The Band Should Slip Off But It Does The Opposite!
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- เผยแพร่เมื่อ 26 ก.ย. 2024
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Crowned Pulleys do this bizarre counterintuitive thing. Instead of slipping off the curved surface, the band actually moves to the middle and stays there.
Not to be confused with snatch block type pulleys! Destin's video here:
• Why Snatch Blocks are ...
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SNATCH BLOCK!.... er... uh, I mean. . NOT A SNATCH BLOCK
Still one of my favorite moments 😂
Ayyyy!!!!! 🤣🤣🤣
HAHA i was totally hoping to see this comment
@@canofpulp screw you. Dont hate on him
@@cbrooksusmc he's not
That explains it..
It don't remember what for, but a few years ago, I designed the concave thingy for a homemade belt system, and I couldn't understand why the belt was, always flying off.
I had to put on guards to prevent it... It was a mess.
Now I know. Thanks! :)
Would have been fun to watch that frustration
reminds me of 45 years ago when i tried to square up a radial saw table with a square that wasn't square, drove me nuts.
That concave pulley clip really answered all lingering questions in one shot for me! Great work as always Steve!
Yes... I've done that wrong many times over the years, and now know why.
He really covered all the bases.
This example is gold
2:12
"Our intuition is wrong."
Learning physics summed up in one sentence.
You've just turned everything around that i knew about conveyors. I work in the metal recycling industry and usually we have to track conveyors to keep them in line. Usually we tighten the side to make the conveyor move opposite of the side we tighten. Then we'd get some conveyors that just didn't seem to wanna do that. They'd move opposite the way they should and everyone was always confused about it and just chocked it up to basically being a odd quirky attribute of that particular conveyor.
That’s awesome! It’s so fun to learn something that explains something you encountered in the past. Love that feeling. Like answering a question you’d forgotten you ever asked.
I'm wondering if the difference was how tight the particular conveyor was relative to the others. I'd guess a looser one would have the intuitive effect and a tighter one would have the effect described in this video. My thought is that looser would mean less grip and the belt would slide away from the crown while a tighter one would work its way up to the crown
Guessing, may be related to the great width of the belt. If there is bias in any of the belt physical properties, it may throw its behavior out the window. For example if the thickness varied linearly slightly across the width in which case the belt would now be a cone. (and of course just saying this out loud doesn't sound plausible LOL!)
Wait is it chalked up or chocked up?
Sometimes belt arent properly cut and even with a crown pulley you wont be able to fix the drift.
The instant a video starts talking about pulleys I'm already waiting for "SNATCH BLOCK"
SNATCH BLOCK!
No exceptions
S N A T C H B L O C K !!!
Exactly where my mind went as well!
I laughed when it cut to _SNATCHBLOCK!_
Laminar flow!!!
I love how all the science communicators on youtube reference each other in their videos
It's true. All my favorite channels are connected somehow, even ones I wouldn't think would be like Corridor (thru Tom Scott).
Gotta say, though.. Destin is responsible for a lot of those connections.
Just the best ones 😉
6 degrees of Kevin Bacon 🥓
They know what the people want.
@@adamplace1414 Yeah, I got introduced to coridoor through the slo mo guys, who in turn I was introduced to ny Destin. His channel also introduced me to stuff made here. It's just amazing the community built around this people. I would like to add that PBS eons is another amazing channel, I don't exactly remember, but I think I got into it because I am an old vlogbrothers subscriber.
You can never miss "Destin", when you say snatch block
LAMINAR FLOW!!!!!
Yess
Destin will forever be the Snatch Block and Laminar Flow guy in the Science/Engineering community. It’s, of course, all in good faith though.
String trimmer fight announcer voice was the best.
@@350speedfreak Destin could do voice work.
I've worked in manufacturing for years and have observed this effect on lots of conveyors, belt drives, belt sanders, etc. And this is the first real explanation I've heard. Thanks for clearing up something I've been mystified about!
The belts on such things as thrashing machines and circular saws, driven from the pulley wheel on a tractor, are often slack when running and are not elastic so this explanation doesn't fit.
@@Hanoverauto I'd love to hear your alternative explanation.
@@Hanoverauto Flat Pulleys on tractor takeoff
that’s exactly what im trying to sort out. no belt sander has a stretchy belt, so why are they crowned? maybe there’s some tiny amount of stretch that seems imperceivable but idk about that, im still skeptical
@@Hanoverauto There is no such thing, as "absolutely slack", they all do stretch a little. Because they are more rigid, than a rubber band, the same force causes them to stretch by a little amount (in length) but the effect is the same
Hey Steve! I've followed you for years, so it was super exciting to see our belt grinder in the video Tom sent you. I definitely didn't expect that when I started watching. Obviously, belt tracking is a phenomenon we spend a lot of time thinking about in belt sander design, so it was nice seeing someone explain the crowning effect scientifically. Home builders often run into problems when they add a tracking adjustment because the interaction with the crown isn't necessarily intuitive. The belt seems to ride to the high point of a crown, but it also looks like it rides down the slope when you tilt a wheel to adjust the tracking (as it does in the video Tom sent you). We have our own working theories on how crowning interacts with adjustable belt tracking, but I'm sure I would learn something and see it in a new light if you ever looked into it.
Eric
This Channel here reminds me of Hbomberguy;
my Favorite Place to learn.
Well, that and Veritsaium.
That ruzzian flag on your avatar though. :D
4:45 Still don't understand why it would bow upwards. I don't see anything pushing "up" just material stretching along the line. He did a terrible job at explaining. Why would those for springs be pushed up? I don't see any deformation that would push them in that direction?
Anthropomorphising a rubber band is streching it a bit! ;)
🏆🤦♀️🏆
Stop stop stop stop
@@ViratKohli-jj3wj LOL!
That sounds like a line straight from a Terry Pratchett book..
Anthropomorphizing a rubber band is tight.
There is a pulley on my car that always bothered me that it's crowned, always felt like it was gonna be a problem one day. Guess I was wrong lol
The idler pulley!
Well, it won't be a problem until your belt starts becoming brittle. I'd assume that when it loses elasticity that this crowning effect won't be as strong.
@@alexanderunguez9633 nope, as long as there's even a very small amount of stretch and elasticity the belt will re-center. this works even on high strength fiber belts, such as aramid cloth, or even steel bands. there isn't a need for the belt to be highly elastic.
@@wyattroncin941 That's neat!
I used to own a Chevy Blazer and the belt would constantly fall off, From what I've seen in this I should have put some crowned pulleys on it lol
"Heat is just molecular jiggle"
It's kind of unsettling how simple and accurate this is.
Wow,
Still NOT linear.....
Yep, and when you measure the temperature of something, you're actually measuring the kinetic energy of the atoms.
Sound is just wiggly air.
My body does a lot of molecular jiggling but no one seems to think it's hot.
@@jamirovega1332
That's because to make it hot, you have to get your molecular jiggle in resonance with your macro wiggle. 🤓
Amazing!!! I have been working on a homemade conveyor and tracking was proving a problem. Based off this video, I wrapped layers of tape around one of the pullies (to make it convex) and it immediately started tracking perfectly! (And when I manually disrupt it, it returns to center.) Thank you!
That was strange for me. When I first saw it, my intuition told me the band should ride up on the pulley, but at the same time that _felt_ unintuitive. Excellent explanation.
Also worth noting: Take two tires and connect them with an axle, but leave them free spinning. Now, accelerate the system. Next, slow down one tire but not the other. The system will turn in the direction of the breaking tire, because there is more friction on that side.
Now, you have a band across a curved pulley. When you stretch the band, the side that is further from the opposite end is pulled tighter and thus has more friction. This will turn the band in the direction of the tighter side.
In short, there are probably two effects causing this behavior. The stretch widening the band on one side is one effect, but the asymmetrical friction is probably also causing the band to turn toward the higher portion of the pulley as well.
I was thinking of just this effect before I heard his explanation!
The “turning in the direction of higher friction side” feels like a better explanation than the one in the video. The one in the video only explains why the band’s width contracts.
1:37 I was about to make a cheeky comment like, "What if we won't permit you?" I felt clever until you showed you're more clever...
… but then you'd made THIS comment! So, win-win?
@@SreenikethanI Nope.
@@SreenikethanI That feels very gracious of you XD I just won't underestimate Steve's sense of humor ever again.
I explore ghost towns and mining camps, and have seen a lot of old mines and mills which used belt-driven machinery. I have often wondered why the pulleys were slightly crowned. Now I finally know! Thanks!
I do a lot of the drives for conveyors most of them are always crowned because of the belt wandering if it’s a long conveyor with a belt it’s likely to try and wander but with a crowned and lagged pulley it does pull it back to normality :)
This was the most positive reply ive ever seen
The belt goes the direction it leaves the surface until balance or failure. Susually.
I'm trying to make a middle school lesson plan about this. Would you happen to have a photo of one of the antique crown pulleys you'd be willing to let me use?
@@grahampcharles I don't know if I have a suitable shot of a crowned pulley, but I'll go through some of my photos and see what I can find.
I was expecting Destin to jump and say "snatchblock" and he is there...less than a minute into the video...
SNATCHBLOCK!
It's not a snatch block. Alright?😎
@@TheAeonflux74 SNATCHBLOCK!!!
He didn't just say it, he's shouting.
Something else interesting (and entropy related) is when you stretch an elastic band, it gets hot. If you let it cool down and then retract it, the same area (middle mostly) that heated up will actually turn cool. Yes, it works like a refrigerant.
Didn't someone actually make a "refrigerator" using elastic bands stretching and contracting to illustrate that?
@@robertellis6853 at least JoergSprave did an experiment where he cooled a can of beer 2 degrees Celsius by using a rubber band
"Just for completeness" is so satisfying. Thank you
Hey now, this type of pulley system looks familiar ; P It's exactly what stabilizes the band on a Van De Graaff Generator.
Its you!
I was thinking the same thing Jay! Nvce to see ya! Tell me what you think of my high voltage stuff. I got vids on my channel.
Hi man!
yes?
Edit: why did i edit
I found the exact comment I was going to say. I'm glad it came from the plasma channel tho.
Hey thanks for this! I work on a plant where we have long conveyor belts. We crown the centre of our head pullies to help centre the belts and prevent them from running skew. Been using this method for years but now i understand why it works!!💪
I saw the title and the thumbnail and was like: "Duh! That's how Bandsaw blades are kept in place" (learned that from Matthias Wandel) Woodworkers ASSEMBLE! :D
Same here!
Exactly what I was also thinking about: my band saw. But never thought about it before in this way....
Yes, Matthias is a wonderful physics teacher!
@@earthbjornnahkaimurrao9542 Indeed.
You mean, "hopefully" kept in place :P
Its a physical visible description of the bernouli principal (in reverse) the slower part of the elastic wants to move faster, while the faster part wants to be the same speed as the slower, so it all pushes towards the slowest lowest energy part.
It was so polite of you to allow me to reject your anthropomorphism of the rubber band! Much appreciation!
I really like that every time you anthropomorfize anything ( a virus, an electron...) you say it at loud :)
Just a recommendation, in the discretization you should use triangles instead of squares. This avoids the rotation of the individual elements at the nodes and produces a more accurate deformation of the whole system
B E S T A G O N
3TRI vs 4QUAD, reminds you of FEM
FEM gang
I suspect the spring demo would work better with a triangular lattice ... because hexagons are bestagons.
Fuck it seems like we do all get suggested the same videos 🤣
I fix old audio equipment as a hobby. Old cassette decks, turntables, open reel tape decks, etc. Crowned pulleys are common, and I’ve always known THAT they work, but now I understand why. Thank you!
Simple yet very effective principle. I first experienced this when I made my own lathe. I needed a set of transmission pulleys and I decided to make them myself. I first tried flat ones. After few trials, I realized the belt climbs(!) the pulley and thus convex-shaped ones self-align the belt. Without any flange, it was very easy to turn with my lathe in a short time with minimal material loss. Still it worked really good. The belt slipped off only when the chuck stall accidentally with too much cutting force.
“Snatch Block!!!”
Steve Mould: "Heat is just molecular jiggle." 2021
Definitely gonna remember that one😁
Heat is just a particles movement speed. Its means, if u want reach 0K (absolute zero) u need stop all particles.
Search "Richard Feynman rubber bands" and you'll actually find a hilarious old video of the brilliant physicist explaining the rubber band phenomenon as jiggling strings. This video was clearly heavily inspired by that original. When Feynman wasn't inventing new physics, he was a huge fan of using accessible language and imagery to explain complex physics, including frequent references to jiggling atoms.
@@TeslaElonSpaceXFan "Are you 0K?" "Yeah, I'm cool."
@@Just_A_Dude Nah, thats CoLD!
My fingers have touched molecular jiggling food...and I didn't enjoy it.
5:14 are those the same metal beads you were using when you discovered the groundbreaking mould effect?! The greatest effect known to science.
They are
@@SteveMould Was this video just an excuse to play with them again?
@@SteveMould you need to put those behind glass. such a historic artifact should be protected!
@@judgeomega You would not have been able to experience their "molecular jiggle", were he to have done that
@@SteveMould Hey you never responded to my comment on your other video. Hope you can respond when you can. Thanks.
0:12: No, when I think of a pulley, I think of any kind of wheel that redirects the force that is applied to a string. This apparatus has four pulleys, two fixed and two loose, and it is called a tackle, which in this case reduces the necessary force to 1/4 of the weight of the load.
Good for you?
The jiggling chains was such an intuitive visual model, amazing video yet again
Always get a good laugh out of Destin's snatch block clip
SNATCH BLOCK!
I found it annoying by the end of the video 🙈
SNATCH BLOCK!
snatch block
SNATCH BLOCK
*SNATCH BLOCK*
He's not funny, he's annoying. I couldn't finish watching Destin's video about that. He's too shouty and overly dramatic.
With your explanation of rubber bands + the video of Richard Feynman explaining them, i think i finally get it
Didn't expect to see you here...
doesn't expect you was here!
He is my favorite rubber band refrigerator designer. Feynman forever🌸
Oh so the scammer is trying to learn some science now
Didn't expect to see you here... (3)
Steve, you are by far one of the best educators on youtube. I love a lot of the popular ones, Tom Scott, Kyle Hill, Destin and Derek Muller, etc. But every video you make I find myself going "Ohhh! Of course!" at some point in time. And your curiosity and passion for things that we otherwise just kinda take for granted is infectious. Thanks for what you do.
Thank you!
Mathias is nuts! I once saw he building a tool that was precise in the nanometers. You'll never need to be more precise than a milimeter in woodworking. He is just that perfectionist
“never” - that word you are using: I don’t think it means what you think it means!
…and you may not be a woodworker.
Sub-millimetre precision in woodworking is very much a thing. Also a tool that's precise in the nanometres seems like hyperbole, given that at the time of writing ASML is basically the only manufacturer who makes nanometre precise tooling of any kind.
Micrometres, yes, I can very much see Mattias tweak and fidget until he gets to that point. Personally in all my years of being a fine furniture maker, I have never bothered with a scale smaller than a tenth of a millimetre. For surfaces that are touched, or that are in direct sight, like say an inlay, sub-mm accuracy and precision are most definitely a thing.
Funny, I've thought about this before in the context of the leather belts that were used up until the early 20th century in industrial or farm machinery, and never created a satisfying answer for myself. Until I looked at the thumbnail for this video and saw that the belt was a rubber band. I just never thought of the leather belt as being elastic. If you think about the friction increasing as the band moves toward the center it makes perfect sense.
"And just for completion..." Oooh yeah. I like the way you try not to leave loose ends. Your videos are well-packaged.
This entire channel is basically the "why" game kids play, I love it
"why" should always be encouraged
@@WolfgangDoW seriously, literally all decisions should have a "why" behind them. It's my favorite thing to ask when someone gets mad at me xd
This seems entirely intuitive to me because I worked with belts and pulleys on newspaper presses and delivery systems for a long time. It was a common practice to move the belt position a bit by adding a small piece of tape to one side of the pulley. Or shift the the entire web of paper passing between press units by putting a small piece of tape on a roller that is acting as a pulley guiding the web. I always imagined it had to do with changing the diameter of the pulley on one side, making the belt 'climb' to the high side but I never thought a lot about exactly why it did this. I imagined it pulling harder on one side of the belt. It sounds like I was making it into a sort of crowned pulley, or altering the crown of a that type of pulley.
Interesting!
I don't know if my explanation is correct but I think the reason the band doesn't fall of is the following: the part of the rubber-band that is closer to the middle is stretched more, therefore it has to cover more distance compared to the part of the band further away from the middle. This creates and internal stress in the band that pulls it towards the middle.
I LOVE LOVE LOVE when you guys feature each other's work.
I hear that Continuum of Springiness are releasing a new album this year.
Maybe they can get Molecular Jiggle to open for them.
Are they heavy metal?
Yes. Pent Up Energy is the follow up to their debut album Spring Sprang Sprung.
Are boing boing and twang some of the tracks.
Rubber band chain analogy is the best part of this video. 5:35 pretty much explains everything!
I used to tell my students that you can actually feel the entropy change in a stretched rubber band as a temperature change, by using your lip as a thermometer as that part of your body is much more sensitive to changes in temperature. So fun to see a room of students stretching and relaxing rubber bands and claiming "I can feel it warmer/cooler!!"
Someone tried to make an elastic band refrigerator. Didn't work out too well as I recall but interesting nonetheless.
@@chaos.corner Not sure if they were the only ones who did it, but the Myth busters did that. I remember the whole whacky contraption with tons of rubber bands designed to stretch outside the "refrigerator" and contract inside.
I too remember it not working particularly well, but it did create a (neglible) temperature difference.
@@kevinthealienfpv I looked it up. It was on the TH-cam channel "applied science".
@@chaos.corner i watched a video about that a long long time ago lol
Yup - always travels the the highest point... I learnt about this working for my Father - he engineered many large industrial band saw machines for the Aluminum industry where the blade was riding a crowned wheel (with no lip to hold the blade on). It reduces the overall stress on the blade = more cuts per blade / better productivity etc.....
This video helped me. The blade on my cheap, poorly made bandsaw kept slipping off due to some combination of misalignments that I couldn't quite sort out. I noticed the wheel holding the blade was flat and I remembered this video and so I used a knife and some sandpaper to reshape it to a crowned profile shape and voilà it fixed the issue!
SNATCH BLOCK! Also, Bandsaws use crowned pulleys on the wheels.
Does this really work with a bandsaw? As the video demonstrates, the self-centering property seems to be caused by elasticity, and bandsaws have very little of that.
Wheels?
@@ps.2 They may be there for different reasons, but bandsaw wheels are definitely crowned.
@@ps.2 The bands of a bandsaw are very elastic, you're just not strong enough to notice :)
@@ps.2 Everything is elastic if you try hard enough ;)
"When you extend it, it wants to be short again."
"You are anthropomorphizing an inanimate object."
"Ok, I'll put it in terms you'll understand: A shorter rubber band is energetically favorable."
I think I'm a reincarnated rubber band Lol! Short....
"Heat is just molecular jiggle"
These are often used in vacuums on the brush and are a great example!
The differential tension is not the reason the belt climbs. The belt in contact with the faster-moving surface is pulled forward faster (& the other side is pulled slower). This causes the belt to angle itself on the crowned pulley. You can demonstrate this by wrapping a paper strip around a cone, initially starting with it perpendicular to the axis. The strip will spiral toward the fatter part.
Key to the centering is the friction between the belt & the pulley. This is put to use as a safety mechanism (especially in the old factories with central engine driving overhead shafts, belted to the individual machines). If the driven torque gets too high, the belt will slip, and the centering function lost. The energy of tension will drive the belt off the pulley, disengaging the load (such as when a lathe tool digs into the work). The belts act like individual "circuit breakers" for the machines.
Matthias Wandel's video is so old it's Mouldy now! :D
But I do remember his explanation back then and it was fantastic! He basically tele-fixed my bandsaw! He is the most underrated youtuber that has ever existed, more people should be aware of his works
As a woodworker, I learned about this when I bought my first bandsaw. The wheels are "crowned" and we adjust the angle of one of the wheels to center the part of the blade we want to ride on the crown.
It's interesting to me that this works even though the bandsaw blade is a fairly rigid structure.
@@DanHoke most 2x72 belts are also pretty stiff.
Horizontal band saws are just like vertical saws, but with a twist
5:18 This entropy has a name, it is called "mixing entropy". When you stretch the rubber, it unmixes (due to becoming ordered in the direction of stretching) and the heat will then remix it back.
Isn't entropy always connected to some kind of mixing / dispersion?
It is amazing. I wish I had had YT when I was young, as it seems I am understanding more by the way these show n tell ways so not so bright people like me can understand better. Thank you for taking the time to teach.
3:12 _"When you turn the pulley, it contacts a piece of band that is higher than the band already on the pulley."_
Yeah, I don't get it.
That describes the obvious part, the "what is happening", but not the "why".
(Also, what does "higher" even mean in this context?)
If I say "when you turn on the switch, the lamp emits light", have I explained electricity?
No, I have explained only what a switch & a lamp do, but not why they do it.
When an elastic is stretched it wants to go back to it's "unstretched" position. Well, the "most stretched" part of the elastic in this case (the upper part) wants to go back more than the least stretched part of the elastic (bottom), and to do that it needs to go up the curve, to equalize the difference in "stretchiness" between to and bottom (well, the whole elastic really). It wants equal tension throughout the elastic. Sorry, I'm terrible at trying to explain in words.
@@ThanksForAllMyToes
That's the thing, if it wants to unstretch, shouldn't it move to a position that it's less stretched?
Why would it move to a position that *more* of the band becomes stretched?
Anyway, thanks for taking the time to try explaining! 🙂
"Heat is just atomic jiggle."
I dunno if you do t-shirts, my guy, but that should be on one.
"Atomic Jiggle" is my new favourite word for thermal energy
What you probably mean by heat is called thermal energy in physics. Thermal energy is what is already there in contrast to heat which is the energy that is transferred.
But the latter would also make sense for atomic jiggle / jiggling. So maybe this what you meant all along.
Atomic Jiggle sounds like a physicist's dance move
New bumper sticker for menopausal women Lol! "Going through an increased Atomic Jiggle. Beware."
@@theincapable thanks, been a "hot" minute since my last physics lesson
I was always wondering, when I saw old pictures about machines with transmission belts, why they wouldn't slip off easily. Because I couldn't see a rim on the wheels.
4:57 That explanation kinda of fits most of what happens in our universe, if you think about it.
Nice explanation of the curve of the belt, it's very similar to slip angles for tires in car steering.
Another application are in long continuous metal coiling lines uses crowned rolls and additionally rolls that change angle to induce the "up hill" climb for steering.
I've seen this type of rubber belt/crowned wheel arrangements on cylinder and platten presses and never thought about how that works. I saw the thumbnail of this video and immediately realized that the belt finds the high spot on the wheel because there is more tension on the belt the higher the diameter, giving the belt more traction and tension to go in that direction.
I hate when reviewers, science channels, etc say they avoid covering stuff other people have already covered.
I watch that channel because I like the way they explain things or their presentation style or because I wouldn’t think to learn about that topic otherwise, etc. like I never would have thought to look up an 11 year old video about crowned pulleys but it’s an interesting thing.
I wish youtubers would just talk about stuff they find interesting rather than worrying so much about what other youtubers are doing.
Interesting perspective, thank you. I'm going to take that on board.
We have been crowning wheels for bandsaw blades for years, amazing how engineering works
Steve: Snatchblock
My brain:SNATCHBLOCK!!
A few Milliseconds later...
Dustin: SNATCHBLOCK!!
I volunteer at a Koreshan State park in Estero Florida in the winters.
We work on and demonstrate antique machines that use pulleys that use this technique.
They still work!
Joerg Sprave of The Slingshot Channel actually did a couple videos showing how you could apply a heating mechanism to something like a slingshot crossbow.
When you stretch the band out, it heats up and so dissipates some of the stored energy if you wait a while before letting your shot go.
By heating the band, it can snap back more effectively.
5:00
I heard "elastic bands are made of rubber witches" and was like "what?"
Issa "pöllymar"
😂 same and I can’t unhear it
Does he mean the sort of witch that wears rubber? Isn't that kinda weird?
I always knew these were self-centering (since seeing them on my hoover), now I know why!
I pictured Destin getting a good laugh out of this video. You’re both so great at presenting a topic/concept.
Mathias is amazing, i feel really Glad to see you recognizing his work.
Adding a bit to the model. Ruber is a thermoset, meaning the spaghetti is held together at specific points in the chain. Those anchor points also help with the "memory" of the elastomeric molecular chain in the very specific case of a rubber band. Great explanation of heat and movement!
As someone who has built conveyors for years I will say that crown pulleys are very important in keeping the belts running true.
"SNATCHBLOCK!" Hahahaha, I died with those clips. loved that episode.
Why couldn’t i stop watching this 🤔
I think it broke my brain and I lost all motor function for a while.
It's ASMR
SNATCH BLOCK!
Legos
It's the atomic jiggle causing entropy!
I worked on a farm with flat belt-driven machinery with uncrowned pulleys like in the video at 2.37. We had to get the pulleys straight to keep the belts on them; however, flat belts do not stretch.
Thank you for requesting permission to anthropomorphize the rubber band (and offer an alternative) because it’s literally my number one pet peeve in science education!
This was absolute class. You can really tell that Steve has *way* deeper knowledge of all of this than what he shows in the video and yet makes it easy to understand for everyone. I'm impressed. Chapeau
Always good to see Destin. Love his channel too.
Cheers for the blinkist recommendation Steve. I sometimes skip over sponsored content but I found blinkist really useful over the past few months to digest content :)
One minute in and this actually makes perfect sense. The part of the rubber band towards the center of the orange is greater then the outer edges. Causing the rubber band to be pulled by the "Grater Force". For example I was driving down the freeway after a snow storm. the freeway was just wet. I came to a particular part of the freeway where some slush had accumulated on the side of the lane. As my tire hit that slush the friction on that side was greater pulling my car off the road. Same with this rubber band because the one side is more stretched the friction of that side is greater causing it to be pulled to the center until all sides are equal in friction.
Something you glossed over in this explanation is that this centering works even on a flat belt with very little tension. Hard to put this into words, but I would say that the end effect of angling the the belt off from its 'length' alignment causes the belt to climb toward the crown of the pulley. For many flat belt machinery tasks the belt is quite laterally stiff (does not flex along its width dimension) and can be under very little tension.
Often times a tractor does not need to line up its drive pulley perfectly parallel to the driven pulley to keep the belt in place well enough. Twisting the belt is done to reverse the pulley rotation as needed. The broad surface of the belt provides enough friction to turn the pulleys even with low tension. One rule of thumb I have heard is 1 hp per inch (of belt width). This power ratio works even with a slack belt, but it increases with tension.
I would have imagined that the more stretched out part experiences a different amount of friction due to more contact area and higher pressure, resulting in a net force, or something like that.
That’s what I assumed as well
Both explanations are probably true at the same time, his curvature explanation in part explains the increased contact area.
This is the more formal explanation whereas the furthest rotational surface of the ball is rotating faster generating more "pull" on the wide surface causing the wider band to creep up the ball. Old farm equipment as pictured were not rubber so the theory of the curvature of the band being the simple answer is not the full one. This answers why the thin band moved downward as well due to the lack of surface frictional differences. Its kind of funny because physicists have been struggling with the same problem of why bicycles tend towards staying upright while moving forward with no rider. This is the outline for the solution and shows the frictional differences in how the ground actually tugs at the tire to pull the steering mechanism in the direction of the fall, thus moving the center of gravity to the opposite side of the fall.
For the convex barrel it is understandable. For the concave can you try a wider belt to see if it will center due to each side pulling away from end to end. It will be interesting to see the resulting shape.
It is a phenomena that is very common on farm machinery. Wide flat belts run on pulleys that have a crown surface to keep the belt running straight down the centre of the pulleys.
I respect you so much for always trying to give credit to the other people who have also made videos about whatever the topic is. It's something not many people do on TH-cam.
New nerd-meme: "SNATCH-BLOCK!"
the rule is u gotta say it after commiting a horrendous crime on video
heat=jiggle, i will remember this forever now
2:24 even if you don't add nothing new, what you actually add is exposure. At the very least if you don't want to republish existing content maybe a way to share it would be great!
So technically gifted with words, thanks for giving my brain a break when you say "not doing the thing" at 4:00 😆
"A rubber band is a continuum of springiness" my new favorite quote :D
Entropy in layman terms:
That what you experience when you open a drawer full of sorted wires after a month and find them entangled
So, do we assume that if you use two spheres in the pulley system it still goes to the centre? What about if you use a sphere and the concave spool?
They’re not pulleys, they’re sheaves. The “pulley” is the complete system.
Sheaves are the "Pulleys" of a Vee belt system. Sheaves involve wedging. Flat belts use pulleys.
There is an easy way to see most of what is going on, something that is very familiar to most mechanically inclined people. For the convex pully, do your calculus. View it not as a single continuous pulley, but a series of sliced pulleys of varying diameter. It's actually 10, 20, or 100 pulleys of different diameters. And the wide rubber band is really 10 thin rubber bands that are linked sideways similar to the springs.
Look at that stack of separate pulleys of different diameters from the side and it becomes much easier to see how if there's a small sideways force you could easily end up climbing onto that next pulley. Most of the force to pull you onto that next higher pulley actually comes from the ROTATIONAL force not the sideways force.
It's the same as when you have a very tight belt or tire to put onto a pulley or wheel. You shove it on slightly down lower on the pulley until the edge grips, and then you rotate it and the rotation gives you the mechanical advantage and stretches and pulls the belt or tire onto the pulley or rim. This is something most people will be intuitively familiar with doing if they have worked on cars or tires or similar items.
Because the surface is continuous, even a tiny sideways force can cause it to move toward the larger side, because the rotational force then grabs it and pulls it out that way, stretching it onto the larger diameter and pulling it off of the smaller diameter.
Those "SNATCH BLOCK!" clips were golden. I've only been able to say "SNATCH BLOCK!" two times in real life, but I swear I will do it every time I can.
Hi Steve! I was wondering if you could do a video about fan blades at relativistic speeds. What would it look like if the faster edge had more time dilation and applying that same logic what about a solid circle or sphere at those speeds?
This Channel here reminds me of Hbomberguy;
my Favorite Place to learn.
Well, that and Veritsaium.