Emergency backup ascenders, Petzl Tibloc?

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Postby cob » Sep 8, 2006 2:03 pm

thanx hank. I knew the french prusik (thought it was only with rope), had heard of the bachmans, and the kleimhorst is news to me.

much appreciated. tom
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Postby hunter » Sep 8, 2006 3:29 pm

Yes - personal preference can also change as a result of the experience of others, if you keep an open (but somewhat critical) mind.


So, as I posted before my experience with the tibloc is that it can damage the sheath in an ascending system if not perfectly tended. To further what someone said before, this is fuzzing where a couple of teeth rip down, tearing threads in the sheath. I never saw a core shot but the tearing was enough I decided to never use the tibloc as a regular ascender.

I'm curious, does anyone have access to destructive testing info on the tibloc under extreme load? I'm curious what happens, my hunch is that the tibloc would tear a chunk of sheath off but not cut the rope. I'm still trying to decide if I'm curious enough to wreck my tibloc though...

James
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Postby hank moon » Sep 8, 2006 3:43 pm

hunter wrote:I decided to never use the tibloc as a regular ascender.


Good decision as it's for emergencies, not regular use.

hunter wrote:I'm curious, does anyone have access to destructive testing info on the tibloc under extreme load?


Destructive testing info may be found in the technical notice:

http://en.petzl.com/ProduitsServices/B0 ... 020799.pdf

or are you looking for more "extreme" scenarios?

hank
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Postby hunter » Sep 8, 2006 8:53 pm

Hank,
Thanks for the pointer, after some deciphering I think this is what I was after.

someone correct me if I'm reading these diagrams wrong)
The diagrams seems to say that given a static load the tibloc strips the sheath off of any rope at 6-7kn. This means that with the proposed burly scenario a tibloc used as a main haul ascendor would strip the sheath if the system stuck and you got 7kn.

With a dropped weight scenario the dynamic ropes do ok but I read the diagram as saying the sheath is stripped at 5-6kn on static ropes. I read this as meaning, if you had the tibloc as a PCD and you shockloaded it over 6kn you would strip the sheath.

Also of note, it shows 8mm ropes as being cut but nothing thicker.

I don't remeber all the force stuff but my gut feeling is that these forces are way to low to be using the tibloc in a rescue pulley system even in a crunch. Personally I think carrying some prussik cord or building some part of your system out of prussik instead of webbing would be much safer.

James
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Postby NZcaver » Sep 9, 2006 7:23 pm

hunter wrote:<snip>
The diagrams seems to say that given a static load the tibloc strips the sheath off of any rope at 6-7kn. This means that with the proposed burly scenario a tibloc used as a main haul ascendor would strip the sheath if the system stuck and you got 7kn.

With a dropped weight scenario the dynamic ropes do ok but I read the diagram as saying the sheath is stripped at 5-6kn on static ropes. I read this as meaning, if you had the tibloc as a PCD and you shockloaded it over 6kn you would strip the sheath.

Also of note, it shows 8mm ropes as being cut but nothing thicker.

Your assessment seems to be fairly accurate, but try to keep all this in perspective. Bear in mind that most regular toothed-cam ascenders (like Petzl Basics/Ascensions, Jumars, etc) and some lever-cam ascenders (Gibbs etc) will also fail (or cause the rope to fail) under similar conditions. Rescuecenders are a different animal - they should "safely slip" when overloaded. So should Prusiks, IF they are the right diameter and type of cord AND they are properly tied and applied. But if the rope is too muddy/icy etc, they may slip even when a "normal" load is applied.

I don't remeber all the force stuff but my gut feeling is that these forces are way to low to be using the tibloc in a rescue pulley system even in a crunch. Personally I think carrying some prussik cord or building some part of your system out of prussik instead of webbing would be much safer.

Again - there needs to be a conscious separation between what might be useful (and available) in a small-party improvised rescue, versus what is required in a full-scale technical response by an agency. See one of my previous posts for details.

It seems your mind is made up on retiring the Tibloc you have, and sticking with Prusiks for emergencies. That's fine, and I'm sure you're not the only one who feels this way. One thing I would suggest, though. Perhaps find some NCRC instructors (or other suitably qualified/experienced persons) in your region, and ask them if they might be willing to put on some small party rescue training. Nothing beats training and practicing with this stuff! :big grin:
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Postby fuzzy-hair-man » Sep 10, 2006 7:10 pm

hunter wrote:Hank,
Thanks for the pointer, after some deciphering I think this is what I was after.

someone correct me if I'm reading these diagrams wrong)
The diagrams seems to say that given a static load the tibloc strips the sheath off of any rope at 6-7kn. This means that with the proposed burly scenario a tibloc used as a main haul ascendor would strip the sheath if the system stuck and you got 7kn.

With a dropped weight scenario the dynamic ropes do ok but I read the diagram as saying the sheath is stripped at 5-6kn on static ropes. I read this as meaning, if you had the tibloc as a PCD and you shockloaded it over 6kn you would strip the sheath.

Also of note, it shows 8mm ropes as being cut but nothing thicker.

I don't remeber all the force stuff but my gut feeling is that these forces are way to low to be using the tibloc in a rescue pulley system even in a crunch. Personally I think carrying some prussik cord or building some part of your system out of prussik instead of webbing would be much safer.

James


hunter, I think the second part of what you said is a bit out...

the manuals mention testing on fall factor 1 and 0.5 with a 80kg weight. I think the kN forces you quote are the forces expecienced by the load. ie this is trying to put numbers to how much the ascender will act as a shock absobing device given a dynamic load. I could have read it wrong so correct me if I'm wrong.

Comparing static loadings of the Tibloc with the other petzl ascenders and the Tibloc seems to out perform the Basic, Ascension and Croll, these others don't get up to the 7 kN territory. As a PCD these are never intended to take a shock load and should only experience static loads up to 200kg (supposedly).

NZCaver:
As you suggested, Life On a Line mentions putting a weight or bungy cord to pull the ascenders down when rigging a PCD. When compared to rigging on the other side of the pullley this should minimize the rollback experienced. :kewl:
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Postby volica » Sep 13, 2006 7:46 pm

It is gonna be pretty tough to open bottle of beer with Prusik knot. Ttibloc is perfect for that.
OK, seriously now. You will have to pay lot of attention to not shred shed of rope using tibloc.
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Postby cob » Sep 13, 2006 7:59 pm

volica wrote:It is gonna be pretty tough to open bottle of beer with Prusik knot. Ttibloc is perfect for that.
OK, seriously now. You will have to pay lot of attention to not shred shed of rope using tibloc.



I KNEW there was a reason for the tibloc!!! (just kidding guys) personally I prefer a Bic lighter for opening my Pacificos....

tom
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Postby NZcaver » Sep 13, 2006 9:04 pm

volica wrote:It is gonna be pretty tough to open bottle of beer with Prusik knot. Ttibloc is perfect for that.
OK, seriously now. You will have to pay lot of attention to not shred shed of rope using tibloc.

What is the MBS of a bottle cap, anyway? :question: :tonguecheek:
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Postby NZcaver » Sep 25, 2006 1:36 pm

Following up on earlier discussion...

cob wrote:In another post you said you had seen where prusiks had torn the sheath from a rope??? This is news to me (not being sarcastic, seriously, I have never heard that). I thought the main advantage of a prusik was it could NOT damage the rope (in that way at least).

I just confirmed this story with a very credible eyewitness. Prusiks can strip the sheath from ropes. The NCRC has proved this in controlled testing - and no, unfortunately I still don't have any photos of it. Again, the issue goes back to the particular types, diameters, and conditions of the ropes and Prusik cords being used. Plus we are (of course) talking about significant loads being applied before damage occurs.

And further to the previous comments about Prusiks not always gripping and operating like they should... I experienced another perfect example of this yesterday. We were operating a counterbalance haul system - 2:1, with pulley and Prusik resting on a carpet pad at the edge. Because the Prusik was in contact with the surface (rope pad), of course it had no gripping function at all. Interestingly, when the Prusik was replaced (re-tied) with a Klemheist, it worked perfectly. (No, we didn't use a Tibloc that time - but I'm sure that would have worked OK too.) :wink:
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Postby hank moon » Sep 25, 2006 2:01 pm

Prusiks can cause coreshots, but I have not seen this happen outside of severe drop tests conducted with rescue loads.

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Postby NZcaver » Sep 25, 2006 2:02 pm

NZcaver wrote:
cob wrote:
NZcaver wrote:Dude - if your haul cam cuts your rope, there is no load for the PCD to capture! :shock:


Dude, correct me if I am wrong (it has been 10 yrs) but does the PCD go above or below your haul system???

Oh - OK. Yes the PCD can go below the haul system, but if so it usually needs to be tended. In fact now that I think about it, haul systems are often (usually?) taught this way - good call. Personally, I prefer to have it riding by the first pulley above the haul cam - but your preferences may vary.

I just received clarification on this. In the past, a PCD has generally been placed below the haul cam when using an odd mechanical advantage system, and above when using even MA. The NCRC has recently changed it's teachings to reflect the fact that using a PCD in either position is perfectly acceptable (when properly applied).
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Postby NZcaver » Sep 25, 2006 2:21 pm

hank moon wrote:Prusiks can cause coreshots, but I have not seen this happen outside of severe drop tests conducted with rescue loads.

Fair comment - which supports my point that stripping the sheath with a Prusik is a possible failure mode for a system. Put in other words, Prusiks do not always slip (without harming the rope) when overloaded.
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Postby cob » Sep 25, 2006 6:18 pm

NZ... been away from this thread of late. appreciate the updates.

tom
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Postby ljthawk » Sep 25, 2006 9:08 pm

IMHO, I like having gear that serves multiple purposes. Since I don’t cave with bottled beverages (biners will work as a church key if you do) I have never considered carrying a tiblock over soft rigging (prussic, bachman, etc) for emergency ascending.

Here’s why.

1. Short prussic cords or webbing loops serve well as leashes to carry ropes, clip rock hammers, hand drills, etc.

2. Longer accessory cord loops (like cordellete (sp?)) or lengths of webbing can be used to improvise rigging when needed.

3. Longer accessory cord loops or lengths of webbing can be used to rig hand lines when needed without sacrificing a rope required for another drop.

4. Longer accessory cord loops or lengths of webbing can be used with biners to rig up a quick and dirty small party crack & crevice rescue system.

Should I go on with the potential uses of longer accessory cord loops or lengths of webbing?

L.J.

P.S. How’s life out west Hank? I’m now in fly over country Peoria, IL.
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