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

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Presentation on theme: "Rotary Motion A Pulley Mechanism uses rotary motion to transmit rotary motion between two parallel shafts."— Presentation transcript:

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

2 Mechanisms using Rotary Motion

3 Pulley mechanisms can be used to increase or decrease rotary velocity

4 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

5 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 pulley = rotary velocity of driver pulley x diameter of driver pulley diameter of driven pulley

6 What is the rotary velocity of the driven pulley shaft? rotary velocity of driven pulley = rotary velocity of driver pulley x diameter of driver pulley diameter of driven pulley = 450 x revs/mi n = 150 revs/min

7 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

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

9 Chains and sprockets Bicycle chain and sprockets Graphical symbols

10 Velocity Ratio = number of teeth on the driven sprocket number of teeth on the driver sprocket = = 1 : 3

11 Example

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

13 Movable single pulley

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

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

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

17 Cams

18

19 Uses Pear shaped cams are used in valve control mechanisms

20 Cams used in a four cylinder engine

21 Cam motions

22 Types of cam follower

23

24 Springs are used to keep the follower in contact with the cam

25 Cam Profiles

26 Displacement graph for a pear shaped cam

27 Displacement Graphs

28

29 Bearings

30 Thrust Bearings

31 Bearings

32 Bronze Nylon PTFE Air White metal Cast Iron Sintered

33 Gears

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

35 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

36 Gears

37 Gear Ratio = Product of teeth on the driven gears Product of teeth on the driver gears

38 Gears

39

40

41

42 Basic Gear Geometry si.com/D190/PDF/D190T25.PDF

43 The inclined plane

44

45 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:

46 The screw thread

47 Screw thread terms

48 Screw thread forms

49

50

51 B.S. PD7308

52 Newtons 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)

53 Newtons 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)

54 Newtons Laws Third Law – To every action there is an equal and opposite reaction


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