How can one alter a common analog quartz clock mechanism to do 13 hours or decimal time? One can create a mechanism from scratch with garage tools, but that's still not nearly as accessible as tinkering with the gears inside clock mechanisms that one can find at a hobby shop.
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$\begingroup$ I take it you don't want to swap out the timing cap for one that changes the pulse rate? That's the easiest way. Otherwise, you'll need to swap a gear with N*12 teeth for one with N*13 teeth, for example. $\endgroup$– Carl WitthoftCommented Feb 8, 2022 at 13:10
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$\begingroup$ Changing the pulse rate is the easy part. The harder part is altering the ratio between the hour hand and minute hand. Once the hour hand rotates 27.923 degrees per complete rotation of the minute hand (13-hour dial), then I can decide how long the pulse interval should be. $\endgroup$– FrotzCommented Feb 8, 2022 at 21:11
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$\begingroup$ In principle, you change the ratio of gears. In practice this is hard to implement as finding just the right size of gears is unlikely and the centers of rotation would change with gear size. $\endgroup$– Eric SCommented Feb 8, 2022 at 21:18
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Look in the clock and see if you can see and remove the crystal. They're usually 32.768 kHz. That frequency is an integer power of two so it's easy to generate a 1 s clock by division $ \frac {32768}{2^{15}} = 1 $.
Have a look in the electronics catalogues for crystals with the relative frequency you require and try them out. If you're lucky the oscillator may be able to lock in on the new crystal frequency.
Figure 1. Note the number of options for a 32.768 kHz crystal from Farnell compared with the nearest values below and above.
answered Feb 8, 2022 at 15:52
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$\begingroup$ I edited the subject to make it clear that I'm talking about an analog movement. I'm trying to figure out what I need to do to make the hour hand turn a thirteenth (or tenth) of a turn per complete turn of the minute hand. $\endgroup$– FrotzCommented Feb 8, 2022 at 21:15
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$\begingroup$ I am talking about an analog movement too. They're all crystal frequency controlled. The frequency divider gives one-second pulses and that's why the second hand moves in 60 steps per revolution. "* I'm trying to figure out what I need to do to make the hour hand turn a thirteenth (or tenth) of a turn per complete turn of the minute hand.*" Forget that. I'd say you are very unlikely to be able to change the gearing of one hand relative to the others unless you are a whizz at making miniature gears. With the crystal modification no modifications to the gearing is required. $\endgroup$ Commented Feb 8, 2022 at 22:13
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$\begingroup$ For 1 revolution of minute hand you'll have to change the gearing of the hour hand movement ratio and stay inside the geometrical confines of the current movement. You may have to generate your own gears, and fabricate them to accomplish this. Maybe check on line for watchmakers supply houses. You'll likely have to ream out volumetric clearance for the alternate gear set (as long as it doesn't impact adjacent pivot points). Maybe spread out gears, make your own housing, and separate minute and hour pivots. $\endgroup$ Commented Feb 9, 2022 at 16:18