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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|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.