response of some 3:1 haul systems to excessive...

Response of Some 3:1 Haul Systems to Excessive Loading Thomas Evans, [email protected]

SAR3, http://sarrr.weebly.com/

Abstract:

Haul systems are used when extra force is required to raise a load, so they are frequently

capable of generating large forces. Some haul systems are able to generate enough force to either

break components of systems or load the system enough that system components start to behave

differently (e.g., prusiks start to slip). Knowing how haul systems change or break with high

loading will help identify overloaded systems and determine how safe the systems are.

Presented here are observations of 3:1 haul systems built with three different ropes in two

configurations pulled with a hydraulic ram: (1) During a haul, and (2) When the progress capture

prusik is holding the load.

New unused rope was donated by Pigeon Mountain Industries (PMI), and included

11.5mm Isostatic, 11mm Classic Sport Max, and 11mm Classic Pro EZ. In addition, PMI

donated new unused 8mm accessory cord. The rope and cordage were cut into predetermined

lengths and used to build inline 3:1 haul systems (Z-rigs). The systems were pulled to failure

using a hydraulic ram at CMC Rescue in Goleta, CA using a calibrated Omega load cell.

The haul systems did not behave as expected, with results depending on the rope type and

system configuration.

When haul systems were pulled in the hauling configuration, the Isostatic rope broke at

the knot at the load end (average of 20.4kN or 4577lbs, N=12), the Classic Pro EZ rope usually

showed prusik slippage with occasional knot or prusik breakage (average 20.2kN or 4540lbs,

N=13), while the Classic Sport Max yielded perpetual slippage of the prusiks with a peak force

average of 21.6kN or 4847lbs (N=11).

When haul systems were pulled during a reset the results were mixed. Isostatic rope often

yielded broken mantles (N=11) or a broken prusik (N=2), and out of 16 observations, the rope

was cut by the prusik twice. Isostatic rope broke with an average failure strength of 14.6kN or

3293lbs (N=16). The Classic Pro EZ usually displayed prusik failure (N=12) with occasional

mantle failure (N=3) and an average failure strength of 15.2kN or 3408lbs (N=16). The Classic

Sport Max most frequently displayed prusik failure (N=7) with occasional mantle failure (N=3)

and an average strength of 15.6kN or 3498lbs (N=10). All haul systems in all configurations

displayed prusik slippage prior to the failure of any system component (prusik, mantle, or rope).

There is no “one” behavior pattern for 3:1 haul systems. Notably, the polyester rope

(Isostatic) behaved markedly differently than the other two nylon ropes (Classic Pro EZ and

Classic Sport Max). On all rope types, prusiks slipped at least once before eventual failure of the

prusik, mantle, or rope, but prusiks slipped at different forces in each case, with additional slips

at higher forces. In short, the traditional prusik clutch effect was observed only sometimes

(Classic Sport Max), or not at all (Isostatic). Lastly, the forces at which some system components

broke were low enough that some agencies may not have the required strength to achieve the

Static System Safety Factors outlined in their SOPs or SOGs. Clearly, the inline 3:1 haul system

is safe and effective due to its extensive history of use, but it is important to acknowledge the

variability in behavior and actual strength of the system.

Introduction:

Given the choice, most rescuers would prefer to lower patients rather than raise them; lowering is

faster, requires less equipment, and is physically easier. Occasionally, due to the geometry of the

environment and patient location, a raise is preferable, so nearly all teams train to perform raises or hauls.

This necessitates building and operating systems that meet the strength requirements of our organizations.

There are two dominant philosophies of how to ensure systems are “safe enough” for use, the

adoption of a predetermined static system safety factor (SSSF), or building systems with load limiters

(e.g., Yates Screamer) so the system can never reach high forces where component breakage could occur

(Mauthner 2014). In either case, many haul systems can generate forces that surpasses both the maximum

force used to calculate the SSSF or trigger the load limiter. Consequently, it is useful to know how haul

systems behave when loaded more than they were designed for, so we know how to identify when

systems are experiencing forces that should cause us concern.

This study focuses on the inline 3:1 haul system (Figure 1), because it is most often used in the

field and written about in training manuals (Table 1). Presented here is a suite of empirical observations

of inline 3:1 haul systems (Z-rigs) loaded until component pieces break or slip, in two configurations: (1)

During hauling, and (2) When the load is held with a single progress capture prusik. The goals are to

determine how systems respond to extreme loading, what the forces required to cause changes in system

operation (slippage or breaking pieces) are, and the difference in responses when using different

equipment combinations. (Only three combinations were observed here due to time limitations and

equipment availability.)

Figure 1: A frequently taught and used version of the inline 3:1 haul system (Z-rig) built with two

pulleys and two prusiks. Many other configurations are possible; this configuration appears most

common in training manuals.

It should be noted that the systems observed here may not, and probably do not, behave similarly

to other haul systems built in other configurations or using different equipment (e.g., a Rescucender vs. a

three wrap prusik). For example, the results here would not be comparable to building a 3:1 haul system

with an integrated MPD and using a Rescucender to reset the haul system. While the results have limited

applicability, they do describe the behavior of one common system, and give a general idea of how other

haul systems may work. Extrapolations from the data presented here should be tested empirically, but

useful extrapolations are possible. Other haul systems built with pulleys and prusiks may have similar

behaviors when loaded (e.g., prusik slippage, prusik failure, or mantle damage, etc.).

Materials and Methods:

New unused rope and cordage was donated by Pigeon Mountain Industries (PMI), the details of

which are displayed in Table 2. The accessory cord was cut into forty-two lengths 41” long, forty-two

lengths 48” long, alternating between lengths along the spool. Each piece was tied with a double

fisherman’s knot into a prusik loop. All knots were tied by the author for consistency. The rope was cut

into 129” lengths and used to build haul systems in two configurations: (1) During a haul, and (2) With

the load held by the progress capture prusik.

Table 1: Citations and page numbers for training documents that teach the inline 3:1 haul system (Z-

rig). Within these citations numerous pieces of equipment are used to build the system, so not all of

the citations teach the inline 3:1 haul system built with two pulleys and two prusiks.

Citation Pages Citation Pages

Black 2013 182 Marbach and Tourte 2002 240, 295

Brennan 1999 227-228, 242-244 Matthews 2009 160-161, 169

Briggs 2013 145, 154-169 Merchant 2007 147-149

Brown 2000 259-261 Pendley 2003 39

CMC 1997 42-43 Rhodes 2013 80-82, 126

Fasulo and Clelland 2011 130-133 Roop et al. 1998 237-243

Federation Francaise de

Speleologie 2006

60-63 Shepherd 2007 242-245

Frank 1998 94-96, 101, 112 Smith and Padgett 1996 245

Frank 2014 143, 150, 155 Tyson and Loomis 2006 131-141

Hempel and Fregeau-

Conover 2001

216 Vines and Hudson 2004a 279, 282, 284-285,

291-292

Hudson and Lawrence 1988 167 Vines and Hudson 2004b 96

Lipke 1997 59, 63, 117 Warild 1990 106

Table 2: Details of the software donated by PMI, including; type of rope or cord, diameter, lengths of

spools, total lengths donated, and the sheath/core composition of each product.

Rope/Cord Diameter (mm) Lengths (m) Total Length (m) Sheath/Core Composition

Isostatic 11.5 46+92 138 Polyester/Polyester

Classic Pro EZ

(EZ Bend)

11 46+92 138 Nylon/Nylon

Classic Sport Max

(Pit Rope to cavers)

11 130 130 Nylon/Nylon

Accessory Cord 8 100 100 Nylon/Nylon

Pull testing took place at CMC Rescue in Goleta, California. They generously donated their

testing facilities and help of staff to run the equipment. The two haul system configurations were built on

the CMC drop tower with the following components:

1. Figure 2A: Haul systems were built with SMC steel carabiners (46kN) and two 3” NFPA G rated

pulleys (36kN) connected to the load anchor with a long tailed bowline. Short 8mm three wrap

prusiks were used in all trials with the haul prusik placed 12” from the bowline. The tail of the haul

line was tied off to a carabiner with a clove hitch with an overhand safety. Force was applied to the

anchor pulley because initial tests demonstrated that hauling on the haul side of the system only

pulled the slack/stretch out of the system rather than resulting in component breakage or changes to

system performance. These two approaches are functionally equivalent.

2. Figure 2B/C: Haul systems with a bowline with a long tail on the load end, with long 8mm three wrap

prusiks (Figure 2B). The pulleys used were 2” SMC pulleys, and the haul prusik was a spare 6mm

prusik. One pulley and the 6mm prusik were removed for most trials (Figure 2C) because they were

never loaded so were clearly not important in system function in the configuration loaded. Force was

applied to the load end of the line.

Figure 2: Configurations of the inline 3:1 haul system observed. (A) During a haul, (B) Original

configuration with the load held by the progress capture prusik, (C) The configuration used during

trials with the load held by the progress capture prusik.

Haul systems were pulled at a rate of 8” per minute with a hydraulic ram, with a sampling rate of

200 measurements a second using a calibrated Omega LCCA-15K load cell. For both sets of observations

the load cell was placed where it measured the force applied to the prusik carrying the load.

Data were scaled for samples pulled in the hauling configuration because the load cell was

experiencing only two thirds of the total peak load that the load end of the system experienced. The data

was multiplied by 3/2 to yield the maximum peak load. For samples pulled in the configuration

simulating the load being held by the progress capture prusik, no data scaling was needed.

It should be noted that the sample sizes for each trial are small (low teens), so the results

presented here are subject to the vagaries of small sample sizes. This means that the precision of the

numbers presented is suspect, however the large scale results probably have merit.

Results:

The raw and processed data are available for your use; please e-mail the author, and any materials

you are interested in will be sent as soon as possible.

Table 3 (at the end of the paper) provides the details for each sample pulled with the inline 3:1 in

the hauling configuration including: sample number, measured peak load, scaled peak load, breaking

strength/peak load in kN, notes on prusik slippage during pulling, and any location of failure if present.

Table 3a details Isototatic rope results, Table 3b Classic Pro EZ, and Table 3c Classic Sport Max (Pit

Rope).

Systems built with Isostatic rope broke where the rope entered the knot (bowline) in the load end.

The average strength of twelve pulls (N=12) was 20.4 kN (4577 lbs), with a standard deviation of 1.7 kN

(389 lbs), maximum of 23.8 kN (5357 lbs), minimum of 17.6 kN (3965 lbs), and a range of 6.2 kN (1392

lbs). These samples were characterized by prusiks slipping and sticking at ever greater values resulting in

ever higher forces culminating in failure at the knot. In other words, prusik slippage did not keep forces

low enough to prevent component failure.

Systems constructed with Classic Pro EZ (EZ Bend) rope were characterized by prusiks slipping

until the testing apparatus ran out of throw or a component broke. Two samples broke at the knot, and two

broke at the haul prusik, with the rest not failing at all (N=13). For most trials no part of the system broke,

rather the rope stretched, prusiks slipped, and the forces stayed lower than trials using Isostatic rope. The

average peak load for Classic Pro EZ trials was 13.5 kN (4540 lbs), with a range of 9.9 kN (3328 lbs),

which is a large range given the number of samples (N=13). This suggests that prusik slippage kept the

forces lower, though the rope or prusiks that did fail broke at lower values than the breakage of a bowline

in Isostatic rope.

Similarly, systems built with Classic Sport Max (Pit Rope) displayed prusik stick/slip behavior

until the apparatus ran out of throw. At no point did any component fail, though the peak loads that

developed were high. Two samples displayed continuous slipping when pulled, whereas the other nine

samples displayed prusik stick/slip behavior. Those samples that stick/slipped (N=9) developed high peak

loads, minimum of 20.0 kN (4502 lbs) and a maximum of 26.3 kN (5916 lbs). Thus it appears that the

prusik clutch effect was partially working for systems built out of Classic Pro EZ and Classic Sport Max

rope with prusiks slipping enough to prevent system component failure. The value at which prusiks first

slipped was highly variable, and for many samples consecutive prusik slips occurred at higher forces.

Consequently, the idea that prusiks slip at around one value was not observed in most samples (only

observed in two samples made from Classic Sport Max), so the clutch effect should no longer be taught

simplistically to novice riggers.

Table 4 (at the end of the paper) provides the details for each sample pulled with the load held by

the progress capture pursik, including: sample number, measured peak load, breaking strength in kN,

notes on prusik slippage during pulling, and location of failure. Table 4a details Isostatic rope results,

Table 4b Classic Pro EZ (EZ Bend) rope, and Table 4c Classic Sport Max (Pit Rope) rope.

Systems built using Isostatic rope (N=16) displayed a range of failure modes after prusiks slipped

a few times. The rope mantles broke in eleven samples, two prusiks broke, two prusiks cut the rope in

half, and in one sample the prusik slipped enough that no failure occurred before running out of throw.

The average breaking strength across all failure modes was 14.6 kN (3293 lbs) with a standard deviation

of 0.5 kN (120 lbs), maximum of 15.8 kN (3560 lbs), minimum of 13.7 kN (3074 lbs), and a range of 2.2

kN (486 lbs).

Systems built from Classic Pro EZ rope (N=16) provided similarly consistent results. Twelve

samples broke at the prusik, three resulted in mantle failure, and one sample had a prusik slip more or less

consistently until the apparatus ran out of throw (this sample was removed to calculate descriptive

statistics due to the low peak load of 5.6 kN). The average breaking strength was 15.8 kN (3552 lbs) with

a standard deviation of 0.6 kN (137 lbs), a maximum of 16.4 kN (3684 lbs), minimum of 14.1 kN (3181

lbs), and a range of 2.2 kN (503 lbs).

Systems built with Classic Sport Max (N=10) showed similar failure modes with seven samples

breaking at the prusik and three breaking at the rope mantle. The average breaking strength was 15.6 kN

(3498 lbs) with a standard deviation of 0.7 kN (162 lbs), a maximum of 16.7 kN (3749 lbs), a minimum

of 14.3 kN (3222 lbs), and a range of 2.3 kN (527 lbs).

The small standard deviations and ranges for all three sample sets indicate that these populations

show a remarkable consistency in their breakage strengths, indicating that all three data sets should be

largely indicative of the results if larger sample sizes were employed.

Discussion and Conclusions:

The author was taught that overloaded prusiks would all slip at around 5.3 kN or 12000 lbs, a

behavior that was not observed here. What is clear is that the ways the systems react to high forces vary

with the different equipment used. This means that there is no one piece of advice that applies to all rope

types and haul systems. These results underscore that variability in haul system behavior is important to

acknowledge and teach early in a rescuer’s training.

Generally during hauling, prusiks slip prior to any component breaking, however the slip can

occur at a variety of forces, and could occur once or many times prior to part of the system breaking

(assuming continued load). When a system component breaks it is usually the knot at the load (frequently

this is a long tail bowline at a litter bridle, etc.) or the haul prusik. For the Isostatic rope (all polyester

construction) a prusik can even sever the rope with very little warning (a prusik slip). It should be noted

that during a haul operation the load is over the edge and there is edge friction between the knot in the

load end and the haul system. This means that the force applied to the system is highest between the haul

system (e.g., haul cam/prusik) and the edge because the force applied over the edge is comprised solely of

the load. Similarly, the haul prusik in an inline 3:1 haul system only experiences 2/3 of the force imparted

to the load (ignoring friction). Consequently, it is a matter of the force applied, where it is applied, and the

friction inherent in the system that will determine if the haul prusik or the knot will fail first.

While the progress capture prusik is holding the load, during extreme loading events the rope

mantle fails, a prusik breaks, or sometimes the rope is cut in half by the prusik. All three of these

responses happen at more or less the same forces so it is impossible to tell which will occur first with new

equipment.

What is important is that the range of responses to loading in both configurations is wide, and the

responses occur at loads that are the same. This means that haul teams are likely to see a prusik slip

(hopefully they notice!), then after that any number of system changes could occur. There could be more

prusik slippage, a prusik break, a knot break, or the rope cut in half. In any of these scenarios having a

slipped prusik indicates that something bad could occur if something is not altered in the system (most

likely too much edge friction).

For organizations that have SOPs/SOGs with required SSSFs, these results can help calculate

what SSSF you actually have in this system. For a 1 kN load a 10:1 SSSF is maintained, however for a

2kN load the SSSF is not always above 10:1. This may or may not be a concern for your organization

depending on the loads permitted and the SSSF required. The take home message is, we may not have the

SSSFs we think we have with some haul systems.

This study was not designed to determine the differences in system responses based on different

rope fiber types, but it is clear that the Isostatic rope behaved differently than the Classic Pro EZ or the

Classic Sport Max. During hauling, the prusiks gripped stronger on the Isostatic rope with greater forces

developing, ultimately causing the knot at the load to fail. The two nylon ropes displayed far more prusik

slippage, so forces did not get as high. When the load was held by the prusik, the Isostatic rope displayed

considerably more mantle failures than the nylon ropes, and in two observations, the rope was cut. These

observations raise the question of if the different results are caused by the different fiber properties (e.g.,

polyester has a lower melting point, so prusik compression is causing failure due to heat generation and

partial melting?).

Consequences For Rigging Practice:

It is important to know how your equipment behaves during extreme loading because results vary

depending on the equipment used. Readers are encouraged to do their own testing (back yard testing is

great!!!) and publish the answers with ITRS or other permanent archive. Only three gear combinations

were used here, primarily focusing on the equipment used in organized cave rescue in the US. The

National Cave Rescue Commission gear caches primarily contain PMI Classic Pro EZ (EZ Bend) and

PMI Classic Sport Max (Pit Rope) rope, so this study was performed to determine how these ropes

behave for the author’s most frequent rescue rigging needs. However, these are certainly not the only rope

types in use in the US!

The author was taught that when prusiks are loaded they slip around 5.3kN (1200 lbs), thus

reducing the forces a system experience. In this way prusiks limit the load the system experiences during

loading. This phenomenon was called the “prusik clutch”. If prusiks behave in this way, prusiks would

not ever fail during a haul, but slip whenever overloaded. The results presented here show that the prusik

clutch phenomenon works only sometimes. While all the systems observed did display prusik slip under

load, prusiks slipped at different values, slippage occurred at different frequencies with continued loading,

and system component failure was not predictable based on prusik slip behavior. This means that a

slipped prusik generally indicates the system is overloaded, but it is unclear how the system will react to

continued loading. When teaching the prusik clutch concept, it is crucial to point out that prusiks do not

slip at the same kN or lbs value (there is variability) depending on the equipment used, and further clutch

behavior cannot be reliably relied upon to prevent breakage of system components, unless the prusik and

rope combination has been tested to see if continual slippage will occur (e.g., Classic Sport Max and 8mm

accessory cord).

Haul systems may have lower strengths than expected, so your SSSF may not be what you think.

Breaking the systems you use, and publishing the data, can help identify what SSSFs are being used in

practice.

It is possible to generate high forces in hauling operations. However, to do so requires ignoring

some big warning signs, the first of which is that it is incredibly difficult to raise the load! If hauling is

difficult, rather than adding mechanical advantage or haul team members, reduce friction in the system. In

other words, pay attention to the system in operation, when it gets too hard to haul, fix how the system is

rigged, rather than hauling so hard that prusiks slip. While this may seem trite, we have all heard stories

of systems rigged so tightly that prusiks slipped or “smoked” as they slid down the rope.

Acknowledgements:

This research would not have been possible without the continuing support of both PMI and CMC. They

are wonderful examples of cooperation between business competitors who both support research that can

improve the safety of all rescuers. Both should be commended for their service to the community. PMI

donated the software observed and CMC provided the facilities and personnel to facilitate data

acquisition. Cedric Smith and Mike Hohlmeier helped with data acquisition, and Sarah Truebe helped

manage samples and data throughout. In addition, Sarah Truebe provided invaluable editorial suggestions,

though all mistakes are solely the responsibility of the author.

Literature Cited:

Black, D., 2013. Canyoneering: A Guide to Techniques for Wet and Dry Canyons, Second Edition,

Falcon Guides, Guilford, Connecticut

Brennan, K., 1999. Rope Rescue for Firefighting, Fire Engineering Books

Briggs, Tom, 2013. Vertical Academy, Briggs, Milton Keynes, UK

Brown, M.G., 2000. Engineering Practical Rope Rescue Systems, Delmar, Thompson Learning, United

States

CMC Rescue, 1997. Rope Rescue Manual Field Guide, Third Edition, CMC Rescue Inc., Santa Barbara

California

Fasulo, D., and Clelland, M., 2011. Self-Rescue, Second Edition, Falcon Guides, Guilford, Connecticut

Federation Francaise de Speleologie, 2006. Cave Rescuer’s Manual, English Edition, Beta, France.

Frank, J.A., 2014. CMC Rope Rescue Manual, Revised Fourth Edition, CMC Rescue Inc., Santa Barbara,

California

Frank, J.A., 1998. CMC Rope Rescue Manual, Third Edition, CMC Rescue Inc., Santa Barbara,

California

Hempel, John, Fregeau-Conover, Annette, 2001, On Call: A complete Reference for Cave Rescue, 2001

Edition, National Speleological Society, Huntsville, Alabama

Hudson, Steve, Lawrence, Judi, 1988, Manual of U.S. Cave Rescue Techniques, Second Edition, National

Speleological Society, Huntsville, Alabama

Lipke, R., 1997. Technical Rescue Riggers Guide, Revised Edition, Conterra Technical Systems Inc.,

Bellingham, Washington

Marbach, G., and Tourte, B., 2002. Alpine Caving Techniques: A Complete Guide to Safe and Efficient

Caving, First English Edition, Urs Widmer, Switzerland

Matthews, J., 2009. Technical Rescuer: Rope Levels I and II, Delmar, Cengage Learning, Clifton Park,

New York

Merchant, D., 2007. Life On A Line: The Underground Rope Rescue Manual, Published by Lulu.com

Mauthner, Kirk, 2014, Moving Beyond 10:1 SSSF, Introducing Force Limiting Systems and Managing

the Right Risk at the Right Time, International Technical Rescue Symposium, Denver, Colorado,

November 6-9, 2014, 4 pages

Pendley, R., 2003. The Essential Technical Rescue Field Operations Guide, Third Edition, Desert Rescue

Research, Arizona

Rhodes, Pat, 2013. A Practitioner’s Study: About Rope Rescue Rigging, Rhodes

Roop, M., Vines, T., Wright, R., 1998. Confined Space and Structural Rope Rescue, Mosby Inc.

Shepherd, N., 2007. The Complete Guide to Rope Techniques: A Comprehensive Handbook for Climbers,

Falcon Guides, Guilford, Connecticut

Smith, B., and Padgett, A., 1996. On Rope: North American Vertical Rope Techniques, New Revised

Edition, National Speleological Society, Huntsville Alabama

Tyson, A., and Loomis, M., 2006. Climbing Self-Rescue: Improvised Solutions for Serious Situations,

Mountaineers Books, Seattle, Washington

Vines, T., and Hudson, S., 2004a. High Angle Rescue Techniques, Third Edition, Elsevier Mosby, St.

Louis, Missouri

Vines, T., and Hudson, S., 2004b. Field Guide to Accompany: High Angle Rescue Techniques, Third

Edition, Elsevier Mosby, St. Louis, Missouri

Warild, A., 1990. Vertical: A Technical Manual for Cavers, Second Edition, Speleological Research

Council Ltd, Sydney, Australia

Sample # Observed

Peak Load

(lbs)

Scaled

Peak Load

(lbs)

Breaking

Strength

(kN)

Prusik Slippage Notes Location of Failure

7-7-I 2947 4421 19.7 Two major prusik slips and one small prusik slip prior to knot failure

8-8-I 2878 4317 19.2 Three major prusik slips prior to knot failure

9-9-I 2924 4386 19.5 One major prusik slip and two small prusik slips prior to knot failure



12-12-I 2643 3965 17.6 Two major prusik slips and three small prusik slips prior to knot failure

13-13-I 3255 4883 21.7 Two major prusik slips prior to knot failure



2-2-I 3285 4928 21.9 Two major prusik slips and two small prusik slips prior to knot failure

3-3-I 3571 5357 23.8 Three major prusik slips and one small prusik slip prior to knot failure

4-4-I 3272 4908 21.8 One major prusik slip and one small prusik slip prior to knot failure

Average 3052 4577 20.4

Std. Dev. 259 389 1.7

Maximum 3571 5357 23.8

Minimum 2643 3965 17.6

Range 928 1392 6.2

http://sarrr.weebly.com/

Table 3a: 11.5mm Isostatic rope in hauling configuration.

All samples broke at the

knot (bowline) where the

standing line enters knot

Sample # Observed

Peak Load

(lbs)

Scaled

Peak Load

(lbs)

Peak

Load

(kN)


15-1-C 2934 4401 13.0 One major prusik slip prior to running out of throw

16-2-C 2567 3851 11.4 One major prusik slip and two small prusik slips prior to running out of throw

17-3-C 3390 5085 15.1 One major prusik slip and three small prusik slips prior to running out of throw

18-4-C 1492 2238 6.6 Continuous slipping (just under 1200 lbs), not stick/slip behavior

19-5-C 1828 2742 8.1 Continuous slipping (around 1300 lbs), not stick/slip behavior

20-6-C 3131 4697 13.9 Two major prusik slips and two small prusik slips prior to running out of throw

22-8-C 3504 5256 15.6 One major prusik slip and four small prusik slips prior to running out of throw

23-9-C 3124 4686 13.9 One major prusik slip and three small prusik slips prior to running out of throw

25-11-C 3210 4815 14.3 Two major prusik slips and two small prusik slips prior to running out of throw

21-7-C 3356 5034 14.9 One major prusik slip and four small prusik slips prior to knot failure

27-12-C 3711 5567 16.5 One major prusik slip and two small prusik slips prior to knot failure

24-10-C 3413 5119 15.2 One major prusik slip and two small prusik slips prior to prusik failure

26-13-C 3682 5523 16.4 One major prusik slip and four small prusik slips prior to prusik failure

Average 3026 4540 13.5

Std. Dev. 682 1023 3.0

Maximum 3711 5567 16.5

Minimum 1492 2238 6.6

Range 2219 3328 9.9


None

Table 3b: 11mm Classic Pro EZ (EZ Bend) rope in hauling configuration.

Broke at knot where

standing line enters knot

At prusik where load side

strand entered the bridge

Sample # Observed

Peak Load

(lbs)

Scaled

Peak Load

(lbs)

Peak

Load

(kN)


1-1-P 3001 4502 20.0 Two major prusik slips and seven small prusik slips prior to running out of throw

2-2-P 3502 5253 23.4 Two major prusik slips and four small prusik slips prior to running out of throw

3-3-P 3944 5916 26.3 Two major prusik slips and three small prusik slips prior to running out of throw

4-4-P 3615 5423 24.1 Two major prusik slips and five small prusik slips prior to running out of throw


6-6-P 3738 5607 24.9 Two major prusik slips and three small prusik slips prior to running out of throw

7-7-P 3646 5469 24.3 Two major prusik slips and six small prusik slips prior to running out of throw

8-8-P 3658 5487 24.4 Two major prusik slips and four small prusik slips prior to running out of throw


10-10-P 1653 2480 11.0 Continuously slipped down the rope with continuous minor stick/slip behavior

11-11-P 1424 2136 9.5 Continuously slipped down the rope with continuous minor stick/slip behavior

Average 3231 4847 21.6

Std. Dev. 870 1305 5.8

Maximum 3944 5916 26.3

Minimum 1424 2136 9.5

Range 2520 3780 16.8


None

Table 3c: 11mm Classic Sport Max (Pit Rope) rope in hauling configuration.

Table 4a: 11.5mm Isostatic rope in holding the load configuration.

Sample # Observed Peak

Load (lbs)

Breaking

Strength (kN)

Prusik Slippage Notes Location of

Failure

17-I-L 3220 14.3 Three major prusik slips and one small prusik slip prior to mantle failure Mantle

18-I-L 3560 15.8 Four major prusik slips and two small prusik slips prior to mantle failure Mantle

19-I-L 3332 14.8 Fourteen major prusik slips and eight small prusik slips prior to prusik failure Prusik

20-I-L 3138 14.0 Four major prusik slips and three small prusik slips prior to mantle failure Mantle

21-I-L 3197 14.2 Three major prusik slips and one small prusik slip prior to prusik failure Prusik

22-I-L 3435 15.3 One major prusik slip and three small prusik slips prior to mantle failure Mantle

23-I-L 3245 14.4 One major prusik slip and two small prusik slips prior to rope failure Rope Cut

24-I-L 3384 15.1 Six major prusik slips and one small prusik slip prior to mantle failure Mantle

25-I-L 3360 14.9 Ten major prusik slips prior to mantle failure Mantle

26-I-L 3342 14.9 Two major prusik slips prior to mantle failure Mantle

27-I-L 3284 14.6 Six major prusik slips and two small prusik slips prior to mantle failure Mantle

28-I-L 3383 15.0 One small prusik slip prior to mantle failure Mantle

29-I-L 3238 14.4 One major prusik slip and four small prusik slips prior to mantle failure Mantle

30-I-L 3074 13.7 Nineteen major prusik slips prior to running out of throw None

31-I-L 3280 14.6 Two major prusik slips and two small prusik slips prior to rope failure Rope Cut

32-I-L 3214 14.3 Seven major prusik slips and one small prusik slip prior to mantle failure Mantle

Average 3293 14.6

Std. Dev. 120 0.5

Maximum 3560 15.8

Minimum 3074 13.7

Range 486 2.2


Table 4b: 11mm Classic Pro EZ (EZ Bend) rope in holding the load configuration.


Load (lbs)

Breaking

Strength (kN)


Failure

1-EZ-L 1257 5.6 Continuous slipping, not stick/slip behavior None

2-EZ-L 3642 16.2 One major prusik slip and one small prusik slip prior to mantle failure Mantle

3-EZ-L 3508 15.6 Two major prusik slips and one small prusik slip prior to prusik failure Prusik

4-EZ-L 3621 16.1 One major prusik slip and one small prusik slip prior to prusik failure Prusik

5-EZ-L 3313 14.7 Three major prusik slips prior to mantle failure Mantle

6-EZ-L 3684 16.4 One major prusik slip prior to prusik failure Prusik




10-EZ-L 3181 14.1 Four major prusik slips prior to mantle failure Mantle







Average 3552 15.8

Std. Dev. 137 0.6

Maximum 3684 16.4

Minimum 3181 14.1

Range 503 2.2


Note: Sample 1-EZ-L was removed when calculating descriptive statistics

because it is a clear outlier in both peak load and system behavior

Table 4c: 11mm Classic Sport Max (Pit Rope) rope in holding the load configuration.


Load (lbs)

Breaking

Strength (kN)


Failure

33-P-L 3520 15.7 Two major prusik slips and one small prusik slip prior to mantle failure Mantle

34-P-L 3222 14.3 Two small prusik slips prior to prusik failure Prusik

35-P-L 3653 16.2 One major prusik slip and one small prusik slip prior to mantle failure Mantle

36-P-L 3527 15.7 One major prusik slip and one small prusik slip prior to mantle failure Mantle

37-P-L 3424 15.2 One major prusik slip and one small prusik slip prior to prusik failure Prusik




41-P-L 3258 14.5 Six small prusik slips prior to prusik failure Prusik


Average 3498 15.6

Std. Dev. 162 0.7

Maximum 3749 16.7

Minimum 3222 14.3

Range 527 2.3


response of some 3:1 haul systems to excessive...

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