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I've always wondered why the typical plates bolted to rock in order to secure climbers are that thin. I imagine them behaving like a knife under a sudden load in a falling scenario. Wouldn't increasing the surface area in solid to solid contact with the quickdraw carabiner reduce this problem? Even if this effect is well under the safety margins, wouldn't be great for the durability of whatever clipped to them?

plate

As for the bolt-plate contact, the problem should be less if properly tightened, what makes forces rely not only on the bolt, producing shear stress, but on the rock, via friction.

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    can you elaborate? what part of the anchor are you talking about? surely those parts are designed with specifications and are built to meet both strength and durability requirements, no?
    – njzk2
    Commented Oct 25, 2022 at 17:54
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    @Andrestand if you’re worried about carabiners bending or breaking you need to buy better carabiners!
    – Darren
    Commented Oct 25, 2022 at 21:02
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    @Andrestand I think you strongly underestimate how much the cost would go up if you made changes that would make the contact point wider while keeping appropriate safety properties and weight. If you look at the anchor now it is very low cost to make. You drill a couple of holes in a sheet of metal and bend it. You might than (or before) apply some extra steps to ensure strength but the creation is low cost. Any way to make the contact point thicker would mean either extra weight (thicker plate) or extra steps (thickening the contact point only.
    – DRF
    Commented Oct 26, 2022 at 20:04
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    Do we really have industry inertia here? I have some bolts mounted in the ceiling of my living room and the hangers are like 3-4mm thick. I have definitely seen thinner ones outdoors. So I think the market already provides thicker hangers if you prefer those for routes you want to develop
    – Manziel
    Commented Oct 27, 2022 at 8:52
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    Understanding and correctly evaluating mechanical stresses and failure modes is a well-honed art at this point in time. Those meet the UIAA standards. Should you wish to exceed those standards, fine, but likely you won't find many hangers that greatly exceed UIAA standards because, well, they don't have to.
    – Jon Custer
    Commented Oct 27, 2022 at 13:58

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They are that thin because there isn't really a need or desire for them to be thicker. Having them thin makes them lighter and cheaper to manufacture (meaning more people willing to pay for them and carry them to bolt a route). They are plenty strong, being rated to 20+kN typically, which makes them not the weakest link in the system, so strength isn't an issue either.

In terms of the knife cutting a quickdraw, it's just not really a big enough problem. The way a carabiner hangs off it's not really on a sharp edge. In fact, the EN 959:2018 standard, which the hanger pictured is rated to, requires the edges be designed in a safe manner. You'll see aluminum carabiners get knicked up a bit sometimes so it's often considered good practice to keep the metal and rope sides of draws/biners separate/consistent. But it's not a big enough problem that climbers want heavier and more expensive anchors. If you're very concerned you can get Steel carabiners (Lots of examples) or steel insert carabiners (Edelrid Bulletproofs). I personally use Edelrid Bulletproofs on TR achor biners where the rope will be in constant contact and sliding over the biner. In terms of bending, that's all part of the strength rating in the EN certification process.

4.2.3 All edges that can be handled after placement of the rock anchor in the rock shall be free from burrs and sharp edges. The inner edges of the eye shall be rounded to a radius R of minimum 0,2 mm or bevelled to a minimum of 0,2 mm × 45°

If you want, HowNot2 have great videos on YouTube such a this one that show how hangers (and other climbing gear) break.

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    It is precisely the just 0,2 mm radius what annoys me. The surface area in contact with the biner, given its typical rod radius, is less than a square mm, so shear stress exerted by the plate on the biner when loaded is not small. The same for bending stress, as this single and small contact point is about 2 cm far from the ends of the upper, horizontal shaft of the carabiner, where the downwards force is exerted. The point is if slightly heavier and expensive plates wouldn't compensate by far the lifetime extension for what we connect there.
    – Andrestand
    Commented Oct 26, 2022 at 16:07
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    @Andrestand, 0.2mm is plenty. 316L stainless is extremely ductile; under a sudden load, the edges will deform to match the curve of the carabiner, greatly increasing the contact area.
    – Mark
    Commented Oct 26, 2022 at 22:01
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    @Andrestand I’m curious what you think the lifespan of a quickdraw is compared to what you think it should be. I have friends with quickdraws that are over ten years old and the biners are still perfectly serviceable (if not a bit heavy by modern standards). The dog bone is the real weak point and those I mentioned have had new ones, keeping them going for another 10+ years if required.
    – Darren
    Commented Oct 28, 2022 at 2:31
  • This adds to my concerns :D youtu.be/fcyrvyn6880
    – Andrestand
    Commented Jan 19, 2023 at 19:56
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    Genuinely, why? Ropes and carabiners are totally different. Nobody is recommending you rap directly off the hangers. That's what rap rings and other specialized anchor gear is for.
    – noah
    Commented Jan 20, 2023 at 1:36

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