Thin Ropes in ATC Guide = Danger

The Black Diamond ATC Guide is a near-essential, ever-popular piece of gear designed for multi-pitch rock climbing. When belaying a follower from above, one can easily belay off an anchor, rather than the body, by using "guide mode", increasing safety and comfort. One excellent feature of guide mode is that the ATC acts as an auto-locking belay device. It works because the device is oriented such that the climbing strands cinch down on the belay strands when loaded, halting downward movement. Here I report a failure of this auto-locking feature when used with thin ropes.
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I was recently belaying a follower from above using a Black Diamond ATC Guide in guide mode. We were climbing on two 7.8 mm half ropes. My follower fell, and instead of the climbing strands cinching down on top of the belay strands, they fell next to the belay strands in the cage of the ATC, and began to slip, slowly lowering the climber. I tried to brake the device, but this is actually difficult and awkward, since the brake direction in guide-mode would be into the wall. Fortunately, the slippage was minimal, and simply pulling hard on the brake strand was enough, combined with the friction between the ropes, to halt downward digression. Nevertheless, this was a fairly scary experience, since I was unsure what was going to happen.

Of course, 7.8 mm is towards the thinnest dynamic rope available, but the technical specifications for the Black Diamond ATC Guide indicate that the minimal rope diameter for safe use is 7.7 mm. Thus, I argue that this was proper use of the gear, and warn of this potential safety issue. One possibility is that my specific ATC is worn from years of use, and thus the minimum rope diameter safely useable in guide mode has increased since it was purchased, but it is only a few years old and has a common amount of wear.

Bottom line: If you’re belaying in guide-mode with double or twin ropes, best keep the diameter at 8.0 mm or above, but I’m just pulling that number out of nowhere. This issue should be tested. I also do not know anything about other “guiding” belay devices, such as the Petzl Reverso – these too should be tested.

Furthermore, if anybody has any suggestions for how to increase safety with thin ropes, please comment.

Which locking biner did you use for the belay? I've always use two locking biners for belay biner or rappel to provide more friction.

Was the rope running straight down below the device, or was it running off at an angle?
(Last piece of gear off to the side some...)

The device will slip, and not totally auto lock if that is the case.
(This has been a known fact for some time. So always keep hands on the lines...)

its a known issue ... when it happens the device usually seizes up and is a biatch to unlock

and yes the belay device "should" be replaced when the groves are worn out, for thinner ropes anyways

with single ropes its not an issue

theres a reason that the mammut alpine smart comes in a version just for twins/doubles

there is no real device that can handle any diameter reliably and smoothly from 7.7mm-10.5mm ... despite the propaganda from BD/PETZL/etc ...

for thinner ropes the reverso 3/4 works better ... for thicker ropes the ATC guide is smoother

its all a tradeoff

;)

divnamite wrote:Which locking biner did you use for the belay? I've always use two locking biners for belay biner or rappel to provide more friction.

Cool tip. Thanks. Do both biners hold both ropes, or one rope per biner?

Cor wrote:Was the rope running straight down below the device, or was it running off at an angle? (Last piece of gear off to the side some...) The device will slip, and not totally auto lock if that is the case. (This has been a known fact for some time. So always keep hands on the lines...)

Thanks for your reply. I do think that the ropes were running at a bit of an angle. Hadn't been warned of this before. Cheers.

You had better read the instructions on your device!!

WTF?

1 large locker.

I don't want to hear about you getting hurt! :)

bearbreeder wrote:its a known issue ... when it happens the device usually seizes up and is a biatch to unlock and yes the belay device "should" be replaced when the groves are worn out, for thinner ropes anyways with single ropes its not an issue theres a reason that the mammut alpine smart comes in a version just for twins/doubles there is no real device that can handle any diameter reliably and smoothly from 7.7mm-10.5mm ... despite the propaganda from BD/PETZL/etc ... for thinner ropes the reverso 3/4 works better ... for thicker ropes the ATC guide is smoother its all a tradeoff ;)

Thanks. I'll check out these other devices.

I use a madrock madlock belay device it has a removable pin for use with double or twin ropes to create a tighter bend in the rope for more friction with the smaller diameter ropes. I keep the pin in the zipper pocket of my chalkbag when using single ropes.

Dang Farkas, first you nearly rap to your death, now this? You better get your sh:t together. (and I mean that in the most positive, loving way!)

This scenario is even worse with the new Reverso. There is a groove cut out of the sides of the Reverso which allow the ropes to slide to the side of the device and not directly on the break strand. Not sure if I am explaining it clearly here. I actually had a 10.2 invert in one of those things when I was using it to ascend. Nothing like switching from ascending to rappelling in a split second.

farkas.time......I think, from your response, that you may have misinterpreted divnamite's suggestion regarding the use of two locking carabiners to belay. By doubling or even tripling the locking carabiners the resulting additional surface area greatly increases the friction and thus the control of the belay.

the double biner belay technique is also good for a light person belaying a heavy person

I've had this same creep with a 9.8 sterling velocity dry treated... it was the dry treat but it freaked the hell outta me when I couldn't actually stop when I was rapping.

something is fundamentally wrong if you can't stop while you rap...

Spent a weekend climbing at Laurel Knob on a buddy's 7.8's with an ATC guide and BD gridlock. Used an old petzl atache spin ball (large diameter) through the loop. Not sure if this is a better combination than what you used but I didn't have any problems. Rapping on the other hand was scary slick.

Regularly use PMI Verglass 8.1 twins with my ATC Guide and any number of lockers and have yet to experience such a problem.

YGD!!!!

CaptainMo wrote:I've had this same creep with a 9.8 sterling velocity dry treated... it was the dry treat but it freaked the hell outta me when I couldn't actually stop when I was rapping.

How does the "autoblock mode" of these new devices, and specifically slippage of one strand over/past the other, relate to rapping?

I'd say this had to be a special circumstance regarding the rope being pulled sideways during the auto-lock. I've experimented a little with a 7mm accessory cord and an ATC Guide, never in a real scenario, but I played around with and jump/fell onto it. It locked every time, no problem.

Gunkiemike wrote: How does the "autoblock mode" of these new devices, and specifically slippage of one strand over/past the other, relate to rapping?

Slippage rapping vs slippage in autolock belay mode. . . Both devices should be locked off but still the ropes are creeping through the device. The correlation isn't obvious? Slippage. In my case Sterling said it was normal and just the dry. Seriously wigged me out...

CaptainMo wrote: Slippage rapping vs slippage in autolock belay mode. . . Both devices should be locked off but still the ropes are creeping through the device. The correlation isn't obvious? Slippage. In my case Sterling said it was normal and just the dry. Seriously wigged me out...

Two different things, if you haven´t enough braking power when abseiling then the ropes are too thin or you are too fat. In autobloc mode the ropes pass each other inside the device (they exchange their relative positions) and they don´t autobloc any more though the problem is still the ropes are too thin or the load was too high. I´ve posted the pull test results for the ATC Guide and Reverso³ previously, while Patzl highlight the limitations of their device in autobloc mode Black Diamond don´t seem to care enough about their customers to bother.