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Making a flip clock count backwards in seconds

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    Making a flip clock count backwards in seconds

    Hi all - my first post here and a weird one.
    For a film based in the sixties, they need as a suspense building prop, a large flip clock that is at least 6 digits long (HH:MM:SS) and that is also required to count DOWN to doomsday in seconds. Now before you all point out that counting in seconds will be noisy and it'll wear out the mech in no time, please just remind yourself that this is film and everything in films is just pretend and very temporary! OK? This will only have to work for an hour or two whilst being filmed. Nothing on the market I'm sure that does this? Obviously you can't just turn the motor backwards as the flaps move down by gravity and where I live at least, gravity works strictly top to bottom. A stylish Cloudnola clock has been bought to experiment on with the possibility of adding another (unlinked) to the left to give days and hours.
    https://www.cloudnola.me/product-page/flipping-out-bs
    I initially thought that I could simply remove all 60 of the minutes flaps from the drum & reassemble them in reverse order. However this won't work as they're all printed double sided and the tops and bottoms of characters won't match if they've been put out of their original order. So I'm thinking that one side of each flap at least would have to be reprinted - vinyl lettering or something which is very tedious but I suppose doable. Being battery powered, I also initially thought that this clock would contain some kind of simple impulse motor driven by a pulse every 60 seconds. Wrong again as the purpose made motor is synchronous, spinning continuously from an 8 Hz sine wave produced from a battery powered tiny electronics module stabilised with a quartz crystal. To make the clock count in seconds, everything needs to be running 60 times faster than the original design. Being electronics minded, I tried feeding in a variable frequency sine wave from a signal generator directly into the motor coil but found that the motor only works over a fairly narrow frequency range of about 5 - 40 Hz. I need it to run on 480 Hz so it's still spinning way too slow. The motor is followed by a cascade of six tiny nylon gears to bring the final minutes spindle speed down to 1 Rev Per Hour. I hoped I might be able to reverse the order of some of some gears but they're all different sizes so this isn't possible either. I think the gear train would have to be re-engineered which I'm not too keen on as I've never yet managed to so much as drill a hole in exactly the right place & these things are very tiny so machining accuracy would be critical.

    For the curious I'm including some pictures of the clock, its components and closeups of the motor mech. The motor assembly fits into a circular well in the central support column which also contains the D size battery.

    So I'm wondering if anyone has ever heard of such an extreme level of electro-mechanical customisation that is required for such a project or is there any clock available that is driven by a simple solenoid mechanism that can be jabbed at one sec intervals with a simple switch rather than a continuously running motor? Thanks if you can help.

    #2
    It seems there are various sellers of the same clock & guess what I've found out? The seconds flaps are just decorative and not motor driven. I guess you can flip them round with your fingers to whatever you fancy. I had wrongly assumed with flip clocks that they'd have a solenoid driving some kind of simple ratchet & pawl mech which would have suited me ideally. I realise now that although this would be simpler to manufacture, assemble and align than spinning motors and long trains of gears, it would likely make a significantly loud clunk every minute. Also it could make for a very peaky power draw if it's battery driven which may not be good for battery life. The Cloudnola clock is extraordinarily quiet. You barely notice each flip unless you're very close to it and only by pressing the frame hard against your skull do you sense a very gentle whirring of the motor spinning at just 480 RPM. It looks like the same mechanism contained in the central pillar is used for many other modern flip clocks. One thing that does me make ponder is the longevity of this design? There are precision aligned hard scratchy steel hooks restraining the tops of the flaps which are made of soft ABS plastic and which are already looking scored from slowly scraping past the hooks. Has anyone worn a modern flip clock out yet?

    Anyway it's back to the drawing board for my project and this has been a useful learning experience. I would suggest to the film people a rotating drum type clock like the old fashioned car odometers. My first choice would be a nixie clock which would be spot on for early sixties period and very easy for me as I do have one already but they tell me it has to be large as they want it to be visible across a big room.

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      #3
      Yeah I almost fell off my chair when I read the seconds flaps are "decoration" on the Amazon clock!

      I have just found from China on ebay some truly tiny stepper motors with a worm gear on the output shaft. This looks very useful as I may be able to mount one sideways in the very shallow space available where the original motor was in the Cloudnola so that the worm meshes with the cog driving the main flap shaft. Worm gears are good as they right angle the output drive so can be overall much shorter than a motor with in line gearbox. Steppers too are good - very accurate and controllable. It may be too late for this project though but worth doing for the future. Looks like I'd still need to reprint all the flaps for backwards counting though which is a real downer.

      Another nixie fancier? You're very lucky to have Z568M tubes. There's a talented fellow making modern reproductions of them now but for serious money. I've bought quite a few nixie clock kits myself and a couple of sets of IN18s for about the price you mention and although I've built various smaller clocks, I still haven't got around to building those particular tubes into anything yet. I really wish I'd thought ahead only a few years ago when boxes of 25 of IN18s from Ukraine were FAR cheaper than they are now. I wonder if the Russian military are still selling these off for very little money to those in the right place at the right time? Of course the ultimate tubes are the 6" tall CD47s but they come onto the market once every few years and the last lot to appear on ebay were snapped up for 800 something Euros EACH. For nixies in film use, because they need the option of quickly jumping to preset times, pausing and the option of both up and down counting, none of the commercial kits allow this flexibility so I have to design and build my own nixie driver controlled from a GUI running on a laptop. Works well but tedious to build.

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