Bend radius for rigging

Brummel is excellent theory, and maybe close enough;
>>just going with model of imperfect exchange, always has to be some even trickle of friction etc. co$t of conversion(or maybe 'Kennedy bullet' would still be flying)
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Some of my many lessons of Iron Cross on still rings chase in gymnastics(w/Lseat floated of legs out front); finding the binary flip between can and can't of perseverance etc., clock numbers across the gym in accordance to geometry and what FELT etc.,
Was that it did not matter if a 'man' was ultra muscled or not so much;
They could NOT use that power over own weight w/o the 'bat wing lats'(on ground, harder to see off ground/stretched in action)
>>w/o the as if a lats 'brace' angled for a 90° shelf, best if flared 45°, could NOT attain to then hold position for the longest 3seconds in eternity...
No matter how much power to weight (x arm length), if just a 90° corner at intersection/shoulder and not the 'brace' angle across, fall thru every time.
GEOMETRY as access to potential.
(But even then as get to the peak, have to get in own headspace to pull off..)
 
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Muggs,
"So if I tie onto a 100lb piece, then the rigging line sees 150lb at the hitch?"

In a "least" worst case snubbed catch
5 G's in the line so 5 x 100 lbs = 500lbs
Two line segments pulling the rig pulley so 2 x 500lbs = 1000 lbs at the pullley
50% more in the pulley sling legs so 1.5 x 1000 lbs = 1500 lbs in each leg
50% more in the -if single- girth hitch legs 1.5 x 500 lbs = 750 lbs in each leg

hanging after catch, 50% more in the -if single- girth hitch legs 1.5 x 100 lbs = 150 lbs in each leg

if standard marl/half hitch plus girth then the load gets split up between them

:)


Idea - they should have a groundie competition for the smoothest lower i.e. who kept the peak force the lowest without the log striking the ground, Would be enlightening numbers and entertaining.
 
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Playing it backwierdz, to scale, immediately know/warn more force on cross axis to watch out for, than main target now at that efficiency ratio given is below 70.7%median as a benchmark:
If 100# hang takes 150# of tension to be supported
>>the 150# tension of POTENTIAL support is only expressed @66.66% efficiency AGAINST target 100# load dimension direction attributes.
>>therefore the deformity only allows a cosine of 66.66% expressed against the 100#load dimension to reach a balance point of force (static load not rising nor falling)from 150#tension input against 100# load
FYI:should always know benchmark 45° cos would be 70.7%
>>so the deformity is greater than 45°(~48°), to get throttled/filtered down to the lesser 66.66%expression to the target dimension direction against load.
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Just as if length was 150" as material attribute; therefore potential of the material
>> @ same cos:66.66% would throttle potential down to get 100"reach expressed AGAINST the vertical support dimensional direction to load as reach against free space.
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BUT: Math also reveals/warns that at the same 48° are expressing 74.31% of potential 150units of attributes of pull and reach AGAINST the crossing/horiz dimension as a byproduct of 111.47units expressed each(length and force)
>>so is GREATER expression byproduct to the horiz dimension of 111.47#(and length)than the 100#(and inches)expressed on the target/working vert dimension as efficiency of expression as faded to this much against target.
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FYI: 45° is meridian/halfway betwixt 0° and 90° deflections (target and crossing dimensions) from benchmark of domain force line direction.
>>45° is also unique for it is only place that cos=sine(70.7%)
>>as see here deflections from force line direction greater than 45°
>>ALWAYS, MUST have/risk greater byproduct expression to crossing dimension(sin) than expression to target dimension(cos), aligned dimension(which is vert here)
>>of course if deflection is less than 45° 'meridian'/halfway point between target and crossing dimensions, then express more on the target/aligned dimension than expressed to the byproduct crossing dimension.
MOST MATERIAL FAILS OF ROPE, WOOD, STEEL, PLASTIC etc. etc. ARE FROM CROSSING DIMENSION FORCE, NOT ALIGNED DIMENSION
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Alignment gives clean reach, but side drift the changing numbers of mechanical change. Linears in rope are extensions sometimes at nominal co$t, but machines of large potential mechanix change are in deflections, and so organically to fullest dramatic mechanical changes to exploit in radial/not linear rope parts. The arcs are the machines, linears just extensions to the works.





Full potential 150units (reach, force etc. etc.) cos=100%
has a non(e) of Zer0 expression @90° cos=0% to the original dimension >>as non(e)s of each other to the sum of the whole
Logically between 0%-100% are ALL potential expressions of a material attribute
The change from given full potential dimension to it's dimension of non(e) is UNIVERSALLY and ALWAYS the same bell curve of change, NOT a simple, scalar of evenly incremented change. Force, distance, speed, light/shadow etc. etc.
>>cos:sin value pair are 'simply' snapshot coordinates of the universal bell curve of change between full and zero expressions of the potential attribute assigned to the material.
>>Whether that attribute is length, force, speed etc.
>>or even going into sound, electric, hydraulic etc. waveforms
IS ALL THE SAME MATH STUDY of applying cos:sin value pair as to how much of material attribute is expressed/throttled to target dimension and it's non(e) of the crossing into other dimension, in all things.
 
Daniel said:
did you ever break one?

I haven't

Who do you know that has broken a sling?

Have you ever put a dyno on a negative rigging system?

I have...




ps... The lowering line was locked off as part of this experiment, meaning there was no run in the system
Click to expand...
I broke one years ago. There';s a thread on here somewhere about it. All factors were not equal though. Good rope and rigging. Poor sling for the sorta wrap. Failed at the base and the porty rocketed into the block where I was.
 
Bart_ said:
Idea - they should have a groundie competition for the smoothest lower i.e. who kept the peak force the lowest without the log striking the ground, Would be enlightening numbers and entertaining.
Click to expand...
This brings up an interesting comparison for me - dynamic ropes/ an ATC on a belay and catching a leader fall v.s. porta wrap/ negative rigging with essentially "static lines" and letting a piece run. In both cases, forces can become considerable quickly and "the catch" takes practice.
 
I did some drop testing with a locked-off line, 1/2" true blue, to show that Blair's formula is way off because it didn't account for stretch in the line. We dropped an 1,100 lb piece into the true blue that fell many feet and the max load was 2,300 lbs and also many other pieces that were 2-3x max load as the piece weight... some of them dropping over 10'...
 
I’m glad you posted this. @Daniel this was the class I was referring to with notches, type and push / pull forces.
The ‘issue’ with rings vs blocks is interesting, nothing we haven’t discussed here. Where there is more strain on the load leg and less on the anchor leg due to… duh the friction!. It’s important to know that there is LITTLE CHANGE in forces, BUT a different distribution of those forces.
That and COM (center of mass) trumps sling length (choke to block, and the rope drop into the rigging). I’m sure this all plays a part, yet COM plays a huge factor
 
Wicked gravity (F=m x a) is a constant across fields, but as a comment on the last two posts, I've always wondered why there is much attention paid to things like fall factor in alpine ice climbing circles, yet I see much less focus on things like amount of rope in the system etc. in treework (i.e. fall factors v.s. safety factor/ WLL's, rough rules of thumb, etc.). I often wonder what each field could learn from "read across" to other rope disciplines/ sports and their own "ways of thinking". Each in their own paradigms. Anyway, my two cents. Enjoyed this. Cheers.

Addenda: Maybe it'll be in the papers, but this is why I think it's important to document the type of rope used, elongation value, amount in the system and other variables in any "research" or trials going on. So much of the "science" I see going on lately fails to take into account or document all the possible variables and ends up only with "more study needed (to get the value of "s" lower) . . . .
 
i believe Blair was properly looking for potential force to define a finite region.
Then would factor in elasticity as working within that domain, to yes lessen the hit.
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A different rope, of different elasticity as a factor dialed up or down to a different yield, but always resulting within the domain of the defined finite range possible.
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Just as with cos:sin; seek potential first then less cos is less support realized from the potential. Or 1000# on 1 line, or divided to 3; has less tension per rope, but same potential etc.
 
Keeth said:
This short came across my Facebook feed this morning. The amount of rope in the system makes a huge difference!
Click to expand...
Amount of rope from block to the Porty/GRCS or to the ground guy/ belayer? Since most of the friction occurs at the capstan (yes?) does that argue for a block at the bottom as a directional and friction from the capstan moved to another galaxy far far away? Just wonderin' out loud . . . Again, in climbing, the "arrest friction" occurs at the belayers ATC (for e.g.) rigged to the belayers harness and him/her moved away outta harms way.
 
If you're going to lock it off, add rope to the system.

That video looked like poor choices.

I'm super impressed it didn't break, somewhere.
 
The rope in it's elastic range, has a quantity X amount of rubber band yielding some shock absorber, more length in system gives more shock dampening. But, then for lesser loads, invading tensile capacity less, has then less elastic, more static response from rope.
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model:
BUT not more dampening in system with a 2/1 on load for extra strength and dampening, for has opposite (d)effect for are making dual legs of lower tension, invading tensile strength less to then get less elastic response, so incurring more raw hit...
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Every bit of elasticity, friction slip, give in support parts etc. matters like relief of knocking pressure cooker valve open a half second, to just as like trim peak steam from either system. Preloading overhead line can lessen change in impact. I liked super tight line out from hinge and pivot on hinge for final self tighten when can.
 
Daniel sorry for the late reply. I believe Muggs' quote was referring to the attachment to the falling log so I gave all the numbers. (minus tension ratio effects for simplicity) One vid (the 4 examples vid) has a beautiful pic of the double whip pulley's sling forming up the leg angles in a single girth configuration.

In a rigid tower/hardware configuration the only give is rope elasticity so it dominates but in tree rigging knot reconfiguration and slippage dominates. If I remember your video correctly you had a redirect pulley at the base of the tree where one normally has the porty (snubbed off or groundie run). You could add to your analysis a 1.15 tension ratio at the rig tip pulley and perhaps 1.1 tension ratio at the 90 degree redirect bend to correct the dynamometer readings vs actual log weight/force. i.e. the dynamometer read low.


In ring vs pulley, the log side rope force profile remains the same and if you draw the torque creation diagram the down rope leg contributes nearly zero to bending the trunk so the trunk still gets yanked the same but the rig tip sling has a little easier life. In non-spar rigging the ring's advantage is more apparent e.g. deceasing rig tip load.
 
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Sounds like I recall the video. Don't know if I posted at the time but as I recalled further I identified another shock absorption feature added by your configuration. The horizontal rope hangs in a catenary prior to loading and straightens up more during loading. Another contribution to absorbing the fraction of a second long peak force.

In someone's (Samson?) tower drop testing they ended by just being puzzled why the rope didn't suck up the hit per the area under the stress strain graph i.e. more rope absorbs more hit. Was disappointing but lead to further investigation/curiosity. In my test rig I couldn't get down to 5 G's until I ensured all tied connections could adjust. Just the rig tip accounted for x2 higher hit. I played with line elasticities and they didn't have big effect.


Got the Facebook video to play. Another example of sling leg angles- about the same as the other videos.



edit - 48 minutes into Matt's video same approximate weight piece, LESS rope in the system, LOWER force.... huh? well, actually he explains it rather well

@MattFollett - respect, keep up the good work!
 
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