Have a pair of Beal Gully 7.3MM doubles/twins on the way - Need a new belay device

I doubt they are only certifying the half ropes diameter when used as twins. That wouldn't make sense. Considering most half ropes are not double certified as twins aside from a handful.

Im having a hard time wrapping my head around this too.

Im going to call black diamond and get the info. Or maybe i'll direct them to this thread and see if we can get clarification.

rgold wrote:Actually, I think I know what they are thinking. They are only certifying their device for half ropes if the half ropes are used as twin ropes.

No, that's not the explanation. Have a look at the ATC XP instruction sheet (there's a PDF on BD's product page). There are different ratings for use with single, twin and half ropes. It's rated 9-11mm with a single rope, 7-11mm with twins (which makes sense) and 8-11mm with half ropes (which as you point out doesn't make sense in real-life conditions).

To the OP: Best not to rely solely on published specs. I've got a pair of Mammut Twilight 7.5mm ropes and I've rappelled on them with an ATC XP (with a second biner) and a DMM Bugette. On paper the the two devices have very similar ratings - the ATC XP is supposedly good down to 7.7mm (without a second biner) and the Bugette to 7.5mm -- but in practice I've found the Bugette to be much more effective.

rgold wrote:Actually, I think I know what they are thinking. They are only certifying their device for half ropes if the half ropes are used as twin ropes.

Think I may have found the answer. The UIAA test for braking devices is based on a 7kN force for single ropes but only 5kN for half ropes (one strand). For twin ropes it's 7kN, two strands. See theuiaa.org/upload_area/Saf…, page 5.

rgold wrote: ...according to Jim---you suffer an additional grip penalty from having two ropes in your hand, only one of which is loaded.

Jim, are you saying that? Yes there is a penalty c.f. a rope of the sum of the two diameters, but c.f. a single stand of half rope, I'm surprised: it is much easier to catch a fall on a 8mm half rope if you have another strand in your hand, than if you only have hold of one 8mm strand. The latter is almost impossible.

PS. Jim, are you coming to your Brother's Swanage guidebook bash at the end of the month?

Interesting! The test figure of 5kN seems to be an artifact of the drop test standard of 55kN for a single strand of a half rope, since (55/80)*7=5 (approx).

If true, this would seem to misunderstand the point of the 55kg test weight, which was to have a statistically effective way to conclude that a single strand could hold at least one UIAA fall with 80kg. In other words, the 55kg test was there to estimate the ability of a single strand of half rope to function as a single strand (but without the safety margin expected of single ropes).

But it seems absurd to believe that the UIAA engineers don't understand the point of their own protocols, so I suppose there has to be some other explanation for the 5 kN pull threshold rather than the 7kN expected for single and twin ropes. Whatever that explanation is, it will be of no consolation to a half-rope belayer failing to hold falls on a single strand.

Martin le Roux wrote: Think I may have found the answer. The UIAA test for braking devices is based on a 7kN force for single ropes but only 5kN for half ropes (one strand). For twin ropes it's 7kN, two strands. See theuiaa.org/upload_area/Saf…, page 5.

But that is a test of the physical strength of the belay device, it has nothing to do with the braking force. The logic of the different forces used for this escapes me as well!

David Coley wrote: Jim, are you saying that? Yes there is a penalty c.f. a rope of the sum of the two diameters, but c.f. a single stand of half rope, I'm surprised: it is much easier to catch a fall on a 8mm half rope if you have another strand in your hand, than if you only have hold of one 8mm strand. The latter is almost impossible. PS. Jim, are you coming to your Brother's Swanage guidebook bash at the end of the month?

The numbers rarely lie! I´ve tested this a couple of ways and it´s there is a drop in braking performance of 20-25% with two strands and only one loaded. Both loaded equally there is a similar increase over a single strand. The CAI came to a similar conclusion as well, they noted a loss of 40% from loading both strands to loading only one.

Doubt I´ll be coming over, long way for a few beers!

Jim

I have heard the Grivel master pro works with skinny ropes, anyone have experience with them?

grivel.com/products/rock/be…

You can add a second carabiner for more friction. I would be fine with using the ATC Guide, regardless of it's minimal diameter rating, on twin 7.3s with two carabiners. The second carabiners adds about 20% more friction.

To the OP;

I'm also choosing a device to use with the 7.3mm Gullys and tested them in the gym using the Smart Alpine (7.5-9.5). The Smart did not lock a fallen climber. In the test, the ropes moved slowly thru the device under the weight of the climber.
Adding a second locking 'biner does not work as it locks up the Smart.

And for reference; this device DID lock nicely on a set of Mammut Genesis 8.5mm's.

As has already been suggested, the only device that has 7.3mm somewhere in the middle of its range seems to be the Edelrid Microjule. (Micro, not mega.) The Smart Alpine (small model) and the DMM Bugette only go down to 7.5mm, and the Alpine Up has 7.3mm as its lower limit, which is not encouraging.

Yes, we know the marketing numbers. Just adding some real test data to the discussion. Note that the difference between 7.5 and 7.3mm is .0079" and is meaningless in the combined tolerances of the belay device and rope diameter.

Just tested the Gullys with an ATC-Guide and 2 locking 'biners. This is no good. Way too fast and not enough friction in the system. The Smart Alpine (small diameter) works much better than this.

Honestly, the Microjul is the best. Simple and intuitive to use, assisted locking (better than the smart), it weighs next to nothing and is made of stainless steel so not going to wear out as fast as aluminum devices and won't add more aluminum dust into your ropes.

Donno wrote:Just tested the Gullys with an ATC-Guide and 2 locking 'biners. This is no good. Way too fast and not enough friction in the system. The Smart Alpine (small diameter) works much better than this.

FYI, BD claims using a Vaporlock carabiner will add 30% more friction. Still might not be enough for comfort with the skinny Beals, but helpful for a lot of other situations. I have rapped on Beal Ice Floss with ATC guide and now prefer a Reverso 4.

I have been using ropes for awhile now, both Alpine and on ice, I find 2 carabiners works with the ATC. I would back with an auto block. It is a slight pain to get the extra biner clipped in, and some extra checking is required. I have heard good things about the grivel master pro for adding friction : grivel.com/products/rock/be…
I might give it a try

Linnaeus wrote: FYI, BD claims using a Vaporlock carabiner will add 30% more friction. Still might not be enough for comfort with the skinny Beals, but helpful for a lot of other situations. I have rapped on Beal Ice Floss with ATC guide and now prefer a Reverso 4.

I was just going to say try using a vaporlock, the tight radius edge really does add a bit of friction over more round biners like the minipear, attache, etc..

Rappels nicely with a reverso on 8mm mammut half rope. I also like using it to rappel with the mega jul (not set to lock) if it's free.

FYI guys the new DMM pivot is rated down to 7.3 and is apparently a damn good device like the bd guide. I bought one but haven't tried it out yet.