|
stoneguy
Jan 25, 2013, 1:38 PM
Post #1 of 15
(8267 views)
Shortcut
Registered: Apr 8, 2011
Posts: 139
|
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, 2:32 PM
Post #2 of 15
(8236 views)
Shortcut
Registered: May 9, 2003
Posts: 429
|
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, 2:41 PM
Post #3 of 15
(8230 views)
Shortcut
Registered: Apr 8, 2011
Posts: 139
|
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, 4:11 PM
Post #4 of 15
(8193 views)
Shortcut
Registered: Aug 7, 2008
Posts: 1002
|
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, 6:17 PM
Post #5 of 15
(8155 views)
Shortcut
Registered: Apr 8, 2011
Posts: 139
|
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, 8:17 AM
Post #6 of 15
(8081 views)
Shortcut
Registered: Aug 7, 2008
Posts: 1002
|
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, 8:48 AM
Post #7 of 15
(8070 views)
Shortcut
Registered: Nov 6, 2007
Posts: 2667
|
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.
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, 1:35 PM
Post #8 of 15
(8048 views)
Shortcut
Registered: Apr 8, 2011
Posts: 139
|
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, 9:19 PM
Post #9 of 15
(7989 views)
Shortcut
Registered: Nov 6, 2007
Posts: 2667
|
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.?
|
|
|
|
|
stoneguy
Jan 27, 2013, 3:01 AM
Post #10 of 15
(7942 views)
Shortcut
Registered: Apr 8, 2011
Posts: 139
|
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 27, 2013, 5:43 AM
Post #11 of 15
(7921 views)
Shortcut
Registered: Nov 6, 2007
Posts: 2667
|
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.
|
|
|
|
|
JimTitt
Jan 27, 2013, 8:00 AM
Post #12 of 15
(7908 views)
Shortcut
Registered: Aug 7, 2008
Posts: 1002
|
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, 12:46 PM
Post #13 of 15
(7889 views)
Shortcut
Registered: Apr 8, 2011
Posts: 139
|
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, 8:16 AM
Post #14 of 15
(7752 views)
Shortcut
Registered: Nov 6, 2007
Posts: 2667
|
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.
(This post was edited by USnavy on Jan 29, 2013, 8:17 AM)
|
|
|
|
|
curt
Jan 29, 2013, 7:07 PM
Post #15 of 15
(7692 views)
Shortcut
Registered: Aug 27, 2002
Posts: 18275
|
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
|
|
|
|
|
|
|
|
|
