Steve Mould - 2021-05-27
The first 100 people to go to https://blinkist.com/stevemould will get unlimited access for 1 week to try it out. You'll also get 25% off if you want full membership. 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: https://youtu.be/M2w3NZzPwOM Here's the video I made with Tom Lipton: https://youtu.be/HcVA-4mcXQQ Here's Tom's channel: https://www.youtube.com/user/oxtoolco Here's Matthias's channel: https://www.youtube.com/user/Matthiaswandel Here's my video about Entropy: https://youtu.be/w2iTCm0xpDc You can buy my books here: https://stevemould.com/books You can support me on Patreon here: https://www.patreon.com/stevemould just like these amazing people: Matthew Cocke Glenn Watson Joseph Rocca Joël van der Loo Doug Peterson Rashid Al M Paul Warelis Will Ackerly Heather Liu Alnitak Twitter: http://twitter.com/moulds Instagram: https://www.instagram.com/stevemouldscience/ Facebook: https://www.facebook.com/stevemouldscience/ Buy nerdy maths things: http://mathsgear.co.uk
"Heat is just molecular jiggle"
It's kind of unsettling how simple and accurate this is.
You mean heat can /cause/ jiggle.
@Veritas et Aequitas
There's no "can" to it, and heat isn't actually a thing.
What we call hot and cold is just different energy levels. The names come from how those different energy levels feel to us. But more energy equals more vibration.
It is not quite 100% accurate, but it is good enough for most discussions. An atom still 'jiggles' at zero Kelvin (aka zero heat), it depends on what type of jiggle we are talking about.
@Kyle
No, an atom does not jiggle at absolute zero. It never reaches absolute zero because of that jiggling.
It's literally impossible to reach absolute zero. And the reason it's literally impossible, is because of the 3rd law of thermodynamics.
My heat is just jiggle jiggle
God I effing hate that song, the word jiggle is forever ruined lmao
Anthropomorphising a rubber band is streching it a bit! ;)
🤣🤣🤣
I'd say it's more of a personification than an anthropomorphization, but I wouldn't want to get anyone bent out of shape.
Best nerd humor ever!
@Claes Wikberg Lol :D
yeah, but its rubbing off on me
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.
You can never miss "Destin", when you say snatch block
It's destiny
@SmarterEveryDay Destin is the man
@lescrooge You have no idea how "The Man" that dude is. Not a lot of YouTubers get big while working for the US military, but all of them who do have something in common. They still work for the US military.
@GTechno13 e we guy
SNATCH BLOCK
I appreciate your awareness of your anthropomorphism of physical systems. It was very satisfying to hear you offer both an anthropomorphized and non-anthropomorphized explanation of a rubber band's behavior. It's an excellent example of your effortlessly meticulous thought process and communication style, the things that keep me coming back to this channel.
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
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.
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.
@John Wafford I'd love to hear your alternative explanation.
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
When I did my degree (mechanical engineering, a long time ago) we spent half a lecture on this. The lecturer (a tenured professor) actually explained it in terms of velocity and angular acceleration of elements of the belt. I was more confused after than before. This deflection-based explanation is way better, and makes me wonder if the comparative angular acceleration explanation was just totally wrong. Also had no idea elastomer elasticity was from entropy... awesome
I have the impression both explanations are different ways to say the same. Like how LaGrangian mechanics end up being Newtonian mechanics just with another philosophical approach. I like Steve's explanation better, tho
I would agree with angular acceleration more... What he showed seemed to be true about rubber bands.. I wish he had gone into more explanation of practical example.. Sandpaper and leather belt are intuitively not stretchy... Both of which he showed video of though
I LOVE LOVE LOVE when you guys feature each other's work.
We have been crowning wheels for bandsaw blades for years, amazing how engineering works
As someone who has built conveyors for years I will say that crown pulleys are very important in keeping the belts running true.
SNATCH BLOCK!.... er... uh, I mean. . NOT A SNATCH BLOCK
Lmao
Destin'ed to snatch the block 😬😄👍
Ayyyyyyyy!!!! 😂😂
Steve got Destined!
I just saw that thumbnail and it made this comment even more funny. (Also why did my phone try to auto correct to "funnier"? Lol)
2:12
"Our intuition is wrong."
Learning physics summed up in one sentence.
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!
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.
Thanks for the informative video! 👌 however all natural changes are driven by maximizing entropy, I believe your analogy on why the rubber band contracts is hard to get. The rubber molecules have low entropy & low potential energy, while relaxed (not stretched). They tend to contract when being stretched since their molecule bonds deform ( net of springs are handy), thus to get back to their original form(lower energy & a bit higher entropy status), they contract.
Hey now, this type of pulley system looks familiar ; P It's exactly what stabilizes the band on a Van De Graaff Generator.
No, i think it was the buckles...
https://www.youtube.com/watch?v=48tU3P8f46Y
exactly what I was thinking
@DaryxFox I will never forget that smell either lol
doesn't spect jay was here!
This crowned pulley has also been used on bandsaws for over 100 years.
I've never heard tension explained with entropy, how does this explain tension force in a crystal? One would assume applying any force to a perfect crystal would increase its entropy, and so it would relax into a lower entropic state
Mathias is amazing, i feel really Glad to see you recognizing his work.
I always wondered how Victorian factory contraptions kept their strap connections to steam engine flywheels.
I suppose the belts were a bit stretchy and the pulleys were convex.
When “training” a conveyor belt, we see that it always creeps towards the side that is tighter. I did not realize that this would work in the case of an extremely crowned pulley. Very interesting 🙂
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 whole video has a consistent layer of discontinuity. As one thing is just starting to get explained, there is a jump to a new topic, and just as THAT is starting to be explained, there is a jump to a new topic, and just as THAT is starting to be explained, there is a jump to a new topic, and just as THAT is starting to be explained, there is a jump to a new topic. See what I did there? That is what is happening in the video. In the end, nothing really got explained fully.
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
It depends on the type of belt. If the belt is wide enough, it will stay on the pulley. This is because the belt is elastic not just across its length but also across its width. Since the surface of the belt is stretched more on the side facing the wider part, it will always try to nudge itself to tensile equilibrium. It will move toward the one place on the pulley where both sides could be stretched with equal tension: the middle.
@Karl with a K There's not really anything more left to be explained in each thing. The video could have ended after 4 minutes and I would have called it overexplained.
@Matthew Parsons Lots and lots of things are left out, that you don't know what they are is the same problem as the uploader. It is not the length of the video that is the problem. It is the usage of English to describe something in a standardized, clear, well-established format, which this video does not represent.
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
1:26 - Wow, that image of a centre-lathe at the top-right corner brings back some memories! The Graziano Sag-12 is an incredible lathe (although with a nightmare of electrics to maintain) which make working on it a breeze. Had them in a technical school in Malta. Incredible to work with. An electrician's nightmare to maintain especially with those electro-mechanical clutches in the gearbox.
This was a great collaboration with Destin. You guys should work together more often.
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.....
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.
It’s been in the last couple of Vaccum’s I’ve owned. The belt/band that spins the agitator brush centers itself on a rounded egg-like wheel and I always wondered why it didn’t just slip down the side ever.
Matthias is an incredible creator. I love his vaned extraction blowers etc
Thanks for this, i have always wondered why that type of "pulley" worked. Now i understand the difference between using a V belt and a banded belt.
This was the first time I have understood how crowned pullies and belts work, and I have been aware of them for around 50 years... Great video! Thanks.
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
Using a grid of springs to represent elastic bands was very helpful in making it click!
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.
If someone demoed this for me when I was training to be a technician, I might not have struggled so much when aligning the conveyor belts.
LOL... I hear ya. Tread mill rollers are slightly crowned as well... 😉
I've always wondered about this effect in relation to band saws. A band saw has a pair of crowned wheels that pull the blade around and around, much like the setup Steve showed. But, the saw blade is metal, not elastic. I doubt it deforms much to pull it back to the high center. BUT, the wheels are covered with rubbery tires. Are they doing the deforming to keep the blade traveling in the center?
The metal is exactly like a rubber band
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!!!
The jiggling chains was such an intuitive visual model, amazing video yet again
The elasticiy of the band causes unequal force against the crowned "wheel" making it "crawl toward the area of most tension, thus centering on the crown
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.
I have spent many hours mulling over this one because I use a belt grinder with an adjustable roller head. As you say, it works entirely counterintuitively.
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.
From the bandsaw to the entropy in 8 minutes. Brilliant!
Steve - i love your videos! Came here from Destin's channel. You guys are so great. Thanks for doin' what you're doing.
Actually I knew exactly what it would do because I've used belt sanders for decades. Although I always thought that the way the belt worked was weird. It's especially weird because a sanding belt isn't very stretchy.
My mom's handheld dust devil used this to drive the brush. I was always amazed how the belt didn't slip off. Thanks for making this video
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 🤣
raydunakin - 2021-05-31
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!
Malavoy L - 2021-10-27
And machinery that uses 2 separate belts on the same pulley use a double crowned pulley.
Gorillainthemist - 2021-11-15
@ozricstormbringer I don't know where your from but road's here aren't that good, I mean they are layed with a slight crown in the centre to aid with water run off, but that's it.
Ragnawreck - 2021-11-25
Nobody's watching because of your comment
raydunakin - 2021-12-04
@Eileen Ulick Never. People like to think that anything old and abandoned must be "haunted" but that's just a lot of bunk.
Michael Hansen - 2021-12-15
Now that you mention it, I've seen this in ghost mines. This is everywhere and I had no idea. I thought of train wheels but someone else mentioned a bandsaw.