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Pulley Systems. Pulley Systems - Uses Lifting the rescue package. Pulley Systems - Uses Lifting the rescue package Lowering under control. Pulley Systems - Uses Lifting the rescue package Lowering under control Small jiggers for pick offs. Pulley Systems - Uses

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slide2
Pulley Systems - Uses
    • Lifting the rescue package
slide3
Pulley Systems - Uses
    • Lifting the rescue package
    • Lowering under control
slide4
Pulley Systems - Uses
    • Lifting the rescue package
    • Lowering under control
    • Small jiggers for pick offs
slide5
Pulley Systems - Uses
    • Lifting the rescue package
    • Lowering under control
    • Small jiggers for pick offs
    • Pretensioned backties
slide6
Pulley Systems - Uses
    • Lifting the rescue package
    • Lowering under control
    • Small jiggers for pick offs
    • Pretensioned backties
    • Directionals
slide7
Pulley Systems - Considerations
    • Hauling area & incline
slide8
Pulley Systems - Considerations
    • Hauling area & incline
    • Throw length
slide9
Pulley Systems - Considerations
    • Hauling area & incline
    • Throw length
    • Number of haulers
slide10
Pulley Systems - Considerations
    • Hauling area & incline
    • Throw length
    • Number of haulers
    • Load to be lifted
slide11
Pulley Systems - Considerations
    • Hauling area & incline
    • Throw length
    • Number of haulers
    • Load to be lifted
    • Equipment needed
slide12
Pulley Systems - Considerations
    • Hauling area & incline
    • Throw length
    • Number of haulers
    • Load to be lifted
    • Equipment needed
    • Resetting
slide13
Pulley Systems - Considerations
    • Hauling area & incline
    • Throw length
    • Number of haulers
    • Load to be lifted
    • Equipment needed
    • Resetting
    • Lowering ability
slide14
Pulley Systems - Definitions
    • Sheave is the grooved wheel that the rope runs on
    • The larger the diameter of the sheave, the less friction and the more efficient
    • Usually made out of nylon or aluminum
slide15
Pulley Systems - Definitions
    • Side Plate can have holes or not, and can swivel or not
    • Larger top attachment point allows for the use of larger or multiple carabiners
slide16
Pulley Systems - Definitions
    • Bearing or Bushing are the points where the axle meets the other parts of the pulley
    • Bearings are more efficient than bushings
    • This pulley with bearings has an efficiency of 216% and with bushings it is 198%
slide17
Pulley Systems - Definitions
    • Becket is a lower attachment point between the two sheaves
    • Can be used to attach a rope or a second pulley
slide18
Pulley Systems - Definitions
    • PMP or Prusik Minding Pulley has side plates that help keep a prusik knot from being jammed in the pulley
    • The prusik knot has to be wider than the distance between the side plates
slide19
Pulley Systems - Definitions
    • Directional is a pulley that is between the pulley system and the load
    • Does not add any MA to the system
slide20
Pulley Systems - Definitions
    • Change of Direction is a pulley on the anchor that is closest to the haulers
    • Does not add any MA to the system
slide21
Pulley Systems - Definitions
    • Pr is a ratchet prusik which is a type of progress capture device
slide22
Pulley Systems - Definitions
    • Ph is a haul prusik for attaching to the rope
slide23
Pulley Systems - Definitions
    • Collapsed Pulleys or Two Block is when the system can not be made any shorter
slide24
Pulley Systems - Types
    • Simple is if all of the traveling pulleys move towards the anchor at the same rate of speed
slide25
Pulley Systems - Types
    • Simple
    • Compound is any combination of two or more simple pulley systems acting on each other
slide26
Pulley Systems - Types
    • Simple
    • Compound
    • Complex does not follow any of the rules for a simple or compound pulley system
slide27
Pulley Systems - Types
    • Simple Pulley System Rules
      • The number of pulleys plus one equals the mechanical advantage (MA)
      • End of rope attached to the load means the MA is odd
      • End of rope attached to the anchor means MA is even
      • Cumulative friction from more than five pulleys significantly works against MA
slide28
Pulley Systems - Types
    • Compound Pulley System Rules
      • Total MA equals the product of each simple pulley system’s MA (2:1 acting on 3:1 = 6:1)
      • The greatest MA created using the fewest pulleys comes from 2:1 acting on 2:1 (2:1 x 2:1 x 2:1 x 2:1 = 16:1)
      • Having the greater MA system acting on the lesser means less resets
      • Traveling pulleys move toward anchors, but not necessarily at the same speed
slide29
Pulley Systems - Types
    • Compound Pulley System Rules
      • Compound systems need people at each haul prusik for fastest action
      • Anchors should be offset so that each simple system collapses at the same time
slide30
Pulley Systems - Types
    • Complex Pulley System Rules
      • Determining total MA requires the use of the “T” method, which can also be used for simple and compound systems
      • Systems that have pulleys moving towards the load are complex
slide31
Pulley Systems – “T” Method
    • Assumes no loss from friction or ideal mechanical advantage
slide32
Pulley Systems – “T” Method
    • Assumes no loss from friction or ideal mechanical advantage
    • Assumes that the rope angle through a pulley is very close to 180 degrees
slide33
Pulley Systems – “T” Method
    • Assumes no loss from friction or ideal mechanical advantage
    • Assumes that the rope angle through a pulley is very close to 180 degrees
    • Assumes the tension input on one side of a pulley equals the tension output on the other side of the pulley

T=1

T=1

slide34
Pulley Systems – “T” Method
    • Always assume that the tension (T) input is equal to 1, whether it is one person or a haul team

T=1

slide35
Pulley Systems – “T” Method
    • Trace the rope through the system and add Ts as the rope passes through a pulley or tension point

T

T

slide36
Pulley Systems – “T” Method
    • Trace the rope through the system and add Ts as the rope passes through a pulley or tension point

T

T

T

T

slide37
Pulley Systems – “T” Method
    • Ts adds together at junction points

T

T

T

T

2T

slide38
Pulley Systems – “T” Method
    • Ts adds together at junction points

T

T

T

T

2T

3T

slide39

2T

  • Pulley Systems – “T” Method
    • Ts adds together at junction points

T

T

T

T

2T

3T

slide40
Pulley Systems – “T” Method
    • Simple, compound, complex?
    • Total MA?
    • Name?
    • Input force?
slide46

2T

  • Pulley Systems – “T” Method

T

T

T

T

T

2T

slide47

2T

  • Pulley Systems – “T” Method

T

T

T

T

T

T

T

2T

slide48

2T

  • Pulley Systems – “T” Method

T

T

T

T

T

T

T

2T

2T

slide49

2T

  • Pulley Systems – “T” Method

T

T

T

T

T

T

T

T

T

2T

2T

slide50

2T

2T

  • Pulley Systems – “T” Method

T

T

T

T

T

T

T

T

T

2T

2T

slide51

2T

2T

T

T

T

T

T

T

T

T

T

2T

5T

2T

  • Pulley Systems – “T” Method
    • Simple pulley system
    • Total MA is 5
    • Name would be (5:1)s
    • Input force is 1T
slide52
Pulley Systems – “T” Method
    • Simple, compound, complex?
    • Total MA?
    • Name?
    • Input force?
slide56

T

  • Pulley Systems – “T” Method

T

T

T

T

2T

slide57

T

  • Pulley Systems – “T” Method

T

T

T

T

2T

2T

slide58

T

  • Pulley Systems – “T” Method

T

T

T

T

2T

2T

2T

slide59

T

  • Pulley Systems – “T” Method

T

T

T

T

2T

2T

2T

4T

slide60

T

  • Pulley Systems – “T” Method

T

2T

2T

T

T

T

2T

2T

2T

4T

slide61

T

4T

  • Pulley Systems – “T” Method

T

2T

2T

T

T

T

2T

2T

2T

4T

slide62

T

4T

T

2T

2T

T

T

T

2T

2T

2T

4T

6T

  • Pulley Systems – “T” Method
    • Compound pulley system
    • Total MA is 6
    • Name is (2:1)(3:1)c
    • Input force is 1T
slide63
Pulley Systems – “T” Method
    • Simple, compound, complex?
    • Total MA?
    • Name?
    • Input force?
slide70

3T

  • Pulley Systems – “T” Method

2T

3T

T

T

T

T

T

T

2T

slide71

6T

3T

  • Pulley Systems – “T” Method

2T

3T

T

T

T

T

T

T

2T

slide72

6T

3T

2T

3T

T

T

T

T

T

T

2T

5T

  • Pulley Systems – “T” Method
    • Complex pulley system
    • Total MA is 5
    • Name shorthand does not work for a complex system
    • Input force is 1T
slide73
Pulley Systems – “T” Method
    • Simple, compound, complex?
    • Total MA?
    • Name?
    • Which anchor point should be the strongest?
    • Input force?
slide77

2T

  • Pulley Systems – “T” Method

T

T

T

T

T

2T

slide78

2T

  • Pulley Systems – “T” Method

T

T

T

T

T

T

2T

slide79

2T

  • Pulley Systems – “T” Method

T

T

T

T

T

T

3T

2T

slide80

2T

  • Pulley Systems – “T” Method

T

T

T

T

T

T

3T

2T

3T

slide81

2T

  • Pulley Systems – “T” Method

T

T

T

T

T

T

3T

2T

3T

6T

slide82

3T

2T

  • Pulley Systems – “T” Method

T

T

T

T

T

T

3T

2T

3T

6T

slide83

3T

2T

  • Pulley Systems – “T” Method

T

T

T

T

T

T

3T

2T

3T

6T

6T

slide84

3T

2T

  • Pulley Systems – “T” Method

T

T

T

T

T

T

3T

2T

3T

6T

6T

12T

slide85

3T

6T

2T

T

T

T

T

T

T

3T

2T

3T

6T

6T

12T

  • Pulley Systems – “T” Method
    • Compound pulley system
    • Total MA is 12
    • Name is (3:1)(2:1)(2:1)c
    • The right anchor point should be the strongest since the force on it is 6T
    • Input force is 1T
slide86
Pulley Systems – Ideal and Real MA
    • Do you actually work less to move a weight using a pulley system?
    • Real world pulley systems lose efficiency through friction
    • 2” pulley with 7/16” rope has an efficiency of about 85%
    • 4” pulley with 7/16” rope has an efficiency of about 95%
    • Bushings have an efficiency of about 85%
    • Bearings have an efficiency of about 95%
slide87
Pulley Systems – Ideal and Real MA
    • People are assumed to be able to pull about 50 pounds of force using gloved hands
    • Assuming a rescue load of 450 lbs and our “standard” 5:1 simple pulley system, it should only take 2 people to lift the load
    • 2 people pulling 50 lbs each is 100 lbs of force through a 5:1 pulley system generates 500 lbs of force
    • But, some is lost through friction at each pulley
slide88
Pulley Systems – Ideal and Real MA
    • Assuming an IMA of 500 pounds, a loss of 90% per pulley results in 328 lbs of force
    • Further, assume a loss of 25% where the rope bends over an edge using the “ice tray” edge protection
    • It could be much greater for carpet or canvas
    • Our total force is now down to 246 lbs
    • So, using our normal raising system, we would need about 4 people to lift a rescue load
slide89
Pulley Systems – Ideal and Real MA
    • What can improve the RMA?
      • Each person pulls more than 50 lbs
      • Edge friction is reduced
      • Use the most efficient pulley as close to the initial input as possible
slide90

171

139

  • Pulley Systems – Ideal and Real MA
    • Example using an

assumed input of

100 lbs and a pulley

effeciency of 90%

90

81

66

73

100

81

90

100

73

190

410

154