8 ms·

An Elastic Model of the Holding Power of Rock Climbing Anchors

35 points by Phithagoras 5y ago

chrispeel 5y ago
For the climbers out there, this is an analysis of cams, or "Spring Loaded Camming Devices" as the article and Wikipedia calls them. I have never heard of a cam called an "anchor" in contrast to the article title and the HN title. Wikipedia does not use the word "anchor" in the entire article. https://en.wikipedia.org/wiki/Spring-loaded_camming_device https://en.wikipedia.org/wiki/Spring-loaded_camming_device
- pcthrowaway 5y ago
  Specifically, this is an analysis of the strength of anchors built with cams. 'Anchor' in the title is relevant, but the title here leaves out critical information, because the overwhelming majority of anchors in rock climbs are bolted. "An Elastic Model of the Holding Power of Gear Anchors in Rock Climbing" would be much more apt (though gear anchors can include several other types of protection, "Cam Anchors" is not something I've ever heard) edit: upon further reading, you're right. There's no mention of anchors in the article, other than referring to a cam placement as 'a type of anchor'. It seems that the article was not written by climbers, which is surprising.
- petee 5y ago
  In fall arrest this is a common term, and it's super accurate, regardless whether it's common with rock climbers, these are definitely anchors. So it's not surprising that a MIT paper would use it. A more specific example, Black Diamond's camalot z4 are described in their manual as 'frictional anchors' Edit: of course there is a standard hah - EN 12276:2013 Mountaineering Equipment – Frictional Anchors
- meheleventyone 5y ago
  Definitely common to call any protection placed an anchor particularly in reference to building a belay position at least in British climbing.
  - johtso 5y ago
    An anchor would usually refer to the collection of gear placements equalised together, not an individual placement. (Although rarely you might have a 1 piece anchor). The term anchor is more a description of the purpose than what it's made of.
japhyr 5y ago
This article looks to be 15+ years old. The cam pictured in Fig. 1 looks look one of the earliest models of SLCDs, from sometime in the 80s when cams were all rigid, if I remember my climbing history correctly. If you follow the link to the home page, you can end up on a page that refers to more recent work having been done in 2005. http://web.mit.edu/custer/www/rocking/rocking.html http://web.mit.edu/custer/www/rocking/rocking.html
WalterBright 5y ago
I'd never rock climb without a backup rope. I can't even watch the videos of free climbers in Yosemite, and knowing that they didn't fall.
- mnky9800n 5y ago
  Single ropes are plenty safe these days. But I guess I climb half ropes when trad climbing usually because pulling a single ends up being a drag.
  - WalterBright 5y ago
    > Single ropes are plenty safe these days. So are airplane parts. But there is always a backup part.
    - deleted 5y ago
      [deleted]
    - 7952 5y ago
      Maybe a rope is more like the wings of a plane than a discrete component. You could have two sets of wings. But is that really a good idea? And climbing is not expected to be 100% safe. In the same way that the single engine in a GA plane can fail and cause a crash. You have to balance the risks with the enjoyment.
      - WalterBright 5y ago
        Every part in the wings is redundant. For example, there are two main wing spars. Each can support the wing. The backup plan for losing the engine is to glide and land. But still, can't fly passenger jets over water with one engine. > You have to balance the risks with the enjoyment. You can take whatever risks you like. But I don't see how having a dual rope subtracts from your enjoyment.
        mnky9800n 5y ago
londons_explore 5y ago
I'm always amazed that these kind of devices don't just make the crack in the cliff wider and fail... A climber falling, even on an elasticated rope, might briefly put 800kg into the cam. The cam itself is effectively a 10:1 lever, so exerts 8000kg in each direction on the rock. I'm just surprised that something that is already a crack (ie. Has already moved in the past) doesn't sometimes move when 8000kg is applied to it... And if it moves, the climber likely dies.
- morsch 5y ago
  Isn't it common to use multiple anchors? Kind of happens automatically in the process of climbing in a team of two. That's not to say that an anchor failing is a pleasant experience...
  - amitport 5y ago
    The anchors are often far apart, especially in trad climbing. If the first one failed the next one will have to absorb a bigger hit... so, it can be more than unpleasant... The common advice when you don't trust your anchor is don't fall ;)
- pcthrowaway 5y ago
  I think 800KG is exceedingly rare, and also the upper limit of what a climber can tolerate even if their protection (the camming device) holds. It does happen with massive lead falls, especially when not much rope has been paid out. 1000 KG is likely to cause injury. And of course, the cams are typically rated from 600KG to 1600KG of force, depending on manufacturer, size, and material. But it's rare for them to experience these loads. Even with smaller falls though, say 200-300 KG of force, they do occasionally break the rock they're set in, or cause the rock to 'flex', causing it to come out (this is more common with a type of feature called a 'flake', which is a semi-detached piece of rock, rather than a typical crack which is unlikely to move). Ideally, you have more protection beneath the one you placed. Then if one piece blows, you'll fall a little bit further to the next one, which is hopefully placed in better rock.
- japhyr 5y ago

35 points by Phithagoras 5y ago

For the climbers out there, this is an analysis of cams, or "Spring Loaded Camming Devices" as the article and Wikipedia calls them. I have never heard of a cam called an "anchor" in contrast to the article title and the HN title. Wikipedia does not use the word "anchor" in the entire article. https://en.wikipedia.org/wiki/Spring-loaded_camming_device https://en.wikipedia.org/wiki/Spring-loaded_camming_device

pcthrowaway 5y ago
Specifically, this is an analysis of the strength of anchors built with cams. 'Anchor' in the title is relevant, but the title here leaves out critical information, because the overwhelming majority of anchors in rock climbs are bolted. "An Elastic Model of the Holding Power of Gear Anchors in Rock Climbing" would be much more apt (though gear anchors can include several other types of protection, "Cam Anchors" is not something I've ever heard) edit: upon further reading, you're right. There's no mention of anchors in the article, other than referring to a cam placement as 'a type of anchor'. It seems that the article was not written by climbers, which is surprising.
petee 5y ago
In fall arrest this is a common term, and it's super accurate, regardless whether it's common with rock climbers, these are definitely anchors. So it's not surprising that a MIT paper would use it. A more specific example, Black Diamond's camalot z4 are described in their manual as 'frictional anchors' Edit: of course there is a standard hah - EN 12276:2013 Mountaineering Equipment – Frictional Anchors
meheleventyone 5y ago
Definitely common to call any protection placed an anchor particularly in reference to building a belay position at least in British climbing.
- johtso 5y ago
  An anchor would usually refer to the collection of gear placements equalised together, not an individual placement. (Although rarely you might have a 1 piece anchor). The term anchor is more a description of the purpose than what it's made of.

japhyr 5y ago

This article looks to be 15+ years old. The cam pictured in Fig. 1 looks look one of the earliest models of SLCDs, from sometime in the 80s when cams were all rigid, if I remember my climbing history correctly. If you follow the link to the home page, you can end up on a page that refers to more recent work having been done in 2005. http://web.mit.edu/custer/www/rocking/rocking.html http://web.mit.edu/custer/www/rocking/rocking.html

WalterBright 5y ago

I'd never rock climb without a backup rope. I can't even watch the videos of free climbers in Yosemite, and knowing that they didn't fall.

mnky9800n 5y ago
Single ropes are plenty safe these days. But I guess I climb half ropes when trad climbing usually because pulling a single ends up being a drag.
- WalterBright 5y ago
  > Single ropes are plenty safe these days. So are airplane parts. But there is always a backup part.
  - deleted 5y ago
    [deleted]
  - 7952 5y ago
    Maybe a rope is more like the wings of a plane than a discrete component. You could have two sets of wings. But is that really a good idea? And climbing is not expected to be 100% safe. In the same way that the single engine in a GA plane can fail and cause a crash. You have to balance the risks with the enjoyment.
    - WalterBright 5y ago
      Every part in the wings is redundant. For example, there are two main wing spars. Each can support the wing. The backup plan for losing the engine is to glide and land. But still, can't fly passenger jets over water with one engine. > You have to balance the risks with the enjoyment. You can take whatever risks you like. But I don't see how having a dual rope subtracts from your enjoyment.
      - mnky9800n 5y ago

londons_explore 5y ago

I'm always amazed that these kind of devices don't just make the crack in the cliff wider and fail... A climber falling, even on an elasticated rope, might briefly put 800kg into the cam. The cam itself is effectively a 10:1 lever, so exerts 8000kg in each direction on the rock. I'm just surprised that something that is already a crack (ie. Has already moved in the past) doesn't sometimes move when 8000kg is applied to it... And if it moves, the climber likely dies.

morsch 5y ago
Isn't it common to use multiple anchors? Kind of happens automatically in the process of climbing in a team of two. That's not to say that an anchor failing is a pleasant experience...
- amitport 5y ago
  The anchors are often far apart, especially in trad climbing. If the first one failed the next one will have to absorb a bigger hit... so, it can be more than unpleasant... The common advice when you don't trust your anchor is don't fall ;)
pcthrowaway 5y ago
I think 800KG is exceedingly rare, and also the upper limit of what a climber can tolerate even if their protection (the camming device) holds. It does happen with massive lead falls, especially when not much rope has been paid out. 1000 KG is likely to cause injury. And of course, the cams are typically rated from 600KG to 1600KG of force, depending on manufacturer, size, and material. But it's rare for them to experience these loads. Even with smaller falls though, say 200-300 KG of force, they do occasionally break the rock they're set in, or cause the rock to 'flex', causing it to come out (this is more common with a type of feature called a 'flake', which is a semi-detached piece of rock, rather than a typical crack which is unlikely to move). Ideally, you have more protection beneath the one you placed. Then if one piece blows, you'll fall a little bit further to the next one, which is hopefully placed in better rock.
japhyr 5y ago