Mechanical Technology Welding and Metalwork Memo 1 (English)

May-June 2021 — Grade 12 / Matric — Mechanical Technology

Memo 2021 Grade 12 English

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🎯 200 marks 📄 20 pages 📝 100 items found 📚 3 topics

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Questions — A Preview of What to Expect in the Document

100

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Q1— Section header —

1.5(1\ (1\ (1\ (1\

1.6(1\ [6] Me chanical Te ch nolog6

Q2— Section header —

2.1First aid basic treatment: Examination Diagnos is Treatment (3\

2.2Drill press (Already been switched on Never leave the drill unattended while in motion. Switch off the drill when leaving. Use a brush or wooden rod to remove chips. When reaching around a revolving drill, be careful that your clothes do

2.3Isolation of electrode holder: To prevent electric shock. (1\

2.4Disadvantages of the process layout: Production is not always continuous. Transportation costs between process departments may be high. Additional time is spent in testing and sorting as the product moves to the

2.5Advantages of the product layout: Handling of material is limited to a minimum. Time period of manufacturing cycle is less. Production control is almost automatic. Control over operations is easier. Greater use of unskilled labour is possible.

Q3— Section header —

3.1Heat treatment: Heat the metal slowly to a certain temperature Soak the metal for a certain period to ensure a uniform temperature

3.2Quenching mediums: Water Brine Liquid salts Oil Soluble oil and water Sand Molten lead Air

3.3Annealing: To relieve internal stresses of the steel Soften steel to make machining possible Make steel ductile Refine grain structure Reduce brittleness Any 1 x 1\

3.4Carbon steels: Low carbon steel Medium carbon steel High carbon steel (3\

3.5Iron carbon equilibrium diagram: Percentage carbon

4.5(1\ (1\ (1\ (1\

4.10(1\ (1\ (1\ (1\

4.13(1\ (1\ (1\

4.14(1\ [14] Me chanical Te ch nolog14

Q5— Section header —

5.1Compression tester labels: Pressure auge Pressure ete

5.2Function of Cylinder Leakage Tester: To check where the combustion chamber/cylinder leaks gases during compression stroke/power stroke. To determine the percentage pressure loss from the combustion chamber.

5.3Cylinder leakage test procedure: Turn the crank shaft until both valves, on the cylinder to be tested, are closed. Remove the HT leads spark plug

5.4Exhaust gas analyser: Hydrocarbon (fuel and oil vapour\ HC Carbon dioxide / CO Sulphur dioxide

5.5Exhaust gas analysis test precautions: Always calibrate the exhaust gas analyser with the pick

5.6Function of Turn tables: To make it possible to turn the front wheels in and out side to side when checking the wheel alignment angles.

5.7Use of optical lignment gauge: To measure check the toe in and toe

5.8Functions of OBD canner: Scan for faults (diagnostics\. Programme the ECU. Reset fault codes. Programme the keys to vehicle's ignition system. Any

Q6— Section header —

6.1Correcting static imbalance: By fitting balance mass pieces to the crank webs. By removing metal from the crank webs. By arranging the crank pins of the crankshaft. Any 2 x 1\ (2\

6.2Crankshaft balancing:

6.2.1Dynamic balancing: Balancing in all directions while crankshaft is rotating. (2\

6.2.2Reciprocating mass: The mass of the pistons, gudgeon pins and the upper third of the connecting rod. (2\

6.3Features to improve engine balance: Connecting rods and pistons are kept as light as possible static balanced Flywheel is carefully balanced.

6.4Types of vibration dampers: Friction face type Combined rubber and friction disc Rubber type Inertia ring type

6.5Different types of cylinder arrangements: Inline type Straight arrangement

6.6Three cylinder inline engine: Marking: Labelling ower impulse angle

6.7Types of superchargers: Roots Twin screw Centrifugal and Vane Any

6.8Advantages of using a turbocharger: More power is obtained from an engine with the same engine capacity. A turbocharger is driven by the exhaust gases of the engine and therefore there is no power loss.

6.9Turbocharger: Intercooler/air cooler Compressed air flow Turbine/Turbine housing

Q7— Section header —

7.1Terms:

7.1.1Power: Power is the rate at which work is done. (2\

7.1.2Compression Ratio: It is the ratio between the total volume of a cylinder when the piston is at bottom dead centre BDC\ to the volume in a cylinder when the piston is at top dead centre (TDC

7.2Calculation of compression ratio:

7.2.1Swept volume (3\

7.2.2Original clearance volume (3\ cm 288,63

7.2.3New bore diameter: (6\

7.3Power c alculati ons

7.3.1Torque: (3\ cm 305,64 SV 1\ 96(10

7.3.2Indicated power: OR OR (8\ 0,086 1000 86 mm

7.3.3Brake power (3\

7.3.4Mechanical efficiency (NO UNIT, NO MARK FOR FINAL ANSWER\ (2\ [32] kW 9932

Q8— Section header —

8.1Cooling system pressure test:

8.1.4Repair or replace water hose or clamp. Cylinder head gasket blown. / Cylinder head warped. Replace Welch or core plug. Replace radiator cap with suitable replacement. (1\ (1\ (1\

8.2Function of the radiator cap: Regulates the pressure in the cooling system Allows coolant to return to the radiator from the expansion tank The radiator cap seals / close the cooling system

8.3Exhaust gas readings causes:

8.3.1Possible causes of high carbon monoxide (CO\ading: Too rich mixture Ignition misfire Dirty or restricted air filter Impr oper operation of the fuel delivery system

8.3.2Possible causes high nitrogen oxide (NO \ reading: Lean fuel mixture Improper spark advance Malfunctioning EGR valve Malfunctioning catalytic converter

8.3.3Possible causes h igh oxygen (O \ading: Too lean air fuel ratio Ignition problems Vacuum leaks

8.4Safety requirements when setting up the oil tester: Ensure the tester can read the expected pressures of the engine. Clean the sender unit area before fitting the tester. Ensure that the rubber hoses of the tester are not perished.

8.5Fuel pressure test/manufacturers' specifications: Fuel pressure (suction\fore the fuel pump. Fuel pump delivery pressure (after the fuel pump\ Fuel line pressure at idle speed. Fuel

8.6Compression test:

8.6.1High tension leads: The ignition system will be disabled. Prevent electrical shock. To have access to the spark plugs in order to remove them. Any 1 x 1\ (1\

8.6.2Throttle valve fully open: To ensure maximum amount of air enters the cylinder o obtain a correct reading. (Any 1 x 1\ (1\

8.6.3Recording the readings: ompared to the specification s reading. To note the differences in readings between the cylinders. Any 1 x 1\ (1\

8.7Increase in compression after wet test: Piston ring / Compression ring Cylinder sleeve / walls

Q9— Section header —

9.1Differences between an automatic gearbox and a manual gearbox: Manual clutch pedal operated. Automatic no clutch pedal operated. Manual Gears selected manually with gear lever

9.2Function of torque converter: Multiplies engine torque automatically according to road and engine speeds. Transfers drive from the engine to the transmission. Acts as a Flywheel to keep the engine turning during the idle strokes.

9.3Lockup clutch: To overcome slip that occurs inside the torque converter. (2\

9.4Stall speed: The condition when the impeller of a torque converter rotates at maximum speed and the turbine is almost stationary When the pump has reached the highest velocity and the turbine is at stall (standing still\.

9.5Single epicyclic gear system:

9.5.1Epicyclic gear train: Sun gear Annulus Ring gear

9.5.2Advantages of an epicyclic gear train: The input shaft and output shaft have the same axis of rotation. Load is distributed to several planetary gears. Many transmission

9.6Function of the alve body: It detects the load and adjust the gear ratio according to the torque requirements

9.7Methods of cooling the automatic transmission oil: By using a special oil cooler alongside the engine cooling radiator and circulating transmission fluid through it. Circulating transmission fluid through

10.1Requirements of a well planned steering mechanism: light and easy to control. free from vibration and road shocks. as direct as possible without needing too much driver attention or effort. self

10.2Wheel alignment angles:

10.2.1Function of Positive camber: Less steering effort The vehicle mass being carried by the larger inner front wheel bearing. Any 1 x 1\ (1\

10.2.2Function of Ackermann's angle: It allows for variable toe out to the front wheels on turns. (1\

10.3Caster:

10.3.1Wheel a lignment angle: Negative caster angle (2\

10.3.2Negative caster angle purpose: Negative aster ensures easier turning and provides better cornering to the vehicle. (2\

10.3.3Caster angle labels: D. King pin Steering axis

10.4Engine management system:

10.4.1Function of sensor: It detects the engine operating conditions. It gives the input information to the ECU. (Any 1 x 2\

10.4.2Function of actuators: It gets the output information signal from the ECU. It makes the necessary adjustments. (Any 1 x 2\ (2\

10.5

10.6Lambda sensor: The lambda sensor is fitted on the exhaust sy tem (1\

10.7Adaptive speed control: Maintain a speed as set by the driver. Adapt th speed to maintain a safe distance from the vehicle in front. Provide a warning if there is a risk of a collision. Prevent driver fatigue.

10.8Diode:

10.8.1Diode (1\

10.8.2Function of the diode: The function of the diode is used to change alternating current into direct current. It allows the current flow in the circuit in one direction only and blocks it from flowing in the opposite direction.

10.9Function of components in the alternator:

10.9.1Rectifier: Converts alternating current AC\ to direct current DC\ (1\

10.9.2Stator: To provide a core that concentrates the magnetic lines of force onto the stator windings. To provide a coil into which a voltage is induced which is used to charge the battery. Converts the rotating magnetic field

10.9.3Rotor: Provides a rotating electro magnet. Induces an electric voltage into the stator windings. Fitted with slip rings to allow for a moving electrical

10.10Functions of the check valve in the electric fuel pump: It ensures the pressure in the fuel line is maintained. It allows the fuel to flow in one direction only from the fuel tank. (2\ [32] TOTAL: 20032

Topics Identified

CircuitsMaterialsConstruction

Mark Allocation

Total200 marks

Sections6 + 10 + 14 + 14 + 23 + 28 + 32 + 23 + 18 + 32 = 200 marks

Paper information

SubjectMechanical Technology

Year2021

SessionMay-June

TypeMemo

PaperPaper 1

LanguageEnglish

Pages20

Downloads4

Examination context

Decade2020s

Years ago5y

Season—

Start day—

Exam period—

Days since exam—

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