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Today we are looking at the MightyLock and what sort of strength retention values we get on different types of slackline webbing. Not only are we interested in what strength the MightyLock can get us on our webbings, we want to look at the two main ways of loading webbing in the MightyLock to see if there is a significant different between these methods in terms of strength retention.
We will look at both configurations on 17 different webbings to see if there is a correlation or any sort of trend given a type of webbing.
In order to look at strength retention values, we need a baseline strength for every slackline webbing we test (Control Group). In order to do this, we have opted to follow the guidelines of the ISA with how they test slackline webbing in order to be ISA certified. They use a device called the "Whale", which is a webbing anchor with an 80mm diverter and no webbing overlap on the first bend. We built our own version of this device, dubbed the "Blue Whale", and used it on every webbing we tested. Our version requires a sewn loop on each end of the webbing we test, which is anchored to a grade 9 bolt going through the Blue Whale.
The webbing wraps around the Blue Whale main diverter, around the center bolt, and then back up to the back bolt, where the sewn loop is anchored. Each side of the sample wraps around the main diverter in the opposite direction, giving an even loading through the thickness of the webbing.
Each sample starts as a 6.5 foot (roughly 2 meters) piece, then a 5.5 inch (14 cm) length is folded over on each end and a sewn loop is added. The final sample length is then 5 ft 7 inches (170 cm). We have learned throughout these tests that long samples are a necessity. We get drastically more variance with short samples.
Each webbing tested has at least 4 samples, and up to 8 samples done. The 4 sample types were done because we ran out of material.
After having a Control Group to test against, we ran our test samples. This includes two main groups: Right-Side-Up and Upside-Down. The Right-Side-Up group is loading the MightyLock in the standard, approved way, with the loaded strand on the outside of the wrap of webbing, pictured below.
The Upside-Down group is the same configuration, but pulling on the other strand of webbing leaving the MightyLock (load strand on the inside of the wrap). You can see this loading style pictured below.
Each webbing tested has a minimum of 5 samples and up to 8 samples. The larger sample sizes were done on webbings we experienced a lot of variance on. Most of the time this was attributed to short sample lengths.
Each webbing starts as a 5 foot sample and we tried to maximize this length by installing the MightyLock at the very end of the sample. Early on in the testing process, we weren't as diligent in this process, which accounted for a lot of the variance we saw in the testing.
For 25mm/1-inch webbings, we used a 12mm bow shackle with a 1/2" pin diameter to terminate the webbings with the MightyLock. For 20mm webbings, we used a 1/2" Van Beest Shackle with a 5/8" pin diameter to terminate the webbings with the MightyLock. All tests were done on the pin-side of the shackles.
Here you can see a photo of our test results on the webbings we tested for the Control Group. Please note, not all of these webbings were tested in the MightyLock study, as some of them are not compatible with the MightyLock due to webbing or MightyLock dimensions.
As we can see, the average strength retention across all webbings for the Right-Side-Up Group stands at 87.73% compared to the Upside-Down Group, which is 79.89% across all webbings. The lower number on the Upside-Down orientation is attributed to several webbings slipping in this configuration.
You can see here the graph from our Feather PRO (Yellow Blue) webbing in this orientation. You can see the various spikes that occur during the test. The webbing is slipping multiple times before finally breaking well below 20 kN. This slippage occurred on multiple different webbings, with a variety of material types. This is the primary reason why we have opted to suggest against using this method for anchoring webbing with the MightyLock.
Another interesting comparison is material type. Does nylon retain more strength than polyester or high tech in a MightyLock? Yes, it does. Here are the averages for the material types (number of webbings in that group in parenthesis):
The High Tech needs more data as we only had 2 different webbings to test. With our coming high tech webbings, we will be able to double that sample size, which will then be added to this test report.
Furthermore, another interesting comparison is width. Do 20mm webbings do better in the MightyLock than 25mm? Maybe only because of the larger pin diameter on the shackle used (1/2" vs. 5/8")? The answer is no, not really. However 40% of our 20mm webbings are high tech, so that may be throwing the results off a bit:
Throughout the testing, one thing became very clear to be a major influence on the result: sample length. A lot of our early tests were done with long tails on the MightyLock. For these webbings, we saw very large variance in the samples. If we were to do this study again, the tail lengths would be a standard for the experiment. I apologize about that inconsistency. For others that are interested in doing tests like this, we highly recommend maximizing your sample lengths as much as possible. Not only does that represent real-life usage more, it also allows room in the sample to equalize a lot better. Webbing flaws are exaggerated with short sample lengths.
One other configuration that we looked at was pulling on both strands exiting the MightyLock. This type of configuration might be used in a segmented rig, where you want to attach your backup to an intermittent connection on a mainline (maybe a T-Loop or DLV loop). We only tested this configuration with 2 different webbings as we have TONS of data here on how other webbings perform. Below you can see our results:
We had to stop short on this testing because we kept breaking MightyLocks. This loading orientation puts substantial leverage on the MightyLock such that it is breaking well below its MBS. We were also bending our 1/2" Grade-9 Steel Bolts (rated at 160 kN in double shear). This tells me that the leverage inside of this type of loading is astronomical. All the more reason to steer clear of this type of loading.
The biggest take-aways from this study are that more than material type can influence how a slackline webbing will behave when anchored with the MightyLock. The biggest thing that effects retention in the MightyLock is the sample length. Beyond that, thickness, material type, specific weave, and maybe even width (more tests needed) can impact how well a webbing does with the MightyLock. However, regardless of these variables, the MightyLock continues to prove itself as a reliable and safe way to anchor your slackline, provided you load it correctly.
Lastly, remember, your loaded strand should be on the outside of the MightyLock. Do not pull on the inner strand as it can lead to premature failure of your webbing.
Thanks for reading through our tests results. If you have any questions or comments, please leave them below or get in contact with us.