Author Topic: In search of the goldilocks bend! (joining abseil ropes)  (Read 19563 times)

Dan_Lehman

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Re: In search of the goldilocks bend! (joining abseil ropes)
« Reply #60 on: July 19, 2011, 09:15:44 PM »
You can stop straining your eyes because I replaced the first images in each post with the correct zero load images...

???
There are two knots STILL shown : the first, in power-blue & yellow ropes;
the second (tested), in orange-ish & green ropes --they are STILL different.

I see your edit note
Quote
last image in series located in next post below...
EDIT: Images fixed!

... but don't understand.  It precedes four blue-with-question-mark boxes
(and there area already 4 images in the post below these, so no room for
any more images, whatever they are supposed to be).

Soooo, I disagree with your "Anyhow, they're fixed now - so alls good." :
they aren't, it isn't.

--dl*
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agent_smith

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Re: In search of the goldilocks bend! (joining abseil ropes)
« Reply #61 on: July 20, 2011, 01:20:04 AM »
Dan,

I've gone back and edited my words to add clarity. I have also gone back and deleted the blue/yellow rope images from my post #51 to further remove any possible confusion.

Note that a total of 10 images were taken in the test as follows:
[ ] 5 images (in a sequence) showing the top aspect
[ ] 5 images (in a sequence) showing the bottom aspect

Hopefully it all makes sense now?

I am moving on to the next phase of the testing soon... and it will be with the end bound offset overhand bend and also with different rope diameters (eg 9mm joined to 11mm).

Mark

Dan_Lehman

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Re: In search of the goldilocks bend! (joining ropes)
« Reply #62 on: July 25, 2011, 04:23:35 AM »
The search for the Goldilocks bend continues (for joining abseil ropes so they will translate around a 90 degree edge from low set anchors)...
.
.
.
DL; The image in your post #34 (the lower knot) - would like to test this too...

Still curious as to why you took the UPPER knot in post#34
(the "offset 9-oh" end-2-end joint) and loaded it in reverse
as the "Offset choked overhand bend" --i.e., loaded its tails
vs. SParts ?!  Why not test the original, which was designed expressly
for this task, and no other (and not the lazy adoption of the asymmetric
fig.9 bend )?

--dl*
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agent_smith

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Re: In search of the goldilocks bend! (joining abseil ropes)
« Reply #63 on: July 27, 2011, 03:43:27 PM »
Next data set courtesy of agent smith:

Rope data:
[ ] 9.0mm joined to 9.1mm diameter EN 892 'dynamic' climbing ropes
[ ] age of both ropes less than 5 years
[ ] both ropes were in a dry condition - not wet or moisture laden
[ ] 2 different ropes from different manufacturers (9.0mm Edelrid and 9.1mm Beal Joker)

Test rig:
[ ] Dynafor 5 ton digital load cell
[ ] hand operated winch (lever type)
[ ] rope was held by 3 wrap Prusik hitches positioned either side of the specimen test knot
[ ] load cell was positioned at one of the anchorage ends to record force

Test method:
[ ] initial photos were taken at zero load
[ ] protruding tails were initially set at 100.0mm (accuracy to + or - 2.0mm)
[ ] a series of 'milestone' load points were recorded: 0.0kN | 0.5kN | 1.0kN | 1.5kN | 2.0kN
[ ] indicated loads were induced directly on the joining knot in a linear pull (I did not form a rope sling since I wanted 2 different colored ropes for ease of study)
[ ] Another reason I did not form a rope sling is that the loads required would have had to be doubled (thereby placing more stress and strain on my rope and equipment)
[ ] at each 'milestone' load, tail lengths were measured
[ ] observations and photos were taken at each milestone load
[ ] load was increased as quickly as possible by operating lever on winch (back and forth motion)
[ ] load was progressively increased after reaching each milestone point - load was not released until final 2.0kN force was achieved.
[ ] tail 'draw-in' occurred as the load increased as follows:
- at 0.0kN = 100.0mm tails
- at 0.5kN = 90.0mm tails (Note: this would be equivalent to 1kN if descending on retrievable abseil ropes - ie 0.5kN force acting on each supporting rope)
- at 1.0kN = 85.0mm tails (Note: this would be equivalent to 2kN if descending on retrievable abseil ropes - ie 1.0kN force acting on each supporting rope)
- at 1.5kN = 85.0mm tails (Note: this would be equivalent to 3kN if descending on retrievable abseil ropes - ie 1.5kN force acting on each supporting rope)
- at 2.0kN = 80.0mm tails (Note: this would be equivalent to 4kN if descending on retrievable abseil ropes - ie 2.0kN force acting on each supporting rope)
(test stopped at 2.0kN load)

Observations / Comments:
[ ] no fracture of any component occurred during the testing up to 2.0kN
[ ] the joining knot did not fail - ropes held together
[ ] no gradual slippage or 'creep' was observed during pauses to take photos or tail measurements - the joining knot held firm at each load milestone
[ ] Easy to untie the knot - even after 2.0kN load (little effort required) - although the upper portion of the knot was cinched very tight, the lower (bottom) portion was easy to 'break' by hand

NOTE: A total of 10 photo images were taken during this test (5 images showing the 'top' aspect and 5 images showing the 'bottom' aspect of the knot at various load milestones). Due to the posting limitations on this website, only 4 images can be shown per post. The 5th image in each sequence is shown immediately below in the next post.

Structure and tying method shown below...




« Last Edit: July 27, 2011, 04:07:30 PM by agent_smith »

agent_smith

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Re: In search of the goldilocks bend! (joining abseil ropes)
« Reply #64 on: July 27, 2011, 03:52:49 PM »
Test data for 'Offset End Bound OH' :

Images shown at various load milestones: 0.0kN | 0.5kN | 1.0kN | 1.5kN | 2.0kN
Tails initially set at 100.0mm + or - 2.0mm
Knot drawn tight and dressed by hand before commencing load test

5 images in sequence (showing top view and then bottom view).

5th image shown at next post

Mark




« Last Edit: July 27, 2011, 03:59:09 PM by agent_smith »

agent_smith

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Re: In search of the goldilocks bend! (joining abseil ropes)
« Reply #65 on: July 27, 2011, 03:53:49 PM »
Continued from above...
5th image in data set:

Mark
« Last Edit: July 27, 2011, 03:58:45 PM by agent_smith »

agent_smith

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Re: In search of the goldilocks bend! (joining abseil ropes)
« Reply #66 on: July 27, 2011, 03:56:08 PM »
Next data set showing 'bottom view' of Offset End bound OH knot' :

5th image of the sequence is shown at next post...

Mark




agent_smith

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Re: In search of the goldilocks bend! (joining abseil ropes)
« Reply #67 on: July 27, 2011, 03:57:27 PM »
Continued from above...
5th image in the sequence.

Mark

Dan_Lehman

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Re: In search of the goldilocks bend! (joining abseil ropes)
« Reply #68 on: July 28, 2011, 12:25:10 AM »
Continued from above...
5th image in the sequence.

Mark


Thanks for the work & many good images.

To my eye, it looks as though the knot could've been set
more snugly.  I see that in order to to this one will need to
leave some loose material between the intial & 2nd ("end-binding")
tuck of the blue tail, so as to be able to haul hard at this point
--i.e., as though it were an offset water knot --,
and then haul the tail snug to lock the tightening (just as
the tying of an overhand knot  of this tail around the other
would suffice to lock the underlying knot.

Note that you have dressed & set the knot at one extreme of
the 180deg range of orientations of it.  In this final image, showing
the offset face, the knot can be rotated about 180deg clockwise
(and set at any point in this range), with perhaps some little variance
coming upon loading.  In the given orientation, the yellow rope is
making a backward loop-de-loop, the blue a forward arc; tails are
coming out roughly perpendicular to the axis of tension, at the
viewer (though this has been mitigated for the photo).

Now, how about some test & photos of the two knots shown
previously --offset 9-oh & offset 8-oh ??  The former, esp.,
should show a marked contrast on the underside view; i.e.,
there should be less opening of its choking wrap.

Btw, you might be able to (should be...) reach the moderate-load
state with a knot in one extreme of the 180deg range and after
phot-ing it, rotate it to the mid-point, re-load a bit, phot- that,
rotate it to the other extreme, and .... document that as well
(neverminding the full testing per orientation).  I think that this
will give us an idea of effects of this orientation aspect on the
knot integrity.  (And maybe that procedure is load & photo,
relax & rotate, re-load & photo, ... .)

--dl*
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