September TCIA SRT article

DSMc

DSMc

Been here much more than a while
Location
Montana
Kevin mentioned this in one of his other posts and I just finished reading it myself. Has anyone else read this? I would like to hear your thoughts.

This article is by Brian Kane and Mark Reiland, entitled Applied Research for Climbing and Rigging: Single Rope Technique. Pg 44 in the September issue of TCIA Magazine.

I feel there are a lot of errors of omission and confusion regarding cross-applied safety criteria from different rope access disciplines. But the biggest thing I don't understand, is the purpose of their chart on tie in point load measurements. The chart presents four different scenarios: Ddrt on isolated limb, SRT isolated limb anchored at base, SRT anchored at base with non-isolated limb and SRT with not isolated anchored at base with four trunk wraps.

No mention was made at what angles were involved with the non isolated limbs. As we know through rigging, multiple angles change the load. And what was the point of the different base tie ins relevant to tie in point load? Why were no alternatives for reducing loads at a tie in point with SRT given?

The whole article left me with a "don't do it" feeling as opposed to "this is the way to do it safely" feeling.

What do you guys think?

Dave

http://www.tcia.org/Digital_Magazine/September11/TCI-Magazine-September-2011/index.htm#?page=44
 
No discussion of compression wood vs. tension wood. no discussion of angles. Was all excited to read it. THey kept referring to the TIP as being the main redirect which is incorrect. TIP = Tie In Point. The that they were testing had only one redirect with zero angle. Compression wood versus tension wood is where you want to start looking.

Positives
Clever way to measure the forces using the dynometer.
learned a little about rope types and ascender testing. Very confusing.
 
didn't get much out of the article that hasn't already been readily discussed here and other forums. I agree that if you are really going to test the SRT way of climbing you need to test it in a multiple redirect senerio.

this article gives good reason not to tie into ascenders for life support. (on arb ropes anyway).

has there ever been any instances or studies into what kind of damage a tied hitch could do to a rope in a shock load senerio?
 
I want you guys to really look at the chart. Measuring the force on both ends of the rope tells the load on the rope NOT the load being applied to the redirect points.
The fear of over loading, by doubling the load at a crotch (redirect point), is one of the most comon reasons given for not trying SRT.

Dave
 
Kane has been doing a lot of research directly related to our work, and the TCI article was describing an experiment on one aspect of SRT climbing, namely load at TIP with different anchorages. I had read a different article not too long ago that suggested friction addded to the system at the TIP crotch and trunk wraps would lessen the force applied at TIP. Kane's research shows that is not the case.

Sharing load between multiple points, redirects, etc. was not the point of the article. It was the first article I've read that describes the problem of using ANSI approved ropes with non-compatible ascenders, or using ascenders with manufacturer-approved static lines, but not approved by Z133.

For more on the use of ascenders, look up the July 2011 Arboriculture & Urban Forestry. Kane's paper "Compatibility of Toothed Ascenders with Arborist Climbing Ropes", like the TCI article, urges us to be cautious. For as much as the tools have been sold and promoted for use, caution isn't a negative thing.
 
I believe this video is by Brian Kane or one of his students:
Toothed ascender drop test

Shows a 195 lb. weight being dropped 3.3' on to a toothed ascender attached to an "arborist rope", no specs given for the rope or ascender.

Rope appears to be shredded, looks like the ascender slid 10-12 ft. before it stopped moving, rope did not completely sever, held the weight.
-AJ
 
[ QUOTE ]
namely load at TIP with different anchorages. I had read a different article not too long ago that suggested friction addded to the system at the TIP crotch and trunk wraps would lessen the force applied at TIP. Kane's research shows that is not the case.

[/ QUOTE ]

I disagree taking extra wraps at the bottom of the tree does nothing. The wraps should be spread out more concentrated towards the TIP. I don't think he set it up appropriately. This can't be measured simply.
 
In my setups I add trunk wraps to aid the belayer in case of a rescue.

If there is some reduction in load at the TIP that's just a side benefit. I think Kane's chart shows some load reduction but it's negligible in his setups.

I have always talked about how SRT theoretically doubles the climber's load at the TIP. It is up to the climber to choose a proper SRT TIP which MUST be stronger than what they might be used to if they've climbed DdRT up until now.

How does ANYONE 'really' know how strong a TIP is? We all might be climbing on TIPS with zero safety factor!

Taking time to look at what works for slam dunk rigging will teach a climber what to look for in a proper TIP.
 
What I didn't understand about the article was the point in doing the tests. The answer to the primary question asked can be found in any 10th grade physics book. The unknown variable is the friction present at the redirect which can be plugged into the equation if it can be calculated for each redirect based on diameter, texture, and size. Angles can also be calculated into the equation as well and the equations are simple enough that a climber can calculate them roughly on the spot while climbing. The VTIO article is superb in helping a climber do this.

I have a hanging Meat scale that you can play around with ropes and varying degrees of friction and angles. I hang a 15 lbsd dumbull and the results are easily read by the scale. Sort of a mini dynometer. What is cool is playing around with angles and the scale will read the force and also point in the direction that the force is exerted.

I just don't see the need to conduct these tests to study a question to which the answer has been known for a very very long time.

The question on ascenders was more interesting to me but it felt a little inconclusive as to what the data means practically speaking. Should we be SRT climbing only on Nylon lines not approved by ANSI? or Arborist lines not approved for use with Ascenders? I hardly ever tie into an ascender but it is an interesting question to debate.
 
[ QUOTE ]
I just don't see the need to conduct these tests to study a question to which the answer has been known for a very very long time.

[/ QUOTE ]

I couldn't agree more. The Vtio report on SRT addressed the doubling of force immediately. But the difference is they went on to explain ways to deal with it. This is helpful.

I also believe you are correct in that a lot of confusion is propagated by the misuse of terms. A tie in point is not one unless you are actually tied to it.

When you base tie an SRT line, that is the anchor/tie in point. Your suspension point, with a base tie, is a redirect, as you pointed out, Kevin, over and over. You have to base your calculations on force multipliers and ways to minimize them with that knowledge.

This is of great importance to understand if you want to use the physics involved to your advantage.

SRT is becoming common enough to get beyond the initial prejudices and have, instead, helpful articles on safely and appropriately utilizing it.

Dave
 
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