Mechanical Technology Grade 12 Eastern Cape Mock 2012 Memo

Downloaded from hlayiso.com Province of the EASTERN CAPE EDUCATION NATIONAL SENIOR CERTIFICATE GRADE 12 SEPTEMBER 2012 MECHANICAL TECHNOLOGY MEMORANDUM MARKS: 200 This memorandum consists of 12 pages.

Downloaded from hlayiso.com 2 MECHANICAL TECHNOLOGY (Memo) (SEPTEMBER 2012) QUESTION 1 is to be answered on this answer sheet. VRAAG 1 moet op hierdie antwoordblad beantwoord word. NAME/NAAM: ANSWER SHEET/ANTWOORDBLAD (MULTIPLE CHOICE QUESTION/VRAAG 1 QUESTIONS)/(MEERVOUDIGEKEUSE-VRAE) 1.1 A 1.2 D 1.3 B 1.4 A 1.5 A 1.6 C 1.7 A 1.8 D 1.9 B 1.10 A 1.11 D 1.12 C 1.13 D 1.14 A 1.15 B 1.16 A 1.17 C 1.18 C 1.19 C 1.20 D TOTAL Tear off this page and submit with answer book.

Downloaded from hlayiso.com (SEPTEMBER 2012) MECHANICAL TECHNOLOGY (Memo) 3 QUESTION 2 FORCES AND SYSTEMS AND CONTROL (LEARNING OUTCOME 3: ASSESSMENT STANDARDS 6 AND 8) 2.1 2.1.1 Area = √ √ = 0,000452389 m2 √ Stress = = √ = 132629119,2 Pa = 132,63 MPa √ (5) 2.1.2 Strain = √ = √ = 0,001037735 √ (3) 2.1.3 Young modules = √ = √ = 127,81 GPa √ (3) 2.2 Stress = √ Area = √ = 0,000904761 m2 √ BUT: Area = √ 0,000904761 = D = √ = 0,020571047 m D = 20,57 mm √ Say diameter of hole is 21 mm (6)

Downloaded from hlayiso.com 4 MECHANICAL TECHNOLOGY (Memo) (SEPTEMBER 2012) 2.3 Strain is directly proportional to the stress it causes, provided the limit of proportionality is not exceeded. √ √ (2) 2.4 force Stress = area force = stress x area √ 200 5 = (300 x 103) x ( ) √ 1000 1000 = 300N that is T1 √ T1 2,5 √ T2 1 300 T2 = √ 2,5 T2 = 120N √ Te = 300 – 120 = 180 N √ Torque: T T = Te x radius 1000 = 180 x ( )√ = 180 x 0,5 m 2 = 90 N.m √ Power: P = OR P = = √ = = 1884,96 watt = 1884,96 = 1,88 kW √ = 1,88 kW (11) 2.5 2.5.1 Force on piston A: √ F = √ = 75 N √ (3) 2.5.2 areaA 0,015 x “X” = 0,16 x 10 √ “X” = √ = 106,7 mm √ (3) 2.5.3 No effect because the pressure in the system is unchanged √ Piston A and B area did not change therefor no effect. √ (2)

Downloaded from hlayiso.com (SEPTEMBER 2012) MECHANICAL TECHNOLOGY (Memo) 5 2.6 2.6.1 M “F” √ = 392,5 N √ (2) 2.6.2 V √ = 14 : 1 √ (2) 2.7 2.7.1 Consider a three start or even a four start screw thread √ A three start will move - 3 x 10 = 30 mm A four start will move - 4 x 10 = 40 mm √ COMPARED TO Two start will move - 2 x 10 = 20 mm (2) 2.7.2 Lead = pitch x number of starts = 10 x 2 = 20 mm EFFECTIVE DIA(DE) = BD – (0,5 X PITCH) = 55 – (0,5 x 10) = 50 mm Helix angle TAN θ = 20 = 50 Θ = 7,26° (3) 2.8 “P” power OR T = µWnR 43,982 x 103 = √ = 0,35 x 2,5 x103 x 2 x T √ = 140 N.m = 139,999 Say= 140 N.m √ (3) [50]

Downloaded from hlayiso.com 6 MECHANICAL TECHNOLOGY (Memo) (SEPTEMBER 2012) QUESTION 3 TOOLS AND EQUIPMENT (LEARNING OUTCOME 3: ASSESSMENT STANDARD 2) 3.1 1. Scale √ 2. Indicator √ 3. Upper platform √ 4. Lower platform √ 5. Compressing lever √ (5) 3.2 3.2.1 Determines the amount of CO being produced √ OR Analyse the exhaust gases (1) 3.2.2 To measure the pressure created in one cylinder √ (1) 3.2.3 To check whether the engine leaks gases from one cylinder during the compression stokes √ (1) 3.3 1. Shielding gas cylinder √ 2. Wire-feed unit√ 3. Continuous wire reel√ 4. Welding gun √ 5. Gas flow meter √ 6. Power source OR AC transformer √ (6) 3.4 1. Check radiator for air bubbles - Air from cylinder is leaking into the water jackets√ 2. Listen for air coming out of the carburettor/air cleaner - this indicates that inlet valve is leaking√ 3. Air escaping through exhaust pipe - exhaust valve leaking√ 4. Check for air escaping through the oil filler cap - worn or broken rings 5. Air escaping through adjacent cylinders - cracked or blown head gasket (Any 3) (3) 3.5 Keep the meter dry √ Keep it away from dust and dirt √ Use and store it in normal temperature environments √ Do not drop it Use only charged cells of correct size Remove cells when not in use (Any 3) (3) [20]

Downloaded from hlayiso.com (SEPTEMBER 2012) MECHANICAL TECHNOLOGY (Memo) 7 QUESTION 4 MATERIALS (LEARNING OUTCOME 3: ASSESSMENT STANDARD 3) 4.1 1. Create a harder, tougher metal √ 2. Producing a stronger metal √ 3. Increase the resistance to corrosion and rust √ 4. Changing the colour of the metal √ 5. Increase electrical resistance √ 6. Improve ductility and elasticity 7. Improving casting properties 8. Strengthening the metal against wear and tear 9. Lowering the cost of the metal 10 Lowering the melting point to below the mean of the metal components (Any 5) (5) 4.2 4.2.1 Copper + zinc √ √ (2) 4.2.2 A hard alloy able to resist wear √ Very good resistance to corrosion √ Easily machined Lead acts as a lubricating agent (Any 2) (2) 4.3 Properties Uses 4.3.1 Very light, ductile, malleable, Transmission lines, electric soft, resist corrosion conduct cables, electric conductors, electricity and non-magnetic√ cooking utensils, gear crank cases, gear boxes, marine, aeroplane, motor vehicle, roofing, gutters, doors, etc. √ (Any 1) (Any 1) (2) 4.3.2 Work-hardens, ductility, Electrical cables, malleability, electrical- and switchboard parts, heat-conductivity, resist electrical bolts and nuts, corrosion √ water supply tubing and roofing √ (Any 1) (Any 1) (2) 4.3.3 Very soft, malleable, Soft solder, bullets, lead ductile and tough, bends cables, plumbing, sinkers and stretches easily √ etc. √ (Any 1) (Any 1) (2) 4.4 Salt and oil √ √ (2) 4.5 Water resistant √ Oil resistant √ Heat resistant √ Corrosion resistant Needs no lubrication (Any 3) (3) [20]

Downloaded from hlayiso.com 8 MECHANICAL TECHNOLOGY (Memo) (SEPTEMBER 2012) QUESTION 5 SAFETY, TERMINOLOGY AND JOINING METHODS (LEARNING OUTCOME 3: ASSESSMENT STANDARDS 1, 4 AND 5) 5.1 1. Never use damaged equipment √ 2. No oil or grease close to oxygen equipment √ 3. Never use oxygen to blow dirt or dust off clothing √ 4. Never use matches or gas lighter to ignite the flame √ 5. Sniff cylinders before assembling the regulators 6. Always make sure regulators have their adjusting screws released and purge them 7. Wear proper welding goggles, gloves and clothing 8. Make sure to have a fire extinguisher handy 9. Always use the proper regulator for the gas in the cylinder 10. Always use cylinders in the upright position 11. Always keep the acetylene cylinder valve wrench on the cylinder 12. Cylinder valve a maximum of one and a half turns open 13. Do not carry lighters or matches or other flammable objects in your pocket when welding 14. Take note of the area when welding 15. Be careful not to let welding hoses come in contact with the torch, flame or sparks from cutting (Any 3) (3) 5.2 1. Wear safety goggles √ 2. Make sure that the test piece is properly mounted √ 3. Do not exert too much stress in the beginning √ 4. Only use apparatus if in good order 5. Make sure that machine stands firm 6. Make sure that all bolts and nuts on the apparatus are tight 7. Wear the correct personal protective safety wear 8. Before testing commences, make sure that the safety shield is in place 9. Work with care with the dial indicator, it can easily be damaged (Any 3) (3) 5.3 1. Test only in well-ventilated area √ 2. Make certain that the exhaust probe is fitted correctly to the exhaust pipe √ 3. Do not run the engine for too long √ 4. Make sure that the inlet hose is not stepped on or restricted √ 5. Make sure that the hose connections are airtight 6. Check the valve on the condenser and be in the horizontal closed position 7. Check for leaks in the exhaust system, manifold or vacuum system 8. Clean the condenser and hose by blowing it with an air line 9. Drain the condenser after each test by means of the valve 10. Replace filter if it is light grey 11 Change fuel filter on condenser stand regularly 12. Make sure that the terminals are clean (Any 4) (4)

Downloaded from hlayiso.com (SEPTEMBER 2012) MECHANICAL TECHNOLOGY (Memo) 9 5.4 1. It keeps the work piece in position during machining √ 2. It divides the circumference of the work piece in equal divisions √ 3. It provides a turning action to work piece when doing helical milling √ 4. It provides movement to the bed when milling a rack (Any 3) (3) 5.5 Angle 16°30’ change (16 x 60’) + 30’ = 990’ Angle = OR Angle = = √ = = √ = = one full turn of the index crank and = one full turn of 20 holes on the 24 hole circle √ the index crank and 20 holes on the 24 hole circle (3) 5.6 Rapid indexing √ Differential indexing √ Normal indexing/Simple indexing√ Angular indexing (3) 5.7 5.7.1 Addendum = module √ = 2,0 mm √ (2) 5.7.2 Dedendum = 1,157 x m = 1,157 x 2 √ = 2,314 mm √ (2) 5.7.3 Cutting depth = 2,157 x m OR cutting depth = add + ded = 2,157 x 2 √ = 2 + 2,314 = 4,314 mm √ = 4,314 mm (2) 5.7.4 Circle pitch = = √ = 6,28 mm √ (2) 5.7.5 Clearance = 0,157 x m = 0,157 x 2√ = 0,314 mm √ (2) 5.7.6 PCD = OR PCD =Txm = √ = 40 x 2 = 80 mm √ = 80 mm (2) 5.8 Chance of teeth being sheared off is less √ Less cost √ Less power is required to drive the cutter √ Can use high arbour speed Less vibration on the arbour (3)

Downloaded from hlayiso.com 10 MECHANICAL TECHNOLOGY (Memo) (SEPTEMBER 2012) 5.9 r/min of cutter: N √ = √ = 137,1181048 r/min √ Feed speed (f) = f1 x T x N √ = 0,06 x 16 x 137,1181048 √ = 131,63 mm/min √ (6) 5.10 5.10.1 CAUSES CORRECTION Speed too fast √ Weld slowly √ Electrode too large √ Select correct electrode Current too low Set current up Leave enough space at bottom of the weld (3) 5.10.2 CAUSES CORRECTION Speed too fast √ Weld slowly √ Current too low √ Select correct current Faulty electrode Change the electrode Impaired base metal to a short Check for impurities in metal arc Hold a longer arc (3) 5.11 Cut a nick on the length of the joint approximately 6,5 mm deep √ Place the test piece on two steel supports √ Use a sledge hammer to break the welded joint √ Examine the broken surface of the weld for any possible defects √ (4) [50]

Downloaded from hlayiso.com (SEPTEMBER 2012) MECHANICAL TECHNOLOGY (Memo) 11 QUESTION 6 TURBINE AND MAINTENANCE (LEARNING OUTCOME 3: ASSESSMENT STANDARD 7 AND 9) 6.1 1. Lubricating insufficient √ 2. Operating temperature too excessive √ 3. Oil/grease supply has foreign materials √ 4. Incorrect lubricant √ 5. Faulty design 6. Lubricant contaminated with water 7. Misalignment (Any 4) (4) 6.2 6.2.1 1. V-belts are used over short distances √ 2. V-belts come in standard size for immediate replacement √ 3. Silent in operation √ 4. Requires very little maintenance 5. Is able to absorb shock loads 6. Operate at low bearing pressure 7. A number of v-belts can be used for heavy duty application 8. In a multi v-belt drive if one belt breaks the machine can still run on the remaining belts (Any 3) (3) 6.2.2 1. V-belt tension is too slack √ 2. Oil on v-belt √ 3. Grease on v-belt √ 4. V-belt worn out/damaged sides (Any 3) (3) 6.3 6.3.1 1. Make sure engine is at working temperature 2. Place container under sump. Remove oil filler cap. 3. Unscrew sump plug and drain oil into container. 4. Use a filter spanner and remove oil filter. 5. Allow enough time for oil to drain. 6. Apply sheen of oil to rubber seal of oil filter and mount with hand 7. Screw sump plug fitted with new copper washer to sump. 8. Refill engine with oil according to specifications and replace oil filler cap. (8) 6.3.2 (a) SAE “society of automotive engineers” √ (1) (b) 20 A thinner oil for when the engine is still cold √ (1) (c) W Indicates winter/colder conditions √ (1) (d) `50 A thicker oil for when the engine is at optimal working temperature √ (1)

Downloaded from hlayiso.com 12 MECHANICAL TECHNOLOGY (Memo) (SEPTEMBER 2012) 6.4 1. The work piece and cutting tool are kept cool √ 2. The life of the cutting tool is prolonged √ 3. A better finish is imparted to the surface √ 4. Cuttings are washed away √ 5. The machine is protected because the cutting process is eased √ 6. The machine operator is protected from metal chips 7. Productivity is increased because of the cutting process is faster 8. The soluble oil prevents corrosion 9. It lubricates the machine (Any 5) (5) 6.5 6.5.1 Roots-blower √ (1) 6.5.2 Vane-blower √ (1) 6.5.3 Centrifugal-blower √ (1) 6.6 1. Inlet √ 2. Outlet √ 3. Rotor √ 4. Casing √ (4) 6.7 Centrifugal-blower √ OR Figure 6.5.3 (1) 6.8 TURBO SUPERCHARGER Driven by exhaust gases √ Mechanical driven √ (2) 6.9 1. Special shutdown procedure is required √ 2. Special exhaust system needed√ 3. Lag because of the exhaust gases to overcome the rotational inertia √ (3) [40] TOTAL: 200