Stunt vest extreme drop test

Fall always leads to dynamic load

When we talk about falls we talk about dynamic load or shock load. In the climbing world there is a standard to test harnesses for vertical fall – EN364. To test the harness you drop the 100kg dummy from 4 meters height with Fall Factor 2 on climbing rope length of 2 meters.

Typically climbing ropes sit around 25-35% dynamic elongation and this number is very closely related to the maximum impact force we will get on test.

Watch the stunt harness cross point test during climbing fall here.

Fall + ultra static rope

But when we switch to ultra static lines like Dyneema/Spectra/Technora we are getting tremendous loads on the fall. In our tests we will use steel chain to simulate load coming from a fall where there is no elasticity in the line.

video: FF1 on steel chain - Side point test
Source: Institute for safety at height - MGTU lab (Moscow, Russia)
video: FF1 on steel chain - Cross point test
Source: Institute for safety at height - MGTU lab (Moscow, Russia)
FF2 on steel chain

FF2 on steel chain leads to significant damage or breakage of the harness. Especially if you are using small radius shackles which act like a knife in a speedy fall.

How dynamic load affects impact force

With 4 meters deep fall on Fall Factor 2 on 2 meters climbing rope you will get around 9kN.
Same fall with steel chain will give you more than 18kN.

Never use ultra static lines with the fall. If you do always use brake bar, other shock absorbing devices or techniques.

Never think about load only.

  • heating in the stressed point (can easily affect damaging Dyneema/Spectra)
  • square of impact (thickness and diameter of the shackle/carabiner)
  • friction

That’s why static load tests do not give the full understanding. To get more info on how the elasticity of material affects forces in dynamic load check Nylon and Dyneema slings drop tests here.


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