A Young Person's Guide to.....
Two-Tensioned Rope Systc I
V
ReedThor of Ropes that Rescue (FUR) www.ropesthatrescue.com
■
From a purely North American perspective, it seems that just about the
time you feel that a rescue-related controversy is subsiding and you can finally breath easier, another surfaces, in the late eighties/early nineties
to action - sometimes abruptly -- in the event that the beleaguered first half
fails to support. A climber climbing a pitch of rock with a belay rope (whether from the top of from the bottom) is just such a parallel situation
the debate about soft versus hard ascenders used for rescue loads raged on
even though at first glance it resists such a comparison. The rock onto which
unencumbered. The usage of figure of eight family over bowline family knots
the climber clings is the supporting element and the belay rope is the
still produces much heat (and seldom any light). Now, it seems, there is a new one on the horizon....and like a speeding
instrument which ensures the climber ends the day safely. In the two rope system common in rescue or rope access work, two ropes are involved and
race car on the Bonneville salt flats of Utah, it will soon be upon us - if it is
again one supports and the other is the insurance policy again the
not already here. You no doubt have mused over the title of this article and
unanticipated failure of the that element.
have an idea of what I reference. It is the Two-Tensioned Rope Systems or what we will call TTRS. Perhaps this one was a longtime incoming, but
2. SELF BELAYS:
nevertheless, it is here and in our face. As with the earlier mentioned
Self belays rely on the same separately anchored rope, again without any
skirmishes of a decade or two ago, the new issue stems from the old. But
tension but is managed by the very same person needing the protection. Fall
make no mistake, the TTRS is reshaping how we look at the safety rope --
arrest systems or rope access back up safety line systems are examples of
that parallel (not series) back up in a two rape system. By definition, a two-
self belays. You don t need a belayer per-se. You do it yourself if you are in
tensioned rope system is a rope system relying on two equally or unequally loaded ropes operated on two separate independent anchors by two
exposure. Simple and cost effective and hence so often used in industry. The belay, if done properly, passes the all important critical point test
independent operators.
which most team members of a rescue team within a litigious society like ours bow before daily. The Critical Point Test or CPT is pass or fail and states:
1, THE BELAY:
Is there any one point in the system that were it to fail would lead to
TTRS challenges the foundation of what a "belay" is in the classic sense.
catastrophic failure of the entire system?. Until lawyers are no more, this is
Again, in North America the term belay generally refers to a rope that is
the alter at which we all pay homage.
independently anchored, managed by another person other than the one
Again, it has to do with parallelness and not having a system safety in
needing the belay and remains without tension until called into play by some
series with the "chain". In a series system, one link of that chain breaks, and
means of failure of a supporting system or a fall, etc.. The system bespeaks
you arenot having a good day!
"parallel-ness" (a roughly-hewn term coined in abject spontaneity) because there is one half that does the "supporting" and another half which is called
28
In the classic definition of the belay given above, you should notice three key points when considering it. They are: 1) the anchoring for the belay
ISSUE 63 TECHNICALRESCUE
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jms
§~rnzs
IN
Single (Tensioned) Rope
100%
Two-Ten si on ed Rope
50%
50%
DEFINITIONS i.
* should be independent from that of the supporting element in keeping with
DEFINITIONS
the CPT, 2) the beiay is managed by another person {often called the belayer) other than the one needing the protection, and 3) the belay rope should remain without tension during the belay process until the failure of the supporting element. In the case of the climber, this would mean they fell off the route (the rock failed to support). In the two rope system, this would mean the failure of the parallel supporting rope (called the main line). In either case, the belay line is slack, and then abruptly becomes loaded with
the initial mass and also the addition of any impact forces associated with the failure, and consequent drop, of that supported mass. When two ropes in our parallel system come under load, things can get blurry. In an instant, the belay rope definition stipulation "remaining without tension" no longer fits. Both ropes have tension in this case. So, what to do? Well, at this juncture, we could offer thai the mass is no longer on a true belay but rather something else- So the question is. does that something else provide the same level of protection as the true belay? As we will see, it depends on the WAY the two rope s tension is administered. The
administration of that tension in each half of the parallel system is the speeding car headed right for us. It is that "something else" thnl this article
offers to investigate in these installments within TRm,
of Rigging for Rescue in Invermere, BC, Canada and a member of the British Columbia Council of Technical Rescue (BCCTR). He had been my final rope
The most difficult thing for any technical author to do is to remain
rescue mentor and his well-reasoned apologetic for why one rope should
unbiased in their analysis of a procedure or technique borne of a new device
remain without tension as in the case of the belay are still with me today. I
or gadget coming onto the market. For me. I would have had trouble even
remember the lectures in his small two story home basement in the mid
beginning to write this article as little as a year ago because I bad not gained
eighties - Arnor delivered good arguments regarding dual rope, double rope,
much in-the-hand experience. Also, some of the issues here smacked of all
twin rope, two rope and eventually single rope, which he had hung bis hat of
that Arnor Larson had railed against. Amor was the original instructor/owner
approval on. An early test of the various TTRS In Leavenworth, Washington
TEC9NICALRESCUE ISSUE 63
.t-rescue.com with Arnor, Jon Olson and Denny Fenstermaker of
3. CONDITIONAL BELAY:
Seattle Fire Ladder 7 were tantamount to delivering
In order to get our head around the subject of two
knock out punches to many of the earliest two-
tensioned ropes sharing the support, we need to look
tertsioned rope proponents, some of them from the UK.
closely at another definition that Arnor expounded upon
The counter arguments to TTRS were the bulwark for
with regularity. That was the conditional belay. The
my early development as a rope rigging and rescue
definition (relative to TTRS only) goes something like
instructor. So, you can see why this article may be
this: A rope already under tension from all or part of
difficult to reckon with for someone set in their ways.
the load. When employing tvso-tensioned rope
But don t give up. I think there is merit out there lurking
systems, care must be taken in insuring that the
for the TTRS. I think now is the time for such an article.
second rope system will survive and adequately hold
Such is the case with the introduction of the CMC
the entire load if the first system fails. If the total
MPD (Multi Purpose Device) which is the latest device
system depends on the survival of both parallel halves,
in a series of previous attempts that is serving as the
the system is said to be "conditional".
petrol in the engine of the TTRS speeding race car
So the glaring difference between the belay and the
closing fast upon us. It should be noted that the
conditional belay is the tension. But a further distinction
reason it is called "multi purpose" is because it can be
needs to be drawn here. What if, as in the case of the
used on both parallel lines in the TTRS. Not only that,
I D or the MPD, each half of the parallel system could
but it is also good for our standard single-rope lowers
hold the entire load? This is the claim that the MPD
where one MPD has 100% of the load in the main line
makes in its literature. In other words, if two identical
and another MPD belays the operation again using a
MPD are used on each half of the system and either one
non- tensioned belay line. Delayed due, apparently to
fails, the survivor wifl instantly be able to catch the
some engineering bugs which needed rectification, it
falling load -- even if there is an impact onto the
is finally out with some long overdue fanfare Icheck
survivor. In the Leavenworth testing, this was exactly
out the ad opposite]. The MPD is a device similar to
what Arnor was trying to illustrate, During those early
the Petzl i D in iha! it is an auto-stop friction
90 s tests, the auto stop Petzl 1 D and the CMC MPD
appliance which can be released by an operator-
did not yet exist so manually operated friction
controlled handle to lower, but doubles as a simple hands-free
CONDITIONAL
ratchet (progress capture) in the
uptake of rope as in a pulley system.
2
1
What the MPD and I D do is simplify the conversions from down to up or vice versa. That is particularly advantageous during mid-wall "hot"
changeovers with the main line. Both devices are designed to be used
•
r
.4*"*
as fixed friction appliances meaning
50%
they are anchored and not moving,
50%
100%
I
whereas the i D is also very popular as a traveling friction appliance, especially in the world of rope access. The MPD is not a good traveling brake due to its size and handle position. One of the big issues with the I D which is particularly annoying is its lack of
efficiency during the uptake of rope through it. It requires a rather torturous route for the
appliances like the ever popular brake rack were used.
poor rope to iake which produces heaps of friction
Of course, these devices require the brakeman to
(the author contends this is the REAL reason for global
actively participate in arresting any fail caused by the
warming). This becomes particularly evident when
failure of the other system. So, depending on the way
using the I D as a fixed brake progress capture in a
the single or double yoke attachments were made to the
rescue pulley system. Of course during lowering, the
stretcher (and this gets into the province of two rope,
torturous route is of no concern since friction is a
twin rope, dual rope and double rape TTRS lowers
required element. Still, people all over the world were
discussed below) would determine if the rescue
using it because it reduced the normal brake rack
package of 200kg (single yoke) and 280kg (double
conversion from lower to raise from 13 pieces of
yoke) would hit the ground. More often than not, it was
equipment down to 5 only (if you were only building a
determined that the added impact force caused by the
simple 3:1 zed rig).
violent swing of the stretcher onto the surviving main
Since, in the TTRS, there are two ropes under tension
line of a double yoke system would send it careening
(sometimes to varying degrees) either rope is really not
into the ground. Crrrtr-ash! (Arnor would gleefully
a belay in the true definition of the term. So another
chuckle) On single stretcher yoke systems, this was not
definition is needed. Not a bad thing by any means, but
as much of a problem since there was no huge swing
it is still important to see the rank differences in the
and the rescue package was only 200kg. The brakeman
engineering of the system you might be hanging from.
using a brake rack couid hold it each time. Clearly the
As we know, engineering is vastly important and
280kg lowers with parallel rope, double stretcher yoke
paramount to the safety throughout the vertical
lowers were on conditional belays which failed the
operation.
critical point test hands down.
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TWO-TENSIONED ROPE BELAY:
1. TWO ROPE:
Another definition is therefore needed for the the phenomenon of each half of
Definition:
a TTRS holding the entire load plus the resulting impact force if the other
A two-tensioned rope system using two main lines set apart on two anchors
failed. Hence the TTRB or "Two-Tension Rope Belay" suits the condition well.
on top and employing two identical friction appliances for lowering and two
Unlike the conditional belay, this system relies on each half of the system to
identical pulley systems for raising attached to a single stretcher yoke.
arrest any fall insuring that the system will pass the critical point test,
Discussion:
So, where we going with all of this? Well, I have been thinking about that very question for years now, especially since the MPD has come out. To me,
DEFINITIONS
it seems that we are headed towards a dichotomy of sorts here within rescuedom. Is there a place for TTRS within our discipline? I feel that the honest answer to that is a resounding YES, but in the same breath, I would have to
TYP6S OF- TWO ROX>£ SyST^MS
set forth that the TTRS is not the panacea for all rope rescue applications.
1. TWO
Also keep in mind that what the Lochaber Mountain Rescue Team does on the side of Ben Nevis in the middle of a nasty, dreach winter to lower an injured climber off will be substantially different to that of the San Bernardino
RAISE
(California) Sheriff s SAR team in an abandoned mine shaft rescue. Each team given their own exclusive environment will have solutions warranted from years of wisdom and know-how -- and from having performed so many rescues in the past. So, we are not saying here that it is our way or the highway. Not at all. As we have come to see it, the TTRS is a tool in the tool bag. We don t use it all the time but rather, only when it is THE tool for the job.
Think fora moment about all the places that you employ a single loaded main line and a slack belay line? So what if any are the indications for the TTRS? VARIATIONS IN THE TWO ROPE SYSTEMS: As mentioned, there are basically five different configurations for two rope systems and there may even be more. All of them are used in large part all over the globe. For instance, Colorado has at least four of the five of them
DEFINITIONS
represented in that one state. Lack of rope rescue standards within the US has allowed, and even encouraged, this diversity. We have to ask then what
es cf two
types of hazards lurk within the rigging that go unidentified until there is a failure. What engineering issues are present that may not be easily identified
±. TWO
until a mishap? Armed then with the definitions of a true belay and a conditional belay lets take a look at the various systems out there: 1. TWO ROPE 2. TWIN ROPE 3. DUAL ROPE
50/50%
4. DOUBLE ROPE 5. SINGLE ROPE These variations certainly give the rescue team the ability to adapt to any given environment and terrain type out there. Also, it should be noted that special tools are used in some of these which allow, say, the lowering of two
ropes through a single friction appliance at the same time and at different rates fso as to be able to control the head-end to foot-end attitude of the
stretcher). Certain teams had these appliances specifically manufactured to accommodate the particular lowering method they adhere to.
• In this system, two anchors are used separated according to the terrain features. • Both rope systems share the load and each must b engineered so that in the event that one fails, the other would catch. Otherwise, the belay would be considered conditional. If each half can catch the package including a shock toad, then the belay would be considered a TTRB. • There is the issue of a descending V which means that the loaded ropes continually wipe the face, possibly knocking rocks down on the rescue package. • Getting over an edge can also be problematic as the ropes under tension
want to take differing paths to the single stretcher yoke connection. • There would be a slight pendulum swing if one side failed and the package loaded onto the surviving element. • Fails the CPT if each half of the Two Rope System cannot survive the failure of the other.
ISSUE 63 TECHNICAL RESCUE
rock exotica
2.TWIN ROPE:
EXPERT USE ONLY
GEAR FOR THE Z AXIS
Definition:
A two-tensioned rope system using two main lines to a single backed up anchor on top and employing one large friction appliance for lowering and two identical pulley systems for raising attached to a single stretcher yoke.
Discussion:
DEFINITIONS Ana. hi v/Bil
of two iao • •• •
.. TWIN
DEFINITIONS
UK & Ireland Distributor
types oftwo
1 see website for details
www.gustharts.com
2. TWIN
50/50%
• In this system, a single anchor which should be backed up is used. A tensioned back tie anchor would preferred over a non-tensioned slack back up since this focuses the main anchor. • Both rope systems share the load and each must b engineered so that in
the event that one fails, the other would catch. Otherwise, the belay would be
considered conditional. If each half can catch the package including a shock load, then the belay would be considered a TTRB. • There is no issue of a descending V which means that the loaded ropes do not continually wipe the face as with the two rope system. • A friction appliance which can accommodate two ropes at the same time
must be used. The Rock Exotica TUBER is a manual lock version of just such an appliance and the Australian SRTe Double Rope Descender is an example
of an autolcking version which has been around since at least the midnineties.
• Fails the CPT if each half of the Twin Rope System cannot survive the failure of the other.
ROCK-N-RESCUE PO BOX 213 VALENCIA, PA 16059-0213 USA
P 724.898.7673 F 724.898.3139
TECHNICALRESCUE ISSUE 63
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3. DUAL ROPE:
4. DOUBLE ROPE:
Definition:
A two-tensioned rope system using two main lines set apart on two anchors on top and employing two identical friction appliances for
lowering and two identical pulley systems for raising attached and
each rope attached to a double stretcher yoke. Two stretcher atten dants are required to control the foot and head ends (280kg) Discussion:
Definition: A two-tensioned rope system using two main lines set upon a single anchor on top and employing two identical friction appliances for
towering and two identical pulley systems for raising attached and
each rope attached to a double stretcher yoke. Two stretcher atten dants are required to control the foot and head ends (280kg) Discussion:
DEFINITIONS
DEFINITIONS
ROP6-
RAI.se
50/50%
50/50%
DEFINITIONS
50/50%
50/50%
• In this system, a single anchor which should be backed up is used. A tensioned back tie anchor would preferred over a non-tensioned slack back up since this focuses the main anchor.
• Both rope systems share the load and each must b engineered so
that in the event that one fails, the other would catch. Otherwise, the belay would be considered conditional. If each half can catch the package including a shock load, then the belay would be considered a TTRB. • Getting over an edge can also be problematic as the ropes under tension want to take differing paths to the double stretcher yoke connection.
Types of two viove SYSTEMS
3.
50/50%
• There would be a massive pendulum swing of the stretcher with
attendant in the event of one half s failure leading to a significant impact force. • Fails the CPT if each half of the Dual Rope System cannot survive the failure of the other (and resulting impact force caused by the pendulum swing).
■ In this system, two anchors are used separated according to the
terrain features. • Both rope systems share the load and each must be engineered so that in the event that one fails, the other would catch. Otherwise, the belay would be considered conditional. If each half can catch the package including a shock load, then the belay would be consid ered a TTRB. • In the traveling brake mode, each attendant is in control of half the 280kg load in order to keep the stretcher level on descent. • Getting over an edge can also be problematic as the ropes under tension want to take differing paths to the single stretcher yoke con nection.
• There would be a massive pendulum swing of the stretcher with
attendant in the event of one half's failure leading to a significant impact force.
• Fails the CPT if each half of the Dual Rope System cannot survive the failure of the other (and resulting impact force caused by the pendulum swing).
The Petzl Tuba (previously Rock Exotica) is a large lowering device capable
of variable friction and knot passing. Its large, tubular construction dissipates heat much better than smaller devices and is therefore extremely useful, if not vital, on very long lowers.
ISSUE 63 TECHNICAL RESCUE
5. SINGLE ROPE:
CONCLUSION
A system employing a single main rope which carries the entire load
between a "conditional belay" and the "two-tensioned rope belay" is perhaps the most important to take away from the seemingly dis parate quagmire of two-tensioned rope systems in this installment.
Definition:
In conclusion, this final illustration which delineates the differences
and a parallel single unloaded belay rope for the purpose of backing up the main in the case of failure. The belay can receive significant shock loading In the event the main line's failure.
DEFINITIONS
CONtXTIONAL
TWD-TENSIONEU
TWO TEOPE Sf&TBMS
5".
DEFINITIONS TWO KOTB .SySTEMS
Of course there is much more to come in Part 2 and i can hardly wait to get into it as it appears to be the most relevant. But this groundwork was necessary. However, for now, it is incumbent upon the rope rescue or rope access practitioner of any roped system employing two equally or unequally loaded main lines to insure that they are not erroneously engineering a conditional belay without
realizing it. This should also be observed and the same precautions practiced on any traveling brake system loading two fixed lines over the edge. Each half of the parallel system MUST be able to survive the failure of its partner in both fixed brake and traveling brake sce
narios in order to fully pass the all-important critical point test. It is
not enough to say that we have never had any problems with our system. Unfortunately, we hear this much more than we want. Indeed, only the unexpected and unanticipated failure of one half would spotlight the inherent weaknesses in your system. Then it would be too late.
In the next issue we'll look in detail at the potential fall distance in the various systems we have discussed in Part 1. The two-tensioned
rope system has many advantages, but at the same time, many dis advantages. Again, we see it as a tool for making roped endeavors
safer in the long run. If you have comments or questions regarding
this subject please write us on Facebook (Ropes That Rescue). We Discussion:
welcome your input as we all enter the queue.
■ In this system, parallel ropes on separate anchors have differing roles: One is the main with 100% of the load and the other is a slack belay rope which
is managed with the least amount of slack possible to limit fall dis
Thanks to Ken Phillips (far right in the title picture) and his team at the US
tance in the event of main line failure.
National Park Service - Grand Canyon.
main line and associated impact forces.
All photos and Illustrations from RTR collection by the author including Grand Canyon National Park Service training with RTR.
• Passes the CPT if the belay is able to survive the failure of the • Easier to lower and raise single element rather than two as in Two
Rope, Twin Rope, Dual Rope and Double Rope systems.
■ No pendulum issues with two loaded ropes. • Slack belay rope is un-tensioned so harder to cut rope accidental
ly-
• In traveling brake mode, easier for attendant to control one rope
rather than two.
ISSUE 63 TECHNICAL RESCUE
A Young Person's Guide to
Two-Tensioned Rope Systems
w
Part 2
of Ropes that Rescue (RtR) www. ropesthatrescue.com
s StOOrn Ijigh Sky Tower (Ne
■C
. S
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We left off In Part 1 with the definition of a TTRB or "Two-Tension
Rope Belay" for the phenomenon of each half of a TTRS holding the entire load plus the resulting impact force if the other failed. Unlike
With Two Rope/Twin Rope Combinations, there is an obvious difference in the system when raising and lowering. When lowering, the system is 50/50
but during the raising, the existence of only one pulley system or raising
the conditional belay, this system relies on each half of the system to arrest
system lends itself to a twin rope. This was the system we used with National
any fall ensuring that the system will pass the critical point test.
Park Ranger, Butch Farabee back in the early 80's. The friction appliances
ROPS
VARIATIONS IN TWIN ROPE TWO Rj^PB TWl N
50%
50%
So, where are we going with all of this? Are we headed towards a
were figure of eight rings with a prusik in front to catch the load if one half
dichotomy of sorts within rescue-dom and is there a ptace for TTRS within
failed {■). The rationale here especially with the tandem prusik belay was that
our discipline? I feel that the honest answer to that is a resounding YES. but
all the slack could be taken out of the rope through a pulley just behind the
in the same breath, I would have to set forth that the TTRS is not the
TPB so it was believed that there was no need for a second duplication of the
panacea for all rope rescue applications. Also keep In mind that what the
raising system. The potential fora huge fall during the raise is more acute
Locliaber Mountain Rescue Team does on the side of Ben Nevis in the middle
than in other systems discussed here.
of a nasty, bleak winter to lower an injured climber off will be substantially different that which the San Bernardino (California) Sheriff's SAR team will do in an underground abandoned mine shaft rescue. Each team given their
own exclusive environment will have solutions warranted from years of wisdom and know-how - and from having performed so many rescues in the past. As we have come to see it, the TTRS is a tool in the tool bag. We don't use it all the time but rather, only when it is THE tool for the job.
Think for a moment about all the places that we still employ a single loaded main line and a slack belay line? • Solo and semi solo rescue pick offs • Edge transitions under a high directional • Offsets (or deflections) • Highlines (Kootenay and other)
There are probably countless others that warrant the use of a single main line with slack belay line. What about all the variations being employed out
there as well. Are there any? VARIATIONS IN TWIN ROPE The following variations exist within rope circles:
0
TWO ROPE/TWIN ROPE COMBINATIONS
0
NON-IDENTICAL TWIN ROPE
0
DELAYED LOADING TWIN ROPE: 1
HI - LO
2
2-HI
3
2-LO
TECHMICALRESCUE ISSUE 64
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In Non-Identical Twin Rope systems there is a variation in the tension
pulley in the AHD. Care should be taken at this point to protect the rescue
between both rapes. Of course, in the illustration, 80 on one and 20 on the
package from a huge potential fall over the edge since the slack belay line is
other is completely hypothetical. With two independent operators of two friction appliances (like the MPD) it is extremely difficult to get this sharing
VARIATIONS IN TWIN ROPE
anywhere around those numbers. Too often it ends up 70/30 and then an
instant later 55/45, then 50/50 then 60/40. It takes a good amount of skill
(TRANSiTiONINGTHE EDGE)
in two brake operators to make this anything other than a continual battle to lower the rescue package down. Yet, I have seen prominent rope instructors
NG TWff-J
teach this technique using two MPD's as the brake.
100%
VARIATIONS IN TWIN ROPE
80%
^20%
80%
20% elevated at this point! We use the AZ7TK set of fours to give the belay line a temporary high point whilst the edge is being negotiated in either up or down mode. The main line still has 100% of the load at this point. Notice the blue belay line is still dotted indicating that it is still unloaded as in a single rope
1 In Delayed Loading Twin Systems, the belay remains dedicated through the edge transition process and the main line takes 100% of the load as we would in a standard single rope system (discussed in part 1). Once the rescue
system.
VARIATIONS IN TWIN ROPE f RANSITIONINGTHE EDGE)
package is over the edge a ways (and that will vary as well adding to the quandary) tension is added to the belay line, turning the system into a TTRS.
This eliminates or greatly reduces the back and forth fighting between ropes going in opposite directions under an artificial high directional (like the Arizona Vortex) during times when the belay and the main are moving paradoxically.
The illustrations that follow show the progression through what we refer to as "paradoxical movement" when approaching an AHD at the edge. The belay (blue dotted line not under tension) will belay the rescuer out to the edge while the main line takes up slack. Belay is going out and main is coming in - again, paradoxically.
VARIATIONS IN TWIN ROPE (TRANSiTiONINGTHE EDGE) r-EL-AY^^ LOAiXNCi TWIN K.OPG
As the attendant reaches the edge they are ready to load 100% onto the
main line. The pulley system shown is if there is a casualty in the litter which may need to be lifted to where the yoke knot is just below the high directional
32
ISSUE 64 TECIIHICALRESCUE
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Then, at a prescribed location somewhat below the edge, tension is added
VARIATIONS IN TWIN ROPE
to the belay in a true TTRS or Non-Identical Twin Rope fashion. The belay
(TRANSITfONINGTHE EDGE)
will need its own set of low directionals to reduce friction (something we never do in a true single rope system as we want to absorb energy in the
VARIATIONS IN TWIN ROPE rTRANSITIONINGTHE EDGE)
So what if any are the indications for the TTRS? Being the digresser that I am, lets return to Amor Larson.
LONG LOWERS: (>100M) As much as Amor resisted two tensioned ropes, he did see the advantages in belay line). This procedure is called a High-Low Delayed Loading TTRS- It
providing some tension In the belay line during extra long lowers. For contextual
remedies many of the issues with using a TTRS throughout the paradoxical
reasons, lets define what is meant by '"tension" here. Arnor would teach the use
motion process at the top leading to or away from the edge.
of a friction appliance on the belay line (anathema, some say) to take some of
Other variations on this theme are the 2 - HI Delayed Loading TTRS. With
the slack out of the belay rope for lowers of, say, over 100m. So in these cases of
it, the belay still acts as the safety while the rescue package approaches the
what was called an extreme lowering, the belay line is slack and moving over the
edge and then is added to the AHD when at that location. So paradoxical
edge. With every meter that goes over the edge, more and more fall potential is
motion is still part of the procedure for this technique.
introduced into the system in the event of a main line failure. The farther down the rescue package got, the more exposed to a huge fall. The reason? Rope
VARIATIONS IN TWIN ROPE (TRANSiTIONING THE ED" I
stretch in the belay line. So, to reduce this fall potential is to introduce just
enough back-tension via a friction appliance distal of the belay to hold the actual weight of the belay rope itself. In that way, excess slack is controlled. The way
the belayer knew just how much friction to apply to the belay was to watch the actual main line brake, If the belayer applied too much friction on the belay, the main line brakeman felt like they needed to reduce their brake's friction. Then they knew you were turning the operation into a partial TTRS. All the belayer had to do while applying this tension via the friction appliance distal of the belay was watch the main line friction appliance. They continually talked to each other. Basically, the belayer was holding up the weight of the belay rope as it got longer and longer. But it is important to realize here that the belay rope was NOT holding any part of the rescue package mass in this practice. It was undisputed that without this belay friction appliance, the rescue package would fall an enormous distance proportional to the amount of rope out over the edge. With
the friction appliance pulling back on the belay rope, the fall was reduced, but of course not eliminated,
ROPE STRETCH IN A STANDARD RESCUE BELAY:
Now what about the belay rope in a rope rescue system (200 - 280kg)? What characteristics should it have? Stretchy to absorb energy? Or low stretch to In the 2 - LO variation on this (above right), an important distinction is made in that the ropes (belay and main) can both move "similarly" instead of
reduce fall distance? To me, there has always been a symbiosis between shock absorption and maximum arrest force in a two rope system. Too stretchy of a
paradoxically. Some like the simplicity of this technique since the TTRS can
rape and your fall distance will be increased. That translates into hitting things
be used right out of the gate. No ropes moving in juxtaposition or anything
on the way down as you fall. Not good. Too static and you run the risk of a high
like that. Of course the lack of a high directional makes this a bit
impact force on the entire system and consequently blowing an otherwise
cumbersome, but this was the mainstay in decades past for many mountain
dubious anchor. In long lowers, the problem is significantly worse. Using
teams.
dynamic climbing rope for a belay (or even a TTRS) on a long lower would be
suicide. The fall would be exacerbated due to the fact that the climbing rope would have to stretch enormous distances with that much slack belay rope in the system.
In the highlands of northern Arizona we use a 11.1mm {7/16") diameter polyester rope that has less stretch than nylon static kemmantle rescue rope
(having less than half the elongation). The reason is because we feel we can absorb the energy of a fall on either end of the long belay rope but have little absorption In between. On the belay function end, we use either tandem prusik 34
ISSUE 64 TECHNICALRESCUE
belay (no LRH) or the MPD, and on the rescue package end, we are relying on the yoke knot (doubled long-tailed bowline), the litter bridle (the AZ Tri-Bridle) and the "sloshiness" of the attendant/patient package to absorb gobs of energy. This reduces the length of the fall on our huge sandstone cliffs. ROPE STRETCH IN ATWO-TENSIONED ROPE BELAY: Similarly, if each half of a two-tensioned rope system "belays" the other, then it
would only make sense to also have minimal rope stretch in the surviving element since to use the opposite would lead to a larger fall. In my view, this is acute in anything over about 70M but that figure could be adjusted downward to 50M if the rope you are using is a semi-stretchy nylon static kernmantle. Many rope manufacturers use the term "static" to delineate their nylon ropes but I prefer to use the terms low stretch, medium stretch and high stretch- Most static ropes today are not low stretch but rather medium stretch. Sterling Rope Company makes a truly static rope called HTP ("High Tenacity Polyester") which is also very popular with worldwide rope access technicians and US, Canadian and Australian/NZ rope rescue teams. The HTP is also very abrasion resistant on our stone.
At 10% of its MBS (manufacturers breaking strength) it stretches only 2.9% compared to 6% for nylon static (by the same manufacturer). HTP will stretch
1.7% at a load of 1.4kN (300#) whereas nylon static will stretch to 3.1% at a load of 1.4kN (300#). So. bottom line, the rope you use is important in the full equation, but more acute in the long lower. So, whether in Yosemite Valley or on Ben Nevis where lowers are extreme, the stretch in the rope becomes a major consideration in a two tensioned rope lower.
COMPARISON: So, how far will we fall with all of these differing systems which have quite frankly given me a headache in writing this! I have done a comparison using the elongation factors for very low stretch HTP or similar. These are rough comparisons to be sure. However, if you are using nylon rope for your main/belay
lines, the fall distance would be worse than those shown here. To me, that is a huge concern on a long drop.
We are then comparing three differing, previously discussed plans for the long lower of over 5OM to 70M again depending on the rope (amount of stretch) you use:
0SINGLE ROPE LOWERING WITH A SLACK BELAY LINE El SINGLE ROPE LOWERING WITH FRICTION APPLIANCE IN FRONT OF BELAY LINE
B TWO-TENSIONED ROPE SYSTEM WITH 50/50 LOAD SHARING
TECHrllCALRESCUE ISSUE 64
ROPE RESCUE
www.trescue.com
la) SINGLE ROPE LOWERING WITH A SLACK BELAY LINE The Set Up:
Discussion: Here we would expect the belay rope to
be hanging free completely unloaded as we are accustomed to in many situations in rescue work. In the illustration, the red line under
tension is the main line and the blue dotted line is the belay completely unloaded. The topside black zig-zag line is the friction appliance and the blue circle B is the belay station.
Notice the variations in amount of rope out: 10M, 40M, 70M and 100M.
These drawing are not to scale.
lb) SINGLE ROPE LOWERING WITH A SLACK BELAY LINE Drop Distance:
; Discussion: Main line is failed and load quickly transfers to slack belay line. Obviously, the more slack belay line that is out over the edge will affect the
7CM
drop distance.
Other factors like the nature of the rope and the mass will determine fall
I OEM
distance as well. L L
D I
isn tvt» f\
S T
A
N C E
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ISSUE 64 TECHfJICALRESCUE
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2a) SINGLE ROPE LOWERING WITH FRICTION APPLIANCE IN FRONT OF BELAY LINE The Set Up:
Discussion: Here, the belay line itself is being held up by a distal friction
p
appliance. You can see the addition
e
of this topside black zig-zag line on
the blue belay line. A second person to manage this belay line friction may be needed (second blue person) The topside black zig-zag line on the main line is the friction appliance and the blue circle B is the belay station.
Notice the variations in amount of rope out: 10M, 40M, 70M and 100M. Again, all drawings are not to
T E w
FRfCTION APPLEANCE ADDED IN FRONT OF BELAY TO HOLD WEIGHT OF BELAY RORE
I A
7CM
L ■■ CM
F
A L
L
scale.
D S T A
N C
2b) SINGLE ROPE LOWERING WITH FRICTION APPLIANCE IN FRONT OF BELAY LINE DROP DISTANCE:
O T
Discussion:
E
Main line is failed and load quickly
N
transfers to beiay line. Drop distance is reduced as all obvious slack in system has been eliminated due to topside friction appliance holding the weight of the
belay line. Other factors like the nature of the rope and the mass will determine fall distance 3S well.
This was the system that Arnor Larson ascribed to with the Brittish
Columbia Council of Technical Rescue
F
A L L
D I
S
T A
N C
B
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ISSUE 64 TECHNICALRESCUE
ROPE RESCUE
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3a) TWO-TENSIONED ROPE SYSTEM WITH 50/50 LOAD SHARING THE SET UP:
Discussion:
Here a true 50/50 TTRS exists and the two halves are synonymous. This will put at least half of the mass (200kg - 280kg) on each system. This in turn will stretch the corresponding system with at least
100kg to 140kg depending on how the friction is applied by the two brakes on top.
Notice the variations in amount of rope out: 10M, 40M, 70M and 10OM. These drawing are not to scale.
3b) TWO-TENSIONED ROPE SYSTEM WITH 50/50 LOAD SHARING DROP DISTANCE:
p
Discussion:
o
One line is failed in the 50/50 TTRS
T
and load quickly transfers to surviving
E
line.
N
«.-. *-] 1
IC
f
KM
|
-
I
r
;
': f
i
Drop distance still occurs as each f
half is only stretched to half the actual mass being lowered (or raised). Other factors like the nature of the rope and the mass will determine fall distance as well.
A
3M
L
F
A
i
J ^ ■::..-. r
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COMPARISON OF ALL THREE Opposite Top; you can see the comparison of all three methods we have discussed in Part 2. Discussion:
0 The greatest fall, seen on the far
•
1CO.1 ;
(
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L
D 1
s
s
left of each, is the single rope method
T
of belaying using a totally slack belay
A
line. The drop is significant and again
N
determined by Hie belay technique
C
and the nature of the rope used.
■*
•
E
4
0 The middle example shows the dis
)
tal friction appliance holding back on
the belay line as it is increasing in length over the edge. Note that in the 10M, 40M and 70M many teams
0 The far right example above shows the definite advantages of a true TTRS
would not apply this friction appliance on the belay line but would apply back
by the fact that fall distance is drastically reduced. But, it should be noted
tension by other means not discussed in Pt 2.
that it is NOT eliminated entirely.
4fl
Ifyj
ISSUE 64 TECHHICALRESCUE
ROPE RESCUE
www.trescue.com
Conclusion: While much has been covered in these two articles on the Two-Tensioned Rope
Systems, it is by no means complete. Much more could be written. The preponderance
of variation touched upon in these two articles appears at first glance to present a quagmire of disparate methodologies. So. as part 2 finishes up in this issue we are not faced with the quandary of perhaps not enough choices -- but too many. The variations on the TTRS theme appear to be boundless. These of course give the true rope technician endless opportunities to explore the vast world opened up with a
TTRS. To be sure, the introduction of devices like the MPD have spurred the interest in this subject. Up until this point, a twotensioned rope belay was not possible without the introduction of secondary adjunct systems to guarantee the
survivability of the half of the rope system in the event of the other half fails. The ultimate question then is to understand when to use a TTRS and when not to. To the seemingly unbiased rope rescue instructor, that understanding is somewhat mired by the apparent stampede to instigating this system by
failure of one half of the TTRS. QpinioniThe "human element" is always a
TTRS proponents. This should be resisted until the jury is in on devices like
wee bit dodgy if you asked me. People still fail to react in lock step with the
the MPD in particular. Questions remain about whether the operator of
printed instruction manual, don't they?
appliances like this will ultimately let go of the release handle during the
So....queue up for the quandary.
|T
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TECHf!ICflLRESCUE ISSUE 64
16m/S floors
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■II
