Proximity to the lowering device

Pardon if I'm repeating myself, a $3 ratchet strap pulling on the upper fairlead (hook tip facing away from rope or replace hook with smoother hardware) is super useful for avoiding floppy POW syndrome. You can tighten your anchor sling to take out some of the slack at initial set-up and adjust for stretch and settling very easily between rigs.

Thinking about it now, before unloading the POW, a roper might snug the ratchet strap if easy, right before landing on the ground if it's coming down slowly.
 
A few numbers. 2 1/2 turns on a BMS belay spool is 18.0 tension ratio, so adding the extra 90 degree exit turn on a porty let's call that 20 tension ratio. 5/8" stable braid 14 lbs per 100 feet. Let's call 20 feet 3 lbs rock n roll math. So 3 lbs x 20 tension ratio = 60 lbs difference in the up line. 60 lbs in up line x 1.2 tension ratio at rig pulley = 72 lbs difference at the log tie on point.

So in the rigging being considered, how big of a deal is the 72 lbs? Thoughts welcome.

Higher porty # wraps turns up the tension ratio exponentially fast, if you're contemplating a rig scenario with more wraps.


This calculation is for 20 feet of vertical rope weight. Same 20 feet in a catenary making tension - who wants to figure out that part?
 
Last edited:
Bart_ said:
A few numbers. 2 1/2 turns on a BMS belay spool is 18.0 tension ratio, so adding the extra 90 degree exit turn on a porty let's call that 20 tension ratio. 5/8" stable braid 14 lbs per 100 feet. Let's call 20 feet 3 lbs rock n roll math. So 3 lbs x 20 tension ratio = 60 lbs difference in the up line. 60 lbs in up line x 1.2 tension ratio at rig pulley = 72 lbs difference at the log tie on point.

So in the rigging being considered, how big of a deal is the 72 lbs? Thoughts welcome.

Higher porty # wraps turns up the tension ratio exponentially fast, if you're contemplating a rig scenario with more wraps.


This calculation is for 20 get of vertical rope weight. Same 20 feet in a catenary making tension - who wants to figure out that part?
Click to expand...
Smooches..
and I suck at higher complex math, but I’m pretty certain having 20 lbs or 10 for that matter stretched out a span might add considerable force to the area of the dynamic anchor.

So that 3# with your rock and roll math will be much more before the porty when loaded
 
Last edited:
Ok here goes a stab at catanery tension. This is like pushing sideways at the center of a tie line to create big tension gains at the rope ends.

A workhorse cause my brain hurts:

Cable Sag Error (Catenary Curve Effect) Calculator

Calculates displacement cable sag based on the equation of a catenary curve.
www.spaceagecontrol.com

set the tension at 3 lbs like it was vertical rope weight
20 feet straight-line distance
0.14 lbs/foot rope weight
32 ft/sec sq gravity acting on the rope - horizontal, hands same height as porty
gives:20.7 ft of rope sagging 2.4 feet

uhhuh

next try 9 lbs tension just cause, a hunch
gives 20.1 feet of rope sagging 0.8 feet

Shazam, Daniel, I think we have your answer. 20 feet of rope bouncing up into a straighter catenary shape throws a dynamic variation into the rope tension you're trying to control with your hand. That's 3 lbs of rope kicking around 9 lbs tension change into a 24x gain system. Rough numbers.

Whaddaya think? Makes sense?
 
Last edited:
Yes,
Very nice savable link, ty/stolen/adding to my deck.
.
The rope as a support column, is sheared across by it's own weight at the Samson angle..
>>It's own weight acts towards leveraged sweat/swig; just no 'purchase'(ABoK) taken/captured from the tensioned side of the system.
.
In a rigid support could fight this some; BUT
In rope/flexibles class, simply only support is tension column, and there ain't none
>>Taking the forceline as like a horizontal cosine wave aligned/ported down rope as cosine =100%
>>then 90degrees across is Zer0, elZilcho, nada column support against the weight of the rope/cable
.
Capitalizing on the sine force to sweat/swig/leverage/wrench rope as abomination of support as cosine/co(lumns)ine theory/other end of the arc/radial paradigm
>>is as a quantity of wrench leveraging function against(cos=0/sine=1) column , not a quantity of support column (cos=1/sine=0).
 
@Bart_
@TheTreeSpyder

You guys rock, and thank you for being able to articulate what I 'know' but fail to be able to effectively communicate. There is so much to it, and I do stand by with the easiest spot to control a porty or any other bollard device is about close as possible (6' or so). But this is rarely the best spot to stand for too many reasons to list, and rarely its the safest.
 
In a 24x gain system like the analysis, 20 lbs hand force would hold 480 lbs of log. Seems nominal. As a proportion, 3 lbs of rope catanery tension bouncing around potentially up to 10 lbs represents a substantial portion of the force you feel at your hand. This may be the crux of why it feels less controlled. Holding the rope close to the porty all this bouncing doesn't exist. The rest of the normally occurring transient forces would still occur.
 
evo said:
@Bart_
@TheTreeSpyder

You guys rock, and thank you for being able to articulate what I 'know' but fail to be able to effectively communicate. There is so much to it, and I do stand by with the easiest spot to control a porty or any other bollard device is about close as possible (6' or so). But this is rarely the best spot to stand for too many reasons to list, and rarely its the safest.
Click to expand...
unless I set it up...

and your knowledge isn't dependent on any online feedback... truth is what it is... it's not up for a vote
 
Might try right hand pull back waist high w/body lean; guarded ready for leg to stop forward movement if impacted.
>>And (s)light upward pull as also grip with left, ready to go with straighter pull w/o upward
>>turn some of the maths upside down with direction reverse of upward, not downward on that section/ropePart.
Then even ready to drop left hand down lower than right, working the more errant axis of the 90 to greater not lesser utility.
>>just light changes on Left from inline, most of left does pull back, just some deflection.
.
Oh so kind mrEvo.
Might step towards some math, to then see how it translates what you L-earned to feel so innately knowing from working all these raw forces so long, hearing their whispers.
It can be absolutely haunting and then re-affirming, when the numbers translate to same as what you've felt;
then even translates some stuff stuck in head/undigested history of wtf's unraveled.
Then tuning your senses more to numbers to correct skew and even grow on.
At some point, finding self ending up at the numbers for explanation and analysis every time;
find it better to simply start there.
This all has a logic to it, a mechanical logic of if this /then that invoked etc.
.
For there is absolutely, positively no physical(keyword) displacement (keyword) against(keyword) space (distance) that cannot be defined by cosine/sine on this planet, galaxy nor any other galaxy is that which they found.
This stuff 'simply' works.
We include then physical displacement against force in this too
>>for force is the reciprocal traded for in changes of distance.
>>they are antagonistic reciprocals to the sum of a whole volume in the event
>>one CANNOT be increased w/o co$t to the other, to the sum of the whole volume
It is a counterintuitive , but not impossible key, handed down, as decoded as found to rule even the star's movements.
By folks w/o TV distractions etc., touching and subject to forces in all their rawness, w/o modern buffers.
>>on some days we might come closer to that touching and subject to forces in all their rawness than about any other civilians, to have the same door aspect opened.
>>to look at world in more fuller view, than a few peeks under the crack of the door.
Earth is just in the middle of this larger sea, not an exclusive outpost that can evade these rules.
.
 
Daniel said:
unless I set it up...

and your knowledge isn't dependent on any online feedback... truth is what it is... it's not up for a vote
Click to expand...
That’s cute.. another tree guy with a ego.. now please elaborate on the finer points of these words. Are you accusing me, and my experience of nothing more than a “YouTube Arborist,” or are you attacking my experience because it was backed up with some logical sound experienced math and vocabulary that I lack?
In all fairness, there is the skill of the subtle nuances of rope work. Meaning one can learn to control a porty from 100’ away, and do it as second nature. This hypothetical person can become habituated in doing this task to the point where they do not have the read or muscle memory (or never gained it in the first place) to do any other task with the porty. This doesn’t change the reality of having more rope between the hand and the porty increases the amount of friction which can in turn become another variable.
Since when has adding more variables become equatable to more predictable? Proof in point, I’m sure these words will be waisted.
 
evo said:
That’s cute.. another tree guy with a ego.. now please elaborate on the finer points of these words. Are you accusing me, and my experience of nothing more than a “YouTube Arborist,” or are you attacking my experience because it was backed up with some logical sound experienced math and vocabulary that I lack?
In all fairness, there is the skill of the subtle nuances of rope work. Meaning one can learn to control a porty from 100’ away, and do it as second nature. This hypothetical person can become habituated in doing this task to the point where they do not have the read or muscle memory (or never gained it in the first place) to do any other task with the porty. This doesn’t change the reality of having more rope between the hand and the porty increases the amount of friction which can in turn become another variable.
Since when has adding more variables become equatable to more predictable? Proof in point, I’m sure these words will be waisted.
Click to expand...
I didn't make myself clear... you're pretty much the only one talking sense on this thread... that's what I meant by truth isn't determined by a vote....

when working with the bucket truck, I almost always attach porty to the truck which isn't in the drop zone anyhow, using a low redirect on the trunk so sideloading isn't an issue.

when setting the rigging up in the tree, I try to use a LZ that's away from the main stem, using multiple overhead rigging points. generally that helps both the climber to keep pieces swinging away from him, and helps the groundies as the porty isn't right under the overhead rigging point. more applicable on spreading hardwoods than western conifers
 
Daniel said:
I didn't make myself clear... you're pretty much the only one talking sense on this thread... that's what I meant by truth isn't determined by a vote....

when working with the bucket truck, I almost always attach porty to the truck which isn't in the drop zone anyhow, using a low redirect on the trunk so sideloading isn't an issue.

when setting the rigging up in the tree, I try to use a LZ that's away from the main stem, using multiple overhead rigging points. generally that helps both the climber to keep pieces swinging away from him, and helps the groundies as the porty isn't right under the overhead rigging point. more applicable on spreading hardwoods than western conifers
Click to expand...
fair enough, I always know I’m articulate and choose all words carefully….
 
KentuckySawyer said:
Especially, if that's how they always run the Port-O-Wrap, any perceived "lag" won't be an issue.

Learn from a safe distance, so you'll be an expert at a safe distance.
Click to expand...


When Marv was teaching me to lower...natural crotch/hemp rope/take three wraps...he always had me at least ten feet away from the tree and away from the drop zone. That training protocol carried forward as the gear improved over the years.
 
You must log in or register to reply here.

New threads New posts

Kask Stihl NORTHEASTERN Arborists Wesspur TreeStuff.com Teufelberger Westminster X-Rigging Teufelberger
Back
Top Bottom