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Author Topic: Moon Dial  (Read 474 times)
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John T
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« on: January 12, 2020, 09:51:44 AM »

I'm wondering if anyone has some good ideas on correctin g my moon dial-
The "facts as I am working with them are:
1 I am working with only two arbors spaced 3.75 inches apart. (This is a design limitatio n for this clock)
2 The mean moon period I'm working with is 29.5 days
3 I have two shadows that provide waxing and waining or the moon
4 With the two shadows I need 59 increment s based on 24 hours or since I'm driving off a 12 hour wheel so I need 118 increment s.

The problem is I need the Moon Dial to move in 118 discrete  increment s for a complete full moon cycle and a pinion of one tooth or actually a pin in my case.  Currently the pin engages the moon dial for too long and the pin causes the moon dial to too much (3 teeth instead of 1). 

The only solution i can think of is to have the driving pin at 0.2 inches from centre on the hour and the 118 tooth moon dial. 

Gearotic will only go down to 4 leaves so my 0.2 is still only an estimate.  Art could you allow 1 tooth (pin) as a minimum on a pinion?  The best I can get with Gearotic is 4 leaves as shown in the photo.
Any other ideas?


* MoonDial.jpg (19.64 KB, 78x75 - viewed 69 times.)
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Mooselake
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« Reply #1 on: January 12, 2020, 10:54:46 AM »

I vaguely remember something about stripping teeth in the past but not if it was all or nothing.

Would it be cheating if you made that pinion bigger (those look like pretty spindly teeth) and then applied a file or scroll saw to all but one of them?

Kirk
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ArtF
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« Reply #2 on: January 12, 2020, 11:00:50 AM »

Hi:

  You could just load the DXF of a 4 tooth in Vexx, and cut off 3 teeth.
You can extrude in vexx if its an STL requireme nt...

Art
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Mooselake
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« Reply #3 on: January 12, 2020, 11:03:41 AM »

For a random thought, would a geneva work?

Kirk
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John T
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« Reply #4 on: January 12, 2020, 02:21:12 PM »

Thanks for the ideas.  I looked at a Geneva but 118 “tooth” Geneva is beyond my abilities to cut
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