Are we building our Z-rig the wrong way?
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- čas přidán 7. 07. 2024
- After posting a story on Instagram asking the question: "Where should we put our most effficient pulley in a pulley system?" I was surprised at how few got it right. That's why I am adding this video in between. I think this principle is important to understand! Consider this a video where I lay the foundation for understanding real application of our theoretical mechanical advantages. They are rarely as efficient as we think them to be....
Video referenced :
Hauling System Awareness - IRATA Level 1 Training
• Hauling System Awarene...
Welcome video where I explain the philosophy behind The Rope Access Channel
• Welcome to THE ROPE AC...
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Chapters
0:00 Intro
0:55 Setup 1 - The common error
2:40 How much friction in a carabiner?
4:28 Setup 2 - Moving the carabiner
6:10 Setup 3 - Is this the best place?
7:45 Conclusion
8:55 TMA vs PMA vs AMA - Jak na to + styl
Good demo. We learned in Slackline tensioning that the real MA depended on how big and awesome your first pulley is. Your demo shows the math behind that. 🎉
I hope to be able to show the effect of friction and pulley size on the real MA later on when lifting some loads. It should be fun😃
Nice one dude, well explained. I've cut out pictures of pulleys, descenders and biners and had them laminated with magnets for the white board. Bit of work but I I felt it helps the candidates visualise the lesson better. Love your passion!
I was literally in the shop today looking at magnets and told my daughter the same thing haha.
One assessor once told me he had it at his place to. Besides being a great educational tool it can also help just taking each other through different scenarios. With experienced people you could actually skip the execution of some methods. Or limit the amount of times they have to do it and conserve their energy.
Very useful to know this! And you made it very easy to understand, looking forward to the part 2 :)
Glad it was helpful! Thank you Sasha :-)
Man, this was an eye opener! Great explanation!
Glad it was helpful!
Great description. I've had classes in statics and dynamics in college and watched pulley system videos by others that remind me of those classes. You made it very easy to visualize and understand. If I know that I will need to haul, I grab my Aztec and an extra Basic, I love that thing. Bulky compared to a few pulleys but so fast. Thanks for your time making and posting these videos!
Glad it was helpful! The Aztec is a great piece of kit! I never bought one but made one of some pulleys and prussiks I had lying around ;-)
Well done
Thank you🙏🏻
Thank you for this video !
My pleasure!
I always learn so much and you make it very easy to follow.
Beautiful! Glad it helps. Thank you 🙏🏻
🤯. Great video and well explained.
Thank you! I’m diving deeper into that subject soon 👍🏼👍🏼
I was completely wrong until now, I thought the best pulley goes where the maximum weight is (C). Thanks for clarifying this.
Glad to help! That is a common misconception 😉
Great question and explanation of the answer. I put B and was wondering why it was A. Thanks for sharing and putting the time to create the videos, really appreciate it
Glad it was helpful😃. Thank you for letting me know
Keep on pushing videos out Alex 🫡
🙏🏼Thank you Levi🤩
Well explained master. I had the wrong knowledge about this, but now i think that im understanding the forces actuation at a pulley system. Thank you very much. You are a realy master 💪🏼💪🏼
😁Thanks my friend!
You earned a sub, well done.
Awesome! Thank you!
This is GREAT! I really love how you walk through all the steps especially keeping the math simple. You are a very gifted teacher. I'm going to link to this from my website and articles about mechanical advantage at Alpinesavvy.
Thank you so much! I just had a look at your site! What a beauty with a wealth of information! Incredible!! I follow the Alpinesavvy IG but had never actually looked at the site. Amazing
I'm honored you would use my video. That's so cool🙏🏼🙏🏼🙏🏼😃😃
I've got 3 more (whiteboard only) videos coming up on simple, compound and complex pulley systems👍🏻
@@TheRopeAccessChannel I would love to see those pulley system videos. Check your Instagram messages, I sent you a link as to where I added your video on my website.
Excellent, thank you. Never thought of it that way before. I would like to reference this in one of my upcoming videos. Wondering where you got the carabiner = 50% efficient math from? Thanks. - Patrick
Thanks man!!
Share away👍🏼. Just give credit where credits due😉.
That 50% is something I learned becoming a rock climbing instructor. So I never did any math on it.. I’ve measured it a couple of times and it’s true. If you look up the FRICTION video you’ll see it happening.
These kinds of "puzzles" are right up my alley, but I never considered this one. I love to draw pulley systems just for fun and try to answer "mathy" questions about them, but always in theoretical MA. For example, if you have n pulleys, what's the most TMA you can get? Pretty certain it's 2^n:1 (no redirect), by compounding 2s; you would need n-1 extra ropes though. Another fun one is we know, with 3 pulleys, we can do 3:1 w/ redirect (it's in the video) and we can do 8:1 (no redirect) by compound 2s with the same 3 pulleys. But can you find ways to rig 4:1, 5:1, 6:1 and 7:1 with 3 pullies? Even though it's just pen and paper and all theoretical, I feel like playing with stuff like that gave me a better understanding of pulley systems at large. Loved this vid! 👍
6 and 7:1 with 3 pulleys??? I haven't played that game for a decade haha Around that time I started testing and measuring what actually happened in real life and concluded that our basic z-rig is a 2:1 at best haha. In real life I have rarely gone beyond 9:1 and since I started thinking about it better 6:1 is about the highest I'll go. Now you got me thinking again haha
@@TheRopeAccessChannel I used a z-rig to pull on a set of fours to give me a 12:1 ratio (or a 15:1 ratio if you turn it upside down) to move logs far too heavy for me to move by hand. I could rig another 15:1 pulley system to pull the first (for a 225:1 ratio). The limiting factor is the quality of your gear because you can just keep adding more complexity to the system. Compound systems give you almost unlimited power.
@@TheRopeAccessChannel Don't know how well this will work in text, but here goes. 6:1 is fairly easy, I know of 2 ways. If we took the 3:1 from the video and took out the redirect, we still have 3:1, with 2 pulleys. We use that pulley to make a 2:1 to pull on the 3:1, giving us 6:1 to the load with 3 pullies, but we need an extra rope/cord. A better way would be to put the 2:1 on the load and then pull that with the 3:1, still giving 6:1, but in this order we can do it with just the haul line.
From my experiments, odd systems pulling odd systems are ideal, like a 3:1 pulling a 5:1, you can always rig these with a single rope. Evens pulling evens and evens pulling odds will require additional ropes/cords to rig. You can pull on an even with an odd, but only at the end of the system, at the load. Basically you can chain together a bunch of odd systems and then have a single even system at the load and not need an extra rope, if that make any sense. It's what we did for 6:1, took a 3:1 (odd) and then doubled it (even) at the load.
7 is a bit trickier, but also teaches a neat trick with even systems. If this is confusing, Petzl has a picture of it on their site, just search "7:1 mechanical advantage", should come up. So again we can start with the 3:1 in the video, but count the tensions on the anchor, we get 4:1 to the anchor because of the redirect. If we took out the redirect we only have 2:1 to the anchor. From my testing I've always found that if I have T:1 on the load, I'll have T-1:1 on the anchor if you pull with the load, or T+1:1 if you have a redirect. Even in complex/compound systems, this seems to hold true, though I have no mathematical proof of it.
With an even system, the rope would be terminated at the anchor. If we instead redirect that back to the load, the result is that we have added together both the MA to the load and the MA to the anchor. If you really study a 3:1, this is exactly what's happening. It starts with a 2:1 (even) on the load, which gives 1:1 to the anchor. And then we redirect that 1 back to the load giving us the sum, 3:1. With all that, we're laughing because we know 7 is 4+3. So all we need to do is rig a 4:1 (even), which would normally give 3:1 to the anchor. Of course we redirect that 3 back to the load giving us our sum 7:1.
The only problem now is the 3 pulley constraint. If you go for your standard zig-zag 4:1, you need 3 pulleys just for that, and you don't have enough to get the 7. The final trick is you need to rig that 4:1 as a compound stack of 2's. That will only require 2 pullies (but requires an extra cord), leaving the 3rd pulley to redirect that anchor MA to get the 7:1. A less satisfying way of doing it would to be to rig a compound 8:1, that takes 3 pulleys and puts 7:1 on the anchor. Now just flip it upside down and you got 7:1 on the load with a redirect, still with just 3 pulleys, but that's no fun.
For 4 pulleys the low end is 4:1 (zigzag w/ redirect) and the max goes up to 16:1 (4 compound 2s). I haven't found solutions for everything in between, the game gets hard quick. And it gets super theoretical from this point. Sure I might be able to find a way to rig 5:1 on 4 pulleys, but I can already do it with just 3 and less pulleys is always going to be better in the real world. It's still a fun game though.
very very good video sar i like your video i like a pully systam
Thanks for liking🙏🏻🙏🏻😃
If I had had you as my math teacher, I probably would have learned something at school too. 😂 81 or 80 percent.. let's keep it simple. thank you very much a great video!
Thank you! With my performance in school my math teacher would not have thought anyone would ever say that to me hahahahahaha
Learning to use pulley systems is one of the best skills I can think of for anyone that enjoys climbing with ropes. It is one of the best skills a hunter can have as well for hauling game. I keep an AZTEC pulley kit and numerous other single and double-sheave pulleys in my climbing and hunting gear always, along with rope clamps, prusiks, and other necessities. I consider pulleys to be one of the most important tools in my kit.
That's interesting! I hadn't thought about that. Your game can weigh more than we can comfortably carry right? And if you need to go uphill or up steep parts, having a good haul kit is essential. Do you make a sort of emergency harness for the game? Like a hasty harness sort of thing?
@@TheRopeAccessChannel To begin with, I am a small older man (71 years), so moving anything heavy is hard for me. I learned to utilize ropes and pulleys so that I could haul or hoist game by myself if I had to. My ropes and pulleys were also a wonderful aid when a tree was damaged in my back yard by a storm. I used them to move and lift logs so I could cut it into firewood. As to hauling game, we tie our rope at the base of their antlers and throw a loop around their nose, and then just pull them along. Whenever possible we use looooong ropes to reach our game and use vehicles to do the pulling, but sometimes you just have to use muscles. Though it would be difficult and slow, I believe I could haul an 800-pound elk up a steep hillside by myself. I just hope I never have to try!
If the redirect was placed with a rope clamp on the downward traveling part of the rope (under the decender in the first example) the result would improve greatly... For a TMA of 5:1 in my calculation...
Sure, and not the topic of the video. The topic is where to put your most efficient piece of gear. The complex 5:1 is in two other pulley system video's 👍
@@TheRopeAccessChannel True. Sorry for sounding negative. Not my intention. Your video is very good and to the point. And shows the importance of using efficient pulleys when rigging MA. I some times use 4 double pulleys to rig a 5:1 on a 5:1 system for a TMA of 25:1 to pull backleaning trees over the tipping point. Wonder what the PMA is... Shure gives me a lot of pulling power though. Thanks for good movies.
@@bjertnestrefelling8839 25:1 is pretty wild MA😃. If it does the job the Actual MA doesn’t really matter right. As long as your not overloading your gear..
How do you think rope stretch effects all this?
It does, I think I mentioned that when switching to the practical bit. When we add friction, stretch, pulley age, sheave diameter the results change definitely.
Check out this video by @hownot2:
czcams.com/video/tUDLNVdSQNw/video.html
Your Physics is WRONG
Really?? Please, enlighten us. I am pretty sure everything I say in this video is correct and applicable to rope access technician.
If not, I would love to learn.
Engineer here very well verse in Physics. Your first carabiner example when you said 100k on one side resulting in 50k on the other. No matter friction losses, the system must be in balance.@@TheRopeAccessChannel
If I understand correctly you are referring to the fact I say that if you pull on a rope with 100k you can only lift 50k on the other side. Now I am not an engineer and I know when I test this the fact is that my linescale registers I have to pull with 200k to lift 100k. In my simple mind that means that the friction loss of the carabiner is what how the sides even out. I dont know how to explain it differently. Like I said, I do know the numbers the Linescale produce and how it feels when lowering something heavy. Friction makes it (feel) lighter.
Or maybe you as a better versed physics person is used to different words being used to what I describe?
I did a whole video on the subject testing different devices and how much friction they produce. Have you seen it? You can check it out here:
czcams.com/video/uq7AhJYXOQ4/video.htmlsi=Hwno9aA6ltYDByvI. How do you call the carabiner example? There is friction loss and 200k needed to lift 100k, so the sides do not even out
I am not being sarcastic. If I am wrong I like to learn.
Try a simple pulley. Your results will be different. I am saying that for the system to be in equilibrium, the force on both side must be equal. That sir is Statics 101.@@TheRopeAccessChannel
Yes of course the results will be different. There is less friction in the pulley so I need more force on the opposite site to balance it out. That is what that video shows. To overcome friction I need to put in more. Or because of friction what comes out on the other side is less than what I put in. It gets "lost" in friction.
How else would you explain the results in the "Friction" video??? It is clear that that I need 200k to lift 100k through a biner, or 120k to lift 100k through a decent pulley.
Also in this video czcams.com/video/vD9SzJsan5Y/video.html the numbers really tell the story.