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ChuckMcMlast Wednesday at 9:09 PM12 repliesview on HN

Worst D-4 ever! But more seriously, I wonder how closely you could get to an non-uniform mass polyhedra which had 'knife edge' type balance. Which is to say;

1) Construct a polyhedra with uneven weight distribution which is stable on exactly two faces.

2) Make one of those faces much more stable than the other, so if it is on the limited stability face and disturbed, it will switch to the high stability face.

A structure like that would be useful as a tamper detector.


Replies

ortusduxlast Wednesday at 10:15 PM

You jest, but I knew a DND player with a dice addicting that loved showing off his D-1 Mobius strip dice - https://www.awesomedice.com/products/awd101?variant=45578687...

For some reason he did not like my suggestion that he get a #1 billard ball.

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schiffernyesterday at 5:59 AM

  >useful as a tamper detector
If anyone's actually looking for this, check out tilt and shock indicators made for fragile packages.

https://www.uline.com/Cls_10/Damage-Indicators

https://www.youtube.com/watch?v=M9hHHt-S9kY

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cbskslast Wednesday at 10:07 PM

The keyword is "mono-monostatic", and the Gömböc is an example of a non-polyhedra one: https://en.wikipedia.org/wiki/G%C3%B6mb%C3%B6c

Here's a 21 sided mono-monostatic polyhedra: https://arxiv.org/pdf/2103.13727v2

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jayd16last Wednesday at 11:38 PM

I imagine a dowel that is easily tipped over fits your description but I must be missing something.

tlbyesterday at 8:29 AM

If you're not limited to a polyhedron, a thin rod standing on end does the job.

A rod would fall over with a big clatter and bounce a few times. I wonder if there's a bistable polyhedron where the transition would be smooth enough that it wouldn't bounce. The original gomboc seemed to have its CG change smoothly enough that it wouldn't bounce under normal gravity.

ErigmolCtyesterday at 6:50 AM

Sort of like a mechanical binary state that passively "remembers" if it's been jostled

gus_massalast Wednesday at 11:21 PM

A solid tall cone is quite similar to what you want. I guess it can be tweaked to get a polyhedra.

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Evidlolast Wednesday at 9:51 PM

> A structure like that would be useful as a tamper detector.

Why does it need to be a polyhedron?

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nancysmith865last Wednesday at 10:07 PM

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