This String Shooter Is SO Weird

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I love string shooters because they behave so counterintuitively. I was able to get hold of this prototype and make a few modifications to try and explain why the string does what it does!
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[@SteveMould]

I really want to try a string shooter with variable speed because I think there will be some interesting behaviour at the boundary of instability! Maybe I can modify this one... You can also discuss this video on REDDIT: stvmld.com/7htxvr_f The sponsor is KiwiCo: Get your first month free here: kiwico.com/stevemould

[@saifmohammed9070]

First

[@alexlexo59]

2rd

[@DennisXiloj]

Second

[@bigsteve6729]

Just put a potentiometer between it and the power source

[@CarlVardeman]

A high speed camera (Ala The Slo Mo Guys) might also be interesting to show the behavior immediately after various disturbances. Our perception of the disturbance at real time might be different from what a high speed camera catches.

[@ilikaplayhopscotch]

I used to think my cat was real stupid for finding such entertainment in a piece of string, but then here I am, wanting to buy one of these.

[@shannon1267]

Our cats have been trying to discern this the entire time

[@goldentortoisebeetle9741]

If cats could speak they would illuminate us with many insights about string dynamical properties.

[@jaywaghthegreat]

This, this is the comment that the internet was made for 💯

[@piotrarturklos]

The secret cat court is now debating whether to punish you for your past arrogance by ordering a soiling all shoes you will ever have.

[@JohnDlugosz]

I worked for a small company where the software engineering offices was a small enclosed room built inside a large warehouse space. One day the owner comes by to find all the engineers (including machine and EE) gathered around watching the door close via a automatic closing gadget attached to the top. It would start to accelerate, as you would expect from any spring, but then slow down suddenly as if damped, but then _reverse direction_ briefly, slowly, before closing the rest of the way.

[@shookings]

I'm beginning to think that you just want as many scientific papers as possible to mention a "Mould effect"

[@SteveMould]

Could be, could be

[@avesh_sayyed]

@@SteveMould omega lol

[@catmadeofdog]

Steve’s out here pumping up his h-index like it’s nothing. Researchers hate this special trick!

[@russellwarren9595]

i am just waiting for the day that Steve discovers a fungus that can be used for making fancy blancmange or jelly castings.

[@babylonfive]

@@russellwarren9595 Or if he figures out certain characteristics of tooling in plastics manufacture?

[@YeanyScience]

Hi Steve, thank you for kind words for my video and suggesting my channel This piece has been one of my favorites for years and also one of the most baffling. A far simpler analogy that I like to use to describe the wave movement is somewhat like a throwing a rock in a pond and seeing the waves move out in all directions at the same speed. Now try throwing a rock in a moving stream and the waves moving down stream will move very quickly and the waves going upstream tend to move very slowly. This suggests that at some point where string speed and the wave speed match there would be no wave moving through it. I have a similar piece that produces slow moving waves through hanging string, ribbons, or chains ( 2 videos on this are on my channel) I can easily vary the speed on these pieces and it's much easier to observe the speed of the wave changing as the speed of the chain changes, also fascinating as to how rigid the chain becomes or string on the opposing side. However I have not been able to match the chain speed and wave speed to get a standing wave where I thought it would have. I suspect that as the speed increases the tension increases enough to keep this from occurring (I'll have to get a faster drill and try it again). Another interesting note, is that the string flies due to lift created by drag as it moves through the air (studies have shown this doesn't work in a vacuum). I used to build these and sell them and we noticed that the old worn string fly better than newly made strings. We found that by rubbing new string with sandpaper, little hairs form on the string surface increasing the drag force, thus allowing for longer loops, my longest loop is about 20 feet of string. I do have some additional thought on the string's strange behavior and hope to share more on it in a future video.

[@domenicobianchi8]

Nice, hope to see a collab for part 2

[@marc3542]

The wave on a moving stream was easier to understand for me. Thanks a lot for this comment.

[@SteveMould]

Really interesting! About the wave speed matching thing, it's interesting that the *average* wave speed seems to match the string speed (a little slower on the pushing side and a little faster on the pulling side). It makes me think that you're never going to get it to match, no matter the speed of the dtill, but I'd love to see an attempt. Will definitely experiment with varying the speed on the zipstring. And very interesting about drag.

[@MatthewStauffer]

@@SteveMould This is your guy! Do another explorative knowledge collaboration with Bruce!

[@sonnenklang6925]

The waves in a pond move actually not all in the same speed because of dispersion of the pulse, also if you look very carefully at some wave group it looks like the individual waves are faster then the group and seem to roll in at the inner edge and dissapear at the outer edge of the moving packet ..:) (Solitons and Solitary waves are another Story for sure ;)

[@MedlifeCrisis]

Brilliant. But I’ve got all the way to the sponsor read and not a single String Theory gag. I’m not angry, I’m just disappointed.

[@SteveMould]

It's after the sponsor read

[@JinKee]

@@SteveMould it’s just a theory, A STRING THEORY aaaand CUT

[@BeeKisses]

Yeah, Steve? Don't bait medlife into the next beef, you're not winning that one.

[@morkovija]

Mould string theory - you heard it here first folks! Now with whom should we start a new beef though?

[@SmashedHatProject]

it's because this is String Practice

[@Nighthawkinlight]

Bruce Yeany is a treasure. Also I can't believe that opening clip is real. I've wanted a string thing for a while myself. I had forgotten about it.

[@DavidvanDeijk]

so happy to hear this shoutout, really made me smile

[@2.7petabytes]

Agreed!! As a matter of fact, I would posit that Steve! Bruce and your channels are ALL treasures! 👍

[@jankcitycustoms]

so much cool stuff out there, just isn't enough time for it all.

[@justpaulo]

With a bit of luck this could well be the new fidget spinner...

[@cleanlens]

sure monke

[@ZipStringOfficial]

We just saw your video! What a great explanation! ZipString on a drill was so cool. Love seeing others use creative ways to solve a problem🔥🔥🔥

[@AtomMan523]

What an amazing device. I felt the same as Steve when I saw it - I have to have one! Just submitted my ZipString pre-order a few minutes ago. 🙂

[@timfromkerncountyca2006]

Every thinking person needs a String Thing!

[@Jamesvandaele]

And just like that, a zillion pre orders appear.

[@jasonkrise495]

So instead of attaching the sting shooter to a drill, what if you connected it to a speaker and played different tones? What patterns would the tubes impart in the string?

[@SteveMould]

I tried that actually but the amplitude was just too low. Need something else I think. Maybe a jig saw.

[@DavidLindes]

@@SteveMould Oh wow. Please!

[@Abcdefg25152]

@@SteveMould ofcourse you tried it

[@nagriffin3561]

@@SteveMould Your speakers weren't powerful enough. No... it doesnt matter how big your current speakers are, you need bigger ones.

[@bvoyelr]

@@nagriffin3561 I think Mark Rober made a megaphone that might fit the bill.

[@petersmythe6462]

Reminds me of the idea of an active support structure like a space fountain or orbital ring. It's particularly interesting that it has such incredible stiffness.

[@iseriver3982]

Steve 'put it on a drill' Mould.

[@andrewseburn]

Nono, that's an electric screwdriver..... Never heard it called that before.

[@fellipec]

So we found the inventor of the drilldo? (don't google it!)

[@shottysteve]

im gonna be honest i didnt understand a single thing u said but i watched the whole thing to see u play with the string thing

[@ricardoreyes9470]

didnt we all?

[@ethanm3842]

Glad to see you're not dead shottysteve

[@GreenFox1505]

Are you a cat?

[@FrostedSapling]

*zipstring

[@cleanlens]

monke?

[@dfgaJK]

7:29 When the string falls off it looks like a lagged out desynced object in a game!

[@ikkonoishi]

When you move side to side you are adding a vector to velocity of the string so the effect propagates at the speed the string is moving. When you rotate you are changing the vector of acceleration of the string which propagates as the new acceleration vector overcomes the inertia of the previous one.

[@ku3kyc]

Being able to vary the roller speed will help explain the wave speed "doppler" effect better. If you could slow it enough and still have a loop, the wave may propagate both ways.

[@ikitclaw7146]

Would be a simple setup if he has some way to control the power going in, its jst 2 small electric motors, less power less speed.

[@maxthexpfarmer3957]

He could also use strings of different densities and cross-sectional areas.

[@TlalocTemporal]

@@ikitclaw7146 -- I would think it's just one motor, with the rollers geared together. Two motors would tend to run at different speeds, especially with wear, and would also be more expensive.

[@ZM1306]

​@TlalocTemporal I figured one motor and one idler. You just want to have adjustable pressure or spring-loaded tension on the idler. Think of the feed mechanism on a "mig" welder

[@emfournet]

I feel like a stationary one that would plug into the wall and quietly keep a randomly-rotating string in a corner of you living room like a sculpture would be really cool...

[@zechsblack5891]

One like this with the rotational axis to make the spiral he shows at the end would be neat

[@thomasbarlow4223]

Yes maybe if it was inside of like a glass soundproof box cuz this thing is definitely not cuz I don't

[@JohnDlugosz]

On a stand, yes, but with some motion like a spinning platter on another platter to make it an interesting shape.

[@oisiaa]

If you notice he never has sound of the device. I have a feeling that it's quite noisy.

[@1gorSouz4]

I think it could be great for an art installation...

[@AgentJohnSteed]

This is one of the best video's I've ever seen on the internet. I've seen many videos about wave propagation, standing waves, etc. This is such a new twist on that interaction, and the reminder that motion is relative to the context. The part where you explain that the string moving past rollers is the same as the roller moving around the sting blew my mind, and made the whole thing snap into clarity. Thanks so much for making these video's. I learn more about science every time I watch.

[@MrNicePotato]

I think you can colour a part of the string so that you can keep track of the string speed compared with the wave speed. Also, I think it would be an interesting wave equation to solve with periodic boundary conditions and setting a moving 0 displacement point where the rollers are.

[@Iceman259]

A string with a checkered pattern might be interesting for visualizing the waves’ speed relative to the string’s.

[@AtomicShrimp]

The sideways movement vs turning thing does seem quite gyroscope-y; if it was a solid ring of material that you were rotating in front of you, it would behave like the disc of a gyroscope - resisting its axis being turned, but not resisting movement along its axis. The resistance to turning is, I think, the same thing that manifests the effect of the furthest part appearing to move in unison with the nearest part - if it didn't do that, it would require turning the axis of rotation. However, I was wrong about the chain fountain thing, so... pinch of salt and all that.

[@wildcodefox7313]

Ayy didn't expect to see you here atomic

[@peacefroglorax875]

Could it be just a maximum propagation speed? Like, if he moved side to side really fast, would the end of the string thing show the same lag? Because when you rotate, the outside edge has to move really fast compared to the inside portion.

[@cleanlens]

shrimps are great

[@bubblinebee]

@@peacefroglorax875 ^ this

[@Josh729J]

thats because its self correcting like a bicycle

[@WaRe1992]

Just found your channel Steve and it is awesome. Just pure information and explanation from a kind humble guy, even shouting out other yt channels. Pleased keep up this good stuff.

[@makcatchem9614]

I have so much respect for this KZbin channel not only does he do informational informative and great content with science. But he also gives full credit where credit is due and that you don't see very much and I appreciate that in a channel

[@erbro]

Actually, I was taught that this effect and the gyroscope are the same effect, but in the other order. The gyroscope is much easier to onderstand is you first make one from a chain, connected to a hub by a number of strings, a bit like a bicycle wheel. When you try to change the direction of that while it is spinning you see where all the links are trying to go. When you make the system rigid then and integrate over the wheel, you realize that that is where the gyroscope's precession comes from.

[@cleon_teunissen]

About that idea of integrating over the circumference of the wheel, where did you learn that? The reason I'm so curious: on my own website there is an explanation of gyroscopic precession, and at the end of that explanation I corroborate the reasoning with an integration around the wheel. So I'm keen to find out whether someone else has had the same idea. Incidentally, I think the persistence of orientation of the string is not an instance of gyroscopic effect

[@erbro]

@@cleon_teunissen I was taught that at the university physics class in the 80s. If you make a ring, very narrow, and you can imagine it flexible and elastic to better understand the forces working on it, then you calculate the forces on the ring when you tilt the axis of rotation, you will see a function of the angle. In some points the ring will simply translate, but in some points you will see that the "links of the chain" have to change direction, requiring a transversal force. If you do this for all the points and integrate over the circumference of the ring you will find exactly the forces in the gyroscope.

[@matejlieskovsky9625]

Exactly! I like to explain gyroscopes by first teaching basic orbital mechanics. XD

[@cleon_teunissen]

@@matejlieskovsky9625 I disagree. For the gyroscopic precession to occur the spinning wheel must be rigid. With a flexing disk energy will dissipate. It is true that the plane of orbit of Earth satellites is subject to shift. As we know, this is put to use in the case of sun-synchronous orbit; the shift of the plane of orbit is such that it has a cycle of a year. That way the desired orientation wrt the Sun is maintained without having to expend propellant on that. If you would have a constellation of satellites, distributed roughly in the same plane, and at the same orbital altitude, then while their planes of orbit would all shift at roughly the same rate, the respective planes of orbit will not be _shared_ plane. This shows that the case of plane of orbit is not comparable to the case of gyroscopic precession of a rigid wheel.

[@matejlieskovsky9625]

@@cleon_teunissen ah, but if a satelite does an inclination change burn, then the plane of the orbit rotates around the point of the burn.

[@jamielapsley4933]

That bit at the end with your kid explaining how his new gadget works was so wholesome :') thanks for sharing your random but intriguing knowledge once again!

[@steventhehistorian]

Very cool of you to give Bruce Yeany the credit he deserves! He has inspired so many, as do you, Steve!

[@tomfeng5645]

Have you tried moving the shooter quickly towards/away from you? I was thinking that maybe *lateral* motion is fast but linear motion might be different, which might account for the rotational motion effect (a combination of the two). Additionally, does the time taken to restore the string to the standard location under rotation increase linearly with additional motion? (or alternatively, does the deflection increase linearly with rotation rate) If it's instead superlinear, that would make sense with slower restroation under forward/reverse motion.

[@tomfeng5645]

Upon further looking at this video, I also noticed an effect of the top "projected" part of the shoorter loop getting shorter under lateral motion, which may or may not be related? Also, let's compare what the actual velocity at the end of the string is under each type of motion. I count about 8 steps taken in 10 s, which is an average velocity of under 1 m/s and a peak of I presume around 2-3 m/s. Taking a 2 m estimate of the projection of the string, that means a rotation period of about 6 s (3 s if you use a shorter 1 m estimate) gives a same velocity as the peak, and about 20 s (10 s with 1 m estimate) for the average velocity. Notably at 5:25 the quarter turn takes about 3 s to readjust and about 5 s for a half turn which matches this rate.

[@tomfeng5645]

In summary I think at the moment my preferred hypothesis is that it's *not* slower to react under rotation, the rotation just has a much higher velocity towards the end of the projection than the linear motion as done in the video. To test this, we can try moving sideways at a faster rate to see if it shows the delay, or moving circularly slower to see if it removes the lag.

[@maxthexpfarmer3957]

I think the end of the loop definitely moves slower when rotating than moving laterally. I think that the gyroscope hypothesis should not he discounted so suddenly as an obvious difference between lateral and rotational motion is that rotation changes the angular momentum of the string.

[@johnquest3102]

Much more study needed, vary key parameters.

[@DennisXiloj]

Me looking at the title: oh no, mould effect 2.0?

[@TheRecycledToys]

that's why I subscribe to you ! You point out things that every day people see but don't know it.

[@dripppztv7246]

Bro I've been following him since like 50 followers, this was by far the invention I've been most excited about and now your doing a video about it, thats crazy.

[@mehrad_ai]

Loved the Doppler effects reference for explaining the wave. The beauty of it gets clear when you realise the string is in a loop and basically the handle is “approaching” and “distancing” at the same time towards and away from the wave and that’s why the wave length is different. What makes it interesting is that the amplitude also changes

[@keanamrazek3745]

I think your gyroscope analogy actually really explains it well, where there is momentum stored in the string that resists being distributed. It’s response differs because it’s a competently flexible gyroscope. I’d be interested to see what happens if you put it on a mechanism that allows it to pivot freely👀I suspect you’ll see a very similar response to a rigid gyroscope

[@marksainsbury2422]

This is just fascinating. I wondering about similarity with Orbital dynamics (gyros etc) just as you got to that section ... The interpretation of all of this in terms of waves and tension seems the best fit and it certainly got me thinking! Awesome! Thanks!

[@chillidawg4531]

your channel is pure quality steve, keep it up!

[@Justsevenwords]

Dang. I had a handheld one of these at least 15 years ago my dad found at an airport. Thing was cool

[@klaudspeed]

I really thought this was a common toy till I went through comments... I remember easily breaking the motor when the string would get knotted.

[@wymondgoolsby8070]

when I was 10 years old my mother took me to Disney land. The first day she picked one of these string rollers. I played with that thing non-stop for the entire trip. Rolling it all over walls, ceilings, anything I could find. I lost it on that trip and I haved never found a toy more simple and fascinating to play with as a child.

[@JohnDlugosz]

You "lost" it on the trip? Tell your mother to give it back and you'll only play with it at your own house.

[@MRSIvanSama]

Thank you for the ending! So satisfying!

[@catastrophe8336]

I absolutely live how you take the time to see if anyone else has done a video on a subject and even go the distance to tell us some of the differences between your videos and the others. The way you present the information is really cool makes it amazingly entertaining, have you ever thought about being a teacher?

[@pedrowaki7376]

It’s so satisfying to watch Steve getting amazed by a toy, feels like we’re never old enough to stop questioning why stuff happens. Great video!

[@better.better]

I think the second clip from the end is where you'll find your answer, because there you can see two different types of waves transitioning into each other. I think it's going to be more of the same as what you've already mentioned: the difference between one side being in tension and the other side not, vs coordinate change of the equal tension zone.

[@jonnyreverb]

You are such a gentleman. I honestly watch your videos and try to incorporate your frank/open approach into my classroom.

[@RufotrisRootedRockhound]

Fun stuff. Glad I found this channel! 🤘

[@MrLareneon]

The difference between the side-to-side steps and the turning really seems to be an agular momentum issue. Something that big moving in a circular path has a lot of angular momentum. Side to side is simply not as much momentum to overcome. Great vid!

[@Lprsti999]

Yeah, I'd be interested to see how the string reacts to faster lateral movement, like holding it out of the window of a moving car, perpendicular to travel. I'll bet that as the car's velocity approaches the angular velocity of the far end of the string when turning, you'd start seeing distortions similar to rotating the shooter. That said, I think there's also a large inertial factor to why the string responds to rotation so slowly.

[@dariusduesentrieb]

That's what I am thinking, too. Maybe this effect would already show when walking side to side a bit faster (or better running).

[@TlalocTemporal]

@@Lprsti999 -- A linearly moving reference frame and a stationary reference frame are indistinguishable. You'd want either the car's *acceleration* or the higher wind resistance, although the wind would be a different effect.

[@tmarritt]

Yup it still moves in the side to side but distance travelled at the far end is so little that its barely noticeable. Turn it in the radius of a circle and you have massive increased the difference between the distance moved and the far end and the projection point.

[@Arzack711]

Looks like I've been enchanted by Steve's big, blue, anime eyes. Mehdi's words had been deeply planted into my mind and I can't get rid of it.

[@DeclanMBrennan]

This was really cool. Thank you. I wonder if a heavy rotating belt could support a fairly light gadget on rollers at the top? Maybe you'd need two belts rotating in opposite directions to keep the gadget at the top and twisting might also be an issue.

[@NandR]

Instantly pre-ordered one. I have ideas for this already. I need a strobe light too. And some glow in the dark string would be cool.

[@samudrajs5409]

You should make another video on this topic. About the waves. Explaining wave's group velocity and phase velocity in detail. You can also include slowing down of light in this way. Waiting for that.

[@agmessier]

The string still has inertia. When you move it sideways, you're moving the whole system in translation, and it is very light so it moves quickly. When you rotate it, it has to change the angular position of the string. It has a moment of inertia, and conservation of angular momentum dictates that the whole string needs to transfer its angular momentum to you and the ground via the device you're holding. It doesn't generate much torque immediately when you twist it so it takes time for the dynamics to propagate. I know invoking conservation laws doesn't give much insight of the dynamics of the system, but it lets you understand that it has to evolve more slowly given that it's not a rigid body. Thinking 'out loud' so to speak, the impedance-matching picture isn't a bad analogy. The impedance of the system determines how quickly the wave propagates. For rotation, the wave propagation likely slows down as you go out, because while you're at the center of rotation, an angular change requires a larger displacement as it goes out. When you twist the handle, the system isn't a rigid body. It can't respond with any knowledge of the length of the string (and therefore has no knowledge of the necessary translation at the end)....it just has to propagate outward based on the local tension and velocity until the wave reaches the other end and meets its counterpart.

[@kubburdigital]

its been really interesting watching this series, you could have taken it step further and used integral calculation on the string to go deeper into why it behaves like that looking forward to seeing what you do next

[@skoodledoo]

When I first saw these, I instantly thought of you Steve :D was waiting for this video!

[@justrecentlyi5444]

I'm thinking that this analysis would benefit a lot from slow-motion footage! Also, I love the mesmerizing images from the double spinning demos.

[@toohardtowatch]

I'd like to see this operate with a section of the string dyed black, as well. It's hard to get a sense of how quickly the string is moving.

[@Vlow52]

The string shooter should be tested in a vacuum conditions to see how much of air pressure with molecules coming from the roller are affecting the path.

[@kenshiromilesvt.7037]

I doubt it would be much beacause of the small surface area, but would definitely be cause for testing!!!

[@Vlow52]

@@kenshiromilesvt.7037 open space would be perfect hah, but talking about more grounded setups, I think two long plexiglass panels could be placed in parallel, so having a small gap enough to have a space for a linear string path

[@kenshiromilesvt.7037]

@@Vlow52 that’s a great idea

[@adaetz1042]

@@Vlow52 Could be very interesting, although large flat surfaces are extremely susceptible to failing under the immense pressure gradient caused by pulling a total vacuum at sea level. That's why most vacuum chambers you'll find are circular, since the radial symmetry resists deformation. Very thick plexiglass might do it :)

[@Vlow52]

@@adaetz1042 you’re right, it got to be thick ones. Yet, another idea without vacuum chamber is to blow a white smoke near with the shooting mechanism, similar to the automotive aerodynamics test, but it may be tricky to get a stable flow. Or maybe film the sound waves using a concave mirror, like Dustin from SmarterEveryDay did with the bullet tracks :)

[@latenightcereal2390]

I love that you're talking about it as if you're personally interested, and then in the video you're completely tuned out, just looking at your phone. It's like your a hot back stage that has to shake a tree or something, and you're just sitting there shaking randomly, with no real concern or discernment

[@lasersbee]

Have never seen one of these String Shooters before. Thanks for sharing.... Now I have to get one.

[@spliter88]

As for why the string looks like it doesn't have waves when moving side to side, I think I may have an explanation: When you pluck a string on the top part the one coming to you is slowed enough that it start going away from you. However when you move side to side, the origin of that movement is at the string shooter's rollers. So that wave still exists it just goes down the string fighting against the speed (higher tension at the rollers give it the boost to not go up), meanwhile the part of the wave that goes with the string just goes around so fast you don't see it. I also think you might be wrong about the turning, it's not that you impart a wave on top and bottom at the same time, that still works just like translation. I think it is essentially the gyro effec of the string, and the reason you don't see any procession, is because you're holding onto the string shooter. I think what's happening is that you have the linear momentum of the string coming out of the shooter trying to fight the angular momentum of the entire string, and as you keep adding linear and angular momentum on one end, and rooting yourself to the world so you don't counter-spin eventually the angular/linear momentum from the string shooter wins. Still I wonder if when you turn if the string rolls along its movement axis, would make sense to me as that's yet another way of preserving the original angular momentum.

[@georgmagi4403]

Ok

[@deadfishyarou]

Yea I had the same idea, sideways movement doesnt cause a backwards wave because the boundary itself is what is acting on the string!

[@JanBartnik]

It looks like the speed/tension work as a parameter in a low pass filter. Reminds me of guitar strings... or rubber bands - if you don't put too much tension the amplitude of vibration is high and the frequency is lower. I also think that the velocity makes that string "tenser" in one axis.

[@toshley6192]

When you pivot around the handle, the far end of the string has to travel along a much longer arc than the handle does. The string itself isnt rigid so the small force you apply to move the handle a few inches can only move the far end of the string an equal distance in the same amount of time, it takes more time for the far end of the string to complete its arc ater you stop rotating by reacting against your now stationary hand. When you move in a straight line from left to right the near and far ends of the string are travelling the same distance. Not sure if thats actually the reason, but it makes sense intuitively. You can also consider how a slack line would behave if you held it in your hand and rotated. The far end of the line would only be moved by an amount equal to the distance your hand travelled. The more i think about this the more complex it gets. The string is experiencing a centrifugul force thats perpindicular to the rotational force you apply when you rotate the handle, theres gyroscopic procession involved, possibly some sort of mechanical advantage, the role that the speed of the string has on the propogation of waves...

[@pligon09]

This is what I love about the KZbin science community; the rivalries are entirely friendly in the spirit of discovery, everyone supports each other and promotes great content and genuinely wants every other content creator to succeed and build off of each other, causing all of us to go down this rabbit hole of real science from what started as essentially a school demonstration. Bravo everyone involved

[@ericgoldman7533]

It seems to me that we've forgotten to account for the difference between linear displacement and angular displacement when trying to explain the behavior. When you move or rotate the device, you impart a discrete change in velocity to each discrete part of the loop. To simplify things, we will make a few assertions- 1. Our side-to-side movement is at a constant velocity, and our rotation is at a constant rate. 2. Our acceleration is applied in a single discrete unit of time. In other words, the velocity instantly changes from 0 to the final value. 2. The displacement is propagated to all points in the loop quick enough that we will consider it instantaneous. In the case of linear displacement, the same velocity (in both magnitude and direction) is applied along all parts of the loop. As a result the entire loop moves together with the source (i.e. the device). In the case of angular displacement, all points along the loop move through arcs of equal length (since we are still applying the same change in linear speed to each point), but arcs farther away from the source radially will sweep through smaller angles, thus causing the loop to appear to curve. It is also worth noting that there is probably some interesting relationship between the forces that cause the loop the hold its shape, and the torque applied to rotate it about the device. I suspect we could see some interesting phenomenon by tweaking both the rate at which the device "generates" the loop, and the rate at which we rotate it about the device.

[@SpectrumDIY]

Lol, "and here we have a wild mould in his natural habitat, playing with his effects"

[@The_RC_Guru]

I’m glad you decided to stay on here and making videos.

[@kpatriots8]

Something about him lying on the ground and watching the wave spin makes me so happy about the love he has for the beauty of the laws of physics.

[@Paul-sj5db]

My first reaction when I saw this was "oh no, it's another Mould effect".

[@byronwatkins2565]

Wave speed on a string is sqrt(T/mu) and the chain's tension varies with height; so exactly what point in the chain is the chain speed equal to the wave speed? In fact, the tension in a vertically dropped chain (suspended from one end and dropped) is zero if you neglect earth's tidal force. Immediately after the rollers the tension approaches zero -- possibly is negative for some circumstances -- in which case wave speed is zero (or possibly imaginary and dissipative); thus no wave propagates. Applying friction to the top of the loop increases tension after the touch and greatly increases wave speed... the wave is then reflected by the rollers and the reflection is inverted. The string motion is the sum of these two waves.

[@barefootalien]

Yus! Glad for the shoutout to Bruce!

[@dim1723]

Great video I think I will wait to order one. I wanted to show it off at work to the kids as a fun physics example and toy. Honestly I thought they would be easier to find.

[@theSwoderman]

I love the faces Steve makes when he's testing stuff like "wtf is going on here"

[@patman8137]

I have questions. Have you tried to rotate the strinthing, so that up goes down ? Could you manage to build this into a device, with a very, very long string? What would happen to the wave?

[@UnwrittenSpade]

I had one in the early 2000s from Spencer’s that had rainbow string and was handheld. It made awesome colors when they blended

[@vickirick4219]

the doppler effect explication was really helpful

[@scottmarshall1414]

Some of this would be easier to communicate if, instead of saying the top and bottom string, you called them the departing and returning parts of the string. A dark mark on the string would also make the movement of the string more clear

[@patrickruelas5629]

Agreed, as well as letting us know from the start which direction the the string is spinning.

[@RadicalPi32]

I'm still confused as to which was departing. The top?

[@scottmarshall1414]

@@RadicalPi32 yea, the "upper string" is being ejected from the device, but that's impossible to tell from this video until you notice Steve is firing it like a pistol and the "bottom string" is passively returning

[@scottmarshall1414]

@King Pistachion Not a hater. When you tell the truth, people sometimes get hurt

[@davidonfim2381]

I think it would be incredibly useful to dye a bit of the string so that we could easily see the direction that the string is moving. It's not easy to tell, and I keep getting confused about what direction it's spinning.

[@fweaks]

I feel like it's moving waay too fast to see such a mark.

[@elfarcherdv]

When hovering the thumbnail I thought that was CGI or effects or something. But wow that makes sense and looks so unreal. Coolest thing I've seen in a good while

[@MrRudyart]

Amazing! Preordered 2 of them 😇

[@stephenbarnard2856]

When you attached it to thd drill, the helix shape was pretty interesting. The frequency in the z direction of the outside string is far less than the frequency of the inner string.

[@sebbes333]

8:10 And "they" said: *"yOu cAn'T pUsH a StRiNg!"* and here is proof of how wrong they were! :D

[@ZataMachi]

NO WAY! I saw the original video in a random compilation video months ago and the video disappeared on me, and I've been trying to google it since! I immediately wanted to buy it off the creator as well. I'm super happy to hear that he is going to produce them! :D

[@kindbud]

I had a few of these as a kid, we modified 2 of them to combine em and spin a double size string and also play with it as a jump rope

[@joewwilliams]

Just gonna keep milkin that chain fountain, eh Mr. Mould Effect?

[@FaultyMuse]

I think we actually *do* see the wave propagating from the top of the string when you move the shooter laterally. The problem is that the wave originates from the shooter itself so unlike when you pluck the top part of the string, the wave is only propagating AWAY from the shooter and moves far too fast to see. In fact, I think what you're interpreting as the string following the shooter when moved laterally, is actually just the propagation of the wave away from the shooter till it hits the vertical "boundary region". Would be interesting to see slow-mo of the shooter being moved laterally to see if we can verify/disprove this hypothesis.

[@brendanmcculloch2406]

Exactly my thoughts

[@suchgaming7614]

yessss the day I've been wanting for is for you to react on this

[@nokichou8059]

When you slightly push the string, it gets tight and becomes more like a solid rod; when you slightly pull the string, it stretches and becomes more like a chain. That's why the upper part behaves more rigid and the lower part behaves more relaxed. When you move sideways, the upper part is still pushed tight so still acts like a rod; when you rotate, the upper part loosens and stretches a bit due to the centrifugal effect and acts more identical to the lower part which is always loose.

[@korishan]

You already have a Mould Effect named after you. Once you figure this one out, you can't have another Mould Effect. Unless, this is an extension of the same physics, which would be interesting.

[@outside8312]

I had one of those toys as a kid. It had flashing lights and played music too! I loved it until my friend "borrowed" it and I never saw it again sadge 😔

[@OneOfDisease]

I would be interested in seeing a scaled up version that can shoot ball chain to see if there is any differences with the extra mass and the more rigid structure.

[@1gorSouz4]

Man, that is simple but the visual effect is so cool. I can see something similar being used in art installations...

[@BooBaddyBig]

I think you made an incorrect assumption that the tension in the top of the string is lower. The device is NOT the only source of tension here! The tension along the length of the string travels at high speed (maybe a hundred miles an hour or something), the weight (and momentum) of the string itself creates tension. The bottom is actually at LOWER tension. And that's why you can see the waves. The waves at the top go too FAST, and are likely being damped out by the air and the string itself, as well as being carried along with the motion, at the bottom they are somewhat under-damped, and move much more slowly. The rotation effect is basically gyroscopic-but there's no strong bearing. If you look at the string entering the device, it lags, and it leaves leading. That's the device creating the precession. Note that the loop is angled to the vertical, that's the wobbly string version of precession.

[@pianosidechat]

the part of the loop being pulled into the rollers definitely has higher tension

[@BooBaddyBig]

@@pianosidechat Not necessarily. It depends on the air drag, the g-force, the weight of the string etc.

[@pianosidechat]

@@BooBaddyBig those forces would be negligible. The weight of the string is equal on all parts of the string. The centrifugal force clearly is much greater than gravity. The loop would perform similarly in 0G and in a vacuum.

[@BooBaddyBig]

@@pianosidechat Potential energy is a whole thing. It's obviously not insignificant relative to the centrifugal potential otherwise the string trajectory would be essentially circular.

[@GodsCourier]

I've never seen a youtube video say uploaded 20 seconds ago, cool

[@ValpoPhysics]

Brilliant job with the drill. A marvelous new observation. To see the wave propagating around the loop, you need to change the string speed. I'll make a video for you.

[@ValpoPhysics]

You missed something. kzbin.info/www/bejne/pJiZqn2PYtiHkJI

[@hart-of-gold]

2:43 You can see the wave in the top string, because of the angle of the spring to the camera compressing the appearent wavelength, it stands out.

[@y.kennard3381]

I saw this item on a french channel. The man spoke about chain fountain as well. But he didn't mention the "Steve Mould effect". Which was disappointing.

[@laurensschroder5560]

Jes🙌, I've massaged you on Instagram about this and i already know it's gonna be such a cool video

[@Clarionut]

Fascinating! The trajectory of the rotating string shooter looks similar to that of some strange attractors - particularly the Sprott attractor which has a central rather tight spiral and returns via wider loops around the outside. Coincidence???

[@judeevans8303]

I'll be honest, your videos are a treasure and delightful to watch.

[@Alan_Hans__]

Watching that video was so cool. Not only is the string shooter cool but every one of the channels mentioned by Steve are ones that I'm subscribed to and watch. The world would be a much better place if all teachers were as good and as engaging as Bruce Yeaney.

[@sapandream]

So much integrity and honesty 👍🤩😍❤️❤️

[@michaelallen8374]

Steve, interesting video as always, thanks! Re the wave not propagating along the top half when moving from side to side, I think you already explained it. When you demonstrated plucking the top half of the string (7:36) the wave seemed to move away from the handle which as you explain is actually the wave which is moving towards the handle only the string is moving faster than the wave so it appears to travel slowly ( the wrong way ) along the string away from the handle. Hopefully that is correct. When moving from side to side the wave which is moving away is whisked away very quickly by the string making it invisible due to its speed, the wave which is moving the other way should emerge upstream of the rollers only again it is not moving fast enough so it travels downstream as before, but immediately meets the rollers all the time so any vibration in the upstream direction is immediately dampened to zero by the rollers themselves. maybe....

[@PentodeSensations]

This reminds me of electricity, quiescent draw, instrument amplification, and signal-driven changes in impedance against a coil. The speed of the string is a "voltage", the energy of the moving mass is kind of like a big battery/capacitor/filtering network, and there's a "quiescent draw" against that constant charging of the system like a bias against a tube passing current, which I think is a result of exterior forces imposed onto the system (friction and gravity). Your impressions onto the string and the movements/axis accelerations of the shooter/spinner would be changes in the control grid voltage of either a triode or pentode, and the behaviour of the string demonstrates changes in impedance. The simpler demonstration is in just touching the top or bottom of the string as it moves along. This is most like a triode, in my opinion. I like to see this like resolving the signal path and draw characteristics on a circuit. When tapping from the edge of spinner's top, you can see the effect/signal amplify at the "peak impedance point" for a moment. If you keep your finger in place, you've create a new bias/impedance point; and if you waggle it, we can see an amplified waveform. Plus, we can see the draw can be seen/felt at the returning edge at the bottom of the spinner. When tapping it from the bottom, I think this is what might me a "cathode follower" in tube circuits. I think the bottom taps and friction slows the string down, and drags the whole system down (increasing the system's impedance), like adding a resistor to restrict cathode flow, affecting the global bias point. Not to get super nerdy about it, but this "cathode follower" design is a common low-impedance drive circuit in tube amps, and is known for smoother overdrive characteristics. Tapping from the top is maybe like a later Fender design (AA864 circuits) which sound a little harsher and blockier, exaggerated even when overdriven. When you tap the outside edge (where impedance is greatest), it's more like a microphone, or, your finger effectively turns into a resistor/capacitor, eating some voltage/speed, feeling current/heat on your finger, and ability to sense other waves travelling through the system in the form of reductions and increases in voltage/speed and friction/current/heat. The less obvious/probably incorrect effect I'm seeing here is in the side-to-side motion. I feel this looks like pentode behaviour, where the voltage is held more constant (we're not messing with the spinner's Y-axis), and we're applying a considerable X-axis. Watching it be resolved, I want to say there's a smaller drop in speed/voltage/Y-axis energy for a considerably larger distance travelled across the X-axis, and the system resolves the energy on the X-axis as if it were "capacitively" more efficient as a result of your arm become a part of the impedance network. Which is a mixed blessing. Smaller forces might not require any extra input from your arm to control the system gently. Just as well, too strong a swing would overwhelm beyond reasonable correction, and your string turns into a whip (this is when vacuum tubes arc). Also, when you're rotating the string-spitter with a drill on your back, I think this is maybe a "visual" of a parasitic oscillation. With guitar amplifiers especially, it's sometimes possible to produce a high-pitch parasitic ring with too much high frequency bypass. It's also possible to produce oscillating hums with over-filtered or poorly arranged power filtering schemes (usually an inaudible low 4-Hz up and down drift that shows up on the speaker output).

[@krimboslice7998]

my uncle had a string thing growing up and he had another one that seemed off brand that had led lights that lit up the string colors it was awesome

[@amontaval]

I ordered a Zipstring in the US on November 21, 2021 and it FINALLY arrived today! It is lots of fun.

[@jaredf6205]

I ordered one yesterday and it shipped today lol.

[@schwuzi]

Same here ordered Nov.21, arrived yesterday

[@AaronAlso]

I NEED ONE!!!! I have a transcendental experience planned and this thing is an essential piece of entertainment.

[@PhillipH-san]

Yup, definitely preordering this.