"It won't hurt you," they say
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- Опубликовано: 17 май 2024
- Purcell Prusiks are personal anchors that are supposedly "safer" because they slip. We show you how to tie them and we tested them a bunch in this episode. Our data is on our blog at www.hownot2.com/post/purcell
Other episodes referenced:
Prusik Tests • Prusik, Auto Blocks, a...
Falling on Ascenders • Does PURCELL PRUSSIK s...
Can you Prusik 2 ropes • Can you prusik double ...
Girth Hitch Testing • This seems sharp
Cow Tail Testing • This would BREAK your ...
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00:00 It slips they say
00:39 What is a prusik
02:01 What is a purcell prusik and how to tie it
05:27 Uses for Purcell Prusik
07:59 Pros and cons
09:12 Slow pulls
10:43 When do you break
11:51 Drop Tests
14:09 Rabbit trails
17:54 Graphs and Charts
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Much love, thank you *I wish we were neighbors
This beginner who's trying not to die appreciates knowing that prusiks should be 3mm narrower than the host rope. Thank you!
This is interesting to get more into different type of personal anchors. Looking forward to seeing Petzl adjust and hopefully Kong slyde as well. I guess that would cover almost all common personal anchors.
Absolutely! Do the Petzl adjust and Kong Slyde!😊
@@testboga5991 for the Kong Kisa also!
Petzl adjust is just so smooth and with an eashook it's so fast. Bulky, yes, but so quick to deploy and take slack
Vote for petzl adjust
@@thefack149 I never noticed eashook. That could be so handy in some applications and you can attach it to a sawn loop too (unlike some other similar models I have).
In general use I tend to find triple locking carabiners or ball lock ones quite fast to use.
I've tried the two finger method and it really makes the hole bigger. Excellent
Phrasing lol
I find an easy way to make the purcell is to make the Prussik on an empty toilet paper roll, that way it's shaped nicely and easy to dress. then put the other end through and then pull out the roll and tighten.
Yes other methods are easy enough, but especially on longer purcells its nice to get all the twists out and such before putting it through the prussik and this holds it all in place nicely.
Glad I'm a caver, not a climber. We don't have to worry about shock-loading. All of our lines are static, most of them 11mm pit rope. Avoid sharp edges and you're fine. In fact, we have a couple of 13mm static ropes that will cut a groove in the limestone rather than get damaged themselves. We use those for fast and dirty recon of new sites. The only drawback is they're very heavy.
as a user of the Purcell Prusik, this is a super useful video! I use a 3 /2 wrap instead of just having 3 wraps on each side.
I appreciated this simply because of the knit tying tutorial. Then, additionally the shock absorption was quite interesting. I’m not a fall-geek, and still enjoyed your efforts.
Been using things like this purcell prussik for roof and chimey jobs for years. Never taught , but seemed good use of knot skills learned in my youth helping arborists. So glad to see testing on something I do. But yes, It is not my sole safety for steep pitch or other serious consideration where I may think a deadly whipper would be on the agenda before the next break.
Not sure if this is going to make sense, but there are two concepts I was given for the Purcell Prusik.
1st: You can tie it with the knot inside the prusik loop to maximize how short you can make the loop, but limits the extension a little. The std design with the knot outside of it limits how short you can make it.
2nd: This concept came from an OG SAR climber I know...you can make double Purcell Prusik by using a much longer cord (30'?), and tying a second Prusik on the tail end (where you usually connect to your harness) after completing the construction of the std Purcell. You then pass the first/completed Purcell Prusik through that second one and you can girth hitch the middle to your hard points. This gives you two adjustable tethers (and a mountain of cord).
There is a reason via ferrata gear moved away from friction-based shock absorbers and now excluseively uses tearing shock absorbers.
I use this as an adjustable manual handbrake on a temporary rope zip line on my property. It trails behind the zip line pulley with no weight on it. You lightly wrap your hand around it (with gloves on of course) and as you’re approaching the end of the line you take your hand off. As the prusik is trailing the pulley and all of your forward momentum and weight are on the pulley which is clipped into your harness as the prusik starts to engage it starts to shift your weight from the pulley to having your weight on the prusik giving you a soft catch. Work’s beautifully! As the pulley then naturally travels back to you as it has less resistance, it shifts your weight back onto the pulley at which point you can easily reach up and tend the prusik with your hand again. The system also does a wonderful job at not turning you into a human pendulum. I know this is not ideal zip line setup but for a line that gets moved around the property and setup with dramatically varying levels of speed and height the system works extremely well. Way better than trying to rig and re rig tire, compression spring or bungee breaking systems all the time.
Nice! just check it for wear often, going fast on a zip line you'd have to worry about friction melting the prusik
Very interesting, goes to show that no matter what kind of PAS you're using DO NOT FALL ON IT, at best you'll be hurting.
Cool to see these results! I use a 60cm nylon sling (girth hitched) for my PAS when single pitch climbing and when I am multipitch climbing I always clove in using my rope. Seems like regardless of what method you use, the basic gist is don't go above the anchor and if you do then don't fall onto your PAS
Great stuff. I use a Purcell prusik as a personal anchor, but I place the double fisherman close to the prusik knot to maximise the length adjustability. Probably doesn't effect the strength much but a friend had the double fisherman get partially inside the prusik when the prusik got loose, so that's a risk to be aware of.
This is all super interesting!! But, I'd also love to see some less "extreme" fall examples.
Yes, I know these fall factor ~2 falls are interesting to see, and it's always fun to see gear break.
However, I think some "sensible" falls where the person isn't really above the attachment point (FF < 1) would be very informational!!
It would be amazing to be able to see the different forces one would feel if one fell on pas (dyneema loops), dyneema sling, nylon sling, purcell, connect adjust, etc.
"secure the victim" that sounds way more ominous than "secure the patient" 😂
The consistency of inconsistent materials is super comforting, and these videos are great for understanding climbing systems.
Thank you
Love the Purcell Prusik on a loop! I've been using them for over 10 years as my primary anchor system. I use 2 of them as my PAS for sport climbing and 1 when multi-pitch climbing. 6mm accessory cord tied with a double fishermans knot girth hitched to my harness hard points It's so nice to be able to easily get into the most comfortable position at an anchor. Great video, thanks for testing!
This is an outstanding video. So informative, covering the topic so well. I will recommend it to many people.
Dude, your videos have gotten soooo much better! And still improving man, this was such a good video!! Thank you!
From now on, this will be the youtube video I'll search for when i try to remember how to tie this!
Great video Ryan. Loved the "how to" set it up with different examples. Thank you.
Super informative, and love some Prusik knots!
Thanks for the testing.
Been waiting for this!!! Thank you so much, can’t wait wait for the next one
Great video! Even though it was a long one you packed in so much information and clever tests.
I can see myself sharing this with people in the future :)
Second video on your channel that covers a topic I was just researching by chance 😂
13:08: the tip of making the PP extra short is GOLD!!!
Great work. Thanks.
Love to see it! Thank you
With dyneema slipping at 300N, you don’t even need a fall for it to slip. If you just let it hang with the weight of a person, it would already slip.
I've been using the klemheist version of this for years with a 6mm cord. Not sure I'd ever go to anything else for the price. I've got mine set to a fully stretched arms length. I'd love to see what you could get if you fell with your super long one. Haha
Finally! Thanks so much!
Thank you! What a great video!!
I kinda just want to use a screamer as a personal anchor now. Yikes!
Absolutely breaking my gear fear and placing it where it should be. On fall factor twos!
@hownot2
Thanks for the video. I do rescue so we use Purcell Prusiks all the time. Are you familiar with the Aztek Edge Kit? We use them as personal anchor, travel restraint and for patient rescue and a million other things.
You already covered a lot but I feel like if people are really worried about shock load they could just do one less wrap when setting up the Purcell Prusik.
The effect you describe with the maximum force is called jerk or jolt, thats the change of acceleration over time (da/dt).
Love your videos, great job!
My new favorite 3 words....
Super good enuff.
Love it
All your videos are interesting, this one especially Thanks.
My takeaway is that for factor falls greater than 1.5 ish you really need a screamer of some sort. But that's not really a thing when climbing and walking around above the anchor is really common.
Great content Ryan. Regarding the long high line one you used. I found it more practical to use a climbing rope or section of rope tied in with a standard tree climbing system. Weave it through/around the anchor, clove hitch one side to a biner/harness, and leave a tail for a Blake's hitch. Super practical and you can have about as long of a system as you want while being able to wrap it around things like trees and poles if you want. Perhaps even more practical with a split tail or eye n eye. Idk maybe one more thing to play with.
Great tips 👍
Will you test some Via Ferrata kits as well? Curious about the results
I'd be interested if the friction of the Purcell Prusik could be tuned with a lower friction material lining the knot or a sheath. Granted it would either have to melt during the slide as to not slip too much or the sheath would need to have a gradient where the friction would increase the farther the knot slips.
2:20 - 3:15 very helpful sling / general purpose loop knot tying.
thanksalot for all that content 🌞
I made my own Personal Anchor out of a section of Resc Tech (teufelburger) and a 7mm Sterling acc cord in a michoacan hitch, and use a kong Ottino as a prussik tender. it works great for single handed adjustment to shorten or lengthen, and is #supergoodenough that I don't feel the need to buy a connect adjust, etc.
Sobering. Outstanding. Mans out here doing God's work.
So would a two-wrap nylon version be best? Or would it then slide too much and compromise the rope? Either way, these are single use it seems as the rope gets a bit of damage and the knot gets too tight
FYI: spine breaking is probably what you worry about when talking about the body taking the force.
The part of the spine that is probably most worrisome can resist about 2kN before accounting for soft tissue that'll absorb some force. (in vitro)
When they studied forces on patients in vivo, it seems that the back can take about 3.4/3.7 kN before ~50% of folks will break their low/mid back (granted, the studies include older folks, avg age ~50 since that's who gets most back fractures in the medical world). Younger folks can tolerate ~4-6kN and part of that depends on how much time the force is spread over (as Ryan mentions), but also other factors like if you're upright/vertical vs horizontal when you the rope catches (e.g. horizontal = more torque and force on weaker parts of the spine vs vertical = more compression on the parts of the spine that are used to seeing some compression... same concept as compressive vs shear forces when you're talking about breaking bolts... except on your spine...).
Also, in the physics/biomechanics world, the technical term for force over time is "impact". Force spread out over more time = less impact. Concentrated into less time = more impact. Makes sense if you think about a whip. Barely any force, yet cracking a whip hurts because it's such a short time = more impact.
Im a boulderer and about a month and a half ago fell 25 feet, thus breaking my spine exactly where you just said (L1 burst fracture) I’ve been curious about how many kilonewtons the fall was but it’s hard to tell. I’m assuming it was somewhere in the 6-8kn zone. Got surgery and am doing better now, soon to return to climbing
That search and rescue guy is a pretty cool guy ;)
I've been using this setup for multipitch rock climbing with 5m of 6mm cord, but I use a double fisherman's and add a butterfly above for an extended rappel!
Thank you stranger! I'll be trying this next time I'm outdoors
Did you clip the end of the daisy or shorten it? If you clipped the end it’s equivalent to testing the fully extended Purcell. A (correctly) shortened daisy seems more useful to test and might absorb better
Terrific video . Why can't We tie a double bowline on bight for the belt anchor point?
I played with tying one with a single strand.
I tied the prusik first and then tied off the short end.
It makes it a bit less clumsy. Opinions?
Ive been using two long slings with knots for my PAS and cleaning gear for years, what system is your best recommended option for everyday climbing?
New to your videos, Can you test car seat belt? I've done many engine replacement where I've used seat belt to hoist the motor back into the vehicle. Engine varies from 3 Cylinders to 4 Cylinders to 5 Cylinders to 8 Cylinders. I usually used two seat belts, been doing this for over 20 years, never head a engine fall, never had a seat belt rip. Just curious how strong are seat belts. It's just easier to swing the engine while it's on the engine hoist with seat belts rather than chain links. Thanks in advance!
What about making a prusik with two "wraps" rather then 3? Would not it allow more slip, therefore absorbed better?
Suggestion when you test the petzl adjust test the breaking strength if you just clip the metal and not the rope as well
Can I use it for negative arborist rigging for dropping logs?? With a 5/8 or 3/4 rope.
You can add a little loop above and adjust in both directions with one hand
I've broken out of a tree twice and was saved by my rope without my split tail slipping. The bounce in my True Blue made both events comfortable so my opinion is that whether or not your fiction knot slips doesn't matter.
11:52 after doing the drop test on the prusik, were you able to move the... knot? up and down again or does it just fuse to the rest after stretching and pulling?
Have you done testing on the multitude of friction hitches arborists use for ascent, descent, fliplines/ adjustable personal anchors?
Good video👍🏻
08/02/2023 Hello How. This video was very interesting. I did not know about using this rope knot on a rescue basket. The second point is what if you use one additional loop in the prusikis. I have used this knot but not very often because I do not do tree work. My weight is over 300 lbs when loaded to work. My naked weight is just under 250 lbs. The four loop prusiks are both for climbing and movement in the tree. I do enjoy watching the profession plan for a fall. That tales BALLS Thanks again, DON
Nice video! I was hoping you'd try taking loops out of the pruzuk. Maybe if it was 2 on one side and 1 on the other, instead of 2 on both sides, it would slide more. Having the too loops above and the single loop below i would expect to slide easiest
Very cool!! I've just converted my original style petzl Zyper by updating the rope in it and using a couple of Petzl Adjusts so that the cow's tails can be adjusted. I'd love to send you some photos if that's possible? Thanks
8mm dynamic half rope (available by the meter?
Could it be made of dynamic rope instead and be more absorbable?
I can appreciate the skill, knowledge and consideration of so many factors demonstrated in these tests. The one thing missing, I think, is an explanation of the relevance/meaning for the "average climber". Is one sling construction significantly better/safer than the others? Or are these sling variations just for use in 'advanced' climbing and not relevant for the rest of us? Yes, I did watch the last few minutes of this video. But telling us to go watch other videos and blogs and suggesting (sort of) that we shouldn't use "personal anchor systems" (at all?) because the tests seem to show that they aren't safe doesn't seem like a satisfactory conclusion to a 18 minute 'technical analysis'.
Hey, How much difference in the load between the solid weights and a bag of meat?? (or something similar to use as a dummy)
I'm not asking for all the drop tests to be done with something softer because would be much harder to set them up, specially for the short drops, but some particular one, specially in static rope, to consider the difference in shock load for the compliance of the weight.
Have you tested the Blake’s hitch that’s what I use to climb
I wonder if you were to add a screamer to the system how it would affect the numbers?
Can you also please test a Petzl Connect Adjust lanyard under the same sort of conditions? Drop test & slow pull to destruction.
Hey, would You test via-ferrata kits eg. compare fall on dynamic rope vs kit with absorber. More interesting is how to carabiner lay on the steel line anchor, during the fall on vertical route, it makes the carabiner is cross loaded and side way loaded when hit the anchor point and the steel line is pre-tensioned high - I think this is the weakest point.
I know it's an old video but the updated way of tying a purcell does not have a bfk; just a double fish, a prusik and the girth hitch to your hard points. If you need a shelf you can add or remove an overhand. It's much more simple to tie and can be easily converted to a loop of cordalette.
Even in the best case, the results are a bit too inconsistent to be truly considered a reliable safety device. Has the Petzl Adjustable Anchor been drop tested? Curious if it slips at all.
I never intend to climb anything more difficult than a 15 foot ladder. However, I would not do anything with any sort of string, rope or line without checking your videos first. I have seen others do videos on splicing Dynemma and realized your videos are the only ones I trust. BTW, Dynamma is an interesting product. It is super strong, but has some interesting quirks that I discovered on your videos.
So call me crazy, but the only application I've ever considered for the PP is for rope soling (on lead) a bolted route where finding a ground anchor (boulder, tree, good low crack) is not an option. The idea being: climb to the first bolt, clip a PP to it, then clip the end of the rope to the sliding end of the PP (having pre-connected other end of rope to my grigri on my belay loop). Crazy? Indeed. But potential advantages: (1) if you fall shortly above the 1st bolt, the PP should keep the fall force below factor 2 (but seeing the video, I'd keep the PP on 6mm or less to get more slippage and lower forces), and (2) once clipped into the 2nd bolt, the PP would add a little bit of dynamic quality for a fall (not much due to friction thru 'biners, but more is better in this case IMHO) and so that's good. I do loads of rope-solo leading and don't bother with a PP if I have a good ground anchor, as there's plenty of dynamic quality in the system once several meters of rope are out and the first piece has been placed, especially given that I'm not (and no one should) ever taking big whippers while rope soling... So I'd love to see the PP tested in this kind of application...
i made my Prucell out of Edelrid Aramid cord sling. been working amazing for years. since the aramid is a lot stiffer its a lot easier to handle and adjust, but id love to know how it compares to nylon or dyneema that you tested here.
Super good enough
I don't use a BFK on my purcell, I just girth hich it on the harness loops. I wonder what the force would be like then without the BFK in the system
Can you test the Kong Slyde as well? :D
Could you also try other friction hitches? Would an autoblock be shock absorbing enough for a safe fall?
for the knots - how much would a hangmans knot reduce the ropes strength?
Just remember, if you don’t know how to tie knots tie lots. 🤣
“Super not good enough”
I use the Purcell Prussik as my personal anchor/leash with a 7mm nylon cord but I drop one of the loops on the load side of the prussik knot. This (in theory) will reduce the friction in the prussik knot and maybe reduce the peak loads on your tree drop test.
I do the same but I recently switched to 5.9mm Powercord
I use double Purcell Prusik (PP),
1 big loop with 2 PP at the ends girth hitch it to the harness, with big wirelock carabineer.
Find it super useful,
Apples to apples seems safe enough.
If you get the chance to it might be fun to test the petzl adjust vario it would be interesting to see how strong it is compared to the regular petzl adjust with a sewn end
hi, I was wandering... close to4:30min, is there any reason why not to do first the prusik and after the figure 8 knot? isn't it be easier to go through the pursik knot if we have the tail free?
thanks for the video, by the way :)
I've never done climbing, but I am a sailor & Tugboat operator, so I've done a lot with ropes. In construction and shipboard safety harnesses, they include an engineered shock absorber that is a replace after it dose its job tool . I'm sure it weighs more than the slings you are making, but you can count on the amount of shock absorption it will provide.
In climbing, a single use absorber is called a screamer.
They're not used very much at all because of the cost of replacement, bulk, and at we simply avoid taking any falls that generate enough force to need a screamer. They are used in ice climbing for marginally strong ice anchors, but on rock you'll pretty much never see them.
Something similar is used in Via Feratta sets.
Super damn cool dude
Question: were your drop tests in 6 or 7mm? Indications are that if they were in 7mm, the impact forces would be less in 6mm.
With the dyneema you tested near then end, with it slipping well below 1KN, we shouldn't even expect it to slow you down, only make you accelerate slightly less quickly. That slight drop in the rate of acceleration is completely counteracted though I would suspect from the additional travel distance of the fully extended prussik. Meaning it basically it is worse than nothing and you are taking a hard fall on static protection.
Try the same with one of those Edelrid aramid slings, 22kN rated and they work as a Purcell prusik, would be interesting to find out the numbers.
It would i terresting to know how much shock is absorbed by the persobal anchor for Via Ferratas in comparison
tying the Prusik that way (on your hand) one could tie a lopsided "directional" Prusik - making it easier to extend, and bite a little harder. ???
In case you want to attach yourself to an anchor, is it acceptable to use those loops separately?