Enhancing Fall energy absorption

B

Bart_

Carpal tunnel level member
Location
GTA
Perhaps these rubber units could be paralleled with the rip/zip unit in an SRT base tie to gain more soft catch capability


good background zip/rip screamer operation

 
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Yates Screamers.


Like an air bag/ seat belt or chainsaw breakaway lanyard... do everything you can to avoid deploying it, happy to have it if you have it deploy.
 
That is a cool feature I didn't know about the ART Snakes.
@Bart_ I was thinking the same about the rubber pieces when I saw the video, but I would reserve their use for sketchy TIPs that you worry may break and drop you to the next fork and still incorporate a screamer in the backup, as our ropes don't stretch as much as theirs.
 
I haven’t implemented a screamer yet, but intend to.
Shit happens, I got distracted by a client when in a rush to get up the tree. Large Doug fir where my srt base tie was over a few small Epicormics that I planned on busting out to settle the line into the bigger limbs about 10’ below. I had to use my long lanyard to lengthen my base tie as my 200’ line was out of reach.
Made it about 50’ just under the first limbs before the epicormics broke out. Saw nothing but blurred bark, and if it happened lower I would have decked. The ‘fall’ was actually fairly soft from all the line in the system but my footie still partly tore the sheath.
Some sort of energy absorption on a base tie should be mandatory imo. Granted that was about 10 years ago and I haven’t gotten a screamer yet..
 
After 30 or so years in the alpine and waterfall ice and trees, my take is don't fall on an arborist static rope - ever. F= m x a squared. Non arb falls are belayed on dynamic ropes - I'd rather have a system with lotsa dynamic rope in it than a static rope and a screamer or rubber dookies or even pocket slings. Like US Forest Service cone collecting procedures of old. For me a screamer may save an ice screw but prayer is involved usually. And alpine/ ice belays aren't onto a static terminations but an atc or something that'll slip as your belayer yells "Gotcha" (usually while cringing)! Always the idea is to spread the force over time (more or less). And under the "Z" work positioning not fall arrest. Just my two cents though. Stay safe out there. Cheers.
 
Dynamic ropes saw back and forth. Sharp stubs can damage ropes I've heard told by @evo .


I prefer the more static ropes when having 150-250' of rope in the system for performance with a safety backup.
 
Maybe depends on how high you're going but just today I still used a leather cambium saver - easy to install/ uninstall with a slip knot in the line. No bark/ branch damage. I still really like those things. I get back to UIAA fall/ belay practices - the forces are enormous quite quickly. To each their own though. Static is nice for the up for sure, for the fast down not so much. SOS (Save Our Spines). Cheers
 
To be clear, for me this entire concept is about making the first ascent safer. I would only want some fall protection to get to the TIP safely to reset up close, not for work postioning.

The sawing action Sean mentioned is still an issue with base-tied SRT over thin, springy stuff, which is why I canopy anchor those after first ascent.
 
One big difference between arb falls and rock and ice climbing falls is that cliffs and ice routes don’t move and absorb shock while trees do to some degree. I’ve taken factor 2 falls on rock and have taken some exciting tumbles in the trees as well. The movement of trees seems to me that it would limit the possible forces on a climber and their system but I’d love to see data disproving that.
 
On the ART pockets popping at 2.5 kN, the length of the sewn junction makes the amount of energy absorbed at a 2.5 kN limited impact force. It looks like a single screamer has multiple feet of stitching to blow out vs the short junctions of an ART unit. Hownot2 went over the top with the huge rock drops and the many feet of "screaming" action. I think they could've run a few numbers first but hey makes for entertaining vids.

The rubber can't seem to run in series because it would stretch and saw like a bugger. However it offers an ability to soften a catch. Maybe it could be used parallel with something like an ART snake where the snake eliminates the crazy sawing but would only make a short 2.5 kN spike as it tore, then letting the rubber do a soft catch, that is up until your main line slack runs out and the main line takes up the load.

Best I can come up with after learning about the ART pockets behaviour and one coffee.
 
Bart_ said:
On the ART pockets popping at 2.5 kN, the length of the sewn junction makes the amount of energy absorbed at a 2.5 kN limited impact force. It looks like a single screamer has multiple feet of stitching to blow out vs the short junctions of an ART unit. Hownot2 went over the top with the huge rock drops and the many feet of "screaming" action. I think they could've run a few numbers first but hey makes for entertaining vids.

The rubber can't seem to run in series because it would stretch and saw like a bugger. However it offers an ability to soften a catch. Maybe it could be used parallel with something like an ART snake where the snake eliminates the crazy sawing but would only make a short 2.5 kN spike as it tore, then letting the rubber do a soft catch, that is up until your main line slack runs out and the main line takes up the load.

Best I can come up with after learning about the ART pockets behaviour and one coffee.
Click to expand...
Only way I’d want chunk of rubber in my system is if a ‘fuse’ would deploy first before engaging the rubber.
So something like a screamer to start ripping and then engage the rubber.
Had to add length on my 200’ xstatic yesterday, not a high climb at all just the only available tip. Simple base tie and I had to take out about 4’ if stretch before I left the ground and was still boinging. Tolerable but far from what I consider ideal for me
 
A person could use a single link from an ART snake as the fuse. A whole snake would be like a screamer with intermittent sewing.

Spring theory would come into play. Paralleling rubber links adds spring rate (stiffer) just like paralleling ropes and eg two in series halves the spring rate. So if you wanted twice the fall distance capability you would put two in series but have to also parallel another two to keep the original spring rate. Hey! looks like square law x2 distance leads to x4 energy absorbed. And you can abuse the crap out of them 600% elongation if you're willing to give up re-usability cycles. or go big, 3x series 3x parallel 9x energy absorbed same spring rate.

oh oh - 2x or 3x stroke winds up a lot of rebound boing. the force at the end of full stretch would be very big. gotta ponder on that. series screamers just keep applying the tear-out force to decelerate you and don't try to shoot you back upwards
 
RyanCafferky said:
One big difference between arb falls and rock and ice climbing falls is that cliffs and ice routes don’t move and absorb shock while trees do to some degree. I’ve taken factor 2 falls on rock and have taken some exciting tumbles in the trees as well. The movement of trees seems to me that it would limit the possible forces on a climber and their system but I’d love to see data disproving that.
Click to expand...
implication there for the difference between the forces the climber is subjected to from a fall on a basal anchor vs a canopy anchor
 
Order of smack factor: DRT two ropes parallel 2x spring rate and "single length spring" = double smack level, SRT canopy cinch 1x spring rate and single length spring = single smack level, SRT base tied 1x spring rate but 2 to 3 x spring length and hence 1/2 to 1/3 smack level. neglecting other factors like basal tie ropes side loading/deflecting branches further softening the smack.

technical wurds :)
 
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