Pulley SystemsPulley Systems

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

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

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%

Pulley Systems - Definitions• Becket is a lower attachment point

between the two sheaves• Can be used to attach a rope or a

second pulley

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

Pulley Systems - Definitions• Directional is a pulley that is between the

pulley system and the load• Does not add any MA to the system

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

Pulley Systems - Definitions• Pr is a ratchet prusik which is a type of

progress capture device

Pulley Systems - Definitions• Ph is a haul prusik for attaching to the rope

Pulley Systems - Definitions• Collapsed Pulleys or Two Block is when the

system can not be made any shorter

Pulley Systems - Types• Simple• Compound is any combination of

two or more simple pulley systems acting on each other

Pulley Systems - Types• Simple• Compound (multiple)• Complex does not follow any of the

rules for a simple or compound pulley system

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

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

Pulley Systems – “T” Method• Assumes no loss from friction or

ideal mechanical advantage

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