I would like to build a clock where the face rotates. Imagine a standard clock, but instead of hands pointing to the hour, there would be a rotating face plate with a small window, as it were. The face plate would obscure everything except the current hour, which would be visible through the window. If it makes any difference, I need it to be a 24-hour, not a 12-hour, clock.

I have considered buying a 24-hour high-torque clock movement (because I'm not interested in building the actual gears, etc.), but I get the impression that it would be hard to attach anything to it other than standardized clock hands. I could try to glue the face plate onto the hour hand, but I don't know if that would hold effectively.

Any ideas?

Thank you. (Also, if this isn't the right forum, please send me in the right direction.)

  • $\begingroup$ the better balanced your load is the less torque you will need $\endgroup$ Sep 20 '17 at 18:38
  • $\begingroup$ How are the clock hands fastened? $\endgroup$
    – JMac
    Sep 20 '17 at 19:48
  • $\begingroup$ How about mounting the face on a centre bearing and using a small motor / clock gear to drive via the rim either inside or outside? $\endgroup$
    – Solar Mike
    Sep 20 '17 at 20:10
  • $\begingroup$ Take a look at Klokers' wristwatch. They beat you to it. klokers.com/en/12-klok-01 $\endgroup$ Sep 21 '17 at 17:21
  • $\begingroup$ there should be no issue for an off the shelf clock mechanism to turn a full disk. (google "24 hour clock kit" ). The main issue with the concept I see is getting your disk aligned so it never touches anything. Friction will kill it. $\endgroup$
    – agentp
    Sep 22 '17 at 20:16

With the disks light enough, mounting (gluing) them to the clock hands (trimmed short enough not to obscure the disks) shouldn't pose much of a problem.

Print the disks on transparency (transparent foil for overhead projectors; printable with inkjet or laser, be sure to pick the type that matches the printer you have), obscuring (printing over) everything that's not supposed to show, leaving the windows unprinted (transparent) plus a ring on the bottom disk to let the top disk's window "see through" all the way down to the fixed face plate with the digits (you can print that one too). Carefully cut the transparencies to shape, detach the clock hands (they are usually push-on, plain friction / tight fit mount), cut short not to obscure the windows and paste them to the reverse side of the transparencies, then mount on the clock. With each disk weighing about a gram, and being a centered weight, they won't affect performance of the clock in the least.

If you want the windows to be immobile and the number dials to turn instead, you need to print three disks: bottom with hour numbers, middle with minutes and a transparent ring to reveal the hours beneath, and topmost which would be larger than the two, affixed to the clock case, with the windows.

  • $\begingroup$ Aha! This looks like a very practical solution. Thank you for breaking it down into these steps; it's really helpful for me. $\endgroup$
    – Théophile
    Nov 29 '17 at 3:23

Could it be over engineered to ridiculous levels? Perhaps costly, but there would be major advantages.

  • Faceplate of any size. Mounted directly onto a stepper motor so easily adequate torque for all conceivable plate sizes. 400 steps per revolution.
  • Add a belt drive and reducing wheels for even more resolution.
  • Controlled by an Arduino and motor controller. Mains powered so no batteries.
  • Add a GPS receiver for infinitely accurate time keeping.
  • Can probably download all the necessary code as someone's already done each bit of this.

Too silly?

  • $\begingroup$ Thank you for your answer. It looks like an Arduino would do the trick, although I wish there were a simpler, self-contained way to do it... $\endgroup$
    – Théophile
    Nov 28 '17 at 18:36

Mount a very balanced, VERY flat set of disks (one for hour, one for minute) to the hour and minute shafts. The lighter and thinner the disk is, the better. Clock hands don't weigh very much. You could prototype using some aluminum foil.


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