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How to Cllimb Safe: Top Roping is Not So Safe

04-Jan-2013
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Photo by <a target="_blank" href="http://www.onsight.com.au/">Simon Carter</a>Toproping is the laziest way to climb—and often the most fun. If leading a testy route is the pinnacle of mind-and-body focus, toproping is surely the pinnacle of pure recreation; a chance to relax and enjoy climbing solely for the movement, without the nagging tension of an ever-present lead fall. Assuming your toprope anchor doesn’t fail.

The day I witnessed an anchor pull, I was in Ouray, Colorado. Three years ago, mid-winter. My partner had led a mixed route and clipped into a small tree overhanging the edge of the cliff. Black webbing noosed around the narrow trunk revealed that it had been used before for an anchor. My partner clipped it, and yelled “Take!”

“Don’t you want to back that up?” I shouted.

“It’s fine,” he said. “Lower me.”

I had lowered him less than five feet when the tree pulled, sending him hurtling earthward. He was saved only because he hadn’t yet cleaned his top piece, a piton hammered in a horizontal crack.

Toprope anchors don’t often fail. In fact, they should never fail. And when they do, pilot error is usually to blame—the homemade bolt hanger broke, the single tree pulled out, the slung block cut loose. In most cases, climbers simply fail to understand the loads that toproping can generate. Logic tells us that toprope forces equal at least our bodyweight and then some, but beyond that, it’s anybody’s guess—until now. For this issue of Climb Safe, I had lowered him less than five feet when the tree pulled, sending him hurtling earthward. Rock and Ice wanted to determine the loads that toprope falls place on anchors—with both a taut rope and a “lazy belay” scenario with several feet of slack in the system.

The fall tests were conducted on a pulley-style toprope, i.e. one where the belayer stands on the ground and the rope runs up through the top anchor and back down to the climber. The lessons learned, however, can apply to any type of toproping or following situation.

The Fall Scenario

To determine how a lazy belay affects the loads on an anchor, we staged two series of test falls and measured the maximum impact forces. In the first series, a 200-pound climber fell near the anchors of a taut pulley-style toprope. In the second series, using the same pulley-style setup, the same climber fell with four feet of slack in the rope—a common scenario if the belayer’s attention has lapsed for a moment. For consistency, both tests were performed with 35.5 feet of rope between the climber and the belayer, and the belay was virtually static. (We used a belay device clipped directly to a belay bolt—certainly not a recommended use of the device nor a good belay style because it doesn’t allow for dynamic load absorption, but one that allowed us to remove most of the variables from the belay setup.)

The Results
First Series: a standard pulley-style toprope fall with virtually no slack in the rope. The details: 200-pound climber, static belay, 35.5 feet of rope in the system. Forces were measured at the toprope anchor.
Fall 1: 800 pounds load on the anchor.
Fall 2: 750 pounds load.

Fall 3: 700 pounds load.

Second Series (the lazy belay): same details as the first series, but a pulley-style toprope fall with four feet of slack.
Fall 1: 1,300 pounds load on the anchor.
Fall 2: 1,550 pounds load.
Fall 3: 1,500 pounds load.

==

Illustration by <a target="_blank" href="http://jercollins.com/">Jeremy Collins</a>Lessons Learned
The dramatic increase in forces generated by only four feet of slack should serve as a wake-up call to all us lazy belayers. You know how it happens: As your partner works his way slowly up the warm-up route, you stare at your feet, kicking dust and thinking about what’s for lunch; or the lovely Francine starts up the neighboring route and you begin wondering what she’d look like in ... never mind. “TAKE!” breaks your daydream—a big U of slack hangs at your waist.
The good news is that a little bit of slack won’t come close to testing the holding power of your gear if you’re using a safe anchor, which will have several thousand pounds of holding power to spare. But the fact that four feet of slack essentially doubles the toprope impact forces should reinforce the need to build totally bombproof anchors. Suddenly, slinging that gnarled juniper tree, or clipping two TCUs and yelling “Off belay!” seems questionable. Would the anchor hold a harsh toprope fall?
To put the forces in perspective, consider that for last issue’s Climb Safe series, we tested 9-foot-2-inch leader falls on 57 feet of rope with a 145-pound climber, and generated far lower loads (see issue No. 132). In fact, with a dynamic belay, loads on the bolt reached a maximum of only 750 pounds—about half of what our 200-pound climber generated with a four-foot fall on the toprope anchor using a static belay. The lesson: Even when toproping, build your anchor to be 100-percent failsafe.

Why a Pulley-Style Toprope Increases the Forces

There are two ways to toprope. One is to belay from the top of the route or pitch, and belay your partner directly up; the other is to belay pulley-style from the ground, with the rope running in an inverted V up to the anchor and back down to the climber. This is the most popular style of toproping because both partners can base from the ground, and it’s easy to rig when one climber leads and lowers. What you should know, however, is that this method dramatically increases the forces on the anchor. The pulley-style toprope loads the anchor with not just the climber’s weight, but also the counterweight of the belayer (that’s why you feel an upward tug when holding your partner’s fall, and sometimes get pulled into the air). In a frictionless world, a climber hanging on the rope would load the anchor with twice his weight. But because of friction, rope stretch and other real-world variables, the load on the anchor is lower—more often roughly 1.6 times the climber’s weight.
Belaying directly from the top of the pitch, either with the belay device clipped to the anchor or to the belayer, eliminates the pulley effect. In this situation, the second loads the anchor with just his body weight—assuming that the rope is kept snug.

Descending from a Sketchy Anchor

You should never toprope on a questionable anchor—always back it up with bomber gear—but sometimes, like it or not, we are forced to descend from sketchy anchors that can’t be backed up. In this situation, it may You should never toprope on a questionable anchor—always back it up with bomber gear be safer to rappel rather than lower. Why? Because rappelling puts only your weight on the anchor (assuming you perform a smooth, controlled rappel without any bouncing or jerking), rather than the multiplied forces created by pulley-style lowering. If you can clip a solid piece of protection just below the anchor, however, it may be safer to lower since that piece (assuming you leave it in place) will back up the anchor.

Not All Anchors Are Created Equal

A final scenario that affects the loads on the anchor is the position of the gear in the anchor, and how each piece is equalized to the master anchor point. In fact, the angle at which each piece is connected can wildly change the actual load on each piece of gear—it’s easy to double the loads if the angles are high. And that leads us to the topic for next issue’s Climb Safe column: How to build the safest possible multiple-point anchors.



 

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Kyle Pease commented on 09-Feb-2013 11:27 AM3 out of 5 stars
This article is misleading. A pulley toprope does not increase the maximum force exerted on the anchor. The maximum force will occur when the climber falls or takes. In case of a fall, there will be a much lower impact force with a pulley, as there is much more rope in the system to absorb fall energy.

Delete the section "Why a Pulley-Style Toprope Increases the Forces."
Ant Onio commented on 27-Mar-2013 01:33 PM1 out of 5 stars
7KN is not that much... I mean, if you don´t set up a top rope anchor that you are absolutely shure that can handle at least two times that and obviously a backup as same as good, it means that you are doing something wrong.
Top roping isn´t an emergency abseil.
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