what's the first mistake made in this rigging failure

TheTreeSpyder

Well-Known Member
#21
Part of the problem is this is 'legally' a backleaner...

Because the CoG forcepoint starts behind, not in front of the compressed part of hinge that forms the DEFINING pivot of the works.
The first thing you do with a backleaner, is make it a Zer0 /balanced/no leaner
then; make it a shallow leaner.
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Shallow leaners to me have a mathematical fault in birthing a hinge.
To me, if carefully walking a backcut, cutting 1 fibre at a time until fails
Forms formulae: strength in the hinge = can hold that much load at given sine - 1 fibre (to incite fhold further cutting weakens this setting)
>>the sidelean angle across long axis profile of hinge/none here; determines the loading pattern across the narrow axis profile of hinge
>>forward push/pulls to target across narrow axis profile of hinge just intensify the same pattern of loading in hinge; perhaps adding another row across of tensioned fiber at a now higher leveraged position/distance from compressed part of hinge as pivot
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The sine of the FORWARD angle from CoG to the pivot is the leverage;
The lean forces so much strength into hinge for us!
The change to the next degree, tests this imbued strength.
The amplitude of change of the sine from degree to degree is the impact of change that we fight and try to prep hinge to fight.
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Sine is changing so fast in shallow leans; that by comparison
a 30degree /1 o'clock lean forces a hinge stronger ;more suited to loading at 31 degrees
Than, forging it's strength at 1degree lean; and the MUCH GREATER IMPACT of change incurred at 2 degrees.
The hinge is much weaker to it's purpose AND then has even farther to fall in shallow leaners...
We be playing into a stacked deck... and not to our benefit!
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The load i say goes from a range of hold to fall; we try to capture control in thru gradients between thru range of' controlled 'fhold' (hopefully) before fairly uncontrolled free-fall
The load forces it's own hinge strength; the more load/angle the more intense arm wrestling done to birth stronger hinge.
We pull with rope, and lift with wedge, to arm wrestle/challenge/fake-out/exercise more strength in hinge by falsley loading the math until hinge births
THEN relieve extra wedge, rope loadings to leave the strengthened hinge carrying a lighter load than it was made for!
This is especially needed in shallow leaners;due to the rapid HIGH IMPACT of loading change as fhold starts.
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i would have roped over the top for highest leveraged pull
>>rope position chosen is lesser, straight line, leveraged reduced at first movement forward
>>over the top gives best leverage, rotational input, maintains/even can INCREASE leverage as moves
as we try to leverage more, to birth a stronger hinge to usher load thru arc on hinge as far as possible
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Whenever i see something working against me; like span between block hitch and load hitch;try to figure how can use that same force someday,mebbe even today!..
i would have prussiked to span between and had another pull line to sweat this line
>>more pull on load
>>IF ground control is slick enough and extra frictions ready to apply (rope around tree after Porty):
would have ground control try to snatch even more purchase from line, thru Porty, then add extra frictions at drop.
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i'd look to use semi-truck tire spoon(small lip for kerf, lever made by super strong forging ) rather than wedge to urge from back, replaced by push when she moves
ANYTHING to forge stronger hinge as birthing it
When, load movement is committed/ will not stop all false hinge loadings of rope pulls and pushes are to stop!
We have challenged hinge stronger,but now don't want to extra load to essentially weaker!!
Then, strength is already set into hinge; must trust to hand off to it to control acceleration/hit.
We used extra load forces to strengthen hinge/fhold with more fibers; now remove extra fake loadings so hinge is stronger to it changes it will meet on tour around hinge.
My crazy azz at this point mite even be seen pulling back on load !!
ANYTHING to slow the acceleration(but not stop motion)
farther out bod in opposite direction, just like guy line would ballast against some loading to more so have the balance of forces conducted more INLINE properly down the stem as a support device.
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If using guy line would to same theory pre-tighten it over compensating/ tighten it TOO much;
so is leaning back some, this way you know it is tight;
and look for hit to compensate Naturally by pulling stem more into pure inline at the peak loading impact.
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Rope still looks puny to me.
BUT no matter the rope, i would have tried to give the device the most chance/done the same dance.
Force as much strength in hinge, whatever else to drop the peak force input from acceleration.
If had to rig, probably would have had hitch points closer, and favored not facing on worst side to do so..
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If watch can see skinny hinge/no strength. CoG rolls up the hill over pivot, then pretty much freefalls w/o hinge restriction.
Longer piece, more risky due to CoG rotation to farther out pull when moving, more need for opposing force guy rope to ballast peak forward pull forces and more usher and inline flow of force down spar properly during peak loading pulse thru system of the hit.
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i probably would have cut into or closer to time of fhold
>>climber set minimal hinge, of minimal strength, then load was pulled
>>didn't really try to set a hinge strength in youth; for hinge then to arm wrestle the load ; ushering longer hand-off and slower hit into system.
 
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#22
That piece seemed small to me.... guessing he had to keep it small to clear the ground.... I rig pieces that heavy on 1/2" true blue all the time..
You asked for the first mistake made. Plan was first, execution was second. I understand you may do this all the time with your 1/2 true blue but let’s look at the numbers.
That piece is approximately 6’ long and definitely looks better that 36” diameter (comparing to the climber as scale)
Not being able to tell exactly what species here is a variety (not taking into account the heavier crotch wood from those limbs).
White pine 1,524 pounds, Doug fir would be 1,656, and hemlock 1,740. Even the lightest on GWLC western red cedar weighs in at 1,326. (I believe Adams green weight log chart (the really big one)).
This still doesn’t take into account your perfect block placement at no more that 1 foot drop which can as much as double the force.
Samson true blue. Average strength (assuming that means breaking) 7,300, minimum strength 6,600 (treestuff product page).
If Samson rates it’s true blue at 10% or even 20% working load limit just the piece of wood is over weight (unless you found western red cedar around here). They were using 3/4” Polydyne rated, according to yale, 23,400. With perfect block placement and 20% WLL there is plenty of strength (on a new rope).

Now it may look like I just contradicted my two posts, but I still say that plan was flawed and another technique would have been better suited. I would even argue with a sharp saw, that could have been cut into 1 foot cookies almost as fast as setting that rigging..... that didn’t work anyhow. At some point you either have to drop the spar or chunk it, so what’s 6 feet. I don’t punish my ropes like that because I want to make sure they are going to hold, when I need them to instead of beating them to a pulp senselessly.
 

Daniel

Well-Known Member
#23
Excellent analysis... I took a closer look after reading your post and I definitely underestimated the size of the piece... (they ALWAYS look smaller on a computer screen)... SO you make a good point about the rigging plan being the first mistake... I agree...

For the sake o conversation and any learning that comes from it, one important factor that could radically bring those numbers down (given there is no run in the system) would be stretch in the line... When you're cutting so low like that there is less line in the system, so less stretch. One way of adding stretch is to put a redirect and move the ground anchor back away from the tree.... But that wasn't in his rigging plan either.
 
#25
DBR if you must!
There have been threads about double block rigging and this actually would have been a great place for that technique. Although it may not be the fastest or easiest way it certainly would have changed the forces and where they go. Then probably a half inch rope would be adequate with a good rope man.

For the sake o conversation and any learning that comes from it, one important factor that could radically bring those numbers down (given there is no run in the system) would be stretch in the line... When you're cutting so low like that there is less line in the system, so less stretch. One way of adding stretch is to put a redirect and move the ground anchor back away from the tree.... But that wasn't in his rigging plan either.
Absolutely correct! In my first post I mentioned the end of day bla’s, where we tend to take the easy way out on the most critical parts of the tree. Moving the friction point (add the redirect of course) is one of this simple things that just make life easier and a bit safer. The DBR also adds more rope and parts the line giving more security. It also adds another block (or ring) and an anchor point giving additional locations where shock can be absorbed. When we put enforcers in the system it was amazing the reductions and where things went. I will admit it’s more effort for the climber which brings us back to making sure we aren’t taking short cuts. Switch climbers out, or come back for the wood tomorrow. A piece of wood rocketing to the ground that was intended to go much slower is dangerous, because it’s not expected, guys may not be ready to react as needed to get out of the way of a bounce. Everyone knows the Jimmy I’m talking about.
 

TheTreeSpyder

Well-Known Member
#26
wrong side to cut, shallow face, cut out all tensioned fibers; just free falls off pivot after rolled into position.
>>pull considerations are more important if hinge fiber not cut all out
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Pulley on load will drop line tension, and if all rigged thru 1 point drop support load from 2xPeak to 1.5xPeak
>>BUT less elasticity in system at lower tension, impact pulse thru system doesn't drop as far as would hope!
>>line elasticity increases with tension
>> (until hits in-elastic range in more of a brittle, pre-break state)





Lots of motion per 1 second youTube clock (speed) X heavy X non-deforming load
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i view the shape as empty shell container/contact points;
>>weightless until put heavy CoG ball into position as it's only force.
Everything else is just a position on the container to act/work against CoG; and it back!
Schematically plot-able flow of force thru conducting container devices; like hydralic, electric pressures etc.
 
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#27
I Think this scenario could be comparable to the above video. What are your thoughts on this set up.... ASH 1.jpg
This was a 29 inch 5.5ft long White Ash piece in a 2 tier deck. Weight approx 1400-1500lbs. Similar in weight to the above. 3/4 Samson Stable Braid Rig Rope with 3/4 Samson Stable Slide line. 1/2 Samson BRW tip line. 2 Nylon Loop Runners with 3 steal carabiners and a 8 wrap friction hitch. 3/4 40,000MBS CMI Block 1/2 Dyneema eye sling, with no slack in system We cut big pieces slow pulling slack out as The TreeSpyder stated cut reload line inching the hinge closed so by the time the wood breaks it doesn't shock the rope '. Cut cookies last 15 feet to deck. ASH 2.jpg ASH8.jpg ASH5.jpg ASH6.jpg ASH4.jpg 93 feet.
 

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colb

Well-Known Member
#28
I Think this scenario could be comparable to the above video. What are your thoughts on this set up.... View attachment 49826
This was a 29 inch 5.5ft long White Ash piece in a 2 tier deck. Weight approx 1400-1500lbs. Similar in weight to the above. 3/4 Samson Stable Braid Rig Rope with 3/4 Samson Stable Slide line. 1/2 Samson BRW tip line. 2 Nylon Loop Runners with 3 steal carabiners and a 8 wrap friction hitch. 3/4 40,000MBS CMI Block 1/2 Dyneema eye sling, with no slack in system We cut big pieces slow pulling slack out as The TreeSpyder stated cut reload line inching the hinge closed so by the time the wood breaks it doesn't shock the rope '. Cut cookies last 15 feet to deck. View attachment 49827 View attachment 49828 View attachment 49829 View attachment 49830 View attachment 49831 93 feet.
I like how the zipline backs up the 3/4" line in the event that the 3/4" line takes a direct pinch from the edge of the rigged piece. Not judging, but I'm noticing that your chain is a little stretched, lol. It's great that you were that on point at such a late stage on what looks like an intense project.
 
#29
I like how the zipline backs up the 3/4" line in the event that the 3/4" line takes a direct pinch from the edge of the rigged piece. Not judging, but I'm noticing that your chain is a little stretched, lol. It's great that you were that on point at such a late stage on what looks like an intense project.
 
#30
Thanks. I didn't notice the chain while cutting but now that you point it out it does look pretty sloppy. It was the first tree for the brand new chain and saw Husq 562 28" bar. Good observation. Always learning.
 

southsoundtree

Well-Known Member
#31
Looks like a big chunk to snub off with a small amount of rope in the system on a long dead tree. I wonder if it would be faster and easier to cut two chunks that were half as much, with smaller, lighter gear, no pull rope or hinge.


Everything is rated, but the tree.
 

Bucknut

Well-Known Member
#32
Daniel wasn’t there showing how it should be done?
Correct.

@Daniel, I think we can all agree that the better plan would have been an inverse "V-rig" utilizing a 35 to 1 whip tackle system. All rigging should be set with your 75' bucket, and of course it should be 1/2" True Blue. The piece should be pulled over with 4 Wraptors acting in concert, or the largest bobcat you have. Oh, and at least 7 redirects should be used for that pull line. Easy peasy.

Kidding. ;) I always enjoyed your old videos where it seemed like you were pulling over trees that I would not have dreamed of. I agree with your analysis above, and also that piece was bigger than I originally thought too. It was so big it made that rigging line look like half inch when it was actually three-quarter inch. I bet he put the sling so low because his last cut was so close to the stub, and he was worried that there wasn't enough good trunk above the stub for the sling. I like the idea of double block rigging, but I think we all know why he did not do that. What a pain.
 

owScott

Active Member
#34
I would argue the removal plan was flawed and thus the rigging plan was flawed. Why was a piece that large and that close to the ground being rigged in that manor? Certainly there should have been no expectation that the piece was going to be slowed safely to avoid a crater, so why rig it. If bouncing away is a concern, vertical speed line is a great option. Rig a smaller piece or chunk smaller pieces. All safer options.
There is a propensity in our industry to get sloppy when we get to wood. Probably because it’s the end of the day, we are tired and we have had enough. The eyes get bigger, we get braver and take bigger chances. “Go big or go home”, right?
I agree, should have just "chunked down small pieces or that close to the ground go to the bigger line. I keep a 5/8 on the truck for that reason. 1/2 line with that size wood ok if you have some height to let it run , that's been stated. 1/2 line even with tighter rigging that close to the ground locked off, that's pushing it, even a new rope. my initial response was , not enough rope. Saying that you have bombed that size wood many times onto a 1/2 line shows how many times you have been very close to a failure. Something to think about. I bet faced with this scenario again you tighten the rigging and go to a bigger line. No disrespect to you Daniel, I know you know your business. The rope broke that's a fact, even if tighter rigging would have prevented the failure that's cutting it very close to the ropes limit. Why do that?
 

SomethingWitty

Well-Known Member
#35
Man, is that much slop commonplace? Especially in such a dynamic setup? I rarely have the distance from my hinge to my block (facing down as if loaded) more than a foot when I am blocking things down.
 

Stephen Moore

Well-Known Member
#36
Rigging line looked old and diameter looked too small. Sure the sling was set low and the piece was not allowed to run, but I have done that on occasion with out a problem.
Rope diameter can be misleading, there are 3/4" ropes that have less breaking strength than some 1/2" ropes. Some 1/4" ropes that are stronger than some 1/2" ropes. I think That dynamic loading played a major part in this failure as did exceeding the required safety factor for the intended loads. Had they stepped up another level in Bull rope, sure it may not have broken but the dynamic loading may still cause internal damage to the rope. Repeating that abuse will eventually cause a ropes failure.
 

Stephen Moore

Well-Known Member
#37

your thoughts???
the dead eye was at least 3/4" or bigger and the rope was 1/2" maybe 5/8" but I'd guess 1/2"? And could well have been previously abused? Anyways, the rope was too pussy for that kind of piss poor rigging technique. If you plan on being that sloppy at least use huge gear!
 
#38
What's everyone's maths on the weight of the log? 600kg to 800kg?
If so, how intense is the force multiplication of such a long drop.

Great video to see the potential side effects of poor workmanship and overloading equipment.
Were the trunk not there the rope or pulley could have kissed the climber!
Ouch
 
#39
At the end of the vid it says it’s 3/4” polydyne rope. ABS 26,000lbs. WLL on that rope is 5,200lbs. Tie a knot, and it cuts that to 2600lbs. I’m not the best at gauging size on logs, especially through video, but that piece would probably be heavier than that with dynamics. Looks like the piece was not run either, but I’m not sure if I can see enough to speculate that. The 4 foot of slack between the block and the piece was killer, but if that truly was 3/4” polydyne, in good shape, it should not have broken. I think the rope was worn
 
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