If the windlass has a diameter of 300mm, calculate the torque produced by the load. (Show all working and units.)

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Bryan Conley
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1 8. A winch system used to raise a 5N load is shown. (a) If the windlass has a diameter of mm, calculate the torque produced by the load. (Show all working and units.) T = r = 5 5 = 875Nmm = 8. 75Nm substitution correct answer from given working. (b) If the motor is rotating with a speed of rev/min, calculate the rotational speed of the windlass. (Show all working and units.) 5 Speed of B rev/min Speed of Windlass rev/min (Allow follow through) substitution correct answer. The system makes use of a flat belt to connect the motor to the simple gear train. (c) (i) State one disadvantage of this type of belt. Flat belts tend to slip. KU (ii) State the name of two other types of belt which could be used instead of a flat belt. Vee belt Toothed belt Round belt KU KU

2 . The mechanism shown below is used to convert rotary to reciprocating motion in a door lock. (a) (b) (c) State the name of the mechanism shown. crank and slider any order State the name of another mechanism which could be used to provide the required motion conversion. cam KU and follower any order After a period of time, it was found that it had become increasingly difficult to lock the door due to a large amount of friction in the moving parts. Describe how this friction could be reduced. add some lubrication OR bearings KU KU. The free body diagram of a support structure is shown below. (a) Calculate, by taking moments about R, the size of reaction R. CWM = ACWM (8 ) + ( )= ( R ) + ( ) substitution 8 + = R + R = 8 transposition R = kn answer from given working (b) Determine the size of reaction R. = R + = substitution allow for FTE from (a) [44/4] R = 7kN answer from given working Page two

3 . (a) The following symbols have been numbered to Complete the table below by inserting the symbol number for each device. The first one has been done for you. Device Symbol Number Resistor Lamp 6 Transistor 8 Cam LDR Rack & Pinion 5 Belt drive (b) Two drive systems are shown below. Driven Driven Drive system Drive system A (i) Indicate ( ) in the box below, the direction of rotation of the driven in drive systems and when the input turns anti-clockwise. Clockwise Drive system Anti-clockwise Clockwise Drive system Anti-clockwise (ii) State the name of gear A shown above in drive system. Idler [44/4] Page two

4 . A boat lift is designed to transport vessels from one level to another on a canal as shown. (a) (i) State what happens to the potential energy when a boat is raised. Increases (ii) Calculate the potential energy of a boat of mass 5kg when it has been raised 6m. (Show all working and units.) EP = mgh = J substitution = 5974J answer from given working. (continued) (b) (i) State the name of parts A and B. any order (A) Worm and (B) Wheel (ii) Calculate the speed of B which has 5 teeth if the motor speed is 75 revs/min. Speed (driven) Speed (driver) = Teeth (driver) Teeth (driven) Speed (driven) = S D R TDR TDN Speed = 75 substitution = 5rev/min answer from given working (c) Calculate the torque required to overcome the frictional force and rotate the shaft. T = F r = substitution = 6. 5kNm answer from given working (65Nm) [44/4] Page four

5 7. The belt drive system used in a chairlift is shown in Figure Q7. motor Marks WRITE IN diameter. 5 m diameter. 5 m diameter m drive wheel diameter. m Figure Q7 chairlift pulley (a) Calculate, showing all working and units: (i) the total velocity ratio for the drive system;. 78 (reduction) (ii) the rotational speed of the chairlift pulley in rev/min when the motor speed is rev/min.. 8 rev/min (b) Calculate the linear speed in m/s at which the chair will travel if the effective diameter of the chairlift pulley is. m..4 m/s (c) State one method of altering the flat belt that would reduce slippage in the system. [X6/] Jockey wheel OR v belt, toothed belt, chain drive Page ten (9)

6 . (continued) A motor is used to raise the carriage to position A using the drive mechanism shown in Figure Q(c). Marks WRITE IN Motor A D Output rev/min rev/min B C Gear A teeth Gear B 4 teeth Gear C 5 teeth Gear D? Figure Q(c) (d) If the output speed is rev/min, calculate: (i) the velocity ratio for the drive mechanism; VR = (ii) the number of teeth on gear D. Teeth = 6 (e) Gear D is replaced with a smaller gear with fewer teeth. Describe how this gear affects: (i) the output speed; output speed increases (ii) the output torque. output torque decreases () [X6/] Page twenty-two

7 6. An air compressor on a heavy goods vehicle is driven by a belt. X Pulley B Pulley A (a) State the name of device Xin the sketch above. Jockey wheel Pulleys can rotate either clockwise or anti-clockwise. Pulley A rotates clockwise, as shown in the diagram above. (b) State the direction of rotation of device X. Anti-clockwise Three different types of belts are shown below. (c) State the name of each belt. (i) V belt (ii) Flat (iii) Tooth Friction is the resistance of one surface to move over another. (d) State two methods of reducing friction. Use a lubricant (oil, grease or solid) Reduce contact force on surfaces Use low friction materials for rubbing parts Use ball bearings Smoothing surface [44/4] Page twelve

8 6. (continued) The mechanism shown below is used in the compressor. mm F 9 D C Stroke (e) State the names of parts C and D. (f) C Crank D Connecting rod (slider) names round the wrong way mark Determine the length of stroke for the above mechanism. 6 m m Part C has a radius of mm and, as it rotates, the force F in part D is 5N in the position shown. (g) Calculate the torque. T = F r = 5. = 7. 5 N m KU substitution KU answer [44/4] Page thirteen

9 Question Mark Allocation Marks KU 8. The structure below is used to transport a 5 kg container. 587 m 7 m R R Container (a) Calculate the weight of the 5 kg container. F = mg = substitution = 49,5 N answer from given working (b) Draw the Free Body Diagram of the structure, showing all forces and distances. (Ignore the weight of the beam.) 49,5 N 7 m R R 587 m BOTH reactions (must have arrows) force both dimensions Page 5

10 Question Mark Allocation Marks KU (c) (i) Calculate, by taking moments about R, the size of the reaction R. MR = CW = ACW 587R = substitution R = 695 transposition 587 = 6 8 N answer from given working (accepted without unit & arrow) (ii) Determine the size of the reaction R. V = R = 495 substitution R answer from given working (d) (i) The container is moved using the mechanical system shown below. Part B Part A State the names of the parts of the mechanical system. Part A Pinion mark wrong way round Part B Rack (ii) State the change in motion that this mechanism produces. Page 6

Graphical representation of a gear

Graphical representation of a gear Homework 4 Gears Gears are designed to transmit rotary motion. Often they are arranged in a gear train (meshed together). Gear trains provide a change in speed, torque (turning force) and direction (clockwise