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Hylton Smith's Meccano Moon Phase Clock

Hylton writes: "This clock was driven by a 20rpm synchronous motor with gearing to the hour hand shaft. The clock shows the day, date and the moon phase. The day dial shows the days (Sunday to Monday) twice over around the dial. The shaft that carries the pointer also carries a 14 tooth tooth sprocket wheel that is tripped once every 24 hours at midnight and never needs setting. The date dial is numbered 1 to 31 and the shaft that carries the pointer carries a 36 tooth sprocket that is tripped one tooth every 24 hours at midnight to the next date and needs adjusting again at the begining of the new month.

Standard clocks use a moon phase of 29 and a half days, the moon dial has two full moons and revolves one half turn every month. Now let's take 29 and a half X 2 = 59 X 2 = 118. We need a 118:1 ratio from the hour hand shaft. This is not always easy but I did get very close. The gear train to the moon dial has a gear ratio 4:1 X 4;1 = 16 X 2 = 32 X 2 = 64 X 1.84 = 117.76. I found that matching a Meccano 25 tooth pinion with a N G NEERO gear with 46 teeth (that is how it is spelled on the gear) gave me the 1.84 ratio needed, the 4:1 gear ratio is standard in the Meccano system as is 2:1, etc., etc."

Hylton in the 1950s with a Meccano grandfather clock he built.