Large Spirograph Set

This is a variation of the spirograph toy with several rings and discs for spiral patterns.

Nice for kids to wile away a rainy day, as well as adults who have to endure boring meetings.

Please let me know if you come upon interesting patterns or have a good idea for another disc or ring. I'll collect ideas and may publish extensions for the set.

Patterns

If the number of teeth on the ring is divisible by the number teeth of the disc, then the result will be a relatively simple regular pattern equal to the result - e.g. the 25 disc in the 75 ring will create a tri-angle.

If both numbers are divisible by the same (relatively) large number, then you will get an overlapping pattern that is still quite simple. E.g. the 36 disc in the 48 ring (36/48 = 3/4) will yield a pattern similar to a 4 leaf clover.

If the numbers do not cleanly divide, then you will get a very dense overlapping pattern.

To predict the number of leaves put both numbers into a fraction and then reduce the fraction as far as you can - it will be the bigger one of the two numbers. See the images for some examples.

The holes in the discs should be fine for most fine liners, pencils and ballpoint pens. The center hole always draws a circle.

If you put the pen into a hole close to the center of the disc then the pattern will look like an intricate 2D donut, a hole closer to the edge will produce a pattern that fills more of the inside.

Use the triangles to create flattened lines on the outside of the pattern.

Printing

The entire set takes quite a long time to print, but you can get very interesting results with even a small subset of rings and discs.

There are prepared sets of rings and discs in the 3mf projects (made for PrusaSlicer). The projects also print the number of teeth on each ring and disc. Those numbers are missing from the STLs. The 3mf projects are grouped by divisibility of the discs and rings - this enables you to print related objects with the same color if you want to color code for certain effects.

There are two sets of rings: divisible by 12 and divisible by 25. And several sets of discs that match the divisibility of the rings for simple patterns and other factors for more complex patterns.

If you start from the STLs you need to flip the rings by 180 degrees before printing to avoid overhangs, the discs are already oriented the right way. No special infill, supports or other settings are necessary.

Simple PLA will be fine as a material. Any non-flexible material will do okay.

Drawings

I included a simple PDF with drawings of the entire set - you can use it for identifying rings/discs. Print it without scaling - otherwise the drawings will not match reality. It should print fine on A4 and letter.

FreeCAD Design

I included the FreeCAD (version 1.0) model if you want to modify or extend the set. Individual models are grouped in the FreeCAD file.

Each disc starts with a Pad for the gearing, then a Pocket for the holes and finally a Chamfer to make it easier to insert a pen. To make a new disc simply copy one with a similar number of teeth and then modify the copy.

Rings start with a Pad for the overall shape and then continue with a pocket for the gearing. The shape is hand-optimized for the size of the gearing, so you may need to experiment a bit when changing a ring.