GRAAD 12 NATIONAL SENIOR CERTIFICATE GRADE 12

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1 GR 12 NTIONL SENIOR ERTIFITE GRE 12 MEHNIL TEHNOLOGY EXEMPLR 2014 MRKS: 200 TIME: 3 hours This question paper consists of 18 pages and a 3-page formula sheet. opyright reserved

2 Mechanical Technology 2 E/2014 NS Grade 12 Exemplar INSTRUTIONS N INFORMTION 1. Write your centre number and examination number in the spaces provided on the NSWER OOK. 2. Read LL the questions carefully. 3. nswer LL the questions. 4. Number the answers correctly according to the numbering system used in this question paper. 5. Start EH question on a NEW page. 6. Show LL calculations and units. Round off final answers to TWO decimal places. 7. andidates may use non-programmable scientific calculators and drawing instruments. 8. Take the value of gravitational force as 10 m/s ll dimensions are in millimetres, unless stated otherwise in the question. 10. formula sheet for your use is attached at the back of this question paper. 11. Write neatly and legibly. 12. Use the criteria below to assist you in managing your time. QUESTION ONTENT MRKS TIME (minutes) 1 Multiple-choice questions Safety Tools and Equipment Materials Terminology Joining Methods Forces Maintenance Systems and ontrol Turbines TOTL opyright reserved

3 Mechanical Technology 3 E/2014 NS Grade 12 Exemplar QUESTION 1: MULTIPLE-HOIE QUESTIONS Various options are provided as possible answers to the following questions. hoose the answer and write only the letter ( ) next to the question number ( ) in the NSWER OOK, for example What safety measure is applicable to the milling machine in terms of the Occupational Health and Safety ct? o not apply a wrench to revolving work. Guards could be removed when cutting soft material. Make sure the wheel is dressed. Use the machine table as an anvil. (1) 1.2 Which ONE of the following safety procedures is applicable to the cylinder leakage tester? Use water to remove dust around the spark-plug area. lean the oil-filler cap. o not exceed the prescribed pressure in the cylinder. The tester must be well tightened until no hissing sounds can be heard. (1) 1.3 What is the function of a gas analyser? nalyse inlet gases nalyse oil gases nalyse fuel gases nalyse exhaust gases (1) 1.4 rinell tester is used to test the... of a material. tension elasticity hardness brittleness (1) 1.5 What will be the result when steel is heated in the second phase 2? Grain structure is at its smallest. It will become liquid. It only loses its magnetism. It becomes a stronger magnet. (1) 1.6 Which ONE of the following is a property of pearlite? It is ductile. It is weak. It is malleable. It becomes brittle. (1) opyright reserved

4 Mechanical Technology 4 E/2014 NS Grade 12 Exemplar 1.7 Identify the type of key shown in FIGURE 1.1. FIGURE 1.1 Square key Gib head key Pratt and Whitney key Woodruff key (1) 1.8 Which milling method is shown in FIGURE 1.2? FIGURE 1.2 own-cut milling Up-cut milling Gang milling Straddle milling (1) 1.9 How are defects shown by applying an X-ray test? efects visible on the weld efects visible on film efects determined by sound efects visible on an oscilloscope screen (1) opyright reserved

5 Mechanical Technology 5 E/2014 NS Grade 12 Exemplar 1.10 What is the reason for applying a nick-break test on a welded joint? To test the skill of the welder To check the size of the weld To train welders To approve welds and welders to certain standards (1) 1.11 What do you understand by the term stress in materials? Internal force in a material resisting a/an... shearing load. pulling load. compressive load. external load. (1) 1.12 Tensile stress can be defined as an internal force in a material resisting a shearing load. a pulling load a compressive load. any load. (1) 1.13 What do you understand by the term Young's modulus of elasticity? The force value required to produce a unit area in a tensile test specimen The ratio between stress and strain in a metal, provided that the limit of elasticity is not exceeded measurement of the extension or contraction of material due to the load experienced ratio of the deformation because of the application of an external force (1) 1.14 What do you understand by the term viscosity? Resistance of a fluid to... an external load. heat. flow. internal stress. (1) 1.15 SE 20W50 oil is used for engine lubrication. gearbox lubrication. differential lubrication. automatic gearbox lubrication. (1) opyright reserved

6 Mechanical Technology 6 E/2014 NS Grade 12 Exemplar 1.16 Which ONE of the following statements defines oyle's law? n ideal gas law where,... at constant pressure, the volume of an ideal gas is inversely proportional to its absolute temperature at constant volume, the temperature of an ideal gas is inversely proportional to its absolute pressure at constant temperature, the volume of an ideal gas is inversely proportional to its absolute pressure at constant temperature, the volume of an ideal gas is directly proportional to its absolute pressure (1) 1.17 What is the velocity ratio of the pulley system in FIGURE 1.3 if pulley is the driver? Pulley = river Ø 25 mm Ø 50 mm FIGURE : 1 3 : 1 1 : 2 2 : 1 (1) 1.18 etermine the width of a key if the diameter of the shaft is 60 mm. 15 mm 30 mm 20 mm 6 mm (1) 1.19 What do you understand by the term boost as related to superchargers? The pressure the supercharger makes in the inlet manifold Where the blower is positioned before the carburettor or throttle body The centrifugal force of the air to make compression Where the blower is positioned after the carburettor or throttle body (1) opyright reserved

Mechanical Technology 7 E/2014 NS Grade 12 Exemplar 1.20 Identify the hydro-turbine in FIGURE 1.1. FIGURE 1.1 Francis Pelton Kaplan Turgo (1) [20] QUESTION 2: SFETY 2.

7 Mechanical Technology 7 E/2014 NS Grade 12 Exemplar 1.20 Identify the hydro-turbine in FIGURE 1.1. FIGURE 1.1 Francis Pelton Kaplan Turgo (1) [20] QUESTION 2: SFETY 2.1 State FOUR safety measures to be observed while the lathe is in operation after it has been switched on. (4) 2.2 State THREE safety rules to be applied when using the torsion tester. (3) 2.3 State THREE common safety measures to be observed with arc and gas welding. (3) [10] opyright reserved

8 Mechanical Technology 8 E/2014 NS Grade 12 Exemplar QUESTION 3: TOOLS N EQUIPMENT 3.1 Mr Jack conducted a compression test on a four-cylinder petrol engine. He found that cylinder two had a lower compression than the other cylinders. State TWO causes for low compression. (2) 3.2 Princess uses the rinell hardness tester to test the hardness of a specimen given to her by the supervisor. FIGURE 3.1 shows the specimen under test. Write down the letters in your NSWER OOK and the correct names of the parts next to the corresponding letters. 3.3 escribe the purpose of the tests below. FIGURE 3.1 (4) Gas analysing test (2) eam-bending test (2) 3.4 Mr Raj did a cylinder leakage test and obtained certain results. State ONE possible result and the fault of the cylinder. (2) [12] opyright reserved

9 Mechanical Technology 9 E/2014 NS Grade 12 Exemplar QUESTION 4: MTERILS 4.1 Name ONE property of each of the structures below Ferrite (2) ementite (2) ustenite (2) 4.2 FIGURE 4.1 shows a diagram. nswer the questions that follow E Temperature ,2 0,4 0,6 0,8 1,0 1,2 1,4 arbon content % FIGURE What type of diagram is shown in FIGURE 4.1? (2) Write down the letters E in your NSWER OOK and then the correct labels for the diagram next to the corresponding letters. (5) [13] opyright reserved

10 Mechanical Technology 10 E/2014 NS Grade 12 Exemplar QUESTION 5: TERMINOLOGY 5.1 Explain the screw-cutting procedure using the compound-slide method. (7) 5.2 gib head key must be made to fit a 84 mm diameter shaft. alculate the following: The width of the key (2) The thickness of the key (2) The length of the key (2) The thickness of the key at the small end (4) 5.3 State TWO advantages of EH of the following milling operations: Up-cut milling (2) own-cut milling (2) 5.4 gear with 17 teeth has to be machined on a milling machine. alculate the indexing required. (4) 5.5 FIGURE 5.1 shows a milling procedure. nswer the questions that follow. FIGURE Identify the milling process. (2) Write down the letters in your NSWER OOK and the correct names of the parts next to the corresponding letters. (3) [30] opyright reserved

11 Mechanical Technology 11 E/2014 NS Grade 12 Exemplar QUESTION 6: JOINING METHOS 6.1 For EH of the following welded joints, identify the defect, state ONE possible cause and ONE preventive action: Gas is trapped in the weld metal. (3) Non-metallic solids are trapped in the weld metal. (3) groove appears in the parent metal, directly along the edges of the weld. (3) 6.2 Name THREE destructive tests exerted onto metals. (3) 6.3 Explain how you will conduct a dye penetration test on a welded joint. (7) 6.4 What does the abbreviation MG/MIGS stand for in terms of welding equipment? (1) 6.5 Name FOUR basic components of a MG/MIGS welding machine. (2) 6.6 State THREE advantages of using a MG/MIGS welding machine. (3) [25] opyright reserved

12 Mechanical Technology 12 E/2014 NS Grade 12 Exemplar QUESTION 7: FORES 7.1 efine the concepts below Stress (2) Strain (2) 7.2 Four forces of 9 N, 11 N, 10 N and 8 N as shown in FIGURE 7.1 are acting onto the same point. etermine by means of calculations the equilibrant for the system of forces in FIGURE N 8 N N 10 N FIGURE 7.1 (13) 7.3 compressive force causes internal stress of 16 MPa in a round bar made of an unknown metal. The resistance area of the round bar is 1,26 x 10-3 m 2 and the original length is 80 mm. The force causes the round bar to shorten by 14,4 x 10-3 mm. etermine by means of calculations: The strain in the metal caused by the force (3) The elasticity modulus for this metal (3) opyright reserved

13 Mechanical Technology 13 E/2014 NS Grade 12 Exemplar 7.4 What does point represent in FIGURE 7.3? E Stress Strain FIGURE 7.3 (1) 7.5 FIGURE 7.4 shows a uniform beam that is supported by two vertical supports, and. uniformly distributed force is exerted on the beam over a distance of 4 m from the left side of the beam. etermine by means of calculations the magnitudes of the reactions in supports and. 150 N/m 400 N 500 N 3 m 1 m 2 m FIGURE 7.4 (6) [30] opyright reserved

Mechanical Technology 14 E/2014 NS Grade 12 Exemplar QUESTION 8: MINTENNE 8.1 Explain the following properties of oils: 8.1.1 Viscosity (1) 8.1.2 Pour point (1) 8.2 Mr Sunir owns an old car.

14 Mechanical Technology 14 E/2014 NS Grade 12 Exemplar QUESTION 8: MINTENNE 8.1 Explain the following properties of oils: Viscosity (1) Pour point (1) 8.2 Mr Sunir owns an old car. He does not keep proper service records of his car. This resulted in his car not being serviced on time, causing the timing chain to become noisy. nswer the questions that follow. E FIGURE Write down the letters E in your NSWER OOK and then the correct labels for the figure next to the corresponding letters. (5) Explain how you would go about replacing the timing chain. (6) 8.3 What does the abbreviation SE stand for regarding oils? (2) [15] opyright reserved

15 Mechanical Technology 15 E/2014 NS Grade 12 Exemplar QUESTION 9: SYSTEMS N ONTROL 9.1 FIGURE 9.1 shows a gear drive system. river gear on the shaft of an electric motor has 20 teeth and meshes with gear with 36 teeth on a countershaft. On this countershaft is another driver gear,, with 18 teeth that meshes with gear with 46 teeth on a second countershaft. The second countershaft has a driver gear, E, with 42 teeth that drive gear F with 80 teeth on the output shaft. Electrical motor E ountershaft 42 F 36 ountershaft 18 Output shaft 80 etermine by means of calculations: FIGURE The rotation frequency of the output shaft if the electric motor rotates at r/min (revolutions per minute) (3) The velocity ratio between the input shaft and output shaft (2) 9.2 FIGURE 9.2 shows a belt-drive system. pulley with a diameter of 0,24 m drives a driven pulley with a diameter of 0,36 m. The driver pulley rotates at r/min. T 1 = 200 N and T 2 = 90 N. N N =? r/min N = 0,36 m T 2 N R = r/min R = 0,24 m T 1 FIGURE 9.2 opyright reserved

16 Mechanical Technology 16 E/2014 NS Grade 12 Exemplar etermine by means of calculations: The rotation frequency of the driven pulley in r/min (2) The power transmitted (2) The belt speed of the system in metres per second (2) 9.3 hydraulic system is being used to lift a machine part into position. The specifications of the system are diagrammatically represented in FIGURE 9.3. Ø 40 mm 275 N Ø 180 mm Load =? Piston Piston etermine by means of calculations: FIGURE The fluid pressure in the hydraulic system when in equilibrium (3) The load that can be lifted by piston when a force of 275 N is applied to piston (4) 9.4 What do the following abbreviations stand for? S (1) EU (1) 9.5 What is traction control? (2) 9.6 Explain the operation of the central locking system of motor vehicle doors. (3) [25] opyright reserved

Mechanical Technology 17 E/2014 NS Grade 12 Exemplar QUESTION 10: TURINES 10.1 FIGURE 10.1 shows a water turbine driving a generator. nswer the questions that follow. F E TURINE FIGURE 10.1 10.1.1 Write down the letters F in your NSWER OOK and then the correct labels for the figure next to the corresponding letters.

17 Mechanical Technology 17 E/2014 NS Grade 12 Exemplar QUESTION 10: TURINES 10.1 FIGURE 10.1 shows a water turbine driving a generator. nswer the questions that follow. F E TURINE FIGURE Write down the letters F in your NSWER OOK and then the correct labels for the figure next to the corresponding letters. (6) Explain the operation of the water turbine. (3) 10.2 Many modern motor vehicles make use of superchargers. nswer the questions below State TWO advantages of a supercharger. (2) State ONE disadvantage of a supercharger. (1) 10.3 State TWO advantages of a gas turbine as used in a jet plane. (2) opyright reserved

Mechanical Technology 18 E/2014 NS Grade 12 Exemplar 10.4 large number of trucks make use of turbochargers to enhance their performance. FIGURE 10.

18 Mechanical Technology 18 E/2014 NS Grade 12 Exemplar 10.4 large number of trucks make use of turbochargers to enhance their performance. FIGURE 10.2 shows a turbocharger arrangement. Write down the letters F in your NSWER OOK and then the correct labels for the figure next to the corresponding letters. F E FIGURE 10.2 (6) [20] TOTL: 200 opyright reserved

19 Mechanical Technology 1 E/2014 NS Grade 12 Exemplar 1. ELT RIVES FORMUL SHEET 1.1 πn elt speed = 60 π ( + t ) N 1.2 elt speed = (t = belt thickness) elt mass = area length density ( = thickness width) 1.4 Speed ratio = diameter of diameter of driven pulley driver pulley 1.5 elt length( flat ) = [( + d ) 1,57] + ( 2 centre distance ) 2 π( + d ) ( - d ) 1.6 Open - belt length = + + 2c 2 4c 2 π( + d ) ( + d ) 1.7 rossed-belt length = + + 2c 2 4c 1.8 Power ( P ) = 2 π N T T Ratio of tight side to slack side = T (T1 T2 ) π N Power ( P ) = where T1 = force in the tight side 1.11 T1 Width = permissible tensile force 2. STRESS N STRIN force F 2.1 Stress = or ( σ = ) area 2.2 change in length ( ΔL ) Strain ( ε ) = original length ( L ) stress σ 2.3 Young' s modulus ( E ) = or ( ) strain ε opyright reserved

20 Mechanical Technology 2 E/2014 NS Grade 12 Exemplar 3. HYRULIS 3.1 Pressure ( P ) = Force ( F ) rea ( ) 3.2 Volume = cross-sectional area stroke length ( l or s ) 3.3 Work done = force distance 4. GER RIVES 4.1 Power ( P ) = 2 π NT Gear ratio = Number of teeth on driven gear Number of teeth on driving gear 4.3 Torque = force radius 4.4 Torque transmitted = gear ratio input torque 4.5 Module ( m ) = Pitch-circle diameter ( P ) Number of teeth ( T ) 4.6 circular Pitch-circle diameter ( P ) = pitch ( P ) number of π teeth ( T ) 4.7 Outside diameter ( O ) = P + 2 module 4.8 ddendum ( a ) = module ( m ) 4.9 edendum ( b ) = 1,157 m or edendum( b ) = 1,25 m 4.10 utting depth ( h ) = 2,157 m or utting depth ( h ) = 2,25 m 4.11 learance ( c ) = 0,157 m or learance ( c ) = 0,25 m 4.12 ircular pitch ( P ) = m π opyright reserved

21 Mechanical Technology 3 E/2014 NS Grade 12 Exemplar 5. PULLEY RIVES 5.1 N 1 1 = N Power ( P ) = 2 π N T Velocity ratio = diameter of diameter of driven pulley driver pulley 5.4 r/min of r/min of driven pulley = driver x diameter of driver diameter of driven pulley pulley 6. KEYWYS diameter of shaft Width of key = 4 diameter of shaft Thickness of key = Length of key = 1,5 x diameter of shaft 6.4 Standard taper for taper key: 1 in 100 or 1 : ININNTI IVIING HE TLE FOR MILLING MHINE Hole circles Side Side Standard change gears 24 x Indexing formula = ( where n = number of n divisions ) opyright reserved

NATIONAL SENIOR CERTIFICATE GRADE 12

NATIONAL SENIOR CERTIFICATE GRADE 12 NTIONL SENIOR ERTIFITE GRE 12 MEHNIL TEHNOLOGY NOVEMER 2017 MRKS: 200 TIME: 3 hours This question paper consists of 15 pages and a 4-page formula sheet. Mechanical Technology 2 E/November 2017 INSTRUTIONS