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Ratchet Prusik- also referred to as a progress capture device (PCD), the ratchet Prusik
within a pulley system works in conjunction with a pulley to advance it up a line during
movement of a load. A ratchet Prusik holds tension on the line during a reset,
preventing it from going backward, so that progress is not lost. A ratchet Prusik used in
conjunction with a Prusik minding pulley creates a self-minding ratchet, which will tend
itself during operation of the pulley system (Figure 172).

Figure 172- Ratchet Prusik

Pulley systems can be rigged by either using the main line itself or using a separate line
"ganged" (also referred to as piggy-backed) onto the main line (Figure 173). In order to
have a working knowledge of pulley systems, it is important to understand some basic
principles that distinguish one system from another.

Figure 173- Simple 2:1 ganged onto the mainline

Pulley Strength- in a single pulley half the
load is on one side of the rope and half is on

the other. The total load on the pulley is
thus 2X the mass that is being moved. In a
double pulley the total load on the pulley is

Figure 174- Pulley strength. This CMC Rescue Pulley
(model 300301) has a rated breaking strength of 47
kN, which means a limit of 23.5 kN load to one strand
of rope entering the pulley. Image © CMC Rescue.

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