Reconstruction of unknown mechanisms of a pagoda clock in the Forbidden City

Abstract

The ancient European mechanical clock with automata is one of the indicators of manufacturing technology, and the clocks exported to Asia offer evidence of cultural exchange at that time. The Gilded Copper Rising and Falling Pavilion Clock Inlaid with Gemstones is one of the ingenious mechanical work made in Britain and exported to China in the 18th century. Although it's well preserved in the Forbidden City in Beijing (Palace Museum currently), the internal mechanical structure is not open to the public, because of its historical value. In order to reconstruct the pagoda automaton attached to the clock, structural analysis is presented according to the text records of the other four clocks with similar automata. A systematic design approach is proposed herein. The feasible mechanisms are synthesized by going through generalization, specialization, and particularization. As the result, nine, three, and four feasible mechanisms with linkage, gear, and cam are generated, respectively. One of the feasible designs with the largest output motion range is selected, and dimensional synthesis is made to achieve the motion characteristics. Its performance is verified through prototype testing.