Mechanical Advantage is a Myth
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- Опубліковано 2 жов 2024
- We all know friction in a mechanical advantage block and tackle pulley systems can reduce output, but I haven't heard anyone talk about stretch. I am always using semi static or climbing ropes, which have a lot of stretch. We test all the way up to a 13:1 with dynamic, semi static and 0 stretch dyneema. We did NOT use multipliers or brakes to simplify this already long experiment.
*All numbers are in kN. Trying to keep a lot of data easy to look at!
This unlisted video of our 81:1 (that doesn't work) inspired our "9:1 is not 900%" video • 81 to 1 pulleys for br...
►►►DYNAMIC ROPE
►1:1 pulleys n/a - 1.34 INPUT x 1.19 OUTPUT / 100% vs Actual 88%
►3:1 with pulleys - 1.13 INPUT x 2.26 OUTPUT / 300% vs Actual 200%
►3:1 without pulleys - 1.19 INPUT x 1.99 OUTPUT / 300% vs Actual 167%
►5:1 with pulleys - 0.89 INPUT x 3.84 OUTPUT / 500% vs Actual 431%
►5:1 without pulleys - 1.39 INPUT x 2.38 OUTPUT / 500% vs Actual 171%
►9:1 with pulleys - 0.85 INPUT x 5.92 OUTPUT / 900% vs Actual 696%
►9:1 without pulleys - 1.12 INPUT x 2.38 OUTPUT / 900% vs Actual 212%
►13:1 with pulleys - 1.01 INPUT x 5.04 OUTPUT / 1300% vs Actual 499%
►►►SEMI-STATIC ROPE
►1:1 pulleys n/a - 1.62 INPUT x 1.26 OUTPUT / 100% vs Actual 78%
►3:1 with pulleys - 1.31 INPUT x 3.46 OUTPUT / 300% vs Actual 264%
►3:1 without pulleys - 1.72 INPUT x 2.48 OUTPUT / 300% vs Actual 144%
►5:1 with pulleys - 1.10 INPUT x 5.15 OUTPUT / 500% vs Actual 468%
►5:1 without pulleys - 1.18 INPUT x 2.67 OUTPUT / 500% vs Actual 226%
►9:1 with pulleys - 1.31 INPUT x 7.48 OUTPUT / 900% vs Actual 696%
►13:1 with pulleys - 1.4 INPUT x 6.98 OUTPUT / 1300% vs Actual 498%
►►►DYNEEMA ROPE
►1:1 pulleys n/a - 2.33 INPUT x 2.07 OUTPUT / 100% vs Actual 89%
►3:1 with pulleys - 1.34 INPUT x 4.04 OUTPUT / 300% vs Actual 301%
►3:1 without pulleys - 1.47 INPUT x 2.97 OUTPUT / 300% vs Actual 202%
►5:1 with pulleys - 1.67 INPUT x 6.71 OUTPUT / 500% vs Actual 402%
►9:1 with pulleys - 1.47 INPUT x 9.62 OUTPUT / 900% vs Actual 654%
►13:1 with pulleys - 1.51 INPUT x 8.54 OUTPUT / 1300% vs Actual 565%
►►►THOUGHTS:
*** % wasn't that different but my input is so much greater not fighting stretch
***9:1 is better than a 13:1 and might be worth using, but a 5:1 is the most optimal to get as close to theoretical as possible
This is a very helpful article overtheedgeres...
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Its a Myth!
01:34 Dynamic Rope
5:04 Semi Static Rope
06:53 Dyneema
09:45 Applying the science!
12:01 Conclusion
What we learned in this video was vital in making this episode a possibility! ua-cam.com/video/Hy_W10xMrCM/v-deo.html
Check out our new store! hownot2.store/
When you have a long rope and your doing short jerking pulls, you'll get lower peak values at the other end. If you statically load the long rope you'll get rid of that difference (for the most part). When you're jerking on the rope you'll see that the elasticity effects the force that the other end experiences.
I loved this video and think it does a great job at demonstrating how mechanical advantage really works!
Yes, this would have been the better conclusion
Yup, under dynamic loading it’s acting more like a mechanical capacitor and smoothing the peaks.
I was going to mention a similar thing. I would think that if you loaded a stretchy rope quasistatically, that is to say infinitely slowly such that dynamic loading is negligible or zero, the force would be the same as an infinitely non stretchy rope. But, some of the mechanical work would be consumed in stretching the stretchy rope.
I agree. the bounce applies all the force to the first load cell, and the stretch absorbs the impulse before it is applied to the second load cell. it's why dynamic load ratings are WAY less than static load ratings.
just what i wanted to say if he wanted to get proper values he would have to statically load the stretchy rope to get. If he wanted to do this he should use a tree or whatever to do this vertically than he then apply his body weight statically to the system
I suggest revisiting this strictly using the winch. It seems you are just measuring shock loads with just pulling with manpower. You want a repeatable same force applied during each test.
He used to do that exact test with his old bolt breaking machine. Then he switched to hydraulic.
As a whitewater boater, I'd say this is pretty realistic for a small paddling group with a pin (except for the large number of pulleys available)
The purpose of the test was explained at the beginning.
Exactly what I was going to say. Stretch affects shock loads, not constant loading. With constant loading you will reach a point where maximum stretch is reached and it will no longer absorb load changes. Also, when you lock a rope into a specific load on the pulling end, the stretch will cause the loading to equalize across the system and the output will be more accurate. What you're doing in these tests is showing how the stretch of the rope equates to the shocks on a car.
Or just use a progress capture on the pulling end to ensure the rope has time to stretch evenly all the way through.
Dynamic loading and peak force measurement are somewhat incompatible here. The springiness of the rope act as a damper, widening the peak force in a broader peak, while the force shockwaves may also be interfering which each other. You should do the same thing, but while keeping a constant force (maybe do 2kN and 4kN)
do it vertically. use weight. this is a bunk science on purpose with the intent to be dishonest. {click bait}
@@DieselRamcharger definitely. That jerking pull is useless.
For the next test, I would suggest one of the follwing:
- constant pulling force (such as a weight in free space)
- progress capture device, again providing static load to the rope
If you apply a constant force, you don't get a video to post... lmao the results will be a lot different, and a lot closer to what intuition expects from those pulleys.
Also calibrated force gauges. It doesn't matter how much stretch is on the rope, in a 1:1 system the force at both ends is equal
so a ratchet
"Mechanical Advantage is a Myth" is definitely the better "get views" title, but I suppose what you're saying is "Mechanical Advantage is Oversimplified" and I love your investigation into real-world variables and results. Great work!
Right. You can still pull a boat or a truck with a simple pully system.
Kinda of rubbed me the wrong way too. But "multiplying stretch with mechanical advantage" has nothing on "mechanical advantage is a myth" for clicks
Stretch and friction
@@NoExceptions109 Totally, it's fair play on UA-cam, but nice to drum up some convo about it
Ryan stated what he means, in the first 30 seconds. But if you're justifying lying, and calling it fair play for $$... Lookup how "Fair Game" was used by the admin of VP Dick Cheney (Haliburton profiteer), Scooter Libby outing a US spy for revenge, cause her husband Joe, called out Dick's lying about Iraq buying uranium to justify their invasion. Don't say lying is okay... for profit. Ryan knows that and is why he tests, for truth.
To reduce the length of rope needed, you could extend the pulley block away from the anchor tree to just a couple of feet from the other end. This way, the back and forth between the pulleys is only a few feet of rope instead of 100+ feet. Less stretch and less elastic losses, and less rope length and weight.
I think bouncing is having the effect of systematically increasing the input force more for the least dynamic cords. Also you could pick up a short length 1.5 to 2" thick wooden dowel to make a pulling 'handlebar'. I'm using a portable fingerboard similarly for tightening my longer slackline setups. I can get way more force without the finger pain.
Maybe a rigging plate could work.
It definitely would, but I appreciate this because this jerky motion is how I tend to tighten things. Now I know the dynamic rope is eating up a ton of force.
I think we also need to consider static vs kinetic coefficients of friction: it takes more force to set something in motion than to keep it moving.
There's one more variable that you threw in by accident, it's the duration of the pull. A single straight line should have equal values, unless you're yanking on it quickly, without giving it the time for the forces to equalize.
With the 13:1, the rope is so long that the pull takes a while to travel all the way to the end, and if the pulls are so sharp, you aren't using all the pulleys, you're just fighting against the inertia of the rope.
Slow pull the next one?
But of you think about it, that is how you would normaly pull things by yourself on a wall or just in general.
@@pedroferreira3371 True, it is still a variable though.
The straight pull with no multipliers also shows a big difference in the scale readings. This might be worth re-visiting after checking that both scales read the same and calibrating them if they don't.
These test are for a system he can take into the woods to test in real rock, so it is quite close to intended use. Though he should do a test with capture so that the system has time to equalize
@@pedroferreira3371 except that normally you would be building up that tension in something (like a highline) with it's own stretch, and not just a solid piece such as the linescale.
Considering how you aren't slow pulling it, there is likely a whole bunch of dynamic stuff going on as well, likely skewing the results a lot.
Not to mention that the friction of a pulley isn't constant, it has a stationary and moving friction just like any other mechanical system. And under load, the stationary friction would logically require a larger force to overcome it.
In short, you might get closer to the actual ratio if using a more constant pulling force, like the new kapstand.
Love the vid Ryan, very informative. Hope there's one delving into multipliers too at some point.
One thing I think would help: A bar chart at the end displaying all the different % results from each rope type and pulley setup. Every result on one graph would make it much easier to compare the results I think, rather than trying to keep them in my head.
You’d have better results with complex/compound systems. Put a 2:1 or even a 3:1 on the tail of a 5:1 and you can get some huge forces.
👆that would cut out a lot of the internal system friction from ropes running back and forth next to each other - probably the biggest reason the 13:1 couldn’t out perform the 9:1
It would be interesting to repeat the tests with different total length of rope per configuration. Suspect doing 1to1 testing with very short length of rope incrementally increasing the length would give you a factor reduction in efficiency per meter length. Probably best to use mechanical clamps to remove variance in knot tying between each test.
I was thinking this also mostly. same setup, different rope lengths. Clamps might be a bit overkill/impractical for their level of benefit.
I'd love to see if you get closer to the exact ratios with slow/constant force pulls.
I would imagine it takes time for the stretch to travel through the system. Giving it time to settle would probably have some effect. That would just be more for curiosity though as what he's trying to test is the efficacy of the setup the way it's used in the field. I'd also be curious to see the old 81:1 setup tested with he new line scale 3s. But that's a lot of work for what would probably be a predictable and not very exciting result.
I'd guess that it has a large effect on it. Imagine lifting a weight with a soft bungee cord. You could yank really hard and not lift the weight if you didn't get all the stretch pulled up and start lifting the weight but once you had the weight lifted and the bouncing stopped you'd be pulling exactly the weight of the bungee and attached weight. If he used that capstan winch to load the line slowly he'd get much more consistent results regardless of stretch but he'd have to pull more line through on ropes that stretch more. By yanking he's loading a bunch of kinetic energy into anling length of rope and then letting it dissipate between yanks. I understand that this is how he intended to use the system so I get why he did it this way but it's a bit disappointing that he didn't repeat the test with the winch.
@WungusBill I would go for a small ratchet system in which he can gradually increase the force. He still can generate force spikes by forcing the Rope to one side and thus creating a massive force with very little input.
Will be nice to see calibration of those linescales. Worked with load cells and is important to do the calibration process often if you are putting a lot o stress on them.
Maybe, maybe not. You could check their 0 point by just turning it on. (I'm no engineer, but have used load cells on man lifts). They get calibrated upon install by setting a zero weight in bucket then max weight in bucket. The stuff in between is linear. They do look allot different then the line scales though so don't bank on my info.
Boby: It's excatly same if you are dyslexic.
me, dyslexic: no joke, that's static, and they are same, OH SHII
Thanks for another great video. The physics 101 graphic at the beginning of video assumes frictionless (as you noted) but also a constant force being pulled with zero stretch line. Bouncy dynamic inputs are damped out by the stretchy rope, less by the semi-static and even less by the Dyneema. I'd be interested to see the Input v Output when using the portable winch set up as it's less bouncy. Appreciate the video and look forward to more content from the drop tower and testing of sailing components.
There are two separate issue going on that are incorrectly getting linked together here. These are (1) how impulse loads are generated on a system and (2) the sum of all forces acting on a system (each rope end) incorrectly not equaling zero. These actions exist independently.
Regarding the force generated from the duration of the dynamic loading. This deals with Newtons second law. In this case you placed kinetic energy into the rope by pulling on it. The amount of time the rope takes to absorb this kinetic energy determines the peak impulse force placed on the rope. The more stretch, the longer the time duration, the lower the force. The less stretch, the shorter the time duration, the higher peak force. This is why the static rope saw a larger impulse load.
The second issue is the question of “will a rope that is fully constrained by one end ( with no other external forces restraining it) and loaded at the other end see different force values at its end”? Newtons 3rd law states no. The tensile load throughout the entire segment is equal at all points regardless of the load being dynamic or static. This exact rope problem is littered throughout intro level physics text books and commonly appears on midterm exams.
With regard to the different measured values at each rope end it is not that Newtons 3rd law is incorrect, it is more likly that the way you set up and performed the test failed to collect representative data points, for all forces acting within the system.
There is probably a couple reason why your load cell values are different
Load cells only measure force in a predefined axis. Placing the rope horizontally causes the anchored load cell to rotate more when loaded the force vector of the rope was not always concentric with the anchored load cell axis. The way you held the input load cell when loading the system placed the force aplied ro the rope directly inline with the loading load cells axis . Because the load was more in line with this load cell a higher value was recorded more often. With regard to the end of the rope you were not continually measuring the total force placed on the rope. Form most of the time you were only measuring the vector component that was acting in line with the end load cell’s axis.
This would not be an issue if you had a load cell with an extremely high sampling rate and where then downloading this data into a laptop running data acquisition software. As the duration of the peak impulses can be very very short. However it is highly probable your load cells were not sampling at a high enough rate to capture the peak data point at the exact instance it was 100% aligned with the end load cell.
I would recommend re doing this experiment and see if you get more accurate data. Anchor the rope overhead and perform this test by pulling straight down with the force being transferred straight through both load cells axis. Crank the sampling rate to the highest value you can and try and apply the dynamic force at a rate that will not exceed the sampling rate of the load cell.
It would be interesting to see the results
I love you channel and it has lots of great information
Awesome content my dude! You guys are constantly growing and learning and sharing it all with us.
Much appreciated!
Do those pulleys have ball bearings? You should look into sailboat hardware, they make some pretty trick stuff. The nicer stuff rides on ball bearings and has almost no friction, even under load.
Agreed. I've got 5 to 1 in pulleys plus a block on deck for 6 to 1 on my main sheet before the winch with sta-set line (dyneema core). Curious what it would show.
The 3” smc pulleys do have ball bearings. The others dont
@@HowNOT2 Harken makes some blocks that are rated for 44000 Lbs, can you test one of those? ; )
Fun fact, I am pretty sure ball bearings are a Swedish invention :D
Best video!
Love the pulley science!
More please
'Mechanical advantage' is, unfortunately, mis-named. It should be called 'speed ratio'. One is the reciprocal of the other ONLY in the case of zero friction, which never happens. We should say mechanical advantage = efficiency/speed_ratio, and sometimes efficiency can be really sh*te, especially where ropes slide over other ropes, or even 'biners. Shock-loading a rig is a real good way to get non-reproducible results, guaranteed to confuse any otherwise good readings you might have got. It takes a lot of careful instrumentation to handle the pulse case correctly. It's an especially favoured trick by the over-unity community, for exactly that reason. It's a pity you've tarred yourself with that brush.
Fantastic! Sometimes I use a 3:1 or a 5:1 when working. I thought I'd be getting much more pull than your results show.
I will have to take this in to account when I'm tipping trees over in the future 🤔
I was thinking the same thing mabee I will hook it to the winch now.
Ryan consider a sailboat winch as a mechanical advantage.
Theres an enormous one used for arborist work.
Lol i like the set up in this video, there's no way I'm pulling at a constant and consistent way myself
It would be interesting to look at how much the pulley lenght affects the result, especially with stretchy rope. I would do it but I don't have 2 linescales
Efficiency of pulleys in a system is a compound problem seen in the video.
For example, if 90% of the force is redirected from a pulley. If you haave a 5:1 system. The ropes will pull at:
100%, 90% 81%, 73%, 65%. These forces are added up 309%, so 40% of the systems total pulling force is lost in friction. So.. pulley efficiency in series is pretty important.
A dynamic rope basically adds rope to the system upstream under tension, which means you'll have less opposing force and therefore less pulling power.
I'm a engineer btw, and I do enjoy this backyard science, and trying to explain the results.
"It's exactly the same if you're dyslexic" -- me not realizing they were different until he said that...
This channel is amazing. Thanks for all your hard work and dedication. You are making the world a better place. This is like myth busters of rated gear!
i think it is not there yet :) but it could be, i the channel gets even more popular and budget increases :D
Most would never read the boring studies on the advantages of elevator music. Your channel allows us without a music degrees to see how effective the musical advantage really is.
Hey, have you ever thought about testing a petzle ASAP fall arrestor for use in rope soloing? Its been a topic of debate around the shop recently!
I don’t think you are supposed to count the line you are pulling. So your 5 to 1 was only 4 to 1. On the 3 to 1 the pulley furthest from you is just a change of direction. If you have 1 pulley you get 2 lines but it’s not 2 to 1 it’s 1 to 1.
I thought you only counted the Xtra lines, like when you were saying 9 to 1, it would be 8 Xtra lines to 1 cause you would always have the 1 to start with
I think you got pulleys mechanical advantage wrong…
3:1, 5:1, 9:1 does not apply on peak force, but on equilibrium force !
What you are seeing is that dynamic ropes prevent force from being transmitted instantaneously, and therefore it takes time for equilibrium to be reached.
The deformation of the rope absorbs energy. I think that's pretty much how it breaks a fall. But it's very cool to see some numbers, this definitely improves our understanding of climbing gear.
My degree was chemistry, and I was one of those guys who took extra physics classes as "hour fillers" and for fun.
It was a oet oeeve of mine that calculations always had so many idealized exclusions.
Friction is rarely negligible, and unless you are flying REALLY high or going REALLY slow air resistance is always a factor. It's nice to be able to make approximations but the real world is always so much more complicated. Unless you are PTFE in space.
2:00 According to my knowledge you have 3 wires and 2 blocks, so force should be 200% but you expect 300%. And you got 1.13 and 2.26 which is exactly 200%.
Dunno how this isn't top comment, he kept counting redirects as mechanical advantage. Every test was calculated wrong.
You present a lot of awesome data, would be nice if there was a summary at the end. A chart of the numbers or something. Looking at a chart or graph, especially if you divide the actual numbers by the theoretical numbers, you can really see a sweet-spot right around 5:1 for efficiency. Unless you really need some extra capacity then 9:1 works.
Should the scale be on the other end of the rope
The fact that your handle was a soft shackle, I think you have an obsession brother
Gear ratio is best example for mechanical advantages but it had limitation nothing can overcome because some specification of tasks demand certain torque
Great video. Looking on the theory of mechanical systems, they consider no stretch on the rope, no friction on the pulleys and no weight on the rope, but also no weight on the pulleys plus a lot more variables, so as the video shows, the theory most of the times deviates from the reality. I usually use 4:1 system or 3:1, beyond that I think only adds weight and complexity to the system instead of giving advantage.
I tend to use a 4:1 with a 4:1 jag on the end. The key is constant pull with a progress capture. Next time I do it I'll put a meter on it and see how it compares.
We use much larger capstan winches at work at work (I build cell phone towers) and this video got me thinking…if you bolted a larger capstan to your drop tower you could easily pull 5,000lbs up with zero mechanical advantage and a single block, would be relatively easy to put together once you acquired the winch.
You should try with the exponential compound pully system next!
Long story short: Design your block and tackle system for what you are using it for, not for it's theoretical output.
So as a sailor on traditional vessels I use block and tackles all the time. Most are fixed, but I often have an extra one lying around (normally 3:1 or 5:1) in case I need the extra purchase (I'm tiny, so I never have enough weight to so anything). The line we mostly use is semi static, as we can use it for everything. There are a few things where static would be better, but dyneema is expensive. Otherwise a bit of stretch is good because it prevents the rest of our gear from being shockloaded and breaking. When we don't want stretch in a line we will actually pre-stretch it. This means we will set it up under tension and leave it for 48 hrs or so, while continuously tightening it as it stretches. Only then will we actually rig it. This takes a good amount of stretch out of the line and means we can permanently rig it and then we don't have to be constantly adjusting it for the first few days and instead can adjust it every few weeks or even months depending.
Back to block and tackles. The test you did here actually gives decent realistic numbers by the looks of it. Of course they are not accurate and there are better ways of getting closer to theoretical numbers, but these are what you would get in a practical application. Friction kills. Even with perfect blocks and slippery dyneema. The problem with adding more purchase is that you always add more friction and you add more weight. The blocks get bigger and the amount of line makes a big difference. This means that lighter pulls are more difficult than they should be. Take the main halyards, the lines that pull sails up. You often see these riggen as 6/7:1. This seems to be a pretty good number. It lets two big people or three or four smaller people set the sail with relative ease. The last little bit is always really difficult, but if we would set up our purchase to accommodate that in theory, the friction and the extra length of line would make things difficult and take a long time (more line to pull). So instead we add and extra block and tackle to the other end of the line. This is often another 6:1 made from a smaller line that is only 5 or so meters in length (total sail height is around 15). It is this extra 6:1 that lets us pull the sail up that last meter or lets us do adjustments while the sail is under load (full of wind). Also we can use stoppers and smaill block and tackles to adjust things that are under load. Rolling hitches or prussik hitches work perfect to add and extra purchase to an existing system. (Would love to see you test these as well).
After 8:1 the friction overcomes the efficiency of adding more parts. . .most of the time. Cranes will have more than 8 parts but use super efficient sheaves to do so.
I'm not sure what you are trying to measure, but on the dynamic ropes you are storing energy in the stretching and YOU are accelerating and recoiling. It isn't "springyness" as much as your mass times acceleration. (Are you looking for max force in an arrest?) You need to apply a force and hold it to get a static reading. When you lunge back and are quickly decelerated to zero by the rope, the force will be proportional to how stiff the rope is or how quickly you come to a stop. SO basically your measurements are rather eccentric and the setup lacks reasonable analysis.
If you are looking forhow much force a body experiences, then your single line measurements are sort of reasonable. In essence I would say you have made a stretchy indicator - if you measure right.
Considering this not to simulate theoretical or lab conditions, and its done in the field but thrown in a couple of dynos to get an idea of whats going on, I'd say the results and conclusions were super good enough.
He wasn't trying to teach Pysics 101 here.
Great vid and interesting results! Certainly using the capstan will give more control over loading, perhaps invest in some ground anchors to avoid "towing error".
Regarding technique (and haters) I used to teach experimental technique as a Physics teacher and see no problem in what you do. You are looking for the big picture not the fine detail, I love it.
I can't be the only one excited for him to test cams so we can get a discount?!
Hay rayen. Garage video.
It will be also interesting to see 3:1 multiple by 3:1 (9:1 with less rope).
Please test multipliers! If 5 and 9 to 1 are the best but if you multiply another 5 or 9 to 1
That capstan winch is awesome
Nice use of pulleys on the straight pull.
Looks like you where wrong on the Ratio eg your 3 to 1 was in fact 2 to 1 you don’t count the leg your pulling on it is the 1
Now I wonna know what would happen with static load ...
that joke was pretty good, makes me feel better about the pulley I rigged to carry out a water heater that was sealed up by calcium deposits
It's be interested to see how this goes with dynamic rope and a keeper, like say a petzl micro traxion. The stretch between the keeper and the output should be locked in after the first few tugs and I suspect you'll get better efficiency. This would be more analogous to a haul/crevasse rescue scenario.
so the sweetspot for max power is somewhere between 13:1 and 5:1. would love to see 6,7,8 and 11 to 1 tested.
Did you try pulling one scale directly hooked up to the other to see if you get any difference? I wonder if there is a 'calibration issue' between the two devices. Or run tests swapping scales end for end with the same line/pulley set-up to see if your readings are accurate. Also, like others have stated, either repeat the test vertically with a static hanging weight or use the capstan winch for a steady pull for each test.
As a sailor first and a climber second, I appreciate this video. Could you test some sailing-oriented line for us? I think most of it will have a dyneema core for strength and being static, but covers for this core vary widely depending on friction needed, pulleys being used, the handfeel, and workability of the rope. An interesting experiment would be to see how much extra force we get on a jibsheet for every extra wrap around a winch we take. More wraps takes more time to do and undo, but also lets you hold hundreds of pounds of force. Too few wraps means your winch will slip against the rope, and you won't be able to pull the sail in anymore.
So a wrap will just increase the friction. It will highly depend on the type of and thickness of your line, the size and the material of the winch.
Have you tried an aluminum framed come a long for input power. I pull trees over with a 5 to 1 and a 1 ton come a long. Great videos. Always good info. Thanks
This was very helpful, just like all of your videos. Thank you!
You're clearly not doing it right. This is way too entertaining.
So I think you should definitely do this test again but this time use a steady increase of pull to see if the energy at the other end of the system levels out with time. My theory is that you’re jerking motion put only a momentary pull on one end of the rope which didn’t have time to work its way through to the other end. Still not going to be a perfect result but I’ll bet it’s a lot closer. Awesome video thank you
What if you try making a gearbox for mechanical advantage instead of ropes and pulleys, maybe less losses or more overall multiplication?
You are describing carrying up a winch.
I assume it is just too heavy.
There are so many issues with this testing method that the results are not useful. Use a winch with a known, repeated force and pull and hold the tension until the system stabilizes. You are measuring highly inconsistent shock loads, not steady pulling force.
This was very informative. Thank you for making this video.
I think that the results woulp be very different if you pulled continously, here the tension si probably not established in all the system when you stop pulling, the "traction wave" does not propagate instantly in the rope and the system.
I think you pulleyed a great joke... harhar.
moment of silence for this man's spine
I pulled my back from watching this video and required eight weeks of physical therapy.
@@Frostbiker I know all too well. If you lock your shoulder blades while extending your chest forward, you can minimize the pain caused by tugging. The way he was doing it...that's a one way ticket to the chiropractor.
If using a loaded dynamic rope with a progress capture (like when you're hauling), wouldn't that eliminate a lot of the effect of stretch you're seeing? Because the rope would already be pre-stretched?
Ryan, haven’t even watched the whole video yet, but please, let me know! Do you even know the origin of that meme you used? (Lady confused with calculations) haha It is funny to see how that is circling the globe. That was a famous villain in a Brazilian soap opera. Pretty famous actress too.
When I pull my soft shackles to 10KN+ on my theoretical “15:1” system I found I can maximize the force of my “1” by putting on my harness and clipping to my belay loop. Like a saddle on a horse!! Helps especially when you have no homies to pull with you. I’d need an extra linescale if I want to do a similar test like this one though. Thanks for this info I’ve been waiting for some good MA testing!!!
Haven’t seen that many comments appreciating the fact that this is helpful to understand why it’s soo hard to pull someone out of a crevasse. Yes there’s stretch and yes I am yarding on the rope just like he does here. So now thanks to him I’m considering separate static for glacier travel even with a dynamic for the climb.
Do you think the 9:1 is greater than the 13:1 could be something to do with losing a percentage of the pull at each pulley meaning you want you most efficient pulleys first and the 13:1 has those small pulleys first?
I like the tree:1 joke more than the pulley
Any plans on testing multipliers in the future? also, an interesting experiment would be side pulling a tight line, maybe in conjunction to a pulley system
Did you have sore shoulders after this?
what if you had a 3 to 1 pulling the end of another separate 3 to 1 system, would we see a proper mechanical advantage of a 6 to 1 without any losses cause your reducing theoretical friction of one system info 2 separate smaller systems? i have no idea but it may work??
Thats a multiplicative system. turns into a 9:1 theoretically.
logic being the input is mulptiplied by three.
the output of your first 3:1 becomes input of the second and is multiplied not added.
ua-cam.com/video/01dUEhPolfA/v-deo.html
check out this set up for the logic.
Would be curious what the actual results would be in a practical test .
Joke was perfect. Great video.
Just a note for everyone...be very careful using a ball-hitch as a rigging point (i still see it with off roaders and it makes me cringe) but they snap off surprisingly easy and shoot the 2 pound steel ball like a cannon. This has and, sadly, will kill more people.
Congrats sir you are a scientist!
Hi you two,
I am a Math and Physics teacher, and I would like to use some scenes of your video to show how reality and theory sometimes don’t match.
Would it be ok for you guys, I will also link and mention you in my video. Thanks a lot
Matti
His results , seemed to be rigged!
I was thinking about this whenever choosing between 3to1 and 5to1, thanks for sharing!
Do you still keep collecting the results in a spreadsheet or similar? I cannot find it.
I like graphs! - would love to see a comparison of both linescales' graphs for some more insight. :)
Hi. I see what you were trying to do, BUT you are effectively using a SHOCK LOAD. If you were to do this on your test pulling bench you would find it would be much closer to the theory.
Also, do the readings depend on which way you link up the linescales? Because this time you had the pulley system attached to the top of the "yanking" scale on one end, and to the bottom side of the "stationary" scale.
Of course this wouldn't matter for a slow loading, but might be one of the confounding factors when yanking.
Progress capture would be helpful
I was born for this job, haha!
In all seriousness though, pulleys and mechanical advantage have always blown my mind. In researching my namesake I came across this awesome video by SmarterEveryDay on pulleys: ua-cam.com/video/M2w3NZzPwOM/v-deo.html
I loved seeing these numbers and how it plays out practically in your tests. Thanks as always for quality content!
Really nice test!
I'm about to build a simple pulley system (classed shackles and ball bearings and washers what could go wrong! Soft shackle friendly too.)
And the test really beggs the question:
If I have say 8 bearing pulleys, it's probably better to do a 1:5+1:5 multiplier, rather than having a 1:6 with a 1:3 multiplier or 1:9 without multiplier.. hope that's understandable.
And.. I'll be using a 8mm static rope and a nice handle, for now!
"Handles tested!" Lol.
Best regards swede patreon.
Great videos Ryan & Bobby, thank you!
first?
Yes!
I would be curious to see if you get better results on the dynamic / semi-static ropes with a progress capture on the pulling end. This should let the rope get evenly loaded through its whole length, rather than just measuring stretchy-waves of pull force. Great video as always!
You're pulling in too jerky of a manner to really test this, you've gotta get the system statically loaded and then you'll see much less effects from friction and stretch. Repeated yanking isn't a good way to test this and introduces so many variables that it's hard to get any meaningful results in a test like this. Mechanical advantage when statically loading straps or chains reaches pretty much 100% theoretical, and a single person can safely pull a heavy vehicle out of a ditch without motor assistance if the setup is good enough and the chain can help it. Stretchy rope is always going to cause losses but trying to load it statically is going to naturally produce better results.
3:08 you have a loss of 12.5% from a perfect 5:1 ratio as 0.89 x 5 is 4.45 and ( |4.45 - 3.84| / 4.45) x 100 = 12.5%
That's not terrible considering friction, stretch and any air resistance friction from the ropes interaction with the atmosphere.
The system here is ~ 87% efficient which honestly isn't terrible.
Serious question: hope someone can answer seriously, what if you were to capture the stretch in the rope not allowing it back into the system. As you jerk the input side you are taking up the stretch but then you let it return into the system. Is it still such high loses when you’re slow pulling with say a winch or a van where that stretch is continually being taken up…would you not eventually reach the point where the stretch is stretched and then acts like a semi static or static rope where your input more closely matches the theory or would there alway be loses to keep the stretch stretched. Sorry wish I knew more technical terms but hopefully it’s clear enough.
This actually causes most of the loss due to stretching. If you progressively load a stretchy rope and have a lot of patience you can get it to transfer very large forces, but if you jerk on it that'll never happen.
kinda bugs me that you use the tree as leverage while testing the force on some of them but not all...
Why not use some sort of ratchet?