![]() An earlier variation of the ATC-type device is known as a Sticht plate, which basically swaps the tube for a plate that the rope wraps through in a similar way. To be clear, there are other belay devices. The difference is all in the length of rope available to stretch and absorb the impact. If the same climber had the same 4 meter fall from a position 10 meters above the belayer, the factor would be. So, if a climber has ascended 2 meters above their belayer (imagining the belayer belaying from some ledge as below), and then falls 4 meters to below the belay point, they've had a fall of factor 2, which is as bad as it gets. How much extra stopping power this slippage offers depends on what's known as the fall factor, which is calculated as the distance a climber falls divided by the length of rope between themselves and the belayer. ![]() The rope slips for some distance through their hand. This is what happens now when the falling force exceeds that of the ATC and the belayer's grip. Rather than jerking to a stop and placing a huge shock-load on the rope, the climber would be decelerated over time. In a dynamic belay, should the climber fall, the partner would allow the rope to slip around them for some distance. Rather than running ropes through machined tubes, belayers then wrapped them around their bodies. This changed thanks to some Sierra Club guides who developed a technique known as dynamic belaying. Consequently, even protected falls hurt like hell, but there was also a much greater chance of the rope breaking. Ropes then were made of hemp and were thus "static." That is, when a climber fell, the rope had little or no give. Prior to the 1930s, climbing was a rather more grim activity. ![]() This isn't quite the problem it seems, however. Thus, given an average fall, the rope is going to move through the belayer's hand and through the ATC device. So, if a falling climber exerts 4.5 Kilonewtons of downward force (200-ish pound climber falling for five-ish feet before being caught by the rope), then the belayer needs to soak up about 2.5 Kilonewtons of upward force.Īn ATC device maxes out at about 2 Kilonewtons of braking power, while the upper limit for a single human hand holding a rope is a few hundred Newtons, according to a paper prepared by the German climbing bolt manufacturer Bolt Products. Again, about half (52 percent, according to a widely-cited paper by Stephen Attaway) of the downward force of the falling climber actually reaches the other climber, with the remainder being taken up by the friction against the upper anchor (a carabiner) and the rope itself. It takes surprisingly little effort to arrest even the biggest fall and a relatively light belayer can protect a big fall from a much larger climber safely. To prevent the rope from traveling upward through the device (and allowing us to travel downward toward the ground), our partner has to drop their hand to "lock" the rope off via the friction provided by the ATC tube. ![]() This anchor, the one attached to our partner, will be augmented, however, by the ATC, which serves to guide the rope vertically downward through the carabiner and then immediately back upward. The rope will run downward from the anchor above us through this carabiner and back up as a sort of mirror of the anchor above. Attached to this second climber's harness is a carabiner, a small metal oval with a locking or spring-loaded gate. Our climbing partner below is left to manage the rest. The friction of the first anchor above us soaks up over half of the falling force. First, ahh! Next, we feel the rope catch. Say we tried to plant a foot on an unexpectedly slick nub of rock and with no warning we're airborne. The spoilers are out, the airbrakes scrape through the now-dense air, the plane flares. And the ground is coming so quickly until it's suddenly there. Every foot closer to the ground means one less foot to recover from … an incident. It will be just a small portion of the total flight time, but it's where consequences start happening really, really fast. As someone that climbs rocks and dreams about airplanes, I can give you this assurance: the metaphor is sound. It comes together, as it always does, but the experience will never not feel novel. Like the aircraft, you are capable of this and have done it many times, but every ascent-every moment spent suspended against the acceleration of gravity is by virtue of technical ability, whether granted by aerospace engineers or years of physical and mental conditioning. Now nearing arrival and preparing to descend, you the rock climber have spent one or perhaps many pitches nervously and with absolute deliberation warring against gravity. Rappelling does feel a lot like landing in a jetliner.
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