i believe that the BFly is a great lacing that gives max service when the ends pull as SParts equally as the primary loaded axis.
The eye, to be loaded less, if at all; and to pull cross-axis to the primary/ not along the primary loaded axis defined above. Anything else but this maximum peak, is a compromise to lesser. If pull by eye is not perpendicular pull against primary axis; then eye pulls unevenly on the ends that noted should be balanced pulls etc.
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In trucker usage the eye of the BFly pulls inline to the primary axis as worst pull position and then is loaded more than one of the ends in this pattern of usage; breaking the rules above for max peak performance.
BFly is so gracefully stable, don’t really get it to look unfriendly until a worst of the worst scenario of worst loading position (like Trucker’s)at highest loading to distort balanced BFly to where can’t untie easily.
Many times best solution was to pull it back to ‘square’ with hard pull thru the ends as was designed for, to then step closer to easier untie.
But that is after maybe 3 men, truck or tractor pull thru the Trucker’s system to target to make it unfriendly in worst position pattern at high loading, and thu pulleys on 2x and 3x positions for greatest return. Stiffer, more ‘frictive’ , textured etc. rope mating surfaces as another multiplier against untie that is usually easy.
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The lay of Bellringer Lesson#1148 with 3-4 HHs lays more amicably to this service. i use BFly when can get away with it, within it’s very large powerband, even in it’s distorted position of pulls in Trucker’s with eye pulled in worst possible direction , and imbalanced pulls; until higher loading getting out of BFly getting into this worst of the worst. A heck of a ‘knot’, but still with limits.
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In safety/fail-safe speak, would always have another trick/path per the 2is1, 1isNone mantra.
And a pin or stick thru BFly to remove after loading to loosen knot is doable.
Irrespective of eye choice(sorry fave topic showing rope powers outside of a small knot where we may see better) :
3 positions of pull in Truckers of 1x,2x,3x power POTENTIAL; typically 1x is input, 2x position is machine pivot and 3x as output position, but can rotate where input, pivot, output each engage the 1x,2x,3x positions to use as a transmission to manipulate distance/speed etc. But in normal usage of 3x Output POTENTIAL , powered by input of hand pull to 1x position, limited by bodyweight.*
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Friction inefficiencies count against the power tradeoff, not the distance tradeoff.
So if net output of Trucker’s after frictions is 1.65x as power tradeoff, still the distance factor is still 3/1 tradeoff etc.
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In vertical position of pulling rope down over a load etc.; can hang bodyweight (pick up legs sharply) on the 1x as input that comes out of the eye, and then pull up on the rope part going into eye also (2separate hand pulls as if another person helping, just inputting at lesser input position now as dual inputs). This delivers full bodyweight thru the 2x and 3x position multiplier positions, BUT also 4xEffort at each of these positions as is now a closed/simpler/more force conserving system. And not limited to part of bodyweight as input but using full bodyweight and then 4xEffort on top of that (all POTENTIALS less frictions) in the 2hand input strategy, so as to capture the equal & opposite force of the effort and funnel it back into the system; rather than letting equal & opposite of effort express outside the system. This becomes magnified when stand in loop on end, and use 2hand strategy but this time input leg lift to be magnified, instead of arm pull. In rescue or other lift climber can be in key position if at or higher than litter position to employ this factor.
i think by far, the most efficient usage of bodyweight, effort and equal and opposite of effort all captured against target thru the dual input.
Similarly a typical 5x rig (1x,4x,5x positions) can amp up to 5xBodyweight, 4xBodyweight when input in 1xBodyweight with hang, then add 8xEffort to each of the output ends as a POTENTIAL/pre-friction with the 2 hand strategy applied correctly!
With short run for truck input have anchored the 3x at top of hill using pulley that sometimes was after turns on terminal end, put 2x end on pulley pulled by truck , and 1x on the load to pull load half as hard, 2x as far(and thus 2x as fast) as truck input pull; as solution. The handiness of Trucker’s is beyond just the 3x pull output aspect!