Kit #41, The Auto Writer


(Image from the Gakken site. Used for review purposes only.)

At some point, Gakken stopped printing volume numbers on the Otona no Kagaku kits, but they kept them in the online URLs.


(Starting out. Note the thing at the top of the photo that looks like a stir stick. It’s used for prying the cams off the cam spindle when you want to change patterns.)

Auto Writer, kit #41. 3,500 yen (w/o tax).
The original image for this kit, released almost 9 months ago, was of an old-fashioned automaton dressed up as an 19th century woman. The actual implementation is something a bit different. Novumichi Tosa, president of the art company Meiwa Denki, was instrumental in the design and testing of the kit, which kind of looks like a clown hand on a cassette tape player. The name is a gag – “automa-te”, which is derived from “AUTOMAton” and “te” (for hand), or “automate”.


(Top half, top view, with cam sliders and power button in place.)

The mook starts out with a look at Meiwa Denki, and the two brothers running the company, then discusses the development and principles behind the kit. Several pages cover the operation of a full-scale machine writer used for transcribing kanji for art prints, which is followed by a pictorial on how the cams were made for the kit. We then get a photo history of several automatons,including one of the machines by Friedrich von Knauss, and three by Pierre Jaquet-Droz. The suggested mods are to turn the kit into a UFO to make mini-crop circles, clamping two kits to a guitar to play music, and interfacing a tablet computer through an Arduino to make a kind of plotter/printer.


(Top half, bottom view. Cam slider mounting.)

There’s a section on robotic prosthetics for the handicapped, examples of figurines made using 3D printers, and a hand-held 3D doodler (think hot-glue gun that makes 3D structures) ($160). 6 pages on what the 4th dimension would look like, 2 on what children think space looks and sounds like, and 2 pages on a guy that makes model Japanese castles out of cardboard. 2 more pages on a guy that hand-makes actual transformer robot models (they change from a car to a robot), and 2 pages of entries from last year’s “15-Second Special Effects Movies” contest.


(Bottom half, top view. DC motor and gear chain. The kit uses one AA battery.)

Have you heard of “rare sugar”? I haven’t. There’s a 6-page section on “kishoutou”, which literally translates to “rare sugar”. The Japanese wiki has a page on it, but there’s no English version. The primary link is to the Rare Sugar Research Center, located in Japan. The website is Japanese, only. Example sugars are D-Allose and L-Glucose. Rare sugars seem to be promoted as having special health properties, but there’s some dispute over this.


(Top half, top view. X-axis and y-axis sliders in place.)

The rest of the mook contains construction instructions for the kit, and ends with Yoshitou Asari’s Manga Science (this one on water surface tension).


(Top half, top view. Mounting the hand. Note that the springs for the hand and the x-axis slider are in the wrong places. The black piece in the hand casing is just used to hold the pen.)

The kit is based on the same principles as the von Knauss and Jaquet-Droz machines. 3 separate motor-driven cams control the x-, y- and z- axes of the pen hand, and the movement along the slider bars is pretty much the same as for a plotter. Only the x-axis slider is directly connected to a cam lever. The y-axis slider is advanced with fishing line tied to one cam lever, pulling against a spring. The z-axis works the same way for lifting the pen off the paper. Two ribbed pieces of tubing are used to maintain tension on the fish line between cam lever wall and the connecting wall on the pen arm. This is where the first error comes in. The parts list photo shows the 2 pieces of tubing to be the same lengths, while the instructions refer to a “long” piece and a “short” piece. If you use the tubing as-is, the fish line for the z-axis will be too short. I ended up cutting 2″ off of one piece to use it for the z-axis, and even then there was more tubing than is needed to compensate for the action of the sliders.


(Top half, top view. Putting on the upper hand cover, and mounting the top and bottom halves of the main unit together. Tubing to the right is for the fish line controlling the y-axis movement.)

A second problem comes in with the springs. There are three springs, one for each axis, labeled as “big”, “medium” and “small”. The big spring is used for the y-axis, and it’s pretty obvious which is the big one. However, “medium” is the same diameter as “big”, just a bit shorter; while “small” is the same length as “medium” but with a smaller diameter. If you mix up medium and small, you’ll mash up the x-axis spring when you tighten down the screws, and the z-axis spring won’t fasten right under the smaller screws. So, use the smaller diameter, shorter spring for “small”, and larger diameter, shorter spring for “medium”. Regardless, the x-axis spring should be another 10% shorter in order to fully retract the slider arm to the “resting” position; as it is, it’s too long.


(Bottom view with both halves mounted together. The ribbed tubing shown here is for the fish line controlling the hand z-axis. Note that one end of the line isn’t connected to the hand, yet. I think the key-hole in the case is so you can hang it on the wall when not using it.)

The fishing line is held in place at one end with a knot, and the other by wrapping it around a screw. When you get the kit fully built, it’s a good idea to loosen the screws to take all of the slack out of the lines. And again, after you’ve played with the slider arms to see how they work, it might be wise to shorten both ribbed tubings to get rid of excess that could get snagged on something.


(Bottom view. Rubber feet attached to the case. Fish line attached to the hand for the z-axis movement. Spring wire inserted in the disk at the top left. That disk is a retainer used to hold the cams in place on the main gear spindle.)

You get three sets of cams, one for the kanji that appears on the front of the mook, one for the name “Tosa”, and one for a peace sign. While the full range of the sliders is about 2.5cm x 2.5cm, the height of the kanji is just over 2cm (3/4″). So, while the auto writer is a fun idea, what it can write “out of the box” is kind of limited and kind of small. If you want to make your own personalized cams, you can design them using an online app, trace the patterns out on a thin sheet of plexiglass and cut them out yourself. Personally, I don’t have plans for making new cams or for modding this kit. I thought of using it to move the stylus for the Pocket Miku, but the note play time would be too slow.


(Top view. Cams and cam retainer in place.)

A couple final notes. There are actually 2 switches on this kit, wired in parallel. The first one is the push button mounted in the corner, with the light blue button cap. You need to hold this down for about a second for the kit to go into auto mode. The second is a leaf switch driven by the main drive gear at the bottom of the kit. As the gear starts rotating, it closes the leaf switch, which lets the motor continue running after you let go of the push button. When the gear makes a full rotation, the leaf switch reaches a notch in the gear and opens up, causing the motor to stop. It’s a fairly elegant way to avoid using an electronic timer circuit.


(Using the “kanji” cams. The arm kind of sticks during movement, so it may be a good idea to spray the slider rods with lubricant.)

The second note regards what to write with. The hand doesn’t push down against the paper all that hard, although it does push enough that the pen will drag the paper around unless you hold the sheet in place with something heavy. If you use a pencil, the writing will be too faint. You can use a good ballpoint pen, a thin-line marker, or a paint brush. I suggest turning on the kit, and when the hand goes into full “down” position, pull the battery out. Put the pen in the hand and adjust the positioning so the pen writes the way you want on a sheet of test paper. Wrap masking tape on the pen to show where to slide it next time when you remove it or cap it during storage. Put the battery back in and wait until the kit turns itself off. Put a fresh piece of paper under the pen, anchor it in place, and then start the kit again.
The next kit is scheduled to be the electronic steel drums, 3,500 yen, in September.

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