How does a pulley system work?

If trickline is your domain, a ratchet is probably what you prefer. But if you’re tempted by longlines, a pulley system is a must. So what is it, and how does it work?

A pulley system is a tensioning system that consists of several pulleys (block and tackle), a rope, a rope brake, an ascender and connectors. Besides great efficiency, a pulley system offers great variability as well – all parts can be combined. That way, you only take the stuff you really need when going on the line.

Two double pulleys (EQB Minima FX) or two quadruple pulleys (EQB Quatron FX) form the base of the system. The front pulley is the tackle (movable), which increases the system’s efficiency, while the back one is a fixed block pulley (at the anchor point) that only redirects the rope without affecting its mechanical efficiency.

The basic efficiency ratio of a system with two double pulleys (e.g. Minima FX) is 5:1, whereas two quadruple pulleys (Quatron FX) increase the ratio to 9:1. Efficiency can be increased further with a multiplier, which is simply another small pulley system attached to the loose end of the main system’s rope. You can use either a simple multiplier, which multiplies the main pulley system by 3:1, or a double multiplier (with an extra pulley), which multiplies it by 5:1.

5:1

Minima FX

9:1

Quatron FX

3:1

Simple multiplier

5:1

Double multiplier

Minima FX pulley system with a multiplier diagram

A rope brake plays an important role in the pulley system. It can be either a primitive self-locking system, where the rope locks against itself, or a cam brake.

Self-locking brakes

E.g. Elephant FX. They are lighter and cheaper, but less efficient due to increased friction, which also causes faster rope wear.

Cam brakes

E.g. GriGri. They are more efficient, but far more expensive and heavier, too.

Elephant FX rope brake diagram — Elephant FX rope brake

A rigging plate, such as EQB Tribit or EQB Alien, can be used to mount the rope brake. Alternatively, an extra anchor sling can be used instead. Some pulley designs allow you to attach the rope brake directly to the pulley, which makes the system easier to use. For example, both Minima and Quatron are based on this design.

A static rope of corresponding diameter (mostly 8–11 mm) is used to connect the pulleys. The rope can be made of polyamide (PAD), polyester (PES) or high-tech materials such as Dyneema or Vectran.

The lower the rope stretch (PAD > PES > hi-tech), the greater the pulley system’s efficiency.

The design of the pulleys affects efficiency too: the bearings used (bushings or ball bearings, which are much more efficient under heavy load), the sheave diameter (the bigger, the better) and other aspects.

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