Dead Banger

Beware the hidden dangers of short, static falls

From Rock and Ice, Oct 2004. -- reprinted with author permission.

Common scenario: You are working a sport route, when you clip in directly to your high bolt with a quickdraw attached to your belay loop. Resting on the draw, you suss and brush the holds, then rest some more until you feel virile strong again. With fresh blood pumping through your forearms, and nary a word to your belayer, you pull back onto the rock, crank a move then fall.

CRACK!

The jolt back onto the bolt, into which you are still quickdraw-tethered, stuns you. You only fell two feet, but your neck is getting stiff and your guts feel like they’ve been kicked by a mule. “Lower me,” you say. “I don’t feel so hot. I think my spleen exploded.”

Another common scenario: You are leading a pitch on a big-wall aid route. It’s dicey, so for extra security you always keep one daisy chain clipped to a lower piece. As you ease onto a high placement, a RURP, it pops and dings you in the forehead, drawing blood. That smarts, but it’s nothing compared to the rude awakening you receive when you drop onto your daisy chain. That impact feels as if it will snap you in two. But just as that begins to happen—SNAP—your daisy chain breaks and you cartwheel 20 feet down the wall until the rope catches you on a lower bomber cam.

Though you only fell three feet onto your daisy chain, your back is getting stiff and your guts feel like they’ve been tromped. There’s also the acorn-sized knot and drip of blood on your forehead. “Lower me,” you tell your belayer, “I think it’s your lead.”

What happened?

In both situations you fell prey to shock loading, and, although your falls were short, both were fall factor 2—the severest possible. To calculate the fall factor, divide the distance you fell by the amount of rope (or in this case, the length of the draw plus biners) that caught the fall. Fall 50 feet on 100 feet of rope, for example, and the fall factor is 0.5, i.e., not too bad. Fall 100 feet on 50 feet, however, and the fall factor is 2—heinous.

Fact is, the falls outlined above are more severe in terms of impact forces than most lead falls. In the first example, when you neglected to unclip from that draw, you removed your dynamic rope from the protection chain. Since quickdraws and carabiners don’t stretch (or stretch so little as to be inconsequential), your two-foot fall, rather than gradually being decelerated by the rope, was instantly stopped by the draw. Add to that the fact that you fell two feet on just one foot of quickdraw (fall factor 2), and it’s no wonder you are now damaged goods.

In the second, aid-climbing example, you did essentially the same thing. Rather than boinging onto the dynamic rope, you shock-loaded onto the daisy chain, which, unable to stretch, simply blew apart when pushed beyond its load-bearing capacity. And, as in the first example, you cranked off a fall factor 2.

Shock loading is among climbing’s most insidious and effective hazards. It waits out there, lurking, for you to screw up. Shock loading is why, with a lightweight hammer and a short bit of cable, you can funk out welded pins, or break carabiners. Even a small mass moving at high speed and abruptly stopping can generate a lot of energy.

An object going from quickly moving to deathly still may be the hangman’s friend, but it is our enemy. To ferret out the foe, Rock and Ice conducted a series of drop tests using common items on your rack—quickdraws, runners (nylon and spectra) and daisy chains—in the aforementioned common scenarios. For the quickdraw test, we replicated the time you fell onto it at its maximum extension (about 12 inches) above the protection. The resulting 24-inch drop sounds tame, but shock loads peaked at 1,600 pounds force, much higher than you’d expect from a mere plop onto a draw. Draw drops from six inches above the pro impacted the anchor with 1,200 pounds force.

Though the forces from the quickdraw falls didn’t approach the gear’s load limits, they were quite tangible--the crash-test dummy (yours truly) walked away with a sore back--and are high enough to pull or even break marginal gear placements or funky bolts, such as old quarter-inchers or desert spinners.

For the sling and daisy chain drops, a 165-pound weight volunteered to take my place. The caveat to comparing one to the other is the human body is gelatinous and absorbs energy. A climbing harness also has some load-absorbing capacity. Replacing the body in a harness with a dead weight will increase the forces in any drop test. Nevertheless, it gives indicates how equipment when pushed to its limits will behave in the real world.

The results of the sling drops were startling. Brand-new, 22-inch-long 8mm, sewn spectra runners, CEN rated to nearly 5,000 pounds, broke at the end of their 44-inch fall (a grim testament to the forces you can achieve when you fall directly onto a sling). Interestingly, nylon runners, even old faded ones scrounged off desert towers, subjected to the same test did not break, although the shock loads were still over two tons. Attribute the nylon slings’ durability to the material itself. Nylon, even when it is woven into a static weave, such as that in a runner, stretches some. Spectra, meanwhile, is like steel and does not stretch—it breaks. Note that some of the tests had to be discounted because when the weights fell, the carabiners rotated causing minor-axis loading, and their gates failed. Such failures reveal the element of chaos, of inherent unpredictability when rope, sling, carabiners and your body are flying willy nilly through the air. Carabiners that were properly oriented at the beginning can rotate into weaker orientations—pay attention to your carabiners’ minor-axis and gate-open strengths.

The broken spectra slings, while shocking, aren’t an indictment of the textile. Instead, the slings graphically illustrate the limitations of a material when it is misused, and show that nylon slings are more forgiving of our mistakes, though they, too are not designed to absorb energy. Of all the components in the protection chain, only the rope is meant to stretch.

The forces generated in the daisy chain drops varied depending on which “pocket” the weight was clipped to. A sewn, 54-inch nylon daisy chain with the weight was clipped to the chain’s middle pocket (allowing a 54-inch drop), and peaked at 2,200 pounds force, at which point the pockets began blowing out “Screamer” style. Four pockets ultimately ripped before the fall was stopped. Ditto when the weight was clipped to a pocket a third of the way down the daisy. In both cases, the daisy chains behaved a bit like the load-absorbing Yates Screamer runners, which have stitching designed to rip apart under a specified load, and are often used in aid and ice climbing when protection is marginal. The action of the daisy chain pockets zippering from pocket to pocket slowed the fall dynamically—another reason, along with being lighter weight and more compact, to choose sewn daisy chains over knotted ones. When the weight was clipped to the end of the daisy chain, however, and dropped from its full 54-inch extension, both of the daisy chains subjected to this punishment broke cleanly in two.

“Using your daisies or slings to catch falls is asking your system to fail, because there is nothing to absorb energy,” says Bill Belcourt, who works in Black Diamond’s equipment design department. “When the forces get high enough, something has to give. It’s just physics.”

But if micro falls onto static slings, draws and daisy chains are so severe, and climbers routinely misuse gear this way, the question begs: Why haven’t we seen a rash of accidents?

Thankfully, the dynamic capacity, slight though it is, of the human body, harness and other links in the system builds in fudge factor that somewhat softens shock loading. To be sure, in some cases, such accidents do happen, but are chalked up to other causes. For example, when we fall onto a daisy chain, which shock loads the placement, which rips, we blame the accident on “pulled pro.” In other cases, the cause is clear. Recently, a climber fell onto a daisy chain, which broke. He then fell to the ground, breaking his leg.

Lastly, many of us have just been dodging the bullet. Time to change our ways. After witnessing carabiners, slings and daisy chains explode in what I previously considered minor falls, I’m rethinking the way I aid-climb: instead of clipping a daisy chain to a placement and keeping it clipped in until after I’ve climbed above the piece, I’m going to clip the rope to that piece and unclip the daisy before I climb past it. Then, if I fall, I can ride on down the easy way.

POINTS TO REMEMBER

Quickdraws, slings and daisy chains, for practical purposes, don’t stretch.
Any fall directly onto a draw, sling or daisy chain creates a very high fall factor—much higher than if you take the same short fall onto the rope. In some cases, the fall factor is 2, the highest (worst) attainable, and one large enough to have serious repercussions.
Keep the dynamic capacity of the rope active in the protection system at all times.
When you lead aid pitches, use a system where your daisy chains function as keeper cords only for overhead attachments. Don’t clip them to placements in lieu of the rope, even when the attachment is temporary.
Mix up nylon and spectra slings, using the more dynamic nylon slings on protection at the beginning of pitches, where fall factors can be highest.
Use sewn daisy chains instead of knotted ones. The pockets on a knotted daisy will break; while the pockets on a sewn chain will usually zipper out, dynamically limiting an accidental shock loading.
When you rest on a piece connected to your harness via a draw or sling, remember to unclip from the pro before you climb again. Do not work a move while clipped directly to a piece of pro.

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