Forums: Climbing Information: The Lab: Re: [wiki] Bolt tester: Edit Log


Jan 15, 2010, 2:02 AM

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Re: [wiki] Bolt tester
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wiki wrote:
USnavy wrote:
wiki wrote:
what size bolts are you putting in?

70mm deep m16?

Seriously 15kn is 1.5 tonnes. Your body will break first.
I use 1/2" Power-Bolts or more commonly, glue-in bolts with a failure strength of 40 kN. But that's irrelevant. No I promise you, your body will not break first. Do you think the UIAA pulled that 25 kN requirement out of their ass? They require bolts to hold 25 kN in sheer and 20 kN in tension because 20 kN is the approximate force the top anchor is subjected to with a factor 1.78 fall w/ 80 kg on a rope with an impact force of 12 kN with the pulley effect in play. Also the anchor must be robust enough to withstand big falls without deformation. If the anchor has a failure strength of 15 kN, repeated 10 kN loads will very likely cause the anchor to fail as the anchor will bend with every load. Thus there must be an additional margin of strength well beyond the maximum load the anchor will be subjected to on a regular basis.

The UIAA actually recommends 20kn not 25kn.

Yes you will break first...

RE your other comments... I will allow you to research them yourself as my internet is playing up.

"2.2.3. When tested in accordance with 3.3, all types of rock anchors shall have an axial load
bearing capacity of 20 kN."

"Axial load" is tension, they require 25 kN for sheer, as I said previously.

Click the "rock anchors" pictorial and look at page two.

Itís pointless to argue, UIAA requires 25 kN for a reason. An anchor with a failure strength of 15 kN will not meet EN or UIAA requirements and installing such is complete utter negligence. A standard good quality 3/8Ē bolt is capable of withstanding around 20 kN in sheer. Some can withstand close to 30 kN so there is no excuse to install substandard bolts. The UIAA and the Air Force have conducted extremely in-depth research regarding the application of serious force on the human body and they have found the maximum impact force a human body can sustain for a very short period of time with the spine aligned upright is 12 kN. Thatís the reason why the UIAA requires their ropes have an impact force of 12 kN or lower. If the impact force on the climber side of the rope is 12 kN the impact force on the belayer side will be 6 - 8 kN and the force on the top anchor will be 18 - 20 kN. Once again, thatís why they require biners to hold 20 kN along the major axis and bolts to hold 20 kN in tension and 25 in sheer. Thatís also why they require slings to hold 22 kN and harnesses to hold 15 kN.

Using the UIAA testing standards as a reference is a good tool to help understand the maximum impact force involved in a worst case scenario fall. All of UIAA's certifications for free climbing equipment are based around a factor 1.78 fall with 80 kg and a rope with an impact force specification of 12 kN. All the requirements for harnesses, slings, ropes, carabiners and the related are based on this worst case scenario fall.
So itís been clearly proven that the maximum impact force the average healthy human can withstand with their spine aligned upright is 12 kN. Accordingly if the climber weighs 80 kg and takes a fall serious enough to produce 12 kN on his/ her side of the rope, the anchor will see close to 20 kN, thus a bolt that only holds 15 kN is insufficient.

(This post was edited by USnavy on Jan 15, 2010, 2:05 AM)

Edit Log:
Post edited by USnavy () on Jan 15, 2010, 2:05 AM

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