Friction for lifting and lowering
Friction will work against whichever direction the rope is moved in – it will help to slow objects as they are lowered or brought to a halt but it will make it more difficult to lift loads or pre-tension ropes .
A rough description of the amount of friction in an anchor point is its efficiency – very efficient pulleys will have a small amount of friction , while ropes passed over a branch will experience a large amount of friction .
This does not make one better than the other – rather , each should be selected for its correct application .
The image on the left compares two casualty lifting operations . In both operations the casualty weighs 100kg . It is important to note that :
• With more efficient anchor points , less force is required for lifting .
• With more efficient anchor points , less force is applied to the anchor point .
If the casualty was to be lowered , the reverse would be true – the more efficient the anchor point , the more force must be applied by the belay on the fall side of the rope to control the lowering . Applying friction at the anchor point can be an effective way of reducing forces on the anchor point .
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