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My friend

Are you asking me about how things in watches work.....? I haven't even worked out how to change bracelets yet.

Anyway while it doesn't quite answer your question, though it may, here's a couple of related articles from the same author who we must find a way to invite to WTF.


http://www.geocities.com/mtflight/theproject/project5b.htm

http://www.geocities.com/mtflight/theproject/VJ7751b.htm


Be well now


ZIN
Hey Zin,

These are fantastic articles by a great horological mind. The work involved in adding the moon phase indicator to the Valjoux 7751 is particularly fascinating.

However, the relevant section in these articles for MrTimefinder is at the end of the 2nd article where the author talks about the real moon phases: A true moon cycle is 29 days, 12 hours, 44 minutes and 3 seconds. Really simple movements will simply have a moon phase indicator that cycles every 30 days. In the Valjoux 7751, like most middle-to high end movements there is a 59 tooth cog that cycles every 24 hours. This gives two moon phases every 59 days (moon phase display split into two) and therefore a moon phase of 24 days and 12 hours (24.5). This is clearly inaccurate by 44 minutes and 3 secs every moon cycle. The real grail for high end movement manufacturers is to create a perpetual moon phase display (usually with a perpetual calendar which has it's own complications) which removes this inaccuracy.

To do this is simply a case of adding more cogs to the movement to create the correct ratio of 1:24.530588 instead of 1:24.5 used in the Valjoux 7751.

Hope this helps,
 

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These things are usually too technical for me.... ;)

I agree about the perpetual moon phase display - that would be something alright :thumbup1:

Another question - aesthetics apart, who buys Moonphase watches anyway?

That said, Alex has done an amazing job though - I am truly staggered.


Be well pal


ZIN
 
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