TIP load

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.....To Ron's comment about it being a good idea to always assume 2x loading, I think that's what everyone does as a baseline. Unless I misunderstood I believe Laz is saying that if we actually measured load on each different natural crotch SRT ground-anchored setup we might find that the load on the TIP is much less than 2x due to the variables described (angles and friction).
-moss

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That's my point; if we don't assume the 2x loading, then we have to either measure or estimate each different setup to get a more definitive value. And for what? If it's not good for 2x, we need to find another TIP anyway.

moss, I have to completely disagree with your assessment of what Laz meant, consider what I said in an earlier post and his response to it, I said, "But don't you think its easier and safer to use the 2x approximation rather than calculate the friction and angular contributions for every trunk tie situation?"

to which Laz replied, "In a word - No...." So that means he does not think it'd be easier and safer to use the 2x approximation. Right?

Then, without offering any evidence, he said,
"...I also think the 2x approximation and your percentages are a good way off the mark too."

So the 2x is way off? What would be a better estimate to stake our lives on and what would the rationale be?

He then followed all that up with, "Armchair rigging has its limits."

Armchair rigging? Gee, I wonder what that means?
 
[ QUOTE ]
I hung a dyno off of a block and measured the force while footlocking the far end of the rope while the standing end was tied to the tree. It read 540 lbs. I weight 165. I tried it with several different rope placments and angles, meaning ,the rope went through several crotches at times, the dyno was always around 500lbs. give or take a bit. Rope was 11mm km111.

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tod_k,

That's very interesting, but how could a trunk tie produce a load on the TIP of 3 times your weight? Could the dyno be off, or maybe there's some kind of offset option built in that needs to be zeroed???? Any chance you wound up with a 3:1 configuration due to some unexpected rope routing? Could it be measuring a peak load due to a slip or something?

Or, LOL, have you weighed recently? Just kiddin' ya!
 
Ron, you'll have to ask Laz (nicely) to clarify his stance on the 2x rule.

[ QUOTE ]
He then followed all that up with, "Armchair rigging has its limits."

Armchair rigging? Gee, I wonder what that means?

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It means he's a very experienced professional climber with vast amounts of rigging experience. And us? We're non-professional climbers being theoretical on a pro climber message board. That is defacto armchair :-) No need to take it personally, it is what it is.
-moss
 
[ QUOTE ]
I hung a dyno off of a block and measured the force while footlocking the far end of the rope while the standing end was tied to the tree. It read 540 lbs. I weight 165. I tried it with several different rope placments and angles, meaning ,the rope went through several crotches at times, the dyno was always around 500lbs. give or take a bit. Rope was 11mm km111.

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How does the dynometer work? Is it capturing averages or can you see the changes as you dynamically load when you're footlocking? I'd head similar numbers from a dyno test of SRT'ing with ascenders, caused by dynamic loading from the climber's motion.

What was your average load when you were hanging static on the rope?
-moss
 
The Dyno is right on the money.The lowest it ever read was 445lbs. If you bounced it would go up to well over 500lbs. Off setting the rope thru multiple unions makes sense on paper but most the friction happens at the heightest point, the fall end. As the standing part goes thru other unions it has little weight because the frition is at the hieghest point which also usually has the greatest bent. Calculations and physics on paper are correct but difficult to apply on the job. I feel the direction of pull at the TIP is moore important (trying to compress the wood not bend it). I spent about 3 hours messing around with the dyno and was quite surprised. To argue about theory seems pointless when dealing with so many factors like rope angle, friction, rope length, rope type, living organisom etc.
 
Thanks, good stuff. So what does it all mean? It's really closer to 3x than 2x for a trunk or ground anchor?

Obviously the major advantage of going over multiple crotches besides how easy it is to set up is the TIP back-up. So in real-world use we know healthy branches/crotches are very strong and can take a 3x or more load. Part of the cautious approach on estimating load and capturing multiple branches is to protect the climber from structural flaws not visible in a high TIP, right?
-moss
 
[ QUOTE ]
I footlock pretty smooth but there is always going to be some dynamics especially with a static rope.

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I didn't mean to sound like I was implying that you weren't smooth. I'm sure you are. Did you ever do some serious bounces just to see what the dyno read? I'm assuming your dyno readings are 'captured peak'.
 
tod k wrote:


[ QUOTE ]
I hung a dyno off of a block and measured the force while footlocking the far end of the rope while the standing end was tied to the tree.

[/ QUOTE ]


Did you first measure the force at the dyno with you just hanging on the rope before you started footlocking? That would show both how much the redirected line changed the force at the dyno, and how much dynamic force is created by footlocking.

Did you also measure the load while footlocking a doubled line? Or a single line tied off at the block/dyno?



Ron wrote:

[ QUOTE ]
tod_k,

That's very interesting, but how could a trunk tie produce a load on the TIP of 3 times your weight? Could the dyno be off, or maybe there's some kind of offset option built in that needs to be zeroed???? Any chance you wound up with a 3:1 configuration due to some unexpected rope routing? Could it be measuring a peak load due to a slip or something?


[/ QUOTE ]


Ron;

A dyno has different settings. It can act as a scale and simply measure the static weight of a piece, or it can be set to 'Peak Hold' and show the maximum force experienced by the system where the dyno is hanging.

The 3X body weight is not surprising, based on other situations where I have used a dyno. I'm curious to see what the forces are for the situations I mentioned above.
 
moss wrote:


[ QUOTE ]
And us? We're non-professional climbers being theoretical on a pro climber message board.

[/ QUOTE ]


Just to clarify:


I'm not sure whom you meant by 'us'. It was probably unintentional, but, because both Ron and Tod were part of the discussion that ensued prior to your post someone could assume that you consider not only yourself, but both of them to be 'non-professional climbers'. I don't know and can't speak for Ron, but Tod is a very talented arborist with years of experience, including working with a dyno.


Still needs to work on his geography though....
tongue.gif
 
Actually, to follow my theories of anything that can work against you can work for you; i think the bounce can work either way.

It will load the system more; yes. But, at some points you can find yourself fighting it. A seeming loss, extending the distance you have to exert, perhaps easier seen as a lower distance yield from each extension(as some goes into the stretch). But; at some points you can find yourself 'dancing with the flow' correctly; whereby it can help toss you up better; if you are in rhythm with it. i think an inherent problem with that is; that the elastic response is changing/ lessening as you climb higher; and have less 'rubber-band'/rope left to gain the elastic response from.
 
I've never used a field dynomometer like this, so help me along here...

I'm not clear on what the dyno measured, one leg of the rope or both? Is it placed between the trunk anchor and the rope or was it part of the TIP?

If it was on a single leg of a trunk tied SRT wouldn't that mean the TIP was supporting (545# x 2)?

The dynamic forces are way higher but think about the safety factors used when you're negative rigging blocks... that's the whole problem with a rigging point below the load, shock multiplies the load.

It doesn't make sense to me to split hairs on the strength of a TIP unless you're up there where you can inspect it close up. If I have to jug up a rope, I want the TIP to be bombproof... then I'll climb up to the iffy ones a bit at a time and set a double if necessary. I like to be able to rely completely on my TIP when I'm working so I can focus on moving around and positioning... I mean, busting out a TIP while you're swinging between stems would be just... rude.
 
So say you want to set a floating false crotch climbing system anchored at the base of the tree. Say you set the line from the ground with a throwline, run your KMIII up, tie on a CMI RP 102 pulley (or something similar) and run your climbing line through it. hoist the whole jazz up the tree then get your butt up there. You proceed to climb normally, jumping, swinging, flailing and swearing about the deadwood you just can seem to get out to.

What kind of forces are being unleashed on your TIP? Sure everyone climbs differently, but has anyone measured the peak forces from an entire climb?

I should write a grant to buy a DYNO!
 
I believe what Todd did was hang a block from the dyno which was tied to the tree. This way both legs of the climbing line(anchored leg and leg being ascended. where both applying force on the dyno. Is thid correct? If so it would measure force on the entire TIP.
A dyno mesures the Peak load and is constantly changeing the current load. So he was probably able to get a readin from the top of the static load when not moving also.
 
I'm a bit short on time so I have to make this speedy (couple of young kids.). Ron and Moss, I did not read your posts completely. I do feel that both of you have a positive contributation to this discussion regaurdless of your profession. You create critical thinking to everyone reading this post in a positive way. I learned a long time ago by a great tree worker he said " listen to everone because in this business you never know it all". Mahk the dyno was set on peak hold. I only did it on a single rope with a floating false crotch. I used a hand held cam backed up with some HRC with a block in the upper holes. When I bounced as hard as I could it was up to 600lbs. When with a normal movement it was between 440lbs and 500lbs. ish. Zac. If you put a doubled roped system into an srt system the forces would be the same unless you opened the doubled system which would create 4x theoreticly.What I did was not science but it would be close to impossiable to create lab science in a living enviroment I was just messin around and found some interesting results.
 
Guys, I don't mean to slight anyone or show disrespect to any experienced climbers, I'm really a nobody compared to you guys. I'd never attempt to tell anyone here how to do their job, rig a tree or anything of the sort.

But, we're not talking about that. We're talking about how much force a trunk-tie exerts on the TIP. How many of us have actually measured that in all of our years of experience? Only a few. So the question would be, with all those years of tree work experience, how does an expert arborist quantify forces in ropes and TIPs? The accurate answer is, they don't, and there's nothing at all wrong with that. So I'm not challenging anybody's experience, not at all, but this is not about how to remove a tree, etc. it's about quantifying forces involved in ropes and TIPs; that is kinda my field. So if we've never actually measured the forces, what do we base our numbers on? Well one way is by the physics involved, and I can talk about physics, especially static physics such as being discussed here.

So please don't think I'm disrespecting anyone over arborist issues, I'm not, this thread is about forces in ropes and on TIPs.

When the question is asked about how much force is produced by something, how do we arrive at an answer? Do the laws of physics give us the theoretical results? Yes, and quite accurately IF all the variables are included. For example, we could make two simple measurements with a dyno and determine how much friction is produced by the rope over the TIP and what force is exerted on the TIP. If we can't do that, then I concede that physics is completely useless and a worthless waste of time to study.

But the whole purpose of physics, statics, dynamics, and even statistics is to help us quantify things we could not otherwise know.

From a theoretical perspective, it is impossible for a trunk tie to triple the weight of the climber at the TIP. I'll be specific: the climber is tied to one end of the rope, the rope is passed over a single TIP, or over a block for a frictionless TIP, brought back down and tied to the tree trunk. The dyno is connected between the limb (TIP) and the rope or block if a block is used. I'm saying, in a static condition, i.e. with the climber hanging motionless, it is impossible for this configuration to produce three times the climber's weight on the TIP. The absolute max will be 2x.

It would seem that there is a need to establish the loading on the TIP in a static condition first, then look at dynamic forces. If we can't figure out the static conditions, we sure won't be able to figure out the dynamic effects.

Mahk,

I was thinking along the same lines you mentioned, I would be extremely interested to see what the dyno measures Tod's weight at. I.e. attach the dyno to the saddle TIP, connect the other end of the dyno to a rope attached to a TIP in the tree and 'sit' on it. I know it doesn't take much of a 'sit' to produce high dynamic forces, but once the dynamic forces settle out, and they will if the climber doesn't move, all that will be left is the static force, which should be the climber's weight plus the weight of his gear. If the dyno reads peak, it should display a weight much higher than Tod's 165 lbs which would of course be the peak loading due to dynamic loading. If it's simply reading average, or real-time, it should read very close to Tod's weight, plus the weight of his gear. If it doesn't, something is very wrong somewhere.
 
[ QUOTE ]
From a theoretical perspective, it is impossible for a trunk tie to triple the weight of the climber at the TIP. I'll be specific: the climber is tied to one end of the rope, the rope is passed over a single TIP, or over a block for a frictionless TIP, brought back down and tied to the tree trunk.

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Of course you are correct if the climber stays perfectly still....and if there is no wind!

I was climbing srt one time in the method being discussed.....and a gust of wind came up and lifted me up more than two feet! Ron what forces would you think it would take to lift 200lbs through the friction of a tree crotch 70ft in the air? I don't know the answer but I do know it took a lot more than 200lbs of pull. Maybe double or triple. I now pay special attention to tree exposed to a lot of wind when climbing srt tied to the base of another tree. I'm glad I hadn't climbed all the way to the crotch when that gust hit! If it's windy I suggest tying back to the base of the tree you are climbing.

Great subject!
 
Ron and Treeco. both great points. The enviroment plays a huge role and I believe there will never be a textbook rule, still something to think about. When I did this I was alone. There was no way to read the dyno unless it was on peak hold. Plus the info was truly mute because the rope ran through a block and not a nature union. The number on the TIP would be even higher if there was friction involved. It would be very difficult to come up with a real number when dealing with a tree because it will also absorb energy. Still good to discuss.
 
Very interesting discussion going on!

TK...thanks for taking the time to sort out a few things. Using a dyno answers some questions and opens up more.

You're exactly right about where the highest load and friction are in a system. This brings up an application in the opposite direction. At the risk of highjacking...if you only have one block for rigging or a mechannical advantage system use it at the first redirect, that's where the highest load is and the most effeciency gain can be gained or lost when we use it for SRT.

Pete Donzelli did a research project on the efficiency of blocks that opened a lot of eyes.
 
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