Maharashtra HSC Automobile Technology - Vocational (MSBSHSE) flashcards

33 cards. Read the term and the definition here. The deck at the top of this page is optional.

Ladder frame chassis

A chassis made of two longitudinal side members joined by cross members, carrying engine and body loads. It resists bending and torsion and is common on trucks and older utility vehicles.

Monocoque body

A unitised body construction in which the floor pan and body panels form the load-bearing structure. It is lighter and stiffer than a separate frame but harder to repair after a collision.

Wheelbase

The horizontal distance between the centres of the front and rear axles of a vehicle. It affects interior space, weight distribution, and ride stability.

Compression ratio

The ratio of total cylinder volume to clearance volume when the piston is at bottom dead centre compared with top dead centre. Petrol engines typically use 8:1 to 12:1.

Four-stroke cycle

The sequence of suction, compression, power, and exhaust strokes completed in two crankshaft revolutions. Only the power stroke produces useful work, so a flywheel smooths output.

Firing order

The sequence in which cylinders deliver power, for example 1-3-4-2 in an inline four-cylinder engine. It is chosen to balance loads on the crankshaft and reduce vibration.

Valve timing

The crank angles at which inlet and exhaust valves open and close, expressed in degrees before or after top and bottom dead centre. It controls breathing and engine performance.

Clutch free play

The small clearance between the release bearing and clutch release mechanism, felt as pedal movement before resistance. Too much free play prevents full disengagement; too little causes slip.

Torque converter

A fluid coupling with impeller, turbine, and stator that transmits engine torque to an automatic gearbox. It multiplies torque when the turbine turns slower than the impeller.

Differential

A gear unit that allows the driven wheels to rotate at different speeds during a turn while still transmitting engine torque to both wheels through the final drive.

Ackermann steering

A steering geometry in which the inner front wheel turns through a larger angle than the outer wheel, so both wheels follow paths around a common centre without tyre scrub.

Caster angle

The tilt of the steering axis from vertical when viewed from the side. Positive caster gives self-centring and straight-line stability but increases steering effort.

Brake bleeding

The process of removing trapped air from hydraulic brake lines by opening bleeder screws and pumping fluid until no bubbles appear. It restores a firm brake pedal.

Ohm's law

The relationship V = I × R, where V is voltage in volts, I is current in amperes, and R is resistance in ohms. Power is calculated as P = V × I.

Alternator

A belt-driven generator that produces alternating current, rectified to direct current by a diode bridge. A regulator holds charging voltage near 14 volts.

Specific gravity of electrolyte

A measure of battery electrolyte density, about 1.26 when fully charged and lower when discharged. It indicates state of charge in lead-acid batteries.

Cast iron

An iron-carbon alloy with high carbon content, offering good wear resistance and vibration damping. It is used for cylinder blocks, brake drums, and flywheels.

Aluminium alloy

A light non-ferrous alloy with good thermal conductivity and machinability, widely used for pistons, cylinder heads, and radiators to reduce vehicle weight.

Vernier calliper least count

The smallest measurement a vernier calliper can read, equal to one main scale division minus one vernier division. Typical value is 0.02 millimetres.

Micrometer least count

The smallest reading of a micrometer, calculated as screw pitch divided by thimble divisions. A 0.5 millimetre pitch with 50 divisions gives 0.01 millimetre.

Feeler gauge

A set of thin metal blades of known thickness used to measure small gaps such as valve clearance, spark plug gap, and piston ring end gap.

Tyre rotation

Periodic swapping of wheel positions to equalise tread wear, following a pattern suited to the drive layout. It extends tyre life and maintains even grip.

Spongy brake pedal

A brake pedal that feels soft and travels too far, usually caused by air in the hydraulic system or a fluid leak. It requires bleeding and inspection.

Jack stand safety

Jack stands placed under the chassis or axle support the vehicle after lifting with a jack. Never work beneath a vehicle held only by a hydraulic jack.

Fire extinguisher classes

Classification of extinguishers by fire type: water for solids, foam for liquids, carbon dioxide or dry powder for fuel and electrical fires. Metal fires need special powder.

Battery terminal disconnection

Disconnect the negative terminal first and reconnect it last to avoid short circuits and sparks. Hydrogen gas around a charging battery is explosive.

ABS

An anti-lock braking system that uses wheel speed sensors and an electronic control unit to modulate brake pressure, preventing wheel lock and maintaining steering control during hard braking.

Common rail diesel injection

A system where a high-pressure pump supplies a common rail feeding electronically controlled injectors. The engine control unit sets injection timing and duration for each cylinder.

Turbocharger

A device driven by exhaust gas that compresses intake air to increase engine power. A wastegate limits boost pressure to protect the engine.

Three-way catalytic converter

An exhaust device that converts carbon monoxide, unburnt hydrocarbons, and nitrogen oxides into carbon dioxide, water, and nitrogen. It works best near stoichiometric air-fuel ratio.

Exhaust gas recirculation

An emission control method that routes a small portion of exhaust gas back into the intake. This lowers combustion temperature and reduces nitrogen oxide formation.

Positive crankcase ventilation

A system that draws blow-by gases from the crankcase back into the intake manifold through a PCV valve, reducing hydrocarbon emissions and preventing pressure build-up.

Practical record

A written report of workshop activity containing the aim, tools used, procedure, observations, calculations, and conclusion. It is assessed during practical examinations and viva.