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Hourglass Mechanical Clock

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Instead of a pendulum escapement, this mechanical wall clock uses a sand-filled hourglass timer that lasts one minute, and when the sand has all fallen it updates the display and inverts the timer to count the next minute.

In order to explain how it works, I have to talk a little about physics. Imagine an hourglass that's just been inverted, sitting on a weighing scale. With the sand falling, but not yet hitting the bottom of the glass, there are fewer grains in contact with the glass, so it appears to get progressively lighter. When a grain of sand hits the bottom, it delivers an impulse equal to the gravitational potential energy it had. So for most of the time it's operating, the continuous stream of sand delivers a force exactly equal to the weight it apparently lost at the beginning, and the hourglass appears to weigh its usual amount. As the timer approaches the end, it stops losing weight to the falling grains, but continues to receive impulses at the bottom, so the whole hourglass momentarily appears heavier.

That last sentence is the important one: when the timer finishes its run, there is a sudden spike in its weight. This is only a tiny increase (determined by the weight of sand 'in flight' during operation) but nonetheless detectable.

Hence, the Hourglass Mechanical Clock has its hourglass on a balanced arm, with a sensitive hair trigger listening for that signal pulse. When the mechanism fires, the minutes of the display rolls over, the arm twists to invert the timer, and the hair trigger is cocked again. All powered by a falling weight, of course.

mitxela, Feb 22 2016

Another interesting solution https://www.youtube...watch?v=3cJdUz4Lan8
[pashute, Feb 25 2016]

similar to what I wrote https://www.youtube...watch?v=0EKnJAbUgXo
Except that mine words mechanically [pashute, Feb 25 2016]

Wheel affected by flow http://thumbs3.ebay...3DCTRD5bqbg95FQ.jpg
This timer uses flowing liquids instead of sand, but has a feature relevant to an alternate version of this Idea. The falling sand could turn a little wheel and the wheel could connect to a normal clock-face mechanism. Two such wheels and associated mechanical connections would be needed, of course. Other things could be similar to things already described in this Idea. [Vernon, Feb 27 2016]


       Very clever. Can I get one with a wrist strap?
whatrock, Feb 22 2016

       maximum observed mass delta = (mass of total sand load) x sqrt( (2 x drop distance)/(acceleration of gravity) ) / (total time duration of hourglass)   

       ([+] sign that doesn't fit in equation)
lurch, Feb 22 2016

       Interesting. Presumably it would weigh slightly less during the interval while sand is falling but hasn't impacted.
AusCan531, Feb 22 2016

       The device will be susceptibe to changes in gravity (i.e. tidal pull) but these would even out in the long term. Short-term errors could be qute high.
8th of 7, Feb 22 2016

       This is an awesome idea. I have a microgram balance, and if I can find an egg-timer...
MaxwellBuchanan, Feb 22 2016

       [+] Where everybody see sand falling, you see a complex timer.
piluso, Feb 22 2016

       Easier: The lower part (B) is detached from the upper part (A) and held in position with a lever (L) holding a weighted balance (w).   

       There's a permanent glass funnel (F) in between the two parts.   

       When the bottom part (B) is full its weight is above the balancing weight at the end of the lever (L), causing it to tip down and out of place, which mechanically flips the sand clock parts, so (B) is now the upper part and (A) is the lower part. The permanent funnel is still between the two.   

       The lever movement also moves the clock hands.   

       .........\ a /
........./ b \
........../ - the lever
pashute, Feb 25 2016

       [pash] Although that might work, the problem is that the hourglass isn't sealed any more, which means it's open to the air, and as I understand it, humidity has a huge effect on the speed the sand is falling.   

       Interesting video though.
mitxela, Feb 27 2016

       Trying to get my brain to decipher the methodology behind this clock is like trying to get two fists full of peanut butter down my throat in one swift swallow. In other words...it ain't happening.   

       However, after viewing the links I have a somewhat clearer picture in my head. Thanks to [pashute] for bringing this to clarity. A + for the idea, [mixie].
blissmiss, Feb 27 2016

       So many good ideas lately.
I like this one, very... surreal. I likey long time.


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