1. Mechanisms Dean Hackett March 2012

2. Types of motion Linear Rotary Reciprocating Oscillating

3. Simple (Basic) Machines Two ‘families’ –Inclined plane –lever

4. Simple Machines Inclined plane Wedge Screw Lever Wheel and axle Pulley

5. Work = Force x distance

6. Classes of Lever Class 1 Class 2 Class 3

7. Types of Linkage Parallel Reverse motion Bell crank Treadle Crank slider

8. Have a think...

9. Lever Mechanisms Fulcrum 4 m1 m Effort 10N Load xN Fulcrum 4 m1 m Effort 10N Load yN

10. Mechanical Advantage = Load Effort 4 m1 m Effort 10N Load 40N Mechanical Advantage

11. Velocity Ratio 4 m1 m Effort 10N Load 40N 50mm 200mm Velocity Ratio = Distance moved by Effort Distance moved by Load

12. Efficiency 4 m1 m Effort 10N Load 40N 50mm 200mm Efficiency = M.A. V.R. x 100%

13. Lever Mechanism What load can this person lift?

14. Rotary Motion A Pulley Mechanism uses rotary motion to transmit rotary motion between two parallel shafts.

15. Discuss... How do you attach a pulley to a shaft?

16. Mechanisms using Rotary Motion

17. Pulley mechanisms can be used to increase or decrease rotary velocity

18. Velocity Ratio Velocity Ratio = Distance moved by Effort Distance moved by Load Velocity Ratio = Distance moved by the driver pulley Distance moved by the driven pulley Velocity Ratio = Diameter of Driven Pulley Diameter of Driver Pulley

19. Velocity Ratio Pulley Shaft Rotary Velocities can be calculated using the following formula rotary velocity of driven pulley x diameter of driven pulley = rotary velocity of driver pulley x diameter of driver pulley rotary velocity of driven = diameter of driver pulley diameter of driven pulley rotary velocity of driver x

20. What is the rotary velocity of the driven pulley shaft? rotary velocity of driven = diameter of driver pulley diameter of driven pulley = 30 90 revs/min = 150 revs/min rotary velocity of driver x 450 x

21. Pulleys and Belts A section through a grooved pulley and round belt Vee pulley and section through a vee pulley and belt Stepped cone pulleys provide a range of shaft speeds

22. Flat belts and pulleys A section through a flat pulley and belt Flat belt in use on a threshing machine Jockey pulley in use

23. Chains and sprockets Bicycle chain and sprockets Graphical symbols

24. Velocity Ratio = number of teeth on the driven sprocket number of teeth on the driver sprocket = 12 36 = 1 : 3

25. Example

26. Pulleys and Lifting Devices The pulley is a form of Class 1 lever

27. Movable single pulley

28. Pulleys Velocity Ratio = Distance moved by Effort Distance moved by Load Velocity Ratio = the number of rope sections that support the load

29. Two Pulley System Velocity Ratio = Distance moved by Effort Distance moved by Load Velocity Ratio = 2x x Velocity Ratio = 2:1

30. Four Pulley System Velocity Ratio = Distance moved by Effort Distance moved by Load Velocity Ratio = 4x x Velocity Ratio = 4:1

31. Cams

33. Uses Pear shaped cams are used in valve control mechanisms

34. Cams used in a four cylinder engine http://www.youtube. com/watch?v=OXd1 PlGur8M&feature=re lated

35. Cam motions

36. Types of cam follower

38. Springs are used to keep the follower in contact with the cam

39. Cam Profiles

40. Displacement graph for a pear shaped cam

41. Displacement Graphs

43. Bearings

44. Thrust Bearings

45. Bearings

46. Bronze Nylon PTFE Air White metal Cast Iron Sintered

47. Gears

48. Gears are not only used to transmit motion. They are also used to transmit force.

49. Gears Mechanical Advantage = Number of teeth on the driven gear Number of teeth on the driver gear Velocity Ratio = Gear Ratio = Number of teeth on the driven gear Number of teeth on the driver gear

50. Gears

51. Gear Ratio = Product of teeth on the driven gears Product of teeth on the driver gears

52. Gears

55. http://www.youtube. com/watch?v=9NoQ m0wnK_c&feature=r elated http://www.youtube. com/watch?v=K4Jhr uinbWc&NR=1

56. Basic Gear Geometry http://www.sdp- si.com/D190/PDF/D190T25.PDF

57. The inclined plane

59. Effort required to pull trolley up slope F = effort E F = 1000 x sin  F = 1000 x 0.01 F = 10N  E = 10N sin  = 1/100 = 0.01  M.A. = 1000/10 = 100 Follow link to see effects of steeper incline: http://lectureonline.cl.msu.edu/~mmp/applist/si/plane.htm

60. The screw thread

61. Screw thread terms

62. Screw thread forms

65. B.S. PD7308

66. Newton’s Laws First Law –A body continues in its state of rest or uniform motion in a straight line unless compelled by some external forces to change that state. (sometimes know as the law of inertia)

67. Newton’s Laws Second Law –Rate of change of momentum is proportional to the applied force and takes place in the direction in which the force acts. (Continued force means continued acceleration)

68. Newton’s Laws Third Law –To every action there is an equal and opposite reaction