Build: The Gakken Karakuri Tea Serving Robot

The Gakken Tea Serving Robot is designed to be a replication of the karakuri zui, an illustrated manual written in the Edo period (1603-1868). This mechanical doll has a tray that holds a cup of tea, and it is designed to approach the guest with the tea, bow his head, and then carry the empty teacup away. Using only springs as power, the term “robot” might at first seem a little strange, as there is no electricity used to make this doll do what it does, nevertheless, this doll has been called one of the original forms of the modern robot, in that it does follow (rudimentary) programmed instructions relating to variables such as if, then, and when. Check it out:

You don’t have to be thirsty for a small cup of tea to see the appeal in this kit. Making the karakuri gives you a chance to experience what it was like for innovators and dreamers before the flood of modern technology, to see the trouble they went to as they carved their “code” into pieces wood, metal and other materials instead of uploading it onto microcontrollers like many makers do now. The karakuri is, by definition, a robot, but it is a robot that uses no electricity, and instead of using code as its instructions, it uses a series of mechanical processes to react to its physical environment.

View the Gakken Karakuri Tea Serving Robot in the Maker Shed.
How does this doll react to its physical environment? First off, we can see that there are a few main parts of the doll that move.

• The wheels/feet: Although the doll technically moves via its wheels, there are feet that protrude from the front that move back and forth when the wheels are spinning. There is also a front wheel that does the steering, and this wheel turns for a period that is dependent on how the adjuster piece is placed.
• The head: The doll is designed to bow its head, indicating that it’s ok for you to take your tea. The doll bows its head shortly before it begins to turn back in the direction it came from. The role of the head bow is twofold: It makes the robot seem more lifelike, and it indicates that it is time for you to take your tea. In fact, failure to take the tea will result in the robot turning around and leaving and taking the full teacup with it, so don’t forget to take the tea!
• The arms: The arms hold a tray for the tea cup, and they pop up when the tea cup is removed from the tray. When the arms pop up, this causes a pin to go down near the wheels that keeps the wheels from spinning. This is why the doll stops when you pick up the tea cup. This is the mechanism that reacts with the user, as the wheels stop when the tea is removed, and start again once it is replaced.

Assembling the doll:

Putting the karakuri doll together was a fun hour or two, and assembling everything really helped me to get a really a better idea of how the robot works. As with other Gakken kits, don’t freak out when you see only a Japanese instruction booklet. The English assembly instructions are here. Aside from this, everything is provided for you in the box, including a screwdriver and a cute pair of tweezers for attaching the springs to their bases.

First you make the chassis, or the “cart” as the call it in the instructions. It asks you to put the feet on over the wheel bases, and don’t worry if they don’t stay straight quite yet, it will take putting the body of the doll onto the cart for those to finally fit in properly.

There are three “springs” of different lengths that are used to make the doll move. These springs actually just long strips of flexible plastic with loops of string that are tied on to make things move in certain directions. There are two of each kind of spring provided with the kit, the second one can be used as a backup should one of the springs lose its spunk.

Gears keep things rotating in the proper direction. This gear is used for winding up the coiled spring (called the mainspring in the instruction manual), and this spring is the main source of stored power for the doll.

Below is a picture of the adjuster, attached to the rotary plate. The adjuster is the piece you use to adjust the amount of time that the doll spends turning. If you make the notch wider (by turning the guide counter-clockwise as it appears in this picture) then the doll will turn for a longer period of time. Once you have everything put together, you’ll probably need to adjust this so that the doll makes a full 180° turn so that it can return the tea cup.

Note the nice plastic-that-looks like wood that this kit is made of. It’s actually quite pretty.

Here I am, attaching the tray to the hands of the doll. As you can see, the doll is “naked,” and although it is tempting to want to dress the doll up once you have the body put together, be sure to put that off until all of the necessary adjustments have been made. You’ll want to have your doll undressed (<- I feel so sketchy typing that) because you'll have to make adjustments with the adjustment screws.

Once you’re done adjusting everything and the karakuri is walking straight and making 180° turns, your friends will probably fight over who has done a better job of dressing the little guy.

Tips:
A few things to take note of during the construction of this kit:

• There are a lot of screws that you’ll be putting into holes that aren’t threaded. The material that the kit is made out of is a kind of fibrous, textured plastic that looks and feels sort of like wood, so use the same basic skills you would for putting a screw into wood for putting these screws in. Because the holes are already there and the material is not particularly hard, you should be able to get the screws in without too much elbow grease, but make sure that you’re putting them in straight to begin with.
• Use the provided tweezers to put the strings from the springs onto their bases.
• Make sure that the piece they call the escapement is not running into the body or the rotary plate. There are two rudders attached to the escapement shaft, and they can and may in fact need to be rotated a little so that they aren’t hitting anything. If they hit the rotary plate, this will cause the robot to stop on its own just before it is about to turn, and then it won’t be able to start again unless you advance the rotary plate by hand. The escapement is supposed to swing back and forth in order to regulate the speed of the escape wheel that gets turned by the rotation coming off of the mainspring.

(Here’s a video of a properly adjusted escapement, notice that the auto-adjustment pin moves very slightly as I press down on the tea tray to let the escape wheel move. Also notice that the escapement does not hit either the side of the doll or the rotary plate. When I put on my escapement straight out of the box, the rudders were placed so that the escapement would hit the adjuster on the rotary plate when it spun down – it took a few tries adjusting the rudders on the shaft of the escapement before it was not hitting anything on either side.)

• Make sure that you run the robot in an area that allows it enough space to run long enough to bow its head and make a turn. Carpet seems to be a little tricky, a smooth, flat surface such as a large tabletop or floor seems to work best.
• In order to preserve the mainspring, don’t leave the doll wound up for long periods of time. Also, take the teacup off of the tray as this can weaken the tension of the spring that moves the arms. Or, if you must, for decorational purposes, keep the tea cup on the tray, either remove the string from its base temporarily, or wedge something in there so that the arms remain in the up position.

Adjustments:

As noted on page 23 of the instruction manual, there are four things you can adjust on the doll.

• You can adjust the doll’s head so that it goes down more or less when it bows. This is purely a cosmetic adjustment, it has little to do with how the doll runs.
• You can adjust the angle of the tray so that it becomes level when the teacup is placed on it. This is important if you’re going to be filling the cup with actual liquid (although the cup alone is typically heavy enough to make the doll move even if there isn’t any liquid in the cup).
• You can adjust the screw on the bottom panel to make sure that the doll heads in a straight direction when it is heading to and from its target tea drinker. Turn the screw clockwise to make the doll go more right, turn the screw counter-clockwise to make the doll go more to the left.
• You can (and will most likely need to) adjust the adjuster on the rotary plate so that the doll makes a 180° turn once it completes its tea serving. A wider overall notch makes for a longer, and thus more profound turn, while a smaller overall notch (where the adjuster is completely flush with the notch underneath it) makes for less turn time. The length of this protruding notch is what makes the front wheel turn to the right when the guide wheel comes and pushes the front wheel connector.

Be patient, and with a few adjustments you will eventually get the doll running back and forth with precision.

Reflections:
All in all, it just goes to show how how clever these Edo period thinkers were, using sophisticated mechanics to accomplish tasks that many many makers now take for granted. You want the robot to stop when the tea has been lifted? In modern electronics, this could be accomplished by using a switch that starts and stops the motor from spinning depending on whether the arms are up or down, but in much simpler terms, these early engineers thought to stop the movement of the wheels by having a pin ram into the gears that control the wheels. Both work, but accomplish the task by very different means. Perhaps this is why steampunk has captured the imagination of so many people as of late: Because it envisions a world in which human imagination, craft, and innovation continue to thrive, regardless of the specific manifestations of these technologies.

Looking at mechanisms like the karakuri also remind us how easy we have it these days when it comes to making our ideas into reality. Never before has there been such a wide spread of information about how to create things, as well as accessibility to the tools that allow people to realize their ideas, but what better way to understand the tools we have now, than to examine the processes people used in the past? This makes the Gakken Karakuri kit a great for anyone wanting to learn about mechanics, primitive robotics, or history.

View the Gakken Karakuri Tea Serving Robot in the Maker Shed.