The Karakuri Mechanical Doll in action

The movement of the Karakuri doll involves a variety of mechanisms. The mechanisms for individual actions are described here.

Start and stop mechanisms

The start and stop switch mechanism is worked using the auto-adjustment pin linked to the arms. When you place a tea cup on the tray, the arms go down and the pin moves up. The auto-adjustment pin works as the stopper for the cogwheel, so when it goes up, the stopper releases, and the cogwheel starts to turn. When the guest picks up the tea cup, the arms rise and the stopper engages, stopping the cogwheel. (Figure a)

Forward motion mechanism

The force of the spring unwinding is transmitted first to an 80-tooth wheel. The second wheel powered by this force (on the cart) has 120 teeth. The projection catches after about 5 revolutions, although it calculates out to 7. The cart advances 18 cm per revolution, so it goes about 90 cm before the projection catches, at which point it starts to turn. The "Karakuri Zui" told its readers to use a whalebone for the mainspring. (Figure b)

Bowing mechanism

When the doll brings in the tea, it does a proper bow. The rotary plate controls the bow. When the projection hits the part extending from the neck, it pulls on the neck and the head lowers. When the projection releases, the pulling stops and the head returns to its previous spot, pushed by the spring. The rotary plate also controls forward motion, so bowing is combined with turning. (Figure c)

Direction change mechanism

The little wheel on the bottom changes direction. The direction of forward travel changes by the angle of the front wheel just like the three-wheeled cart. The angle changes when the rotary plate presses the wheel. The doll rotates to the right as long as it is pressing. When the projection releases, the wheel returns to its original position and goes straight ahead. You can control the angle of the turn by adjusting the projection. (Figure d)

Shuffle mechanism

When the doll walks, its feet shuffle back and forth. It looks as though it is shuffling in proper style for a tea ceremony. This movement is realized by he center of the left and right drive wheel being offset from the center of the rotation shaft that controls foot movement, and the cranking movement makes the feet appear to shuffle. According to the "Karakuri Zui", the left side should be installed forward of the center and the right side to the rear of the center. (Figure e)

Speed adjustment mechanism

A rear cogwheel called the "gyojirin" (photo) adjusts the speed. Two stoppers on the escapement catch on the cogwheel, controlling its rotation. This is the same technique that is used in speed regulators in Japanese clocks. Doll speed can be fine-tuned further by placing weight plates on the speed control bar. (Figure f)