Can a Belay Device Jam Open?

Is it possible for a belay device to jam open when it gets pulled into a bolt, or will it automatically re-lock after the initial impact?

By Gear Guy | June 12th, 2017

Most “assisted-braking” devices will lock up without any effort from a human belayer, but unjamming one still requires a sentient being. Photo by Klaus Fengler.


I was about 10 feet above a bolt, couldn’t keep it together, fell, and took a big ride. So did my belaying girlfriend, whom I outweigh by 80 pounds. She went flying up the route and slammed into the first bolt.

Is it possible for a belay device to jam open when it gets pulled into a bolt, or will it automatically re-lock after the initial impact?  —Ryan Stefani

 

A belay device can jam open when it is sucked into a quickdraw clipped to a bolt, and it may not re-engage because it is under load. An astute belayer might be able to push away from the rock, re-engaging the device, but that is a big if with everything happening faster than you can spit. Having the device re-engage also assumes that the belayer hasn’t been knocked unconscious or broken his shoulder or hand when slammed into the rock. Most “assisted-braking” devices will lock up without any effort from a human belayer, but unjamming one still requires a sentient being.

It all comes back to fundamentals and physics. You can read about the large forces generated in a fall in my answer to the highball-bouldering question (on this page). In route climbing, rope stretch, friction and drag will reduce the force, but these factors are difficult to predict accurately, and the belayer should expect a worst-case scenario, and be positioned and braced accordingly. Since you vastly outweigh your girlfriend (ex-girlfriend now?), it is no surprise that she launched like a pop-bottle rocket.

Here is how you can be a better partner next time.

1. Anchor the belayer to an immovable object on the ground. You know, a tree, a boulder, even a bumper. I hate doing this because belayers like to move around and fetch all sorts of interesting objects from their packs, but safety first!

2. Get your belayer a nice pair of leather gloves. These will keep those hands from being coated in rope guck and, if you neglected to heed the advice I dispensed in #1, will protect her hands against being trashed by the quickdraw or rock, and will prevent rope burn when the rope zips through the device at warp speed.

3. Buy your belayer a really nice helmet. I don’t think I need to explain why.

 

This article appeared in Rock and Ice issue 243 (July 2017).

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