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 = Velocity Ratio = Velocity Ratio =
Distance moved by Effort
Velocity Ratio =
Distance moved by Load
Distance moved by the driver pulley
Velocity Ratio =
Distance moved by the driven pulley
Diameter of Driven Pulley
Velocity Ratio =
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 driver pulley
x diameter of driver pulley
rotary velocity of driven pulley =
diameter of driven pulley

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

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

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

9. Bicycle chain and sprockets
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 12 = 36 =
1 : 3

11. Example

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

13. Movable single pulley

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

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

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

17. Cams
Rotary Cam
Linear Cam
Barrel or Cylindrical Cam

18. Cams
More complex cams
Box cam
Swash cam

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

20. Cams used in a four cylinder engine

21. Cam motions
Rotary to reciprocating / oscillating
Not other way round

22. Types of cam follower
Point
Sliding and oscillating
Roller
Angled foot

23. Types of cam follower
Flat
Knife
Edge
Sliding yoke

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

25. Cam Profiles Pear shaped Circular Heart shaped
Uniform acceleration and retardation cam

26. Displacement graph for a pear shaped cam
Very common cam
Long rest (dwell) period
Quick rise and fall

27. Displacement Graphs
Desired displacements can be used to construct cams

29. Bearings Flat bearings consist of two or more sliding flat surfaces
Journal Bearing is a bearing that supports a cylindrical shaft

30. Thrust Bearings Thrust bearings for longitudinal load or axial load
Nylon bush
Bronze washer - alloy of copper and tin
commonly used type contain phosphorous
known as phosphor-bronze
hard but softer than steel

31. Bearings

32. Bearings Bronze Nylon PTFE Air White metal Cast Iron Sintered
Bronze - alloy of copper and tin
commonly used type contain phosphorous
known as phosphor-bronze
Nylon
plastic cheep to produce
quiet running
PTFE
Polytetrafluoro-ethane
coating
resistance to high temperatures
hard – good friction qualities
Air
Air pressure is sometimes used to support a moving part
hovercraft vacuum cleaner lawn mower
White Metal
tin alloy with copper and antimony
it is soft and will adapt to the shape of the shaft
if the bearing over heats the metal melts and runs leaving the shaft undamaged and gives a warning of what has happened
Cast iron
forms a flat sliding surface
high graphite content
no other metal will run on itself
Sintered
made from oil soaked powder of copper, tin and graphite that are pressed together (in shape) when hot

33. Gears
Drawing gears- note the spline

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

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

36. Gears
Guess the ratio. How many turns of the driver = a turn of the driven?
Try different idlers

37. Gears Gear Ratio = Product of teeth on the driven gears
Calculate ratio
Product of teeth on the driven gears
Gear Ratio =
Product of teeth on the driver gears

38. Gears
Spur gear- straight cut
Parallel Helical
Double helical

39. Gears
Face cut
Bevel gears
Spiral bevel

40. Gears
Crossed helical
Worm and wormwheel
Rack and pinion

41. Gears
Internal
Differential

42. Basic Gear Geometry

43. The inclined plane

44. The inclined plane

45. The inclined plane M.A. = 1000/10 = 100
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. Screw thread forms

50. Screw thread forms

51. B.S. PD7308

52. 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)

53. 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)

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