Help with understanding WLL

[stig]

Dave, who are you calling a kid?
Me

Of course I have Don's book.
I have also written Jonchitect porivately and told him what the rest of us here think of " The World's greatest treeman" ( Bucket access only)

Just to make sure he doesn't follow some of Murphy's moronic advice and gets himself maimed or killed.

 

[theTreeSpyder]

Weakest link is the 'fused' strength of the system
>>fuse function can be used to good to protect rest of system sometimes
>>but here a failure when overloads
.
Blair's Formulae assumes a lot, like no forgiveness in system and nominal speed. Speed is squared, so exponential as Kyle says. Blair gives glimpse of nominal drops under 10' total I think was said thumbrule falls far behind at on that growth ratio. So that means CoG 4' off hinge pivot, then inverted to total 8, then play out any slack etc. and formulae close to faultline if not over before rope tension increase STARTS to de-accelerate but still running, just 'lighter' but gaining speed all the time...


https://www.hse.gov.uk/research/rrpdf/rr668.pdf
references from Donzelli, Mueiller, Blair, Bavaresco and Kotwica(wasSherrill artist) drawings and the ArboMaster calculator
page.190 : FORCES GENERATED IN RIGGING OPERATIONS

edit:
Think of hammer effect of the impact of that light head.
E=MCsquared
total force is equal to the (static wt. x length leveraged factor) x dynamic SQUARED
(in electricity this is total power =watts = (resistance x length) x ampsSQUARED >>cuz amps is speed and resistance is as weight in line over distance..)
If take hammer choked up handle to head and place/then press on scale, and press down
>>is less than if normal position and place/then press on scale
(non impacts just pressure)
But w/o messing up wife's scale know should not swing hammer at scale, can destroy it
>>and now the less leveraged /normal grip >> covrs more distance in same time(speed)
Is the larger force, not lesser

.

 

[Bart]

2nd on reading the HSE report. I ploughed through the whole thing and it's good info. One nugget was the -ve blocking rig line taking peak force at 19 degrees angle which put about 30% of the peak load into side loading the stem. They had a base tied portawrap so their peak force would hit a bit sooner than Daniel's where he explicitly wanted/put extra line into the system to get the benefit. It takes more motion to bring the longer line up to the same tension.

 

[stikine]

Geeze, I thought forest engineering was bad...you guys are nuts!

 

[Bart]

It's an incremental journey, this learning about forces stuff. Seems simple till you look close enough to realize the parts you don't really know and then it can be hard to tease out the understanding. I still consider myself a novice in the wood fiber category. The tree is the other half of the WLL situation and is not as simple to analyze as rigging equipment which is quite well understood.

WLL gets interesting when you consider dynamics and not just simple pulleys and vectors. Rope on rope (knots) and rope on non-rope is its own bag too.

Sometimes we seem too ... enthusiastic? Is that the right word? Dunno. I find it interesting.

 

[theTreeSpyder]

To me it is kinda like seeing if what you think is happening is what science says.
True your understandings, encourage you when what you feel is right is really headed in the rite direction.
.
If not be more conservative, and reset how you read things.
So that can then predict better, do more purposefully, and then read the aftermath better to learn more.
Also, to drill to the pivotal points that are the ruling class and extend to more things.
That can witness in more thinks, to learn from until more instinctive and correct.
To shoot from the hip truer and more purposefully confident and cleanly.
NOT to carry calculator into field, but only it's lessons of patterns revealed.

 

[pantheraba]

Kenny, That was a great post about seeing, analyzing, thinking, learning, evaluating, synthesizing and inculcating with purpose what one studies.

You describe the process to work to build until something is instinctive...hopefully, something correct. Well said, sir.

 

[theTreeSpyder]

Thanx, sorry i missed this.
To me, this is about honestly knowing self; and verifying.
.
i always say each is their own savant; there are things that each does rite Naturally while other things counter-intuitive slow downs.
So that you know when can throw hard forward, and when to slow down; with initial analysis.
.
So when say can't L-earn this from a book, means need observed to be guided to see and understand what is complete(hopefully)
how yours stacks up, and what needs fortified, where the holes are, cuz everyone has them and can be different.
.
Also, the numbers are a check that are visualizing things correctly as read to plot, troubleshoot or later assess
>>polished points that in a pinch, can get quicker more correct action, when really matters/on da'fly.
.
The clock imagery for checking sine/cosine/tangent i have presented has been so much of the above to me.
>>my translation guide to what is going on in so many things around before even get to tree work
>>to translate and view to see same patterns in all things, just more expressed in length, weight, rigidity and height of trees
But all the same lessons, all day everyday; once can translate what are seeing correctly, can become light play.
>> w/o mind boggling tables nor carrying calculator etc., just memory of clock!
.
That is my story!
-and i'm sticking to it!

 

[SeanKroll]

Skimmed...

in Rock Climbing, possibly the original FF, FF = length dropped/ amount of rope. This would only happen when negative blocking, with a Narural Crotch rig or lowering device up top, and snubbing it off.

In rock climbing, this is only if you lead-fall directly onto the belay anchor.

 

[CurSedVoyce]

Oldie but a goodie popped up on my feed thanks to Willie today. Hey Frans!

 

[treesmith]

All I can say is, the sound of 5/8” Stable Braid popping and watching a 600-700# chunk free-fall is a bit...unsettling...at least until it lands safely and no harm is done.

Happened years ago, before I went to blocks and porty for heavy stuff. I had used that 5/8” Stable Braid for quite some time natural crotching...it had come a quick shower, soaking the rope, and it wouldn’t run on the porty like it did dry. I told the groundie how many wraps (it had worked fine when the rope was dry). He complied, I cut the piece, it didn’t run 2’ before snapping the line.