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Webbing, Cord direct attachment to bolt hanger:
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majid_sabet
Sep 30, 2007, 10:36 PM
Views: 15598
Registered: Dec 13, 2002
Posts: 8390
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Few months ago, a climber on Supertopo was asking about tying webbing or cord directly in to bolt hanger as an attachment link without using a biner and he was wondering whether webbing was stronger than similar size (strength) cord when tied in to a bolt hanger. That got me thinking about doing a test to see how webbings or cords fail during a direct tension via bolt hanger. Yesterday (Sat 29-2007), I accidentally ran in to a friend of mine Bob (RC Boku) in one of the parking lots in Yosemite who happened to be there trying to recalibrate his homemade pull tester using a dynamometer so I took the opportunity to gather few pieces of webbing and some 6 mm cord and ran a quick test to see how webbing and utility cords fail when tied directly in to a bolt hanger under tensions. This is what we noticed.
Bob K calibrating his puller.
[URL=http://www.picoodle.com/view.php?img=/9/9/30/f_PICT0013m_15c6a42.jpg&srv=img39]
First, we took a standard size 1 inch webbing (tied it with an over hand bend) and ran the webbing through a FIXE bolt hanger. Shortly after we begin to pull, the webbing got crimpled in the corner of the hanger and at 2350 pound of force, the webbing suddenly snapped in half.
[URL=http://www.picoodle.com/view.php?img=/9/9/30/f_PICT0015m_1712587.jpg&srv=img39]
[URL=http://www.picoodle.com/view.php?img=/9/9/30/f_PICT0018m_30d7ed5.jpg&srv=img39]
[URL=http://www.picoodle.com/view.php?img=/9/9/30/f_PICT0024m_19d43f1.jpg&srv=img39]
[URL=http://www.picoodle.com/view.php?img=/9/9/30/f_PICT0026m_41c2b7a.jpg&srv=img39]
[URL=http://www.picoodle.com/view.php?img=/9/9/30/f_PICT0028m_34e4d4d.jpg&srv=img39]
[URL=http://www.picoodle.com/view.php?img=/9/9/30/f_PICT0034m_cb3e7b5.jpg&srv=img39]
Test 2; we placed the webbing directly over the flattest part of bolt hanger so the webbing stayed completely flat as we pulled. The webbing broke at 2200 pounds of force.
[URL=http://www.picoodle.com/view.php?img=/9/9/30/f_PICT0066m_42e6d9b.jpg&srv=img39]
[URL=http://www.picoodle.com/view.php?img=/9/9/30/f_PICT0068m_c868f00.jpg&srv=img39]
[URL=http://www.picoodle.com/view.php?img=/9/9/30/f_PICT0070m_45fa48a.jpg&srv=img39]
[URL=http://www.picoodle.com/view.php?img=/9/9/30/f_PICT0148m_0804f21.jpg&srv=img39]
Test 3; we doubled the webbing on the bolt hanger only- not the anchor point- and pulled. At 2550 pound of force, the inner part of the webbing (directly contacting bolt hanger) started to break; soon after, the tear started to rotate toward the outer part of the webbing, it suddenly snapped.
[URL=http://www.picoodle.com/view.php?img=/9/9/30/f_PICT0072m_43a3829.jpg&srv=img39]
[URL=http://www.picoodle.com/view.php?img=/9/9/30/f_PICT0078m_7c4f06c.jpg&srv=img39]
Inner core breaking apart
[URL=http://www.picoodle.com/view.php?img=/9/9/30/f_PICT0084m_a9e1ef0.jpg&srv=img39]
[URL=http://www.picoodle.com/view.php?img=/9/9/30/f_PICT0085m_0a9da0e.jpg&srv=img39]
[URL=http://www.picoodle.com/view.php?img=/9/9/30/f_PICT0255m_92d8e90.jpg&srv=img39]
Test 4; we used a piece of standard 6 mm utility cord and pulled it and at @1700 pounds of force, the inner core of the 6 mm cord started to break apart and shortly after, the outer sheath slowly came apart. The 6 mm cord roughly stretched to three times of its original loop size before it snapped. A great portion of this stretch was caused by the knots tightening significantly as tension was applied.
[URL=http://www.picoodle.com/view.php?img=/9/9/30/f_PICT0036m_3bb8791.jpg&srv=img39]
[URL=http://www.picoodle.com/view.php?img=/9/9/30/f_PICT0053m_931d827.jpg&srv=img39]
[URL=http://www.picoodle.com/view.php?img=/9/9/30/f_PICT0057m_6830358.jpg&srv=img39]
[URL=http://www.picoodle.com/view.php?img=/9/9/30/f_PICT0058m_548ae0e.jpg&srv=img39]
[URL=http://www.picoodle.com/view.php?img=/9/9/30/f_PICT0062m_8781036.jpg&srv=img39]
[URL=http://www.picoodle.com/view.php?img=/9/9/30/f_PICT0064m_5842a0d.jpg&srv=img39]
Test 5; we tied a piece of webbing with a piece of 6mm cord looped together and applied tensions. We removed the bolt hanger from this test. Both the webbing and cord were on rounded anchor points. As the cord drew tight, its loop narrowed and crimped the webbing where they joined. The cord broke at this joint at 1500 Pounds of force. The webbing showed signs of fusing caused by the friction of the cord breaking. The ends of the core of the cord were also fused from the heat.
[URL=http://www.picoodle.com/view.php?img=/9/9/30/f_PICT0088m_a93b116.jpg&srv=img39]
[URL=http://www.picoodle.com/view.php?img=/9/9/30/f_PICT0100m_f0de065.jpg&srv=img39]
[URL=http://www.picoodle.com/view.php?img=/9/9/30/f_PICT0108m_3ea0119.jpg&srv=img39]
[URL=http://www.picoodle.com/view.php?img=/9/9/30/f_PICT0120m_2d3519a.jpg&srv=img39]
[URL=http://www.picoodle.com/view.php?img=/9/9/30/f_PICT0123m_70310d9.jpg&srv=img39]
Inside the webbing
[URL=http://www.picoodle.com/view.php?img=/9/9/30/f_PICT0128m_e3d362e.jpg&srv=img39]
Our conclusions:
Running webbings or any type of utility cord directly through any bolt hanger should be avoided however, based on what we noticed, the 6 mm utility cord even though smaller and weaker than the standard one inch webbing ( rated to 4000+- lbs), handles the tensions and forces gradually, compared to the 1 inch webbing, which was subject to suddenly snapping under the gradual load. This discrepancy was definitely due to the different elongation properties of the webbing and utility cord. Also, the doubled piece of webbing handled the forces slightly higher (by 200+ POF) than a single flat piece of webbing.
Our testing is unofficial and the accuracy of this test still is questionable however, based on what we noticed, the inner part of bolt hanger acts as a sharp knife and eventually will cut soft material under gradual tension or sudden impact. We think that the breaking forces will be significantly lower if we shock load the webbing and cord on the bolt hanger, though we have yet to do any tests.
Thanks to Bob K, Werner B, and Chris Nanamura.
Any questions, comments, and suggestions are welcome for future tests.
(This post was edited by majid_sabet on Oct 1, 2007, 4:50 PM)
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Edit Log:
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Post edited by majid_sabet
() on Oct 1, 2007, 4:19 PM
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Post edited by majid_sabet
() on Oct 1, 2007, 4:25 PM
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Post edited by majid_sabet
() on Oct 1, 2007, 4:43 PM
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Post edited by majid_sabet
() on Oct 1, 2007, 4:45 PM
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Post edited by majid_sabet
() on Oct 1, 2007, 4:50 PM: Missing, hosted images
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