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Is anyone familiar with an Euler's Disk? (physics, conservation of energy and angular momentum demonstration). Answered

At this one site I haunt now and then, looking for new science toys and things to hack, I came across this little item called a Euler's Disk

I am assuming at this point, that there is quite a bit of specificity in the way this needs to be made so that it works, thus the $25 price tag.

Anyone have any information (not contained in the ad) on this?   It'd be most appreciated.


I've been looking into it, and it seems that a disk of metal with the required density and hardness (to have the momentum and all that) of this size just doesn't come cheap, then there's the base and the interchangeable magnetic stick-ons, and they have to make a profit. I think you might get a pretty similar effect with a plain stainless steel disk of sufficient size, on a glass surface, but I haven't found anything close for under $20. I have seen some YouTube videos of a similar long-lasting rotation effect using a stack of magnets suspended under glass using a magnet on top of the glass.


8 years ago

 This reminds me of another toy I have from a science kit from a long time ago. It is a purple piece of plastic, that is shaped like a long oval with a curved bottom. When you spin it clockwise, it immediately starts wobbling until it stops spinning and reverses direction, if you spin it counter clockwise though, it remains spinning for a longer time. I believe it has to to with the shape of the bottom which has curves that make it act like a propeller. None the less it is very cool and interesting like the disk here.

Yeah, I have seen that under several different monikers.  Edmund Scientific sold them at one time (they may still).

Have you ever seen these? (video not mine)   I have a pair of these that were given to me at a bistro my wife and I ate out at one night.  I am not sure what "ELSE" one can do with these things, but there you are. 


 Those are called rattlesnake eggs. I don't think I have any but that is what they are usually called.

Hmmm,  when I was younger, we made something we call "rattle snake eggs"  which consisted of a rubber band,  two paper clips (bent appropriately)  and a small envelope with the words Rattle Snake Eggs on the outside.   IF someone was curious enought to open the small envelope,  the paper clip would spin inside (because of the rubberband that it was wound up with)  rattling against the envelope and then someone could shout "Sounds like they hatched !"   LOL 

My set of magnets (given to me btw) like those in the video, are called something else...but I suppose every company that makes them, uses a different name.

 The ones I have seen have been called that or buzzing magnets. What were yours called?

Wow, no matter how hard I look i can't find anything better than http://www.eulersdisk.com/ <-- that website, which has a few things but not as many as one would like.

I searched DIY euler's disk and this was the first on Google, which just goes to show how many people have tried it.


Hope you find something.

Thanks,  I had looked through some of the links I'd found but came up just as short.

It seems that it has to be machined perfectly, and you need the designs as well.

You pronounce him "oiler" don't you?


.  Yuck! The C&P quote from Wikipedia didn't work very well. Follow the first link if you're interested.

If it had the ü sound, it would be more like  ewYoo but as one syllable (I think). 
Supposedly.  Before you pointed this out, and I looked it up, I would have pronounced it like it had an Ü  (umlat) over the U...but that is obviously wrong :-) 

Judging by this video, mass seems to play a part in things as well - that's a much weightier disc that a coin.

.  I don't think it's mass so much as rigidity. Less energy is lost to making the disc (and rather massive/rigid plate) vibrate. According to the Wikipedia article, friction is the major factor.

Yes, friction is the main energy-loss, but a more massive disc has more kinetic energy to lose, if you see what I mean.

Here is a little history that kind of backs up what you were saying.

.  If you say so, but my gut still tells me that mass is not a factor. Or maybe I've just got Galileo contaminating my thoughts. Isn't the disc just taking a circuitous route to fall?

You are thinking, then, that no matter the mass, it would have to pull that mass upwards, as well as use the kinetic energy of its downward movement, once it reaches that stage;  still, when it is in it's spinning (only) stage, it's mass plays the same roll it does with, say, a spinning planet; whereas it is more difficult to bring to rest a mass like Jupiter, as opposed to a mass like that of a penny. More energy. 

.  <shrug> I'll leave this to all you thinkers. It looks and sounds neat is all I really need to know. ;)

No, it's ok to bat things around; I am not so informed on the subject, or I wouldn't have asked about it ;-) 

I'd agree with the mass aspect.



8 years ago

I would guess that having a small contact area and hard surfaces is more important than a low-friction surface.  I'd actually guess a hard steel disk on smooth glass would be better than on teflon. 

Note that the product description says the mirror is 9 inches across, so the spinning disc is probably much bigger than a coin.  I don't know what a suitable replacement would be if you wanted to make one this large, but a simple coin on a mirror would do largely the same thing.

Here's a link where the give the dimensions of the "coin".

Additionally here's a paper from the toys homepage where they mention in section 2 that elastic deformation of the spin surface enhances spin time (seems counter intuitive, but....)


Well, I am not so sure it is counter-intuitive, I just meant that if the surface itself flexed (point of contact) such as with rubber, it would slow much more quickly.

It looks like a heavy or dense hockey puck or really thick coaster for drink glasses.  Maybe the concave mirror or surface causes the disk to oscillate better, kinda getting pushed or bounced side to side more violently to get it to spin longer.  I do see a slight shimmy as it goes down.

.  "concave surface"
.  That would make it more expensive than a flat surface

Well, I am assuming the surface is concave, but I mean to achieve this "effect" I suppose some extra careful machining had to go into the making of that curve. Do you think? 

.  I don't know how careful they have to be, but it would involve some extra machining. After reading the Wikipedia page (see L's link), it seems to me that the concave surface is not necessary, but only keeps the disk from falling off the polished surface. You should be able to get the same effect with any rigid, smooth surface. Apparently, Teflon is a good choice.

I wonder if glass would work better.  Teflon is a plastic and does dent to a degree (although I am not sure just how "strong" it is, I know when it peels off it feels like it could be easily dented).

.  According to the Wiki article, it's the low friction properties that make PTFE perform well.

well, the disk looses energy through two means air friction and surface friction. you can lower surface friction by polishing the edge of a coin mirror bright, and then spin it on a mirror as they do. The concavity is irrelevant.

It is dependent on what you mean by JUST a spinning disc, since this particular spin seems to go on for an abnormal length of time, or so the ad says.
This is an honest question :-)