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Chockstone Forum - Gear Lust / Lost & Found

Rave About Your Rack Please do not post retail SPAM.

Author
Dropping Gear

shmalec
28/10/2003
3:05:03 PM
Hypothetical scenario-you're 30m up a climb and drop a bunch of gear (lets say 3 or 4 cams or biners) and watch them free fall onto a flat rock at the bottom of the cliff. When you retrieve the gear, do you
A)-destroy them and chuck them out; B)-tell your mate that you will chuck them out and slip them back into your rack before the next trip; or C)-clip them back on your harness considering them to be undamaged?
There is a theory out there that dropping aluminium gear from some height (I've heard lots of heights from as little as shoulder height) can cause invisible cracks that can reduce their failure strength to dangerously low levels. I had 2 mountain guides in NZ a few years back that said this was a myth. I haven't had to decide one way or the other yet but I'm less than convinced that this can actually happen.
Aluminium can have large invisible cracks. But I have only seen evidance of these resulting from low loads repeated thousands of times. This is called metalic fatigue failure. The dropped gear scenario is completely different and I suspect that this type of impact damage would always be clearly visible.
Any metalurgists out there? Anyone have some added background to this?
Alec.
joemor
28/10/2003
3:30:16 PM
i think it depends on if they show signs of the fall.......
Dalai
28/10/2003
3:35:06 PM
I don't have a scientific answer to the question. But another slant is how much do you think your life is worth?
If in doubt, it was an expensive mistake but to be on the safe side...

nmonteith
28/10/2003
3:38:58 PM
I certainly wouldn't throw it out.

I read a study where (might have been Black Diamond?) collected dropped biners, cams ect form the base of El Cap in Yosemite (1000m high cliff) and then tested them. There was no early failures with this gear when there was no visable surface cracks. I can't find the link... anyone?

I think most gear manufacturers would 'advise' replacemnt to cover their insurance arses and so you spend more money with them.

Phil Box
28/10/2003
4:01:07 PM
I think that study has been oft repeated on rec.climbing so a google search of the newsgroups may reveal a link. The very interesting thing about that study was the fact that steel biners tended to break after being dropped from so high up whereas the alloy biners were ok.

Rich
28/10/2003
4:03:12 PM
heres a link of the discussion on tradgirl
V
28/10/2003
4:17:11 PM
You can't just throw them out, they need to be properly destroyed, in case someone finds them on a rubbish heap and tries to use them for climbing. Give your dropped gear to me and I'll make sure it's properly disposed of. ;-)
tom_brennan
28/10/2003
5:37:00 PM
I did some researching of the research :) and wrote up my comments. See
http://www.ozultimate.com/canyoning/myths.htm

In short, there is very little evidence for the 'microscopic cracks' theory. The general view is to inspect the gear carefully, and retire if damaged. There are a number of links on my page to other pages with comment/research.

The bottom line is - if you feel uncomfortable climbing on the dropped gear - then don't.

jens
29/10/2003
1:19:20 PM
What if you drop an Alien down half the mountain on your third pitch, and your trusted second stumbles across it on his way up?

Do you:
A) Not use it again
B) Pocket it (second) and say you couldn’t find it?
C) Or call collect on a drink?

Answers, dodgy, anyone? :-)
dodgy
29/10/2003
5:35:08 PM
I posted the following on "dropped gear" on the general topics area, here it is again (thanks Neil)
Quite correct Jens, Bundy wasn't it?

I always wondered about the "necessity" of scrapping gear that had been dropped,
I always figured the stuff had to be stronger than most of us give it credit for, or it
couldn't be trusted anyway. I mean, if a krab couldn't cope with a fall from the first clip on a route, I really might as well solo the lot...
Then there is this: from "Rock and Ice - Gear" (page 46)

"Conventional wisdom says that a carabiner that has been dropped must be retired, even when there are no signs of damage. Perhaps not.
In a test conducted by REI, thirty carabiner bodies (half ovals, half Ds) were each dropped six times onto a concrete floor from a height of 33 ft. (10 m). Following the drops, their open-gate strength was measured and compared to thirty control samples from the same production batch that had not been dropped. The statistical result was no loss of strength.
According to Chris Harmston, the quality assurance manager at Black Diamond, “I have test-broken hundreds of used, abused, and dropped ‘biners (even some that fell 3000 ft. (1000 m) from the top of the Salathe Wall on El Capitan). Never have I noticed any problem with these unless there is obvious visual damage to the ‘biner. While somewhat reassuring, this does not give you carte blanche to use carabiners that have been dropped a significant distance. Immediately retire any carabiner that is crooked, has deep indentations, or has a gate that doesn’t operate smoothly."

The Blond Gecko
30/10/2003
2:33:50 PM
Going way, way back to my materials science course in my undergrad days...

Alloys such as these are tempered specifically to have very small crystal sizes (a few tens of microns). Cracks essentially only form and travel along the fracture planes of crystals. Thus, if a crack forms in one of the crystals, it will only travel across that crystal, before being stopped at the boundary. Aluminium is also naturally relatively ductile compared to steel, meaning that it will stretch, bend or dent preferably to cracking. Steel, on the other hand, has a relatively high ductile-to-brittle transition temperature (depending on the specific alloy used), often above freezing. I remember hearing about some early US navy ships breaking in half in cold water due to this. In addition, it's much more dense than aluminium, so a fall of equal height will develop a whole lot more force when it impacts. I wouldn't use anything steel that I'd dropped from a significant height, but I can't see any problem with re-using aluminium items (within reason).
A bit of a ramble, but hopefully useful.

Cheers,
Tristan

jens
30/10/2003
2:39:42 PM
good call, young einstein!

it makes perfect sense.

ecowain
3/11/2003
10:09:34 PM
In addition to the Chris Harmston mention, which I'm sure used to be findable on Google, but blowed if I can find it now... Those tests were good enough for me.

http://www.smr001.net/news/Newsletter_2001-03.htm
"At the International Technical Rescue Symposium, 2000, Garin Wallace and Kevin Slotterbeck of SMC presented data on the strength of carabiners that had been dropped 27’ or 54’ onto concrete or asphalt. One by one, they dropped 115 new, SMC locking D aluminum carabiners. Then they broke the carabiners, measuring the breaking strengths."

Can anyone track down a copy of those test results?

As far as it goes, I agree with Tom's comments. Check out the gear, and it it gives you mental strife, don't use it.
owain.
bob
4/11/2003
11:07:00 PM
I think you have to make a judgment on it but if you do drop any thing or knock something like a rock off the edge or any thing make sure you yell “below” so people can hear you I’m sure no one wants to get hit by a cam, hex or draw falling at 120 km.

bob

Paulie
8/11/2003
11:39:20 PM
...better not go climbing with me then ;)

IdratherbeclimbingM9
6/03/2014
1:12:17 PM
On 3/11/2003 ecowain wrote:
>In addition to the Chris Harmston mention, which I'm sure used to be findable
>on Google, but blowed if I can find it now... Those tests were good enough
>for me.
>
>http://www.smr001.net/news/Newsletter_2001-03.htm
>"At the International Technical Rescue Symposium, 2000, Garin Wallace
>and Kevin Slotterbeck of SMC presented data on the strength of carabiners
>that had been dropped 27’ or 54’ onto concrete or asphalt. One by one,
>they dropped 115 new, SMC locking D aluminum carabiners. Then they broke
>the carabiners, measuring the breaking strengths."
>
>Can anyone track down a copy of those test results?
>
>As far as it goes, I agree with Tom's comments. Check out the gear, and
>it it gives you mental strife, don't use it.
>owain.

It would be interesting to come across that data, if it is still available...
mikllaw
6/03/2014
1:35:49 PM
If the 'action' (gate closing, cam moving smoothly ect) is damaged, throw the gear out. Otherwise use it.
kieranl
6/03/2014
1:50:01 PM
Richard Delaney of Rope Test Lab has recently done a lot of drop-tests on krabs, including some with 200m free-fall onto concrete and steel down a power-station stack.
You should be able to access that on farcebook I don't have access from work so can't give links. The vast majority of alloy krabs with no visible damage broke at or above the rated strength. A small number of alloy krabs broke below but close to their rated strength.
The interesting thing is that it was steel krabs that suffered. I can't remember the figures but a number of those broke significantly below their rated strength. It is surmised that it's the extra mass of the steel krab that does the damage.

There are 18 messages in this topic.

 

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