Author Topic: Parbuckle  (Read 231 times)

KC

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Parbuckle
« on: January 03, 2021, 01:50:47 PM »
In examinations of knots as rope mechanix, generally in a fixed/static state;
but still rope mechanix.
We have dynamic /moving knots of Muenter, Prussic, Poldo, Fiction Hitches, Parbuckle etc.
>>whose forces can be used statically against loading, but usual highlights are the ropes in motion.
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Especially Parbuckle, that may not even tie any single known complete knot
>>just use the rope in a certain geometry to extrude the desired effects
Parbuckle can give a 2x1 multiplier hanging or further multiplier of ramp
>>or back to 2x1 on flat ground
>>hanging is constant 2/1>>but flat surface can be just needed to get, then keep going, keep just enough light tension
>>as separate consideration

As any contact to ramp or flat ground (not hanging) also shows this is not 2x1 x ramp advantage dragging
>>we are ROLLING a log etc., and coming up over the edge of a trailer, the spar texture can even be as a gear wheel!
>>system autonomously presses the log texture into this mating

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Parbuckling is a verb.  They use it for lifting and delivering spars (and corpses) to water, also for rolling massive ships upright against ramp of sea bed (or  make one from) when can w/o crushing pressures(need to cradle).
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i also found when using truck as the pulling force, rather have the bight on the input, not anchor as pivot
>>if have bight around anchor as typical shown and pull ends/tie to truck
>>they don't pull as clean and even, have to go around and under massive log to self adjust to pull and deliver even
>>else can get slanted to side and lose on ramps
>>bight thru tow hooks or even around ball hitch if must
>>is more immediately self adjusting
would pull across trailer 90 degrees with truck on far side from ramps
>>fill a layer, anchor down rope over logs on truck side
>>swap sides for ramps and truck and fill next layer from opposite direction
>>rinse and repeat
Sorry one of my 90's drawings  drawings from my msPaint era

.
But, unless was told specifically the unknotted line in pic was a knot
>>would assume is just a mechanical usage of rope, not a knot , especially static as usually implied.
This is how work gets done!
https://forestryforum.com/gallery/albums/userpics/12054/Red_Oak_121~0.jpg

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1943 Righting the USS Oklahoma from the depths after Pearl Harbor with parbuckling.





« Last Edit: January 04, 2021, 11:39:07 AM by KC »
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DerekSmith

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Re: Parbuckle
« Reply #1 on: January 20, 2021, 10:57:23 PM »
This was my introduction to the Parbuckle and remains by far my favorite.


Posted by TheTreeSpider back in 2008.


Derek

KC

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Re: Parbuckle
« Reply #2 on: January 27, 2021, 11:15:25 AM »
Sorry missed this,
yeah i often wonder what happened to him too! 
Last i heard, accused of kibitzing with some knot brotherer.
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i have often looked at that photo tho.
2/1 effect for not a hanging, nor dragging but rather rolling load is significant change.
>>and more neatly , is it's own pulley; yet not on a (physical) axle as pivot
>> looking for pulley pivot I find the log's own CoG (Center of Gravity) as most loaded point in model
Seems also that it is on a slight grade, and if it got going, would not want to be in it's way....
And that said, once bumped forward, could take very little force to maintain, even accelerate in some scenarios.
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As it stands tho, this huge circle of 1 point on the ground(side view of model) with 2/1 compound effect of 180 arc applied
But with other changes that make it unique:
>>Half the weight sits in front (per direction of proposed travel) of 'pivot' of ground contact
>>Half the weight/remaining sits behind the pivot as ballast and balanced like this, happily stays put
>>any weight visualized over pivot, is neutral, just reducing the amount balanced to each side of pivot
Upset balance to enrage(not happy) to movement/roam seeking balance of equal/opposite
>>need to only move rear weight in target direction, cuz weight forward of pivot already pulling that way?
>>mite take more effort at some points if front half in front of pivot gone
>>then would see still had to move rear half forward, but w/o forward weight helping pulling from in front of pivot of ground contact?
>>what if all same weight concentrated to rear half, w/o front face?
Then same weight, but none in front of pivot, have to rotate all from rear to front..
« Last Edit: January 27, 2021, 01:55:25 PM by KC »
"Nature, to be commanded, must be obeyed" -Sir Francis Bacon
We now return you to the safety of normal thinking peoples.
~ Please excuse the interruption; thanx -the mgmt.~