough, ductile core.

CHROMIUM PLATING – Electrolytic deposition of chromium on a metal surface, as a protection against corrosion, to provide improved wearing properties, or to build up an undersized part.

CHROMIZING – Similar to carburizing. Low carbon steel parts are packed with a mixture of alumina and chromium powder and heated in a hydrogen atmosphere, forming a surface layer of chromized material of 10 to 20% chromium, according to time and temperature of heating.

COLOURING METAL – Production of a coloured surface on a metal or alloy by the use of heat or chemical action, or by a combination of the two.

COSLETTIZING – Rust proofing process in which an iron phosphate skin is formed on the surfaces of ferrous parts, the skin follows even the microscopic irregularities, yet is remarkably tough and corrosion resistant.

CAM – A rotating lobe of irregular shape or eccentric or offset portion of the shaft (cam). It changes rotary motion of cam shaft to reciprocating or variable motion of valve lifter resting on it.

CAM FOLLOWER (valve lifter) – A part which is held in contact with the cam and to which the cam motion is imparted and transmitted to the push rod.

CAM GROUND PISTON – A piston that is ground slightly oval in shape. It becomes round as it expands with heat.

CAM NOSE – Also called CAM LOBE. That portion of the cam which holds the valve wide open. It is the high point of the cam.

CAM SHAFT – The shaft in the engine which has a series of cam lobes (simply called cams) for operating the valve mechanisms, driven by gears or sprockets and chain from the crankshaft.

CAM SHAFT GEAR – The gear that is fastened to the cam shaft.

CAST IN SLEEVE – An aluminium cylinder block cast around an iron cylinder sleeve.

CAST IRON CYLINDER – A one piece cylinder assembly made of cast iron with a machined bore.

CAST PISTON – A piston made by pouring molten aluminium alloy into the mould of desired shape.

CENTRIFUGAL GOVERNOR – A governor which uses flyweight force to sense speed, in order to control the amount of fuel supplied to the combustion chambers.

CENTRIFUGAL OIL SLINGER – Cup shaped centrifugal oil filter mounted to the end of the crankshaft. As oil passes through the slingers, centrifugal force removes impurities that are heavier than oil.

CHROME PLATED RING – A piston compression or oil ring that has its cylinder wall face lightly plated with hard chrome.

CIRCLIP – A circular clip or snap ring that fits into a groove, used to locate or retain a shaft or component.

CLEARANCE – The amount of space between two moving parts or between a moving and a stationary part, such as a journal and a bearing, piston and cylinder.

CLEARANCE VOLUME – The volume remaining above the piston when the piston is at TDC.

CLOSED CRANKCASE VENTILATION SYSTEM – A system in which the crankcase vapours (blow by gases) are discharged into the engine intake system and pass through the engine cylinder rather than being discharged into the air.

COATED BORE – Thin coating of chrome or iron applied to the inside of the cylinder by electroplating, or wire explosion spray coating.

COATED RING – A piston ring having its cylinder wall face coated with ferrous oxide, soft phosphate or tin. This thin coating helps new rings to seat by retaining oil and reduces scuffing during break-in.

COMBUSTION CHAMBER – The space at the top of the cylinder and in the cylinder head or piston or both, in which combustion of fuel and air charge takes place. The space enclosed by the piston, when the piston is at TDC.

COMBUSTION CHAMBER VOLUME – The volume of the combustion chamber when the piston is at TDC, measured in cubic centimetres.

COMBUSTION CYCLE – A series of thermodynamic processes through which the working gas passes to produce one power stroke. The full cycle is intake, compression, power and exhaust.

COMPRESSION CHECK – Measurement of compression pressure in all the cylinders at cranking speed.

COMPRESSION PRESSURE – Pressure in the combustion chamber at the end of the compression stroke, but without any of the fuel being burned.

COMPRESSION RATIO – The ratio between the total volume of the cylinder when the piston is at BDC and the volume when the piston is at TDC.

COMPRESSION RELEASE – A device to prevent the intake valve or exhaust valve from closing completely. This permits the engine crankshaft to be turned over without compression and with ease. Also called DECOMPRESSOR.

COMPRESSION RINGS – The upper ring or rings on a piston designed to hold the compression in the cylinder and prevent or reduce combustion gas leakage i.e., blowby.

COMPRESSION STROKE – The piston stroke from BDC to TDC during which both valves are closed and the charge is compressed into a smaller space creating heat by molecular action.

COMPRESSION TESTER – An instrument for testing the amount of pressure, or compression, developed in an engine cylinder during cranking. Also called COMPRESSION GAUGE.

CONNECTING ROD – The rod made of steel or aluminium alloy usually having an I beam cross-section. A piston pin connects the connecting rod and the piston.

CONNECTING ROD BEARING – Bearings used in the connecting rod small end or big end holes.

CONNECTING ROD CAP – The part of the connecting rod big end assembly that attaches the rod to the crankpin.

CONNECTING ROD TIP – Amount of radial (side) play at the top of the connecting rod. Measurement of rod tip is one way of determining the condition of the rod big end bearing.

CONTROLLED PORT SCAVENGING – Scavenging method using ports which are controlled by valves in addition to the power piston.

COOLANT – The liquid mixture of antifreeze and water circulated in the cooling system of an engine or machinery.

COOLING SYSTEM – In an engine, the system that removes heat by the natural or forced circulation of the coolant and thereby prevents engine overheating. It includes the water jackets, water pump, radiator and thermostat, or cooling fins, blower and cowl.

CORE (radiator) – A number of coolant passages surrounded by fins through which air flows to carry away heat from the coolant.

COUNTER FLOW CYLINDER HEAD – has the intake and exhaust passages on the same side of the cylinder head.

COUNTER WEIGHT – Weights that are mounted on the crankshaft opposite each crank throw. These reduce the vibration caused by the crank and also reduce bearing loads due to inertia of the moving parts.

CRANK – A device for converting reciprocating motion into rotary motion or vice versa.

CRANKCASE – The lower part of an engine in which the crankshaft rotates. It consists of the lower section of the cylinder block, and the oil pan.

CRANKCASE VENTILATING SYSTEM – The system that permits air to flow through the engine crankcase when the engine is running to carry out the blow by gases and relieve any pressure build up.

CRANKPIN – That part of the crank throw of the crankshaft to which the connecting rod is attached.

CRANKPIN RIDGING – A type of crankpin failure typified by deep ridges worn into the crankpin bearing surfaces.

CRANKSHAFT – The main rotating member or shaft running along the length of the engine. Portions of the shaft are offset to form throws or cranks to which the connecting rods are attached. Crankshaft is supported by main bearings.

CRANKSHAFT AXLES – Extension at each end of the crankshaft to provide a mounting place for main bearings, and alternator rotor of magneto flywheel.

CRANKSHAFT GAUGE – A special type of micrometer which can measure crankshaft wear without removing the crankshaft from the block.

CRANKSHAFT GEAR – A gear or sprocket, mounted on the front of the crankshaft. Used to drive the camshaft gear or chain.

CRANKSHAFT WHEEL – Portions of an assembled crankshaft, in the form of wheels that provide a mounting place for crankpin and crank-axles.

CRANK THROW – One crankpin with its two webs (the amount of offset of the journal).

CRANK WEB – The portion of the crank throw between the crankpin and main journal. This makes up the offset.

CRITICAL SPEEDS – Speeds at which the frequency of the power strokes synchronize with the crankshafts natural frequency. If the engine is operated at one of its critical speeds for any length of time, a broken crankshaft may result.

CROSS FLOW CYLINDER HEAD – has the intake and exhaust lines on opposite sides of the cylinder head.

CYCLE – A series of events which continuously repeat in definite order. In an engine, the cycle constitutes the four operations that complete the working process and produce power.

CYLINDER – A round hole or tubular shaped structure in a block or casting in which a piston reciprocates.

CYLINDER BLOCK – The basic framework of the engine to which the other engine parts are attached. It includes the engine cylinders and the upper part of the crankcase.

CYLINDER BORE – Diameter of cylinder opening.

CYLINDER BORING – Bore diameter in a cylinder machined to accept oversize piston. This renews a worn cylinder.

CYLINDER DEGLAZING – Use of a hone to slightly roughen the cylinder walls. It produces a cross hatch pattern which aids in seating of new rings.

CYLINDER HEAD – The part that encloses the cylinder bores, used to cover tops of cylinders. Metal section bolted on top of block. It contains the water jackets, and on I head engines, the valves. Also forms part of combustion chamber.

CYLINDER HONE – An expandable rotating tool with abrasive fingers turned by an electric motor, used to clean and smooth the inside surface of a cylinder to exact measurements.

CYLINDER LEAKAGE TESTER – A type of cylinder tester that forces compressed air into the cylinder through the sparkplug hole when the valves are closed and the piston is at TDC on the compression stroke. The percentage of compressed air that leaks out is measured, and the source of leakage accurately pin points the defective part.

CYLINDER SLEEVE – A replaceable sleeve, or liner, put into the cylinder block to form the cylinder bore. It is either pressed or pushed into the cylinder block.

CALIPER – Instrument used for measuring distances between or over surfaces, or for comparing dimensions of workpiece with such standards as plug gauges, graduated rules etc.

CENTRE SQUARE – is intended for marking the centres of round or square stock.

CLINOMETER – Instrument used for measuring angles relative to the horizontal plane.

CAP SCREW – A finished screw, used for fastening two pieces together by passing the screw through a clearance hole in one part and screwing it into a tapped hole in the other. Heads may be hexagon, round, flat, fillister or socket type.

CARRIAGE – A principal part of lathe. The carriage carries the cutting tool and moves along the ways of the lathe. It contains the saddle, compound slide, and apron.

CARRIER – Tool for driving work which is held between centers, as in a lathe.

CATCH PLATE – Plate screwed to the nose of the lathe spindle for the purpose of driving work held between centers, through the medium of a carrier or driving dog.

CENTRE SQUARE – Device to enable the rapid location of the centre of the flat end of a cylindrical workpiece.

CHANGE GEARS – An assortment of gears which are supplied with a machine for changing speed ratio between driver and driven parts of the machine. Change gears on a lathe make it possible to cut threads of different pitches and obtain different feeds per revolution. On milling machines they are used to obtain different leads when milling spirals and helices.

CHUCK – Appliance for gripping tools, such as drills, or for holding work in a lathe.

CLAPPER BOX – A part of the shaper tool head that holds the tool post. A clapper block is hinged into the clapper box to permit the cutting tool to swing upward on the return stroke.

COLLET – Means of gripping a bar to give quicker chucking, particularly in capstan work for rapid and accurate setting.

CLAMP – Device for holding work during marking out, measuring, machining, fitting or grinding.

COMPOUND SLIDE – A principal part of a lathe, frequently called a COMPOUND REST, consisting of an upper and lower part dovetailed together. The lower part or base is graduated in degrees and can be swivelled to any angle for turning short tapers and angles. The upper slide carries the tool post and tool holder.

CONE PULLEY – A stepped pulley having two or more diameters and made in one piece.

CAM – A plate or cylinder which transmits variable motion to a part of a machine by means of a follower.

CAP SCREW – A finished screw 5mm or larger, used for fastening two pieces together by passing the screw through a clearance hole in one part and screwing in into a tapped hole in the other.

CENTER – A fixed point about which the radius of a circle or an arc moves.

CENTER LINE – A line used on drawings to show the centers of objects and holes. The center line consists of alternate long and short dashes.

CHAMFER – To bevel or remove the sharp edge of a machined part.

CHECK VALVE – A valve which permits flow in one direction only.

CIRCULAR PITCH – The distance from the center of one gear tooth to the center of the next gear tooth measured on the pitch line.

CIRCUMFERENCE – A curved line forming a circle and the length of this line.

COIL SPRING – A spring steel wire wound in a spiral pattern.

COMMUTATOR – A number of copper bars connected to the armature windings but insulated from each other and from the armature.

CONVOLUTION – One full turn of screw.

CORE – The central or innermost part of an object.

COUNTER BORING – The operation of enlarging a portion of a hole for part of its depth and to a given diameter, as for the head of a fillister head screw.

COUNTER SINK – To cut or shape a depression in an object so that the head of a screw may set flush or below the surface.

CREST CLEARANCE – Defined on a screw form as the space between the top of a thread and the root of its mating thread.

CREST OF SCREW THREAD – The top surface joining the two sides of flanks of a thread.

CROWNED – A slight curve in a surface e.g., on a roller or race way.

CAPSTAN LATHE – Lathe designed to use a number of cutting tools mounted on a rotating turret or capstan, and arranged to perform turning operations successively.

CENTRE LATHE – Machine for carrying out turning, boring, and screw cutting operations on a work held between centers or in a chuck, but not for repetition work.

CENTRIFUGAL GOVERNOR – A governor which uses fly weight force to sense speed in order to control the fuel supplied to the combustion chambers.

CENTRIFUGAL PUMP – A pump using the centrifugal force produced by a rapidly rotating impeller to displace liquid.

CENTRIFUGE – A device with a rapidly rotating bowl which separates the impurities of a fluid by intense centrifugal force.

CIRCUIT BREAKER (lighting system) – A device that opens the circuit when the current draw becomes excessive and closes when the current flow is reduced.

CIRCULATING PUMP – The term applied to cooling water/ lubricating oil pumps which effect circulation of fluid.

COMPRESSOR – A mechanical device to pump air, and thereby increase the pressure.

CONDENSER (electrical) – An arrangement of insulated conductors and dielectrics for the accumulation of an electric charge.

CUPOLA – Special type of blast furnace, chiefly used for the melting of cast iron.

CYLINDRICAL GRINDER – Grinding machine designed to true up and bring to size cylindrical parts such as shafts, spindles, rollers etc.

CANTILEVER RACKS – Racks supported only on one end, leaving the other end open for placing and removing the long bars, rods etc.

CAPSTAN DRUM – Equipment used for hoisting anchors on board ships, hauling various loads etc.

CAR PULLERS – Equipment used for shunting railroad cars at ports and docks.

CAROUSEL – A rotating or circulating storage device. The worker stays in one place while the needed item comes to the work station.

CHAIN CONVEYORS – Conveyors which employ chains of various designs as the driving traction element. Chain conveyors carry aprons, pans, buckets, cradles, pockets, cars etc.

CHOCKS – Supports used to keep boxes off the ground.

CHUTE – An inclined surface with sides for material movement by gravity.

COLD STORAGE WAREHOUSE – A warehouse used for storing highly perishable goods and foods.

CONTAINERIZATION – Transportation of freight in sealed portable containers.

CONVEYOR – A mechanism that moves material along a fixed path. A mechanical device for carrying packages or bulk material from place to place (as by an endless moving belt or a chain of receptacles).

COUNTER WEIGHTS – Weights provided on cranes to offset the dead weight of metal structure and, to a certain extent, the moment due to the hook load.

COVERED HOPPER – A freight car with a closed top designed to meet the needs of malt and grain shippers.

CRANE – A machine for raising, shifting and lowering heavy weights by means of projecting swinging arm or with the hoisting apparatus supported on an overhead track.

CRANE DERRICK – The distance between the loads centre of gravity and the axis about which crane boom can swing.

CRANE HELICOPTER – A crane hung from a helicopter, used as a means of moving loads and doing a variety of jobs in regions which are difficult of access, capable of descending vertically on the load and lifting it from the ground directly.

CRAWLER CRANE – A crane mounted on a crawler mounting, e.g., a frame supported by track laying assemblies which obtain the drive from an engine mounted on a rotating part of the crane.

CREEPING DRIVE UNIT – An arrangement frequently employed on electric hoists to obtain extra low spotting speeds.

CAVITATION – The formation and instantaneous collapse of innumerable tiny voids or cavities within a liquid subjected to rapid and intense pressure changes.

CEMENTATION – Process of introducing elements into the outer layer of metal objects by means of high temperature diffusion.

CEMENTITE – Iron carbide, Fe3C, a hard brittle, crystalline compound observed in the microstructure of iron base alloys.

CHAFING FATIGUE – Fatigue initiated in a surface damaged by rubbing against another body.

CHLORINATION – A refining or degasification process, wherein dry chlorine gas is passed through molten aluminium base and magnesium base alloys to remove entrapped oxides and dissolved gases.

CLEAVAGE – Splitting (fracture) of a crystal in a crystallographic plane of low index.

CLEAVAGE FRACTURE – A fracture, usually of a polycrystalline metal, in which most of the grains have failed by cleavage, resulting in bright reflecting facets. It is one type of crystalline fracture.

CLEAVAGE PLANE – A characteristic crystallographic plane or set of planes on which cleavage fracture easily occurs.

COALESCENCE – The union of particles of a dispersed phase into larger units usually effected at temperatures below fusion point.

COHESIVE STRENGTH – (1) The hypothetical stress in an unnotched bar causing tensile fracture without plastic deformation. (2) The stress corresponding to the forces between atoms.

COLD SHORT – A condition of brittleness existing in some metals at temperatures below the recrystallisation temperature.

COLD SHUT – (1) A discontinuity that appears on the surface of cast metal as a result of two streams of liquid meeting and failing to unite. (2) A portion of the surface of a forging that is separated, in part, from the main body of metal by oxide.

COLUMNAR STRUCTURE – A coarse structure of parallel columns of grains having the long axis perpendicular to the casting surface.

COMPLETE FUSION – Fusion which has occurred over the entire base metal surfaces exposed for welding.

COMPOUND – A combination of two or more elements that are mixed together.

COMPRESSIBILITY – The property of a substance (e.g., air) by virtue of which its density increases with increase in pressure.

COMPRESSIVE STRENGTH (ultimate) – The maximum stress that can be applied to a brittle material in compression without fracture.

COMPRESSIVE STRENGTH (yield) – The maximum stress that can be applied to a metal in compression without permanent deformation.

COMPRESSIVE STRESS – Compressive stress is compression load per unit area perpendicular to the load.

CONDUCTIVITY – The quality or power of conducting or transmitting heat, electricity etc.

CONGRUENT TRANSFORMATION – An isothermal or isobaric phase change in which both of the phases concerned have the same composition throughout the process.

COOLING STRESSES – Residual stresses resulting from non-uniform distribution of temperature during cooling.

CORROSION – The destructive chemical or electro-chemical reaction of a material and its environment, usually associated only with metals in contact with liquids.

CORROSION EMBRITTLEMENT – The severe loss of ductility of a metal resulting from corrosive attack, usually inter-granular and often not visually apparent.

CORROSION FATIGUE – Effect of the application of repeated or fluctuating stresses in a corrosive environment characterized by shorter life than would be encountered as a result of either the repeated or fluctuating stresses alone or the corrosive environment alone.

COUPON – A piece of metal from which a test specimen is to be prepared, often an extra piece as on a casting or forging.

COVALENT BOND – A bond between two or more atoms resulting from the completion of shells by the sharing of electrons.

CRAZING – Minute surface cracks on the surface of materials often caused by thermal shock.

CREEP – Slow plastic deformation in steel and most structural metals caused by prolonged stress under the yield point at elevated temperatures.

CREEP LIMIT – (1) The maximum stress that will cause less than a specified quantity of creep in a given time. (2) The maximum nominal stress under which the creep strain rate decreases continuously with the time under constant load and at constant temperature. Sometimes called CREEP STRENGTH.

CRITICAL POINT – The temperature or pressure at which a change in crystal structure, phase, or physical properties occur.

CRYSTALLIZATION – Act or process of forming crystals or bodies formed by elements or compounds solidifying so that they are bounded by plane surfaces.

CRYSTAL UNIT STRUCTURE OR UNIT CELL – The simplest polyhedron that embodies all the structural characteristics of a crystal and makes up the lattice of a crystal by indefinite repetition.

CURIE TEMPERATURE – The temperature of magnetic transformation below which a metal or alloy is magnetic and above which it is paramagnetic.

CAM – A reciprocating, oscillating or rotating body which imparts reciprocating or oscillating motion to a second body, called the FOLLOWER with which it is in contact.

CALCIUM CHLORIDE – A chemical having the formula CaCl₂ which is in granular form is used as drier. Soluble in water.

CALCIUM SULPHATE – A solid chemical of the formula CaSO4 which may be used as a drying agent.

CAPACITY – In a refrigerating machine, it is the heat absorbing capacity per unit time, usually measured in ton or kcal/hr.

CAPILLARY – A tube with a very small inside diameter, its diameter and length control the flow of the refrigerant; dividing point between the high side and the low side of the system.

CARBON – One of the elements used in refrigeration.

CARBONDIOXIDE – One of the earliest compounds used as a refrigerant.

CARBON TETRA CHLORIDE – A liquid having the formula CCl₄ (also known as carbona) which is non -inflammable solvent used for removing grease and oil and loosening sludges.

CENTRIFUGAL COMPRESSOR – A compressor in which the necessary increase in the pressure of the refrigerant vapour being obtained by imparting a high velocity to it by the rotation of an impeller.

CHANGE OF STATE – A change from one state to another as from liquid to solid, from liquid to gas etc.

CHARGE – The amount of refrigerant in a system.

CHARGING CYLINDER – A cylindrical container for refrigerant that has a calibrated sight glass so that the mechanic can measure the flow of refrigerant into the air conditioning system.

CHLORINATED FLUORO CARBON – The chemical family into which air conditioning refrigerants such as refrigerant 12 fall.

CIRCUITS – The flow of a refrigerant through separate rows of tubes rather than through one single tube.

CLEARANCE VOLUME EFFICIENCY – Ratio of the weight of the refrigerant circulated by a compressor having no losses except that due to clearance, to the weight circulated by a perfect machine.

CLOSED SYSTEM – Chilled water from the flash tank is pumped through a coil to cool air and is then returned to the flash tank.

COEFFICIENT OF PERFORMANCE – The ratio of the refrigerating effect to the heat equivalent of the indicated horse power of the refrigerant compressor.

COIL – Any cooling element made of pipe or tubing.

COLD STORAGE – A trade or process of preserving perishables on a large scale by refrigeration.

COMFORT CHART – A psychrometric chart; strictly a chart showing the effective temperatures.

COMPOUND COMPRESSION – In compound or multistage compression, the refrigerant is compressed through part of the pressure range in one compressor (or in one stage of a multistage compressor) and then passed to a second compressor, or stage, of smaller swept volume, which carries the compression further.

COMPOUND GAUGE – A typical low pressure test gauge, which has a scale that indicates both pressure and vacuum.

COMPRESSOR – A device that takes a refrigerant vapour at a low temperature and pressure and compresses it to a lower volume and thereby raises it to higher temperature and pressure.

COMPRESSOR CRANKSHAFT SEALS – Prevent air from entering the compressor, and oil and refrigerant from escaping.

COMPRESSION RATIO – The ratio of two pressures, the absolute discharge pressure divided by the absolute suction pressure.

COMPRESSION SYSTEM – A refrigerating system in which the pressure imposing element is mechanically operated.

CONCENTRATORS – Evaporate excess water from brine which has been diluted by melted ice and frost.

CONDENSATION – Process by which a vapour is changed into a liquid without changing temperature. Condenses the hot, high pressure refrigerant vapour from the compressor to a warm, high pressure liquid which flows to the receiver dehydrator.

CONDENSER (general) – That part of the refrigeration system in which the refrigerant condenses and in so doing gives off heat.

CONDENSER DUTY – Amount of heat transferred in a given time from the refrigerant to the cooling medium in the condenser.

CONSTANT PRESSURE VALVE – An automatic expansion valve that holds the pressure at a constant level regardless of the load.

CONSTANT TEMPERATURE VALVE – A valve responsive to temperature of thermostatic bulb, of the throttling type, located in suction line of an evaporator to reduce refrigerating effect on coil to just maintain a desired temperature.

CONTAINER CAPACITY – The ability of a container to hold the material the quantity of material which may safely be contained in a container.

COOLING UNIT – A specific air treating combination consisting of means for air circulation and cooling within the prescribed temperature limits.

COOLING WATER – Water used for condensation of the refrigerant.

COPPER PLATING – Formation of a film of copper usually on compressor walls, pistons or discharge valves.

CRYOGENICS – Science of producing and applying temperature below –250° F.

CRYOGENIC SUPER CONDUCTOR SYSTEM – Uses helium to cool conductors to within a few degrees of absolute zero where they offer no electrical resistance.

CRYOHYDRATE – A eutectic brine mixture of water and any salt, mixed in proportions to give the lowest temperature.

CYCLE OF REFRIGERATION – A complex course of operation of a refrigerant back to the starting point, measured in thermodynamic terms, also used in general for any repeated process for any system.

CYCLING CLUTCH CONTROL SYSTEM – One in which the compressor is run intermittently to maintain a desired temperature.

CAM PROFILE – The surface profile of the cam that decides the desired motion of the follower.

CENTRIFUGAL FORCE – Radial outward force acting on a body moving along a circular path with uniform velocity.

CENTRIFUGAL GOVERNOR – The effort of the governor is obtained from the change in centrifugal force on (usually) two rotating masses, known as balls, when an increase or decrease in the governor speed occurs.

CENTRIPETAL FORCE – The force that must act radially inward in order to constrain a particle to follow a curved path at uniform velocity.

CIRCULAR PITCH – Length of arc round the pitch circle between the corresponding points on adjacent teeth of a gear.

COMPLEX MECHANISMS – Mechanisms which have two or more floating links.

COMPOSITION OF VECTORS – Composition refers to the adding together of any number of vectors. The sum is called their resultant and the vectors are called the components of the resultant.

COMPOUND CHAIN – A kinematic chain in which there are more than four pairs.

COMPOUND GEAR TRAIN – A gear train containing compound gears i.e., gears, two or more in number integral with one another being used on the same shaft.

COMPOUND PENDULUM – A rigid body suspended vertically so as to oscillate with small amplitude under the action of gravity.

CONSERVATION OF ENERGY – The total energy possessed by a system of moving bodies is at every instant constant, provided no energy is rejected to or received from a source external to the system.

CONSERVATION OF MOMENTUM – For a system of moving bodies which is not acted upon by any external forces, the sum of the moments remain constant.

CONTROLLING FORCE OF A GOVERNOR – The inward radial force exerted on each ball of a centrifugal governor by the arms, springs etc., which are attached to it.

CURVILINEAR MOTION – A translation in which points in the body move along curved path (motion of a wheel).

CYCLE OF MOTION – Motion of a mechanism when it moves through all its possible configurations and returns to its starting position. The time required for one cycle is called PERIOD.

CYCLOIDAL TEETH – Profile of the teeth formed by the locus of a point on a circle rolling on the inside (for the flank) and on the outside (for the face) of the pitch circle.

CYLINDRICAL CAM – Type of cam in which the motion of the follower is controlled by a path traced out on the surface of a cylinder which is rotating about its axis.

CAM ANGLE (ignition) – Number of degrees breaker cam rotates from the time breaker points close until they open again. Also called DWELL ANGLE.

CAPACITOR DISCHARGE IGNITION (CDI) – An electronic ignition system designed to produce very high voltage, consisting of an exciter coil, a capacitor, diode, trigger coil, silicon controlled rectifier and ac ignition coil.

CARBURETION – The actions that take place in the carburettor, converting liquid fuel to vapour and mixing it with air to form a combustible mixture.

CARBURETTOR – The mixing device in the fuel system which meters and mixes gasoline into the air stream (vaporizing gasoline as it does so) in varying proportions to suit engine operating conditions.

CARBURETTOR ADAPTER – Adapter used to fit or place one type of carburettor on an intake manifold that may not be originally designed for it.

CARBURETTOR CIRCUITS – Series of passages and units designed to perform a specific functions—idle circuit, full power circuit etc.

CARBURETTOR ICING – Formation of ice on throttle plate or valve. As fuel nozzles feed fuel into air horn it turns to a vapour. This robs heat from air. When weather conditions are just right (fairly cold and quite humid) ice may form.

CARBURETTOR INSULATOR – A spacer, or insulator, used to prevent excess engine heat from reaching the carburettor.

CENTRIFUGAL ADVANCE (distributor) – Unit designed to advance and retard ignition timing through action of centrifugal force resulting from changes in engine speed.

CHOKE – Near the top of the carburettor, a butterfly valve that is closed when starting a cold engine. It chokes off the air flow through the air horn, producing a partial vacuum in the air horn for greater fuel delivery and a richer mixture supply to the engine.

CHOKE STOVE – Heating compartment in or on the exhaust manifold from which hot air is drawn to the automatic choke device.

COIL (ignition) – Unit used to step up the relatively low voltage supplied by the battery to the extent necessary to create a spark across the spark plug terminals.

COIL BUILDUP – Build up of a magnetic field while current is flowing through primary windings of the coil.

COLD PLUG – has a shorter heat path. Hence it runs at a much lower temperature than a hot plug.

COMBUSTION LAG TIME – A period of slow burning that occurs before the burning of the air fuel mixture, which spreads throughout the engine combustion chamber.

CONDENSER (ignition) – Unit installed between breaker points and coil to prevent arcing at breaker points. Condenser absorbs and retains momentary surge of current when the breaker points open.

CONSTANT CHOKE CARBURETTOR – is the carburettor in which the air and fuel flow passages (i.e., areas) are always maintained to be constant. But the pressure difference or depression which causes the flow of fuel is being varied as per the demand on the engine.

CONSTANT VACUUM CARBURETTOR – is the carburettor in which the air and fuel flow areas are being varied as per the demand on the engine, while the depression or vacuum is maintained to be always same.

CONTACT POINTS – In the conventional ignition system, the stationary and the movable points in the primary circuit, usually made of tungsten, platinum or silver. Also called BREAKER POINTS.

CONVENTIONAL IGNITION – Ignition system which uses breaker points.

CRITICAL COMPRESSION RATIO – The lowest compression ratio at which any particular fuel air mixture will ignite by compression under prescribed test procedure. The lower the critical compression ratio, the better ignition qualities the fuel has (Gasoline engine 4 :1, oil engine 7 :1 diesel engine 12.5 :1).

CARRY OVER – It is entrained moisture and associated solids passing from a boiler with the steam.

CAULKING – Upsetting or burring up of the edge of the plate or strap after riveting so as to make the edges press down tightly on the plate beneath and thus form a water and steam tight joint.

CHECK VALVE – A form of non return valve used to control the flow of water as in pump operation.

CHIMNEY – A tall, hollow cylindrical column built of steel, brick or concrete used to produce the required natural draft effect.

CHIMNEY EFFECT – The upward movement of warm air or gas, compared with ambient air or gas, due to the lesser density of the warm air or gas. Chimney effect may be a cause of uneven heating in buildings two or more stories high.

CLEANING THE FIRE – Operation of removing clinkers, etc., from the burning coal at regular intervals.

CLOSED HEATER – A type of heater in which the steam and feed water are separated by a metal surface.

CLYDE BOILER – A boiler similar to a scotch boiler, but instead of a water space at the back end of the combustion chamber, a removable back which is lined with some insulating material such as asbestos or fire tile, is existing.

COCK – A device for regulating the flow of fluids through a pipe.

COLLECTOR or DRY PIPE – A pipe placed inside a boiler at a high point and having small perforations throughout its length so as to take off steam at a multiplicity of points and thus avoid turbulence caused by taking off steam at only one point.

CORROSION – Chemical action which causes destruction of the surface of a metal by oxidation, rusting. It is an electrochemical attack.

CARRY-OVER LOSS – Loss of kinetic energy at the exit of the turbine. Also called LEAVING LOSS.

CHOKED FLOW – When a nozzle operates with the maximum mass flow it is said to the choked.

COMPOUND TURBINE – A multistage steam turbine in which the pressure energy of the steam is progressively transformed into kinetic energy in two or more stages with or without velocity compounding in each stage.

COMPOUND STEAM ENGINE – An engine which has two or more cylinders of successively increasing diameters, so arranged that the exhaust steam from the first cylinder (high pressure cylinder) is passed on to do work in the second cylinder (low pressure cylinder), and to a third cylinder in triple expansion engine, before being finally exhausted into a condenser.

CONDENSER – A vessel into which steam is exhausted and condensed instead of being rejected into the atmosphere after doing work in an engine cylinder or turbine. This is primarily for removing the back pressure upon an engine or turbine and thereby improve the plant efficiency.

CONDENSING CYCLE – A steam power plant cycle in which the exhaust steam is discharged into a condenser having a low back pressure, so that more energy can be extracted per unit weight of steam.

CONSTANT VELOCITY FLOW – Type of flow that takes place in parallel ducts.

COOLING POND – A shallow reservoir having a large surface area for removing heat from the cooling water used to condense steam in condensers.

COOLING TOWER – An apparatus designed to remove from the cooling water, used in a condenser, as much heat as can possibly be abstracted per unit space occupied by the apparatus.

COUNTERFLOW STEAM ENGINE – The engine in which the steam leaves the cylinder at the same end at which it entered.

CRITICAL PRESSURE OF NOZZLE – The pressure at which the velocity of the fluid equals the local sound velocity.

CRITICAL PRESSURE RATIO – Ratio of critical pressure of nozzle to the initial pressure.

CRITICAL SPEED OF A SHAFT – The speed at which the shaft displacement tends to be very large, and the shaft may become permanently bent.

CUSHION STEAM – The steam present in the cylinder during compression which occurs just after the exhausting of steam by the inward movement of the piston.

CUTOFF GOVERNING – Control of engine speed is accomplished by changing the volume of steam admitted to an engine cylinder as the load fluctuates. The points of steam cut off comes early in the stroke of the engine piston with light loads and later when they increase.

CALORIE – The heat per unit weight, one gram, required to raise the temperature of water through one degree centigrade.

CELSIUS – The scale of changes of temperature which uses 0 degree as the freezing point and 100 degree as the boiling point for water at standard pressure.

CHARLE’S LAW – At constant pressure, the volume of a gas is proportional to its absolute temperature. At constant volume, the pressure is proportional to its absolute temperature.

CLOSED SYSTEM – The system which will have boundaries across which both heat and work can penetrate, but no mass will be permitted to cross them.

Cp – Specific heat at constant pressure-Heat to be supplied to raise the temperature of 1 kg of gas through 1°C, the pressure being kept constant (in other words external work is done).

Cv – Specific heat at constant volume-Heat to be supplied to raise the temperature of 1 kg of gas through 1°C, the volume being kept constant (in other words no external work is done).

COEFFICIENT OF EXPANSION – The fractional increase in length or volume per degree rise in temperature.

COEFFICIENT OF LINEAR EXPANSION – Amount of expansion per unit length, per degree rise in temperature.

COEFFICIENT OF PERFORMANCE OF A HEAT PUMP – COPHP = Heat added to the hot body/work supplied.

COEFFICIENT OF PERFORMANCE OF A REFRIGERATOR – COPRef = Heat removed from cold body/work supplied.

COEFFICIENT OF THERMAL CONDUCTIVITY – The quantity of heat that will flow across a unit area in unit time if the temperature gradient across this area is unity.

COLD – A comparative lack of heat, indicating chillness.

COMPRESSED SOLID – is a solid at a temperature below its saturation temperature.

COMPRESSIBILITY FACTOR, Z – is the factor introduced to modify the ideal gas equation Pv = RT, and to describe the behaviour of a real gas. Z = Pv/RT.

CONDENSATE – The liquid formed by the condensation of a gaseous substance.

CONDENSATION – The change of state of a substance from the gaseous to the liquid form.

CONDENSING – The process of giving up latent heat of vaporization in order to liquefy a vapour.

CONDUCTION – Transfer of heat from one part of a material to another or to a material with which it is in contact.

CONDUCTIVITY – The relative value of a material, as compared with a standard, in affording a passage through itself or over its surface for heat.

CONSTANT VOLUME PROCESS – is one wherein a gas is heated (or cooled) in a fixed enclosed space (no change in volume occupied by the gas). There will be no workdone by the gas. The whole heat supplied will be stored in the form of internal energy.

CONSTANT PRESSURE PROCESS – Also called isobaric process. Heat supplied to a system exhibits as the change in enthalpy.

CONSTANT TEMPERATURE PROCESS – Also called isothermal process. There is no change in temperature and hence internal energy and enthalpy remain constant. Heat supplied = work done.

CONVECTION – Passage of heat from one point to another by means of a gravity fluid circulation due to changes in density resulting from picking up and giving up heat. Also transfer of heat to or from a fluid (liquid or gas) flowing over the surface of a body.

COSMIC RADIATION – Radiation of many sorts, but mostly atomic nuclei (protons) with very high energies, originating outside the earth’s atmosphere.

COUNTER FLOW HEAT EXCHANGER – A heat exchanger in which the warm substance flows in the opposite direction to the flow of the cool substance.

CRITICAL STATE OF A SUBSTANCE – is that state at which liquid and vapour coexist in equilibrium. At critical state, latent heat of evaporation becomes zero.

CRITICAL PRESSURE – The critical pressure of a vapour is the pressure required to liquefy it at the critical temperature and is the highest pressure on the temperature -pressure graph for saturated vapour.

CRITICAL TEMPERATURE – Temperature of the vapour above which no pressure, however high, will produce liquefaction.

CRITICAL VELOCITY – The velocity above which fluid flow is turbulent.

CYCLIC PROCESS – is a process (or a series of processes) which returns the system to the state it was before the process began.

CAST ALLOY WHEEL – A one piece wheel made of cast aluminium or magnesium alloy. This design is more rigid than the wire spoked wheel.

CENTRIFUGAL CLUTCH – Clutch engaged by centrifugal force as engine speeds up.

CHAIN DRIVE – Use of a chain and sprockets to connect gear box output shaft to rear wheel.

CHAIN STRETCH – Wear of pins and bushings of a roller or hypo chain, causing the chain to lengthen.

CHAMFER – To bevel an edge of an object or to chamfer edges of port openings in a two stroke cycle cylinder to prevent piston ring breakage.

CLOSE RATIO GEAR BOX – A gearbox with gear ratios spaced close together.

CLUTCH – Device used to connect and disconnect engine power to gearbox input shaft.

CLUTCH BASKET – Part of clutch assembly containing drive plates. Primary drive gear engages teeth on the outside of the clutch basket.

CLUTCH HUB – Part of the clutch that engages with plain driven clutch plates. Clutch hub is mounted on the gearbox input shaft.

CLUTCH PRESSURE PLATE – Part of a clutch assembly providing pressure against the clutch disc or clutch plates.

CLUTCH RELEASE MECHANISM – Mechanism that moves the clutch pressure plate away from the clutch pack allowing the clutch to slip.

CONICAL HUB – A wheel hub (wire wheel) with spoke holes on the brake side of a wheel at a greater distance from the center of the hub than spoke holes on the opposite side of the hub.

CONVENTIONAL REAR SUSPENSION – Suspension used on dual purpose and road bikes which provide less than 152 mm of suspension travel.

COUNTERSHAFT SPROCKET – Output sprocket from gearbox. Mounted on output shaft in indirect drive gearbox and on high gear pinion in direct drive gear box.

CRADLE FRAME – Frame built of tubing which supports and surrounds the engine.

CRANKSHAFT AXLES – Extension at each end of the crankshaft to provide a mounting place for the main bearings, primary drive gear or sprocket, and alternator rotor or magneto flywheel.

CURB WEIGHT – The weight of a vehicle without passengers or payload, but including all fluids (oil, gas, coolant etc.) and other equipment specified as standard.

CARBON ARC CUTTING – Cutting of base metals by melting them with the heat of an arc produced between a carbon electrode and the base metal.

CARBON ELECTRODE – A non-filler metal electrode used in arc welding or cutting, consisting of a carbon or graphite rod, which may be coated with copper or other coatings.

CARBON ARC WELDING – A brazing process that produces coalescence of metals by heating them with an electric arc produced between two carbon electrodes. The filler material is distributed in the joint by capillary action.

COLD WELDING – A solid state welding process in which pressure is applied at room temperature to produce coalescence of metals with substantial deformation at the weld.

COMPOSITE ELECTRODE – Multi component filler metal electrodes in various physical forms such as standard wires, tubes and covered wire.

CONTINUOUS WELD – A weld that extends continuously from one end of a joint to the other.

COVERED ELECTRODE – An electrode consisting of a core of a bare electrode or metal cored electrode to which a covering, sufficient to provide a slag layer on the weld metal, has been applied.

COVER PLATE (eye protection) – A removable pane of colourless glass, plastic coated glass or plastic that covers the filter plate and protects it from weld spatter, pitting or scratching when used in a helmet, hood or goggles.

CRATER – A depression at the termination of a weld bead.

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