UKC

Hopping onto a route last week I spotted my mate belaying had an extra krab hanging from his belay device, through the retaining loop I think, as he said it was to prevent his belay device jamming. He said he'd been shown it by an instructor at Glenmore as an older plate he had kept jamming (he had a new ATC last week). I said I thought it was unnecessary and maybe even a bit dangerous having something else rattling around there you could get your hand caught in, but is it a done thing in certain circumstances e.g. winter?

In reply to stouffer:
I can't really answer your question but if I'm understanding it correctly I've seen other people doing it because the rope can get jammed in the device if it gets loaded.

I don't think it's dangerous as I've seen a few experienced climbers using it, personally I've never had the problem with my ATC (I don't think it effects them as much) so haven't tried it myself.

In reply to stouffer:

I do that regularly when using a Reverso, for instance. It does just what your friend says, ie reduces the tendency of the device to jam up when you try to pay out slack to the leader. However, it doesn't just hang from the device (maybe you just didn't explain it very well) it clips into the rope along side your screwgate. It doesn't have to be clipped into the device or anything else. It's just a 'spacer'.

In reply to stouffer:
On some old sticht plates or bettabrakes, or similar very 'sticky' devices, an extra krab clipped in through the 'retaining loop' AND the rope can ease the tendency to jam.

On a new ATC it shouldn't be needed. I think that might be a 'top tip' that was pretty device specific has been retained inappropriately.

In reply to stouffer: Ok cool, ta. I didn't get a proper look at it I was just kind of 'eh?'. He took it off when I questioned it (although I said not to if he was more comfortable using it.) Yeah maybe sounds like a trick for the old device that he saw as accepted practise.

In reply to stouffer:
Ack! The whole point of a belay device is to jam when the leader falls. Messing with the "design" like this could be really nasty for the leader - especially if they are doing it based on advice for a previous bit o' kit. It would be interesting to try a leader fall a few feet off the ground w/out warning to see what happens. Be prepared to hit the ground hard.

In reply to tallsteve:

Having used it in this way since I got my first Sticht plate, so well over thirty years, I can tell you that it just doesn't hinder braking. An addition to the original Sticht plate was a spring that helped keep the plate away from the krab to do exactly what the extra krab does. They were, however, a pain to carry as they had a tendency to snag on everything...! If you think about it, when the rope is being paid out through the device (ie, not loaded) the extra krab lies behind the screwgate due to gravity and simply prevents the jamming of the rope by being a spacer. In the event of a fall it gets pulled into a position side by side with the screwgate increasing the angles the rope runs through and if anything will increase the braking effect. A lot depends on the ropes you are using - a couple of new skinny ropes will glide easily through the device, whereas a couple of older/fluffier ropes will have far more resistance and will jam far more readily. If you don't like the technique then don't use it, but please don't assume that it's a dangerous practise.

In reply to jon: Agree with your last post. It was a commonplace technique on old 'un sprung' stick plates and betabrakes when I first started climbing.

In reply to various: FWIW I never used a 2nd krab with an ATC for belaying, but I certainly used a 2nd krab regularly when abseiling on one, where it nicely increased the friction when using 8.5mm or thinner ropes.

In reply to tallsteve:

The point of a belay device is not to 'jam' when a leader falls. Perhaps you're talking about a grigri, but even that doesn't jam, it cams shut. The purpose of a belay device is to create friction, and its up to the belayer to provide that.
My old reverso used to be a pain in the arse when trying to feed out rope to the point I rarely used it apart from belaying on multipitch routes and that was mainly down to it being light. Nothing wrong with using a spacer if you know what you're doing.

In reply to stouffer:
I used this method on friday.
I had a verry light climber (pettite 9 year old), a grabby belay device (wild country vcproII) and a super fluffy 11mm rope.
The addition of an extra crab into the system as described by others alowed me to lower the youngster smoothly rather than jerkily.
I had known of this previously but it was the first time that this specific scenario warrented it.
Certainly not dangerous but not usually necessary I think.

In reply to jon:

Hesitant to disagree with you, Jon (and ex-engineer) but as far as I'm aware the increase in the radius the rope goes round actually decreases the braking effect; the increased surface area of polished metal is pretty irrelevant. Your comment that older ropes will have their 'resistance' lessened tends to support that?
I recall getting very twitchy hearing an 'instructor' informing people that if you used two krabs on a top-anchor instead of one it increased the friction if you are top-roping. Just wrong.

In reply to andyathome:

No, you are wrong. Using two karabiners increases the friction in both cases.

In reply to jimtitt:
It will increase the surface that the rope runs over - hence an increase in the potantial 'friction'. However the bigger radius reduces the braking effect is what I've been told.

You run a rope over a standard crab and load it; you run the same rope over a polished 10cm bar and load it. My experience is that the latter is harder to hold.

Isn't that how a Wild Country VRC operates; by provided a more or less acute angle on the rope?

In reply to andyathome:

No, increasing the area doesn´t increase the friction. Amontons' Second Law: The force of friction is independent of the apparent area of contact.

However the majority (ca.60%)of what we call friction over a karabiner is in fact not friction but the work done bending the rope or bending resistance. This is why the tighter the bend radius the more resistance is felt.
Using two karabiners is not increasing the radiius but splitting it into two parts, for example 180° around a karabiner becomes 2 X 90° as the rope goes straight between the two karabiners. To bend the rope around the first karabiner takes force and to straighten it again some more force, the same occurs on the second karabiner and the total of these forces is greater than the force required for a single karabiner.

The increased resistance for two karabiners versus a single one is around 10-20% (depending on rope/karabiner and load) and increases at a decreasing rate with every subsequent karabiner until for normal equipment and loads no increase is seen after about 5 karabiners.
For a normal belay plate such as an ATC XP the increased braking force is about 20% with two karabiners as there is a certain amount of interference with the body of the belay plate as well as increasing the bending angles of the rope.

In reply to stouffer: If you scroll down on this lnk the photos explain it all!
http://www.ukclimbing.com/articles/page.php?id=167

In reply to jimtitt:
Jim, Thanks. You live and you learn!

In reply to stouffer:

The way the rope handles through a belay plate can be modified by the addition of a carabiner, either doubling up the one to your belay loop (increases friction) or free floating through the rope loop between plate and the main carabiner (reduces friction). It's handy to know if you have an unfriendly combination of rope and plate but generally unnecessary.

jk

In reply to jkarran:

But see Jim Tott's last post. It would seem that either way increases 'resistance' for want of a better word.

In reply to andyathome:

Well not quite! As the article says if you clip the karabiners side by side the friction is increased but if you position the second krab so that it lies between the back of the device and the main krab the rope only runs over a single karabiner but is further away and the bends through the device are a bit gentler so you get less friction. Confusing though!
How much difference this makes I´ve no idea but I shall test this in a minute when I´m in the workshop.
Omega Pacific make a belay plate (SGB11) which uses this principle with two karabiner holes in the body for different friction levels. http://www.omegapac.com/op_products_sbgii.html

In reply to andyathome:

I think you're misreading him. <edit> Ah, he beat me to it while typing
jk

In reply to jkarran:

While you were typing I´ve pull tested it!

ATC XP and 12mm round stock Petzl Attache HMS. two strands 9mm rope.

The "loose" karabiner gives 20% less friction. Clipped into the belay loop so they lie side by side 66% more friction.

Jim

In reply to jimtitt:

What took you so long?

In reply to john arran:

Had to find my climbing gear and brush the mould and dust off it!

In reply to jimtitt:
Jim,
Just to clear things up. I think you are saying that whether the second krab is clipped to the belay loop or not doesn't matter, one still gets an increase in friction as long as the rope passes around both krabs.

And, to reduce the friction one clips a krab to the belay loop then a second krab to this and runs the rope through the plate and down to the first krab.

In reply to David Coley:

It matters whether you clip the belay loop! If you just clip into the rope and keeper loop and not the belay loop when the load comes on the karabiner moves and sits between the belay karabiner and the plate and you get less friction.
If you clip the belay loop with both karabiners then they are forced to sit side by side and you get more friction.

There are pictures of both set-ups in the link given above in the thread, though not one under load unfortunately.

In reply to jimtitt:

As long as they are both the same size, I'd imagine...

In reply to jimtitt:


Come on Jim,this just is`nt fair next you will saying I`ll nip out to the workshop and prove the non existence of God! What would happen to all the UKC speculation and arguments then?

In reply to jon:

Well yes, I´d assumed that it was understood that both the krabs were the same! However the first tests on this I did some years ago were using the karabiners which I´d normally be carrying so one 12mm Petzl Attache and a 10mm Salewa round stock screwgate which is naturally quite a bit smaller, 50% increase in resistance for these two.
Another test we did was wrapping the rope completely around a single HMS so 540° under an ATC XP. 250% more resistance this way.

A note of caution:- We did screw up some of the ropes with these various methods of increasing the friction, the underside rope entry of some belay plates is not as smooth and rounded as one might hope and we got a core shot on one admittedly very old rope. Check and get the file out!

In reply to deepstar:

If you saw my workshop you´d at least believe that the fairies come in the night and throw everything around!

I´ve never done 3PS, tie on with a re-threaded bowline and think Swanage grades are correct, isn´t that enough to be going on with:~)

In reply to jimtitt:


I've been using one of those for years, excellent bit of kit and the rigid stem prevents it from locking up at an inappropriate moment.

In reply to Niall:

According to testing at Black Diamond, adding an additional 'biner increase braking force on an ATC.

Link: http://www.blackdiamondequipment.com/en-us/journal/climb//qc-lab-autoblock-...

In reply to ghf:

I think that article is only about using a plate in guide mode, not abseiling. (Unless I missed a bit.)