/ Cams - thumb loops or no thump loops
Looking at getting some new cams.
What are people's opinions on thumb loops? Is there an advantage to having them?
I have some Camalots with them and also some older Camalots without. Never notice the difference personally.
TBH having used and having owned both varieties I don't think it matters very much.
It's useful for somewhere nice to press your thumb and for the trigger and thumb catch to work nicely but I've never missed or been encumbered by the attachment loop being above or below the sling attachment point.
IMO the main advantage of the loop is that very occasionally it is useful to be able to directly clip the loop rather than the sling - normally for hanging sarnies out of the way at a belay or something like that.
Relegate this attribute to "doesn't matter"...
The impression I get is that the thumb-loop diehards fall into two categories:
You'd know if you were in either of those categories and if you're not, it probably doesn't matter.
I think the way the mechanism feels to you is way more important. A big part of how well you climb is how happy you are with your gear and for me, whether a cam feels solid is a big part of how happy I am. It's probably totally subjective, but then a lot of climbing is.
Have used both quite a bit and much prefer the thumb loops.
They’re easier to handle on lead and easier to clean on second. I don’t see that the extendable slings properly extend placements and unextending them on second is a faff I’d rather not have. If you need to extend something then use a sling draw like a gentleman/lady. ;-)
I don't think it makes much difference. However if you decide you must have thumb loops you will be ruling out the larger totem cams which are my favourite cams for limestone. The smaller Totem "basics" do have thumb loops however.
Thumb loops can be a weak point and it's often where cams break, this is why dragons don't have them. That said they can still be engineered to break at a far higher load than any fall you'd want to take. Also see below at 1:30 for some cams breaking.
It’s not so much as the thumb loop snapping but the thumb loop deformation pinching and cutting the sling, hence the very specific sling design on the Camalots and the lower rating of friends.
Luke90’s reply is spot on. I was very used to my Camalots and hated my climbing partner’s dragons at first but now would probably buy dragons as the sling extensions is pretty handy and I have got over my hatred of the pigs nose.
Thumbloops in practice do not break. The rock and cam to surface friction will fail long before the thumbloops plays a part.
Other way around, the sling makes the cable fail. But you've really got to be trying!
I've found thumb loops to be really handy if you are placing gear and you are really pumped. They aren't as fiddly at a key moment.
I stand corrected (as I know you worked on the new friends) but I’m sure I read something by BD about their sling design and it being the deformation of the cable effectively cutting the sling. I might be wrong though. I guess no one wants a deformed cable loop after every big whipper either!
The things you have to do to give people the 14kN rating they want...........
edit: BD link
> It’s not so much as the thumb loop snapping but the thumb loop deformation pinching and cutting the sling, hence the very specific sling design on the Camalots and the lower rating of friends.
Yes it's the thumb loop/sling interaction that is the weak point. Camalots use a polyamide (nylon) sling that wraps around three times to help improve this. It was wanted with the dragons to use UHMWPE (dyneema) and thumb loops. The prototype dragons had thumb loops but because of the pinching caused by the tapes, and the resulting weak spot, the thumb loops were dropped and we have the design seen today.
I'm not saying one is better than the other but it is good to understand the design decisions.
I think there is an FAQ on BDs website somewhere about why they use the big fat nylon slings in the thumb loops. If you clip directly into the thumb loop as protection or re-sling your thumb loops with skinny slings then you run a risk of breaking the cable. If you need to extend a cam with a thumb loop, always do so by clipping into the sling rather than the loop - you'll kill yourself.
It was really surprising how low the force was that they failed at with skinny slings.
Have you got a link to not clipping directly into thumb loops? Not something I’ve heard before, not that it’s somthing I do.
I've never seen anything specifically refer to clipping but the reason they fail with skinny slings would only be worse with a karabiner. The force needs to be spread over a wider horizontal axis otherwise the loop cable pinches and breaks.
> I think there is an FAQ on BDs website somewhere about why they use the big fat nylon slings in the thumb loops. If you clip directly into the thumb loop as protection or re-sling your thumb loops with skinny slings then you run a risk of breaking the cable. If you need to extend a cam with a thumb loop, always do so by clipping into the sling rather than the loop - you'll kill yourself.
> It was really surprising how low the force was that they failed at with skinny slings.
Actually BD say "may reduce strength by up to 2kN" so I'll put dying from that well down the list.
Weird that a dyneema sling is thin enough to snap the loop but a solid karabiner isn't?
Either way there's no reason to clip the cable loop unless you're aiding, and then it's only taking body weight. If you want to extend it, clip a draw into the existing nylon sling or a 60cm sling into the karabiner. Less chance of it walking then as well.
Why not go into a shop that stocks both systems and have a play with both and see how they feel.
The problem here is spreading load across a wider section of cable and creating a soft radìus for the cable to bend around. BD used the extra wraps to do this, distributing the load more effectively and preventing the sling from pinching the cable until a higher load.
A carabiner has innate rigidity and an already present soft radius, usually of the order of between 4-7mm on the rope bearing surfaces.
Using no means of extra wraps means the cable can crush the sling down to a very small cross section, but the longitudinal fibres are still extremely strong. The cable on the other hand will have a minimum bending radius, the structure of the cable will mean that excessive tensile forces will be present on the outer radius of the bend, above the yield strength of the steel. Individual wires will begin to snap and as these go, the next later of wire sees the same forces move towards the inside radius and the same happens to these until the whole lot goes. Hope that's not clear as mud?
What you say makes sense. When curved round the outer radius is under more tension and stress. I work with offenders and they use this principle to cut cable locks on bicycles. Simply bending the cable into a tight radius makes hacksawing the outer radius much more effective.
Most bike thieves are not particularly deterred by cables. (Small bolt cuttters carried) To deter thieves make sure cables and chains are not close to the ground. Use a D lock not cables.
Digress - DMM Dragons for me with Basic Totems in the smaller sizes.
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