Moss Cinching Lanyard prototype

[moss]

Do Slic pins used in life support applications need 2 internal cotters, and other applications just 1 cotter is ok? Rope runner and quickie slics are 2, the wrench is 1 because it’s not primary life support?

Yes and yes. I guess you could describe the locker as a spring loaded tooth pin. Two for life support and one for something like the wrench.
-AJ

 

[moss]

Working on a two leader river birch with a wide "V" structure, using my 85' "Woods Lanyad" anchored in the top of this side. Sharing the load between these upper tops just above a union. Wasn't comfortable committing to just one of them. The arrangement on the shackle creates a non-slipping bight

Gives me a more robust canopy anchor for getting up to the tips and back and forth between the two leaders.
-AJ

 

[Phil]

Sharing the load between these upper tops just above a union.

Not to nitpick but I don't think you're sharing load between the two tops in the traditional sense of "sharing". You are magnifying your load and applying that magnification to each top. You are also changing the direction your force is applied to the tops. It's a death triangle configuration.

Assuming you weigh 200 lbs and the angle made at your carabiner/ring lock off is 90 degrees, each angle made at the tops is 45 degrees. The force multiplier for 45 degrees is 1.84. So if you weigh 200 lbs, the rope legs at the carabiner ring lock is 100 lbs each (big assumption here). Each of those tops is seeing a load of 100*1.84=184 lbs. That's 184 lbs at each of those two tops, not shared. While the 184 is less than your weight, it's being applied to each stem. The friction of rope on bark will lower that number but still, load is not shared but applied to each stem equally.

Richard did a video about this topic:

This is the best link describing what's going on that I've found so far:

The American Death Triangle and driving on the wrong side of the road - Over The Edge Rescue

Understand the forces involved in the American Death Triangle. Explained in as simple terms as possible with no trig equations to be seen. Gives you a set of principles to assess your rigging in the field.

overtheedgerescue.com

 

[LordFarkwad]

@Phil,

The vertical component of the load is indeed distributed between the two stems (if climber weighs 200lbs, then there is 100lbs on each stem, but only in the vertical direction). The horizontal component of the force is, as you noted, potentially increased, dependent upon line angles (and can be between zero and many multiples of the climber's weight).

What is the official definition of "load-sharing"? I would think that all we're going for in these types of anchor arrangements is a reduction of force relative to the climber's weight, applied to each stem. The only way you could truly and mathematically get half of the climber's weight applied to each stem (in this situation) is to have each of the resultant force vectors on each stem to be aiming straight down to earth, requiring infinite-length legs of line between the saddle carabiner and the limb anchors.

In other words, 50% weight applied to each stem (total force vector magnitude, not vert./horiz. component forces) is the absolute lowest force which could be applied.

Right?

 

[Phil]

@Phil,

The vertical component of the load is indeed distributed between the two stems (if climber weighs 200lbs, then there is 100lbs on each stem, but only in the vertical direction). The horizontal component of the force is, as you noted, potentially increased, dependent upon line angles (and can be between zero and many multiples of the climber's weight).

What is the official definition of "load-sharing"? I would think that all we're going for in these types of anchor arrangements is a reduction of force relative to the climber's weight, applied to each stem. The only way you could truly and mathematically get half of the climber's weight applied to each stem (in this situation) is to have each of the resultant force vectors on each stem to be aiming straight down to earth, requiring infinite-length legs of line between the saddle carabiner and the limb anchors.

In other words, 50% weight applied to each stem (total force vector magnitude, not vert./horiz. component forces) is the absolute lowest force which could be applied.

Right?

Cinch a strap to each stem individually. Clip in to both straps. Load is now shared and also redundant. If one tip fails, you're still on the other.

I do not think the birch would fail the way moss tied in, but the load isn't shared is all. Sharing implies 50% to each stem. Which is not what's happening. Like Richard mentioned in his video, someone fell because they assumed they were sharing load, not realizing the load was being applied to each stem. It's important to know this dynamic.

 

[LordFarkwad]

Even if you have a single line, cinched anchor to each stem, as you described, and they coalesce at the saddle in a 90 deg angle, you still have 0.7x of your weight applied to each stem (the magnitude of each of the vectors from the individual stem anchors). Until the legs arriving at the saddle are completely parallel (zero degrees, in other words), you don't have 50% of the climber's weight being applied to each leg; there is some degree of load-multiplication going on, and each leg bears > 50% weight.

I think the "load-sharing" that @moss was referring to, means that 1) the force from climber's weight at each stem is less than 1x the climber's weight, and/or 2) the load - whatever it ends up being - is indeed distributed between the two anchoring limbs/unions.

 

[Phil]

Even if you have a single line, cinched anchor to each stem, as you described, and they coalesce at the saddle in a 90 deg angle, you still have 0.7x of your weight applied to each stem (the magnitude of each of the vectors from the individual stem anchors). Until the legs arriving at the saddle are completely parallel (zero degrees, in other words), you don't have 50% of the climber's weight being applied to each leg; there is some degree of load-multiplication going on, and each leg bears > 50% weight.

I think the "load-sharing" that @moss was referring to, means that 1) the force from climber's weight at each stem is less than 1x the climber's weight, and/or 2) the load - whatever it ends up being - is indeed distributed between the two anchoring limbs/unions.

In any case, there are entire websites and many, many articles talking about how bad the triangle configuration is for load sharing. There's a reason for that. Plenty of green, newbie climber's peruse these forums. They may take what they see done here as gospel. Now they have more information to study.

 

[LordFarkwad]

In any case, there are entire websites and many, many articles talking about how bad the triangle configuration is for load sharing. There's a reason for that. Plenty of green, newbie climber's peruse these forums. They may take what they see done here as gospel. Now they have more information to study.

Mo info is mo betta, fo sho.

The rule of thumb I've heard is never let the angle of the legs at the saddle become greater than 90 degrees from each other (NOT applicable in the ToD scenario, since the legs appear to be 90 degrees apart, but are effectively 135 degrees apart).

I was just messing around on a sheet of paper, and here's an interesting outcome: the ToD anchor scenario can never end up applying less than 70% the climbers weight at each of the anchor points. In other words, if the ToD is set up with the best possible loading scenario - climber is hanging at such a distance below the anchors, that the two incoming rope legs are, for all intents and purposes, parallel - the two anchor points will still each have a force vector of 0.7x the climber's weight applied to them; 0.5x climber's weight straight down, 0.5x climber's weight straight across to the opposing anchor, resulting in a vector sum of 0.7x.

 

[moss]

Not to nitpick but I don't think you're sharing load between the two tops in the traditional sense of "sharing". You are magnifying your load and applying that magnification to each top. You are also changing the direction your force is applied to the tops. It's a death triangle configuration.

Assuming you weigh 200 lbs and the angle made at your carabiner/ring lock off is 90 degrees, each angle made at the tops is 45 degrees. The force multiplier for 45 degrees is 1.84. So if you weigh 200 lbs, the rope legs at the carabiner ring lock is 100 lbs each (big assumption here). Each of those tops is seeing a load of 100*1.84=184 lbs. That's 184 lbs at each of those two tops, not shared. While the 184 is less than your weight, it's being applied to each stem. The friction of rope on bark will lower that number but still, load is not shared but applied to each stem equally.

Richard did a video about this topic:

This is the best link describing what's going on that I've found so far:

The American Death Triangle and driving on the wrong side of the road - Over The Edge Rescue

Understand the forces involved in the American Death Triangle. Explained in as simple terms as possible with no trig equations to be seen. Gives you a set of principles to assess your rigging in the field.

overtheedgerescue.com

Good news is I didn’t die ;-) For the situation in the photo the two legs of Y birch top were sufficiently strong to resist the compression force from the encircling choke. If I choked on just one of them and went to the second leader in the two leader tree with a horizontal rope path when I reached a working position (which I did) I felt much more confident with the side loading on the first leader with the choke in the photo than I would’ve choked to just on of the Y legs. Good to know the death triangle math but was not a negative factor for the anchor shown.
-AJ

 

[moss]

Went back and reviewed some death triangle anchor resources... I think that at least a couple of the issues are related to typical implementation in rock or alpine climbing, like the use of slings and carabiners and the lack of redundancy. With the configuration shown there’s quite a bit of friction where the rope wraps each vertical. When I set it I loaded it up while still tied in with my lanyard and observed the response of the two uprights, very solid. I guess what I really was doing was mitigating the danger of breaking out one side of the Y, not sharing load. Anyhow... it worked. To the question of tempting newbies with unconventional or potentially dangerous setups, this will always be a question in a public tree climbing forum that discusses climbing techniques.

Appreciate your raising the death triangle issue Phil!
-AJ

 

[Chaplain242]

Went back and reviewed some death triangle anchor resources... I think that at least a couple of the issues are related to typical implementation in rock or alpine climbing, like the use of slings and carabiners and the lack of redundancy. With the configuration shown there’s quite a bit of friction where the rope wraps each vertical. When I set it I loaded it up while still tied in with my lanyard and observed the response of the two uprights, very solid. I guess what I really was doing was mitigating the danger of breaking out one side of the Y, not sharing load. Anyhow... it worked. To the question of tempting newbies with unconventional or potentially dangerous setups, this will always be a question in a public tree climbing forum that discusses climbing techniques.

Appreciate your raising the death triangle issue Phil!
-AJ

Must remember that the death triangle doesn’t really apply to leaders of the same tree - not all the time as one still needs to Inspect for defects. But two leaders is different from two different trees.

 

[Flying~Squirrel]

I've done what Moss did, and usually my goal is to reinforce the union between the two leaders by compressing the two stems, not to put half my weight in each leader.

 

[oceans]

Went back and reviewed some death triangle anchor resources... I think that at least a couple of the issues are related to typical implementation in rock or alpine climbing, like the use of slings and carabiners and the lack of redundancy. With the configuration shown there’s quite a bit of friction where the rope wraps each vertical. When I set it I loaded it up while still tied in with my lanyard and observed the response of the two uprights, very solid. I guess what I really was doing was mitigating the danger of breaking out one side of the Y, not sharing load. Anyhow... it worked. To the question of tempting newbies with unconventional or potentially dangerous setups, this will always be a question in a public tree climbing forum that discusses climbing techniques.

Appreciate your raising the death triangle issue Phil!
-AJ

Moss, if you can make a bight in the horizontal span and pull that down into the ring along with the splice and left side bight, you can focus the forces more directly into each leader. You could even choose to focus more to one side or the other by placing the ring where you want along the horizontal span.

 

[rope-a-dope]

Or take the horizontal span and clip it in the biner.
I have built this anchor between 2 skinny tops before with a biner and butterfly, clipping the butterfly, middle span and splice all together. Fits fine in one biner! It's a little tricky to measure out legs, but you can get pretty close to a nice three way 120ish degree angle.

 

[oceans]

Or take the horizontal span and clip it in the biner.
I have built this anchor between 2 skinny tops before with a biner and butterfly, clipping the butterfly, middle span and splice all together. Fits fine in one biner! It's a little tricky to measure out legs, but you can get pretty close to a nice three way 120ish degree angle.

Yep. There’s an interesting trade off though. A butterfly can eat up a decent amount of rope from an already short lanyard. Setting up the shared anchor point for a main system is less of a concern with usable rope left, but also...a shared anchor like moss’ triangular version allows the anchor to realign with the rope angle as your position changes in all directions. A fixed shared anchor only follows your movement through one axis. Moving along the other axis will eventually slack one side of the anchor.

it’s funny because this all leads to the benefit of the TRT system. Maybe @moss should use a mini TRT Lanyard!!! What do you think @SoftBankHawks ?

 

[Phil]

TRT system

What is TRT?

 

[oceans]

What is TRT?

Twin Rope Technique. It’s a true hybrid of SRS and MRS with the right kit. Not so much when building it with a Rope Runner, but definitely when building it with two full size climb lines and Independant hitches.

there’s a good thread on it here under that title. I’ll find the link and edit this post to include it.

 

[moss]

Moss, if you can make a bight in the horizontal span and pull that down into the ring along with the splice and left side bight, you can focus the forces more directly into each leader. You could even choose to focus more to one side or the other by placing the ring where you want along the horizontal span.

Yep. There’s an interesting trade off though. A butterfly can eat up a decent amount of rope from an already short lanyard. Setting up the shared anchor point for a main system is less of a concern with usable rope left, but also...a shared anchor like moss’ triangular version allows the anchor to realign with the rope angle as your position changes in all directions. A fixed shared anchor only follows your movement through one axis. Moving along the other axis will eventually slack one side of the anchor.

it’s funny because this all leads to the benefit of the TRT system. Maybe @moss should use a mini TRT Lanyard!!! What do you think @SoftBankHawks ?

Indeed I had some interesting and excellent realignments happen as I worked the tree from that anchor, went all directions. One of the obvious ones was lanyard in and pass my system through the "V" and work that side. working off the sides of the V worked well too with some realignment and favorable shifts in loading on the two legs of the V.

My short lanyard does have a ring sewn in the second eye so it can be configured the same way.

I'm going to be down at Shelter Tree, N. Attleboro 11:00 AM today 1/28, be there a little while, helping a friend buy some gear, I'll bring my ring and bow shackle/slic pin lanyards if anyone is around.
-AJ

 

[oceans]

Indeed I had some interesting and excellent realignments happen as I worked the tree from that anchor, went all directions. One of the obvious ones was lanyard in and pass my system through the "V" and work that side. working off the sides of the V worked well too with some realignment and favorable shifts in loading on the two legs of the V.

My short lanyard does have a ring sewn in the second eye so it can be configured the same way.

I'm going to be down at Shelter Tree, N. Attleboro 11:00 AM today 1/28, be there a little while, helping a friend buy some gear, I'll bring my ring and bow shackle/slic pin lanyards if anyone is around.
-AJ

Wish I could be there. Would love to catch up. Air High 5 from my current location!

 

[oceans]

What is TRT?

TRT

I was watching old Johnny Pro videos today. I find them inspiring; dude has some serious passion for getting high. Does anyone play with his TRT system? I checked out this 9mm cord and it feels amazing doubled in my runner http://www.samsonrope.com/Pages/Product.aspx?ProductID=480 It is more...

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