Shackles Test Results

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Test Results - Shackles

Destructive Testing Web Site
Created by Delbert L. Hall, Ph.D.
ETCP Certified Rigger - Theatre and ETCP Recognized Trainer

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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 two questions: 1) It is known that the WLL of domestic shackles is based on a design factor of 6, but is this also true of imported shackles; and 2) It is generally acknowledged, based in part from information published by The Crosby Group (page 68 of product catalog) that when screw pin shackles are side-loaded (the load is 90 degrees from in-line) that the WLL should be reduced by 50%, but is this true? To help answer these questions I have destructively tested 3/16" imported galvanized screw-pin anchor shackles. Here are the results of these tests:

Shackles Pulled In-Line Shackles Pulled Side-Loaded



Sample #	Breaking Strength	DF*	Sample #	Breaking Strength	DF*
1	4717	7.45	1	4622	7.30
2	4384	6.93	2	4597	7.26
3	4313	6.81	3	4464	7.05
4	4221	6.67	4	4235	6.69
5	4479	7.08	5	4250	6.71
6	4705	7.43	6	3846	6.08
7	3672	5.80	7	3651	5.77

High:	4717	7.45	High:	4622	7.30
Low:	3672	5.80	Low:	3651	5.77
Deviation:	1045		Deviation:	971
Mean:	4356	6.88	Mean:	4238	6.69
Median:	4384	6.93	Median:	4250	6.71


* Design Factor is based on a WLL of 1/3 ton (633 lbs.)

Breaking strength is given in pounds.
Shackles were purchased from Fehr Bros. and were marked "FBI" on the shackle

Notes:
In all of the "In-Line" tests, the failure of shackles were do to the pin shearing.
In the "Side-loaded" tests, the course of failure seems more varied, and sometime more difficult to determine. Some sample had broken pins, other had broken pins and broken bells (although I do not know which occurred first, and one same had the threads of the pin stripped out and the bell sheared.

Photos of typical failures

Shackle broken - in-line pull Shackle broken - side-loaded pull
pin sheared pin broke

My Conclusions (you decide for yourself)

1) It is known that the WLL of domestic shackles is based on a design factor of 6, but is this also true of imported shackles? Based on the data from these tests, I feel comfortable in answering this question "Yes."

2) It is generally acknowledged, based in part from information published by The Crosby Group (page 68 of product catalog) that when screw pin shackles are side-loaded (the load is 90 degrees from in-line) that the WLL should be reduced by 50%, but is this true? No. There appeared to be no significant difference in the breaking strength pulled in a Side-Loaded fashion from those pulled In-Line. The results of this test do not support the statement in the Crosby catalog. I will contact The Crosby Group and ask them for data or other evidence used to support their statement about reducing the WLL of shackles. I will publish this information when it is available.

Understanding the results of tests

It is not unusual for there to be some variation in test results withing the samples of any given test. However, at times the deviation may seem extraordinarily great. To help understand why such variations occur, you may want to look at the section on Testing Equipment.