Author Topic: Trucker's Hitch compounded  (Read 217 times)

James Petersen

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Trucker's Hitch compounded
« on: November 18, 2021, 07:00:20 AM »
Don't remember seeing this particular method of the Trucker's Hitch described or discussed here before, though it has been several years since I have gone clear through previous threads on the same. The video is clear enough, though the language is Korean, and some of the terms in the captions (if you turn them on) are novel/strange -- possibly word by word translations.

At any rate, here it is:



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Re: Trucker's Hitch compounded
« Reply #1 on: November 25, 2021, 01:12:12 AM »
Rumors of increased mechanical advantage by such
rope-on-rope structures is greatly exaggerated!!
Try it yourself, with barbell weights, e.g..

I hung 45# vs. 62.5# on half-inch thin cable-pulling
polyester tape over a smooth oval carabiner :: NO movement,
and movement of heavier wgt. downwards started by me soon
ground to a halt!  At +5# (=67.2) there was some movement,
but slowwwww.  And note that this is tape vs. metal, which
I THINK is well better than w/o metal,
though OTOH and rule of thumb for friction of 'biners
and rope is around 60-66% efficiency.

(The start of the video is the best!  ;D  )



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Re: Trucker's Hitch compounded
« Reply #2 on: November 26, 2021, 10:07:44 AM »
i remember this lesson well from you; as oh so true.
>>The nominally ADDED potential force, also multiplicatively COMPOUNDS the inefficiencies.
Here, the pulls are not all inline, so also note some loss there of lesser focused cosine than if pulls pure inline.
>>but then also here that could fortify against some side pulls with those more sidewards legs.
The potential force increases are per leg/folded legs against load in single increments potential as inline pull from single input.
Operating 2 pulls within this, at proper points in opposite directions can give more single increments of potential added.
>>so instead of 1xPull into multiplier have bodywieght + that same pull thru most multiplier, then another pull of equal and opposite force/direction inserted at a lesser multiplier point.  But still working linear pulls down length, not across.
Leveraging/sweating/swigging ACROSS (not inline) each leg can get more pull at that point
>>then also the dragging frictions holding potentials back convert to friend at some point as help hold that purchase on the other side of that friction buffer.
>>making that now tighter leg that bent even more rigid/less rubbery a lever for higher return on leveraging/sweating/swigging across
>>the more rigid leg resists the bend more, returning more leverage when bent.
Can rinse and repeat per leg, then start over.
At end can lock down and then bend the whole rigid support structure to tweak out more leveraged pull against load.
"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.~

James Petersen

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Re: Trucker's Hitch compounded
« Reply #3 on: November 29, 2021, 04:55:07 AM »
Actually, what I found interesting was his method of tying. For the initial loop (the firs "sheave") he uses a bell ringer's knot with a riding round turn. This is the only method I have seen used in this part of the world (Taiwan) in the 30 years I have been here. It is important the second turn rides over the first.

But his method of tying the compounding sheaves is what caught my attention. How much he gains from compounding may or may not merit discussion, but this is my first time seeing the second subsequent sheaves formed in this way -- all others I have seen simply duplicate the manner of tying the first sheave, which can make the whole affair tedious to untie, especially if it has been pulled very tight, which is the whole point. It starts at about 5:20.