NATIONAL SENIOR CERTIFICATE

GRADE 11

NOVEMBER 2015

MECHANICAL TECHNOLOGY

MARKS: 200 TIME: 3 hours

This question paper consists of 18 pages, including a formula sheet.

*IMCHTE*

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INSTRUCTIONS AND INFORMATION 1. Write your name and surname in the spaces provided on the answer book. 2. Answer ALL the questions. 3. Read all the questions thoroughly. 4. Number the questions carefully according to the numbering system used in

this question paper. 5. Write neatly and legibly. 6. Show ALL calculations and units. Round off final answers to TWO decimal

places. 7. Candidates are allowed to use non-programmable, scientific calculators and

drawing/mathematical instruments. 8. Begin each question on a NEW page. 9. Use the criteria below to assist you in managing your time: QUESTION TOPIC MARKS 1 Multiple-choice questions 20 2 Safety 10 3 Tools and equipment 12 4 Materials 13 5 Terminology 30 6 Joining methods 25 7 Forces 30 8 Maintenance 15 9 Systems and control 25 10 Pumps 20 TOTAL: 200

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QUESTION 1: MULTIPLE-CHOICE QUESTIONS 1.1 Which TWO items of safety equipment are used when working on the

lathe? A Aprons and gloves B Helmets and goggles C Safety shoes and goggles D Gloves and goggles (1) 1.2 Which ONE of the following safety precautions applies to surface grinders? A Never clean or adjust the machine whilst it is in motion. B Protective clothes and eye protection are essential. C Do not operate the machine unless all guards and safety devices are

in place and working correctly. D All of the above. (1) 1.3 Which of the following tools is used to determine the diameter of a cylinder

block in a four-stroke engine? A Outside calliper B Telescopic gauge C Dial gauge D Outside micrometer (1) 1.4 Which of the following statements refers to a clearance size or tapping size,

when using taps and dies? A The hole size of the bolt that is being used. B The size of the hole that must be drilled so that it will clear the outside

diameter of a screw. C The size of the tap. D The size of the die. (1) 1.5 Identify the furnace in FIGURE 1.5 below.

FIGURE 1.5 A Bessemer converter B Blast furnace C Open hearth furnace D Oxygen furnace (1)

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1.6 Hardness refers to the material’s ability to ... A resist penetration. B be permanently shaped. C stretch. D absorb forces. (1) 1.7 Which taper-turning method is applicable on the centre lathe? A The tailstock can be offset for longer external tapers. B The taper-turning attachment can be used for external tapers and for

short internal boring. C The compound slide rest can be rotated for turning short internal and

external tapers. D All of the above. (1) 1.8 Calculate the indexing for a gear with 38 teeth. Choose the correct answer. A 2 turns and 2 holes in a 38 hole circle B 1 turn and 2 holes in a 38 hole circle C 1 turn and 13 holes in a 49 hole circle D 2 turns and 1 hole in a 49 hole circle (1) 1.9 Identify the component below that is supplementary to a milling machine.

A Arbour B Saddle C Compound slide D Dividing head (1) 1.10 Which of the following statements defines the term ‘purge’ during gas

welding? A To release fumes from the equipment B To flush out gas before igniting the welding torch C To mix the oxygen and acetylene D To compress the fuel in the shank (1)

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1.11 Given a sketch of a welding flame as shown below, select the correct procedure to achieve a suitable welding or brazing flame.

A Adjust the oxygen until both first and second flame cones touch the

third flame cone. B Adjust the oxygen until the tip of the second flame cone touches the

tip of the first flame. C Adjust the oxygen until the tip of the first flame cone touches the third

flame cone. D Adjust the oxygen until the second flame cone touches the third flame

cone. (1) 1.12 Which of the following constitutes the equilibrium of three forces? A Two forces acting on a body B The calculation of forces C The concept of triangle of forces D The reaction on the supports (1) 1.13 Calculate the moment as shown in the figure below.

Choose the correct answer: A 8 Nm B 18 Nm C 15 Nm D 10 Nm (1) 1.14 Complete the following: The lack of lubrication or incorrect lubrication … A speeds up the motion of a rolling object. B increases engine speed. C ensures that operating systems malfunction. D converts motion from one form to another. (1) 1.15 Which of the following should be checked, before balancing a wheel? A The wheel rim must be examined for damaged edges. B The suspension should be firm. C The kingpin should be tilted back. D The pivot angle radius should be 90°. (1)

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1.16 Which of the following statements is an advantage of the single helical gear as shown below?

A The gears are expensive. B The contact between the meshing teeth takes place very gradually. C Friction due to the sliding motion between the meshing teeth is high. D It must run in an oil-bath. (1) 1.17 When will you be able to make use of a worm and worm gear drive?

A When parts must be adjusted with reference to one another. B When the direction of the drive must change through 90° and the

centre lines of the drive shafts are situated on the same plane. C When the drive is very rough. D When the rotary movement is changed to reciprocating motion. (1)

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1.18 Which of the following is an example of a third class lever? A B

C D

(1)

1.19 Which of the following pumps is used mainly to pump sandy, muddy or sewerage water with ease?

A Rotor pump B Reciprocating pump C Centrifugal pump D Vane pump (1) 1.20 Which of the following is an advantage of a Vane pump in its operation? A The drive is always positive. B They are very efficient for slow-speed engines. C It has no valves or springs. D It has no moving valves. (1) [20] QUESTION 2: SAFETY 2.1 State whether the following statements are TRUE or FALSE. 2.1.1 Use a machine ONLY once the safety guards have been correctly

fitted. (1) 2.1.2 Never clean or adjust a machine whilst it is in motion. (1) 2.1.3 Leave the chuck key in the chuck when you are NOT at the lathe. (1) 2.1.4 A drill should run at a high speed when drilling a 30 mm hole. (1)

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2.2 Name any FOUR safety rules to be taken into account before working with a bench grinder.

(4) FIGURE 2.2 2.3 Mention TWO safety precautions to be taken when starting or stopping

machinery. (2) [10] QUESTION 3: TOOLS AND EQUIPMENT 3.1 Name THREE important usages when operating the tap wrench.

(3) 3.2 Which lubricant would you use when cutting a thread on bronze, copper or

steel? (1) 3.3 What is the function of a pitch gauge? (1) 3.4 Describe how you would care for a power saw. (2) 3.5 What is the function of the inverter (DC) welding machine? (1) 3.6 Give TWO reasons for using the torque wrench. (2) 3.7 What is the function of a power-driven shearing machine? (1) 3.8 How would you care for manual and electric guillotines? (1) [12]

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QUESTION 4: MATERIALS 4.1 Identify the steel-making furnace in the FIGURE below. (1)

4.2 Define the properties of the following: 4.2.1 Elasticity (2) 4.2.2 Ductility (2) 4.2.3 Brittleness (2) 4.2.4 Malleability (2) 4.2.5 Plasticity (1) 4.3 Identify THREE of the several quenching media that are used to give

different rates of cooling. (3) [13]

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QUESTION 5: TERMINOLOGY 5.1 Use a milling machine to cut a hexagon on a 100 mm shaft.

Calculate the depth of the cut. (6) 5.2 Explain the cutting procedure to cut a taper on the centre lathe, using the

compound slide parallel with the lathe bed.

(10) 5.3 A taper 180 mm long, has to be turned on the end of a 90 mm diameter

shaft. If the diameter of the small end of the taper is 80 mm, calculate the angle to which the compound slide must be set in order to cut this taper.

(6) 5.4 A shaft with a diameter of 70 mm must be machined on a milling machine to

a square. Calculate the distance across the flat side that must be cut away.

x Distance across the flat side 70 mm (6)

5.5 Calculate the index to cut a pentagon using simple indexing. (2) [30]

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QUESTION 6: JOINING METHODS 6.1 What do you understand by permanent joining applications? (1) 6.2 Explain step-by-step the application of soft solder. (4) 6.3 What joining application is being performed in the illustrations below?

(1)

FIGURE 6.3 6.4 How does the number of welds on a welding joint influence the parent metal?

(2) 6.5 How does the size of the weld influence the welding joint? (2) 6.6 Identify the welding joints as shown in the illustrations below.

(8)

6.7 Identify the remaining FOUR primary factors that influence a welding joint,

excluding the number of welds and size of welds. (4) 6.8 Identify the following welding symbols in the illustrations below. 6.8.1

6.8.2 6.8.3 (3) [25]

A B

C

D

E

F

G

H

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QUESTION 7: FORCES 7.1 Define the following basic concepts of systems of forces: 7.1.1 Equilibrant (2) 7.1.2 Bow’s notation/Triangle of forces (2) 7.1.3 Components of a force (2) 7.2 The following system of forces contains three forces. Use Bow’s notation to

construct a triangle of forces and show how they are in equilibrium.

7.2.1 Draw the space diagrams using the scale 4 cm = 10 N. (3) 7.2.2 Draw the vector diagram using the scale 4 cm = 10 N. (3) 7.2.3 Why do you think the triangle of forces is in equilibrium? (1)

7.3 A beam is subjected to two point loads and one UDL, and is supported at each end by RL and RR.

7.3.1 Calculate the magnitude of RR and RL. (4) 7.3.2 Calculate the bending moments at points A and B. (4) 7.3.3 Test the beam for equilibrium. (1)

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7.4 Calculate the compressive stress in a 32 x 32 x 3 mm square tube if it is subjected to a load of 70 kN.

(5) 7.5 A 220 N force is inclined at 30° to the horizontal. 7.5.1 Draw the diagram and indicate the two components (X and Y) of the

force that need to be calculated. (1) 7.5.2 Determine (by calculation) the horizontal and vertical components of

the force. (2) [30] QUESTION 8: MAINTENANCE 8.1 Inadequate maintenance affects operating systems. Explain how inadequate

maintenance will affect the following: 8.1.1 Balancing of wheels (4) 8.1.2 Overloading of machines (2) 8.2 Define positive camber with regard to wheel alignment. (2) 8.3 Briefly explain kingpin inclination.

(2) 8.4 Make a sketch showing the Ackerman principle (toe-out on turns), indicating

the different steering angles and relevant components on the drawing. (5) [15]

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QUESTION 9: SYSTEMS AND CONTROL 9.1 With the aid of the illustrations below, explain the operating principle of the

handbrake on a motor vehicle.

(3) 9.2 Explain the basic operating principles of the hydraulic clutch in a motor

vehicle.

(6) 9.3 Calculate the rotational frequency (speed) of the driven shaft in FIGURE 9.3.

FIGURE 9.3 (5)

Drive shaft 12 r/s Driven shaft? 𝑇𝐶 −63 teeth

𝑇𝐴−20 teeth

𝑇𝐵−80 teeth 𝑇𝐷−42 teeth Intermediate shaft

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9.4 A driving pulley with an effective diameter of 300 mm rotates at 950 rpm. The tension at the tight side of the belt is 600 N and the ratio of tensions is 2:1.

Calculate the power transmitted.

300 mm (6)

9.5 A piston acts on liquid with a force of 7 500 N and the area of the piston is

3 m2. Find the pressure in the liquid.

(3)

9.6 Describe the use of a piston in hydraulics/pneumatics systems. (2) [25]

Piston

Liquid

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QUESTION 10: PUMPS 10.1 FIGURE 10.1 below shows a gear-type pump. Label the parts A–E.

(5) FIGURE 10.1 10.2 Describe the operating principle of a vane pump.

(6) 10.3 Identify TWO specific uses of the mono pump. (2) 10.4 Identify TWO typical areas where you will use a mono pump. (2) 10.5 Explain the operating principles of a centrifugal pump.

(5) [20] TOTAL: 200

B

A C

D

E

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GRADE 11 FORMULA SHEET 1. GAUGE BLOCKS Set nr. M.50 Range increment in mm number of blocks 1,0025 to 1,0075 0,0025 3 1,01 to 1,09 0,01 9 1,1 to 1,9 0,1 9 1 to 25 1,0 25 50; 75; 100 3 0,5 1 2. FRICTION: 𝐹 = 𝑓𝑜𝑟𝑐𝑒 𝑜𝑓 𝑓𝑟𝑖𝑐𝑡𝑖𝑜𝑛 µ = co-efficient of friction N = Normal force 𝐹 = 𝜇 × 𝑁 3. TORQUE: T T = Force x Distance were T = N.m. 4. BELT DRIVES 4.1 Belt speed =πDN

60 4.2 Belt speed = π(D+t)N

60 (t = belt thickness) 4.3 Belt mass/kilogram = Area × length × density

(A = thickness × width) 4.4 Speed ratio = Dia.of driven pulley

Dia.of driver pulley 4.5 Output speed = 𝑑𝑟𝑖𝑣𝑒 𝑝𝑢𝑙𝑙𝑒𝑦

𝑑𝑟𝑖𝑣𝑒𝑛 𝑝𝑢𝑙𝑙𝑒𝑦 × 𝑑𝑟𝑖𝑣𝑒 𝑝𝑢𝑙𝑙𝑒𝑦𝑑𝑟𝑖𝑣𝑒𝑛 𝑝𝑢𝑙𝑙𝑒𝑦 × 𝑖𝑛𝑝𝑢𝑡 𝑠𝑝𝑒𝑒𝑑

4.6 Open-belt length = π(D+d)2 + (D−d)2

4c + 2c 4.7 Crossed-belt length = π(D+d)

2 + (D+d)2

4c + 2c 4.8 Power (P) = 2πNT

60 4.9 Ratio of tight side to slack side = 𝑇1

𝑇2

4.10 Power (P) = (T1−T2)πDN60

4.11 Width = 𝑇1𝑃𝑒𝑟𝑚𝑖𝑠𝑠𝑖𝑏𝑙𝑒 𝑡𝑒𝑛𝑠𝑖𝑙𝑒 𝑓𝑜𝑟𝑐𝑒

4.12 DiaA x NA = DiaB x NB

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5. GEAR DRIVES: SPUR GEAR 5.1 Power (P) = 2πNT

60 5.2 Gear ratio = 𝑝𝑟𝑜𝑑𝑢𝑐𝑡 𝑜𝑓 𝑑𝑟𝑖𝑣𝑒𝑛 𝑔𝑒𝑎𝑟𝑠 𝑡𝑒𝑒𝑡ℎ

𝑝𝑟𝑜𝑑𝑢𝑐𝑡 𝑜𝑓 𝑑𝑟𝑖𝑣𝑒 𝑔𝑒𝑎𝑟𝑠 𝑡𝑒𝑒𝑡ℎ 5.3 𝑁𝑖𝑛

𝑁𝑜𝑢𝑡= 𝑝𝑟𝑜𝑑𝑢𝑐𝑡 𝑜𝑓 𝑑𝑟𝑖𝑣𝑒𝑛 𝑔𝑒𝑎𝑟𝑠 𝑡𝑒𝑒𝑡ℎ

𝑝𝑟𝑜𝑑𝑢𝑐𝑡 𝑜𝑓 𝑑𝑟𝑖𝑣𝑒 𝑔𝑒𝑎𝑟𝑠 𝑡𝑒𝑒𝑡ℎ

5.4 Torque = force × 𝑟𝑎𝑑𝑢𝑖𝑠 5.5 Torque transmitted = 𝑔𝑒𝑎𝑟 𝑟𝑎𝑡𝑖𝑜 × 𝑖𝑛𝑝𝑢𝑡 𝑡𝑜𝑟𝑞𝑢𝑒 5.6 TA x NA = TB x NB 6. HYDRAULICS 6.1 Pressure =

Force (F)Area (A)

6.2 Volume = cross-sectional area x stroke length (ℓ or s) 6.3 Work done = force x distance 7. Forces 7.1 Stress = 𝐹𝑜𝑟𝑐𝑒

𝐴𝑟𝑒𝑎 7.2 Strain = 𝐶ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝐿𝑒𝑛𝑔𝑡ℎ

𝑂𝑟𝑖𝑔𝑖𝑛𝑎𝑙 𝐿𝑒𝑛𝑔𝑡ℎ 8. Indexing 8.1 Crank T = 40

𝑁 9. Taper Turning 9.1 Tan Ө = 𝑫−𝒅

𝟐 𝒙 𝑳 10. Depth of hexagon cut = 𝑫𝒊𝒂𝒎𝒆𝒕𝒆𝒓 𝒐𝒇 𝒔𝒉𝒂𝒇𝒕−𝒅𝒊𝒔𝒕𝒂𝒏𝒄𝒆 𝒂𝒄𝒓𝒐𝒔𝒔 𝒇𝒍𝒂𝒕 𝒔𝒊𝒅𝒆

𝟐

NATIONAL SENIOR CERTIFICATE

GRADE 11

NOVEMBER 2015

MECHANICAL TECHNOLOGY MEMORANDUM

MARKS: 200

This memorandum consists of 10 pages.

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QUESTION 1: MULTIPLE-CHOICE QUESTIONS 1.1 C 9 1.2 D 9 1.3 B 9 1.4 B 9 1.5 B 9 1.6 A 9 1.7 D 9 1.8 B 9 1.9 D 9 1.10 B 9 1.11 B 9 1.12 C 9 1.13 C 9 1.14 C 9 1.15 A 9 1.16 B 9 1.17 B 9 1.18 A 9 1.19 C 9 1.20 B 9 (20 x 1) [20] QUESTION 2: SAFETY 2.1 2.1.1 True 9 (1) 2.1.2 True 9 (1) 2.1.3 False 9 (1) 2.1.4 False 9 (1) 2.2 x Ensure that there is no oil or grease on the floor. 9

x Check that the tool rest is not more than 3 mm away from the grinding wheel surface. 9

x If the wheel is running unevenly dress it with an emery-wheel dresser. 9 x Grind only on the face of a straight grinding wheel and never on the side

of the wheel. 9 x Use the various wheels only for their intended purpose. x Never force grind so that you cause the motor to slow or stop.

(Any 4 x 1) (4) 2.3 x All machinery must be fitted with an efficient stopping and starting

device. 9 x Never start a machine while another person is repairing, cleaning, oiling

or adjusting or even dangerously close to it. 9 x Machines with foot-operated pedals should have an automatic locking

device to stop. (Any 2 x 1) (2) [10]

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QUESTION 3: TOOLS AND EQUIPMENT 3.1 x Should be used in the correct order (taper tap first). 9

x A tap must be entered squarely in the tap wrench. 9 x The correct size tapping drill must be used. 9 x A tap is at a right angle to the stock once cutting has started. x The tap is turned forwards a part-turn and then turned backward about half

a turn to break off the chippings. (Any 3 x 1) (3) 3.2 Cutting fluid or cutting paste 9 (1) 3.3 To compare the threads on a bolt to the teeth cut on the gauge or

To assess the pitch of the bolt. 9 (1) 3.4 x Always select correct blade. 9

x Always clean cuttings out of slots and guides to prevent blades from becoming clogged. 9

x Always adjust down pressure in order not to overload. x Check that the filler tank is in a serviceable state. (Any 2 x 1) (2)

3.5 Changes the welding current from AC to DC. 9 (1) 3.6 x It prevents bolts and nuts from loosening. 9

x It prevents bolts or studs from breaking. 9 x It prevents castings from warping. (Any 2 x 1) (2)

3.7 To cut material by means of an electrical method. 9 (1) 3.8 Always keep blades sharp and in good condition. 9

Ensure guards are in place and operational. (Any 1 x 1) (1) [12] QUESTION 4: MATERIALS 4.1 Open-hearth furnace 9 (1) 4.2 4.2.1 Refers to the material’s ability to absorb forces and flex in different

directions 9and return to its original shape when the load is removed. 9 (2)

4.2.2 Refers to the material’s ability to change shape by stretching it along

its length, 9 or to be drawn into wire form. 9 (2) 4.2.3 Refers to the material’s behaviour when fractures occur 9with little

or no deformation e.g. glass. 9 (2) 4.2.4 Refers to the materials ability to be reshaped in all directions 9

without cracking e.g. lead. 9 (2) 4.2.5 Refers to the material’s ability to change shape permanently. 9 (1)

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4.3 x Water and salt. 9 x Tap water. 9 x Fused or liquid salts. 9 x Molten lead. x Soluble oil. x Oil or air. (Any 3 x 1) (3)

[13] QUESTION 5: TERMINOLOGY 5.1 Set the indexing for 6(six) divisions(six flat sides)

Calculate the distance x across the flat sides.

Sin Ө = 𝑥100 9

X = Sin 60° x 100 9

X = 0,866 x 100 9

X = 86,6 mm 9

Depth of cut = 𝐷𝑖𝑎.𝑜𝑓 𝑠ℎ𝑎𝑓𝑡 − 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑎𝑐𝑟𝑜𝑠𝑠 𝑓𝑙𝑎𝑡 𝑠𝑖𝑑𝑒2

= 100−86,62 9

Depth of cut = 6,7 mm 9 (6) 5.2 x Release the lock nuts of the compound slide. 9

x Swing the compound slide to half the included angle. 9 x Tighten the lock nuts (take care not to over tighten). 9 x Mount the cutting tool in the tool holder in the tool post. 9 x Set the cutting tool to the centre of the tailstock. 9 x Use the compound slide feed handle and feed the cutting tool slowly into

the work piece. 9 x Proceed to the end of the cutting length. 9 x Return to the starting position and feed the cutting tool in for the next

cut. 9 x Repeat the procedure until the taper is completed. 9 x On completion, test the taper with the taper ring gauge for size and

correct angle. 9 (10) 5.3 Taper angle = 𝐷−𝑑

2 𝑥 𝐿

= 90−802 𝑋 180 9

= 10360 9

= 0,O27 9

Ө = 1°59′9

Ө = 1°35′9

The angle is 1 degree and 35 minutes. 9 (6)

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5.4 Sin Ө = 𝑋70

X = 70 Sin Ө 9

= 70 Sin 45° 9 x = 49,5 mm 9

Depth of cut = 70−𝑥2 9

= 70−49,52 9

= 10,25 mm 9 (6)

5.5 Indexing: Number of turns = 40

𝑁

Number of turns = 405 9

Number of turns = 8 full turns of the shank 9 (2) [30] QUESTION 6: JOINING METHODS 6.1 It is permanent joints that do not have to be dismantled or serviced. 9 (1) 6.2 x Flux is used together with soldering to dissolve metal oxides and

impurities on the metal 9 x This allows the solder to flow into the joint. 9 x The soldered joints are usually heated by an electric soldering iron or LP

gas blowtorch. 9 x The solder is applied when the surfaces are heated to melting point. 9 (4)

6.3 Hard soldering. 9/Brazing (1) 6.4 x The more welding runs that are required in a welding joint, the greater the

heat in the parent metal. 9 x It can lead to stress and distortion if not managed correctly. 9 (2)

6.5 x Sizes of weld depends on the type of weld. 9

x The size of the weld will affect how many weld runs will be needed to complete the joint. 9 (2)

6.6 A Square butt 9

B Single bevel butt 9 C Double bevel butt 9 D Single V-butt 9 E Double V- butt 9 F Edge 9 G Single-U-Butt 9 H Stud 9 (8)

6.7 x Type of material. 9

x Type of welding rod. 9 x Presence of oxygen/hydrogen 9 x Preparation 9 (4)

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6.8 6.8.1 Fillet 6.8.2 Plug or slot 6.8.3 Stud (3) [25] QUESTION 7: FORCES 7.1 7.1.1 If a system of forces acts on a body but a single force keeps the body

at rest, 9the single force is known as the equilibrant of the system of forces. 9 (2)

7.1.2 If three forces, whose lines of action meet at a point, 9 can be

represented in magnitude and direction by the sides of a triangle, they are in equilibrium. 9 (2)

7.1.3 If two or more forces have the same effect as a single force, 9 these

forces are called the components of the single force. 9 (2) 7.2 7.2.1

8 cm C 9 8 cm 30° 30° B 9 A 9 Scale: 4 cm = 10 N 8 cm (3)

7.2.2 a

9 Draw to scale 8 cm 8 cm 9 c 8 cm 30° b 9 (3)

7.2.3 Because the force diagram’s end point is the same as its starting

point. 9 (1)

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7.3 7.3.1 RR x 10 = (6 x 3) + (5 x 8) 9 = 18 + 40 RR = 58/10 RR = 5,8 N 9 RL X 10 = (5 x 2 ) + (6 x 7) 9 = 10 + 42 L = 52/10 RL = 5,2 N 9 (4)

7.3.2 BM A = (5,2 x 3) 9 = 15,6 N/m 9

BM B = (5,2 x 8) – (6 x 3) 9 = 23,6 N/m 9 (4) 7.3.3 RL + RR = DOWN FORCES

5,2N + 5,8N = 6N + 5N 11N = 11N 9 (1)

7.4 Cross sectional area = (32 x 32) – (26 x 26) 9 Load: 70 kN = 70 x 103

= 1024 - 676 = 348 mm² 9 Stress = 𝐹𝑜𝑟𝑐𝑒

𝐴𝑟𝑒𝑎

= 70 𝑥 103348106

9

Stress = 2011494253 Pa 9 OR = 2011,49 x 106 Pa Stress = 2011,49 MPa 9 (5)

7.5 7.5.1

Y 9 30°

O X (1) 7.5.2 X = F Cos 30°

= 220 x 0,866 Horizontal component = 190, 52 N 9 Y = F Sin 30° = 220 x 0,5 Vertical component = 110 N 9 (2)

[30]

8 MECHANICAL TECHNOLOGY (EC/NOVEMBER 2015)

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QUESTION 8: MAINTENANCE 8.1 8.1.1 Unbalanced wheels will cause:

x Unnecessary tyre wear. 9 x Poor driving condition. 9 x Excessive wear on the steering and suspension. 9 x Shaking of the wheel assembly from side to side (wheel

shimmy). 9 (4) 8.1.2 Overloading of machines:

x When a machine is overloaded it will cause the lubricating barrier of oil to be squeezed out of the machine bearings. 9

x This results in metal to metal contact that causes more friction due to heat. 9

x Metal surfaces become scratched and scored, which will finally seize the operating system. (Any 2 x 1) (2)

8.2 It is the outward tilt of the wheel at the top 9 away from the vehicle when

viewed from the front. 9 (2) 8.3 It is the setting of an angle relative to the true vertical line, 9 as viewed from

the front or back of the vehicle. 9

OR

Kingpin inclination is the inward tilt from the vertical in degrees. (2) 8.4 23° 9 20° 9

(5)

[15]

Steering control arms 9 marms

Rear axle 9

Centre of turning wheels 9

(EC/NOVEMBER 2015) MECHANICAL TECHNOLOGY 9

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QUESTION 9: SYSTEMS AND CONTROL 9.1 The handbrake lever pulls on a single cable, 9which is coupled to a pivoted

T-piece to transmit the pull identically or evenly to both rear brakes, 9or there may be two cables from the handbrake lever, one to each of the rear brakes. 9 (3)

9.2 x When the driver pushes down on the clutch pedal, a push rod is forced

into the master cylinder. 9 x As the push rod moves down into the master cylinder, the rod forces a

piston down the cylinder. 9 x This action puts pressure on the hydraulic fluid in the cylinder, and some

of the fluid is forced out. 9 x The fluid flows through a tube or pipe into a servo cylinder at the clutch. 9 x The fluid flowing into the servo cylinder from the master cylinder, forces

the piston in the servo cylinder to move. 9 x This movement is carried through a push rod to the release lever, thus

releasing the clutch. 9 (6) 9.3 𝑅𝑒𝑣𝑠 𝑜𝑓 𝑓𝑖𝑛𝑎𝑙 𝑑𝑟𝑖𝑣𝑒𝑛

𝑅𝑒𝑣𝑠 𝑜𝑓 𝑓𝑖𝑟𝑠𝑡 𝑑𝑟𝑖𝑣𝑒𝑟 = 𝑃𝑟𝑜𝑑𝑢𝑐𝑡 𝑜𝑓 𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑡𝑒𝑒𝑡ℎ 𝑜𝑛 𝑎𝑙𝑙 𝑡ℎ𝑒 𝑑𝑟𝑖𝑣𝑒𝑟𝑠𝑃𝑟𝑜𝑑𝑢𝑐𝑡 𝑜𝑓 𝑁𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑡𝑒𝑒𝑡ℎ 𝑜𝑛 𝑎𝑙𝑙 𝑡ℎ𝑒 𝑑𝑟𝑖𝑣𝑒𝑛

𝑁𝐷𝑁𝐴

= 𝑇𝐴𝑇𝐵

x 𝑇𝐶𝑇𝐷

9

𝑁𝐷 = 𝑇𝐴𝑇𝐵

x 𝑇𝐶𝑇𝐷

X 𝑁𝐴 9

= 2080 X 63

42 X 12 9 𝑁𝐷 = 4,5 9 Rotational frequency of driven shaft = 4,5 r/s. 9 (5)

9.4 Determine the effective tension:

Given:𝑇𝐴𝑇𝐵

= 2 : 1 = 2 AND 𝑇𝐴 = 600

𝑇𝐵 = 6002 = 300 N 9

Effective tension in belt = 𝑇𝐴 - 𝑇𝐵 = 600 – 300 9 = 300 N 9 𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑚𝑜𝑣𝑒𝑑

𝑆 = ∏ X D X N

= ∏ X 3001000 X 950

60 9 = 14,92 m/s Power transmitted = 300 𝑋 14,92

1000 9 = 4,48 kW 9 (6)

9.5 Pressure = 𝐹𝑜𝑟𝑐𝑒

𝐴𝑟𝑒𝑎

= 75003 9

= 2 500 Nm² 9 = 2 500 Pa 9 (3)

9.6 It draws in fluid as it is pulled back (or retracted) 9 and expels it on the

forward stroke. 9 (2) [25]

10 MECHANICAL TECHNOLOGY (EC/NOVEMBER 2015)

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QUESTION 10: PUMPS 10.1 A Inlet port 9 B Driven gear 9 C Driver gear 9 D Casing 9 E Outlet port 9 (5) 10.2 x When one of the vanes moves past the inlet port, the space between

this vane, the rotor and the housing increases gradually. 9 x This causes a vacuum in the space, which causes oil to be drawn from

the sump. 9 x When the next vane moves past the inlet port, the oil is trapped and is

carried along by the rotating rotor. 9 x Due to the eccentric rotor, the space now decreases and the oil is

pressurised. 9 x The first vane now moves past the outlet port while the space is still

decreasing. 9 x The decreasing space and the next vane force the oil through the outlet

port to the oil channels. 9 (6) 10.3 x Pumping grout/cement 9

x Pumping lubrication oil 9 x Pumping marine diesel fuel 9 x Pumping mining slurry 9 x Pumping oilfield mud (Any 2) (2)

10.4 x Grout/cement pump 9

x Lubrication oil pump 9 x Marine diesel fuel pump 9 x Mining slurry pump 9 x Oilfield mud motors 9 x Winery use 9 (Any 2) (2)

10.5 x The centrifugal pump consists of a casing which contains a rotating

wheel with blade or vanes. 9 x This rotating wheel is known as an impeller of the pump. 9 x If the pump casing is filled with fluid and the impeller is in operation, the

impeller will sling the fluid outwards by centrifugal force, and force it out at the outlet. 9

x This creates a vacuum at the centre, or eye, of the impeller. 9 x As a result of atmospheric pressure, fluid is again drawn through this

eye into the pump casing. 9 (5) [20] TOTAL: 200