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

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.

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

n8man8 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.
n8man n8man8 years ago
 Through the wonders of Google and Wikipedia, I found out that it is called a rattle back, more on it here
Goodhart (author)  n8man8 years ago
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. 

n8man Goodhart8 years ago
 Those are called rattlesnake eggs. I don't think I have any but that is what they are usually called.
Goodhart (author)  n8man8 years ago
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.
n8man Goodhart8 years ago
 The ones I have seen have been called that or buzzing magnets. What were yours called?
Goodhart (author)  n8man8 years ago
Kryptonite8 years ago
Wow, no matter how hard I look i can't find anything better than <-- 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.
Goodhart (author)  Kryptonite8 years ago
Thanks,  I had looked through some of the links I'd found but came up just as short.
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