Fall comparison with rigid/human mass - Petzl Canada

Fall comparison with rigid/human mass

The tests presented above were designed to help us evaluate falls involving real people. For comparison, we redid the same series of falls based on the standard model: rigid mass with a GRIGRI 2 fixed to the anchor.


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Test with rigid mass

Factor 0.3

Factor 0.7

Force on the anchor
Force on the climber

These tests revealed very significant differences between the two protocols: the force on the climber increases by up to 70% with a rigid mass.

These differences are explained by the many factors, other than the rope, that contribute to fall energy dissipation: the absorption of the two bodies, belayer displacement, rope slippage in the device...


These tests help us evaluate falls involving real people.

Such measurements necessarily carry a high degree of uncertainty, but help provide important information:

  • The forces at work in a real fall differ greatly from the results of standard testing.
  • In practice, factors other than the rope contribute to dissipating the energy of a fall.
  • To understand a fall, one must take into account all of these factors and not focus only on the rope.
  • It is difficult to control all of the factors that dissipate fall energy. However, it is easy to influence the potential for belayer displacement. Belayer displacement helps dissipate a significant part of the energy and thus limits the forces at work. On the ground, it is essential to allow displacement to occur for a dynamic belay. At the belay station, it is wise to use a long tether, when the situation allows it, to allow displacement to occur.