Important Terms and their Meaning of Mechanical Engineering- Friction and Bearings:
ABSOLUTE
VISCOSITY – Force per unit area required to move a surface at unit
velocity, when it is separated by a fluid of unit thickness from a stationary
surface.
ADDITIVES
– Chemical compounds used to alter the characteristics of lubricating oils.
ANGLE OF
REPOSE – The minimum inclination which a plane can have consistent with the
body on it sliding down the plane by the force of gravity. It is the same as
the friction angle.
ANTI
CORROSION ADDITIVES – Chemical compounds added to lubricating oil to reduce
or prevent the chemical reaction of acids (formed by the oxidation of oil)
which destroy some bearing materials, such as lead in lead copper bearings,
used for crankshafts and connecting rods of engines.
ANTI
OXIDATION ADDITIVES – Chemical compounds added to decrease oxidation of the
oil. These have a greater affinity for oxygen than does the oil.
API HEAVY
DUTY TYPE OIL – Motor oil having oxidation stability, bearing corrosion
preventive properties, and detergent-dispersant characteristics necessary to
make it generally suitable for use in both high speed diesel and gasoline
engines under heavy duty service conditions.
API
PREMIUM TYPE OIL – Motor oil having the oxidation stability and bearing
corrosion preventive properties necessary to make it generally suitable for use
in internal combustion engines where operating conditions are more severe than
regular duty.
API
REGULAR TYPE OIL – Motor oil generally suitable for use in internal combustion
engines under moderate operating conditions.
BALL
BEARING – An antifriction bearing where the rolling elements are spherically
shaped. Bearing consists of an inner and outer hardened steel races separated
by a series of hardened steel balls.
BATH
LUBRICATION – Lubrication system in which the bearing contains a space
filled with oil, which is in contact with a portion of the journal.
BEARING –
The part which transmits the load to the support and in so doing, takes the
friction caused by the moving parts in contact. Area of the unit in which the
contacting surface of a revolving part rests.
BEARING
CAPS – On an engine, caps held in place by bolts or nuts which, in turn, hold
bearing halves in place.
BEARING
CRUSH – The additional height over a full half which is purposely manufactured
in each bearing half. This ensures complete contact of the bearing back with
the housing bore when the unit is assembled.
BEARING
FAILURE – Failure of a bearing due to continued flexing of the bearing
surface from the applied load.
BEARING
OIL CLEARANCE – The space purposely provided between the revolving shaft
and the bearing in which it rotates. Through this space lubricating oil can
flow.
BEARING
PRELOAD – Amount of static pressure exerted on a bearing or a set of
bearings. Preload is usually adjusted by a threaded collar or shims.
BEARING
PRELUBRICATOR – A special tank attached to an airline which supplies oil at
a predetermined and maintained pressure to the engine lubricating system when
the engine is not operating.
BEARING
SPACER – A piece of tubing used between the two wheel bearing inner races
to prevent unwanted bearing preload as the axle is tightened.
BEARING SPIN
– A type of bearing failure caused by lack of lubrication which overheats
the bearing while the crankshaft is still in place.
BEARING
SPREAD – A purposely manufactured small extra distance across the parting
faces of the bearing half in excess of the actual diameter of the housing bore.
BYPASS
FILTER – An oil filter that constantly only filters a portion of the oil
flowing through the engine or machine.
BOUNDARY
FRICTION – The resistance to relative motion when one solid surface is
caused to move tangentially over another, the surfaces being covered only by an
adsorbed contamination film.
BOUNDARY
LUBRICATION – Type of lubrication in which the two surfaces have between
them a more or less complete layer of oil which is only, at the most, a few molecules
thick.
BUSHING –
A member that takes up space and usually allows movement at the attachment
point. A one piece replaceable sleeve placed in a bore to serve as a bearing
surface. Bearing for shaft, spring shackle, piston pin etc. A metallic or synthetic
lining for a hole.
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.
DETERGENTS
– Added to lubricating oils to improve the tendency of the oil to wash or
cleanse the surface where oxidation products form, thereby resulting in a
marked reduction in ring sticking, particularly in heavy duty service, and a
marked improvement in cleanliness of pistons.
DETERGENT
OIL – An oil which keeps particles and contaminants in suspension and has
ability to neutralize acids resulting from combustion process.
DIRECT
BEARING LUBRICATION – An oil injection system which feeds undiluted oil to
two stroke cycle engine main bearings and rod big end bearings.
DRY
SUMP-LUBRICATION – In this system, oil is gravity fed to supply side of oil
pump from the remote oil tank. After the oil has been pumped through four
stroke cycle engine, it is returned to the oil tank by return side of oil pump.
FILM
LUBRICATION – Type of lubrication in which the two metallic surfaces are
separated by a continuous film of liquid oil of measurable thickness which
forces itself between them.
FIRE
POINT OF OIL – The temperature at which the oil vapour on the oil surface
ignites and burns for at least five seconds, when heated gradually, under
specified test conditions.
FLASH
POINT OF OIL – The temperature at which a momentary flash appears on the
heated oil surface when a test flame is applied, under specified test
conditions. It is a rough indication of the tendency of the oil to vaporize.
FOOT STEP
BEARING – The bearing at the foot of a vertical shaft.
FORCE
FEED LUBRICATION – A gear pump takes oil from the sump and delivers it to
the distributor ducts which connect with all the main bearings and camshaft
bearings, from where the oil reaches the various parts that need lubrication.
FORCE OF
FRICTION – The least force acting parallel to the sliding surfaces of the
bodies in contact, which will cause one body to slide over the other.
FRICTION –
The force which acts between two bodies at their surface of contact so as to
resist their sliding on each other, due to roughness of the surfaces. Also
called FRICTIONAL FORCES.
FRICTION
ANGLE – Angle which the resultant force makes with the normal to the plane
when sliding begins. Also called LIMITING ANGLE OF RESISTANCE or LIMITING ANGLE
OF REACTION.
FRICTION
BEARINGS – Bearings having sliding contact between the moving surfaces.
Sleeve bearings, such as those used in connecting rods, are friction bearings.
GEAR OIL
PUMP – An oil pump with gear type teeth to move oil.
GREASE –
The term is applied to a mixture of mineral oil with fats that have been
saponified with an alkali. To this mixture fillers may or may not be added.
HYDRODYNAMIC
LUBRICATION – A condition that occurs when a film of oil is constantly
maintained between moving parts.
INNER
RACE – In a bearing assembly, the part that connects a rotating shaft to
the bearing.
JOURNAL –
In a shaft, the hardened polished area that is used with a bearing.
LAWS OF
FRICTION – The force of friction is (1) directly proportional to the pressure
between the surfaces in contact, (2) independent of the extent of the surfaces
in contact and (3) independent of the velocity of sliding.
LOAD
MOTION – Rolling or sliding motion found at the bearing surfaces.
LUBRICANT
– A fluid having two essential properties namely viscosity and oiliness,
and used to reduce friction.
LUBRICATING
FILM – A thin coating of lubricant (oil) which prevents contact between
moving parts.
LUBRICATING
SYSTEM – The system in the engine that supplies lubricating oil to the moving
engine parts, to prevent actual contact between the moving surfaces.
LUBRICATION
– Use of lubricant (oil or grease) to reduce friction.
MAIN
BEARINGS – In the engine block, the bearings that support the crankshaft.
MICHELL
THRUST BEARING – Type of tilting pad thrust bearing, the thrust supporting
surface is divided into a number of segmental pads, which pivot on a radial
edge at the back, and so automatically adjust themselves to the required slope.
MULTIGRADE
OIL – An oil that retains its viscosity under varying temperature
conditions better than a single weight oil.
ML OIL –
Oil for light automotive service.
MM OIL –
Oil for medium or average automotive service.
MS OIL –
Oil for severe automotive service.
MULTI
WEIGHT OIL – Type of oil that provides adequate lubrication at both high
and low temperatures.
MULTIPLE
VISCOSITY OIL – An engine oil which has a low viscosity when cold (for
easier cranking and a higher) viscosity when hot (to provide adequate
lubrication).
NEEDLE
BEARING – Antifriction bearing of the roller type, the rollers are very
small in diameter (needle sized). Rollers have a length over four times greater
than their diameter.
NEEDLE
LUBRICATOR – A needle which rests on a journal and exposed at top to the
oil in an inverted glass bottle or reservoir, causes oil to flow slowly onto
the journal, due to the vibration set up during shaft rotation.
OIL –
A liquid lubricant derived from crude oil used to provide lubrication between
moving parts.
OIL
CLEANER – The filtering device through which oil passes, which filters dirt
and dust from the oil.
OIL
CONSUMPTION – Oil pumped into the combustion chamber of an engine by the
piston and rings and burnt there in a given time.
OIL
CONTROL RINGS – The lower ring or rings on the piston of an engine,
designed to prevent excessive amounts of oil from working up into the
combustion chamber.
OIL
COOLER – A small radiator through which the oil flows to lower its temperature.
OIL
DILUTION – Dilution of oil in the crankcase of a SI engine, by leakage of
liquid gasoline from the combustion chamber past the piston rings.
OIL
FILTER – Unit in the lubrication system through which oil passes to remove
any impurities from oil. It may be paper, wire screen or rotor designed to keep
oil clean.
OIL LEVEL
INDICATOR – The indicator usually called the dipstick, that can be removed
to determine the level of oil in the crankcase of an engine or machine.
OIL PAN –
The detachable lower part of the engine made of sheet metal, which encloses the
crankcase and acts as an oil reservoir.
OIL
PASSAGES – Holes and passages drilled in the block and in the engine parts
through which oil flows.
OIL
PRESSURE GAUGE – An instrument used to measure and indicate the amount of
oil pressure in the lubrication system.
OIL PUMP –
In the lubricating system, the device that delivers oil from the oil pan to the
various moving engine/machine parts.
OIL PUMP
BLEEDING – Removal of air from the supply line and the pump in a two stroke
cycle oil injection system.
OIL PUMPING
– Passing of oil past the piston rings into the combustion chamber because
of defective rings, worn cylinder walls etc.
OIL
RESERVOIR – That space in the base of the oil separator where oil is accumulated
prior to its return to the pump.
OIL SEAL –
A seal placed around a rotating shaft or other moving part, to prevent passage
or escape of oil.
OIL SEAL
AND SHIELD – Two devices used to control oil leakage past the valve stem
and guide into the ports or the combustion chamber.
OIL SPILL
RING – Collars or oil throw rings put on the rotating shaft, prevent oil
leakage along the shaft, utilizing the increase of centrifugal force with the
increase of diameter.
OIL
STRAINER – A wire mesh screen placed at the inlet end of the oil pump
pickup tube to prevent dirt and other large particle from entering the oil
pump.
OUTER
RACE – In a roller/ball bearing assembly, the stationary part that supports
the rotating load on the bearing.
OXIDIZED
OIL – Oil that has been chemically combined with oxygen as a result of
excessive heat, oil agitation, and exposure to combustion contaminants.
PAD
LUBRICATION – A part of the bearing surface upon which there is no pressure
is dispensed with, and its place is taken by a soft pad, which is kept
saturated with lubricant.
PICKUP
SCREEN – A screen in the oil pan that prevents any large particles from
entering the oil pump.
PIVOT
BEARING – Pivot portion (flat or conical) which is on the end of a shaft,
that takes up the thrust produced along the axis of the shaft.
PLAIN BEARING
– A one or two piece assembly consisting of a hard metal backing piece with
a softer metal mated to it.
PLUNGER
OIL PUMP – An oil pump that uses a piston or plunger and check valves to
move oil.
POUR
POINT OF OIL – The temperature at which the oil will not flow when cooled
under specified conditions, due to formation of wax.
PREMIX –
Two stroke cycle engine lubrication is provided by oil, mixed with fuel in the
fuel tank.
PRESSURE
RELIEF VALVE – A spring loaded valve used to regulate the pressure in the
lubrication system.
PRESSURIZED
FEED OIL SYSTEM – A type of engine lubricating system that makes use of an
oil pump to force oil through tubes and passages to the various engine parts
requiring lubrication.
PROFILOMETER
– Instrument used to measure the surface irregularities.
RING
LUBRICATION – Two loose rings carried by the journal rotation, being driven
by frictional contact with the journal, dip into an oil bath and carry oil to
the top of the journal so as to flow over the surface of the journal through
oil grooves in the bearing, and finally return to the bath below.
ROLLER
BEARING – An antifriction bearing consisting of hardened steel inner and
outer races, separated by hardened steel rollers, which are two or three times
as wide as their diameter.
ROLLING
FRICTION – The force resisting the motion when a body rolls on a surface.
ROTARY
OIL PUMP – An oil pump which uses an inner and outer rotor to move oil.
SCHIELE’S
PIVOT – A pivot bearing on a shaft, designed to give uniform wear in the
direction of the axis with uniform pressure, the coefficient of friction being
assumed to be constant.
SCRAPER
RING – A piston ring that assists in compression and wipes off the excess
oil from the cylinder walls.
SEAL –
A material, shaped around a shaft, used to close off the operating compartment
of the shaft, preventing oil leakage.
SEIZING –
The phenomenon in which the metal surfaces adhere and then tear owing to
relative motion, caused by the attraction between molecules on opposite sides
of the common surface between two elements of a bearing.
SERVICE
RATING – For lubricating oils used in engines, a designation that indicates
the type of service for which the oil is best suited.
SHIM
(bearing) – A strip of copper or similar material used under a bearing cap,
for example, to increase bearing clearance.
SKIMMING –
Using a machine to remove oil or scum from the surface of the water.
SLUDGE –
Accumulation in oil pan, containing water, dirt and oil, sludge is very viscous
and tends to prevent lubrication.
SPLASH
FEED OIL SYSTEM – A type of engine lubricating system that depends on the
splashing of oil for lubrication of moving parts. The engine is enclosed, and
the crankcase contains oil into which the cranks dip and splash as they rotate,
throwing the oil over the various bearings.
STATICAL
FRICTION – Friction at starting from rest, and this is greater than the
friction of motion and depends on the hardness of the bodies and the length of
time during which they have been in contact.
SUMP –
A system for storing oil, either in the crankcase (wet sump) or in a separate
tank (dry sump).
SYNTHETIC
OIL – Oil made from material other than petroleum.
SYPHON
LUBRICATOR – The unit in which the oil stored in a cup above a journal, is
delivered slowly to the bearing through a wick which acts as a syphon.
TAPERED
ROLLER BEARING – An antifriction bearing where the rolling element is
similar to a roller bearing, however it has a taper along its axis, allowing it
to accept axial loads in one direction.
THICK
FILM LUBRICATION – Lubrication arrangement wherein there is no metal to
metal contact. Also called PERFECT LUBRICATION.
THIN FILM
LUBRICATION – Type of lubrication that occurs when the condition of bearing
operation reduce the thickness of the oil film sufficiently to make the rubbing
of the bearing surfaces a near possibility. Oiliness of the lubricant is
important in this type of lubrication.
THRUST
BEARING – In the engine, the main bearing has thrust faces
which
prevent excessive endwise movement of the crankshaft.
VALVE
STEM SEAL or SHIELD – A device placed on or surrounding the valve stem to
reduce the amount of oil which can get on the stem and thereby work its way
down into the combustion chamber.
VARNISH –
A build up of oxidized oil or fuel.
VISCOSITY
– Resistance of oil to flow. The thickness of oil is determined by its rate
of flow, a thick oil has a greater viscosity than a thin oil. Unit of viscosity
is centipoise.
VISCOSITY
INDEX – A measure of the change of viscosity with temperature of an oil
compared with two reference oils having the same viscosity at 210°F one of
naphthenic base and the other of paraffinic base.
VISCOSITY
INDEX IMPROVERS – Additives added to an oil, to reduce the change of
viscosity with increase in temperature.
VISCOSITY
RATING – An oil classification based on the time it takes for an amount of
oil to flow through a capillary tube, under specified conditions, the higher
the rating, the thicker the oil.
WARNING
LIGHT – A light on the instrument or control panel that turns on to warn of
low oil pressure.
WORK OF
FRICTION – Product of the frictional force and the distance through which
it moves.
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