Mechanical Technology Automative Memo 1 (English)

November 2021 — Grade 12 / Matric — Mechanical Technology

Memo 2021 Grade 12 English

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🎯 200 marks 📄 21 pages 📝 123 items found 📚 2 topics

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Q1— Section header —

1.1(1\

1.2(1\

1.3(1\

1.4A / (1\

1.5(1\

1.6(1\ Mechanical Technology: Automotive DBE/November 2021 NSC

Q2— Section header —

2.1First aid applications to an open wound: Use surgical gloves. Do not remove anything that is stuck to the wound. Never use sticky plaster on the wound. Cover the wound with a clean, lint free cloth.

2.2Surface grinder: (Already switched on Never leave the grinder unattended. Switch off the machine when leaving. Do not force the grinding wheel on to the work piece. Approach the work piece slowly and evenly.

2.3Gauges calibrated: To ensure accurate readings. To prevent overloading. (Any 1 x 1\ (1\

2.4The finger protector prevents the hazards of getting the fingers cut by the blades. To be crushed by the hold downs. (2\ Mechanical Technology: Automotive

2.5Welding or flame cutting operation safety: An operator has been instructed on how to use the equipment safely. A workplace is effectively partitioned off. An operator uses protective equipment. Ensure that all equipment is in safe working condition.

2.6Workshop layout: Product layout. (1\ [10] Mechanical Technology: Automotive DBE/November 2021 NSC Marking Guidelines10

Q3— Section header —

3.1File test:

3.1.1Difficult (1\

3.1.2Easy (1\

3.1.3Difficult (1\

3.2Heat treatment: A. Grain growth. B. Recrystallisation. C. Recovery. (3\

3.3Bending test: Bend the test piece through a specific angle or around a mandrel or bar, having a defined radius, until a rupture in the metal occurs. Place the material in a vice and bend it then observe

3.4Purpose of case hardening: Creates a hard surface with a tough core. (2\

3.5Quenching media for hardening Water Brine (saltwater\ Oil Soluble oil and water Nitrogen air

Q4— Section header —

4.1(1\

4.2(1\

4.3(1\

4.4(1\

4.5(1\

4.6(1\

4.7(1\

4.8(1\

4.9(1\

4.10(1\

4.11(1\

4.12(1\

4.13(1\

4.14(1\ [14] Mechanical Technology: Automotive DBE/November 2021 NSC Marking Guidelines Copyright reserved14

Q5— Section header —

5.1Compression est (Please note that if one step is missing and others still follow the sequence marks can still be allocated accordingly\

5.1.4Completely open the throttle valve. (1\ Crank the engine until maximum pressure is reached ( normally 4 to 10 revolutions\/ needle stops moving. (1\ Read the pressure that the piston created, off the gauge.

5.2Cylinder leakage tester

5.2.1Labelling Leakage meter / gauge Control valve

5.2.2Unit of measure Percentage or % (1

5.3Exhaus t gas analyser ater trap aper filter ondenser

5.4Set up of the on board diagnostics OBD\ s canner: Plug the

5.5Wheel balancer

5.5.1Wheel b alancer (1\

5.5.2Function of the wheel balancer: To balance wheels / statically / dynamically

5.5.3Safety feature: Wheel safety cover / guard hood Mechanical Technology: Automotive

5.6Wheel alignment angles Caster Camber King pin inclination (KPI / steering ax

5.7Wheel alignment precautions Ensure the wheels are in a straight ahead position Ensure the steering box is on its high spot.

Q6— Section header —

6.1Crankshaft firing order: To overcome the twisting effect of the power stroke on the crankshaft. To reduce vibrations on the crankshaft. Increase the lifespan of the crankshaft. To improve engine cooling evenly

6.2Crankshaft dynamic mbalance Fit balance mass pieces to the crank webs. Remove metal from the crank webs. Arrange the crank webs

6.4Power Impulses:

6.4.1180 (1\

6.4.2144 (1\

6.4.3120 (1\

6.4.490 (1\ Mechanical Technology: Automotive 10 DBE/November 2021 NSC Marking Guidelines Copyright reserved

6.5.1Labels Casing housing Air i nlet

6.5.2Oper ation of the Roots supercharger: The engine drives the rotors by means of gears , belt or a chain. Two symmetrical rotors spin.

6.6Variable geometr turbocharger

6.6.1Function of intercooler: Intercooler is used to cool air that has been compressed by a turbocharger It reduces the volume and increases the density of the air.

6.6.2Function of vanes: Vanes alter the air flow path of the exhaust gases to optimize the turbine speed (2\

6.7Advantages of a supercharger over a turbocharger: Does not suffer lag. It is more efficient at lower r/ in Simpler installation. Cheaper to service and maintain. Does not always need an intercooler.

Q7— Section header —

7.1Definitions

7.1.1Brake power Brake power is the useable power / actual power / output ower developed at the flywheel or at the

7.1.2Torque Torque is the twisting effort / force on a shaft or wheel. Torque is the twisting effort / force

7.2Indicated power diagram: Compression stroke pressure rise / increase Power stroke

7.3Calculations

7.3.1Clearance volume (1\

7.3.2Swept olume (1\

7.3.3Cylinder volume (3\

7.3.4Bore diameter in mm (5 cm 330 ml 330

7.3.5Compression ratio: (2

7.4Methods to lower the compression ratio Fit thicker gasket between cylinder block and cylinder head. Fit piston with suitable lower crowns. Fit crankshaft with shorter stroke. Fit s

9.4639 369 volume Clearance volume cylinder Total CR Mechanical Technology: Automotive

7.5Calculations

7.5.1 Torqu (4\

7.5.2 Indicated ower in kW: (6\

7.5.3Mechanical efficiency: (2\ [32] N.m 70,52 500 6032

Q8— Section header —

8.1Low CO exhaust gas reading:

8.1.1Possible causes: Too rich air/fuel mixture. Ignition misfire Blown cylinder head or block Dirty or restricted air filter. Improper operation of the fuel delivery system / Excessive fuel delivery pressure.

8.1.2Corrective measures: Note: The answer for 8.1.2 must correspond with the causes mentioned in 8.1.1 Reset fuel mixture. Correct cause of misfire Replace cylinder head or

8.2Indicate ean air/ fuel mixture High xygen (O

8.3Cylinder leakage test:

8.3.1Hissing sound at the exhaust pipe: Cause Corrective measure Leaking exhaust valve Replace the exhaust valve Re seat (lap\he exhaust valve

8.3.2Bubbles in the radiator water: Cause Corrective measure (2\ Blown cylinder head gasket Cracked cylinder head Cracked cylinder

8.4Engin temperature: To allow the expansion of the components to obtain accurate readings. (2\

8.5Fuel pressure test 8. .1 eplace fuel filter (1\

8.6Oil pressure test: Oil pressure when engine is idling. Oil pressure when engine is cold. Oil pressure when engine is hot. Oil pressure when engine is at high revolutions. Any 3 x 1\

8.7Radiator cap pressure test: Obtain the radiator cap's opening pressure specifications ( stamped on the cap Install the cap on

Q9— Section header —

9.1Torque c onverters

9.1.1Torque converter labels: A. Turbine B. Casing housing C. Pump

9.1.2Functions of torque converters: Multiplies engine torque automatically according to road and engine speeds. Transfers drive from the engine to the transmission. Acts as a f lywheel to keep the engine turning during the

9.1.3Maximum torque multiplication When there is the largest speed difference between the impeller and turbine. Maximum torque multiplication occurs at rest as the

9.2Epicyclic gear train orward o verdrive The sun gear is locked with the planet carrier as driving

9.3Gearshift lever positions

9.3.1ark

9.3.2reverse

9.3.3drive

9.4(2\ [18] Mechanical Technology: Automotive 19 DBE/November 2021 NSC Marking Guidelines18

Q10— Section header —

10.1Reasons for wheel alignment To achieve desirable steering Drive with least resistance.

10.2Camber:

10.2.1Cambe r wear causes Suspension misalignment. A bent strut. Dislocated strut tower A weak or broken spring. A bent

10.2.2Positive camber angle: Positive camber angle refers to the outward tilt of the top of the wheel

10.2.3Camber adjustment: Camber is adjusted by means of a cam wedge bol ts or wedge plates (shims\ on the suspension.

10.3Toe in: (3\

10.4Effects of wheel imbalances Wheel shimmy (wobble\ Wheel bounce (hop\ Uneven tyre wear Premature wheel bearing failure

10.5Types of injectors olenoid injector iezo injector (2\

10.6Purpose of the diesel particulate filter: It is a filter that converts particulate matter or soot into ash. (2\

10.7The headway sensor The headway sensor detects an obstruction ahead of a vehicle. The headway sensor will send a signal to the ECU (2

10.8The alternator:

10.8.1Component: Stator (1\

10.8.2Stator f unction It provides a coil into which a voltage is induced, Converts the rotating magnetic field to electric current

10.8.3Stator windings Delta connected stator windings (2\

10.8.4Stator windings Star or Y connected stator windings (2\

10.9Advantages of an electric fuel pump: Immediate/ quicker supply of fuel when the ignition switch is turned on. Low sound during operation Less discharge pulsation of fuel.

Topics Identified

CircuitsMaterials

Mark Allocation

Total200 marks

Sections10 + 14 + 14 + 28 + 32 + 23 + 18 + 32 = 171 marks

Paper information

SubjectMechanical Technology

Year2021

SessionNovember

TypeMemo

PaperPaper 1

LanguageEnglish

Pages21

Downloads2

Examination context

Decade2020s

Years ago5y

SeasonSpring (SH)

Start dayFriday

Exam periodNovember 2021

Days since exam1,813

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