How to Mitigate Risk of TIP Branch Breaking?

[SeanKroll]

The limb supporting the climber takes force off the rope.


I used three strand in my maasdam on a tipped tree, natural crotched, and double-whip tackled. I cranked that thing pretty tight in an open alder crotch, but the second leg stayed pretty slack. It was enough to do the job, and notes taken. I definitely wasn't at 180 degrees, more like 140 or less. I couldn't really get any signficant tension on one side while the other was Tight.

Seems like that math is using theoretical vector force angles from a 'frictionless' pulley scenario, where there is no friction anywhere. I don't think it translates. Could be wrong.

 

[brydan]

For reduced friction sure, but aren't you forgetting something?

Yes I did ...When I was going to bed I realized I'd gotten sidetracked and forgot what the point of calculating the angle was, it was to show that less rope contact around the branch equals less friction so more force at the TIP. The example off the top of my head was a limbwalk but yeah that didn't work unless they slip off the branch, then the force is there . But seriously, rigging, redirects, etc, there's lots of situations where the angles change. The bigger point being, friction matters and it seems to me the more complicated climbing and rigging systems get the more people need to consider what all is going on.

 

[DMc]

https://www.masterblasterhome.com/showthread.php?17472-Srt-anchor-tip-loads
Some nice charts and discussion in this old thread.

Yes, friction absolutely does matter, as do all the other components in the situation being examined. The pieces of the puzzle that are explained by math and other sciences, though thought-provoking, must be arranged with all the other pieces in order to get a true picture. Many false beliefs are carried forward by citing "a" truth.

It is important to remember that friction works in both directions and can help to reduce or help to multiply. A movement that is captured and held by friction, is adding load. Many TIP failures happen after a climber has almost reached that point. Climbers would be well-advised to smooth out their climbing and not rely on static rope to take the bounce out.

 

[adaycj]

I tried an experiment. I'm sure the isn't in any way original. It may be apples to oranges compared to a real TIP with real world conditions. I used Sampson velocity rope over an old pull up bar in my basement. The chin up bar has two wraps of friction tape, the adhesive is towards the bar not the rope. I can "climb" Ddrt on this bar and the friction isn't noticeably different than a crotch in a tree. I "basal" tied it to a softener tank, and I used a fish scale. It is not even really science, since there are likely 100 things that could influence the numbers that are out of my control.

The hypothesis. A TIP point may have more or much more than the suspended weight on it when in use. One theory is that it will have close to the suspended weight because of friction. Another theory is that it will have 2 times the suspended weight because of lever and pulley math. A final theory is that is can have more than 2 times the weight on the TIP because of friction.

Step 1. Zero the 50# fish scale.
Step 2. Tie and weigh the weights with fish scale. 10.60#
Step 3. Rig basal tied SRT line without weights. Scale on basal side rope. 0.22#
Step 3. Hand tie weights on two bights of rope 5.26#
Step 4. Use a sum to estimate weight on TIP (Note: the basal side rope isn't perpendicular to the suspended weight rope, this number is off a bit) 10.60# + 5.26# = 15.86#
Step 5. Pull down on the suspended rope with my hand, maybe with and additional 20# of force for 1 second and release smoothly in 1 second. No jerking, no slow release, no body weight.
Step 6. Read scale stabilized scale after my hand is off the line. 23.96#
Step 7. Use a sum to estimate weight on TIP (Note: the basal side rope isn't perpendicular to the suspended weight rope, this number is off a bit) 23.96# + 5.26# = 29.22#

All values were taken in "static" conditions. The value was stabilized on the screen and my hands were away from the test setup. The fish scale screen only updates about every 2 seconds, there is no "peak hold" function. I made no attempt to read any values that wouldn't stay on the screen for more than 10 seconds, all reading were hands off.

Conclusion: If a conclusion can be drawn from this limited test, it is that the TIP forces can be 1.5 times, 2 times, or greater than 2 times the suspended weight. Some level of mechanical advantage is at play. As I type this there is almost 3 times the suspended weight on the TIP in my basement.

My opinion is that a basal tied system may expose the TIP to forces much greater than the climber's weight over an extended period of time. Sometimes much more than the approximate calculated 2:1 mechanical advantage.

https://www.amazon.com/photos/share/jG5rMVdPte2lx4pCY2OhYtQlycEJpr6el2D88inereI

 

[DMc]

.....My opinion is that a basal tied system may expose the TIP to forces much greater than the climber's weight over an extended period of time. Sometimes much more than the approximate calculated 2:1 mechanical advantage.....

Well, with a closing statement like that, a climber would be crazy to use a basal tied system. I use one in almost every tree I climb. Could there be something else to this or are the guys with straitjackets coming for me?

 

[SeanKroll]

There are no opinions in physics.


Theory are well proven.


Most laymen have no idea what a hypothesis or theory are.


There is the Theory of Gravitational attraction, for example.


There are ideas. Sometimes these are formed into a testable hypothesis.


Anytime anyone says that my theory is..., means they aren't using theory correctly, unless their Albert Einstein or the Steven Hawkings-types.




You have some data, and some assumptions, and an opinion.


What could be the magic that makes mass increase, therefore force?

 

[adaycj]

Definition of theory from internet "an idea used to account for a situation or justify a course of action."

I'm fine if you don't like my experiment. It has flaws. I'm allowed my ideas, and I'll continue to use the word theory correctly. Picking apart word choice is typically left for situations where there can be a significant misunderstanding, or situations where where words are used to demonstrate that others aren't smart enough to be part of the conversation.

In this case you are right. I am not smart enough to be part of a conversation about magic. It is not about conservation of mass, it is about stored energy. A spring can pull down on something.

 

[adaycj]

Well, with a closing statement like that, a climber would be crazy to use a basal tied system. I use one in almost every tree I climb. Could there be something else to this or are the guys with straitjackets coming for me?

I wouldn't let any statement of mine deter you. I think the conclusion in the real world, if there is one that can be drawn, is that our TIPs need to be sturdy. I use a basal tie quite a bit, and I won't stop now. I just think that the TIP points have more force than just the suspended weight sometimes. I think some of this happens on a cinched tie in as well, with bouncing and such. It is just that the 1 times the climber's weight, or two times the climber's weight, or some number in between is not the real force to worry about. My point isn't that we should stop using basal ties, or any other established technique. In fact, I'm not sure I have a point here. I was just trying to contribute to the conversation. I did a 10 minute experiment and a 10 minute post because I thought it was relevant to the conversation.

Plus I think the experiment has flaws. The friction fighting against the rope pulling like a spring is imparting at least part of the force on the TIP as a twisting force. So the scale shows forces that aren't all really pulling the TIP straight down. However, twisting might contribute to TIP failure in a tree, so maybe the twisting shouldn't be discarded.

A better experiment would likely involve three load cells. One that holds up the TIP, and one on each leg. A system that could log bouncing events at an acceptable rate would be useful too. Of course even if I did a year long experiment with tens of thousands of data points, on calibrated and appropriate equipment someone would come along and tell me I violated the laws of physics, or would just choose to substitute their own misunderstandings of a complex system. It would cost me $800 to do it better and $2500 to do better than that, but likely to no greater effect.

The OP was about TIP failure. There is no perfect solution. I think all of us but a few agree that basal tie can put higher forces on the TIP with everything else equal. But a branch as big as my thigh can hold a passenger car. For the much smaller ones that we do our best to evaluate and test, I think a cinch much be better. But if a basal tie vs a cinch TIP is the difference that causes a failure, I don't want to climb it.

 

[SeanKroll]

Definition of theory from internet "an idea used to account for a situation or justify a course of action."

I'm fine if you don't like my experiment. It has flaws. I'm allowed my ideas, and I'll continue to use the word theory correctly. Picking apart word choice is typically left for situations where there can be a significant misunderstanding, or situations where where words are used to demonstrate that others aren't smart enough to be part of the conversation.

In this case you are right. I am not smart enough to be part of a conversation about magic. It is not about conservation of mass, it is about stored energy. A spring can pull down on something.

Ok. Sure.

Since we were discussing science, I was using the scientific definition of theory. I can be pedantic. Sorry.



DdRT TIPs obviously (to me) sometimes experience more than the climbers full weight.




The 100% versus a supposed 200% are relative to each other.


Perhaps do your testing with three load cells, with and without a low friction pulley.


Again, using high mechanical advantage, in the real world, in a guying system, I had major force imbalances between the two legs of rope, easily accounted for by friction.

 

[SeanKroll]

https://www.masterblasterhome.com/showthread.php?17472-Srt-anchor-tip-loads
Some nice charts and discussion in this old thread.

Yes, friction absolutely does matter, as do all the other components in the situation being examined. The pieces of the puzzle that are explained by math and other sciences, though thought-provoking, must be arranged with all the other pieces in order to get a true picture. Many false beliefs are carried forward by citing "a" truth.

It is important to remember that friction works in both directions and can help to reduce or help to multiply. A movement that is captured and held by friction, is adding load. Many TIP failures happen after a climber has almost reached that point. Climbers would be well-advised to smooth out their climbing and not rely on static rope to take the bounce out.

Dave, you are smart and a good communicator.




Time to go do some work. Zero TIPs involved.

 

[Marc-Antoine]

I take this experiment as a valuable approach.
There isn't any magic here and the mass of the hanging load surely doesn't change. But the hand added some force transiently in the system, which adds (or subtracts if opposite) to the weight of the load.
Same with dynamic.
The weight is a force exerted on a mass by the gravity. Gravity is an acceleration. Add any other acceleration / force to the system (start, stop, increase or decrease the speed, deflect the trajectory) and the weight changes accordingly.

In this experiment the same result can be got by dropping the load from a certain height, instead of pulling it down by hand. The inertia at the deceleration increases drastically the weight as you all know.

The friction between the rope and the bar doesn't allow any move until a certain amount of unbalanced force is reached. Then that slips, and stops as the tensile of the anchor part increases and comes closer to the pulling force. Pull a little more, that stays put, then slips and stops again.
If you reduce the working load, that gives the same effect in the other direction. The anchor part keeps its initial tension, until the load is lightened enough by the same said amount of force (more or less). Then the rope slips and loose part of its tensile off the anchor part.
As you can see, to get the rope moving in both ways, you have to pass a gap wide of two times the unbalance from either side of the equilibrium point. This unbalance depends directly from the friction.
It's called hysteresis: it's like something doesn't take the same path when it comes back. It's obvious with a graph.
With a lot of friction, you can "store" a substantial amount of force on one side without affecting the other side. With a good pulley, the difference is small enough that you can barely feel it, if not at all.

The climbing line sees exactly that, either in SRT with a basal anchor, or in DdRT. For the last, the tying point doesn't care. For the first, that matters a lot, as a bouncy climb or a foot loosing can "send" an unexpected tensile on the anchor side and store it there. So the Tip has to stand for an extended time more likely 2,5 body weight instead of 1,5 (if you plan initially that the friction will work only in your favor). The tip can hold on an impulse but gives away with the same but continuous force.

In this case, I agree that's really border line and we have to choose an other plan than this Tip.

 

[SeanKroll]

I don't quite get that hysteresis.






Friction involves a Normal Force, and a coefficient of Static friction until it starts to move, then there is the coefficient of dynamic friction involved.

Also in real world work, bark get polished, smoother with slight movement back and forth.

There are so many variables to account for.

Just inspect and test your TIP. Climb smoothly if not super duper bomb proof. Once I climbed on a tiny branch as a redirect, 1' above a 12" fork, for a good 80' without using. Species and health should be considered.





For clarity, Weight net vector force, and is a function of gravity, which is a function of mass of objects and distance between them. You can't change gravity/ weight except to move objects closer/ farther apart.






Everything had gravitational attraction.

I have gravitational attraction to Marc-antoine to Stig, to Gerry, Butch, Jupiter, etc.

Weight and gravity are very commonly misunderstood principles.


I've been climbing SRT since before the rope wrench came in the scene.
SRT should be understood, functionally, like all other aspects of tree work, not feared.


It's not rocket science or space travel with humans. We're not trying to shoot a human out of our atmosphere into orbit, and bringing them back to earth, through blazing heat, and having them be normally functioning people.

 

[Marc-Antoine]

Give me a little time for the hysteresis.

For the weight, we should use the term "apparent weight", because for us, in our environment, the mass is never affected by only the gravity. Plenty of factors play on it and the resulting force can vary greatly. In a static way, it could be approximately well guessed as the weight (think of Archimede, air movements, earth rotation ... though). But dynamically, it goes from almost zero in a parabolic fly to many many time its usual value when a chock /hard stop is involved. It can be directed toward any direction, as being a resultant force.
The reference point in regard with the movements is very important too. The parabolic fly is a little far from the tree work but it's a good example : we can look at the object as stationary and weightless in the plane, but it still goes at hundreds of miles per hour in the sky. Change the plane's trajectory suddenly, and the weightless object is instantly transformed in a wrecking ball, always the same mass and same path in the sky, but with an enormous apparent weight in the plane.

Back to tree work : if you take a big swing on your rope (or make a pendulum with a rigged log). Your Tip becomes your reference point. At the bottom of the swing, all you can feel is being like as much as 3 times your usual weight, no worry (excepted for me, I hate that). For the tree it isn't so simple though, since its reference point is the ground and he's actually side loaded from one side to an other with a max load of 5 to 6 times your weight (in Srt ground anchored), and that could become bad.

I agree to better knowing what's going on. Even an "old" technique like the DdRT isn't clearly understood by many users. For example, the false thought that DdRT gets more elasticity by the rope than SRT canopy anchored seems very common.

 

[SeanKroll]

Sorry Marc (is your first name Marc-Antoine, or is Antoine your family name, or something?), I didn't understand your point about apparent weight. My thinking is that we need to look at vector forces (force plus direction of force) all the time. As you pointed out, a pendulum swing acts on the anchor point in different ways, and also sideloads the whole tree.

I don't know how much that "doubling" affects things during a pendulum swing. A load cell that could record many data points offorce and direction, in a real world scenario, would be really informative.


A good point about the misconception about two strands giving more elasticity than one.
That being said, ropes in the past, before fancy modern ropes designed more for SRT, were more elastic.

 

[Tree09]

Doubling doesn't exist in a swing, only a constant change in direction, therefore you are continuously accelerating. Shock loading will exist at the bottom of the arc tho (by shock loading I mean the highest force). Forces are measured in 3 dimensional space as vectors, and side loading limbs is very bad, however, it can be used to your advantage as well. Going over several points spreads out the weight, both by friction and reducing the angle. The most stress on an anchor point is when the line is base tied and coming straight in the direction where it came (0 angle between). The factor is 2 in that case. The many multiples force vs weight is on a highline scenario, but that is only on the rope itself. The anchor receives very little force. That is what we are exploiting when we sweat a line.

 

[DMc]

..... Forces are measured in 3 dimensional space as vectors, and side loading limbs is very bad, however, it can be used to your advantage as well. Going over several points spreads out the weight, both by friction and reducing the angle. The most stress on an anchor point is when the line is base tied and coming straight in the direction where it came (0 angle between). The factor is 2 in that case. The many multiples force vs weight is on a highline scenario, but that is only on the rope itself. The anchor receives very little force. That is what we are exploiting when we sweat a line.

I think this sketch by Andrew Joslin, aka as moss on treebuzz, nicely illustrates the above points. Understanding and utilizing the combination of force and the structure you are working with are key in preventing canopy tear outs.

 

[biggun]

I know there is a science behind it, but all the calculations make it extremely complicated. Perhaps over thinking it.

Decision making becomes easier with experience.

The working climber DVD has a good section on vector forces. That was good enough for me. I don't need to know the angles, I just need to know that one angle may exert more force than another.

 

[DMc]

I know there is a science behind it, but all the calculations make it extremely complicated. Perhaps over thinking it....

Spot on, Rich. In working with trees, understanding the concept is far more valuable than any specific number. There are world-class mathematicians that have been studying biomechanics for years, trying to put numbers out that are repeatable. They are still working....

 

[MasterBlaster]

I don't understand that crazy drawing at all!

 

[SeanKroll]

I think this sketch by Andrew Joslin, aka as moss on treebuzz, nicely illustrates the above points. Understanding and utilizing the combination of force and the structure you are working with are key in preventing canopy tear outs.

I believe it is setting a high-line to suspend the climber over a bad tree. The arrow shows the deflection of the highline downward, under the load of the climber.


The right/ higher side is using many redirection points to compress each stem, rather than lever sideways on the small branches.

As the rope approaches the base tie, the sideloading of the limbs decreases, as the load decrease, because friction through 6 crotches eats up the force/ load pulling lengthwise on the rope.

 

[rfwoody]

Ok. Sure.... I can be pedantic. Sorry......

hahaha... that is why my bosses often didn't love me so much at work! ... haha, that and over-analyzing everything trying to account for all possible risks. (e.g. security and data loss). But it did get me through some tough spots (by God's mercy).

[going back now several pages and try to soak in and do justice to all the posts from 4 or 5 days ago]

 

[Weaves]

View attachment Working-the-Angles-i (1).pdf

Downloaded this awhile ago. Some good explanations/diagrams here.