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Lead Falls in Climbing Gyms - How much Force?

Most climbers know the general ratings of their gear, but how many know what kind of forces they generate in a fall? We did some human testing to find out. Pipeworks Gym in Sacramento let us use their facility and brave volunteers Ryan Kowalski, TJ Gillick, Michael Melner, and Ryan Jenks took whips for science.

We put Dynamometers on our climbers, belayers, and the bolts that held the falls. Our testers took small falls and big falls. We tested a "static" fall where the belayer was anchored to the ground so they would not move in a fall and could not absorb any force. Michael Melner donned a weighted vest to see how much difference more weight would make. To simulate the effect of rope drag on fall forces we clipped a rope on an irregular path through a bunch of protection.

Our Results

The first takeaway is that our gear is super good enough. Our climbers saw a maximum of 2.65kN / 596 lbf while UIAA rated harnesses can handle minimum of 10kN. Our belayers saw even less force, maxing out at 1.85kN. Our bolts took the most force in every fall, averaging 3.54kN. Modern bolts and hangers break well above 30kN.

The highest force we generated was 4.78kN, or 1,075 lbf. Ironically, our lightest tester achieved this result with a medium length fall. He fell on our setup to simulate rope drag, so the rope was clipped in a non-linear path through a ridiculous amount of protection. The drag meant that barely any force transferred to the belayer and it limited the rope's ability to absorb energy, essentially raising the fall factor. 4.78kN is a little surprising because many micro-cams and small nuts are rated at 5kN (anything less is intended for body weight only) and a light climber nearly generated this with a modest fall.

The rest of our tests are pretty consistent with only moderate forces being generated. It's useful to have an idea of what these forces are, especially for trad climbing. There are a lot of other factors that can make falling dangerous, like inattentive belayers, ledges, and sharp edges to name a few. Bolts aren't always solid either, although that's a concern in the wild and not in the gym. However, in most normal conditions go ahead and whip, your gear can take it.

What's Next

What happens if a big climber takes a whipper?


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