Canyon Rope Systems
A HowNOT2 Course
Episode 7 of 10
This is a free course featuring Brent Roth about different ways to set up rappels through a canyon. This considers ease of rigging, abrasion, ease of rescue and how efficient it is to move people through the canyon.
Our courses are A-Z content in blog format, glued together with an overarching blog we call a textbook. A blog format is easy to read, easy to update, and easy to translate. Be sure to begin at the TEXTBOOK and at the end of each episode we'll point you to the next.
Twin Isolated Systems Friction Testing
Brent set up a mechanical disadvantage so he could put more weight than himself on different lowering devices in different modes. How much friction do the different devices generate using the same 8mm rope on every device. The tail of the rope was just dangling down into the rope bag and we wrapped all these devices several different ways: Petzl Eights, Camp Ovo, Rock Exotica Totem, Palikoa Pivots, Critter, and Hoodoo.
In the simplest modes, it took 20-30 lbs to get the rope to move. In the higher friction modes, it took up to 500lbs to get it to move! The forces themselves are irrelevant but how they compare to each other is what's interesting. This information isn’t really worth charting or graphing as it requires the context of how we rigged it and this episode is edited quite tightly so it’s easy to skip through it in 5 minutes to get a general idea or watch the whole thing to admire Brent's ingenuity.
This test came about when I was working on the Hangman rigging technique. I was constructing different ways to achieve a Twin Isolated system, but did not know what was an acceptable amount of friction in order to use a system like this. I could 'feel' that some had more than others, but that is not enough to change the minds of old canyoneers. 😂
So I devised this test to put some numbers to what I was doing. It still takes field use and practice to determine if a system is acceptable for everyone to use, but I feel comfortable using a Hangman system after see these results. You must make you own choice.
No matter what Twin Isolated system you use, you should never solely trust the friction of the device to hold someone on rappel!
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