Load
Lab
Test Results - "Used" Hardware
Destructive
Testing Web Site
Created
by Delbert L. Hall,
Ph.D.
ETCP
Certified Rigger - Theatre and ETCP Recognized Trainer
Load
Lab Home Test
Data Testing
Equipment Support/Sponsors
Disclaimer: This
site contains the currents results of ongoing research and is
not a finished presentation of findings. The
information on this site may be the results of a
small sample of tests and are NOT conclusive evidence of
anything –
they are
just my results. Take them for what they are. Any conclusions
drawn from these results are yours
and not are necessarily mine. Go the Load
Lab Home to read the complete disclaimer.
The purpose of this series of test is to help answer the
question: Does the normal use of hardware weaken it, and if so, to what
degree? To help answer this question I took new (imported)
1/4" shackles and applied between 1100 lbs. and 1200 lbs. of tension to
them (this exceeded the WLL of these shackles which is 1000 lbs).
This force was held for approximately 10 seconds before being
released. This process was repeated for a total of ten times
before the the shackle was destructively tested and the breaking
strength record. Below is a comparison of this test group to
a control group of identical shackles destroyed on the first pull.
Control Group
"Used" Shackles
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| Sample # |
Breaking
Strength |
% of rated BS |
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Sample
# |
Breaking
Strength |
% of rated BS |
| 1 |
7334 |
122.2 |
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1 |
6240 |
104 |
| 2 |
6469 |
107.8 |
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2 |
6295 |
104.9 |
| 3 |
5558 |
92.6 |
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3 |
6329 |
105.5 |
| 4 |
6425 |
107 |
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4 |
6407 |
106.8 |
| 5 |
5840 |
97.3 |
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5 |
7040 |
117.3 |
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| High: |
7334 |
122.2 |
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High: |
7040 |
117.3 |
| Low: |
5558 |
92.6 |
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Low: |
6240 |
104 |
| Deviation: |
1776 |
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Deviation: |
800 |
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| Mean: |
6325 |
105.4 |
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Mean: |
6463 |
107.7 |
| Median: |
6425 |
107.1 |
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Median: |
6329 |
105.5 |
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| * Design Factor is based on a WLL of 1/2 ton
(1000 lbs.) |
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Breaking strength is
given in pounds.
My Conclusions (you
decide for yourself)
1) The breaking strength of all of the samples
from the test group exceed the rated breaking strength of the shackle.
Based on the results these tests, I feel that the "normal"
use hardware (not exceeding its WLL) does not reduce its breaking
strength. This did not a surprise to me.
2) What did surprise me was in
both groups there was one sample that far exceeded the results of
the other samples, and that two samples from the control group did not
hold the min. rated breaking greaking strength (6000 lbs).
I contribute this to poor quality control in the manufacture
of the shackles. As was evident in some of my test on
galvanized aircraft cable, all hardware is not created equal.
I believe that tests on better quality shackles would have
provided more "even" results. Still, I do not believe that
this negates my conclusion above.
Copyright 2008 - Delbert
L. Hall