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# Yo-Yo Clock

Instead of a pendulum, timing is done with a yo-yo.
 (+6) [vote for, against]

A regular yo-yo, except the string is run through the dowel, not around, so it rewinds automatically.

Clock hand advancement is done at the bottom of the yo when the string is pulled by the start of the rewind, which is also when the extra bit of energy is dumped into it to keep it yoyoing.

 — FlyingToaster, Jul 18 2016

 // the extra bit of energy is dumped into it to keep it yoyoing. //

How ?
 — 8th of 7, Jul 18 2016

 With great aplomb. Look, I was too lazy (just off to bed) to calculate string length when I posted it, what makes you think I'm gonna do stuff with momentum ? The fact that you can make a regular yoyo wind itself up faster than it unwound means it's possible.

The point is "yoyo clock". :)
 — FlyingToaster, Jul 19 2016

But can you make it walk the dog?
 — RayfordSteele, Jul 19 2016

This would be brilliant. [+]
 — MaxwellBuchanan, Jul 19 2016

 Well, yes; not terribly accurate of course: the timing gets bollixed up a bit since the string rewinds itself a bit differently each time, though it should average out, more or less.

The jerk at the bottom releases a pawl, which (business as usual) allows the sprung second-hand gear to advance, but also trips a mechanism to yank the string up a bit (subsequently the string is lowered back down, at a rate not exceeding the take-up on the dowel, during the yo-yo ascent). The slight bit of rotational momentum lost at that moment is more than made up for by the vertical momentum added (the overage balancing out the various frictions).
 — FlyingToaster, Jul 19 2016

I'm imagining, since energy isn't a problem here, a robotic arm. The ticking is shown by standard play with some tricks randomly thrown in for boredom control. If asked the time,the arm displays time by the angle of throw.
 — wjt, Jul 21 2016

Like [wjt]'s suggestion. Have it simultaneously chewing gum with a simulated baseball cap on some obtuse angle.
 — RayfordSteele, Jul 21 2016

 // The jerk at the bottom //

A Democratic voter, presumably …
 — 8th of 7, Jul 21 2016

well now I want to see robots do yo-yo tricks
 — 2 fries shy of a happy meal, Jul 25 2016

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