Forums: Climbing Information: General:
Shock loading
RSS FeedRSS Feeds for General

Premier Sponsor:

 


stoneguy


Jan 25, 2013, 5:38 AM
Post #1 of 15 (3146 views)
Shortcut

Registered: Apr 7, 2011
Posts: 139

Shock loading
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

FF2 falls are well documented, but does anyone have some real numbers on shock loading that you would get on nylon slings when body weight testing a placement.
That's a light jump from 6"-12" above a piece.

Thanks


viciado


Jan 25, 2013, 6:32 AM
Post #2 of 15 (3115 views)
Shortcut

Registered: May 9, 2003
Posts: 413

Re: [stoneguy] Shock loading [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

What you describe would be painful to say the least. I don't know of anyone who tests pieces on static nylon with a small jump as you describe it. Most bounce testing is done after simple body weight has been applied and even then it is debatable (and conditional) as to whether it is a good idea or if a yank on the piece or runner is sufficient.

If you are asking if there is data on peak forces under the conditions you describe, try a search on this site for peak forces rather than ff2. Jim Titt and John Long among others have also posted a lot of info about your question if you are willing to dig through their posts.


stoneguy


Jan 25, 2013, 6:41 AM
Post #3 of 15 (3109 views)
Shortcut

Registered: Apr 7, 2011
Posts: 139

Re: [viciado] Shock loading [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

To be clear, yes body weight test first. "Bounce test" is perhaps closer to a more definitive term. I searched shock load, but will search peak forces as you suggested. Thanks.


JimTitt


Jan 25, 2013, 8:11 AM
Post #4 of 15 (3072 views)
Shortcut

Registered: Aug 7, 2008
Posts: 976

Re: [stoneguy] Shock loading [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

stoneguy wrote:
FF2 falls are well documented, but does anyone have some real numbers on shock loading that you would get on nylon slings when body weight testing a placement.
That's a light jump from 6"-12" above a piece.

Thanks

USNavy measured some bounce tests:- http://www.rockclimbing.com/cgi-bin/forum/gforum.cgi?post=2588143;search_string=bounce%20test;#2588143
and the small amount of testing I did agrees pretty well, I couldnīt get over 3kN and Iīm substantially bigger than most guys (with more padding for my harness though!).


stoneguy


Jan 25, 2013, 10:17 AM
Post #5 of 15 (3034 views)
Shortcut

Registered: Apr 7, 2011
Posts: 139

Re: [JimTitt] Shock loading [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

I have seen some guys wear a few nylon slings as back up safety's, likely for top of the cliff anchors, and suspect it would hurt.
Gotta give the US Navy guy credit for his tests. Love it.
I had thought he got similar results for full fall tests on rope (like 3-4 Kn). I don't Aid but assume those daisies are nylon, and surprised they don't hit harder.

My bounce test was straight sling to nut, no rope. Seemed harder than rope. I was actually looking at deflection/movement of the nut, but my question here was directed at the force only.

Thank you for that link.


JimTitt


Jan 26, 2013, 12:17 AM
Post #6 of 15 (2960 views)
Shortcut

Registered: Aug 7, 2008
Posts: 976

Re: [stoneguy] Shock loading [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

In an aider bounce test the limitation is how far you can spring up standing in a foot loop and what your legs can withstand when you hit. My legs start buckling at 3 times body weight just like most peoples otherwise Iīd probably be a weightlifter!
A daisy test is different but the proportion of stretch in the harness and squashing of the body is huge compared to the stretchiness of the sling/daisy. Start taking falls like this though and the harness/body effect becomes proportionally smaller and it starts to hurt.
Comparing both the above with short fall impacts on a rope are meaningless unless you pre-tighten the knots/s since they are the dominant cushioning effect in short lengths.


USnavy


Jan 26, 2013, 12:48 AM
Post #7 of 15 (2949 views)
Shortcut

Registered: Nov 5, 2007
Posts: 2660

Re: [stoneguy] Shock loading [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

stoneguy wrote:
I have seen some guys wear a few nylon slings as back up safety's, likely for top of the cliff anchors, and suspect it would hurt.
Gotta give the US Navy guy credit for his tests. Love it.
I had thought he got similar results for full fall tests on rope (like 3-4 Kn). I don't Aid but assume those daisies are nylon, and surprised they don't hit harder.

My bounce test was straight sling to nut, no rope. Seemed harder than rope. I was actually looking at deflection/movement of the nut, but my question here was directed at the force only.

Thank you for that link.
Yes, I was able to hit up to 4kN on legitimate whippers on sport routes. I was also able to surpass 3kN bounce testing on a nylon daisy chain (very aggressively though).

I also did a bit of testing on a real shockloading scenario with a steel weight.

http://www.rockclimbing.com/cgi-bin/forum/gforum.cgi?post=2609818;search_string=shockloading%20quick%20and%20dirty;#2609818


stoneguy


Jan 26, 2013, 5:35 AM
Post #8 of 15 (2927 views)
Shortcut

Registered: Apr 7, 2011
Posts: 139

Re: [USnavy] Shock loading [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

Ha..! I remember that and thinking what your landlord would say if you ripped out the ceiling.

Yes, you got huge forces. So, without ropes and knots then a climber using slings alone, anywhere in the system even in the 12-24" drop range might risk breaking the sling or wire. Slings being 20Kn but 1/8 wire about 1760 lbs, and lots of wire is less (some at .110")
What would be your best guess if the 3800% is close.?


USnavy


Jan 26, 2013, 1:19 PM
Post #9 of 15 (2868 views)
Shortcut

Registered: Nov 5, 2007
Posts: 2660

Re: [stoneguy] Shock loading [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

stoneguy wrote:
Ha..! I remember that and thinking what your landlord would say if you ripped out the ceiling.

Yes, you got huge forces. So, without ropes and knots then a climber using slings alone, anywhere in the system even in the 12-24" drop range might risk breaking the sling or wire. Slings being 20Kn but 1/8 wire about 1760 lbs, and lots of wire is less (some at .110")
What would be your best guess if the 3800% is close.?
I dont really understand your question. Why would someone take a fall on steel cable? Anyway, that test involved a steel mass. In the real world, the mass is fleshy and it is wearing a harness, so the force increase will be lower. Therefore, a factor 1 fall on a nylon sling by a climber would not likely break the sling.


stoneguy


Jan 26, 2013, 7:01 PM
Post #10 of 15 (2821 views)
Shortcut

Registered: Apr 7, 2011
Posts: 139

Re: [USnavy] Shock loading [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

Reference was the nut is attached to a galvanized or stainless cable often about 1/8" and a 10KN rating in a climbing application, then a sling clipped to that, then to the harness of the climber. That was my bounce test.
The wire would break before the sling.
Your test hit 3-4KN with the sling and a steel mass. Was just wondering how bad it would be in the above application. Obviously the harness would absorb some.


USnavy


Jan 26, 2013, 9:43 PM
Post #11 of 15 (2800 views)
Shortcut

Registered: Nov 5, 2007
Posts: 2660

Re: [stoneguy] Shock loading [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (1 rating)  
Can't Post

stoneguy wrote:
Reference was the nut is attached to a galvanized or stainless cable often about 1/8" and a 10KN rating in a climbing application, then a sling clipped to that, then to the harness of the climber. That was my bounce test.
The wire would break before the sling.
Your test hit 3-4KN with the sling and a steel mass. Was just wondering how bad it would be in the above application. Obviously the harness would absorb some.
Both the harness and your body would absorb a considerable amount of force when compared to a steel weight drop test. It would also depend on if the sling was made out of Dyneema or nylon. I would say that if the sling was made of nylon, the climber weighed 160 lbs and the fall was a factor one or less, then the sling and cable would likely hold.


JimTitt


Jan 27, 2013, 12:00 AM
Post #12 of 15 (2787 views)
Shortcut

Registered: Aug 7, 2008
Posts: 976

Re: [stoneguy] Shock loading [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

Youīll notice USNavy uses "likely" in his replies. This is because there is a gap in our knowledge of the forces involved in falls, taking drops on slings is painful and causes injuries and so we donīt have reliable factors for the harness/body aspect above a certain level. If you want to be the test object then volounteer here!
Falling on gear direct without a section of dynamic rope in the system (or some other purpose designed impact attenuator) isnīt included in the safety chain system used by the UIAA, is not foreseen in the standards and isnīt researched to any real extent since it should never occur (though it is researched to the extent we know itīs a really bad idea).


stoneguy


Jan 27, 2013, 4:46 AM
Post #13 of 15 (2768 views)
Shortcut

Registered: Apr 7, 2011
Posts: 139

Re: [JimTitt] Shock loading [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

That's pretty clear. It's a bad idea. Probably the sling would hold, but other stuff maybe not.
Therefore guys that use a sling around their waist in the event of a needed safety while setting their anchors is also a really bad idea.Would be painful.
Bounce testing in this fashion could hurt, altho' it might be a useful test.

Thanks to all for the insight.


USnavy


Jan 29, 2013, 12:16 AM
Post #14 of 15 (2631 views)
Shortcut

Registered: Nov 5, 2007
Posts: 2660

Re: [stoneguy] Shock loading [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (1 rating)  
Can't Post

stoneguy wrote:
That's pretty clear. It's a bad idea. Probably the sling would hold, but other stuff maybe not.
Therefore guys that use a sling around their waist in the event of a needed safety while setting their anchors is also a really bad idea.Would be painful.
Bounce testing in this fashion could hurt, altho' it might be a useful test.

Thanks to all for the insight.
Who uses a sling around their waist? You mean like a swami belt instead of a harness? That is a really bad idea. The human spine can withstand 10-12kN briefly with a standard sit harness. But with a swami, the spine cannot hold nearly that much.


(This post was edited by USnavy on Jan 29, 2013, 12:17 AM)


curt


Jan 29, 2013, 11:07 AM
Post #15 of 15 (2571 views)
Shortcut

Registered: Aug 26, 2002
Posts: 18228

Re: [USnavy] Shock loading [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

USnavy wrote:
stoneguy wrote:
That's pretty clear. It's a bad idea. Probably the sling would hold, but other stuff maybe not.
Therefore guys that use a sling around their waist in the event of a needed safety while setting their anchors is also a really bad idea.Would be painful.
Bounce testing in this fashion could hurt, altho' it might be a useful test.

Thanks to all for the insight.
Who uses a sling around their waist? You mean like a swami belt instead of a harness? That is a really bad idea.

That's merely your opinion, of course. Your chances of inverting in a fall, and thus incurring a head injury are actually somewhat less when wearing a swami versus a harness with leg loops.

USnavy wrote:
The human spine can withstand 10-12kN briefly with a standard sit harness. But with a swami, the spine cannot hold nearly that much.

I'm not saying it's never happened, but I have never heard of anyone experiencing a spinal injury from falling in a swami belt. The most common injuries resulting from falling in a swami are caused by the swami belt riding up and compressing the ribcage.

Curt


Forums : Climbing Information : General

 


Search for (options)

Log In:

Username:
Password: Remember me:

Go Register
Go Lost Password?
$1.35 (10% off)
$87.75 (10% off)
$53.96 (10% off)
$8.96 (10% off)



Follow us on Twiter Become a Fan on Facebook