Guide mode with two different ropes.

Quick question..

When belaying two climbers at once off a single belay device like DMM Pivot in guide mode, will its braking ability be compromised by using a 9.8mm single and a 8.5mm half simultaneously?

Thanks!

Benjixxx wrote:Quick question.. When belaying two climbers at once off a single belay device like DMM Pivot in guide mode, will its breaking ability be compromised by using a 9.8mm single and a 8.5mm half simultaneously? Thanks!

Benji

Your belay device will work fine. Following on a half rope is interesting I have followed on a single half rope a few time. Once following a long pitch i fell near the beginning I slowly sank down quite a ways lots if rope strech for that system. Just make sure to keep your second pretty tight near the bottom or they might hit the ground. Otherwise you should be fine using that system.

when in doubt use a Kong GiGi or a CAMP Ovo

Thanks guys. Sorry for the spelling mistake.. Typing on my phone!

The different guide mode devices vary a bit in their design which can affect the co-locking of two ropes in guide. For example, if you look at the bottom side of a BD ATC-G and Kong GiGi it has a raised middle rib between the two rope slots. The Petzl Reverso 4 does not have this; all the 'ribs' of the device are essentially level. (Kong GiGi users will note that the manual for the device outlines that this rib needs to be on the belay-biner side for guide belaying; when rapping, the device is set up in reverse.)

The raised center rib mentioned above allows the belay biner to 'rock' a bit and prevents simultaneous locking of both ropes if you have two followers and one follows. With the Reverso 4, in theory you can have both ropes lock up if only one second falls. (Like anything else in climbing, there are some caveats, and depending on which belay binder you use and how you set it up [i.e. with the ropes centered on the curved basket or on a straight spine] this can help mitigate the simultaneous locking of both ropes.)

Now with that background, to answer your question, if you are using one large fat rope and one really skinny rope, there are several atypical scenarios that can happen. One is that one second climber falls on the skinny rope with a Reverso 4, which then causes both ropes to lock, because with the belay biner weighted it blocks the larger rope from easily moving. The other is that if one second falls on the fat rope with a ATC-G or Gigi (set up per manufacturer) it will allow some slippage of the skinny rope, even if it is weighted, because the belay biner can't fully position itself for optimal locking due to the large rope and rib in the center of the device. Much of this is belay device, belay biner, and ropes dependent. I have noticed slippage with different diameter ropes in guide mode, but nothing I couldn't overcome with my brake hand. However, my live testing is limited because my seconds never fell that much or at all. Play around with your intended device and ropes and see what happens.

Good advice thanks Linnaeus