2565Views45Replies

Author Options:

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

Picture of
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.
 

45 Replies

user
DreamDabbler (author)2016-05-25

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.

Select as Best AnswerUndo Best Answer

user
n8man (author)2009-12-03

 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.

Select as Best AnswerUndo Best Answer

user
n8man (author)n8man2009-12-03

 Through the wonders of Google and Wikipedia, I found out that it is called a rattle back, more on it here en.wikipedia.org/wiki/Rattleback

Select as Best AnswerUndo Best Answer

user
Goodhart (author)n8man2009-12-04
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. 


 

Select as Best AnswerUndo Best Answer

user
n8man (author)Goodhart2009-12-10

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

Select as Best AnswerUndo Best Answer

user
Goodhart (author)n8man2009-12-10

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.

Select as Best AnswerUndo Best Answer

user
n8man (author)Goodhart2009-12-10

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

Select as Best AnswerUndo Best Answer

user
Kryptonite (author)2009-12-01

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.

Select as Best AnswerUndo Best Answer

user
Goodhart (author)Kryptonite2009-12-02
Thanks,  I had looked through some of the links I'd found but came up just as short.
 

Select as Best AnswerUndo Best Answer

user
Kryptonite (author)Goodhart2009-12-03

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

Select as Best AnswerUndo Best Answer

user
lemonie (author)2009-11-28

You pronounce him "oiler" don't you?

L

Select as Best AnswerUndo Best Answer

user
NachoMahma (author)lemonie2009-11-29

.  I would have thought it was pronounced ewe-ler, but, according to Wikipedia, that is incorrect.
.
.  "His surname is pronounced /ˈɔɪlər/OY-lər in English and [ˈɔʏlɐ] in German; the common English pronunciation /ˈjuːlər/EW-lər is incorrect."

Select as Best AnswerUndo Best Answer

user
NachoMahma (author)NachoMahma2009-11-29

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

Select as Best AnswerUndo Best Answer

user
Goodhart (author)lemonie2009-12-02
If it had the ü sound, it would be more like  ewYoo but as one syllable (I think). 
 

Select as Best AnswerUndo Best Answer

user
Goodhart (author)lemonie2009-11-28
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 :-) 
 

Select as Best AnswerUndo Best Answer

user
Kiteman (author)2009-11-28

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


Select as Best AnswerUndo Best Answer

user
NachoMahma (author)Kiteman2009-11-28

.  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.

Select as Best AnswerUndo Best Answer

user
Kiteman (author)NachoMahma2009-11-28

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

Select as Best AnswerUndo Best Answer

user
Goodhart (author)Kiteman2009-11-28
Here is a little history that kind of backs up what you were saying.
 

Select as Best AnswerUndo Best Answer

user
Goodhart (author)Kiteman2009-11-29
UGH!  Someone stole my link !  :-)   Looks like I forgot to include it: so here it is now....
 

Select as Best AnswerUndo Best Answer

user

I'm kid of surprised they don't use a hoop.

Select as Best AnswerUndo Best Answer

user
NachoMahma (author)Kiteman2009-11-28

.  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?

Select as Best AnswerUndo Best Answer

user
Goodhart (author)NachoMahma2009-11-28
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. 
 

Select as Best AnswerUndo Best Answer

user
NachoMahma (author)Goodhart2009-11-28

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

Select as Best AnswerUndo Best Answer

user
Goodhart (author)NachoMahma2009-11-28
No, it's ok to bat things around; I am not so informed on the subject, or I wouldn't have asked about it ;-) 
 

Select as Best AnswerUndo Best Answer

user
lemonie (author)Kiteman2009-11-28

I'd agree with the mass aspect.

L

Select as Best AnswerUndo Best Answer

user
PKM (author)2009-11-28

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.

Select as Best AnswerUndo Best Answer

user
Tool Using Animal (author)PKM2009-11-28

Here's a link where the give the dimensions of the "coin".
http://www.officeplayground.com/Eulers-Disk-P741.aspx

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....)

http://www.eulersdisk.com/rollingdisk.pdf

Select as Best AnswerUndo Best Answer

user
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.
 

Select as Best AnswerUndo Best Answer

user
caitlinsdad (author)2009-11-28

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.

Select as Best AnswerUndo Best Answer

user
Goodhart (author)caitlinsdad2009-11-28
Yeah, I was wondering about that.
 

Select as Best AnswerUndo Best Answer

user
NachoMahma (author)2009-11-27

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

Select as Best AnswerUndo Best Answer

user
Goodhart (author)NachoMahma2009-11-27
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? 
 

Select as Best AnswerUndo Best Answer

user
NachoMahma (author)Goodhart2009-11-27

.  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.

Select as Best AnswerUndo Best Answer

user
Goodhart (author)NachoMahma2009-11-27
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).
 

Select as Best AnswerUndo Best Answer

user
NachoMahma (author)Goodhart2009-11-28

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

Select as Best AnswerUndo Best Answer

user
Tool Using Animal (author)2009-11-27

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.

Select as Best AnswerUndo Best Answer

user
Goodhart (author)lemonie2009-11-27
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.
 

Select as Best AnswerUndo Best Answer

user
Goodhart (author)2009-11-27
This is an honest question :-)
 

Select as Best AnswerUndo Best Answer