Structural Synthesis of the Trigger Mechanism in an Ancient Japanese Automaton “Ryomon Waterfall”

Japanese automata, representing a significant facet of mechanical art development, have historical roots dating back to the 8th century. This paper focuses on the reconstruction design of the trigger mechanism in the automaton “Ryomon Waterfall” from the 18th-century compendium “Karakuri Zui.” The automaton narrates a mythical tale of a carp transforming into a dragon and ascending to the sky. Despite historical significance, the internal mechanisms are not fully illustrated. A systematic design procedure is proposed, involving the synthesis of feasible mechanism structures and subsequent dimensional design. The process is applied to the trigger mechanism, and a prototype is constructed, showcasing the applicability of the method. The study contributes to the understanding and reconstruction of ancient automata, shedding light on Japan's mechanical craftsmanship during the 18th century.