Taking reference from Jack B Du's pen plotter because I've been fixating a goal to forge my signature (or at least my initial 'e' or 'k') with an automaton. Thanks to Tunapee for sending this!

Main components found in this project are:

- 1 shaft to weight things to stay on the ground - i'm using a thick, heavy long screw in replacement of that.

- 2 gears - I'm using 18 teeth and 24 teeth to create 1:1.33 ratio with 3mm module (just eyeballing measurement).

- 4 hands, 2 of them have slits to allow an object to slide within it

- 2 screws for connection between 2 hands

- 2 screws for the gears

- Pencil / pen / writing tool

- 2 shafts with a washer on top that can be slit into the slits on the hands - i'm using the sex bolt Cody gave me. Thanks Cody!

Process

Assuming both arms are same length, these are my probably-wrong calculation (because the gear that i ended up cutting is somewhat not perfectly matching the intended pitch diameter). But i get the idea that the difference of the distance between the sliding shaft at the most retracted and most protracted moment will decide the radius of the drawing arc.

While the drawing is in place, I'm not sure of the measurement so I went to a helper website to generate the gears and sort of let it decide for me the measurement.

Helper website to generate gear template.

Gear 1 information

Gear 2 information

The smaller gear has 18 tooth and the bigger has 24 tooth.For every 3 rotations of the bigger gear (2), the smaller gear (1) makes 4 rotations. The smaller gear rotates 24/18=1.33324/18=1.333 times faster. For 2 gears to mesh / touch, their module needs to be the same.

To find module = pitch diameter / number of teeth.

Therefore m1 = m2 => d1 / 18 = d2 / 24. Let's do d2 with 10cm, then d1 will be 7.5cm.

I printed this on a paper to use as a stencil and pasted it on the cardboard, then cut them together.

Initially cutting with box cutter, I realized it is too large of a tool and then changed to painstakingly stabbing the cardboard with a toothpick. Broke a few toothpicks in the process, and also scraped my skin. Another option for the cardboard teeth is just to use the corroded part but at that point when I realize that I was already deep into the manual technique, and also i’d like to make this 2D. So i roll with this.

It is kinda tiring to cut and keep the shaft on the gears aka toothpick stand still. Thankfully Cody came to the rescue and gave some sex bolts and screw that helped pin everything down.

At first it was a bit confusing to figure out how the slider works. But doing the automaton by hand instead of 3D printing it has made me “accidentally” discover the way the slider works. The slider never fully slides along the slit, the slider maximum movement will be the same as the gear diameter that it is in placed in, assuming that the slider part is put at the radius of the gear. It moves back and forth, automatically creating a cyclical movement. The fact that the gear is rotating against each other also causes the slider that rotates along it to be moving the hands above it in a flipped direction.

For the hands, for them to be able to follow the cyclical movement of the slide, both ends of the hands also need to be united into another axis. This common axis will allow the hands to be changing the angle of its hands, as 1 end has to be fixed (the axis side) and when the slider moves, it forces the other end to be moving, causing the hand to change position.

The full diameter of the smallest gear will determine the slider movement length, which will be divided into 2 movement of back and forth. This linear back-and-forth movement causes the second linkage arms to pivot, translating it into an arc-like movement at the pen. The drawing follows the direction of the rotation on the smaller gear (gear 1). So when I turn the bigger gear, it tuns the smaller gear anti-clockwise and the drawing is curved anti-clockwise as well.

Gears

More reference

My slider does not fully slide until the end. It slides about halfway and then go back and forth. I didn't precisely aim the sliding shaft hole on the gear 2, it was a little too close to center. The sliding shaft will travel no longer than the smallest radius made by any of the sliding shaft - gear center.

Reflection

I hurt my fingers while trying to cut the gears. And this made me appreciate the fact that we have it easy here at ITP, with the luxury of laser cutting and 3D printing. But also it made me appreciate myself, that without those machineries, even with my human imprecision, I still able to make some part of the automaton works. It reminds me of the rigorous physical training one must do if you want to be a shaolin master, like you have to carry rice sack up the mountain. Of course what I'm doing here is nothing in comparison to that, but you know what I mean.