Reply With QuoteWhat a great post and a fascinating timepiece.
I tip my virtual hat to you Sir, bravo. Any chance of a video of it running?
I've mentioned this in passing, but thought it worthy of a thread.
Traditional Japanese timekeeping divides daytime into six equal measures between sunrise and sunset, and nighttime into six different equal measures. During the Edo period (1603-1868), Japanese clockmakers designed a double escapement mechanism that could allow mechanical clocks to follow this uneven seasonal pattern. These are known as wadokei.
Otona no Kagaku produce a rather nifty kit to construct a modern version of a mechanical double-foliot clock based on these early Japanese designs. Naturally this is right up my street.
The instructions that arrived with the kit were in Japanese but they helpfully provide a link to the instructions in English: https://www.adafruit.com/datasheets/...leclockkit.pdf
There are a fair number of parts, I took my time in an attempt to learn about the mechanism.
Here's the body going together with mainspring assembly on the right.
It's a mainly plastic kit, but very nicely made nevertheless.
Here are the two foliot units (large for day hours and small for night hours).
The completed foliot assembly.
And the foliots attached to the main unit. The string is used to adjust their heights so that they sit just above the ratchet pawls which lift the night foliot away from the escape wheel during day hours, and vice versa.
The complete clock, ready for adjusting. The hand needs to move from the "9 o'clock" position to the "3 o'clock" position during daylight hours and then on round to the "9 o'clock" position during the night. First the hand needs setting so that it points directly left and directly right when the ratchet pawls trigger.
Then it gets more complicated. Daytime hours in Bogotá are near enough 05:30 to 18:30, giving 13 hours of daylight and 11 hours of night. Fortunately there is not much seasonal variation as we are close to the equator so I don't need to worry about adjusting it on a regular basis. I need the hand to move clockwise from directly left to directly right during a 13 hour period by adjusting the weights on the day (upper) foliot. The weights on the lower foliot need to be closer in so that the hand moves faster for the remaining 11 hours and returns to the daylight start position at 05:30. The dial is marked in 120 segments to assist in the adjustment. The hand needs to move one segment in 13 minutes during daylight and one segment in 11 minutes at night. Is that all clear?
It took a few days to fine tune, but my first attempt wasn't bad with it running about 15 minutes fast after 12 hours.
It has got a blooming loud tick!
What a great post and a fascinating timepiece.
I tip my virtual hat to you Sir, bravo. Any chance of a video of it running?
Thanks very much! Yes, I'll sort out a video clip this afternoon.Originally Posted by kungfugerbil
Gets a plus one from me!
Excellent post and info. That company has some intriguing kits. Kind of Japanese "Remus Kits" (remember those?) for adults.
Quality post, sir, and fascinating stuff - thanks! Look forward to the video.
Here's a short demonstration video as promised. The ratchet pawl triggers (quite loudly) at around 0:20, switching from day to night foliots and again at 1:07 switching from night to day. The differing night and day oscillation rates can just be detected. Obviously in reality there would be a number of hours in between!
Very interesting thank you.
'Against stupidity, the gods themselves struggle in vain' - Schiller.
Cracking piece of kit.......might need one for the study!!!
mike
Love that - how satisfying it must have been to assemble and regulate, too. Thanks for sharing.
Last edited by DMC102; 26th April 2017 at 00:05.
Thanks for sharing, a really interesting clock.
Fascinating - thanks for sharing (even if I could build one I think the tick might be a little on the loud side :) )
ATB
Jon
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