Mechanical Advantage is a Myth

[@HowNOT2]

What we learned in this video was vital in making this episode a possibility! kzbin.info/www/bejne/fqrCiGRmrbKlea8 Check out our new store! hownot2.store/

[@matthewluttrell9413]

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!

[@michaelm8624]

Yes, this would have been the better conclusion

[@diamondflaw]

Yup, under dynamic loading it’s acting more like a mechanical capacitor and smoothing the peaks.

[@davidpetrela383]

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.

[@kenbrown2808]

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.

[@colt45lmer]

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

[@patrickradcliffe3837]

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.

[@elmeradams8781]

He used to do that exact test with his old bolt breaking machine. Then he switched to hydraulic.

[@davidseslar5798]

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)

[@arlodillon1659]

The purpose of the test was explained at the beginning.

[@ianbelletti6241]

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.

[@FallLineJP]

Or just use a progress capture on the pulling end to ensure the rope has time to stretch evenly all the way through.

[@johnnylavoie]

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)

[@DieselRamcharger]

do it vertically. use weight. this is a bunk science on purpose with the intent to be dishonest. {click bait}

[@christopherforsyth5284]

@@DieselRamcharger definitely. That jerking pull is useless.

[@goskascience]

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

[@guilhermetorresj]

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.

[@TheTomco11]

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

[@punkazecke3881]

so a ratchet

[@BrandonRadtke]

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.

[@error.418]

"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!

[@MattShine11]

Right. You can still pull a boat or a truck with a simple pully system.

[@NoExceptions109]

Kinda of rubbed me the wrong way too. But "multiplying stretch with mechanical advantage" has nothing on "mechanical advantage is a myth" for clicks

[@NoExceptions109]

Stretch and friction

[@error.418]

@@NoExceptions109 Totally, it's fair play on KZbin, but nice to drum up some convo about it

[@jr.6199]

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.

[@stevebarratt888]

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.

[@SafetyBoater]

Maybe a rigging plate could work.

[@kevinmcdonough9097]

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.

[@DustyLambert]

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.

[@lleberghappy]

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.

[@therflash]

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?

[@pedroferreira3371]

But of you think about it, that is how you would normaly pull things by yourself on a wall or just in general.

[@therflash]

@@pedroferreira3371 True, it is still a variable though.

[@theaykay]

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.

[@olesvren2906]

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

[@iura0]

@@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.

[@_joac]

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.

[@elmeradams8781]

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.

[@glynroberts4802]

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.

[@stevebarratt888]

I was thinking this also mostly. same setup, different rope lengths. Clamps might be a bit overkill/impractical for their level of benefit.

[@fishman241]

I'd love to see if you get closer to the exact ratios with slow/constant force pulls.

[@msilva3084]

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.

[@xidarian]

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.

[@theonly5001]

@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.

[@johnjohnstone8506]

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

[@408murph]

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.

[@jessebrighten6319]

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.

[@jakegotta4334]

👆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

[@sinclairearl]

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.

[@ziggyx27]

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.

[@skysocalbalen6075]

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.

[@francescovaroli6893]

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.

[@georgebridgewater2573]

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.

[@gallonofcactus]

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!

[@brainstroem1]

i think it is not there yet :) but it could be, i the channel gets even more popular and budget increases :D

[@matthewgough9533]

I have been so curious to see this series of tests done. Thanks for doing this!

[@lighterguy82]

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

[@todayonthebench]

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.

[@Sokattash678]

Awesome content my dude! You guys are constantly growing and learning and sharing it all with us. Much appreciated!

[@biggs8729]

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

[@jakemonaghan1659]

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!!!

[@borosecrans]

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.

[@DxPru]

Now I wonna know what would happen with static load ...

[@theralmackey8066]

As many below are saying, dynamic loading is wasting a bunch of the force/energy into friction and heat as the rope stretches. You will also find that putting the linescale currently on the tree on the opposite side (using an even number multiplier/pulling from the same side as the "load"), it will register even less, considerably less when using carabiners, since that first carabiner will eat a bunch of the force/energy as the highest friction point. As the force put into the rope goes up, the amount of that force required to even just start moving the rope around the carabiner will go up. . To prove out the actual advantage you should add the second linescale between the van/anchor and portable winch in that last break test.

[@FallLineJP]

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!

[@skysocalbalen6075]

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).

[@johnrutkowski9005]

You're still getting the force increase minus friction, but only at your maximum sustained pulling force. The rope will act as a mechanical capacitor and smooth out the impulses you produce by yanking on it. The proper way to test this would be to pull the free end with something like a ratchet strap and record the settled force readings on either end. This does however show an interesting aspect, where a lower reduction pully system will allow you to produce higher peak force than the higher reduction due to the smoothing effect

[@guilhermetorresj]

The problem lies in those short bursts when you pull. If you apply a constant force, the stretch doesn't have the same effect. The stretchiness of the rope makes it spread the changes in applied tension over time. The best analogy I can come up with is with capacitors being used as a low pass filter in a circuit by smoothing out high frequency changes in voltage.

[@HerbaMachina]

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.

[@rustytygart405]

I’ve been a subscriber for a few years thanks for the great content

[@larryseibold4287]

Friction is a thing, and is largely an independent variable of dynamic loading. Using dynamic forces with a dynamic rope, is going to give dynamic results, where the system (rope) acts like a capacitor/inductor to smooth/dampen the input to the load. moving to a slow load increase (to say 2kN) will show the quality/effectives of the pully selection. If large great pullies are used, the rope selection will not matter. Using sharp bends in carabiners etc., will turn into a brake system at about 5:1 or less. Using static rope allows the "bite" with the people (walk distance to rope break rebound anchor) to be far shorter for the same pull length at the load (the working end of the 5:1 is only moving 1 ft for 5 ft of travel. 2:1 stretch drops that to 1 ft for 10 ft of travel or more due to cumulative loses). 2:1 and 3:1 are my favorite ratios if you have enough people to pull. It is not easy, but it goes much faster, with minimal gear. How do you hold that 5mm Dyneema cord (think four pairs of hands vs 11mm static line).

[@petesmith1]

This is exactly why we use Dynamic rope for climbing, Semi static rope for where it is possible to fall, or a super Static rope where there is zero/no chance of falling. Lets see the difference of a FF1 and a FF2 on each type of rope. I think it's an eye opener!! Keep up the great work.

[@Aeronaughtica]

Great videos Ryan & Bobby, thank you!

[@Puddyglum]

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.

[@williamplovanic329]

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!

[@ikesquirrel]

I worked with a tree company where the boss kept saying "this is a 13:1" or "this is a 5:1" or whatever, and they were not. The number of ropes is not how many times it is multiplied. Redirecting is not multiplying and the pulleys have to be in the right pattern, not just thrown together.

[@joshuaknight96]

The relationship would be closer to 5:1 or 3:1 or whatever arrangement there is if it was equating total work on each side of the pulleys. Work being equivalent to force by distance (w=F•d) this also means we could add other variables onto this function such as the stretch of the rope. The stretch of the rope is ultimately the limiting factor when applied to multi pulley systems. That’s why cranes will utilize dyneema (amsteel) on a winch

[@ianproctor8069]

the stretch definitely makes a difference but only because the force is not constant, energy is being put into stretching the rope and that doesnt come out as force on the other side of the pully system. Once the rope is stretched out the force would look quite similar to the static rope if you had a constant load: perhaps hanging a weight on the drop tower with the reduction pully system?

[@CasperEngineering]

One way to get repeatable static pulls with systems like this is to add two redirect pulleys, one at the anchor you are standing next to and one above the anchor you are standing next to. Run the rope up and back down then use your body weight by hanging or standing on the rope instead of relying on your arms.

[@allensandven0]

You need a repeatable force method of tension using the recommended pullley / block system for rope / line size and if dynamic or fail point is your criteria then you must. Load vertically with a uniform dead load to create dynamic or live load

[@johne1097]

The size of the pulley vs the diameter of the rope has an effect on the friction. That is another reason that the 5 mm Dyneema did better than the 10 and 11 mm lines

[@Mrwhomeyou]

Lol i like the set up in this video, there's no way I'm pulling at a constant and consistent way myself

[@ЮрийЛипшиц]

Boby: It's excatly same if you are dyslexic. me, dyslexic: no joke, that's static, and they are same, OH SHII

[@nohands3255]

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.

[@RomanFedorov]

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%.

[@TheRetnuh1]

Dunno how this isn't top comment, he kept counting redirects as mechanical advantage. Every test was calculated wrong.

[@levio1463]

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.

[@bockjess]

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.

[@HowNOT2]

The 3” smc pulleys do have ball bearings. The others dont

[@levio1463]

@@HowNOT2 Harken makes some blocks that are rated for 44000 Lbs, can you test one of those? ; )

[@SonnyKnutson]

Fun fact, I am pretty sure ball bearings are a Swedish invention :D

[@infbajuk]

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

[@davidbrewer7937]

You have to add in the divided values of stretch as well as the effect of gravity pulling down on the rope... This is why by the time you got to 13:1 you had slack ropes dangling...

[@tommysmith8801]

I wonder what the numbers would be if you used a static load. Use a winch to get a 1 kn load sustained for 10 seconds then see what the force load is.

[@glotzfisch]

I am not sure you can just look at maxima in dynamic force. With the elastic rope you also built a low pass dynamic system damping your input spike of force. You take out the high frequency part of the input pull. The input reads the spike of your pull. But the other end does not. The difference goes into the rope. Try a static setup with weights.

[@WetDoggo]

Elastic ropes smoothen out the force Spike. So you'll need to pull constantly to get the best result. Also, friction will increase to an equilibrium level, where you loose more energy than gained through mechanical advantage. Combine that with spike smoothening and you get a sh*tty pulley system. The interesting part is: Where's the sweetspot for the number of pulleys when applying constant force

[@devinholland2189]

Ryan consider a sailboat winch as a mechanical advantage. Theres an enormous one used for arborist work.

[@johnathandietz615]

I think a more consistent force, and making the pulley system vertical will provide improved results. When you jerk on the rope, you also have to take up the sag of the rope due to gravity. This takes a large portion of the impulse force you are imparting on the system. If the force was held over a longer time, the sag in the rope would only have to be taken up once. Having the pulley system vertical would eliminate the sag on the rope, and make adding a consistent force easier using weights. I think that would give the best conditions for testing mechanical advantage.

[@OllyBoardy]

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?

[@scottnichol4617]

Should the scale be on the other end of the rope

[@jacobfurnish7450]

moment of silence for this man's spine

[@Frostbiker]

I pulled my back from watching this video and required eight weeks of physical therapy.

[@jacobfurnish7450]

@@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.

[@syborg64]

Theoretically, stretch shouldn't affect force, only work. Though it's understandable in an imperfect context, it would generate a measurable force difference. I think that difference would be a result of rope mass: as it resists acceleration it smooths out the force curve, with an equivalent integral but lower peak (which isn't the case for stretch, as a perfect elastic would have the same force either side of it at any point in time). I would suspect that on a continuous pull, the reduction from stretch would be less significant as the peak input force is held. You did provide graphs for the output LS3, but I'd be interested in comparing the graphs for input and output sides of the pulleys.

[@tonkmonster]

Best video! Love the pulley science! More please

[@wflynnification]

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?

[@brodie661114]

You need an ID and grabs in your system. You can take out all the stretch in the system then your system will be more efficient and more likely to be closer to the values of 3:1 5:1 etc.

[@stevegreen2432]

You are better off combining say a three to one pulling on a three to one to get nine (?) to one. Adding another three to one will get 27 to 1 with losses. BUT you will not be able to pull over the same distance, or close up all the pulleys. Agree with earlier post, static loading will give much better results.

[@alexnone5720]

Some sort of progress catch on the final pull strand should help you build more overall tension/force in the system and give a more constant load on either the line or whatever you are trying to break. To get a better idea of how friction effects the amount of force this can be repeated by hanging it from the drop tower and adding the tractor weights to the pull side. Using a constant weight and changing up the pulleys from the 3" SMC pulleys, to the carabiner rollers to regular carabiners as well as testing a dynamic rope vs dynema to see how stretch and creep can affect the total force.

[@KamakaZex313]

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??

[@kylelewis6567]

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.

[@kylelewis6567]

kzbin.info/www/bejne/ZmLHhniehdSfnKM check out this set up for the logic. Would be curious what the actual results would be in a practical test .

[@nick11crafter]

You could take a bar and leverage against the tree to get some more consistent and less springy data if you were to do this again.

[@pavlodeshko]

the biggest problem you had with your portable pulley systems we've seen previously is gri-gri on the first strand from the puller. High friction basically halfs your input force

[@neilthomas2549]

'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.

[@lordofnothing.]

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.

[@MCKoolperson9]

Have you thought about using a progress capture pulley on the tail end? I'm not sure how much additional force youd be able to generate, but it would at least keep the rope between the pulleys tensioned between pulls so you don't have to pull that extra slack each time

[@jonflannery8984]

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.

[@kylehart8829]

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.

[@m.agilnajib345]

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.

[@halcyon510]

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.

[@diegoconverslaverde9605]

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.

[@dgardil]

The exact problem Aron Ralston (127 hours) faced trying to pull the rock (as he explain in his book). Stretch and friction played a big role!

[@joshbrown3572]

I'd like to see you try a compound pulley set up? I bet it would dramatically increase your force.

[@jasonbowers4388]

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

[@flyn2274]

it would be awesome to see a repeat of this with the same length of rope in used in all the tests.

[@iura0]

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.

[@340wbymag]

When someone tells you they are using a 3:1 pulley system (or any other numbers), they are describing the configuration of the system, and NOT the actual ratio of mechanical advantage. The efficiency of the system is affected by many variables.

[@frankwitte1022]

It is a good reminder that the pulleys in your crevasse rescue kit are very important :)

[@lysander3262]

This comment is mostly for the benefit of the curious, and not for those with a prior understanding of Statics. "Nobody really talks about stretch" Yes! But also...don't they? Adding the dynamometers to those physics diagrams, and suddenly you've already introduced *two* stretchy things to your setup. That is, after all, how they work: the metal of the load cell inside stretches eeeeeever so much, and the strain gauge translates that into a force reading. If you already have that in mind, then you should already have the thought in your mind that all solid materials experience strain when stress is applied. All of the connecting apparatus before the "far" load cell can be thought of as acting like another strained part of the "near" load cell *that isn't picked up by the strain gauge*. I think explaining this would be a crucial additional step to educating viewers on how physics drawings differ from experiment. The output on the "far" end is reduced just as much by strained rope if there are no measuring devices, of course, but including them in the discussion gives the fullest picture for others to attempt their own experiments. I leave it to other commentators to thoroughly, thoroughly discuss why dynamic loading and peak load measurements are not great experimental choices. As far as the load cells being thrown off by the shock loads: dynamometers are built to take a hell of a beating. Unless it's a super no name imitation device from lands unknown, at most him throwing his weight into would might throw the reading off by a division or two. Easy way to check is to see if the Zero has changed.

[@anotherriddle]

Great testing! I'm not stoked about the title though and hope that's worth it for the views. I'll never understand it, but i'll live with it. Cheers!

[@bemk]

Maybe a cool test to do is to pull a line between 2 line scales twice, but switch the line scales around between the two tests, to see how much of a difference there is from line scale to line scale. I'm guessing it's small, but it'd give an indication of the quality of the scales as well as the error margins on these kinds of tests.

[@lebulba]

Might be time for another buying guide now that you got the new site goin. Also new climbers like me would love your opinion on good gear to buy right now. Keep up the good work

[@BrandonRadtke]

What if you try making a gearbox for mechanical advantage instead of ropes and pulleys, maybe less losses or more overall multiplication?

[@Ammoniummetavanadate]

You are describing carrying up a winch. I assume it is just too heavy.

[@Pakkotehdataapska]

I plotted these out and it seems that the stretch might not be the reason for the results. The reason might be in the dynamic loading and even gravity affecting the rope that's between the pulleys, as the static rope is also the lightest. Here is the data if some one wants to take a look: DYN In out ratio 1:1 1.34 1.19 88.81% 3:1 1.13 2.26 200.00% 5:1 0.89 3.84 431.46% 9:1 0.85 5.92 696.47% 13:1 1.01 5.04 499.01% semi static 1:1 1.62 1.26 77.78% 3:1 1.31 3.46 264.12% 5:1 1.1 5.15 468.18% 9:1 1.31 7.48 570.99% 13:1 1.4 6.98 498.57% Static 1:1 2.33 2.07 88.84% 3:1 1.34 4.04 301.49% 5:1 1.67 6.71 401.80% 9:1 1.47 9.62 654.42% 13:1 1.51 8.54 565.56%

[@Pakkotehdataapska]

Also in csv: DYN,In,out,DYN 1:1,1.34,1.19,88.81% 3:1,1.13,2.26,200.00% 5:1,0.89,3.84,431.46% 9:1,0.85,5.92,696.47% 13:1,1.01,5.04,499.01% semi static,,,semi static 1:1,1.62,1.26,77.78% 3:1,1.31,3.46,264.12% 5:1,1.1,5.15,468.18% 9:1,1.31,7.48,570.99% 13:1,1.4,6.98,498.57% Static,,,Static 1:1,2.33,2.07,88.84% 3:1,1.34,4.04,301.49% 5:1,1.67,6.71,401.80% 9:1,1.47,9.62,654.42% 13:1,1.51,8.54,565.56%

[@mattfleming86]

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.

[@ianbelletti6241]

I'd love to see the results when you use a come-along winch to apply the force. I suspect that you will see better results once you max out the stretch of the rope.

[@kaidwyer]

You also have not accounted for horizontal tension force from the rope weight. Think if you have a weightless rope, it will have a mechanical advantage with a straightforward ratio, e.g. 9 to 1. However, the weight of the rope (when strung horizontally) creates an additional (equal) pair of forces pulling from the middle ropes all the way to your input and your output device. This "x" factor makes your ratio go from 9:1 to something looking like (9+x):(1+x). If you solve for that "x" for each ratio, I would imagine you'll find a trend where "x" becomes bigger when you add more ropes, because the middle ropes gain more advantage over your measuring devices. Alternately, you could string the ropes vertically and then the weights will cancel out (unless you have your measuring devices on opposite ends, then I believe you would need to subtract the weight of one segment of rope, pulley to pulley, from the output force to get a good theoretical approximation).

[@Mike-rx5uu]

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.

[@tripham2850]

Gear ratio is best example for mechanical advantages but it had limitation nothing can overcome because some specification of tasks demand certain torque

[@elitaube3273]

Alway have loved the content man❤️keep it up

[@scubamech707]

Your using a rope. Use a cable and check again. Prob be a bit closer to what's it supposed to be over a short section (weight of cable will add force if too long) When we're off roading we depend on the stretch of a kinetic rope to help recover rigs using what you've shown today. The additional help to standard mechanical advantage of smoothing out points and adding a little extra at the end of stretch is a game changer that helps alot.

[@RileyOutside]

"It's exactly the same if you're dyslexic" -- me not realizing they were different until he said that...

[@bauncey-chillups4638]

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.