MECHANICAL TECHNOLOGY: AUTOMOTIVE
GRADE 12
NATIONAL SENIOR CERTIFICATE
NOVEMBER 2019
MEMORANDUM 

QUESTION 1: MULTIPLE-CHOICE (Generic)
1.1 B ✓(1)
1.2 C ✓ (1)
1.3 A ✓ (1)
1.4 C ✓ (1)
1.5 A ✓ (1)
1.6 C ✓ (1)
[6]

QUESTION 2: SAFETY (Generic)
2.1 Machine safety rule:

• Know how to switch the machine off / emergency stop.✓
• Wear personal protective equipment (PPE). ✓
• Know how to use the machine.✓
• Ensure that all guards are in place. ✓
• No tools lying on the machine. ✓
• Work piece is properly secured. ✓
• Check the condition of the machine. ✓
• Follow manufacture's specifications before operating a machine. ✓
• Operator must have authorization to working on a machine. ✓
• Make sure the machine is not locked out. ✓
• Ensure that the machine setup is correct and safe. ✓
• Ensure that the machine area is clean and safe. ✓
  (Any 1 x 1) (1)

2.2 Drill press safety precautions:

• To prevent injuries. ✓
• To improve accuracy. ✓
• To prevent work piece rotating/moving. ✓
• To prevent the drill bit from breaking. ✓
  (Any 1 x 1) (1)

2.3 Hydraulic press safety rules:

• Make sure the press is in a good working condition. ✓
• Take notice of the pre-determined maximum pressure of the hydraulic press. ✓
• Make sure the area around the press is clean and free of oil, grease and water. ✓
• Ensure that the platform is rigid and square to the cylinder. ✓
• Ensure that suitable jigs and prescribed equipment is available. ✓
• Check hydraulic pipes for leaks or cracks. ✓
• Check supporting pins are not worn out and fitted properly. ✓
• Check fluid levels. ✓
• Compressive force must be applied at 90° to the object.✓
• Check cable and pulleys on the platform if equipped. ✓
• Correct PPE. ✓
• Pressure gauge must be checked and calibrated. ✓
• Ensure that all guards are in place. ✓
  (Any 2 x 1) (2)

2.4 Reasons for wearing surgical gloves:

• To prevent HIV/AIDS or any blood related infections being transmitted✓
• To prevent contamination of the open wounds✓ (2)

2.5 Safe handling of portable electrical equipment:

• Ensure the electrical cord and plug, are in a good condition. ✓
• Ensure all safety guards are in place. ✓
• Ensure that the correct attachments (drill bits, blades etc.) are fixed in the correct way. ✓
• Do not force the machine/equipment.✓
• Operate according to manufacturer instructions. ✓
• Avoid contact with water.✓
• Keep the cable away from heat, oil, sharp edges and moving parts. ✓
• Make sure that the wires don't wrap around each other. ✓
• Avoid dropping the machine. ✓
• Check the condition of the equipment. ✓
  (Any 2 x 1) (2)

2.6 Responsibility of employer:

• Provide and maintain working systems, work area, equipment and tools in a safe condition. ✓
• Eliminate or reduce any potential hazard. ✓
• Produce, handle, store and transport goods safely.✓
• Ensure that every person employed complies with the requirements of this OHS Act. ✓
• Enforce measures if necessary in the interest of health and safety. ✓
• Appoint a person who is trained and who have the authority to ensure that the employee takes precautionary measures. ✓
• Inform employees of the hazards to his health and safety attached to any duty or work situation. ✓
• Provide first aid equipment. ✓
  (Any 1 x 1) (1)

2.7 Responsibility of employee:

• Pay attention to their own and other people's health and safety. ✓
• Co-operate with the employer regarding the OHS Act. ✓
• Carry out a lawful order given to them. ✓
• Report any situation that is unsafe or unhealthy.✓
• Report all incidents and accidents. ✓
• Not to interfere with any safety equipment or misuse such equipment.✓
• Obey all safety rules. ✓
  (Any 1 x 1) (1)

[10]

QUESTION 3: MATERIAL (Generic)
3.1 Filing test:

• Use the right ✓ filing skills. ✓
• File on the tip or edge ✓✓ of the metal.
• By applying chalk ✓ to the file surface. ✓
  (Any 1 x 2) (2)

3.2 Purpose of heat treatment of steel:
Heat treatment of steel is done to change ✓ the properties/grain structure ✓ of steel. (2)
3.3 Reasons for tempering hardened steel:

• To reduce ✓ the brittleness ✓ caused by the hardening process.
• To relieve ✓ strain ✓ caused during hardening process.
• To increase ✓ the toughness ✓ of the steel.
• To give hardened work piece a more ✓ fine-grained structure. ✓
  (Any 2 x 2) (4)

3.4 Heat treatment processes on steel:
3.4.1 Annealing:

• The steel is heated to the prescribed temperature. ✓
• The steel is soaked at that temperature for the required time. ✓
• The steel is then cooled very slowly to produce maximum softness.✓ (3)

3.4.2 Hardening:

• The steel is heated slightly higher than the upper critical temperature. (AC₃) ✓
• The steel is soaked at that temperature for the required time. ✓
• The steel is then rapidly cooled by quenching in rapid cooling medium. ✓(3)

[14]

QUESTION 4: MULTIPLE-CHOICE QUESTIONS (Specific)
4.1 A ✓ (1)
4.2 C ✓ (1)
4.3 D ✓ (1)
4.4 B ✓ (1)
4.5 C ✓ (1)
4.6 D ✓ (1)
4.7 A ✓ (1)
4.8 B ✓ (1)
4.9 C ✓ (1)
4.10 B ✓ (1)
4.11 C✓ (1)
4.12 D & B ✓ (1)
4.13 B ✓ (1)
4.14 B ✓ (1)
[14]

QUESTION 5: TOOLS AND EQUIPMENT (Specific)
5.1 Cylinder leakage tester:
5.1.1
Labels:

1. – Pressure control valve/Knob/Regulator ✓
2. – Gauge/Meter✓
3. – Compressor hose/Air hose/Pipe ✓
4. – Spark plug connector/adapter/Hose/Pipe ✓ (4)

5.1.2 Purpose of cylinder leakage tester:

• To determine the percentage ✓ of gas leakage from a cylinder. ✓
• To determine the location ✓ of gas leaks from a cylinder. ✓
  (Any 1 x 2) (2)

5.1.3 Procedure for cylinder leakage test:

• Turn the crank shaft until both valves on cylinder no. 1 are closed (piston no.1 is on power stroke). ✓
• Remove the spark plug and connect the spark plug adaptor (tester) to the spark plug hole. ✓
• Use a spanner to lock the crankshaft pulley so that it cannot turn. ✓
• Release air into the cylinder according to the prescribed pressure. ✓
• The reading will indicate the percentage gas leakage. ✓
• A hissing sound at various points indicates the location of the leak. ✓ (6)

5.2 Compression tester:
5.2.1 Purpose of compression test:

• To determine the amount of compression pressure ✓ from a specific cylinder during compression stroke (BDC – TDC). ✓
• To determine the condition ✓ of the engine's valves, valve seats and piston rings. ✓
  (Any 1 x 2) (2)

5.2.2 Compression tester release valve:

• Remove the pressure from the gauge ✓ to ensure an accurate reading. ✓
• Remove the pressure from the gauge ✓ to prevent damage to the gauge. ✓
  (Any 1 x 2) (2)

5.3 Gases analysed:

• Carbon monoxide (CO) ✓
• Hydrocarbon (HC) ✓
• Carbon dioxide (CO₂) ✓
• Nitrogen oxide (NOx) ✓
• Sulphur dioxide(SO₂) ✓
• Oxygen (O₂) ✓
  (Any 2 x 1) (2)

5.4 Purpose of turn tables:
Turn table makes it possible to turn ✓ the front wheels when conducting wheel alignment settings. ✓ (2)
5.5 Outcomes of dynamic wheel balancing is to check:

• The plane of imbalance. ✓
• The extent of unbalancing forces. ✓
• The direction of these forces. (clockwise or counter-clockwise)✓
• Wheels balanced on all planes. ✓
• Less vibration on the steering.✓
• Even tyre wear. ✓
  (Any 3 x 1) (3)

[23]

QUESTION 6: ENGINES (Specific)
6.1 Crankshaft vibration:

• The action upon the shaft of unbalanced forces. ✓
• The torsional or twisting effect of the power strokes upon the shaft. ✓
• Worn vibration damper. ✓
• Uneven flywheel wear. ✓
• Unbalanced crankshaft. ✓
  (Any 2 x 1) (2)

6.2 Vibration Damper:
6.2.1 Vibration damper ✓ (1)
6.2.2 Labels:

1. – Crankshaft ✓
2. – Crankshaft flange/pulley ✓
3. – Secondary flywheel ✓
4. – Friction disc/Rubber✓
5. – Friction spring ✓
6. – Spring plate/Disc ✓ (6)

6.2.3 The vibration damper adds mass to the crankshaft on the opposite side ✓ of the normal flywheel in order to counteract the torsion of the crankshaft. ✓ (2)
6.3 Firing order of an engine:

• The position of the cranks on the crankshaft. ✓
• The arrangement of the cams on the camshaft. ✓ (2)

6.4 'V8' angle:
90°✓ (1)
6.5 Intercooler:
To cool the air that has been compressed by the turbo-charger. ✓ (1)
6.6 Purpose of a supercharger:

• To fill the cylinder with an increased air pressure ✓✓that is higher than atmospheric pressure. ✓
• To increase ✓✓the compression pressure ✓✓in the cylinder.
• To increase ✓✓the volumetric efficiency ✓✓of the engine.
• To improve ✓ the performance. ✓✓
  (Any 1 x 2) (2)

6.7 Centrifugal supercharger:
6.7.1 Centrifugal supercharger/blower ✓ (1)
6.7.2 Labels:

1. – Air inlet ✓
2. – Air outlet/Exhaust ✓
3. – Casing/Housing/Cover/Body ✓
4. – Impeller/Turbine ✓
5. – Fins/Vanes/Blades ✓ (5)

6.7.3 Operation:

• This blower can be driven mechanically by means of a belt drive from the crankshaft. ✓
• The shaped fins on the impeller move the air around to the outer edge of the impeller into the housing.✓
• The rotating fins leave a low pressure behind it. ✓
• Due to atmospheric pressure, air rushes in to fill the low pressure at the centre of the impeller. ✓
• The impeller rotates so fast that a continuous movement of air is present, which now builds up a pressure as it is thrown at the rim or the edge. ✓ (5)

[28]

QUESTION 7: FORCES (Specific)
7.1 Swept volume:
Volume when the piston moves✓ from bottom dead centre to top dead centre.✓✓ (2)
7.2 Method to increase compression ratio:

• Remove shims between the cylinder block and cylinder head. ✓
• Fit thinner cylinder head gasket. ✓
• Machine metal from cylinder head. ✓
• Fit a piston with a higher crown. ✓
• Fit a crankshaft with a longer stroke/through. ✓
• Increase the bore of the cylinders/bigger pistons. ✓
  (Any 3 x 1) (3)

7.3 Compression ratio:
7.3.1 Swept volume: πD²  x L
                                   4
= π(9,0) ² 10,0
      4
= 636,17 cm³ (3)
7.3.2 Original clearance volume:
Compression Ratio = SV + CV
                                       CV
CV =   SV   
         CR - 1
= 636,17 
  10,5 - 1
= 636,17 
      9,5
= 66,97 cm³ (3)
7.3.3 New bore diameter:
New compression ratio = SV+ 1
                                           CV
11:1 =   SV   + 1
           66,97
SV = 66,97 x 10
πD² x L = 669,7
  4
D² = 669,7 x 4
          π x 10
D = √85,27
= 9,23cm
= 92,34 mm (6)
7.4 Power:
7.4.1 Indicated Power:
IP = P x L x A x N x n
P = 1300 kPa
L =  160  
      1000
= 0.16m
A = πD²
       4
= π0,12²
       4
= 1,13 x 10^-2 m
n = 4500 
     60 x 2
= 37,5 ps/s
n = 4 cylinders

IP = P x L x A x N x n
= (1300 x 10³) x 0,16 x (1,13 x 10^-2) x 37,5 x 4
= 352560
= 352,56 kW
7.4.2 Brake Power:
BP = 2π x N x T
= 2π 610 x 4500 
                    60
= 2 π 610 75
= 287455,73 W
= 287,46 kW (4)
7.4.3 Mechanical efficiency:
= BP 100%
   IP
= 287,46 x 100%
   352,56
= 81,54% (2)
7.5 Mechanically efficiency is based on the relationship of the power developed within the engine ✓ and the actual brake power delivered at the fly wheel. ✓ (2)
7.6 Brake Power is the useable power ✓developed at the flywheel. ✓ (2)
[32]

QUESTION 8: MAINTENANCE (Specific)
8.1 Radiator cap pressure test:

• Install the cap on the cooling system pressure tester. ✓
• Pump up the tester while watching the pressure gauge.✓
• The pressure cap should release air at the rated pressure stamped on the cap. ✓
• The cap should hold the pressure for at least one minute. ✓
• If not install new cap. ✓(5)

8.2 Causes and correction for pressure drop:
Causes:

• Leaks between components of the cooling system. ✓
• Leaks at water hose. ✓
• Blown cylinder head gasket. ✓
• Leaks at water pump. ✓
• Leaks at radiator. ✓
• Leaks at corroded welsh or core plug. ✓
• Leaks at interior heater radiator.✓
• Leaks at heater tap. ✓
  (Any 2 x 1)

Corrections:

• Renew the gaskets and seals. ✓
• Renew faulty hoses and secure clamps. ✓
• Skim the cylinder head and replace cylinder head gasket. ✓
• Renew water pump. ✓
• Renew the radiator. ✓
• Renew welsh or core plugs. ✓
• Renew interior radiator.✓
• Renew radiator tap. ✓
  (Any 2 x 1) (4)

8.3 Specification to conduct cooling system pressure test, check for:

• Water and anti-freeze ratio. ✓
• Pressure allowed in the radiator. ✓
• Pressure of radiator cap. ✓
• Reading of the cooling system pressure tester. ✓
  (Any 2 x 1)(2)

8.4 Safety: Compression test:

• Ensure that tester can handle the pressure you want it test. ✓
• Clean spark plug area to prevent dirt entering when you remove spark plug.✓
• Ensure rubber hoses on tester are in good order. ✓
• Ensure release valve on the tester is working. ✓
• Ensure using the right spark plug adaptor. ✓
• Disconnect high tension leads. ✓
• Disconnect the fuel feed. ✓
• Make sure the tester is at zero mark. ✓
• Ensure that the air filter is clean. ✓
  (Any 4 x 1). (4)

8.5 Gas analyser results:
8.5.1 High carbon monoxide (CO) reading:
Causes:

• Too rich mixture.✓
• Ignition misfire. ✓
• Dirty or restricted air filter. ✓
• Improper operation of the fuel delivery system.✓
• Faulty thermostat or coolant sensor. ✓
• Non-functioning PCV valve system. ✓
• Faulty catalytic converter. ✓
  (Any 1 x 1) (1)

8.5.2 Corrective measures:

• Reset fuel mixture.✓
• Check for misfire and repair. ✓
• Replace air filter. ✓
• Check and correct fuel delivery system. ✓
• Check and repair coolant sensor. ✓
• Check and repair PCV valve. ✓
• Check and repair or replace catalytic converter. ✓
  (Any 1 x 1) (1)

8.5.3 Low carbon dioxide (CO₂) reading:
Causes:

• Fuel mixture too rich or lean. ✓
• Exhaust system leaks. ✓
• Ignition misfire. ✓
• Dirty or restricted air filter. ✓
• Improper operation of the fuel delivery system.✓
• Faulty thermostat or coolant sensor. ✓
• Non-functioning PCV valve system. ✓
• Faulty catalytic converter. ✓
  (Any 1 x 1) (1)

8.5.4 Corrective measures:

• Reset fuel mixture. ✓
• Repair or replace exhaust system. ✓
• Check for misfire and repair. ✓
• Replace air filter. ✓
• Check and correct fuel delivery system. ✓
• Check and repair coolant sensor. ✓
• Check and repair PCV valve. ✓
• Check and repair or replace catalytic converter.✓
  (Any 1 x 1) (1)

8.5.5 High hydrocarbon (HC) reading:
Causes:

• Excessive unburned fuel by incomplete combustion. ✓
• Improper timing. ✓
• Vacuum leak. (Low fuel pressure)✓
• Leaking fuel injector. ✓
• Defective cold start valve. ✓
• Faulty air management system. ✓
  (Any 1 x 1) (1)

8.5.6 Corrective measures:

• Reset fuel mixture. ✓
• Check and reset ignition system. ✓
• Check and repair vacuum leaks. ✓
• Check and repair/replace fuel injector. ✓
• Check and repair/replace cold start valve. ✓
• Check and repair air management system. ✓
  (Any 1 x 1) (1)

8.6 Specification to conduct fuel pressure test, check for:

• Fuel pressure before the carburettor. ✓
• Fuel pressure before and after the injector pump. ✓
• Fuel pressure when engine is idling. ✓
• Fuel pressure on high revolutions. ✓
  (Any 2 x 1) (2)

[23]

QUESTION 9: SYSTEMS AND CONTROL (Automatic gearbox) (Specific)
9.1 Purpose of an automatic gearbox:

• To relieve ✓ the driver of clutch and gearshift operation. ✓
• To promote ✓✓smoother and easier ✓✓driving of the vehicle.
  (Any 1 x 2) (2)

9.2 Advantages of vehicle fitted with an automatic gearbox:

• It reduces driver fatigue. ✓
• It reduces wheel spin under bad road conditions. ✓
• The vehicle can be stopped suddenly without the engine stalling. ✓
• The system dampens all engine torsional vibrations. ✓
• It is easier to drive. (e.g. Disabled persons) ✓✓
  (Any 2 x 1) (2)

9.3 Disadvantages of vehicle fitted with an automatic gearbox:

• Automatic gearbox is more expensive to manufacture/maintain. ✓
• If a car with automatic gearbox has to be towed for along distance the propeller shaft must be removed. ✓
• Automatic gearbox makes the vehicle heavier that with a manual gearbox. ✓
  (Any 2 x 1) (2)

9.4 Torque converter:
9.4.1 Labels:

1. – Ring gear/flex plate ✓
2. – Casing ✓
3. – Stator ✓
4. – Impeller/Pump ✓
5. – Transmission/Shaft/Spigot ✓
6. – Fluid path/Impeller/Pump ✓
7. – Vanes ✓
8. – Turbine ✓

(8)
9.4.2 Advantages of torque converter:

• Torque increases automatically. ✓
• Torque is transferred smoothly to reduce shocks on the gearbox, chassis and wheels. ✓
• Minimum servicing is required.✓
• Disconnects at low revolutions. ✓
  (Any 2 x 1) (2)

9.4.3 Increasing torque converter speed:
Torque multiplication tapers off ✓ (reduce/decrease) gradually.✓ (2)
[18]

QUESTION 10: SYSTEMS AND CONTROL (Axles, steering geometry and electronics) (Specific)
10.1 Tyre wear:
10.1.1 Feathering:

• Toe-in or toe-out wear ✓
• Worn out king pin ✓
  (Any 1 x 1) (1)

10.1.2 One side of the thread worn:

• Camber wear ✓
• Worn out king pin ✓
• Incorrect wheel alignment ✓
  (Any 1 x 1) (1)

10.2 Requirements of well-designed 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 centring. ✓
• Able to operate without being affected by the action of the suspension or braking system. ✓
  (Any 2 x 1) (2)

10.3 King pin inclination:
10.3.1 Label:

1. – Offset/Scrub radius/pivot angle radius ✓
2. – 90° - Perpendicular ✓
3. – Wheel centre line ✓
4. – King pin inclination angle ✓
5. – Steering axis centre line/King-pin centre line ✓ (5)

10.3.2 King pin inclination is the inward tilt ✓ of the top of the king pin viewed from the front. ✓ (2)
10.4 Ackerman angle layout: (3)

Labels:

1. – Rear axle ✓
2. – Longitudinal axis ✓
3. – Front wheels ✓
4. – Steering arms ✓
5. – Extended centre lines from steering arms ✓
6. – Intersection/Centre point✓
   (Any 3 x 1) (3)

10.5 Purpose of Toe-out on turns:
The toe-out effect in a turn, gives a true rolling motion ✓ to the front wheels in a corner without scuffing. ✓ (2)
10.6 Wheel balancing pre-checks:

• The tyres for bruises, cracks and damaged side walls. ✓
• The wheel rims for damaged beads. ✓
• For foreign matter on rim and tyres.✓
• Tyre pressure. ✓
• Tyre thread wear. ✓
  (Any 2 x 1) (2)

10.7 Purpose of catalytic convertor:
The catalytic convertor converts the pollutants ✓ in the exhaust gases of the engine into non – toxic substances making it environmentally friendly. ✓ (2)
10.8 Adaptive speed control:

• Maintain a speed as set by the driver. ✓
• Adapt this speed and maintain a safe distance from the vehicle in front.✓
• Provide a warning if there is a risk of a collision. ✓
• Prevent driver fatigue. ✓
• To control the set speed. ✓
• Improve fuel economy. ✓
• A constant controlled speed setting prevents speeding fines. ✓
  (Any 3 x 1) (3)

10.9 Function of slip-ring and brush assembly:
Provide a moveable connection ✓ in order to allow current flow. ✓ (2)
10.10 Diode symbol: (2)

10.11 Advantages of electric fuel pump:

• Immediate supply of fuel when the ignition switch is turned on. ✓
• Low operation noise. ✓
• Less discharge pulsation of fuel. ✓
• Compact and lighter design. ✓
• Characterised to prevent fuel leak and vapour lock. ✓
• Delivers fuel at higher pressures. ✓
• Can be placed anywhere in the fuel line. ✓
  (Any 2 x 1) (2)

[32]
TOTAL: [200]