Скачать или смотреть Designed to fail?!

We really wanted to drop big rocks and a bunch of Screamers got in the way. Screamers are shock absorbing packs designed to deploy during a high force event, usually a fall. Aid and Trad climbers use them on sketchy pieces of gear in hopes that they will deploy before the force gets high enough to rip the cam or nut out of the wall.

For the cool graphs and more details check out this post
https://hownot2.com/pages/screamers

To establish the force a large climber can put on a piece of gear we had Mike (206lbs with gear) take 3 lead climbing falls with a dynamometer at the bolt measuring force. 6.54 kN, 6.75 kN and 6.73 kN. Notice the force climbs as the rope looses stretch after repeated catches without time to rest.

Next we swapped out Mike out for a 206 lbs boulder. 7.53 kN, 8.08 kN and 8.25 kN. Which pencils out to about 15% more force than the bolt was seeing during Mike's drops. Definitely not the worse case scenario, but in the upper range of forces that is possible to generate using screamers in an aid or trad climbing context.

All of the screamers we tested claim to reduce the force to less that 4 kN. Yates Zipper Screamer. Fully deployed. 6.1 kN. Edelrid G Screamer. Stopped rock before full deployment. 3.78 kN. Yates Zipper Screamer x2. Fully deployed. 3.54 kN. Early 90s Yates Screamer. Fully deployed. 6.75 kN. Petzl/Charlet Moser Nitro Screamer. Fully deployed. 6.34 kN.

Not satisfied with the carnage we had created we replaced the 206 lbs rock with a 650 lbs stone. We linked a chain of screamers to see if they could absorb enough force to stop the rock before their extension allowed the boulder to hit the ground. Nope, but the bolt only saw 3.77 kN.

Ryan was pretty sure we could stop the 650 lbs rock using Edelrid G Screamers if we took the rope out of the system. Despite deploying fully the rock broke the eye of the last screamer and crashed into the ground. Our linescale 3 recorded 21.41 kN. Even recording force 1280 times a second the 21. 41 kN peak was only recorded once making it possible we missed the peak force. That force still exceeds the standard even if it doesn't quite meet the 22 kN the G Screamer is rated for.

For even more fun we put a Yates Zipper Screamer and an Edelrid G Screamer on the SlackSnap UTM. Pulling at 500mm/min the Yates kept the force around 2.3 kN before it deployed fully and broke at 23.57 kN. The G Screamer saw up to 5.26 kN before full deployment and failure at 24.65 kN. It is interesting we saw a higher force as extended on the slow pull than when dropped. Of course drop tests are much closer to how screamers are meant to be used.

https://hownot2.com/products/g-screamer
https://hownot2.com/products/zipper-s...
https://hownot2.com/products/linescale-3

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