The latest, greatest 2:1 hauling kit

Andy Wiesner wrote:

This is one of my favorite threads. It’s the one where less experienced wall climbers like myself get their mind blown by the Skot / Mark setup, then rack their brains to try and improve it, maybe waste a little money along the way (I offloaded my Jag at Rock and Snow Annex), learn some stuff, and then cheerfully concede defeat. Carry on!

Good times mate!!   White flag wave accepted!!!  

I just watched this VIDEO where there wire dog-bone snapped (at around 21:00). 

Skot is the one in the picture below 7x7 or 7X19? 

Thanks for checking it out. Cheers. 

Nice compact rig!  Going big wall climbing, are we?  

Question about the Micro-Trax on top - it's being used only as a pulley.  Do you find that the cam will accidentally close at times? That would be a real pain in the ass.  I use a regular pulley on top in that position, a big-ass 97% efficient pulley. 

Peter Zabrok wrote:

Nice compact rig!  Going big wall climbing, are we?  

Question about the Micro-Trax on top - it's being used only as a pulley.  Do you find that the cam will accidentally close at times? That would be a real pain in the ass.  I use a regular pulley on top in that position, a big-ass 97% efficient pulley. 

I think that's a Rock Exotica Omni pulley in the photo and not a Micro-Trax

Christopher Chu wrote:

I think that's a Rock Exotica Omni pulley in the photo and not a Micro-Trax

You are correct 

John Shultz wrote:

I just watched this VIDEO where there wire dog-bone snapped (at around 21:00). 

Skot is the one in the picture below 7x7 or 7X19? 

Thanks for checking it out. Cheers. 

I can’t possibly tell from this picture.  Count the wires in each strands and email me….

Here's a screen shot of the failed 2:1 haul system in TK's Native Son video, and another screen shot of the same system deployed a few days earlier lower on the route. The video was posted in April of this year. 

It's pretty clear (if you open the first picture and zoom in) that the wire draw broke at the main haul carabiner (the other end of the draw is still attached to the microtrax). This deserves more discussion here. I should think the best case, were that to happen under a full load, would be that the haul bags would fall, pulling the Basic ascender down, which would jank the person doing the hauling up into the omniblock pully. Darn spooky.

Andy Wiesner wrote:

Here's a screen shot of the failed 2:1 haul system in TK's Native Son video, and another screen shot of the same system deployed a few days earlier lower on the route. The video was posted in April of this year. 

It's pretty clear (if you open the first picture and zoom in) that the wire draw broke at the main haul carabiner (the other end of the draw is still attached to the microtrax). This deserves more discussion here. I should think the best case, were that to happen under a full load, would be that the haul bags would fall, pulling the Basic ascender down, which would jank the person doing the hauling up into the omniblock pully. Darn spooky.

The cable dogbone broke, not the carabiner.

Tyler was on space haul too. He was caught by the 2:1 ascender, which was connected to the hauler by Z cord.

Looks like Tyler also had like 190 feet of lead rope as a backup. That couldve been a ride with the end being a haul bag whip on his belay loop.

My guess is that the core shot rope wouldve busted and saved their lives. 

Christopher Chu wrote:

The cable dogbone broke, not the carabiner.

The text you quoted never said the carabiner broke.

Chris Cragsocks wrote:

My guess is that the core shot rope wouldve busted and saved their lives.

Not likely. The sheath isn’t much of the strength of the rope. The core (which was in good shape based upon what you can see in the Cid) would have held. (Though it's likely Tyler’s ascenders would have severed the haul line when the haul bag finished falling.)

Fail Falling wrote:

The text you quoted never said the carabiner broke.

My mistake.  Said wire draw, so I understood it as wire carabiner.

Not likely. The sheath isn’t much of the strength of the rope. The core (which was in good shape based upon what you can see in the Cid) would have held. (Though it's likely Tyler’s ascenders would have severed the haul line when the haul bag finished falling.)

The sheath is typically about 30% of the strength of an intact kernmantel rope.  If the rope was static with 4% elongation, a fall of 10m (distance along rope from bag to Tyler), and 100 kg bag, we're looking at a peak impact force of 24 kN.  If it was a dynamic rope with 30% elongation, maybe 3 kN.

Kevin and CC, I don't think the bags would fall more than a few feet unless there were a secondary failure somewhere in the 2:1 system. After the wire dogbone broke (primary failure), the hauling person tethered to the z-cord would be pulled up against the top pulley (Omni Block in this case), which would jam up the system and stop the bags from falling further. You guys seem to be debating what the secondary failure might have been.

In any case, the wire dogbone should not have failed in the first place ("not chill" as TK aptly put it) -- especially under what ought to have been relatively low loads.

I sorta wonder where the wired draw came from and if it was from a legit manufacturer.  If it was from someone like Climbtech I sure hope they sent it in for inspection.  Pretty hard to put that much force on that piece in even if they were space hauling.  Always scary when anything fails in a climbing situation.

I have a question.

Is it standard practice to place a quickdraw attached at the anchor and to the haul line as backup to the device? This assumes 1:1 haul techniques.

Assuming 2:1 haul technique, does the zed cord really count as a reliable backup to this type of failure? Surely, the strength of the cord matters.

Sometimes, I just use the zed cord as a foot stirrup rather than connected to my belay loop. In that case I’d better hope a knot jams in the Omni block otherwise my foot would probably break?

So would the zed cord backup situation really rely on a jammed knot to catch falling haul bags?

That doesn’t seem adequate.

Andy Wiesner wrote:

Kevin and CC, I don't think the bags would fall more than a few feet unless there were a secondary failure somewhere in the 2:1 system. After the wire dogbone broke (primary failure), the hauling person tethered to the z-cord would be pulled up against the top pulley (Omni Block in this case), which would jam up the system and stop the bags from falling further. You guys seem to be debating what the secondary failure might have been.

The assumption for our hypothetical was a case where the zed cord failed in sequence as well since without this assumption, nothing we're talking about regarding the haul bag fall length would make sense. But you are correct, this wasn't clear in our posts. 

Alex Fletcher wrote:

I have a question.

Is it standard practice to place a quickdraw attached at the anchor and to the haul line as backup to the device? This assumes 1:1 haul techniques.

It is best practices to place a draw between the anchor and the haul line as a backup. Whether people do this consistency is up to them and I certainly don't do this every time unless I'm bored and need something to do for a few seconds. In reality, that backup that goes to the haul line isn't going to do much if the connection between the anchor and the progress capture pulley breaks. In a 1:1 haul, what will stop the bags will be the last knot connecting the haul line to the anchor. There's always one at the end of the haul line, but whether there's one sooner than will depend upon how the person is managing their rope. And when you're at the top of the route, there's less likelihood that the end of the haul line is connected to the anchor

I don’t always use a backup draw either usually because I don’t have any left. I was always under the impression the purpose of the backup draw was to counterbalance the bag against the hauling person via their ascender used as the rope grab. Even without the draw wouldn’t the bag just land on the ascender hanging upside down from the belay loop (ideally) long before the knot at the top end of the haul line?

Alex Fletcher wrote:

Even without the draw wouldn’t the bag just land on the ascender hanging upside down from the belay loop (ideally) long before the knot at the top end of the haul line?

Assuming the climber is attached to the anchor, yes. If one is hauling at the top of the route and not attached to the anchor then it would be an interesting trip for them right off the edge. 

I want to chime in to address the failure of my 2:1 system that occurred on Native Son. I read this very thread back when Mark first posted it and procured the advertised wire draw directly from Skot in May 2019. I used the 2:1 system with Skot’s wire draw for my first route up El Cap in June 2019 and used it on 6 or so other routes up to Native Son in April of 2021. I bought the fancy cord Skot linked as well which I can confirm is awesome but did actually get core shot on one of the first pitches of Native Son and was therefore replaced by the 6 mil cord seen in the video. 

On the final pitch of Native Son, (Pink Pantz) Lance was hauling with the 2:1 and I untied to organize gear back from the lip. I noticed the bag was getting caught up on the low angle terrain and opted to walk back over to the lip and help with a space haul. I put a single ascender on the haul line and clipped a carabiner into the top hole of the ascender since I wasn’t tied in… I felt that was enough of a backup. The cable draw holding the micro unexpectedly failed and I fell backwards, caught by a Petzl Basic (the haul ascender) attached to the Z cord. As you can see in the video, the bags were on nearly flat terrain so they did not weight the z cord and Lance did not get pulled into the anchor. If we were on vertical terrain, the bags would be hanging on one side of the Petzl Basic (held to the anchor by the z cord) and I would be hanging on the other… most likely, the rope would have popped out of the Basic since it’s not a pulley and the bags and myself would have fallen to the ground. I am incredibly lucky this wire draw failure did not result in injury or death and I certainly realize that it was a mistake to have not backed myself up with the lead rope. 

As soon as I got down, I emailed Skot to let him know of the failure and strongly urged him to issue a recall. The wire draw he made me was made with 1/8” 7x7 cable which typically has a minimum breaking strength of 1700 lbs. I assumed that the failure may have been related to the swage but I am no expert and after sending the cable back to Skot, he determined the failure was due to the cable alone. I am still confused as to why the cable broke as the force was certainly less than 1700lbs and the cable was in good shape with no twisting. Regardless, skot, had apparently only made a handful of 1/8” 7x7 wire draws before switching to 5/32” 7x19 cable. He let me know that he contacted everyone who he previously shipped a 7x7 draw to and he also posted up a recall notice as a comment on the YouTube video.

Skot sent me a new 7x19 wire draw and did some break strength testing on it to confirm the break strength is 3500 lbs. I have since used the 7x19 draw on multiple El Cap routes and even a wall in Kyrgyzstan. I have full faith in Skot’s new 7x19 draws. Getting back to the main topic of this thread, the 2:1 system Mark originally posted is truly amazing, I’ve tried hauling a bunch of different ways and its by far my favorite for big loads.

Skot also sent me a replacement for my wire draw I got from him without my asking. Top notch service. 

Tyler Karow wrote:

I want to chime in to address the failure of my 2:1 system that occurred on Native Son. I read this very thread back when Mark first posted it and procured the advertised wire draw directly from Skot in May 2019. I used the 2:1 system with Skot’s wire draw for my first route up El Cap in June 2019 and used it on 6 or so other routes up to Native Son in April of 2021. I bought the fancy cord Skot linked as well which I can confirm is awesome but did actually get core shot on one of the first pitches of Native Son and was therefore replaced by the 6 mil cord seen in the video. 

On the final pitch of Native Son, (Pink Pantz) Lance was hauling with the 2:1 and I untied to organize gear back from the lip. I noticed the bag was getting caught up on the low angle terrain and opted to walk back over to the lip and help with a space haul. I put a single ascender on the haul line and clipped a carabiner into the top hole of the ascender since I wasn’t tied in… I felt that was enough of a backup. The cable draw holding the micro unexpectedly failed and I fell backwards, caught by a Petzl Basic (the haul ascender) attached to the Z cord. As you can see in the video, the bags were on nearly flat terrain so they did not weight the z cord and Lance did not get pulled into the anchor. If we were on vertical terrain, the bags would be hanging on one side of the Petzl Basic (held to the anchor by the z cord) and I would be hanging on the other… most likely, the rope would have popped out of the Basic since it’s not a pulley and the bags and myself would have fallen to the ground. I am incredibly lucky this wire draw failure did not result in injury or death and I certainly realize that it was a mistake to have not backed myself up with the lead rope. 

As soon as I got down, I emailed Skot to let him know of the failure and strongly urged him to issue a recall. The wire draw he made me was made with 1/8” 7x7 cable which typically has a minimum breaking strength of 1700 lbs. I assumed that the failure may have been related to the swage but I am no expert and after sending the cable back to Skot, he determined the failure was due to the cable alone. I am still confused as to why the cable broke as the force was certainly less than 1700lbs and the cable was in good shape with no twisting. Regardless, skot, had apparently only made a handful of 1/8” 7x7 wire draws before switching to 5/32” 7x19 cable. He let me know that he contacted everyone who he previously shipped a 7x7 draw to and he also posted up a recall notice as a comment on the YouTube video.

Skot sent me a new 7x19 wire draw and did some break strength testing on it to confirm the break strength is 3500 lbs. I have since used the 7x19 draw on multiple El Cap routes and even a wall in Kyrgyzstan. I have full faith in Skot’s new 7x19 draws. Getting back to the main topic of this thread, the 2:1 system Mark originally posted is truly amazing, I’ve tried hauling a bunch of different ways and its by far my favorite for big loads.

As a mechanical engineer I wanted to add a hypothesis to the failure analysis. The hauling action will torque the cable draw repeatedly if the load isn't fully aligned (the primary purpose of the cable draw is to allow this degree of freedom). It looks like the length of cable is very short between the two swages. Since there is such a short distance the torquing action is focused on a small length creating a large amount of rotation per length of cable. High enough that it may be exceeding the yield stress of the outer cable strands. Cyclic stressing like this may eventually fatigue the cable enough to cause a failure below the original breaking strength of the cable.

If this is indeed the failure mode, I would recommend future cables be lengthened to allow 180 degree rotation easily. Thickening the cable without lengthening to allow more freedom of rotation might not fully address the possibility of cyclic fatigue failure, in fact a wider diameter cable may exacerbate the yielding on the outer cable strands. Unfortunately, this type of failure cannot be tested with simple pull testing since it will present over repeated use over a long time.

Hanson Boyd wrote:

As a mechanical engineer I wanted to add a hypothesis to the failure analysis. The hauling action will torque the cable draw repeatedly if the load isn't fully aligned (the primary purpose of the cable draw is to allow this degree of freedom). It looks like the length of cable is very short between the two swages. Since there is such a short distance the torquing action is focused on a small length creating a large amount of rotation per length of cable. High enough that it may be exceeding the yield stress of the outer cable strands. Cyclic stressing like this may eventually fatigue the cable enough to cause a failure below the original breaking strength of the cable.

If this is indeed the failure mode, I would recommend future cables be lengthened to allow 180 degree rotation easily. Thickening the cable without lengthening to allow more freedom of rotation might not fully address the possibility of cyclic fatigue failure, in fact a wider diameter cable may exacerbate the yielding on the outer cable strands. Unfortunately, this type of failure cannot be tested with simple pull testing since it will present over repeated use over a long time.

The length may not play too much of a factor as the loading of a free ended cable will introduce torque into the cable simply because the cable is a twisted set of wires.  Below is a link to a technical paper by a cable manufacturer that explains situation:

https://www.camesawireline.com/Portals/0/Documents/Technical/Mechanical-Characteristics-Specifications/Cable-Breaking-Strength.pdf

Cliff notes version, a closed ended cable loop, such as cable on a bridge maintains the strength characteristics of a static loaded cable.  When the cable is open ended like that of a truck winch or in the case of this wire draw, rotational forces (torque) are introduced essentially weakening the cable by untwisting itself.  The outer wires of the cable will unwind and only the inner wires will be left to handle the direct force, thus reducing the break strength.

By Tyler being on the space haul, additional torque was also introduced since now there is load on both ends of the microtrax misaligning the direction of force.  As Hanson mentioned above, this can exacerbate the situation which ultimately lead to failure.  Cyclic loading is another part of the problem.  Just to think only ~2kN of static force was applied to make this thing snap.