Giant Euler's Disk | Machining + Test
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- เผยแพร่เมื่อ 16 ก.ย. 2024
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Machining and testing out our new giant Euler's disc physics educational toy.
PlaDoh will absorb energy like crazy! Epoxy the plate to the concrete and you’ll really have something!
Use glass.
Hardened glass might be okay
Put the metal plate or a glass plate on some fresh concrete.
If the plate flexes just a little bit, it looses a lot of energy, so if you cast it into concrete there is no air gap underneath the plate and it is not able to flex at all.
I saw it shifting. Also I would have polished more and better, but that's what I do is make mirror finish surfaces by hand. Not machine precise. Really cool stuff though guys. More toys than I have.
When they were crouching down I was expecting things to get cheeki breeki
There's actually a mathematically optimal ratio of thickness to diameter (t:D = 1:6) for the maximum initial sum of angular momentums. (Leonhard Euler was the physicist/mathematician that defined and figured it out)
I would recommend cutting a smaller diameter to a greater thickness to still get to the same/similar weight.
With a slightly concave mirror polish and a minimal radius (none if possible) you should get a howling banshee for at least 5 minutes (more like 25-30).
I'd very much like to see that done, maybe with a heavier and harder alloy that machines and polishes well like inco718 or the like. Having both pieces polished to a truly mirror finish and then shining lights or lasers onto the piece would also be a magnificent spectacle
@@CtrlAltRetreat Ah yes. Everyone has a 30cm Diameter scrap cutoff of Inconel laying around.
@@cayleependerass , what? You don’t?
I actually do! Hahaha
@@mynameismatt2010
The magic of TH-cam! I was actually thinking that if no one did, I'd call up some of my buddies back in the place I worked in 2008. The shop got acquired by allegheny but them and wyman gordon I know for sure are still making turbine blanks for forging out of inco718 and they always used to have about 8" end cuts of scrap off of each billet. Since we know we want a 1/6 ratio, that's actually pretty easy to buy something to work with. Even a 12" billet would only need about 2" of depth and they typically didn't use ones that big. Theoretically, the increased density and hardness should result in a much more efficient disk even with a little less diameter.
If there happens to be a guy who has a nice lathe who's looking for some work near central to east Texas who's looking at this, post a comment replying to this maybe we can make something work. I'd be inclined to go through this just to have one of these around
DEFINITELY MORE ENGINEERING AND LATHE STUFF PLEASE.
Timo's Triumph is the best!
Such a nice sound on that machine. If this is what a midlife crisis looks like i can't wait xD
@@mojolotz I'm way past midlife crisis!
Watching lathes is quality machinist porn.
The Slav Squats are real here
I tried it once and lost all circulation to my legs. Pfftt...weak American legs..!
Careful now. The fragile majority will take offense, without even knowing who, what, where, why, when, and or how.
Get the hard bass going!
If they had AKs and wind breaker jackets it would be complete
I was looking for that comment
you really need to mirror polish them up
then they spin for ages
and the final "scream" will be better ;)
Indeed! And to avoid any loss of energy, the plate should be fully fixed to the foundation (no damping stuff in between!). Maybe put the plate on a "perfectly" level concrete area.
@@perribru Grinding the plate concave will help as well. The closer to optically perfect the better, but of course that is a complex task.
@@BixbyConsequence A hollow grind certainly seems easier to do than a perfectly level surface.
Even the small amount of playdough under the plate will bleed off energy quickly as it compresses. A rigid tripod arrangement around the rim would be more efficient, I think. Maybe just weld three "spikes" 120 degrees apart around the circumference - to stop the plate moving laterally. The noise could be deafening though as the plate flexes...
I'd try adding hundreds of playdough lumps under the plate. The idea is to minimise flexing of the plate which means if you can hear the disk rotating then it's wasting energy.
@@olsmokey The thickness of the plate could be increased to reduce the flexing - but the softness of the playdough will always be the major loss of energy - it allows the plate to move laterally and also changes thickness - both eating energy out of the system. If the plate was concreted/epoxied to the floor completely and allowed to set - I'd agree with you - but I don't think they want a metal plate concreted to the floor...
@@dav1dsm1th They could just bolt it to the floor so when they are done they are only left with 6 or so small holes that can easily be filled
this was my thought the moment I seen the playdough, why he didn't even consider it at any point this tells a first time view a lot
The spinning surface should be slightly concave so it self-centers, it can be smaller that way. I made a 3" diameter disc out of tungsten carbide, and it wobbles for a very long time.
I'm curious. How did you machine/grind it and in what form was the original TC piece?
@@jeromeprater183 It came in the form of a solid rod. I am a machinist. I did it all on the surface grinder, first with a diamond cutoff wheel then a regular diamond wheel to true it up
@@SuperAWaC I'm thinking of having a few manufactured for me. Do you think it wobbles long enough (compared to steel) to be worth it?
@@Sgt.Hartman It depends on what you pay for it. It is mostly just for fun. The tungsten carbide will scratch everything up over time.
The bottom plate needs to be flat or else it won't spin the same
A granite slab from a monument maker could be an excellent base. They usually have damaged pieces already polished.
Counter top manufacturers always have piles of slabs for free. Mostly sink cutouts. Polished on one side, textured and ready to adhere on the other.
Stone wouldn't keep its flat under a steel disk and it would spray particles of sand all over the base.. especially granite, it's very brittle and the edge the disk would chew it up like a saltine
@@Faesharlyn I thought of this also and it would depend on the granite, radius and hardness of the steel. Black granite would be my go-to because of it's tight grain structure and would probably fare well with the radii in the video. But sure, a hardened steel disc with a sharp edge would score it like a glass cutter.
@@ross9580 definitely, a hard corner would do more damage than a rounded one but spin longer
I was thinking about how different stones would sound, gritty or smooth depending on the hardness i would think, but the harder the more brittle.. what kind of force hits the plate when the disk lands flat? If on a piece of obsidian i think it would shatter like the obsidian ball under the press, just *splash*.. or an obsidian disk, spinning and whistling like a singing bowl? Shattering on landing? Wouldnit even hold together or chip at the edges? Physics fun!
And a discussion made out of Osmium ( YIKE$)
The english word is in fact "concave" you nailed it.
He said something like conwaved
A good way to remember is if the center goes in, like a "cave", it is concave. The other is convex, if the center comes out.
@@mtnvortex Thanks, really useful tip for a non-native speaker =)
@@mursmumies123 No problem. I had a teacher tell me that when I was very young. It was something I used myself to remember.
@@mtnvortex same. had a good physics teacher
I was waiting see the performance difference between the large radius corner and the small radius corner. Also could you mark it so we can see the rotational speed? I see more videos coming to explore this !
Thanks for sharing!
The rotational speed (on the floor plate) is at its greatest at the moment the disc hits it, and it gradually slows down from there; yes, I know that's obvious, but it needs to be said to address posts I've seen elsewhere, stating that the disc is spinning fast, like a top, AND GOES FASTER AND FASTER. For a 3" diameter disc (which, not weighing much, can be spun much more quickly than the monster disc shown in the video), a good spin for a long run for me starts at about 2 full rotations per second. So -- unless one is incredibly strong -- the 60 lb. monster disc must have a _much_ lower starting rotational speed than my 1 lb. disc.
I wonder how much heat was generated while that was spinning, would be cool to look at it with an infrared camera.
I don't think you would see anything. All energy this system is the potential energy of the steel plate. And even just a part of that actually gets converted into heat. Thats almost nothing compared to the heat capacity of that ammount of steel. The temperature probably changes about 1/100 - 1/1000 of a °C
@@sushi3377 yeah you’re probably right, the thermal mass of the disc is far to big to register much of a change. I was just thinking of the loss of energy being converted to heat via friction but didn’t consider that. Good point!
Yeah probably at least 12 heat
I'm assuming something like: E=mgh+0.5mv^2+0.5Iw^2. With m=mass of disk, g=gravitational constant, h=vertical displacement of the centre of mass of the disk from initial position to final position, v=Initial velocity of the centre of mass of the disk imparted when spun, I=rotational inertia, w=rotational velocity when spun. Not too sure how that'll interpolate together but something like that, ignoring losses.
@Pandacat 666 sounds like my kind of party.
There’s lots of flex and lost energy in the bottom plate. I could even see it moving at one point
And Lauri said it was very noisy, thats additional proof, but the biggest proof is the short duration, very severe energy loss.
@@pflaffik good point about the noise. Great example of something that seems obvious once you know about it but isn’t actually so obvious until you pointed out that the noise is a form of energy emission.
With some surface hardening it could last even longer I think.
That and backing the plate with some tacked on studs then pouring say a foot of concrete would stiffen up the surface so it isn’t bleeding out so much energy as noise.
Yeah get them nitrocarburated
Bit difficult to harden literal “mystery steel” and if I recall correctly from the surface hardening video, the cost involved as well as the amount of time required with even the most superficial surface hardening is just completely unrealistic on a project like this one.
@@Jay22222 Nitrocarburation is relatively cheap, it happens on quite a huge scale in the Nordic countries. Minimum charge at a place I used to deal with was only around €80.
@@jcims A bigger thicker plate would be simpler.
Hey! I am going to try this at home with a coin and table, probably the only time it’s safe to recreate a video of yours.
You didn’t warn us not to, so that must mean it’s safe! 👍
Unless you have Play-Doh hands.
@@sdspivey Yes, if you have friends who are Play-Doh people then you must supervise them when performing this experiment! 😂
Or unless your coin weighs like 50+ pounds
Unless you do it in front of my old study hall teacher for 20 minutes or so. Then it is not safe.
Beyond The Comments
I have an Euler's disc made from a precision ground ring of Tungsten Carbide that weighs 30 pounds (13.6 kg) and is 14 inches (35.56 cm) in diameter. I have spun it on a sliding glass door that was aligned horizontally at the four corners. The hard part is to keep it centered and to avoid breaking the glass. Some of these discs can spin more than 3 minutes.
do you got a video? :)
Cast iron, due to the carbon precipitated between the steel grains, actually has a lot of natural damping as well. So using a steel would have even lower losses. But that natural damping is why cast iron is used for machine tool bases.
I think the play-doh probably absorbs some energy, you need a hard surface to maximize the elasticity of the collision (bounce).
Attach with bolts from edges to a heavy steel plate. Should be fine then.
Set it in grout perhaps?
*playdoo lol
I agree. They need to put that plate on the granite surface plate they have in the shop. I bet the play-doh robbed a good bit of energy from that system.
My instrumentation lecturer Bob Drinkall (who was really old school, in the late 80s), said that the action of the disc was "nutation" - there is a meter which uses a nutating disc to make measurements, hence him knowing about it.
Use it as a giant Ice-hockey puck on the lake ! next winter :)
Make a Puck-launcher ?
Love your channel !!!
PL.
U must be Canadian eh? lol
@@mgtowrules1649 Nope Dutch ;)
07:35 starts to sound something familiar....oh yes...my washing machine 🤣🤣🤣🤣
Almost seems like it represents the human experience of their whole lifespan. When it starts, it feels like each rotation is quite long but then feels shorter and shorter until it finally stops....
Uhhh, I'm fucking baked guys.
I hate to say this but ...
you are right! 😲
entropy at its finest
No no, you have a point
He's got a point
420 to ya man 👍
I love Annis laugh. It's Pretty Good!
I thought Timo would drive into the sunset. Oops, yeaaah...
It looks like you guys are back in full swing and healthy. Great, and thank you!!
Men are never to old to get exited about new toys.
As you grow older, the things you regret the most are the ones you never did when you had the chance.
I love how something can be in Finnish and a native Finn could still get confused by the saying. I wish my great great grandmother and grandfather kept Finnish in the family after coming to Canada...
Prettty sure the base plate trembles as it is not fixed to floor in any way.
You could extend the revolving time by fixing the base plate.
My father always used to love "Triumph" motorcycles. He swore that they were some of the best motorcycles for what they cost. I love to see people that work hard, get good things from life. I am happy for your family, and hope you continue to get good things from life!
Any chance you can re do the spin on this with some marks on the disk showing how fast its spinning? Even just pen marks would be interesting, to see how much it slows down as it's height gows down. For science right :)
I don't think It's spinning fast. I think the rotation even slows down over the process, because the rotation momentum is tranformed to the up and down movement!
@@GuaranaMontana Initially while it's mostly vertical it's rotating on a very small axis and going fast, but as it lowers the area that it's rotating on expands and the spinning slows down, a visual representation would highlight this.
@@JosephParker_Nottheboxer
Slowmotion footage from above would solve the miricle ;)
Include a clockface in the background that has a second hand. So there is a known frame of reference speed.
I can say this about the channel and the both of you.....
your english has gotten much better over the years. there is still a charming quirk to the syntax of your sentences and pronunciation of your words, but it's not as bad as it was years ago. also the content of the channel is much more varied, and i love seeing both of you grow and evolve as creators and humans.
Would be awesome to see footage from a GoPro mounted to the spinning disc! I know it wouldn’t spin as long, but I think it would be fascinating to see.
Watch how the spin angular momentum axis parallel to the diameter revolving the disk bleeds into spin angular momentum rotating the disk. Nice! Put a mark on the narrow edge and use a tachometer to measure the spin-up.
if you can find an extremely hard metal for and then machine the surface of the base plate to within a 0.001 tolerance, along with the outside surface and edge of the heavy disc (using as hard a metal as you can for it also), then, the effect will go on for longer still 👍😉
Also, if you can epoxy the plate to a surface too, that may work better than playdough
Tyrkisk Peber is such an awesome candy! Had a danish penpal that used to send it to me.
Your pronounciation of Euler is funny :D Just for info: The German "eu" in Euler is pronounced just like the British "Oi!" (or Oy)
The property you mentioned is called the square cube law, and rather more simple in English.
Anni, we need a Rock & Garden update lol!!! Even if nothing has changed, we love the random yard stuff.
Those are long overdue.
That really long thing you said about if it doubles in size it 8x in weight is called the square-cubed law in English! Works the same way! If you increase the size of an object by 2, you are increasing the surface area by 4, and increasing the volume by 8. (2^1 in the 1 dimension, 2^2 in the 2 dimensions, and 2^3 in all 3 dimensions)
It works for all size differences.
Say you have a 2 inch diameter cylinder that weighs 1 pounds and bump it up to 6 inches in diameter. You increased the scale by 6/2, or 3^1. You've increased the surface area by 3^2, and you've increased the volume by 3^3 so instead of it weighing 1 pound, it now weighs 27 pounds.
It's the square-cubed law!
Need to ask the real questions: Lauri, please tell us about that t-shirt you wear in the second part of the video!
It's a funny meme shirt from cheap market. It says in Finnish that my well being is at knife's edge :D It's a bit of inside joke since we used to do way too much work and sometimes it felt like it's taking its toll from you.
I was wondering that myself.
It's kind of hard to not notice the shirt.
That was impressive how well it worked and how long it went was also very cool. Great video content. Keep em coming.👍💪👍
What would happen if you coated it in a very fine oil like 'slick snot' that skateboarders use on their bearings to make them go faster?
holy crap, 60 pound euler's? there's nothing left to watch on youtube now, you guys hit the peak.
Would be good if you could concave the surface/face of the disk slightly and see how that affects performance
that's kinda what I was thinking, but I figured removing mass from the centre would be the bigger factor rather than the concavity. So I suggested using a steel hoop made from round bar... you might get more rotations out of it that way, but in any case, once it lays flat it's game over.
This video was great, guys. Euler's discs are so awesome
They should put this in the strongman competition... WOuld can pick up the heaviest steel disc when it's flat on the ground lol
Intresting and I would say to dangerous. But considering the stone comp... I think it's a great idea
@@peterzingler6221 yea that atlas stone thing looks super dangerous. Figure this would fit the bill also.
Have you seen the video where the dudes spine just gave out while lifting the stone? And then it fell on him too, jeezus.
@@peterzingler6221 its too dangerous. Atlas stone might crush something but its difficult because of the diameter. It tends to push the legs away from the stone when its dropped. This can lop a toe or fingertip off with ease
6:49 when you drop something on the floor in the middle of the night when everybody else is sleeping
Hello Lauri ans Anni, another great video. Is there a relationship between the size of the disc and how fast it will eventually spin?
No. In theory, the speed will always go towards infinity but due to the imperfections of the reality, the disc will never reach that speed. Those small imperfections are the only thing that effects the final speed. Of course, larger the disc, smaller those imperfections are in relation to it's size, so that causes larger discs to reach higher speed usually.
Matt Parker has several great videos about Euler discs.
I have done that on and off a few times as loads of lads would have done - First about 50 years ago... Seriously... Except it was often much better with a extreme rising frequency. Can't remember the materials... Apart from it being smaller of course. So boys have been ''inventing'' this well before 1990... I started in the 70s... Anyhow I love this channel.
Can you make a huge tensegrity table and put a car on top? :D
That's actually really good idea! I will check out would it be too expensive build but I think I could pull it off
Yep probably shit load of steel beams and one day of welding :D I will do some calculations on cad to solve would it be too difficult
@@Beyondthepress I mean you could also press test a tensegrity table :D
@@peterzingler6221 I think I have to do both. I will laser cut smaller one out of sheet metal and then weld large one out of steel beams
This took so long to show up in my recommendations despite having every notification turned on. Glad I'm seeing it now anyway.
And that's why trains are so efficient, almost zero contact area so friction is almost negligible
'if the track is clean' ;)
In English that long Finnish phrase (not even going to try to translate) is called the Square Cube Law. When the dimension of an object doubles, the surface area is squared, and the volume is cubed.
The louder it is, the more energy is "lost"...
So, when you talk load or shout, is it less efficient?
Depends on what you mean by efficiency. If you shout loud enough to stop further questions it might be more efficient ;-)
@@benbaselet2026 If you do not allow someone to speak, you will give cause for violence.
And violence is definately wasteful, as you have to break something that
can not be unbroken. Perhaps mended or healed over time, but
not unbroken.
My tungsten carbide wedding ring on my phone screen makes a fantastic Euler’s disk. Highly recommend trying it.
Just don't put your hand down hard on anything. The rings are notoriously easy to shatter
@@kristianstaalby8499 I've heard that from so many people but I've worn mine for 8 years with no issue. It's actually saved my hand from getting crushed once.
@@nickjh85 I'm very happy to hear that.
being about the same age I finally figured it out it's not really a mid life crisis it's just finally having enough money to get the toys you always wanted but were to poor to afford when you were younger . the only ones who call it mid life are the poor young bastards with no money. the kids are out of the house and you can afford to have a bit of fun with a new toy so why not. your friend has good taste getting a Triumph
What would you do if you could afford anything? First...think about it. A large fraction of desire is being beyond reach.
A mid life crisis is when you buy the toy - even though you can't really afford it - because you want to fool yourself that you're still young.
Lol it kills me that he explains why they need to remove every possibility or energy loss while applying playdugh to the base. Love these guys.
Great but three things to improve it:
1 The original has one sharp edge and one soft and it’s the latter that it spins on. That will probably improve the spin.
2 the surface it spins on is concave. That is probably one of the most important factors. Not just for self centering but for the quality of the spin.
3 As many already mentioned: the original has no damping underneath but instead there are three rigid contact points
Yep. I agree, swap out the pladoh for epoxy. Polish your edges and surfaces until they are mirror-like. Then for the big friction removal, rig a set up so it can be spun in a vacuum-that big disk is moving a lot of air.
Thanks, fun to watch. Aloha
I'm reminded of a colleague who used to be a welder and got caught under a giant one of these. Learned to program during his recovery.
In case you know Swedish there is a trick to knowing the difference between concave and convex: konVEX = VÄXer på mitten, konkAV = smalnar AV på mitten.
A trick in English is that caves go in.
Lauri has said a few times the only Swedish he knows is "Jag talar inte svenska" 😅
The play doh is going to absorb energy since it is constantly deforming as the weight shifts around. The surface needs to be as stable as possible.
The result would also be better if you gave the disc more rotation. It was hardly rotating at all.
I'm calling for another attempt - if the result is the same you can just mention that in another video.
I loved the stunt hand. This was quite interesting. Thank you
That large disc would make a great flywheel for experiments
That thing is kind of terrifying. I think if someone made one the size of a pickup truck and spun in the middle of a crowded area, everyone would start running away thinking it was some kind of doomsday device.
The noise represents lost energy. The noise volume is roughly proportional to the mass. It would be interesting to see what would happen if the middle of the disc was cut away to leave a thick ring.
I was thinking it would be interesting to see if they squirted some oil under while it was spinning, but they went the opposite direction with a play doh hand. Very funny. Cool video.
The more flat and more polished the two surfaces the longer it will spin. The two should just about "wring" together like gauge blocks.
Totally mesmerising as it spun 👍🏼👍🏼👍🏼👍🏼🇦🇺🇦🇺🇦🇺🇦🇺🦘🦘🦘🦘
"Pretty Good" hoodie is SO GOOD and so pretty!!! 😅
"Cast iron, It might explode.... but thats a bonus in a way..." lol
Oh, and it's pronounced Oiler - like something that would oil a mechanism or something. Just remember one of my professors making that super clear to us!
Ok so that worked a hell of a lot better than I expected with out a mirror finish to the steel plate..well done , great video.
What a big ass coin spin. The heavy steel held a lot longer though and we could nicely hear as it was speeding up toward the end.
I have a practical use for this phenomenon. make the disk into a container and put paint in it , one spin and the paint gets mixed !
slightly polishing the corner edge allows it to "wobble" and angle more efficently. best of luck!
Regular speed: sounds like a steam engine locomotive accelerating down the track.
Slow speed: sounds like the engines of the Titanic.
Triumph Bobber, very nice. Congratulations on the new bike Timos!
It would be really interesting to see the effect of lubricating both discs. on how long they spin for. I'm pretty sure the heat energy from the friction and the sound/vibrations of it are the only ways it loses energy. Besides air resistance. I'd love to see even a normal Euler's disc spun in a vacuum chamber while lubricated, so you can get rid of at least the air resistance and friction between the discs. Or mitigate it anyways. And see what sort of effect that has on how long it rotates for. But then you'd need to make some sort of device that would spin it in the exact same way every time so you don't introduce unknowns by spinning it different every time.
Anyways, those are just some ideas for either the channel, or someone else who has a vacuum chamber and Euler discs. But I'd be really interested to know the results if anyone does bother doing it.
Glad to see you guys back at it! 😊
Glass would still have far lower friction than that setup.
If you used tempered glass it most likely wouldn't shatter under the pressure - 27 kg on edge isn't that much pressure.
My grandpa thought it was so funny he kept saying GET TO THE CHOPPERS over and over again😂
I think what happened to the Stunt Hand was a pretty accurate depiction. I grew up in both a machine shop and the forests, and then spent my adulthood cutting wooden trees and also building concrete ones.
Losing digits from Metal Pinch is no fun. Fortunately, I've avoided that. So far.
Where i work we call it "carpenters Allergy" because it makes fingers fall off.
The edge around bottom circumference of the disc should have the edges rounded slightly to reduce friction and greatly increase the rotation time.
After starting the spin. Use a leaf blower on the edge to pick up speed.
Then use compressed air to go even faster.
For some reason, hard drive platters make excellent examples. Leave them intact with the motor attached and all three platters (usually)
Nicely done, that thing was huge! I would have loved to see a decibel meter (DB meter) nearby to see how loud that big one was. I have a small desk Euler's disk and its so loud it annoys everyone in the office.
I expect you are popular
@2:55 -Say that 10 time fast......
🤣🤣
Good show.... I like this.. .
My legs started hurting just watching yall squatting for so long. Great video as always.
Triumph isn't mid-life crisis, that's a classic! Tell him nice ride! I love the squats, I used to get teased for "sitting" like that, but it is very convenient.
It really seems like it is spending a lot more energy than it has, so cool!
I'm sure this was said already, but both the disc and the plate it spins on should be polished to a mirror finish for the least possible amount of friction. And the plate should have a ridge to stop the disc from "walking" off the edge and possibly taking damage.
I love the sound of the last few seconds of movement!
Many years ago in college, we had one class in a a conference room where there were large ashtrays on the tables - several of those spinning at the same time were enough to deafen everyone.
If you wanted to eliminate all energy loss, you should have affixed it to the concrete floor by first pouring about 5 gallons of concrete, then setting the large plate into it before leveling.
Also, you would need to ball-peen it, polish it, then heat-treat and anneal through at least three successively lower temperature cycles.
In the future, consider repeating the experiment with a rotated ellipse. I think you will find it settles with some very smooth motion and some wildly different sound.
The playdough under the plate is not good enough because its still moving a bit and you can hear it rattling against the concrete. I would recommend getting a plate that is more flat and riggid so it cannot move at all, and then try spinning the giant eulers disk and see the difference.
07:40 My Washer when I have too many towels on one side.
Awesome. It would be interesting to see how much longer it would spin in a vacuum.
Congrats on the bike Timo!
I witnessed this phenomenon when I was in school playing quarter basketball on the lunchroom tables.
I just commented similar, as us schoolboys likely invented this a hundred years ago at least...
@@martinda7446 kids today probably aren't allowed to play it as someone could lose an eye, it's considered gambling, or somehow not inclusive. 😒
Oh gawd!...@@RustyorBroken
That was really cool- I love seeing giant versions of science toys. A giant rattleback would be at least as much fun to watch but a lot harder to make, I think.
I should have known you guys would make this! Awesome
you can sand the platform a little inwards so the disk can can stay in it, like an apple on a plate