
The story of the Gömböc  - ignifero
http://plus.maths.org/content/story-goumlmboumlc
======
jbyers
If a Gömböc is built to 10 micron tolerances, does that mean I need a
cleanroom and the world's flattest table to be assured it will work?

~~~
ori_b
According to Wikipedia, yes:

 _The balancing properties of a gömböc are affected by mechanical defects and
dust both on its body and on the surface on which it rests. If damaged, the
process of restoring the original shape is more complex than producing a new
one._

~~~
mishmash
So do the self-righting properties simply degrade or fail completely, if say
an eyelash drops on it?

~~~
jgmmo
The self-righting properties degrade in imprecise environments -- from the
level of "100% mathematical certainty it can right itself" -- to something
sort of absolute mathematical certainty. Not from self-righting to complete
failure.

Dropping an eyelash on it, and using a standard kitchen table probably won't
make it fail, and it will probably still work -- but it does impact it at the
theoretical absolute level.

------
zdw
Hmm... you can buy a variety of these starting at €119 here:

[http://www.gomboc-
shop.com/app/urwfilter/catalog/do/action/S...](http://www.gomboc-
shop.com/app/urwfilter/catalog/do/action/SubmitCatalogSearch/mainCategoryId/1/subCategoryId/2/makeId/-1/sortingList/5/sortingList/11/minPrice/0/maxPrice/0/index.html)

------
mattme
I've played with one. Domokos gave a lecture at Trinity College, Cambridge.
Most ways that you place it, it behaves unremarkably, but there's one way of
placing it such that it rocks back and forth and has almost settled down to
the almost-stable point when it falls over perpendicular and ends up at the
single stable point. This is the way to demonstrate it.

------
Unseelie
I'm interested in the tolerances on that 10 micron distance...if you could
build an approximation that works most of the time with much less precision,
then you might be able to make sale-able objects that do such...

~~~
pavel_lishin
> if you could build an approximation that works most of the time with much
> less precision, then you might be able to make sale-able objects that do
> such...

They're called turtles.

[http://www.naturalhistorymag.com/biomechanics/10309/the-
livi...](http://www.naturalhistorymag.com/biomechanics/10309/the-living-g-
mb-c)

~~~
phlux
I am surprised we dont make ships with this general shape.

~~~
hugh3
Why? So they'll right themselves if they're capsized? If a ship (not a boat)
capsizes you've got pretty serious problems already.

Besides, self-righting is a very different sort of problem when you're
floating.

~~~
Someone
It is fairly standard for lifeboats to be self-righting. Google "self-righting
boat" for examples. The typical shape is not a gömböc, though. A gömböc would
self-right, even when completely under water.

~~~
hugh3
I'm sure a gomboc would self-right when completely underwater, but what about
a floating gomboc half-submerged? Different problem.

~~~
euccastro
Also, ships are not solid (as in 'filled'), let alone uniform in density. On
top of that, hydrodynamics imposes more important constraints on shape. You
can make a ship pretty stable by loading its keel heavily.

------
kgp7
There is an episode of QI : <http://www.youtube.com/watch?v=XCAg5_vHFmI> where
in they discuss about this , and also a brief interview with the mathematician
involved.

------
hop
If anyone can find a cad model, I'll machine one out of aluminum or print an
SLA.

~~~
zdw
Would be OK for personal use, but for commercial production it looks like
they've put a variety of legal protections on the shape/design of it:

[http://www.gomboc-
shop.com/app/urwfilter/license/do/action/S...](http://www.gomboc-
shop.com/app/urwfilter/license/do/action/ShowForm/index.html)

So much for not being able to patent math.

~~~
pavel_lishin
How fault tolerant are they? What if I made one to within 100 microns - I
imagine it would still self-balance itself pretty well, and that specific
shape would probably not be covered.

------
tejask
I can see possibilities of simulating a Gomboc surface on the back of a four-
legged robot. However, the robot will either need small "legs" or some servo's
to bring the "legs" inside the body (like a turtle) to correct its position

~~~
Deestan
You'd have to recalculate the shape after that, as the interior density is no
longer uniform.

~~~
tejask
Yes, you are right. Given this consideration, I think maybe the surface needs
to be configurable? Not sure but it will be pretty complicated to dynamically
adjust to changing density.

------
rbanffy
Am I the only one who thought about food?

~~~
rbanffy
If you don't speak Hungarian you could just reply "yes".

<http://www.google.com/search?q=gomboc+food>

~~~
lkozma
Nice :) But still, there is a bit difference with or without the umlauts on
the o's:

there's gombóc (=dumpling), probably from gomb (=button, knot) plus
diminutive,

and

gömböc, from gömb (=sphere) with diminutive. "Kis gömböc" is the "meatball"
that eats up everyone, until he bursts, in an old folk tale, probably the
source of the name here. Ultimately I guess both words are from the same root.

<http://www.google.com/search?q=A+kis+g%C3%B6mb%C3%B6c>

<http://en.wiktionary.org/wiki/gomb%C3%B3c>

------
MaysonL
interesing variation in reactions to previous postings:
[http://www.hnsearch.com/search#request/all&q=gömböc&...](http://www.hnsearch.com/search#request/all&q=gömböc&start=0)
and
[http://www.hnsearch.com/search#request/all&q=gomboc](http://www.hnsearch.com/search#request/all&q=gomboc)

------
gnosis
There's a scifi story begging to be written about building a perpetual motion
machine or trying to generate energy from an unbalanced Gömböc.

------
jolleon
Isn't a sphere with it's centre of gravity shifted from it's geometrical
center a gömlöck ?

------
phlux
> _Gömböcs are not much to look at, and seem like they could be children's
> toys. Don't try to buy one, though. They're actually upwards of a thousand
> dollars each. They may look like they were knocked together in a toy shop,
> but the different angles and proportions have to be measured to within ten
> microns – one tenth of the thickness of a human hair - to make the shape
> work. So it's unlikely anyone will get to use one as a paperweight._

Sounds like the best reason to makerbot these things.

~~~
ent
Sounds like the best reason one can't makerbot these things. Makerbots have a
nozzle size of 0,5mm according to the makerbot wiki.

------
Geekette
Oh, that. I know it by its more common name/appearance; a lump of bocconcini
cheese. :) At least that's what immediately came to mind.

