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Tetsting of slackline equipment by team
March 10, 2016

Tetsting of slackline equipment by team

It has been more than 2 years that we did not communicate on endurance tests on this blog. We were still working on it, but not publishing anything. We have a bit more time now, so we digged out and compile our results.

Here are the results on our gear. Some results are satisfying, others less and will lead to new tests. The Natural Games accident was schocking for us and led us to rethink what strength we wanted for every piece of gear of a slackline. And this process is long.

The test :
We wanted to simulate a Jumplining use by the APAVE, an independant laboratory, to check the difference with a classic breaking test.

Concretely, we realized 2 tests :

  • to break a new piece of gear. Get the result.
  • to test the same piece of gear with 100000 cycles between 8-10kN and 18-20kN at 1Hz. If this piece of gear resists this endurance test, then proceed to a break test. Get the final result.

Why such an endurance test ?
While jumplining, slackliners jump at a rate close to 1 jump a second (1Hz frequency).
Then we simply counted how many jumps a competition setup can hold during a day, and we concluded that a competition setup can hold 10000 bounces a day.
Then, during the competition, our jumplines are rigged at 9kN, with load peaks at 17kN on the hardest bounces. Most of the jumps are at 14kN, and we heard of people bouncing hard at 18kN or even 20kN.

Here is the test we have with these facts :
The endurance test represents 10 days of jumplining with the highest load peak each time.
This is an arbitrary choice, and more hardcore than in real life. This is also a compromise between the price of such a test and -yet to define- product expiration. Yes, 10days is short, we know that. We would like to push those tests later at a million cycle, which is really endurance in the industry field (1-2 million cycles or more.)

Results :
12mm shackle : 91,1kN breaking test.
12mm shackle : 92,2kN breaking test after 100000 cycles from 10 to 18kN

14mm shackle : 129,7kN breaking test.
14mm shackle : 120,5kN breaking test after 100000 cycles from 10 to 18kN

16mm shackle : 161,5 kN breaking test.
16mm shackle : 164,3kN breaking test after 100000 cycles from 10 to 18kN

Ratchet with black sling :

We are interested by the body strength of the ratchet. We assumed that there is a good chance that the teeth will be damaged in normal use before the body. This will be a test to run for next time. The black slings breaks at 58,2kN after 100000 cycles from 10 to 18kN.

The ratchet breaks at 93,3kN after 100000 cycles and the first breaking test of the sling.

Leashring (one ring) : 99,1kN breaking test.
Leashring (one ring) : 108,9kN after 100000 cycles from 1 to 8kN (100000 Leash fall !) You can fall on our rings with no problem (by pair of course).

Sladlock Power : 49,3kN breaking test
Sladlock Power : 3984 cycles from 10 to 18kN. The sladlock is used over the WLL which is 10kN, but shows the weakness of it on a jumpline use.


Prototype of 5cm Steel Sladlock for Jumpline - 700g : 93,7kN breaking test.
Endurance test : holds 84084 cycles from 8 to 20kN.

Double pulleys :

Setup Skylab01 vs Skylab03 : 42,3kN breaking tests (Skylab 01 breaks).
Endurance test : the skylab 01 breaks after 31488cycles from 8 to 18kN.

Conclusion :
12mm, 14mm et 16mm shackles are good for jumplining. They don't show signs of reduction of their strength despite the endurance test.

The black sling of the ratchet is the weakest link on the breaking test. It needs to be checked regularly. Its breaking load limit is lower than the ratchet and can be weakened by other ways (dirt, sun). We strongly recommend to change this sling every year in an intensive use, or as soon as you see something wrong on it. The ratchet should be changed every 2 years in intensive use. It's hard to promote this kind of preventive behaviour, we know it.

Sladlocks power are clearly not made for a jumplining use, as jumplining tensions are over the working load limit.

Pulleys are more resistant but also too weak for a jumpline use. Skylab 03 with the integrated rigging plate is of course more resistant, and would have been good to test alone, but still we do not recommend it for a jumpline use.
From our side, these results completely bans the use of aluminum gear on jumpline.
Aluminium gear can still be use on other types of slacklining, as all the slackliners do with all the aluminium gear from all the brands.
And it would be a shame to have no lightweight equipment for everyday slacklining, wouldn't it ?

Then, it appears that even a 700g weblock with stainless steel plate does not resist long enough at this test. For us, the use of weblocks for jumplining, and by extension pulleys is not good enough to guarantee the safety of the jumpliners, if they are not clearly changed regularly.
As a result, we decided to stop to develop those weblockers, as the concept is not safe enough, and lead to too heavy gear.

The good old ratchet finally appears to be a good solution, which allies simple setup with a correct safety, as long as it is well backed up. The teeth that should normally be damaged after some years of use is a safety key to oblige people to change their old gear for a new one. The endurance of the teeth are still to be defined.

At last, we continue to search how to prevent from any slackline gear to be projected.
Our latest test showed that a piece of gear can be projected more than 40m around a slackline setup, without any prefered direction. Unfortunatelay, we already knew that slackliners can be hit by gear, but this test shows that even the audience around the line can be hit. An extreme care should be made on the contest lines, where the audience is numerous and the line has a lot of stress. We have become paranoïd for sure, haven't you ?

Be safe on the lines.