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SRENE anchors may go the way of the dinosaur

uwhp510

14-Mar-2006
10:57:10 AM

a) I reckon that 10% extra strength in a belay is easily realisable with a sensible setup over a non-sensible one.

b) If you've got the option of throwing another 5 pieces in the belay, then thats great but its not always possible. Talk to skinny Dave the Queenslander and ask him about his ascent of Red Super Giant (which involved getting off route and benighted) and some of his belay "anchors".


cruze

14-Mar-2006
1:17:49 PM

Yeah Dave is a good friend. He was actually trying to put up a new route and found himself retrospectively somewhere near RSG. Ask him about his rest on a "bomber" yellow alien on the Low Down. Three crystals of contact I believe. I think "skinny" is the optimum word here.

I think you guys can probably tell I am being the devil's advocate on this one. It is discussions like these that help the climbing evolution I just think they need to be appropriately balanced.


shmalec

15-Mar-2006
3:51:13 PM

It would be interesting to know whether they are talking 2 leg cordolette or 3 leg cordolette vs 2 leg sliding X. 2 legs of anything will distribute load according to angles only. Doesn't matter whether there is a knot. Its just angles and is not really affected by stretch/extension unless the two pieces are sitting next to each other with no V effect.

Three pieces are harder to equalize but that doesn't mean the loads are higher. "Three legs good, two legs bad....." :-)

The greatest equalising element is the knot.

This all sounds like a beat up to sell more books. Let them publish a paper with some scientific rigour instead of spreading bullshit rhumours on a forum!!

Edit:
Thinking about this further, there is a valid argument that by failing one leg of a 3 point cordolette, the peak load resulting in the rope will be less because of the energy absorbed and additional time/extension in blowing one piece. A bit like a "screamer" sling.
This would hold true for the sliding X, maybe even more so, but personally I'd rather not blow a piece on a two piece anchor.

uwhp510

15-Mar-2006
4:54:31 PM

Well, having tried to do the full 2d analysis which takes into account the lateral shifting of the knot towards the shorter leg (which is really hard since its non-linear) and having considered the issue; having really stretchy cordalette will help a little bit (apart from the energy absorption aspect) because the knot shifting will be more pronounced but this effect will be, in most if not all physical situations, very small. This is because its a geometric effect and so is limited by how much the geometry can change, whereas the unequal length = unequal tension, is based on internal forces within the cordalette. The sliding x obviates this by notionally creating equal tension over the whole sling (of course limited by friction in the biners).

> Doesn't matter whether there is a knot.
>Its just angles and is not really affected by stretch/extension unless
>the two pieces are sitting next to each other with no V effect.

This is almost completely wrong.

>The greatest equalising element is the knot.

What does this mean?

I know I'm not putting my money where my mouth is but I haven't given up trying. The two piece thing is for computational simplicity, and the results will, I imagine, generalise to n legs.

I reckon cordalettes are a pain in the arse (to carry) but I'm not trying to tell people not to use them based on this info, I am just saying you should be aware of what is going on when you are setting up an anchor.

But maybe its too complicated for some people who want an easy, one size fits all proscription for their anchors.


anthonyk

15-Mar-2006
5:26:43 PM

hey just playing around with some ideas about practical uses for all this & came up with a novel approach for making a rope anchor based on the sliding-X approach

so.. you get to the belay spot, put a piece in, pull out a length of rope long enough for a leash and clip the rope in to the piece with a clove hitch or fig-8. put in subsequent pieces and loosely clip the tail rope into each, leaving enough slack between pieces to pull to equalise (keep a hold of the loops as you go). after clipping the last piece, pull some more tail and clip it into the first piece (where you are clipped in already) with a fig-8 or clove hitch (maybe need second biner), with a bit of slack to allow equalising. put a twist in each loose loop (except the one from the last piece back to the beginning) and pull to equalise, clip, done. basically you've made a big rope sling & are using it just like a normal sliding-x arrangement, should be self-equalising.

(note just a thought experiment, haven't sussed out the practicalities..)


shmalec

16-Mar-2006
3:52:14 PM

On 15/03/2006 uwhp510 wrote:
>> Doesn't matter whether there is a knot.
>>Its just angles and is not really affected by stretch/extension unless
>>the two pieces are sitting next to each other with no V effect.
>
>This is almost completely wrong.
>
>>The greatest equalising element is the knot.
>
>What does this mean?

Clarification - if you have a two leg anchor with 45 deg angle, having a knot will make little difference even if one leg is twice as long as the other. The angle isn't going to change that much. If all your pieces are colinear then you may have issues like the one dimensional case described earlier.

As far as the knot goes. The knot tightens a fair bit under load (especially if its a fig 8). I imagine that if one leg is taking more load, this knot tightening would bias towards extending that one. Given how little most shock cord/tape stretches, this is probably important.

uwhp510

17-Mar-2006
3:04:35 PM

>Clarification - if you have a two leg anchor with 45 deg angle, having
>a knot will make little difference even if one leg is twice as long as
>the other. The angle isn't going to change that much. If all your pieces
>are colinear then you may have issues like the one dimensional case described
>earlier.

Thats what I said.

>As far as the knot goes. The knot tightens a fair bit under load (especially
>if its a fig 8). I imagine that if one leg is taking more load, this knot
>tightening would bias towards extending that one. Given how little most
>shock cord/tape stretches, this is probably important.

Maybe, but its never going to equalise as well as if there was no knot at all.

rolsen

21-Mar-2006
8:26:42 AM

Thanks to Phil for pointing out this the RC thread, I read most of it and set up my first sliding X (with limiter knots) on the weekend, 2 pieces (bomber wires) with a third thread (backing) them up with a touch of extra slack. The sliding X with a long (static) sling even with the limiter knots was as quick to set up as any other method. My placements were close to each which helped.

I'm keen to try this also with a top rope set up sometime soon,
Richard

cragrat

21-Jan-2007
2:18:01 PM

So where are all the testing outcomes?


IdratherbeclimbingM9

29-Mar-2009
1:00:54 PM

On 21/01/2007 cragrat wrote:
>So where are all the testing outcomes?

Bump.

How'd it go Phil?


Phil Box

30-Mar-2009
2:06:09 PM

The Lab forum on rockclimbing.com has some awesome test results and is quickly becoming the resource one must go to for anything close to scientific experimentation and empiracle data.

Rodney and I are about to start a battery of tests after a long hiatus caused by the death of Simon Vos. Rodney has gotten a handle on Labview and we fixed up a broken cable on the strain guage carabiners. Won't be long now until we can start to present some findings complete with graphs and pics. I can't wait.

Richard Delaney

30-Mar-2009
3:01:58 PM

I'd be very interested in proposing a view possible test scenarios especially around the
ideas:
- the differences in behaviour of a anthropomorphic vs static test masses
- as an extension, near and not so near vertical axis bodies supported by sit harnesses

If you're interested, email me - rdelaney "at" epacrisenviro.com.au

mikl law

30-Mar-2009
5:16:01 PM

Very interesting. I hope that the differences between "humans" and "lumps" are less than those between cables and climbing ropes.

On 30/03/2009 Richard Delaney wrote:
>I'd be very interested in proposing a view possible test scenarios especially
>around the
>ideas:
>- the differences in behaviour of a anthropomorphic vs static test masses
>- as an extension, near and not so near vertical axis bodies supported
>by sit harnesses
>
>If you're interested, email me - rdelaney "at" epacrisenviro.com.au


Phil Box

30-Mar-2009
7:18:29 PM

On 30/03/2009 Richard Delaney wrote:
>I'd be very interested in proposing a view possible test scenarios especially
>around the
>ideas:
>- the differences in behaviour of a anthropomorphic vs static test masses
>- as an extension, near and not so near vertical axis bodies supported
>by sit harnesses
>
>If you're interested, email me - rdelaney "at" epacrisenviro.com.au

Yep, we are very interested in the same things actually.

matthewp

31-Mar-2009
11:31:08 AM

what about using the Equalette. It seams to me it has all of the advantages of the sliding X, without many of the disadvantage.

gfdonc

31-Mar-2009
11:44:38 AM

On 31/03/2009 matthewp wrote:
>what about using the Equalette. It seams to me it has all of the advantages

It's got such a girly-sounding name though. "Equalette". Could be a brand of weight-loss tablets for all I know. Or some technique for show-jumping in pony school. Or a brand of tampon?

matthewp

31-Mar-2009
11:48:38 AM

http://www.supertopo.com/climbing/thread.html?topic_id=314475


ajfclark

31-Mar-2009
11:57:03 AM

On 31/03/2009 matthewp wrote:
>what about using the Equalette. It seams to me it has all of the advantages of the sliding X, without many of the disadvantage.

I've been using this arrangement since I read about it in John Long and Bob Gaines' book. I think it's a really good idea. There's a lot of really useful stuff in that book actually.

Richard Delaney

31-Mar-2009
12:21:06 PM

On 30/03/2009 Phil Box wrote:
>Yep, we are very interested in the same things actually.

I had a good chat with University of NSW and NSW RTA (Roads and Traffic Authority)
Crashlabs about commissioning some tests. One of their problems was that the
$120,000 dummies they have are good for seated frontal and side impact testing but not
necessarily for 'flop back' type tests. I was also exploring some small very low fall
factor tests using real people vs static masses and measuring/filming differences.

I've spoken with someone who had a fall (less than ff1) who was off vertical and snapped
the transverse processes off L4 and L5. I'm also aware of many workers at height using
6kN energy absorbing lanyards but I think that their weight may prevent these from
limiting the deceleration to that observed with 80kg static test masses - or from hitting
the end of the energy absorbing section. The rate of deceleration (as opposed to force)
applied to different organs (unsupported organs like the heart), brain, and off axis spine
would seem worthy of testing as all the info used currently seems to originate from US
air-force ejector seat/parachute deployment tests with vertical spines.

Hmmm...

patto

31-Mar-2009
12:36:38 PM

I find this whole thing a case of attempting to solve a non existant problem.

Most often I use the climbing rope for my anchor. And it typically seems fairly well equalised. This can be roughly tested by plucking each strand.

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