Yacura clock (lantern clocks)

There are various types of wadokei or Japanese clocks : kake dokei (wall clocks), Yagura dokei (lantern clocks), dai dokei (grandfather clocks), makura dokei (pillow clocks) and shaku-dokei (ruler clocks). Among these, the Yagura dokei (lantern clocks), the most typical Japanese clock in form, are clocks on high pyramid stands. There are different speed control devices among wadokei such as the single foliot escapment, double foliot escapment, circulare balance and pendulum weight, with the single foliot escapment generally being the oldest device. The early period single foliot wadokei had to be adjusted daily with 6 weights at sunrise and 6 weights at sunset. The Nicho Tenpu or double fokiot mechanism is a clock unique to Japan invented in the mid-Edo period aiming to solve the labor intense aspect of the former wadokei. With the Nicho Tenpu device, the two foliots regulators, one for daytime (top part) and one for nighttime (bottom part) with each having 6 weights. The two foliots automatically switched from one to the other at sunrise and sunset. The night time foliot. According to the Japanese time system based on sunrise and sunset, nighttime is considered to be two hours shorter than daytime on average.