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I am wondering if anyone knows of an active forum with discussions about designing clocks? There used to be a wooden gear clock forum, but it seems to have died out. NAWCC has a forum that focuses on collecting and restoring old clocks. There is very little discussion about designing clocks.
Perhaps we can turn this into an active forum for discussions.
I am interesting in learning how to design a perpetual calendar watch/clock mechanism, but could not find any source to read or study.
I am currently trying to reverse engineer the MB&F perpetual calendar. Would any one be interest in collaborating?
That sounds like a good idea. I would be willing to contribute. There appears to be at least a few other active clock designers on this site. Maybe a few of them would also join in.
A perpetual calendar seems like it should be possible to add on to a clock. I recall having a windup wrist watch with the function. The day of the week should be easy. Just divide the hour hand by 14 and click to a solid position. The simplest solution for the day of the month is just a divide by 31 function. I had to advance the time manually during the short months, although it may not be too difficult to properly advance the days at the end of each month. Skip the complexity of leap years and the clock would be off by one day every 4 years. Add the simple leap year complication and it would only be off one day every 100 years. These functions take place at an extremely slow pace so they would not impact the run time of the clock.
Sounds good Steve. I hope more people join in on the project.
Yes, the day of the week is easy. Now need we need to keep track of the day of the year, day of the current month, the current month of the year, the year and if it is a leap year or not. I have heard that most perpetual calendar mechanism have 31 days in a month and then subtract from this the appropriate number of days for each month.
The MB&F is based upon a 28 month days and add the appropriate number of days. This approach is what I trying to reproduce. Search you tube for MB&F perpetual calendar and some animation videos on how this system works should appear. I watched the videos many time and have a gist of how the system works, but to put it down in a functioning design will not be easy. Attached is an imagine of the mechanism.
Here is another style of design with a 48 month leap year cycle https://www.youtube.com/watch?v=YERho3Q4Abo
I am trying to imagine an even simpler mechanism. Stack 3 cams on the same shaft. The first cam rotates once every 24 hours and allows a lever to drop up to 4 positions every night at midnight. The second and third cams limit the depth that the lever can drop. The second cam rotates once every 31 days. The depth is 1 position deep on most days, 4 positions deep on the 28th and 2 positions deep on the 30th. The third cam rotates once per year but only advances in steps on the 27th and 29th days.
The combinations of all three cam depths determines how many days to advance the calendar. Days 1 through 27 will only advance by 1 day because of the second cam. The second cam will allow an advance of 4 days on the 28th only if the third cam allows it in February. All other months will be limited to a single day advance on the 28th by the depth of the third cam. Another decision is made on the 30th day. The third cam allows for 2 days of advance during some months and only 1 day advance on the rest.
Thanks Steve. I came across that video before and skipped over it since it was one of those that skipped over days in months with less than 31 days, but now I think this version may be easier to reverse engineer since the parts are all out in the open to see.
Having no background in mechanical design, I am not following you proposed mechanism. If it works and simplify things I am all for it.
The idea was just a rough design that would need some additional work.
There is also a design called a Brocot perpetual calendar that also looks promising. The clock has 3 dials for the day of the week, day of the month, and month.
This seems like a concept that will be in the back of my mind for a while. Sometimes a really elegant solution emerges.
Here is another video of a perpetula calendar
The Lisa Boyer website sell a perpetual calendar plan, with levers and gears, for wood construction.