We report results of science classes in which the fourth, fifth, or sixth year pupils in elementary schools made Renrigaeri models. Renrigaeri is a kind of Japanese traditional automata, namely Karakuri dolls. In a recent year, Karakuri dolls have been lightened at Japanese manufacturing factories because their movements with spiral springs or gravity instead of motors or engines can be applied to many kinds of machines with low energies. Renrigaeri consists of two puppets shouldering two cylinders in which little amounts of mercury are sealed, and a stairs. When the puppets are put on two consecutive steps of the stairs, the amounts of mercury are accumulated to lower ends of the cylinders, rotate the cylinders around shoulders of a lower puppet because force moments by gravity working the amounts generate around the shoulders, and make an upper puppet jump over the lower one. In order to prepare Renrigaeri models for the classes, many trials and errors were required. Consequently, some important principles were revealed. For example, puppets are better to be made of light materials and to have the same size. On the basis of the principles, the models were developed to be checked whether they moved or not. In the classes, pupils assembled parts of Renrigaeri models under instruction of students in our college and tried to move the models. They seemed to be glad as if they got toys and understood force moments. Students learned importance of group work through the classes and the preparation.
Kazuki Hiro, Nara National College of Technology, Japan
Toshio Hira, Nara National College of Technology, Japan
Mitsunori Ozaki, Nara National College of Technology, Japan
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