Negative rigging

[TheTreeSpyder]

In my home-made self taught terms gritty treeman view:
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Force needs equal and opposite to express against, or is just falling/displacing distance as Dan said, otherwise is displacing against space not force. Displacement is key term to use, think of like from engine world, more displacement takes more energy. Energy can be stored(even as fuel) or else used to displace against space/distance or other force(or compound mix of both). Note that in either case, space OR FORCE, must pre-exist, to then be expressed against.
Energy=mcSQUARED is still the basic form here i think.
Speed is SQUARED factor then of most relevance. i look at speed Squared as the dynamic part, and the Mass as the static part to make the whole of the scenario. Discussion is more about how that total sum of energy can be used/expressed (rather than stored) i think; to displace against other space or force with the force expressed against them.
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Thumbrule:
The length displacement of CoG formula works fair to about 8-10 feet they say; but is an approximation, bird's eye view of the worx. But still only a peek under the door trying to see the whole world of this on the other side. Thumbrule formula has the 2 factors, static (1 unit of self) and dynamic(1 unit of self per foot) elements to me. But speed is ever increasing until Terminal Velocity of air friction equaling mass/can't continue acceleration. So the thumbrule worx in the lowest/slowest accelerations rite off the starting line, but really not much further as things really gets going. Speed is that important and ever increasing in this importance until terminal velocity.
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Relevance of Speed Models:
Shoulder/arm is 3rd class lever, so longer is LESS power, so choking up on hammer handle until right under head gives GREATER leverage, when simple static press on a scale. Grip far end of handle and can press LESS leverage STATIC press on common weight scale. BUT a speed of the hit as DYNAMIC force, from the less leveraged, as more arc in same amount of time OUTPUT(so also diluting force, not concentrating it), gives the devastation from the speed squared as it trumps equation sum larger in spite of the leveraged decrease LOSS of the more static expression of the leverage x mass.
also model:
A matching vehicle of 2x more mass in a head on collision will over rule the lighter vehicle @ matching speeds. But if lighter is later moving 2x as fast, will walk thru the heavier with about double devastation greater beating to heavier that the heavier gave the lighter with at matching speed.
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Friction:
The calculation of friction is on arcs, compounded with the same formulae base as compound interest, population growth, disease spread etc. from Euler's number (log. of 1) with an exponent of:
Flat, linear friction table for the mated surfaces(nylon on aluminum etc.) X PI X number of 180 arcs collectively.
So in my mind flat/linear CoF converted to radial by multiplying by PI, then the amount of arc units as exponent. Spreadcheat link.




Distance and force are 'antagonistic reciprocals' to me, as one is used to overtake the other to the sum total of energy expressed/not saved from the pool of energy in the shituation. That worx funneling forceDistance into or out of the work fair/square. Deacceleration can be started at what we call impact that is really a moment, where deacceleration is more a range started from that moment actually as i think Mitch tries to lend; just as acceleration can not be a single moment, needs at least another moment to show change over range. This can be hit transfer or heat conversion (from frictions and elastics) but all changes and continuances can be mathematically accounted for to the same sum as input into this phase. Braking distance/ deacceleration distance is as to acceleration distance, everything must always be fair/square backwards and forwards to same balanced equation.
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Eastern philosophy says to be as water flow, for you only incur the force you resist(rest travels past you).
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Force, is force; E=mcSQUARED is just shown here as expressed in physical forces.
And prevails so importantly over all, this even works in electricity as:
Total watts of power = Resistance x Amps SQUARED
so R is the static 'weight' against movement in the device/line, and A is the SPEED, dynamic part of the force,
so again even here E=mcSQUARED prevails across physical and electric forces as it does the rest; that are just different translations/expressions of same principle.
Electric example not shown to confuse, but rather reveal the persistence of the formulae and also what i look at as also the persistence of the static and dynamic components as well, to be the main focuses.

 

[Neill]

Will keep searching but thought I’d ask to speed up the process.

I have seen somewhere before the forces explained when negative rigging, it explained really simply how the forces multiply for a given weight over a certain distance.
Can anyone shed any light

Parts 1,2, and 3

 

[Birdyman88]

This topic keeps coming up again and again, and Yale has an answer. If you really want to know how to calculate the dynamic forces on the rope, go visit Yale's website and look up something called "Energy Absorption Factor". They have an EA for each of their rigging lines. It is the only way to reliably do a dynamic load estimation, because dynamic loads ARE HIGHLY ROPE DEPENDENT, not just on the size, but on the model as well. The video above is mainly to demonstrate that the forces get really high, but it is not meant to be a tutorial on how to calculate the force. Warning - there's math involved in Yale's method, but it's pretty unavoidable. Force is not energy. A falling object has energy, until a force acts on it to speed it up or slow it down. Here's an example of using Yale's EA factor:

*6 ft log @ 600 lbs, block 1 ft below hinge, COG 3 ft above hinge
1) COG fall is (3 ft + 1 ft) x 2 = 8 ft
2) Potential energy before cut is 600 lb x 8 ft = 4800 ft-lb
3) After cut, 4800 ft-lb potential energy converted to 4800 ft-lb kinetic energy while falling
4) Log hits rope and converted to 4800 ft-lb elastic energy and rope stretches
5) Divide 4800 ft-lb elastic energy by Yale's EA factor, say 575 ft-lb/lb for polydyne, and you get 4800 [ft-lb]/575 [ft-lb/lb]= 8.3 lb of rope needed to keep max force at 20% MBS or less - their EA is given for 20% MBS - more later
6) If you're using 5/8" polydyne at 13.6 lb per 100 ft, then you need 61 ft of rope.
7) Now that 61 ft is needed to keep the max force on the line at or less than 20% of the lines MBS, which for the 5/8 is about 4,014 lb [seen on line].
8) If you use more rope than 61 ft, the max force will be less, if you use less rope, the max force will be more.
9) If you're really math savvy, then you could go spend some time with this and come up with an equation that tells you exactly how much force on line for any given length and model of rope. But, at the end of the day, on an actual job, you really just need to know if you have enough rope in the system or not based on whatever max load you can tolerate.
10) This is based on dropping a log of known weight. In reality, wind resistance on brushy pieces, condition of rope, letting it run, friction at rigging point, and other factors can come into play to alter the actual load on the line.
11) For shits and giggles, a long while back, I actually used Yale's EA factors and applied it to the scenario in the video based on the numbers they stated. My estimation of max load on line was only off by about 50-ish lb from what they measured if I recall right.
12) Yale can provide more information on how to use other numbers for the EA, such as EA for 10% MBS, as the derivation of those numbers can be complicated and subject to the shape of the elasticity curve for that particular rope.

Sorry if I sound terse, but like I said this questions pops up over and over, and for something that can have such devastating consequences, you'd think the industry would spend more time educating on the topic.

 

[Birdyman88]

From Yale. Look at the column that says "Working energy Absorption". This will show you how different the dynamic absorption capability of Yale's flavor are. Also note that the value is based pounds of rope, not any specific diameter or length, and it's also based on keeping peak load at 20% MBS or less.​

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Engineering Data​

Product	Strength Scale 1-5 (5 = strongest, diameter to diameter)	Elastic Elongation at Working Load %	Weight Scale 1-5 (5 = heaviest, diameter to diameter)	Working Energy Absorption Ft Lbs/Lb of Rope	Maximum Energy Absorption Ft Lbs/Lb of Rope	Rope Average Specific Gravity g/cc	Splice Complexity Scale 1-5 (5 = most complex)	Dielectric Leakage, New/Dry, at 100 kV AC, 2ft. Spacing, in Micro-Amperes*** (250 Max allowable)
Aracom Miniline	2.9	0.6	4.0	100	4,906	1.40	5	NA
Aracom T	3.1	0.7	4.4	157	4,409	1.40	3	NA
Aracom 100	3.8	0.9	3.9	426	8,144	1.44	1	<250
Crystalyne	2.7	0.5	4.3	187	3,403	1.40	3	<100
Double Esterlon	1.4	2.2	3.9	291	7,711	1.38	2	<20
Hy-Dee Brait	0.7	2.7	2.8	116	12,673	0.93	3*	<10
Kernmaster	1.2	6.2	3.8	622	9,775	1.23	3	>500
Lugger Line	1.0	2.2	2.4	330	11,400	0.95	1	<100
Maxibraid	3.5	0.7	3.3	226	6,342	0.97	1	<100
Maxibraid Plus	2.7	0.6	3.7	115	4,295	1.18	3	<100
Mega Max	2.9	0.5	2.7	318	8,300	0.97	3	<100
Nylon Brait	1.3	10.0	2.9	1,426	23,680	1.14	3	NA
Oceanographer’s Brait	1.3	17.5	2.9	2,739****	26,074	1.14	3	NA
Optimus ROPE	1.8	3.5	4.6	351	9,915	1.38	1	<100
PE-12	1.7	3.0	4.3	406	8,738	1.38	1	<100
Phantom-12	1.3	1.0	2.3	212	4,521	1.40	1	NA
Polydyne	1.5	5.1	3.8	576	11,187	1.24	2	>500
PolyPlus Braid	1.1	3.4	3.1	395	8,228	1.25	1	<100
Portland Braid	1.3	2.0	4.0	265	5,929	1.38	2	<20
Shark Byte 12	1.2	1.2	2.2	296	3,884	1.10	1	NA
Shark Byte 8	0.4	3.3	2.7	478	10,365	1.14	3	NA
SP-12	2.1	1.1	3.9	292	5,851	1.12	1	<100
Tech-Kern	2.8	0.7	3.8	233	4,571	1.44	3	NA
Ultrex Plus	2.9	0.5	3.7	140	5,428	1.18	3	<100
Ultrex	5.0	0.6	3.1	318	8,300	0.97	1	<100
Uniline	1.4	3.5	5.0	262	5,230	1.38	5	<50
Unitrex XS 8	3.5	0.5	4.6	NA	NA	1.10	4	<50
Unitrex XS Max Wear	3.5	0.5	4.6	247	6,893	1.10	5	<50
Vectrus	4.3	0.6	3.8	232	4,446	1.40	1	<100
Yalex	1.7	3.0	4.5	409	10,700	1.38	1	<100
Yalon	1.1	7.0	3.5	796	11,871	1.14	2	>2000

 

[TheTreeSpyder]

The less headroom/ the more the rope tensile is used, gives greater elastic response returned.
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This is so true, that if make a 2x1/pulley on load, where the system has more capacity, and less loaded per support leg yields LESS elastic dampening response thru the system to deal with the dynamic component/hit.

 

[Dan Cobb]

Somebody correct me if I'm wrong, but E = mc² seems irrelevant here as we're not converting mass to energy or energy to mass. Many equations contain a squared value.

If somebody is doing some negative rigging where E = mc² does come into play, I don't want to be anywhere near it!

 

[TheTreeSpyder]

Sorry for the delay
i believe amount of energy induced into support as receiver;
would 'simply' be = mass x velocity SQUARED*.
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By different version i mean the 2 part break from static resistance to dynamic state change of the sitting force waiting to be overcome, then how much dynamic force/speed squared applied once state changed.
The formulas given all have this in my view, the thumbrule seeks to approximate in lower/nominal ranges for mechanical type. And also has the terminal velocity limit on chain of increasing acceleration in actual physical model. But is really ever increasing to limit so only works in low, nominal ranges.
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Just that in the model of Relativity, the speed is of light squared.
In the Electric model it is the Amps as speed squared.
In the fall model it is speed of the falling 'body' squared.
And the thumbrule given has the same 2 part breakdown , 1 for static overcome to dynamic state, 1 for speed/dynamic amount once in that dynamic state.
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Just that in the kinetic/motion it really is 1/2mgh SQUARED (mass, gravity rate, height)
for in magic/ideal perpetual energy machine if get half the weight moving can slam to other half and continue i think.
But then doubled back (mite have said this wrong) thru pulley is more 'full cycle' than 'stroke' so more
2x 1/2mgh SQUARED. or mgh SQUARED as mass times acceleration rate x height/distance of acceleration squared. (gravity rate has square internal too). So more mass X velocity SQUARED as closer to the rest of the formulas, at full cycle model.
As a pattern start to look familiar with mostly adjustments to speed type that is then squared to me.
Many physical things alter a formula to half point (position by midpoint) or other (CoG) determinate, so the 1/2 is normal here to me as well. Especially as a stroke of a cycle.
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Very powerful gifts handed down to us are these formulas where a single term is defined by only 2 pivotal variables (as cos/sin does too), neither of which is the element itself. Logically can't break anything down farther than that, w/o being again itself kinda.
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Am all self taught, try to use rite terms, sorry if some lines blurred, but these are consistent patterns i see and can't refute in cross comparative usages or studies; even when try very hard. The whole Einstein-ic imagery seems to lend towards this relativity, connectivity even as chases counter-intuitively into light bending around black holes and time/space continuum etc.
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We work touching closer to the raw Nature of these things than most, about as the Ancients did.
i would never have seen this far w/o tree work.













*Other formulas giving versions of same, are just particular to physical, electro-magnetic, gravitational, kinetic, chemical etc. studies.

 

[Noodle]

I know this is a far far simplified version that doesn’t account for a lot of factors but it’s easy to quickly figure out on the job to really make you think about the force involved.

I think Don Blair’s rule of thumb was for every 30cm an object dropped it gained a unit of weight plus one. So a 100kg log dropped 120cm would stop with a force of 500kg on that side of the line.

In practice I just setup the rigging to reduce free fall/dynamic loading. Then calculate/estimate weight of piece and multiple by five to get the possible peak load.

 

[TheTreeSpyder]

Mostly i think models direction to groom to/forces to minimize; and the immediate important reason for doing so to control what can. Trying to lend a feel for what is going on.
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On job the numbers blur, as aim just mostly at most reactive points in the pattern. Hopefully now with renewed urgency, targeted focus, smoothed confidence forward. Grooming/polishing too each part that easily can as go to correct math direction. To orchestrate best outcomes. Many times just by a few polished points as go along, to simply put as many chips on your side as possible, knowing which are critical, general or nominal. And then just for the art, to develop the habit of seeing and doing smoothly , seamlessly as nothing.
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My chase always to pattern, just have to hit the numbers to find patterns.
Chase numbers to learn, confirm, cross compare etc., but always testing to make sure training sense of these things in right direction.

 

[Bart_]

An unstated part of my equal fall/equal stop = x2 force is that the onus is on the arborist to mix and match rigging setup, how much run and rope stretch contributions - to get a fairly uniform force during the equal stop. Energy absorption in the rope via Blair's(?) pure elasticity or Yales presumed elasticity plus damping is not needed to be quantified, it's just by feel. If you're snubbing the load off in a hard stop the rope properties become critical - different ball game, you're into the Birdyman Yale energy absorption calculation.

Daniel had a dynamometer video with basal redirect and fair bit of rope with interesting results.

 

[Bart_]

Noodle, here's a thought. If you drop a piece into a chain, or a 3/4" rigging line or a 3/8" cough-rigging-cough line you'll get three different values one or none of which might be the x5 value.

So a rule of practice line sizing to max load at 1/5 line strength means in a snubbing situation, for a given weight like say 500 lbs, you stick in your rope length, drop and run the Birdyman Yale calculations - which are affected by the choice of rope diameter say 1/2" and see what peak force happens (smaller rope damps down the magnitude of the peak) and see if it exceeds the x5 safe rigging limit. Or the max energy absorption. The result of such an exercise should be log weight matched to line diameter for hard snubbed quick stops. This ought to be a chart standardized for industry use. It's a worst case. Hard snubbing with the same short fall but into longer rope is gentler, and so is let er run plus stop.

Who wants to make the chart? Chance for fame and fortune. Well, fame anyway.

 

[Birdyman88]

which are affected by the choice of rope diameter say 1/2" and see what peak force happens (smaller rope damps down the magnitude of the peak) and see if it exceeds the x5 safe rigging limit. Or the max energy absorption. T

This is a good point made here. The discussion thus far has been on the force generated and whether it exceeds the safe working load of the rope. But, there is also the consideration of the max force relative to the rigging point strength. While using a larger rope may keep the max force at a lower percentage of the ropes MBS, it will generate a larger peak load due to the lower elasticity of the larger diameter. Just assume we're talking about the same rope model, just different diameter.