QC LAB: TO SCREAMER OR NOT TO SCREAMER?

This post comes direct from QA Manager Corey LaForge, who returned from a recent ascent of the Eiger Norwand with some questions about Yates Screamers that he promptly put to the test here in our lab.

A couple of months ago I climbed the North Face of the Eiger with some friends. On one particular pitch above the Waterfall chimney, I was climbing some harder mixed moves right above the belay. My gloved hands groped a rounded rail, while my crampons scraped on marginal limestone edges and a thin layer of verglasse. The single piece between me and my belayer was a half-pulled-out, bent over piton. As I moved further above this piece, questions formed in the back of my mind: "Will that manky pin hold?" "Should I have a Yates Screamer on that thing?" "Do Screamers even help?" Luckily, I didn't have to find out the answer to any of these the hard way. As soon as I got back, however, I decided to do some drop tests in the lab to give myself some rough answers to these questions.

Analysis

From the data above, it became clear that we were not too far off in our hypothesis: the Screamers did reduce the peak force on the first piece of gear, while nylon absorbed a bit of energy, and Dynex behaved similarly to steel chain. The Screamer did reduce the peak force by 14-17%, or a reduction of 1.4-1.8 kN.

We figured that the very severe nature of a Factor 1 fall very near the anchor is perhaps not showing us the difference between Screamers and other dogbones as well as it could because the forces generated in such a fall are WAY above the activation force for the Screamer. We decided to repeat the experiment with a lower fall factor to get peak forces that are less severe and more typical of a real climbing scenario.

We hypothesized that the steel chain would not stretch at all, resulting in the highest force to the piece of gear. We presumed that the Dynex runner would behave about like steel, while the two types of nylon runners would stretch absorb slightly more energy, and ultimately that the Screamers would absorb the most energy to reduce the peak force by upwards of 50% when compared to the baseline peak force established in the drop with the chain.

Results: 9-foot Factor 1 Fall on to 1stPiece of Gear