One Step Forward, One Step Back
The original plan was to have an 11 cm hole to fit your arm through, a size just larger than the average human arm. When I started designing, I had everything rotate around an axis 5.5 cm away from center. What I didn’t take into account was, while some things would be rotating at that distance, others pieces would move in closer than that 11 cm diameter.
In response to this I redesigned the stepper motor portion to rotate around a circle that is 16 cm in diameter, so at its closest it is a full 13.5 cm wide (better to be safe than sorry). The pen can still be positioned to be as far or close as it needs to be, but there is now less chance of your arm brushing up against one of the moving pieces.
When I rebuilt the timing belt, I was able to make it run just as well as the smaller one did (as shown in my last video) but I wasn’t very satisfied with that as a result. My next step is to abandon the timing belt altogether, and replace it with gears that I can print out and attach to the timing pulleys.